Regeneration of СO2 Physical Solvents at Elevated Pressures in Gas-Liquid Membrane Contactor

Abstract

In the present work, a membrane contactor with asymmetric flat-sheet poly(vinyltrimethylsilane) (PVTMS) membranes was proposed for the CO2 desorption process from physical solvents at elevated trans-membrane pressures. Different solvents were studied: water, a mixture of polyethylene glycol dimethyl ethers (Genosorb® tradename, Selexol process) and a number of ionic liquids (ILs). The compatibility of PVTMS with physical solvents was evaluated. Thorough sorption and swelling degree tests, FTIR experiments, and solvent permeation study provided insights into PVTMS-solvent interaction and allowed the selection of water, Genosorb® and 1-ethyl-3-methylimidazolium tetrafluoroborate ([Emim][BF4]) as demo solvents for proof-of-concept. CO2 desorption experiments were successfully realized at elevated trans-membrane pressure (10 bar) and different temperatures (30 and 50oC). Increasing the temperature from 30 tо 50oС allowed obtaining higher CO2 desorption flux for all studied solvents. The combination of such parameters as CO2 flux (up to 4.5 m3 (STP)/(m2.h)) and the pressure difference between gas and liquid phases (up to 10 bar) is the best among the available literature data. The detailed investigation of [Emim][BF4] possessing the highest CO2 flux revealed that an increase of CO2 content in [Emim][BF4] provided by increasing absorption pressure up to 20 bar resulted in a signifcant CO2 desorption flux growth up to 7.5 m3 (STP)/(m2.h). Finally, the SEM and EDXS study of membranes after CO2 desorption tests revealed the deposition of particles containing Na and F elements from ionic liquid [Emim][BF4] on the membrane surface. Nevertheless, the same study proved the stability of the membrane morphology structure at elevated transmembrane pressures even up to 20 bar.