WO1996009106A1 - Solid-state oxygen ion conductors and oxygen separation device - Google Patents
Solid-state oxygen ion conductors and oxygen separation device Download PDFInfo
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- WO1996009106A1 WO1996009106A1 PCT/NZ1995/000092 NZ9500092W WO9609106A1 WO 1996009106 A1 WO1996009106 A1 WO 1996009106A1 NZ 9500092 W NZ9500092 W NZ 9500092W WO 9609106 A1 WO9609106 A1 WO 9609106A1
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- Prior art keywords
- oxygen
- material according
- gas
- membrane
- ionic
- Prior art date
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- 229910052760 oxygen Inorganic materials 0.000 title claims abstract description 57
- 239000001301 oxygen Substances 0.000 title claims abstract description 56
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 title claims abstract description 55
- 238000000926 separation method Methods 0.000 title claims abstract description 16
- 239000010416 ion conductor Substances 0.000 title description 7
- 239000000463 material Substances 0.000 claims abstract description 72
- 239000012528 membrane Substances 0.000 claims abstract description 46
- 239000007789 gas Substances 0.000 claims abstract description 32
- 229910052709 silver Inorganic materials 0.000 claims abstract description 10
- 229910052787 antimony Inorganic materials 0.000 claims abstract description 6
- 229910052737 gold Inorganic materials 0.000 claims abstract description 5
- 229910052718 tin Inorganic materials 0.000 claims abstract description 5
- 229910052802 copper Inorganic materials 0.000 claims abstract description 3
- 229910052725 zinc Inorganic materials 0.000 claims abstract description 3
- 150000001875 compounds Chemical class 0.000 claims description 21
- 239000000758 substrate Substances 0.000 claims description 13
- 210000004379 membrane Anatomy 0.000 claims 3
- NUVIWMRYHSSRHP-UHFFFAOYSA-N bismuth;oxolead Chemical class [Bi].[Pb]=O NUVIWMRYHSSRHP-UHFFFAOYSA-N 0.000 abstract description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 19
- 238000000034 method Methods 0.000 description 13
- 239000007784 solid electrolyte Substances 0.000 description 9
- 239000011532 electronic conductor Substances 0.000 description 7
- 229910052759 nickel Inorganic materials 0.000 description 7
- 238000000634 powder X-ray diffraction Methods 0.000 description 7
- 238000005259 measurement Methods 0.000 description 6
- 229910052751 metal Inorganic materials 0.000 description 6
- 239000002184 metal Substances 0.000 description 6
- 239000000203 mixture Substances 0.000 description 6
- 229910000108 silver(I,III) oxide Inorganic materials 0.000 description 5
- 238000005245 sintering Methods 0.000 description 5
- QPLDLSVMHZLSFG-UHFFFAOYSA-N Copper oxide Chemical compound [Cu]=O QPLDLSVMHZLSFG-UHFFFAOYSA-N 0.000 description 4
- WMWLMWRWZQELOS-UHFFFAOYSA-N bismuth(iii) oxide Chemical compound O=[Bi]O[Bi]=O WMWLMWRWZQELOS-UHFFFAOYSA-N 0.000 description 4
- 239000000919 ceramic Substances 0.000 description 4
- 239000004020 conductor Substances 0.000 description 4
- 239000000843 powder Substances 0.000 description 4
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 3
- WATWJIUSRGPENY-UHFFFAOYSA-N antimony atom Chemical group [Sb] WATWJIUSRGPENY-UHFFFAOYSA-N 0.000 description 3
- -1 bismuth-lead-oxide compound Chemical class 0.000 description 3
- 238000007865 diluting Methods 0.000 description 3
- 239000010931 gold Substances 0.000 description 3
- 229910044991 metal oxide Inorganic materials 0.000 description 3
- 150000004706 metal oxides Chemical class 0.000 description 3
- 150000002739 metals Chemical class 0.000 description 3
- 239000002243 precursor Substances 0.000 description 3
- 239000004332 silver Substances 0.000 description 3
- 230000007704 transition Effects 0.000 description 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 2
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical group [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 2
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 2
- 230000000903 blocking effect Effects 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000005229 chemical vapour deposition Methods 0.000 description 2
- 150000001860 citric acid derivatives Chemical class 0.000 description 2
- 238000010276 construction Methods 0.000 description 2
- GNTDGMZSJNCJKK-UHFFFAOYSA-N divanadium pentaoxide Chemical compound O=[V](=O)O[V](=O)=O GNTDGMZSJNCJKK-UHFFFAOYSA-N 0.000 description 2
- 239000002019 doping agent Substances 0.000 description 2
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 2
- 238000011065 in-situ storage Methods 0.000 description 2
- 239000008188 pellet Substances 0.000 description 2
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
- 238000006467 substitution reaction Methods 0.000 description 2
- QTBSBXVTEAMEQO-UHFFFAOYSA-M Acetate Chemical compound CC([O-])=O QTBSBXVTEAMEQO-UHFFFAOYSA-M 0.000 description 1
- 229910002651 NO3 Inorganic materials 0.000 description 1
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 229910004369 ThO2 Inorganic materials 0.000 description 1
- 150000001242 acetic acid derivatives Chemical class 0.000 description 1
- 239000003570 air Substances 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- 239000011324 bead Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 229910052797 bismuth Inorganic materials 0.000 description 1
- WUKWITHWXAAZEY-UHFFFAOYSA-L calcium difluoride Chemical group [F-].[F-].[Ca+2] WUKWITHWXAAZEY-UHFFFAOYSA-L 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 150000004649 carbonic acid derivatives Chemical class 0.000 description 1
- 229910010293 ceramic material Inorganic materials 0.000 description 1
- 239000004035 construction material Substances 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- RKTYLMNFRDHKIL-UHFFFAOYSA-N copper;5,10,15,20-tetraphenylporphyrin-22,24-diide Chemical compound [Cu+2].C1=CC(C(=C2C=CC([N-]2)=C(C=2C=CC=CC=2)C=2C=CC(N=2)=C(C=2C=CC=CC=2)C2=CC=C3[N-]2)C=2C=CC=CC=2)=NC1=C3C1=CC=CC=C1 RKTYLMNFRDHKIL-UHFFFAOYSA-N 0.000 description 1
- 230000003111 delayed effect Effects 0.000 description 1
- 238000000151 deposition Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000003085 diluting agent Substances 0.000 description 1
- 229910001882 dioxygen Inorganic materials 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- VQCBHWLJZDBHOS-UHFFFAOYSA-N erbium(III) oxide Inorganic materials O=[Er]O[Er]=O VQCBHWLJZDBHOS-UHFFFAOYSA-N 0.000 description 1
- 238000007656 fracture toughness test Methods 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 239000011872 intimate mixture Substances 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 238000000608 laser ablation Methods 0.000 description 1
