Mechanism of Hydrocarbon Formation in Methane and Methanol Conversion over Copper-Containing Mordenite

Methane conversion over copper-containing zeolites can lead to the formation of C–C bonds, yielding hydrocarbons. By employing in situ MAS NMR spectroscopy, we elucidated the pathways of the transformation of methane and its partial oxidation and coupling products over copper-containing mordenite. Below 773 K, the direct coupling of methane is not possible, while the transformation of methanol, methoxy species, and dimethyl ether takes place via the methanol-to-hydrocarbons (MTH) process. In the presence of carbon monoxide, surface acetate species are formed from methanol via the Koch carbonylation reaction. The nature of the hydrocarbon pool species and concomitantly the formed hydrocarbons are strongly affected by the reactants: conversion of pure methanol leads to methyl-substituted cyclopentenyl cations, and the presence of carbon monoxide results in methyl-substituted benzenes. The study clarifies the mechanism of C–C bond formation during the conversion of methane and methanol over copper-containing mordenite and provides insights into the mechanism of the MTH process.