Zeolite membrane composite and membrane reactor

Abstract

This zeolite membrane composite (1) comprises: a porous support body (11); and a zeolite membrane (12) which is provided on the support body (11) and contains aluminum, silicon and carbon. The molar ratio of carbon relative to the sum of aluminum and silicon in the zeolite membrane (12) is 0.1 or more. The zeolite membrane (12) can improve hydrothermal durability. In addition, in a case where a mixed liquid at 60°C containing 50 mass% of water and 50 mass% of ethanol is supplied to the zeolite membrane composite (1) at -94.66 kPaG on the permeate side, the total permeation flux is 1.0 kg / m2h or more and the water / ethanol separation coefficient is 1000 or more. The zeolite membrane composite (1) can achieve high water separation performance.

Description

[Technical Field]

[0001] The present invention relates to a zeolite membrane composite and a membrane reactor. [Reference to Related Application] This application claims the benefit of priority from Japanese Patent Application JP2021-184980, filed on November 12, 2021, the entire disclosure of which is incorporated herein by reference. [Background technology]

[0002] Zeolite membranes have been used as separation membranes utilizing molecular sieving. Zeolite membranes are usually provided on a porous support and treated as zeolite membrane composites. For example, Japanese Patent Laid-Open Publication No. 7-185275 (Reference 1) discloses a separation membrane in which a zeolite membrane having an LTA-type crystal structure (A-type zeolite membrane) is formed on a porous support, and stable and efficient separation of a water-ethanol mixture or the like is realized. Furthermore, in "Synthesis and Characterization of A-Type Zeolites" by R.H. Jarman and two others (ACS Symposium Series, American Chemical Society, 1983, Vol. 218, pp. 267-281) (Reference 2), it is reported that tetramethylammonium ion (TMA) + A method for synthesizing powder of LTA-type zeolite crystals using ) as a structure-directing agent has been disclosed.

[0003] However, zeolite membrane composites that contain aluminum and silicon and have high water separation performance, such as the LTA zeolite membrane described in Reference 1, usually tend to have low hydrothermal durability. Therefore, there is a demand for zeolite membrane composites that have high water separation performance and improved hydrothermal durability. Summary of the Invention

[0004] The present invention is directed to a zeolite membrane composite, and an object of the present invention is to provide a zeolite membrane composite having high water separation performance and improved hydrothermal durability.

[0005] A first aspect of the invention is a zeolite membrane composite, comprising a porous support and a zeolite membrane provided on the support and containing aluminum, silicon, and carbon. ,before In the zeolite membrane, the molar ratio of carbon to the sum of aluminum and silicon is 0.1 or more. and 3.0 or less Yes the law of nature, The zeolite membrane comprises a zeolite of the LTA, RHO or SOD type, When a mixture containing 50% by mass of water and 50% by mass of ethanol at 60°C was supplied to the permeation side at -94.66 kPaG, the total permeation flux was 1.0 kg / m 2 h or more, and the separation factor between water and ethanol is 1000 or more.

[0006] According to the present invention, it is possible to provide a zeolite composite membrane having high water separation performance and improved hydrothermal durability.

[0008] Aspects 2 The invention is 1 of The zeolite membrane composite has a molar ratio of carbon to the sum of aluminum and silicon in the zeolite membrane of 0.3 or more and 3.0 or less.

[0009] Aspects 3 The invention of the present invention is or 2 The zeolite membrane composite of claim 1, wherein the zeolite membrane further contains nitrogen.

[0010] Aspects 4 The invention is as follows: 3 The zeolite membrane composite according to any one of the above items, wherein the silicon / aluminum molar ratio in the zeolite membrane is 1 or more and 6 or less.

[0013] The present invention is also directed to a membrane reactor.

[0014] Aspects 5 The present invention is a membrane reactor, and 4a catalyst for promoting a chemical reaction of a raw material, a reactor containing the zeolite membrane composite and the catalyst, and a supply unit for supplying the raw material to the reactor. The zeolite membrane composite separates a highly permeable substance from other substances by allowing it to pass through the zeolite membrane composite, which is a mixture of substances including a product produced by the chemical reaction of the raw material in the presence of the catalyst.

