Optimal reaction conditions for the minimization of energy consumption and by‐product formation in a poly(ethylene terephthalate) process

Abstract

ABSTRACT:We determined the optimal reaction conditions to minimize the energy cost and the quantities of by-products for a poly(ethylene terephthalate) process by using the iterative dynamic programming (IDP) algorithm. Here, we employed a sequence of three reactor models: the semibatch transesterification reactor model, the semibatch prepolymerization reactor model, and the rotating-disc-type polycondensation reactor model. We selectively chose or developed the reactor models by incorporating experimentally verified kinetic models reported in the literature. We established the model for the entire reactor system by connecting the three reactor models in series and by resolving some joint problems arising when different types of reactor models were interconnected. On the basis of the simulation results of the reactor system, we scrutinized the cause and effect between the reaction conditions and the final quality of the polymer product. Here, we set up the optimization strategy by using IDP on the basis of the integrated reactor model, and the process variables with significant influence on the properties of polymer were selected as control variables with the help of a simulation study. With this method, we could refine the reaction conditions at the end of each iteration step by contracting the spectra of control regions, and the iteration process finally stopped when the profile of the optimal trajectory converged. We also took the constraints on the control variables into account to guarantee polymer quality and to suppress side reactions. Constituting six different strategies by setting weighting vectors differently, we examined the differences in optimal trajectories, the trend of optimality, and the quality of the final polymer product. For each of the strategies, we conducted the optimization to examine whether the number-average degree of polymerization approached the desired value.

Modeling of Poly(Ethylene Terephthalate) Homogeneous Glycolysis Kinetics

“…If this assumption is violated, the actual conversion of the process will be lower than the one calculated by the model. The effect of the catalyst is included in the effective constants [ 42 , 43 ] in Equations (2) and (3) (see below). The model was verified using the values for the antimony trioxide catalyst used;…”

“…The effective polycondensation rate constant can be determined from Equation (2): where is the effective polycondensation rate constant; k 1 is the polycondensation rate constant; —catalyst concentration, mol/L; A is the pre-exponential factor, 5.66 × 10 8 L 2 /(mol 2 ·min 1 ) [ 42 , 43 ]; E a —activation energy, 18,500 cal/mol [ 42 , 43 ]; R is the universal gas constant, 1987 cal/mol·K, and T is temperature, K.…”

“…Models describing a reversible polycondensation reaction in the production of vPET [ 42 , 43 , 44 , 45 ] take into account the interactions between bound, terminal, and free ethylene glycol molecules in the reaction mixture. The aim of this work is to develop and verify a kinetic model of homogeneous poly(ethylene terephthalate) glycolysis that also takes into account these interactions.…”

Feasible Regions for Step-Growth Melt Polycondensation Systems

“…They recently extended their analysis to forced-gas sweeping processes applied to PET and BPA BC . A model of an industrial PET wiped-film reactor was also developed by Bhaskar et al Similar models, also combined with neural network models (“hybrid models”), have been applied to an industrial reactive extrusion process for the production of Nylon 6,6. , Dynamic models have also been proposed to address startup and grade transition operations. − More recently optimization studies have been done on existing reactor models. − …”

“…[22][23][24] More recently optimization studies have been done on existing reactor models. [25][26][27]…”