Co-reporter:Xue Liu, Hao Xu, Lin Zhang, Lu Han, Jingang Jiang, Peter Oleynikov, Li Chen, and Peng Wu
ACS Catalysis December 2, 2016 Volume 6(Issue 12) pp:8420-8420
Publication Date(Web):November 11, 2016
DOI:10.1021/acscatal.6b02032
The crystalline structure of UTL zeolite experienced an unusual orientated collapse and reconstruction within an extremely narrow time window during the structural stabilization process by nitric acid treatment at elevated temperature. Taking full advantage of this unique structural change, extra-large-pore Sn-UTL zeolites were postsynthesized via the reaction between the SnCl4 molecules and the silanols in the hydroxyl nests, which occurred concomitantly with the removal of Ge and/or Si species from the dense layer. The original UTL topology was restored thereafter, leading to a Sn-incorporated analogue. The usage of the most seriously collapsed intermediate structure, which was captured by timing during the precisely controlled acid treatment, was vital for achieving Sn-UTL zeolites with a larger amount of isolated Sn species effectively incorporated. With tetrahedrally coordinated Sn ions in the highly stabilized UTL topology consisting of intersecting 12- and 14-membered ring (MR) pore channels, Sn-UTL showed promising catalytic performance in the Meerwein–Pondorf–Verley reaction as well as in the Baeyer–Villiger oxidation reactions of ketones using H2O2 or even bulky tert-butyl hydroperoxide (TBHP) as an oxidant.Keywords: extra-large pore; germanosilicate; selective oxidation; stannosilicate; structural rearrangement;
Co-reporter:Yun Wang, Pei Zhang, Gang Huang, Qingqing Yuan, Yejun Guan, and Peng Wu
ACS Sustainable Chemistry & Engineering August 7, 2017 Volume 5(Issue 8) pp:6645-6645
Publication Date(Web):June 12, 2017
DOI:10.1021/acssuschemeng.7b00891
The synthesis of new biomass-derived ethers is of great interest for the development of biofuels and biofuel additives. In this study, we report the facile synthesis of a novel bioether ethyl-4-ethoxy pentanoate (EEP) from γ-valerolactone (GVL), a well-known biomass platform compound. The formation of EEP involves the etherification of ethyl-4-hydroxyl pentanoate (EHP) formed by GVL ring opening catalyzed by H-β-zeolite in ethanol. When operated at 140 °C for 2 h under autogenous pressure, the highest EEP yield of 55% was achieved at 62% GVL conversion and 89% EEP selectivity. The EEP yield was significantly improved to 86% by increasing the reaction temperature to 160 °C, where the EEP selectivity reached ∼97%. The extraordinarily high selectivity to EEP over H-β is likely correlated to its unique structure, which has strong Lewis acid sites as well as an optimal pore size.Keywords: acid catalysis; bioether; etherification; pore size effect; β-zeolite;
Co-reporter:Zhiguo Zhu, Hao Xu, Jingang Jiang, Haihong Wu, and Peng Wu
ACS Applied Materials & Interfaces August 16, 2017 Volume 9(Issue 32) pp:27273-27273
Publication Date(Web):July 20, 2017
DOI:10.1021/acsami.7b06173
All-silica beta zeolite, synthesized by conventional hydroxide route, usually possesses small crystal size of a few hundred nanometers but poor hydrophobicity, whereas the fluoride-mediated one exhibits to be highly hydrophobic but microsized. To obtain nanosized all-silica beta zeolite with excellent hydrophobicity, an innovative and efficient hydrothermal route via interzeolite transformation for synthesizing all-silica beta zeolite is proposed in present study. With the assistance of beta seeds and tetraethylammonium hydroxide as the structure-directing agent, siliceous beta zeolite is well-crystallized at a high solid yield via dissolution-recrystallization of all-silica ITQ-1 crystals at an extremely low water content (H2O/SiO2 molar ratio of 1). The obtained all-silica beta crystals are composed of 30–70 nm nanoparticles and highly hydrophobic just next to siliceous beta-F zeolite synthesized by environmentally unfriendly fluoride route, which is derived from relatively small amounts of internal defect sites. Thus, this beta zeolite is superior to other pure silica beta zeolites in the adsorption of large-sized volatile organic compounds (VOCs), which is mainly attributed to its high total pore volume and specific surface area as well as excellent hydrophobicity.Keywords: all-silica zeolite; beta zeolite; interzeolite transformation; MWW zeolite; VOCs removal;
Co-reporter:Peng Ji;Kun Lu;Xinqing Lu;Hao Xu
Dalton Transactions 2017 vol. 46(Issue 18) pp:5776-5780
Publication Date(Web):2017/05/09
DOI:10.1039/C7DT00640C
Ti-SSZ-70 and Ti-ECNU-6, with identical intralayer structures but distinct interlayer connections, were prepared from similar synthetic gels free of alkali metal ions and boric acid. Ti-SSZ-70, composed of vertically misaligned MWW layers, was transferred to Ti-ECNU-6, structurally analogous to the Ti-MWW zeolite with a well-aligned layer stacking, upon the addition of an appropriate amount of hexamethyleneimine to the gel. These two titanosilicate catalysts exhibited outstanding catalytic activities in the liquid-phase alkene epoxidation.
Co-reporter:Peng Ji, Ming Shen, Kun Lu, Bingwen Hu, Jin-Gang Jiang, Hao Xu, Peng Wu
Microporous and Mesoporous Materials 2017 Volume 253(Volume 253) pp:
Publication Date(Web):15 November 2017
DOI:10.1016/j.micromeso.2017.07.004
•1-Adamantanamine is used for the synthesis of a new aluminosilicate ECNU-10.•ECNU-10 is the second direct-synthesized example of 3-dimensional MWW-type analogue after MCM-49.•The morphology of ECNU-10 crystals is possibly controlled by the crystallization mode.•With similar framework Al distribution as MCM-22, ECNU-10 shows catalytic activity in the disproportionation of toluene.ECNU-10, an analogue of MCM-49 with the 3-dimensional (3D) MWW topology, was synthesized using 1-adamantanamine as structure directing agent (SDA), which is the second example of 3D MWW zeolite obtained by direct hydrothermal synthesis. The synthesis condition was investigated and proton-type ECNU-10 showed similar Al distribution with conventional MCM-22 obtained by the interlayer condensation of a layer precursor, as revealed by 27Al 3Q MAS NMR analysis. The catalytic performance of ECNU-10 was evaluated in the alkylation and disproportionation reactions in comparison to another two MWW-type aluminosilicates of MCM-22 and SSZ-25.ECNU-10P was synthesized using 1-adamantanamine as structure directing agent, which is the second example of direct-synthesized 3-dimensional MWW zeolite. ECNU-10 is an efficient MWW-type solid acid catalyst in the disproportionation of toluene.Download high-res image (356KB)Download full-size image
Co-reporter:Pei Zhang, Chun-Hsia Liu, Li Chen, Jin-Ming Chen, Yejun Guan, Peng Wu
Journal of Catalysis 2017 Volume 351(Volume 351) pp:
Publication Date(Web):1 July 2017
DOI:10.1016/j.jcat.2017.04.017
•Ni or NiO in bimetal PdNi catalysts maintains their oxidation state under mild hydrogenation conditions.•Bimetal PdNi catalyst deactivates in the hydrogenation of α-AL and the deactivation rate depends on the oxidation state of Ni, particle size of NiO or Ni, as well as the solvent used.•The deactivation is linked to the dissociated adsorption of α-AL, which mainly takes place on reduced Ni predominating surfaces.We have previously reported the superior catalytic activity of Pd-NiO/SiO2 to Pd-Ni/SiO2 in hydrogenation of α-angelica lactone (α-AL) to gamma-valerolactone (GVL) in a batch reactor. To gain deeper insight into the structure-activity relationship of Pd-Ni bimetal catalyst, a series of NiO/SiO2 with different NiO particle sizes (about 3, 9, and 20 nm in average) were prepared by impregnation method in the presence or absence of ethylene glycol. These materials were used as the support of Pd catalysts for the liquid-phase hydrogenation of α-AL in a fixed bed reactor. The corresponding reduced catalysts, namely Pd-Ni(3, 9, 20)/SiO2 with different Ni particle sizes were obtained by in situ reduction before reaction and then their catalytic activities were investigated. By comparing the catalytic performances of Pd-NiO/SiO2 and Pd-Ni/SiO2 in water or tetrahydrofuran (THF), the effects of oxidation state and particle size of nickel species on the hydrogenation of α-AL in terms of activity and stability were systematically studied. The bimetal catalysts were characterized by BET, XRD, TEM and in situ XAS. The catalytic tests suggested that there was no clear correlation between the initial activity and the particle size of NiO or Ni species, whereas the catalyst durability was particle size dependent and solvent dependent as well. The deactivation mechanism is likely associated with a strong adsorption of organic species on the catalyst surface according to FTIR study on the adsorption behavior of α-AL and GVL on various materials, as well as the C1s XPS spectra of the spent catalysts. The beneficial effect of water in hydrogenation is thereby explained by the less coke tendency due to the relative stronger interaction between water and catalyst surface than that between THF and surface.Download high-res image (66KB)Download full-size image
Co-reporter:Gang Huang, Peng Ji, Hao Xu, Jin-Gang Jiang, Li Chen, Peng Wu
Microporous and Mesoporous Materials 2017 Volume 248(Volume 248) pp:
Publication Date(Web):1 August 2017
DOI:10.1016/j.micromeso.2017.03.060
•Hierarchically structured Beta zeolite nanocrystals were prepared with a layered silicate precursor as silica source.•The nanosized Beta was synthesized rapidly within 4 h.•Nanosized Beta is highly active in the Friedel-Crafts acylation reaction.Hierarchical Beta zeolite composed of uniform nanocrystals with high pore volume and external surface area was fast synthesized within 4 h at a high yield using layered silicate precursor (H-kanemite) as silica source. The transformation process of layered silicate precursor into Beta zeolite is investigated carefully by XRD, FT-IR, NMR spectroscopies, SEM, and TEM techniques. TEM and SEM images indicated the obtained Beta zeolite is consisted of self-sustaining macrosized zeolitic aggregates assembled from uniform nanosized crystals, and it possesses relatively narrow distributed intercrystal mesopores. The hierarchically structured Beta zeolite, with an enhanced accessibility for bulky molecule to acid sites in the framework, shows better catalytic behaviors in the industrially-relevant Friedel-Crafts acylation reaction in comparison to commercially available or traditional Beta zeolite.Download high-res image (194KB)Download full-size image
Co-reporter:Lin Zhang;Yunlei Chen;Jin-Gang Jiang;Le Xu;Wenping Guo;Hao Xu;Xiao-Dong Wen
Dalton Transactions 2017 vol. 46(Issue 45) pp:15641-15645
Publication Date(Web):2017/11/21
DOI:10.1039/C7DT03420B
An ECNU-20 nanosheet zeolite of around 10 nm thickness along the c axis, with a hollow sphere morphology and IWR topology, was synthesized in a germanosilicate system using a commercially available organic amine, 1,8-diazabicyclo[5.4.0]undec-7-ene, as a structure-directing agent. DFT calculations confirmed that a preferential adsorption of these amine molecules took place on the (001) surface, leading to an oriented crystal growth. Moreover, the concentration of the amine determined the aggregation style of these nanosheets.
Co-reporter:Lin Zhang;Yunlei Chen;Jin-Gang Jiang;Le Xu;Wenping Guo;Hao Xu;Xiao-Dong Wen
Dalton Transactions 2017 vol. 46(Issue 45) pp:15641-15645
Publication Date(Web):2017/11/21
DOI:10.1039/C7DT03420B
An ECNU-20 nanosheet zeolite of around 10 nm thickness along the c axis, with a hollow sphere morphology and IWR topology, was synthesized in a germanosilicate system using a commercially available organic amine, 1,8-diazabicyclo[5.4.0]undec-7-ene, as a structure-directing agent. DFT calculations confirmed that a preferential adsorption of these amine molecules took place on the (001) surface, leading to an oriented crystal growth. Moreover, the concentration of the amine determined the aggregation style of these nanosheets.
Co-reporter:Bing Ma;Huimei Cui;Darui Wang;Chen Zhao
Nanoscale (2009-Present) 2017 vol. 9(Issue 18) pp:5986-5995
Publication Date(Web):2017/05/11
DOI:10.1039/C7NR00471K
Ni based catalysts are wildly used in catalytic industrial processes due to their low costs and high activities. The design of highly hierarchical core–shell structured Ni/HBEA is achieved using a sustainable, simple, and easy-tunable hydrothermal synthesis approach using combined NH4Cl and NH3·H2O as a co-precipitation agent at 120 °C. Starting from a single-crystalline hierarchical H+-exchanged beta polymorph zeolite (HBEA), the adjustment of the precipitate conditions shows that mixed NH4Cl and NH3·H2O precipitates with proper concentrations are vital in the hydrothermal synthesis for preserving a good crystalline morphology of HBEA and generating abundant highly-dispersed Ni nanoparticles (loading: 41 wt%, 5.9 ± 0.7 nm) encapsulated onto/into the support. NH4Cl solution without an alkali is unable to generate abundant Ni nanoparticles from Ni salts under the hydrothermal conditions, whereas NH3·H2O seriously damages the pore structure. After studying the in situ changes in infrared, X-ray diffractometry, temperature-programmed reduction, and scanning electron microscopy measurements, as well as variations in the filtrate pH, Si/Al ratios, and solid sample Ni loading, a two-step dissolution–recrystallization process is proposed. The process consists of Si dissolution and no change in elemental Al, and after the dissolved Si(IV) concentrations have promoted Ni phyllosilicate nanosheet solubility, further growth of multilayered Ni phyllosilicate nanosheets commences. The precursor Ni phyllosilicate is changeable between Ni3Si2O5(OH)4 and Ni3Si4O10(OH)2, because of competition in kinetically-favored and thermodynamically-controlled species caused by different basic agents. The superior catalytic performance is demonstrated in the metal/acid catalyzed biomass derived bulky stearic acid hydrodeoxygenation with 90% octadecane selectivity and a promising rate of 54 g g−1 h−1, which highly excels the reported rates catalyzed by Ni catalysts. Significant improvements in activity and selectivity are related to the highly dispersive Ni nanoparticles onto/into intra-mesopores of hierarchical HBEA, hence enhance the accessibility of bulky substrates to metal sites and mass transfer capacity.
Co-reporter:Xinqing Lu;Wen-Juan Zhou;Yejun Guan;Armin Liebens
Catalysis Science & Technology (2011-Present) 2017 vol. 7(Issue 12) pp:2624-2631
Publication Date(Web):2017/06/20
DOI:10.1039/C7CY00428A
Fluorine-implanted titanosilicate Ti-MWW, with greatly enhanced catalytic performance in the liquid-phase epoxidation of ethylene with aqueous hydrogen peroxide, has been post-synthesized by fluorinating conventional Ti-MWW with NH4F. The effects of fluorination conditions, such as solvent, the amount of NH4F addition and temperature, on the zeolite structure and the catalytic performance of the resultant fluorine-implanted Ti-MWW were investigated in detail. Methanol proved to be a better solvent for fluorination than water in terms of preserving the crystalline structure and improving the selective epoxidation activity. Fluorine-implanting generated SiO3/2F species in the framework to increase the electropositivity of the tetrahedral Ti active sites. A stronger hydrogen-bond was thus formed between Hend in Ti–Oα–Oβ–Hend intermediates and the adjacent Si–F species, which were helpful to significantly increase the catalytic activity in the epoxidation of ethylene with H2O2. In addition, the fluorination also generated secondary mesopores which are useful to improve the accessibility of the active sites, making the fluorine-implanted Ti-MWW catalyst possess better reusability than the parent one.
Co-reporter:Peng-Cheng Liu;Ye-Jun Yu;Bo Peng;Shi-Yu Ma;Tian-Yu Ning;Bing-Qian Shan;Tai-Qun Yang;Qing-Song Xue;Kun Zhang
Green Chemistry (1999-Present) 2017 vol. 19(Issue 23) pp:5575-5581
Publication Date(Web):2017/11/27
DOI:10.1039/C7GC02139A
We have demonstrated a facile and green way to synthesize dendritic mesoporous silica nanoparticles (DMSNs) on an ultra-large scale (kg) with cetyltrimethylammonium bromide (CTAB) and an anionic surfactant as dual templates free of organic solvents. In contrast to its co-template role in tuning the packing parameter of the surfactant molecule organization, the anionic surfactant herein acts as a more strongly competitive counterion against the adsorption of negatively charged silicate oligomers (I−) on the micelles. Based on the new understanding of the interaction between the cationic–anionic surfactant ionic pairs and the silicate oligomers, we proposed a dual template synergistically controlled micelle self-aggregated model to understand the formation mechanism of dendritic MSNs where the anionic surfactant stabilized micelles or micelle blocks are basic self-assembling building units for the formation of center-radial pore channel networks. By using one-pot in situ isomorphous substitution, the metal Ti atom can be easily incorporated into the silica frameworks of DMSNs, and the obtained Ti-DMSN catalyst shows a superior catalytic performance in the epoxidation of cyclohexene over the typical mesoporous Ti-MCM-41 silicas.
