MXPA97010396A - Solid electrolyte membrane with mechanically improving components and catalytically poro improvers - Google Patents

Abstract

A solid electrolyte ion transport membrane comprising a matrix material that conducts at least one type of ion, such as oxygen ion, and at least one component that is physically distinguishable from the matrix material and that improves at least less the mechanical properties, the catalytic properties and / or the concrete behavior of the matrix material. The component is present in a manner that avoids the continuous electronic conductivity through the component from one side of the membrane to the other. A porous coating is preferably placed on the membrane to improve the speed of surface reactions involving the gaseous species

Description

SOLID ELECTROLYTE MEMBRANE WITH MECHANICALLY IMPROVING COMPONENTS AND CATALYTICALLY POROUS IMPROVERS FIELD OF THE INVENTION This invention relates to electrolyte ion transport membrane compositions and more particularly to such membranes having one or more components that improve the mechanical properties, the catalytic properties and / or the concretion behavior of the membranes.

RIGHTS OF THE GOVERNMENT OF THE UNITED STATES This invention was made with the support of the Government of the United States according to Cooperation Agreement No. 70NANB5H1065 granted by the National Institute of Standards and Technology. The Government of the United States has certain rights in the Invention.

BACKGROUND OF THE INVENTION Solid electrolyte ion transport membranes have significant potential for the separation of oxygen from oxygen-containing gas streams. Of particular interest are the mixed conductor materials which conduct both oxygen and electron ions and which can therefore be operated in a pressure-driven mode without the use of external electrodes. Composite ceramic mixed conductive membranes comprising multiple phase mixtures of an electronically conductive material and an oxygen ion conducting material are described by T.J. Mazanec et al. In U.S. Patent No. 5, 306,411 for electrochemical reactors and partial oxidation reactions. M. Liu et al discloses in U.S. Patent No. 5,478,444 composite blended conductive materials containing oxygen ion conducting materials such as bismuth oxide and electronically conductive materials. Real blended conductors, exemplified by perovskites such as La.2Sr.8CoOx, La2Sr.eFeOx, La2Sr.8Fe and others, are materials that have intrinsic conductivity for both electrons and ions. Some of these materials possess the highest known oxygen ion conductivity and also rapid surface exchange kinetics. Although there is great potential for these materials in gas separation applications, there are some disadvantages in their use. A common problem of most ceramics is their fragility and low mechanical resistance in tension which makes it difficult to manufacture large elements such as tubes and deploy them in commercial systems of high reliability.

Yamamoto et al. They reported the microcracking in LaCoOx specified in "Perovskite-type Oxides as Oxygen Electrodes for Hioh Fuel Cells, Solid State Lonics" 22241-46 (1987). Such microcracks are probably related to structural transformations during concretion and frequently occur in perovskites. The vacancy concentration in most ion-transport membrane materials such as perovskites is a function of the partial pressure of oxygen in the surrounding gas. Since the unit cell size depends on the vacant concentration, in many ion transport membrane materials the volume of the unit cell increases as the PO2 is reduced. For example, in the perovskites the size of the unit cell ABO3 is increased as the partial pressure of the oxygen on the anode or the permeate side is reduced. The change in the size of the unit cell gives rise to a coefficient of expansion composition in addition to the thermal coefficient of the expansion. Composition gradients in the materials therefore give rise to mechanical stresses that could result in failures. This often requires close control of the atmosphere during ignition, shutdown or processing B Fu et al reported in Material for Solid Oxide Fuel Cells, Proc 3rd Intl Symp on Sohd Fuell Cells, SC Singhal, De The Electrochem Soc, Vol 93-4 276-282 (1993) "that microaggregation was a problem in the perovskites of Y? -X (Sr or Ca) xMnO3 due to either the change in polymorphic symmetry of high temperature, or coefficients of thermal expansion highly anisotropic of the system.The efforts made to avoid this problem were not successful.It was found that high levels of doping with Sr or Ca (x >; 0.3) can reduce microcracking, although it resulted in poor performance for fuel cell cathode applications, apparently due to lower physical properties including reduced ionic conductivities. Due to the difficulties described above, the manufacture of perovskite tubes has required carefully controlled, complex process steps that sometimes involve a sophisticated, controlled atmosphere concretion process. This increases the cost and complexity of manufacturing and could result in problems during the transient operation of manufactured items that involve temperature, atmospheric or compositional changes. It is highly desirable to minimize the sensitivity of the ion transport membrane to the ambient atmosphere. Likewise, many of these materials have very high coefficients of thermal expansion (for example, LaLxSrxCoOs is approximately 20 x 10.6 / ° C), which give rise to high thermal stress during processing and operation, which is why it frequently results in the failure of those materials.

