Selective Oxidation of Saturated Hydrocarbons Using Au–Pd Alloy Nanoparticles Supported on Metal–Organic Frameworks

Abstract

Gold (Au) and palladium (Pd) nanoparticles dispersed on a zeolite-type metal–organic framework (i.e., MIL-101) were prepared via a simple colloidal method. The catalysts were characterized by powder X-ray diffraction, N2 physical adsorption, atomic absorption spectroscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. Au and Pd were mostly in the form of bimetallic alloys on the MIL-101 support. The Au–Pd/MIL-101 was active and selective in the oxidation of a variety of saturated (including primary, secondary, and tertiary) C–H bonds with molecular oxygen. For the liquid-phase oxidation of cyclohexane, cyclohexane conversion exceeding 40% was achieved (TOF: 19 000 h–1) with >80% selectivity to cyclohexanone and cyclohexanol under mild solvent-free conditions. Moreover, the Au–Pd alloy catalyst exhibited higher reactivity than their pure metal counterparts and an Au + Pd physical mixture. The high activity and selectivity of Au–Pd/MIL-101 in cyclohexane aerobic oxidation may be correlated to the synergistic alloying effect of bimetallic Au–Pd nanoparticles.

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

“…1wt%Au-Pd/MgO (Au: Pd molar ratio = 1:1) exhibited a conversion of 11% and a total selectivity of 95% which represents a potential improvement over the commercial cobalt naphthenate initiator (Table 1 and Figures 2a and 2b; for full by-product analysis and methodologies see supporting material, Figure S1 and S2, and Tables S1 and S2).By comparison, the monometallic Au/MgO and Pd/MgO counterparts display a much poorer catalytic performance, which confirms that neither Au nor Pd alone, act as an effective catalyst [9,11,26]. Moreover, the supported Au-Pd catalyst displayed excellent stability, maintaining a 12% conversion and 98% selectivity even after being re-used multiple times ( Table 2).…”

Chemical Preparation of Supported Bimetallic Catalysts. Gold-Based Bimetallic, a Case Study

“…This is also a 3-D structure forming mesoporous cages built with trimers of Cr(III) oxide octahedra and dicarboxylate linkers but containing much larger pore sizes PVP-colloids of Au-Pd obtained by co-reduction of HAuCl 4 and PdCl 2 by NaBH 4 in the presence of PVP at 0˝C were adsorbed in MIL-101 [128]. After washing and drying, the sample was heated in H 2 at 200˝C, leading to NPs of 2.4 nm in average, but their location was not investigated.…”

Catalysing sustainable fuel and chemical synthesis

“…A strong synergy between Pd and Au centres was also demonstrated by Hutchings et al, wherein Au-Pd alloy nanoparticles supported on titania exhibited increased reactivity towards a diverse range of primary, allylic and benzylic alkyl alcohols compared to monometallic palladium analogues. The versatility of Au-Pd catalysts has also been shown in selox of saturated hydrocarbons [201], ethylene glycol [202], glycerol [203] and methanol [204], wherein high selectivity and resistance to on-stream deactivation is noted.…”