Co-reporter:Xinqing Lu;Yejun Guan;Hao Xu;Haihong Wu
Green Chemistry (1999-Present) 2017 vol. 19(Issue 20) pp:4871-4878
Publication Date(Web):2017/10/16
DOI:10.1039/C7GC02069D
The clean synthesis of furfural oxime (FO) has been realized through titanosilicate-catalyzed liquid-phase ammoximation of furfural with ammonia and hydrogen peroxide. A detailed investigation of furfural ammoximation over three representative titanosilicates Ti-MOR, TS-1 and Ti-MWW reveals that the reaction involves the hydroxylamine route and the imine route. The hydroxylamine route accounts for the formation of the target product (FO), while the imine route leads to the formation of undesired products such as 2-furylamide and 2-furoic acid. With a high efficiency for hydroxylamine formation, Ti-MOR proves to be superior to TS-1 and Ti-MWW. The catalytic performance of Ti-MOR depends greatly on the operating conditions of the reaction, which is closely related to its activity in catalyzing hydroxylamine decomposition. The decomposition of hydroxylamine and the non-catalytic oxidation of furfural can be effectively suppressed in Ti-MOR-catalyzed ammoximation when employing water as the solvent and adding H2O2 dropwise into the reaction system. Under optimized conditions, Ti-MOR is capable of providing furfural conversion and oxime selectivity both above 97%.
Co-reporter:Zhiguo Zhu;Hao Xu;Jingang Jiang;Haihong Wu
Chemical Communications 2017 vol. 53(Issue 93) pp:12516-12519
Publication Date(Web):2017/11/21
DOI:10.1039/C7CC06778J
A novel structural reconstruction strategy is proposed to prepare an active Sn-Beta catalyst with high Sn contents and a hydrophobic nature. Compared with post-synthesized Sn-Beta and state-of-the-art classic fluoride-mediated Sn-Beta-F, this Sn-Beta zeolite exhibits unparalleled active site-based turnover frequency for desirable products and in particular catalyst weight-based space-time-yields in various redox reactions of ketones.
Co-reporter:Zhiguo Zhu, Hao Xu, Jingang Jiang, Yejun Guan, Peng Wu
Journal of Catalysis 2017 Volume 352(Volume 352) pp:
Publication Date(Web):1 August 2017
DOI:10.1016/j.jcat.2017.04.031
•A novel and fast hydrothermal synthesis route for Sn-Beta is developed.•The obtained Sn-Beta zeolite possesses very high isolated Sn content of 3.03 wt%.•The selectivity of ε-caprolactone in the Baeyer–Villiger oxidation can be controlled.•The prepared Sn-Beta zeolite demonstrates unique catalytic properties.An innovative hydrothermal synthesis strategy of heteroatom-containing zeolite, in this case Sn-Beta, via interzeolite transformation is reported in present study. To the best of our knowledge, this prepared Sn-Beta zeolite possesses the highest isolated Sn contents (3.03 wt% or Si/Sn molar ratio of 63) in comparison to other hydrothermally synthesized ones. The success of this synthesis strategy to Sn-Beta synthesized from MWW silica is mainly due to its nucleating and growing readily compared with those prepared from amorphous silica source. The introduction of Beta seeds and the structural similarity between the parent zeolite (MWW) and the targeted zeolite (*BEA) are found to be indispensable factors in the crystallization of Sn-Beta zeolite. The obtained Sn-Beta zeolites possess isolated tetrahedral Sn4+ in the framework and high hydrophobicity. Additionally, lowering the molar ratio of H2O2 to cyclohexanone and moderately reducing reaction time are proved to be effective methods to improve the selectivity of ε-caprolactone in the Baeyer–Villiger oxidation of cyclohexanone with H2O2 using Sn-Beta as Lewis catalyst. Thus, the prepared Sn-Beta zeolite demonstrated promising catalytic properties, especially for the desired products selectivity, in the Baeyer–Villiger oxidation of ketones as well as the isomerization–esterification reaction of dihydroxyacetone in ethanol, far outperforming the conventional Sn-Beta-F catalyst, which were attributed mainly to its high Sn content in the framework and excellent diffusion properties resulting from the relatively small crystal size.Download high-res image (153KB)Download full-size image
Co-reporter:Hao Xu
Chinese Journal of Chemistry 2017 Volume 35(Issue 6) pp:836-844
Publication Date(Web):2017/06/01
DOI:10.1002/cjoc.201600739
Titanosilicates, with tetrahedrally coordinated Ti4+ ions in highly crystalline zeolite frameworks, are a class of unique heterogeneous catalysts useful for the liquid-phase selective oxidation reactions. The great success of green Ti-zeolites/H2O2 reaction system has aroused considerable scientific and industrial interests. The catalytic properties of titanosilicates relay on zeolite topologies, crystal morphology, the content and micro-environment of tetrahedral Ti4+ ions. The ever-growing needs for the oxidation catalysts in processing bulky molecules in petrochemical and fine chemical industries have set off a new tide of developing novel titanosilicates with significantly improved catalytic performance than traditional ones. This mini review summarizes recent progresses in developing the titanosilicates with novel topology, morphology as well as chemically modified micro-environment.
Co-reporter:Jianghong Ding;Hao Xu;Haihong Wu
Science China Chemistry 2017 Volume 60( Issue 7) pp:942-949
Publication Date(Web):02 May 2017
DOI:10.1007/s11426-016-0480-y
The liquid-phase oxidation of ethylamine with hydrogen peroxide was studied over tungsten-doped zeolites to develop a clean and simple route for producing acetaldehyde oxime. The investigations were firstly performed over W/MOR, where the coordinated state as well as the acidity of the W species were characterized. The reaction parameters, including H2O2 amount, solvent, temperature, tungsten content as well as catalyst amount, governed the activity and oxime selectivity. Under optimized reaction conditions, W/MOR showed an ethylamine conversion and corresponding oxime selectivity of 18.3% and 88.9%. W/MOR showed a superior performance in comparison to other tungsten-containing zeolites of W/Beta, W/MWW and W/Y. Although W/MOR exhibited lower amine conversion than titanosilicates of TS-1 and Ti-MWW, it gave higher selectivity to the main product of oxime. Moreover, W/MOR proved to be a robust catalyst, exhibiting a stable catalytic performance after being reused at least for 5 times.
Co-reporter:Xinyi Ji;Le Xu;Xin Du;Xinqing Lu;Wanpeng Lu;Junliang Sun
Catalysis Science & Technology (2011-Present) 2017 vol. 7(Issue 13) pp:2874-2885
Publication Date(Web):2017/07/03
DOI:10.1039/C7CY00756F
A novel multilamellar titanosilicate composed of MWW-type nanosheets, Ti-ECNU-7P layered precursor, was directly synthesized for the first time with the assistance of boron atoms as the crystallization-supporting agent and a simple surfactant cetyltrimethylammonium bromide (CTAB) as the interlayer swelling and pillaring agent. The new Ti-ECNU-7P materials were hydrothermally synthesized readily in a wide Si/Ti molar ratio range of 10–200, when the Si/B molar ratio was 10. Ti-ECNU-7P possessed a multilamellar mesostructure, which was constructed via alternate stacking of 2.5 nm MWW zeolite nanosheets and ca. 2.4 nm CTAB molecules. This lamellar titanosilicate possessed large interlayer spacing hardly achieved by conventional hydrothermal synthesis. Subsequent acid treatment and calcination on the multilamellar precursor effectively removed the extraframework Ti species, the organic species intercalated and the majority of framework boron atoms, leading to a hierarchical titanosilicate Ti-ECNU-7 catalyst with relatively high external surface area and high concentration of Ti species on the crystal surface. The catalytic performance of hierarchical Ti-ECNU-7 nanosheets was comprehensively investigated and compared with that of typical titanosilicates in the epoxidation of various bulky alkenes with different oxidants, including aqueous H2O2, tert-butyl hydroperoxide and cumene hydroperoxide. Owing to the hierarchical architecture and more accessible active sites on the external surface, the hierarchical Ti-ECNU-7 catalyst proved to be more active than conventional titanosilicates for selective oxidations involving either bulky substrates or oxidants. Additionally, it was robust against Ti leaching and irreversible deactivation.
Co-reporter:Darui Wang;Bo Wang;Yu Ding;Qingqing Yuan;Haihong Wu;Yejun Guan
Chemical Communications 2017 vol. 53(Issue 73) pp:10172-10175
Publication Date(Web):2017/09/12
DOI:10.1039/C7CC05007K
A novel bifunctional ZSM-5@(Co/SiO2) material with a hierarchical core/shell structure was successfully prepared through a simple chemoselective interaction between the crystal surface silica species of zeolite and the external Co2+ source in basic media, which served as an excellent catalyst in the synthesis of green fuels from biomass-derived ethyl esters.
Co-reporter:Boting Yang, Jin-Gang Jiang, Kun Zhang, and Peng Wu
Chemistry of Materials 2016 Volume 28(Issue 15) pp:5295
Publication Date(Web):July 11, 2016
DOI:10.1021/acs.chemmater.6b00750
A facile and cheap method for the postsynthesis of large-pore titanosilicates from layered zeolitic silicate precursors is presented, in which isomorphous substitution of Ti for Si and interlayer expansion with mobile Si debris are realized simultaneously using aqueous H2TiF6 solution at room temperature. This versatile and convenient one-pot postsynthesis was used to construct several different 3D interlayer-expanded zeolite (IEZ) structures with tetrahedrally coordinated Ti incorporated into the framework without the use of external silane. The structural transformation and the incorporation of Ti in the preparation of IEZ-Ti-PLS-3 were monitored using Rietveld refinement and NMR studies. Furthermore, IEZ-Ti-PLS-3 exhibited unique catalytic properties in the epoxidation of alkenes with hydrogen peroxide, and was active not only for linear alkenes but also for bulky cyclic alkenes.
Co-reporter:Le Xu, Xinyi Ji, Shenhui Li, Zhengyang Zhou, Xin Du, Junliang Sun, Feng Deng, Shunai Che, and Peng Wu
Chemistry of Materials 2016 Volume 28(Issue 12) pp:4512
Publication Date(Web):June 6, 2016
DOI:10.1021/acs.chemmater.6b02155
Construction of hierarchical zeolite catalysts from lamellar zeolite precursor is challenging and promising for industrial catalysis. Although numerous efforts have been dedicated to control the organization of zeolite nanosheets by postsynthetic approaches or employing complex surfactants in hydrothermal synthesis, there is still no successful case that the hierarchical lamellar zeolite is hydrothermally synthesized by the self-assembly of the commercially available simple surfactant cetyltrimethylammonium bromide (CTAB) and inorganic zeolite precursor. In traditional syntheses, the self-assembly of simple surfactants and the growth of microporous framework are hardly compatible from both thermodynamic and kinetic viewpoints, preferring to cause phase separation. Herein, we approach for the first time the hydrothermal synthesis of a mesostructured multilamellar zeolite ECNU-7P, consisting of an alternative stacking of inorganic MWW zeolite nanosheets and organic CTAB layers with large interlayer spacing (25 Å), by a zeolite seed and CTAB-assisted dissolution–recrystallization route. Correlated 2D 1H–29Si solid-state NMR, X-ray, electron microscopy, and rotation electron diffraction analyses provide molecular-level insights into the guest–host interactions between organic surfactant and inorganic framework during the self-assembly and structure evolution process. Moreover, the calcined Al-ECNU-7 possessing a hierarchical mesostructure proves to serve as a highly active, selective, and stable solid acid catalyst for triisopropylbenzene cracking as well as acylation of anisole.
Co-reporter:Zhixia Deng, Yulin Yang, Xinqing Lu, Jianghong Ding, Mingyuan He and Peng Wu
Catalysis Science & Technology 2016 vol. 6(Issue 8) pp:2605-2615
Publication Date(Web):05 Jan 2016
DOI:10.1039/C5CY02002F
The epoxidation of methallyl chloride (MAC) to 2-methyl epichlorohydrin (MECH) with H2O2 using TS-1 microsphere catalysts (TS-1-MS) in a continuous slurry reactor was investigated. The reaction parameters, which governed the effective conversion of hydrogen peroxide, selectivity to MECH epoxide and catalyst deactivation, were studied in detail by simulating the operating conditions of its industrial process. Under the most beneficial conditions, the process was successfully run for 257 h at a high MECH selectivity (>95%) as well as a high effective conversion of hydrogen peroxide (>97%). The microsphere morphology and particle size were highly maintained for the deactivated TS-1-MS catalyst, which was regenerated readily by a combination of hydrogen peroxide washing and calcination. This research verified that it was possible to develop a green, safe and efficient route for producing MECH by direct epoxidation of MAC with hydrogen peroxide in a slurry reactor. Employing TS-1 microsphere aggregates as a catalyst exhibits the advantage of easy solid–liquid separation.
Co-reporter:Le Xu and Peng Wu
New Journal of Chemistry 2016 vol. 40(Issue 5) pp:3968-3981
Publication Date(Web):20 Jan 2016
DOI:10.1039/C5NJ02829A
In recent years, great efforts have been devoted to the synthesis and modification of layered zeolites, a new family of microporous crystalline materials that are viewed as covalently bonded continuous frameworks extended in only two dimensions. This leads to a very interesting and attractive research area in porous materials science, since the stacking modes of zeolite layers could be constructed into various types of structures by direct synthesis or postsynthetic treatments, endowing zeolitic materials with structural diversity. The potential of layered zeolite precursors for generating hierarchical catalysts or incorporating organic functional groups into two dimensional structures is of particular interest. In this contribution, the most attractive achievements in the research area of layered zeolites are summarized, including synthetic approaches, strategies for modification of layered structures and catalytic applications. Last but not least, the challenges for future research on these types of porous materials are proposed.
Co-reporter:Zongbo Shi, Wenqian Jiao, Li Chen, Peng Wu, Yimeng Wang, Mingyuan He
Microporous and Mesoporous Materials 2016 Volume 224() pp:253-261
Publication Date(Web):April 2016
DOI:10.1016/j.micromeso.2015.11.064
•Flower-like boehmite was template-free synthesized from a bayerite precursor via phase transformation.•The transformation procedure of bayerite to boehmite was clarified.•Flower-like boehmite consists the nano-sheets of 1–5 nm thickness.•Flower-like alumina showed an improved catalytic cracking performance in comparison to commercial alumina.Flower-like boehmite, composed of the nanosheets with 1–5 nm thickness, was synthesized from a bayerite precursor via phase transformation in a clean way. This template-free method is featured with the advantages that the mother solution containing ethanol, water and ammonium sulfate could be recovered and reused. The transformation procedure of bayerite to boehmite was clarified, in which bayerite gradually dehydrated and evolved to boehmite from the crystal outside to the inside, with the primary crystallite size of boehmite and the coordination state of aluminum remaining almost unchanged. The corresponding flower-like γ-Al2O3 derived by calcination of flower-like boehmite exhibited not only a large specific surface area (281 m2 g−1) but also bimodal porosities with the diameter distributions centered at 5.2 nm and 18.4 nm, respectively. Possessing large pore size and open pore structures, the flower-like γ-alumina showed an improved catalytic performance in the cracking of 1,3,5-triisopropylbenzene in comparison to the commercial alumina catalysts.
Co-reporter:Zongbo Shi;Peng Ji;Zhiguo Zhu;Jin-gang Jiang;Dr. Wenhua Fu; Yimeng Wang ; Mingyuan He
ChemCatChem 2016 Volume 8( Issue 11) pp:1891-1895
Publication Date(Web):
DOI:10.1002/cctc.201600211
Abstract
A versatile dealumination strategy was proposed to stabilize low-silica zeolites through cannibalistic interaction between the host framework Al (FAL) and the guest aluminum salt. It is possible to capture selectively the FAL and Na ions in NaY zeolite by employing a special external Al source such as aluminum sulfate as the dealuminating agent. This unique postmodification reduces the FAL amount efficiently and converts the chemically reacted Al species into a γ-alumina support for the catalytically active component of zeolite, which avoids wasting Al sources. Possessing greatly enhanced hydrothermal stability, newly generated intracrystal mesopores, as well as an optimized distribution of FAL, the resultant dealuminated Y zeolite catalysts can be used practically in heavy oil cracking.
Co-reporter:Zongbo Shi;Peng Ji;Zhiguo Zhu;Jin-gang Jiang;Dr. Wenhua Fu; Yimeng Wang ; Mingyuan He
ChemCatChem 2016 Volume 8( Issue 11) pp:
Publication Date(Web):
DOI:10.1002/cctc.201600626
Co-reporter:Zhiguo Zhu, Hao Xu, Jingang Jiang, and Peng Wu
The Journal of Physical Chemistry C 2016 Volume 120(Issue 41) pp:23613-23624
Publication Date(Web):October 4, 2016
DOI:10.1021/acs.jpcc.6b07947
Sn–Y zeolite, with hierarchical pore systems and extremely low Al content, was successfully prepared via a convenient postsynthetic route which involves proper predealumination and subsequent (NH4)2SnCl6 treatment under mild aqueous condition. The Sn ions were incorporated into the framework of properly dealuminated Y zeolite through reacting with the defect sites generated in the industrial steaming treatment, the first-step acid treatment, and the second Sn incorporation process under acidic conditions. The acidic medium achieved by adding HCl in the Sn incorporation process affected not only the amount of incorporated Sn and residual Al but also the coordination state of inserted Sn ions. Compared with hydrothermally synthesized Sn-Beta, postsynthesized Sn–Y zeolite exhibited outstanding catalytic performances in the Baeyer–Villiger oxidation reactions of ketones especially when bulky tert-butyl hydroperoxide was employed as the oxidant due to an open pore structure of 3-dimensional 12-membered ring (12-MR) channels of FAU topology as well as the dealumination-derived intracrystal mesoporosity. Moreover, alkali metal ions modification was shown to be an effective approach for enhancing the selectivity of lactones.
