Effect of sulphidation temperature on the performance of NiO–MoO3/γ-Al2O3 catalysts for sulphur-resistant methanation

Abstract

The effect of the sulphidation temperature on the activity and selectivity of a NiO–MoO₃/γ-Al₂O₃ catalyst for sulphur-resistant methanation was systematically investigated. The prepared catalysts were subsequently characterised by N₂-physisorption, temperature-programmed sulphidation, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy. The results obtained from characterisation demonstrated that the NiMoO₄ species in the NiO–MoO₃/γ-Al₂O₃ catalyst was sulphided when the sulphidation temperature was at or above 300 °C. Evaluation of the catalysts in sulphur-resistant methanation from syngas indicated that the sample sulphided at 400 °C has the highest likelihood of possessing a greater NiMoS type I structure. The catalytic activity decreased when the sulphidation temperature was above 400 °C. This decrease was primarily caused by the formation of MoS₂ crystals and the progressive transformation of the NiMoS phase with increasing sulphidation temperature. The NiMoS type II structure did not display good performance for sulphur-resistant methanation because it resulted in the over-sulphidation of the NiMoS structure to form crystalline MoS₂, which exhibited lower methanation activity.