JPH1192961A - Coating film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid membrane produced from a perovskite structure or multiphase structure, which is stable from at room temp. to high temp. and contains a fluid flux in a high proportion so that the membrane is effective to separate a specified fluid from a flow. SOLUTION: This solid membrane has a first surface and a second surface and consists of a structure (A) and a coating film (B) described below. The structure (A) is selected from (a) a substantially perovskite material, (b) a dense multiphase mixture of an electron conductive phase and an oxygen ion conductive phase which does not permeate gas in which the electron conductive phase forms an electron conductive passage between the first surface and the second surface while the oxygen ion conductive phase forms an oxygen ion conductive passage between the first surface and the second surface, and (c) a combination of these. The coating film (B) is a porous chemically active electron conductive coating selected from metals, metal oxides and a combination of these.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a novel mixed conductor membrane capable of separating an industrial fluid stream.

[0002] Applicants have filed a product flux.
Solid compositions with enhanced x) and methods to exploit this property have been discovered. Membranes formed from perovskite or multiphase structures and having chemically active coatings have been shown to exhibit very high rates of fluid flux. One application is to separate oxygen from oxygen-containing feeds at elevated temperatures. These membranes are conductors of oxygen ions and electrons and are substantially stable in air over a temperature range from 25 ° C. to the operating temperature of the membrane.

[0003]

BACKGROUND OF THE INVENTION Solid membranes formed from ion-conducting materials have shown promise in commercial processes for the separation, purification and conversion of industrial fluids, especially in processes for the separation and purification of oxygen. Is beginning to be revealed. Envisioned applications range from small-scale oxygen pumps for medical applications to large-scale gas generation and purification plants. There are numerous conversion processes, including catalytic oxidation, catalytic reduction, heat treatment, distillation, extraction and the like.
Fluid separation techniques involve two distinctly different membrane materials, solid electrolytes and mixed conductors. In the process for fluid separation, membranes formed from mixed conductors are preferred over solid electrolytes. The reason is that the mixed conductors carry the ions and electrons of the desired product fluid and can be operated without external circuits (eg, electrodes, interconnects and power supplies). In contrast, solid electrolytes carry only the ions of the product fluid and ionize the membrane.
To maintain the deionization process, an external circuit is needed to maintain the flow of electrons. Such a circuit adds to the cost of the unit and complicates the three-dimensional structure of the cell.

[0004] Membranes formed from solid electrolytes and mixed conducting oxides can be designed to be selective for a particular product fluid (eg, oxygen, nitrogen, argon, etc.), and at elevated temperatures (typically, When operated at temperatures in excess of about 500 ° C), the solid state lattice dynamically formed
Product fluid ions may be transported through the anion vacancy. Examples of solid electrolytes include yttrium stabilized zirconia (YSZ) and bismuth oxide for oxygen separation. Examples of mixed conductors include titania-doped
YSZ, praseodymia-modified YZZ
S), and more importantly, various mixed metal oxides, some of which have a perovskite structure. Japanese Patent Application No. 61-21717 discloses a film formed from a multi-component metal oxide having a perovskite structure, and this structure has a structure of La _1-x Sr _x Co _1-y Fe _y O _3-d ( Here, x is 0.1 to
1.0, y is in the range of 0.05 to 1.0, and d is in the range of 0.5 to 0). Other suitable perovskite structures are described in co-pending US patent application Ser. No. 08 / 311,295, which is owned by the assignee of the present application. The subject matter of this application is incorporated herein by reference.

[0005] Membranes formed from mixed conducting oxides and operated at elevated temperatures select this product fluid from the feedstock when a difference in partial pressure of the product fluid is on the opposite side of the membrane. Can be used to separate them. For example, oxygen transport occurs when oxygen molecules dissociate into oxygen ions, which migrate to the lower oxygen partial pressure side of the membrane where they recombine to form oxygen molecules Or reacts with a reactive fluid. Electrons move through the membrane in the opposite direction to these oxygen ions, maintaining their charge.

The rate at which fluid ions penetrate through a membrane is:
It is mainly controlled by three factors. They are,
(a) the kinetic rate of ion exchange of the product fluid at the feed-side interface, ie, the rate at which product fluid molecules in the feed are converted to mobile ions at the feed-side surface of the membrane; b) the rate of diffusion of product fluid ions and electrons within the membrane; and (c) the kinetic rate of product fluid exchange at the permeate interface, ie, the product fluid ions of the membrane And returned to the permeate side of the membrane, or to a reactive fluid (e.g.,
Rate of reaction of hydrogen, methane, carbon monoxide, C ₁ -C ₅ saturated and unsaturated hydrocarbons, such as ammonia) and.

[0007] Thorogood et al., US Pat. No. 5,240,480, the contents of which are incorporated herein by reference, discloses a method for controlling the pore size of a porous structure that supports a non-porous dense layer. 4 illustrates the kinetic rate of gas exchange at the side interface. Many references (e.g., Yoshisato et al., U.S. Pat.No. 4,330,633; Yamaji et al., JP 56-92103)
No., and Teraoka and co-workers' literature, Chem. Let
ters, The Chem. Soc. of Japan, pp. 503-506 (1988))
Describes substances with enhanced ionic and electronic conductivity.

No. 4,791,079 to Hazbun and US Pat.
No. 4,827,071, the contents of which are incorporated herein by reference, are bilayer membranes, where one layer is an impermeable mixed ion and an electronically conductive ceramic, FIG. 2 illustrates the kinetic rate of gas conversion at the permeate interface by utilizing a porous layer containing a hydrocarbon oxidation catalyst).