Co-reporter:Le Xu, Xinyi Ji, Jin-Gang Jiang, Lu Han, Shunai Che, and Peng Wu
Chemistry of Materials 2015 Volume 27(Issue 23) pp:7852
Publication Date(Web):November 10, 2015
DOI:10.1021/acs.chemmater.5b03658
Zeolites with intergrown structures are particularly interesting because they often exhibit unique performance in heterogeneous catalysis. This raises the bar of the structural characterizations and remains an enormous challenge to understand the synthesis conditions and the formation mechanisms of such intergrown materials. Herein, a novel intergrown zeolite (ECNU-5) was successfully synthesized via a rapid dissolution–recrystallization (RDR) route, which reorganized the conventional MWW layer stacking into two new different polymorphs, ECNU-5A and ECNU-5B. Structure elucidation indicates both polymorphs are reconstructed from the same MWW layer but are different in relative shift between adjacent layers. ECNU-5 is the first structure-determined zeolite with interrupted structure that MWW layers shift in the horizontal direction, in which the two polymorphs are never predicted before and are additional members of the MWW family. The unique geometry mismatch between the organic structure-directing agent (OSDA) and inorganic silicate framework is ascribed to causing the zeolite layer shift. Moreover, the implementation of silylation technique readily expanded the interlayer pore of as-made ECNU-5, producing the interlayer-expanded zeolite (IEZ-ECNU-5), which maintained the original stacking sequence of MWW sheets.
Co-reporter:Darui Wang, Lin Zhang, Li Chen, Haihong Wu and Peng Wu
Journal of Materials Chemistry A 2015 vol. 3(Issue 7) pp:3511-3521
Publication Date(Web):16 Dec 2014
DOI:10.1039/C4TA06438K
Mesoporous ZSM-5 zeolites with unique hydrocarbon cracking properties have been postsynthesized from conventional ZSM-5 samples using small molecular organic amine-assisted desilication technique. The parent ZSM-5 zeolites, with regular crystal size of 1–2 μm and Si/Al ratios of 15–500, were first hydrothermally synthesized using inorganic silicon and aluminum sources and piperidine as structure-directing agent (SDA) with the assistance of active seeds. Controllable mesopores were successfully introduced into as-synthesized ZSM-5 crystals by alkaline-derived desilication with the addition of piperidine or hexamethyleneimine. The addition of organic amines shielded the zeolite crystals from extensive dissolving by NaOH attacking. The mesopores were thus generated controllably within zeolite crystals and also minimized the loss of microporosity and solid acidity. The incorporation of mesopores made the micropores well interconnected, shortened the average diffusion path lengths as well as maintained more catalytic active sites showing a higher propylene yield and a longer lifetime in the cracking of n-hexane.
Co-reporter:Le Xu, Da-Ding Huang, Chen-Geng Li, Xinyi Ji, Shaoqing Jin, Zhaochi Feng, Fei Xia, Xiaohong Li, Fengtao Fan, Can Li and Peng Wu
Chemical Communications 2015 vol. 51(Issue 43) pp:9010-9013
Publication Date(Web):17 Apr 2015
DOI:10.1039/C5CC02321A
A novel organic–inorganic layered titanosilicate consisting of Ti-containing MWW-type nanosheets and piperidine ligands was constructed. It exhibited an unprecedented high catalytic activity and recyclability in alkene epoxidation.
Co-reporter:Chen-Geng Li, Yiqun Lu, Haihong Wu, Peng Wu and Mingyuan He
Chemical Communications 2015 vol. 51(Issue 80) pp:14905-14908
Publication Date(Web):18 Aug 2015
DOI:10.1039/C5CC05278E
A hierarchical titanosilicate, with epitaxially grown MFI nanosheets on microsized TS-1 crystals, has been prepared through a desilication–recrystallization method using a diammonium surfactant as the secondary structure-directing agent (SDA). This core/shell material features multiple mesoporosities, significantly improved epoxidation activity as well as easy separation in synthesis and catalytic reactions.
Co-reporter:Darui Wang, Bing Ma, Bo Wang, Chen Zhao and Peng Wu
Chemical Communications 2015 vol. 51(Issue 82) pp:15102-15105
Publication Date(Web):04 Sep 2015
DOI:10.1039/C5CC06212H
Hierarchically porous zeolite supported metal nanoparticles are successfully prepared through a base-assisted chemoselective interaction between the silicon species on the zeolite crystal surface and metal salts, in which in situ construction of mesopores and high dispersion of metal species are realized simultaneously.
Co-reporter:Boting Yang, Jin-gang Jiang, Hao Xu, Peng Ji, Peng Wu
Microporous and Mesoporous Materials 2015 Volume 203() pp:54-62
Publication Date(Web):February 2015
DOI:10.1016/j.micromeso.2014.10.028
•Sub-zeolite of FER topology ECNU-8 was post-synthesized by acid treatment of PLS-3 lamellar precursor.•ECNU-8 consists of a disordered collection of FER sheets.•ECNU-8 possesses an enlarged external surface area.•ECNU-8 shows advantages in catalyzing bulk substrates.A simple HCl–EtOH solution treatment has been conducted to modify the structure of Al-PLS-3, a kind of FER lamellar precursor with various Si/Al ratios (60–∞). With prolonging the treatment time from 15 min to 24 h at 443 K, the precursors underwent a variety of structural changes, including removal of occluded organic species, loss of layer stacking order and restoration of an ordered structure by interlayer pillaring. The post structural modification gave rise to a sub-zeolite of FER topology within a short time of 40 min, which possessed disordered stacking of FER sheets, named as ECNU-8. The physicochemical properties of ECNU-8 were characterized by means of various techniques and in comparison to those of conventional FER topology. Still composed of a collection of FER sheets but without an ordered stacking manner along (1 0 0) direction, the structure of ECNU-8 was constructed by a reorientation of interlayer hydrogen bond moieties caused by partial removal of interlayer organic structure directing agent. The ECNU-8 materials with different Al contents possessed external surface areas enlarged by 23.1–36.8% in comparison to corresponding three-dimensional FER zeolites. Containing the FER laminates and tetrahedral Al in framework, but mitigating the spatial restrictions in particular for the bulk molecule reactions, ECNU-8 proved to be a promising solid acid catalyst for processing larger substrates.
Co-reporter:Yulin Yang
The Journal of Physical Chemistry C 2015 Volume 119(Issue 45) pp:25377-25384
Publication Date(Web):October 15, 2015
DOI:10.1021/acs.jpcc.5b07175
Monodispersed amphiphilic zeolite/mesosilica composite material TS-1@KCC-1 (TK), which could stabilize Pickering emulsions for the benzene/H2O2 system, has been synthesized, and its physicochemical properties have been investigated in detail. The amphiphilic TK catalyst displayed a higher catalytic activity under Pickering interfacial catalysis (PIC) than under phase-boundary catalysis (PBC) and conventional reaction conditions in the hydroxylation of benzene by hydrogen peroxide without cosolvent and under static conditions. Under optimized conditions, a TS-1@KCC-1 catalyst grafted with octyl chains (2.42 wt %) could afford an interfacial activity of 1.1 mol (Ti-mol)−1. Moreover, PIC reaction conditions exhibited an excellent thermal stability and good reusability.
Co-reporter:Kai Xue;Boting Yang
Science China Chemistry 2015 Volume 58( Issue 1) pp:139-147
Publication Date(Web):2015 January
DOI:10.1007/s11426-014-5248-y
Co- or Mn-substituted LTL zeolites were hydrothermally synthesized by a novel organic-ligand-assisted method. XRD, UV-Vis DRS, XPS, and EPR techniques verified that the Co and Mn ions were incorporated into the zeolite framework. No organic species were retained in as-synthesized Co or Mn-LTL zeolites, which resulted in porous materials without calcination. In the oxidation of cyclohexane with tert-butyl hydroperoxide (TBHP), the Co-LTL and Mn-LTL gave a 40%–48% KA oil (cyclohexanone and cyclohexanol) yield as well as nearly 100% TBHP conversion under mild reaction conditions. The reactions were confirmed to be heterogeneous and to have proceeded catalytically. No loss of catalytic activity or leaching of metal active sites ions were observed during 4 reuses.
Co-reporter:Le Xu, Chen-geng Li, Kun Zhang, and Peng Wu
ACS Catalysis 2014 Volume 4(Issue 9) pp:2959
Publication Date(Web):July 23, 2014
DOI:10.1021/cs500653p
Tandem catalysis has been realized on the multilayered zeolites with organic-structure-directing agent (OSDA) molecules occluded within micropores. A combination of mild acid treatment and ion-exchange with ammonia solution was carried out on as-synthesized multilamellar MFI aluminosilicate, giving rise to an acid–base bifunctional catalyst. Containing tripropyl head groups, the Gemini-type quaternary ammonium OSDAs were firmly immobilized in the intersection of straight and sinusoidal 10-membered ring channels, with the other one exposed to the layer surface of the nanosheets. The resulting organic–inorganic materials possessed simultaneously the acid sites related to the framework Al and the base sites derived from coexisting OSDAs. In particular, two types of base sites were present, that is, the Lewis base sites due to the SiO– species and Brønsted base sites due to the OH– counteranion of exposed quaternary ammonium cations. The rigid materials were highly active and reusable in the one-pot reaction of tandem deacetalization–Knoevenagel condensation. Supporting palladium nanoparticles (Pd NPs) on the organic–inorganic hybrid zeolite led to bifunctional catalysts, which catalyzed effectively one-pot synthesis of benzylidene malononitrile from benzyl alcohol under soluble-base-free conditions, in which the benzyl alcohol was first aerobic oxidized to intermediate benzaldehyde followed by Knoevenagel condensation with malononitrile.Keywords: bifunctional catalysis; hybrid material; multilamellar; tandem reaction; zeolites
Co-reporter:Peng Wu, Yoshihiro Kubota, and Toshiyuki Yokoi
ACS Catalysis 2014 Volume 4(Issue 1) pp:23
Publication Date(Web):December 4, 2013
DOI:10.1021/cs4006056
On the occasion of Professor Takashi Tatsumi’s retirement and winning of the Alwin Mittasch Prize, some of his main achievements in zeolite catalysis are summarized, with a focus on the design, synthesis, and catalytic application of new titanosilicate catalysts. He and his co-workers succeeded in the direct synthesis of the MWW-type titanosilicate, Ti-MWW, by employing boric acid in the synthesis and thereafter developed a dry gel conversion method for boron-reduced Ti-MWW as well as a secondary isomorphous substitution route for boron-free Ti-MWW molecular sieves. In particular, the postsynthetic conversion involved a reversible structure interchange between three-dimensional silicalite and a two-dimensional layered precursor. Taking advantage of the structural diversity of the layered MWW zeolite precursor, phase-delaminated Ti-MMW and interlayer expanded Ti-MWW were also prepared. Using hydrogen peroxide as an oxidant, the Ti-MWW/H2O2 system was highly efficient for liquid-phase oxidation of a variety of substrates, particularly the epoxidation of alkenes and ammoximation of ketones. Some of the Ti-MWW-catalyzed reactions have already led to or are becoming practical catalytic technologies in industrial practice. Several other recent achievements in the synthesis and catalytic applications of other titanosilicates, zeolitic hydrid materials, and solid acid zeolite catalysts are also briefly summarized.Keywords: aluminosilicate; hydrocarbon cracking; methanol to olefins; MWW topology; selective oxidation; titanosilicate; zeolite
Co-reporter:Wen-Juan Zhou, Raphael Wischert, Kai Xue, Yu-Ting Zheng, Belén Albela, Laurent Bonneviot, Jean-Marc Clacens, Floryan De Campo, Marc Pera-Titus, and Peng Wu
ACS Catalysis 2014 Volume 4(Issue 1) pp:53
Publication Date(Web):November 21, 2013
DOI:10.1021/cs400757j
Various types of Ti-containing zeolites, i.e., Ti-MWW, TS-1, Ti-MOR, and Ti-BEA, have been evaluated as candidates for the liquid-phase oxidation of cyclohexane using t-butyl hydroperoxide (TBHP, 7–8 wt %) as model oxidant. Ti-MWW zeolite displayed the highest activity for cyclohexanol and cyclohexanone (KA oil) with an overall selectivity higher than 90% at 80 °C, making this catalyst a candidate of choice for industrial KA oil production by deperoxidation of cyclohexyl hydroperoxide. The effect of the reaction temperature, reaction time, catalyst amount, and catalyst stability on Ti-MWW was surveyed in detail. The Ti-MWW catalyst showed a stable performance and could be recycled at least four times without detectable Ti leaching and loss of structural stability. The active sites for cyclohexane oxidation appeared to be located near external 12-ring cups in the Ti-MWW framework as suggested by a series of position-selective poisoning tests with tripropyl- and triphenylamine, impelling cyclohexane diffusion within the internal 10-ring channels. EPR experiments supported by DFT calculations suggested the coexistence of both Ti(IV)-OO• (peroxyl) and Ti(IV)-O• (oxyl) species generated through bimolecular pathways, implying simultaneously (SiO)3Ti(OOtBu) species and tBuOOH. The catalytic activity was strongly inhibited in the presence of alkenes, leading to the preferential formation of the epoxidation product with no detectable formation of radicals. Notably, this is the first time that oxyl species have been detected particularly with the help of DFT calculations. Predicted differences of g tensors between peroxyl and oxyl species at various hydration levels in the presence of cyclohexane were consistent with the EPR spectra.Keywords: cyclohexane; KA oil; oxidation; oxyl radical; Ti-MWW; titanosilicate
Co-reporter:Darui Wang, Le Xu and Peng Wu
Journal of Materials Chemistry A 2014 vol. 2(Issue 37) pp:15535-15545
Publication Date(Web):28 Jul 2014
DOI:10.1039/C4TA02740J
A series of well-defined, core–shell-structured composite materials comprising microporous/mesoporous ZSM-5 as core and mesoporous aluminosilicate as shell were synthesized by combining controlled desilication using sodium hydroxide solution with subsequent self-assembly using a triblock copolymer. An aluminosilicate shell with uniform mesopores was grown closely around the crystals of mesoporous ZSM-5, with a tunable thickness of 60–300 nm, by adjusting the extent of desilication. The obtained composite zeolites exhibited a hierarchical porosity containing the original regular MFI micropores (ca. 0.56 nm) and desilication-induced, randomly distributed mesopores (5–50 nm), both within the core ZSM-5 crystals, as well as relatively uniform mesopores (ca. 6 nm) inside the shell part on the zeolite surface. The mesoporous aluminosilicate shell, self-assembled from the MFI zeolite fragments as a result of partially dissolved ZSM-5 crystals, demonstrated weak acidity and much higher hydrothermal stability in comparison to the shell synthesized by the additional silica source. Taking advantage of the confining effect of the mesopores, Pt nanoparticles were incorporated into the mesoporous shells, giving rise to bifunctional catalysts, which exhibited a higher selectivity of C5–C11 liquid products compared to the conventional Pt/ZSM-5 catalyst in the hydrocracking of n-hexadecane.
Co-reporter:Chen-Geng Li, Le Xu, Peng Wu, Haihong Wu and Mingyuan He
Chemical Communications 2014 vol. 50(Issue 99) pp:15764-15767
Publication Date(Web):28 Oct 2014
DOI:10.1039/C4CC07620F
Organic–inorganic hybrid zeolites with the MFI-type lamellar structure serve as efficient solid Lewis base catalysts for solvent-free synthesis of a variety of cyclic carbonates from corresponding epoxides and carbon dioxide. The ion-exchange with iodide, in particular, renders these materials an excellent catalytic activity and good recyclability.
Co-reporter:Hao Xu, Lili Jia, Haihong Wu, Boting Yang and Peng Wu
Dalton Transactions 2014 vol. 43(Issue 27) pp:10492-10500
Publication Date(Web):21 Feb 2014
DOI:10.1039/C4DT00120F
Nu-6(1) zeolite, the lamellar precursor of NSI topology, was firstly synthesized with 4′4-bipyridine as the structure-directing agent (SDA) and then subjected to HCl–EtOH treatment for the purpose of structural modification. Interlayer deconstruction and reconstruction took place alternately in this acid treatment. An intermediate named ECNU-4 was separated at the initial stage of this continuous treatment process, which exhibited a special X-ray diffraction pattern without obvious reflection peaks at low angles. The zeolitic structure in the intralayer sheets was supposed to be well preserved in ECNU-4, whereas the interlayer structure became extremely disordered. The ECNU-4 intermediate showed structural diversity. It was converted into the reconstructed and interlayer expanded zeolite IEZ-NSI without an external silicon source by prolonging the HCl–EtOH treatment to 24 h. Moreover, with a partially delaminated structure, ECNU-4 was easily interlayer swollen at room temperature with cetyltrimethyl ammonium bromide in the presence of tetrapropyl ammonium hydroxide. The swollen material was further sonicated to yield a more deeply delaminated zeolite, Del-Nu-6. ECNU-4 and Del-Nu-6 differed in delamination degree, structural disordering and textural properties, especially surface area.
Co-reporter:Hao Xu, Liyan Fu, Jin-Gang Jiang, Mingyuan He, Peng Wu
Microporous and Mesoporous Materials 2014 Volume 189() pp:41-48
Publication Date(Web):1 May 2014
DOI:10.1016/j.micromeso.2013.09.041
Co-reporter:Bo-Ting Yang, Peng Wu
Chinese Chemical Letters 2014 Volume 25(Issue 12) pp:1511-1514
Publication Date(Web):December 2014
DOI:10.1016/j.cclet.2014.09.003
A titanosilicate Ti-ECNU-8 with a FER type sub-zeolite structure was developed by pots-synthesis and applied to the epoxdiation of alkenes with hydrogen peroxide. A controlled acid treatment on the pure silica layered precursor PLS-3 of FER topology gave rise to a sub-zeolite ECNU-8. Composed of a collection of FER sheets without an ordered stacking manner along layer related [1 0 0] direction, the structure of ECNU-8 was constructed by a reorientation of interlayer hydrogen bond moieties caused by partial removal of interlayer organic structure directing agent. ECNU-8 possessed an external surface area enlarged by ca. 30% in comparison to corresponding three-dimensional FER zeolite. Through a solid–gas reaction with TiCl4 vapor, tetrahedral Ti active sites were introduced into the framework. The resultant Ti-ECNU-8 retained the structural properties of ECNU-8, and exhibited an excellent catalytic performance for the epoxidation of cycloalkenes owing to the accessible Ti sites located in open reaction space.Titanosilicate Ti-ECNU-8 with a FER type sub-zeolite structure was post-synthesized by structural reorganization of layered silicate PLS-3 followed by solid–gas titanation with TiCl4 vapor. With an exposed external surface, Ti-ECNU-8 turned out to be an active oxidation catalyst for the epoxidation of cycloalkenes with hydrogen peroxide.
