Direct oxidation of hydrogen to hydrogen peroxide over Pd-containing fluorinated or sulfated Al₂O₃, ZrO₂, CeO₂, ThO₂, Y₂O₃ and Ga₂O₃ catalysts in stirred slurry reactor at ambient conditions

Abstract

Direct oxidation of H₂ to H₂O₂ over powdered PdO-containing fluorinated or sulfated Al₂O₃, ZrO₂, CeO₂, ThO₂, Y₂O₃, Ga₂O₃ catalysts with or without pre-reduction by hydrazine, using a pure water or 0.02 M H2SO4 as reaction medium and a gaseous feed consisting of 1.7 vol.% H₂ in O₂, in a magnetically stirred glass reactor at 22 ° C and atmospheric pressure has been investigated. The catalysts have been characterized for their surface area and also by CO chemisorption. The performance of the catalysts in the decomposition of H₂O₂ at 22 ° C has also been studied. The results showed a strong influence of catalyst reduction, fluorination (or chlorination) or sulfatation of the catalyst support and the acidity of reaction medium on both the conversion and H₂O₂ selectivity in the direct oxidation of H₂. An acidic medium is essential for achieving both the high conversion and high selectivity in the H₂ oxidation. The reduced catalysts showed much lower H₂O₂ selectivity in the H₂ oxidation process and much higher H₂O₂ decomposition activity. The water in the H₂ to H₂O₂ oxidation over the above catalysts is formed in parallel and/or consecutive reactions, depending upon the catalyst used.