Membrane reactor

Abstract

To provide a membrane reactor that can suppress cracks in a separation membrane.SOLUTION: A membrane reactor 1 includes a catalyst layer 21, a separation membrane 3 and a buffer layer 22. The catalyst layer 21 includes a catalyst for advancing shift reaction from a raw material gas containing hydrogen and carbon oxide to a liquid fuel. The separation membrane 3 transmits water vapor that is a by-product of the shift reaction therethrough. The buffer layer 22 is disposed between the separation membrane 3 and the catalyst layer 21 to transmit the water vapor to a side of the separation membrane 3.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a membrane reactor. [Background technology]

[0002] In recent years, membrane reactors have been developed that can improve the efficiency of the conversion reaction from a feed gas containing hydrogen and carbon oxides (carbon monoxide, carbon dioxide, etc.) to liquid fuel (fuel that is in a liquid state at room temperature and pressure, such as methanol) by separating the by-product water vapor.

[0003] Patent Document 1 discloses a membrane reactor that includes a catalyst that promotes a conversion reaction from a raw material gas containing carbon dioxide and hydrogen to methanol, and a separation membrane that allows water vapor, a by-product of the conversion reaction, to permeate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-8940 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the membrane reactor described in Patent Document 1, the catalyst is in direct contact with the separation membrane, and therefore, when the catalyst is heated by the heat of reaction, cracks may occur in the separation membrane starting from the contact point with the catalyst.

[0006] The present invention has been made in consideration of the above-mentioned circumstances, and has an object to provide a membrane reactor capable of suppressing cracks in a separation membrane. [Means for solving the problem]

[0007] The membrane reactor according to the present invention comprises a catalyst layer, a separation membrane, and a buffer layer. The catalyst layer contains a catalyst that promotes a conversion reaction from a feed gas containing hydrogen and carbon oxides to liquid fuel. The separation membrane allows water vapor, which is a by-product of the conversion reaction, to pass through. The buffer layer is disposed between the separation membrane and the catalyst layer, and allows water vapor to pass through to the separation membrane side. Effect of the Invention

[0008] According to the present invention, it is possible to provide a membrane reactor capable of suppressing cracks in a separation membrane. [Brief description of the drawings]

[0009] [Figure 1] Perspective view of a membrane reactor [Diagram 2] Cross section AA of Figure 1 [Diagram 3] Cross-sectional view of a membrane reactor according to Modification 3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Next, an embodiment of the present invention will be described with reference to the drawings. However, the drawings are schematic and the ratio of dimensions may differ from the actual ones.

[0011] (Membrane Reactor 1) Fig. 1 is a perspective view of a membrane reactor 1. In Fig. 1, a cross-sectional structure of the membrane reactor 1 is partially shown.

[0012] The membrane reactor 1 is used to convert a raw gas into a liquid fuel. The raw gas contains hydrogen and carbon oxides. Examples of carbon oxides include carbon monoxide, carbon dioxide, and mixtures thereof. The liquid fuel may be any fuel that is in a liquid state at normal temperature and pressure, such as methanol, ethanol, C n H 2(m-2n) (m and n are integers less than 30), and mixtures thereof.

[0013] For example, the reaction formula when methanol is synthesized by catalytic hydrogenation of a raw material gas containing carbon monoxide, carbon dioxide and hydrogen in the presence of a catalyst is as follows.

[0014] CO+2H2⇔CH3OH (1) CO2+3H2⇔CH3OH+H2O (2) CO2+H2⇔CO+H2O (3)

[0015] The above reactions are all equilibrium reactions, and in order to increase both the conversion rate and the reaction rate, it is preferable to carry out the reactions under high temperature and pressure (e.g., 200°C or higher, 2 MPa or higher). The liquid fuel is in a gaseous state when it is synthesized, and is maintained in this gaseous state at least until it flows out of the membrane reactor 1. It is preferable that the membrane reactor 1 has heat resistance and pressure resistance according to the production conditions of the liquid fuel.

[0016] The membrane reactor 1 according to this embodiment can further increase the conversion efficiency by separating water vapor, which is a by-product of the conversion reaction from the raw material gas to liquid fuel, by utilizing the equilibrium shift effect. By utilizing the equilibrium shift effect, the reaction equilibrium of the above formulas (1) to (3) can be shifted to the product side.

[0017] The membrane reactor 1 comprises a porous substrate 2 , a separation membrane 3 , a first seal portion 4 and a second seal portion 5 .

[0018] The porous substrate 2 has a monolith shape extending in the longitudinal direction. The monolith shape refers to a shape having a plurality of cells penetrating in the longitudinal direction, and is a concept that includes a honeycomb shape.

