Effects of Pressure and Temperature in Hydrothermal Preparation of MoS₂ Catalyst for Methanation Reaction

Abstract: Unsupported MoS₂ catalysts were prepared for the methanation reaction by varying the pressure and temperature in the hydrothermal reaction by using ammonium tetrathiomolybdate (ATTM). The physical and chemical characteristics of the catalysts were analyzed by using XRD, SEM, TEM, BET, XPS, H₂-TPR, and CO-TPD techniques. The catalyst particles were formed in the bent fringe shape by stacking the (0 0 2) planes, and consisted mostly of MoS₂, with some Mo₂S₅ and MoS₃. It was found that the BET surface and active sites such as surface Mo⁴⁺ and sulfur vacancies increased with increasing preparation pressure, which could contribute to the improvement of MoS₂ catalytic activity. The increase in preparation temperature not only favored the decomposition of ATTM into MoS₂, but also lowered the number of active sites accessible for the reaction. Thus, it was suggested that the preparation temperature should be controlled at 350 °C to improve the catalytic activity. Graphical Abstract: [Figure not available: see fulltext.].