Unraveling the role of CH3S* intermediates for efficient methane and hydrogen sulfide reforming over Mo/Al2O3 catalysts

Abstract

The catalytic methane(CH₄) and hydrogen sulfide(H₂S) reforming (H₂SMR) represents a promising approach for producing high-value sulfur-carbon compounds and hydrogen without generating the greenhouse gas of CO₂. Despite its significant potential, the mechanistic understanding of interactions between CH₄ and H₂S remains contentious, posing substantial challenges for catalyst development. In this study, we employed a Mo/Al₂O₃ catalyst to elucidate synergistic conversion pathways between CH₄ and H₂S during H₂SMR. At 1173 K with a reaction duration of 0.5 h, conversion rates of CH₄ and H₂S reached 63.7 % and 59.2 %, respectively, accompanied by H₂ and CS₂ production rates of 688.8 μmol g⁻¹ min⁻¹ and 444.3 μmol g⁻¹ min⁻¹, respectively. Notably, the catalyst exhibited stable performance over 5 h without significant deactivation, in contrast to pure methane cracking reactions where CH₄ conversion rapidly declined from 43.6 % to 14.3 %. Through in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) combined with alternating CH₄/H₂S exposure experiments, we successfully tracked the synergistic conversion pathway on the Mo/Al₂O₃ catalyst. These investigations revealed that the formation of CH₃S intermediates serves as a critical step facilitating CS₂ generation. This mechanistic insight not only advances fundamental understanding of H₂SMR reaction pathways but also provides a rational foundation for designing optimized catalysts with enhanced stability and extended operational lifetimes. The identification of this intermediate-driven mechanism addresses previous controversies regarding CH₄-H₂S interactions and offers strategic guidance for developing efficient sulfur-resistant catalytic systems.