A mathematical model for computer simulation of the direct continuous esterification process between terephthalic acid and ethylene glycol. Part II: Reaction rate constants

It has been confirmed that the reaction model proposed previously, which can express simultaneously the oligomer properties and the distillate properties under low esterification pressure, is applicable to a continuous direct esterification process in a practical plant. The experimental data of the first esterification reactor (RA-1) was obtained under low reaction pressures (atomospheric or 1 kg/cm2G) with the pilot plant throughput based on poly(ethylene terephthalate) (PET) polymer production of about 50 kg/h. The Arrhenius' parameters, frequency factor, and apparent activation energy, were determined fitting the experimental data of the pilot plant by using the Simplex method as an optimization technique. The activation energy of diethylene glycol (DEG) formation, E7, is about twice as much as those of the esterifications, E1, E2, E3, and E4. The activation energies are E1, = 19640 cal/mol, E2 = 18140, E3 = 22310, E4 = 18380, E5 = 2810, E6 = 14960, and E7 = 42520 cal/mol. Good agreement was obtained between experimental data and calculated predictions for several oligomer and distillate properties. The vapor-liquid equilibrium can be expressed by Raoult's law with little problem of practical use.