Co-reporter:Jing Gu, Yanhua Jin, Yu Zhou, Mingjue Zhang, Yajing Wu and Jun Wang
Journal of Materials Chemistry A 2013 vol. 1(Issue 7) pp:2453-2460
Publication Date(Web):13 Dec 2012
DOI:10.1039/C2TA01009G
A facile one-pot method without organic templates and seeds is reported for the fabrication of framework-substituted heteroatomic zeolites for the first time. Such a breakthrough is achieved by the acidic co-hydrolysis of tetraethylorthosilicate (TEOS) with metal salts, followed by basic aging and hydrothermal crystallization. Fe(Mo, Ti, Co, Cr) MFI zeolites can be obtained with high crystallinity, thermal stability and tunable chemical composition, in which Fe3+ and Al3+ are proposed to act as co-structure-directing agents, inducing the growth of the zeolite crystal and their special poly-nanocrystalline morphology. Structural characterizations and Knoevenagel condensations were conducted to evidence the incorporation of Fe3+ into the MFI framework. The catalytic activity on the as-synthesized framework-substituted Fe-ZSM-5 is not only tens of times higher than that of Fe3+-exchanged or ferric oxide impregnated analogues, but also much higher than that of its as-calcined analogue, suggesting the unique ability of our method to inhibit the transfer of heteroatoms out of the framework. This easy, controllable and green new strategy may be extended to other heteroatomic MFI zeolites, and is potentially important for practical utilization.
Co-reporter:Pingping Zhao, Jun Wang, Guojian Chen, Yu Zhou and Jun Huang
Catalysis Science & Technology 2013 vol. 3(Issue 5) pp:1394-1404
Publication Date(Web):07 Feb 2013
DOI:10.1039/C3CY20796J
A new nitrile-tethered pyridinium polyoxometalate (POM) was prepared by anion-exchange of the ionic liquid precursor [N-butyronitrile pyridine]Cl ([C3CNpy]Cl) with the Keggin phosphovanadomolybdic acid H5PMo10V2O40 (PMoV2), and the obtained organic POM salt [C3CNpy]4HPMoV2 was characterized by XRD, SEM, TG, 1H NMR, 13C NMR, ESI-MS, CHN elemental analysis, nitrogen sorption experiment, and melting point measure. When used as a catalyst, [C3CNpy]4HPMoV2 causes the first example of reaction-controlled phase-transfer hydroxylation of benzene with H2O2, showing high activity and stable reusability. Based on spectral characterizations and comparisons of reaction results, plus the reversible color change between fresh and recovered catalyst, a unique reaction mechanism is proposed for understanding the highly efficient [C3CNpy]4HPMoV2-catalyzed phase-transfer catalysis. The formation of dissolvable active species [VO(O2)]+ is responsible for the phase-transfer behavior, while the intramolecular charge transfer and the protonated nitrile in cations accelerate the reaction and favor a better catalyst recovery rate.
Co-reporter:Yanyan Deng, Yu Zhou, Yue Yao and Jun Wang
New Journal of Chemistry 2013 vol. 37(Issue 12) pp:4083-4088
Publication Date(Web):18 Sep 2013
DOI:10.1039/C3NJ00665D
A solvothermal route was developed to synthesize nanosized nickel phosphides with controllable phase and morphology using non-toxic red phosphorus as the P3− ion source. The crystal phases and morphologies of nickel phosphides were facilely controlled by adjusting the counter anions of nickel salts and the solvents without additional additives. Four nickel sources (NiCl2·6H2O, Ni(CH3COO)2·4H2O, NiSO4·6H2O and Ni(NO3)2·6H2O) and six solvents (H2O, methanol, ethanol, glycol, glycerol and polyglycol) were applied in the synthesis. The obtained nickel phosphides were characterized by XRD, SEM and TEM. The results indicated that two pure phases of Ni2P and Ni12P5 with different exposition of the crystal surface and varied micro-morphologies can be achieved in this system, thus providing a facile way to prepare nickel phosphides with controllable phases and morphologies.
Co-reporter:Jianhong Wang, Jingyan Xie, Yu Zhou, Jun Wang
Microporous and Mesoporous Materials 2013 Volume 171() pp:87-93
Publication Date(Web):1 May 2013
DOI:10.1016/j.micromeso.2012.12.027
A new facile way was reported to incorporate high amount of chromium ions into the framework of BEA by a directly static hydrothermal route through the co-hydrolysis of TEOS with metal ions in acidic media. Various synthesis parameters including the co-hydrolysis route, Cr2O3/SiO2, alkalinity, and crystallization time were investigated to obtain the suitable conditions. The synthesized samples were characterized by IR, ICP, UV–vis and SEM. The results showed that the metal ions were incorporated into the crystal lattice of BEA. The catalytic performance was assessed in the oxidation of benzyl alcohol reaction, and the framework Cr demonstrated superior activity than impregnated Cr2O3 particles. Meanwhile, the recycling test of Cr-substituted β zeolite was studied for the first time, and the good catalytic stability gave a further proof of incorporation of Cr into zeolite framework.Graphical abstractA new facile way is applied to prepare Cr-substituted β zeolite by a directly static hydrothermal route through the co-hydrolysis of TEOS with metal ions in acidic media, which favors superior catalytic performance.Highlights► A new acidic co-hydrolysis route is applied to synthesize Cr-substituted BEA. ► The obtained zeolite exhibits high crystallization and superior Cr content. ► Framework Cr can improve the catalytic activity in oxidation reaction. ► The reusability of Cr-β is studied for the first time, showing good stability.
Co-reporter:Jing Gu;Yajing Wu;Yanhua Jin
Journal of Porous Materials 2013 Volume 20( Issue 1) pp:7-13
Publication Date(Web):2013 February
DOI:10.1007/s10934-012-9569-y
Ce and La incorporated ZSM-5 zeolitic materials with different metal loadings were synthesized via the multiple pH-adjusting procedures involving a co-hydrolysis of TEOS (tetraethyl-orthosilicate) with rare earth salts under a strong acidic condition, a further gelation under a weak acidic condition, and a final basic hydrothermal crystallization. Thus obtained Ce(La)-ZSM-5, as well as Ce or La ion-exchanged ZSM-5 samples, were characterized by XRD, SEM, TG, UV–vis, 29Si MAS NMR, FT-IR, N2-physisorption, and elemental analysis. The characterizations provide systematic and complementary evidences to demonstrate the incorporation of Ce(La) ions into the tetrahedral sites of ZSM-5 framework. The upper limits of the rare earth loadings in the synthesis gel and the final product are ca. 50 and 70 of the molar ratio of Si/Ce(La), respectively. It is observed that the synthesized Ce(La)-ZSM-5 zeolites possess an unusual morphology of microspheres that are assembled by numerous cubic prism-shaped nanocrystallines.
