Effect of zeolite preheat treatment and membrane post heat treatment on the performance of polyvinyl acetate/zeolite 4A mixed matrix membrane

Mixed matrix membranes were prepared from PVAc as a polymer and zeolite 4A as filler by solution casting method using dichloromethane solvent. Zeolilte 4A as a dispersed phase was preheated at 200 °C in one case and calcined at 550 °C in another case. MMMs comprising 15 wt%, 25 wt% and 35 wt% 4A were prepared and compared in both the cases. The cross sections of the membranes were characterized using FESEM. Comparison of the results shows that a better adhesion of zeolite 4A particles to PVAc is achieved in the case of MMMs prepared from calcined zeolite 4A. Comparison of DSC thermograms shows that higher Tg is obtained in the case of MMMs prepared from calcined zeolite 4A. TGA analysis reveals improved thermal stability of the MMMs prepared from calcined zeolite 4A. These results were further verified by FTIR analysis, which shows less amount of adsorbed water in the zeolite 4A, calcined at 550 °C. Single gas permeation of N2, O2, H2 and CO2 was conducted using in house built permeation rig. The obtained results were compared for both the cases and found that the separation properties of gas pairs O2/N2, H2/N2 and CO2/N2 were improved for the calcined zeolite 4A case, both in terms of permeability and selectivity. MMMs developed with 15 wt%, 25 wt% and 35 wt% calcined zeolite 4A were further investigated using membrane annealing temperature of 50 °C, 75 °C and 100 °C. Increasing the annealing temperature was found to improve the selectivity and reduce permeability with 50 °C found optimum for 15 wt%, 75 °C for 25 wt% and 100 °C for the 35 wt% MMMs.