A high-yield, liquid-phase approach for the partial oxidation of methane to methanol using SO3 as the oxidant

A direct approach for producing methanol from methane in a three-step, liquid phase process is reported. In the first step, methane is reacted with SO3 to form methanesulfonic acid (MSA) at 75 degrees C using a free-radical initiator and MSA as the solvent. Urea-H2O2 in combination with RhCl3 is found to be the most effective initiator (57% conversion Of SO3; 7.2% conversion of CH,). MSA is then oxidized by SO3 at 160 degrees C in a second step to produce a mixture containing methyl bisulfate and some methyl methanesulfonate (87% conversion of MSA). In the third step, the mixture of methyl bisulfate and methyl methanesulfonate is hydrolyzed in the presence of an organic solvent, to produce an organic phase containing methanol and an aqueous phase containing sulfuric acid and some MSA (63% conversion of methyl bisulfate;, 72% conversion of methyl methanesulfonate). Overall, 58% of the MSA (of which 23% is derived from methane) is converted to methanol.