JP2005279439A - Oxygen separation membrane element, oxygen production method, and reactor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oxygen separation membrane element having a higher oxygen transmission rate and an efficient oxygen production method and reactor using the same.
SOLUTION: At least one of a front surface 14 and a back surface 16 of an oxygen separation membrane 12 is provided with a plurality of projections 24 having a uniform size regularly arranged along two directions at a constant center interval. The surface area of the front surface 14 or the back surface 16 is significantly larger than that in the case where irregular protrusions in the size and arrangement direction are provided. That is, when the surface area of the surface 14 is increased by providing the protrusions 24, the ionization rate is increased, and when the surface area of the back surface 16 is increased, the recombination rate is increased. Therefore, since these are suitably suppressed from reducing the oxygen permeation rate, coupled with the fact that the oxygen separation membrane 12 is thinned to about 0.5 (mm), thereby increasing the transport rate in the membrane, High transmission speed can be obtained. [Selection] Fig. 3

Description

  The present invention relates to an oxygen separation membrane element for selectively permeating oxygen and use thereof.

  Provided with a dense oxygen separation membrane having oxygen ion conductivity, oxygen is dissociated from the gas on one side of the oxygen separation membrane, and ionized oxygen ions are recombined on the other side, thereby allowing oxygen to flow from one side to the other. Oxygen separation membrane elements are known for selective permeation to and separation from the gas. For the purpose of promoting dissociation and recombination, for example, a dissociation catalyst layer for dissociating and ionizing oxygen is formed on one side of the oxygen separation membrane, and oxygen ions are formed on the other side. A recombination catalyst layer is formed to recombine. Each of the dissociation catalyst layer and the recombination catalyst layer is, for example, a porous film that allows easy gas flow. According to such an oxygen separation membrane element, oxygen can be easily separated from a gas containing oxygen. Therefore, by using this, for example, a cryogenic separation method or a PSA (pressure fluctuation adsorption) method can be used. An alternative and inexpensive method for producing oxygen can be provided. In particular, in the case where the oxygen separation membrane is composed of an electron-oxygen ion mixed conductor, the oxygen separation membrane itself has electronic conductivity, so that an external electrode and an external circuit for short-circuiting one surface and the other surface are unnecessary. In addition, there is an advantage that a high oxygen transmission rate can be obtained by increasing the moving speed of oxygen ions by the potential difference between both surfaces (see, for example, Patent Documents 1 and 2).

The oxygen separation membrane element as described above can be used as a reactor for an oxidation reaction apparatus such as a partial oxidation reaction of hydrocarbons. For example, if a gas containing hydrocarbon such as methane (CH ₄ ) is supplied to the other side of the oxygen separation membrane, the hydrocarbon can be oxidized by the permeated oxygen ions. Therefore, it can be used for GTL (Gas to Liquid: a technology for synthesizing liquid fuel from natural gas by chemical reaction), production of hydrogen gas for fuel cells, and the like. Even in such a utilization mode, the reaction can be promoted by providing a catalyst layer or increasing the oxygen transmission rate using an electron-oxygen ion mixed conductor.
JP 2002-326021 A JP-T-2003-527958 Japanese Patent No. 2813576

  By the way, the oxygen permeation rate in the oxygen separation membrane element as described above is the dissociation rate and ionization rate of oxygen on one side (hereinafter collectively referred to as ionization rate), the ion transport rate in the membrane, and the oxygen transport rate on the other side. It is determined by the recombination rate and the like. When the material of the oxygen separation membrane and the catalyst layer is determined, the ion transport rate is constant, and the time required to reach from one side to the other (substantial transport rate) is the oxygen transport rate. Depending on the thickness of the separation membrane, the ionization rate and recombination rate depend on the size of the contact area between the oxygen separation membrane and the catalyst layer and the gas. Therefore, conventionally, for the purpose of increasing the oxygen transmission rate, the thickness of the oxygen separation membrane is made as thin as possible and the surface area thereof is made as large as possible. For example, in Patent Documents 1 and 2, the surface area is increased by forming at least one surface on one side and the other side as an uneven surface.

  However, in the conventional techniques described in Patent Documents 1 and 2, even if the surface of the oxygen separation membrane is uneven and the surface area is increased, a sufficient oxygen transmission rate can still be obtained. could not.

  The present invention has been made on the basis of the above knowledge, and an object thereof is to provide an oxygen separation membrane element having a higher oxygen transmission rate, and an efficient oxygen production method and reactor using the same. It is in.

  The gist of the oxygen separation membrane element of the first invention for achieving such an object includes a dense oxygen separation membrane having oxygen ion conductivity, dissociated from a gas on one surface side of the oxygen separation membrane, and An oxygen separation membrane element for selectively permeating oxygen from one surface to the other surface and separating it from the gas by recombining ionized oxygen ions on the other surface side, comprising: (a) the oxygen It is to include a plurality of protrusions of a uniform size arranged at a constant center distance along each of the first direction and the second direction intersecting each other on at least one of the one surface and the other surface of the separation membrane.

  Further, the gist of the oxygen production method of the second invention is that the oxygen separation membrane element of the first invention is used, a source gas containing oxygen is supplied to the one surface side, and oxygen separated from the source gas is supplied. Is to be recovered from the other side.

  The gist of the reactor of the third invention is that (a) the oxygen separation membrane element of the first invention and (b) a gas containing oxygen is supplied to one surface side of the oxygen separation membrane element. A first gas supply path; (c) a second gas supply path for supplying a gas containing a predetermined compound to the other surface side; and (d) a reaction between oxygen and the predetermined compound on the other surface side. And a gas recovery path for recovering the generated gas.

  According to the first invention, since at least one of the one surface and the other surface of the oxygen separation membrane has a large number of protrusions of uniform size regularly arranged along at least two directions at a constant center interval, The surface area of one surface or the other surface on which this is provided becomes significantly larger than when irregular projections in the size and the arrangement direction are provided. Therefore, since the ionization rate or the recombination rate is increased according to the amount of increase in the surface area, the projection forming surface is set to one or both so that the rate of at least the rate-limiting factor can be increased, The oxygen permeation rate can be increased by determining the mutual interval and the like in consideration of the mutual balance such as the above speeds and the ion transport rate in the oxygen separation membrane.

  For example, in the case where a large number of protrusions are provided on the one surface, the contact area between the oxygen separation membrane surface and the gas containing oxygen is significantly increased as compared with the conventional case, so that the ionization rate of oxygen is significantly increased. Further, when a large number of protrusions are provided on the other surface, the area of the other surface, that is, the area where oxygen is recombined is remarkably increased, so that the recombination rate of oxygen ions is significantly increased. That is, the reaction is promoted by regularly arranging a large number of protrusions of uniform size on one side and the other side. Such an action can be obtained regardless of whether a catalyst layer (dissociation catalyst layer or recombination catalyst layer) is provided on one side or the other side of the oxygen separation membrane. The catalyst layer may be provided on at least one of the other surfaces, or the catalyst layer may not be provided on any of both surfaces.

  Incidentally, in order to further increase the transmission speed compared with the prior art, the present inventors have made additional tests on the method of forming protrusions by sputtering, etching, etc. described in Patent Documents 1 and 2, but variously changed the conditions. Even when the surface area was further increased, no significant change in permeation rate was observed. That is, if unevenness is formed on the surface of the oxygen separation membrane, the oxygen transmission rate is dramatically improved as compared with the case where there is no unevenness, but there is no correlation with the surface area and the transmission rate cannot be improved further. It was. Therefore, further research was conducted by variously changing the method of forming the irregularities, and as a result, when the projections were formed on the surface using a diamond grindstone, the oxygen transmission rate was remarkably improved. The protrusions thus provided have regular irregularities as described above on the surface of the oxygen separation membrane, and the reason why the permeation speed remained low in the prior art is that the size and position of the protrusions are irregular. I came to think that it was because it was. Irregular irregularities have a smaller surface area than regular irregularities due to the difficulty in miniaturization. The improvement in the transmission speed is so remarkable that it cannot be considered that it is caused only by the difference in surface area, and the effect is not clear. However, when regular irregularities are formed, irregularities are formed by sputtering or etching. From this case, a remarkable improvement in the transmission rate was recognized that could not be predicted. The present invention has been made based on such findings.

