负载杂多酸催化剂的表征及催化合成乙酸正丁酯的研究 Ⅱ.负载杂多酸催化剂的酸性及催化酯化反应性能

STUDY ON THE SYNTHESIS OF NORMAL BUTYL ACETATE OVER SILICOTUNGSTIC ACID SUPPORTED CATALYST Ⅱ.Acidity and Catalytic Esterification Performance of Silicotungstic Acid(SiW_(12))Supported Catalyst

对浸渍法制备的以硅胶、中性氧化铝和β沸石为载体的SiW12杂多酸负载型催化剂,采用TPD法测试了催化剂酸性,在间歇反应器中测定了催化剂的酯化活性。结果表明:载体种类对负载杂多酸催化剂的催化活性有很大影响,催化活性由大到小顺序为:硅胶>Hβ分子筛>中性氧化铝。酸性载体制得的负载型杂多酸催化剂,较原载体酸量增大,酯化活性有很大提高。说明催化酯化反应的活性中心是催化剂表面的B酸中心。催化剂B酸量和催化活性均与负载量呈顺变关系,但增加的趋势逐渐减缓。

The acidity of a series of 12-silicotungstic acid （SiW12）immobilized catalysts supported on silica gel, neutral alumina and zeolite β was characterized by TPD mathod, and their esterification activities were determined by a batch reactor. The results showed that the esterification activities of heteropoly acid catalysts were greatly affected by various carriers since the activity was related to the interaction of heteropoly acid and the carrier. The activities of catalysts were in the order of catalyst with silica gel carrier〉with zeolite β carrier〉with neutral alumina carrier. The acidity of the heteropoly acid catalyst supported on acidic carrier was higher than that of the original carrier,thus the esterification activity of the catalyst was enhanced. The number of Bronsted acid sites,i, e. catalytic active sites,increased with the loading of heteropoly acid, yet the increment droped with the increase of loading.