Study on the reaction mechanism of SO2 hydrogenation over Mo-based catalyst

Mo-based catalysts are widely used for the SO2 hydrogenation process. However, the detailed reaction mechanism is still unclear and some details should be further supplemented. In this article, the SO2 hydrogenation processes over the Mo-based catalyst were systematically studied. Several technologies including temperature-programmed experiments, isotope-tracing experiment, fourier transform infrared spectroscopy, and switching experiment were adopted to investigate the reaction steps. The results indicated that during the SO2 hydrogenation process there were three reaction processes containing six steps: First SO2 would adsorb on the active sites, which could start at relatively low temperature. Then the adsorbed SO2 would react with H-2 and gradually form elemental sulfur that could be strongly anchored with S atoms of the MoS2 surface. Afterward, the sulfur further reacted with H-2 to generate H2S. Alongside with the consumption of S atoms, the sulfur would be reduced and the active sites was recovered, thus starting the next reaction cycle.