Co-reporter:Hualan Zhou;Jing Gu;Yajing Wu
Journal of Porous Materials 2013 Volume 20( Issue 3) pp:523-530
Publication Date(Web):2013 June
DOI:10.1007/s10934-012-9624-8
SUZ-4 zeolite was synthesized by the dry gel conversion (DGC) process with water vapor as gas phase, and characterized by XRD, SEM and N2 adsorption. The dry gel was prepared with the assistance of a small amount of crystalline seed and organic template tetraethylammonium hydroxide (TEAOH). Molar ratios of SiO2/Al2O3, KOH/SiO2, TEAOH/SiO2 and H2O/SiO2, amounts of seed and dry gel, types of silica sources, and crystallization temperature and time, were changed to optimize synthesis conditions. The results show that the DGC method leads to formation of SUZ-4 zeolite in a broad range of crystallization temperature 120–180 °C. Under the optimal conditions, i.e., SiO2/Al2O3 = 22.5, KOH/SiO2 = 0.44, TEAOH/SiO2 = 0.044, H2O/SiO2 = 22.2, seed amount = 0.1 wt%, fumed silica as the silica source, 160 °C and 5 days, SUZ-4 zeolite is obtained with a high crystallinity. Compared to hydrothermal synthesis, the present DGC approach employs far less amount of organic template and allows using inert fumed silica as silica source, producing smaller rod-like SUZ-4 zeolite crystals.
Co-reporter:Qi Wang;Yu Zhou;Xiao Lin
Journal of Porous Materials 2013 Volume 20( Issue 6) pp:1519-1523
Publication Date(Web):2013 December
DOI:10.1007/s10934-013-9738-7
Framework-substituted Co-mordenite zeolite was synthesized by a dry gel conversion (DGC) method, using inorganic raw materials of silica sol, aluminum sulfate, cobalt nitrate and sodium hydroxide. Typical synthesis conditions were Co/SiO2 = 0.01–0.05, SiO2/Al2O3 = 20–50, H2O/SiO2 = 40, Na2O/SiO2 = 0.4 molar ratios, 170 °C, and 3 days. The obtained samples were characterized by X-ray diffraction, UV–vis, scanning electron microscope, and nitrogen sorption technique. The results showed that Co ions were incorporated into the tetrahedral framework structure of mordenite without forming extra-framework Co species. Products obtained by the present all-inorganic systems possessed open micropores and required no traditional high-temperature calcination. The DGC approach also avoided the separation of the final product from solvent phase.
Co-reporter:Xuan Zhang;Dan Mao;Yan Leng;Yu Zhou
Catalysis Letters 2013 Volume 143( Issue 2) pp:193-199
Publication Date(Web):2013/02/01
DOI:10.1007/s10562-012-0939-5
The heteropolyanion-based ionic liquid (IL) material [MIMPS]3PW12O40, propane sulfoacid-functionalized imidazolium salt of phosphotungstate, was used as a solid catalyst for liquid-phase Beckmann rearrangements of ketoximes in the presence of zinc chloride. The resultant liquid–solid biphasic rearrangement reaction of cyclohexanone oxime shows a high yield 83 % with good recyclability. The testing of control catalysts, reaction conditions, oxime substrates, and recycling property were carried out and the results are discussed.
Co-reporter:Guojian Chen;Dr. Yu Zhou;Pingping Zhao;Zhouyang Long ;Dr. Jun Wang
ChemPlusChem 2013 Volume 78( Issue 6) pp:561-569
Publication Date(Web):
DOI:10.1002/cplu.201300105
Abstract
A mesostructured ionic liquid–polyoxometalate (IL-POM) hybrid has been prepared through designing a new dihydroxy-tethered guanidinium-based IL, N′′-(2,3-dihydroxypropyl)-N,N,N′,N′-tetramethylguanidinium chloride, to interact with Keggin-type POM phosphotungstic acid (H3PW) in a self-assembly process. Scanning electron microscopy and transmission electron microscopy showed its special coral-shaped micromorphology. Nitrogen sorption analysis indicated the formation of a porous structure with a moderate surface area of about 30 m2 g−1 and narrowly distributed pore size located in the mesoscale. Assessed in the cis-cyclooctene epoxidation with H2O2, the mesostructured hybrid exhibited superior heterogeneous catalytic activity and steady reusability, and the conversion was more than four times that of homogeneous H3PW itself, and more than 14 times that of the nonporous analogues. On the basis of the experimental results, a unique “substrate–solvent–catalyst” synergistic mechanism is proposed and discussed for understanding the dramatically enhanced catalytic performance.
Co-reporter:Pingping Zhao, Yan Leng, Mingjue Zhang, Jun Wang, Yajing Wu and Jun Huang
Chemical Communications 2012 vol. 48(Issue 46) pp:5721-5723
Publication Date(Web):12 Apr 2012
DOI:10.1039/C2CC31919E
An ionic solid catalyst by pairing Keggin polyoxometalate-anions with PdII-coordinated nitrile-tethered ionic liquid cations was synthesized, characterized, and tested for aerobic oxidation of benzene to biphenyl. A unique heterogeneous intramolecular electron transfer mechanism is proposed to understand its high activity.
Co-reporter:Pingping Zhao, Mingjue Zhang, Yajing Wu, and Jun Wang
Industrial & Engineering Chemistry Research 2012 Volume 51(Issue 19) pp:6641-6647
Publication Date(Web):April 25, 2012
DOI:10.1021/ie202232j
A group of ionic liquid (IL)-based polyoxometalate (POM) salts were prepared via anion-exchange of imidazolium IL precursors tethered by different carbon chain alkyls with various Keggin POMs. The resultant imidazolium POM salts were tested as the catalysts for oxidation of sulfides with aqueous H2O2. For understanding the POM salt-catalyzed oxidation of sulfides, catalyst compositions, substrates, and reaction conditions were changed. The results show that the imidazolium POM salts are very active and selective heterogeneous catalysts for oxidations of sulfides, adding the advantages of convenient recovery, steady reuse, simple preparation, and flexible composition. Characterizations by Fourier transform infrared (FT-IR), ultraviolet–visible (UV–vis), X-ray diffraction (XRD), and elemental analysis further reveal that the heterogeneous nature of the oxidation processes associates with the good crystallinities of the butyl- and hexyl-functionalized imidazolium POM salts and the hydrogen bonding networks among cations and anions. The POM salts’ excellent performances arise from the promoted redox property of the POM-anions by the intramolecular charge transfer from the IL-cations.
