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

Abstract

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