  According to the second invention, when a source gas containing oxygen is supplied to the one surface side of the oxygen separation membrane element as described above, oxygen therein is selectively ionized and permeated through the oxygen separation membrane. Since it is recombined and recovered on the other side, oxygen in the raw material gas is efficiently separated, so that oxygen can be produced at low cost and high efficiency.

  According to the third aspect of the invention, the oxygen separation membrane element as described above is provided, and a gas containing oxygen from the first gas supply path to the one surface side is predetermined from the second gas supply path to the other surface side. Each of the gases containing the compound is supplied, and the gas generated by the reaction between oxygen and the predetermined compound is recovered from the gas recovery path. Therefore, since the oxygen permeation rate is increased by increasing the ionization rate or recombination rate of oxygen, the reaction efficiency with a predetermined compound in the gas supplied to the other surface side is increased, so that high efficiency is achieved. A reactor is obtained.

  The above-mentioned many protrusions are preferably provided on the entire surface of one surface or the other surface of the oxygen separation membrane. For example, a portion where the protrusions are not provided depending on manufacturing, handling, or structural reasons. There is no problem even if there is. If most of the protrusions are provided regularly, the effects of the present invention can be enjoyed even if the protrusions are provided irregularly in part.

  In the present invention, “dense oxygen separation membrane” means that the oxygen separation membrane has a structure that does not allow gas molecules in the atmosphere to which the oxygen separation membrane is exposed to permeate in the thickness direction as it is when the oxygen permeable membrane element is used. It means that you are doing. That is, the preciseness mentioned here is not uniquely determined, and it is sufficient if it has the above-described characteristics in the intended use mode.

  Here, preferably, the oxygen separation membrane element has regular irregularities based on the numerous protrusions on the surface thereof. In this way, when the protrusion is provided on one side, the ionization rate of oxygen is increased, and when some gas is supplied for the purpose of reacting with oxygen even when provided on the other side. The reaction rate is increased. Such an effect is obtained because the gas supplied to one side or the other side of the oxygen separation membrane is subjected to substantially the same flow resistance on the entire surface, and is formed by regular irregularities. It is thought that by flowing in one direction along the straight groove, a uniform flow rate is obtained near the surface of the oxygen separation membrane and a rectifying effect is obtained. That is, since the gas supplied toward one surface or the other surface of the oxygen separation membrane element is uniformly brought into contact with the entire surface, it is estimated that the entire surface is effectively used, thereby improving the efficiency. The

  Preferably, in the oxygen separation membrane, a catalyst layer for promoting dissociation or recombination of the oxygen is provided on a projection forming surface provided with the plurality of projections among the one surface and the other surface, The catalyst layer has unevenness on the surface following the projection forming surface. In this way, even when the catalyst layer is provided, the oxygen permeation efficiency is further enhanced as compared with the case where the surface is flat. This is presumed to be because a rectifying effect or the like is given to the gas by the concave groove provided on the surface of the catalyst layer. Such a catalyst layer can be provided by making the thickness dimension of the catalyst layer sufficiently thinner than the height dimension of the protrusion formed on the oxygen separation membrane, for example. Further, the catalyst layer may be dense or porous, and the oxygen separation membrane can also serve as this.

  Preferably, the plurality of protrusions have a rectangular cross section along at least one of the first direction and the second direction. That is, a groove having a rectangular cross-sectional shape is provided between a large number of protrusions. The shape of the protrusion can be arbitrarily determined as long as it is provided with a substantially uniform size and shape on the entire surface, and may be various shapes such as a rhombus, a triangle, a hexagon, and a circle in plan view, Further, a groove having a semi-circular or semi-circular cross section may be formed between the protrusions, but in this way, the cross-sectional shape is a wavy shape, that is, a shape in which the side surface of the protrusion is gently inclined. Compared with the case where it comprises, the surface area of an oxygen separation membrane element can be made still larger. The plurality of protrusions more preferably form a rectangle in plan view, and more preferably form a square.

  Preferably, the oxygen separation membrane is a mixed conductor having oxygen ion conductivity and electron conductivity. In this way, oxygen ions can be continuously transmitted between them without using an external electrode or an external circuit for short-circuiting the one surface and the other surface, and the moving speed of the oxygen ions is increased. Therefore, there is an advantage that the oxygen transmission rate can be further increased.

Preferably, the oxygen separation membrane has a general formula Ln _1-x Ae _x MO ₃ (where Ln is a lanthanoid, Ae is one or a combination of two or more selected from Ba, Sr, and Ca, M is Fe, Mn, Ga, Ti, Co, Zr, Ce, Mg, Ge, Zn, Cu, Sc, V, Cr, Ni, Y, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, One or a combination of two or more selected from Sb, Pb, Bi, Po, Al, In, and Sn, composite compounds represented by 0 ≦ x ≦ 1), ZrO ₂ oxides, CeO ₂ oxides It consists of one or a combination of two or more selected from among products. Since these compounds are both dense and have a high oxygen transmission rate, they are suitable as the oxygen separation membrane material of the present invention.

Preferably, the oxygen separation membrane is Ce _2-x Zr _x O _4-σ (where 0 <x <2, 0 ≦ σ ≦ 4), CeGd oxide, CeSm oxide, Ba (CaNb) _It consists of one or a combination of two or more selected from _two oxides, BiVCu oxides, and ZrO ₂ oxides. These compounds are also suitable because they are dense and have a high oxygen transmission rate. In particular, with Ce-based materials, the movement of oxygen ions in a reducing atmosphere is expected to increase. More preferably, the oxygen separation membrane is made of a material containing one or a combination of two or more selected from MgO, Al ₂ O ₃ and Y ₂ O ₃ . Films made of these materials have the advantage of having a relatively high strength.

  Preferably, the oxygen separation membrane is made of a material containing a metal or metal oxide having electron conductivity. In this case, the metal or metal oxide imparts electron conductivity to the oxygen separation membrane or further enhances the electron conductivity, so that the transmission rate of oxygen ions is further increased, and consequently the transmission rate. Has the advantage of being enhanced.

  Preferably, the oxygen separation membrane is provided on the porous support so as to cover the entire surface. This porous support may be located on either the one side or the other side of the oxygen separation membrane. In this way, since the gas can easily pass through the inside of the porous support, by configuring the porous support to have an appropriate thickness dimension, the oxygen separation membrane element machine is not affected without affecting the oxygen transmission rate. Can increase the mechanical strength. Moreover, since the mechanical strength of the oxygen separation membrane element is ensured by the porous support, it becomes possible to reduce the thickness dimension of the oxygen separation membrane to such an extent that the oxygen transmission rate is not limited by the film thickness, The effect of improving the permeation speed by increasing the surface area can be obtained more remarkably. In the case where such a porous support is provided, when a dissociation catalyst layer or a recombination catalyst layer is further provided, one is on the surface of the oxygen separation membrane and the other is the oxygen separation membrane and the porous support. The other side may be provided on the surface of the porous support, preferably in a state of being permeated therewith.

  In the above embodiment, “covering the entire surface” means that one surface of the porous support is the same as the surface of the oxygen separation membrane on the side opposite to the porous support when the oxygen separation membrane element is used. It means not being exposed to space. For example, even if one surface of a porous support provided with an oxygen separation membrane in a non-use state is partially exposed, such a mode can be used as long as that part is covered by an apparatus or the like during use. It is included in the above “covering the entire surface”.

Preferably, the porous support has the general formula Ln _1-x Ae _x MO ₃ (where Ln is a lanthanoid, Ae is one or a combination of two or more selected from Ba, Sr, and Ca) , M is Fe, Mn, Ga, Ti, Co, Zr, Ce, Mg, Ge, Zn, Cu, Sc, V, Cr, Ni, Y, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd , Sb, Pb, Bi, Po, Al, In, Sn selected from one or a combination of two or more, a composite compound represented by 0 ≦ x ≦ 1), ZrO ₂ oxide, CeO ₂ It is composed of one or a combination of two or more selected from oxide, magnesium oxide (MgO), aluminum oxide (Al ₂ O ₃ ), silicon nitride (Si ₃ N ₄ ), and silicon carbide (SiC). . The material of the porous support is not particularly limited, but by doing so, the difference in thermal expansion from the film material is reduced, and film peeling and the like are further suppressed.

