Rigorous Design and Optimization of Methyl Glycolate Production Process through Reactive Distillation Combined with a Middle Dividing-Wall Column

The heterogeneously catalytic esterification of glycolic acid (GA) and methanol (MeOH) is superior to other approaches for the mass production of methyl glycolate (MG) due to several advantages. However, there is no research on the chemical process for the industrial synthesis of MG via esterification so far. Therefore, the rigorous design and optimization of a reactive distillation-based process for the MG production via the esterification of GA and MeOH are first proposed and investigated in this work. The overall process consists of a reactive distillation column (RDC) to convert GA and MeOH into MG and a separation section to purify the crude MG into the final product. In the study, a realistic GA feed stream including significant amounts of other impurities such as water, diglycolic acid, and methoxyacetic acid is assumed. The systematic optimization of minimizing the total annual cost (TAC) through sequential iterations is performed to find the optimal sets of design variables for RDC and the downstream separation section. From the optimization of RDC, the authors found that the molar feed ratio of MeOH to GA is the most influential variable, and its optimal value is 1.88. For the separation section, from the comparison of the optimized direct sequence, indirect sequence, and prefractionator sequence (PFS) processes, the PFS arrangement is the most economical design configuration. Furthermore, the two-column PFS process is integrated into the middle dividing-wall column that significantly saves 23.21% operating cost and 15.94% TAC.