Co-reporter:Hualan Zhou, Yajing Wu, Wei Zhang, Jun Wang
Materials Chemistry and Physics 2012 Volume 134(2–3) pp:651-656
Publication Date(Web):15 June 2012
DOI:10.1016/j.matchemphys.2012.03.045
The static hydrothermal synthesis of SUZ-4 zeolite with the assistance of crystalline seed and using tetraethylammonium hydroxide (TEAOH) as the structure-directing agent (SDA) was studied systematically. The key synthesis parameters, such as reactant molar ratios, seed amount, and crystallization time were changed to optimize the synthesis conditions. The products were characterized by XRD, SEM, N2 adsorption and ICP elemental analysis. The results show that the seed-aided TEAOH-templated hydrothermal approach leads to the formation of SUZ-4 zeolite in a broad SiO2/Al2O3 range of 21–33. The crystallization time for creating a highly crystallized SUZ-4 phase increases with the raise of SiO2/Al2O3 ratios. Under the optimal conditions, i.e., SiO2/Al2O3 = 21, KOH/SiO2 = 0.38, TEAOH/SiO2 = 0.12, H2O/SiO2 = 23.8, seed amount = 0.1 wt.%, and static hydrothermal crystallization at 160 °C, SUZ-4 zeolite is obtained within a very short time of 1 d. The morphology of SUZ-4 is altered by TEAOH content from separated needle-like thin crystals to thick rod-like assemblies.Highlights► SUZ-4 is synthesized by the static hydrothermal approach. ► The crystallization time is much shortened within 1 day in the presence of seed and structure-directing agent. ► SUZ-4 can be produced with a broad range of SiO2/Al2O3 molar ratio 21–33.
Co-reporter:Mingjue Zhang;Pingping Zhao;Dr. Yan Leng;Guojian Chen;Dr. Jun Wang;Dr. Jun Huang
Chemistry - A European Journal 2012 Volume 18( Issue 40) pp:12773-12782
Publication Date(Web):
DOI:10.1002/chem.201201338
Abstract
An acid–base bifunctional ionic solid catalyst [PySaIm]3PW was synthesized by the anion exchange of the ionic-liquid (IL) precursor 1-(2-salicylaldimine)pyridinium bromide ([PySaIm]Br) with the Keggin-structured sodium phosphotungstate (Na3PW). The catalyst was characterized by FTIR, UV/Vis, XRD, SEM, Brunauer–Emmett–Teller (BET) theory, thermogravimetric analysis, 1H NMR spectroscopy, ESI-MS, elemental analysis, and melting points. Together with various counterparts, [PySaIm]3PW was evaluated in Knoevenagel condensation under solvent and solvent-free conditions. The Schiff base structure attached to the IL cation of [PySaIm]3PW involves acidic salicyl hydroxyl and basic imine, and provides a controlled nearby position for the acid–base dual sites. The high melting and insoluble properties of [PySaIm]3PW are relative to the large volume and high valence of PW anions, as well as the intermolecular hydrogen-bonding networks among inorganic anions and IL cations. The ionic solid catalyst [PySaIm]3PW leads to heterogeneous Knoevenagel condensations. In solvent-free condensation of benzaldehyde with ethyl cyanoacetate, it exhibits a conversion of 95.8 % and a selectivity of 100 %; the conversion is even much higher than that (78.2 %) with ethanol as a solvent. The solid catalyst has a convenient recoverability with only a slight decrease in conversion following subsequent recyclings. Furthermore, the new catalyst is highly applicable to many substrates of aromatic aldehydes with activated methylene compounds. On the basis of the characterization and reaction results, a unique acid–base cooperative mechanism within a Schiff base structure is proposed and discussed, which thoroughly explains not only the highly efficient catalytic performance of [PySaIm]3PW, but also the lower activities of various control catalysts.
Co-reporter:Yue Yao;Jianhong Wang;Yanyan Deng
Reaction Kinetics, Mechanisms and Catalysis 2012 Volume 107( Issue 1) pp:167-177
Publication Date(Web):2012 October
DOI:10.1007/s11144-012-0454-0
A bifunctional catalyst Pt/Hβ-n (Pt loading: 0.4 wt%) was prepared by the impregnation of an aqueous solution of chloroplatinic acid with β zeolite, wherein the β zeolite support has an unusual morphology of egg-like microspheres assembled by nanocrystallites. Other two control catalysts were also prepared using a β support with micro-sized crystals and a commercial one with varying crystal sizes. The catalysts were characterized by XRD, SEM, ICP, N2 sorption isotherms and mesopore size distribution, and evaluated in the hydroisomerization of n-heptane in an atmospheric fixed bed flow reactor. Though Pt/Hβ-n has similar acidity and Pt loading (0.4 wt%) to the two control catalysts, it exhibits remarkably higher conversion of n-heptane and selectivity to isomerization. According to the characterization data, the higher activity of Pt/Hβ-n is the result of the faster diffusion of reactants in shorter channels of nanocrystallines and the uniformly distributed mesopores within the microspheres.
Co-reporter:Yan Leng;PingPing Zhao;MingJue Zhang;GuoJian Chen
Science China Chemistry 2012 Volume 55( Issue 9) pp:1796-1801
Publication Date(Web):2012/09/01
DOI:10.1007/s11426-012-4722-7
An ionic hybrid catalyst 1,1′-(butane-1,4-diyl)-bis(3-methylimidazolium) phosphotungstate (abbreviated [Dmim]1.5PW) has been prepared by anion-exchange of the divalent ionic liquid (IL) 1,1′-(butane-1,4-diyl)-bis(3-methylimidazolium) di(bromide) with the Keggin phosphotungstic acid H3PW12O40, and characterized by IR, 1H NMR, 13C NMR, ESI-MS, TG, SEM, XRD, BET surface area measurements, elemental analysis, and melting point. The hybrid material was evaluated as a catalyst for the oxidation of alcohols with aqueous hydrogen peroxide under various conditions. The catalytic performance of [Dmim]1.5PW was also compared with related catalysts bearing other cations or anions. The new hybrid [Dmim]1.5PW proved to be an efficient liquid-solid heterogeneous catalyst for H2O2-based oxidation of alcohols, with the advantages of high conversion and selectivity, easy recovery, and quite good reusability.