  Preferably, the oxygen separation membrane and the porous support are made of the same material. In this way, since the thermal expansion coefficients of the two coincide with each other, even when heated or cooled during the manufacturing process or in use, damage due to the difference in thermal expansion amount is suitably suppressed.

Preferably, the oxygen separation membrane and the porous support are made of materials having different compositions. Since the strength of the entire oxygen separation membrane element must be ensured by the support, the required properties of the support and the oxygen separation membrane are different. For example, when the required strength is relatively high, oxygen separation is required. It is desirable that the membrane and the support are made of different materials. In addition, in the case where only the membrane side is in a reducing atmosphere (for example, when CH ₄ is flowed), the oxygen separation membrane may be reduced and expanded. It is preferable to relatively increase the thermal expansion.

  Preferably, the porous support has an average pore diameter r in the range of 0.1 <r <20 (μm) and a porosity p in the range of 5 <p <60 (%). This range is preferable in order to suppress the decrease in the oxygen permeation rate and increase the strength of the oxygen separation membrane element as much as possible. If the pore diameter and the pore diameter are too small, the gas permeation resistance of the porous support increases, so even if the oxygen separation membrane is made thin, the porous support becomes a rate-limiting factor, so the oxygen permeation rate is remarkably high. descend. On the other hand, if the pore diameter and the pore diameter are too large, the mechanical strength is lowered and the function as a support is lost.

  Preferably, the plurality of protrusions are fine protrusions having a height dimension in a range of 5 to 1000 (μm) and a center interval in a range of 5 to 1000 (μm). In order to maintain the strength of the protrusion and not to disturb the gas rectifying property, it is preferable to have such a size. More preferably, the height dimension is in the range of 10 to 500 (μm), and the center distance is in the range of 10 to 500 (μm). For example, the height dimension is preferably about 100 (μm), and the center interval (pitch) is preferably about 150 (μm).

Preferably, the dissociation catalyst layer is a La-Sr-Co-based oxide, a La-Sr-Mn-based oxide, or a platinum-based element. More preferably, it is made of La _x Sr _1-x CoO ₃ (0 <x <1, preferably x = 0.6). According to such a catalyst, oxygen in the gas supplied to the one surface side of the oxygen separation membrane is suitably ionized, permeated through this, and guided to the other surface side. In addition to the above materials, the catalyst layer is composed of Sm _x SrCoO ₃ (0 <x <1, preferably x = 0.5), La _1-x Sr _x MnO ₃ (0 <x <1, preferably x = 0.15), La _1-x Sr _x Co _1-y Fe _y O ₃ (0 <x <1, 0 <y <1, preferably x = 0.9, y = 0.1) are also preferably used. In addition, the dissociation catalyst layer can also be comprised with the same material as an oxygen separation membrane, and in that case, a dissociation catalyst layer can be comprised with a part of the oxygen separation membrane.

  Preferably, the recombination catalyst layer includes Ni, Co, Ru, Rh, Pt, Pd, Ir, and the like. Preferably, it is made of Ni formed by reducing NiO. According to such a catalyst, oxygen ions guided to the other surface side of the oxygen separation membrane are suitably recombined, and oxygen is recovered from the other surface side. In addition, even when the dissociation catalyst layer and the recombination catalyst layer are made of any of the materials described above, oxygen can permeate through the grain boundaries or the inside of the grains, so that a porous catalyst layer is formed as well as a porous layer. Can do.

  Preferably, the oxygen separation membrane has a thickness dimension in a range of 50 to 5000 (μm) in an aspect in which the porous support is not provided, and the porous support In the embodiment in which the body is provided, the body has a thickness dimension of 1000 (μm) or less. In this way, since the film thickness of the oxygen separation membrane is sufficiently thin as long as the mechanical strength of the oxygen separation membrane element can be ensured, it is suitably suppressed that the rate of oxygen permeation is limited and is high. It becomes easy to obtain the oxygen transmission rate. If the porous support is not provided, it is necessary that the oxygen separation membrane itself has sufficient mechanical strength, so that it is necessary to have a thickness greater than or equal to the above thickness. In this case, since the mechanical strength of the oxygen separation membrane itself is not required, it is desirable to make it as thin as possible. Note that there is no particular lower limit on the thickness dimension of the oxygen separation membrane as long as its denseness is maintained.

Further, the oxygen separation membrane element, other such partial oxidation reactions of oxygen production or hydrocarbons as described above, by supplying the NO _x on one side, it can also be used for the reduction.

  Preferably, the oxygen separation membrane has a flat plate shape as a whole. Further, in the aspect in which the catalyst layer is provided, the dissociation catalyst layer is provided on one surface, and the recombination catalyst layer is provided on the other surface. With such a shape, it is easy to form the fine protrusions on one surface and the other surface. In an aspect in which such a plate-like oxygen separation membrane is provided on a porous support and a catalyst layer is provided, after the catalyst layers are provided on both sides of the separately formed oxygen separation membrane, the porous support is provided. Alternatively, an oxygen separation membrane element is produced by sequentially forming one catalyst layer, an oxygen separation membrane, and the other catalyst layer on a porous support. Examples of the flat plate shape include a disk shape and a rectangular plate shape.

  Preferably, the oxygen separation membrane has a cylindrical shape with one end closed. In an embodiment in which a catalyst layer is provided, one of the inner peripheral surface and the outer peripheral surface is provided with the dissociation catalyst layer. It corresponds to the one surface, and the other corresponds to the other surface provided with the recombination catalyst layer. The oxygen separation membrane is not limited to a flat one, and may be such a three-dimensional one. In the aspect in which the gas is supplied to the inner peripheral surface side, for example, a gas introduction tube may be inserted inside the cylindrical oxygen separation membrane and the gas may be supplied from the tip.

  Preferably, the porous support has a cylindrical shape with one end closed, and the oxygen separation membrane or the two kinds of catalyst layers and the oxygen separation membrane are sequentially laminated on the inner peripheral surface or the outer peripheral surface thereof. Is provided. In this way, the mechanical strength can be ensured by the porous support even in an aspect in which the oxygen separation membrane element has a cylindrical shape.

  Further, the above-mentioned many protrusions, preferably fine protrusions, can be formed by various methods. Specific examples include the following. That is, after forming a film without projections, it is an example to perform mechanical processing such as fine grinding or laser processing using a diamond grindstone or the like. There is also a method in which a large number of protrusions are formed at the time of molding using a micro-patterned mold and fired as it is. There are also micro-patterning film forming methods such as masking the surface to form a film by dip coating or CVD, or patterning printing. Further, after forming a film without projections, the surface can be masked and fine projections can be formed by chemical etching. These are appropriately selected according to the size, distribution density, accuracy, manufacturing cost, etc. of the projections to be formed.

  Preferably, when the oxygen separation membrane or the porous support has a bottomed cylindrical shape and the plurality of protrusions are formed on the inner peripheral surface thereof, the plurality of protrusions are A grindstone that is rotated around a rotation axis that is parallel to and does not coincide with the axis of the inner peripheral surface of the shape is formed by rotating around the axis while pressing the grindstone against the inner peripheral surface.

  Preferably, the oxygen separation membrane element is provided with the plurality of protrusions on one surface and the other surface of the oxygen separation membrane, respectively, and the dissociation catalyst layer and the recombination as necessary on the one surface and the other surface. After the catalyst layer is formed, it is manufactured by fixing it to the surface of the porous support. At this time, in the case where the large number of protrusions are provided on one surface thereof, the other surface of the oxygen separation membrane is preferably positioned on the porous support side. In this way, the surface of the dissociation catalyst layer can have unevenness due to the protrusions, so that the effect when the unevenness exists can be enjoyed.

  Preferably, the oxygen separation membrane element comprises: (a) dipping the porous support separately manufactured in slurry containing the constituent material of the oxygen separation membrane to separate it on the surface thereof. A dipping process for forming a membrane slurry layer, and (b) a firing process for forming the oxygen separation membrane by firing the separation membrane slurry layer at a predetermined temperature and sintering it on the porous support, and (c) A projection forming step of forming the plurality of projections on the surface of the oxygen separation membrane formed, and (d) a first catalyst slurry containing one constituent material of the dissociation catalyst layer and the recombination catalyst layer. An impregnation step of impregnating the porous support, and (f) a first catalyst layer forming step of forming one of the dissociation catalyst layer and the recombination catalyst layer by calcining the first catalyst slurry at a predetermined temperature; g) The other structure of the dissociation catalyst layer and the recombination catalyst layer An application step of applying a second catalyst slurry containing a material to the surface of the oxygen separation membrane; and (h) calcining the applied second catalyst slurry at a predetermined temperature to thereby dissociate the catalyst layer and the recombination catalyst. And a second catalyst layer forming step for forming the other of the layers.