In summary, the use of composite blended conductors in the prior art is confined mostly to materials comprising multiple phase mixtures of oxygen ion conductors and electronic conductors. The first objective in the prior art was to introduce electronic conductivity into the ion conductor. In general, this requires that the second electronically conductive phase be present in more than 30% up to 35% by volume when it is randomly distributed to allow operation over the filtration limit. Shen et al states in column 6 of each of the US Patents 5,616,223 and 5,624,542 which in a silver system obtains a continuous phase of about 20 to about 35% by volume while the silver / palladium alloys require "slightly larger amounts" Shen et al prefer to have the electronic conductive phase present in quantities approximately 1 to 5 percent larger to obtain high ambipolar conductivity The '542 patent discloses ceramic / metallic materials having a predominantly electronic conductive metallic phase which provides improved mechanical properties compared to a predominantly ionic conductive ceramic phase alone. Compound volume superconductors have been synthesized to achieve the desirable physical properties and high superconducting characteristics of Tc. Wong et al., in U.S. Patent No. 5,470,821 discloses composite superconducting materials with ceramic matrices. continuous superconducting ca and elemental metal. The elemental metal is located within the interstices between the crystalline grains to increase the transport current density. The transport of oxygen is driven by the partial pressure of oxygen in the gas streams. The Nernst potential is developed internally and drives the flow of oxygen vacancies against the ionic resistance of the electrolyte as described in Prasad et al. Patent No. 5,547,494 to Prasad et al entitled "Staged Electrolyte MembraneP which is incorporated to the present by reference Generally, thin electrolyte films are desirable because the ideal oxygen flow is inversely proportional to their thickness.Therefore, thinner films lead to higher oxygen fluxes, reduced area, lower operation and lower oxygen pressure differentials through the electrolytes Also, when the anode side of the membrane is purged with a reactive gas, such as methane or hydrogen, the oxygen activity on the anode side is reduced significantly, leading to increased oxygen flow through the membrane in this way, however, as and it increases the oxygen flow, the surface resistance for transport becomes more pronounced and finally the general resistance for transport dominates. The surface resistance arises from several mechanisms involved in the conversion of an oxygen molecule in the gas phase to oxygen ions in the glass lattice and vice versa. Even for dense transport membranes, surface kinetics on the cathode or anode side may limit the flow of oxygen through the membrane. Yasutake Teraoka et al reported solid state gas separation membranes formed by depositing a dense mixed conductive oxide layer on a porous mixed conductive support in "Jour.Ceram.Soc. Japan International De.p Vol. 97, No. 4 , pp. 58-462 and No. 5, pp.523-529 (1989) .The relatively thick porous mixed conductive support provides mechanical stability for the relatively fragile, thin, dense mixed conductive layers, considering the thickness of the dense layer, the The authors expected that the oxygen flow would increase by a factor of ten for the composite thin-film membrane compared to a dense mixed conductor disk., obtained an increase in oxygen flow less than a factor of two using the thin film membrane. U.S. Patent No. 4,791,079 discloses catalytic ceramic membranes consisting of two layers, an impermeable mixed ion layer and electronic conductive ceramic and an ion conducting ceramic layer containing porous catalyst. The preferred composition for the ceramic layer is zirconia stabilized with about 8 to 15 mol percent of calcium, triazone, scandia, magnesia and / or mixtures thereof. U.S. Patent No. 5,240,480 discloses solid state membranes composed of multiple layers, comprising a porous layer of multiple component metal oxide and a dense layer, which are capable of separating oxygen from oxygen-containing gas mixtures. at high temperature. U.S. Patent No. 5,569,633 discloses surface catalyzed multiple layer ceramic membranes consisting of a dense mixed conductive multiple component metal oxide layer and a catalysed metal or metal oxide coating on the feed side (air). ) to increase the oxygen flow. The catalytic coating on both sides does not improve the oxygen flow.

OBJECTS OF THE INVENTION It is therefore an object of the invention to provide an improved solid electrolyte ion transport membrane having improved mechanical properties. It is a further object of this invention to provide such a membrane which minimizes microglasses during their manufacture.

Even another object of this invention is to provide the membrane that does not require a special atmosphere during its processing or operation. A further object of this invention is to provide such a membrane that adapts to changes in temperature and atmosphere. It is also an object of the invention to provide the solid electrolyte ion transport membrane that substantially decreases the limitations imposed by surface kinetics and / or chemical kinetics to obtain high oxygen flow.

It is a further object of the present invention to provide such a membrane having a modified surface which has an improved catalytic effect on the membrane.

OBJECTS OF THE INVENTION This invention comprises a solid electrolyte ion transport membrane having a matrix material which conducts at least one type of ion, preferably oxygen ions, and at least one component that is physically different from the matrix material and which improves the mechanical properties, the catalytic properties and / or the concrete behavior of the matrix material. The component is present in a manner that avoids continuous electronic conductivity through the membrane.

In a preferred embodiment, the matrix material is a mixed conductor that exhibits both electronic and oxygen ion conductivity. The component is preferably a metal such as silver, palladium, or a mixture thereof. In other embodiments, the component is a ceramic or other electrically non-conductive material. This invention also comprises a solid electrolyte ion transport membrane compound for separating a gaseous species from a gas mixture in which the compound has a dense matrix material and a porous coating. The dense membrane has a first surface and a second surface, and is comprised of a matrix material that conducts at least one type of ions and, at least one membrane component that is physically distinguishable from the matrix material, improves at least less one of the mechanical properties, the catalytic properties and the concretion behaviors of the matrix material and is present in a manner that avoids the continuous electronic conductivity through the membrane component. The porous coating is placed on at least one of the first and second surfaces to improve the velocity of the surface reactions involving the gaseous species. As used herein, the term "double phase" refers to the combination of a phase that conducts at least one type of ion and a phase comprising the component.

As used herein, the term "ion transport material" is interchangeable with "matrix material".