[0015] The above and other objects, features, aspects and advantages will become more apparent from the following detailed description of the invention which proceeds with reference to the accompanying drawings. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a cross-sectional view of a zeolite membrane composite. [Figure 2] FIG. 2 is an enlarged cross-sectional view showing a part of the zeolite composite membrane. [Figure 3] FIG. DETAILED DESCRIPTION OF THE INVENTION

[0017] FIG. 1 is a cross-sectional view of a zeolite membrane composite 1. FIG. 2 is an enlarged cross-sectional view of a portion of the zeolite membrane composite 1. The zeolite membrane composite 1 includes a porous support 11 and a zeolite membrane 12 provided on the support 11. The zeolite membrane refers to at least a zeolite membrane formed on the surface of the support 11, and does not include a membrane in which zeolite particles are simply dispersed in an organic film. The zeolite membrane 12 may contain two or more types of zeolite with different structures or compositions. In FIG. 1, the zeolite membrane 12 is depicted with a thick line. In FIG. 2, the zeolite membrane 12 is depicted with parallel diagonal lines. In FIG. 2, the thickness of the zeolite membrane 12 is depicted thicker than it actually is.

[0018] The support 11 is a porous member that is permeable to gases and liquids. In the example shown in FIG. 1, the support 11 is a monolithic support having a single, continuous columnar body formed integrally with the support 11, and multiple through-holes 111 extending in the longitudinal direction (i.e., the left-right direction in FIG. 1) are provided in the support 11. In the example shown in FIG. 1, the support 11 is substantially cylindrical. The cross section perpendicular to the longitudinal direction of each through-hole 111 (i.e., cell) is, for example, substantially circular. In FIG. 1, the diameter of the through-holes 111 is drawn larger than in reality, and the number of through-holes 111 is drawn smaller than in reality. The zeolite membrane 12 is formed on the inner circumferential surfaces of the through-holes 111, covering the inner circumferential surfaces of the through-holes 111 over substantially the entire surfaces.

[0019] The length of the support 11 (i.e., the length in the left-right direction in FIG. 1) is, for example, 10 cm to 200 cm. The outer diameter of the support 11 is, for example, 0.5 cm to 30 cm. The distance between the central axes of adjacent through holes 111 is, for example, 0.3 mm to 10 mm. The surface roughness (Ra) of the support 11 is, for example, 0.1 μm to 5.0 μm, and preferably 0.2 μm to 2.0 μm. The shape of the support 11 may be, for example, a honeycomb shape, a flat plate shape, a tubular shape, a cylindrical shape, a columnar shape, or a polygonal pillar shape. When the shape of the support 11 is tubular or cylindrical, the thickness of the support 11 is, for example, 0.1 mm to 10 mm.

[0020] The material of the support 11 can be various substances (for example, ceramic or metal) as long as they are chemically stable in the process of forming the zeolite membrane 12 on the surface. In this embodiment, the support 11 is formed of a ceramic sintered body. Examples of ceramic sintered bodies that can be selected as the material of the support 11 include alumina, silica, mullite, zirconia, titania, yttria, silicon nitride, and silicon carbide. In this embodiment, the support 11 contains at least one of alumina, silica, and mullite.

[0021] The support 11 may contain an inorganic binder, which may be at least one of titania, mullite, sinterable alumina, silica, glass frit, clay minerals, and sinterable cordierite.

[0022] The average pore size of the support 11 is, for example, 0.01 μm to 70 μm, and preferably 0.05 μm to 25 μm. The average pore size of the support 11 near the surface on which the zeolite membrane 12 is formed is 0.01 μm to 1 μm, and preferably 0.05 μm to 0.5 μm. The average pore size can be measured, for example, by a mercury porosimeter, a perm porometer, or a nanoperm porometer. Regarding the pore size distribution throughout the support 11, including the surface and interior, D5 is, for example, 0.01 μm to 50 μm, D50 is, for example, 0.05 μm to 70 μm, and D95 ​​is, for example, 0.1 μm to 2000 μm. The porosity of the support 11 near the surface on which the zeolite membrane 12 is formed is, for example, 20% to 60%.

[0023] The support 11 has, for example, a multilayer structure in which multiple layers with different average pore sizes are stacked in the thickness direction. The average pore size and sintered particle size in the surface layer, including the surface on which the zeolite membrane 12 is formed, are smaller than the average pore size and sintered particle size in the layers other than the surface layer. The average pore size in the surface layer of the support 11 is, for example, 0.01 μm to 1 μm, and preferably 0.05 μm to 0.5 μm. When the support 11 has a multilayer structure, the materials described above can be used for each layer. The materials of the multiple layers forming the multilayer structure may be the same or different.

