Ru/MCM-41催化剂表面的Ru物种

采用等体积浸渍法制备了用于苯选择加氢制环己烯的Ru/MCM-41催化剂,对其进行了X射线衍射、透射电镜、程序升温还原和原位漫反射红外光谱等手段表征,以确定MCM-41表面Ru物种的存在状态.结果发现,Ru物种颗粒均匀地分散在MCM-41孔道内,平均粒径为2.1 nm.在MCM-41表面存在Ru0、RuOx、RuClO和RuCl3等Ru物种；并且随着助剂Zn的加入,RuOx、RuClO等物种变得不稳定,而对于Ru0的影响较小.Ru0的加氢活性较强,易于使苯发生深度加氢得到环己烷；而RuOx、RuClO的加氢活性较弱,更易得到环己烯.Zn的加入使Ru/MCM-41催化苯选择加氢制环己烯的活性和选择性同时下降.

Ru Species Over the Surface of Ru/MCM-41 Catalyst

Ru/MCM-41 catalysts were prepared by dry impregnation method for selective hydrogenation of benzene to cyclohexene.XRD,TEM,TPR and in-situ DRIFTS were conducted to determine the Ru species over the MCM-41 support.It was found that the particles of Ru compounds were dispersed well in the channels of MCM-41 with average diameter of 2.1 nm.There are several Ru species on the surface of MCM-41 support,such as Ru0,RuOx,RuClO and RuCl3.With the addition of promoter Zn,RuOx and RuClO became unstable.However,Zn showed a relatively weak influence on Ru0.Cyclohexane is easily obtained by further hydrogenation of benzene over Ru0,which has strong hydrogenation ability.Nevertheless,more cyclohexene could be obtained over the weak hydrogenation sites of RuOx and RuClO.With the addition of Zn,the activity and cyclohexene selectivity decreased simultaneously over Ru/MCM-41 catalyst was observed.