- 229910052745 lead Inorganic materials 0.000 description 1
- 229910001960 metal nitrate Inorganic materials 0.000 description 1
- 239000011533 mixed conductor Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000004570 mortar (masonry) Substances 0.000 description 1
- 150000002823 nitrates Chemical group 0.000 description 1
- 239000000615 nonconductor Substances 0.000 description 1
- 230000037361 pathway Effects 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 239000002798 polar solvent Substances 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 238000004626 scanning electron microscopy Methods 0.000 description 1
- 238000007569 slipcasting Methods 0.000 description 1
- 238000010583 slow cooling Methods 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 238000007582 slurry-cast process Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000010345 tape casting Methods 0.000 description 1
- 229910052716 thallium Inorganic materials 0.000 description 1
- 238000005382 thermal cycling Methods 0.000 description 1
- 238000005979 thermal decomposition reaction Methods 0.000 description 1
- 238000002207 thermal evaporation Methods 0.000 description 1
- ZCUFMDLYAMJYST-UHFFFAOYSA-N thorium dioxide Chemical compound O=[Th]=O ZCUFMDLYAMJYST-UHFFFAOYSA-N 0.000 description 1
- 229910052720 vanadium Inorganic materials 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G31/00—Compounds of vanadium
- C01G31/006—Compounds containing, besides vanadium, two or more other elements, with the exception of oxygen or hydrogen
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/22—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by diffusion
- B01D53/228—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by diffusion characterised by specific membranes
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
- B01D71/02—Inorganic material
- B01D71/024—Oxides
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B13/00—Oxygen; Ozone; Oxides or hydroxides in general
- C01B13/02—Preparation of oxygen
- C01B13/0229—Purification or separation processes
- C01B13/0248—Physical processing only
- C01B13/0251—Physical processing only by making use of membranes
- C01B13/0255—Physical processing only by making use of membranes characterised by the type of membrane
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G29/00—Compounds of bismuth
- C01G29/006—Compounds containing, besides bismuth, two or more other elements, with the exception of oxygen or hydrogen
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G30/00—Compounds of antimony
- C01G30/002—Compounds containing, besides antimony, two or more other elements, with the exception of oxygen or hydrogen
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G53/00—Compounds of nickel
- C01G53/006—Compounds containing, besides nickel, two or more other elements, with the exception of oxygen or hydrogen
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
- C04B35/453—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on zinc, tin, or bismuth oxides or solid solutions thereof with other oxides, e.g. zincates, stannates or bismuthates
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2325/00—Details relating to properties of membranes
- B01D2325/26—Electrical properties
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B2210/00—Purification or separation of specific gases
- C01B2210/0043—Impurity removed
- C01B2210/0046—Nitrogen
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2002/00—Crystal-structural characteristics
- C01P2002/50—Solid solutions
- C01P2002/52—Solid solutions containing elements as dopants
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2002/00—Crystal-structural characteristics
- C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
- C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2002/00—Crystal-structural characteristics
- C01P2002/80—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70
- C01P2002/88—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70 by thermal analysis data, e.g. TGA, DTA, DSC
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/40—Electric properties
Definitions
- the invention comprises modified bismuth-lead-oxide compounds having ionic conductivity or mixed ionic and electronic conductivity useful for forming oxygen-permeable membranes or similar in particular for use in oxygen separation devices to separate oxygen from gases containing oxygen such as air.
- Solid-state oxygen-ion conductors and mixed ionic/electronic conductors often referred to as solid electrolytes have been studied for a number of years. Although they hold great promise for the development of new technologies in the form of oxygen pumps, fuel cells, electrochemical reactors and similar, their practical application has been limited due to the high operational temperatures required.
- oxygen-ion conductors currently in development for commercial use are based on the fluorite structure. They include ZrO 2 stabilised with Y 2 O 3 (YSZ), ThO 2 /CeO,/HfOJZrO, solid solutions and d-phase Bi 2 O 3 stabilised with Er 2 O 3 and Y 2 O 3 or SrO.
- YSZ is chemically very stable and exhibits high ionic conductivity at temperatures in the vicinity of 1000°C. but its conductivity is significantly reduced at lower temperatures.
- Oxygen pumps in which a thin oxygen-permeable membrane is used to separate oxygen from other gases, require materials with a very high oxygen-ion conduction.
- oxygen ion conductors used in them meet two further requirements: they should exhibit mixed ionic/electronic conductivity, ideally with the ionic and electronic components of the conductivity being of similar magnitude, to avoid the need for surface electrodes; and they should be able to be used at temperatures significantly below 1000°C.
- the present invention provides modified BPO materials having improved ionic conductivities or ionic and electronic conductivities, and/or improved mechanical strength and toughness.
- Some BPO materials of the invention are mixed ionic and electronic conductors with high ionic and electronic conductivity and are therefore particularly useful for forming oxygen- permeable membranes or similar and for use in oxygen separation devices to separate oxygen from gases containing oxygen such as air.
- the invention comprises materials of formula:
- P and Q are each Ag, Au, Cu, Sb, Sn, Zn. Ni. Tl or V, or any combination thereof;
- One preferred material of the invention is off stoichiometric BPO of formula Bi g Pb a O I7 approx where 2.0 ⁇ a ⁇ 8.0, preferably 5.5 ⁇ a ⁇ 8.0, and more preferably 6.0 ⁇ a ⁇ 7.0. These materials are believed to in general have higher ionic conductivities than the basic BPO compound.
