Methane dehydroaromatization over Mo-modified H-MFI for gas to liquid catalysts

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.

Catalytic Hydration of Aromatic Alkynes to Ketones over H-MFI Zeolites

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.

Delft Molecular Mechanics Study on the Structures of Monoclinic MF Iand H[ Al] ZSM-5

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.

甲烷在含镓沸石(MFI)上无氧活化性能的研究

采用水热法合成了不同Ｓｉ／Ａｌ、Ｓｉ／Ｇａ比的含镓分子筛．催化反应活性表征结果表明，对丙烷芳构化反应具有良好催化活性的含镓分子筛，没有显示出任何催化甲烷芳构化反应的特性；ＭｏＯ３作为添加组分显著地改变了催化剂的反应性能．３％ＭｏＯ３负载的含Ｇａ分子筛（Ｓｉ∶Ａｌ∶Ｇａ＝５０∶２∶１），在９７３Ｋ温度条件下给出了约６％甲烷转化率和大于８０％的芳烃选择性．与ＺＳＭ－５相比，在相同的ＭｏＯ３担载条件下，含Ｇａ分子筛催化剂甲烷芳构化活性较低，但是镓的引入提高了乙烯的选择性．

Molecular dynamics simulation of ethene adsorption,polarization and diffusion in three kinds of zeolites

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 10-9, 2.1 x l0-9, 1.6 x 10-9 m2·s-1, respectively. The infrared spectrum of ethene in the framework of H[Al] ZSM-5 shows five vibration peaks (v10,v7, v12, v11 and V9), which is consistent with the experimental result.