The Study On The Oxidation Of Glyoxal To Glyoxylic Acid By Air Over Nano Gold Catalyst

The specific performance of gold catalysts has been extensively paid attention, since the discovery of its excellent catalytic behavior for CO oxidation in low temperature. However, most studies of nano-gold catalysts focus on the catalytic oxidation in gas-solid phase, few investigations in liquid phase. The synthesis of organic chemicals through the methodology of oxidation and reduction is a challenging subject. In this paper, the influence of the preparation conditions of gold catalysts has been systematically investigated using liquid phase oxidation of glyoxal to glyoxylic acid as the probe reaction.In this paper, the gold catalysts were prepared by different method and the influence of preparation and reaction conditions, such as preparation method, loading of gold, selective of support, calcinations temperature, reaction time, reaction temperature, pH value as well as catalyst weight on the performance for the oxidation of glyoxal has been investigated. Absorbance ratio differential method and chemical analysis method were developed for the simultaneous determination of glyoxal and glyoxylic acid.The results show that the catalyst with 3% gold loading which was obtained from immobilization gel method and calcined at 200℃demonstrated high activity. At the reaction temperature of 50℃, the reaction time of 8h and the pH value of 7.7, the conversion of glyoxal was 28% and the yield of glyoxyiic acid was 9.9%.Au-Pd catalyst supported on carbon was also prepared under the same condition. The performance of Au/C and Au-Pd/C on oxidation of glyoxal was compared. The results demonstrate that, at the optimum reaction time of 20h, the conversion of glyoxal was 58.9% and the yield of glyoxylic acid was 13.7%, which implied the bimetallic catalyst showed higher performance than the monometallic catalyst obviously.The cataltsts were characterized by X-ray diffraction pattern(XRD), X-ray photoelectron spectra(XPS), BET and atomic absorbtion spectra techniques. The active species catalysts and the reaction mechanism were discussed as well.