BRIEF DESCRIPTION OF THE DRAWINGS Those skilled in the art will devise other objects, features and advantages from the following description of the preferred embodiments and the accompanying drawings, in which: Figs. 1 to 1d are enlarged photographs of the membranes having different amounts of components in accordance with the present invention; Fig. 2 is a graph of fracture stresses of the four membranes shown in Figs. 1 a to 1 d; Fig. 3 is a graph of the diffraction results of X-rays for the membranes of Figs. 1a and 1d; Fig. 4 is a graph of oxygen transport at different temperatures for the membranes of Figs 1a and 1d; Fig. 5 is a graph of the oxygen flow at different levels of reactive purge for the membranes of Figs. 1a and 1d; Fig. 6a is an electronic scanning micrograph of another membrane in accordance with the present invention; Fig. 6b is a dispersed spectrum of surface energy of the membrane shown in Fig. 6a; FIG. 7 is an enlarged cross-sectional view of a solid electrolyte ion transport membrane having a porous crystalline layer coating for increasing surface reactions in accordance with the present invention; and Fig. 8 is an enlarged cross-sectional view of a solid electrolyte ion transport membrane composite having a porous crystalline layer coating on both sides of the dense membrane to increase surface reactions and, in which one of the porous coatings is placed on the porous support to increase the mechanical strength of the compound. DETAILED DESCRIPTION OF THE INVENTION This invention can be accomplished by a solid electrolyte ion transport membrane comprising a matrix material that conducts at least one type of ion, preferably oxygen ions, and at least one component that is physically different from the matrix material and which improves the mechanical properties, the catalytic properties and / or the concretion behavior of the matrix material. The component is present in a manner in which it avoids the continuous electronic conductivity through the component across the membrane. The invention therefore relates to a composite material, of multiple phase, preferably comprised of a first phase of mixed conductor such as a perovskite and a second component phase that can prevent micro-cracking during manufacturing, eliminate special atmospheric control during processing and operation, and improve mechanical properties, thermal cycling capacity, cycling capacity of atmosphere and / or surface exchange rates over those of the mixed conductor phase alone. The invention introduces a second phase of suitable component within the mixed conductor to establish a composition with improved mechanical properties and, preferably, with improved catalytic properties, without sacrificing its oxygen transport performance. This second phase can release the composition and other stresses generated during the concretion, inhibit the propagation of micro cracks in the mixed conductor phase and thus improve the mechanical properties (especially the tensile strength) in a significant way. Since control of the atmosphere can be eliminated during concretion, it is easier and less expensive to increase manufacturing. The ability to eliminate atmospheric control during thermal cycling makes it substantially easier to deploy the membranes in practical systems that are more resistant to variation in temperature or gas composition. This invention can also be carried out by a solid electrolyte ion transport membrane compound having a dense membrane and a porous coating for separating a gaseous component from a gas mixture. The dense membrane has a first surface and a second surface and is comprised of a matrix material that conducts at least one type of ions and includes at least one of the mechanical properties, the catalytic properties and the concretion behaviors of the matrix and is present in a manner that avoids the continuous electronic conductivity through the membrane component from one side of the membrane to the other. The porous coating is deposited on at least one of the first and second surfaces of the membrane to improve the speed of surface reactions involving the gaseous species. The invention introduces a porous coating on the multiple phase dense solid electrolyte ion transport membrane to establish a composition with improved catalytic properties by improving the kinetic exchange of surface towards the dense membrane. The porous coating provides a significantly improved catalytic activity or surface exchange rate on the dense electrolyte ion transport membrane alone. The porous coating layer is deposited on the reactive surface of the dense membrane. For illustration purposes, when the anode side of the composite membrane is purged according to the present invention using a methane-containing gas, the surface reaction velocity of the methane can be greatly increased by achieving a greater surface area towards the membrane surface. This is particularly true for depositing the porous layer on the anode side of the membrane, as the limiting stage generally resides on the anode side of the membrane when the methane is the reactive component of the purge gas. There may be certain chemical reactions in which the speed limit stage resides on the cathode side of the membrane. In such a case, the porous coating is deposited on at least the cathode side. As a preferred embodiment, the coating is deposited on the cathode side. the surface of both the anode side and the cathode side This is particularly preferred due to the ease of fabrication of dense double coating membranes. Depositing a coating layer on both sides of the dense matrix material balances the coatings to avoid or reduce the possible effects of mechanical stress on the membrane surface. When cured, the porous coating layer can produce mechanical stress on one side of the material. of dense matrix if the coating occurs only on one side Therefore, it is preferred to deposit a coating layer on both sides of the dense matrix material to reduce the unbalanced tension as a result of the coating Dense membranes of mixed conductive oxides transporting ions of oxide have an infinite selectivity of oxygen / nitrogen. Examples of such materials are given in Table I below and include various oxides with a perovskite structure or a structure that can be derived from that as A2B2O5, a millerite. A common problem with such ceramic membranes is their fragility and low mechanical resistance in tension which makes it difficult to manufacture large elements such as tubes and use them in commercial systems of high reliability. Those limitations in the present invention using a double-layer material comprised of a conductive material such as a perovskite and a second phase of a suitable component such as a metal to prevent micro-cracking during air manufacturing, improve the mechanical properties, the thermal / atmospheric cycling and the possibility of producing surface exchange speeds over those of the mixed conductor phase alone. Suitable ion transport membrane materials include only ionic and mixed conductors that can carry oxygen ions. As used in accordance with the present invention, the ion transport materials comprising the first phase preferably transport both oxygen ions and electrons independent of the presence of the second component phase. In the Examples below, a more comprehensible description of the first phase materials to which a second phase component according to the present invention can be added is provided. In other embodiments, suitable ion transport membrane materials include mixed conductors that can carry oxygen ions. As used in accordance with the present invention, the mixed conductor phase can carry both oxygen ions and electrons independent of the presence of the second electron conduction phase. In Table I below, examples of mixed conductive solid electrolytes of this invention are provided, although this invention is not limited only to those material compositions listed herein. Dense matrix materials other than those comprised only of mixed conductors are also contemplated by this invention.

