Co-reporter:Pengfei Wu;Miao Yang;Wenna Zhang;Shutao Xu;Peng Guo;Peng Tian
Chemical Communications 2017 vol. 53(Issue 36) pp:4985-4988
Publication Date(Web):2017/05/02
DOI:10.1039/C7CC01834G
[3-Piperazinepropylmethyldimethoxysilane (PZPMS)] as a low-cost co-template, a crystal growth inhibitor, and a part of the silica source was used together with triethylamine to synthesize SAPO-34 nanoaggregates with tunable compositions. Note that the piperazinyl group of PZPMS prompts the formation of a perfect CHA structure by eliminating the CHA/AEI intergrowth, which ensures the excellent MTO catalytic performance of SAPO-34 nanoaggregates.
Co-reporter:Dr. Xinqiang Wu;Dr. Shutao Xu;Dr. Wenna Zhang;Dr. Jindou Huang;Jinzhe Li;Dr. Bowen Yu; Yingxu Wei; Zhongmin Liu
Angewandte Chemie International Edition 2017 Volume 56(Issue 31) pp:9241-9241
Publication Date(Web):2017/07/24
DOI:10.1002/anie.201705757
The first carbon–carbon bond formation in the methanol to hydrocarbons (MTH) reaction over zeolite catalysts has been a highly controversial issue and has puzzled scientists for 30 years. In their Communication on page 9039 ff. Z. Liu, Y. Wei et al. propose a direct mechanism for the formation of the first C−C bond in the MTH reaction, based on the detection of the crucial intermediate, a surface methyleneoxy analogue species originating from activated DME or methanol, by in situ solid-state NMR spectroscopy.
Co-reporter:Dr. Xinqiang Wu;Dr. Shutao Xu;Dr. Wenna Zhang;Dr. Jindou Huang;Jinzhe Li;Dr. Bowen Yu; Yingxu Wei; Zhongmin Liu
Angewandte Chemie 2017 Volume 129(Issue 31) pp:9369-9369
Publication Date(Web):2017/07/24
DOI:10.1002/ange.201705757
Der erste C-C-Verknüpfungsschritt bei der Umwandlung von Methanol in Kohlenwasserstoffe über Zeolithkatalysatoren wird seit 30 Jahren kontrovers diskutiert. In ihrer Zuschrift auf S. 9167 ff. schlagen Z. Liu, Y. Wei et al. einen Mechanismus für diesen Schritt vor. Ihr Postulat gründet auf dem Nachweis einer Methylenoxy-analogen Oberflächenspezies, gebildet aus aktiviertem Dimethylether oder Methanol, durch In-situ-Festkörper-NMR-Spektroskopie.
Co-reporter:Dr. Xinqiang Wu;Dr. Shutao Xu;Dr. Wenna Zhang;Dr. Jindou Huang;Jinzhe Li;Dr. Bowen Yu; Yingxu Wei; Zhongmin Liu
Angewandte Chemie 2017 Volume 129(Issue 31) pp:9167-9171
Publication Date(Web):2017/07/24
DOI:10.1002/ange.201703902
AbstractIn the past two decades, the reaction mechanism of C−C bond formation from either methanol or dimethyl ether (DME) in the methanol-to-hydrocarbons (MTH) process has been a highly controversial issue. Described here is the first observation of a surface methyleneoxy analogue, originating from the surface-activated DME, by in situ solid-state NMR spectroscopy, a species crucial to the first C−C bond formation in the MTH process. New insights into the first C−C bond formation were provided, thus suggesting DME/methanol activation and direct C−C bond formation by an interesting synergetic mechanism, involving C−H bond breakage and C−C bond coupling during the initial methanol reaction within the chemical environment of the zeolite catalyst.
Co-reporter:Dr. Xinqiang Wu;Dr. Shutao Xu;Dr. Wenna Zhang;Dr. Jindou Huang;Jinzhe Li;Dr. Bowen Yu; Yingxu Wei; Zhongmin Liu
Angewandte Chemie International Edition 2017 Volume 56(Issue 31) pp:9039-9043
Publication Date(Web):2017/07/24
DOI:10.1002/anie.201703902
AbstractIn the past two decades, the reaction mechanism of C−C bond formation from either methanol or dimethyl ether (DME) in the methanol-to-hydrocarbons (MTH) process has been a highly controversial issue. Described here is the first observation of a surface methyleneoxy analogue, originating from the surface-activated DME, by in situ solid-state NMR spectroscopy, a species crucial to the first C−C bond formation in the MTH process. New insights into the first C−C bond formation were provided, thus suggesting DME/methanol activation and direct C−C bond formation by an interesting synergetic mechanism, involving C−H bond breakage and C−C bond coupling during the initial methanol reaction within the chemical environment of the zeolite catalyst.
Co-reporter:Beibei Gao, Dong Fan, Lijing Sun, Hongyu An, Fengtao Fan, Shutao Xu, Peng Tian, Zhongmin Liu
Microporous and Mesoporous Materials 2017 Volume 248(Volume 248) pp:
Publication Date(Web):1 August 2017
DOI:10.1016/j.micromeso.2017.04.035
•Aminothermal crystallization process of SAPO-34 was investigated.•A semicrystalline AlPO layered phase containing D6Rs forms in the initial gel.•An intense interaction between TEA+ and inorganic species in precursor is revealed.•Aminothermal environment facilitates the quick activation of Al source.•Water affects the intermediate species formation and alters the crystallization rate.Aminothermal synthesis reported by our group recently, in which organic amine is used as the solvent and template, could obviously enhance the solid yield and crystallization rate of SAPO-34 as compared with the corresponding hydrothermal one. Herein, aminothermal crystallization process of SAPO-34 is investigated to gain insights into this novel synthetic method by XRD, SEM, IR, UV-Raman and various solid-state NMR techniques. It is found that aminothermal environment facilitates the fast formation of a semicrystalline AlPO layered phase, which further promotes the quick activation of Al source. The lamellar phase, which is water-soluble and contains double 6-rings in the framework, could be stabilized by protonated triethylamine (TEA+). SAPO-34 nucleates from the rearrangement of the double 6-rings in the layered phase through bond breaking, reforming and Si incorporation after heating at 160 °C for 3 h. For the hydrothermal process, the interaction between TEA+ and inorganic species is weak and the formation of layered phase is retarded due to its high solubility in water. Correspondingly, the activation of Al source is slow and SAPO-34 appears after 24 h. This work demonstrates the importance of water concentration in the synthetic system, which may influence the formation of intermediate species and alter the crystallization process and rate.Download high-res image (345KB)Download full-size image
Co-reporter:Liang Qi;Jinzhe Li;Linying Wang;Lei Xu
Catalysis Science & Technology (2011-Present) 2017 vol. 7(Issue 4) pp:894-901
Publication Date(Web):2017/02/20
DOI:10.1039/C6CY02459A
Temperature-programmed methanol to hydrocarbon (TP-MTH) reactions were performed over HZSM-5 zeolite to monitor the change of reaction performance along with reaction temperature in order to understand the mechanistic reason for the temperature influence on the reaction. With a gradual increase of reaction temperature (0.5 °C min−1), the MTH reaction could evolve from the induction period with low methanol conversion to the state with 100% methanol conversion. Four different reaction stages could be clearly observed: the initial reaction stage, the auto-catalysis reaction stage, the deactivation stage and the activity recovery stage. An unusual deactivation behavior was observed following the auto-catalysis period. Further investigations revealed that 1,2,3,5-tetraMB was the main active species during the initial autocatalytic stage and its “overloading” effect resulted in the unusual deactivation phenomenon, i.e. despite its high intrinsic reactivity, too quick formation of poorly mobile 1,2,3,5-tetraMB and lower methylbenzenes will lead to the occupation of most catalyst channels and channel intersections and cause the deactivation of HZSM-5 at low temperature. Further study demonstrated that the “overloading” effect could be alleviated or eliminated by enhancing the catalyst diffusivity or decreasing the acid site density of the zeolite catalyst.
Co-reporter:Liang Qi;Jinzhe Li;Linying Wang;Chan Wang;Lei Xu
Catalysis Science & Technology (2011-Present) 2017 vol. 7(Issue 10) pp:2022-2031
Publication Date(Web):2017/05/22
DOI:10.1039/C7CY00024C
The deactivation mechanism for the methanol conversion reaction at low temperature was comparatively investigated over HZSM-5 and HSAPO-34 catalysts. Two obviously different deactivation phenomena were directly observed: two-staged deactivation behavior over the HZSM-5 catalyst and exponential-type deactivation behavior over the HSAPO-34 catalyst. Since the start of the deactivation, the amount of the retained species over the HZSM-5 catalyst kept unchanged while the amount over the HSAPO-34 catalyst obviously increased. Both types of deactivation behavior presented an intimate relationship with the accumulation of retained species and their changing reactivity. After detailed characterization and analysis, it was interestingly found that the deactivation of the HZSM-5 catalyst originated from the “overloading effect” of methylbenzenes (smaller than pentamethylbenzene) which are intrinsically active during the autocatalysis reaction stage, while the deactivation of the HSAPO-34 catalyst was caused by accumulation of inactive methyladamantanes, and it was further deduced that the deactivation proceeded from “external to internal” for the HSAPO-34 catalyst. Enhancement of the catalyst diffusivity could effectively extend the catalyst lifetime for the HZSM-5 catalyst, but seemed less effective for the HSAPO-34 catalyst.
Co-reporter:Xuebin Zhao;Linying Wang;Jinzhe Li;Shutao Xu;Wenna Zhang;Yingxu Wei;Xinwen Guo;Peng Tian
Catalysis Science & Technology (2011-Present) 2017 vol. 7(Issue 24) pp:5882-5892
Publication Date(Web):2017/12/11
DOI:10.1039/C7CY01804E
Large pore high-Si beta zeolites (Si/Al = 136 to 340) were synthesized by a HF-assisted method, and their catalytic performance for the conversion of methanol to propene was explored. It is demonstrated that beta zeolites with low acid density facilitate the achievement of high propene selectivity and a high propene/ethene ratio. The HF dosage in the synthesis has great influence on the Al distribution in the framework, as evidenced by 27Al MAS NMR and 27Al MQ MAS NMR spectroscopy, which may influence the acidity and microstructure of acid sites and lead to a remarkable catalytic lifespan. A HF/SiO2 ratio of 0.45 is found to facilitate the synthesis of high-Si beta enriched with Al atoms located at the T9 sites; this helps the catalyst show the longest lifetime, with a propene selectivity of 49.7–58.3% at 550 °C and WHSV = 2 h−1. With the aid of 12C/13C-methanol switch experiments, we elucidated that the olefin-based mechanism dominates the reaction and contributes to the formation of ethene, propene, and higher olefins. Moreover, two phenol compounds are identified in the coke species, which have not been observed previously and have been found to be detrimental to the reaction.
Co-reporter:Youming Ni;Lei Shi;Hongchao Liu;Wenna Zhang;Yong Liu;Wenliang Zhu
Catalysis Science & Technology (2011-Present) 2017 vol. 7(Issue 20) pp:4818-4822
Publication Date(Web):2017/10/16
DOI:10.1039/C7CY01621B
Acetic acid is one of the most important bulk commodity chemicals and is currently manufactured by methanol carbonylation reactions with rhodium or iridium organometallic complexes and halide-containing promoters named Monsanto or BP Cativa™ homogeneous processes, respectively. Developing a halide-free catalyst and a heterogeneous process for methanol carbonylation is of great importance and has recently attracted extensive research attention. Here, we report a green route for direct synthesis of acetic acid via vapor-phase carbonylation of methanol with a stable, selective, halide-free, and noble metal-free catalyst based on pyridine-modified H-mordenite zeolite. Methanol conversion and acetic acid selectivity can reach up to 100% and 95%, respectively. Only little deactivation is observed during the 145 hour reaction.
Co-reporter:Jiawei Zhong;Jingfeng Han;Yingxu Wei;Peng Tian;Xinwen Guo;Chunshan Song
Catalysis Science & Technology (2011-Present) 2017 vol. 7(Issue 21) pp:4905-4923
Publication Date(Web):2017/10/30
DOI:10.1039/C7CY01466J
The recent advances in synthesis and catalytic applications of nano-hierarchical SAPO-34 for methanol-to-olefin (MTO) conversion and other reactions have been elaborated in this minireview. The structure, unique properties (e.g., shape selectivity), and diffusion of zeolites and molecular sieves are briefly covered in the first part. An overview of the development of synthetic methods for the preparation of nanosized SAPO-34 and hierarchical SAPO-34 is included in the second and third parts, with focus on the novel and green preparation strategies. The advantages and disadvantages of the different synthetic approaches are discussed in detail, and the relationship between the catalytic performance and the diffusion and acidity is also elucidated. Finally, the updated characterization techniques considering the interconnectivity between the pore channels are outlined.
Co-reporter:Zhanling Ma;Xiangang Ma;Hongchao Liu;Yanli He;Wenliang Zhu;Xinwen Guo
Chemical Communications 2017 vol. 53(Issue 65) pp:9071-9074
Publication Date(Web):2017/08/10
DOI:10.1039/C7CC04574C
A one-step aldol condensation reaction to produce MA and AA is a green and promising strategy. Here, the aldol condensation reaction was first conducted with DMM and MAc over different types of zeolite catalysts. The H-ZSM-35 zeolite demonstrates excellent catalytic performance with a DMM conversion of 100% and a MA + AA selectivity of up to 86.2% and superior regeneration ability, with great potential for industrial operation.
Co-reporter:Guannan Li, Haibo Huang, Bowen Yu, Yun Wang, Jiawei Tao, Yingxu Wei, Shougui Li, Zhongmin Liu, Yan Xu and Ruren Xu
Chemical Science 2016 vol. 7(Issue 2) pp:1582-1587
Publication Date(Web):23 Nov 2015
DOI:10.1039/C5SC03837E
Hierarchical zeolite monoliths with multimodal porosity are of paramount importance as they open up new horizons for advanced applications. So far, hierarchical zeolites based on nanotube scaffolds have never been reported. Inspired by the organization of biominerals, we have developed a novel precursor scaffolding-solid phase crystallization strategy for hierarchical zeolites with a unique nanotube scaffolding architecture and nanotube-trimodal network, where biomolecular self-assembly (BSA) provides a scaffolding blueprint. By vapor-treating Sil-1 seeded precursor scaffolds, zeolite MFI nanotube scaffolds are self-generated, during which evolution phenomena such as segmented voids and solid bridges are observed, in agreement with the Kirkendall effect in a solid-phase crystallization system. The nanotube walls are made of intergrown single crystals rendering good mechanical stability. The inner diameter of the nanotube is tunable between 30 and 90 nm by varying the thickness of the precursor layers. Macropores enclosed by cross-linked nanotubes can be modulated by the choice of BSA. Narrow mesopores are formed by intergrown nanocrystals. Hierarchical ZSM-5 monoliths with nanotube (90 nm), micropore (0.55 nm), mesopore (2 nm) and macropore (700 nm) exhibit superior catalytic performance in the methanol-to-hydrocarbon (MTH) conversion compared to conventional ZSM-5. BSA remains intact after crystallization, allowing a higher level of organization and functionalization of the zeolite nanotube scaffolds. The current work may afford a versatile strategy for hierarchical zeolite monoliths with nanotube scaffolding architectures and a nanotube-multimodal network leading to self-supporting and active zeolite catalysts, and for applications beyond.
