Effect of K₂O on hydrodesulfurization performance of Co-Mo/MCM-41

K₂O was introduced to Co-Mo/MCM-41 catalyst precursor by a consecutive impregnation method and a co-impregnation method. The obtained catalysts were denoted as K-CoMo/MCM-41 and KCoMo/MCM-41, respectively, and characterized by means of XRD, UV-Vis and TPR. The hydrodesulfurization (HDS) performances of the three sulfide catalysts were studied by using a model fuel containing 0.8% (mass fraction) DBT in decalin. The results indicated that the introduction of K₂O to Co-Mo/MCM-41 by co-impregnation method not only destroyed the structure of MCM-41, but also led to a decrease in the octahedrally coordinated Mo species. Nevertheless, neither the distributions nor the coordination states of the active species were affected by the introduction of K₂O with the consecutive impregnation method, except that the reducibility of K-CoMo/MCM-41 precursor was decreased. The HDS of DBT predominately took the route of direct desulfurization (DDS) over the Co-Mo/MCM-41 sulfides. KCoMo/MCM-41 showed lower DDS catalytic activity and hydrogenation (HYD) catalytic activity than CoMo/MCM-41, and therefore exhibited lower overall catalytic activity in HDS of DBT. However, the introduction of K₂O to CoMo/MCM-41 by the consecutive impregnation method had little influence on the overall HDS catalytic activity of the CoMo/MCM-41catalyst, but led to an enhancement of catalytic activity in the DDS pathway and a decrease of catalytic activity in the HYD pathway, and therefore a decrease of the H₂ consumption in the HDS reaction.