Co-reporter:Weihong Zhang, Yan Leng, Pingping Zhao, Jun Wang, Dunru Zhu and Jun Huang
Green Chemistry 2011 vol. 13(Issue 4) pp:832-834
Publication Date(Web):16 Feb 2011
DOI:10.1039/C0GC00729C
New organic heteropolyacid (HPA) salts prepared by exchanging counter protons of Keggin HPAs with N-methyl-2-pyrrolidonium proved to be highly efficient, conveniently recoverable, and steadily reusable heterogeneous catalysts for the organic solvent-free Prins reactions of styrenes with formalin.
Co-reporter:Yan Leng, Jun Wang, Dunru Zhu, Mingjue Zhang, Pingping Zhao, Zhouyang Long and Jun Huang
Green Chemistry 2011 vol. 13(Issue 7) pp:1636-1639
Publication Date(Web):09 May 2011
DOI:10.1039/C1GC15302A
Polyoxometalate(POM)-based ionic hybrid nanospheres prepared by protonating and anion-exchanging amino-attached ionic liquid cations with Keggin POM-anions have proven to be highly efficient heterogeneous catalysts for the epoxidation of alkenes with H2O2, presenting advantages of convenient recovery, steady reuse, simple preparation, and flexible composition.
Co-reporter:Wei Zhang, Yajing Wu, Jing Gu, Hualan Zhou, Jun Wang
Materials Research Bulletin 2011 46(9) pp: 1451-1454
Publication Date(Web):
DOI:10.1016/j.materresbull.2011.05.006
Co-reporter:Hui Teng, Jun Wang, Demin Chen, Ping Liu, Xiaochen Wang
Journal of Membrane Science 2011 381(1–2) pp: 197-203
Publication Date(Web):
DOI:10.1016/j.memsci.2011.07.025
Co-reporter:Yajing Wu ; Jun Wang ; Ping Liu ; Wei Zhang ; Jing Gu ;Xiaojun Wang
Journal of the American Chemical Society 2010 Volume 132(Issue 51) pp:17989-17991
Publication Date(Web):December 8, 2010
DOI:10.1021/ja107633j
Incorporation of Ce and La into the framework of MCM-22 zeolite has been achieved by cohydrolysis and condensation of tetraethylorthosilicate and lanthanide salts in moderate/weak acidic media followed by a switch of synthesis gels to basic conditions for hydrothermal crystallization. The promotion effect of the framework Ce (La) when Ce(La)-MCM-22 serves as the catalyst support for hydroisomerization of n-heptane is demonstrated. Framework substitutions of lanthanides are evidenced by a set of mutually complementary characterizations, catalytic tests, and item-by-item comparisons with the impregnated and ion-exchanged counterparts. The novel synthesis strategy may give further outlines for the production of other types of heteroatomic zeolites.
Co-reporter:Changjiang Zhou;Yan Leng;Hanqing Ge
Catalysis Letters 2010 Volume 135( Issue 1-2) pp:120-125
Publication Date(Web):2010 March
DOI:10.1007/s10562-010-0260-0
The organic–inorganic hybrid catalyst L-Mn-PMoV was prepared simply by combining a schiff base Mn complex (L-Mn, L: N,N′-disalicylidene-1, 6-hexanediamine) with the Keggin-structured molybdovanadophosphoric heteropolyacid (PMoV). The proposed composition and structure of the catalyst were evidenced by TG, elemental analysis, FT-IR, and UV–Vis characterizations. Its catalytic performance was evaluated in the direct hydroxylation of benzene to phenol by molecular oxygen with ascorbic acid as the reducing agent. Various reaction parameters were changed to attain the optimal conditions. The hybrid catalyst has a formula [{Mn(C20H22N2O2)(Cl)}2(H4PMo11VO40)], with the two terminal oxygen atoms in the PMoV Keggin structure coordinately linked to the two Mn(III) ions in two L-Mn units, respectively. It exhibits a remarkably enhanced yield to phenol compared to the pure PMoV due to the synergy effect between the Schiff-base manganese complex and PMoV.
Co-reporter:Demin Chen;Xiaoqian Ren;Hui Teng;Haiwei Gu
Catalysis Letters 2010 Volume 136( Issue 1-2) pp:65-70
Publication Date(Web):2010 May
DOI:10.1007/s10562-010-0309-0
The cylinder-shaped ZSM-5 extrudate with a diameter 2 mm and a length 4–5 mm was coated with a silicalite-1 shell at its external surface by a hydrothermal synthesis with TEOS (tetraethylorthosilicate) as a silica source and TPAOH (tetrapropylammonium hydroxide) as a structure-directing agent. Catalytic performance of the obtained core/shell zeolite composite was measured in disproportionation of toluene using a pressured fixed-bed reactor. Ratios of H2O/SiO2 and TPAOH/SiO2, crystallization time and temperature, and synthesis cycles were adjusted to get optimal synthesis conditions, at which the selectivity to para-xylene is enhanced from the thermodynamic equilibrium value 24% to nearly 80%. SEM and XRD results further confirm the formation of the ZSM-5/silicalite-1 core/shell structure, which is responsible for the evident shape-selective production of para-xylene.
Co-reporter:Xingguang Zhang;Ping Liu;Yajing Wu;Yue Yao
Catalysis Letters 2010 Volume 137( Issue 3-4) pp:210-215
Publication Date(Web):2010 July
DOI:10.1007/s10562-010-0367-3
The framework-substituted manganese β zeolite was synthesized by an unseeded hydrothermal method, using manganese nitrate, colloidal silica, sodium aluminate, and tetraethylammonium hydroxide as raw materials. The optimized synthetic conditions were obtained by adjusting the key synthesis parameters, such as SiO2/Al2O3 ratio, TEAOH/SiO2 ratio, pH value, crystallization temperature, and SiO2/MnO ratio. The resulting samples were characterized by powder XRD, UV–vis spectroscopy, nitrogen physical adsorption, and ICP, which complementarily demonstrate the incorporation of manganese into the zeolite framework. Tested in hydroisomerization of n-heptane as a carrier for Pt catalyst, the Mn-incorporated sample showed a very high selectivity for isomerized products 94.7% with a high conversion of n-heptane 71.1% at 230 °C.
