Effect of sulfidation temperature on CoO–MoO3/γ-Al2O3 catalyst for sulfur-resistant methanation

Abstract

The effect of sulfidation temperature on the catalytic activity of CoO–MoO₃/γ-Al₂O₃ catalyst toward sulfur-resistant methanation was studied. The prepared catalysts were characterized by N₂-physisorption (BET), Temperature-programmed sulfidation (TPS), X-ray diffraction (XRD), Raman spectroscopy (RS), and Transmission electron microscope (TEM). The combined results of TPS, XRD, and RS indicated that CoMoO₄ species in CoO–MoO₃/γ-Al₂O₃ catalyst would be sulfided when the sulfidation temperature was at or higher than 300 °C. The catalyst sulfided at 400 °C exhibited the highest catalytic activity because there were the most CoMoS structures in the catalyst. When the sulfidation temperature was higher than 400 °C, the catalytic activity decreased with increasing sulfidation temperature. This decline was primarily caused by the formation of Co₉S₈ and MoS₂ crystals. The CoMoS(II) formation did not favor the catalytic activity, because the formation of this species resulted in the occurrence of Co₉S₈ and crystalline MoS₂ in catalysts.