- Another preferred compound of the invention is Ag-substituted BPO of formula Bi g . x Ag x Pb a ..Ag,O I7 approx where 0.0 ⁇ x and/or y ⁇ 1.0 and 0 ⁇ x+y and 5.0 ⁇ a ⁇ 6.5. and more preferably 0.0 ⁇ x and/or y ⁇ 0.3 and most preferably 0.0 ⁇ x and/or y ⁇ 0.1. These materials are believed to have in general higher ionic conductivity than the basic BPO compound and also exhibit significant mixed ionic and electronic conductivity.
- Another preferred compound of the invention is antimony-substituted BPO of formula Bi 8 . x Sb x Pb a .
- Another preferred compound of the invention is nickel-doped BPO of formula Bi 8 . x Ni x Pb 5 . y Ni y O, 7 approx where 0.0 ⁇ x and/or y ⁇ 4.0 and 0 ⁇ x+y, and a is about (5/8)(8-x)+y and more preferably 0.5 ⁇ x and/or y ⁇ 2.5, and most preferably 1.0 ⁇ x and/or y ⁇ 2.0.
- These materials are believed to in general have mixed conductivities and show improved thermal expansion characteristics.
- These materials are believed to have in general higher ionic conductivity than the basic BPO compound and also exhibit significant mixed ionic and electronic conductivity.
- Figures la and lb are powder x-ray diffraction patterns for Bi g Pb 5 O 17 at room temperature (in
- Figure 2 is a room temperature powder x-ray diffraction pattern for the off-stoichiometric Pb- rich material Bi 8 Pb 6 5 O, 8 5 ;
- Figure 3 is a powder x-ray diffraction pattern for the antimony substituted material
- Figure 4 is a powder x-ray diffraction pattern for the tin substituted material BigSi-o 5 Pb 4 5 O 17 ;
- Figure 5 is a powder x-ray diffraction pattern for silver doped Bi 8 Pb 5 Ag 0 15 O 17 ;
- Figure 6 is a plot comparing the inverse temperature dependence of the conductivity of the tin substituted materials Bi 72 Pb 5 Sno 8 O
- Figure 7 is a plot comparing the inverse temperature dependence of the conductivity of the
- Figure 8 is a plot showing the dependence of the electric potential developed across a membrane of the silver doped material Bi g Pb 5 Ag 0 ,0 17 on the log of the oxygen partial pressure
- Figures 9a and 9b are plots showing the dependence of the mechanical properties of the antimony substituted materials Bi 8.x Sb ⁇ Pb 5 O 17 on the dopant concentration x - Figure 9a plots
- Figure 10 is a schematic diagram of an oxygen separation device utilising an oxygen ion conducting membrane
- Figure 11 is a schematic of an improved oxygen separation device
- Figure 12 is a powder x-ray diffraction pattern for the nickel doped material Bi 8 Pb 5 Ni 2 54 O ]7 ;
- Figure 13 is a plot showing the inverse temperature dependence of the conductivity of the nickel doped material Bi 8 Pb 5 Ni 2 54 O 17 ;
- Figure 14 is a plot showing the dependence of the relative ionic (t-) and electronic (t e ) components of the conductivity of nickel doped materials Bi 8 Pb 5 Ni 2 O 17 on the dopant concentration z;
- Figure 15 is a plot comparing the thermal expansion behaviour of the nickel doped material
- Materials of the invention can be formed by -any known method for forming ceramic oxide compounds.
- precursor materials such as metals, metal oxides, metal carbonates and/or metal nitrates are intimately mixed in stoichiometric quantities and sintered in air or oxygen or oxygen containing atmosphere to form a ceramic.
- Sintering temperatures should normally be in the range 500 - 650 °C.
- the compounds may be formed by
- nitrate, acetate and/or citrates or similar - in this method nitrate, acetate and/or citrate salts are dissolved in a polar solvent and the solvent is evaporated to form a dry powder which is then sintered to form the ceramic material.
- a polar solvent e.g. benzyl alcohol
- an intimate mixture of metals and/or metal oxides and stoichiometric BPO may be formed and sintered.
- materials may be deposited by chemical vapour deposition onto a permeable substrate.
- Another technique is to deposit a metallic precursor film onto an appropriate substrate and oxidise the film in situ by sintering in an oxygen-containing atmosphere.
- Each of these compounds was prepared using stoichiometric mixtures of Bi 2 O 3 .
- the starting materials were ground together with an agate mortar and pestle, pressed into pellets then baked at 500 - 620 °C for between 8 and 16 hours in air.
- the pellets were reground, re-pelletised and sintered at 500-620°C in air for between 8 and 16 hours.
- Powder x-ray powder diffraction and scanning electron microscopy measurements were made to determine the phase purity of the materials.
- Thermal expansion, hardness and three-point fracture toughness measurements were made to characterise the physical properties of the materials.
- Ionic and electronic conductivities were measured by a number of techniques including AC impedance analysis in a temperature controlled cell with platinum or gold electrodes, DC conduction measurements using gold blocking and non blocking electrodes, and oxygen concentration cell measurements.
- Sb substituted BPO of formula Bi 8.x Sb x Pb 5 O ]7 forms a single phase material for low Sb concentrations as shown in Figure 3. It has significantly increased mechanical strength and hardness as antimony substitution increases as shown in Figures 9a and 9b. Sn can be substituted for both Bi and Pb to form a single phase material as evidenced in Figure 4. Sn-doping is beneficial to the mechanical strength of the material and there is no significant drop in the conductivity of materials as shown in Figure 6.
- Ag substituted BPO of formula Bi g Pb 5 Ag x O 17 formed by grinding stoichiometric BPO with 0.75 micron Ag powder and sintering in air at a temperature between 540 and 565 °C exhibits mixed conductivity.
- the addition of Ag also increases th conductivity of the material in the BCC phase above that found in pure stoichiometric BPO a shown in Figure 7.
- the Ag-doped BPO is a mixed ionic/electronic conductor as shown by Figur 8, as can be seen by the reduced concentration cell voltage measurements.
- the mixed ionic/electronic conductivity and reduced operating temperature are properties particularly suited to the requirements of an oxygen separation membrane.
- Ni to BPO at levels of 0.3-5% by weight forms a single phase material as shown by Figure 12, with conductivity similar to that of BPO in the temperature range 590-650°C as shown in Figure 13.
- This material is a mixed ionic/electronic conductor, as determined by concentration cell measurements and AC/DC conductivity measurements.
