Preparation of Cu/ZnO and Cu/TiO[subscript 2] catalysts via deposition technique using critical carbon dioxide

Abstract

A novel method for preparation of Cu/ZnO and Cu/TiO² catalysts using supercritical carbon dioxide was investigated. Supercritical carbon dioxide was employed as a solvent to dissolve the copper compound. The dissolved compound was then used to deposit the metal on ZnO and TiO² support. Both ZnO and TiO² supports were synthesized by a solvothermal method using 1,4-butanediol as a solvent. The catalysts were characterized by various techniques, including X-ray diffractometer, nitrogen physisorption, inductively-coupled plasma atomic emission spectroscopy, and chemisorption. Cu/ZnO and Cu/TiO² were then employed as catalysts for oxidation of CO. Both Cu/ZnO and Cu/TiO² catalysts that were prepared by deposition technique using supercritical carbon dioxide and methanol exhibited higher activities for oxidation of CO than the catalysts that were prepared by incipient wetness impregnation technique. This could be attributed to higher dispersion of copper on the supports brought about by the use of supercritical carbon dioxide. Cu/ZnO and Cu/TiO² catalysts that were prepared by deposition technique using supercritical carbon dioxide and a sulfer-contaning compound, Cyanex 301, exhibited very low activities for oxidation of CO due to poisoning of the catalysts caused by remaining organics on the surface of the catalysts.