Co-reporter:Yuyan Qiao, Miao Yang, Beibei Gao, Linying Wang, Peng Tian, Shutao Xu and Zhongmin Liu
Chemical Communications 2016 vol. 52(Issue 33) pp:5718-5721
Publication Date(Web):23 Mar 2016
DOI:10.1039/C5CC10070D
Hollow SAPO-34 crystals are created via selective etching of their precursor under controlled alkaline or acid conditions. The abundant/interconnected Si–O–Al domains and Si–O–Si networks at the outer layer of SAPO-34 crystals are revealed to be decisive factors for the base and acid treatments respectively to achieve a well-preserved hollow structure.
Co-reporter:Chan Wang, Miao Yang, Mingrun Li, Shutao Xu, Yue Yang, Peng Tian and Zhongmin Liu
Chemical Communications 2016 vol. 52(Issue 38) pp:6463-6466
Publication Date(Web):12 Apr 2016
DOI:10.1039/C6CC01834C
Mesoporous SAPO-34 single crystals with tunable porosity and Si content have been fast synthesized within 4 hours by a reconstruction strategy, which show excellent hydrothermal stability and MTO catalytic activity. This new strategy is further proven to be applicable to prepare other mesoporous SAPO molecular sieve single crystals.
Co-reporter:Liang Qi, Jinzhe Li, Yingxu Wei, Lei Xu and Zhongmin Liu
Catalysis Science & Technology 2016 vol. 6(Issue 11) pp:3737-3744
Publication Date(Web):14 Mar 2016
DOI:10.1039/C5CY02238J
The role of methylnaphthalenes in a methanol to hydrocarbons (MTH) reaction on HZSM-5 zeolite was systematically studied on a fixed-bed reaction system. As this is a polycyclic aromatic species, it was interesting to find that co-feeding a small amount of naphthalene could also promote methanol conversion at a low temperature. For the first time, methylnaphthalenes were found to be able to act as initial active HCP species on HZSM-5. The introduced naphthalene could help generate more active methylbenzene HCP species and enhance the aromatic-based cycle during the induction period. As a result, ethene selectivity was promoted due to the co-fed naphthalene. Moreover, despite the large molecular size of naphthalene, it can still function as an active HCP species on the internal acid sites of the HZSM-5 catalyst.
Co-reporter:Jinbang Wang, Yingxu Wei, Jinzhe Li, Shutao Xu, Wenna Zhang, Yanli He, Jingrun Chen, Mozhi Zhang, Anmin Zheng, Feng Deng, Xinwen Guo and Zhongmin Liu
Catalysis Science & Technology 2016 vol. 6(Issue 1) pp:89-97
Publication Date(Web):16 Sep 2015
DOI:10.1039/C5CY01420D
The mechanism of the methanol to olefin (MTO) reaction over H-ZSM-22, a TON-type zeolite without cavities or channel intersections, has been investigated in the temperature range of 250–350 °C. For the first time, an induction period in low-temperature methanol conversion and the methylcyclopentenyl cation (MCP+) formed during this period have been observed directly and successfully. 13C magic angle spinning (MAS) NMR, 13C-labeling experiments and theoretical calculations have been employed to confirm the important active intermediates during methanol conversion at 300 °C. The reactions performed at different temperatures were comparatively studied and the differences in the reaction route for alkene formation from methanol conversion and the modes of H-ZSM-22 catalyst deactivation were revealed.
Co-reporter:Dehua Wang, Miao Yang, Wenna Zhang, Dong Fan, Peng Tian and Zhongmin Liu
CrystEngComm 2016 vol. 18(Issue 6) pp:1000-1008
Publication Date(Web):04 Jan 2016
DOI:10.1039/C5CE01798J
An aminothermal co-templating strategy has been developed to explore the synthesis of SAPO molecular sieves. Nanosized SAPO-56 (AFX) with a hollow morphology is, for the first time, obtained by utilizing triethylamine (TEA) and trimethylamine (TMA) as both the solvent and the template in the presence of HF. The prepared material is well characterized, and the coexistence of TEA and TMA in the crystals is proved by 13C NMR. Molecular modelling indicates that the most stable status for the as-made SAPO-56 is 2TEA per aft cage and 1TMA per gme cage in the AFX structure, which is consistent with the TG results and verifies the co-templating behaviour of the two amines. In addition, the aminothermal crystallization process of SAPO-56 is examined, revealing an interesting in situ phase transformation from SAPO-34 (only containing TEA) to nano SAPO-56 followed by a further in situ post-synthetic leaching to achieve the hollow structure. Both F− anions and organic amines are proposed to be responsible for the dissolution of SAPO-34 and the etching of SAPO-56 nanocrystals. The Si-rich outer layer with abundant Si coordination environments (more Si–O–Al bonds and less Al–O–P bonds) helps the shell of SAPO-56 survive the leaching. This work offers an effective way to prepare SAPO-56 nanocrystals and demonstrates the huge potential of the aminothermal co-templating route for new material synthesis.
Co-reporter:Liang Qi, Jinzhe Li, Yingxu Wei, Yanli He, Lei Xu and Zhongmin Liu
RSC Advances 2016 vol. 6(Issue 57) pp:52284-52291
Publication Date(Web):23 May 2016
DOI:10.1039/C6RA08393E
The influence of acid site density on the three-stage methanol to hydrocarbons (MTH) induction reaction was systematically investigated over three HZSM-5 catalysts (average size of 1–2 μm) with different Si/Al ratios. The initial active species can be formed more easily over catalysts with higher acid site density during the initial two stages and co-feeding toluene could shorten the initial two stages in the temperature-programmed MTH reaction. For each catalyst, the kinetics of the autocatalysis reaction during the induction period was investigated and the corresponding activation energy was calculated and compared. It was found that the formation rate of the retained species and its autocatalytic effect can both be enhanced over samples with high acid site density. Organic materials occluded in the catalyst during the MTH induction reaction were also analyzed ex situ by thermal analysis and GC-MS after extraction. The characterization results corresponded with the kinetic results very well.
Co-reporter:Chan Wang, Miao Yang, Wenna Zhang, Xiong Su, Shutao Xu, Peng Tian and Zhongmin Liu
RSC Advances 2016 vol. 6(Issue 53) pp:47864-47872
Publication Date(Web):16 May 2016
DOI:10.1039/C6RA06428K
With the aid of self-designed organophosphorous surfactant [2-(diethoxylphosphono)propyl]hexadecyldimethylammonium bromide (DPHAB), SAPO-34s with various special morphologies have been hydrothermally synthesized by using tetraethylammonium hydroxide (TEAOH), diethylamine (DEA) and triethylamine (TEA) as templates, respectively. The synthesized SAPO-34s were well characterized by XRD, XRF, SEM, N2 adsorption–desorption, solid state NMR and NH3-TPD measurements. The status of DPHAB was also investigated by using FT-IR, 13C NMR, TG–DTA and 31P NMR measurements as well as density functional theory calculations. It is found that the addition of DPHAB changes the crystal morphology dramatically and the aggregation degree of the crystals increases with the rising DPHAB/H3PO4 ratio. Moreover, microporous templates play an important role in the synthesis of mesoporous SAPO-34. TEAOH, which has the strongest interaction energy with the CHA framework among the investigated templates, shows the best cooperating ability with an organophosphorous surfactant to direct the formation of nanosized and mesoporous SAPO-34. The prepared SAPO-34s showed improved catalytic properties in the methanol-to-olefins (MTO) reaction.
Co-reporter:Xiao Xiang, Miao Yang, Beibei Gao, Yuyan Qiao, Peng Tian, Shutao Xu and Zhongmin Liu
RSC Advances 2016 vol. 6(Issue 15) pp:12544-12552
Publication Date(Web):25 Jan 2016
DOI:10.1039/C5RA22868A
A facile and direct ion-exchange (DIE) method has been developed to prepare Cu-exchanged SAPO-34s, in which as-synthesized SAPO-34 is used as a precursor. This approach is simple and economical as compared with the conventional multistep ion exchange procedure. The ion exchange behavior of the as-synthesized SAPO-34s is found to be template-dependent. For SAPO-34s templated by smaller amines, they show a better Cu exchange ability than the corresponding NH4+-SAPO-34 and the Cu loadings rise with the increasing template size. Coordination between amine and Cu2+ in the as-prepared DIE sample is clearly evidenced. However, oversized amine in the CHA cage may cause a failure of the DIE process due to the steric effect. An obvious surface Cu enrichment is observed for the as-prepared DIE sample, which migrates to the interior of the crystals upon calcination. The Cu-SAPO-34 catalyst prepared by DIE method displays excellent performance in the selective catalytic reduction of NO with NH3 (NH3-SCR). Its better low-temperature activity as compared with that of the conventional one is likely due to the higher isolated Cu2+ amount and surface Cu content. This promising strategy is expected to facilitate the large-scale industrial preparation of NH3-SCR catalyst.
Co-reporter:Dong Fan, Peng Tian, Shutao Xu, Dehua Wang, Yue Yang, Jinzhe Li, Quanyi Wang, Miao Yang and Zhongmin Liu
New Journal of Chemistry 2016 vol. 40(Issue 5) pp:4236-4244
Publication Date(Web):14 Jan 2016
DOI:10.1039/C5NJ02351C
In this work, a comprehensive study of the hydrothermal synthesis and catalytic performance of SAPO-34 templated by the isomeric dipropylamine (DPA) and diisopropylamine (DIPA) was carried out. SAPO-34 with a faster crystallization rate and lower Si content could be obtained with DIPA as the template, suggesting the better templating efficacy of DIPA than DPA. Theoretical calculations reveal that DIPA possesses more favourable non-bonding interactions with the CHA framework and the electronic configuration is of vital importance in determining the template efficacy. SAPO-34-DIPA with low silicon contents exhibits excellent performance, over which a maximum selectivity of ethylene plus propylene (87.2%) is observed. This value should be among the top ever reported. The surface Si enrichment on the crystals, which is both template- and condition-dependent, is revealed to be of significant influence in the catalytic performance. The relatively homogenous Si distribution in the crystals, lower acid concentration and weaker acid strength corporately make SAPO-34-DIPA an excellent MTO catalyst.
Co-reporter:Wenna Zhang, Yueying Chu, Yingxu Wei, Xianfeng Yi, Shutao Xu, Jindou Huang, Mozhi Zhang, Anmin Zheng, Feng Deng, Zhongmin Liu
Microporous and Mesoporous Materials 2016 Volume 231() pp:216-229
Publication Date(Web):1 September 2016
DOI:10.1016/j.micromeso.2016.05.029
•The reactions involved in the alkenes-based cycle in MTO reaction were discussed in-depth by theoretical calculations.•Confinement effect from the zeolite framework can strongly stabilize the transition states by the vdW interactions.•Acid strength can effectively enhance the catalytic activities by decreasing the reaction barriers.•The reactions related to ethene formation and transform need overcome higher barriers in the alkenes-based cycle.Methanol-to-Olefins (MTO) conversion over acidic zeolite catalysts has become the most important non-petrochemical route for the production of light olefins. The ‘dual-cycle’ mechanism (i.e., alkenes-based cycle and aromatics-based cycle) over H-ZSM-5 zeolite has been generally accepted for olefins generation from methanol conversion. However, the relationship between the catalytic performance and the confinement effect/acid strength of the catalyst is still unclear. Herein, the methylation, isomerization and cracking processes involved in the alkenes-based cycle are discussed in-depth by density functional theory (DFT) calculations. The calculation results predicted that the transition states can be considerably stabilized by the van der Waals (vdW) interactions from the zeolite framework, resulting in the reduction of the activation barriers. And acid strength can also enhance the reaction activities. However, the catalytic reactivity of all elementary steps in the alkenes-based cycle can be improved at a different degree with increasing the acid strength. In addition, the ethene formation, transformation and the precursor of ethene formation need higher energy. And increasing acid strength can sharply decrease the activation barriers of ethene formation of cracking reaction, indicating that ethene formation may need strong acid strength.The methylation, isomerization and cracking processes involved in the alkenes-based cycle of Methanol-to-Olefins conversion (MTO) on H-ZSM-5 are discussed in-depth by density functional theory calculations. The transition states can be considerably strongly stabilized by the van der Waals (vdW) interactions from the zeolite framework, and acid strength can also effectively enhance the reaction activities. In addition, the ethene formation, transform and the precursor of ethene formation need higher energy.
Co-reporter:Hui Zhou, Wenliang Zhu, Lei Shi, Hongchao Liu, Shiping Liu, Youming Ni, Yong Liu, Yanli He, Shuliang Xu, Lina Li, Zhongmin Liu
Journal of Molecular Catalysis A: Chemical 2016 Volume 417() pp:1-9
Publication Date(Web):June 2016
DOI:10.1016/j.molcata.2016.02.032
•Methoxyls and acetyls on HMOR were observed by in situ DRIFT spectroscopy.•High pressure and appropriate temperature promoted the formation of acetyls.•Side reactions were favored at low pressure and high temperature.•Acetyls were observed in 12MR channels, which were more active for side reactions.In situ diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy was used to study the reaction of dimethyl ether (DME) carbonylation to methyl acetate (MAc). Methoxyl and acetyl groups were observed in situ, confirming the reaction mechanistic proposal. DME adsorption bands on SiOH, AlOH and SiOHAl (Brønsted acid sites) groups were identified respectively. The effect of temperature and pressure on acetyl formation and side reactions were systematically studied. It was found that methoxyls formed by DME chemisorbed on Brønsted acid sites could be observed above 433 K. High pressure and appropriate temperature interval promoted the formation of acetyls. Side reactions, DME transformed into olefins and then into cokes, were favored at low pressure and high temperature. Carbonylation reactions on catalysts with acid sites only in 8MR side pockets and 12MR main channels of mordenite (samples noted as HMOR-SP and HMOR-MC) were conducted by in situ DRIFT spectroscopy and catalytic testing. Pyridine molecules adsorbed in 12MR main channels resulted in the low utilization of acid sites in 8MR side pockets. The synthesis rate of MAc on HMOR-SP was stable but lower. HMOR-MC presented the lowest MAc synthesis rate with the production of coke, which was also observed in DRIFT spectra.
Co-reporter:Dehua Wang
The Journal of Physical Chemistry C 2016 Volume 120(Issue 22) pp:11854-11863
Publication Date(Web):May 24, 2016
DOI:10.1021/acs.jpcc.6b00300
A pure fluorinated aluminophosphate [Al8P8O32F4·(C3H12N2)2(H2O)2] (ULM-6) has been synthesized via an aminothermal strategy, in which triisopropanolamine (TIPA) is used as the solvent together with the addition of propyleneurea and HF. The 13C NMR spectrum demonstrates that 1,3-diaminopropane, the in situ decomposer of propyleneurea, is the real structure-directing agent (SDA) for ULM-6 crystals. The local Al, P, and F environments of the dehydrated ULM-6 are investigated by 1D and 2D solid-state NMR spectroscopy. The spatial proximities are extracted from 19F{27Al}, 19F{31P}, 27Al{19F}, and 31P{19F} rotational-echo double resonance (REDOR) NMR experiments as well as 19F → 31P heteronuclear correlation (HETCOR) NMR and {31P}27Al HMQC NMR experiments, allowing a full assignment of all the 19F, 27Al, and 31P resonances to the corresponding crystallographic sites. Moreover, it is found that the structure of ULM-6 is closely related to that of AlPO4-14. A combination of high-temperature powder XRD, thermal analysis, and 19F NMR reveals that the removal of fluorine atoms at higher temperature is crucial to the phase transformation of ULM-6 to AlPO4-14. The calcined product shows high CO2/CH4 and CO2/N2 selectivity with ratios of 15.5 and 29.1 (101 kPa, 25 °C), respectively.