Co-reporter:Boting Yang ; Haihong Wu
The Journal of Physical Chemistry C 2014 Volume 118(Issue 42) pp:24662-24669
Publication Date(Web):September 29, 2014
DOI:10.1021/jp507719y
An interlayer expanded zeolite IEZ-PLS-3 was postsynthesized from the lamellar precursor of PLS-3 aluminosilicate by interlayer silylation with diethoxydimethylsilane (DEDMS) in HCl–EtOH solution at 443 K for 20 h. The resulting material was characterized by various techniques such as XRD, SEM, adsorption of N2, water, and benzene, and IR and NMR spectroscopies, and its catalytic properties were investigated by comparison to those of other zeolites with similar Si/Al ratios in m-xylene isomerization/disproportionation, Friedel–Crafts alkylation of anisole with benzyl alcohol, and acylation of anisole with acetic anhydride. The interlayer expansion created new 12 × 10-membered ring (MR) pores in IEZ-PLS-3. IEZ-PLS-3 showed a larger adsorption capacity of benzene than conventional PLS-3 with 10 × 8-MR channels. In the m-xylene isomerization/disproportionation reaction, IEZ-PLS-3 showed a higher conversion than PLS-3 and gave an isomerization to disproportionation ratio close to that of Beta zeolite, characteristic of shape-selective properties of 12-MR zeolites. IEZ-PLS-3 was more active than Beta in Friedel–Crafts alkylation and acylation reactions, implying that it is a promising solid acid catalyst for processing bulky molecules.
Co-reporter:Hao Xu;Jin-gang Jiang;Boting Yang;Lin Zhang; Mingyuan He ; Peng Wu
Angewandte Chemie 2014 Volume 126( Issue 5) pp:1379-1383
Publication Date(Web):
DOI:10.1002/ange.201306527
Abstract
Germanosilicates, an important family of zeolites with increasing number of members and attractive porosities, but containing a large quantity of unstable Ge atoms in the framework, meet with great obstacles in terms of limited thermal and hydrothermal stability when it comes to practical use. A facile stabilization method thus has been developed to substitute isomorphously Ge atoms for Si atoms, giving rise to ultrastable siliceous analogues of the pristine germanosilicates.
Co-reporter:Hao Xu;Jin-gang Jiang;Boting Yang;Lin Zhang; Mingyuan He ; Peng Wu
Angewandte Chemie International Edition 2014 Volume 53( Issue 5) pp:1355-1359
Publication Date(Web):
DOI:10.1002/anie.201306527
Abstract
Germanosilicates, an important family of zeolites with increasing number of members and attractive porosities, but containing a large quantity of unstable Ge atoms in the framework, meet with great obstacles in terms of limited thermal and hydrothermal stability when it comes to practical use. A facile stabilization method thus has been developed to substitute isomorphously Ge atoms for Si atoms, giving rise to ultrastable siliceous analogues of the pristine germanosilicates.
Co-reporter:Le Xu, Hong-gen Peng, Kun Zhang, Haihong Wu, Li Chen, Yueming Liu, and Peng Wu
ACS Catalysis 2013 Volume 3(Issue 1) pp:103
Publication Date(Web):November 28, 2012
DOI:10.1021/cs3006007
Core–shell-structured MWW-type titanosilicate (Ti-MWW) with a well-defined micro-meso hierarchical porosity was fabricated by using self-assembly technique. This composite material Ti-MWW@meso-SiO2 was applied as the catalyst for the ammoximation of cyclohexanone in a continuous slurry reactor. The combination of characterizations, such as XRD, SEM, HR-TEM, and N2 adsorption, verified that the composite material was composed of zeolite crystallites as core and mesosilica as shell and that the micropores and mesopores were penetrated well with each other, which significantly facilitated the diffusion of large molecules. In continuous ammoximation of cyclohexanone as a probe reaction, the composite exhibited significantly prolonged lifetime in comparison to the parent Ti-MWW catalyst and the physical mixture of Ti-MWW and mesosilica. The unique catalytic behaviors of Ti-MWW@meso-SiO2 were ascribed to protecting effect of the mesosilica shell. It served as a sacrificial lamb that protected the active component of zeolite core against rapid desilication and coke formation, leading to a stable duration of the catalysts.Keywords: ammoximation; core−shell structure; cyclohexanone; MWW; titanosilicate; zeolite
Co-reporter:Yong-Jun Ji, Hao Xu, Da-Rui Wang, Le Xu, Peng Ji, Haihong Wu, and Peng Wu
ACS Catalysis 2013 Volume 3(Issue 8) pp:1892
Publication Date(Web):July 9, 2013
DOI:10.1021/cs400284g
Mesoporous MCM-22 zeolite (meso-MCM-22) has been prepared by treating MCM-22 with sodium hydroxide solution through an organic amine-assisted reversible structural change. The alkaline treatment conditions, such as temperature, time, organic amine type, and its amount, were examined in detail. The desilication with sole NaOH caused an easy collapse of the crystalline structure of MWW topology. In contrast, the NaOH treatment with the coexistence of piperidine introduced mesopores of ∼20 nm into the MCM-22 crystals. Meanwhile, the calcined MCM-22 with three-dimensional (3D) MWW crystalline structure was converted to a 2D layered precursor with a well retained framework. The acid sites related to framework aluminum cations were almost intact after mesopore creation, as evidenced by pyridine or ammonia adsorption–desorption and 27Al NMR investigation. In comparison with MCM-22, meso-MCM-22 possessed a larger external surface, which mitigated effectively the steric restrictions to bulky molecules imposed by the intracrystal micropores. Meso-MCM-22 was superior to MCM-22 in the cracking of 1,3,5-triisopropyl benzene as well as the alkylation of benzene with isopropyl alcohol.Keywords: alkaline treatment; amine; desilication; MCM-22; mesoporous zeolites; structural conversion
Co-reporter:Jin-gang Jiang, Lili Jia, Boting Yang, Hao Xu, and Peng Wu
Chemistry of Materials 2013 Volume 25(Issue 23) pp:4710
Publication Date(Web):November 5, 2013
DOI:10.1021/cm4022326
Interlayer-expanded zeolite, IEZ-NSI, has been post-synthesized from a two-dimensional (2D) layered precursor Nu-6(1) (Si/Al ratio = 30 – ∞) by intercalating with diethoxydimethylsilane in hydrochloric acid solution. Ethanol was demonstrated to be a suitable solvent for inducing an effective interlayer pillaring with monomeric silane. IEZ-NSI was revealed to possess a 3D crystalline structure composed of 10-membered ring (MR) channels by using Rietveld crystal structure refinement of the PXRD pattern of IEZ-Nu-6(1)-H (Si/Al = ∞). The 10-MR pores in IEZ-NSI were constructed through the linkages between the pillaring Si atoms and the NSI layers. IEZ-Nu-6(1)-H(Si/Al = ∞) crystallizes in space group P121/a1 (No. 14) with a = 22.9372(4) Å, b = 5.0205(5) Å, c = 13.8209(1) Å, and β = 103.294(22)°. IEZ-NSI with more accessible channels gave a higher catalytic activity in the esterification of acetic acid with ethanol in comparison to Nu-6(2).Keywords: interlayer pore expansion; lamellar zeolite; Nu-6(1); silylation;
Co-reporter:Hong-gen Peng, Le Xu, Haihong Wu, Kun Zhang and Peng Wu
Chemical Communications 2013 vol. 49(Issue 26) pp:2709-2711
Publication Date(Web):08 Feb 2013
DOI:10.1039/C3CC38546A
A center radially fibrous silica encapsulated TS-1 zeolite (TS-1@KCC-1) has been synthesized in a microemulsion system for the first time. Supporting the Rh(OH)3 species, this novel core–shell structured material serves as a robust bifunctional catalyst for one-pot synthesis of benzamide from benzaldehyde, ammonia and hydrogen peroxide, in which the aldehyde ammoximation and oxime rearrangement occur in a tandem way.
Co-reporter:Jianghong Ding, Le Xu, Yejun Yu, Haihong Wu, Shijie Huang, Yulin Yang, Jing Wu and Peng Wu
Catalysis Science & Technology 2013 vol. 3(Issue 10) pp:2587-2595
Publication Date(Web):18 Jul 2013
DOI:10.1039/C3CY00471F
Acetaldehyde oxime has been synthesized though the liquid-phase ammoximation of acetaldehyde with ammonia and hydrogen peroxide over various titanosilicate catalysts. Titanium mordenite (Ti-MOR), prepared from highly dealuminated mordenite and TiCl4 vapor by a secondary synthesis method, was superior to TS-1 and Ti-MWW catalysts both in aldehyde conversion and in oxime selectivity. The reaction parameters were investigated systematically in a batch-type reactor for Ti-MOR, such as solvent effect, temperature, time, catalyst loading, amounts of ammonia and hydrogen peroxide relative to aldehyde as well as addition methods of the reactants. Under optimized conditions, Ti-MOR was capable of showing an aldehyde conversion of 99% and an oxime selectivity of 97%. In comparison with TS-1 and Ti-MWW, the advantage of Ti-MOR in acetaldehyde ammoximation was mainly attributed to its lower ability for oxidation to convert the aldehyde to acetic acid. There was almost no effect resulting from the addition mode of the reactants; Ti-MOR with its special characteristics was unique in catalytic behavior and easy handling. An overview of the reaction routes involved in acetaldehyde ammoximation has been provided.
Co-reporter:Xiangqing Fang, Qiang Wang, Anmin Zheng, Yueming Liu, Longfei Lin, Haihong Wu, Feng Deng, Mingyuan He and Peng Wu
Physical Chemistry Chemical Physics 2013 vol. 15(Issue 14) pp:4930-4938
Publication Date(Web):30 Jan 2013
DOI:10.1039/C3CP44700F
F-Ti-MWW was post-synthesized by implanting fluorine species into a Ti-MWW framework through an acid treatment process in the presence of ammonium fluoride. The effects of NH4F addition amount, acid treatment temperature and precursor Ti content were investigated on the incorporation of F species, the zeolite structure and the coordination sites of Ti. Fluorine-implanting improved the surface hydrophobicity of the zeolite and altered the electropositivity nearby the tetrahedral Ti sites through forming the SiO3/2F and SiO4/2F− units. The negative effect of SiO4/2F− units in F-Ti-MWW was eliminated selectively by convenient anion-exchange with various alkali chlorides. F-Ti-MWW containing the SiO3/2F units possessed better catalytic activity and reusability, and a longer catalyst lifetime than conventional Ti-MWW.
Co-reporter:Bin Zhang, Zhendong Wang, Peng Ji, Yueming Liu, Hongmin Sun, Weimin Yang, Peng Wu
Microporous and Mesoporous Materials 2013 Volume 179() pp:63-68
Publication Date(Web):15 September 2013
DOI:10.1016/j.micromeso.2013.05.004
•Mesoporous MCM-22 zeolites were synthesized using carbon black particles as hard templates.•Mesoporous MCM-22 possesses intercrystal mesopores and a larger external surface area.•It exhibited a better catalytic performance in the ethylation of benzene than conventional MCM-22.Mesoporous MCM-22 zeolites with Si/Al ratios of 15–45 were hydrothermally synthesized through a hard template technique by carbon black particles. The physicochemical properties of mesoporous MCM-22 were characterized by XRD, SEM, N2 adsorption, TEM, XPS, ICP, TGA-DTA and NH3-TPD techniques. In comparison with conventional MCM-22, mesoporous MCM-22 showed an obvious hysteresis loop in N2 adsorption–desorption isotherm, and possessed 4–10 nm mesopores as well as a larger external surface area. The presence of mesopores was beneficial to increase the accessibility of zeolitic acid sites and to decrease the mass transfer limitations of bulky molecules. When employed to liquid-phase ethylation of benzene with ethylene, mesoporous MCM-22 exhibited higher ethylene conversion, higher selectivity to ethylated benzenes and better stability than conventional MCM-22, potentially serving as a solid-acid catalyst in petrochemical industry.
Co-reporter:Guanqi Liu, Jin-Gang Jiang, Boting Yang, Xiangqing Fang, Hao Xu, Honggen Peng, Le Xu, Yueming Liu, Peng Wu
Microporous and Mesoporous Materials 2013 Volume 165() pp:210-218
Publication Date(Web):1 January 2013
DOI:10.1016/j.micromeso.2012.08.025
A series of novel stannosilicates with the MWW topology, Sn-MWW, was hydrothermally synthesized in alkali medium using boric acid as a crystallization-supporting agent. The Sn-MWW lamellar precursors with a high crystallinity were obtained from the synthetic gels even at Si/Sn ratio of 60. UV–visible and 119Sn MAS NMR characterizations verified that the Sn species were incorporated in the framework, occupying mainly the tetrahedral sites. A mild acid treatment was conducted on the precursors to induce a structural transformation to tin-containing materials structurally analogous to MCM-56. Sn-MCM-56 thus post-synthesized comprised partially delaminated MWW sheets, and possessed larger external surface as well as more open reaction space. Sn-MCM-56 analogue alleviated effectively the steric restriction and diffusion limitation to bulky molecules that the microporous zeolite catalysts usually encountered. It appeared to be more efficient than Sn-MWW in the Baeyer–Villiger oxidation of 2-adamantanone with H2O2. Moreover, Sn-MCM-56 turned to be more active than Sn-Beta when tert-butyl hydroperoxide was employed as an oxidant.Graphical abstractHighlights► Sn-MWW precursors were hydrothermally synthesized using boric acid as a crystallization-supporting agent. ► A mild acid treatment of the precursors induced a structural transformation to Sn-MCM-56 analogues. ► Sn-MCM-56 analogues possess a partially delaminated structure consisting of disordered array of MWW sheets. ► Sn-MCM-56 proves to be more active than Sn-MWW in the Baeyer–Villiger oxidation of ketone.
Co-reporter:Hao Xu, Boting Yang, Jin-gang Jiang, Lili Jia, Mingyuan He, Peng Wu
Microporous and Mesoporous Materials 2013 Volume 169() pp:88-96
Publication Date(Web):15 March 2013
DOI:10.1016/j.micromeso.2012.10.005
PLS-4 lamellar precursors, comprised of FER layers and organic structure-directing agent of diethyldimethylammonium cations, were interlayer expanded by silylation with Me2Si(OEt)2 molecules, yielding PLS-4-sil materials with a larger porosity than directly calcined PLS-4 with the CDO topology. The silylation conditions were optimized to obtain a highly ordered interlayer-expanded structure. The silylation introduced about four additional silicon atoms per unit cell to pillar the FER layers. The silicon insertion not only widened the interlayer entrance but also endowed the inorganic zeolite with organic functionality by introducing two methyl groups per silane molecule. As an organic–inorganic hybrid material, PLS-4-sil possessed changeable pore openness and hydrophilicity/hydrophobicity after controlled removal of methyl groups by calcination. Coherently, its adsorption capacities varied with calcination temperature for the adsorption of water, n-hexane and benzene molecules.Graphical abstractHighlights► Interlayer expanded zeolites were prepared by silylation of PLS-4 lamellar precursor. ► The silylation conditions were optimized to achieve a well ordered expanded structure. ► The pore opening and hydrophilicity/hydrophobicity were controlled by calcination. ► Interlayer expanded PLS-4 exhibits unique adsorption properties.
Co-reporter:Hong-Gen Peng, Xiao-Hong Li, Le Xu, Peng Wu
Chinese Chemical Letters 2013 Volume 24(Issue 7) pp:559-562
Publication Date(Web):July 2013
DOI:10.1016/j.cclet.2013.04.004
Trimodal hierarchical yolk–shell materials consisting of TS-1 core and mesoporous carbon shell (YS-TS-1@MC) was successfully synthesized by using TS-1@mesosilica as hard template, sucrose as carbon source and organic base tetrapropylammonium hydroxide (TPAOH) as silica etching agent. The resultant YS-TS-1@MC contains the micropores (0.51 nm) in TS-1 core, the mesopores (2.9 nm) in carbon shell as well as a void or a stack pore between TS-1 fragements (TS-1 intercrystal mesopores, ∼18.4 nm). Under the rigorous etching conditions, the crystalline structure of TS-1core was well retained. The YS-TS-1@MC served as a good support for palladium nano-particles (Pd NPs) or Rh(OH)x species, giving rise to efficient bifunctional catalysts for the tandem reactions including one-pot synthesis of propylene oxide or amides.Yolk–shell material TS-1@MC with a trimodal hierarchical pore structure was successfully prepared and applied to support Pd nanoparticles or Rh(OH)x species, giving rise to novel bifunctional catalysts for tandem reactions.
Co-reporter:Huan Zhang, Ying Li, Songxue Shao, Haihong Wu, Peng Wu
Journal of Molecular Catalysis A: Chemical 2013 Volume 372() pp:35-43
Publication Date(Web):June 2013
DOI:10.1016/j.molcata.2013.01.034
A series of novel heterogeneous olefin metathesis catalysts have been developed by immobilizing Ru species on SBA-15 mesoporous silica with tunable ordered pores and different textural properties. Various techniques such as X-ray diffraction, N2 adsorption–desorption, high resolution transmission electron microscopy have been used to characterize the physicochemical properties of the catalysts. The catalytic activity of thus prepared Ru-based catalysts has been studied in ring closing metathesis (RCM) and other metathesis reactions. Among these immobilized catalysts, the SBA-15 support with the largest pore size gives rise to the highest catalytic activity because the large pores are benefit for the diffusion of reactants and products. The immobilized Ru catalysts prove to be reusable in RCM reactions. Their catalytic activity is closely related to the confinement effect and high hydrophobicity of SBA-15 mesopores.Graphical abstractHighlights► New heterogeneous olefin metathesis catalysts are prepared. ► The Grubbs catalysts are immobilized on SBA-15 mesosilica. ► The immobilized Grubbs catalysts are effective and reusable in RCM and CM reactions.