[0024] The zeolite membrane 12 is a porous membrane having fine pores (micropores). The zeolite membrane 12 can be used as a separation membrane for separating a specific substance from a mixture of multiple substances. The zeolite membrane 12 is less permeable to other substances than to the specific substance. In other words, the amount of the other substances that permeates the zeolite membrane 12 is smaller than the amount of the specific substance that permeates the zeolite membrane 12.

[0025] The thickness of the zeolite membrane 12 is, for example, 0.05 μm to 30 μm. The thickness of the zeolite membrane 12 is preferably 10 μm or less, and more preferably 5 μm or less. The thinner the zeolite membrane 12, the higher the permeation rate. The thickness of the zeolite membrane 12 is preferably 0.1 μm or more, and more preferably 0.5 μm or more. The thicker the zeolite membrane 12, the better the separation performance. The surface roughness (Ra) of the zeolite membrane 12 is, for example, 5 μm or less, preferably 2 μm or less, more preferably 1 μm or less, and even more preferably 0.5 μm or less.

[0026] The average pore diameter of the zeolite membrane 12 is, for example, 1 nm or less. When the maximum number of rings in the zeolite constituting the zeolite membrane 12 is n, the average pore diameter is the arithmetic mean of the minor and major axes of the n-membered ring pores. An n-membered ring pore is a pore in which the number of oxygen atoms in the portion where an oxygen atom is bonded to a T atom (described later) to form a ring structure is n. When a zeolite has multiple types of n-membered ring pores with the same n, the arithmetic mean of the minor and major axes of all types of n-membered ring pores is the average pore diameter of the zeolite. In this way, the average pore diameter of a zeolite membrane is uniquely determined by the skeletal structure of the zeolite, and is listed in the "Database of Zeolite Structures" [online] of the International Zeolite Society, the Internet, and the like.<URL:http: / / www.iza-structure.org / databases / > The values ​​can be obtained from the values ​​disclosed in

[0027] The type of zeolite constituting the zeolite membrane 12 is not particularly limited, and may be, for example, AEI, AFT, AFX, ANA, CHA, ETL, ERI, FER, KFI, LTA, MER, RHO, SOD, MOR, FAU, BEA, or HEU zeolite. Preferred zeolites have a maximum ring number of 8 or less (e.g., 6 or 8) and are AEI, AFT, AFX, ANA, CHA, ETL, ERI, KFI, LTA, MER, RHO, or SOD. The zeolite membrane 12 may be composed of one type or two or more types. The type of zeolite can be identified, for example, by X-ray diffraction measurement.

[0028] An example of the zeolite constituting the zeolite membrane 12 is an aluminosilicate zeolite in which the atom (T atom) located at the center of the oxygen tetrahedron (TO4) constituting the zeolite is composed of silicon (Si) and aluminum (Al). Silicon and aluminum form the zeolite framework. Some of the T atoms may be substituted with other elements (Ti, B, P, etc.). This allows for changes in adsorption properties, etc.

[0029] The silicon / aluminum molar ratio (the value obtained by dividing the number of moles of silicon atoms by the number of moles of aluminum atoms; the same applies hereinafter) in the zeolite membrane 12 is preferably 1 or more and 10 or less, more preferably 1 or more and 6 or less. This increases the hydrophilicity of the zeolite membrane 12 and improves its water separation performance (i.e., dehydration performance). Depending on the type of zeolite, the silicon / aluminum molar ratio may be 5 or less, 4 or less, or 3 or less. The silicon / aluminum molar ratio in the zeolite membrane 12 can be adjusted by adjusting the blending ratios in the raw material solution, which will be described later (the same applies to the ratios of other elements). The silicon / aluminum molar ratio can be measured by EDS (energy dispersive X-ray spectroscopy) analysis of a cross section of the zeolite membrane 12. The zeolite membrane 12 may contain an alkali metal or an alkaline earth metal. Examples of alkali metals include sodium (Na), potassium (K), rubidium (Rb), and cesium (Cs). Examples of alkaline earth metals include magnesium (Mg), calcium (Ca), strontium (Sr), etc. The zeolite membrane 12 may contain other alkali metals or alkaline earth metals.