- the mixed ionic/electronic conductivity is suited to the requirements of an oxygen separation membrane.
- the ratio of ionic to electronic conductivity can be varied as shown in Figure 14. This property is a particularly desirable feature as it allows the ionic/electronic conductivity to be tuned for particular applications. For example, in an oxygen separation membrane the ratio of ionic
- Ni-doped material at doping levels as low as 0.3% by weight
- the thermal expansion of Ni-doped material is significantly more linear than that of pure BPO across the temperature range 20-620°C - see Figure 15, and is similar to those of potential support and construction materials such as stainless steel and MgO. This simplifies the task of developing a suitable supported membrane structure which is not over-stressed as a result of thermal cycling.
- Pb rich BPO according to the formula Bi g Pb a O, 7 sintered in air at 610°C, was prepared as described above, with non-stoichiometric starting compositions. As shown in Figure 2 the compound forms a single phase material across a wide compositional range 2.5 ⁇ a ⁇ 8.0, with the same structure as pure BPO. Across the whole compositional range the ionic conductivity of the material is high. The maximum conductivity for the off-stoichiometric compound Bi 8 Pb 6 5 O ]8 5 was almost twice that for pure BPO produced with the same sintering conditions.
- compounds of the invention having high ionic and electronic conductivity such as Ag and Ni doped BPO may be used to form oxygen permeable membranes.
- oxygen permeable membranes There are a number of compounds of the invention having high ionic and electronic conductivity such as Ag and Ni doped BPO may be used to form oxygen permeable membranes.
- a solid electrolyte membrane may be free-standing and consist solely of the conductor formed by pressing, rolling, tape-casting of a slurry or slip-casting or other techniques.
- a solid electrolyte may be mixed with other materials such as ceramics or metals in the form of beads, needles, powders, meshes or other morphologies and formed into a membrane by such techniques.
- the solid electrolyte may
- the solid electrolyte may b embedded in a porous substrate or mixed with another material which is then further treated to for a porous substrate.
- the solid electrolyte membrane may be deposited on a prepared porous o oxygen-permeable substrate or it may be pre-formed and then attached to a porous substrate.
- Th solid electrolyte may also be formed by depositing or embedding or attaching a metallic precurso material onto or into a porous or oxygen-permeable substrate and then oxidising the metalli
- the substrate material may be an electrical insulator or alternatively ca itself be an oxygen-ion conductor or an electronic conductor or a mixed ionic/electronic conductor.
- Membranes may in addition include electronically conducting electrode materials on one or both of their surfaces.
- the solid electrolyte membranes may be in planar, tubular or corrugated geometry or any other geometry that permits a first gas to contact one side o the membrane and a second gas to contact the other side of the membrane.
- Oxygen permeable membranes formed from compounds of the invention may be used in oxygen separation devices.
- Figure 10 shows a simple oxygen separation device which consists of two chambers 1 and 2 separated by an oxygen-permeable membrane 3 formed as described above.
- a first gas such as air or other oxygen containing gas (the supply gas), preferably equal to or greater than 10% oxygen concentration, is supplied to the first chamber 1 (the supply chamber) via inlet 4, as indicated by arrow A, and hence to the first surface of the membrane 3. Oxygen undergoes the reaction
- the transport of electrons to support the ionisation/deionisation process can be via the membrane's internal electronic conductivity or by means of an electronic conductor mixed into the membrane or via a conductive support structure, or externally by means of surface electrodes and an external conductive pathway.
- a second gas containing a higher relative concentration of oxygen (the yield gas) can be pumped from the second chamber 2 via outlet 5, as indicated by arrow B.
- a pressure difference is maintained between the two chambers such that the oxygen partial pressure of the supply gas is greater than the oxygen partial pressure of the yield gas.
- Oxygen depleted gas exits the supply chamber via outlet 6, as indicated by arrow C.
- oxygen partial pressure differential across the membrane in order to maximise the chemical potential which drives the oxygen across the membrane. For example, if air is the supply gas and pure oxygen is pumped from the other side of the membrane, a pressure ratio of 5: 1 is required before oxygen will flow across the membrane. If the supply gas is at one atmosphere a certain thickness of membrane will be required in order to withstand the pressure differential. If air is supplied at higher pressures, or the yield chamber is pumped to lower pressures, a thicker, stronger membrane will be required - negating the advantages of a higher oxygen partial pressure differential. However, if a diluting gas is supplied to the yield chamber at sufficient rate and pressure, the total pressures across the membrane can be equalised while a large oxygen partial pressure is maintained.
- a thinner membrane may be utilised without the risk of rupture.
- Requirements for the diluent gas are that it should be non- reactive with oxygen at the temperatures and pressures found in the separation device and that it should be simple to separate it from the yield oxygen.
- examples of the diluting gas include, but are not limited to, water and carbon-dioxide.
- the pressure differential across the membrane may be minimised by controlling the pressure of the supply gas or the diluting gas, or by limiting the rate at which gas is pumped from the yield chamber or by use of a one way valve which allows the contents of the yield chamber to leak across to the supply chamber.
- Figure 17 shows this arrangement.
- the device also includes an inlet 7 through which the dilutant gas enters the yield chamber, as indicated by arrow D and an optional one-way pressure relief system 8, connecting the two chambers which allows oxygen and the dilutant gas to flow from the yield chamber to the supply chamber.
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Abstract
A material of the formula: Bi8-xPxPba-yQyOb, wherein P and Q are each Ag, Au, Cu, Sb, Sn, Zn, Ni, Tl, or V, or any combination thereof, 2.0 « a « 8.0, 0.0 « x < 4.0, 0.0 « y < 3.5, 17 « b « 19, and either x ¸ 0 or y ¸ 0, or a ¸ 4.5 - 5.5. The invention comprises modified bismuth-lead-oxide compounds having ionic conductivity or mixed ionic and electronic conductivity useful for forming oxygen-permeable membranes or similar in particular for use in oxygen separation devices to separate oxygen from gases containing oxygen such as air.
Description
SOLID-STATE OXYGEN ION CONDUCTORS & OXYGEN SEPARATION DEVICE
FIELD OF INVENTION
The invention comprises modified bismuth-lead-oxide compounds having ionic conductivity or mixed ionic and electronic conductivity useful for forming oxygen-permeable membranes or similar in particular for use in oxygen separation devices to separate oxygen from gases containing oxygen such as air.
