ELECTROCHEMICAL PRODUCTION OF SORBITOL FROM SUGAR SYRUPS

SORBITOL, GLUCONIC ACID AND METAL GLUCONATES ARE USED IN MANY DIVERSE FIELDS, INCLUDING FOODS, PHARMACEUTICALS, COSMETICS, TEXTILES, AND POLYMERS. AT PRESENT, GLUCOSE IS COMMERCIALLY REDUCED TO SORBITOL BUT THE OPERATING CONDITIONS USED (HIGH TEMPERATURE AND HIGH HYDROGEN GAS PRESSURE) ARE UNDESIRABLE AND DANGEROUS. AN ALTERNATIVE APPROACH IS THE PAIRED ELECTROCHEMICAL SYSTHESIS OF SORBITOL AND GLUCONIC ACID IN AQUEOUS SOULTIONS AT AMBIENT TEMPERATURE AND ATMOSPHERIC PRESSURE. HOWEVER, A MAJOR DRAWBACK TO THIS APPROACH AT PRESENT IS THE NEED FOR A DISSOLVED ELECTROLYTE TO PROVIDE IONIC CONDUCTIVITY IN SOLUTION AND TO SUPPLY THE REDOX MEDIATIOR FOR THE INDIRECT OXIDATION OF GLUCOSE TO GLUCONIC ACID. THIS PROPOSAL DESCRIBES A NOVEL DIRECT ELECTROCHEMICAL APPROACH FOR THE PAIRED SYSTHESIS OF SORBITOL AND GLUCONIC ACID. THE APPROACH AVOIDS THE NEED FOR A DISSOVED ELECTROLYTE IN THE GLUCOSE SOLUTION. THE PROPOSED PROCESS IS DESIGNED SO THAT THERE IS NO POSSIBILITY OF CONTAMINATION OF THE FINAL PRODUCTS WITH FOREIGN CHEMICALS OR TOXIC MATERIALS. THE PROCESS IS UNIQUE IN THAT IT WILL ALLOW ALL REACTIONS (HYDROLYSIS, ACID CATALYSIS, ELECTROCATALYTIC OXIDATION AND ELECTROCATALYTIC REDUCTION) TO TAKE PLACE IN THE SAME REACTOR WITHOUT INTRODUCTION OF AN EXTERNAL ACID OR LIQUID ELECTROLYTE. THIS AVOIDS THE PROBLEM OF SEPARATING SUCH ADDITIVES FROM THE FINAL PRODUCTS.