Direct oxidation of H2 to H2O2 over different supported PdO catalysts in aqueous acidic medium: Influence of the reduction, calcination temperature and support of the catalyst on its net H2O2 formation activity

Effects of the catalyst reduction (by hydrazine), calcination temperature (400–800 °C) and support (viz. Al2O3, SiO2, CeO2, ZrO2, Hβ or HM) on the performance of supported PdO (2.5 wt%) catalyst in the H2-to-H2O2 oxidation (with H2:O2 = 1:1) in an aqueous acidic (0.1 M H3PO4) medium under ambient conditions have been investigated. All the supported PdO catalysts showed lower H2 conversion activity, but higher H2O2 selectivity, as compared to their reduced counter parts. The catalyst performance for the net H2O2 formation is strongly influenced by both the support and calcination temperature of the supported PdO catalysts. The catalysts calcined at 400 °C showed better performance. Among the catalysts, PdO/Al2O3 catalyst (calcined at 400 °C) showed the best performance (17.0% H2O2 yield) in the H2-to-H2O2 oxidation. The influence of the calcination temperature of PdO/Al2O3 catalyst on its H2O2 decomposition and hydrogenation activities has also been investigated. Both the H2O2 decomposition and hydrogenation activities increased with increasing the calcination temperature.