title: Dual Phase Membrane for High Temperature CO2 Separation
creator: Lin, Jerry
contributor: United States. Department of Energy.
publisher: Arizona State University
date: 2007-06-30
language: English
description: This project aimed at synthesis of a new inorganic dual-phase
 carbonate membrane for high temperature CO{sub 2} separation. Metal-carbonate
 dual-phase membranes were prepared by the direct infiltration method and the
 synthesis conditions were optimized. Permeation tests for CO{sub 2} and N{sub
 2} from 450-750 C showed very low permeances of those two gases through the
 dual-phase membrane, which was expected due to the lack of ionization of those
 two particular gases. Permeance of the CO{sub 2} and O{sub 2} mixture was much
 higher, indicating that the gases do form an ionic species, CO{sub 3}{sup 2-},
 enhancing transport through the membrane. However, at temperatures in excess
 of 650 C, the permeance of CO{sub 3}{sup 2-} decreased rapidly, while
 predictions showed that permeance should have continued to increase with
 temperature. XRD data obtained from used membrane indicated that lithium iron
 oxides formed on the support surface. This lithium iron oxide layer has a very
 low conductivity, which drastically reduces the flow of electrons to the
 CO{sub 2}/O{sub 2} gas mixture; thus limiting the formation of the ionic
 species required for transport through the membrane. These results indicated
 that the use of stainless steel supports in a high temperature oxidative
 environment can lead to decreased performance of the membranes. This
 revelation created the need for an oxidation resistant support, which could be
 gained by the use of a ceramic-type membrane. Work was extended to synthesize
 a new inorganic dual-phase carbonate membrane for high temperature CO{sub 2}
 separation. Helium permeance of the support before and after infiltration of
 molten carbonate are on the order of 10{sup -6} and 10{sup -10} moles/m{sup 2}
 {center_dot} Pa {center_dot} s respectively, indicating that the molten
 carbonate is able to sufficiently infiltrate the membrane. It was found that
 La{sub 0.6}Sr{sub 0.4}Co{sub 0.8}Fe{sub 0.2}O{sub 3-{delta}} (LSCF) was a
 suitable candidate for the support material. This support material proved to
 separate CO{sub 2} when combined with O{sub 2} at a flux of 0.194 ml/min
 {center_dot} cm{sup 2} at 850 C. It was also observed that, because LSCF is a
 mixed conductor (conductor of both electrons and oxygen ions), the support was
 able to provide its own oxygen to facilitate separation of CO{sub 2}. Without
 feeding O{sub 2}, the LSCF dual phase membrane produced a maximum CO{sub 2}
 flux of 0.246 ml/min {center_dot} cm{sup 2} at 900 C.
subject: Carbonates
subject: Oxidation
subject: Membranes
subject: X-Ray Diffraction
subject: Transport
subject: Oxygen
subject: 36 Materials Science
subject: Feeding
subject: Gases
subject: Stainless Steels
subject: Ionization
subject: Lithium
subject: Mixtures
subject: Electrons
subject: Iron Oxides
subject: Synthesis
subject: Helium
subject: Performance
type: Report
format: Text
identifier: grantno: FG26-02NT41555
identifier: doi: 10.2172/969327
identifier: osti: 969327
identifier: https://digital.library.unt.edu/ark:/67531/metadc927393/
identifier: ark: ark:/67531/metadc927393