Table r Mixed Solid Driving Electrolytes 0 One of the materials of the Lai family? Sr? Cu? ? M? 03 d, gift of M represents Fe or Co, x equal from zero to approximately 1, and equal from zero to approximately 1, d equals a number that satisfies the valences of La, Sr, Cu and M in formula 1 One of the materials of the Ce? _? A? 2 family < -, where A represents a lanthanide, Ru, or Y, or a mixture of the same, x is equal from zero to approximately 1, and is equal from zero to approximately 1, d equals a number that satisfies the valences of Ce and A in formula 12 One of the materials of the Sn? Bi? Fe03 - family, where A represents a lanthanide or Y, or a mixture of the same, x is equal from zero to about 1, and is equal from zero up to about 1, d equals a number that satisfies the valences of Ce and A in formula 13 One of the materials of the Sr? FeyC? zOw family, where x is equal from zero to about 1 and is equal from zero to about 1 z is equal from zero to approximately 1 w equals a number that satisfies the valences of Sr Fe and Co in formula 14 Mixed conductors of double phase (electronic / ionic) (Pd) 0 s / (YSZ) 0 5 (Pt) or 6 / (YSZ) or 5 (B-MgLaCrO?) or 5 (YSZ) os (lngo% Pt10%) or 6 / (YSZ) 0 s (ln9o% Pt? o%). 5 / (YSZ) os ( ln9 s% Pr25% Zr2 s%) or s / (YSZ) 05 Any of the materials described in 1-13 to which a high temperature metal phase is added In general, the main considerations in the selection of the materials of the second component phase are (1) coefficient of thermal expansion (TEC) coupling between the second phase and the ion transport material, (2) the chemical compatibility between the second phase and the ion transport material, (3) good bond between the second phase and the matrix of the ion transport material, (4) the ductility of the second phase to release the tensions during concretion and cooling and ( 5) low cost TEC coupling is important because tension is usually established in and around the second fas as the composite material cools down from fabrication. The selection of an incorrect second phase material can cause possible delamination or cracking by the thermal stress induced during manufacturing and operation. This can be minimized by reducing the difference in the two coefficients of expansion between the ion transport material and the second phase. In an alternative embodiment, the ion transport material is described as a matrix material and the second phase as a component. Chemical compatibility is important because the operation at a high temperature and the processing of ion transport materials will cause interactions and the interdiffusion between the ion transport material and the second phase that can lead to the degradation of materials and reduce the performance of the membrane. Therefore, the second phase must be chemically inert to or not react undesirably with the ion transport material to avoid adverse interactions and interdiffusion at high temperatures. Good bonding is important because the delaminations that occur between the second phase and the ion transport material can be harmful to the strength of the material. Cracks or imperfections could easily bond and cause material failure. The ductility of the second component phase is important because many of the ion transport materials have the coefficient of thermal expansion very high. High TEC's give rise to high thermal stress during the processing and operation of ion transport materials, which can result in material failure. The ductility of the second phase can release the stresses generated during concretion and / or cooling. In addition to the above considerations, the catalytic activity of the second phase preferably improves the surface reaction kinetics of the composite ion transport membranes. The increased catalytic activity can therefore mitigate an otherwise high cost for a given component or electronic driving phase. The component phase according to the present invention is not electrically continuous through the ion transport membrane. However, the components can be physically continuous if they are made of electronically non-conductive materials. The randomly distributed electronically conductive components are less tthirty percent by volume to ensure that such components are present in a manner below the limit of filtration of the electrons across the membrane. The second component phase can be selected from metals, such as silver, palladium, platinum, gold, rhodium, titanium, nickel, ruthenium, tungsten, tantalum or alloys of two or more such metals that are stable at operating temperatures. of the membrane Suitable high temperature alloys include, inconel, nickel-iron-molybdenum alloy, monel and "ducrolloyP Silver, palladium or silver / palladium are preferred.The second phase can also be selected from ceramics, such as mixture of praseodymium-indium oxide, mixture of niobium-titanium oxide, titanium oxide, nickel oxide, tungsten oxide, tantalum oxide, cerium oxide (ceria), circonia, magnesia or a mixture thereof. Second ceramic phases, such as titanium oxide or nickel oxide, can be introduced in the form of oxides, then reduced to metal during operation under a reducing atmosphere. for practicing the invention include using electronically non-conductive, physically continuous second phase components, such as glass, asbestos, ceria, zirconia or magnesium fibers or wires, or flakes of a material such as mica, to reinforce the transport matrix of ion. The second continuous phase can be distributed substantially uniformly in the ion transport matrix, provides structural reinforcement and improves the meccal properties of the ion transport membrane. The fibers typically have a diameter of less t1 mm, preferably less t0.1 mm, more preferably less t0.01 mm and more preferably less tone mm. The aspect ratio (length to diameter) is typically greater t10, preferably larger. 100 and more preferably greater t1000 The invention will now be described in detail with respect to a composite ion transport membrane containing a La.2Sr.8Fe.69Co.1Cr.2 or? O? mixed conductor and a second phase of silver / palladium alloy.