Co-reporter:Jinzhe Li, Yingxu Wei, Jingrun Chen, Shutao Xu, Peng Tian, Xiaofeng Yang, Bing Li, Jinbang Wang, and Zhongmin Liu
ACS Catalysis 2015 Volume 5(Issue 2) pp:661
Publication Date(Web):December 19, 2014
DOI:10.1021/cs501669k
Organic reaction intermediates confined in zeolite cavities are very important for product formation during methanol-to-olefins (MTO) conversion; however, direct evidence is still required to understand the particular function of these intermediates. Herein, for the first time, by careful selection of SAPO molecular sieves with different cavity size but identical 8MR pore openings, the reactivity and role of these intermediates played in olefin generation are verified by isotopic tracing method and theoretical calculations based on the observation of two types of carbenium intermediates, polyMB+ and polyMCP+, under the real MTO reaction conditions. It demonstrates that cavity size controls the molecular size and reactivity of these confined species, which results in different MTO activity and product selectivity.Keywords: C1 chemistry; confinement effects; MTO; selectivity control; shape selectivity
Co-reporter:Peng Tian, Yingxu Wei, Mao Ye, and Zhongmin Liu
ACS Catalysis 2015 Volume 5(Issue 3) pp:1922
Publication Date(Web):February 10, 2015
DOI:10.1021/acscatal.5b00007
The methanol-to-olefins (MTO) reaction is an interesting and important reaction for both fundamental research and industrial application. The Dalian Institute of Chemical Physics (DICP) has developed a MTO technology that led to the successful construction and operation of the world’s first coal to olefin plant in 2010. This historical perspective gives a brief summary on the key issues for the process development, including studies on the reaction mechanism, molecular sieve synthesis and crystallization mechanism, catalyst and its manufacturing scale-up, reactor selection and reactor scale-up, process demonstration, and commercialization. Further challenges on the fundamental research and the directions for future catalyst improvement are also suggested.Keywords: DMTO; fluidized bed; methanol to olefins; reaction mechanism; SAPO molecular sieve; scale-up
Co-reporter:Liang Qi, Yingxu Wei, Lei Xu, and Zhongmin Liu
ACS Catalysis 2015 Volume 5(Issue 7) pp:3973
Publication Date(Web):May 22, 2015
DOI:10.1021/acscatal.5b00654
The reaction behavior in the induction period of the methanol to hydrocarbon (MTH) reaction over HZSM-5 (Si/Al = 19) zeolite has been investigated in a fixed-bed reactor. It is found that the induction period could be more than 2 h when the reaction was performed at a temperature of 255 °C and below. Meanwhile, three reaction stages can be clearly distinguished in the induction period: i.e., the initial C–C bond formation stage, the hydrocarbon pool (HCP) species formation stage, and the autocatalysis reaction stage. For each reaction stage, the kinetic parameters as well as the apparent activation energies have been evaluated. The HCP species formation stage is shown to be the rate-determining step. Addition of a ppm amount (molar) of benzene, toluene, or p-xylene to the methanol feed leads to a shortened induction period due to a lower energy barrier for both the HCP species formation and the autocatalysis reaction. A critical value of HCP species, [HCP]c, that is required for starting the autocatalysis reaction (the third stage) has been proposed. This critical value was measured to be 1 toluene molecule per 276 unit cells for HZSM-5 zeolite when toluene is cofed with methanol.Keywords: activation energy; HZSM-5; induction period; kinetics; methanol
Co-reporter:Beibei Gao, Peng Tian, Mingrun Li, Miao Yang, Yuyan Qiao, Linying Wang, Shutao Xu and Zhongmin Liu
Journal of Materials Chemistry A 2015 vol. 3(Issue 15) pp:7741-7749
Publication Date(Web):18 Feb 2015
DOI:10.1039/C5TA00888C
A low-temperature strategy to fabricate hierarchical aluminophosphate-based molecular sieves has been developed without the assistance of surfactants. The facile synthesis results in cylinder-like SAPO-5 (AFI) composed of oriented attached nanosheets with a thickness of 40–100 nm. The main exposed surface of the nanosheets is revealed by the SAED pattern to be the {001} plane, implying a short path for molecular diffusion in the one-dimensional 12-membered ring channel. Investigation on the crystallization process demonstrates that low temperature retards the crystal growth along the c-direction in SAPO-5 and the ordered architecture forms via a nanosheet formation and oriented attachment process. The aggregated morphology of SAPO-5 is template-dependent, which may be modified/changed by varying the template in the system. The low-temperature strategy is also successfully extended to the preparation of metal-containing aluminophosphate molecular sieves. The obtained MeAPO-5 (Me = Co, Mn, and Cr) and a novel CHA/AEI intergrowth CoAPO molecular sieve also possess hierarchical structures with nanosheet-assembled morphology. Remarkably, the present self-assembled AFI crystals exhibit an obvious improvement in catalytic reactions. This facile method provides a new way for the long-range organization of nanosized building blocks to fabricate hierarchical nanostructures.
Co-reporter:Chan Wang, Miao Yang, Peng Tian, Shutao Xu, Yue Yang, Dehua Wang, Yangyang Yuan and Zhongmin Liu
Journal of Materials Chemistry A 2015 vol. 3(Issue 10) pp:5608-5616
Publication Date(Web):12 Feb 2015
DOI:10.1039/C4TA06124A
A spherical self-assembly of SAPO-34 nanosheets was hydrothermally synthesized by using a quaternary ammonium-type organosilane surfactant [3-(trimethoxysilyl)propyl]octadecyldimethylammonium chloride (TPOAC) as the mesoporogen and a part of the silica source, and diethylamine (DEA) as the microporous template. The prepared materials were well characterized by XRD, XRF, SEM, TEM, N2 adsorption–desorption, NH3-TPD, NH3-adsorbed IR and pyridine-adsorbed IR measurements. It revealed that the morphologies, compositions and acidity of the SAPO-34 products changed significantly with the increased TPOAC/TEOS ratio, showing that the TPOAC/TEOS ratio had a significant impact on the crystallization process of SAPO-34. Solid state 13C, 29Si NMR and TG-DTA analyses were further conducted to investigate the status of TPOAC in the final products. A possible crystallization process involving TPOAC was proposed. The catalytic performances of the synthesized SAPO-34s were evaluated using the MTO reaction. The optimal SAPO-34 nanosheet assemblies with a hierarchical porous structure displayed a remarkably enhanced catalytic lifetime and high yields of light olefins.
Co-reporter:Hui Zhou, Wenliang Zhu, Lei Shi, Hongchao Liu, Shiping Liu, Shutao Xu, Youming Ni, Yong Liu, Lina Li and Zhongmin Liu
Catalysis Science & Technology 2015 vol. 5(Issue 3) pp:1961-1968
Publication Date(Web):07 Jan 2015
DOI:10.1039/C4CY01580K
A series of Fe-modified mordenite zeolite samples were synthesized by a template-free method and employed in dimethyl ether (DME) carbonylation reaction for the production of methyl acetate (MAc). XRD, UV-Vis, and UV-Raman characterization studies proved that Fe atoms have been introduced into the mordenite zeolite framework by partial substitution of Al atoms, which led to evident changes of activity and MAc selectivity. With the increase of iron content (as metal) from 0.0 to 3.6 wt%, DME conversion first increased and then decreased. MAc selectivity and catalyst stability were enhanced for all Fe-modified samples. TG and GC-MS analysis of deactivated catalysts showed that the amount of coke retained in the catalysts decreased as the iron content of the zeolites increased. The enhancement effects were expounded in terms of the decrease of the acid strength and acid density in the 12MR channels of mordenite after introduction of Fe, resulting in the reduction of carbon deposition.
Co-reporter:Miao Yang, Peng Tian, Lin Liu, Chan Wang, Shutao Xu, Yanli He and Zhongmin Liu
CrystEngComm 2015 vol. 17(Issue 44) pp:8555-8561
Publication Date(Web):07 Oct 2015
DOI:10.1039/C5CE01702E
The present work investigates the effect of cationic surfactants on tuning the crystalline phase and morphology of SAPO molecular sieves. First, we explore the cationic surfactant-assisted hydrothermal synthesis of DNL-6, which is a newly developed SAPO molecular sieve with RHO structure and can be prepared only in a narrow silica concentration. Comparative experiments reveal that the cationic surfactant with a longer alkane chain can help to obtain pure DNL-6 with an adjustable Si content, and the product with a higher Si content presents a spherical morphology composed of DNL-6 nanocrystals. It is believed that the strong adsorption of the cationic surfactant molecules on the SAPO species protects the DNL-6 from dissolving and inhibits the crystallization of SAPO-34. It is thus concluded that the cationic surfactant favors the formation of SAPO crystals having a relatively high structural symmetry although the surfactants are not retained in the product. Moreover, the crystal morphology may be modified due to the abundant interactions of the cationic surfactant with the anionic SAPO framework. Based on the above understanding, flower-like SAPO-35 and Si-rich SAPO-16 were further synthesized by designed cationic surfactant-assisted syntheses. These confirm that the cationic surfactant-assisted hydrothermal synthesis has huge potential in the control of the SAPO crystalline phase and crystal morphology. More importantly, the obtained hierarchical porous DNL-6 exhibits high catalytic activity and selectivity for the cycloaddition of CO2 with epichlorohydrin without any solvent and co-catalyst.
Co-reporter:Dehua Wang, Peng Tian, Dong Fan, Miao Yang, Beibei Gao, Yuyan Qiao, Chan Wang, Zhongmin Liu
Journal of Colloid and Interface Science 2015 Volume 445() pp:119-126
Publication Date(Web):1 May 2015
DOI:10.1016/j.jcis.2014.12.029
Figure optionsIn the present study, N-methyldiethanolamine (MDEA) is demonstrated to be a multifunctional structure-directing agent for the synthesis of aluminophosphate-based molecular sieves. Four types of molecular sieves, including SAPO-34, -35, AlPO-9 and -22, are for the first time acquired with MDEA as a novel template. The phase selectivity of the present synthesis is found to be condition-dependent. SAPO-34 (CHA) crystallizes from a conventional hydrothermal system with a higher MDEA concentration. When using MDEA as both the template and solvent, pure SAPO-35 (LEV) is obtained from the synthetic gel with a high P2O5/Al2O3 ratio of (2–3), in which the concentration of MDEA could be varied in a wide range. AlPO-9 and AlPO-22 (AWW) are synthesized under the similar conditions to SAPO-35, except without the addition of Si source. The physicochemical properties of the obtained samples are investigated by XRD, XRF, SEM, N2 physisorption, TG-DSC, and various NMR spectra (13C, 29Si, 27Al and 31P). Both SAPO-34 and SAPO-35 show good thermal stability, large surface area, and high pore volume. The catalytic performance of SAPO-34 is evaluated by the methanol-to-olefins (MTO) reaction and a good (C2H4 + C3H6) selectivity of 82.7% has been achieved.
Co-reporter:Jinbang Wang, Shutao Xu, Jinzhe Li, Yuchun Zhi, Mozhi Zhang, Yanli He, Yingxu Wei, Xinwen Guo and Zhongmin Liu
RSC Advances 2015 vol. 5(Issue 108) pp:88928-88935
Publication Date(Web):15 Oct 2015
DOI:10.1039/C5RA18438J
Nanosized HZSM-22 has been successfully prepared using ball milling combined with alkaline and acid leaching treatment. The samples were characterized by XRD, XRF, nitrogen physical adsorption–desorption, SEM and solid state NMR. The results showed that the size of the zeolite crystal was greatly reduced after ball milling treatment, and that the crystallinity of the milled sample can be almost totally restored after further alkaline and acid treatment. The prepared nanosized HZSM-22 exhibited enhanced catalytic stability compared with the parent sample in the MTH reaction. Detailed product analysis implied that the improvement of the diffusion effect and the correspondingly reduced secondary reaction would be the most important factor for the long-term MTH operation over the nanosized catalyst.
Co-reporter:Yangyang Yuan, Peng Tian, Miao Yang, Dong Fan, Linying Wang, Shutao Xu, Chan Wang, Dehua Wang, Yue Yang and Zhongmin Liu
RSC Advances 2015 vol. 5(Issue 13) pp:9852-9860
Publication Date(Web):06 Jan 2015
DOI:10.1039/C4RA14295K
Hierarchical beta zeolites have been hydrothermally synthesized by using commercial cationic polymer PDADMA as both microporogen and mesoporogen. The influence of various synthetic parameters on the products was systematically investigated. Products with narrow SiO2/Al2O3 ratios were obtained under static crystallization conditions. By employing rotational conditions and adding seeds in the initial gel, higher SiO2/Al2O3 ratios over a wider range of 25 to 50 could be successfully achieved, which showed an obvious improvement. The 13C NMR, TG, XRF, N2 sorption as well as molecular mechanics simulation results indicated that PDADMA was incorporated in the final product without decomposition, acting as a SDA for the formation of beta zeolite and mesoporogen simultaneously. Further studies on the crystallization process revealed that hierarchical structures templated by PDADMA had been formed in the early solid. The amorphous Si–Al species around the micropore channels gradually evolved to the beta structure with the assistance of PDADMA, whereas the mesopores formed in the initial period remained less changed. A solid-mediated mechanism is thus proposed for the synthesis. Characterization results showed that the obtained products had sphere-like morphology composed of 10–20 nm crystalline domains, high mesopore volumes, and large external surface areas. More importantly, the hierarchical beta zeolites exhibited greatly enhanced catalytic activity and stability in the cracking reaction of triisopropylbenzene.
Co-reporter:Danhua Yuan, Dawei He, Shutao Xu, Zhijia Song, Mozhi Zhang, Yingxu Wei, Yanli He, Shuliang Xu, Zhongmin Liu, Yunpeng Xu
Microporous and Mesoporous Materials 2015 Volume 204() pp:1-7
Publication Date(Web):1 March 2015
DOI:10.1016/j.micromeso.2014.10.049
•High silica Y zeolite was synthesized using imidazolium salt as novel organic SDAs.•Imidazolium cations can partially replace the sodium cations of the Y zeolite framework.•Y zeolite synthesized with [E(B)MIm]Br as SDAs displayed higher thermal stability.Alkyl-substituted imidazolium-based ionic liquid as a novel type of organic structure-directing agent (SDA) was employed to synthesize high-silica Y zeolite with a SiO2/Al2O3 ratio of approximately 6.20–6.40. The XRD, SEM, BET and 27Al NMR characterizations showed that the products synthesized with the ionic liquids 1-ethyl-3-methylimidazolium bromide or 1-butyl-3-methylimidazolium bromide were highly crystalline pure phase Y zeolite. Moreover, the TG, TOC, XRF and 13C NMR results suggested that 1-ethyl-3-methylimidazolium or 1-butyl-3-methylimidazolium cations were trapped within the pores of the faujasite structure and played the role of structure-directing agents. 1-Ethyl-3-methylimidazolium and 1-butyl-3-methylimidazolium cations can partially replace the sodium cations to balance the negative charges of the zeolite framework, which facilitated the formation of a high SiO2/Al2O3 ratio faujasite structure.
