Multicriteria optimal control of polypropylene terepthalate polymerization reactor

Tetrabutoxytitanium (TBOT) is a proven catalyst for the esterification step of the polypropylene terepthalate (PPT) polymerization process. Previous studies show that the performance of TBOT is superior in terms of the enhanced degree of polymerization and less processing time to other competitive catalysts. But, interesting observation left was to investigate whether with other process objectives like by-product minimization and controlled growth of desired functional groups, any other catalyst offers better system performance or not. Present study carries out the exercise of searching other catalytic options along with TBOT for the process improvements and gives a detailed process analysis through different sets of optimized operations. A well-validated kinetic model for esterification step of PPT polymerization process and the advanced Real-Coded Nondominated Sorting Genetic Algorithm-II (Real-Coded NSGA-II) optimization routine have been used in this current effort. For process objectives like by-product minimization, TBOT though become a marginal winner, Sn- and Zn-based catalysts compete with each other. Zn-based catalyst is found probably the most suitable catalyst in terms of the overall process performance with excellent by-product minimization (similar to 10 times better), higher degree of polymerization (similar to 1.75 times better), and tight quality control (similar to 5 times better).