Transesterification reactive extractive distillation process using ionic liquids as entrainers: From molecular insights to process integration

Abstract

In this work, the transesterification reactive distillation coupled with extractive distillation process for n-propanol (PROH) and methyl acetate (MEAC) was developed based on pseudo homogeneous kinetic parameter model using ionic liquids (ILs) as entrainers. The COSMO-RS model was used for screening ILs entrainers. Here, 1-ethyl-3-methylimidazolium acetate [EMIM][AC] was selected as a potential entrainer due to its excellent solvent capacity and selectivity. Further, the COSMO-RS model was performed to calculate the polarization charge density (σ-profile) of methanol (MEOH), methyl acetate and [EMIM][AC], and to explore the molecular polarity. Based on quantum chemistry (QC) theory, the interaction energy between different molecular pairs is calculated. Independent gradient model (IGM) analysis identifies the interaction types of molecular pairs from the perspective of visualization. Owing to the strong hydrogen bond between anion [AC]− and MEOH, the extractive distillation process performance was significantly improved. Based on Aspen Plus platform, the effects of the theoretical stage number, reflux ratio, feed position and entrainer dosage on the cost and energy consumption of the new process was investigated. Based on the sensitivity analysis method, the operating conditions were optimized. Compared to the conventional process, the new reactive distillation coupled with extraction distillation process has higher energy efficiency and lower economic cost. The new process can save the total annual cost of about 3.42 × 105 $/year.