Co-reporter:Le Xu;Ningning Li;Hong-gen Peng ; Peng Wu
ChemCatChem 2013 Volume 5( Issue 8) pp:2462-2470
Publication Date(Web):
DOI:10.1002/cctc.201300126
Abstract
Rhodium-loaded titanosilicates were prepared and employed as efficient bifunctional catalysts in the one-pot synthesis of benzamide from benzaldehyde, hydrogen peroxide, and ammonia, which took place through a tandem reaction including ammoximation of benzaldehyde to benzaldehydeoxime and a sequential dehydration–rehydration reaction to benzamide. Various parameters that influenced the activity and product selectivity were investigated, such as crystalline topologies of the titanosilicate supports, types of transition metals, rhodium content, reaction temperature, time, solvent, and NH3/benzaldehyde molar ratio. Ti-MWW was proved to be a suitable support for loading the Rh(OH)x species. Rh(OH)x/Ti-MWWgave 84.9 % of benzaldehyde conversion and 86.9 % of benzamide selectivity, and it was also catalytically active for the transformation of a variety of aldehydes to the corresponding amides. The reusability of the bifunctional catalyst was also investigated. The in situ FTIR technique confirmed that the one-pot reaction included Ti-catalyzed ammoximation of benzaldehyde to the benzaldehyde oxime intermediate and sequential rhodium hydroxide related dehydration–rehydration reaction of oximes to amides.
Co-reporter:Rong Xing, Lin Wu, Zhenghao Fei, Peng Wu
Journal of Molecular Catalysis A: Chemical 2013 Volume 371() pp:15-20
Publication Date(Web):May 2013
DOI:10.1016/j.molcata.2013.01.022
A novel sulfonated palladium phthalocyanine (PdPcS) modified FDU-15 mesoporous polymer (FDU-PdPcS) has been prepared by rationally chemical modification process. The PdPcS molecules were highly dispersed inside the confined mesopores, and were further stabilized through a π–π interaction with mesopolymer, which may prevent the PdPcS molecules from agglomerating and deactivating in photodegradation reactions. The physicochemical properties of thus prepared FDU-PdPcS material were characterized by XRD, N2 adsorption-desorption, UV–vis and inductively coupled plasma techniques. FDU-PdPcS proved to be highly efficient heterogeneous photocatalyst for the degradation of 4-chlorophenol (4-CP) in the presence of H2O2 under visible light irradiation. The photodegradation of 4-CP with an initial concentration 0.6 mM was completed within 5 h at pH 11 using a dose of 0.2 g/L of the 0.12 wt% FDU-PdPcS photocatalyst. The photodegradation intermediates were identified by GC-MS. A possible mechanism involved in the photodegradation of 4-CP has also been discussed.Graphical abstractHighlights► Novel sulfonated palladium phthalocyanine modified mesopolymer was prepared. ► The photocatalyst has the advantages of mesopolymer and palladium phthalocyanine. ► Excellent photoactivity and stability under visible light irradiation. ► A possible photodegradation mechanism was discussed.
Co-reporter:Honggen Peng, Le Xu, Liyan Zhang, Kun Zhang, Yueming Liu, Haihong Wu and Peng Wu
Journal of Materials Chemistry A 2012 vol. 22(Issue 28) pp:14219-14227
Publication Date(Web):30 Apr 2012
DOI:10.1039/C2JM31788E
Core–shell structured TS-1@mesocarbon (TS-1@MC) materials with mesoporous carbon as the shell and microporous TS-1 titanosilicate as the core were synthesized through a nanocasting and selective silica etching strategy. The faithful replica structure was constructed from the composite of TS-1@mesosilica and carbon when tetrapropylammonium hydroxide (TPAOH) was employed to selectively remove the amorphous mesosilica shell while the core zeolite crystal structure was not destroyed. In contrast, the protective effect was not seen when sodium hydroxide or hydrogen fluoride was employed as a silica-leaching agent. The obtained TS-1@MC had a bimodal pore structure consisting of 2.9 nm mesopores in the carbon shell and 0.51 nm micropores in the TS-1 core. Its specific surface area and total pore volume reached 883 m2 g−1 and 0.63 cm3 g−1, respectively. TS-1@MC was used as the support to load palladium nanoparticles (Pd NPs) in the carbon shell. Having an average particle size of approximately 2 nm, the Pd NPs were highly dispersed and confined in the mesopores of the carbon shell. Pd/TS-1@MC thus obtained served as an efficient tandem catalyst in the direct epoxidation of propylene with hydrogen and oxygen.
Co-reporter:Xiangqing Fang, Qiang Wang, Anmin Zheng, Yueming Liu, Yuning Wang, Xiujuan Deng, Haihong Wu, Feng Deng, Mingyuan He and Peng Wu
Catalysis Science & Technology 2012 vol. 2(Issue 12) pp:2433-2435
Publication Date(Web):25 Jul 2012
DOI:10.1039/C2CY20446K
Fluorine species were successfully implanted into a MWW-type titanosilicate via post-treatment, which generates the SiO3/2F units in the zeolite framework. The incorporated fluorine species significantly improved the catalytic performance in the epoxidation of alkenes as a result of enhancing the Lewis acid strength and the hydrophobicity of the zeolite.
Co-reporter:Honggen Peng, Le Xu, Haihong Wu, Zhendong Wang, Yueming Liu, Xiaohong Li, Mingyuan He, Peng Wu
Microporous and Mesoporous Materials 2012 Volume 153() pp:8-17
Publication Date(Web):1 May 2012
DOI:10.1016/j.micromeso.2011.11.055
Micro-/mesoporous composite materials that possessed core–shell structure were prepared through oriented assembly of mesoporous silica on premade titanosilicate zeolite TS-1 using triblock copolymer surfactant P123 as template in an acid-free system. When the pH value of P123/NaCl/H2O/EtOH/TEOS/TS-1 synthetic system was controlled in the range of 3.5–5.5, the crystalline particles of TS-1 were negatively charged, whereas P123 micelles were partially protonated. Thus induced an electrostatic interaction between inorganic zeolite and organic micelles probably via enhanced hydrogen bonding, and made an oriented assembly of silica oligomer or silica-micelle composite on the surface of P123/TS-1 and further condensation. Otherwise, the silica was self-assembled in a phase separation manner, or failed to form a mesophase. The mesopores in silica shell were of wormhole-like and interconnected with the micropores in TS-1. When as-synthesized core/shell composites were hydrothermally post-treated, the pore volume, specific surface area and pore size of shell increased with increasing temperature. The average shell thickness and particle size were conveniently adjusted in the range of 30–90 nm and 350–500 nm, respectively, by changing the synthesis time, temperature, and amount of silica source added.Graphical abstractHighlights► Core–shell structured TS-1@mesosilica was prepared using triblock copolymer. ► The thickness of mesosilica shell was adjustable in the range of 30–90 nm. ► The electrostatic interaction is essential to induce an oriented assembly of mesosilica shell.
Co-reporter:Zhendong Wang, Le Xu, Jin-gang Jiang, Yueming Liu, Mingyuan He, Peng Wu
Microporous and Mesoporous Materials 2012 Volume 156() pp:106-114
Publication Date(Web):1 July 2012
DOI:10.1016/j.micromeso.2012.02.025
Mesoporous TS-1 microspheres, denoted as M-TS-1-MS, were directly synthesized by adding triblock copolymer (F127 or P123) into the synthetic system for crystallizing conventional TS-1 (C-TS-1). With the assistance of surfactant, TS-1 nanoparticles of 50–100 nm were self-assembled into microspheres which contained regular intercrystal mesopores in the range of 6–10 nm in addition to original micropores. The crystallite aggregates in microspheres did not collapse after ultrasonication for 2 h or refluxing in 2 M HNO3 for 20 h. The high mechanical strength implied their potential applications in slurry reactors where an easy separation of solid catalyst from reaction mixture is required. M-TS-1-MS was comparably active to C-TS-1 in pyridine oxidation and 1-hexene epoxidation with H2O2 as the oxidant, whereas exhibited a higher activity in the oxidation of bulky substrates such as 3-picoline and cyclohexene due to the presence of mesopores. By tracking the crystallization process at different stages, a tentative mechanism is proposed to explain the role of triblock copolymer in inducing the aggregation of nanocrystals to microspheres.Graphical abstractHighlights► Mesoporous TS-1 microspheres were prepared via self-assembling of nanocrystals with the aid of triblock copolymer. ► A tentative mechanism is proposed for the assembling of TS-1 nanocrystals. ► TS-1 microsphere is mechanically robust and catalytically active to liquid-phase oxidations.
Co-reporter:Liyan Zhang;Le Xu;Jingjing Sun;Jingang Jiang;Yueming Liu;Haihong Wu
Chinese Journal of Chemistry 2012 Volume 30( Issue 9) pp:2205-2211
Publication Date(Web):
DOI:10.1002/cjoc.201200637
Abstract
Novel ammonia-treated titanosilicates have been prepared by heating the samples of Ti-MWW, TS-1 and Ti-Beta under pure ammonia gas flow at 673 K for a period of time. The ammonia modification improved their catalytic performance in liquid-phase oxidations. Especially, the catalytic activities of ammonified Ti-MWW, N-Ti-MWW, were enhanced greatly in the epoxidation of 1-hexene with H2O2. The reason that the ammonia treatment played such an important role in post-modification of titanosilicate was investigated in details. In comparison to the parent Ti-MWW catalyst, N-Ti-MMW was more robust and produced less coke in oxidation reactions.
Co-reporter:Le Xu, Yingjie Ren, Haihong Wu, Yueming Liu, Zhendong Wang, Yingtian Zhang, Jiajia Xu, Honggen Peng and Peng Wu
Journal of Materials Chemistry A 2011 vol. 21(Issue 29) pp:10852-10858
Publication Date(Web):16 Jun 2011
DOI:10.1039/C1JM10483G
Hierarchically ordered materials with core/shell structures were synthesized through a layer-by-layer approach. The novel microporous/mesoporous hybrid materials were composed of a TS-1 zeolite particle for the core and mesoporous silica for the shell. The as-synthesized TS-1 crystals were modified with polydiallyldimethylammonium chloride to make their external surface positively charged, which induced an oriented self-assembly of tetraethoxysilane (TEOS) with cetyltrimethyl ammonium bromide on the TS-1 particle surface to form a shell of mesophase silica. The thickness of the mesoporous silica shell was controlled to be in the range 30–55 nm by changing the amount of TEOS added in the synthesis. The mesoporous channels in the shell were perpendicular to the zeolite core, which made the micropores inside the core accessible from the outside through the mesopores. Taking advantage of the confining effect of the mesopores, Au nanoparticles were incorporated into the shell, resulting in bifunctional catalysts which were more selective than conventional Au/TS-1 catalysts in the direct epoxidation of propylene to propylene oxide with H2 and O2.
Co-reporter:Ailing Lv, Hao Xu, Haihong Wu, Yueming Liu, Peng Wu
Microporous and Mesoporous Materials 2011 Volume 145(1–3) pp:80-86
Publication Date(Web):November 2011
DOI:10.1016/j.micromeso.2011.04.027
High-silica mordenite (MOR) zeolites were hydrothermally synthesized by a dual-templating method using tetraethylammonium hydroxide (TEAOH) and hexamethyleneimine (HMI) as co-structure-directing agents (SDAs). The MOR zeolites were crystallized readily with the addition of NH4NO3 from the gels that had a Si/Al ratio up to 60. The synthesis resulted in highly crystalline MOR zeolites possessing a Si/Al ratio of 37.1. The chemical coordination states of the Al ions in the MOR zeolites were characterized by 27Al and 29Si NMR MAS spectroscopy. The Al ions occupied dominantly the tetrahedral sites in the framework. The dual-templating effect that the two amines exhibited on the zeolite crystallization was investigated by 13C MAS NMR spectroscopy and elemental analyses. Both organic SDA molecules were incorporated simultaneously into the zeolite products, corresponding to 65% of TEA+ and 35% of HMI. These two kinds of SDAs played a cooperative role in the nucleation and crystallization of the MOR structure under high silica conditions.Graphical abstractHighlights► High-silica mordenite (MOR) zeolites were synthesized with a dual-templating method. ► The synthesis was carried out with the assistant of seeding crystals in the absence of fluoride media. ► Pure MOR phase was obtained from the synthetic gels with a Si/Al ratio up to 60. ► The Si/Al ratio of MOR product reaches 37.1. ► Two amines show a cooperative role in the crystallization of MOR.
Co-reporter:Chaochao Yue, Wei Xie, Yueming Liu, Haihong Wu, Xiaohong Li, Peng Wu
Microporous and Mesoporous Materials 2011 Volume 142(Issue 1) pp:347-353
Publication Date(Web):June 2011
DOI:10.1016/j.micromeso.2010.12.021
The borosilicates and titanosilicates with a crystalline structure analogous to the MWW topology were hydrothermally synthesized by using linear organic quaternary ammonium hydroxides, CH3(CH2)nN+(CH3)3OH with n = 5, 6 and 7, as structure-directing agents (SDAs) with the co-existence of boric acid and alkali hydroxide mineralizers. The MFI zeolite appeared to be the main competitive phase that affected the purity of the MWW structure. The Ti-MWW lamellar precursors were synthesized successfully at a greatly reduced amount of boric acid in comparison to the conventional system using piperidine. The SDA cations were confirmed to be incorporated into both the interlayer spacings and the intralayer sinusoidal 10-MR channels of the MWW sheets, keeping intact in their molecular structures. The Ti-MWW precursors contained both tetrahedral and octahedral Ti species. The octahedral Ti species were selectively removed by acid treatment, leading to active titanosilicate catalysts for the epoxidation of 1-hexene with H2O2.Graphical abstractResearch highlights► MWW-type analogues were synthesized successfully by using a series of linear-type quaternary alkylammonium hydroxides as SDAs. The quaternary ammonium cations have the structures of CH3(CH2)nN+(CH3)3OH with n = 5, 6 and 7. ► The synthesis conditions for the MWW-type borosilicates were optimized for each linear-type quaternary alkylammonium, which led to the preparation of corresponding titanosilicates at a greatly reduced amount of boron in comparison to conventional piperidine system. ► The titanosilicates with the MWW topology were efficient catalysts for the liquid-phase oxidation of alkenes with H2O2.
Co-reporter:Yuting Zheng, Yingtian Zhang, Zhendong Wang, Yueming Liu, Mingyuan He, and Peng Wu
Industrial & Engineering Chemistry Research 2011 Volume 50(Issue 16) pp:9587-9593
Publication Date(Web):July 7, 2011
DOI:10.1021/ie200757f
TS-1 particles were loaded on stainless-steel-net (SSN) to form an integrated material (TS-1/SSN) by secondary hydrothermal synthesis. This avoided completely the filtration separation in both catalyst preparation and catalytic applications in liquid-phase reactions. Seeding-assisted secondary crystallization prevented zeolite from detaching from the support during the synthesis process. The TS-1 particles were coated on the SSN support uniformly, and their loading amount was adjustable in the range of 7–25 wt % by repeating the seeding and crystallization processes. UV–visible and IR spectra verified that the titanium species in TS-1/SSN mostly occupied the tetrahedral coordination sites in the zeolite framework. TS-1/SSN was comparably active to conventional TS-1 particles in batchwise epoxidation of 1-hexene with H2O2. The zeolite particles maintained the catalytic activity and did not detach from the SSN after five reuses. Moreover, TS-1/SSN proved to be efficient and reusable in continuous epoxidation of allyl chloride where the separation of products and catalyst occurred easily.
Co-reporter:Pei Li ; Guanqi Liu ; Haihong Wu ; Yueming Liu ; Jin-gang Jiang
The Journal of Physical Chemistry C 2011 Volume 115(Issue 9) pp:3663-3670
Publication Date(Web):February 11, 2011
DOI:10.1021/jp1076966
Nanosized Beta zeolites were postsynthetically modi-fied through the solid−gas reaction of highly dealuminated Beta zeolite with SnCl4 vapor at elevated temperatures. The incorporation mechanism of Sn ions and the physicochemical properties of resultant Sn-Beta-PS were characterized by various techniques. Its catalytic performance in Baeyer−Villiger oxidation was compared with the micrometer-sized Sn-Beta-F hydrothermally synthesized by conventional fluoride method. The Sn species were inserted into the framework via the reaction of the SnCl4 molecules with the silanols in the hydroxyl nests that were created by dealumination and thus occupied predominately the tetrahedral coordination sites. The Sn content gained by postsynthesis reached up to 6.2 wt %, corresponding to a Si/Sn ratio of ca. 35. The isolated Sn species exhibited Lewis acidity useful for the Baeyer−Villiger oxidation of ketones. Containing higher Sn contents and more importantly proposing less diffusion limitations to the substrates with a large molecular dimension, nanosized Sn-Beta-PS was superior to Sn-Beta-F in the selective oxidation of 2-adamantanone with hydrogen peroxide.
