The Role of Copper Speciation in the Low Temperature Oxidative Upgrading of Short Chain Alkanes over Cu/ZSM-5 Catalysts

Partial oxidative upgrading of C-1-C-3 alkanes over Cu/ZSM-5 catalysts prepared by chemical vapour impregnation (CVI) has been studied. The undoped ZSM-5 support is itself able to catalyse selective oxidations, for example, methane to methanol, using mild reaction conditions and the green oxidant H2O2. Addition of Cu suppresses secondary oxidation reactions, affording methanol selectivities of up to 97%. Characterisation studies attribute this ability to population of specific Cu sites below the level of total exchange (Cu/Al<0.5). These species also show activity for radical-based methane oxidation, with productivities exceeding those of the parent zeolite supports. When tested for ethane and propane oxidation reactions, comparable trends are observed.