Co-reporter:Ping Liu;Yue Yao
Reaction Kinetics, Mechanisms and Catalysis 2010 Volume 101( Issue 2) pp:465-475
Publication Date(Web):2010 December
DOI:10.1007/s11144-010-0239-2
β-MCM41 composite molecular sieves were hydrothermally synthesized using NaOH treated β zeolite as precursors, and Pt/β-MCM41 bifunctional catalysts were prepared by impregnation. Hβ, desilicated Hβ by NaOH treatment (Dβ), and the physical mixture of Hβ and MCM41 (β+MCM41) were also used as control supports for bifunctional catalysts. All the catalysts were characterized by ICP, XRD, BET, nitrogen adsorption–desorption isotherm and NH3-TPD, and evaluated in the hydroisomerization of n-heptane using an atmospheric fixed bed flow reactor. Dβ, β+MCM41, or β-MCM41 supported Pt catalysts showed higher selectivity to isoheptanes than the counterpart Pt/Hβ did due to the presence of mesopores in addition to the zeolite micropores. Moreover, Pt/β-MCM41 was demonstrated to be a much more selective catalyst among them because the connection between mesopores and micropores accelerated the diffusion of larger molecules of isoheptanes. Under optimal conditions, Pt/β-MCM41 provided a very high selectivity to isomerization of 96.5%, coupled with a considerable high conversion of n-heptane of 56.0%.
Co-reporter:Dengjie Chen, Ran Ran, Kun Zhang, Jun Wang, Zongping Shao
Journal of Power Sources 2009 Volume 188(Issue 1) pp:96-105
Publication Date(Web):1 March 2009
DOI:10.1016/j.jpowsour.2008.11.045
A-site cation-ordered PrBaCo2O5+δ (PrBC) double perovskite oxide was synthesized and evaluated as the cathode of an intermediate-temperature solid-oxide fuel cell (IT-SOFC) on a samarium-doped ceria (SDC) electrolyte. The phase reaction between PrBC and SDC was weak even at 1100 °C. The oxygen reduction mechanism was investigated by electrochemical impedance spectroscopy characterization. Over the intermediate-temperature range of 450–700 °C, the electrode polarization resistance was mainly contributed from oxygen-ion transfer through the electrode–electrolyte interface and electron charge transfer over the electrode surface. An area-specific resistance as low as ∼0.4 Ω cm2 was measured at 600 °C in air, based on symmetric cell test. A thin-film SDC electrolyte fuel cell with PrBC cathode was fabricated which delivered attractive peak power densities of 620 and 165 mW cm−2 at 600 and 450 °C, respectively.
Co-reporter:Yajing Wu, Xiaoqian Ren, Jun Wang
Materials Chemistry and Physics 2009 Volume 113(2–3) pp:773-779
Publication Date(Web):15 February 2009
DOI:10.1016/j.matchemphys.2008.08.008
MCM-22 zeolite was synthesized via a two-step sol–gel route (low pH sol–gel reaction followed by high pH crystallization) under static hydrothermal conditions using tetraethyl orthosilicate (TEOS) as silica source. Various parameters that significantly influence the synthesis results during both the hydrolysis reaction of TEOS in acid media and the hydrothermal reaction in base media were investigated in detail. The produced samples were characterized by XRD, ICP, and SEM techniques. It is found that pure MCM-22 with high crystallinity can be obtained via the novel two-step sol–gel route in a broad window of reaction conditions. The increase of temperature and pH value for the hydrolysis of TEOS favors the shortening of crystallization time and decreasing of MCM-22 particle size. Moreover, by adjusting the hydrothermal reaction parameters, such as increasing the crystallization temperature, increasing the alkalinity of the synthesis gel mixture, and decreasing the SiO2/Al2O3 ratio, the crystallization is accelerated substantially. Also, rose-like or lamellar-like morphologies of MCM-22 particles with different sizes can be achieved by changing these reaction parameters. Using this two-step sol–gel route, MCM-22 is able to be well produced in a wide range of the SiO2/Al2O3 ratio from 20 to 100.
Co-reporter:Shanshan Wu;Ping Liu;Yan Leng
Catalysis Letters 2009 Volume 132( Issue 3-4) pp:
Publication Date(Web):2009 October
DOI:10.1007/s10562-009-0123-8
Amino-functionalized MCM-41 was synthesized via direct condensation, as well as post-grafting, using 3-aminopropyltrimethoxysilane as the functionalization agent. Keggin and Preyssler-structured heteropolyacids (HPAs) were anchored on the surface of amino-functionalized MCM-41 by chemically bonding to amino groups. HPAs directly supported on MCM-41 by impregnation were also prepared for comparison. These catalysts were characterized by Infra-red spectroscopy, X-ray diffraction, N2-adsorption, Hammett indicator and UV–Vis spectroscopy, and evaluated in esterification of n-butanol with acetic acid. HPAs anchored on amino-functionalized MCM-41 via condensation give very stable and substantially higher activity than the ones via grafting. In contrast, MCM-41 supported HPA catalysts prepared by direct impregnating lose their catalytic activities rapidly due to the leaching of HPA active sites. The catalyst activity is discussed in relation with physicochemical properties.
Co-reporter:YaJing Wu;XiaoQian Ren;YouDong Lu
Science China Chemistry 2009 Volume 52( Issue 5) pp:549-551
Publication Date(Web):2009 May
DOI:10.1007/s11426-009-0090-3
Small crystal zeolites ZSM-5 with sizes of 150–300 nm were synthesized using the colloidal silicate precursors as the silica source created by the acid-catalyzed hydrolysis of tetraethylorthosilicate with tetrapropylammonium bromide as the structure-directing agent within a short crystallization time of 20–35 h. The precursors and final products were detected by XRD, SEM, ICP and DLS.
Co-reporter:Yan Leng, Jun Wang, Dunru Zhu, Yajing Wu, Pingping Zhao
Journal of Molecular Catalysis A: Chemical 2009 313(1–2) pp: 1-6
Publication Date(Web):
DOI:10.1016/j.molcata.2009.08.011
Co-reporter:Yajing Wu, Xiaoqian Ren, Youdong Lu, Jun Wang
Microporous and Mesoporous Materials 2008 Volume 112(1–3) pp:138-146
Publication Date(Web):1 July 2008
DOI:10.1016/j.micromeso.2007.09.022
MCM-22 zeolite was synthesized in various static hydrothermal systems with hexamethyleneimine (HMI) as the structure-directing agent. Synthesis parameters, such as silica source, alkaline source (Na+, K+ or NH4+), alkalinity of the reaction mixture, HMI/SiO2 ratio and seeding, were changed to investigate their effects on the crystallization and morphology of zeolite MCM-22. The produced samples were characterized by XRD, IR, SEM, N2 physisorption and ICP. Reaction conditions were revealed to influence the induction period and crystallization rate remarkably, and the sodium metasilicate as the silica source, the medium OH−/SiO2 molar ratio (0.15), the high HMI/SiO2 molar ratio and the addition of seeding could accelerate the crystallization. Moreover, by altering the reaction parameters, various morphologies of MCM-22 product with different particle sizes were achieved, such as spherical, rose-like, doughnut-like and platelet-like structures. The noteworthy observation was that with K+ as the alkaline source instead of Na+, a much shorter induction period and faster crystallization rate were obtained, resulting in a higher crystallinity and a smaller crystal size. K+ is more favorable to the formation of MCM-22 crystal than Na+ even at very low HMI/SiO2 ratios.
