Selective Oxidation of Glycerol to Lactic Acid Catalyzed by CuO/Activated Carbon and Reaction Kinetics

Abstract

Activated carbon-supported CuO catalysts were prepared by an ammonia evaporation method and applied to catalyze the selective oxidation of glycerol to lactic acid. The effects of CuO loadings on the structure and catalytic performance of the catalyst were investigated. Results showed that CuO could be dispersed uniformly on the surface of activated carbon, promoting the increase of the reaction rate and accelerating the glycerol conversion significantly. As CuO loadings increased, the rate of glycerol consumption and yield to lactic acid was increased. However, too high CuO loadings would destroy the original pore structure of activated carbon and aggravate the agglomeration of CuO, resulting in a decrease in the catalytic performance of the catalyst. The best catalytic performance was obtained over 10% CuO/AC when the reaction temperature was 190 °C and the reaction time was 5 h. At this point, the selectivity to lactic acid reached 92.61%. In addition, power-function type reaction kinetic equations were used to evaluate the effect of glycerol and NaOH concentrations and the reaction temperature on the oxidation of glycerol to lactic acid over 10% CuO/AC. The activation energy of the reaction is 134.39 kJ•mol −1 , which is higher than that using single CuO as the catalyst. This indicates that CuO/AC is more temperature-sensitive than CuO and can probably achieve a higher lactic acid yield at high temperatures. At the same time, it is indicated that CuO supported on activated carbon can enhance the catalytic activity of CuO effectively.

Direct Synthesis of Calcium Lactate through the Reaction of Glycerol with Calcium Hydroxide Catalyzed by Bimetallic AuCu/SiO2 Nanocatalysts

“…It has been reported that small-sized CuO particles facilitate the conversion of glycerol to lactic acid [26]. However, when Cu-ZnO@C catalysts with metallic Cu particle sizes of 36.9, 67.8, and 93.6 nm catalyzed glycerol conversion to lactic acid, the Cu-ZnO@C catalyst with a metallic Cu particle size of 67.8 nm gave the highest lactic acid yield [27].…”

“…Researchers reported that when the oxidation of glycerol to lactic acid was catalyzed by a CuO/C catalyst in a NaOH aqueous solution, the activation energy was 134.39 kJ•mol −1 [26]. The reaction activation energies for glycerol conversion to lactic acid on bimetallic CuAu 1 , CuAu 2 , CuAu 3 , and CuAu 4 catalysts were 64.0, 53.4, 46.8, and 36.9 kJ•mol −1 , respectively [33].…”