Experimental, modeling and Aspen Plus simulation of different configurations of membrane separation systems for highly loaded CO2 selective Pebax 1657-ZIF-8 membrane

Abstract

ZIF-8 powder was synthesized and entered with concentrations from 10 to 60 wt.% in Pebax 1657 matrix modified with Di-butyl-methylimidazolium fluoride (DBMF) ionic liquid. SEM, XRD and 13C-NMR analysis were applied for the characterization of particles and mixed matrix membranes (MMMs). The results of 13C-NMR analysis suggested that there are possible new carbon-carbon bonds at particle-polymer interface. The CO2/CH4 mixed gas test results showed that the utilization of high concentrations of ZIF-8 in Pebax 1657 matrix was effective. MMMs containing 60 wt. % and 30 wt. % of ZIF-8 showed the highest (24.4) and lowest (12) CO2/CH4 selectivity among all synthesized MMM and pure polymeric samples respectively. The results of Microsoft Excel/Aspen Plus modeling and simulation showed that the increase in membrane area, number of membrane modules and the pressure difference across membranes showed performance advantages for the single-step with permeate recycling (SiSRP) and double step with retentate recycling (DoSRR) configurations of separation systems. The highest CH4 recovery was observed for the double-step with permeate recycling (DoSPR) configurations when the feed was nearly pure CH4. The temperature rise showed a notable increasing effect on permeates flow rates of both gases leading to the deterioration of separation effectiveness of all configurations. The analysis of membrane thickness on gas permeation showed that the synthesis of thinner membranes leads to better separation performance utilizing permeant or/and retentate recycle lead to more purified products.