Process Analysis and Multi-Objective Optimization of Ionic Liquid-Containing Acetonitrile Process to Produce 1,3-Butadiene

Using ionic liquid (IL) [C2MIM][PF6] as an additive could remarkably improve the performance of the acetonitrile (CAN) process, which is the most widely used distillation process to produce 1,3-butadiene (1,3-BT). In this work, a rigorous simulation of a new IL process to produce 1,3-BT was carried out to evaluate the performance of IL additive on an industrial scale, using UNIFAC as the global thermodynamic model. Based on the simulation models, some key operation parameters, such as solvent ratio and reflux ratio, were determined by sensitivity analysis. Furthermore, a multi-objective optimization was proposed and performed considering both the energy consumption and environmental impact (green degree) of the new process. A nonlinear mathematical model was established to express this multi-objective optimization problem, which includes six decision variables and involves maximizing the green degree of the process, the purity and the recovery of 1,3-BT, and minimizing the energy consumption of the process. The optimization results showed that the energy consumption of the IL-containing process could be reduced by 22% and that its green degree could be improved by 9.2%.