Effects of the support on the performance and promotion of (Ni)MoS ₂ catalysts for simultaneous hydrodenitrogenation and hydrodesulfurization

MoS₂ and Ni-promoted MoS₂ catalysts supported on γ-Al₂O₃, siliceous SBA-15, and Zr- and Ti-modified SBA-15 were explored for the simultaneous hydrodesulfurization (HDS) of dibenzothiophene (DBT) and hydrodenitrogenation (HDN) of o-propylaniline (OPA). In all cases, OPA reacted preferentially via initial hydrogenation, and DBT was converted through direct sulfur removal. HDN and HDS activities of MoS ₂ catalysts are determined by the dispersion of the sulfide phase. Ni promotion increased its dispersion and activity for DBT HDS and also increased the rate of HDN via enhancing the rate of hydrogenation. On nonpromoted MoS ₂ catalysts, HDS was strongly inhibited by NH₃, and the addition of Ni dramatically reduced this inhibiting effect. The conclusion is that HDS is proportional to the concentration of Mo and Ni on the edges of sulfide particles. In contrast, the direct hydrodenitrogenation of OPA occurs only on accessible Mo cations and, hence, decreases with increasing Ni substitution. The nature of the support influences the dispersion of the nonpromoted catalysts as well as the decoration degree of Ni on the edges of the Ni-Mo-S phase. Furthermore, the acidity of the support influences the acidity of the supported sulfide phase, which may play an important role in HDN.