Co-reporter:Lina Li, Wenliang Zhu, Yong Liu, Lei Shi, Hongchao Liu, Youming Ni, Shiping Liu, Hui Zhou and Zhongmin Liu
RSC Advances 2015 vol. 5(Issue 69) pp:56304-56310
Publication Date(Web):22 Jun 2015
DOI:10.1039/C5RA06619K
Phosphorous (P)-modified ordered mesoporous carbon CMK-3 was used as a catalyst for the direct dehydrogenation (DH) of propane to propylene without any auxiliary stream, and this catalyst exhibited better activity and selectivity than the pristine ordered mesoporous carbon. The prepared samples were characterized by N2 adsorption and desorption, temperature-programmed desorption (TPD), and X-ray photoelectron spectroscopy (XPS). After the introduction of P using an impregnation method, PO groups formed on the surface of the materials and substantially improved the activity and selectivity. The PO groups are believed to be electron donors for CO active centers, or independent active centers for catalytic DH of propane.
Co-reporter:Xiong Su
The Journal of Physical Chemistry C 2015 Volume 119(Issue 5) pp:2589-2596
Publication Date(Web):January 15, 2015
DOI:10.1021/jp511670q
By applying analysis of multiple solid-state MAS NMR spectra, the atomic coordination environment and acidity of a novel SAPO-type molecular sieve, DNL-6, are studied. 27Al MQ-MAS NMR and 31P–27Al MQ-HETCOR NMR spectra reveal the existence of a Si–Al–Si region with Al(OSi)n (n = 1–4) species in the framework of DNL-6, explaining well the high concentration of single Si(OAl)4 species (3 mmol/g) accommodated in the sample. 13C MAS NMR of 2-13C-acetone adsorption indicates that there exist two kinds of strong Brønsted acid sites in DNL-6. One of them has similar strength as those in HZSM-5 and the other is even stronger, which is unusual in SAPO-type molecular sieves. Also, a discrepancy in Brønsted acid concentration between the theoretical and 1H NMR experimental results has been found, revealing the occurrence of a dehydoxylation process during the calcination. The origin of the extremely strong Brønsted acid sites in DNL-6 is investigated by density functional theory calculations, which suggest that the dehydroxylation process may lead to a local structure deformation and remarkably enhance the Brønsted acidity. More importantly, DNL-6 exhibits excellent catalytic activity in the synthesis of methylamines due to its stronger acidity.
Co-reporter:Miao Yang, Peng Tian, Chan Wang, Yangyang Yuan, Yue Yang, Shutao Xu, Yanli He and Zhongmin Liu
Chemical Communications 2014 vol. 50(Issue 15) pp:1845-1847
Publication Date(Web):17 Dec 2013
DOI:10.1039/C3CC48264B
Silicoaluminophosphate SAPO-34 molecular sieve nanocrystals have been prepared by a post-synthesis milling and recrystallization method, which is further proven to be universally applicable to other SAPO molecular sieves. The obtained SAPO-34 with reduced Si enrichment on the external surface shows considerably improved catalytic performance in the MTO reaction.
Co-reporter:Jingrun Chen, Jinzhe Li, Cuiyu Yuan, Shutao Xu, Yingxu Wei, Quanyi Wang, You Zhou, Jinbang Wang, Mozhi Zhang, Yanli He, Shuliang Xu and Zhongmin Liu
Catalysis Science & Technology 2014 vol. 4(Issue 9) pp:3268-3277
Publication Date(Web):10 Jun 2014
DOI:10.1039/C4CY00551A
The mechanism of the methanol to olefin (MTO) reaction over AlPO-18 (without Brønsted acid sites) and two SAPO-18 (with different Brønsted acid site densities) catalysts has been investigated. The Brønsted acid site density of AlPO-18 and SAPO-18 catalysts was determined by 1H MAS NMR spectroscopy. Methanol conversion over the catalysts showed that the catalytic activity of the catalysts was strongly influenced by their Brønsted acid site density. Using 13C magic angle spinning (MAS) NMR, we directly observed the pentamethylcyclopentenyl cation (pentaMCP+) over SAPO-18 under real MTO reaction conditions, but no carbenium ion was detected over AlPO-18. Furthermore, analysis of confined organics by 13C MAS NMR and GC-MS clearly demonstrated that higher Brønsted acid site density improved the formation and accumulation of some important and reactive hydrocarbon pool species, such as pentaMCP+ and polymethylbenzenes. With the aid of the 12C/13C-methanol switch technique, the detailed olefin formation mechanism was elucidated. During the MTO reaction, light olefin generation over SAPO-18 mainly followed the aromatic-based hydrocarbon pool mechanism; however, the olefin methylation and cracking mechanism accounted for the production of light olefins over AlPO-18.
Co-reporter:Shiping Liu, Wenliang Zhu, Lei Shi, Hongchao Liu, Yong Liu, Youming Ni, Lina Li, Hui Zhou, Shutao Xu and Zhongmin Liu
RSC Advances 2014 vol. 4(Issue 77) pp:40999-41002
Publication Date(Web):12 Aug 2014
DOI:10.1039/C4RA06150K
A highly active Nafion-H catalyst is developed for vapour phase carbonylation of dimethoxymethane (DMM) to methyl methoxyacetate (MMAc) with a significant MMAc selectivity as high as 90%. The excellently catalytic performance is because of the unique structure and high acid strength of the Nafion-H catalyst.
Co-reporter:Quanyi Wang, Shutao Xu, Jingrun Chen, Yingxu Wei, Jinzhe Li, Dong Fan, Zhengxi Yu, Yue Qi, Yanli He, Shuliang Xu, Cuiyu Yuan, You Zhou, Jinbang Wang, Mozhi Zhang, Baolian Su and Zhongmin Liu
RSC Advances 2014 vol. 4(Issue 41) pp:21479-21491
Publication Date(Web):24 Apr 2014
DOI:10.1039/C4RA02695K
In this work, two kinds of mesoporous ZSM-5 were synthesized successfully using a hydrothermal methodology by utilizing different soft templates, namely, dimethyl octadecyl [3-(trimethoxysilyl)propyl]ammonium chloride ([(CH3O)3SiC3H6N(CH3)2C18H37]Cl, TPOAC) and hexadecyl trimethyl ammonium bromide (C16H33(CH3)3NBr, CTAB). The obtained mesoporous ZSM-5 samples were compared with conventional ZSM-5, and the effects of different surfactant usages during the synthesis of mesoporous ZSM-5 on the physicochemical and catalytic properties were systematically investigated. Multiple techniques, such as XRD, SEM, N2 adsorption techniques, HP 129Xe NMR, 27Al MAS NMR, 29Si MAS NMR, and 1H MAS NMR, were employed for the characterization. Although the synthesized mesoporous ZSM-5 samples had equal surface areas, they presented different relative crystallinities, morphologies, pore-size distributions, micropore–mesopore interconnectivity, framework atom coordination states and acidities. When using these synthesized ZSM-5 samples as catalysts for methanol conversion, the mesoporous ZSM-5 templated with TPOAC exhibited an extremely long catalyst lifespan compared to conventional ZSM-5, while mesoporous ZSM-5 templated with CTAB showed no advantage in prolonging the catalyst lifetime during the reaction. The differences in the catalytic lifespan and the reduction of coke deposition were correlated to the variation of acidity and porosity with the mesopore generation in the ZSM-5 catalysts by the usage of different structure-directing agents. Compared to the mesopore structure-directing agent, CTAB, with the use of TPOAC as the template and part of the Si source, mesoporous ZSM-5 could be synthesized with good mesopore–micropore interconnectivity, which accounted for the improved catalytic performance in the reaction of methanol conversion.
Co-reporter:Linying Wang, Peng Tian, Yangyang Yuan, Miao Yang, Dong Fan, Hui Zhou, Wenliang Zhu, Shutao Xu, Zhongmin Liu
Microporous and Mesoporous Materials 2014 Volume 196() pp:89-96
Publication Date(Web):15 September 2014
DOI:10.1016/j.micromeso.2014.05.001
Co-reporter:Danhua Yuan, Shutao Xu, Mozhi Zhang, Yingxu Wei, Xinglong Dong, Yanli He, Shuliang Xu, Zhongmin Liu, Yunpeng Xu
Microporous and Mesoporous Materials 2014 Volume 185() pp:149-156
Publication Date(Web):1 February 2014
DOI:10.1016/j.micromeso.2013.11.010
•ZSM-2 nanorods with crystal size about 50 nm were synthesized at 30 °C.•The samples synthesized at 30 °C and 100 °C showed different characteristics.•The crystallization process of ambient synthesis was discussed.ZSM-2 nanorods with crystal size around 50 nm were successfully synthesized at ambient temperature (30 °C). The crystallization process of ZSM-2 zeolite under ambient temperature was studied and discussed according to the measurement of crystallization kinetic curve, and characterizations with multiple techniques, such as X-ray diffraction (XRD), scanning electron microscopy (SEM), low-temperature N2 adsorption/desorption analysis, thermogravimetry analysis (TG) and nuclear magnetic resonance (NMR) etc. The ZSM-2 zeolite synthesized at ambient temperature presented different crystal morphologies and large specific area as compared with the sample synthesized at high temperature (100 °C). Furthermore, 29Si MAS-NMR showed that the nanoscale ZSM-2 obtained by ambient synthesis contained more EMT phase and lower Si/Al ratio than that of micrometer-sized ZSM-2 crystals obtained at 100 °C. More interestingly, NMR and low-temperature N2 adsorption/desorption characterizations revealed that the local environment of Al did not change much while that of Si did change a lot during the ambient crystallization process, and the micropore area increased rapidly while the micropore size distributions of the samples changed little with increasing crystallization time.
Co-reporter:Dehua Wang, Peng Tian, Miao Yang, Shutao Xu, Dong Fan, Xiong Su, Yue Yang, Chan Wang, Zhongmin Liu
Microporous and Mesoporous Materials 2014 Volume 194() pp:8-14
Publication Date(Web):August 2014
DOI:10.1016/j.micromeso.2014.03.028
•SAPO molecular sieves are synthesized with alkanolamines as the novel template.•The obtained SAPO-34 exhibits good CO2 adsorption/separation ability.•The CO2 uptake is in line with the acid concentration of SAPO-34 adsorbent.Alkanolamines are used for the first time as both the solvent and template to explore the syntheses of SAPO molecular sieves. Diglycolamine (DGA) and diisopropanolamine (DIPA) are found to act as novel structure-directing agent for the synthesis of SAPO-34, and N-methyldiethanolamine leads to the crystallization of SAPO-44. The obtained SAPO-34s are well characterized and investigated as adsorbents for selective separation of CO2 from N2 and CH4. A close relationship between the acid concentration of SAPO-34 and CO2 adsorption capacity has been revealed. SAPO-34-DGA with the highest acid concentration (sample D4) exhibits the best CO2 adsorption capacity and high CO2-over-N2 selectivity. Breakthrough experiments are further carried out based on sample D4, which shows an excellent dynamic preferential adsorption ability for CO2 (∼8.2 wt%) from both CO2/N2 and CO2/CH4 mixtures (298 K). These results demonstrate that SAPO-34-DGA could be a promising adsorbent for the CO2 capture.
Co-reporter:Kunyuan Wang, Xinglong Dong, Zhaoan Chen, Yanli He, Yunpeng Xu, Zhongmin Liu
Microporous and Mesoporous Materials 2014 Volume 185() pp:61-65
Publication Date(Web):1 February 2014
DOI:10.1016/j.micromeso.2013.11.007
•A novel route to obtain the high para-selectivity was developed by conversion of anisole.•The hydrolysis of anisole predominates over acid catalysts.•We report that high para-selectivity of 80.67% was obtained over modified ZSM-5.•The acid sites with moderate acid strength were beneficial to synthesis cresol.•The reaction net of anisole was studied.A novel route to obtain the high para-selectivity was developed by conversion of anisole on modified ZSM-5 in a continuous flowing fixed-bed reactor. It showed that the silylation and steaming treatment were significantly benificial to enhance the para-selectivity. Compared with the parent catalysts, the para-selectivity was sharply increased from 18.13% to 69.21% after the second silylation, which was further increased to 80.67% by steaming treatment. The acid sites with different strength of catalysts were studied by NH3-TPD which had an influence on both the para-selectivity and the amount of aromatics in the products.The high para-selectivity of 80.67% was obtained by silylaion and steaming treatment which was ascribed to the decrease in pore-opening size and the inactivation of external acid sites.The formed ortho-cresol and meta-cresol in the intersection of ZSM-5 channel which cannot diffuse out of the channel and only the para-cresol can diffuse out of the channel. Para-cresol diffused out of the channel as the final products when the concentration of external acid sites was very low and the possibility of para-cresol isomerization decreased. The para-selectivity will be enhanced when the external acid sites were passivated and at the same time the pore opening size decreased.
Co-reporter:Dong Fan, Peng Tian, Xiong Su, Yangyang Yuan, Dehua Wang, Chan Wang, Miao Yang, Linying Wang, Shutao Xu and Zhongmin Liu
Journal of Materials Chemistry A 2013 vol. 1(Issue 45) pp:14206-14213
Publication Date(Web):18 Sep 2013
DOI:10.1039/C3TA12829F
Aminothermal synthesis of SAPO molecular sieves, in which organic amines are used as both solvent and template, is explored based on a variety of amines. Di-iso-propylamine (DIPA) and N,N,N′,N′-tetramethylethylenediamine (TMEDA) are found to lead to the rapid crystallization of SAPO-34 with high solid yield. A solid yield of 96.2% could be acquired using the TMEDA system (200 °C, 12 h), which is the highest value ever reported for SAPO molecular sieves. SAPO-44 is obtained for the first time using the hexamethyleneimine (HMI) template. Detailed synthetic investigation shows that the silicon content in the initial gel has an important effect on the crystalline nature of the final products, and higher Si concentration favours the synthesis of pure SAPO-34 and SAPO-44. In addition, it is shown that the Si coordination environment in the samples is closely related to the choice of template. Among the three samples investigated, SAPO-34-DIPA has the lowest threshold of Si content for the formation of Si islands in the framework due to the smallest charge compensation centers occluded in its CHA cage. The catalytic performance of the synthesized samples is tested by the MTO reaction and a high olefin selectivity of 85.8% is obtained on SAPO-34 templated by DIPA.
Co-reporter:Xinglong Dong, Zhaoan Chen, Song Xue, Jinling Zhang, Jiannan Zhou, Yanan Liu, Yunpeng Xu and Zhongmin Liu
RSC Advances 2013 vol. 3(Issue 48) pp:25780-25787
Publication Date(Web):17 Oct 2013
DOI:10.1039/C3RA43850C
This paper investigated the process of catalytic pyrolysis of lipid-rich microalga Chlorella pyrenoidosa for the production of light olefins (ethylene, propylene and butene). A modified ZSM-5 zeolite catalyst was used in the reactions, and it had high selectivity for the light olefins production. The catalytic pyrolysis performances of microalga Chlorella pyrenoidosa in nitrogen and steam reaction atmospheres were investigated. The catalytic pyrolysis performances in one-step and two-step processes were investigated and compared. The effects of reaction temperatures and water flow rates on the catalytic pyrolysis performances were also explored. The results showed that higher yield of light olefins was obtained in the steam reaction atmosphere as compared with that in the nitrogen atmosphere. The carbon yield of light olefins obtained from two-step catalytic pyrolysis was nearly three times that from one-step catalytic pyrolysis. The two-step catalytic pyrolysis process also facilitated the production of aromatic hydrocarbons in the liquid products. The maximum carbon yield of light olefins could reach 31.9% in the two-step process under the reaction temperature of 923 K and water flow rate of 30 ml h−1.
