ORIGINAL PAPER The Selective Oxidation of 1,2-Propanediol by Supported Gold-Based Nanoparticulate Catalysts Yulia Ryabenkova • Peter J. Miedziak • Nicholas F. Dummer • Stuart H. Taylor • Nikolaos Dimitratos • David J. Willock • Donald Bethell • David W. Knight • Graham J. Hutchings Ó Springer Science+Business Media New York 2012 Abstract The oxidation of 1,2-propanediol to form lactic acid and hydroxyacetone has been investigated using supported metal nanoparticles. A series of supported gold, palladium, platinum and combinations of these metals have been investi- gated. In the presence of base the major product formed is lactate, often in excellent yields as, under these conditions the terminal hydroxyl group is oxidised. In the absence of base, more vigorous conditions are required to elicit high conver- sions; surprisingly, a major product from such reactions is a mono-oxidation product hydroxyacetone, along with lactate. Keywords Gold catalysis Á Gold platinum alloy nanoparticles Á Lactic acid Á 1,2-Propanediol oxidation 1 Introduction 1,2-Propanediol can be formed by the catalytic hydrogen- olysis [1] of glycerol which in turn can be obtained as a by-product from biodiesel production. 1,2-Propanediol can be further oxidized to lactic acid, which is a useful inter- mediate for the production of biodegradable polymers, and food additives. There is therefore interest in developing new catalytic routes for the selective oxidation of 1,2-propane- diol. Supported metal nanoparticles are known to be effec- tive for oxidation to the corresponding acids, including monometallic Pd, Pt and Au. Tsujino et al. [2] have shown that 1,2-propanediol oxidation using palladium supported on carbon gave hydroxyacetone, lactic acid and pyruvic acid. Rossi and Prati were the first to report supported gold nanoparticles as being extremely active for oxidation of alcohols to acids under basic conditions [3–6]. Subsequent studies have shown that alloying gold with other metals, for example palladium, gives enhanced activity for the oxidation of various diols, aromatic alcohols and for hydrogen perox- ide synthesis [7–14]. The presence of base with supported gold nanoparticles as catalysts is considered to aid the acti- vation of a terminal hydroxyl group. It has also been reported that some diols can be successfully oxidised in the absence of base. Wang et al. [15] reported the oxidation of non-activated alcohols using colloidal platinum nanoparticles and the selective oxidation of glycerol using supported Pt catalysts has been studied by Liang et al. [16]. Villa et al. [17] have shown that glycerol can be oxidised using supported gold– platinum nanoparticles using base-free conditions, and we recently reported that glycerol can be selectively oxidised under base-free conditions over Au–Pd and Au–Pt nano- particles when supported on MgO [18]. These studies prompted us to extend our previous findings of 1,2-pro- panediol conversion into lactic acid using supported gold nanoparticles [19] where we used basic conditions to achieve high selectivities to lactate. In this paper we investigate the use of supported gold–platinum and platinum–palladium nanoparticles for 1,2-propanediol oxidation. 2 Experimental 2.1 Catalyst Preparation A series of Au, Pt, Pd, Au–Pd, Au–Pt and Pd–Pt catalysts supported on activated carbon (KB-B, Aldrich) were pre- pared using a sol-immobilisation method. Aqueous solutions Y. Ryabenkova Á P. J. Miedziak Á N. F. Dummer Á S. H. Taylor Á N. Dimitratos Á D. J. Willock Á D. Bethell Á D. W. Knight Á G. J. Hutchings (&) Cardiff Catalysis Institute, School of Chemistry, Cardiff University, Cardiff CF10 3AT, UK e-mail: hutch@cf.ac.uk 123 Top Catal DOI 10.1007/s11244-012-9909-9