For direct gas to liquid(GTL),a novel process producing energy sources for methane dehydroaromatization is needed.Supporting MoO3 on H-MFI zeolite shows the high catalytic capacity and a selective activity for dehyd...For direct gas to liquid(GTL),a novel process producing energy sources for methane dehydroaromatization is needed.Supporting MoO3 on H-MFI zeolite shows the high catalytic capacity and a selective activity for dehydroaromatization of methane to benzene at 973 K in a fixed bed reactor.On the other hand,deactivation by coke on the active sites in all the catalysts is formed during the reaction.H2 co-feed suppressed the deactivation,which is probably due to the decrease in coking amount.Mo K-edge X-ray absorption fine structure(XAFS) results showed the formation of dispersed Mo2C species with low crystallinity after dehydroaromatization.Mo LIII-edge XANES(X-ray absorption near-edge structure) indicated the formation of active Mo species including Mo2C and Mo-oxycarbide(MoOxCy),where the redox state should be independent in the absence/presence of H2.It is concluded that Mo-oxycarbide species act as highly active species,and their stability affected the durable activity in the presence of H2.展开更多
The hydration of alkyne represents the most straightforward and simplest route toward the synthesis of ketone. Herein, Brønsted acidic zeolites are explored as potential catalysts for the liquid-phase phenylacety...The hydration of alkyne represents the most straightforward and simplest route toward the synthesis of ketone. Herein, Brønsted acidic zeolites are explored as potential catalysts for the liquid-phase phenylacetylene hydration. The topology structure and Si/Al ratio are disclosed to be key factors controlling the catalytic activity of zeolites. Typically, H-MFI zeolite with a Si/Al molar ratio of 13 exhibits the highest catalytic activity, with turnover frequency of 6.0 h-1 at 363 K. Besides, H-MFI zeolite shows good catalytic stability and recyclability in the reaction of phenylacetylene hydration, and the substrate scope can be simply extended to other soluble aromatic alkynes. The reaction mechanism of phenylacetylene hydration is investigated by means of kinetic and spectroscopic analyses. The Markovnikov electrophilic addition of phenylacetylene by hydrated protons is established as the rate-determining step, followed by deprotonation and enol isomerization to derive acetophenone product.展开更多
Delft molecular mechanics minimization has been performed for the study on the structures of monoclinic MFI and H[Al]ZSM 5. The results were compared with those from quantum chemistry and other force field calculation...Delft molecular mechanics minimization has been performed for the study on the structures of monoclinic MFI and H[Al]ZSM 5. The results were compared with those from quantum chemistry and other force field calculations. For the minimization of H[Al]ZSM 5, significant geometric rearrangements have been investigated in the local environments of Brnsted acidic sites, which resulted from the isomorphous substitution of Al for Si atoms in MFI framework.展开更多
Molecular dynamics (MD) simulation was performed to study ethene adsorption, polarization and diffusion in orthorhombic and monoclinic MFI and H[Al] ZSM-5 at 300 K. The resuits show that the interaction between ethe...Molecular dynamics (MD) simulation was performed to study ethene adsorption, polarization and diffusion in orthorhombic and monoclinic MFI and H[Al] ZSM-5 at 300 K. The resuits show that the interaction between ethene molecule and orthorhombic MFI is the strongest.Ethene molecules possess relatively low energy in the lattice of orthorhombic MFI. The existence of Al and Brnsted H atoms in the framework of H[AI]ZSM-5 can lower the energy of adsorbed ethene molecules. At the edges of intersections of channels, especially those near Al sites,ethene molecules are polarized most. Ethene molecules prefer the locations at the centers of channel intersections. The diffusion coefficients of ethene in the lattices of orthorhombic, monoclinic MFI and H[AI]ZSM-5 are 2.7 x 10<sup>-9</sup>, 2.1 x l0<sup>-9</sup>, 1.6 x 10<sup>-9</sup> m<sup>2</sup>·s<sup>-1</sup>, respectively. The infrared spectrum of ethene in the framework of H[Al] ZSM-5 shows five vibration peaks (v<sub>10</sub>,v<sub>7</sub>, v<sub>12</sub>, v<sub>11</sub> and V<sub>9</sub>), which is consistent with the experimental result.展开更多
