Kinetic Analysis and Multi Objective Optimization of L-Lactide Polymerization

- Biopolymers have emerged as an appropriate replacement for conventional petrochemical polymers consoling our environmental concern. As an alternative to polyolefin, polylactic acid (PLA) has been identified as a capable biodegradable polymer. Lactide ring opening polymerization (ROP) has been demonstrated to be an efficient polymerization method. A well validated moment based kinetic model for lactide ROP referring with homogeneously well stirred batch reactor using 2-ethylhexanoic acid tin (II) salt as the catalyst and an alcohol as co-catalyst has been utilized to formulate the multi objective optimization problem (MOOP). The MOOP is composed of three conflicting objective functions: minimization of time, minimization of PDI and maximization of number average molecular weight (Mn). Decision variables have been implemented to analyse the process performance with the mass balance equation for objective function ranges as constraints. The optimization problem does not contain a single solution but rather contains several equally important solutions (Pareto front) which are called as non-dominated solutions and this Pareto front is obtained by using non-dominated sorting genetic algorithm-II (NSGA II) developed by Deb, 2001. Some of the Pareto front points showed better outcomes rather than the experimental data. The distinct aspect of modeling and optimization from experimental data can be applied directly in the actual large-scale plants.