[0030] As will be described later, the zeolite membrane 12 is manufactured using an organic substance called a structure-directing agent (hereinafter also referred to as "SDA"). An example of an SDA is tetramethylammonium hydroxide. After the zeolite membrane 12 is formed, the zeolite membrane composite 1 is used as a separation membrane with little or no SDA removal. In the zeolite membrane composite 1, SDA is present in the pores of the zeolite membrane 12, and the zeolite membrane 12 contains carbon (C) that constitutes SDA. Typically, carbon does not constitute the framework structure of zeolite. In the zeolite membrane 12 containing SDA, the crystalline structure is stabilized, resulting in improved hydrothermal durability compared to zeolite membranes from which the SDA has been removed. As will be described later, the hydrothermal durability can be evaluated by the degree of deterioration in separation performance before and after immersing the zeolite membrane composite 1 in heated water. The zeolite membrane from which SDA has been removed can be obtained by subjecting the zeolite membrane 12 to a heat treatment in an oxidizing gas atmosphere to burn off and remove the SDA.

[0031] In the SDA-containing zeolite membrane 12, the molar ratio of carbon to the sum of aluminum and silicon (i.e., the molar ratio of carbon / (aluminum + silicon), hereinafter also referred to as the "C / (Al + Si) molar ratio") is 0.1 or more, preferably 0.3 or more. This allows SDA to be present in most of the pores of the zeolite membrane 12, thereby further improving hydrothermal durability. The C / (Al + Si) molar ratio is, for example, 5.0 or less, preferably 4.0 or less, and more preferably 3.0 or less. Preferably, the SDA contained in the zeolite membrane 12 is not carbonized and contains a large amount of hydrogen (H). When the SDA further contains nitrogen (N), the zeolite membrane 12 also contains the nitrogen that constitutes the SDA. Typically, nitrogen does not constitute the zeolite framework. As described below, the C / (Al + Si) molar ratio can be measured by EDS (energy dispersive X-ray spectroscopy) analysis of a cross section of the zeolite membrane 12.

[0032] Here, a water / ethanol separation test in the zeolite membrane composite 1 will be described. The water / ethanol separation test is performed, for example, by pervaporation using a separation apparatus 2 (see FIG. 3) described later. In this test, a mixed liquid containing 50 mass % water and 50 mass % ethanol at 60°C is supplied into the through-holes 111 of the zeolite membrane composite 1 at atmospheric pressure, for example. The pressure around the outer surface of the support 11, which is the permeation side of the zeolite membrane composite 1, is reduced to −94.66 kPaG (approximately 50 Torr). A highly permeable liquid in the mixed liquid permeates the zeolite membrane 12 and the support 11 while vaporizing, and is discharged from the outer surface of the support 11. The discharged gas is cooled and recovered as a liquid. From the mass of the recovered liquid, the total permeation flux (kg / m), which is the amount of fluid permeating the membrane per unit area per unit time, is calculated. 2 h) is calculated. In addition, the concentrations (mass%) of water and ethanol in the liquid are measured, and the value obtained by dividing the water concentration by the ethanol concentration (water concentration / ethanol concentration) is obtained as the separation factor.

[0033] For zeolite membrane composite 1, the total permeation flux in the water / ethanol separation test was 1.0 kg / m 2 h or more, and the separation factor for water and ethanol is 1000 or more. The reason why a high total permeation flux and a high separation factor are obtained in a zeolite membrane 12 in which the pores are blocked by SDA is not clear, but it is thought that separation is possible by forming gaps of appropriate size between the zeolite crystals (grain boundaries). In other words, it is speculated that water, which is more easily adsorbed by zeolite than ethanol, preferentially occupies the adjusted gaps between the zeolite crystals and permeates, thereby obtaining a high total permeation flux and a high separation factor.

[0034] To evaluate hydrothermal durability, the zeolite membrane composite is immersed in water (here, pure water) at 100°C for 6 hours, and then dried at 80°C for 12 hours or more. The separation factor is then measured by repeating the water / ethanol separation test described above. The ratio of the separation factor after immersion to the separation factor before immersion (i.e., separation factor after water immersion / separation factor before water immersion) is obtained as an index of hydrothermal durability. As described above, the zeolite membrane 12 containing SDA has improved hydrothermal durability compared to a zeolite membrane from which SDA has been removed by combustion.

[0035] Next, an example of a flow of manufacturing the zeolite membrane composite 1 will be described. Here, it is assumed that a zeolite membrane 12 made of LTA zeolite is formed, but the same applies to forming other types of zeolite membranes. When manufacturing the zeolite membrane composite 1, seed crystals to be used in manufacturing the zeolite membrane 12 are first prepared. The seed crystals are obtained from LTA zeolite powder, which is produced, for example, by hydrothermal synthesis. It is preferable that the raw material solution for seed crystals used in hydrothermal synthesis contains SDA, and the zeolite powder is used without removing the SDA. The raw material solution for seed crystals does not have to contain SDA, and SDA may be removed from the zeolite powder. The zeolite powder may be used as is as the seed crystals, or the seed crystals may be obtained by processing the powder by pulverization or the like.

