Study On The Process Of Homogeneously Catalyzed Methyl Glycolate Hydrolysis

Glycolic acid (GA) is a widely used organic chemical product. In response to thegrowing demand for high-purity GA and the pressure from environmental protection,it becomes more urgent and important to develop a novel green process for GApreparation.The hydrolysis of methyl glycolate (MG) catalyzed by sulfuric acid was studiedin the paper. Firstly, the hydrolysis kinetics was investigated in an isothermal batchreactor. The effects of catalyst concentration, initial reactants mole ratio andtemperature were examined experimentally. And the hydrolysis mechanism wasproposed, in which the ionization of sulfuric acid, GA and water were all included andthe nucleophilic substitution was assumed as the rate-determining step. Since thecatalysis of sulfuric acid, GA and water were quantitatively described; the kineticmodel developed for sulfuric acid catalyzed hydrolysis can also be applied to theprocess of auto-catalyzed hydrolysis.Then the hydrolysis reaction was introduced into the reactive distillation towerby batch and continuous operation. Modeling and simulation of the reactivedistillation column were carried out using Aspen. The good agreement between theexperiments and the simulation with Aspen indicated that the proposed kinetic modelcould be applicable to the design of hydrolysis reactive distillation process.By the batch simulation study, we found that proper reflux ratio and feed rateduring charge stage could shorten the operating time. And under condition that initialreactants mole ratio5:1, reflux ratio7, high conversion of MG over99.5%wasachieved. Furthermore, a varied reflux ratio policy, such as taking large reflux ratio ininitial and then reduce reflux ratio, can significantly reduce energy consumption.The simulation for continuous distillation results showed that when the stagenumber was17, initial reactants mole ratio5:1, reflux ratio4and initial sulfuric acidconcentration approximately5%, the products got from the top and the bottom ofdistillation tower contained methanol95wt%and GA48wt%respectively.