Cobalt-coordinated chitosan membranes to separate a dimethyl carbonate and methanol mixture by pervaporation

Details

Supervisors

Luis Alconero, Patricia ; Gerin, Patrick A.

Faculty

Faculté des bioingénieurs

Degree label

Master [120] : bioingénieur en chimie et bioindustries, à finalité spécialisée

Abstract

Dimethyl carbonate, an eco-friendly organic component, has gained much attention in the chemical sector due to its wide range of applications. However, its separation from its precursor in its production process, methanol, can be challenging as it forms an azeotrope. Pervaporation offers an energy efficient solution for separating azeotropes and was used within this thesis with the aim to separate the dimethyl carbonate/methanol mixture using a chitosan-based membrane. Chitosan is a biopolymer derived from biowaste that has shown to be effective in the separation of the aforementioned mixture. However, with growing interest in this field, it has been demonstrated that inserting inorganic material within the biopolymer membrane can significantly enhance its separation performance. The aim of this thesis was to develop a cobalt formate metallic organic framework within the chitosan membranes, as this crystalline framework could act as a size-selective sieve for methanol. Unfortunately, in-situ crystal nucleation and growth did not occur. The evidence gathered in this work demonstrates that cobalt-coordinated chitosan membranes were formed. Metal ion coordinated chitosan had never been used in pervaporation. However, our new aim was to investigate the separation performances of these novel membranes. Our work shows that the presence of cobalt ions within the biopolymer served as a crosslinker, increasing the membrane’s stability. The presence of cobalt also enhanced the membrane’s hydrophilicity, increasing its selectivity towards methanol. The 20% cobalt loaded membranes that were developed managed to invert the molar fraction ratio found in the feed. A 11:89 methanol:dimethyl carbonate molar ratio in the feed resulted in a 89:11 ratio in the permeate. These results are similar to what has been found when metal organic frameworks are present within chitosan membranes to separate this mixture. Nonetheless, the production process of the cobalt-coordinated chitosan membranes is more facile and generates less waste, resulting in an effective and more sustainable solution for the separation of dimethyl carbonate/methanol mixtures that are rich in dimethyl carbonate.