Study On Novel Composite Membrane For Olefins And Paraffins Separation

Separation process using membranes has been considered as one of the most potential processes because of high selectivity, low energy consumption, high efficiency, small volume and less occupation of land area, simple manipulation, none pollution, easy to integrate with other technique. Nowadays, more and more attentions have been paid on separation process of olefins and paraffins by using gas separation membranes' technique. PPESK showed both excellent comprehensive performances and high heat-resistances (T_g 263～305℃), better than other dissoluble engineering plastics. By using PPESK as membrane material, the asymmetric hollow-fiber membranes were formed through dry/wet spinning. The composite membrane for olefins and paraffins separation was successfully prepared by inner-coating PVP and complexing silver ion.First, structure and performance of the PPESK hollow fiber membranes prepared based on the phase separation behavior has been systemically researched. The influences of thermodynamics and dynamic factors to the performance of membranes were studied. Such as types of solvent, contiguity factors of casting, concentrations of polymer, molecular weight of polymer, air gap of the dry/wet spinning process, temperature of casting solution, temperature of coagulant media, bore fluid rate of coagulant media. The structure research and character analysis are made with SEM, gas permeability and separation coefficient. Summary from research, the preparation technology of membranes for olefins and paraffins separation is got.Second, with the inner-coating method, the thinnest-layer coating hollow fiber composite membrane has been prepared using water-soluble polymer PVP as the coating material and complexing silver ion. The influences of PVP concentration, proportion of Ag~+ and C=O, PVP coating time, types of silver salts and transition met als, operational pressure and temperature, were systemically studied using the SEM, IR, gas permeability and separation coefficient.Finally, the influences of second-coating has been studied by using PDMS as the coating material, the best coating treatment is got after the research. Summary from research, the preparation technology of composite membranes for olefins and paraffins separation is got.