Direct synthesis of hydrogen peroxide from hydrogen and oxygen over insoluble Pd_(0.15)M_(2.5)H_(0.2) PW_(12)0 ch=ae ttKaelr,y oRsptbos,l yaancdi d

摘要

Palladium-containing insoluble heteropolyacid (HPA) catalysts (Pd_(0. 15) M_(2.5)H_(0.2)PW_(12)0_(40)) were prepared by an ion-exchange ethod using various alkaline netal ions (M=K~+, Rb~+, and Cs~+) (denoted as Pd- KPW, Pd-RbPW, and Pd-CsPW). They were then applied to the direct synthesis of hydrogen peroxide rom hydrogen and oxygen. Conversion of hydrogen over the catalysts was almost dentical with no great difference, while selectivity for hydrogen peroxide increased on the order of Pd-KPW < Pd-RbPW < Pd-CsPW. As a consequence, yield for iydrogen peroxide increased in the order of Pd-KPW < Pd-RbPW < Pd-CsPW. It was found that yield for hydrogen peroxide increased with increasing Pd 3d_(5/2) pinding energy of the catalyst. Among the catalysts tested, Pd-CsPW catalyst with he highest Pd 3d_(5/2) binding energy showed the highest yield for hydrogen peroxide.