Extractive distillation of methylal/methanol mixture using ethylene glycol as entrainer

Ethylene glycol (EG) is proposed as an entrainer for the separation of methylal and methanol by extractive distillation. The COSMO-RS model was used to screen the suitable entrainer in terms of selectivity and solvent capacity. EG is a suitable entrainer with a low environmental impact. Vapor–liquid equilibrium (VLE) experiments demonstrated that the relative volatility of methylal to methanol is significantly improved using EG as an entrainer. The new corresponding interaction parameters were obtained by correlating the VLE data using the UNIFAC model, and then they were introduced into the process simulation software. The extractive distillation process was simulated using the rigorous equilibrium stage model. The optimal operating conditions were obtained by sensitivity analysis. The simulation results showed that EG is effective and efficient for the separation of methylal and methanol. In addition, the COSMO-RS model provides some theoretical insights into the separation mechanism.