Effects of HY addition on NiMoS active phase of NiMo(NH3) impregnated NiMo/Al2O3-HY and its role in 4,6-dimethyl-dibenzothiophene hydrodesulfurization

Effects of HY addition on NiMoS active phase of NiMo(NH3) impregnated NiMo/Al2O3-HY and its role in 4,6-dimethyl-dibenzothiophene hydrodesulfurization was investigated. The results show that HY can promote HDS reaction by changing the morphology of NiMoS nanoclusters even when isomerization of 4,6-DMDBT is not involved. In the absence of strong acid sites, TOF of NiMo/Al2O3 catalyst was still improved by 90%. XRD, H2-TPR, Raman, TEM, and XPS characterization show that proper metal support interaction caused by HY addition is beneficial to the formation of large-scale multilayer NiNoS clusters, the enrichment of Ni in NiMoS clusters and the increase of NiMoS active sites, thereby leading HDS catalyst exhibiting highest intrinsic activity (TOF). However, too strong or too weak metal support interaction will reduce intrinsic activity for HDS catalysts. When pH value of impregnation solution is 10, the strong metal support interaction reduces layer numbers of NiMoS clusters. When pH value of impregnation solution is 11, negative charge hinders the formation of NiMoS clusters. This not only leads to a further decrease HYD pathway selectivity, but also significantly reduces the initial reaction rate of HDS catalyst.