| Oxygen is an important raw material in the process of industrial and agricultural production,which is widely used in medical,chemical,energy and military fields.Cryogenic separation and pressure swing adsorption are the main methods to produce oxygen at present.But these methods are high energy consumption and high cost.The membrane separation method has the advantages of low production cost,low energy consumption and small footprint.Among these membrane separation methods,the utilization of perovskite mixed conductor oxygen permeable membrane and metal oxygen permeable membrane to achieve the oxygen separation and purification reveal the excellent development prospect.The perovskite mixed conductor oxygen permeable membrane possess the properties of oxygen ion conductivity and electronic conductivity with the 100%O2-selectivity at high-temperature environments.While the metal oxygen permeable membrane has high oxygen solubility at low and medium temperatures which can use for oxygen separation.Therefore,this paper prepared oxygen-permeable membranes used for different temperatures.One is the La0.6Sr0.4Co1-yFeyO3-?(LSCF)hollow fiber membrane,which can be used for high temperature.Another is the Ag-based metal membrane,which can be used for low and medium temperature conditions.The membranes were characterized and tested,and the main results are as follows:1.La0.6Sr0.4Co0.2Fe0.8O3-?(LSCF6428),La0.6Sr0.4Co0.5Fe0.5O3-?(LSCF6455)and La0.6Sr0.4Co0.8Fe0.2O3-?(LSCF6482)hollow fiber membranes were prepared by phase inversion sintering technology.The effect of internal coagulant and the metal moalr ratio on the micro structure and oxygen permeability for the hollow fiber membranes were investigated.The dense inner and outer surfaces for the LSCF hollow fiber membranes with asymmetric structures can be obtained when used 100wt%H2O as internal coagulant.However,the dense outer layer and porous inner surface for LSCF hollow fiber can be achieved when 70wt%NMP+30wt%EtOH was used as the internal coagulant.The oxygen permeation showed that a higher oxygen permeability can be obtained for the LSCF prepared with the 70wt%NMP+30wt%EtOH as the internal coagulant.When the sweep gas(He)flow rate was 120 mL·min-1,the oxygen permeation fluxes of LSCF6482 and LSCF6455 hollow fiber membranes with 70wt%NMP+30wt%EtOH were 3.47 and 3.34 mL·min-1·cm-2 at 1000?.Compared with the 100wt%H2O as the internal coagulant,the oxygen permeation fluxes increased by 60.6%and 63%,respectively.When the sweep gas(He)flow rate was 120 mL·min-1,the oxygen permeation flux of LSCF6428 hollow fiber membrane prepared with 70wt%NMP+30wt%EtOH as the internal coagulant was 1.89 mL·min-1·cm-2 at 950?.Compared with the 100wt%H2O as the internal coagulant,the oxygen permeation flux increased by 39%.The oxygen permeation fluxes of LSCF hollow fiber membranes increased with the mole ratio of Co/Fe when using 100wt%H2O and 70wt%NMP+30wt%EtOH as an internal coagulant.2.Ag/Al2O3 composite hollow fiber membranes were prepared on the ?-Al2O3 hollow fibers by electroless plating method.The effects of support surface modification,electroless plating temperature,time and times on the preparation of silver composite membranes were investigated.The oxygen permeability was tested.The results showed that the N2 permeation flux of the silver composite membrane supported on the ?-Al2O3 hollow fiber modified by after pencil was significantly decreased.A continuous Ag-based metal membrane could be obtained with the electroless plating time of 4 h and two electroless plating processes at 45?.The oxygen permeation flux gradually increased with increasing the pressure and temperature between 150 and 300?.The oxygen permeation flux and the oxygen-nitrogen selectivity were 2.74×10-2mol·m-2·s-1 and 6 at 300?. |
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