[0019] In this embodiment, the porous substrate 2 is formed in a cylindrical shape, but there is no particular limitation on the shape of the porous substrate 2. The size of the porous substrate 2 is not particularly limited, but can be, for example, a length of 150 to 2000 mm and a width of 30 to 220 mm.

[0020] The porous substrate 2 has therein three rows of non-permeation side cells C1, seven rows of permeation side cells C2, three supply slits S1, and three discharge slits S2.

[0021] Both longitudinal ends of each non-permeation side cell C1 are plugged with plugging portions 2a. Both longitudinal ends of each permeation side cell C2 open to the first sealed portion 4 and the second sealed portion 5, respectively.

[0022] Each supply slit S1 is formed to penetrate the non-permeation side cells C1 of each row. Each supply slit S1 is disposed on one end side of the porous substrate 2 in the longitudinal direction. Each discharge slit S2 is formed to penetrate the non-permeation side cells C1 of each row. Each discharge slit S2 is disposed on the other end side of the porous substrate 2 in the longitudinal direction.

[0023] The raw material gas is supplied to the non-permeation side cells C1 of each row through each supply slit S1. The raw material gas supplied to the non-permeation side cells C1 is converted to liquid fuel by a catalyst contained in the catalyst layer 21 described below. The generated liquid fuel is discharged from the non-permeation side cells C1 of each row through each discharge slit S2.

[0024] The separation membrane 3 is formed on the inner surface of each permeation cell C2. The separation membrane 3 allows water vapor, which is a by-product of the conversion reaction, to pass through. The separation membrane 3 has a specific resistance of 1000 nmol / (s·Pa·m 2 ) or more. The larger the water vapor permeability coefficient, the more the water vapor generated in the catalyst layer 21 can be moved to the permeation cell C2, so that the reaction equilibrium of the above formulas (2) and (3) shifts to the product side, and high reaction efficiency can be obtained under milder production conditions. The water vapor permeability coefficient can be determined by a known method (see Ind. Eng. Chem. Res., 40, 163-175 (2001)).

[0025] The separation membrane 3 preferably does not allow components other than water vapor (i.e., hydrogen, carbon oxides, and liquid fuel) to pass through. Specifically, the separation membrane 3 preferably has a separation factor of 1000 or more. The larger the separation factor, the easier it is for water vapor to pass through and the less likely it is for components other than water vapor to pass through. The separation factor can be determined by a known method (see Fig. 1 in "Separation and Purification Technology 239 (2020) 116533").

[0026] An inorganic membrane can be used as the separation membrane 3. Inorganic membranes are preferable because they have heat resistance, pressure resistance, and water vapor resistance. Examples of inorganic membranes include zeolite membranes, silica membranes, alumina membranes, and composite membranes of these. In particular, zeolite membranes with a molar ratio (Si / Al) of silicon element (Si) to aluminum element (Al) of 50 or less are preferable because they have excellent water vapor permeability.

[0027] The water vapor that has permeated the separation membrane 3 and flowed into the permeate side cell C2 is discharged from the openings of the first sealed part 4 and the second sealed part 5. Alternatively, a sweep gas may be supplied from the opening of the first sealed part 4, and the water vapor may be discharged together with the sweep gas from the opening of the second sealed part 5. As the sweep gas, for example, nitrogen or air can be used.

[0028] The first sealing part 4 and the second sealing part 5 cover both end faces of the porous substrate 2 so that water vapor discharged from the permeate side cell C2 does not infiltrate into the porous substrate 2. However, the first sealing part 4 and the second sealing part 5 do not cover both ends of the permeate side cell C2. The first sealing part 4 and the second sealing part 5 can be made of glass, metal, rubber, resin, etc.

[0029] (Porous base material 2) FIG. 2 is a cross-sectional view taken along line AA in FIG.

[0030] The porous substrate 2 supports the separation membrane 3. The porous substrate 2 has a catalyst layer 21 and a buffer layer 22. In this embodiment, the catalyst layer 21 and the buffer layer 22 are disposed on the non-permeation side of the separation membrane 3.

[0031] The catalyst layer 21 is a porous body composed of a porous material and a catalyst that promotes the above-mentioned conversion reaction.