A reference of a typical metal oxide film is Japanese Patent Application No. 61-21717. When an oxygen-containing gas mixture under a high oxygen partial pressure is applied to one side of a film having a dense layer formed from the above-described oxide, oxygen is adsorbed on the surface of the film, dissociated, and ionized. It diffuses through the solid, deionizes, associates, and desorbs on the other side of the membrane at a low oxygen partial pressure as a stream of oxygen gas.

The electronic circuitry required to provide this ionization / deionization process, due to its electronic conductivity,
It is maintained inside this oxide. This type of separation process is described as being particularly suitable for separating oxygen from a gas stream containing a relatively high oxygen partial pressure, i.e., equal to or greater than 0.2 atm. . Multi-component metal oxides that exhibit both oxygen ion conductivity and electronic conductivity are typically 0.01 ohm ^-1 under operating conditions.
shows the electronic conductivity in the range of cm ^-1 to 100 ohm ^-1 cm oxygen ionic conductivity ranging from ^-1 and about ^{1 ohm -1 cm -1 ~100 ohm -1} cm -1.

Certain multi-component metal oxides, at elevated temperatures,
It is mainly or exclusively an oxygen ion conductor. An example is (Y ₂ O ₃ ) _0.1 (Zr ₂ O ₃ ) _0.9 , which at 1000 ° C. has an oxygen ion conductivity of about 0.06 ohm ⁻¹ cm ^{−1 and} an ion transport number close to 1 ( Ratio of ionic conductivity to total conductivity). European Patent Application EP 0399833A1 describes a film formed from a composite of this oxide and another electronically conductive phase (eg, platinum or other noble metals). The electron conducting phase provides a back supply of electrons through the structure,
Thereby, oxygen can be ionically conducted through the composite material membrane under the driving force of the partial pressure gradient.

Other categories of multicomponent metal oxides exhibit primarily or exclusively electronic conductivity at elevated temperatures, and their ionic transport numbers are close to zero. One example is Pr _x In _y O _z ,
This is described in European patent application EP 0,399,833 A1. Such a material is a separate oxygen ion conducting phase.
(Eg, stabilized ZrO ₂ ) in a composite membrane. Membranes constructed from this type of composite can also be used to separate oxygen from an oxygen-containing stream (eg, air) by applying an oxygen partial pressure gradient as a driving force. Typically, the multi-component oxide electronic conductor is placed in intimate contact with an oxygen ion conductor.

[0013] Organic polymer membranes can also be used for fluid separation. However, membranes formed from mixed conducting oxides provide significantly better selectivity for important products such as oxygen when compared to polymer membranes. The value of such improved selectivity is in building and operating plants that use mixed conductive oxides, which require heat exchangers, hot seals and other expensive equipment. Must be more important than the associated high costs. Typical prior art membranes formed from mixed conducting oxides have a permeability (defined as the ratio of permeability to thickness) sufficient to warrant use in commercial fluid separation applications. Is not shown.

It is known that the permeability of oxygen through a solid membrane increases in proportion to the decrease in film thickness, and mechanically stable and relatively thin membrane structures have been widely studied.

The second document by Teraoka et al., Jour. Ceram. So
c. Japan, International Ed, Vol 97, pp. 458-462, (1
989) and J. Ceram. Soc. Japan, International Ed,
Vol 97, pp. 523-529 (1989), for example, describes a dense, non-porous mixed conductive oxide layer on a porous mixed conductive support.
(Referred to as a "dense layer"), which describes a solid gas separation membrane formed by vapor deposition. The relatively thick porous mixed conductive support provides mechanical stability to the relatively thin, brittle, dense, non-porous mixed conductive layer. During fabrication and use, structural defects due to thermomechanical stress encountered by the film were substantially minimized due to the chemical compatibility of the respective film layers. Based on the consideration of limiting the thickness of the dense layer, Te
raoka and co-workers found that membranes with mixed-conducting porous layers and thin mixed-conducting dense layers have a 10-fold increase in oxygen flux compared to standard single-layer dense sintered mixed-conducting discs I expected. However, they only gained less than two-fold.

[0016] Perovskite structures include regular perovskites, which have a three-dimensional cubic arrangement of small diameter metal ion octahedra, and single or multiple layers of perovskite-like (ie, arranged in a two-dimensional square arrangement). (A two-dimensional arrangement of octahedrons of small diameter metal ions). These perovskite-like arrangements are charge stabilized by larger diameter metal ions or other charged layers. Examples of perovskite structures include:
Cubic perovskite, brownmillerite
ite), Aurivillius phase and the like. A description of the relationship between perovskites and some of the various perovskite phases can be found in L. Katz and R. Ward, Ino
rg. Chem. 3, 205-211, (1964), which is incorporated herein by reference.

These layer structures can regulate oxygen ion vacancies, and regulation of these vacancies can lead to structural changes (eg, brown millerite phase). Brown millerite is a perovskite lacking one sixth of its oxygen ions, and the resulting oxygen ion vacancies are arranged in continuous lines within the crystal. One example is S. Shin, M.
Yonemura, and H. Ikawa, Mater Res Bull 13, 1017
As described in -1021 (1978), there is SrFeO _3-x . x = 0
Under these conditions, this structure becomes a regular cubic perovskite structure. When the temperature and pressure conditions are changed so that x increases, the oxygen vacancies introduced are initially randomly distributed (ie, "irregular") throughout the crystal. However, as x approaches 0.5, these cavities become "regular", i.e., they become
A regular pattern is formed over the entire crystal. If exactly one sixth of this oxygen ion is missing (x =
0.5), the resulting vacancies are “regular” and this phase
Called brown millerite.

