Green preparation of transition metal oxide catalysts using supercritical CO2 anti-solvent precipitation for the total oxidation of propane

A series of metal oxide catalysts, including Fe3O4, NiO, CuO and Co3O4, have been prepared by supercritical anti-solvent precipitation and evaluated for the total oxidation of propane. Co3O4 was found to be the most active catalyst and our studies have focussed on this oxide. The addition of water as co-solvent in the supercritical anti-solvent preparation was investigated. Powder X-ray diffraction and infrared spectroscopy indicated that the addition of water promoted the formation of carbonate species in the catalyst precursors. The formation of the catalysts from the precursor were optimised by investigating the thermal treatment conditions, by studying variables including time, temperature and atmosphere. The optimal conditions for catalyst preparation required precursor precipitation containing 10 vol% water co-solvent followed by a 2 h calcination at 250 degrees C. These conditions produced Co3O4 with high surface areas (>100 m(2) g(-1)), which were very active catalysts producing 50% propane conversion at 175 degrees C. (C) 2013 Elsevier B.V. All rights reserved.