Preparation,characterization And Catalytic Performance Of Keggin Type Heteropoly Acids(Salts)catalysts

Heteropoly acids(salts) have great utilities in catalysis because of their acidity and oxidation-reduction quality. Compared with the traditional catalysts, it has the determination internal stucture, a unique pseudo-liquid phase, in polar solution, such as the advantages of good solubility. In the organic catalytic reaction, the heteropoly acids(salts) show high catalytic activity and selectivity. Because it is low in the response to equipment,s corrosiveness, the response condition is temperate. Therefore, it received the widespread attentions in the recent years.This thesis was focused on the research of some organic reactions catalyzed by Keggin type heteropoly acids(salts) catalytic systems. The main progress and research results have been obtained as follows:1.Synthesis and characterization of Keggin type P-V-Mo-W heteropolyacidP-V-Mo-W heteropoly acids, H6PV3MoxW9-x O40·nH2O(x=1,2,3,4,5)with Keggin structure, were synthesized and proved by FTIR and X-ray spectroscopies.2.Catalytic synthesis of benzyl acetate over Keggin type heteropoly acid H6PV3 Mo W8O40/MCM-41A supported catalyst H6PV3 Mo W8O40/MCM-41 was prepared by an impregnation method. The supported catalyst was characterized by means of XRD, FTIR and BET. By the esterification of acetic acid with benzyl alcohol, the catalytic performance and reusability of supported catalyst H6PV3 Mo W8O40/MCM-41 were investigated. Under the optimized conditions of benzyl alcohol 0.10 mol, molar ratio of acetic acid to benzyl alcohol 2.5,H6PV3 Mo W8O40 loading 50%(wt.%), reaction temperature 120 ℃, reaction time 2.5 h,catalyst amount 0.6 g, conversion of benzyl alcohol and selectivity of benzyl acetate reached95.33% and 94.48%, respectively. And conversion of benzyl alcohol and selectivity of benzyl acetate was over 82% and 94% after the catalyst was reused for 4 times.3.Catalytic oxidation of benzaldehyde to benzoic acid over Keggin type phosphotungstic ammonium cesium saltsA series of Keggin type heteropoly acids(salts), Csx(NH4)2.5-x H0.5PW12O40(x=0.5,1,1.5,2), were synthesized and proved by FTIR and X-ray spectroscopies. With 30 wt.% aqueous hydrogen peroxid as oxidant,benzaldehyde was efficiently oxidized to benzoic acid over the Cs2(NH4)0.5H0.5PW12O40 heteropoly acids(salts) catalyst. The effects of reaction temperature and time, amount of catalyst and H2O2(in mass concentration of 30 wt.%) were investigated.Under the following optimal conditions as followed:benzaldehyde 0.1 mol, reaction temperature 80 ℃, reaction time 4 h, catalyst amount 0.6 g, molar ratio of H2O2 to benzaldehyde 3.5:1, the mean yield of benzoic acid reached 65.25%.