The Auribillius phase is sometimes called lamellar perovskite and is described in J. Barrault, C. Grosset, MD
Catalysis Le by ion, M. Ganne and M. Tournoux
tters 16, p. 203-210 (1992), consisting of multiple perovskite layers, where the large diameter metal cations are partially or wholly separated from other oxides (usually (Bi
₂ O ₂ ) ²⁺ ). Their general formula is [Bi ₂ O ₂ ] [A _n-1 B _n O _{3n + 1} ], where “A” is
"B" represents a small diameter metal ion and a "B" represents a small diameter metal ion. A. Castro, P. Milla
n, by MJ Martinez-Lope and JB Torrance
As described in Solid State Ionics 63-65, p 897-901 (1993), a wide range of tolerances for A and B metals in this perovskite layer and for Bi in the Bi ₂ O ₂ interlayer Is possible. This document is incorporated herein by reference. W. Carrillo-Cabrera, HD Wiemhof
er and W. Gopel's Solid State Ionics, 32/33, p 1
As described in 172-1178 (1989), so-called superconductors (eg, YBa ₂ Cu ₃ O _7-x ) are also perovskite structures with other types of ordered vacancies.

[0019]

Researchers have continually sought a solid conductive membrane that exhibits excellent flux without sacrificing the mechanical and physical compatibility of the composite membrane. An object of the present invention is to provide a solid film which exhibits a high flux and is stable from room temperature to a high operating temperature.

[0020]

The solid film of the present invention is a solid film having a first surface and a second surface.
Having (A) and (B): (A) a structure selected from the group consisting of the following (a), (b) and (c): (a) a substantially perovskite material; (b) an electron conducting phase A dense gas-impermeable multiphase mixture of an oxygen ion conducting phase and an electron conducting phase forming an electron conducting path between the first surface and the second surface; The phase forms an oxygen ion conducting pathway between the first surface and the second surface; and (c) a combination thereof; and (B) a metal, a metal oxide and a combination thereof. A porous, chemically active electron conducting coating.

In one embodiment, the substantial perovskite material is ｛A _1-x A ' _x ｝ BO _3-δ , ｛Bi _2-y A _y O
Having a composition selected from the group consisting of _{2-δ ′} ｝ {(A _1−x A ′ _x ) _n−1 B _n O _{3n + 1−δ ″} } and combinations thereof, wherein
A is selected from the group consisting of Ca, Sr, Ba, Bi, Pb, K, Sb, Te, Na and mixtures thereof; A 'is La, Y, Ce, P
r, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, L
B is selected from the group consisting of u, Th, U and mixtures thereof; B is Fe, Mg, Cr, V, Ti, Ni, Ta, Mn, Co, V, Cu
And x is a member selected from the group consisting of:
Y is an integer from 0 to 2; n is
And δ, δ ′ and δ ″ are determined by the valency of the metal.

In another embodiment, the substantial perovskite material is cubic perovskite, brownmillerite, Aurivillius.
us) phases and combinations thereof, for example, cubic perovskites or brown millerite.

In yet another embodiment, the solid membrane of the present invention is a solid membrane having a structure of a substantially perovskite material and a porous, chemically active electron conducting coating. Is selected from the group consisting of metals, metal oxides and combinations thereof, wherein the perovskite material is {(Bi _2-y A _y O _{2-δ ′} )} {(A _1-x A ′ _x ) _{n- 1} B _n O
_{3n + 1-δ ″} }, wherein A is Ca, Sr, Ba, B
A 'is selected from the group consisting of i, Pb, K, Sb, Te, Na and mixtures thereof; A' is La, Y, Ce, Pr, Nd, Pm, Sm, E
u is selected from the group consisting of u, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Th, U and mixtures thereof; B is Fe, Mg, C
selected from the group consisting of r, V, Ti, Ni, Ta, Mn, Co, Cu and mixtures thereof; x is about 0.9 or less; y
Is an integer from 0 to 2; n is an integer from 1 to 7;
And δ ′ and δ ″ are determined by the valence of the metal.

In yet another embodiment, the solid membrane of the present invention is a solid membrane having a structure of a substantially perovskite material and a porous coating, wherein the coating comprises a metal,
Selected from the group consisting of metal oxides and combinations thereof, wherein the perovskite material has an Aulivili phase.

In yet another embodiment, the porous coating comprises platinum, silver, palladium, lead, cobalt, nickel, copper, bismuth, samarium, indium, tin,
It is selected from the group consisting of praseodymium, their oxides, and combinations thereof.

[0026]

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel mixed conductor membrane capable of separating an industrial fluid stream. This membrane has a chemically active coating and, as compared to the prior art solid membrane, a higher flux is observed, as shown in FIG.
Over a temperature range from ℃ to the operating temperature of this membrane,
It has a structure and composition that forms a substantially stable, substantially perovskite structure in air. The upper range of membrane operating temperatures is about 400 ° C. for the partial oxidation of C ₂ -C ₄ hydrocarbon and oxygen production processes; selected partial oxidation and oxygen production processes, and industrial gases and liquids About 700 ° C. for the removal of oxygen from water; and about 850 ° C. for the processes described above under certain circumstances, and for the partial oxidation of methane and natural gas.

Although the membrane containing the mixed conductive oxide layer is known, the fluid impermeable membrane of the present invention has a composition that substantially forms a perovskite structure. Such a structure exhibits a high flux, especially a high flux of oxygen. The porous coating of metal or metal oxide enhances the kinetic rate of fluid exchange at the feed side interface, the kinetic rate of fluid exchange at the permeate side interface, or both. In such a manner, membranes made from such materials exhibit a high flux.

