Modelling and Optimisation of a Reactive Distillation Process for Biodiesel Production

Abstract

Reactive distillation is a method that integrates distillation and a chemical reaction into a single entity. The reaction releases heat that automatically drives the separation of the components, which makes the process particularly advantageous for exothermic reactions. The process also offers a novel alternative to liquid-phase chemical reaction processes, in the sense that the separation of products from unconverted reactants enables high conversion, as product removal restores equilibrium and forces the reaction to completion. There are numerous advantages of this method. However, the fusion of chemical activities and separation in the same unit of apparatus has created some difficulties in the process, and chemical engineers are still working on determining the optimal parameters for operating the process effectively. In this article, the authors model and enhance a reactive distillation process that yields biodiesel (methyl propionate) and water as by-products from the esterification of propionic acid and methanol. They accomplished the esterification process by using tests generated with Design Expert and Aspen HYSYS. They optimised the process with MATLAB to maximise the biodiesel yield. The manipulated variables were the reflux ratio and the column's reboiler duty. The results of the optimisation and validation process showed that the best conditions for producing high-purity biodiesel with a mole fraction of 0.8435 were a reflux ratio of 5 and a reboiler duty of 500000 kJ/s, respectively.