Ru/MCM-41催化苯选择加氢制环己烯

SELECTIVE HYDROGENATION OF BENZENE TO CYCLOHEXENE OVER RU/MCM-41 CATALYSTS

采用浸渍法制备了Ru/MCM-41催化剂,用于催化苯选择加氢制环己烯反应。为提高环己烯选择性,向催化剂中加入Zn助剂,考察了不同Zn母体对Ru/MCM-41催化性能的影响。结果表明,Zn的加入影响了Ru的还原,从而影响了其催化性能。当使用ZnCl2或Zn(OAc)2为Zn母体时,Ru容易被还原,Ru/MCM-41催化剂表面活性中心数量增加,从而使其催化活性增加;当使用Zn(NO3)2为Zn母体时,部分Ru不易被还原,相应的Ru/MCM-41催化活性有所降低;ZnSO4为Zn母体时,ZnSO4的存在使MCM-41表面显酸性,在催化苯选择加氢反应中,由于表面酸中心和Ru加氢中心的共同存在,使得苯加氢反应存在两条路径,因此反应速率增加,苯转化率增加,并且由于表面酸中心有利于环己烯的吸附,从而易使其发生深度加氢。

Ru/MCM-41 catalysts were prepared by impregnation method for selective hydrogenation of benzene to cyclohexene. To improve cyclohexene selectivity, Zn promoter was added to Ru/MCM-41 catalysts. Effect of the Zn precursors on the catalytic performance of Ru/MCM-41 was investigated. It was found that the addition of Zn promoter could obvious affect the catalytic activity by influencing the reduction of Ru in Ru/MCM-41. When ZnCl2 or Zn（OAc）2 was used as Zn precursor, Ru was easily reduced, resulting in the increase of the number of active centers on Ru/MCM-41 surface, and the higher catalytic activity. When Zn （NO3）2 was used as Zn precursor, part of Ru was not reduced, so the catalytic activity of Ru/MCM-41 was lowered down. The use of ZnSO4 as Zn precursor made the surface of Ru/MCM-41 having acidity. When the Ru/MCM-41 with ZnSO4 as Zn precursor was used for selective hydrogenation, there were two routes for benzene hydrogenation, causing the reaction rate and benzene conversion increased. Furthermore, the acid sites existing on Ru/MCM-41 surface were in favor of the adsorption of cyclohexene, thereby over-hydrogenation happend easilyand cyclohexane would be the main product.