Co-reporter:Zhendong Wang, Yueming Liu, Jin-gang Jiang, Mingyuan He and Peng Wu
Journal of Materials Chemistry A 2010 vol. 20(Issue 45) pp:10193-10199
Publication Date(Web):22 Sep 2010
DOI:10.1039/C0JM01948H
Hollow and core/shell ZSM-5 spheres were simply synthesized through in situ transformation of mesoporous silica spheres (MSS) into MFI-type zeolite with the assistant of isopropylamine (IPA) as a structure-directing agent (SDA). IPA, with a mild structure-directing ability for the construction of MFI structure, triggered a stepwise crystallization of MSS after Al addition. First, the sphere surface was crystallized to a shell of ZSM-5 crystals. The silica and alumina species in the core condensed and crystallized to ZSM-5 thereafter, forming zeolite crystal aggregates inside the spheres. The obtained ZSM-5 spheres were highly crystalline materials and maintained the shape of pristine MSS, but exhibited a hollow and core/shell structure. The techniques of XRD, FT-IR, SEM, N2 adsorption-desorption, 29Si and 27Al MAS NMR were employed to trace the crystallization process, which allowed us to propose a “templating and surface to core” crystallization mechanism. This strategy may serve as an alternative way for synthesizing hollow zeolite spheres.
Co-reporter:Zhonglin Zhao;Yueming Liu;Haihong Wu;Xiaohong Li
Journal of Porous Materials 2010 Volume 17( Issue 4) pp:399-408
Publication Date(Web):2010 August
DOI:10.1007/s10934-009-9316-1
Mesoporous MFI-type titanosilicates (TS-1) were hydrothermally synthesized with the aid of amphiphilic organosilane and the effects of the amphiphilic organosilane on the structural and textural properties of the resultant materials were investigated. The physicochemical properties of the samples were characterized by various techniques and their catalytic performance was investigated by the epoxidation of cyclohexene with hydrogen peroxide. The content of organosilane added was essential for the formation of uniform mesopore in TS-1, and greatly influenced the crystallinity. Highly crystallined TS-1 with uniform mesopores of 3.7 nm diameter was successfully synthesized. The mesoporous TS-1 preserved tetrahedrally coordinated Ti ions in the framework, but it was featured with more hydrophobic surface and less defect sites in comparison to conventional TS-1. Mesoporous TS-1 showed a higher conversion for the epoxidation of cyclohexene owing to an easier access of bulky molecules to the catalytic active sites. Mesoporous TS-1’s higher hydrophobicity made its epoxide selectivity two times as much as that of conventional TS-1.
Co-reporter:Rong Xing, Haihong Wu, Xiaohong Li, Zhonglin Zhao, Yueming Liu, Li Chen and Peng Wu
Journal of Materials Chemistry A 2009 vol. 19(Issue 23) pp:4004-4011
Publication Date(Web):07 May 2009
DOI:10.1039/B822659H
A series of amine- or diamine-functionalized mesopolymers with cubic or hexagonal mesostructures have been prepared by two-step chemical modification procedures involving chloromethylation of the FDU-type mesoporous resol materials first with chloromethyl methyl ether, and a subsequent amination reaction with methylamine, dimethylamine or ethylenediamine. Various techniques such as XRD, SEM, TEM, N2 adsorption, FTIR, 13C NMR and elemental analysis have been adopted to track the functionalization processes, and to characterize the structures, porosity, chemical compositions and basicity of the materials. The amino group-containing mesopolymer materials prove to be efficient heterogeneous base catalysts in Knoevenagel condensation of benzaldehyde with ethyl cyanoacetate. The possible mechanisms of Knoevenagel reaction on different mesopolymer base catalysts have also been discussed.
Co-reporter:Lingling Wang, Yong Wang, Yueming Liu, Haihong Wu, Xiaohong Li, Mingyuan He and Peng Wu
Journal of Materials Chemistry A 2009 vol. 19(Issue 45) pp:8594-8602
Publication Date(Web):24 Sep 2009
DOI:10.1039/B910886F
Silylation of Ti-MWW lamellar precursor and subsequent calcination constructed an interlayer expanded structure, leading to novel titanosilicates with large pores. The silylating agents suitable for pore expansion were diethoxydimethylsilane, trimethylethoxysilane and triethoxymethylsilane containing methyl groups, which inhibited the intermolecular condensation of silanes effectively. In contrast to well-known 3D Ti-MWW with only medium pores of 10-membered rings, the silylation led to new crystalline structures with more open pores by ca. 2.5 Å, as evidenced by the shift of layer-related diffractions to the lower-angle region in XRD patterns and the enlarged interlayer pores in HRTEM images. The interlayer expanded Ti-MWW was prepared readily from the corresponding hydrothermally synthesized precursors with a wide range of Ti contents (Si/Ti = 20–100). In addition, the pore expansion by silylation was realized under mild acid conditions with 0.1 M HNO3. The interlayer expanded Ti-MWW exhibited 3–7 times higher turnover number than 3D Ti-MWW in the oxidation of cyclohexene with H2O2.
Co-reporter:Haijiao Zhang, Yueming Liu, Zheng Jiao, Mingyuan He and Peng Wu
Industrial & Engineering Chemistry Research 2009 Volume 48(Issue 9) pp:4334-4339
Publication Date(Web):April 9, 2009
DOI:10.1021/ie8016253
Titanium silicalite-1 (TS-1) with the MFI topology has been synthesized successfully in the absence of alkali metal ions with the cooperative effects of active seeds and the structure-directing agent hexamethyleneimine (HMI). The physicochemical properties and structures of the products were characterized by various techniques. The coexistence of HMI and primary and/or secondary building units of the MFI structure in the synthesitic gels was essential for the nucleation and crystallization of TS-1. The nature and preparation conditions of the seed precursors had a great influence on the crystallization process and the incorporation of titanium atoms into the framework. It was found that a synergistic effect between HMI and the precursor seeds led to the full crystallization of TS-1. Other synthesis parameters such as boron addition, silicon source, and crystallization time were also investigated. Moreover, the present synthesis system is also applicable to the preparation of other MFI analogues.
Co-reporter:Zhonglin Zhao, Yueming Liu, Haihong Wu, Xiaohong Li, Mingyuan He, Peng Wu
Microporous and Mesoporous Materials 2009 Volume 123(1–3) pp:324-330
Publication Date(Web):1 July 2009
DOI:10.1016/j.micromeso.2009.04.018
Mesoporous MFI-type zirconosilicates (Zr-MFI) with different Zr contents were hydrothermally synthesized by the aid of amphiphilic organosilane. Their physicochemical properties were characterized by various techniques, and their catalytic performance was investigated for Meerwein–Ponndorf–Verley (MPV) reduction of cyclohexanone with 2-propanol. The mesoporous Zr-MFI preserved the properties of conventional Zr-MFI such as high crystallinity and incorporation of tetrahedral Zr ions in framework, and was further featured with mesoporosity of 3.5 nm diameter, enlarged external surface area, more Lewis acid sites and less defect sites. Compared with conventional Zr-MFI, the mesoporous Zr-MFI showed drastically improved activity for the MPV reduction of cyclohexanone, which was predominantly attributed to the contribution of the mesopores supplying an easier accessibility to the catalytic active sites for bulky molecules. Moreover, the mesoporous Zr-MFI was a stable and reusable catalyst.
Co-reporter:Yong Wang, Yueming Liu, Lingling Wang, Haihong Wu, Xiaohong Li, Mingyuan He and Peng Wu
The Journal of Physical Chemistry C 2009 Volume 113(Issue 43) pp:18753-18760
Publication Date(Web):October 5, 2009
DOI:10.1021/jp904436c
Aluminosilicates with different Si/Al ratios and showing a structure similar to MCM-56 were postsynthesized from fully crystallized lamellar MWW-type precursors under controlled acid treatment. The effects of pretreatment conditions on the construction of MCM-56 analogue structure were investigated, and the physicochemical properties of the resulting materials were characterized by means of various techniques. When the precursors were treated in HNO3 solution with a concentration ≤2 M at temperatures lower than 353 K, a structure analogous to MCM-56 was formed favorably even after further calcination, whereas the treatment at higher temperatures or with 5 M HNO3 resulted in conventional three-dimensional MWW topology. The formation of MCM-56-like structure was closely related to the reorientation of the interlayer H-bond moieties as a result of a partial removal of occluded structure directing agent. Compared with MCM-22, the MCM-56 analogues possessed a structural disorder along the layer stacking direction but had a larger external surface, which mitigated effectively the steric restrictions imposed by the intracrystal micropores to bulky molecules. The MCM-56 zeolites, maintaining the basic structure units of the MWW zeolite, turned out to serve as promising solid acid catalysts for processing larger molecules.
Co-reporter:Rong Xing, Yueming Liu, Haihong Wu, Xiaohong Li, Mingyuan He and Peng Wu
Chemical Communications 2008 (Issue 47) pp:6297-6299
Publication Date(Web):27 Oct 2008
DOI:10.1039/B815186E
A two-step chemical modification process is designed for synthesizing novel diamine-functionalized mesopolymers, which combine the advantage of organic polymers and mesoporous materials, and serve as an efficient scaffold for supporting highly dispersed, catalytically active and robust Pd nanoparticles (NPs).
Co-reporter:Xiaohong Li;Yali Shen;Rong Xing;Yueming Liu;Haihong Wu
Catalysis Letters 2008 Volume 122( Issue 3-4) pp:325-329
Publication Date(Web):2008 May
DOI:10.1007/s10562-007-9381-5
Platinum nanoparticles supported on periodic mesoporous resols by simple impregnation serve as effective, robust and remarkably reusable catalysts after chirally modified with cinchonidine for the asymmetric hydrogenation of ethyl pyruvate, affording up to 62% enantiomeric excess (ee) and a constant activity after 25th re-use. They can also catalyze the reaction in an environmentally benign manner by using water as a solvent.
Co-reporter:R. Xing;N. Liu;Y. Liu;H. Wu;Y. Jiang;L. Chen;M. He;P. Wu
Advanced Functional Materials 2007 Volume 17(Issue 14) pp:
Publication Date(Web):15 AUG 2007
DOI:10.1002/adfm.200600784
Novel solid acid catalysts have been prepared from Fudan University (FDU)-type mesoporous polymers with the Ia
d and P6mm mesostructures through a carefully controlled sulfonation procedure. Various techniques have been adopted to characterize throughout their structures, porosity, acidity as well as the information related to the sulfonic acid groups. The sulfonic acid group-functionalized mesopolymers prove to be efficient heterogeneous catalysts in the reactions such as liquid-phase Beckmann rearrangement of cyclohexanone oxime and condensation of ethylene glycol with the aldehydes having different molecular sizes.
Co-reporter:Rong Xing, Yueming Liu, Yong Wang, Li Chen, Haihong Wu, Yongwen Jiang, Mingyuan He, Peng Wu
Microporous and Mesoporous Materials 2007 Volume 105(1–2) pp:41-48
Publication Date(Web):15 September 2007
DOI:10.1016/j.micromeso.2007.06.043
A novel sulfonic acid group-functionalized mesoporous carbon was prepared through vapour-phase transfer sulfonation of CMK-3 type mesoporous carbon with the controllable carbonization degree. The method of vapour-phase sulfonation, that is, through contacting the sample powders with the vapor from fuming sulfuric acid in a closed autoclave, proved to be more effective than both the direct dipping of the carbon in concentrated or fuming H2SO4 and the treatment with pure SO3 gas. The influence of carbonization temperature on the sulfonation was investigated, suggesting an optimum temperature of 823 K. The SO3H group-functionalized mesoporous carbon, CMK-3-SO3H, was characterized by means of XRD, SEM, TEM, N2 adsorption–desorption, 13C NMR, FTIR and elemental analysis, which indicated that it had uniform mesopores together with an extremely high surface area, and also contained an amount of acid sites as high as 1.3 mmol g−1. CMK-3-SO3H catalyzed efficiently the liquid-phase Beckmann rearrangement of cyclohexanone oxime and condensation reactions involving bulky aromatic aldehydes.
Co-reporter:Haihong Wu, Lingling Wang, Haijiao Zhang, Yueming Liu, Peng Wu and Mingyuan He
Green Chemistry 2006 vol. 8(Issue 1) pp:78-81
Publication Date(Web):01 Nov 2005
DOI:10.1039/B511594A
A much greener synthesis method is discovered for the synthesis of 3,4-epoxytetrahydrofuran (ETHF), an important synthetic intermediate for stereo-controllable synthesis of complex organic compounds. 3,4-ETHF is synthesized with a conversion >95% and a selectivity >99% through a heterogeneous epoxidation of 2,5-dihydrofuran (DHF) with hydrogen peroxide in the liquid phase over a novel titanosilicate catalyst, Ti-MWW.
Co-reporter:Xinqing Lu, Haihong Wu, Jingang Jiang, Mingyuan He, Peng Wu
Journal of Catalysis (October 2016) Volume 342() pp:173-183
Publication Date(Web):1 October 2016
DOI:10.1016/j.jcat.2016.07.020
•The liquid-phase epoxidation of propylene over formed Ti-MWW was investigated.•The reversible deactivation of Ti-MWW is mainly caused by the solvolysis of PO.•Adding an appropriate amount of ammonia enhances the PO yield effectively.•Fluorine implantation enhances the lifetime of Ti-MWW remarkably in the HPPO process.The liquid-phase epoxidation of propylene to propylene oxide (PO) over formed titanosilicate catalysts was investigated in a fixed-bed reactor. The effects of reaction temperature, n(C3=)/n(H2O2) molar ratio, and weight hourly space velocity (WHSV) of H2O2 or solvent on the catalytic performance of the formed Ti-MWW catalyst have been extensively studied. Adding an appropriate amount of ammonia to the reaction mixture prolonged the catalyst lifetime effectively. The main byproduct of propylene glycol (PG) and other heavy byproducts with high boiling points were deposited inside zeolite micropores, which corresponded to the main reason for the catalyst deactivation. The high-temperature calcination in air recovered readily the reactivity of the deactivated catalyst. Fluorine implantation remarkably enhanced the reactivity and lifetime of the catalyst in the hydrogen peroxide propylene oxide (HPPO) process, exhibiting a PO selectivity of >99%.Download high-res image (138KB)Download full-size image
Co-reporter:Jianghong Ding, Peng Wu
Applied Catalysis A: General (November 2014) Volume 488() pp:86-95
Publication Date(Web):November 2014
DOI:10.1016/j.apcata.2014.09.038
Co-reporter:Le Xu, Jianghong Ding, Yulin Yang, Peng Wu
Journal of Catalysis (January 2014) Volume 309() pp:1-10
Publication Date(Web):1 January 2014
DOI:10.1016/j.jcat.2013.08.021
•Ammoximation of cyclohexanone has been compared between Ti-MOR, TS-1, and Ti-MWW.•Ti-MOR, TS-1, and Ti-MWW serve as efficient catalysts for the formation of cyclohexanone oxime.•Ti-MOR and TS-1 catalyze the oxidation of ammonia by hydrogen peroxide to hydroxylamine effectively.•Ti-MWW exhibits a high catalytic activity for the decomposition of hydroxylamine.•Ion exchange with neutral alkali salts improves hydroxylamine formation and thus ketone amomximation.A comprehensive investigation has been carried out to study hydroxylamine formation and decomposition in the ammoximation of cyclohexanone over three typical microporous titanosilicates, Ti-MOR, Ti-MWW, and TS-1. Cyclohexanone ammoximation involved the formation and decomposition of hydroxylamine intermediate as well as noncatalytic oximation. Ti-MOR and TS-1 were found to be extremely effective catalysts for hydroxylamine formation by ammonia oxidation with hydrogen peroxide; meanwhile, they showed low catalytic activity for hydroxylamine decomposition. Thus, Ti-MOR and TS-1 were capable of achieving high hydroxylamine yields such as 82.7–95.1% and cyclohexanone conversion of >97%. Serving as an effective ammoximation catalyst, however, Ti-MWW was less efficient for hydroxylamine formation because of its high catalytic activity for the decomposition of hydroxylamine. Ion exchange with alkali metal cations has been carried out on titanosilicates to remove the hydroxyl-related acid sites. Introduction of alkali cations by ion exchange removed the acid sites of titanosilicates selectively, resulting in enhanced activity for hydroxylamine formation and ammoximation without altering the hydroxylamine decomposition, and the exchange then enhanced their catalytic activity significantly for both hydroxylamine formation and ammoximation.Graphical abstractLiquid-phase ammoximation on titanosilicates involves the formation of hydroxylamine intermediate from catalytic oxidation of ammonia by hydrogen peroxide and subsequent oximation with ketone to oxime. TS-1, Ti-MOR, and Ti-MWW differ greatly in their effects on the formation and decomposition of hydroxylamine. A controlled ion exchange with neutral alkali salts can improve the formation of hydroxylamine and thus the ammoximation of cyclohexanone to oxime.Download high-res image (90KB)Download full-size image
Co-reporter:Yulin Yang, Jianghong Ding, Binshen Wang, Jing Wu, Chen Zhao, Guohua Gao, Peng Wu
Journal of Catalysis (December 2014) Volume 320() pp:160-169
Publication Date(Web):1 December 2014
DOI:10.1016/j.jcat.2014.10.008
•Fluorine-planted Ti-MOR catalysts have been successfully post-synthesized.•The fluorination in methanol is superior to that in water to prepare active oxidation catalysts.•The generated SiO3/2F units increase the electropositivity of the active Ti sites.•Fluorine-implanting enhances remarkably the activity of Ti-MOR in the ammoximation of ketones.Fluorine species were implanted into the framework of Ti-MOR by post-treatment with fluorides in order to modify the microenvironment around Ti active sites and then to improve their catalytic activity in liquid-phase oxidation. The effects of NH4F amount, fluorination temperature, and solvent on the catalytic performance of F-Ti-MOR were investigated in detail. Methanol was found to be superior to water in fluorination. Fluorine implantation increased the electropositivity of Ti active sites through forming SiO3/2F units in the neighborhood, which enhanced the catalytic performance in the ammoximation of cyclohexanone remarkably. F-Ti-MOR prepared under optimized fluorination conditions showed a cyclohexanone conversion of 99% in comparison to only 30% conversion given by primitive Ti-MOR. Meanwhile, the implanted fluorine species captured the organic molecules with a relatively large dimension tightly, creating enormous steric hindrances that prevented other molecules, in particular those with bulky molecular dimensions, from diffusing into channels freely. Thus, F-Ti-MOR showed much lower activity than Ti-MOR in the hydroxylation of aromatics.Download high-res image (172KB)Download full-size image
Co-reporter:Jianggan Wang, Le Xu, Kun Zhang, Honggen Peng, Haihong Wu, Jin-gang Jiang, Yueming Liu, Peng Wu
Journal of Catalysis (April 2012) Volume 288() pp:16-23
Publication Date(Web):1 April 2012
DOI:10.1016/j.jcat.2011.12.023
A lamellar titanosilicate (LTS-1) was hydrothermally synthesized by employing a bifunctional surfactant as the structure-directing agent (SDA). Highly crystalline LTS-1 was obtained at an optimal SDA/Si molar ratio of 0.04. As-synthesized LTS-1 possessed a multilayer structure, which was constructed from a collection of 2-nm zeolite nanosheets and interlayer SDA molecules. Removing the intercalated organic species induced irregular layer stacking to a certain extent, leading to intracrystal mesopores of ca. 3.2 nm in diameter. The catalytic performance of LTS-1 was investigated in the epoxidation of various bulky alkenes with tert-butyl hydroperoxide, cumene hydroperoxide, or aqueous H2O2. LTS-1 was more active than conventional titanosilicates for reactions involving bulky alkenes and oxidants, and it was immune to Ti leaching and irreversible deactivation.Graphical abstractMutilayered titanosilicate consisting of MFI-type nanosheets was hydrothermally synthesized with an aid of a bifunctional structure-directing agent. It proved to be highly active, selective, and reusable for the liquid-phase epoxidation of bulky alkenes using organic hydroperoxides as the oxidants.Download high-res image (167KB)Download full-size imageHighlights► MFI-type mutilayered titanosilicate (LTS-1) was synthesized. ► LTS-1 is a hydrid material containing 0.5 nm micropores and 3.2 nm mesopores. ► LTS-1 is characteristic of titanosilicates and Ti-containing mesoporous silica. ► LTS-1 is robust and reusable in selective epoxidation of cyclic alkenes. ► LTS-1 is more active than TS-1 and Ti-MCM-41 in the epoxidation of propylene.
