CO2-philic moderate selective layer mixed matrix membranes containing surface functionalized NaX towards highly-efficient CO2 capture†
A functional moderate selective layer mixed matrix membrane (F-MSL-MMM) is a promising candidate to obtain superior separation of industrial gases, compared to commonly mixed matrix membranes. In this work, highly permeable and selective F-MSL-MMMs consisting of a moderate Pebax layer filled with functionalized NaX nano-zeolite over a microstructure PES support layer with the desired operating stability were prepared to investigate the effect of –COOH surface functionalization on the NaX nano-zeolites and to achieve the efficient separation of CO2/N2, CO2/CH4 and CH4/N2 gas mixtures. It was found that modification of the nano-zeolite had significant effects on the morphology and gas separation performance of the F-MSL-MMMs. The incorporation of NaX–COOH nano-zeolites into the polymeric matrix showed superior dispersion, capabilities and interactions over unmodified zeolite without any defects. In addition, based on gas permeation results at various filler loadings and feed pressures, different trends were observed for the permeability and selectivity of the F-MSL-MMMs. Combination of NaX up to 1.5% into the moderate selective layer enhanced the CO2 permeability (187.76 barrer) and CO2/N2 (288.86), CO2/CH4 (57.41) and N2/CH4 (5.03) selectivities at 6 bar.