[0032] The average pore diameter of the catalyst layer 21 may be 5 μm or more and 25 μm or less. The average pore diameter of the catalyst layer 21 may be measured by mercury intrusion porosimetry. The porosity of the catalyst layer 21 may be 25% or more and 50% or less. The average particle diameter of the porous material constituting the catalyst layer 21 may be 1 μm or more and 100 μm or less. In this embodiment, the average particle diameter is the arithmetic mean value of the maximum diameters of 30 measurement target particles (randomly selected) measured by cross-sectional microstructural observation using a SEM (Scanning Electron Microscope).

[0033] As the porous material, ceramic materials, metal materials, resin materials, etc. can be used, and ceramic materials are particularly suitable. Examples of aggregates for ceramic materials include alumina (Al2O3), titania (TiO2), mullite (Al2O3·SiO2), cerium oxide, and cordierite (Mg2Al4Si5O 18 ) can be used, and alumina is preferred in consideration of availability, clay stability, and corrosion resistance. As the inorganic binder for the ceramic material, at least one of titania, mullite, sinterable alumina, silica, glass frit, clay minerals, and sinterable cordierite can be used. However, the ceramic material does not have to contain an inorganic binder.

[0034] The catalyst promotes a conversion reaction from the feed gas to a liquid fuel. The catalyst is disposed in the pores of the porous material. The catalyst may be supported on the inner surface of the pores. Alternatively, a support supporting the catalyst may be attached to the inner surface of the pores.

[0035] The catalyst may be any known catalyst suitable for the conversion reaction to the desired liquid fuel. Specifically, metal catalysts (copper, palladium, etc.), oxide catalysts (zinc oxide, zirconia, gallium oxide, etc.), and catalysts made by combining these (copper-zinc oxide, copper-zinc oxide-alumina, copper-zinc oxide-chromium oxide-alumina, copper-cobalt-titania, and catalysts made by modifying these with palladium, etc.) may be used.

[0036] The catalyst layer 21 is disposed between the non-permeation side cell C1 and the permeation side cell C2. Meanwhile, a support layer 21a is disposed between the permeation side cells C2. The support layer 21a has a configuration in which the catalyst is removed from the catalyst layer 21.

[0037] Buffer layer 22 is disposed between separation membrane 3 and catalyst layer 21. Buffer layer 22 is provided to prevent the catalyst contained in catalyst layer 21 from coming into direct contact with separation membrane 3. By physically isolating the catalyst and separation membrane 3 with buffer layer 22, it is possible to suppress the occurrence of cracks in separation membrane 3 originating from points of contact with the catalyst, even if the catalyst is heated by reaction heat.

[0038] The buffer layer 22 may be inserted at least partially between the separation membrane 3 and the catalyst layer 21, but is preferably inserted over substantially the entire area between the separation membrane 3 and the catalyst layer 21.

[0039] The buffer layer 22 is disposed on the inner surface of the catalyst layer 21. The buffer layer 22 is formed in a cylindrical shape. The buffer layer 22 also functions as a carrier (base layer) for the separation membrane 3.

[0040] The buffer layer 22 can be made of a porous material similar to that of the catalyst layer 21, and is preferably made of a ceramic material. As the aggregate of the ceramic material, it is preferable to use at least one of alumina and titania. The buffer layer 22 may contain an inorganic binder similar to that of the catalyst layer 21.

[0041] The average pore diameter of the buffer layer 22 is preferably smaller than that of the catalyst layer 21, and can be, for example, 0.001 μm or more and 2 μm or less. The average pore diameter of the buffer layer 22 can be measured by a perm porometer. The porosity of the buffer layer 22 can be 20% or more and 60% or less. The average particle diameter of the porous material constituting the buffer layer 22 is preferably smaller than that of the porous material constituting the catalyst layer 21, and can be, for example, 0.01 μm or more and 20 μm or less.

[0042] (Membrane Reactor 1 Manufacturing Method) First, the porous material to be used for the catalyst layer 21 is molded by extrusion molding, press molding, casting or the like to form a monolithic porous body.

[0043] Next, a diamond cutting tool (such as a band saw, a disc cutter, or a wire saw) is used to form a slit for the supply slit S1 and a slit for the discharge slit S2 on each of the two end faces of the porous compact.

[0044] Next, a porous material is filled into the formed slits to form a molded body for the plugging portion 2a, and then the porous molded body is fired (for example, at 500°C to 1500°C, for 0.5 hours to 80 hours) to form a porous body.

[0045] Next, a sintering aid, a pH adjuster, a surfactant, etc. are added to the porous material for the buffer layer 22 to prepare a slurry for the buffer layer.

[0046] Next, while the buffer layer slurry is passed through the through holes of the porous body, a molded body of the buffer layer 22 is formed on the inner surface of the through holes by a filtration method.

