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Understanding Zeolites Catalyzed methanol-to-olefins conversion from Theoretical Calculations

Chinese Journal of Chemistry 2018年第5期36卷 381-386页

作者： Chuanming Wang Yangdong Wang Zaiku Xie State Key Laboratory of Green Chemical Engineering and Industrial Catalysis SINOPEC Shanghai Research Institute of Petrochemical TechnologyShanghai 20120B Ch{na

Zeolites catalyzed methanol-to-olefins （MTO） conversion provides an alternative process to produce light olefins such as ethene and propene from nonpetroleum resources. Despite of successful industrialization of the MTO process, its detailed reaction mechanism is not yet well understood. Here we summarize our work on the hydrocarbon pool reaction mechanism based on theoretical calculations. We proposed that the olefins themselves are likely to be the dominating hydrocarbon pool species, and the distribution of cracking precursors and diffusion constraints affect the selectivity. The similarities between aromatic-based and olefin-based cycles are highlighted.

关键词： zeolite catalysis methanol-to-olefins conversion hydrocarbon pool mechanism computational catalysis density functional theory

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Elucidating the dominant reaction mechanism of methanol-to-olefins conversion in H-SAPO-18: A first-principles study

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Chinese Journal of Catalysis 2018年第7期39卷 1272-1279页

作者： Chuan-Ming Wang Yang-Dong Wang Zai-Ku Xie State Key Laboratory of Green Chemical Engineering and Industrial Catalysis SINOPEC Shanghai Research Institute of Petrochemical TechnologyShanghai 201208China

The reaction mechanism of zeolite- or zeotype-catalyzed methanol-to-olefins（MTO） conversion is still a subject of debate. Employing periodic density functional theory calculations, the olefin-based cycle was studied using tetramethylethene（TME） as a representative olefinic hydrocarbon pool in H-SAPO-18 zeotype. The overall free energy barrier at 673 K was calculated and found to be less than 150 kJ/mol in the TME-based cycle, much lower than those in the aromatic-based cycle（〉 200 kJ/mol）, indicating that olefins themselves are the dominant active hydrocarbon pool species in H-SAPO-18. The similarity of the intermediates involved between the aromatic-based cycle and the olefin-based cycle was also highlighted, revealing that both cycles were pattern-consistent. The selectivity related to the distribution of cracking precursors, such as higher olefins or carbenium ions, as a result of the olefin-based cycle for the MTO conversion. The enthalpy barrier of the crack-ing step scaled linearly with the number of carbon atoms of cracking precursors to produce ethene or propene with ethene being much less favored than propene for cracking of C7 and higher pre-cursors. This work highlighted the importance of the olefin-based cycle in H-SAPO-18 for the MTO conversion and established the similarity between the olefin-based and aromatic-based cycles.

关键词： methanol-to-olefins conversion Hydrocarbon pool reaction mechanism Olefin-based hydrocarbon pool Density functional theory H-SAPO-18 zeotype

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Insight into the topology effect on the diffusion of ethene and propene in zeolites: A molecular dynamics simulation study

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Journal of Energy Chemistry 2013年第6期22卷 914-918页

作者： Chuanming Wang Bowei Li Yangdong Wang Zaiku Xie Shanghai Research Institute of Petrochemical Technology SINOPEC School of Chemistry and Molecular Engineering East China University of Science and Technology

Selectivity control is a difficult scientific and industrial challenge in methanol-to-olefins(MTO)*** has been experimentally established that the topology of zeolite catalysts influenced the distribution of *** the topology effect on reaction kinetics,the topology influences the diffusion of reactants and products in catalysts as *** this work,by using COMPASS force-field molecular dynamics method,we investigated the intracrystalline diffusion of ethene and propene in four different zeolites,CHA,MFI,BEA and FAU,at different *** self-diffusion coefficients and diffusion activation barriers were calculated.A strong restriction on the diffusion of propene in CHA was observed because the self-diffusion coefficient ratio of ethene to propene is larger than 18 and the diffusion activation barrier of propene is more than 20 kJ/mol in *** ratio decreases with the increase of temperature in the four investigated *** shape selectivity on products from diffusion perspective can provide some implications on the understanding of the selectivity difference between HSAPO-34 and HZSM-5 catalysts for the MTO conversion.

关键词： methanol-to-olefins conversion diffusion zeolites ethene propene molecular dynamics simulation

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