Choi, Kyu Y.A mathematical model of a semi-batch reactor has been developed to investigate the transesterification of dimethyl terephthalate with ethylene glycol catalyzed by metal acetate catalyst. The detailed kinetic scheme based on molecular species model is used to estimate the conversion of methyl ester groups and the concentrations of various oligomeric species. The numerical simulation of the model shows that the oligomerization reactions lower the overall conversion of methyl ester end groups. Effects of ethylene glycol/dimethyl terephthalate mole ratios, reaction temperature and catalyst concentration on the conversion, oligomer concentration, oligomer molecular weight and molecular weight distribution have alao been analyzed.en-USTechnical Report