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

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Science  22 Mar 2019:
Vol. 363, Issue 6433, pp. 1326-1329
DOI: 10.1126/science.aav0177

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Methane oxidation on the plus side

Industrial conversion of methane to alcohol derivatives involves a circuitous route that starts with overoxidation to carbon monoxide. More direct approaches in highly acidic media have shown promise at small scale but are not cost-effective. Díaz-Urrutia and Ott describe a reaction at pilot-plant scale that combines methane and sulfur trioxide directly in sulfuric acid to form methanesulfonic acid with no by-products (see the Perspective by Schüth). The reaction appears to proceed via a cationic chain mechanism initiated by a low concentration of added sulfonyl peroxide and propagated by CH3+.

Science, this issue p. 1326; see also p. 1282

Abstract

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.

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