Co-reporter:Zhaoan Chen, Yanxia Lyu, Kunyuan Wang, Xinglong Dong, Maicun Deng, Changmin Bai, Yunpeng Xu, Wei Zhang, Zhongmin Liu
International Journal of Hydrogen Energy 2013 Volume 38(Issue 29) pp:13045-13049
Publication Date(Web):30 September 2013
DOI:10.1016/j.ijhydene.2013.03.095
•A novel method for preparing microalgal photoanode was developed.•The preparation process of microalgal photoanode was investigated and optimized.•An optimal photocurrent density of 37.0 μA/cm2 was achieved.•Hydrogen production by photo-bioelectrochemical water-splitting was demonstrated.In this study, a microalga Tetraselmis subcordiformis (synonym: Platymonas subcordiformis)-based photoanode was prepared by a novel method developed in our lab. The optimal photocurrent density of microalgae photoanode, 37 μA/cm2, was achieved under illumination of 145 μmol s−1 m−2 at anode potential of 0.5 V vs Ag|AgCl|sat. KCl, immobilized cell density of 2.08 × 106/cm2 and BQ concentration of 300 μmol/L. The results of measurements showed that oxygen evolution peak, hydrogen evolution peak and photocurrent response were all synchronous to light impulse in a three-electrode system. It revealed that there occurred a process of photo-bioelectrochemical water-splitting. Hydrogen can be produced by the method. The investigation for whole photo-bioelectrochemical process also indicated that the electrons for hydrogen evolution had two sources, microalgal metabolic process in dark condition and photosynthetic water oxidation. The photo-hydrogen evolution was twice more than hydrogen evolution in dark condition.
Co-reporter:Xiong Su;Dr. Peng Tian;Dong Fan; Qinghua Xia;Yue Yang;Dr. Shutao Xu;Dr. Lin Zhang;Dr. Ying Zhang;Dehua Wang; Zhongmin Liu
ChemSusChem 2013 Volume 6( Issue 5) pp:911-918
Publication Date(Web):
DOI:10.1002/cssc.201200907
Abstract
The synthesis of DNL-6 with a high concentration of Si (4 Al) environments [Si/(Si+Al+P)=0.182 mol, denoted as M-DNL-6] is demonstrated. This represents the highest reported concentration of such environments in silicoaluminophosphate (SAPO) molecular sieves. Adsorption studies show that the high Si (4 Al) content in M-DNL-6, with an increased number of Brønsted acid sites in the framework, greatly promotes the adsorption of CO2. M-DNL-6 exhibits a large CO2 uptake capacity of up to 6.18 mmol g−1 at 273 K and 101 kPa, and demonstrates high ratios of CO2/CH4 and CO2/N2 separation. From breakthrough and cycling experiments, M-DNL-6 demonstrates the ability to completely separate CO2 from CH4 or N2 with a dynamic capacity of approximately 8.0 wt % before breakthrough. Importantly, the adsorbed CO2 is easily released from the adsorbent through a simple gas purging operation at room temperature to regain 95 % of the original adsorption capacity. These results suggest that M-DNL-6 can be used as a potential adsorbent for CO2 capture in pressure swing adsorption processes.
Co-reporter:Peng Tian, Bing Li, Shutao Xu, Xiong Su, Dehua Wang, Lin Zhang, Dong Fan, Yue Qi, and Zhongmin Liu
The Journal of Physical Chemistry C 2013 Volume 117(Issue 8) pp:4048-4056
Publication Date(Web):January 29, 2013
DOI:10.1021/jp311334q
The hydrothermal crystallization of SAPO-35 molecular sieve is examined in the present study. Many characterization methods including XRD, SEM, XRF, XPS, EDS, and various solid-state NMR techniques are applied to monitor the formation process of SAPO-35 and the development of the local environments of Si, P, and Al atoms as a function of crystallization time. The results show that an intermediate phase with ordered structure and AlPO compositions first forms. Subsequently, SAPO-35 crystallizes at the expense of the intermediate phase. Si takes part in the formation of SAPO-35 since the initial crystallization. The Si concentration in SAPO-35 shows an increasing trend with time, which leads to the change of both Si and Al coordination environments. More information is obtained from two-dimensional 27Al MQ MAS and 27Al → 31P MQ-MAS HETCOR NMR. Moreover, XPS analysis reveals the enrichment of Si on the crystal surface. On the basis of the characterization results, it is supposed that the distribution of Si in the SAPO-35 crystals is not uniform, showing a gradual increase from the core to the external surface.
Co-reporter:Dr. Shutao Xu;Dr. Anmin Zheng;Dr. Yingxu Wei;Jingrun Chen;Dr. Jinzhe Li;Yueying Chu;Mozhi Zhang;Quanyi Wang;You Zhou;Jinbang Wang;Dr. Feng Deng;Dr. Zhongmin Liu
Angewandte Chemie 2013 Volume 125( Issue 44) pp:11778-11782
Publication Date(Web):
DOI:10.1002/ange.201303586
Co-reporter:Dr. Shutao Xu;Dr. Anmin Zheng;Dr. Yingxu Wei;Jingrun Chen;Dr. Jinzhe Li;Yueying Chu;Mozhi Zhang;Quanyi Wang;You Zhou;Jinbang Wang;Dr. Feng Deng;Dr. Zhongmin Liu
Angewandte Chemie International Edition 2013 Volume 52( Issue 44) pp:11564-11568
Publication Date(Web):
DOI:10.1002/anie.201303586
Co-reporter:Guoju Yang ; Yingxu Wei ; Shutao Xu ; Jingrun Chen ; Jinzhe Li ; Zhongmin Liu ; Jihong Yu ;Ruren Xu
The Journal of Physical Chemistry C 2013 Volume 117(Issue 16) pp:8214-8222
Publication Date(Web):March 25, 2013
DOI:10.1021/jp312857p
In this work, we systematically investigated the size effect of silicoaluminophosphate molecular sieve catalysts SAPO-34 on the catalytic performance of methanol-to-olefin (MTO) reactions. Four highly crystalline SAPO-34 molecular sieves with different crystallite sizes were synthesized under hydrothermal conditions carried out in conventional or microwave ovens with the same starting gel composition using TEAOH as the structure-directing agent. The as-prepared SAPO-34s have similar composition, and their average crystal size can be controlled between 20 nm and 8 μm. Textural properties and chemical environments of framework atoms as well as acid concentration were characterized by N2 adsorption and NMR measurements. The MTO reactions were carried out over these four SAPO-34 catalysts to study their catalytic performances dependent on the crystal size. The occurrence of catalyst deactivation varied considerably with the crystal size of SAPO-34s. Significantly, the nanosized catalysts, especially the sheetlike SAPO-34 catalyst with 20 nm thickness, exhibited the longest catalyst lifetime and lowest coking rate in MTO reactions. On the basis of the measurement of coke formation and the determination of retained coke species, a scheme is proposed to elucidate the reduction in coke deposition and consequently the remarkably enhanced lifetime on the nanosized SAPO-34 catalysts in methanol conversion.
Co-reporter:Dong Fan, Peng Tian, Shutao Xu, Qinghua Xia, Xiong Su, Lin Zhang, Ying Zhang, Yanli He and Zhongmin Liu
Journal of Materials Chemistry A 2012 vol. 22(Issue 14) pp:6568-6574
Publication Date(Web):20 Jan 2012
DOI:10.1039/C2JM15281A
A novel solvothermal synthesis route designated as aminothermal synthesis, in which organic amines are used as both the dispersing medium and the template, is developed for the synthesis of SAPO molecular sieves. Three synthetic systems based on triethylamine (TEA), diethylamine (DEA) and TEA-DEA binary mixture were studied. SAPO-34 with good crystallinity and high yield (ca. 90%) was successfully synthesized from TEA and TEA-DEA systems. By adjusting the crystallization temperature, SAPO-18 was for the first time obtained using TEA template. In the case of DEA, a small-pore molecular sieve DNL-6 with RHO topology was synthesized. In an attempt to make the synthetic process environmentally benign and reduce the waste emission, organic liquid was collected after the synthesis of SAPO-34 and reused in next crystallization. It was found that the crystalline product and yield were almost the same as those synthesized with fresh amines. Moreover, CO2 and CH4 were chosen as the probe molecules to investigate the adsorption properties of products. SAPO molecular sieves synthesized by aminothermal method exhibited good adsorption capacities and high CO2/CH4 ratios.
Co-reporter:Yingxu Wei, Jinzhe Li, Cuiyu Yuan, Shutao Xu, You Zhou, Jingrun Chen, Quanyi Wang, Qing Zhang and Zhongmin Liu
Chemical Communications 2012 vol. 48(Issue 25) pp:3082-3084
Publication Date(Web):31 Jan 2012
DOI:10.1039/C2CC17676A
Formation of adamantane hydrocarbons and their confinement in SAPO-34 caused the long induction period and the quick catalyst deactivation in methanol conversion. Via ship-in-a-bottle synthesis, adamantane and methyladamantanes could be produced from methanol conversion in the cage of 8-ring SAPO catalysts under very mild reaction conditions.
Co-reporter:Yingxu Wei;Cuiyu Yuan;Jinzhe Li;Shutao Xu;You Zhou;Jingrun Chen;Quanyi Wang;Lei Xu;Yue Qi; Qing Zhang; Zhongmin Liu
ChemSusChem 2012 Volume 5( Issue 5) pp:906-912
Publication Date(Web):
DOI:10.1002/cssc.201100528
Abstract
The methanol-to-olefins (MTO) process is becoming the most important non-petrochemical route for the production of light olefins from coal or natural gas. Maximizing the generation of the target products, ethene and propene, and minimizing the production of byproducts and coke, are major considerations in the efficient utilization of the carbon resource of methanol. In the present work, the heterogeneous catalytic conversion of methanol was evaluated by performing simultaneous measurements of the volatile products generated in the gas phase and the confined coke deposition in the catalyst phase. Real-time and complete reaction profiles were plotted to allow the comparison of carbon atom economy of methanol conversion over the catalyst SAPO-34 at varied reaction temperatures. The difference in carbon atom economy was closely related with the coke formation in the SAPO-34 catalyst. The confined coke compounds were determined. A new type of confined organics was found, and these accounted for the quick deactivation and low carbon atom economy under low-reaction-temperature conditions. Based on the carbon atom economy evaluation and coke species determination, optimized operating conditions for the MTO process are suggested; these conditions guarantee high conversion efficiency of methanol.
Co-reporter:Jinzhe Li, Yingxu Wei, Jingrun Chen, Peng Tian, Xiong Su, Shutao Xu, Yue Qi, Quanyi Wang, You Zhou, Yanli He, and Zhongmin Liu
Journal of the American Chemical Society 2011 Volume 134(Issue 2) pp:836-839
Publication Date(Web):December 20, 2011
DOI:10.1021/ja209950x
The heptamethylbenzenium cation (heptaMB+) has been speculated to be one of the most important active intermediates involved in the “hydrocarbon pool” mechanism of methanol-to-olefin (MTO) conversion. By the use of DNL-6, a newly synthesized SAPO-type molecular sieve with large cavities, heptaMB+ has for the first time been directly observed during methanol conversion under real working conditions. 13C-labeling experiments suggested that olefin formation mediated by heptaMB+ mainly follows the side-chain mechanism.
Co-reporter:Peng Tian, Xiong Su, Yingxia Wang, Qinghua Xia, Ying Zhang, Dong Fan, Shuanghe Meng, and Zhongmin Liu
Chemistry of Materials 2011 Volume 23(Issue 6) pp:1406
Publication Date(Web):February 18, 2011
DOI:10.1021/cm103512m
SAPO-34 and a novel SAPO molecular sieve with the RHO framework (designated as DNL-6) were synthesized using SAPO-5 (the denser phase) as the precursor and diethylamine (DEA) as the template. The entire transition process had been investigated by XRD, SEM, XRF, and NMR spectroscopy, which clearly revealed a solution-mediated transport mechanism attributed to the transformation from SAPO-5 precursor to SAPO-34 via oscillating phases [SAPO-5 (FD = 16.9 T/nm3) => SAPO-34 (15.1) + DNL-6 (14.5) → DNL-6 → SAPO-34]. The initially formed SAPO-34 was different from the final one in this transformation due to very different percentages of organic inclusions, indicating that the host−guest interactions played important roles for the phase selectivity during the synthesis. DNL-6, obtained as an intermediate of the transformation process, possessed good thermal stability, large microporous surface area (724 m2/g), and high micropore volume (0.36 cm3/g). Rietveld refinement showed that the framework of calcined DNL-6 had typical features of the RHO structure with a high symmetry [I23, a = 15.08429(9) Å], composed of a body-centered cubic arrangement of α cages linked via double 8-rings.Keywords (keywords): DNL-6; phase selectivity; phase transformation; RHO; SAPO-34;
Co-reporter:Xiong Su, Peng Tian, Jinzhe Li, Ying Zhang, Shuanghe Meng, Yanli He, Dong Fan, Zhongmin Liu
Microporous and Mesoporous Materials 2011 Volume 144(1–3) pp:113-119
Publication Date(Web):October 2011
DOI:10.1016/j.micromeso.2011.04.004
Co-reporter:Dr. Xiao-Yu Yang;Dr. Ge Tian;Dr. Li-Hua Chen;Dr. Yu Li ;Dr. Joanna C. Rooke;Dr. Ying-Xu Wei;Dr. Zhong-Min Liu;Dr. Zhao Deng;Dr. Gustaaf VanTendeloo;Dr. Bao-Lian Su
Chemistry - A European Journal 2011 Volume 17( Issue 52) pp:14987-14995
Publication Date(Web):
DOI:10.1002/chem.201101594
Abstract
Preparation and characterization of well-organized zeolitic nanocrystal aggregates with an interconnected hierarchically micro–meso–macro porous system are described. Amorphous nanoparticles in bimodal aluminosilicates were directly transformed into highly crystalline nanosized zeolites, as well as acting as scaffold template. All pores on three length scales incorporated in one solid body are interconnected with each other. These zeolitic nanocrystal aggregates with hierarchically micro–meso–macroporous structure were thoroughly characterized. TEM images and 29Si NMR spectra showed that the amorphous phase of the initial material had been completely replaced by nanocrystals to give a micro–meso–macroporous crystalline zeolitic structure. Catalytic testing demonstrated their superiority due to the highly active sites and the presence of interconnected micro–meso–macroporosity in the cracking of bulky 1,3,5-triisopropylbenzene (TIPB) compared to traditional zeolite catalysts. This synthesis strategy was extended to prepare various zeolitic nanocrystal aggregates (ZSM-5, Beta, TS-1, etc.) with well-organized hierarchical micro–meso–macroporous structures.
Co-reporter:Yingxu Wei, Dazhi Zhang, Fuxiang Chang, Qinghua Xia, Bao-Lian Su and Zhongmin Liu
Chemical Communications 2009 (Issue 40) pp:5999-6001
Publication Date(Web):18 Sep 2009
DOI:10.1039/B909218H
Hydrocarbon species trapped in the catalyst that work as the reaction center and govern the conversion and product selectivity of chloromethane transformation were revealed by a very efficient home-made ultra-short contact time pulse reaction system over pre-coked SAPO-34.
Co-reporter:Zhengxi Yu, Lei Xu, Yingxu Wei, Yingli Wang, Yanli He, Qinghua Xia, Xinzhi Zhang and Zhongmin Liu
Chemical Communications 2009 (Issue 26) pp:3934-3936
Publication Date(Web):27 May 2009
DOI:10.1039/B907530E
The synthesis of propylene oxide from propylene glycol, a derivative of bio-glycerol, was firstly realized in the presence of alkali-loaded silica catalysts to achieve 44% conversion and 70% selectivity.
