A series of catalysts of 12-Phosphotungstic acid (PW) and its cesium salts immobilizedon dealuminated ultra-stable Y zeolite (DUSY) were prepared. Their specific surface area and acidstrength were characterized, and t...A series of catalysts of 12-Phosphotungstic acid (PW) and its cesium salts immobilizedon dealuminated ultra-stable Y zeolite (DUSY) were prepared. Their specific surface area and acidstrength were characterized, and their catalytic activity, selectivity and stability were evaluated in theliquid-phase esterification of acetic acid with n-butanol. It was found that the catalytic activity could beimproved remarkably by introducing PW onto dealuminated USY (from 49.5% to 86.4%). Howeverthis obvious promotion effect of PW could not be observed on USY supported PW catalyst, whichshowed rather low conversion of less than 25.0%. The supported cesium salt of PW on DUSY catalysgave a very high conversion of n-butanol of 94.6% and the 100% selectivity for n-butyl acetate. Thecatalytic stability test revealed that after 5 reaction cycles, the catalytic activity over PW/DUSY drastically dropped to 47.6%, by contrast, the PW cesium salt/DUSY still showed a high conversion o81.6%. The leaching test for catalysts in water showed that the decrease of activity was closely associated with the solubility of the active heteropoly components on supports into the polar solvent, whichindicates that the catalytic deactivation was mainly due to the lose of the heteropoly species in thereaction medium. The high catalytic stability of the supported cesium salts of PW is suggested to bederived from the water-tolerance of cesium salts of PW in the polar reaction system.展开更多
基金This work was supported by the National Natural Science Foundation of China (Grant Nos. 20306011 & 20476046) the Ph.D. Program Foundation of Chinese University (No. 20040291002).
文摘A series of catalysts of 12-Phosphotungstic acid (PW) and its cesium salts immobilizedon dealuminated ultra-stable Y zeolite (DUSY) were prepared. Their specific surface area and acidstrength were characterized, and their catalytic activity, selectivity and stability were evaluated in theliquid-phase esterification of acetic acid with n-butanol. It was found that the catalytic activity could beimproved remarkably by introducing PW onto dealuminated USY (from 49.5% to 86.4%). Howeverthis obvious promotion effect of PW could not be observed on USY supported PW catalyst, whichshowed rather low conversion of less than 25.0%. The supported cesium salt of PW on DUSY catalysgave a very high conversion of n-butanol of 94.6% and the 100% selectivity for n-butyl acetate. Thecatalytic stability test revealed that after 5 reaction cycles, the catalytic activity over PW/DUSY drastically dropped to 47.6%, by contrast, the PW cesium salt/DUSY still showed a high conversion o81.6%. The leaching test for catalysts in water showed that the decrease of activity was closely associated with the solubility of the active heteropoly components on supports into the polar solvent, whichindicates that the catalytic deactivation was mainly due to the lose of the heteropoly species in thereaction medium. The high catalytic stability of the supported cesium salts of PW is suggested to bederived from the water-tolerance of cesium salts of PW in the polar reaction system.
