Tuning catalysis by surface-deposition of elements on oxidation catalysts via atomic layer deposition

Abstract

Based on the concept that most reaction steps proceed only at the surface layer of a bulk catalyst, the catalytic impact of the surface-modification with POx, BOx, and MnOx in the selective oxidation of ethane, propane, and n-butane is systematically studied. Three different promoter elements are deposited as a sub-monolayer on the surface of oxidation catalysts with high dispersion by sequential and self-limiting reactions at the solid-gas interface, using atomic layer deposition. Oxygenate and olefin selectivities are tuned by the surface deposition of POx and BOx, leading to improved product yields. The mixed metal oxide MoVTeNbOx is used as a case study to demonstrate the effect of the modification in different reactions with yield improvements of up to 24% in the propane oxidation towards acrylic acid. It is shown that the beneficial performance is related to a change in surface composition, a modification in the electronic properties of the redox active element vanadium, and a decrease in acidity. A comparative study considering several bulk catalysts and deposited elements revealed further promoting effects for different oxidation catalysts. In particular, the deposition of POx on V-containing oxides suppresses COx formation. Precisely adjusted surface modifications leading to enhanced product yields demonstrate the potential of atomic layer deposition as a powerful tool for tuning catalytic properties of bulk catalysts.