基金supported by the Joint Studies Program (No. 18-502, and 19-501) of UVSOR-IMS, Japansupported by the Joint Studies Program (No. 2000G274, 2004G110)of KEK-PF, Japan
文摘For direct gas to liquid(GTL),a novel process producing energy sources for methane dehydroaromatization is needed.Supporting MoO3 on H-MFI zeolite shows the high catalytic capacity and a selective activity for dehydroaromatization of methane to benzene at 973 K in a fixed bed reactor.On the other hand,deactivation by coke on the active sites in all the catalysts is formed during the reaction.H2 co-feed suppressed the deactivation,which is probably due to the decrease in coking amount.Mo K-edge X-ray absorption fine structure(XAFS) results showed the formation of dispersed Mo2C species with low crystallinity after dehydroaromatization.Mo LIII-edge XANES(X-ray absorption near-edge structure) indicated the formation of active Mo species including Mo2C and Mo-oxycarbide(MoOxCy),where the redox state should be independent in the absence/presence of H2.It is concluded that Mo-oxycarbide species act as highly active species,and their stability affected the durable activity in the presence of H2.
基金This work was supported by the National Natural Science Foundation of China(No.22025203)the Municipal Natural Science Fund of Tianjin,China(No.18JCJQJC47400).
文摘The hydration of alkyne represents the most straightforward and simplest route toward the synthesis of ketone. Herein, Brønsted acidic zeolites are explored as potential catalysts for the liquid-phase phenylacetylene hydration. The topology structure and Si/Al ratio are disclosed to be key factors controlling the catalytic activity of zeolites. Typically, H-MFI zeolite with a Si/Al molar ratio of 13 exhibits the highest catalytic activity, with turnover frequency of 6.0 h-1 at 363 K. Besides, H-MFI zeolite shows good catalytic stability and recyclability in the reaction of phenylacetylene hydration, and the substrate scope can be simply extended to other soluble aromatic alkynes. The reaction mechanism of phenylacetylene hydration is investigated by means of kinetic and spectroscopic analyses. The Markovnikov electrophilic addition of phenylacetylene by hydrated protons is established as the rate-determining step, followed by deprotonation and enol isomerization to derive acetophenone product.
文摘Delft molecular mechanics minimization has been performed for the study on the structures of monoclinic MFI and H[Al]ZSM 5. The results were compared with those from quantum chemistry and other force field calculations. For the minimization of H[Al]ZSM 5, significant geometric rearrangements have been investigated in the local environments of Brnsted acidic sites, which resulted from the isomorphous substitution of Al for Si atoms in MFI framework.
文摘Molecular dynamics (MD) simulation was performed to study ethene adsorption, polarization and diffusion in orthorhombic and monoclinic MFI and H[Al] ZSM-5 at 300 K. The resuits show that the interaction between ethene molecule and orthorhombic MFI is the strongest.Ethene molecules possess relatively low energy in the lattice of orthorhombic MFI. The existence of Al and Brnsted H atoms in the framework of H[AI]ZSM-5 can lower the energy of adsorbed ethene molecules. At the edges of intersections of channels, especially those near Al sites,ethene molecules are polarized most. Ethene molecules prefer the locations at the centers of channel intersections. The diffusion coefficients of ethene in the lattices of orthorhombic, monoclinic MFI and H[AI]ZSM-5 are 2.7 x 10<sup>-9</sup>, 2.1 x l0<sup>-9</sup>, 1.6 x 10<sup>-9</sup> m<sup>2</sup>·s<sup>-1</sup>, respectively. The infrared spectrum of ethene in the framework of H[Al] ZSM-5 shows five vibration peaks (v<sub>10</sub>,v<sub>7</sub>, v<sub>12</sub>, v<sub>11</sub> and V<sub>9</sub>), which is consistent with the experimental result.