Direct oxidation of H<SUB>2</SUB> to H<SUB>2</SUB>O<SUB>2</SUB> over different supported PdO Catalysts in aqueous acidic medium: Influence of the calcination temperature, reduction and support of the catalyst on its net H<SUB>2</SUB>O<SUB>2</SUB> formation activity

Effects of the catalyst reduction (by hydrazine), calcination temperature (400-800 ° C) and support (viz. Al<SUB>2</SUB>O<SUB>3</SUB> , SiO<SUB>2</SUB>, CeO<SUB>2</SUB>, ZrO<SUB>2</SUB>, Hβ or HM) on the performance of supported PdO (2.5 wt%) catalyst in the H<SUB>2</SUB>-to-H<SUB>2</SUB>O<SUB>2 </SUB> oxidation (with H<SUB>2</SUB>:O<SUB>2</SUB> = 1:1) in an aqueous acidic (0.1 M H<SUB>3</SUB>PO<SUB>4</SUB>) medium under ambient conditions have been investigated. All the supported PdO catalysts showed lower H<SUB>2</SUB> conversion activity, but higher H<SUB>2</SUB>O<SUB>2</SUB> selectivity, as compared to their reduced counter parts. The catalyst performance for the net H<SUB>2</SUB>O<SUB>2 </SUB>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/Al<SUB>2</SUB>O<SUB>3</SUB> catalyst (calcined at 400 ° C) showed the best performance (17.0% H<SUB>2</SUB>O<SUB>2 </SUB> yield) in the H<SUB>2</SUB>-to-H<SUB>2</SUB>O<SUB>2 </SUB> oxidation. The influence of the calcination temperature of PdO/Al<SUB>2</SUB>O<SUB>3</SUB>catalyst on its H<SUB>2</SUB>O<SUB>2 </SUB> decomposition and hydrogenation activities has also been investigated. Both the H<SUB>2</SUB>O<SUB>2 </SUB> decomposition and hydrogenation activities increased with increasing the calcination temperature