[0047] Next, the compact for the buffer layer 22 is fired (for example, at 500° C. to 1450° C., for 0.5 hours to 80 hours) to form the buffer layer 22.

[0048] Next, for example, a glass raw material slurry is applied to both end surfaces of the porous body and then fired (for example, at 800 to 1000° C.) to form the first seal portion 4 and the second seal portion 5.

[0049] Next, a catalyst-containing slurry is prepared by mixing a catalyst for the catalyst layer 21 with an organic solvent, and the catalyst-containing slurry is impregnated into the inner surface of the non-permeation side cell C1 by a filtration method while being fed from the feed slit S1. At this time, the impregnation depth of the catalyst-containing slurry is controlled by adjusting the viscosity with PVA or the like so that the catalyst-containing slurry does not impregnate the buffer layer 22.

[0050] Next, the porous body is subjected to a heat treatment in an inert atmosphere (for example, in a N2 stream, at 50°C to 200°C, for 0.5 to 80 hours) to support the catalyst on the porous material, thereby forming the catalyst layer 21.

[0051] Next, separation membrane 3 is formed on the inner surface of buffer layer 22. The method for forming separation membrane 3 may be appropriately selected according to the type of separation membrane 3. For example, when a zeolite membrane is used as separation membrane 3, the manufacturing method described in JP2004-66188A can be used, and when a silica membrane is used as separation membrane 3, the manufacturing method described in WO2008 / 050812 can be used.

[0052] (Modification of the embodiment) Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the gist of the invention.

[0053] (Variation 1) In the above embodiment, the catalyst layer 21 is in direct contact with the buffer layer 22, but one or more intermediate layers may be interposed between the catalyst layer 21 and the buffer layer 22.

[0054] The intermediate layer is made of a porous material that can be used for the catalyst layer 21. The average pore diameter of the intermediate layer is preferably smaller than the average pore diameter of the catalyst layer 21, and can be, for example, 0.005 μm or more and 5 μm or less. The average pore diameter of the intermediate layer can be measured by a perm porometer. The porosity of the intermediate layer can be, for example, 20% or more and 60% or less. The thickness of the intermediate layer can be, for example, 1 μm or more and 300 μm or less.

[0055] (Variation 2) In the above embodiment, the membrane reactor 1 is monolithic. However, the shape of the membrane reactor 1 may be, for example, a flat plate, a tube, a cylinder, a columnar shape, a polygonal columnar shape, or the like.

[0056] (Variation 3) In the above embodiment, the porous substrate 2 is disposed on the non-permeation side of the separation membrane 3, but the present invention is not limited to this.

[0057] For example, as shown in FIG. 3, a porous substrate 6 may be disposed on the permeate side of a separation membrane 3, while a buffer layer 7 and a catalyst layer 8 may be disposed on the non-permeate side of the separation membrane 3.

[0058] In the configuration shown in Fig. 3, the non-permeation side cells C1 are on the inside of the catalyst layer 8, and the permeation side cells C2 are on the inside of the porous substrate 6. The raw material supplied to the non-permeation side cells C1 is converted to liquid fuel in the catalyst layer 8, and water vapor is generated as a by-product. The generated water vapor permeates the separation membrane 3 and flows into the permeation side cells C2, and is discharged from the slits S1 and S2. Thus, the water vapor flow in this modified example is opposite to that in the above embodiment.

[0059] The porous substrate 6 includes a support layer 61 and a surface layer 62. The support layer 61 has a configuration obtained by removing the catalyst from the catalyst layer 21 according to the above embodiment. The surface layer 62 has the same configuration as the buffer layer 22 according to the above embodiment.

[0060] Buffer layer 7 is disposed between catalyst layer 8 and separation membrane 3. Buffer layer 7 is provided to prevent the catalyst contained in catalyst layer 9 from coming into direct contact with separation membrane 3. By physically isolating the catalyst and separation membrane 3 with buffer layer 7, it is possible to suppress the occurrence of cracks in separation membrane 3 originating from points of contact with the catalyst, even if the catalyst is heated by reaction heat.

[0061] The buffer layer 7 can be made of a ceramic material or an organic polymer material. Examples of the ceramic material that can be used include silica, alumina, chromia, etc. Examples of the organic polymer material that can be used include PTFE, PVA, PEG, etc.

