Preparation Of Glucuronic Acid And Its Lactone By Selective Catalytic Oxidation Of Methyl Glucoside In Na₂WO₄/H₂O₂ System

D-?+?-Glucofuranurono-6,3-lactone is abbreviated as glucurolactone.It is usually used as liver antidote,conditioning agent with immune function and also used widely as the main additive in drinks,foods,diet pills,cosmetic,and so on.For the rapid increase in the field of application,traditional producing method of glucurolactone using starch as the precursor and oxidatived by nitric acid can't meet the demand of market.At the same time,this technology has a series of disadvantages such as its poor oxidative selectivity,the low utility rate of raw material,the more by-products,the high energy consumption,and the serious environmental pollution.Therefore,it is necessary to explore new synthetic route.This paper explored and optimizated new synthetic process of glucuronic lactone from two aspects as follows: raw material and catalyst.Methyl-?-D-pyran glucoside?abbreviated as methyl glucoside?was a acetal formed from glucose's aldehyde with methanol and hydroxyl methyl in C5.Compared with the raw material of starch in traditional nitric acid oxidation method,methyl glucoside has more simple molecular composition,the primary hydroxyl in C6 has smaller space steric hindrance and could be oxidized easily.W?VI?metal ions could combine with H2O2 rapidly and generated transition metal intermediates with suitable oxidative activity.And Na₂WO₄/H₂O₂ system had activity and selectivity on the oxidation of alcohol according to related literature.This work chose methyl glucoside as raw material,Na₂WO₄/H₂O₂ as catalytic system for preparation of glucuronic acid and its lactone by oxidating primary alcohol of methyl glucoside.The reaction mechanism of Na₂WO₄/H₂O₂ system oxidating methyl glucoside were deduced respectively under alkaline and acidic condition.Different oxidation effect under different condition were analysed such as solvents,dropping speed of oxidant,reactant concentration and so on.The results showed that the oxidation rate increased asthe concentration of catalyst and were not associated with concentration of methyl glucoside and hydrogen peroxide.The synthesis reaction of glucuronic acid and its lactone was divided into catalytic oxidation process and hydrolysis process.In catalytic oxidation section,the feeding way of catalyst,the dosage of oxidant,the pH of oxidation reaction,catalyst concentration,reaction temperature were discussed.And the pH of oxidation reaction,n?H2O2?/n?MGP?,temperature,n?Na2WO4?/n?MGP?were chosen as orthogonal experimental levels.The results showed that the pH value was the most important effect on yield of glucuronic acid,then the temperature and the mount of Na2WO4.The best oxidation conditions were as follows: the pH value was 9.7,n?H2O2?/n?MGP?was 2.25,the temperature of oxidation reaction was 70?,n?Na2WO4?/ n?MGP?was 4%.In hydrolysis process,the effect of different acidic catalyst,hydrolysis temperature,reaction time on the yield of glucuronic acid and its lactone were discussed.The results of hydrolysis process showed that the optimized conditions of hydrolysis were sulfuric acid as acidic catalyst,the hydrolysis temperature was 85?,the reaction time was 3h.Under these optimized conditions the total yield of glucuronic acid and its lactone could reach 78%.From the HPLC analysis,it showed that this system had good selectivity in the oxidation of methyl glycoside.Na₂WO₄/H₂O₂ system had good selectivity and reaction activity in the preparation of glucuronic acid and its lactone from methyl glycoside.This technology could adapt the demand of green chemistry by its mild reaction conditions,high rate of atom utilization,easily separation of products and overcoming the deficiency of the traditional production process.