Controllable thermal conversion of thiomolybdate to active few-layer MoS2 on alumina for efficient hydrodesulfurization

Abstract

Sulfur removal is the most challenging task in petroleum refineries for upgrading clean fuel from crude oil. In this regard, an efficient Ni–MoS2 catalyst was prepared using ammonium tetrathiomolybdate (ATM), (NH4)2MoS4 as a precursor for hydrodesulfurization (HDS) reaction. ATM was derived by sulfiding an aqueous ammoniacal ammonium heptamolybdate and impregnated on alumina support with and without nickel promoter to form a series of MoS2/Al2O3, and Ni–MoS2/Al2O3 catalysts with controlled calcination temperature. The prepared ATM and catalysts were characterized by X-ray diffraction (XRD), Infrared spectroscopy and nitrogen adsorption–desorption. The phase transformation of ATM to MoS2 was observed by TGA, and number of MoS2 layer formation was calculated from the frequency difference between the redshift and blueshift by Raman spectrum. The catalytic properties of MoS2/Al2O3, and Ni–MoS2/Al2O3 were investigated using thiophene as the model compound for HDS reaction. The HDS rate, C4 hydrocarbon product distribution and selectivity were quantified by microreactor with refinery gas analyzer system. The prepared MoS2 catalysts (MoS and NiMoS) at 350 °C showed a better conversion rate than another catalyst due to the synergy between the promoter and few-layered MoS2 on support. Thus, ATM is a suitable candidate for the formulation of Ni–MoS2 catalyst at 350 °C for improving thiophene HDS activity.