Co-solvent-assisted contra-diffusion assembly of COF membranes for intensifying esterification

Abstract

Pervaporation is an effective technique to improve the conversion of acetic acid in the esterification reaction through in situ removing the product water. In this study, a co-solvent assisted contra-diffusion strategy was used to prepare covalent organic framework (COF) pervaporation membrane on the polyacrylonitrile porous substrate. Fatty alcohol was used as the co-solvent in the organic phase to tune the reaction region. Subsequently, the COFs were formed in the sub-surface of the substrate to form a nanoconfined composite membrane, which was then modified by polyvinyl alcohol through spinning coating. The obtained COF composite membranes were used to in situ remove water during the esterification from acetic acid and ethanol. Consequently, compared with the esterification without pervaporation, the conversion of acetic acid was enhanced from 74% to 90%, which exhibited an excellent intensification for the esterification reaction.