Research On Supported Palladium Modified Polyimide-silica Hybrid Membrane For Separating H₂ Selectively

As an important raw material and clean energy, the need for hydrogen is growing tremendously with the rapid development in the field of petrochemical engineering. Separation and recycle hydrogen from the related reaction system has been a research focus. In the present work, the combination of organic-inorganic hybrid membrane's high permeace flux and palladium's permeselectivity to hydrogen were systematically studied.In this paper, transition layer ceramic membrane of titania supported on kieselguhr-mullite (K-M) ceramic membrane substrate was prepared by sol impregnating method. Supported polyimide-silica (PI-SiO2) hybrid membrane was synthesized by sol-gel technique. Palladium was induced to modify PI-SiO2 hybrid membrane in two ways: The first way is sol-gel technique, Palladium modified polyamide acid-silica (Pd-PAA-SiO2) sol was plated on the TiO2/K-M ceramic membrane substrate, and then followed by imidisation and reduction. The second way is that palladium was plated electrolessly on the supported PI-SiO2 hybrid membrane. The IR, SEM, BET, XRD and gas permeability measurement techniques were used to characterize each membrane's material structure, micro-surface, pore distribution, crystalline configuration and the permeability of CH4, H2O, H2, CO2, CO and N2.The combined results showed that each membrane is satisfied with well morphology, linked tightly between each membrane layer, narrow pore-size distribution. In the Pd modified PI-SiO2 hybrid membrane, bond conjunctions were generated between PI and SiO2, and Palladium exited in the hybrid membrane in a metallic state with good distribution, which can modify the micro-pore structure of PI-SiO2 membrane. The results obtained from the gases permeability measurements show that gas permeace on supported TiO2/K-M transition membrane is co-controlled by Poiseuille viscosity flow and Knudsen diffusion. Supported PI-SiO2 hybrid membrane has good separation coefficients of H2/N2, CO2/N2, H2O/N2. N2 permeace flux of the supported palladium modified PI-SiO2 hybrid membrane synthesized by sol-gel is 0.2×10-7mol/(m2·Pa·s), and the separation coefficient of H2/N2 is above 500. The separation coefficient of H2/N2 on the hybrid membrane synthesized by electroless plating declined to 100, because it was destroyed by the reaction which happened on the PI-SiO2 membrane surface.