Microwave assisted catalytic reduction of sulfur dioxide with methane overMoS2 catalysts

The catalytic reduction of sulfur dioxide with methane to form carbon dioxi de and sulfur has been studied over MoS2/Al2O3 catalysts. The reaction has been found to occur with microwave (2.45 GHz) heating at recorded temperatu res as much as 200 degreesC lower than those required when conventional hea ting was used. An activation energy of 117 kJ mol(-1) has been calculated f or the conventionally heated reaction, but an Arrhenius analysis of the dat a obtained with microwave heating was not possible, probably because of tem perature variations in the catalyst bed. The existence of hot spots in the catalysts heated by microwave radiation has been verified by the detection of alpha -alumina at a recorded temperature some 200 degreesC lower than th e temperature at which the gamma- to alpha -alumina phase transition is nor mally observed. Among four catalysts prepared in different ways, a mechanic ally mixed catalyst showed the highest conversion Of SO2 and CH4 for microw ave heating at a given temperature. Supported catalysts, sulfided either by conventional heating or under microwave conditions, showed little differen ce in the extent Of SO2 and CH4 conversions. The highest conversions to car bon dioxide and sulfur, combined with low production of undesirable side pr oducts, was obtained when the molar ratio Of SO2 to CH4 was equal to two, t he stoichiometric ratio. (C) 2001 Elsevier Science B.V. All rights reserved .