Three titanium-containing aluminum phosphate catalysts with a general formula Al 0.77 Ti 0.23 PO 4 were prepared by the sol-gel method at room temperature(APTS), and a nonuniform precipitation procedure at ro...Three titanium-containing aluminum phosphate catalysts with a general formula Al 0.77 Ti 0.23 PO 4 were prepared by the sol-gel method at room temperature(APTS), and a nonuniform precipitation procedure at room temperature(APTR) and under reflux(APTF), respectively. The structural features and the surface properties of the three catalysts were determined by means of the physical adsorption of nitrogen at liquid N 2 temperature, XRD, UV-Vis, NH 3-TPD and IR of adsorbed pyridine. The vapor phase O-alkylation of catechol with ethanol over the prepared catalysts was studied. It was found that the activity and the selectivity of these catalysts are greatly dependent on the preparation method, and catalyst APTF shows the highest activity and selectivity. The characterization evidence indicates that the weak Brnsted acid sites were more effective for the reaction.展开更多
The heat capacities of 3-（ 2,2-dichloroethenyl）-2,2-dimethylcyclopropanecarboxylic acid （a racemic mixture, molar ratio of cis-/trans-structure is 35/65） in a temperature range from 78 to 389 K were measured with ...The heat capacities of 3-（ 2,2-dichloroethenyl）-2,2-dimethylcyclopropanecarboxylic acid （a racemic mixture, molar ratio of cis-/trans-structure is 35/65） in a temperature range from 78 to 389 K were measured with a precise automatic adiabatic calorimeter. The sample was prepared with a purity of 98.75% （ molar fraction）. A solid-liquid fusion phase transition was observed in the experimental temperature range. The melting point, Tm, enthalpy and en- tropy of fusion, △fusHm, △fusSm, of the acid were determined to be （331.48±0.03 ） K, （16.321±0.031） kJ/mol, and （49.24±0.19） J/（ K·mol）, respectively. The thermodynamic functions of the sample, Ht-H298.15, Sr-S298.15 and Gr-G298.15, were reported at a temperature intervals of 5 K. The thermal decomposition of the sample was studied using thermogravimetric（TG） analytic technique, the thermal decomposition starts at ca. 418 K and ends at ca. 544 K, the maximum decomposition rate was obtained at 510 K. The order of reaction, preexponential factor and activation energy are n =0.23, A =7.3 ×10^7 min^-1 , E =70.64 kJ/mol, respectively.展开更多
基金Supported by the Foundation of Science of Jilin Province Science and Technique Com mittee( No.990 5 4 6 )
文摘Three titanium-containing aluminum phosphate catalysts with a general formula Al 0.77 Ti 0.23 PO 4 were prepared by the sol-gel method at room temperature(APTS), and a nonuniform precipitation procedure at room temperature(APTR) and under reflux(APTF), respectively. The structural features and the surface properties of the three catalysts were determined by means of the physical adsorption of nitrogen at liquid N 2 temperature, XRD, UV-Vis, NH 3-TPD and IR of adsorbed pyridine. The vapor phase O-alkylation of catechol with ethanol over the prepared catalysts was studied. It was found that the activity and the selectivity of these catalysts are greatly dependent on the preparation method, and catalyst APTF shows the highest activity and selectivity. The characterization evidence indicates that the weak Brnsted acid sites were more effective for the reaction.
基金Supported by the Education Bureau Science Foundation of Liaoning Province,China(No.20040261).
文摘The heat capacities of 3-（ 2,2-dichloroethenyl）-2,2-dimethylcyclopropanecarboxylic acid （a racemic mixture, molar ratio of cis-/trans-structure is 35/65） in a temperature range from 78 to 389 K were measured with a precise automatic adiabatic calorimeter. The sample was prepared with a purity of 98.75% （ molar fraction）. A solid-liquid fusion phase transition was observed in the experimental temperature range. The melting point, Tm, enthalpy and en- tropy of fusion, △fusHm, △fusSm, of the acid were determined to be （331.48±0.03 ） K, （16.321±0.031） kJ/mol, and （49.24±0.19） J/（ K·mol）, respectively. The thermodynamic functions of the sample, Ht-H298.15, Sr-S298.15 and Gr-G298.15, were reported at a temperature intervals of 5 K. The thermal decomposition of the sample was studied using thermogravimetric（TG） analytic technique, the thermal decomposition starts at ca. 418 K and ends at ca. 544 K, the maximum decomposition rate was obtained at 510 K. The order of reaction, preexponential factor and activation energy are n =0.23, A =7.3 ×10^7 min^-1 , E =70.64 kJ/mol, respectively.