  The dipping step and the separation membrane slurry layer forming step can be repeatedly performed an appropriate number of times until a slurry layer having a predetermined thickness is formed. Moreover, when forming the said oxygen separation membrane, a dissociation catalyst layer, and a recombination catalyst layer, a drying process is performed as needed before performing a baking process. This drying process may be performed alternately or repeatedly as needed, for example, when the dipping process is repeated.

  In addition, the slurry for forming the oxygen separation membrane, the dissociation catalyst layer, and the recombination catalyst layer includes a solvent such as water, a binder (binder), a dispersant, and the like in addition to the constituent materials.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the following embodiments, the drawings are appropriately simplified or modified, and the dimensional ratios, shapes, and the like of the respective parts are not necessarily drawn accurately.

  FIG. 1A is a plan view showing an oxygen separation membrane element 10 of one embodiment of the present invention, FIG. 1B is a side view thereof, and FIG. 2 is a plan view showing an enlarged main part thereof. FIG. 3 is an enlarged view schematically showing an example of the cross-sectional structure. 1 to 3, the oxygen separation membrane element 10 has a diameter of about 20 (mm) and has a thin disk shape as a whole, and an oxygen separation membrane 12 constituting an intermediate portion in the thickness direction. And an oxygen dissociation catalyst layer 18 and an oxygen recombination catalyst layer 20 provided on the front surface 14 and the back surface 16 respectively.

The oxygen separation membrane 12 is made of a lanthanum perovskite such as La _0.7 Sr _0.3 Ga _0.6 Fe _0.4 O ₃ or La _0.6 Sr _0.4 Ti _0.3 Fe _0.7 O _3, and has a thickness of about 0.5 (mm). The shape. This lanthanum perovskite is a mixed conductive ceramic having both oxygen ion conductivity and electronic conductivity. Therefore, while being dense, oxygen in contact with the front surface 14 or the back surface 16 can be ionized and transmitted, for example, from the front surface 14 toward the back surface 16.

  The surface 14 of the oxygen separation membrane 12 is provided with a large number of grooves 22 extending along two directions orthogonal to each other. The groove 22 has a rectangular cross section as shown in FIG. 2 and FIG. 3, and each of the grooves 22 extending along any direction has a width dimension W of about 50 (μm) and 100 (μm), for example. It has a depth dimension D of about, and is provided with a uniform mutual interval P of about 100 (μm), for example. For this reason, the surface 14 of the oxygen separation membrane 12 forms a square having, for example, a side of about 100 (μm) between the grooves 22 in a plan view and a height dimension of about D = 100 (μm). The protrusions 24 are provided along the two directions orthogonal to each other, for example, with a mutual interval of about W = 50 (μm), that is, with a center interval of about 150 (μm), and the uneven surface formed by the grooves 22 and the protrusions 24. It has become.

  The groove 22 is formed on substantially the entire surface 14 of the oxygen separation membrane 12, but there is a flat annular region with a width of about 1 to 2 (mm) where the groove 22 is not provided at the peripheral edge. To do. The height of the annular portion is the same as that of the protrusion 24. Note that the back surface 16 is not provided with any grooves 22 or the like, and is configured to be flat.

The oxygen dissociation catalyst layer 18 is a porous layer made of, for example, La _0.6 Sr _0.4 CoO _3, and is formed on substantially the entire surface 14 with a uniform thickness dimension of, for example, about 10 (μm). . The dissociation catalyst layer 18 is provided following the unevenness of the surface 14 in order to promote the dissociation and ionization of oxygen on the surface 14.

  The oxygen recombination catalyst layer 20 is a porous layer made of, for example, NiO, and is formed on substantially the entire back surface 16 with a uniform thickness of, for example, about 100 (μm). The recombination catalyst layer 24 is provided to promote recombination of oxygen ions on the back surface 16.

  However, the dissociation catalyst layer 18 and the recombination catalyst layer 20 are formed in, for example, the circular region shown in FIG. Is provided. Therefore, the oxygen separation membrane 12 is exposed in the annular region outside the catalyst layer forming region.

FIG. 4 is a process diagram for explaining the manufacturing method of the oxygen separation membrane element 10 described above. In FIG. 4, in the granulation step P1, for example, a commercially available La _0.7 Sr _0.3 Ga _0.6 Fe _0.4 O ₃ or La _0.6 Sr _0.4 Ti _0.3 Fe _0.7 O ₃ powder having an average particle size of about 1 (μm), water, and molding aid. A slurry (slurry) is prepared by mixing with an agent (binder) and a dispersant, and a raw material powder having an average particle size of about 60 (μm) is sprayed and granulated using, for example, a spray drier. Next, in the pressure forming step P2, the granulated raw material powder is press-molded at a pressure of about 100 (MPa), for example, and a circle having a diameter of about 25 (mm) and a thickness of about 3 (mm) is obtained. A plate-like molded body is obtained. In addition, the said molded object dimension is a value determined in consideration of shrinkage | firing shrinkage | contraction so that the oxygen separation membrane 12 of the said dimension may be obtained. Next, in the firing step P3, the molded body is held at a temperature of about 200 to 500 (° C.) for about 10 hours in the atmosphere for about 10 hours to decompose and remove organic substances, and further at a temperature of about 1500 (° C.) in the air. The molded body is fired by holding for about 3 hours. In the thickness polishing step P4, the dense sintered body thus obtained is subjected to mechanical polishing using a surface grinder or the like to obtain a flat film having a thickness of about 0.5 (mm), for example. .

  Next, in the protrusion forming step P5, the lattice-like grooves 22 are formed on the surface 14 of the sintered body, that is, the polished film, by, for example, machining using a diamond grindstone or the like. Thus, according to the shape of the outer peripheral cross section of the diamond grindstone, for example, as shown in FIG. 3, the width dimension is about 50 (μm), the depth dimension is about 50 (μm), and the pitch is about 150 (μm). A groove 22 having a rectangular cross section is formed. That is, a large number of protrusions 24 are formed on the surface 14 so as to be arranged in a lattice pattern at a constant interval. In FIG. 3, the bottom surface of the groove 22 is drawn so as to be bent at a right angle from the side surface thereof, but these are actually connected with a curvature corresponding to the outer peripheral cross-sectional shape of the diamond grindstone. Further, as a processing method used here, an appropriate one may be adopted according to the size and shape of the groove to be formed or the constituent material of the oxygen separation membrane 12, and laser processing or the like may be used.

Next, in the first catalyst coating step P6, for example, La _0.6 Sr _0.4 CoO ₃ powder having an average particle diameter of about 2 (μm) is mixed with an organic solvent to prepare a slurry, and this is the surface on which the grooves 22 are formed. 14 and dried at a temperature of about 100 (° C.), for example, in the drying step P7. The La _0.6 Sr _0.4 CoO ₃ powder may be a commercially available appropriate one. The coating thickness is appropriately determined so that the film thickness after baking becomes about 10 (μm) in consideration of shrinkage in the baking process P10 described later. Next, in the second catalyst coating step P8, for example, NiO powder having an average particle size of about 7 (μm) is mixed with an organic solvent to prepare a slurry, which is applied to the back surface 16, and in the drying step P9, For example, it is dried at a temperature of about 100 (° C.). The NiO powder may be a commercially available appropriate one. The coating thickness is determined so that the thickness after firing is about 100 (μm) in consideration of the shrinkage in the firing step P10. Then, in the firing step P10, for example, by holding the catalyst layers 18 and 20 on the front surface 14 and the back surface 16, respectively, at a temperature of about 1000 (° C.) for about 1 hour, can get. The rate of temperature increase in the firing step is, for example, about 1 (° C./min).