BACKGROUND
Solid-state oxygen-ion conductors and mixed ionic/electronic conductors often referred to as solid electrolytes have been studied for a number of years. Although they hold great promise for the development of new technologies in the form of oxygen pumps, fuel cells, electrochemical reactors and similar, their practical application has been limited due to the high operational temperatures required.
The majority of oxygen-ion conductors currently in development for commercial use are based on the fluorite structure. They include ZrO2 stabilised with Y2O3 (YSZ), ThO2/CeO,/HfOJZrO, solid solutions and d-phase Bi2O3 stabilised with Er2O3 and Y2O3 or SrO. YSZ is chemically very stable and exhibits high ionic conductivity at temperatures in the vicinity of 1000°C. but its conductivity is significantly reduced at lower temperatures.
Oxygen pumps, in which a thin oxygen-permeable membrane is used to separate oxygen from other gases, require materials with a very high oxygen-ion conduction. The economics of this technique can be significantly enhanced if the oxygen ion conductors used in them meet two further requirements: they should exhibit mixed ionic/electronic conductivity, ideally with the ionic and electronic components of the conductivity being of similar magnitude, to avoid the need for surface electrodes; and they should be able to be used at temperatures significantly below 1000°C.
In recent years there has been a major ongoing search to discover oxygen-ion conductors which have ionic conductivities similar to that of YSZ, but at significantly lower temperatures. Honnart et al (Solid State Ionics, 9-10, 1981) have reported high ionic conductivity in the bismuth-lead-oxide compound Bi8Pb5O17 (BPO) at temperatures above 590°C. However this material does not have a high electronic conductivity and lacks mechanical strength and toughness.
SUMMARY OF INVENTION
The present invention provides modified BPO materials having improved ionic conductivities or ionic and electronic conductivities, and/or improved mechanical strength and toughness. Some BPO materials of the invention are mixed ionic and electronic conductors with high ionic and electronic conductivity and are therefore particularly useful for forming oxygen- permeable membranes or similar and for use in oxygen separation devices to separate oxygen from gases containing oxygen such as air.
In broad terms in one aspect the invention comprises materials of formula:
Bi8.xPxPba.yQyOb where:
P and Q are each Ag, Au, Cu, Sb, Sn, Zn. Ni. Tl or V, or any combination thereof;
2.0 < a < 8.0,
0.0 < x < 4.0,
0.0 < y < 3.5,
17 < b < 19. and either x ≠ O or y ≠ O or a ≠ 4.5-5.5.
One preferred material of the invention is off stoichiometric BPO of formula BigPbaOI7 approx where 2.0 < a < 8.0, preferably 5.5 < a < 8.0, and more preferably 6.0 < a < 7.0. These materials are believed to in general have higher ionic conductivities than the basic BPO compound.
Another preferred compound of the invention is Ag-substituted BPO of formula Big.xAgxPba..Ag,OI7 approx where 0.0 < x and/or y < 1.0 and 0 < x+y and 5.0 < a < 6.5. and more preferably 0.0 < x and/or y < 0.3 and most preferably 0.0 < x and/or y < 0.1. These materials are believed to have in general higher ionic conductivity than the basic BPO compound and also exhibit significant mixed ionic and electronic conductivity.
Another preferred compound of the invention is antimony-substituted BPO of formula Bi8.xSbxPba.ySbyOI7 approx where 0.0 < x and/or y < 0.5 and 0 < x+y, and 4.5 < a < 5.5 and more preferably 0.0 < x or y < 0.1. These materials are believed to have improved mechanical toughness and strength.
Another preferred compound of the invention is tin-substituted BPO of formula Big.xSnxPb5Sn,O17 approλ where 0.0 < x and/or y < 2.5 and 0 < x+y, and 4.5 < a < 5.5, and more preferably 0.0 < x < 0.5, and y = 0. These materials are all believed to have improved mechanical toughness and strength.
Another preferred compound of the invention is nickel-doped BPO of formula Bi8.xNixPb5.yNiyO,7 approx where 0.0 < x and/or y < 4.0 and 0 < x+y, and a is about (5/8)(8-x)+y and more preferably 0.5 < x and/or y < 2.5, and most preferably 1.0 < x and/or y < 2.0. These materials are believed to in general have mixed conductivities and show improved thermal expansion characteristics.
Another preferred compound of the invention is copper-substituted BPO of formula Bi8Pba Cu,OI7 appro where x = 0, and 4.0 < y < 5.5 and a is about (5/8)(8-3x)+y. These materials are believed to have in general higher ionic conductivity than the basic BPO compound and also exhibit significant mixed ionic and electronic conductivity.
Note that in certain of the above-described compounds, the formula Bi8.xPxPba.yQyOb can be simplified. For example: if a = (5/8)(8-x)+y then, by making the substitutions z = x + y and P=Q(=R), the formula can be rewritten as: Bi8Pb5RA
where b is approximately 17. This corresponds to stoichiometric BPO doped with the metal R or with the oxide of R. This simpler nomenclature will be used in the description of materials produced by doping with a single metal or metal oxide.
