Preparation of Mixed Matrix Membranes Containing ZIF-8 and UiO-66 for Multicomponent Light Gas Separation

Mixed matrix membranes (MMMs) containing zeolitic imidazolite framework-8 (ZIF-8) and UiO-66 as microporous fillers were prepared and evaluated their potential for the separation of a gas mixture produced by a methane reforming process. Hydrothermal synthesis was performed to prepare both the ZIF-8 and UiO-66 crystals, with crystal sizes ranging from 50 to 70 nm for ZIF-8 and from 200 to 300 nm for UiO-66. MMMs were prepared with 15% filler loading for both MMM (ZIF-8) and MMM (UiO-66). MMM (UiO-66) exhibited H2 permeability of 64.4 barrer and H2/CH4 selectivity of 153.3 for single gas permeation, which are more than twice the values that were exhibited by a neat polymer membrane. MMM (ZIF-8) also showed better separation properties than that of a neat polymer membrane with H2 permeability of 27.1 barrer and H2/CH4 selectivity of 123.2. When a gas mixture consisting of 78% Ar/18% H2/4% CH4 flowed into the membranes at 5 bar, the H2 purity increased to as high as 93%. However, no improvement in the mixture gas separation performance was achieved by the MMMs as compared to that of a neat polymer membrane.

Preparation and Gas Permeation of Zeolite 5A Hybrid PR/PVA Based Carbon Membranes

Hybrid carbon membranes were prepared by adopting phenolic resin (PR) and poly(vinyl alcohol) (PVA) blended polymer as precursor, and zeolite 5A as additives through pyrolysis. Thermogravimetric analysis, Fourier transform infrared spectroscopy, scanning electron microscope and gas permeation technique were used to characterize the precursor and carbon membranes. The results have shown that the thermal stability of hybrid polymeric membranes is enhanced by incorporating with 5A and defect-free hybrid carbon membranes were successfully prepared. The H2 permeability of 2125.40 Barrer and the H2/N2 selectivity of 55.9 are achieved when hybrid carbon membranes were fabricated at 700 oC.