Example 1 - Mechanically Enhanced and 50Ag / 50Pd Alloy Transport Membrane Mechanically improved ion transport materials were prepared by mixing various weight ratios (5, 10 and 20% by weight) of an Ag / Pd alloy 50% Ag and 50% Pd by weight, in the following 50Ag / 50Pd, available from Degussa Corp., South Plainfield, NJ, and mixed conductive powder from La.2Sr.8Fe.69Co.1Cr.2Mg.o? O? from SCC, Inc., Woodinvílle, WA, now PSC from Praxair Surface Technologies, Inc., using the Spex mixer (Spex Industries, Inc., Edison, NJ), for 15-20 minutes. The powders were then added into a solution of 2-propanol containing 3% by weight of PVB (Butvar from Montsanto, St. Louis, MO), and mixed by magnetic stirrer at 80 ° C to evaporate the 2-propanol, it was then sieved through a mesh size of 74 microns before pressing. Mechanically improved membrane discs were prepared using a 3.81 cm die under a pressure of 10.4 kpsi followed by binder burning (1 ° C / min from 25 to 400 ° C and maintained for 1 hour), and concreted at 1250 ° C for two hours with a heating / cooling rate of 2 ° C / minute in the air. The microstructures of the concreted discs were examined using an optical microscope and scanning electron microscope (SEM) with energy dispersed spectroscopy (EDS) for the analysis of the chemical compositions. X-ray diffraction analysis (XRD) was carried out using a "Rigaku miniflex" diffractometer with CuKa radiation for the compatibility study of the second phase with the ion transport matrix. The mechanical strength at room temperature was measured by the three-point bending test with an aperture of 19 mm and a cross-head speed of 0.5 mm / min using an Instron tension testing machine. Samples (30 x 4 x 3 mm) were prepared by pressing dry uniaxial drying followed by isostatic pressing at 30 kpsi, then specifying at 1250 ° C for two hours. All samples were cut and polished using synthetic diamond discs before the test to avoid any edge imperfections. The tests were run on five samples for each of the compositions. The oxygen infiltration rate was measured using the sealed disc samples sealed in an alumina test cell with gold pastes. Infiltrations were carried out at a temperature of 900--1000 ° C with inert gas purge He and different reactive purge gases. An HP 5890 Gas Chromatograph, an oxygen analyzer and the moisture analyzer were used to analyze the gas compositions and calculate the oxygen fluxes. The objective of mechanically enhanced ion transport material is to increase the mechanical strength of the ion transport matrix and possibly eliminate the need for a nitrogen atmosphere during concretion. The initial results show that the second phase (alloy Ag / Pd) can release the tensions of composition and others generated during the concretion, inhibits the propagation of microcracks in the phase of mixed conductor and therefore improve the mechanical strength of the material disc e ion transport. Fig. 1 shows the disc density of concreted ion transport material which can be greatly reduced by increasing the amount of the second phase. The effect of the concentration of the second phase on the fracture strength of the ion transport material by 3-point bending tests is shown as the curve 90 in Fig. 2. The results show that the fracture resistance of the ion transport materials increase impressively from 0 to 175 (Mpa) as the second phase increases from 0 to 20% by weight. The use of the Ag / Pd alloy appears to significantly reduce the crack density and increase the mechanical strength of the ion transport disk. It is considered that this is due to the metallic phase that reduces the composition tensions during the concretion as well as prevents the growth of cracks, therefore, the mechanical resistance of the double phase ion transport disks was improved. The XRD results shown in Fig. 3 also demonstrate good compatibility between the 20% Ag / Pd alloy, the 100 spectrum, and La.2Sr.8Fe.69Co.1Cr.2Mg 0.OX, the 102 spectrum, without Additional phase is detected after concretion at 1250 ° C. Oxygen transport tests were run on a 0.85 mm disk at a temperature of 900-1000 ° C under an air / helium gradient with flow rates of 500 sccm (standard cubic centimeters per minute) for each stream at 1.2 atm of pressure. The O2 fluxes are 0.5, 0.7, 0.9 sccm / cm2 at 900, 950, 997 ° C respectively, curve 110, with the activation energy of 1.0 eV which is comparable to that obtained for the single phase sample, curve 112, As shown in Fig. 4. Therefore, the use of the second phase does not seem to decrease the oxygen transport performance of the material. Tests of those double phase disks were also run at 1000 ° C using different concentrations of mixtures. of H2 (10 and 20%) / N2 on the purge side. As the H2 concentration of the reactive side rose from 10% to 20%, the flow of 02 increased from 4.6 to 9.4 sccm / cm2. Compared with the individual phase tube tests, the double phase disk also showed oxygen fluxes above under identical critical reactive purge conditions, as shown in Fig. 5 This is considered to be due to the improvement of the kinetics of surface oxidation due to the catalytic properties of the second phase.

Example II - Membrane of Mechanically Improved Transport of La.2Sr.8Fe.69Co..Cr.2Mg 0? Ox and Alloy of 65Ag / 35Pd A double dense phase disk of La 2Sr 8Fe 69Co TCG 2Mg 0.OX was prepared with 20% 65Ag / 35Pd (65% by weight Ag and 35% by weight Pd) in accordance with the method of Example 1 except that it is replaced 65Ag / 35 Pd instead of 50Ag / 50Pd as a second phase The infiltration test of N2 at room temperature confirmed that the disk is gas tight. The scanning electron micrograph (Fig 6a) showed in a 5180x magnification a second phase well dispersed in the matrix The 2Sr 8Fe 69C0 2Mg? Ox and does not reveal delamination or additional phase formation indicating good compatibility between the Transport Membrane de lón and the second phase The surface EDS spectrum (scattered energy spectroscopy) (Fig 6b) of the sample also exhibits minimal matrix composition losses as well as the concretion of the second phase The Pd to Ag ratio of the second phase after concretion (0 548) is close to that of alloy 65Ag / 35PD (0 538) within the accuracy of the instrument The disc also showed good mechanical strength after concretion at 1200 ° C in air without being observed microgpets The oxygen transport test was run on a 0.9 mm disc at a temperature of 1000 ° C under an air / helium gradient. The O2 flow was 0.8 sccm / cm2 at 1000 ° C which is comparable to that of the double phase sample in Example I (with 20% by weight of the second 50Pd / 50Ag phase). The reactive purge test of this disc was also run at 1000 ° C using the mixture of 10% H2-90% N2 on the purge side. O2 fluxes of 4.5 sccm / cm2 were obtained at 1000 ° C which are also comparable to that of the double phase sample with 20% by weight of the 50Pd / 50Ag alloy.