BRIEF DESCRIPTION OF THE FIGURES
This invention will be further described with reference to the accompanying figures, wherein:
Figures la and lb are powder x-ray diffraction patterns for BigPb5O17 at room temperature (in
the tetragonal β2 phase) and at 600 °C (in the body centred cubic φ phase) respectively (prior art);
Figure 2 is a room temperature powder x-ray diffraction pattern for the off-stoichiometric Pb- rich material Bi8Pb6 5O,8 5;
Figure 3 is a powder x-ray diffraction pattern for the antimony substituted material
Bi7 ,Sb0 8Pb5O17;
Figure 4 is a powder x-ray diffraction pattern for the tin substituted material BigSi-o 5Pb4 5O17;
Figure 5 is a powder x-ray diffraction pattern for silver doped Bi8Pb5Ag0 15O17;
Figure 6 is a plot comparing the inverse temperature dependence of the conductivity of the tin substituted materials Bi72Pb5Sno 8O|7 and
with Bi8Pb5Oπ;
Figure 7 is a plot comparing the inverse temperature dependence of the conductivity of the
silver doped material Bi8Pb5Ag0 2O9 with Bi8Pb5O,7;
Figure 8 is a plot showing the dependence of the electric potential developed across a membrane of the silver doped material BigPb5Ag0 ,017 on the log of the oxygen partial pressure
ratio across the membrane;
Figures 9a and 9b are plots showing the dependence of the mechanical properties of the antimony substituted materials Bi8.xSbλPb5O17 on the dopant concentration x - Figure 9a plots
the modulus of rupture and Figure 9b plots the hardness;
Figure 10 is a schematic diagram of an oxygen separation device utilising an oxygen ion conducting membrane;
Figure 11 is a schematic of an improved oxygen separation device;
Figure 12 is a powder x-ray diffraction pattern for the nickel doped material Bi8Pb5Ni2 54O]7;
Figure 13 is a plot showing the inverse temperature dependence of the conductivity of the nickel doped material Bi8Pb5Ni2 54O17;
Figure 14 is a plot showing the dependence of the relative ionic (t-) and electronic (te) components of the conductivity of nickel doped materials Bi8Pb5Ni2O17 on the dopant concentration z; and
Figure 15 is a plot comparing the thermal expansion behaviour of the nickel doped material
BigPb5Ni2 54017 with that of Bi8Pb5O17 heated and cooled at 3°C/min. - both materials were prepared by sintering at 610°C and slow cooling in air.
DETAILED DESCRIPTION
Materials of the invention can be formed by -any known method for forming ceramic oxide compounds. Typically precursor materials such as metals, metal oxides, metal carbonates and/or metal nitrates are intimately mixed in stoichiometric quantities and sintered in air or oxygen or oxygen containing atmosphere to form a ceramic. Sintering temperatures should normally be in the range 500 - 650 °C. Alternatively the compounds may be formed by
thermal decomposition of nitrates, acetates and/or citrates or similar - in this method nitrate, acetate and/or citrate salts are dissolved in a polar solvent and the solvent is evaporated to form a dry powder which is then sintered to form the ceramic material. Alternatively again
an intimate mixture of metals and/or metal oxides and stoichiometric BPO may be formed and sintered. Again materials may be deposited by chemical vapour deposition onto a permeable substrate. Another technique is to deposit a metallic precursor film onto an appropriate substrate and oxidise the film in situ by sintering in an oxygen-containing atmosphere.
Examples 1-7:
The table below shows a range of modified BPO compounds of the invention, according to
the formula Big.„P.Pba.. Q.Ob, or the simplified formula Bi8Pb5R20I7, which have been
investigated, by their properties:
Example Formula Composition Description
Bi8.xSnxPb >1 177 a aDpDprrooxx x=0.2,0,5,1.5,5.0 Single phase for all compositions. Improved Mechanical Properties
2 Bi8PbJ_. Sn. O17 ipproλ y=0.2,0.5,1.5,4.0,8.0 Single phase for all compositions. Improved Mechanical Properties. 3
x=0.3,0.8,1.5,3.0 Single phase for x < 1.5. Improved Mechanical Properties. 4 BigPb5Cu7O1 177aaπpDprrooxx z=0.11,0.37,0.75,0.84, Mixed phase, mixed ionic/electronic
1.87,2.62,3.75 conductor 5 Bi8Pb5NizO17 approx z=0.15,0.51, 1.52,2.54, Single phase, mixed ionic/electronic 5.08,15.2 conductor 6 Bi8Pb,Vz zO 17approx z=0.1,0.33,0.98 Single phase, high conductivity for x=0.1, mixed phases for x>0.1
7 BigPb5ZnzO17 approx z=0.11,0.37,1.1 Single phase, high conductivity. 8 Bi8Pb5AgzO,7approx 2=0.003,0.01,0.03,0.1, Single phase, mixed ionic/electronic 0.3,1.0,3.0 conductor.
Each of these compounds was prepared using stoichiometric mixtures of Bi2O3. PbO and one or more of Zn, SbO, Sn2O3, Ag2O, Ag, Ni, V2O5, and CuO or stoichiometric mixtures of pure
Bi8Pb5O17 and one of Ag2O, Ag, Ni, or CuO. The starting materials were ground together with an agate mortar and pestle, pressed into pellets then baked at 500 - 620 °C for between 8 and 16 hours in air. The pellets were reground, re-pelletised and sintered at 500-620°C in air for between 8 and 16 hours. A number of analysis techniques were then used on the materials: Powder x-ray powder diffraction and scanning electron microscopy measurements were made to determine the phase purity of the materials. Thermal expansion, hardness and three-point fracture toughness measurements were made to characterise the physical properties of the materials. Ionic and electronic conductivities were measured by a number of techniques including AC impedance analysis in a temperature controlled cell with platinum or gold electrodes, DC conduction measurements using gold blocking and non blocking electrodes, and oxygen concentration cell measurements.
Sb substituted BPO of formula Bi8.xSbxPb5O]7, forms a single phase material for low Sb concentrations as shown in Figure 3. It has significantly increased mechanical strength and hardness as antimony substitution increases as shown in Figures 9a and 9b. Sn can be substituted for both Bi and Pb to form a single phase material as evidenced in Figure 4. Sn-doping is beneficial to the mechanical strength of the material and there is no significant drop in the conductivity of materials as shown in Figure 6.
Ag substituted BPO of formula BigPb5AgxO17, formed by grinding stoichiometric BPO with 0.75 micron Ag powder and sintering in air at a temperature between 540 and 565 °C exhibits mixed conductivity. The material is single phase at low doping levels as shown in Figure 5. However the
transition to the highly conductive BCC phase on heating, and the delayed transition back to th lower conductivity phase on cooling, occur at reduced temperatures in this material. As little a 0.3% Ag by weight (z = 0.1) is sufficient to reduce the transition temperatures by as much as 10° below that found in undoped BPO as evidenced in Figure 7. The addition of Ag also increases th conductivity of the material in the BCC phase above that found in pure stoichiometric BPO a shown in Figure 7. The Ag-doped BPO is a mixed ionic/electronic conductor as shown by Figur 8, as can be seen by the reduced concentration cell voltage measurements. The mixed ionic/electronic conductivity and reduced operating temperature are properties particularly suited to the requirements of an oxygen separation membrane.
