Keggin型杂多酸表面和体相的催化活性和选择性之差异的研究

Investigation on The Catalytic Characteristics in the Bulk of the Keggin Type Heteropoly Acid

本文以异丙醇脱水、甲醇转化等为模型反应,采用改变12-钨磷酸在载体SiO_(2)上担载量的办法,对Keggin型杂多酸催化剂进行了研究,结果表明:HPA的表面和体相酸中心,对于极性较大可进入其体相内部的异丙醇分子的脱水反应,在担载量为5×10^(-5)-1.5×10^(-1)mol HPA/(dm)^(3)SiO_(2)的范围内,具有相同的转化频率。HPA的表面和体相酸中心具有不同的催化选择性。

The catalytic behavior in bulk of the Keggin type heteropoly acid H_(3)PW_(10)O_(40)(abbreviated as HPA)has been investigated by varying amount of HPA on SiO2With the catalysts containing HPA of 5×10^(-5)-1.5×10^(-1)mol/(dm)^(3) of SiO_(3) it was found that the acid site on the surface and in the bulk of HPAshowed the same turnover frequency for the dehydration of iso-propanol.But the selectivity of catalysis in the bulk differed from that on the surface of HPA.Catalysis in the bulk favoured the formation of products with more than four carbon atoms in methanol conversion and the formation of ethylene in dehydration of ethylalcohol.