[0036] Next, the porous support 11 is immersed in the dispersion liquid in which the seed crystals are dispersed, and the seed crystals are attached to the support 11. Alternatively, the dispersion liquid in which the seed crystals are dispersed is brought into contact with the portion of the support 11 on which the zeolite membrane 12 is to be formed, thereby attaching the seed crystals to the support 11. In this way, a seed crystal-attached support is produced. The seed crystals may also be attached to the support 11 by other methods.

[0037] The support 11 with the seed crystal attached thereto is immersed in the raw material solution. The raw material solution is prepared by dissolving and dispersing, for example, a Si source, an Al source, and SDA in a solvent. Examples of the Si source include colloidal silica, fumed silica, tetraethoxysilane, and sodium silicate. Examples of the Al source include sodium aluminate, aluminum isopropoxide, aluminum hydroxide, boehmite, sodium aluminate, and alumina sol. SDA is an organic substance, such as tetramethylammonium hydroxide, tetramethylammonium chloride, tetramethylammonium bromide, diethyldimethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, N,N,N-trimethyl-1-adamantylammonium hydroxide, and 18-crown-6 ether. The solvent for the raw material solution is, for example, water or an alcohol such as ethanol. The raw material solution may also contain a Na source. Examples of the Na source include sodium hydroxide, sodium aluminate, sodium chloride, and sodium silicate. The raw material solution may be mixed with other raw materials such as cesium hydroxide.

[0038] Assuming that the Si source is entirely present as SiO2 and the Al source is entirely present as Al2O3 in the raw material solution, the SiO2 / Al2O3 molar ratio is preferably 4 to 15. The SDA / Al2O3 molar ratio is preferably 1 to 15. The H2O / Al2O3 molar ratio is preferably 200 to 2000. Assuming that the Na source is entirely present as Na2O, the H2O / Na2O molar ratio is preferably 200 to 1200, and the Na2O / SiO2 molar ratio is preferably 0.1 to 1.0. When the raw material solution contains cesium hydroxide (CsOH), the CsOH / Al2O3 molar ratio is preferably 0.1 to 2.0.

[0039] Then, LTA zeolite is grown by hydrothermal synthesis using the seed crystals as nuclei, thereby forming an LTA zeolite membrane 12 on the support 11. The temperature during hydrothermal synthesis is, for example, 70 to 250° C. The hydrothermal synthesis time is, for example, 5 to 200 hours.

[0040] After the hydrothermal synthesis is completed, the support 11 and the zeolite membrane 12 are washed with pure water. The washed support 11 and the zeolite membrane 12 are dried, for example, at 80°C. This produces the above-mentioned zeolite membrane composite 1. As described above, in the production of the zeolite membrane composite 1, little or no SDA contained in the zeolite membrane 12 is removed. In other words, the process of removing SDA is omitted, and the zeolite membrane composite 1 can be produced in a short time.

[0041] Next, separation of a mixed substance using the zeolite membrane composite 1 will be described with reference to Fig. 3. Fig. 3 is a diagram showing a separation device 2.

[0042] In the separation device 2, a mixed substance containing multiple types of fluids (i.e., gases or liquids) is supplied to the zeolite membrane composite 1, and highly permeable substances in the mixed substance (hereinafter also referred to as "highly permeable substances") are separated from the mixed substance by permeating through the zeolite membrane composite 1. Separation in the separation device 2 may be performed, for example, for the purpose of extracting highly permeable substances from the mixed substance, or for the purpose of concentrating less permeable substances (hereinafter also referred to as "lowly permeable substances").

[0043] The mixed substance (i.e., mixed fluid) may be a mixed gas containing multiple types of gases, a mixed liquid containing multiple types of liquids, or a gas-liquid two-phase fluid containing both gas and liquid.

[0044] The mixture may include one or more of hydrogen (H), helium (He), nitrogen (N), oxygen (O), water (H), carbon monoxide (CO), carbon dioxide (CO), nitrogen oxides, ammonia (NH), sulfur oxides, hydrogen sulfide (H), sulfur fluoride, mercury (Hg), arsine (AsH), hydrogen cyanide (HCN), carbonyl sulfide (COS), C to C hydrocarbons, organic acids, alcohols, mercaptans, esters, ethers, ketones, and aldehydes. The highly permeable substance may be one or more of H, He, N, O, CO, NH, and H, preferably H.

