Synthesis and Catalytic Activity of CoMo and CoMoW Catalysts supported on γ-Al 2 O 3 for Efficient Naphtha Hydrodesulfurization

Abstract

Bimetallic Co5Mo15 of 5 wt.% Cobalt as a promoter and 15 wt.% Molybdenum as an active metal and trimetallic Co5Mo15-xWx (x = 1, 3, 5 wt.%) heterogeneous catalysts supported on gamma alumina (γ-Al2O3) were synthesized by an incipient wetness co-impregnation process. The structural and the physicochemical characteristics of the prepared bi- and tri-metallic catalysts were evaluated by the XRD, SEM, BET and BJH, respectively. The role of third W active metal on the catalytic activity was determined through a hydrodesulfurization (HDS) reaction of naphtha at four different reaction temperatures (250, 275, 300, 325ºC) and four liquid hourly space velocities, LHSV (3, 4, 5, 6 hr-1) under constant 1.5 MPa H2 pressure. The trimetallic CoMoW5 catalyst exhibited the maximal HDS efficiency at 325ºC and 3 hr-1 liquid flow of 88% sulfur removed compared to the CoMo catalyst. This was ascribed for the role of the highly dispersed active W metal and presence of the sulfided CoMoWS and CoWS sites on the alumina surface that leads to increase the surface area and the porous structure, and enhancing the metal/sulfur bond.