[0028] The fluid impermeable membrane of the present invention comprises at least 2
Formed from a mixture of different metal oxides, wherein:
The multi-component metal oxide forms a perovskite structure that exhibits electron conductivity and product fluid ionic conductivity at temperatures above about 400 ° C. These materials are commonly called mixed conductive oxides.

Suitable mixed conducting oxides are represented by the following structure: [A _1-x A ′ _x ] BO _3-δ or [Bi _2-y A _y O _{2-δ ′} ] [(A _{1 -x} A ' _x ) _n-1 B _n O _{3n + 1-δ "} ] where A is Ca, Sr, Ba, Bi, Pb, Ca, K, Sb, Te, Na
And A 'is selected from the group consisting of:
La, Y, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, E
B is selected from the group consisting of r, Tm, Yb, Lu, Th, U and mixtures thereof; B is Fe, Mg, Cr, V, Ti, Ni, Ta, Mn,
X is selected from the group consisting of Co, V, Cu and mixtures thereof; x is 0.9 or less, preferably about 0.6 or less, more preferably 0.4 or less, most preferably 0.25 or less; N is an integer from 1 to 7; and δ, δ ′ and δ ″ are determined by the valency of the metal.

The mixed conductive oxide is formed on a fluid-impermeable membrane. At least one surface of the fluid impermeable membrane is coated with a porous layer of a metal or metal oxide. This coating acts as a chemically active site,
This site increases the kinetic rate of fluid exchange at the interface at the surface of the fluid impermeable membrane.

The present invention relates to a solid film, which comprises a substantially perovskite material.
erial), a structure selected from the group consisting of a dense gas-impermeable multiphase mixture of an electron conducting phase and an oxygen ion conducting phase, and combinations thereof; and selected from the group consisting of metals, metal oxides, and combinations thereof. Having a porous coating.

The present invention also relates to the use of one or more membranes formed from the coated mixed conductors described herein. The appropriate use of such membranes, processes for the partial oxidation of C ₁ -C ₄ hydrocarbons, oxygen separation, production and oxygen containing fluids (in particular, air or diluted air other fluids) from A process for removing oxygen is mentioned.

The present invention relates to perovskite membranes having chemically active coatings, and to processes using such membranes. One such process involves the separation of oxygen from an oxygen-containing feed at an elevated temperature. The membrane is a conductor of product fluid ions and electrons and is of such a composition as to form a substantial perovskite structure. Certain compositions stabilize the perovskite structure in a mixed conducting fluid impermeable membrane. Films made from such materials exhibit high fluxes. More specifically, it has been found that the mixed conductor membrane, whose fluid impermeable membrane has the following composition, exhibits an unexpectedly high fluid transport flux, especially the transport flux of oxygen: _1-x A ' _x ] BO _3-δ formula 1 or [Bi _2-y A _y O _2-δ' ] [(A _1-x A ' _x ) _n-1 B _n O _{3n + 1-δ "} ] Where A is Ca, Sr, Ba, Bi, Pb, Ca, K, Sb, Te, Na
And A 'is selected from the group consisting of:
La, Y, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, E
B is selected from the group consisting of r, Tm, Yb, Lu, Th, U and mixtures thereof; B is Fe, Mg, Cr, V, Ti, Ni, Ta, Mn,
Selected from the group consisting of Co, V, Cu and mixtures thereof; x is less than or equal to 0.9; y is an integer from 0 to 2; n is an integer from 1 to 7; 'And δ "are determined by the valency of the metal; wherein the perovskite phase is substantially stable in air over a temperature range of 25-950 ° C and contains platinum, silver, palladium, lead , Cobalt, nickel, copper, bismuth, samarium, indium, tin, praseodymium, oxides thereof, and combinations thereof, coated with a porous layer of a metal or metal oxide.

Applicants' findings can be better understood by developing an understanding of the mechanism by which product fluids are ionically transported through mixed conducting oxide membranes. Typical product fluid, industrial gases (e.g., oxygen, nitrogen, argon, hydrogen, helium, neon, air, carbon monoxide, carbon dioxide, a mixture of synthesis gas (CO and H _2), etc.) Included. The product fluid flux found in conventional mixed conductor membranes is controlled by surface kinetic limitations and bulk diffusion limitations. Surface kinetic limitations are a constraint on the product fluid flux. The product fluid flux converts feed fluid molecules on the feed side of the mixed conductor membrane to mobile ions and converts the ions back to product fluid molecules or converts the ions to On the permeate side of the mixed conductor membrane, it results from one or more of the many steps involved in reacting with reactive fluid molecules. Bulk diffusion limitations are fluid flux constraint factors related to the diffusivity of product fluid ions through this fluid impermeable membrane material.

Membranes consisting essentially of perovskite phase materials exhibit an overall high product fluid flux.
However, this perovskite phase is not formed, or even formed, in all mixed conducting oxide materials, under the required range of fabrication and operating conditions,
Not stable. For example, a film formed from a hexagonal phase material
Shows little or no oxygen flux, if any. In order to produce an effective oxygen film, the film composition must therefore maintain a substantially high percentage of the stable perovskite phase within the film at operating conditions.

In order to achieve a high bulk diffusion rate across this fluid impermeable membrane, the kinetic rate of interfacial fluid exchange must be considered. The feed fluid is provided on the feed side of the fluid impermeable membrane,
The rate at which mobile ions are converted to mobile ions, or the rate at which mobile ions in the fluid-impermeable membrane are converted back to product fluid molecules, is greater than the bulk diffusion rate of the fluid-impermeable membrane. If low, the overall product penetration rate is limited to the slowest of the three processes.