  The results of evaluating the oxygen permeation rate of the oxygen separation membrane element 10 manufactured as described above and configured as described above will be described below. The oxygen transmission rate was evaluated using a reactor 30 shown in FIG. In FIG. 5, a reactor 30 includes cylindrical tubes 32 and 34 made of ceramics such as alumina and having both ends opened up and down with the oxygen separation membrane element 10 interposed therebetween. Gas introduction pipes 36 and 38 made of ceramics such as alumina are inserted. In the oxygen separation membrane element 10, the surface 14 on which the oxygen dissociation catalyst layer 18 is provided is located on the upper side in FIG. 5, that is, on the cylindrical tube 32 side, and the back surface 16 on which the oxygen recombination catalyst layer 20 is provided is the cylindrical tube 34. It is arranged in the direction located on the side. In addition, heaters 40 and 40 are disposed on the outer peripheral side of the cylindrical tubes 32 and 34. The cylindrical tubes 32 and 34 and the oxygen separation membrane element 10 are hermetically sealed with sealing materials 42 and 42 such as glass. The gas introduction pipes 36 and 38 are arranged at a distance from the surface of the oxygen separation membrane element 10 by a distance necessary for gas supply.

  In such a reactor 30, while the inside of the apparatus is heated to a temperature of about 1000 (° C.) by the heaters 40, 40, air, that is, a gas containing oxygen is introduced into the cylindrical tube 32 from the gas introduction tube 36, and fuel A hydrocarbon such as pure methane gas is introduced from the side, that is, the gas introduction pipe 38. Both the air introduction amount and the methane gas introduction amount are, for example, about 10 to 200 (cc / min). Prior to the measurement, for example, while the inside of the cylindrical tube 34 is heated to a temperature of about 1000 (° C.) by the heaters 40, 40, for example, a mixed gas of hydrogen 10 (%) and argon 90 (%) is introduced into the gas introduction tube 38. To the inside of the cylindrical tube 34 and heated in a reducing atmosphere. Thereby, the recombination catalyst layer 24 provided on the lower surface 16, that is, the nickel oxide is partially or completely reduced, and the function as an oxygen recombination catalyst is exhibited.

  The air introduced from the gas introduction pipe 36 as described above is in contact with the surface of the oxygen separation membrane element 10, that is, the dissociation catalyst layer 18 and the surface 14 of the oxygen separation membrane 12, while the gas introduction pipe 36 and the cylindrical pipe 32 are in contact with each other. The gas is exhausted through an exhaust passage 44 formed therebetween as indicated by an arrow in FIG. At this time, oxygen in the air is dissociated and ionized by the oxygen dissociation action and ionization action of the oxygen separation membrane 12 and the dissociation catalyst layer 18 provided on the surface 14 thereof, so that the oxygen ions have oxygen ion conductivity. 5 is transported from the front surface 14 side to the back surface 16 side through the oxygen separation membrane 12 having the structure shown by the arrow in FIG. Further, since the surface 14 is provided with a large number of protrusions 24 that are regularly arranged by forming a plurality of grooves 22 orthogonal to each other, the gas that has reached the vicinity of the surface 14 is indicated by the arrow in FIG. As shown in FIG. 5, the oxygen separation membrane 12 is brought into contact with a large area including the bottom surface of the groove 22 and the side surfaces and top surface of the protrusion 24 while flowing along the groove 22 (ie, rectified). Therefore, since the surface area is increased and the turbulence is prevented, the contact opportunity is dramatically increased. Therefore, the reactivity between oxygen in the air and the oxygen separation membrane 12 is remarkably increased, and the ionization rate of oxygen is remarkably increased. Enhanced.

  The oxygen ions that have reached the back surface 16 become oxygen molecules due to the recombination action of the oxygen separation membrane 12 and the recombination catalyst layer 20 provided on the back surface 16, and are extracted from the back surface 16. Thereby, oxygen permeate | transmits from the surface 14 side to the back surface 16 side. However, since the oxygen separation membrane 12 is dense as described above and other gases cannot be ionized, no gas other than oxygen is transmitted. That is, oxygen with extremely high purity is produced from air.

In addition, the oxygen that has permeated in this way is in the form of ions or recombined, and then on methane gas or the like introduced from the gas introduction pipe 38 and its back surface 16, in the recombination catalyst layer 20, or in the vicinity thereof. The reaction causes a partial oxidation reaction of methane as shown in the following formula (1). The generated synthesis gas of carbon monoxide and hydrogen is recovered from a recovery path 46 formed between the gas introduction pipe 38 and the cylindrical pipe 34. The recovered synthesis gas is used, for example, for liquid fuel synthesis. As is clear from the above description, in this embodiment, the front surface 14 corresponds to one surface and the back surface 16 corresponds to the other surface. Further, as is clear from the above description, when no methane gas is introduced from the gas introduction pipe 38, oxygen can be recovered from the recovery path 46, and the reactor 30 can be used as an oxygen production apparatus.
CH ₄ + 1 / 2O ₂ → CO + 2H ₂ (1)

  The above test is performed for about 3 hours, for example, and the evaluation results obtained by measuring the synthesis gas and the exhaust gas by gas chromatography are shown below together with other examples and comparative examples having different configurations from the oxygen separation membrane element 10. Table 1 shows. The oxygen transmission rate was calculated from the oxygen concentration and flow rate in the synthesis gas, and the oxygen transmission area of the oxygen separation membrane element 10. In Table 1 below, Example 1 has the configuration described above. In Example 2, a protrusion 24 is provided on the back surface 16 instead of the front surface 14, and the recombination catalyst layer 20 is formed on the protrusion forming surface with a thickness of about 20 (μm). The dissociation catalyst layer 18 is formed with a thickness of about 100 (μm). Further, in Example 3, protrusions 24 are provided on both the front surface 14 and the back surface 16 in the same form as in the above-described example, and the dissociation catalyst layer 18 and the recombination catalyst layer 20 are provided 20 ( It is formed with a thickness dimension of about μm). Further, in Comparative Example 1, no protrusions 24 were formed on either the front surface 14 or the back surface 16, and the dissociation catalyst layer 18 and the recombination catalyst layer 20 were formed with thickness dimensions of about 100 (μm), respectively. Is. In Comparative Example 2, irregular irregularities are formed on the surface 14 by sandblasting. In Comparative Example 3, irregular irregularities are formed on the back surface 16 by sandblasting. In Comparative Example 4, irregular irregularities are formed on both the front surface 14 and the rear surface 16 by sandblasting. In each of Examples 2, 3 and Comparative Example, the configuration other than the above is the same as in Example 1. For example, the baking treatment of the catalyst layers 18 and 20 is performed at 1000 (° C.) for 1 hour. To do.

[Table 1]
Examples Comparative examples
Oxygen separation membrane constituent material 1 2 3 1 2 3 4
La _0.7 Sr _0.3 Ga _0.6 Fe _0.4 O ₃ 9.8 9.2 15.5 4.2 6.9 6.6 7.8
La _0.6 Sr _0.4 Ti _0.3 Fe _0.7 O ₃ 8.6 7.9 13.2 3.8 6.2 5.8 7.2
Oxygen transmission rate (cc / min / cm ² )

  As shown in Table 1 above, although it is natural that the oxygen transmission rate of Comparative Example 1 in which no protrusion is provided is extremely low, in Comparative Examples 2 to 4, although the protrusion is provided, The oxygen transmission rate is not improved as much as in Examples 1-3. Examples 1 to 3 in which the regular protrusions 24 are formed have an oxygen transmission rate about twice that of the comparative example in which no protrusions are formed or irregular protrusions are formed. It is clear that the provision of regular protrusions 24 significantly improves the oxygen transmission rate. This is presumed to be due to the fact that the structure provided with the regular protrusions 24 has a significantly larger surface area than the structure provided with the irregular protrusions. Further, it can be seen from the comparison between Examples 1, 2, and 3 that a higher effect can be obtained by providing the protrusions 24 on both surfaces.

  Further, when the oxygen permeation rate was measured when the surface area of the oxygen separation membrane 12 was changed to 0.8 times or 1.2 times by changing both or one of the pitch and width dimensions of the protrusions 24, the results shown in Table 2 below were obtained. It was. In other words, it was confirmed that the higher the surface area, the higher the permeation rate within the experimental range. In Table 2, LSGF and LSTF are the two kinds of materials shown in Table 1, and those having an area of 1.0 are the same as those in Example 1 shown in Table 1.

