Selective CO2 capture through microporous Tb(BTC)(H2O).(DMF)1.1 MOF as an additive in novel MMMs fabricated from Matrimid® 5218

Abstract

Mixed matrix membranes (MMMs) fabricated with porous metal organic frame works have enhanced the separation performance of polymer membranes. In this context microporous 3D Tb(BTC)(H2O).(DMF)1.1 MOF was incorporated into pristine Matrimid® with loadings of 10, 20 and 30 weight percentages. SEM micrographs indicated proper distribution of filler in the Matrimid and no interfacial voids were observed. Gas permeation studies evidenced the CO2 permeability to be 13.2 (82.32%) and 18.34 (153.31%) and 25.86 Barrer for 10, 20 and 30 wt% MMMs respectively. The 257.18% increase in CO2 permeability of 30 wt% MMM than methane was attributed to polar nature of CO2, its smaller kinetic diameter, condensability, and larger solubility within the Matrimid matrix than non – polar and larger CH4 molecules.Addition of filler influenced the pure gas selectivity of all MMMs positively. So, 30 wt% MMM exhibited the highest 58.04% increase in selectivity that was attributed to the molecular sieving property of the filler and the size exclusion phenomena as followed by CH4 and CO2. The high values of mixed and pure gas selectivity were obtained upon increasing filler concentration. The commercial applicability of these MMMs was tested by checking their selectivity under increased feed concentrations of CO2 and checking permeability and selectivities at high temperatures. The study depicted that, competitive sorption of gases, prevalence of size exclusion phenomena and polymer chains relaxation at higher temperature were responsible for low gas selectivity. MMM with 30 wt% of MOF lied close to Robson’s Upper bound 2008 that indicated its good separation potential.

Keywords

• Metal organic frame works
• Matrimid®5218
• Mixed – matrix membranes
• Filler concentration
• Permeability
• CO2/CH4 selectivity