Co-reporter:Shigang Zhang, Lei Xu, Hongchao Liu, Yingfeng Zhao, Ying Zhang, Quanyi Wang, Zhengxi Yu, Zhongmin Liu
Materials Letters 2009 Volume 63(Issue 2) pp:258-259
Publication Date(Web):31 January 2009
DOI:10.1016/j.matlet.2008.10.004
PS/silica core/shell composites were synthesized by the modified Stöber method using polystyrene spheres and cetyltrimethylammonium bromide as dual templates under room temperature. The silicate species and the templates were self-assembled to form mesoporous silica shell on the surface of the PS spheres. Hollow silica spheres with mesoporous shell were obtained by removing the polymer core and the templates through calcination. The hollow silica spheres showed high specific surface area of 1099.5 m2/g and narrow pore size distribution centered at 2.31 nm.
Co-reporter:Jinlong Wan;Fuxiang Chang;Yingxu Wei;Qinghua Xia
Catalysis Letters 2009 Volume 127( Issue 3-4) pp:348-353
Publication Date(Web):2009 February
DOI:10.1007/s10562-008-9687-y
The coupled reaction of n-hexane and ethanol over HZSM-5 zeolite has been, for the first time, investigated with a pulse-reaction system. The catalytic reaction results showed an improvement of the initial conversion activity of n-hexane when ethanol was introduced as co-reactant. The FT-IR analysis revealed that the ethanol molecules adsorbed on Brønsted acidic sites were immediately transformed into surface ethoxy groups, which were active species for converting n-hexane and improving the initial conversion activity of n-hexane by a bimolecular hydride transfer mode. Also, the catalytic tests suggested that alkenes resulting from the transformation of ethanol could not enhance the initial conversion of n-hexane compared to active ethoxy groups at the shortest contact time. A mechanism involving the ethoxy groups was proposed to understand the coupled reaction of ethanol and n-hexane.
Co-reporter:Lei Xu, Aiping Du, Yingxu Wei, Yingli Wang, Zhengxi Yu, Yanli He, Xinzhi Zhang, Zhongmin Liu
Microporous and Mesoporous Materials 2008 Volume 115(Issue 3) pp:332-337
Publication Date(Web):1 November 2008
DOI:10.1016/j.micromeso.2008.02.001
SAPO-34 molecular sieves with different Si coordination environment were synthesized by adjusting SiO2/Al2O3 molar ratio in starting gel. The crystal structure, element composition and Si coordination environment of the as-synthesized samples were characterized by XRD, SEM, XRF and NMR. SAPO-34 molecular sieve could be obtained when the SiO2/Al2O3 molar ratio of the starting gel was higher than 0.075. The content and modeling of Si incorporated into SAPO-34 framework varied with the SiO2/Al2O3 molar ratios in the starting gel and different Si chemical environments were formed correspondingly. SAPO-34 with only Si(4Al) coordination structure could be prepared when the SiO2/Al2O3 molar ratio of the starting gel was in range of 0.075–0.15.
Co-reporter:Dazhi Zhang, Yingxu Wei, Lei Xu, Fuxiang Chang, Ziyu Liu, Shuanghe Meng, Bao-Lian Su, Zhongmin Liu
Microporous and Mesoporous Materials 2008 Volume 116(1–3) pp:684-692
Publication Date(Web):December 2008
DOI:10.1016/j.micromeso.2008.06.001
A series of MgAPSO-34s with various Mg stoichiometries were synthesized, characterized by multiple techniques such as, powder XRD, solid state MAS NMR, DR UV–vis spectrometry, NH3-TPD and FTIR and used as catalysts in the direct conversion of chloromethane into light olefins. XRD results revealed that the unit cell parameters of the CHA structure increased with Mg incorporation. The appearance of some new peaks in the 31P MAS NMR spectra of MgAPSO-34 indicated new P co-ordination states as a result of the substitution of Al by Mg. Mg incorporation also modified the Si co-ordination states. A DR UV–vis spectroscopic study evidenced that, in comparison with an MgO crystal, the Mg species in the MgAPSO-34s were quite different. These changes in crystal structure and the chemical environment of framework elements created by Mg substitution modified the acidity and catalytic properties. The acidity of SAPO-34 and MgAPSO-34 determined with NH3-TPD and FTIR techniques showed that the amount of acid sites, especially those of strong acidity, is reduced with the increase of Mg incorporation. Direct chloromethane transformation was carried out over SAPO-34 and MgAPSO-34. All the samples were very active and selective catalysts for light olefin production from chloromethane. Compared with SAPO-34, MgAPSO-34 showed an enhanced conversion, longer catalyst life and improved light olefin selectivity.
Co-reporter:Guangyu Liu, Peng Tian, Jinzhe Li, Dazhi Zhang, Fan Zhou, Zhongmin Liu
Microporous and Mesoporous Materials 2008 Volume 111(1–3) pp:143-149
Publication Date(Web):15 April 2008
DOI:10.1016/j.micromeso.2007.07.023
SAPO-34 molecular sieve was successfully synthesized using diethylamine (DEA) as a template. The influence of template concentration and silica concentration on the synthesis were investigated. Pure SAPO-34 could be obtained when n(DEA)/n(Al2O3) ⩾ 1.5 and n(SiO2)/n(Al2O3) > 0.1 in the synthesis gel. Further increase of DEA concentration in the starting gel [n(DEA)/n(Al2O3) > 3] has a negative effect on both crystallinity and crystal yield. The products were characterized by XRD, XRF, SEM, NMR, FT-IR, TG-DTA and nitrogen adsorption techniques. It was found that SAPO-34 synthesized with DEA as a template has the characteristic of high silicon incorporation and exhibits good thermal and hydrothermal stability. The catalytic performance of SAPO-34 was tested by methanol-to-olefin (MTO) reaction and high olefins (C2H4 + C3H6) selectivity was obtained.
Co-reporter:Yinfeng Zhao, Yue Qi, Yingxu Wei, Yangyang Zhang, Shigang Zhang, Yue Yang, Zhongmin Liu
Microporous and Mesoporous Materials 2008 Volume 111(1–3) pp:300-306
Publication Date(Web):15 April 2008
DOI:10.1016/j.micromeso.2007.08.004
Nitrided mesoporous silica was used as a host for accommodating nano-silver into the channels. The nitridation of the mesoporous silica host, i.e. SBA-15, with ammonia caused the generation of –NHx groups on the surface. The following impregnation of the nitrided SBA-15 with aqueous AgNO3 solution and further reduction led to formation of silver nanostructures in the channels. The samples were characterized by FTIR, XRD, TEM and XPS techniques. The impregnation time has effect on the morphology of the resulting nanostructures. The interaction between silver species and surface –NHx was the key to immobilize Ag in the channels. A scheme was proposed to illustrate the synthesis of Ag nanostructures using nitrided mesoporous host.
Co-reporter:Yinfeng Zhao, Yue Qi, Yangyang Zhang, Shigang Zhang, Zhongmin Liu
Materials Letters 2008 Volume 62(8–9) pp:1197-1199
Publication Date(Web):31 March 2008
DOI:10.1016/j.matlet.2007.08.012
Nano-Au/silica composite has been synthesized by using nitrided mesoporous silica material as host. The nitridation treatment of mesoporous silica, i.e. SBA-15, with ammonia caused the generation of –NHx groups on its surface. After impregnation with aqueous solution of HAuCl4 and following reduction, highly-dispersed gold nanoparticles with uniform sizes were formed in the channels of the nitrided host. The samples were characterized by FTIR, XRD and TEM techniques. The results showed that the nitridation treatment was an alternative and effective way to modify the surface properties of the silica host for immobilizing gold nanoparticles. It was supposed that the interaction between the surface –NHx groups and gold precursors was the key to immobilizing gold in the channels.
Co-reporter:Hongchao Liu;Hua Wang;Jianghan Shen;Ying Sun
Reaction Kinetics, Mechanisms and Catalysis 2008 Volume 93( Issue 1) pp:11-17
Publication Date(Web):2008 January
DOI:10.1007/s11144-008-5155-3
The high-throughput technique has been successfully employed to investigate systematically NH3 decomposition catalysts for COx-free hydrogen production. Supported γ-Mo2N catalysts not only could be prepared and evaluated by the high-throughput experiment, but are also active for NH3 decomposition luke supported Ni and Co catalysts. Additionally, the preparation process and support play important roles on the catalytic performance of supported γ-Mo2N catalysts.
Co-reporter:Jinzhe Li;Yue Qi;Guangyu Liu;Dazhi Zhang
Catalysis Letters 2008 Volume 121( Issue 3-4) pp:303-310
Publication Date(Web):2008 March
DOI:10.1007/s10562-007-9338-8
Co-reaction of ethene and different methylation agents (i.e. methanol and chloromethane) was carried out over SAPO-34 and ZSM-22 and the results are compared. It was found that the enhancement of ethene conversion was achieved by co-feeding it with methylation agents. In the ethene–chloromethane system, the methylation of ethene by chloromethane was more prominent compared with that of the co-reaction of ethene and methanol. The reasons for the differences between ethene–methanol and ethene–chloromethane co-reaction system are discussed. Complete suppress of direct conversion of methanol or ethene could be achieved over ZSM-22 by pre-coking, and propene selectivity higher than 80% was obtained at lower conversions.
Co-reporter:Yingxu Wei, Dazhi Zhang, Zhongmin Liu, Bao-Lian Su
Chemical Physics Letters 2007 Volume 444(1–3) pp:197-201
Publication Date(Web):17 August 2007
DOI:10.1016/j.cplett.2007.07.019
Adsorption and transformation of chloromethane over SAPO-34 catalyst were studied using deuterated CD3Cl as probe by in situ FTIR spectroscopy and compared with CH3Cl. The detection of the deuterated hydroxyls Si(OD)Al indicated the existence of the H and D exchange reaction due to the interaction of Si(OH)Al and DCl molecules produced by CD3Cl conversion. The reversible breaking of Al–O–P bonds as a result of the interaction of Al–O–P with the produced DCl molecules has been clearly evidenced by the observation of P–OD and P–OD–Al species. Increasing CD3Cl loading favors CC generation and higher hydrocarbons formation. A possible surface species evolution and formation during CD3Cl transformation over SAPO-34 catalyst is proposed.Deuterated chloromethane has been used as a probe molecule to study the mechanism of the chloromethane transformation and the surface evolution of SAPO-34 catalyst during the chloromethane transformation by FTIR.
Co-reporter:Ligang Wang, Shiyun Sang, Shuanghe Meng, Ying Zhang, Yue Qi, Zhongmin Liu
Materials Letters 2007 Volume 61(8–9) pp:1675-1678
Publication Date(Web):April 2007
DOI:10.1016/j.matlet.2006.07.097
Zinc-containing ZSM-5 zeolite with novel morphology was firstly synthesized in a one-step route using [Zn(NH3)4]2+ aqueous solution as zinc resource and n-butylamine as template. The materials were characterized by XRD, SEM, diffuse reflectance UV–vis spectra, FTIR for pyridine adsorption. The results showed that the formation of this novel structure might be related to the introduction of [Zn(NH3)4]2+ aqueous solution and the zinc existent state in zeolite.
Co-reporter:Deren Fang;Huimin Zhang
Reaction Kinetics, Mechanisms and Catalysis 2007 Volume 92( Issue 1) pp:55-60
Publication Date(Web):2007 October
DOI:10.1007/s11144-007-5105-5
A series of ternary mesoporous CuZnMCM-41 materials has been synthesized at ambient temperature and their structure was characterized by XRD, N2 physical adsorption and TPR techniques. Their catalytic applications in CO water gas shift reaction were studied.
Co-reporter:Yingxu Wei;Dazhi Zhang;Yanli He;Lei Xu;Yue Yang;Bao-Lian Su
Catalysis Letters 2007 Volume 114( Issue 1-2) pp:30-35
Publication Date(Web):2007 March
DOI:10.1007/s10562-007-9038-4
SAPO-34s with low and high Si content were synthesized and characterized by XRD, XRF, NMR, FTIR and TG-DSC. Different Si content generated no apparent difference in XRD patterns and 31P and 27Al MAS NMR spectra. The Si coordination states studied by 29Si MAS NMR predicted the acidity difference caused by Si incorporation. The absorbance of bridge hydroxyls in FTIR spectra also showed the amount of active sites differed with Si content. Both of the two samples were employed as catalysts in the transformation of chloromethane to light olefins and proved to be very selective catalysts for light olefins production. The influences of Si content on chloromethane conversion and product selectivity were investigated in details. Coke amount and coke species were determined by TG-DSC and FTIR. Coke formation was related to the Si content of SAPO-34 and corresponded to the catalytic performance.
Co-reporter:Ziyu Liu, Yingxu Wei, Yue Qi, Shigang Zhang, Ying Zhang, Zhongmin Liu
Microporous and Mesoporous Materials 2006 Volume 93(1–3) pp:205-211
Publication Date(Web):28 July 2006
DOI:10.1016/j.micromeso.2006.02.016
A microporous zeolite UTM-1 was prepared and transferred to MCM-41 type materials by refluxing with surfactant at the presence of NaOH and by a subsequent pH adjusting process. The pH value affected the long-range order of these mesostructures greatly, and MCM-41 type products were obtained at pH = 7 and pH = 5 (designated as MS-7 and MS-5, respectively). The as-synthesized MS-7 showed smaller particle sizes (about 500 nm) and cylindrical pores. MS-7 showed a high BET specific surface area of 1003 m2/g and a high pore volume of 1.20 cm3/g after calcination at 823 K as well as two pore size distributions centred at 2.4 and 3.7 nm, respectively. The calcined MS-7 exhibited remarkable hydrothermal stability. After being treated in boiling water for 312 h, the material remained a high BET specific surface area of 922 m2/g and a high pore volume of 1.08 cm3/g without degrading its well-ordered mesostructure. Compared with MS-7, the 823 K calcined MCM-41 showed poor hydrothermal stability and preserved only a BET specific surface area of 150 m2/g and a pore volume of 0.35 cm3/g upon being treated in boiling water for 24 h. The remarkable hydrothermal stability of MS-7 was ascribed by solid-state NMR results to the presence of higher percentage of 4-fold coordinated Al species and the highly polymerized pore walls.
Co-reporter:Shiyun Sang, Zhongmin Liu, Peng Tian, Ziyu Liu, Lihong Qu, Yangyang Zhang
Materials Letters 2006 Volume 60(9–10) pp:1131-1133
Publication Date(Web):May 2006
DOI:10.1016/j.matlet.2005.10.110
Zeolite NaY with small crystals was hydrothermally synthesized using a two-stage variable-temperature program without the presence of organic templates, structure-directing agent, seeding crystals and other additives. The as-synthesized samples were characterized by X-ray diffraction (XRD), laser particle size analyzer, scanning electron microscopy (SEM), and Fourier-Transformation Infrared (FT-IR) spectroscopy and Raman spectroscopy. The temperature was found to be a crucial factor for the control of the crystal size.
