Microwave assisted catalytic reduction of sulfur dioxide with methane over MoS2 catalysts

The catalytic reduction of sulfur dioxide with methane to form carbon dioxide and sulfur has been studied over MoS2/Al2O3 catalysts. The reaction has been found to occur with microwave (2.45 GHz) heating at recorded temperatures as much as 200°C lower than those required when conventional heating was used. An activation energy of 117 kJ mol−1 has been calculated for the conventionally heated reaction, but an Arrhenius analysis of the data obtained with microwave heating was not possible, probably because of temperature variations in the catalyst bed. The existence of hot spots in the catalysts heated by microwave radiation has been verified by the detection of α-alumina at a recorded temperature some 200°C lower than the temperature at which the γ- to α-alumina phase transition is normally observed. Among four catalysts prepared in different ways, a mechanically mixed catalyst showed the highest conversion of SO2 and CH4 for microwave heating at a given temperature. Supported catalysts, sulfided either by conventional heating or under microwave conditions, showed little difference in the extent of SO2 and CH4 conversions. The highest conversions to carbon dioxide and sulfur, combined with low production of undesirable side products, was obtained when the molar ratio of SO2 to CH4 was equal to two, the stoichiometric ratio.