[Table 2]
Area 0.8 1.0 1.2 (relative value)
LSGF 8.1 9.8 11.0
LSTF 7.0 8.6 9.9
Oxygen transmission rate (cc / min / cm ² )

  In short, according to the present embodiment, a large number of projections 24 of uniform size are regularly arranged in two directions at a constant center interval on at least one of the front surface 14 and the rear surface 16 of the oxygen separation membrane 12. For this reason, the surface area of the front surface 14 or the rear surface 16 provided with this is remarkably increased as compared with the case where irregular projections in the size and the arrangement direction are provided. That is, when the surface area of the front surface 14 is increased by providing the protrusions 24, the ionization rate of oxygen is increased as described above, and when the surface area of the back surface 16 is increased, the back surface 16 is increased. By remarkably increasing the interface between the recombination catalyst layer 20 and the oxygen separation membrane 12 provided above, the recombination rate is increased. Therefore, since these are suitably suppressed from reducing the oxygen permeation rate, coupled with the fact that the oxygen separation membrane 12 is thinned to about 0.5 (mm), thereby increasing the transport rate in the membrane, A high transmission rate is obtained.

  Next, another embodiment of the present invention will be described. In the following embodiments, portions common to the above-described embodiments are denoted by the same reference numerals and description thereof is omitted.

  The oxygen separation membrane element 50 shown in FIG. 6 has grooves 22 provided on both the front surface 14 and the back surface 16 of the oxygen separation membrane 52, and a large number of regularly arranged projections 24 are formed. That is, the oxygen separation membrane 52 is obtained by providing the back surface 16 with the groove 22 in the oxygen separation membrane 12. As described above, if the regular protrusions 24 are formed on both surfaces, the ionization rate and the recombination rate can be increased because the surface area is remarkably increased in any case. Note that the oxygen separation membrane element 50 is not provided with the dissociation catalyst layer 18 and the recombination catalyst layer 20, and is constituted only by the oxygen separation membrane 52. The catalyst layers 18 and 20 are for increasing the ionization rate and the recombination rate, and are not essential for the configuration. That is, depending on the required oxygen transmission rate, only one of the catalyst layers 18 and 20 may be provided, or both may not be provided.

  In FIG. 6, the grooves 22 and the protrusions 24 are provided at the same positions on the front surface 14 and the back surface 16 with the same size and mutual spacing, but they need not be the same. That is, depending on the size of the required surface area, etc., they may be provided at different positions with different sizes and intervals. In addition, the front surface 14 and the rear surface 16 do not have to be the same in the direction of the grooves 22, that is, in the arrangement direction of the protrusions 24.

  The oxygen separation membrane element 54 shown in FIG. 7 corresponds to the oxygen separation membrane element 50 provided with the dissociation catalyst layer 18 and the recombination catalyst layer 56. Of these two catalyst layers, the dissociation catalyst layer 18 is provided in the same manner as in the case of the oxygen separation membrane element 10, but the recombination catalyst layer 56 completely fills the groove 22, and on the back surface 16 thereof. It is relatively thick, for example, with a thickness dimension of about 200 (μm). Such an oxygen separation membrane element 54 can also be attached to the reactor 30 for use.

  According to the oxygen separation membrane element 54, on the surface 14 side of the oxygen separation membrane 52, as described above, the ionization rate is increased by the increase in the surface area and the rectification effect. On the other hand, on the back surface 16 side, the contact layer between the oxygen ions and the catalyst is increased by increasing the thickness of the catalyst layer 56 instead of obtaining the rectifying effect, so that the recombination rate is increased, and consequently the oxygen transmission rate. Has the advantage of being enhanced. That is, depending on which contribution of the effect due to rectification and the effect due to the increased chance of contact with the catalyst is large, the thickness is such that irregularities due to the grooves 22 remain on the surface of the catalyst layer as in the surface 14 side of this embodiment. It is also possible to set the thickness so that the groove 22 is filled as on the back surface 16 side.

An oxygen separation membrane element 58 shown in FIG. 8 is obtained by providing an oxygen separation membrane 62 on a porous support 60. In FIG. 8, (a) schematically shows the whole, and (b) is an enlarged cross-sectional view showing a part on the oxygen separation membrane 62 side. In FIG. 8B, the porous support 60 is made of perovskite such as La _0.7 Sr _0.3 Ga _0.6 Fe _0.4 O ₃ or La _0.6 Sr _0.4 Ti _0.3 Fe _0.7 O ₃ , for example, 3 (mm). It is a disk with a diameter of about 20 (mm) with a thickness dimension of about. The oxygen separation membrane 62 is made of, for example, a perovskite material having the same composition as the porous support 60, but is densely configured.

  For example, a recombination catalyst layer 66 is formed on the back surface 64 of the porous support 60 with a uniform thickness of about 100 (μm). The recombination catalyst layer 66 is provided in a state in which a part thereof enters the porous support 60, that is, in a state in which a part thereof is infiltrated. However, it may be completely infiltrated into the inside (that is, for example, to the vicinity of the oxygen separation membrane 62). The oxygen separation membrane 62 is provided on the surface 68 of the porous support 60 with a thickness of about 300 (μm), for example. Similarly to the recombination catalyst layer 66, the oxygen separation membrane 62 is also provided in a state where a part of the oxygen separation membrane 62 is permeated into the porous support 60. Further, the surface 14 of the oxygen separation membrane 62 is provided with a large number of protrusions 24 that are regularly arranged by providing a large number of grooves 22 like the oxygen separation membranes 12 and 52. A dissociation catalyst layer 18 is provided on the surface 14. According to such an oxygen separation membrane element 58, the overall mechanical strength is ensured by the porous support 60, and therefore it is easy to further increase the oxygen permeation rate by making the oxygen separation membrane 62 thinner. . In FIG. 8A, for convenience of illustration, the surface 14 of the oxygen separation membrane 62 and the surface of the dissociation catalyst layer 18 are drawn flat.

  The oxygen separation membrane element 58 is manufactured, for example, by preparing a porous support 60 and following the manufacturing process shown in FIG. The porous support body 60 is manufactured, for example, by the following manufacturing process. First, the porous material powder is mixed and kneaded with a binder, a dispersant and the like, and then dried at a temperature of about 100 (° C.) for about 24 hours to produce an aggregate. As the porous material powder, for example, a commercially available perovskite raw material having the above composition can be used. Next, this is crushed by a ball mill or the like, and is subjected to pressure molding at a pressure of about 100 (MPa), for example, to form a disk having a diameter of about 20 (mm) and a thickness of about 3 (mm). Next, the molded body is heated at a predetermined firing temperature, for example, about 1500 (° C.) for about 3 hours. Thereby, the porous support body 60 is obtained.

  After the porous support 60 is manufactured in this way, in FIG. 9, in the dipping step R1, the constituent material powder of the oxygen separation membrane 62 is mixed with a solvent, a binder, and a dispersant using a ball mill or the like to form a slurry. The surface 68 side of the porous support 60 is dipped in this slurry. Thereby, the surface layer portion on the surface 68 side of the porous support 60 is impregnated with the slurry substantially evenly. Next, in the drying step R2, for example, drying is performed at a temperature of about 60 (° C.) for about 4 hours, and further in the baking step R3, for example, heating in the atmosphere at a temperature of about 1500 (° C.) for about 3 hours. The oxygen separation membrane 62 is formed on the porous support 60. The dipping process R1 and the drying process R2 are repeated an appropriate number of times so as to obtain a desired film thickness of, for example, about 0.3 (mm). The film thickness of the oxygen separation membrane 62 can also be adjusted by adjusting the slurry viscosity, immersion time, and the like.

  Next, in the protrusion forming step R4, for example, by diamond grinding machining, the groove width is about 0.05 (mm), the protrusion width (that is, the mutual interval between the grooves 22) is about 0.1 (mm), and the depth is about 0.1 (mm). A fine protrusion mechanism is formed.

