Influence of Cu-speciation in mordenite on direct methane to methanol conversion: Multi-Technique characterization and comparison with NH₃ selective catalytic reduction of NO_x

The direct conversion of methane to methanol has the potential of substantially reducing methane emissions and flaring, as such a process might provide an alternative for remote natural gas locations. In this report, we investigate the performance of a range of Cu-exchanged mordenite zeolites as active materials for such a reaction, employing a stepwise protocol comprising activation in oxygen, methane loading, and methanol extraction with steam. We employ in situ HERFD XANES, FT-IR spectroscopy with CO as probe molecule, and XPS to investigate the Cu species in the zeolites during the process. The activity of the materials is investigated both for methane to methanol conversion and NH₃ Selective Catalytic Reduction of NO_x. It is demonstrated that, despite the fact that the same zeolite materials are active both for NH₃-SCR and direct methane to methanol conversion, the active site requirements for these two reactions are different.