The pyrolysis of Pubescens over Ni/C catalyst was studied at 350°C in H2 flow.The presence of Ni/C catalyst efficiently improved the degradation of raw materials,and produced bio-oil with high content of phenols ...The pyrolysis of Pubescens over Ni/C catalyst was studied at 350°C in H2 flow.The presence of Ni/C catalyst efficiently improved the degradation of raw materials,and produced bio-oil with high content of phenols but low contents of acetic acid,furfural and water.In the reaction,Ni/C catalyst plays the role of catalytic decomposition and catalytic hydrogenation.The existence of the carbon carrier favors the formation of active Ni in small sizes with more defects,which results in high catalytic activity of Ni in biomass decomposition and selective production of phenols.展开更多
The redox properties of α-Keggin-type heteropolyanion clusters [XM12O40]n-(X = Si,P; M = Mo,W) mainly depend on their constituent outer metal-oxygen cages {M12O36}. They act as "reservoirs",through which th...The redox properties of α-Keggin-type heteropolyanion clusters [XM12O40]n-(X = Si,P; M = Mo,W) mainly depend on their constituent outer metal-oxygen cages {M12O36}. They act as "reservoirs",through which the transfer and transition of electrons and protons may occur. At the atomic and molecular level,the redox properties of these clusters can be controlled and also tuned by modifying the metal M in the cages and the central heteroatom X of the clusters. Combined with relevant experimental results,this review summarizes our recent theoretical investigations of the effect of vanadium substitution on the redox properties of Keggin anion clusters. Theoretical modeling and calculation results showed that the oxidative ability of the modified species was increased by partial substitution of the cage M atoms of the Keggin clusters by vanadium atoms which have lower electronegativity. A linear correlation between the catalytic efficiency per vanadium atom and the microstructures of the vanadium(V)-substituted heteropolyanions [PVnMo12-nO40](3+n)-(n = 1-3) was established for the first time. This relationship may be suitable to interpret the catalytic behavior of the title compounds in the hydroxylation of benzene to phenol,and may also be used in understanding other reactions such as the oxidative dehydrogenation of isobutyric acid and the nitration of adamantine. The establishment of this nearly linear structure-property relationship may lay the foundations of understanding the behavior of the title compounds in homogeneous catalytic oxidation reactions,and may direct the design of future catalysts and the choice of other catalytic reactions.展开更多
基金supported by the National Basic Research Program of China (2007CB210203)the Special Research Fund for the Doctoral Program of Higher Education of China (20050610013)
文摘The pyrolysis of Pubescens over Ni/C catalyst was studied at 350°C in H2 flow.The presence of Ni/C catalyst efficiently improved the degradation of raw materials,and produced bio-oil with high content of phenols but low contents of acetic acid,furfural and water.In the reaction,Ni/C catalyst plays the role of catalytic decomposition and catalytic hydrogenation.The existence of the carbon carrier favors the formation of active Ni in small sizes with more defects,which results in high catalytic activity of Ni in biomass decomposition and selective production of phenols.
基金Supported by the Special Project of Key Laboratory of the Sichuan Provincial Department of Education (Grant No. 2006ZD051)the National Natural Science Foundation of China (Grant No. 20072024)the Doctoral Fund Project of Yibin University (Grant No. 2006B03)
文摘The redox properties of α-Keggin-type heteropolyanion clusters [XM12O40]n-(X = Si,P; M = Mo,W) mainly depend on their constituent outer metal-oxygen cages {M12O36}. They act as "reservoirs",through which the transfer and transition of electrons and protons may occur. At the atomic and molecular level,the redox properties of these clusters can be controlled and also tuned by modifying the metal M in the cages and the central heteroatom X of the clusters. Combined with relevant experimental results,this review summarizes our recent theoretical investigations of the effect of vanadium substitution on the redox properties of Keggin anion clusters. Theoretical modeling and calculation results showed that the oxidative ability of the modified species was increased by partial substitution of the cage M atoms of the Keggin clusters by vanadium atoms which have lower electronegativity. A linear correlation between the catalytic efficiency per vanadium atom and the microstructures of the vanadium(V)-substituted heteropolyanions [PVnMo12-nO40](3+n)-(n = 1-3) was established for the first time. This relationship may be suitable to interpret the catalytic behavior of the title compounds in the hydroxylation of benzene to phenol,and may also be used in understanding other reactions such as the oxidative dehydrogenation of isobutyric acid and the nitration of adamantine. The establishment of this nearly linear structure-property relationship may lay the foundations of understanding the behavior of the title compounds in homogeneous catalytic oxidation reactions,and may direct the design of future catalysts and the choice of other catalytic reactions.
