Production of Ethylene Glycol Diacetate Ester Using a Heterogeneous Titanium (IV) Isopropoxide Catalyst: Response Surface Methodology

In this study, the reactive batch distillation of ethylene glycol monoacetate (EGMA) and ethylene glycol  diacetate  (EGDA)  was  investigated  experimentally  and  numerically  via  the  esterification reaction  of  acetic  acid  (AA)  and  monoethylene  glycol  (MEG)  in  the  presence  of  heterogeneous titanium  (IV)  isopropoxide  catalyst.  Four  operating  parameters,  including  time  (4-12  hr), temperature (60-100°C), the molar ratio of acetic acid to ethylene glycol (0.4-2.2 M), and catalyst weight (1-5wt%), were selected to design experiments, model and optimize the process through the response surface methodology (RSM). By applying the central composite design (CCD) method in RSM, two linear and second-order models were proposed for the responses of MEG conversion and EGD selectivity. The response surface plots showed that the reaction temperature and time had a more  significant  effect  on  increasing  the  reaction  yield,  while  the  molar  ratio  of  reactants  and catalyst  weight  were  two  critical  parameters  in  increasing  selectivity.  The  results  of  process optimization to maximize the responses indicated that the optimum process point in the operating range was at 9.5 hr, the temperature of 90°C, the molar ratio of 2.92:1, and catalyst weight of 2wt% where  the  predicted MEG  conversion  and  selectivity  were  100%  and  94.72%,  respectively. The MEG conversion reduced from 91.1% to 56.7% after using the catalyst four times.