Co-reporter:Zhiguo Zhu, Hao Xu, Jingang Jiang, Xue Liu, Jianghong Ding, Peng Wu
Applied Catalysis A: General (5 June 2016) Volume 519() pp:155-164
Publication Date(Web):5 June 2016
DOI:10.1016/j.apcata.2016.04.001
Co-reporter:Fen Song, Yueming Liu, Lingling Wang, Haijiao Zhang, Mingyuan He, Peng Wu
Applied Catalysis A: General (31 July 2007) Volume 327(Issue 1) pp:22-31
Publication Date(Web):31 July 2007
DOI:10.1016/j.apcata.2007.04.025
Co-reporter:Yong-Jun Ji, Bin Zhang, Le Xu, Haihong Wu, Honggen Peng, Li Chen, Yueming Liu, Peng Wu
Journal of Catalysis (27 October 2011) Volume 283(Issue 2) pp:168-177
Publication Date(Web):27 October 2011
DOI:10.1016/j.jcat.2011.08.007
A shape-selective core/shell-structured Al-MWW@B-MWW composite catalyst has been hydrothermally synthesized through isomorphically overgrowing borosilicate on premade MCM-22 aluminosilicate. The secondary growth of borosilicate enlarged obviously the thickness of the platelet crystallites of MCM-22 and increased the surface Si/Al ratio from 16 to 222. The Fourier transform infrared (FTIR) spectra of adsorbed 2,6-di-tert-butylpyridine indicated that the Brønsted acid sites located on the external surface were virtually covered completely by the generated B-MWW layer, whereas those acid sites within channels were still accessible and detectable by using pyridine or ammonia as probing molecules. When applied to the disproportionation of toluene on a fixed-bed reactor, the Al-MWW@B-MWW composite catalysts exhibited significantly enhanced para-xylene selectivity in comparison with normal MCM-22 and its physical mixture with B-MWW. Al-MWW@B-MWW’s unique catalytic behaviors were ascribed to an effective suppression of para-xylene isomerization as a result of removal of non-shape-selective acid sites on the external surface.Graphical abstractCore/shell-structured MWW-type zeolites prepared by isomorphic overgrowth of borosilicate on premade MCM-22 crystallites are highly shape-selective materials for the disproportionation of toluene as a result of suppressing the isomerization of para-xylene on the external surface of crystallites.Download high-res image (190KB)Download full-size imageHighlights► Isomorphic overgrowth of borosilicate on MCM-22 leads to a core/shell-structured zeolite. ► Secondary growth of borosilicate removes the strong acid sites on the external surface. ► Al-MWW@B-MWW is highly shape selective to toluene disproportionation. ► The removal of surface acidity suppresses the isomerization of para-xylene on the crystallite surface.
Co-reporter:Hao Xu, Yingtian Zhang, Haihong Wu, Yueming Liu, Xiaohong Li, Jingang Jiang, Mingyuan He, Peng Wu
Journal of Catalysis (25 July 2011) Volume 281(Issue 2) pp:263-272
Publication Date(Web):25 July 2011
DOI:10.1016/j.jcat.2011.05.009
Mesoporous titanosilicate with the MOR topology, denoted as Ti-Meso-MOR, was postsynthesized from commercially available mordenite by sequential acid, alkaline, acid, and TiCl4 vapor treatments, and its catalytic oxidation properties were investigated in detail in liquid-phase oxidation reactions with hydrogen peroxide as an oxidant. A controllable acid leaching was first carried out on H-mordenite (Si/Al = 7.8) to induce a partial dealumination to Si/Al = 80, which was suitable for constructing secondary mesopores by subsequent alkaline treatment. Alkaline treatment-induced desilication introduced a large number of intracrystal mesopores. Tetracoordinated Ti species were then inserted into the resultant mesoporous mordenite with a high dealumination degree (Si/Al = 145) through the gas–solid reaction with TiCl4 vapor at elevated temperatures. In comparison with conventional Ti-MOR and TS-1, Ti-Meso-MOR thus prepared exhibited an improved catalytic activity in the hydroxylation of toluene and the ammoximation of cyclohexanone as well. Moreover, Ti-Meso-MOR proved to be a robust catalyst for continuous ammoximation since the mesopores minimized diffusion limitation and suppressed coke formation efficiently.Graphical abstractMesoporous titanosilicate with the MOR topology, postsynthesized by sequential dealumination, desilication, and TiCl4 vapor treatment, are highly active for the liquid-phase ammoximation of cyclohexanone and hydroxylation of toluene with hydrogen peroxide as oxidant.Download high-res image (139KB)Download full-size imageHighlights► MOR-type aluminosilicate was converted into mesoporous zeolite by post-desilication. ► Tetrahedral Ti species were incorporated into the Al-deficient sites by secondary synthesis, leading to mesoporous titanosilicate, Ti-Meso-MOR. ► Possessing an improved accessibility to Ti active sites, Ti-Meso-MOR is highly active for the liquid-phase oxidations with hydrogen peroxide.
Co-reporter:Haihong Wu, Yueming Liu, Lingling Wang, Haijiao Zhang, Mingyuan He, Peng Wu
Applied Catalysis A: General (22 March 2007) Volume 320() pp:173-180
Publication Date(Web):22 March 2007
DOI:10.1016/j.apcata.2007.01.027
Co-reporter:Lingling Wang, Yueming Liu, Wei Xie, Haijiao Zhang, Haihong Wu, Yongwen Jiang, Mingyuan He, Peng Wu
Journal of Catalysis (15 February 2007) Volume 246(Issue 1) pp:205-214
Publication Date(Web):15 February 2007
DOI:10.1016/j.jcat.2006.12.003
The catalytic properties of Ti-MWW in the epoxidation of allyl chloride (ALC) with hydrogen peroxide to epichlorohydrin (ECH) were studied by comparing these properties with those of TS-1, Ti-MOR, and Ti-Beta. Issues concerning the stability and reuse of Ti-MWW were also considered. The investigation on various reaction parameters showed that Ti-MWW is an active and selective catalyst for ALC epoxidation. Ti-MWW prefers aprotic solvents, such as acetonitrile and acetone, over protic alcohols, which is favorable for suppressing the formation of solvolysis byproducts. ALC conversion and ECH selectivity were both as high as 99% on Ti-MWW. 3-Chloro-1,2-propanediol and other heavy byproducts with high boiling points had a negative effect on ALC conversion for both TS-1 and Ti-MWW. A novel secondary synthesis caused a structural rearrangement of the Ti-MWW framework and then improved its stability.
Co-reporter:Yong Wang, Yueming Liu, Xiaohong Li, Haihong Wu, Mingyuan He, Peng Wu
Journal of Catalysis (10 September 2009) Volume 266(Issue 2) pp:258-267
Publication Date(Web):10 September 2009
DOI:10.1016/j.jcat.2009.06.016
The intermolecular condensation of ethylenediamine (EDA) to 1,4-diazabicyclo[2.2.2]octane or triethylenediamine (TEDA) has been carried out over various titanosilicate catalysts. Superior to Ti-MWW, Ti-Beta, Ti-FER, and Ti-MOR, TS-1 showed higher EDA conversion and TEDA selectivity. The effects of reaction parameters, Ti content, and crystal size on the EDA condensation over TS-1 have been investigated. The mechanism for the TS-1-catalyzed condensation of EDA has also been considered. The acid sites, originated from the Si–OH groups adjacent to the “open” Ti sites, were assumed to contribute to the intermolecular condensation of EDA, whereas the Lewis acid sites directly related to Ti(IV) ions were not the true active sites. The primary intermolecular condensation of EDA to 1,4-diazacyclohexane or piperazine (PIP) took place mainly inside the micropores of the MFI structure, while the secondary condensation of PIP with EDA to TEDA was favored by the acid sites located near the pore entrance and on the outer surface of crystals.The internal silanols of TS-1 are active and selective for the intermolecular condensation of ethylenediamine to piperazine and triethylenediamine.Download high-res image (69KB)Download full-size image
Co-reporter:Xinqing Lu, Wen-Juan Zhou, Haihong Wu, Armin Liebens, Peng Wu
Applied Catalysis A: General (10 April 2016) Volume 515() pp:
Publication Date(Web):10 April 2016
DOI:10.1016/j.apcata.2016.02.001
•Selective synthesis of ethylene oxide (EO) is realized through epoxidation of ethylene over titanosilicates.•Ti-MWW is superior to TS-1, Ti-Beta and Ti-MOR in terms of activity and EO selectivity.•Ti-MWW suppresses effectively the formation of byproducts in an appropriate aprotic solvent of acetonitrile.•The formation of heavy products like ethylene glycol may deactivate the Ti-MWW catalyst, which can be recovered by calcination.Liquid-phase epoxidation of ethylene to ethylene oxide (EO) with H2O2 over various titanosilicate catalysts like Ti-MWW, TS-1, Ti-MOR and Ti-Beta has been investigated. The effects of solvent, catalyst amount, reaction pressure, temperature and time on the catalytic performance of Ti-MWW have been studied in detail. Ti-MWW preferred acetonitrile as a solvent and showed the highest reactivity and EO selectivity among the titanosilicate catalysts investigated. Under optimized reaction conditions, Ti-MWW gave a EO selectivity high as 97.9% as well as a reasonable utilization efficiency of H2O2 of 77.7%. Ti-MWW was gradually deactivated after repeated use in ethylene epoxidation. High-temperature calcination easily recovered the catalytic activity of deactivated Ti-MWW after removing ethylene glycol (EG) and other heavy byproducts with high boiling points that were deposited inside micropores. The issues of molecular dimension and reactivity have also been considered by comparing the epoxidation of linear alkenes with different lengths (C2 to C6) between two representative titanosilicates Ti-MWW and TS-1. Ethylene, with the smallest dynamic diameter but containing electron-deficient CC double bonds, was more difficult to be epoxidized than other alkenes with higher intrinsic activities.Download high-res image (138KB)Download full-size image
Co-reporter:Lingling Wang, Yong Wang, Yueming Liu, Haihong Wu, Xiaohong Li, Mingyuan He and Peng Wu
Journal of Materials Chemistry A 2009 - vol. 19(Issue 45) pp:NaN8602-8602
Publication Date(Web):2009/09/24
DOI:10.1039/B910886F
Silylation of Ti-MWW lamellar precursor and subsequent calcination constructed an interlayer expanded structure, leading to novel titanosilicates with large pores. The silylating agents suitable for pore expansion were diethoxydimethylsilane, trimethylethoxysilane and triethoxymethylsilane containing methyl groups, which inhibited the intermolecular condensation of silanes effectively. In contrast to well-known 3D Ti-MWW with only medium pores of 10-membered rings, the silylation led to new crystalline structures with more open pores by ca. 2.5 Å, as evidenced by the shift of layer-related diffractions to the lower-angle region in XRD patterns and the enlarged interlayer pores in HRTEM images. The interlayer expanded Ti-MWW was prepared readily from the corresponding hydrothermally synthesized precursors with a wide range of Ti contents (Si/Ti = 20–100). In addition, the pore expansion by silylation was realized under mild acid conditions with 0.1 M HNO3. The interlayer expanded Ti-MWW exhibited 3–7 times higher turnover number than 3D Ti-MWW in the oxidation of cyclohexene with H2O2.
Co-reporter:Xinqing Lu, Wen-Juan Zhou, Yejun Guan, Armin Liebens and Peng Wu
Catalysis Science & Technology (2011-Present) 2017 - vol. 7(Issue 12) pp:NaN2631-2631
Publication Date(Web):2017/05/16
DOI:10.1039/C7CY00428A
Fluorine-implanted titanosilicate Ti-MWW, with greatly enhanced catalytic performance in the liquid-phase epoxidation of ethylene with aqueous hydrogen peroxide, has been post-synthesized by fluorinating conventional Ti-MWW with NH4F. The effects of fluorination conditions, such as solvent, the amount of NH4F addition and temperature, on the zeolite structure and the catalytic performance of the resultant fluorine-implanted Ti-MWW were investigated in detail. Methanol proved to be a better solvent for fluorination than water in terms of preserving the crystalline structure and improving the selective epoxidation activity. Fluorine-implanting generated SiO3/2F species in the framework to increase the electropositivity of the tetrahedral Ti active sites. A stronger hydrogen-bond was thus formed between Hend in Ti–Oα–Oβ–Hend intermediates and the adjacent Si–F species, which were helpful to significantly increase the catalytic activity in the epoxidation of ethylene with H2O2. In addition, the fluorination also generated secondary mesopores which are useful to improve the accessibility of the active sites, making the fluorine-implanted Ti-MWW catalyst possess better reusability than the parent one.
Co-reporter:Darui Wang, Bo Wang, Yu Ding, Haihong Wu and Peng Wu
Chemical Communications 2016 - vol. 52(Issue 87) pp:NaN12820-12820
Publication Date(Web):2016/09/30
DOI:10.1039/C6CC06779D
A hierarchically core/shell structured base–acid bifunctional catalyst, ZSM-5@Mg3Si4O9(OH)4, was successfully prepared through a simple hydrothermal reaction between the silica species on the ZSM-5 crystal surface and the Mg2+ source in basic solution. The obtained catalyst showed superior activity and stability in one-pot deacetalization-Knoevenagel condensation reaction.
Co-reporter:Rong Xing, Yueming Liu, Haihong Wu, Xiaohong Li, Mingyuan He and Peng Wu
Chemical Communications 2008(Issue 47) pp:
Publication Date(Web):
DOI:10.1039/B815186E
Co-reporter:Zhendong Wang, Yueming Liu, Jin-gang Jiang, Mingyuan He and Peng Wu
Journal of Materials Chemistry A 2010 - vol. 20(Issue 45) pp:NaN10199-10199
Publication Date(Web):2010/09/22
DOI:10.1039/C0JM01948H
Hollow and core/shell ZSM-5 spheres were simply synthesized through in situ transformation of mesoporous silica spheres (MSS) into MFI-type zeolite with the assistant of isopropylamine (IPA) as a structure-directing agent (SDA). IPA, with a mild structure-directing ability for the construction of MFI structure, triggered a stepwise crystallization of MSS after Al addition. First, the sphere surface was crystallized to a shell of ZSM-5 crystals. The silica and alumina species in the core condensed and crystallized to ZSM-5 thereafter, forming zeolite crystal aggregates inside the spheres. The obtained ZSM-5 spheres were highly crystalline materials and maintained the shape of pristine MSS, but exhibited a hollow and core/shell structure. The techniques of XRD, FT-IR, SEM, N2 adsorption-desorption, 29Si and 27Al MAS NMR were employed to trace the crystallization process, which allowed us to propose a “templating and surface to core” crystallization mechanism. This strategy may serve as an alternative way for synthesizing hollow zeolite spheres.
Co-reporter:Rong Xing, Haihong Wu, Xiaohong Li, Zhonglin Zhao, Yueming Liu, Li Chen and Peng Wu
Journal of Materials Chemistry A 2009 - vol. 19(Issue 23) pp:NaN4011-4011
Publication Date(Web):2009/05/07
DOI:10.1039/B822659H
A series of amine- or diamine-functionalized mesopolymers with cubic or hexagonal mesostructures have been prepared by two-step chemical modification procedures involving chloromethylation of the FDU-type mesoporous resol materials first with chloromethyl methyl ether, and a subsequent amination reaction with methylamine, dimethylamine or ethylenediamine. Various techniques such as XRD, SEM, TEM, N2 adsorption, FTIR, 13C NMR and elemental analysis have been adopted to track the functionalization processes, and to characterize the structures, porosity, chemical compositions and basicity of the materials. The amino group-containing mesopolymer materials prove to be efficient heterogeneous base catalysts in Knoevenagel condensation of benzaldehyde with ethyl cyanoacetate. The possible mechanisms of Knoevenagel reaction on different mesopolymer base catalysts have also been discussed.
