Effect of sulfiding conditions on the hydrodesulfurization performance of the ex-situ presulfided CoMoS/γ-Al2O3 catalysts.

Graphical abstract Highlights • Sulfiding agent could effectively react with the supported Mo oxide to form intermediate thiosalts. • The usage of sulfiding agent could generate mononuclear and polynuclear ammonium thiosulfate. • The sulfiding conditions could modify the final morphology of active phase. • The large number of Mo nuclear would lead to the high stacking of MoS 2 slabs. • The catalyst with optimal Mo dispersion and ratios of edge sites to rim sites showed high HDS activity. Abstract The influence of sulfiding conditions in the ex-situ presulfidation process on the morphology and performances of CoMoS/γ-Al 2 O 3 catalysts was studied in details for hydrodesulfurization (HDS) of dibenzothiophene. Surface and bulk characterization using XRD, HRTEM, XPS, TPR and FT-IR confirmed that the sulfiding agent mixture of (NH 4) 2 S and elemental S effectively react with the supported Mo oxide to form intermediate thiosalts from mononuclear ammonium thiomolybdates to polynuclear ammonium thiomolybdates, namely the formed thiosalts from (NH 4) 2 MoS 4 to (NH 4) 2 Mo 2 S 12 and (NH 4) 2 Mo 3 S 13 ,which weaken the strong interaction between the γ-Al 2 O 3 support and Mo oxide, resulting in maximum sulfidation of Mo oxide species. Mo species tend to agglomerate as the number of Mo nuclear increases, which further induces significant changes in the morphology of MoS 2 particles. Such observation was further correlated with HDS activity and selectivity. The CoMoS/γ-Al 2 O 3 catalyst with (NH 4) 2 Mo 2 S 12 as intermediate exhibits suitable slab lengths and stacking numbers of MoS 2 slabs with optimal compromise between the Mo dispersion and ratios of edge sites to rim sites, and show the highest HDS activity. Therefore, a tailor-made catalyst with excellent HDS performance could be developed by adjusting the sulfiding conditions through ex-situ presulfidation method. [ABSTRACT FROM AUTHOR]