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

Abstract

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.

Analysis of the esterification process for poly(ethylene terephthalate)

“…1 Thus, with the Yamada et al's solubility data one cannot get a solution that satisfies the material balance equations having non-zero liquid phase fraction. However, if one uses the Simplex method as used by Yamada et al, 6,7 one may get a rough solution with such a small solubility data, since the method searches for the minima of residuals of the material balance equations.…”

“…One is related to the solution method. In step 8, this study employed a Newton-Raphson iteration method to solve the simultaneous nonlinear equations, while Yamada et al's 6,7 employed the Simplex method. The Newton-Raphson iteration method leads to a solution that satisfies the given equations within a tolerance limit of 10 -9 .…”

“…Modelling of the polymerization has been used to determine how to reduce the amount of diethylene glycol produced, and many investigators have used computer simulations of the process to investigate the reaction characteristics for specific process conditions. [1][2][3][4][5][6][7][8][9][10] The polymerization process of poly(ethylene terephthalate) consists of esterification and polycondensation processes. Esterification takes place in a continuous flow stirred tank reactor while polycondensation takes place in a rotating disk reactor.…”

“…Modelling and simulation of the esterification process have been attempted by many investigators including Ravindranath and Mashelkar 1-4 and Yamada et al [5][6][7][8][9][10] The reaction mechanisms suggested by the two major research groups conform in the mechanisms of the esterification and polycondensation reactions, but differ in the mechanisms of the side reactions that produce diethylene glycol. The mechanisms of the side reactions are not yet clearly identified, so well designed and better experiments are needed.…”

State Observer Design for Monitoring the Degree of Polymerization in a Series of Melt Polycondensation Reactors

“…In each reactor, side reactions take place simultaneously and directly affect product quality. On-line measurements for byproduct concentrations are usually not available or at relatively low sampling rates [29]. Therefore, based on the fact that available on-line measurements are not always of the same nature, it is necessary to develop estimation/monitoring algorithms that can use all of these different kinds of on-line measurements in a synergistic way to provide valuable information of the process.…”