Study On Esterification Of 2-keto-L-gulonic Acid By Ion-exchange Resin

Esterifying of 2-keto-L-gulonic acid is one of the vital processes in the production of Vitamin C. However there are a lot of problems in the existing techno -logical process, such as low yield rate, high-energy consumption and environment problems, because the ester is carried out under catalysts of hydrochloric acid or sulfuric Acid. So it is the great significance both in commercial and environmental to design a new process to synthesis of methyl 2-keto-L-gulonate.In this paper, a new process to synthesis of methyl 2-keto-L- gulonate by strong acidic cation exchange resin was developed. The optimum type of cation exchange resin was selected from 15 type cation exchange resins. The results showed that H11 strong acidic cation exchange resin has the highest level of catalytic activity. Factors that affect the yield have been studied. It is as follows: in the fixed-bed catalytic reactor, reacting temperature 60℃, the space velocity 1.0 ml/min, and the ratio of gulonic acid to Methanol 0.1g /ml. Under the above conditions, the yield rate can be up to 98%, and without any loss of catalytic activity during 5 times.Kinetics of heterogeneous catalyzed esterification of methyl 2-keto-L-gulonate was studied with a cation-exchange resin catalyst H11, in a stirred batch reactor. Effects of various parameters such as speed of agitation, catalyst particle size, mole ratio of reactants, reaction temperature, catalyst loading, and reusability of the catalyst were studied to optimize the reaction condition. The kinetic data were correlated with the Langmuir–Hinshelwood model. The surface reaction is the rate-limiting step and the activity energy is 32kJ. The rate data fits the following model:Separating and purifying of methyl 2-keto-L-gulonate in the methanol on cooling crystallization was studied. It is easy to crystallize in methanol. The effect of...