Co-reporter:Yajing Wu, Xiaoqian Ren, Jun Wang
Microporous and Mesoporous Materials 2008 Volume 116(1–3) pp:386-393
Publication Date(Web):December 2008
DOI:10.1016/j.micromeso.2008.04.027
The synthesis of MCM-22 zeolite under static hydrothermal conditions was performed with the synthesis mixture being treated by a microwave-assisted aging process prior to the onset of crystallization using colloidal silica and tetraethyl orthosilicate (TEOS) as silica sources, respectively. The effects of the chemical compositions of the initial solutions and the conditions of microwave treatment for precursors on the synthesis of MCM-22 zeolite were investigated. The microwave-assisted aging was compared with the ultrasound-assisted aging, stirring aging and without any aging processes. The produced samples were characterization by XRD, ICP, FT-IR, and SEM techniques. The microwave-assisted aging for the initial gel can shorten the crystallization time to form MCM-22 phase and broaden the range of SiO2/Al2O3 ratio both for the initial gel and final solid product. Moreover, the increase of the microwave aging temperature and the aging time favors a decrease of crystallization time and particle size. By using microwave-assisted aging process, the pure and high crystallinity MCM-22 product with the SiO2/Al2O3 ratio being as high as 80 can be obtained. Increasing the SiO2/Al2O3 ratio produces the smaller particles of MCM-22.
Co-reporter:Cheng Wu, Yan Kong, Fei Gao, Yong Wu, Yinong Lu, Jun Wang, Lin Dong
Microporous and Mesoporous Materials 2008 Volume 113(1–3) pp:163-170
Publication Date(Web):1 August 2008
DOI:10.1016/j.micromeso.2007.11.013
A series of Fe-MCM41s with different iron content have been synthesized and characterized by XRD, BET, HRTEM, FT-IR, UV–vis and ICP techniques. Their catalytic performances for the direct hydroxylation of phenol were also studied. Results indicated that the mesoporous structure did not collapse until the Fe/Si molar ratio reached up to 0.20. The iron species were mainly in the framework with isolated tetrahedral coordination as Fe/Si molar ratio was smaller than 0.091 and micro-crystals of Fe2O3 were detected when iron content increased further. The prepared samples exhibited excellent catalytic activities for the direct hydroxylation of phenol by hydrogen peroxide at room temperature, which increased with iron content in the framework of MCM41 and did not decline after being recycled 6 times. As Fe/Si molar ratio increased to more than 0.091, the catalytic activity decreased gradually with iron content due to the covering of some active sites, i.e., the incorporated iron species with tetrahedral coordination, by the accumulated Fe2O3 on the surface of the catalyst.
Co-reporter:Yajing Wu, Xiaoqian Ren, Youdong Lu, Jun Wang
Materials Letters 2008 Volume 62(Issue 2) pp:317-319
Publication Date(Web):31 January 2008
DOI:10.1016/j.matlet.2007.05.026
Using tetraethylorthosilicate (TEOS) as the silica source, zeolite MCM-22 was hydrothermally synthesized with the acid-catalyzed hydrolysis of TEOS to produce siliceous precursors, followed by the addition of the alumina source and the structure-directing agent (hexamethyleneimine (HMI)), and the crystallization in a basic media. The acid used for catalyzing the hydrolysis of TEOS and the HMI/SiO2 ratio were changed to investigate their effects on the crystallization of MCM-22. The resultant materials were characterized by XRD, SEM, N2 adsorption and ICP techniques. It is found that the well crystallized MCM-22 can be successfully synthesized through the acid-catalyzed hydrolysis of TEOS, and hydrochloric acid is most effective in the hydrolysis of TEOS for synthesizing MCM-22 with a very short crystallization time of only 30 h. Moreover, with this synthesis route, it is also possible to obtain MCM-22 at a very low concentration of HMI with the HMI/SiO2 molar ratio of 0.1.
Co-reporter:Shanshan Wu;Weihong Zhang;Xiaoqian Ren
Catalysis Letters 2008 Volume 123( Issue 3-4) pp:276-281
Publication Date(Web):2008 July
DOI:10.1007/s10562-008-9419-3
The Preyssler-structured tungstophosphoric acid catalyst supported on functionalized silica (Preyssler/F-silica) was prepared by means of grafting technique with amine group as coupling media, and its catalytic behavior was investigated in the esterification of n-butanol with acetic acid. The catalyst was characterized by infra-red spectroscopy, UV–Vis spectroscopy, Hammett indicator and N2 adsorption techniques. Catalysts prepared directly by impregnating Preyssler acid on silica (Preyssler/silica) were also studied for comparison. The Preyssler/F-silica catalyst with the 14.3% loading of Preyssler acid exhibits a considerable conversion of n-butanol of 46.7% with 100% selectivity for n-butyl acetate in the esterification of n-butanol with acetic acid, which is comparative to the 15%Preyssler/silica catalyst. Moreover, a six-cycle reaction test reveals a good reusability for Preyssler/F-silica due to the water-resistance property of the Preyssler structure on the surface of the functionalized silica, and Preyssler/silica looses its high activity immediately at the second reaction cycle. The active sites on functionalized silica can retain the Preyssler structure before and after reaction. At 120 °C of reaction temperature, 140 min of reaction time, 1:1 molar ratio of acetic acid with n-butanol, and 0.005 g/mL of the catalyst content in reaction media are the suitable reaction conditions over the Preyssler/F-silica catalyst.