Example III - Improved Transport Membrane of the 2Sr 8Fe 69Co TCG 2Mg, O? and 90Ag / 10Pd Alloy Dense double-phase disks of La 2Sr 8Fe 69Co, Cr 2Mg, O were prepared with 20% 90Ag / 10Pd in accordance with the method of Example 1 except that 90Ag / 10Pd (supplied by Praxair Surface Technologies, Ine) replaced 50Ag / 50Pd as a second fas The discs and rods were prepared by dry pressing under a pressure of 10.4 kpsi followed by binder burning (1 ° C / m? N from 25 to 400 ° C and maintained for 1 hour) and materialized at 1200 ° C for 1 hour with a heating / cooling rate of 2 ° C / m in air Although no microglasses were observed in these samples, they showed lower mechanical resistances (with an average of 135 MPa) compared to those of the double phase samples with 20% of the 50Pd / 50Ag alloy. This may be due to a lower tensile strength of the 50Pd / 50Ag alloy. Oxygen transport tests were carried out on extruded tubes (10 cm long, 1 cm ID, 1 mm wall thickness after concretion) at a temperature of approximately 1000 ° C under the reactive purge tests using the variety of purge gas. The O2 flows are slightly lower (-10-15%) than those of the double phase tubes with 50Pd / 50 Ag alloy under similar test conditions. An O2 flow of 2.2 sccm / cm2 was obtained at 1025 ° C with the purge gas containing 60% CH4 for those tubes. Referring to the most generally suitable first phase materials, microcracking is often present in an ABO3 perovskite structure, or a perovskite structure, or a structure that can be derived from that (eg millerite, A2B2O5), as a result of a phase transition during concretion and cooling. Microcracks were reduced in the perovskite La.2Sr.8Fe 69Co? Cr.2Mg .-? O? adding the different amounts of the second Ag / Pd phase as shown in Example I and II. The invention described herein is intended to cover suitable mixed conducting oxides presented by the structure ArApA "tBuB'vB" wO? where A, A ', A "are selected from groups 1, 2, 3 and the block-F lanthanides; and B, B ', B "are selected from the transition metals of block D in accordance with the Periodic Table of the Elements adopted by the IUPAC where 0 <r <1, 0 <s <1. 1, 0 <t <1, 0 <u <1, 0 <v <1, 0 <w <1 and x is a number that produces the neutral charge of the compound Preferably A, A 'or A "of the structure listed is a Group 2 metal selected from the group consisting of magnesium, calcium, strontium and barium. Preferred mixed conducting oxides are represented by the formula: AsA'tBuBPB" wO? Wherein A represents a lanthanide, Y, or a mixture thereof, A 'represents an alkaline earth metal or a mixture thereof, B represents Fe, B' represents Cr, Ti or a mixture thereof and B "represents Mn, Co, V , Ni, Cu or a mixture thereof and s, t, u, v and w each represent a number from 0 to about 1 Suitable first phase materials also include other cer Ionic conductivity in which the microglasses can occur during concretion due to a shift of pohmórfica symmetry of high temperature, a tension of composition or a coefficient of thermal expansion highly anisotropic For example, the zirconia exhibits transformations of fas to 1170 ° C (monochrome to tetragonal) and 2370 ° C (tetragonal to cubic) Changes of high-temperature symmetry pohmórfica usually result in cracks during the concretion Therefore, the zirconia is usually stabilized in the cubic phase fluorite type by introducing a suitable di- or trivalent oxide to obtain cubic symmetry It is also intended that the present invention cover the mechanical improvement of other ceramics such as zirconia or ceria if they encounter a high temperature polymorphic symmetry change, a compositional tension or a coefficient of thermal expansion highly anisotropic. In addition, an electronic / ionic conductor such as (B-MgLaCrO) or S (YSZ) 05, or a mainly ionic conductor such as zirconia or ceria combined with a perovskite can be further combined with a component in accordance with the present invention to form a membrane having at least three phases The alternative embodiments of this invention are directed to coating a dense membrane by depositing the porous coating on at least one surface of the membrane. The coating modifies the surface of the membrane, which is why it is considered which provides a catalytic effect during ion transport and also provides structural stability over the surface layer. The drawings are representative of certain embodiments of the solid electrolyte ion transport membrane compound of this invention. Fig. 7 shows the coating layers. porous 702 and 703 deposited on both surfaces of the conductive membrane of dense solid electrolyte ion 701 Fig. 8 shows another embodiment in which the porous coating layers 802 and 803 are deposited on both surfaces of the solid electrolyte ion conducting membrane 801 The membrane 801 is supported on a porous support comprising the intermediate support layer 804 and the support layer 805 with the porous coating layer 803 between the membrane 801 and the intermediate support layer 804. Although numerous techniques are available for depositing a layer of material on a dense surface, a process of Preferred manufacture comprises immersing the dense membrane within a liquid precursor of the porous coating (eg, paste, colloidal solution) and subsequent drying and curing of the resulting coating layer. This method is a comparatively easier and more cost-effective method to deposit a porous coating layer on top of a dense surface over other methods available in the art. Suitable ion transport membrane materials include mixed conductors that can carry oxygen ions. As used in accordance with the present invention, the mixed conductor phase can transport both oxygen ions and electrons independent of the presence of the second electronic conduction phase. In Table I, examples of mixed conducting solid electrolytes of this invention were provided, although this invention is not limionly to those material compositions listherein. Dense matrix materials other than those comprised only of mixed conductors are also contemplaby this invention. Suitable coating compositions may comprise mixed conductive oxides that transport oxide as well as electron conductivity. Examples of the porous coating mixed conductor were given in Table I and may be the same or different from the mixed conducting oxides of the dense membrane. As in the dense membrane, the coating may comprise a composition having a mixed conductor phase and a coating component. Suitable porous coating compositions include a combination of a mixed conductor and a coating component that can carry oxygen ions and / or electrons. The mixed conductors can carry oxygen and electron ions independent of the presence of the coating component. of coating constitutes less than about 30 volume percent of the total porous coating The porous coating can be coausing various methods known to those skilled in the art A preferred method is the paste coating coating method This method is preferred because of the ease and efficiency Cost of Dense Membrane Coating Other methods may include spin coating, chemical vapor deposition (CVD), electorchemical vapor deposition (EVD), physical vapor deposition (PVD) such as laser wear and electronic thermal spraying, plasma spraying, RF plasma deposition and a combination thereof The porous coating layer must be thin relative to the surface of the dense membrane, so that the coating improves the speed of the surface reaction of the dense membrane. Accordingly, the porous coating layer has a thickness of less than about 50 microns, preferably less than 10 microns and, more preferably, less than 5 microns. A more understandable description of the porous coating in accordance with the present invention is provided in the following examples. In another embodiment, a porous support can also be used to improve the structural stability of the membrane. The porous support may include mixed, ionic conduction, inert conductive material and electronically conductive (metallic) material, or a combination thereof. Additionally, the porous support may contain catalytic enhancement components in combination with any of the inert, ionic conduction, mixed conduction and electronic conduction materials, or a combination thereof. The porous support is particularly important when the dense matrix material is thin and brittle. Structurally, it is preferable to have at least one of the dense membrane and the porous coating deposion the porous support. An example of this embodiment is found in Fig. 8 as described above.

