Sulfur Converts Methane Controllably

Sulfur can controllably convert methane to ethylene in the presence of MoS₂, RuS₂, TiS₂, and other sulfide catalysts, according to an experimental and theoretical study (Nat. Chem., DOI: 10.1038/nchem.1527). The finding may open new routes to exploiting natural gas reserves to address challenges caused by shrinking petroleum supplies. Natural gas, which is mostly methane, is relatively abundant in many parts of the world, though often in remote locations lacking transportation infrastructure. Chemical companies would like to be able to convert the gas economically to shippable liquids such as methanol or to valuable olefins. Methods for mediating those conversions are known but tend to be costly or difficult to control. Qingjun Zhu and Tobin J. Marks of Northwestern University and coworkers now report that, unlike direct conversion of methane with O₂, which suffers from overoxidation (mainly to CO₂) and generates extreme heat, reaction with sulfur is controllable. Tests show that methane conversion with gaseous S₂ correlates with metal-sulfur bond strengths: Catalyst surfaces that bind sulfur weakly are more active than strongly binding ones. In contrast, ethylene selectivity increases with metal-sulfur bond strength, the team reports.