  Next, in the impregnation step R5, for example, a slurry in which a dispersion medium such as water, a binder, a dispersing agent, etc. is added to a Ni-based oxide is prepared, and the back surface 64 side of the porous support 60 is placed on this for about 3 hours, for example. Soak for a predetermined time. After the immersion, in the drying step R6, for example, drying is performed for about 5 hours at a temperature of about 100 (° C.), and then in the baking step R7, baking is performed by heating at a temperature of about 1000 (° C.) for about 1 hour. The rate of temperature increase up to the maximum holding temperature of 1000 (° C.) is, for example, about 1 (° C./min). Thereby, the recombination catalyst layer 66 is formed on the back surface 64 in a state where a part of the porous support 60 has entered. The thickness dimension of the recombination catalyst layer 66 is controlled by adjusting the slurry viscosity, the immersion time, and the like. Since the recombination catalyst layer 66 is porous, even if the surface layer portion of the porous support 60 is impregnated as described above, the air permeability of the porous support 60 is not hindered at all.

  Next, in the application step R8, a slurry is prepared by dispersing the constituent material powder of the dissociation catalyst layer 18 in water, and this is applied to the surface 14 of the oxygen separation membrane 62, and in the drying step R9, for example, 100 (° C.). After drying at a temperature of about, in the baking step R10, for example, baking is performed by heating at a temperature of about 1000 (° C.) for about 1 hour. Also in this case, the temperature rising rate is about 1 (° C./min), for example. Thereby, the dissociation catalyst layer 18 is formed on the surface 14 of the oxygen separation membrane 62. The thickness dimension is appropriately adjusted by adjusting the viscosity of the slurry and the coating thickness, changing the number of coatings, and the like.

The results of measuring the oxygen permeation rate and the like by variously changing the configuration of the porous support 60 of the oxygen separation membrane element 58 manufactured as described above and having the above-described structure will be described. The evaluation results are shown in Table 3, FIG. 10, and FIG. Regarding the thickness dimension of the oxygen separation membrane 62, the projection height was 0.1 (mm), and the thickness (total thickness) of the portion where the projection was present was 0.2 (mm). In Table 3 below, Example 4 is one in which the porous support 60 and the oxygen separation membrane 62 are composed of La _0.7 Sr _0.3 Ga _0.6 Fe _0.4 O ₃ (LSGF). It is composed of _0.6 Sr _0.4 Ti _0.3 Fe _0.7 O ₃ (LSTF). The pore diameter, porosity, and bending strength are all characteristic values of the porous support 60. The pore diameter and porosity were measured by mercury porosimetry or BET method (for example, nitrogen adsorption method). The oxygen permeation rate was measured using the reactor shown in FIG. 5 in the same manner as the oxygen separation membrane element 10 described above. The bending strength is a three-point bending strength, which is a value measured according to JIS R1601.

[Table 3]
Pore diameter Porosity Oxygen permeation rate Bending strength
13 (μm) 35 (%) 17.0 (cc / min / cm ² ) 20 (MPa)
10 28 16.5 25
Example 4 8 17 13.2 40
(LSGF) 5 8 7.8 65
<0.1 <2.5 0.8 170-200
10 35 16.1 15
8.5 27 15.6 25
Example 5 6 17 12.2 30
(LSTF) 5 10 7.3 55
<0.1 <2.5 0.5 150-180

  As shown in Table 3 and FIGS. 10 and 11, the oxygen transmission rate tends to increase as the pore diameter and porosity of the porous support 60 increase. However, since the bending strength of the porous support body 60 tends to be reduced accordingly, the porous support body 60 needs to determine the pore diameter and the porosity in consideration of these balances. That is, in order to obtain a sufficiently high oxygen transmission rate, it is preferable that the pore diameter is larger than 0.1 (μm) and the porosity is larger than 5 (%). In order to maintain the bending strength of the porous support 60 sufficiently high to ensure the strength of the oxygen separation membrane element 58 as a whole and to make the thickness of the oxygen separation membrane 62 sufficiently thin, the pore diameter should be It is desirable that the porosity is smaller than 20 (μm) and the porosity is smaller than 60 (%). Therefore, due to the balance between the two, in the embodiment including the porous support 60, the average pore diameter is in the range of 0.1 to 20 (μm) (not including the upper and lower limits), and the porosity is 5 to 60 (%). It is desirable to be within the range (not including the upper and lower limits).

  An oxygen separation membrane element 70 shown in FIG. 12 has an oxygen separation membrane 62 provided on a porous support 60 as described above via a recombination catalyst layer 72, and a part of the oxygen separation membrane 62 side. An enlarged cross-sectional view is shown. In FIG. 12, the porous support body 60 is made of, for example, LSGF, LSTF, stabilized zirconia, or the like, and has a thickness dimension of, for example, about 3 (mm). Further, a recombination catalyst layer 66 is formed on the surface 64 with a uniform thickness dimension of, for example, about 100 (μm), and the oxygen separation membrane 62 is formed with a thickness dimension of, for example, about 300 (μm). It is provided on the combined catalyst layer 66. Similar to the oxygen separation membranes 12 and 52, the surface 14 of the oxygen separation membrane 62 is provided with a large number of protrusions 24 that are regularly arranged by providing a large number of grooves 22. A dissociation catalyst layer 18 is provided on the surface 14.

  That is, since both the porous support 60 and the recombination catalyst layer 72 are porous, any of them may be provided on the oxygen separation membrane 62 side in this way. In any case, the rectifying effect and the surface area increasing effect by the groove 22 can be obtained on the surface 14 side where air is introduced.

  An oxygen separation membrane element 74 shown in FIG. 13 is a slight modification of the configuration of the oxygen separation membrane element 70 described above, and the groove 22 is provided on both the front surface 14 and the back surface 16 of the oxygen separation membrane 76. It is a configuration example fixed on a porous support 60. In this embodiment, a recombination catalyst layer 78 that completely fills the unevenness of the oxygen separation membrane back surface 16 is provided, and is fixed to the porous support 60 via the recombination catalyst layer 78.

  Such an oxygen separation membrane element 74 is produced, for example, by producing an oxygen separation membrane 76 having grooves 22 on both sides, and for example, a dissociation catalyst layer 18 on the front surface 14 and a recombination catalyst layer 78 on the back surface 16 respectively. As shown in the figure, the former is fixed along the unevenness, the latter is fixed so as to fill the unevenness, and then fixed to the porous support 60. With such a configuration, the interface between the oxygen separation membrane 76 and the recombination catalyst layer 78 increases as compared with the configuration shown in FIG.

  FIG. 14 is a schematic diagram showing the vicinity of the tip sealing portion for explaining a configuration example in which the present invention is applied to a tubular oxygen separation membrane element 80. The oxygen separation membrane element 80 has a tubular oxygen separation membrane 82 provided with, for example, a recombination catalyst layer 86 on an outer peripheral surface 84 and a dissociation catalyst layer 90 on an inner peripheral surface 88, respectively. As the constituent materials of these parts, for example, the same materials as those in the above-described embodiments can be used.

  A large number of grooves 92 similar to the grooves 22 are provided on the outer peripheral surface 84 of the oxygen separation membrane 82 so as to intersect along the circumferential direction and the longitudinal direction. Therefore, also in the present embodiment, a large number of regularly arranged projections 94 are provided on the outer peripheral surface 84. However, the irregularities formed by the protrusions 94 are filled in the recombination catalyst layer 86. As a result, the inner peripheral surface 88 and the outer peripheral surface 84 of the oxygen separation membrane element 80 are viewed macroscopically. The surface is substantially smooth.

  A gas introduction tube 96 is inserted into the inner peripheral portion of the oxygen separation membrane 82. The gas introduction pipe 96 is configured in the same manner as the gas introduction pipes 36 and 38, for example.

  As shown in the drawing, the oxygen separation membrane element 80 is used by introducing an oxygen-containing gas from a gas introduction pipe 96 while supplying, for example, methane gas to the outer peripheral side thereof. As a result, a partial oxidation reaction of methane by oxygen that has passed through the oxygen separation membrane 82 occurs, and the synthesis gas can be recovered, as in the case of the reactor 30 described above. In the figure, the methane gas supply path and the synthesis gas recovery path are conceptually omitted. Thus, the oxygen separation membrane element is not limited to a flat plate shape such as a disc shape, and can take various shapes such as a tube shape.

