Controllable oxidation of glucose to gluconic acid and glucaric acid using an electrocatalytic reactor

Intense research is being done on the highly efficient and selective conversion of glucose into high value-added chemicals. For this purpose, a functional electrocatalytic reactor was employed to efficiently produce gluconic acid (GA) and glucaric aicd (GLA) from glucose under mild condition. The reactor was assembled by a nano-MnO2 loading tubular porous titanium (Ti) electrode (MnO2/Ti electrode) as anode and a stainless steel mesh as cathode. The effects of MnO2 loading, pH value, glucose concentration (C-0glucos), reaction temperature, residence time and current density on the glucose oxidation were investigated during the reactor operation. The results indicated that 98% conversion of glucose and 98% total selectivity to GA and GLA (43% selectivity to GA and 55% selectivity to GLA) were obtained by electrocatalysis using the MnO2/Ti electrode (4.98 wt% MnO2 loading) under the operating conditions of the reactor: an aqueous glucose solution of 50.5 mmol L-1, a reaction temperature of 30 degrees C, a residence time of 19 min, a current density of 4 mA cm(-2) and pH of 7. By further increasing the current density to 6 mA cm(-2), 99% conversion of glucose and 99% total selectivity to GA and GLA (15% selectivity to GA and 84% selectivity to GLA) were obtained. The excellent performance of the controllable oxidation of glucose is mainly attributed to the electrochemical oxidation and convection-enhanced mass transfer as well as to the timely removal of the desired products in the reactor. (C) 2014 Elsevier Ltd. All rights reserved.