A Mixed Ionic And Electronic Conducting Dual-phase Hollow Fiber Membrane Of Oxygen Permeance

The mixed conducting ceramic membrane for oxygen permeation exhibits a good development for its selectivity of 100%,and therefore is widely applied in the field of preparation of pure oxygen and oxygen-enriched combustion as well as the oxidation coupling reaction between methane and ethylene,ethane.But the traditional mixed conducting oxygen permeable membranes show unstable in CO₂ and reducing atmospheres,restricting their application.In this paper,a novel hollow fiber membrane composed of 50wt% fluorite Pr0.1Gd0.1Ce0.8O₂-? and 50wt% spinel CoFe2O4?50PGCO-50CFO?was developed and modified to improve oxygen permeability using a perovskite Ba0.5Sr0.5Co0.8Fe0.2O3-??BSCF?ceramic materials.Their oxygen permeability and stability were studied to further boost CO₂ resistance of dual-phase membrane.First of all,50PGCO-50 CFO dual-phase powders were prepared via a one-pot method.XRD,XPS,TEM and other technologies were utilized to characterize the dual-phase powders.It was found that these powders distribute homogenously and the electric conducting phase and the ionic conducting phase can form a percolative transporting network through the one-pot method preparation powder.Secondly,50PGCO-50 CFO hollow fiber membranes were obtained through a inversion/sintering method.When helium was used as the sweep gas at 1000 oC,the 50PGCO-50 CFO dual-phase hollow fiber membrane achieved the oxygen permeability flux of 0.54mL·min-1 ·cm-2.When pure CO₂ was used as the sweep gas,the oxygen permeability flux reach 0.40mL·min-1 ·cm-2 and remain almost unchanged in 200 h with the membrane having no obvious degradation,indicating a good resistance to carbon dioxide.In order to improve the oxygen permeability,BSCF powders were synthesized via a sol-gel method to modify the membrane surface of 50PGCO-50 CFO hollow fiber.BSCF hollow fiber membranes were also obtained through a phased inversion/sintering method.When helium was used as the sweep gas at 1000 oC,the oxygen permeability flux of BSCF hollow fiber is up to 6.88mL·min-1 ·cm-2.However,when pure CO₂ was used as the sweep gas,the oxygen permeability flux abruptly decreases from 2.72mL·min-1·cm-2 to 1.79mL·min-1 ·cm-2 in the first 40 h.Though the oxygen permeation flux of BSCF was higher than that of the PGCO-CFO double phase film,it was extremely unstable in CO₂ atmosphere,and the oxygen permeation flux rapidly decreased even to zero.As a modification,the high permeable BSCF mixed conductor was coated on the surface of the double-phase 50PGCO-50 CFO hollow fiber membrane,obviously increasing the three phase boundary,and the oxygen permeability increased by 60% in the same operating conditions.