ZIF filled PDMS mixed matrix membranes for separation of solvent vapors from nitrogen

The efficiency of chemical processes can be improved by recovering high value volatile organic compounds (VOCs). For this purpose PDMS based mixed matrix membranes were prepared by using ZIF-7, ZIF-8, ZIF-67, ZIF-71 and ZIF-L as filler for VOC removal from permanent gases. Membranes were characterized by separating pure or mixed solvent vapors of methanol (MeOH), ethanol (EtOH), isopropanol (IPA), n-propanol (PrOH) and ethyl acetate (EtAc) from nitrogen. The total VOC permeability and VOC/N-2 selectivity increased with the incorporation of ZIF-L and ZIF-71, while other ZIFs had limited influence on the separation performance of membranes. ZIF-L (20% wt.)/PDMS membrane exhibited total VOC permeability of 9874 Barrer and VOC/N-2 selectivity of 45 in the separation of ethanol and IPA vapor from nitrogen in a mixture with molar composition of EtOH:IPA:N-2 = 10:10:980. Those values were higher than the permeability and selectivity of pure PDMS by 60 and 33%, respectively. ZIF-L filled PDMS membrane was also used for the separation of multicomponent mixtures and showed total VOC permeability of 10215 Barrer and VOC/N-2 selectivity of 72 in the separation of ethanol, isopropanol, ethyl acetate and water vapor mixture from nitrogen. A method was also proposed to compare the separation performance of membranes with each other and with the performance of membranes reported in the literature based on the dew point temperature of membrane streams.