Methane is a major component in natural gas and one of the most difficult molecules for 

controlled activation, since most of the product results in carbon dioxide. The industrial 

conversion of methane to alcohol derivatives is typically based on a circuitous route that 

begins with overoxidation to carbon monoxide. Although more direct approaches have sh

own promise in highly acidic media at a small scale, they are not quite cost-effective. In a 

recent study now published in Science, Christian Díaz-Urrutia and Timo Ott at the R&D 

department of Grillo-Werke AG Company describe a reaction at a pilot-plant scale that di

rectly combined methane (CH4) and sulfur trioxide (SO3) in sulfuric acid (H2SO4) to form 

methanesulfonic (CH4O3S) acid without by-products. The reaction appeared to proceed

 via a cationic chain mechanism initiated by adding a low concentration of sulfonyl peroxide, 

propagated by methenium (CH3+) molecules.

Direct functionalization of methane to form value-added products is a challenge due to 

potential overoxidation in many reaction environments and sulfonation is an attractive approach to achieve the selectivity of interest. In the practical process, Díaz-Urrutia and

 Ott produced methanesulfonic acid (MSA) using only two main reactants; methane and 

sulfur trioxide. They achieved 99 percent selectivity and yield of MSA in the work. The 

scientists based the electrophilic initiator on a sulfonyl peroxide derivative, which they 

protonated under superacidic conditions to produce a highly electrophilic oxygen atom 

capable of activating a C-H bond of methane. They proposed mechanistic studies to sup

port the formation of a cation methenium (CH3+)as a key intermediate during the reaction. 

The proposed method is scalable with reactors connected in a series to prospectively prod

uce up to 20 metric tons of MSA per year.