Activation of methane to CH₃ ⁺: A selective industrial route to methanesulfonic acid

Direct methane functionalization to value-added products remains a challenge because of the propensity for overoxidation in many reaction environments. Sulfonation has emerged as an attractive approach for achieving the necessary selectivity. Here, we report a practical process for the production of methanesulfonic acid (MSA) from only two reactants: methane and sulfur trioxide. We have achieved >99% selectivity and yield of MSA. The electrophilic initiator based on a sulfonyl peroxide derivative is protonated under superacidic conditions, producing a highly electrophilic oxygen atom capable of activating a C-H bond of methane. Mechanistic studies support the formation of CH₃ ⁺ as a key intermediate. This method is readily scalable with reactors connected in series for prospective production of up to 20 metric tons per year of MSA.