Low temperature propane oxidation over Co3O4 based nano-array catalysts: Ni dopant effect, reaction mechanism and structural stability

•Demonstration of monolithic nano-array catalysts featuring low catalyst usage.•Cost-effective doped Co3O4 catalyst for low temperature propane oxidation.•Controlled Ni doping leads to enhanced reaction kinetics and catalytic activity.•A redox reaction mechanism of propane oxidation as revealed by in situ spectroscopy.•Declined thermal stability of Ni-doped Co3O4 with Ni concentration due to NiO segregation.

Low temperature propane oxidation has been achieved by Co3O4-based nano-array catalysts featuring low catalytic materials loading (15 mg under flow rate of 150 mL/min). The increased Ni doping into the Co3O4 lattice has led to 100% propane conversion at low temperature (<400 °C) and has enhanced reaction kinetics by promoting the surface lattice oxygen activity. In situ DRIFTS investigations in tandem with isotopic oxygen exchange reveals that the propane oxidation proceeds via a Mars-van Krevelen mechanism where surface lattice oxygen acts as the active site whereas O2 in the reaction feed does not directly participate in CO2 formation. The Ni doping promotes the formation of less stable carbonates on the surface to facilitate the CO2 desorption. The thermal stability of Ni doped Co3O4 decreases with increased Ni concentration despite the increased catalytic activity. A balance between enhanced activity and compromised thermal stability is considered in the Ni doped Co3O4 nano-array catalysts for hydrocarbon oxidation. This study provides useful and timely guidance for rational catalyst design toward low temperature catalytic oxidation.

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