394 / 2018-07-25 09:58:26

Acid-free and Base- free Co-production of Gluconic Acid and HMF from High Fructose Corn Syrup

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This article demonstrates a process for the co-production of gluconic acid and HMF from high fructose corn syrup (HFCS) without the participation of acid or base. HMF is a versatile bio-based platform compound with broad application prospects in bioenergy, biomaterials and fine chemicals. Despite several companies are working on producing HMF at larger scale which would decrease the HMF price to reach the predicts costs of $1000/ton which comes from techno-economic modeling (60 kton/yr), the current price of HMF is still high because fructose is used as raw material. Except the raw materials, catalyst is one of the most immportant key factor in the preparation of HMF. In the process now reported, however, we all need to add additional commercial or self-made catalysts to conduct the dehydration of fructose. Herein，we used a weak organic acid, gluconic acid, which is in situ obtained from enzymatic oxidation of HFCS, to catalyze the dehydration of fructose to prepare HMF. Although the dissociation constant of gluconic acid is low (pKa=3.86), hydrogen ion’s ionizations can be significantly improved by adding some strong electrolyte salts to sufficiently catalyze the fructose dehydration. HMF’s yield reached 85% using 0.125-0.55M gluconic acid as catalyst in a H2O/2-methyl tetrahydrofuran biphasic system at 150 °C for 5 min with 200 w microwave irritations when 2% CaCl2 or 10% NaCl were added. In the enzymatic oxidation of HFCS, only glucose was converted into gluconic acid, whereas no fructose can be consumed. By using an immobilized glucose oxidase (GOD) and catalase (CAT) on an aminated resin, the acid resistances of enzymes were increased. No additional base was added to neutralize gluconic acid when 150 g/L HFCS was converted. By this method, we can obtain 48% gluconic acid and 42% HMF (molar yield ) from F55 HFCS. Addtionally, gluconic acid is another large-scale produced bio-based chemical (3 million tons/yr) that has been wildly used in food, construction, and pharmaceutical fields. Because the revenue of gluconic acid can completely cover the raw material cost of HMF manufacture, this co-production process is more competitive than those exsiting, single HMF preparation methods and has potential industrial application prospects.