K-Mo基催化剂的表面酸性与其合成醇选择性

对500℃和800℃焙烧制得的氧化态K－MoO3／γ－AlO3，K－MoO3／SiO2及非负载K－Mo催化剂进行硫化后，测试其合成醇活性．结果表明500℃焙烧制得的负载型催化剂显示较高的合成低碳烃活性和较低的合成低磷醇选择性，经800℃焙烧后，合成低磷醇的选择性大幅度提高．500℃焙烧的非负载K－Mo催化剂显示较高的合成醇选择性，经800℃焙烧后，促碳醇的选择性保持不变．用氨的吸附及TPD方法测定了各样品的酸性，并与催化剂活性对照，发现催化剂酸性越强，酸量越大，则其合成醇选择性越低．催化剂上的乙醇分解实验证实，催化剂的酸量大小与它的醇分解活性成正变关系，这些结果说明催化剂酸性对其合成醇性能有直接的影响．

Surface Acidity and Catalytic Properties of Sulfided K-Mo Based Catalysts for Mixed Alcohols Synthesis

Oxidized K-Mo catalysts supported on 7-A12O3 or SiO2 were prepared by impregnating the supports with KCl and ammonia heptamolybdate solutions and calcination at 500 ℃Unsupported oxidized K-Mo catalyst was prepared by mixing KCl and ammonia heptamolybdate compounds and calcination at 500 ℃' Both the supported and unsupported catalysts were recalcined at 800 ℃. These samples were sulfided for mixed alcohols synthesis from syngas. It is found that for 500 ℃ calcined samples, the selectivity to mixed alcohols is enhanced in the order of K-MoOa/γ-Al2O3 The acidities of these catalysts were measured with ammonia adsorption and TPD. It is found that low selectivity to mixed alcohols for supported catalysts, by calcination 500 ℃, can be due to that part of acid sites on the supports are still existed, which decompose some of the alcohols during the reaction. With recalcination at 800 ℃, the selectivity to mixed alcohols for supported catalysts become increased, which is due to that stronger interaction between the potassium component and the support suppresses more acid sites. This idea is supported by the activities for ethanol decomposition over both the oxidized and the sulfided catalysts. It is concluded that the surface acidity of the catalysts is important for the reaction tendency to form alcohols or to form hydrocarbons from CO hydrogenation.