[0062] The buffer layer 7 has a contact surface (not shown) that comes into contact with the catalyst layer 8. The surface roughness Ra of the contact surface is preferably at least twice the average particle size of the catalyst. This can improve the adhesion between the catalyst layer 8 and the buffer layer 7. The average particle size of the catalyst is the arithmetic mean value of the maximum diameters of 30 catalyst particles (randomly selected) measured by microstructural observation using a SEM. The value of the surface roughness Ra of the contact surface is not particularly limited, but is preferably 1 μm or more and 20 μm or less. By setting the surface roughness Ra to 1 μm or more, it is possible to suppress the catalyst constituting the catalyst layer 8 from being detached from the buffer layer 7. By setting the surface roughness Ra to 20 μm or less, it is possible to suppress the performance of the membrane reactor from being reduced.

[0063] The catalyst layer 8 contains the constituent material of the buffer layer 7 (ceramic material or organic polymer material) and a catalyst that promotes the conversion reaction. When the catalyst layer 8 contains the constituent material of the buffer layer 7, the adhesion between the catalyst layer 8 and the buffer layer 7 can be improved. However, the catalyst layer 8 does not have to contain the constituent material of the buffer layer 7. In this case, the catalyst layer 8 is composed of only a catalyst.

[0064] The catalyst contained in the catalyst layer 8 can be the same as the catalyst contained in the catalyst layer 21 according to the above embodiment.

[0065] The configuration shown in FIG. 3 is produced by forming the separation membrane 3 according to the manufacturing method described in the above embodiment (excluding the step of impregnating the catalyst-containing slurry), and then forming a buffer layer 7 and a catalyst layer 8 on the inner surface of the separation membrane 3 in that order.

[0066] The buffer layer 7 can be formed by passing a buffer layer slurry, which is a mixture of a ceramic material or an organic polymer material and an organic solvent, inside the separation membrane 3, and then carrying out a heat treatment.

[0067] The catalyst layer 8 can be formed by circulating a catalyst layer slurry, which is a mixture of the constituent material of the buffer layer 7 (ceramic material or organic polymer material), a catalyst, and an organic solvent, inside the buffer layer 7, and then performing a heat treatment in an inert atmosphere.

[0068] [Variation 4] In the above embodiment, the separation membrane 3 is permeable to water vapor, which is a by-product of the conversion reaction from the raw material gas to liquid fuel, but this is not limited to this. The separation membrane 3 may be permeable to the liquid fuel itself, which is the product of the conversion reaction from the raw material gas to liquid fuel. Even in this case, the reaction equilibrium of the above formulas (1) and (2) can be shifted to the product side.

[0069] Furthermore, in the case where separation membrane 3 allows liquid fuel to permeate, even when liquid fuel is produced by a reaction that does not produce water vapor as a by-product (for example, see formula (1) above), the reaction equilibrium can be shifted to the product side. [Explanation of symbols]

[0070] 1. Membrane Reactor 2 Porous base material 21 Catalyst layer 22 Buffer layer 3 Separation membrane 4 First seal part 5 Second seal part 6 Porous substrate 61 Support layer 62 Surface layer 7 Buffer layer 8 Catalyst layer C1 Non-transmitting cell C2 Permeation cell S1 Supply slit S2 Discharge slit

Claims

1. a catalyst layer including a catalyst that promotes a conversion reaction from a feed gas containing hydrogen and carbon oxides to a liquid fuel; a separation membrane that allows permeation of water vapor, which is a by-product of the conversion reaction; a buffer layer disposed between the separation membrane and the catalyst layer and allowing the water vapor to pass through to the separation membrane side; Equipped with Used at pressures of 2 MPa or more. Membrane reactor.

2. a catalyst layer including a catalyst that promotes a conversion reaction from a feed gas containing hydrogen and carbon oxides to a liquid fuel; a separation membrane that allows the liquid fuel to permeate; a buffer layer disposed between the separation membrane and the catalyst layer, the buffer layer allowing the liquid fuel to pass through to the separation membrane side; A membrane reactor comprising:

3. The buffer layer and the catalyst layer are disposed on the non-permeation side of the separation membrane and constitute a porous substrate supporting the separation membrane. The membrane reactor according to claim 1 or 2.

4. the catalyst layer is composed of the catalyst and a porous material, The buffer layer is made of a porous material. The membrane reactor according to claim 3.

5. Further comprising a porous substrate disposed on the permeation side of the separation membrane and supporting the separation membrane. The membrane reactor according to claim 1 or 2.

6. The catalyst layer is composed of the catalyst and a constituent material of the buffer layer. The membrane reactor according to claim 5.

7. the buffer layer has a contact surface in contact with the catalyst layer, The surface roughness Ra of the contact surface is 1 μm or more. The membrane reactor according to claim 4.

8. Used at 200°C or higher. The membrane reactor according to claim 1.

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