Example 4 An individual phase dense solid electrolyte ion (SSC) powder ("LSFCCM") conductive tube (7.1 mm ID, 9.7 mm OD and approximately 15 cm length) was extruded, then concreted at 1250 ° C under nitrogen for 1 hour with a heating / cooling speed of 2 ° C / min. To test the oxygen infiltration through the tube, the following procedure was used: a purge gas (containing 60% CH4, 10% CO2 and 30% inert gas such as N2 or Ar bubbled through water) flowed inside of the tubes countercurrent to the gas fed. A thermocouple located halfway down the ion transport membrane tube monitors the temperature of the purge gas flowing through the tube, which is referred to as the "ion transport temperature" in this description. The oxygen in the fed gas was partially removed by filtration through the ion transport membrane, and a product devoid of oxygen was obtained. The volume fraction of O2 fed (XF), the volume fraction of product 02 (Xp) and the volumetric flow rate of the product ('P'sccm) and the volumetric flow fed (F) used in the test were measured. infiltration was calculated by the following mass balance on non-infiltrated samples: P. (A-XP) = F. (1-XF). The flow of 02 through the ion transport tubes was then calculated using the following equation: O2-flUJ? - (F.XF-P.Xp) / ion Transduction where, ion transduction = area of average ion transport tube through which is transported 02 (cm2) Example 5 Example 5 presents an embodiment of the electrolyte membrane of the present invention. An individual phase dense LSFCCM electrolyte ion tube similar to that of Example 4 was prepared. The tube was coated with an immersion coating method of paste by means of the "Chemat Technology Model 201" to deploy a porous layer of granules of approximately 1 μm size of an individual phase LSFCCM ion transport material on both tube surfaces The coated material was then tested in the same manner that described in Example 4 The improvement of the flow of 02 through the ion transport membrane with the help of a porous coating is illustrated by the following table based on the experimental data. In the experiments carried out under similar conditions, the Coated ion transport tube showed a flow of O2 substantially higher (4 times) than the ion transport tube did not covered In this case, the data points are shown with similar feed flow rates. The individual coated phase tube was observed to remove more oxygen from similar feed currents. Note that the volume fraction of O2 fed used in the test Coated tube was slightly higher than the uncoated tube tests. However, according to Wagner's theory, the O2 flow depends on the logarithm of the volume fraction of O2 fed: therefore, a change from 20.9% in volume to 22.6% in O2 volume is not expected in the feed current significantly affects the average flow reported in the following table Table II Results for the individual phase ion transport tube Example 6 A double-phase ion transport tube of LSFCCM with 20% by weight of 50Ag / 50Pd (50% by weight of Ag and 50% by weight of Pd) was prepared by slip casting. Liquid slurry of ion transport membrane Double-phase LSFCCM was prepared by mixing 20% by weight of the 50Ag / 50Pd alloy (DeGussa) and the 2Sr8Fe 69Co 1Cr2Mg? Ox (SCC) powder and 2 drops of Darvan C dispersant with water to a concentration of 35% solids. liquid paste was milled for 5 hours, cast in slip in a gypsum mold SP then concreted at 1250 ° C in girp for 1 hour with a heating / cooling rate of 2 ° C / min. The double phase tubes were tested in the same manner described in Example 4.