Applicants have reported that fluids ranging in composition from room temperature and atmospheric pressure in air to those used for product fluid separation have previously been unable to maintain a stable perovskite phase. We have discovered a novel composition that stabilizes the perovskite phase in permeable membranes. In particular, certain compositions stabilize the substantially cubic perovskite layer in the substantially perovskite structure of the ABO material. This cubic perovskite (cubic p
The porous coating of one or more surfaces of the erovskite) material increases the rate of fluid adsorption, ionization, recombination or desorption, and increases the overall fluid flux rate.

The present invention provides a coating and allows for the production of mixed conductor oxide structures that are substantially perovskite phases. Films made from such materials thus exhibit relatively high overall bulk diffusion rates.

The film described in the claims of the present application has the formula (1)
And having a composition described in Formula 2, wherein the composition has no interconnected through-porosity and is coated with a porous layer of metal, metal oxide or a mixture of metal and metal oxide in air. Has a substantially stable perovskite structure at 25-950 ° C. and has the ability to conduct electrons and product fluid ions at operating temperatures.

Multicomponent metal oxides suitable for practicing the present invention are referred to as "mixed" conductive oxides. This is because such multicomponent metal oxides conduct electrons and product fluid ions at high temperatures. Suitable mixed conducting oxides are represented by the compositions of Formulas 1 and 2,
In air, at 25 ° C. to the operating temperature of the material, a substantially stable cubic perovskite structure results. The materials described in the prior art exhibit a significantly lower product fluid flux.

The thickness of the material can be varied to ensure sufficient mechanical strength of the film. As mentioned earlier, the thinner the film, the higher the overall bulk diffusion rate for a given film material. To take advantage of this phenomenon, thin membranes may be supported on one or more porous supports. The minimum thickness of the unsupported mixed conductor film of Applicants' invention is about 0.01 mm, preferably about 0.0
5 mm, most preferably about 0.1 mm. The maximum thickness of the unsupported mixed conductor film of the applicant's invention is about 10 m
m, preferably about 2 mm, and most preferably about 1 mm.

The minimum thickness of the supported mixed conductor film of Applicants' invention is about 0.0005 mm, preferably about 0.001 m
m, most preferably about 0.01 mm. The maximum thickness of the supported mixed conductor membrane of Applicants' invention is about 2 mm, preferably about 1 mm, and most preferably about 0.1 mm.

In addition to the high product fluid flux, the membrane of the present invention can be used over a temperature range from 25 ° C. to the operating temperature of the membrane and an oxygen partial pressure range from 1 to about 1 × 10 ⁻⁶ atmospheres (absolute). Shows stability without undergoing phase transition. The substantially stable perovskite structure exhibits no permanent phase transition over a temperature range of 25 ° C. to 950 ° C. and an oxygen partial pressure range of 1 to about 1 × 10 ⁻⁶ atm (absolute), more than 90% Perovskite phase material, preferably 95% or more perovskite phase material, and most preferably 98% or more perovskite phase material.

Applicants' invention also provides a method for forming a dense fluid impregnation of any of the electron conductive materials with any of the product fluid ion conductive materials and / or the gas impermeable "single phase" mixed metal oxide. Include a chemically active coated membrane of an osmotic multiphase mixture, the mixed metal oxide having a perovskite structure and having both electronic and product fluid ionic conductivity. The phrase "fluid impervious" herein means that the mixture does not allow a substantial amount of fluid to pass through the membrane (i.e., the membrane is referred to as porous with respect to the associated fluid). Rather than being non-porous), it is defined to mean "substantially fluid impermeable or gas tight." In some cases, for example, in the presence of hydrogen gas, a slight penetration of the fluid can be tolerated and unavoidable.

With respect to this solid multi-component membrane, the term "mixture" refers to a two- or more solid phase and a single phase material in which atoms of various elements are mixed in the same solid phase (eg, yttrium stabilized zirconia). Including a substance consisting of
The phrase "multiphase mixture" means a composition that contains two or more solid phases interspersed without forming a single phase solution.

In other words, the multiphase mixture is “multiphase”. The reason for this is that the electron-conducting material and the product fluid-ion-conducting material are made of a fluid-impermeable material such that most of the atoms of the various components of the multicomponent membrane are not mixed in the same solid phase This is because there are at least two solid phases in the solid film.

The multiphase solid film of the present invention is substantially different from "doped" materials known in the art. A typical doping operation involves a small amount of an element or its oxide
(I.e., the dopant) in a large amount of the composition (i.e.,
To the host material), wherein the atoms of the dopant are made to be permanently mixed with the host material during the doping step, whereby the material becomes a single phase. Form. On the other hand, the multiphase solid membrane of the present invention has a product fluid ion conductive material and an electron conductive material, which are not present in the above-described dopant / host material relationship, but are substantially separate phases. Exists. Thus, the solid film of the present invention may be referred to as a two-phase, two-part conductor, multi-phase or multi-component film, rather than a doped material.

The solid film of the present invention comprises a first surface, a second surface,
An electron conductive path between the first surface and the second surface and an oxygen ion conductive path between the first surface and the second surface may be provided.