The addition of Ni to BPO at levels of 0.3-5% by weight forms a single phase material as shown by Figure 12, with conductivity similar to that of BPO in the temperature range 590-650°C as shown in Figure 13. This material is a mixed ionic/electronic conductor, as determined by concentration cell measurements and AC/DC conductivity measurements. The mixed ionic/electronic conductivity is suited to the requirements of an oxygen separation membrane. By varying the level of Ni doping in the material, the ratio of ionic to electronic conductivity can be varied as shown in Figure 14. This property is a particularly desirable feature as it allows the ionic/electronic conductivity to be tuned for particular applications. For example, in an oxygen separation membrane the ratio of ionic
to electronic conductivity should be approximately 1 :1. The thermal expansion of Ni-doped material (at doping levels as low as 0.3% by weight) is significantly more linear than that of pure BPO across the temperature range 20-620°C - see Figure 15, and is similar to those of potential support
and construction materials such as stainless steel and MgO. This simplifies the task of developing a suitable supported membrane structure which is not over-stressed as a result of thermal cycling.
Example 8:
Pb rich BPO according to the formula BigPbaO,7 sintered in air at 610°C, was prepared as described above, with non-stoichiometric starting compositions. As shown in Figure 2 the compound forms a single phase material across a wide compositional range 2.5 < a < 8.0, with the same structure as pure BPO. Across the whole compositional range the ionic conductivity of the material is high. The maximum conductivity for the off-stoichiometric compound Bi8Pb6 5O]8 5 was almost twice that for pure BPO produced with the same sintering conditions.
As stated compounds of the invention having high ionic and electronic conductivity such as Ag and Ni doped BPO may be used to form oxygen permeable membranes. There are a number of
morphologies and methods of construction for oxygen-permeable membranes. For example a solid electrolyte membrane may be free-standing and consist solely of the conductor formed by pressing, rolling, tape-casting of a slurry or slip-casting or other techniques. A solid electrolyte may be mixed with other materials such as ceramics or metals in the form of beads, needles, powders, meshes or other morphologies and formed into a membrane by such techniques. The solid electrolyte may
form a contiguous surface deposited on the surface of a porous or oxygen-permeable supporting substrate, by means such as laser-ablation, evaporative deposition, chemical vapour deposition, slip-
spraying or any other technique commonly used to prepare ceramics. The solid electrolyte may b embedded in a porous substrate or mixed with another material which is then further treated to for a porous substrate. The solid electrolyte membrane may be deposited on a prepared porous o oxygen-permeable substrate or it may be pre-formed and then attached to a porous substrate. Th solid electrolyte may also be formed by depositing or embedding or attaching a metallic precurso material onto or into a porous or oxygen-permeable substrate and then oxidising the metalli
precursor in-situ to form the solid electrolyte. Other techniques or methods of construction ar possible so long as the membranes are gas-tight so far as possible. Where the membrane i supported by a substrate the substrate material may be an electrical insulator or alternatively ca itself be an oxygen-ion conductor or an electronic conductor or a mixed ionic/electronic conductor.
Membranes, as described above, may in addition include electronically conducting electrode materials on one or both of their surfaces. The solid electrolyte membranes may be in planar, tubular or corrugated geometry or any other geometry that permits a first gas to contact one side o the membrane and a second gas to contact the other side of the membrane.
Oxygen permeable membranes formed from compounds of the invention may be used in oxygen separation devices. Figure 10 shows a simple oxygen separation device which consists of two chambers 1 and 2 separated by an oxygen-permeable membrane 3 formed as described above. The
inlet chamber, membrane and/or the supply gas are heated to a temperature at which the membrane is highly diffusive to oxygen. The operating temperature is preferably between 500 and 650°C.
A first gas such as air or other oxygen containing gas (the supply gas), preferably equal to or greater than 10% oxygen concentration, is supplied to the first chamber 1 (the supply chamber) via inlet 4, as indicated by arrow A, and hence to the first surface of the membrane 3. Oxygen undergoes the reaction
O2 + 4e" → 2O2-
at the first surface of the membrane and passes across the membrane in the form of O2" ions to the second surface of the membrane where it returns to the atmosphere of the second chamber 2 (the yield chamber) as molecular oxygen after the reaction
2O2- - O2 + 4e
In the case of a mixed ionic/electronic conductor such as the BPO compounds of the invention the transport of electrons to support the ionisation/deionisation process can be via the membrane's internal electronic conductivity or by means of an electronic conductor mixed into the membrane or via a conductive support structure, or externally by means of surface electrodes and an external conductive pathway.
A second gas containing a higher relative concentration of oxygen (the yield gas) can be pumped from the second chamber 2 via outlet 5, as indicated by arrow B. A pressure difference is maintained between the two chambers such that the oxygen partial pressure of
the supply gas is greater than the oxygen partial pressure of the yield gas. Oxygen depleted gas exits the supply chamber via outlet 6, as indicated by arrow C.
A limitation in any practical oxygen separation device utilising oxygen-ion conducting membranes results from the competing aims of using the thinnest possible membrane, in order to minimise the resistance of the membrane to ionic conductivity, and maintaining the largest
possible oxygen partial pressure differential across the membrane, in order to maximise the chemical potential which drives the oxygen across the membrane. For example, if air is the supply gas and pure oxygen is pumped from the other side of the membrane, a pressure ratio of 5: 1 is required before oxygen will flow across the membrane. If the supply gas is at one atmosphere a certain thickness of membrane will be required in order to withstand the pressure differential. If air is supplied at higher pressures, or the yield chamber is pumped to lower pressures, a thicker, stronger membrane will be required - negating the advantages of a higher oxygen partial pressure differential. However, if a diluting gas is supplied to the yield chamber at sufficient rate and pressure, the total pressures across the membrane can be equalised while a large oxygen partial pressure is maintained. A thinner membrane may be utilised without the risk of rupture. Requirements for the diluent gas are that it should be non- reactive with oxygen at the temperatures and pressures found in the separation device and that it should be simple to separate it from the yield oxygen. Examples of the diluting gas include, but are not limited to, water and carbon-dioxide.
