Liquid phase oxidation of glycerol over carbon supported gold catalysts

The heterogeneously catalysed liquid phase oxidation of glycerol over nanosized gold particles has been investigated. The effect of the support only was studied and no glycerol conversion could be detected whereas gold nanoparticles supported on different carbons (carbon black, activated carbon and graphite) and oxides (TiO2, MgO and Al2O3) were active. Under the same reaction conditions and with comparable gold particle size, the carbon supported gold catalysts are highly active in the liquid phase oxidation of glycerol. The reaction conditions have been studied in a batch reactor with oxygen as oxidant and have been optimised. The different regimes have been determined by varying, e.g. catalyst amount, stirring speed and NaOH/glycerol ratio. The apparent activation energy of the Au/C catalysed glycerol oxidation was determined. Moreover, depending on the base concentration and the reaction time, the selectivity of the Au/C catalysed liquid phase glycerol oxidation could be controlled. The structure-sensitivity of the glycerol oxidation was examined and discussed. Experiments with Au/C catalysts with gold particle sizes in the range from 2 to 45 nm indicate clearly that the reaction is structure-sensitive. In fact, a dependence of the catalytic activity and much more of the selectivity on the gold particle size has been observed.