The Direct Synthesis of H2O2 and Selective Oxidation of Methane to Methanol Using HZSM-5 Supported AuPd Catalysts

Richard J Lewis,Simon J Freakley,Nishtha Agarwal,Graham J Hutchings,Alejandro Bara-Estaun,David J Morgan

doi:10.1007/s10562-019-02876-7

Richard J Lewis, Simon J Freakley + Show 4 more

Open Access

https://doi.org/10.1007/s10562-019-02876-7

Copy DOI

Journal: Catalysis Letters	Publication Date: Jun 22, 2019
Citations: 30	License type: open-access

Affiliation: Cardiff University, University of Bath

Abstract

In this study we show that using gold palladium nanoparticles supported on a commercial aluminosilicate (HZSM-5) prepared using a wet co-impregnation method it is possible to produce hydrogen peroxide from molecular H2 and O2 via the direct synthesis reaction. Furthermore, we investigate the efficacy of these catalysts towards the oxidation of methane to methanol using commercially available H2O2. The effect of SiO2: Al2O3 ratio and calcination temperature is evaluated and a direct correlation between support acidity and the catalytic activity towards H2O2 synthesis and methanol production is observed.Graphic

Highlights

Hydrogen peroxide (H2O2) is a powerful oxidant with a high active oxygen content (47%) that offers significant benefits over other commonly used oxidants such as t-BuOOH, NaClO and permanganate which require costly separation and purification of waste by-products from product streams
Density functional theory (DFT) calculations have suggested that increasing numbers of neighbouring Au atoms around Pd can result in a decrease in electron back-donation into the π* orbital of the O–O bond, which in turn inhibits the formation of H2O through the cleavage of the O–O bond [44, 45]
Likewise spectroscopic studies reveal that the addition of Au to Pd clusters is able to reduce the formation of H2O through isolation of contiguous Pd ensembles, known to favour the formation of H2O compared to H2O2 [46, 47]

Summary

Introduction

Hydrogen peroxide (H2O2) is a powerful oxidant with a high active oxygen content (47%) that offers significant benefits over other commonly used oxidants such as t-BuOOH, NaClO and permanganate which require costly separation and purification of waste by-products from product streams. The oxidation of C 1–C3 alkanes utilising H 2O2 in conjunction with HZSM-5 [28,29,30,31,32] in addition to AuPd nanoparticles supported on T iO2 [33, 34] at low temperature have been extensively reported, with the valorisation of methane to methanol in particular an attractive option to produce a versatile chemical feedstock. They report excellent catalytic performance with no deactivation over 90 h, in part due to through inhibiting Pd agglomeration through confinement within the zeolite structure [37] Building on these previous works we investigate the catalytic activity of AuPd nanoparticles supported on HZSM-5 for the direct synthesis of H 2O2 from molecular H2 and O 2 as well as for the selective oxidation of methane to methanol

Catalyst Preparation

Characterisation

Results and Discussion

Conclusion