The multiphase films of the present invention can be used for electron microscopy, X-ray diffraction analysis, X-ray adsorption mapping, electron diffraction analysis, infrared analysis, etc. (these detect differences in composition over the multiphase region of the film). Can be distinguished from the doped material by conventional procedures such as

Typically, the product fluid ionically conductive material or phase comprises an oxide containing divalent and trivalent cations (eg, calcium oxide, scandium oxide, yttrium oxide, lanthanum oxide, etc.), Is a solid solution (i.e., a solid "electrolyte") formed between the oxide containing a multivalent cation (e.g., zirconia, tria and ceria), or the product fluid ionic conductive material or phase has a perovskite structure The product fluid contains an ion conductive mixed metal oxide. It is believed that their high ionic conductivity is due to the presence of vacancies at the product fluid ionic sites. Certain product fluid ion vacancies are created for each divalent or two trivalent cation that replaces a tetravalent ion in the lattice. Numerous oxides (e.g., yttria-stabilized zirconia, doped ceria, thoria-base
d) material or doped bismuth oxide) can be used. Some of the known solid oxide transfer materials include Y ₂ O ₃ stabilized ZrO ₂ , CaO stabilized ZrO ₂ , Sc ₂ O ₃ stabilized Zr
O ₂ , Y ₂ O ₃ stabilized Bi ₂ O ₂ , Y ₂ O ₃ stabilized CeO ₂ , CaO stabilized Ce
O ₂ , ThO ₂ , Y ₂ O ₃ stabilized ThO ₂ , or ThO ₂ , ZrO ₂ , Bi ₂ O ₃ , CeO ₂ or HfO ₂ stabilized by adding any one of lanthanoid oxide and CaO There is. Many other oxides that exhibit product fluid ionic conductivity are known and can be used in this multiphase mixture and are included in the concept of the present invention.

Of these solid electrolytes, Y ₂ O ₃ (yttria) and CaO (calcia) stabilized ZrO ₂ (zirconia) materials are preferred. These two solid electrolytes are characterized by their high ionic conductivity, their product fluid ionic conductivity over a wide range of temperatures and product fluid pressures, and their relatively low cost.

Applicants have also noted that the perovskite structure exhibits excellent electronic and product fluid ionic conductivity in multiphase materials, so that the perovskite material may be an electronically conductive material, a product fluid ionic conductive material or I found that both of them could be used. The resulting multiphase mixture can be coated with a porous, chemically active material to produce a high flux solid film.

The present invention provides a dense, gas-impermeable, multiphase mixture containing from about 1 to about 75 parts by volume of an electron conducting phase and from about 25 to about 99 parts by volume of a product fluid ion conducting phase. It may consist of a solid film having

The porous coating may comprise a metal selected from the group consisting of platinum, silver, palladium, lead, cobalt, nickel, copper, bismuth, samarium, indium, tin, praseodymium, their oxides and combinations thereof. Contains metal oxide. In such a case, the coating, under operating conditions, is less than about 1.0 ohm ^-1 cm ^-1 , preferably less than about 0.1 ohm ^-1 cm ^-1 , and most preferably
It shows an oxygen ion conductivity of less than 0.01 ohm ^-1 cm ^-1 . The porous coating can be applied using standard application methods including, but not limited to, spraying, dipping, laminating, pressing, implanting, sputter deposition, chemical vapor deposition, and the like.

The membrane of the present invention can be used to recover product fluid (eg, oxygen) from a product stream containing product fluid. This recovery includes pumping the product fluid containing feed stream to a first chamber separated from the second chamber by the membrane; applying an excess product fluid partial pressure in the first chamber and / or By applying a low product fluid partial pressure in the chamber,
Establishing a positive product fluid partial pressure difference between the first and second chambers; at a temperature greater than about 400 ° C., contacting the product fluid containing feed stream with the membrane to produce a product fluid containing feed This is done by separating the stream into a permeate stream rich in product fluid and an eluent stream lean in product fluid.

The product fluid in the product fluid containing feed stream present in the first chamber is adsorbed on the first surface of the membrane, ionized by the membrane, and in this ionized form, the fluid impermeable membrane The difference in product fluid partial pressure between the first and second chambers provides the driving force to cause this separation when raising the processing temperature to a temperature sufficient to transport through. The product fluid-enriched permeate is collected or reacts in a second chamber, where the ionic product fluid is passed through the second chamber at the second surface of the membrane to generate electrons. Upon release they are converted to neutral form.

The positive product fluid partial pressure difference between the first and second chambers is such that in the first chamber, the feed fluid (eg, in an oxygen separation process, air or other oxygen-containing fluid) This can occur by compressing the product fluid-rich permeate at a pressure equal to or greater than about one atmosphere to a pressure sufficient to recover the permeate. Typical pressure ranges are from about 15 psia to about 250 psia, with the optimal pressure varying depending on the amount of product fluid in the product fluid-containing feed. Conventional compressors may be used to achieve the required product fluid partial pressure. Alternatively, the positive product fluid partial pressure difference between the first and second chambers is established by evacuating the second chamber to a pressure sufficient to recover the product fluid-rich permeate. Achievable. The exhaust of the second chamber may be performed mechanically using a compressor, a pump, or the like, or may be performed chemically by reacting a permeate flow rich in the product fluid. It may be performed thermally by cooling the body-rich permeate, or it may be achieved by other methods known in the art. In the present invention, the above method can utilize the increase in the product fluid partial pressure in the first chamber while reducing the product fluid partial pressure in the second chamber. The relative pressure may also be changed during operation. It is necessary to optimize the separation of the product fluid, or
This is because it requires a process of supplying raw materials to two chambers or receiving product streams therefrom.

The recovery of the product fluid-rich permeate may be accomplished by storing the substantial product fluid-rich permeate in a suitable vessel or by transferring it to another step. . For an oxygen production process, the product fluid-enriched permeate typically comprises pure oxygen or high purity oxygen (which generally comprises at least about 90% by volume of O ₂ , preferably about 95% by volume). O ₂ exceeds, in particular, contain to) defined as including O ₂ in excess of 99 volume%.

