Promotional effects of Au in Pd-Au bimetallic catalysts supported on activated carbon cloth (ACC) for direct synthesis of H2O2 from H2 and O2

In this study, the promotional effects of gold in Pd-Au bimetallic catalysts supported on activated carbon cloth for direct synthesis of H2O2 has been investigated. The bimetallic catalysts were prepared by simultaneous co-impregnation approach. Direct synthesis was performed batch-wise in a stainless steel autoclave under high pressure (38 bar) at 0 degrees C and methanol (220 ml) was used as the reaction medium. A series of experiments were conducted to assess the effects of: (i) the surface chemistry of the support and (ii) the amount and ratio of palladium and gold on the surface morphology of the bimetallic catalysts and on their catalytic performances, and (iii) the oxidation state of the metallic components on the activity of the catalysts. Moreover, (iv) the effects of heat treatment of the catalysts in H-2 at 185 degrees C and in air at 185-275 degrees C on the surface chemistry of the support, surface morphology of the metallic component, and the performances of the final catalyst were investigated. Almost all of the Pd-Au bimetallic catalysts were more selective than the corresponding Pd monometallic catalysts. The results showed that the surface morphology of the Pd-Au bimetallic catalysts and their catalytic performance were highly influenced by the surface chemistry of the support and the amount and the ratio of Pd and Au in the catalyst. The presence of palladium oxide made the catalysts more selective and active than the corresponding zero-valent palladium (Pd-0) catalysts. (C) 2014 Elsevier B.V. All rights reserved.