Correlation between hydrodesulphurization activity and reducibility of unsupported MoS2-based catalysts promoted by group VIII metals

Abstract

Unsupported FeMo, CoMo and NiMo sulphide hydrodesulphurization (HDS) catalysts have been prepared by one or several different methods: homogeneous sulphide precipitation (HSP), inverse HSP (IHSP), comaceration (CM) and coprecipitation (CP). They have been characterised by (i) differential thermal analysis (DTA) during temperature-programmed reduction/sulphidation (TPR/S) and subsequent air oxidation (TPO), (ii) temperature-programmed sulphur extraction (TPSE), (iii) XPS and (iv) XRD. For catalysts prepared by the HSP, IHSP and CP methods the onset temperature of TPR/S decreases, and the threshold temperature of oxidation, the amount of released H₂S in TPSE and the HDS activity all increase in the sequence Mo < FeMo < CoMo < NiMo. XPS reveals a change in the Co 2p_3/2 and 2p_3/2 binding energies for promoted catalysts with respect to pure Co₉S₈ and NiS, respectively. The results demonstrate a strong correlation between catalytic activities in HDS of thiophene and hydrogenation of cyclohexene on the one hand, and the reducibility of the catalysts on the other.