• C[BOND]H activation;
  • metal catalyst;
  • methane;
  • methanesulfonic acid;
  • molecular oxygen;
  • sulfonation;
  • sulfur trioxide


Direct sulfonation of methane with SO3 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 O2, the catalyst remains effective but the selectivity to MSA decreases to 53% and byproducts, principally CH3OSO3H, are formed. The effects of O2 pressure, catalyst concentration, temperature, SO3 concentration, and methane pressure have been examined on the rate of SO3 conversion to MSA. The conversion of SO3 to MSA was the same when CF3SO3H was used as the solvent instead of H2SO4.