Direct Synthesis of Hydrogen Peroxide Using Cs-Containing Heteropolyacid-Supported Palladium–Copper Catalysts

Abstract

The direct synthesis of hydrogen peroxide (H2O2) from molecular hydrogen and oxygen could represent a green and economically attractive alternative to the current indirect anthraquinone process used for the industrial production of hydrogen peroxide. This reaction has been investigated using palladium supported on the Cs-containing heteropolyacid Cs2.5H0.5PW12O40. In addition, the effect of adding copper as a potential activity promoter was investigated. These catalysts were also evaluated for the subsequent degradation of hydrogen peroxide. The catalytic activity of the 0.5 wt.%Pd/Cs2.5H0.5PW12O40 catalyst towards hydrogen peroxide synthesis was greater than that of both the mono-metallic Cu or bi-metallic Pd-Cu analogues with the incorporation of Cu to Pd resulting in a significant decrease in catalytic selectivity for the formation of hydrogen peroxide. Moreover, 0.5 wt.%Pd/Cs2.5H0.5PW12O40 also showed low activity towards the degradation of hydrogen peroxide. Hence the use of the Cs-containing heteropolyacid as a support for Pd gives higher rates of hydrogen peroxide formation when compared with different supported Pd catalysts prepared using supports used in previous studies.

The Direct Synthesis of Hydrogen Peroxide Over Supported Pd-Based Catalysts: An Investigation into the Role of the Support and Secondary Metal Modifiers

“…Additionally, determination of H 2 conversion indicates a significant reduction in this metric with the introduction of Cu into a supported Pd catalyst (3% H 2 conversion). As such we consider Cu to act as an inhibitor of catalytic activity, with these observations in keeping with numerous previous studies [7,[51][52][53].…”

Shape-Selective Synthesis of Intermetallic Pd3Pb Nanocrystals and Enhanced Catalytic Properties in the Direct Synthesis of Hydrogen Peroxide

“…The Pd 3 Pb NCs were adsorbed from a colloidal CHCl 3 dispersion onto the H 2 SO 4 -treated TiO 2 support (s-TiO 2 ). In the direct H 2 O 2 synthesis, various materials have been used to support the active metal phase (such as TiO 2 , 33,44,76−78 Al 2 O 3 , 79 SiO 2 , 36,80,81 ZrO 2 , 82 Fe 2 O 3 , zeolites, 4,83 heteropolyacids, 84 and carbon-based materials) 33,35,85 and it is well-known that the support significantly influences the catalytic performance. 86 In particular, support materials with acidic properties (i.e., Brønsted acid sites) were reported to enhance selectivity and activity towards the direct synthesis of H 2 O 2 .…”

“…The Pd 3 Pb NCs were adsorbed from a colloidal CHCl 3 dispersion onto the H 2 SO 4 -treated TiO 2 support (s-TiO 2 ). In the direct H 2 O 2 synthesis, various materials have been used to support the active metal phase (such as TiO 2 , ,,− Al 2 O 3 , SiO 2 , ,, ZrO 2 , Fe 2 O 3 , zeolites, , heteropolyacids, and carbon-based materials) ,, and it is well-known that the support significantly influences the catalytic performance . In particular, support materials with acidic properties (i.e., Brønsted acid sites) were reported to enhance selectivity and activity towards the direct synthesis of H 2 O 2 . , Here, commercial TiO 2 (P25, Evonik, 80% anatase/20% rutile, BET surface 54 m 2 /g) was pretreated with H 2 SO 4 to yield s-TiO 2 (BET surface 52 m 2 /g, (interparticle) BJH pore diameter 36 nm), which was chosen as a benchmark support material to compare the effect of metal doping and NC shape on the catalytic properties.…”

The degradation of phenol via in situ H2O2 production over supported Pd-based catalysts

“…S.1 †) reveals that while the introduction of base-metals (Fe, Cu, Co) does enhance Pd 2+ content, a similar shift in Pd speciation is similarly observed with the introduction of Au, and as such we cannot definitively attribute the enhanced catalytic H 2 O 2 synthesis activity of the Pd-X (Fe, Cu, Co) catalysts to the increased presence of Pd 0 -Pd 2+ species. It should be noted that a number of previous experimental 38,39 and computational 40 40 The generation of hydroxyl radicals via Fenton's or photo-Fenton's pathways has been well reported to offer high efficacy in the remediation of organic contaminants, [41][42][43] with this in mind we next investigated the efficacy of these Pd-based bi-metallic catalysts towards the oxidative degradation of phenol via in situ H 2 O 2 production (Table 2). It should be noted that it was not possible to measure residual H 2 O 2 via standard titration or colorimetric procedures given the strong reddish colour that results from the formation of the aromatic oxidation products (catechol, hydroquinone etc.).…”