Enhancing the Activity of Cu-MOR by Water for Oxidation of Methane to Methanol

As clean energy, methane has huge reserves and great development potential in the future. Copper zeolites are efficient in the oxidation of methane to methanol. Water has been confirmed as a source of oxygen to regenerate the copper-zeolite active sites to enable selective anaerobic oxidation of methane to methanol. In this work, we report that the methanol yield increased from 36 & mu;mol/g (Cu-MOR1) to 92 & mu;mol/g (Cu-MOR1-water) as a result of water enhancing the activity of copper ion-exchange mordenite catalyst. We show for the first time that water could convert inactive copper species into active copper species during catalyst activation. A combination of the XPS, FTIR, and NMR results indicates that water dissociates and then converts ZCu(II)Z into ZCu(II)(OH) (where Z indicates framework O (O-fw) bonded to one isolated Al in a framework T-site, i.e., 1Al) and simultaneously produces a Bronsted acid site during catalyst activation. This finding can be used to tune the state of copper species and design highly active copper-zeolite catalysts for methane oxidation to methanol.