Ultra-deep hydrodesulfurization of benzene over Ni/ZnO catalyst

Ni/ZnO catalyst prepared by impregnation and co-precipitation methods for ultra-deep hydrodesulfurization of benzene was studied. The structures and properties of the catalysts were investigated by H₂-TPR, XRD and BET techniques. It was found that the interaction between NiO and ZnO has important influence on the activity and selectivity of the catalysts. NiO with weak interaction with ZnO has high benzene hydrogenation activity after reduction by H₂, resulting in conversion of benzene to cyclohexane, whereas, NiO with strong interaction with ZnO has hydrodesulfurization activity, but has no benzene hydrogenation activity. The catalysts prepared by impregnation showed certain content of weak-interaction NiO, so the benzene exhibited great lose. The NiO, prepared by co-precipitation, has strong interaction with ZnO，so the catalyst has better selectivity toward desulfurization. Furthermore, the catalyst prepared by co-precipitation had a higher BET area. As a result, the activity and selectivity were higher over catalyst prepared with co-precipitation than that over catalyst prepared by impregnation. It was found that reduction temperature has important influence on catalyst activity and selectivity. Catalyst reduced at 400℃showed the best performance while reduction at 500℃ resulted in the decrease of the activity due to crystal particles sintering and specific surface area decrease. Addition of Sn can change the interaction between NiO and ZnO. Due to the inhibition of formation of weakinteraction NiO, Sn addition suppressed greatly the loss of benzene.