It takes two: A high level of conversion of 13C atoms of methane into the products of methane/propane coaromatization on zeolite Zn/H‐BEA has been demonstrated by 13C solid‐state NMR spectroscopic analysis and GC‐MS. The isotope‐labeling experiments show the mechanism consists of the methylation of aromatic compounds formed from the propane followed by ring‐expansion/contraction (see scheme).

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By using 13 C solid-state NMR spectroscopy and GC-MS analysis, the activation of methane and coaromatization of methane and propane have been monitored on gallium-modified zeolite BEA at 573-823 K. A noticeable degree involvement of the 13 C-label from methane-13 C into the aromatic reaction products (benzene, toluene) has been demonstrated. The major intermediate of the methane activation represents gallium-methyl species, which are formed by methane dissociative adsorption on Ga 2 O 3 species of the zeolite. The minor species of methane activation, Ga-methoxy groups, provide the involvement of methane into aromatics by the methylation of aromatic molecules, which are generated exclusively from propane, by the mechanism of electrophilic substitution. Ga-methyl species can serve as methylating nucleophilic agent for the reaction of nucleophilic substitution with participation of aromatic molecules, which contain the electron-withdrawing substitutes.