Ultra-dehydration of a reactive epichlorohydrin-containing organic mixture using a defect-free thin carbon molecular sieve composite membrane

Abstract

A high-performance thin carbon molecular sieve (CMS) composite membrane was prepared using a drop-coating process for dehydration of a ternary mixture (water/IPA/ECH) by a pervaporation process. The amount of polymer solution dripped onto an alumina disc was varied during the drop-coating process to optimize the formation of the desired active-carbon layer. A defect-free CMS membrane was obtained with a dripped amount of 110 μL, resulting in high gas permeance and optimized selectivity. Furthermore, the CMS membrane was carbonized at 650–800 °C, leading to higher selectivity at elevated temperature with the decrease of gas permeance due to the shrinkage of its graphene-like carbon structure. For separation of the water/IPA/ECH ternary mixture, the highest separation performance (total flux 1.05 kg m⁻² h⁻¹) and separation factor (158 692) were obtained from the CMS membrane carbonized at 700 °C. On the other hand, the CMS membrane showed a unique separation property: the water flux increased with increasing water content in the feed, without remarkable reduction of the separation factor (still >150 000). This is attributed to the rigid pore structure of the CMS membrane, which provides a molecular sieving separation mechanism. Furthermore, increasing the feed-solution temperature led to an increase of both the total flux and separation factor. The CMS membrane performance exhibited the highest separation factor (when compared with other membranes) for dehydration of the water/IPA binary mixture via pervaporation. Moreover, it was much higher than that of a polymeric membrane for dehydration of the water/IPA/ECH ternary mixture.