Direct Sulfonation of Methane to Methanesulfonic Acid by Sulfur Trioxide Catalyzed by Cerium(IV) Sulfate in the Presence of Molecular Oxygen

Direct sulfonation of methane with SO 3 to methanesulfonic acid (MSA) is accomplished in sulfuric acid with almost 100% selectivity in the presence of a catalyst, namely, Ce and Rh salts and molecular oxygen as the catalyst regenerator. In the absence of O 2 , the catalyst remains effective but the selectivity to MSA decreases to 53% and byproducts, principally CH 3 OSO 3 H, are formed. The effects of O 2 pressure, catalyst concentration, temperature, SO 3 concentration, and methane pressure have been examined on the rate of SO 3 conversion to MSA. The conversion of SO 3 to MSA was the same when CF 3 SO 3 H was used as the solvent instead of H 2 SO 4 .