The selective oxidation of bioderived molecules by gold catalysts

The selective oxidations of the bioderived molecules, 1,2-propanediol, 1,3-propanediol and glycerol, were investigated using gold based catalysts. These reactions were carried out in both low pressure glass reactors and high pressure autoclaves. The reaction conditions such as temperature and amount of base were investigated to order to achieve the optimum conditions. The gold based catalysts used were prepared by sol immobilisation and impregnation methods. The supports tested were activated carbon, titania, ceria and magnesium oxide. The ceria supported catalyst was demonstrated to be extremely selective for the oxidation of 1,2-propanediol in methanol in which methyl lactate is the desired product. The addition of palladium to the gold catalyst led to an increase in activity for all supports, however, in the case of the ceria supported catalyst a decrease in selectivity was observed. The use of a magnesium oxide support was found to be advantageous in the oxidation of 1,3-propanediol and model compounds 1,4-propanediol and butyrolactone. An increase in activity and selectivity to the desired products, dimethyl malonate and dimethyl succinate, was demonstrated when this catalyst support was used. The structure of the support was found to be Mg(OH)2 when the catalyst was prepared by sol immobilisation. When prepared by impregnation methods the support retained its periclase MgO structure but was found to be far less selective than the Mg(OH)2 support.The use of this support for the oxidation of glycerol was investigated. When gold is alloyed with platinum on this support it is possible to achieve high conversions of glycerol and good selectivities to glyceric acid in base free condition