Co-reporter:Zongbin Wu;Peng Tian;Lei Xu;Haibin Song;Xinhe Bao;Xiumei Liu;Xianchun Liu
Crystal Research and Technology 2006 Volume 41(Issue 10) pp:1049-1054
Publication Date(Web):11 SEP 2006
DOI:10.1002/crat.200610719
Two novel layered CrIII containing metal-hedp compounds, Na20AlCrIII[CH3C(O)P2O6]6·O3·(H2O)26·(H3O)10 (CH3 CH2 OH) and Na6CrIII[CH3C(OH)P2O6]3·(H2O)21(H3O)3 (designated as DLES-AlCr and DLES-CrIII respectively), were hydrothermally synthesized. Their structures were determined by single-crystal X-ray diffraction. The two crystals are isostructural with propeller-like chiral motifs and hexagonal rings along [001]. DLES-AlCr crystal exhibits interesting hollow tubular hexagonal morphology, while DLES-Cr crystal possesses solid hexagonal morphology. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Co-reporter:Zongbin Wu, Zhongmin Liu, Peng Tian, Yanli He, Lei Xu, Yue Yang, Yangyang Zhang, Xinhe Bao, Xiumei Liu, Xianchun Liu
Microporous and Mesoporous Materials 2005 Volume 81(1–3) pp:175-183
Publication Date(Web):6 June 2005
DOI:10.1016/j.micromeso.2005.01.031
Two porous zirconium methylphosphonates (designated as ZMPmi and ZMPme respectively) were synthesized by using dibutyl methylphosphonate (DBMP) as a template. Two efficient post-synthetic treatments were developed to remove the incorporated template without destroying the hybrid structures. The materials were characterized by SEM, EPMA, TG, DTA, FTIR, and NMR. Specific surface area and porosity were evaluated by BET, αs-plots and DFT methods based on N2 adsorption–desorption isotherms. The specific surface areas of ZMPmi and ZMPme are determined to be 279 and 403 m2 g−1 and the maxima of pore size distributions are at 0.7 and 1.3 nm respectively.
Co-reporter:Lihong Qu, Changqing He, Yue Yang, Yanli He, Zhongmin Liu
Materials Letters 2005 Volume 59(29–30) pp:4034-4037
Publication Date(Web):December 2005
DOI:10.1016/j.matlet.2005.07.059
The alumina nanotubes were prepared by using the anionic surfactant, sodium dodecyl sulfonate (SDS), as structure-directing template for the first time with Al(NO3)3·9H2O as precursor via a hydrothermal method. Structure and morphology of the nanotubes were characterized by XRD, TEM, FT-IR, TG and N2 adsorption–desorption. The obtained nanotubes were found having outer diameters from 6 to 8 nm with length up to 200 nm.
Co-reporter:You Zhou, Liang Qi, Yingxu Wei, Zhongmin Liu
Molecular Catalysis (May 2017) Volume 433() pp:20-27
Publication Date(Web):1 May 2017
DOI:10.1016/j.mcat.2017.02.018
•The MTH induction reaction was comparatively investigated over HZSM-5 and HSAPO-34.•The catalysts weight increment was monitored with on line thermogravimetry analysis.•Formation of retained species during the MTH induction reaction was revealed.Methanol to hydrocarbons (MTH) induction reaction was comparatively investigated over HZSM-5 and HSAPO-34 catalysts combined with on line thermogravimetry analysis of catalyst weight increment by intelligent gravimetric analyzer (IGA) studies. The influence of catalyst topology and acidity and reaction temperature on the reaction performance were correlated with the confined organics formation and evolution over the catalysts. For the latter stage of the MTH induction period, methanol conversion over HZSM-5 catalyst was proved a well-defined autocatalysis process, while over HSAPO-34, the increasing rate of methanol conversion was retarded due to accumulation of methyladamantanes. There existed a similar deactivation behaviour for HZSM-5 catalysts with low Si/Al ratios and HSAPO-34 catalysts during the temperature-programmed MTH (TP-MTH) reaction. But the IGA studies showed that the change of the retained species amount was quite different: for TP-MTH reaction over HZSM-5, the amount firstly increased and then decreased to a stable value; while for HSAPO-34, the amount kept increasing until reached a constant value. MTH induction reaction over HZSM-5 catalyst with different Si/Al ratios and HSAPO-34 catalysts with different Si contents were also investigated. All these findings revealed the influence of catalyst topologies on the formation of retained species and then on the catalyst activity during the MTH induction reaction.Download full-size image
Co-reporter:Shiping Liu, Wenliang Zhu, Lei Shi, Hongchao Liu, Yong Liu, Youming Ni, Lina Li, Hui Zhou, Shutao Xu, Yanli He, Zhongmin Liu
Applied Catalysis A: General (May 2015) Volume 497() pp:153-159
Publication Date(Web):May 2015
DOI:10.1016/j.apcata.2015.03.010
Co-reporter:Guangyu Liu, Peng Tian, Qinhua Xia, Zhongmin Liu
Journal of Natural Gas Chemistry (July 2012) Volume 21(Issue 4) pp:431-434
Publication Date(Web):1 July 2012
DOI:10.1016/S1003-9953(11)60387-3
An effective route to improve the catalytic performance of SAPO-34 in the methanol-to-olefin reaction by simple oxalic acid treatment was investigated. The samples were characterized by XRD, SEM, N2 adsorption-desorption, XRF, TG, 29Si MAS NMR and NH3-TPD techniques. The results indicated that the external surface acidity of SAPO-34 was finely tuned by oxalic acid treatment, and the selectivity to C2H4 on SAPO-34 and the catalyst lifetime in the methanol-to-olefin reaction were greatly improved.
Co-reporter:Jinzhe Li, Yingxu Wei, Yue Qi, Peng Tian, Bing Li, Yanli He, Fuxiang Chang, Xinde Sun, Zhongmin Liu
Catalysis Today (30 April 2011) Volume 164(Issue 1) pp:288-292
Publication Date(Web):30 April 2011
DOI:10.1016/j.cattod.2010.10.095
Conversion of methanol to olefins (MTO) over H-ZSM-22 was carried out in the pulse and the continuous-flow reaction systems. 13C labeling technique was used to reveal the reaction mechanism. The materials retained in the deactivated catalyst were detected by GC–MS after dissolving the catalyst framework and then extracting the organic species. The adsorption of these materials in ZSM-22 channels was computationally modeled. The results showed that the olefin methylation-cracking mechanism is the main route for the conversion of methanol over H-ZSM-22. It was suggested that the blockage of the zeolite pore openings by the coke species might be the reason of the relatively rapid deactivation of H-ZSM-22, instead of the prohibition of the formation of large transition-state intermediates involved in hydrocarbon pool mechanism.
Co-reporter:Hongchao Liu, Hua Wang, Jianghan Shen, Ying Sun, Zhongmin Liu
Catalysis Today (29 February 2008) Volume 131(Issues 1–4) pp:444-449
Publication Date(Web):29 February 2008
DOI:10.1016/j.cattod.2007.10.048
CeNi/SBA-15 and LaNi/SBA-15 catalysts were prepared by deposition–precipitation (DP) method and characterized by N2 physical adsorption, XRD, H2-TPR, H2-chemisorption and TEM. Their catalytic performances in the ammonia decomposition reaction were tested and compared with Ni/SBA-15 catalyst. Addition of cerium and lanthanum oxides to the Ni/SBA-15 catalyst caused some decrease of BET surface area and pore volume of the catalysts, but led to a promotion effect to their catalytic activity which was closely related to the ratio of Ce (La)/Ni. The highest conversion of ammonia could be obtained when the Ce (La)/Ni ratio was around 0.3. The promotion effect is more evident on CeNi/SBA-15(0.3) than on LaNi/SBA-15(0.3) catalyst under identical reaction conditions. The CeNi/SBA-15 and LaNi/SBA-15 catalysts show smaller nickel particle size and easier reducibility in comparison with the Ni/SBA-15 catalysts.
Co-reporter:Yingxu Wei, Dazhi Zhang, Lei Xu, Fuxiang Chang, Yanli He, Shuanghe Meng, Bao-lian Su, Zhongmin Liu
Catalysis Today (29 February 2008) Volume 131(Issues 1–4) pp:262-269
Publication Date(Web):29 February 2008
DOI:10.1016/j.cattod.2007.10.055
SAPO-34 and MeAPSO-34s (MeCo, Mn, Fe) molecular sieves have been synthesized and used as catalysts for chloromethane transformation to light olefins. The influences created by metal incorporation are characterized with XRD, XRF, SEM, NMR, TG and H2-TPR. The synthesized MeAPSO-34s have the same CHA topology structure, while metal incorporation gives rise to the increase of unit cell parameter and crystalline particle size. The coexistence of metal species in the synthesis starting gel has effect on the Si substitution into AlPO framework. Co, Mn or Fe incorporation generates a negligible difference on the chemical shift in 31P and 27Al MAS NMR. 29Si MAS NMR study has demonstrated that metal incorporation favors the Si island formation, predicting the stronger acidity. The reducibility of metal species in the synthesized MeAPSO-34s has been investigated by H2-TPR with the comparison of metal-impregnated SAPO-34. Two weight losses in TG analysis from template decomposition in diluted oxygen suggest different chemical location of template molecules in the molecular sieves. For MeAPSO-34, more template removal occurrence at high temperature range indicates stronger template-framework interaction and stronger acidity than SAPO-34 after calcinations. All the SAPO-34 and MeAPSO-34 molecular sieves are very active and selective catalyst for light olefins production. Metal incorporation improves the catalyst life and favors the ethylene and propylene generation. These catalytic properties enhancements are possibly related to the mechanism of chloromethane conversion with deposited coke species as reaction center.
Co-reporter:Hongchao Liu, Hua Wang, Jianghan Shen, Ying Sun, Zhongmin Liu
Applied Catalysis A: General (25 March 2008) Volume 337(Issue 2) pp:138-147
Publication Date(Web):25 March 2008
DOI:10.1016/j.apcata.2007.12.006
Co-reporter:Fuxiang Chang, Yingxu Wei, Xianbin Liu, Yinfeng Zhao, Lei Xu, Ying Sun, Dazhi Zhang, Yanli He, Zhongmin Liu
Applied Catalysis A: General (10 September 2007) Volume 328(Issue 2) pp:
Publication Date(Web):10 September 2007
DOI:10.1016/j.apcata.2007.06.005
The coupled reaction of n-hexane and methanol was studied and compared with the reactions of individual reactants over HZSM-5 zeolite catalyst. The catalytic reaction test results and the temperature-programmed surface reaction (TPSR) results showed an improvement of the initial n-hexane activity when methanol was used as co-reactant. The FT-IR analysis indicated that methanol was adsorbed on acid sites prior to n-hexane and immediately transformed into surface methoxy groups. These species acted as the active sites for the conversion of n-hexane and improved the initial activity of n-hexane by bimolecular hydride transfer. The catalytic test also suggested that alkenes resulting from the transformation of methanol further enhance the conversion of n-hexane, in addition to the improvement by methoxy groups. A faster conversion of methanol was also observed in the coupled system, which highlights a bidirectional promotion effect of the coupled reaction. A reaction mechanism is proposed to explain all observations.Conversions of n-hexane without methanol coupling (▵) and with methanol coupling (□) and ratio of coupled n-C6 conversion and uncoupled n-C6 conversion (●) versus contact time at 400 °C over HZSM-5 zeolite (Si/Al = 19).
Co-reporter:Pengfei Wu, Miao Yang, Wenna Zhang, Shutao Xu, Peng Guo, Peng Tian and Zhongmin Liu
Chemical Communications 2017 - vol. 53(Issue 36) pp:NaN4988-4988
Publication Date(Web):2017/04/03
DOI:10.1039/C7CC01834G
[3-Piperazinepropylmethyldimethoxysilane (PZPMS)] as a low-cost co-template, a crystal growth inhibitor, and a part of the silica source was used together with triethylamine to synthesize SAPO-34 nanoaggregates with tunable compositions. Note that the piperazinyl group of PZPMS prompts the formation of a perfect CHA structure by eliminating the CHA/AEI intergrowth, which ensures the excellent MTO catalytic performance of SAPO-34 nanoaggregates.
Co-reporter:Liang Qi, Jinzhe Li, Linying Wang, Chan Wang, Lei Xu and Zhongmin Liu
Catalysis Science & Technology (2011-Present) 2017 - vol. 7(Issue 10) pp:NaN2031-2031
Publication Date(Web):2017/04/03
DOI:10.1039/C7CY00024C
The deactivation mechanism for the methanol conversion reaction at low temperature was comparatively investigated over HZSM-5 and HSAPO-34 catalysts. Two obviously different deactivation phenomena were directly observed: two-staged deactivation behavior over the HZSM-5 catalyst and exponential-type deactivation behavior over the HSAPO-34 catalyst. Since the start of the deactivation, the amount of the retained species over the HZSM-5 catalyst kept unchanged while the amount over the HSAPO-34 catalyst obviously increased. Both types of deactivation behavior presented an intimate relationship with the accumulation of retained species and their changing reactivity. After detailed characterization and analysis, it was interestingly found that the deactivation of the HZSM-5 catalyst originated from the “overloading effect” of methylbenzenes (smaller than pentamethylbenzene) which are intrinsically active during the autocatalysis reaction stage, while the deactivation of the HSAPO-34 catalyst was caused by accumulation of inactive methyladamantanes, and it was further deduced that the deactivation proceeded from “external to internal” for the HSAPO-34 catalyst. Enhancement of the catalyst diffusivity could effectively extend the catalyst lifetime for the HZSM-5 catalyst, but seemed less effective for the HSAPO-34 catalyst.
Co-reporter:Liang Qi, Jinzhe Li, Linying Wang, Lei Xu and Zhongmin Liu
Catalysis Science & Technology (2011-Present) 2017 - vol. 7(Issue 4) pp:NaN901-901
Publication Date(Web):2017/01/05
DOI:10.1039/C6CY02459A
Temperature-programmed methanol to hydrocarbon (TP-MTH) reactions were performed over HZSM-5 zeolite to monitor the change of reaction performance along with reaction temperature in order to understand the mechanistic reason for the temperature influence on the reaction. With a gradual increase of reaction temperature (0.5 °C min−1), the MTH reaction could evolve from the induction period with low methanol conversion to the state with 100% methanol conversion. Four different reaction stages could be clearly observed: the initial reaction stage, the auto-catalysis reaction stage, the deactivation stage and the activity recovery stage. An unusual deactivation behavior was observed following the auto-catalysis period. Further investigations revealed that 1,2,3,5-tetraMB was the main active species during the initial autocatalytic stage and its “overloading” effect resulted in the unusual deactivation phenomenon, i.e. despite its high intrinsic reactivity, too quick formation of poorly mobile 1,2,3,5-tetraMB and lower methylbenzenes will lead to the occupation of most catalyst channels and channel intersections and cause the deactivation of HZSM-5 at low temperature. Further study demonstrated that the “overloading” effect could be alleviated or eliminated by enhancing the catalyst diffusivity or decreasing the acid site density of the zeolite catalyst.
Co-reporter:Beibei Gao, Peng Tian, Mingrun Li, Miao Yang, Yuyan Qiao, Linying Wang, Shutao Xu and Zhongmin Liu
Journal of Materials Chemistry A 2015 - vol. 3(Issue 15) pp:NaN7749-7749
Publication Date(Web):2015/02/18
DOI:10.1039/C5TA00888C
A low-temperature strategy to fabricate hierarchical aluminophosphate-based molecular sieves has been developed without the assistance of surfactants. The facile synthesis results in cylinder-like SAPO-5 (AFI) composed of oriented attached nanosheets with a thickness of 40–100 nm. The main exposed surface of the nanosheets is revealed by the SAED pattern to be the {001} plane, implying a short path for molecular diffusion in the one-dimensional 12-membered ring channel. Investigation on the crystallization process demonstrates that low temperature retards the crystal growth along the c-direction in SAPO-5 and the ordered architecture forms via a nanosheet formation and oriented attachment process. The aggregated morphology of SAPO-5 is template-dependent, which may be modified/changed by varying the template in the system. The low-temperature strategy is also successfully extended to the preparation of metal-containing aluminophosphate molecular sieves. The obtained MeAPO-5 (Me = Co, Mn, and Cr) and a novel CHA/AEI intergrowth CoAPO molecular sieve also possess hierarchical structures with nanosheet-assembled morphology. Remarkably, the present self-assembled AFI crystals exhibit an obvious improvement in catalytic reactions. This facile method provides a new way for the long-range organization of nanosized building blocks to fabricate hierarchical nanostructures.
