Optimization of a Reactive Distillation Process for Producing Triethyl Citrate

Triethyl citrate is a bio-based plasticizer mostly used in polymers that may have contact with humans (medical devices, toys, etc). Currently it is produced by esterification of citric acid with ethanol in a batch reactor system followed by a striping process to remove excess of ethanol. In order to reduce energy and materials consumption of the traditional process, reactive distillation (RD) can be implemented. In this process high yield triethyl citrate can be obtained as bottom product while ethanol excess and water are removed as distillate.  Some authors reported the feasibility of this process, however low conversion to triethyl citrate and high energy requirements were observed.

In this work it was developed and optimized a RD process for triethyl citrate. By reprocessing reported kinetic data a pseudo homogeneous model was obtained.  NRTL-HOC activity based equation was used for phase equilibria modeling. The method used for the optimization corresponds to a stochastic differential evolution, setting the objective function to minimize energy consumption and the purity of product streams. This optimization was automated by connecting Aspen One^TM and Visual Basic^TM included in EXCEL^TM. A reduction in energy consumption of around 30% with respect to conventional reaction followed by distillation process was observed.