Bifunctional imidazole‐PTSA deep eutectic solvent for synthesizing long‐chain ester IBIBE in reactive extraction

TLDR

Traditional synthesis of long‑chain esters such as BIBE is hindered by homogeneous catalysts and complex thermodynamics. The study introduces a bifunctional deep eutectic solvent that serves as both catalyst and extraction medium to accelerate esterification. The DES, composed of imidazole and PTSA, was tuned to produce weak basic [3Im:PTSA] and strong acidic [Im:2PTSA] phases, whose formation was confirmed by FTIR and COSMO‑RS, and whose dual catalytic/extraction roles were assessed via σ‑potential analysis and esterification tests. High conversion, simple separation, and solvent recyclability demonstrate the superior catalytic and extraction performance of [Im:2PTSA]. © 2018 American Institute of Chemical Engineers AIChE J, 65: 675–683, 2019.

Abstract

The traditional production of long‐chain organic esters like isobutyl isobutyrate (BIBE) suffers from severe problems due to the homogenous catalyst in process and complex system thermodynamics. In this work, an innovative bifunctional deep eutectic solvent (DES) is introduced, playing as both reaction catalyst and extraction solvent, to intensify the esterification process. The DES was formed by imidazole (Im) and p ‐toluenesulfonic acid (PTSA), which was for the first time found acid–base tunable, represented by weak basic DES [3Im:PTSA] and strong acidic DES [Im:2PTSA]. The formation mechanisms of [3Im:PTSA] and [Im:2PTSA] were illustrated by Fourier‐transform infrared spectroscopy (FTIR) and COnductor‐like Screening MOdel for Real Solvent (COSMO‐RS) combined with the Im‐PTSA phase diagram. The dual functions of the acidic [Im:2PTSA] in reactive extraction were evaluated by σ ‐potential analysis and esterification experiments. The high conversion, easy product separation, and good solvent reusability confirm the excellent catalytic and solvent effect of [Im:2PTSA]. © 2018 American Institute of Chemical Engineers AIChE J , 65: 675–683, 2019