Co-reporter:Zhengxi Yu, Lei Xu, Yingxu Wei, Yingli Wang, Yanli He, Qinghua Xia, Xinzhi Zhang and Zhongmin Liu
Chemical Communications 2009(Issue 26) pp:NaN3936-3936
Publication Date(Web):2009/05/27
DOI:10.1039/B907530E
The synthesis of propylene oxide from propylene glycol, a derivative of bio-glycerol, was firstly realized in the presence of alkali-loaded silica catalysts to achieve 44% conversion and 70% selectivity.
Co-reporter:Yuyan Qiao, Miao Yang, Beibei Gao, Linying Wang, Peng Tian, Shutao Xu and Zhongmin Liu
Chemical Communications 2016 - vol. 52(Issue 33) pp:NaN5721-5721
Publication Date(Web):2016/03/23
DOI:10.1039/C5CC10070D
Hollow SAPO-34 crystals are created via selective etching of their precursor under controlled alkaline or acid conditions. The abundant/interconnected Si–O–Al domains and Si–O–Si networks at the outer layer of SAPO-34 crystals are revealed to be decisive factors for the base and acid treatments respectively to achieve a well-preserved hollow structure.
Co-reporter:Jinbang Wang, Yingxu Wei, Jinzhe Li, Shutao Xu, Wenna Zhang, Yanli He, Jingrun Chen, Mozhi Zhang, Anmin Zheng, Feng Deng, Xinwen Guo and Zhongmin Liu
Catalysis Science & Technology (2011-Present) 2016 - vol. 6(Issue 1) pp:NaN97-97
Publication Date(Web):2015/09/16
DOI:10.1039/C5CY01420D
The mechanism of the methanol to olefin (MTO) reaction over H-ZSM-22, a TON-type zeolite without cavities or channel intersections, has been investigated in the temperature range of 250–350 °C. For the first time, an induction period in low-temperature methanol conversion and the methylcyclopentenyl cation (MCP+) formed during this period have been observed directly and successfully. 13C magic angle spinning (MAS) NMR, 13C-labeling experiments and theoretical calculations have been employed to confirm the important active intermediates during methanol conversion at 300 °C. The reactions performed at different temperatures were comparatively studied and the differences in the reaction route for alkene formation from methanol conversion and the modes of H-ZSM-22 catalyst deactivation were revealed.
Co-reporter:Hui Zhou, Wenliang Zhu, Lei Shi, Hongchao Liu, Shiping Liu, Shutao Xu, Youming Ni, Yong Liu, Lina Li and Zhongmin Liu
Catalysis Science & Technology (2011-Present) 2015 - vol. 5(Issue 3) pp:NaN1968-1968
Publication Date(Web):2015/01/07
DOI:10.1039/C4CY01580K
A series of Fe-modified mordenite zeolite samples were synthesized by a template-free method and employed in dimethyl ether (DME) carbonylation reaction for the production of methyl acetate (MAc). XRD, UV-Vis, and UV-Raman characterization studies proved that Fe atoms have been introduced into the mordenite zeolite framework by partial substitution of Al atoms, which led to evident changes of activity and MAc selectivity. With the increase of iron content (as metal) from 0.0 to 3.6 wt%, DME conversion first increased and then decreased. MAc selectivity and catalyst stability were enhanced for all Fe-modified samples. TG and GC-MS analysis of deactivated catalysts showed that the amount of coke retained in the catalysts decreased as the iron content of the zeolites increased. The enhancement effects were expounded in terms of the decrease of the acid strength and acid density in the 12MR channels of mordenite after introduction of Fe, resulting in the reduction of carbon deposition.
Co-reporter:Liang Qi, Jinzhe Li, Yingxu Wei, Lei Xu and Zhongmin Liu
Catalysis Science & Technology (2011-Present) 2016 - vol. 6(Issue 11) pp:NaN3744-3744
Publication Date(Web):2016/03/14
DOI:10.1039/C5CY02238J
The role of methylnaphthalenes in a methanol to hydrocarbons (MTH) reaction on HZSM-5 zeolite was systematically studied on a fixed-bed reaction system. As this is a polycyclic aromatic species, it was interesting to find that co-feeding a small amount of naphthalene could also promote methanol conversion at a low temperature. For the first time, methylnaphthalenes were found to be able to act as initial active HCP species on HZSM-5. The introduced naphthalene could help generate more active methylbenzene HCP species and enhance the aromatic-based cycle during the induction period. As a result, ethene selectivity was promoted due to the co-fed naphthalene. Moreover, despite the large molecular size of naphthalene, it can still function as an active HCP species on the internal acid sites of the HZSM-5 catalyst.
Co-reporter:Jingrun Chen, Jinzhe Li, Cuiyu Yuan, Shutao Xu, Yingxu Wei, Quanyi Wang, You Zhou, Jinbang Wang, Mozhi Zhang, Yanli He, Shuliang Xu and Zhongmin Liu
Catalysis Science & Technology (2011-Present) 2014 - vol. 4(Issue 9) pp:NaN3277-3277
Publication Date(Web):2014/06/10
DOI:10.1039/C4CY00551A
The mechanism of the methanol to olefin (MTO) reaction over AlPO-18 (without Brønsted acid sites) and two SAPO-18 (with different Brønsted acid site densities) catalysts has been investigated. The Brønsted acid site density of AlPO-18 and SAPO-18 catalysts was determined by 1H MAS NMR spectroscopy. Methanol conversion over the catalysts showed that the catalytic activity of the catalysts was strongly influenced by their Brønsted acid site density. Using 13C magic angle spinning (MAS) NMR, we directly observed the pentamethylcyclopentenyl cation (pentaMCP+) over SAPO-18 under real MTO reaction conditions, but no carbenium ion was detected over AlPO-18. Furthermore, analysis of confined organics by 13C MAS NMR and GC-MS clearly demonstrated that higher Brønsted acid site density improved the formation and accumulation of some important and reactive hydrocarbon pool species, such as pentaMCP+ and polymethylbenzenes. With the aid of the 12C/13C-methanol switch technique, the detailed olefin formation mechanism was elucidated. During the MTO reaction, light olefin generation over SAPO-18 mainly followed the aromatic-based hydrocarbon pool mechanism; however, the olefin methylation and cracking mechanism accounted for the production of light olefins over AlPO-18.
Co-reporter:Chan Wang, Miao Yang, Mingrun Li, Shutao Xu, Yue Yang, Peng Tian and Zhongmin Liu
Chemical Communications 2016 - vol. 52(Issue 38) pp:NaN6466-6466
Publication Date(Web):2016/04/12
DOI:10.1039/C6CC01834C
Mesoporous SAPO-34 single crystals with tunable porosity and Si content have been fast synthesized within 4 hours by a reconstruction strategy, which show excellent hydrothermal stability and MTO catalytic activity. This new strategy is further proven to be applicable to prepare other mesoporous SAPO molecular sieve single crystals.
Co-reporter:Miao Yang, Peng Tian, Chan Wang, Yangyang Yuan, Yue Yang, Shutao Xu, Yanli He and Zhongmin Liu
Chemical Communications 2014 - vol. 50(Issue 15) pp:NaN1847-1847
Publication Date(Web):2013/12/17
DOI:10.1039/C3CC48264B
Silicoaluminophosphate SAPO-34 molecular sieve nanocrystals have been prepared by a post-synthesis milling and recrystallization method, which is further proven to be universally applicable to other SAPO molecular sieves. The obtained SAPO-34 with reduced Si enrichment on the external surface shows considerably improved catalytic performance in the MTO reaction.
Co-reporter:Yingxu Wei, Jinzhe Li, Cuiyu Yuan, Shutao Xu, You Zhou, Jingrun Chen, Quanyi Wang, Qing Zhang and Zhongmin Liu
Chemical Communications 2012 - vol. 48(Issue 25) pp:NaN3084-3084
Publication Date(Web):2012/01/31
DOI:10.1039/C2CC17676A
Formation of adamantane hydrocarbons and their confinement in SAPO-34 caused the long induction period and the quick catalyst deactivation in methanol conversion. Via ship-in-a-bottle synthesis, adamantane and methyladamantanes could be produced from methanol conversion in the cage of 8-ring SAPO catalysts under very mild reaction conditions.
Co-reporter:Yingxu Wei, Dazhi Zhang, Fuxiang Chang, Qinghua Xia, Bao-Lian Su and Zhongmin Liu
Chemical Communications 2009(Issue 40) pp:NaN6001-6001
Publication Date(Web):2009/09/18
DOI:10.1039/B909218H
Hydrocarbon species trapped in the catalyst that work as the reaction center and govern the conversion and product selectivity of chloromethane transformation were revealed by a very efficient home-made ultra-short contact time pulse reaction system over pre-coked SAPO-34.
Co-reporter:Chan Wang, Miao Yang, Peng Tian, Shutao Xu, Yue Yang, Dehua Wang, Yangyang Yuan and Zhongmin Liu
Journal of Materials Chemistry A 2015 - vol. 3(Issue 10) pp:NaN5616-5616
Publication Date(Web):2015/02/12
DOI:10.1039/C4TA06124A
A spherical self-assembly of SAPO-34 nanosheets was hydrothermally synthesized by using a quaternary ammonium-type organosilane surfactant [3-(trimethoxysilyl)propyl]octadecyldimethylammonium chloride (TPOAC) as the mesoporogen and a part of the silica source, and diethylamine (DEA) as the microporous template. The prepared materials were well characterized by XRD, XRF, SEM, TEM, N2 adsorption–desorption, NH3-TPD, NH3-adsorbed IR and pyridine-adsorbed IR measurements. It revealed that the morphologies, compositions and acidity of the SAPO-34 products changed significantly with the increased TPOAC/TEOS ratio, showing that the TPOAC/TEOS ratio had a significant impact on the crystallization process of SAPO-34. Solid state 13C, 29Si NMR and TG-DTA analyses were further conducted to investigate the status of TPOAC in the final products. A possible crystallization process involving TPOAC was proposed. The catalytic performances of the synthesized SAPO-34s were evaluated using the MTO reaction. The optimal SAPO-34 nanosheet assemblies with a hierarchical porous structure displayed a remarkably enhanced catalytic lifetime and high yields of light olefins.
Co-reporter:Dong Fan, Peng Tian, Xiong Su, Yangyang Yuan, Dehua Wang, Chan Wang, Miao Yang, Linying Wang, Shutao Xu and Zhongmin Liu
Journal of Materials Chemistry A 2013 - vol. 1(Issue 45) pp:NaN14213-14213
Publication Date(Web):2013/09/18
DOI:10.1039/C3TA12829F
Aminothermal synthesis of SAPO molecular sieves, in which organic amines are used as both solvent and template, is explored based on a variety of amines. Di-iso-propylamine (DIPA) and N,N,N′,N′-tetramethylethylenediamine (TMEDA) are found to lead to the rapid crystallization of SAPO-34 with high solid yield. A solid yield of 96.2% could be acquired using the TMEDA system (200 °C, 12 h), which is the highest value ever reported for SAPO molecular sieves. SAPO-44 is obtained for the first time using the hexamethyleneimine (HMI) template. Detailed synthetic investigation shows that the silicon content in the initial gel has an important effect on the crystalline nature of the final products, and higher Si concentration favours the synthesis of pure SAPO-34 and SAPO-44. In addition, it is shown that the Si coordination environment in the samples is closely related to the choice of template. Among the three samples investigated, SAPO-34-DIPA has the lowest threshold of Si content for the formation of Si islands in the framework due to the smallest charge compensation centers occluded in its CHA cage. The catalytic performance of the synthesized samples is tested by the MTO reaction and a high olefin selectivity of 85.8% is obtained on SAPO-34 templated by DIPA.
Co-reporter:Dong Fan, Peng Tian, Shutao Xu, Qinghua Xia, Xiong Su, Lin Zhang, Ying Zhang, Yanli He and Zhongmin Liu
Journal of Materials Chemistry A 2012 - vol. 22(Issue 14) pp:NaN6574-6574
Publication Date(Web):2012/01/20
DOI:10.1039/C2JM15281A
A novel solvothermal synthesis route designated as aminothermal synthesis, in which organic amines are used as both the dispersing medium and the template, is developed for the synthesis of SAPO molecular sieves. Three synthetic systems based on triethylamine (TEA), diethylamine (DEA) and TEA-DEA binary mixture were studied. SAPO-34 with good crystallinity and high yield (ca. 90%) was successfully synthesized from TEA and TEA-DEA systems. By adjusting the crystallization temperature, SAPO-18 was for the first time obtained using TEA template. In the case of DEA, a small-pore molecular sieve DNL-6 with RHO topology was synthesized. In an attempt to make the synthetic process environmentally benign and reduce the waste emission, organic liquid was collected after the synthesis of SAPO-34 and reused in next crystallization. It was found that the crystalline product and yield were almost the same as those synthesized with fresh amines. Moreover, CO2 and CH4 were chosen as the probe molecules to investigate the adsorption properties of products. SAPO molecular sieves synthesized by aminothermal method exhibited good adsorption capacities and high CO2/CH4 ratios.
Co-reporter:Guannan Li, Haibo Huang, Bowen Yu, Yun Wang, Jiawei Tao, Yingxu Wei, Shougui Li, Zhongmin Liu, Yan Xu and Ruren Xu
Chemical Science (2010-Present) 2016 - vol. 7(Issue 2) pp:NaN1587-1587
Publication Date(Web):2015/11/23
DOI:10.1039/C5SC03837E
Hierarchical zeolite monoliths with multimodal porosity are of paramount importance as they open up new horizons for advanced applications. So far, hierarchical zeolites based on nanotube scaffolds have never been reported. Inspired by the organization of biominerals, we have developed a novel precursor scaffolding-solid phase crystallization strategy for hierarchical zeolites with a unique nanotube scaffolding architecture and nanotube-trimodal network, where biomolecular self-assembly (BSA) provides a scaffolding blueprint. By vapor-treating Sil-1 seeded precursor scaffolds, zeolite MFI nanotube scaffolds are self-generated, during which evolution phenomena such as segmented voids and solid bridges are observed, in agreement with the Kirkendall effect in a solid-phase crystallization system. The nanotube walls are made of intergrown single crystals rendering good mechanical stability. The inner diameter of the nanotube is tunable between 30 and 90 nm by varying the thickness of the precursor layers. Macropores enclosed by cross-linked nanotubes can be modulated by the choice of BSA. Narrow mesopores are formed by intergrown nanocrystals. Hierarchical ZSM-5 monoliths with nanotube (90 nm), micropore (0.55 nm), mesopore (2 nm) and macropore (700 nm) exhibit superior catalytic performance in the methanol-to-hydrocarbon (MTH) conversion compared to conventional ZSM-5. BSA remains intact after crystallization, allowing a higher level of organization and functionalization of the zeolite nanotube scaffolds. The current work may afford a versatile strategy for hierarchical zeolite monoliths with nanotube scaffolding architectures and a nanotube-multimodal network leading to self-supporting and active zeolite catalysts, and for applications beyond.
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