Effect of stepwise sulfidation on a MoO3/CeO2–Al2O3 catalyst for sulfur-resistant methanation

• Stepwise sulfidation methods were used on MoO3/CeO2–Al2O3 catalyst.
• Stepwise sulfidation processes enhanced the methanation activity and stability.
• Stepwise sulfidation decreased the damage to the textural structure of the catalyst.
• Stepwise sulfidation decreased the damage to the CeO2 particles in the catalyst.
• Stepwise sulfidation affected the CeO2 in the catalysts rather than the MoO3.

The effect of stepwise sulfidation on a MoO3/CeO2–Al2O3 catalyst for sulfur-resistant methanation was studied. The prepared catalysts were characterized using N2-physisorption (BET), X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy (RS), X-ray photoelectron spectroscopy (XPS), and temperature-programmed sulfidation (TPS). The methanation activities and stability of the one-step-sulfided MoO3/CeO2–Al2O3 catalysts were enhanced by stepwise sulfidation processes. The XRD, TEM, RS, and XPS results indicated that the enhancement in the stability of MoO3/CeO2–Al2O3 was caused by the reduction and sulfidation of the CeO2 particles, eliminating unstable CeO2 and driving the migration of Ce3+ and Al3+ ions. The catalyst subjected to stepwise sulfidation exhibited improved methanation activity because the stepwise sulfidation reduced the degree of CeO2 sulfidation and mitigated textural structure damage to the catalyst. Finally, a sulfidation mechanism for CeO2 and MoO3 was proposed.

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