Electrochemical reduction of xylose

Abstract

By electrolysis of the solution of xylose and potassium- bromide in the cell with the cationic selective membrane, xylitol and xylonic acid were obtained simultaneously. On the active titanium anodes RuO2 / TiO2 the evolved bromine at low overvoltage hydrolyse into hypobromite which oxidizes xylose to δ – xylolactone, which then by the spontaneous conversion turns into xylonic acid. By the electrolysis of the solution on the cathode apart from the wanted reaction of the reduction of xylose to xylitol, the parallel reaction of the evolution of hydrogen happens. The amalgamated zinc as the cathode was employed considering the reaction of hydrogen evolution on that cathode take place at high overvoltage. By the suitable selection of the parameters of electrolysis from the sulphate bath the layer of zinc with the wanted characteristics was deposited on the copper net. The amalgamated zinc of the suitable concentration was formed by dipping the layer in the solution of HgCl2 for a certain period of time. Experimentally it was found out that the cathodic current efficiency of xylitol depends on the current density, concentration of xylose and the temperature of the solution. By the electrolysis of the solution of xylose the concentration C>0,8M at t>40°C, in the range of the current density of electricity 100 mA/cm2 <j<400 mA/cm2 , on the amalgamated zinc cathode xylitol is obtained with the high current efficiency η>90%. The obtained experimental data show that the zinc amalgamated cathode with the good mechanical and electrochemical characteristics may be used in the industrial cells for producing xylitol.