Although the separation and purification of oxygen are described herein for illustrative purposes, the present invention
It can be used for the separation, purification and reaction of other product fluids, including but not limited to nitrogen, argon, hydrogen, helium, neon, air, carbon monoxide, carbon dioxide, syngas, and the like.

[0060]

The following examples are provided to further illustrate Applicants' invention. This example is illustrative and is not intended to limit the scope of the appended claims.

Example 1 A mixed conductor fluid impervious membrane having an apparent composition of [La _0.2 Sr _0.8 ] [Co _0.1 Fe _0.7 Cr _0.2 Mg _0.01 ] O _3-δ was prepared according to US Pat. No. 5,061,682 (the content of , Incorporated herein by reference) in a manner similar to that described in the Examples.
To about 30 liters of deionized water containing dissolved sucrose, 4232.60 grams of Sr (NO _{3) 2,} 773.80 grams of L
a ₂ O ₃ (Alpha, dried at 850 ° C.), 6927.80 grams of Fe (NO ₃ )
9H ₂ O, 730.50 g of _{Co (NO 3) 3 · 6H} 2 O, and 64.10 g of Mg (NO _{3) 2} was added.

The above ceramic precursor solution was spray-dried using a portable spray dryer. Suitable portable spray dryers are available from Niro Atomizer of Columbia, Md. The spray dryer includes a centrifugal atomizer that can accelerate to 40,000 rpm. This atomizer is installed near the top of the drying chamber. The drying chamber has an inside diameter of 2 feet 7 inches, a cylindrical height of 2 feet and a 60 ° conical bottom. The centrifugal atomizer and the drying chamber are manufactured from stainless steel. The drying chamber is connected to an electric heater for feeding dry air into the drying chamber. Dry air is drawn from the drying chamber by a blower located downstream of the drying chamber. The spray drier includes a cyclone separator that receives drying air and dried product from the bottom of the drying chamber. This cyclone separator separates the dry product from the exhaust dry air. At the bottom of the cyclone separator is an outlet through which the dry particles fall into a vertically oriented tubular furnace capable of maintaining an air temperature of about 300C to 450C. The dried particles are passed through the tube furnace
Pyrolyzed. This tube furnace transforms particles that descend freely into
It is high enough to provide a residence time of about 0.5-2.0 seconds. The bottom of the tube furnace communicates with a collection chamber where the ceramic particles are collected.

The above ceramic precursor solution was introduced into the spray drying chamber at a flow rate of about 1.8 liters per hour. The precursor solution was broken up into droplets having a diameter on the order of about 20-50 microns by a centrifugal atomizer rotating at about 30,000 RPM. Air flow rates through the drying chamber and cyclone ranged from about 35 to 40 standard cubic feet per minute. The air entering the drying chamber was preheated to about 375 ° C. As the droplets force convection toward the bottom of the drying chamber, their diameter decreases by about
They were dehydrated to a critical state of dehydration, dropping below 10.0 microns. The temperature of the drying gas at the bottom of the drying chamber was approximately 125 ° C., which ensured that substantially all of the water had been removed from the particles in the spray dryer. Then, the dried powder and the dried air were separated from each other in the cyclone separator. The separated powder dropped by gravity into the tube furnace and was preheated to about 490 ° C. The residence time of the particles in the furnace ranged from about 0.5 to 2.0 seconds. The temperature in the tube furnace initiated an exothermic anionic redox reaction between nitrate ions and oxides in the individual particles.
Combustion by-products (CO ₂ and water vapor) exited the exhaust through this system while reacting particles dropped into the collection jar. About 1000 grams of particles were collected.

When the obtained powder was analyzed, [La _0.19 S
r _0.8 ] [Co _0.1 Fe _0.69 Cr _0.2 Mg _0.01 ] O _x . With ZrO ₂ media 820 g, the jar mill, 190.10G of powder obtained polyvinyl butyral resin (Monsa
nto, St. Louis MO) and 160 ml of toluene were ground and ground for approximately 3 hours. 20 ml of absolute ethanol was added and the slurry was left overnight without grinding. The product was filtered, the resulting powder was dried and sieved through a 60 mesh Tyler screen. By X-ray diffraction (XRD) of the powder, the substance was found to have 1
It was found to be a 00% cubic perovskite phase.

4 g of the sieved powder was
Under a pressure of 00 psi, they were pressed into 1-3 / 8 inch diameter disks. The disc is placed in air at 105 ° C for 15
Firing for 1 minute, the temperature was raised to 1300 ° C. over 13 hours, maintained for 1 hour, and then cooled to room temperature.

Both sides of the disc were polished with isopropanol to a final thickness of 1 mm with 500 grit SiC. 3.0% by weight of Bi ₂ O ₃ (Flu
ka) was added, the resulting mixture was diluted with toluene,
A low viscosity coating liquid was formed. Both sides of the polished disc,
The coating solution was coated over an area of approximately 2.0 cm ² . The coated disc was heated to 1065 ° C. in air for 10.5 hours and then cooled to room temperature. The coated disc was adhered to a 1 inch outer diameter mullite tube using a 1/8 inch thick Pyrex ring and its exposed surface area was approximately 2 cm ² .

The mullite tube, disk and gas handling device were placed in a thermistor controlled electric heater. 850 ° C (this is
Approximately 1 cm from the tube / disc junction, indicated by a thermocouple fixed to a mullite tube). On one side of the disc, air began to flow at a rate of 1.0 liter / min, and on the other side of the disc, a helium permeate feed began to flow at 150 cm ³ / min. The effluent helium permeate was analyzed using online gas chromatography. The permeate was also analyzed for nitrogen to correct for air leakage into the permeate.

