Radical-initiated oxidative conversion of methane to methanol over metallic iron and copper catalysts

Abstract

Oxidative conversion of methane gas into value-added chemicals such as methanol is of great interest due to high economic feasibility of liquid fuel molecules for storage and transportation purpose. Activation and conversion of methane occur at very high temperatures due to its strong CH bonding and hence the process is highly energy intensive. Therefore, homolytic cleavage of methane to produce CH3 and H radicals and subsequent conversion to methanol could be an alternative way to catalyze the reaction through a less energy-intensive process. In this work, radical-based conversion of methane to methanol was conducted in water-diluted 1-butyl-3-methylimidazolium chloride ionic liquid (IL) using metallic iron and copper as catalysts. The acidic IL, besides producing the high oxidation potential radicals from K2S2O8, enhanced their longevity. ZV Cu was found to be highly active in the reaction catalyzing with steady rate at a lower activation energy (Ea=31.5kJ/mol) and retains its oxidation state even after the reaction. On the other hand, ZV Fe, catalyzed the reaction with slightly slow initial rate ultimately resulting in moderate activation energy (40.77kJ/mol). However, it was observed that ZV Fe fails to retain its oxidation state after reaction.