Theoretical and experimental investigation of CO2 capture through choline chloride based supported deep eutectic liquid membranes

The supported liquid membranes (SLMs) provide a feasible solution to global warming by combining their high CO2 interaction with stripping in a continuous and single step process. Herein, deep eutectic solvents (DESs), possible substitutes to ionic liquids (ILs), were used as material to synthesize novel SLMs. The DESs were prepared from choline chloride and urea using three different mole ratios 1:2, 1:1, and 2:1 respectively. The prepared DESs were impregnated into the pores of polyvinylidene fluoride microporous membrane support to form novel DES-SLMs. The DESs-SLMs were tested using pure and mixed gas CO2 permeability as well as CO2/N-2 and CO2/CH4 separation experiments. Density functional theory calculations were performed to get an insight into the interaction of DES with CO2 over N-2/CH4. The complexation energies (Ec) of the DES with CO2, N-2, and CH4 were in the order of -29.3, -9.9, and -13.0 kJ/mol, respectively which reflected the high interaction of CO2 with DES over CH4 and N-2. The DES with choline chloride to urea molar ratio of 2:1 showed the highest CO2 permeability of 45.6 Barrer and corresponding CO2/CH4 and CO2/N-2 selectivity of 61.62 and 78.62, respectively. Finally, a comparison with the supported ionic liquid membranes (SILMs) literature showed that the DESs-SLMs presented comparable CO2 permeability and a significantly high CO2/CH4 selectivity which enabled them to surpass the well-known Robeson's upper bound proving their commercial potential. This reflects that the DES-SLMs are a green strategy for carbon capture which can replace the SILMs in practical applications. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

Supported liquid membranes (SLMs) utilizing deep eutectic solvents (DESs) as material show high CO2 interaction and excellent separation performance, presenting commercial potential for carbon capture. DES-SLMs demonstrate superior CO2 permeability and selective properties, surpassing established benchmarks and proving to be a green strategy for practical applications.