Preparation of PDA@PEBA2533 membranes for C3H6/N2 separation
In order to recover C3H6 from off-streams of polypropylene plants,PDA@PEBA2533 membranes with stronger affinity for C3H6 were prepared by depositing polydopamine(PDA)layers on the surface of poly(ether-block-amide)copolymer(PEBA2533)membranes using the dip-spin method invented by our group.The synthesized PDA particles and membranes were characterized by scanning electron microscopy(SEM)and X-ray diffraction(XRD).The effect of PDA deposition time on the membrane morphology,structure and separation performance was investigated,as well as the effect of operating conditions such as temperature and pressure on the membrane separation performance.The separation effect of C3H6/N2 mixture with different C3H6 concentration on PDA@PEBA2533 membrane and the long-time separation stability of the membrane were explored.The results showed that the deposition of PDA on the surface of PEBA2533 membranes effectively improved the separation performance of the membranes.When the deposition time was not less than 24h,a continuous PDA layer was formed.With the increase of deposition time,the membrane layer gradually thickened,the gas permeance first increased and then decreased,and the selectivity continued to rise.The membrane with 24h of deposition time indicated the best separation performance among the membranes prepared.Increasing the operating temperature and pressure,the permeance of both C3H6 and N2 increased,while the C3H6/N2 selectivity decreased.Increasing the concentration of C3H6 in the gas mixture,the permeance and selectivity of PDA@PEBA2533 membrane for C3H6 increased and then decreased.On the PDA@PEBA2533 membrane showing the best separation performance,the C3H6 permeance increased from 8.25GPU to 71.42GPU and the C3H6/N2 selectivity decreased from 22.92 to 10.14 for a gas mixture with 20%of C3H6 when the temperature was increased from 0℃ to 50℃ at 0.2MPa.The membrane was stable for C3H6/N2 separation during a 130h experiment.The membrane as synthesized had advantages over other membranes for separating C3H6/N2 mixtures.
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