Co-reporter:Hanqing Ge;Yan Leng;Fumin Zhang;Changjiang Zhou
Catalysis Letters 2008 Volume 124( Issue 3-4) pp:250-255
Publication Date(Web):2008 August
DOI:10.1007/s10562-008-9506-5
Pyridine(Py)-modified Keggin-type mono-vanadium-substituted heteropoly acids (PynPMo11V, n = 1–4) were prepared by a precipitation method as organic/inorganic hybrid catalysts for direct hydroxylation of benzene to phenol in a pressured batch reactor and their structures were characterized by FT-IR. Among various catalysts, Py4PMo11V exhibited the highest catalytic activity (yield of phenol 9.0%) with the high selectivity for phenol, without observing the formation of catechol, hydroquinone and benzoquinone in the reaction with 80 vol% aqueous acetic acid, molecular oxygen and ascorbic acid used as the solvent, oxidant and reducing reagent, respectively. The influences of the reaction temperature, the pressure of oxygen, the amount of ascorbic acid, the amount of catalyst, and the reaction time on the yield of phenol were investigated to obtain the optimal reaction conditions for phenol formation. Pyridine can greatly promote the catalytic activity of the Py-free catalyst (H4PMo11VO40), mostly because the organic π electrons in the hydrid catalyst may extend their conjugation to the inorganic framework of heteropoly acid and thus dramatically modify the redox properties.
Co-reporter:Yan Leng, Dr.;Dunru Zhu;Xiaoqian Ren Dr.;Hanqing Ge ;Lei Shen
Angewandte Chemie 2008 Volume 121( Issue 1) pp:174-177
Publication Date(Web):
DOI:10.1002/ange.200803567
Co-reporter:Yan Leng, Dr.;Dunru Zhu;Xiaoqian Ren Dr.;Hanqing Ge ;Lei Shen
Angewandte Chemie International Edition 2008 Volume 48( Issue 1) pp:168-171
Publication Date(Web):
DOI:10.1002/anie.200803567
Co-reporter:RuiPing Wei;YanBo Gu
Science China Chemistry 2008 Volume 51( Issue 2) pp:120-127
Publication Date(Web):2008 February
DOI:10.1007/s11426-008-0009-4
The bimetal-bearing (CePt or LaPt) 12-tungstophosphoric acid (H3PW12O40 (PW)) catalysts supported on dealuminated USY zeolite (DUSY) were prepared by impregnation and characterized by XRD, BET, IR, and H2-chemisorption. Their catalytic activities were tested in the hydroisomerization of n-heptane with a continuous atmospheric fixed-bed reactor. After the steam treatment combined with the acid leaching, as well as the supporting with PW and the bimetals, the DUSY support retains the Y zeolite porosity and the PW well keeps its Keggin structure in catalysts. The doping of Ce into the catalysts enhances the dispersion of Pt on the catalyst surface. The Pt-bearing PW catalysts doped with Ce or La, especially Ce, exhibit much higher catalytic activity and selectivity than the catalysts without dopants at lowered reaction temperatures. At the optimal reaction conditions, i.e., the reaction temperature of 250°C and WHSV of 1.4 h−1, the catalyst with a Pt loading of 0.4%, PW loading of 10% and a molar ratio of Ce to Pt of 15:1 shows a conversion of n-heptane of 70.3% with a high selectivity for isomerization products of 94.1%.
Co-reporter:Ruiping Wei;Yanbo Gu
Reaction Kinetics, Mechanisms and Catalysis 2007 Volume 90( Issue 2) pp:315-322
Publication Date(Web):2007 April
DOI:10.1007/s11144-007-5034-3
The Pt-bearing SO42−/ZrO2 catalysts doped with Cr and supported on USY zeolite were prepared by impregnation, and characterized by XRD and IR spectroscopy of pyridine adsorption. Their catalytic activities were evaluated in the hydroisomerization of n-heptane with a fixed-bed atmospheric reactor. The Cr-promoted catalysts exhibited much higher catalytic activity and selectivity for isomerization products than the catalysts without the Cr dopant. Both the conversion and selectivity were discussed in relation with the physicochemical properties of catalysts.
Co-reporter:Yan-bo Gu;Rui-ping Wei;Xiao-qian Ren
Catalysis Letters 2007 Volume 113( Issue 1-2) pp:41-45
Publication Date(Web):2007 January
DOI:10.1007/s10562-006-9002-8
A series of Pt-bearing dealuminated USY supported Cs salts of 12-tungstophosphoric acid (PW) catalysts were prepared and their catalytic performances were measured in the hydroisomerization of n-heptane with an atmospheric fixed-bed flow reactor. USY was found to be a poor support for Cs salts of PW, leading to a lower catalytic activity in this reaction, but dealuminated USY supported Cs salts of PW catalysts showed very high catalytic conversion and selectivity. Among the various Cs salts of PW with different Cs/P ratios, Cs2.0PW was revealed to be the most effective active species. Over the dealuminated USY supported catalyst with the Pt loading of 0.4 wt.% and Cs2.0PW loading of 10 wt.%, the conversion of n-heptane was enhanced up to 76.2% with a high selectivity to isomerized products of 92.2%.
Co-reporter:Fumin Zhang;Maiping Guo;Hanqing Ge
Frontiers of Chemical Science and Engineering 2007 Volume 1( Issue 3) pp:296-299
Publication Date(Web):2007 July
DOI:10.1007/s11705-007-0054-0
An environmentally benign method for the synthesis of heteropoly acids H3+nPMo12−nVnO40·xH2O (PMoVn, n = 1–3) was developed by the reaction of an aqueous slurry which contained stoichiometric amounts of MoO3, V2O5 and H3PO4. Characterization of the as-synthesized catalysts with inductively coupled plasma (ICP) elemental analysis, thermogravimetry (TG), X-ray diffraction (XRD) and infrared (IR) spectroscopy indicated that V ions substituted for Mo ions in Keggin-type phosphomolybdic acid. The assynthesized samples were found to be an efficient catalyst for the hydroxylation of benzene which was carried out in a mixed solvent of acetonitrile and acetic acid with aqueous hydrogen peroxide as oxidant. PMoV2 exhibited the highest benzene conversion of 34.5% with phenol selectivity of 100%.
Co-reporter:Qi-Ying Liu, Wen-Liang Wu, Jun Wang, Xiao-Qian Ren, Yan-Ru Wang
Microporous and Mesoporous Materials 2004 Volume 76(1–3) pp:51-60
Publication Date(Web):1 December 2004
DOI:10.1016/j.micromeso.2004.08.001
12-Tungstophosphoric acid catalysts supported on mesoporous silica SBA-15 with various acid loadings were prepared by impregnation, and their physical chemical properties were characterized by XRD, N2-adsorption, FTIR, DSC and NH3-TPD techniques. Their catalytic performances in the isopropylation of naphthalene with isopropanol were investigated in a batch reactor. It was found that 12-tungstophosphoric acid was highly dispersed on the SBA-15 support when the acid loading was as high as 60%, and meanwhile the Keggin structure of heteropolyanions could be retained. In addition, the thermal stability of the supported acid decreased by approximately 100 K as compared with the pure acid. In isopropylation of naphthalene, SBA-15 supported acid catalysts showed much higher conversion and selectivity to diisopropylnaphthalenes, β-isopropylnaphthalene, and β, β-products than those of pure acid. Furthermore, the catalytic performances of SBA-15 supported catalysts were compared with those supported on other siliceous materials such as MCM-41 and amorphous silica, as well as zeolite catalysts such as USY, H-mordenite and dealuminated H-mordenites. The catalytic behavior has been discussed in relation with the physical chemical properties of catalysts.