Example 7 Example 7 presents another embodiment of the present invention. A double-phase LSFCCM transport tube similar to that of Example 6 was prepared. The tube was coated using a dip-coating method by means of "Chemat Technology Model 201" to deploy a porous layer of granules of a Size of approximately 1 μm of a single phase LSFCCM ion transport material on both surfaces of one of the tubes, considering that the tube of example 6 was left uncoated. Substantial improvement of the O2 flow (3.8 times) was observed with the porous individual phase ion transport layer extended over the tubes. In this example, data points with similar product O2 concentrations were selected. A much higher feed flow can be used in the double coated phase tube to remove the O2 to a comparable degree.

Example 8 Example 8 presents another embodiment of the present invention. An extruded double phase LSFCCM ion transport tube similar to that of Example 4 was prepared. The tube was coated using a dipping coating method by "Chemat Technology Model 201" which was employed to deploy a porous layer of granules of an approximate size of 1 μm of a double-phase LSFCCM ion transport material comprising LSFCCM and a component on both surfaces of one of the tubes. The component is made of 50Ag / 50Pd and is approximately 20% by weight (approximately 11% by volume) of the entire porous layer. Substantial improvement of the O2 flow (3.7 times) was observed with the porous individual phase ion transport layer deployed on the tubes. In this example, data points with similar product concentrations of 02 were selected. A much higher feed flow can be used in the double coated phase tube to remove the 02 to a comparable degree. It is also shown that the substantial improvement in the 02 product, the feed flow and the product flow can be achieved.

Table III: Results for the double-phase ion transport tube Note that in each example the ion transport tube with the mixed conductor and the electronic conductive porous layer, the oxygen flow was increased about four times more than that of the dense uncoated ion transport tube.

Example 9 A double phase disk was prepared. Both surfaces of the concreted discs were then polished to obtain a thickness of 0.9 mm. The oxygen infiltration rate was measured on the disk at 900 ° C under an air / helium gradient. The disk sample was sealed in an alumina test cell with Ag paste. An HP 5890 gas chromatograph was used an oxygen analyzer to analyze the gas compositions and calculate the oxygen fluxes. The flow results (in sccm / cm2) at 900 ° C were summarized in Table IV.

Example 10 Example 10 presents another embodiment of the electrolyte membrane of the present invention. A double phase disk similar to that of Example 9 was prepared and polished to obtain a thickness of 0.6 mm. A few drops of an LSFCCM ion transport material similar to that of Example 5 were deposited on the surface of the disk which was fixed on a rotating coater. A rotation speed of 3500 rpm was used for 20 seconds for the deposition of the modification layer. After the spin coating, the deposited coating of this form of LSFCCM transport material on the disk was dried on a plate heated at 80 ° C for 5 minutes, then transferred to a hot ceramic stop plate and heated at about 300 ° C for at least 5 minutes. The entire coating and drying process was repeated until a 1 μm LSFCCM film was formed on the surface of the membrane. The double phase disk was then tested in the same manner as described in example 9. With the surface modification (on the air side) the oxygen flow was increased approximately three times over an air / helium gradient which indicates that the kinetics of surface exchange on air is improved by increasing the surface area for the dissociation of oxygen by means of surface modification.

Table IV: Results for the double phase disk '(Corrected flow for 1 mm thick membrane) The specific features of the invention are shown in one or more of the drawings for convenience only, since each feature can be combined with another feature according to the invention. Those skilled in the art will recognize alternative modalities and are intended to be included within the scope of the claims. For example, suitable first phase materials can conduct proton ions instead of or together with oxygen ions for applications involving hydrogen.

Claims (10)

1. A solid electrolyte ion transport membrane having a first surface and a second surface, the membrane comprising: a matrix material that conducts at least one type of ion; at least one component that is physically distinguishable from the matrix material and that improves at least one of the mechanical properties, the catalytic properties and the concretion behavior of the matrix material, the component that is present in a manner that avoids conductivity electronics continues through the component from one side of the membrane to the other.

The membrane of claim 1, wherein the matrix material is a mixed conductor that exhibits both electronic and oxygen ion conductivity.

The membrane of claim 1, wherein the component is a metal that is present in a manner below the limit of electron infiltration through the membrane

4. The membrane of claim 1, wherein the component is selected of the group comprising silver, palladium, platinum, gold, rhodium, ruthenium, tungsten, tantalum, titanium, nickel, silicon, lanthanide, yttrium, copper, cobalt, chromium, vanadium, zirconium manganese, molybdenum, niobium, aluminum, iron or mixtures thereof

5. The membrane of claim 1, wherein the component is a non-metallic material. The membrane of claim 1, wherein the component is in the form of non-metallic fibers. The membrane of claim 1, wherein the component further improves at least one of the catalytic properties and the concretion behavior of the matrix material. The membrane of claim 1, further comprising a porous coating placed on at least one of the first and second surfaces of the membrane to improve the speed of surface reactions involving the gaseous species. The membrane of claim 8, wherein the porous coating comprises a mixed conducting material that exhibits both electronic and oxygen ion conductivity. The membrane of claim 8, wherein at least one of the dense membrane and the porous coating is placed on a porous support to improve the structural stability of the membrane.