Study On The Morphology And Olefin/Paraffin Permeation Properties Of Metal Doped Polymeric Membranes

Based on the gaseous olefin/paraffin separation application background, PSf/SPSf-Na films were prepared using blend polymers of polysulfone and sodium type sulfonated polysulfone. PSf/SPSf-Ag and PSf/SPSf-Pd films were obtained by exchanging and reducing PSf/SPSf-Na films. PSf/PEO-AgBF₄/SR asymmetric hollow fiber membranes were prepared using double coating method.Deposited"metal particle layer"exists on one film surface, while there is no layer on another surface, and metal particles noncontinuously distribute inside the film. Silver particle is larger than palladium particle when the PSf/SPSf-Ag and PSf/SPSf-Pd films have the same IEC value. Metal particles have chemical valences between zero and that of corresponding metal salts.Permeation experiments on ethylene and ethane show that permeation properties of ethylene are enhanced in PSf/SPSf-Ag and PSf/SPSf-Pd films and permeability coefficients of ethylene are increased with the increase of film IEC. However, permeation properties of ethane don't change much. Metal additives in PSf/SPSf-Ag films have a greater influence on the permeation properties of ethylene than that in PSf/SPSf-Pd films do. Mechanisms and models of olefin/paraffin permeation in metal doped polymeric films were put forward. On the one hand, gas molecules are activated due to the adsorption, especially complex adsorption, on the metal particle surface, which will lead to a higher permeability coefficient. On the other hand, gas diffusion resistance across the film will probably increase when the content of metal composition in the film is relatively higher. These two influences on permeability coefficient compete during the course of gas permeation. As to olefin, the activation effects are stronger than the diffusion resistance effects, which lead to a higher permeability coefficient of...