The oxygen flux of this membrane was calculated using the following equation:

[0069]

Embedded image

The oxygen flux was normalized to compensate for changes in membrane disk thickness using the following equation:

[0071]

Embedded image

The oxygen flux per unit area was calculated by dividing the oxygen flux (q'o ₂ ) normalized for thickness by the membrane disk area (measured in cm ² ).

The operating characteristics of the disc were evaluated over a period of 50 hours. The test data is shown in Table 1 below. At the point where all data were measured, room temperature (T _O ) was kept at 293 ° K and P _O was 741 mm Hg. Air supply speed is 100
Maintained at 0 sccm.

The data in Table 1 shows that in air and at high temperatures,
It shows the excellent long-term stability of this material and the high oxygen flux.

[0075]

[Table 1]

[0076]

The present invention relates to a novel membrane formed from a perovskite structure or a multiphase structure and having a chemically active coating. This membrane exhibits a particularly high proportion of fluid flux. One application is the separation of oxygen from oxygen-containing feeds at elevated temperatures. The membrane is a conductor of oxygen ions and electrons and is substantially stable in air over a temperature range from 25 ° C. to the operating temperature of the membrane.

 ──────────────────────────────────────────────────続 き Continuation of the front page (71) Applicant 595017584 200 Public Square, 39G BP Building, Clevel and, Ohio 44114, U.S.A. S. A. (72) Inventor Thomas L. Cable United States Ohio 44065, Newbury, Pekin Road 10685

Claims (10)

[Claims] 1. A solid film having a first surface and a second surface, the solid film having the following (A) and (B): (A) The following (a), (b) and (c) A structure selected from the group consisting of: (a) a substantially perovskite material; (b) a dense gas-impermeable multiphase mixture of an electron conducting phase and an oxygen ion conducting phase, wherein the electron conducting phase is Forming an electron conductive path between the first surface and the second surface, and the oxygen ion conductive phase forming an oxygen ion conductive path between the first surface and the second surface; and c) a combination thereof; and (B) a porous, chemically active electron conducting coating selected from the group consisting of metals, metal oxides and combinations thereof. 2. The solid film according to claim 1, wherein the structure is a substantially perovskite material. 3. The substantially perovskite material comprises:
｛A _1-x A ' _x ｝ BO _3-δ , ｛Bi _2-y A _y O _2-δ' ｝ {(A _1-x A ' _x ) _n-1 B
_2. The solid membrane of claim 1, having a composition selected from the group consisting of: _n O _{3n + 1-δ ″} } and combinations thereof, wherein A is Ca, Sr, Ba, Bi, Pb, K , Sb, Te, Na and mixtures thereof; A 'is La,
Y, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, T
B is selected from the group consisting of m, Yb, Lu, Th, U and mixtures thereof; B is Fe, Mg, Cr, V, Ti, Ni, Ta, Mn, Co,
Selected from the group consisting of V, Cu and mixtures thereof;
x is about 0.9 or less; y is an integer from 0 to 2;
n is an integer from 1 to 7; and δ, δ ′ and δ ″
Is determined by the valence of the metal. 4. The method of claim 1, wherein said substantially perovskite material is cubic perovskite, brownmillerit.
3. The solid membrane of claim 2, wherein the solid membrane is selected from the group consisting of e), an Aurivillius phase and combinations thereof. 5. The solid membrane according to claim 2, wherein said substantially perovskite substance is a cubic perovskite. 6. The substantially perovskite substance
The solid membrane according to claim 1, having a composition of ｛A _1-x A ' _x ｝ BO _3-δ : wherein A is Ca, Sr, Ba, Bi, Pb, K, Sb, Te,
Selected from the group consisting of Na and mixtures thereof; A '
Is La, Y, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, H
o is selected from the group consisting of Er, Tm, Yb, Lu, Th, U and mixtures thereof; B is Fe, Mg, Cr, V, Ti, Ni, Ta,
Is selected from the group consisting of Mn, Co, V, Cu and mixtures thereof; x is less than or equal to about 0.9; and δ is determined by the valency of the metal. 7. The solid film according to claim 2, wherein the perovskite substance is brown millerite. 8. The porous coating is selected from the group consisting of platinum, silver, palladium, lead, cobalt, nickel, copper, bismuth, samarium, indium, tin, praseodymium, oxides thereof, and combinations thereof. ,
The solid film according to claim 2. 9. A solid film having a structure of a substantially perovskite material and a porous, chemically active electron conducting coating, wherein the electron conducting coating comprises a metal, a metal oxide and combinations thereof. Selected from the group, the perovskite substance is {(Bi _2-y A _y O _{2-δ ′} )} {((A _1-x A ′ _x ) _n−1 B _n
O _{3n + 1-δ ″} } solid film: where A is Ca, S
A 'is selected from the group consisting of r, Ba, Bi, Pb, K, Sb, Te, Na and mixtures thereof; A' is La, Y, Ce, Pr, Nd, P
m is selected from the group consisting of m, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Th, U and mixtures thereof;
e is selected from the group consisting of Mg, Cr, V, Ti, Ni, Ta, Mn, Co, Cu and mixtures thereof; x is about 0.9 or less; y is an integer from 0 to 2; n is an integer from 1 to 7; and δ ′ and δ ″ are determined by the valency of the metal. 10. A solid film having a structure of a substantially perovskite material and a porous coating, wherein the coating comprises:
A solid film selected from the group consisting of a metal, a metal oxide, and a combination thereof, wherein the perovskite material has an Aulivili phase.