Alumina supported CoMo catalysts(CoMo/$Al_2O_3$) were prepared using two different methods. One method was Co impregnation on oxidized Mo/$Al_2O_3$ (P1 method) and the other was Co impregnation on nitrided Mo/$Al_2O_3$(P2 method). All catalysts were activated under three different conditions (sulfidation, nitridation followed by sulfidation, reduction followed by nitridation). Effects of activation and preparation methods were investigated by thiophene hydrodesulfurization, X-ray diffraction, electron spin resonance, scanning electron microscopy, NO titration and temperature programmed desorption of NO.
HDS activities of CoMo/$Al_2O_3$ catalysts were drastically affected by activation conditions. CoMo/$Al_2O_3$ catalysts activated by sulfidation showed the highest activity among activation conditions.
Catalysts prepared by P2 method exhibited higher HDS activity, lower surface area and lower NO uptake than those by P1 method. The crystalline structure and metal species of the catalysts prepared by both methods were very similar. However, the catalysts prepared by P2 method showed higher intrinsic activity and new NO adsorption sites.
It is suggested that the higher HDS activity is due to the creation of more active catalytic site from the interaction of Co and Mo nitride during preparation of catalyst.
