A newly-developed polyamide supported Raney Ni catalyst, which is suitable for use in fix-bed reactions with high selectivity, was studied in this paper. Selective hydrogenation of acetone to isopropanol was chosen as...A newly-developed polyamide supported Raney Ni catalyst, which is suitable for use in fix-bed reactions with high selectivity, was studied in this paper. Selective hydrogenation of acetone to isopropanol was chosen as a probe reaction. It has been found that clean preparation of isopropanol could be achieved, that is to say, the two main byproducts(isopropyl ether and methyl-iso-butyl carbinol) could be eliminated with the newly-developed polyamide supported Raney Ni catalyst. The elimination of these side reactions was attributed to the adsorption effect of polyamide support and a model was proposed. The proposed model was further proved by hydroamination reaction of acetone. According to this model, catalyst support can play an important role in chemical reactions. Different products could be produced when different catalyst support is used, the main reaction and side reactions can even be reversed sometimes when the chemicals, active component of catalyst and reaction condition are the same. This model could help to improve catalytic selectivity of many Raney metal catalysts used routinely in chemical and oil refining industry, and is also useful for hydrogenation reactions in pharmaceutical and food industry.展开更多
By using OCMOSiH\-3(M=Ru, Rh, Pd) as models to imitate the chemisorption of CO on the silica\|supported catalysts, the geometries and frequencies have been performed for the complexes by Gaussian programs, at the B3LY...By using OCMOSiH\-3(M=Ru, Rh, Pd) as models to imitate the chemisorption of CO on the silica\|supported catalysts, the geometries and frequencies have been performed for the complexes by Gaussian programs, at the B3LYP/LANL1DZ level. An influence of the C\_O bond has been studied and the support effects of silica are obtained. The support effects of silica make the CO frequency an upward shift, which means that the weakened degree of C\_O decreases and the bond strength of C\_O increases naturally compared to those of the non\|silica\|supported catalysts. So the products on the silica\|supported catalysts shift to the oxygenates.展开更多
Researchers have been attempting to characterize heterogeneous catalysts in situ in addition to correlating their structures with their activity and selectivity in spite of many challenges.Here,we review recent experi...Researchers have been attempting to characterize heterogeneous catalysts in situ in addition to correlating their structures with their activity and selectivity in spite of many challenges.Here,we review recent experimental and theoretical advances regarding alkyne selective hydrogenation by Pd‐based catalysts,which are an important petrochemical reaction.The catalytic selectivity for the reaction of alkynes to alkenes is influenced by the composition and structure of the catalysts.Recent progress achieved through experimental studies and atomic simulations has provided useful insights into the origins of the selectivity.The important role of the subsurface species(H and C)was revealed by monitoring the catalyst surface and the related catalytic performance.The atomic structures of the Pd catalytic centers and their relationship with selectivity were established through atomic simulations.The combined knowledge gained from experimental and theoretical studies provides a fundamental understanding of catalytic mechanisms and reveals a path toward improved catalyst design.展开更多
文摘A newly-developed polyamide supported Raney Ni catalyst, which is suitable for use in fix-bed reactions with high selectivity, was studied in this paper. Selective hydrogenation of acetone to isopropanol was chosen as a probe reaction. It has been found that clean preparation of isopropanol could be achieved, that is to say, the two main byproducts(isopropyl ether and methyl-iso-butyl carbinol) could be eliminated with the newly-developed polyamide supported Raney Ni catalyst. The elimination of these side reactions was attributed to the adsorption effect of polyamide support and a model was proposed. The proposed model was further proved by hydroamination reaction of acetone. According to this model, catalyst support can play an important role in chemical reactions. Different products could be produced when different catalyst support is used, the main reaction and side reactions can even be reversed sometimes when the chemicals, active component of catalyst and reaction condition are the same. This model could help to improve catalytic selectivity of many Raney metal catalysts used routinely in chemical and oil refining industry, and is also useful for hydrogenation reactions in pharmaceutical and food industry.
文摘By using OCMOSiH\-3(M=Ru, Rh, Pd) as models to imitate the chemisorption of CO on the silica\|supported catalysts, the geometries and frequencies have been performed for the complexes by Gaussian programs, at the B3LYP/LANL1DZ level. An influence of the C\_O bond has been studied and the support effects of silica are obtained. The support effects of silica make the CO frequency an upward shift, which means that the weakened degree of C\_O decreases and the bond strength of C\_O increases naturally compared to those of the non\|silica\|supported catalysts. So the products on the silica\|supported catalysts shift to the oxygenates.
文摘Researchers have been attempting to characterize heterogeneous catalysts in situ in addition to correlating their structures with their activity and selectivity in spite of many challenges.Here,we review recent experimental and theoretical advances regarding alkyne selective hydrogenation by Pd‐based catalysts,which are an important petrochemical reaction.The catalytic selectivity for the reaction of alkynes to alkenes is influenced by the composition and structure of the catalysts.Recent progress achieved through experimental studies and atomic simulations has provided useful insights into the origins of the selectivity.The important role of the subsurface species(H and C)was revealed by monitoring the catalyst surface and the related catalytic performance.The atomic structures of the Pd catalytic centers and their relationship with selectivity were established through atomic simulations.The combined knowledge gained from experimental and theoretical studies provides a fundamental understanding of catalytic mechanisms and reveals a path toward improved catalyst design.