  An oxygen separation membrane element 98 shown in FIG. 15 has a configuration in which the inside and outside of the oxygen separation membrane element 80 are reversed. In this way, the protrusion 100 may be provided on the inner peripheral surface 88. In addition, in such a tubular form, it is of course possible to have a configuration in which the catalyst layer is not provided or a configuration in which the catalyst layer is formed along the uneven surface. For example, in the oxygen separation membrane element 98, for example, if the dissociation catalyst layer 90 is provided on the inner peripheral surface 88 with a thin layer thickness so that regular unevenness is generated on the surface, the above-described rectifying effect can be obtained similarly. It is.

  An oxygen separation membrane element 102 shown in FIG. 16 includes a tubular porous support 104 on the inner peripheral side. For example, a recombination catalyst layer 106 is provided on the outer peripheral surface of the porous support 104, and a dense oxygen separation membrane 108 is provided on the outer peripheral surface. A large number of grooves 110 are formed in a lattice shape along the circumferential direction and the axial direction on the outer peripheral surface of the oxygen separation membrane 108. As a result, a large number of regularly arranged projections 112 are formed on the outer peripheral surface. Is provided. The dissociation catalyst layer 114 provided on the outer peripheral surface of the oxygen separation membrane 108 is formed along the uneven surface formed by the groove 110 and the protrusion 112, and regular protrusions are formed on the surface. .

  The oxygen separation membrane element 102 configured in this way, for example, supplies air to the outer peripheral side thereof and also supplies methane gas to the inner peripheral side, thereby allowing oxygen to flow from the outer peripheral surface to the inner peripheral surface in the same manner as in the above embodiments. It can permeate | transmit toward a surface and can utilize for a partial oxidation reaction.

  In the above embodiment, the irregularities (grooves 22, protrusions 24) of the oxygen separation membranes 12, 52, 62, etc. may be provided also on the recombination catalyst layer side as necessary. It may be provided only on the layer side.

  As mentioned above, although this invention was demonstrated in detail with reference to drawings, this invention can be implemented also in another aspect, A various change can be added in the range which does not deviate from the main point.

(a) is a top view which shows typically the disk-shaped oxygen separation membrane element of one Example of this invention, (b) is the side view. It is a figure which expands and shows the principal part of FIG. It is a figure which shows typically the cross-section of the oxygen separation membrane element of FIG. It is process drawing for demonstrating the manufacturing method of the oxygen separation membrane element of FIG. It is a figure explaining the structure of the reactor using the oxygen separation membrane element of FIG. It is a figure which shows typically the cross-sectional structure of the oxygen separation membrane element of the other Example of this invention. It is a figure which shows typically the cross-section of the oxygen separation membrane element of other Example of this invention. (a) is a side view for demonstrating the structure of the oxygen separation membrane element of the further another Example of this invention, (b) is a figure which expands and shows the principal part of the cross section. It is process drawing for demonstrating the manufacturing method of the oxygen separation membrane element of FIG. It is a figure which shows the relationship between the average pore diameter of the porous support body which comprises the oxygen separation membrane element of FIG. 8, an oxygen permeation rate, and a three-point bending strength. It is a figure which shows the relationship between the porosity of the porous support body which comprises the oxygen separation membrane element of FIG. 8, oxygen permeation | transmission speed | rate, and three-point bending strength. It is sectional drawing which shows the principal part for demonstrating the structure of the oxygen separation membrane element of the further another Example of this invention. It is sectional drawing which shows the principal part for demonstrating the structure of the oxygen separation membrane element of the further another Example of this invention. It is sectional drawing which shows the principal part for demonstrating the structure of the oxygen separation membrane element of the further another Example of this invention. It is sectional drawing which shows the principal part for demonstrating the structure of the oxygen separation membrane element of the further another Example of this invention. It is sectional drawing which shows the principal part for demonstrating the structure of the oxygen separation membrane element of the further another Example of this invention.

Explanation of symbols

10: oxygen separation membrane element, 12: oxygen separation membrane, 14: front surface, 16: back surface, 18: oxygen dissociation catalyst layer, 20: oxygen recombination catalyst layer, 22: groove, 24: protrusion

Claims (15)

Provided with a dense oxygen separation membrane having oxygen ion conductivity, oxygen is dissociated from the gas on one side of the oxygen separation membrane, and ionized oxygen ions are recombined on the other side, thereby allowing oxygen to flow from one side to the other. An oxygen separation membrane element for selectively permeating into and separating from the gas,
It includes a plurality of protrusions of uniform size arranged at a constant center interval along each of the first direction and the second direction intersecting each other on at least one of the one surface and the other surface of the oxygen separation membrane. Oxygen separation membrane element. Of the one surface and the other surface, a protrusion forming surface provided with the plurality of protrusions is provided with a catalyst layer for promoting the dissociation or recombination of oxygen, and the catalyst layer has irregularities following the protrusion forming surface. The oxygen separation membrane element according to claim 1, wherein the oxygen separation membrane element is provided on the surface. The oxygen separation membrane element according to claim 1, wherein the plurality of protrusions have a rectangular cross section along at least one of the first direction and the second direction. 2. The oxygen separation membrane element according to claim 1, wherein the oxygen separation membrane is a mixed conductor having oxygen ion conductivity and electron conductivity. The oxygen separation membrane has a general formula Ln _1-x Ae _x MO ₃ (where Ln is a lanthanoid, Ae is one or a combination of two or more selected from Ba, Sr, and Ca, M is Fe, Mn, Ga, Ti, Co, Zr, Ce, Mg, Ge, Zn, Cu, Sc, V, Cr, Ni, Y, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Sb, Pb, Bi, One or a combination of two or more selected from Po, Al, In, and Sn, selected from complex compounds represented by 0 ≦ x ≦ 1), ZrO ₂ oxides, and CeO ₂ oxides 2. The oxygen separation membrane element according to claim 1, comprising one or a combination of two or more. The oxygen separation membrane is Ce _2-x Zr _x O _4-σ (where 0 <x <2, 0 ≦ σ ≦ 4), CeGd oxide, CeSm oxide, Ba (CaNb) ₂ oxide, BiVCu oxide The oxygen separation membrane element according to claim 1, wherein the oxygen separation membrane element is composed of one or a combination of two or more selected from the group consisting of ZrO ₂ -based oxides. The oxygen separation membrane is made of a material containing one or a combination of two or more selected from magnesium oxide (MgO), aluminum oxide (Al ₂ O ₃ ), and yttrium oxide (Y ₂ O ₃ ). The oxygen separation membrane element according to claim 5 or 6. The oxygen separation membrane element according to any one of claims 5 to 7, wherein the oxygen separation membrane is made of a material containing a metal or metal oxide having electron conductivity. 2. The oxygen separation membrane element according to claim 1, wherein the oxygen separation membrane is provided on the porous support so as to cover the entire surface thereof. The porous support has the general formula Ln _1-x Ae _x MO ₃ (where Ln is a lanthanoid, Ae is one or a combination of two or more selected from Ba, Sr, and Ca, and M is Fe, Mn) , Ga, Ti, Co, Zr, Ce, Mg, Ge, Zn, Cu, Sc, V, Cr, Ni, Y, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Sb, Pb, Bi , Po, Al, In, Sn selected from one or a combination of two or more, a composite compound represented by 0 ≦ x ≦ 1), a ZrO ₂ oxide, a CeO ₂ oxide, magnesium oxide ( 10. The oxygen separation according to claim 9, comprising one or a combination of two or more selected from MgO), aluminum oxide (Al ₂ O ₃ ), silicon nitride (Si ₃ N ₄ ), and silicon carbide (SiC). Membrane element. The oxygen separation membrane element according to claim 9, wherein the oxygen separation membrane and the porous support are made of the same material. The oxygen separation membrane element according to claim 9, wherein the oxygen separation membrane and the porous support are made of materials having different compositions. 10. The oxygen separation membrane element according to claim 9, wherein the porous support has an average pore diameter r in a range of 0.1 <r <20 (μm) and a porosity p in a range of 5 <p <60 (%). Using the oxygen separation membrane element according to any one of claims 1 to 13, a source gas containing oxygen is supplied to one surface side, and oxygen separated from the source gas is recovered from the other surface side. An oxygen production method. The oxygen separation membrane element according to any one of claims 1 to 13,
A first gas supply path for supplying a gas containing oxygen to one surface side of the oxygen separation membrane element;
A second gas supply path for supplying a gas containing a predetermined compound to the other surface side;
And a gas recovery path for recovering a gas generated by the reaction between oxygen and the predetermined compound on the other surface side.

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