Direct synthesis of hydrogen peroxide from hydrogen and oxygen over insoluble Pd0.15M2.5H0.2PW12O40 (M = K, Rb, and Cs) heteropolyacid catalysts

Abstract

Palladium-containing insoluble heteropolyacid (HPA) catalysts (Pd 0.15 M 2.5 H 0.2 PW 12 O 40 ) were prepared by an ion-exchange method using various alkaline metal 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 from hydrogen and oxygen. Conversion of hydrogen over the catalysts was almost identical with no great difference, while selectivity for hydrogen peroxide increased in the order of Pd-KPW \ Pd-RbPW \ Pd-CsPW. As a consequence, yield for hydrogen 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 binding energy of the catalyst. Among the catalysts tested, Pd-CsPW catalyst with the highest Pd 3d 5/2 binding energy showed the highest yield for hydrogen peroxide.

Looking for the “Dream Catalyst” for Hydrogen Peroxide Production from Hydrogen and Oxygen

“…Similar results were observed by Park et al in Pd exchanged heteropolyacid catalysts using various alkaline metal ions [109]. It was found that the catalyst incorporating Cs showed the highest rates of conversion and overall H 2 O 2 yield with respect to those incorporating K and Rb.…”

“…This, however, implies some corrosion problems, especially in view of possible applications on a large scale, and the use of these additives should be avoided as much as possible. This is why a large variety of acidic supports have been tested in H 2 O 2 synthesis, especially in recent years [104][105][106][107][108][109][110].…”

Recent Advances in the Direct Synthesis of H2O2

“…Due to their high acidity numerous studies have investigated heteropolyacids as both catalyst supports,, as well as solid acid additives for the direct synthesis of H 2 O 2 . Problems concerning their low surface area and high solubility in polar solvents can be overcome through the introduction of specific cations, such as Cs + , K + and Rb + into the structure of the heteropolyacid, while other studies have investigated palladium exchanged heteropolyacids immobilized onto mesoporous silica for the synthesis of H 2 O 2 ,.…”

“…The nature of the support is a key factor which can affect catalytic activity and selectivity towards H 2 O 2 . A range of zeolitic, oxide, resin,,, , heteropolyacid, and carbon,,, supports have been investigated to date.…”

Direct synthesis of hydrogen peroxide in water at ambient temperature

“…Choudhary and co-workers [12][13][14][15][16][17][18][19][20][21] use an acidic aqueous medium (sulfuric or phosphoric acid), in most cases with one or more halide promoter. Park and co-workers [22][23][24][25][26][27][28][29][30][31][32] use a solution of methanol with dissolved NaBr. Biasi and co-workers [33][34][35][36][37][38][39] generally use methanol in the absence of promoters, but have also used acidified, bromidepromoted aqueous solutions [40].…”