The pressure differential across the membrane may be minimised by controlling the pressure of the supply gas or the diluting gas, or by limiting the rate at which gas is pumped from the yield chamber or by use of a one way valve which allows the contents of the yield chamber to leak across to the supply chamber. Figure 17 shows this arrangement. The same reference numbers indicate the same parts as in Figure 16 except that the device also includes an inlet 7 through which the dilutant gas enters the yield chamber, as indicated by arrow D and an optional one-way pressure relief system 8, connecting the two chambers which allows oxygen and the dilutant gas to flow from the yield chamber to the supply chamber.
The foregoing describes the invention including a preferred form thereof. Alterations and modifications as will be obvious to those skilled in the art are intended to be incorporated within the scope hereof.
Claims
A material of formula:
Bi8 xP-Pba.yQyOb
wherein:
P and Q are each Ag, Au, Cu, Sb, Sn, Zn, Ni, Tl, or V, or any combination thereof,
2.0 < a < 8.0,
0.0 < x < 4.0,
0.0 < y < 3.5,
17 < b < 19, and
either x ≠ 0 or y ≠ 0, or a ≠ 4.5 - 5.5.
2. A material according to claim 1 wherein 2.0 < a < 4.5 or 5.5 < a < 8.0 and x and y = 0.
3. A material according to claim 2 wherein 5.5 < a < 8.0.
4. A material according to claim 2 wherein 6.0 < a < 7.0.
5. A material according to claim 1 wherein P and/or Q is Sb, and 0.0 < x < 0.5 and 0.0 < y
< 0.5 and 0 < x+y.
6. A material according to claim 5 wherein 4.5 < a < 5.5, and 0.0 < y < 0.1.
7. A material according to claim 1 wherein P and/or Q are Sn, 4.5 < a < 5.5, 0.0 < x < 2.5, and 0.0 < y < 2.5 and 0 < x+y.
8. A material according to claim 7 wherein 4.5 < a < 5.5, 0.0 < x < 0.5, and y = 0.0.
9. A material according to claim 7 wherein 4.5 < a < 5.5, x = 0, 0.0 < y < 0.5, and x = 0.0.
10. A material according to claim 1 wherein P and/or Q are Ag, 5.0 < a < 6.5, 0.0 ≤ x ≤ 1.0, and 0.0 < y < 1.0 and 0 < x+y.
11. A material according to claim 10 wherein 0.0 < x < 0.3, and 0.0 < y < 0.3.
12. A material according to claim 10 wherein 0.0 < x < 0.1, and 0.0 < y < 0.1.
13. A material according to claim 10 wherein a is about (5/8)(8-x)+y.
14. A material according to claim 11 wherein a is about (5/8)(8-x)+y.
15. A material according to claim 12 wherein a is about (5/8)(8-x)+y.
16. A material according to claim 1 wherein P and/or Q are Ni, 0.0 < x < 4.0, and 0 < y < 4.0 and 0 < x+y.
17. A material according to claim 16 wherein 0.5 < x < 2.5 and 0.5 < y < 2.5.
18. A material according to claim 17 wherein 1.0 < x < 2.0 and 1.0 < y < 2.0.
19. A material according to claim 16 wherein a is about (5/8)(8-x)+y.
20. A material according to claim 17 wherein a is about (5/8)(8-x)+y.
21. A material according to claim 18 wherein a is about (5/8)(8-x)+y.
22. A material according to claim 1 wherein Q is Cu, x = 0.0 and 4.0 < y < 5.5.
23. A compound according to claim 22 wherein a = (5/8)(8-3x).
24. An ionic and/or electronic conducting membrane comprising a compound according to any one of claims 1 to 23.
25. A membrane according to claim 24 comprising said compound deposited onto, or attached to the surface of a porous supporting substrate, or embedded or impregnated into a porous substrate or mixed with another material which has been further treated to form a porous substrate.
26. An oxygen separation apparatus comprising two chambers separated by a membran according to either of claims 24 and 25, means to supply an oxygen containing gas to one chambe and means to remove a second gas containing a higher concentration of oxygen from the othe chamber, with a pressure difference maintained between the two chambers such that the oxyge partial pressure of the first gas is greater than the oxygen partial pressure of the second gas.
27. An oxygen separation apparatus according to claim 26 including means to supply a diluen gas to said other chamber at such a pressure that the oxygen partial pressure of the first gas i greater than the oxygen partial pressure of the second gas, but the total pressure difference between the two chambers is reduced.
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AU36213/95A AU3621395A (en) | 1994-09-21 | 1995-09-22 | Solid-state oxygen ion conductors and oxygen separation device |
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NZ264161 | 1994-09-21 | ||
NZ26416194 | 1994-09-21 |
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Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0001598A1 (en) * | 1977-10-14 | 1979-05-02 | Saft | Electrochemical generator with aprotic solvent comprising as cathodic material a derivative of bivalent lead oxide |
EP0127134A1 (en) * | 1983-05-30 | 1984-12-05 | Société Anonyme dite SAFT | Active positive material for a high specific energy electrochemical generator |
EP0467238A1 (en) * | 1990-07-16 | 1992-01-22 | Sumitomo Electric Industries, Limited | Method of preparing bismuth superconductor |
FR2695569A1 (en) * | 1992-09-14 | 1994-03-18 | Air Liquide | Electrochemical cell and its use for the electrochemical separation or extraction of oxygen. |
-
1995
- 1995-09-21 WO PCT/NZ1995/000092 patent/WO1996009106A1/en active Application Filing
- 1995-09-22 AU AU36213/95A patent/AU3621395A/en not_active Abandoned
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0001598A1 (en) * | 1977-10-14 | 1979-05-02 | Saft | Electrochemical generator with aprotic solvent comprising as cathodic material a derivative of bivalent lead oxide |
EP0127134A1 (en) * | 1983-05-30 | 1984-12-05 | Société Anonyme dite SAFT | Active positive material for a high specific energy electrochemical generator |
EP0467238A1 (en) * | 1990-07-16 | 1992-01-22 | Sumitomo Electric Industries, Limited | Method of preparing bismuth superconductor |
FR2695569A1 (en) * | 1992-09-14 | 1994-03-18 | Air Liquide | Electrochemical cell and its use for the electrochemical separation or extraction of oxygen. |
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