The presence of SO2 in methane (CH4) halogenation/chlorination to form methanesulfonyl chloride (CH3SO2Cl, MSC), followed by catalytic decomposition of MSC to produce methyl chloride (CH3Cl) could effectively prevent deeper reactions of CH3Cl to improve the product selectivity. A number of catalytic systems capable of highly selectively decomposing MSC are studied experimentally. Molecular modeling based on density functional theory (DFT) calculations suggest a bimolecular nucleophilic substitution S(N)2 reaction mechanism for the catalytic MSC decomposition reaction. The order of activation energies of different catalytic systems agrees with the laboratory observations.