Direct Synthesis of Hydrogen Peroxide and Benzyl Alcohol Oxidation Using Au−Pd Catalysts Prepared by Sol Immobilization

Abstract

We report the preparation of Au-Pd nanocrystalline catalysts supported on activated carbon prepared via a sol-immobilization technique and explore their use for the direct synthesis of hydrogen peroxide and the oxidation of benzyl alcohol. In particular, we examine the synthesis of a systematic set of Au-Pd colloidal nanoparticles having a range of Au/Pd ratios. The catalysts have been structurally characterized using a combination of UV-visible spectroscopy, transmission electron microscopy, STEM HAADF/XEDS, and X-ray photoelectron spectroscopy. The Au-Pd nanoparticles are found in the majority of cases to be homogeneous alloys, although some variation is observed in the AuPd composition at high Pd/Au ratios. The optimum performance for the synthesis of hydrogen peroxide is observed for a catalyst having a Au/Pd 1:2 molar ratio. However, the competing hydrogenation reaction of hydrogen peroxide increases with increasing Pd content, although Pd alone is less effective than when Au is also present. Investigation of the oxidation of benzyl alcohol using these materials also shows that the optimum selective oxidation to the aldehyde occurs for the Au/Pd 1:2 molar ratio catalyst. These measured activity trends are discussed in terms of the structure and composition of the supported Au-Pd nanoparticles.

Selective Oxidation of Glycerol by Highly Active Bimetallic Catalysts at Ambient Temperature under Base‐Free Conditions

“…As shown in Figure S4 and S5, particles from both sides of the size distribution are all alloyed. However in the Au-Pd system there is a sizedependant composition variation, which we have reported previously: [19] the relative ratio of Au-Ma line and Pd-La line showed that Pd tends to agglomerate on bigger particles. Interestingly, Au-Pt system seemed to not have such an obvious segregation trend, with the two metals distributed more evenly.…”

Liquid phase oxidation of cyclohexane using bimetallic Au–Pd/MgO catalysts

“…Previous studies have shown that the promising properties of Au can be manipulated by the addition of Pd to form Au-Pd bimetallic alloys as green catalysts [13][14][15][16][17]. Herein we report that Au-Pd nanoparticles supported on MgO can improve both conversion and product selectivity in the cyclohexane oxidation reaction as compared to the commercial cobalt naphthenate promoter.…”

Probing the origin of in situ generated nanoparticles as sustainable oxidation catalysts

“…Whilst there is immense potential for the 40 designed porous framework host to be catalytically active in itself; metal nanoparticle-framework interactions and metal-metal interactions (e.g. multimetallic nanoparticles) can be suitably engineered and investigated for eliciting synergistic enhancements [6][7][8][21][22][23] …”

“…7 Recent impressive studies even show the potential of alloyed nanoparticles for catalysing more demanding 65 activation of primary C-H bonds in toluene, 8 as well as in the selective synthesis of hydrogen peroxide, 9 which pave the way for overcoming some of the earlier limitations. 5,6 Heterogeneous nanoparticle catalysts have mostly been supported on porous carbon 10 impregnation, 15 deposition-precipitation 16 and polymer-stabilised colloidal deposition; 17 where precise control of nanoparticle size and distribution have been achieved employing polyvinylalcohol 10 (PVA) and polyvinylpyrrolidone (PVP) as polymer-stabilising agents.…”