Co-reporter:Hualan ZHOU, Yajing WU, Wei ZHANG, Jun WANG
Chinese Journal of Chemical Engineering (January 2014) Volume 22(Issue 1) pp:120-126
Publication Date(Web):1 January 2014
DOI:10.1016/S1004-9541(14)60019-7
Various conditions were investigated in detail for the novel organic template-free static hydrothermal synthesis of SUZ-4 zeolite in the presence of seeds. The obtained samples were characterized by XRD (X-ray diffraction), SEM (scanning electron microscope), TG (thermal gravimetric analysis), ICP (inductively coupling plasma) elemental analysis, nitrogen sorption isotherm and surface area. The results show that pure SUZ-4 zeolites with high crystallinity are obtained in a broad window of synthesis conditions: seed mass concentration 0.2%–2%, SiO2/Al2O3 molar ratio 21–25, KOH/SiO2 molar ratio 0.33–0.43, H2O/SiO2 molar ratio 7.14–38.1, aging time 24 h, crystallization temperature 160 °C, and crystallization time 6–10 d. Also, crystallinity and size of the rod-like SUZ-4 zeolite crystals are found to alter with the conditions.
Co-reporter:Ruiping WEI, Maiping GUO, Jun WANG
Chinese Journal of Chemical Engineering (February 2009) Volume 17(Issue 1) pp:58-63
Publication Date(Web):1 February 2009
DOI:10.1016/S1004-9541(09)60033-1
In order to solve the serious leaching problem of supported heteropoly acid catalysts in polar reactionmedia, 12-molybdophosphoric acid encapsulated in the supercage of Cs+-exchanged Y zeolite was prepared by the “ship in the bottle” synthesis. The influence of ion-exchange conditions and the synthesis parameters on the encapsulation of PMo12 were investigated. The obtained solid sample was characterized by X-ray diffraction (XRD), 31P magic angle spin nuclear magnetic resonance (MAS NMR) and Fourier Transform Infrared Spectroscopy (FT-IR), and its catalytic activity in the esterification of acetic acid and n-butanol was tested. The ion-exchange time, concentration of aqueous Cs+ solution, pH value, and amount of Mo added in the synthesis mixture were revealed toinfluence the encapsulation very remarkably. Under the optimal conditions, 12-molybdophosphoric acid could be successfully encapsulated in the supercage of CsY zeolite, and the samples showed considerable catalytic activityand excellent reusability in the esterification reaction.
Co-reporter:Pingping Zhao, Jun Wang, Guojian Chen, Yu Zhou and Jun Huang
Catalysis Science & Technology (2011-Present) 2013 - vol. 3(Issue 5) pp:NaN1404-1404
Publication Date(Web):2013/02/07
DOI:10.1039/C3CY20796J
A new nitrile-tethered pyridinium polyoxometalate (POM) was prepared by anion-exchange of the ionic liquid precursor [N-butyronitrile pyridine]Cl ([C3CNpy]Cl) with the Keggin phosphovanadomolybdic acid H5PMo10V2O40 (PMoV2), and the obtained organic POM salt [C3CNpy]4HPMoV2 was characterized by XRD, SEM, TG, 1H NMR, 13C NMR, ESI-MS, CHN elemental analysis, nitrogen sorption experiment, and melting point measure. When used as a catalyst, [C3CNpy]4HPMoV2 causes the first example of reaction-controlled phase-transfer hydroxylation of benzene with H2O2, showing high activity and stable reusability. Based on spectral characterizations and comparisons of reaction results, plus the reversible color change between fresh and recovered catalyst, a unique reaction mechanism is proposed for understanding the highly efficient [C3CNpy]4HPMoV2-catalyzed phase-transfer catalysis. The formation of dissolvable active species [VO(O2)]+ is responsible for the phase-transfer behavior, while the intramolecular charge transfer and the protonated nitrile in cations accelerate the reaction and favor a better catalyst recovery rate.
Co-reporter:Pingping Zhao, Yan Leng, Mingjue Zhang, Jun Wang, Yajing Wu and Jun Huang
Chemical Communications 2012 - vol. 48(Issue 46) pp:NaN5723-5723
Publication Date(Web):2012/04/12
DOI:10.1039/C2CC31919E
An ionic solid catalyst by pairing Keggin polyoxometalate-anions with PdII-coordinated nitrile-tethered ionic liquid cations was synthesized, characterized, and tested for aerobic oxidation of benzene to biphenyl. A unique heterogeneous intramolecular electron transfer mechanism is proposed to understand its high activity.
Co-reporter:Jing Gu, Yanhua Jin, Yu Zhou, Mingjue Zhang, Yajing Wu and Jun Wang
Journal of Materials Chemistry A 2013 - vol. 1(Issue 7) pp:NaN2460-2460
Publication Date(Web):2012/12/13
DOI:10.1039/C2TA01009G
A facile one-pot method without organic templates and seeds is reported for the fabrication of framework-substituted heteroatomic zeolites for the first time. Such a breakthrough is achieved by the acidic co-hydrolysis of tetraethylorthosilicate (TEOS) with metal salts, followed by basic aging and hydrothermal crystallization. Fe(Mo, Ti, Co, Cr) MFI zeolites can be obtained with high crystallinity, thermal stability and tunable chemical composition, in which Fe3+ and Al3+ are proposed to act as co-structure-directing agents, inducing the growth of the zeolite crystal and their special poly-nanocrystalline morphology. Structural characterizations and Knoevenagel condensations were conducted to evidence the incorporation of Fe3+ into the MFI framework. The catalytic activity on the as-synthesized framework-substituted Fe-ZSM-5 is not only tens of times higher than that of Fe3+-exchanged or ferric oxide impregnated analogues, but also much higher than that of its as-calcined analogue, suggesting the unique ability of our method to inhibit the transfer of heteroatoms out of the framework. This easy, controllable and green new strategy may be extended to other heteroatomic MFI zeolites, and is potentially important for practical utilization.
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