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...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.展开更多
This special issue of Chinese Journal of Catalysis is dedicated to Professor Mingyuan He on the occasion of his 80th birthday,in recognition of his distinguished contributions to many aspects in the field of catalytic...This special issue of Chinese Journal of Catalysis is dedicated to Professor Mingyuan He on the occasion of his 80th birthday,in recognition of his distinguished contributions to many aspects in the field of catalytic science and technology.Professor He was born on February 8,1940 in Shanghai,China.In 1961,he graduated from East China Textile Engineering Institute(now Donghua University),and earned his B.S.degree in applied chemistry.He then joined the Research Institute of Petroleum Processing,SINOPEC.During 1982?1984,he worked as a visiting scholar at the Northwestern University and the University of Texas at Austin.In 2000,he became an adjunct professor at East China Normal University,and established the Shanghai Key Laboratory of Green Chemistry and Chemical Processes in 2003.展开更多
In this paper, the precise construction on the structure of silicalite-1 microcapsules （S1） was specifically described. The interior carbon modifications and the outside mesoporous functionalizations were successful...In this paper, the precise construction on the structure of silicalite-1 microcapsules （S1） was specifically described. The interior carbon modifications and the outside mesoporous functionalizations were successfully conducted and each sample was characterized in detail, It was found that the carbon networks could be formed inside the zeolite microcapsules via the pretreatment of sugar injections. The uniformity of the distinct microcapsule could be regulated by adjusting the sugar concentrations. With the encapsulated Pt species inside the MSSs, the nano-particles could be dispersed well within the carbon network. On the other hand, during the fabrication of the mesoporous materials outside the microcapsules, the template and the acidity of the system could play an important role in determining the morphology of S1. Besides, the PDDA modification on the shell of SI could help the combination of the meso-layer and the shell of S1 at nano-scale. The thickness of the outside mesopore could be modulated through the controlling of the silica content.展开更多
基金supported by the National Key Research and Development Program of China (2016YFB0701100, 2017YFB0702800)the National Natural Science Foundation of China (21673295)~~
文摘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.
文摘This special issue of Chinese Journal of Catalysis is dedicated to Professor Mingyuan He on the occasion of his 80th birthday,in recognition of his distinguished contributions to many aspects in the field of catalytic science and technology.Professor He was born on February 8,1940 in Shanghai,China.In 1961,he graduated from East China Textile Engineering Institute(now Donghua University),and earned his B.S.degree in applied chemistry.He then joined the Research Institute of Petroleum Processing,SINOPEC.During 1982?1984,he worked as a visiting scholar at the Northwestern University and the University of Texas at Austin.In 2000,he became an adjunct professor at East China Normal University,and established the Shanghai Key Laboratory of Green Chemistry and Chemical Processes in 2003.
基金supported by National Key Basic Research Program of China(Nos.2013CB934101 and 2009CB623500)Science and Technology Commission of Shanghai Municipality(No.11JC1400400)+1 种基金National Plan for Science and Technology(No.14-PET827-02)Shanghai Postdoctoral Scientific Program(No.13R21422000)
文摘In this paper, the precise construction on the structure of silicalite-1 microcapsules （S1） was specifically described. The interior carbon modifications and the outside mesoporous functionalizations were successfully conducted and each sample was characterized in detail, It was found that the carbon networks could be formed inside the zeolite microcapsules via the pretreatment of sugar injections. The uniformity of the distinct microcapsule could be regulated by adjusting the sugar concentrations. With the encapsulated Pt species inside the MSSs, the nano-particles could be dispersed well within the carbon network. On the other hand, during the fabrication of the mesoporous materials outside the microcapsules, the template and the acidity of the system could play an important role in determining the morphology of S1. Besides, the PDDA modification on the shell of SI could help the combination of the meso-layer and the shell of S1 at nano-scale. The thickness of the outside mesopore could be modulated through the controlling of the silica content.
