Preparation Of Gluconic Acid And Gluconolactone

Gluconic acid and gluconolactone are important food additives in food industry. There aresome problems existing in the present preparation tecnologies, such as high energy consumption,long production cycle and heavy pollution. In this research, gluconic acid was preparedrespectively by ultraviolet/H₂O₂（UV/H₂O₂） method using glucose as raw material, and bycation exchange resin using sodium gluconate as raw material. Preaparation of gluconic acidδ-lactone from gluconic acid was also investigated, the main results were as follows:1. Determination of gluconic acid prepared by UV/H₂O₂methodDue to the inference by hydrogen peroxide for determination of gluconic acid, H₂O₂in thesolution was removed by adjustment of pH to9.0. The content of gluconic acid was determinedas sodium gluconate by HPLC. The results showed that this method could effectively eliminateH₂O₂and acquire accurate result of gluconic acid.2. Preparation of gluconic acid by UV/H₂O₂methodGluconic acid was prepared by addition of hydrogen hydroxide into glucose solution underultraviolet irradiation. Effects of reaction time, temperature, glucose concentration and the molarratio of glucose to H₂O₂on the yield of gluconic acid were investigated. Optimal technology wasobtained by using an orthogonal design: the molar ratio of glucose to H₂O₂1:3, glucoseconcentration0.25g/mL, reacting time6h and reaction temperature50℃. Under this reactionconditions, the yield of gluconic acid was78.26%.3. Preparation of gluconolactone using sodium gluconateGluconolactone were prepared from sodium gluconate using the methods respectively bydirect acidificattion and cation exchange resin. The results showed that, due to30.7%of thepurity of gluconolactone, direct acidificattion was not suitable for preparation of gluconolactone.However, after passing through the cation exchange resin, high purity gluconic acid wasobtained and good for preaparation of gluconic acid δ-lactone. The purity of gluconic acidδ-lactone was69.7%.34.2g of gluconic acid δ-lactone was prepared from50g of sodiumgluconate, the yield accounts for83.4%.617.7g of gluconic acid δ-lactone was prepared from1000g of sodium gluconate, the yield accounts for75.3%.The best regeneration conditions of732cation exchange resin was three times volume HCl with5%mass fraction. The exchange capacity was1.57mol/L. After5repeated trials, theexchangge capacity truned into1.55mol/L from1.57mol/L. Because of small overall change intrend,732cation exchange resin was suitable for industrial production.