Co-reporter:Le Xu, Yingjie Ren, Haihong Wu, Yueming Liu, Zhendong Wang, Yingtian Zhang, Jiajia Xu, Honggen Peng and Peng Wu
Journal of Materials Chemistry A 2011 - vol. 21(Issue 29) pp:NaN10858-10858
Publication Date(Web):2011/06/16
DOI:10.1039/C1JM10483G
Hierarchically ordered materials with core/shell structures were synthesized through a layer-by-layer approach. The novel microporous/mesoporous hybrid materials were composed of a TS-1 zeolite particle for the core and mesoporous silica for the shell. The as-synthesized TS-1 crystals were modified with polydiallyldimethylammonium chloride to make their external surface positively charged, which induced an oriented self-assembly of tetraethoxysilane (TEOS) with cetyltrimethyl ammonium bromide on the TS-1 particle surface to form a shell of mesophase silica. The thickness of the mesoporous silica shell was controlled to be in the range 30–55 nm by changing the amount of TEOS added in the synthesis. The mesoporous channels in the shell were perpendicular to the zeolite core, which made the micropores inside the core accessible from the outside through the mesopores. Taking advantage of the confining effect of the mesopores, Au nanoparticles were incorporated into the shell, resulting in bifunctional catalysts which were more selective than conventional Au/TS-1 catalysts in the direct epoxidation of propylene to propylene oxide with H2 and O2.
Co-reporter:Chen-Geng Li, Le Xu, Peng Wu, Haihong Wu and Mingyuan He
Chemical Communications 2014 - vol. 50(Issue 99) pp:NaN15767-15767
Publication Date(Web):2014/10/28
DOI:10.1039/C4CC07620F
Organic–inorganic hybrid zeolites with the MFI-type lamellar structure serve as efficient solid Lewis base catalysts for solvent-free synthesis of a variety of cyclic carbonates from corresponding epoxides and carbon dioxide. The ion-exchange with iodide, in particular, renders these materials an excellent catalytic activity and good recyclability.
Co-reporter:Honggen Peng, Le Xu, Liyan Zhang, Kun Zhang, Yueming Liu, Haihong Wu and Peng Wu
Journal of Materials Chemistry A 2012 - vol. 22(Issue 28) pp:NaN14227-14227
Publication Date(Web):2012/04/30
DOI:10.1039/C2JM31788E
Core–shell structured TS-1@mesocarbon (TS-1@MC) materials with mesoporous carbon as the shell and microporous TS-1 titanosilicate as the core were synthesized through a nanocasting and selective silica etching strategy. The faithful replica structure was constructed from the composite of TS-1@mesosilica and carbon when tetrapropylammonium hydroxide (TPAOH) was employed to selectively remove the amorphous mesosilica shell while the core zeolite crystal structure was not destroyed. In contrast, the protective effect was not seen when sodium hydroxide or hydrogen fluoride was employed as a silica-leaching agent. The obtained TS-1@MC had a bimodal pore structure consisting of 2.9 nm mesopores in the carbon shell and 0.51 nm micropores in the TS-1 core. Its specific surface area and total pore volume reached 883 m2 g−1 and 0.63 cm3 g−1, respectively. TS-1@MC was used as the support to load palladium nanoparticles (Pd NPs) in the carbon shell. Having an average particle size of approximately 2 nm, the Pd NPs were highly dispersed and confined in the mesopores of the carbon shell. Pd/TS-1@MC thus obtained served as an efficient tandem catalyst in the direct epoxidation of propylene with hydrogen and oxygen.
Co-reporter:Peng Ji, Kun Lu, Xinqing Lu, Hao Xu and Peng Wu
Dalton Transactions 2017 - vol. 46(Issue 18) pp:NaN5780-5780
Publication Date(Web):2017/03/28
DOI:10.1039/C7DT00640C
Ti-SSZ-70 and Ti-ECNU-6, with identical intralayer structures but distinct interlayer connections, were prepared from similar synthetic gels free of alkali metal ions and boric acid. Ti-SSZ-70, composed of vertically misaligned MWW layers, was transferred to Ti-ECNU-6, structurally analogous to the Ti-MWW zeolite with a well-aligned layer stacking, upon the addition of an appropriate amount of hexamethyleneimine to the gel. These two titanosilicate catalysts exhibited outstanding catalytic activities in the liquid-phase alkene epoxidation.
Co-reporter:Le Xu, Da-Ding Huang, Chen-Geng Li, Xinyi Ji, Shaoqing Jin, Zhaochi Feng, Fei Xia, Xiaohong Li, Fengtao Fan, Can Li and Peng Wu
Chemical Communications 2015 - vol. 51(Issue 43) pp:NaN9013-9013
Publication Date(Web):2015/04/17
DOI:10.1039/C5CC02321A
A novel organic–inorganic layered titanosilicate consisting of Ti-containing MWW-type nanosheets and piperidine ligands was constructed. It exhibited an unprecedented high catalytic activity and recyclability in alkene epoxidation.
Co-reporter:Hong-gen Peng, Le Xu, Haihong Wu, Kun Zhang and Peng Wu
Chemical Communications 2013 - vol. 49(Issue 26) pp:NaN2711-2711
Publication Date(Web):2013/02/08
DOI:10.1039/C3CC38546A
A center radially fibrous silica encapsulated TS-1 zeolite (TS-1@KCC-1) has been synthesized in a microemulsion system for the first time. Supporting the Rh(OH)3 species, this novel core–shell structured material serves as a robust bifunctional catalyst for one-pot synthesis of benzamide from benzaldehyde, ammonia and hydrogen peroxide, in which the aldehyde ammoximation and oxime rearrangement occur in a tandem way.
Co-reporter:Chen-Geng Li, Yiqun Lu, Haihong Wu, Peng Wu and Mingyuan He
Chemical Communications 2015 - vol. 51(Issue 80) pp:NaN14908-14908
Publication Date(Web):2015/08/18
DOI:10.1039/C5CC05278E
A hierarchical titanosilicate, with epitaxially grown MFI nanosheets on microsized TS-1 crystals, has been prepared through a desilication–recrystallization method using a diammonium surfactant as the secondary structure-directing agent (SDA). This core/shell material features multiple mesoporosities, significantly improved epoxidation activity as well as easy separation in synthesis and catalytic reactions.
Co-reporter:Xinyi Ji, Le Xu, Xin Du, Xinqing Lu, Wanpeng Lu, Junliang Sun and Peng Wu
Catalysis Science & Technology (2011-Present) 2017 - vol. 7(Issue 13) pp:NaN2885-2885
Publication Date(Web):2017/05/31
DOI:10.1039/C7CY00756F
A novel multilamellar titanosilicate composed of MWW-type nanosheets, Ti-ECNU-7P layered precursor, was directly synthesized for the first time with the assistance of boron atoms as the crystallization-supporting agent and a simple surfactant cetyltrimethylammonium bromide (CTAB) as the interlayer swelling and pillaring agent. The new Ti-ECNU-7P materials were hydrothermally synthesized readily in a wide Si/Ti molar ratio range of 10–200, when the Si/B molar ratio was 10. Ti-ECNU-7P possessed a multilamellar mesostructure, which was constructed via alternate stacking of 2.5 nm MWW zeolite nanosheets and ca. 2.4 nm CTAB molecules. This lamellar titanosilicate possessed large interlayer spacing hardly achieved by conventional hydrothermal synthesis. Subsequent acid treatment and calcination on the multilamellar precursor effectively removed the extraframework Ti species, the organic species intercalated and the majority of framework boron atoms, leading to a hierarchical titanosilicate Ti-ECNU-7 catalyst with relatively high external surface area and high concentration of Ti species on the crystal surface. The catalytic performance of hierarchical Ti-ECNU-7 nanosheets was comprehensively investigated and compared with that of typical titanosilicates in the epoxidation of various bulky alkenes with different oxidants, including aqueous H2O2, tert-butyl hydroperoxide and cumene hydroperoxide. Owing to the hierarchical architecture and more accessible active sites on the external surface, the hierarchical Ti-ECNU-7 catalyst proved to be more active than conventional titanosilicates for selective oxidations involving either bulky substrates or oxidants. Additionally, it was robust against Ti leaching and irreversible deactivation.
Co-reporter:Darui Wang, Le Xu and Peng Wu
Journal of Materials Chemistry A 2014 - vol. 2(Issue 37) pp:NaN15545-15545
Publication Date(Web):2014/07/28
DOI:10.1039/C4TA02740J
A series of well-defined, core–shell-structured composite materials comprising microporous/mesoporous ZSM-5 as core and mesoporous aluminosilicate as shell were synthesized by combining controlled desilication using sodium hydroxide solution with subsequent self-assembly using a triblock copolymer. An aluminosilicate shell with uniform mesopores was grown closely around the crystals of mesoporous ZSM-5, with a tunable thickness of 60–300 nm, by adjusting the extent of desilication. The obtained composite zeolites exhibited a hierarchical porosity containing the original regular MFI micropores (ca. 0.56 nm) and desilication-induced, randomly distributed mesopores (5–50 nm), both within the core ZSM-5 crystals, as well as relatively uniform mesopores (ca. 6 nm) inside the shell part on the zeolite surface. The mesoporous aluminosilicate shell, self-assembled from the MFI zeolite fragments as a result of partially dissolved ZSM-5 crystals, demonstrated weak acidity and much higher hydrothermal stability in comparison to the shell synthesized by the additional silica source. Taking advantage of the confining effect of the mesopores, Pt nanoparticles were incorporated into the mesoporous shells, giving rise to bifunctional catalysts, which exhibited a higher selectivity of C5–C11 liquid products compared to the conventional Pt/ZSM-5 catalyst in the hydrocracking of n-hexadecane.
Co-reporter:Xiangqing Fang, Qiang Wang, Anmin Zheng, Yueming Liu, Yuning Wang, Xiujuan Deng, Haihong Wu, Feng Deng, Mingyuan He and Peng Wu
Catalysis Science & Technology (2011-Present) 2012 - vol. 2(Issue 12) pp:NaN2435-2435
Publication Date(Web):2012/07/25
DOI:10.1039/C2CY20446K
Fluorine species were successfully implanted into a MWW-type titanosilicate via post-treatment, which generates the SiO3/2F units in the zeolite framework. The incorporated fluorine species significantly improved the catalytic performance in the epoxidation of alkenes as a result of enhancing the Lewis acid strength and the hydrophobicity of the zeolite.
Co-reporter:Darui Wang, Lin Zhang, Li Chen, Haihong Wu and Peng Wu
Journal of Materials Chemistry A 2015 - vol. 3(Issue 7) pp:NaN3521-3521
Publication Date(Web):2014/12/16
DOI:10.1039/C4TA06438K
Mesoporous ZSM-5 zeolites with unique hydrocarbon cracking properties have been postsynthesized from conventional ZSM-5 samples using small molecular organic amine-assisted desilication technique. The parent ZSM-5 zeolites, with regular crystal size of 1–2 μm and Si/Al ratios of 15–500, were first hydrothermally synthesized using inorganic silicon and aluminum sources and piperidine as structure-directing agent (SDA) with the assistance of active seeds. Controllable mesopores were successfully introduced into as-synthesized ZSM-5 crystals by alkaline-derived desilication with the addition of piperidine or hexamethyleneimine. The addition of organic amines shielded the zeolite crystals from extensive dissolving by NaOH attacking. The mesopores were thus generated controllably within zeolite crystals and also minimized the loss of microporosity and solid acidity. The incorporation of mesopores made the micropores well interconnected, shortened the average diffusion path lengths as well as maintained more catalytic active sites showing a higher propylene yield and a longer lifetime in the cracking of n-hexane.
Co-reporter:Zhixia Deng, Yulin Yang, Xinqing Lu, Jianghong Ding, Mingyuan He and Peng Wu
Catalysis Science & Technology (2011-Present) 2016 - vol. 6(Issue 8) pp:NaN2615-2615
Publication Date(Web):2016/01/05
DOI:10.1039/C5CY02002F
The epoxidation of methallyl chloride (MAC) to 2-methyl epichlorohydrin (MECH) with H2O2 using TS-1 microsphere catalysts (TS-1-MS) in a continuous slurry reactor was investigated. The reaction parameters, which governed the effective conversion of hydrogen peroxide, selectivity to MECH epoxide and catalyst deactivation, were studied in detail by simulating the operating conditions of its industrial process. Under the most beneficial conditions, the process was successfully run for 257 h at a high MECH selectivity (>95%) as well as a high effective conversion of hydrogen peroxide (>97%). The microsphere morphology and particle size were highly maintained for the deactivated TS-1-MS catalyst, which was regenerated readily by a combination of hydrogen peroxide washing and calcination. This research verified that it was possible to develop a green, safe and efficient route for producing MECH by direct epoxidation of MAC with hydrogen peroxide in a slurry reactor. Employing TS-1 microsphere aggregates as a catalyst exhibits the advantage of easy solid–liquid separation.
Co-reporter:Jianghong Ding, Le Xu, Yejun Yu, Haihong Wu, Shijie Huang, Yulin Yang, Jing Wu and Peng Wu
Catalysis Science & Technology (2011-Present) 2013 - vol. 3(Issue 10) pp:NaN2595-2595
Publication Date(Web):2013/07/18
DOI:10.1039/C3CY00471F
Acetaldehyde oxime has been synthesized though the liquid-phase ammoximation of acetaldehyde with ammonia and hydrogen peroxide over various titanosilicate catalysts. Titanium mordenite (Ti-MOR), prepared from highly dealuminated mordenite and TiCl4 vapor by a secondary synthesis method, was superior to TS-1 and Ti-MWW catalysts both in aldehyde conversion and in oxime selectivity. The reaction parameters were investigated systematically in a batch-type reactor for Ti-MOR, such as solvent effect, temperature, time, catalyst loading, amounts of ammonia and hydrogen peroxide relative to aldehyde as well as addition methods of the reactants. Under optimized conditions, Ti-MOR was capable of showing an aldehyde conversion of 99% and an oxime selectivity of 97%. In comparison with TS-1 and Ti-MWW, the advantage of Ti-MOR in acetaldehyde ammoximation was mainly attributed to its lower ability for oxidation to convert the aldehyde to acetic acid. There was almost no effect resulting from the addition mode of the reactants; Ti-MOR with its special characteristics was unique in catalytic behavior and easy handling. An overview of the reaction routes involved in acetaldehyde ammoximation has been provided.
Co-reporter:Hao Xu, Lili Jia, Haihong Wu, Boting Yang and Peng Wu
Dalton Transactions 2014 - vol. 43(Issue 27) pp:NaN10500-10500
Publication Date(Web):2014/02/21
DOI:10.1039/C4DT00120F
Nu-6(1) zeolite, the lamellar precursor of NSI topology, was firstly synthesized with 4′4-bipyridine as the structure-directing agent (SDA) and then subjected to HCl–EtOH treatment for the purpose of structural modification. Interlayer deconstruction and reconstruction took place alternately in this acid treatment. An intermediate named ECNU-4 was separated at the initial stage of this continuous treatment process, which exhibited a special X-ray diffraction pattern without obvious reflection peaks at low angles. The zeolitic structure in the intralayer sheets was supposed to be well preserved in ECNU-4, whereas the interlayer structure became extremely disordered. The ECNU-4 intermediate showed structural diversity. It was converted into the reconstructed and interlayer expanded zeolite IEZ-NSI without an external silicon source by prolonging the HCl–EtOH treatment to 24 h. Moreover, with a partially delaminated structure, ECNU-4 was easily interlayer swollen at room temperature with cetyltrimethyl ammonium bromide in the presence of tetrapropyl ammonium hydroxide. The swollen material was further sonicated to yield a more deeply delaminated zeolite, Del-Nu-6. ECNU-4 and Del-Nu-6 differed in delamination degree, structural disordering and textural properties, especially surface area.
Co-reporter:Darui Wang, Bing Ma, Bo Wang, Chen Zhao and Peng Wu
Chemical Communications 2015 - vol. 51(Issue 82) pp:NaN15105-15105
Publication Date(Web):2015/09/04
DOI:10.1039/C5CC06212H
Hierarchically porous zeolite supported metal nanoparticles are successfully prepared through a base-assisted chemoselective interaction between the silicon species on the zeolite crystal surface and metal salts, in which in situ construction of mesopores and high dispersion of metal species are realized simultaneously.
Co-reporter:Xiangqing Fang, Qiang Wang, Anmin Zheng, Yueming Liu, Longfei Lin, Haihong Wu, Feng Deng, Mingyuan He and Peng Wu
Physical Chemistry Chemical Physics 2013 - vol. 15(Issue 14) pp:NaN4938-4938
Publication Date(Web):2013/01/30
DOI:10.1039/C3CP44700F
F-Ti-MWW was post-synthesized by implanting fluorine species into a Ti-MWW framework through an acid treatment process in the presence of ammonium fluoride. The effects of NH4F addition amount, acid treatment temperature and precursor Ti content were investigated on the incorporation of F species, the zeolite structure and the coordination sites of Ti. Fluorine-implanting improved the surface hydrophobicity of the zeolite and altered the electropositivity nearby the tetrahedral Ti sites through forming the SiO3/2F and SiO4/2F− units. The negative effect of SiO4/2F− units in F-Ti-MWW was eliminated selectively by convenient anion-exchange with various alkali chlorides. F-Ti-MWW containing the SiO3/2F units possessed better catalytic activity and reusability, and a longer catalyst lifetime than conventional Ti-MWW.
![4-oxatricyclo[4.3.1.1~3,8~]undecan-5-one](http://img.cochemist.com/ccimg/21900/21898-84-0.png)
![4-oxatricyclo[4.3.1.1~3,8~]undecan-5-one](http://img.cochemist.com/ccimg/21900/21898-84-0_b.png)