Development of matrimid/zeolite 4A mixed matrix membranes using low boiling point solvent

Abstract

Pure matrimid and matrimid/zeolite 4A MMMs were prepared using dichloromethane as a low boiling point solvent combined with control evaporation. The prepared membranes were characterized by FESEM, DSC, TGA, XRD and single gas permeation. FESEM results show that zeolite 4A particles upto 20wt% are homogeneously dispersed and adhered within the polymer without aggregation. The semi-crystalline structure of matrimid is modified by the addition of zeolite 4A. The addition of 4A particles have improved the thermal stability of matrimid in the MMMs as depicted by an increase in the glass transition temperature (Tg) and TGA results. In single gas permeation of N2, H2, O2 and CO2, the effect of zeolite 4A loading, operating temperature, feed pressure and membrane annealing temperature on the separation properties were investigated. As the loading of zeolite 4A is increased, permeability of the membranes increases but at the expense of losing selectivity over N2. The MMMs were annealed at a higher temperature of 250°C for 3h and permeation was carried out as before. Comparison of the results show that the selectivity has been recovered much with a little expense of permeability such that the overall separation properties of the MMMs have improved. The increase of feed pressure from 2 to 8bars has little effect such that the permeability and selectivity of the MMMs can be considered to remains constant. As the operating temperature is increased from 30°C to 70°C, permeability of all the gases increases with N2 by 632%, O2 by 168%, H2 by 162% and CO2 by 62%. The corresponding decrease in the selectivity of gas pairs O2/N2, H2/N2 and CO2/N2 has been observed as 63%, 64% and 78% respectively.