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

Direct oxidation of H-2 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.% H-2 in O-2, in a magnetically stirred glass reactor at 22 degreesC 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 22degreesC 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 H-2. An acidic medium is essential for achieving both the high conversion and high selectivity in the H-2 Oxidation. The reduced catalysts showed much lower H2O2 selectivity in the H oxidation process and much higher H2O2 decomposition activity. The water in the H-2 to H2O2 oxidation over the above catalysts is formed in parallel and/or consecutive reactions, depending upon the catalyst used. (C) 2002 Elsevier Science B.V. All rights reserved.