Abstract
The direct synthesis of hydrogen peroxide (H2O2) from molecular H2 and O2 offers an attractive, decentralized alternative to production compared to the current means of production, the anthraquinone process. Herein we evaluate the performance of a 0.5%Pd-4.5%Ni/TiO2 catalyst in batch and flow reactor systems using water as a solvent at ambient temperature. These reaction conditions are considered challenging for the synthesis of high H2O2 concentrations, with the use of sub-ambient temperatures and alcohol co-solvents typical. Catalytic activity was observed to be stable to prolonged use in multiple batch experiments or in a flow system, with selectivities towards H2O2 of 97% and 85%, respectively. This study was carried out in the absence of halide or acid additives that are typically used to inhibit sequential H2O2 degradation reactions showing that this Pd-Ni catalyst has the potential to produce H2O2 selectively. This article is part of a discussion meeting issue 'Science to enable the circular economy'.
Highlights
The direct synthesis of hydrogen peroxide (H2O2) would offer an attractive alternative to the current industrial means of production, the anthraquinone oxidation (AO) process and potentially allow decentralized production.royalsocietypublishing.org/journal/rsta Phil
Our initial work focused on the evaluation of 5%PdNi/TiO2 catalysts with varied Pd:Ni ratios for the direct synthesis and subsequent degradation of H2O2
The observed concentration of H2O2 increasing to a maximum of 312 ppm for the 0.75%Pd– 4.25%Ni/TiO2 catalyst before plateauing as the composition was varied to 1%Pd–4%Ni/TiO2 after 30 min of reaction
Summary
The direct synthesis of hydrogen peroxide (H2O2) would offer an attractive alternative to the current industrial means of production, the anthraquinone oxidation (AO) process and potentially allow decentralized production.royalsocietypublishing.org/journal/rsta Phil. By comparison we have recently reported [26] that the well-studied 2.5%Au–2.5%Pd/TiO2 catalyst [29,30] prepared via a conventional wetimpregnation methodology offers significantly greater rates of H2O2 degradation (25%), under identical reaction conditions indicating the beneficial effects of alloying Pd with Ni. It should be noted that, despite the significantly greater activity of the supported AuPd catalyst towards H2O2 degradation the concentration of H2O2 generated (476 ppm) [26] is only slightly greater than that observed for the 0.75%Pd–4.25%Ni/TiO2catalyst.
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