[0045] Nitrogen oxides are compounds of nitrogen and oxygen. Examples of the nitrogen oxides include nitric oxide (NO), nitrogen dioxide (NO2), nitrous oxide (also called dinitrogen monoxide) (N2O), dinitrogen trioxide (N2O3), dinitrogen tetroxide (N2O4), dinitrogen pentoxide (N2O5), etc. X It is a gas called NOX.

[0046] Sulfur oxides are compounds of sulfur and oxygen. Examples of sulfur oxides include sulfur dioxide (SO2), sulfur trioxide (SO3), and other sulfur compounds. X It is a gas called SOX.

[0047] Sulfur fluoride is a compound of fluorine and sulfur. The sulfur fluoride may be, for example, disulfur difluoride (FSSF, S=SF), sulfur difluoride (SF), sulfur tetrafluoride (SF), sulfur hexafluoride (SF), or disulfur decafluoride (SF). 10 ) etc.

[0048] C1-C8 hydrocarbons are hydrocarbons with one or more carbon atoms and eight or less. C3-C8 hydrocarbons may be straight-chain compounds, branched-chain compounds, or cyclic compounds. C2-C8 hydrocarbons may be saturated hydrocarbons (i.e., those without double or triple bonds in the molecule) or unsaturated hydrocarbons (i.e., those with double and / or triple bonds in the molecule). Examples of C1-C4 hydrocarbons include methane (CH4), ethane (C2H6), ethylene (C2H4), propane (C3H8), propylene (C3H6), normal butane (CH3(CH2)2CH3), isobutane (CH(CH3)3), 1-butene (CH2=CHCH2CH3), 2-butene (CH3CH=CHCH3), and isobutene (CH2=C(CH3)2).

[0049] The organic acid may be a carboxylic acid or a sulfonic acid. Examples of the carboxylic acid include formic acid (CHO), acetic acid (CHO), oxalic acid (CHO), acrylic acid (CHO), or benzoic acid (CHCOOH). Examples of the sulfonic acid include ethanesulfonic acid (CHOS). The organic acid may be a chain compound or a cyclic compound.

[0050] The alcohols mentioned above are, for example, methanol (CH3OH), ethanol (C2H5OH), isopropanol (2-propanol) (CH3CH(OH)CH3), ethylene glycol (CH2(OH)CH2(OH)) or butanol (C4H9OH).

[0051] Mercaptans are organic compounds with hydrogenated sulfur (SH) at the end, also known as thiols or thioalcohols. Examples of the mercaptans include methyl mercaptan (CHSH), ethyl mercaptan (CHSH), and 1-propanethiol (CHSH).

[0052] The esters mentioned above are, for example, formates or acetates.

[0053] The ethers mentioned above are, for example, dimethyl ether ((CH3)2O), methyl ethyl ether (C2H5OCH3), diethyl ether ((C2H5)2O) or tetrahydrofuran ((CH2)4O).

[0054] The ketone may be, for example, acetone ((CH3)2CO), methyl ethyl ketone (C2H5COCH3), or diethyl ketone ((C2H5)2CO).

[0055] The aldehydes mentioned above are, for example, acetaldehyde (CH3CHO), propionaldehyde (C2H5CHO) or butanal (butyraldehyde) (C3H7CHO).

[0056] In the following description, it is assumed that the mixed substance to be separated by the separation device 2 is a mixed liquid containing a plurality of types of liquid, and that separation is performed by pervaporation.

[0057] The separation device 2 includes a zeolite membrane composite 1, a plugging section 21, a housing 22, two seal members 23, a supply section 26, a first recovery section 27, and a second recovery section 28. The zeolite membrane composite 1, the plugging section 21, and the seal members 23 are housed in the housing 22. The supply section 26, the first recovery section 27, and the second recovery section 28 are disposed outside the housing 22 and connected to the housing 22.

[0058] The sealing portion 21 is attached to both ends of the support 11 in the longitudinal direction (i.e., the left-right direction in FIG. 3 ), and is a member that covers and seals both longitudinal end faces of the support 11 and the outer peripheral surfaces near these end faces. The sealing portion 21 prevents liquid from flowing in or out from these end faces of the support 11. The sealing portion 21 is, for example, a plate-like member made of glass or resin. The material and shape of the sealing portion 21 may be changed as appropriate. Note that the sealing portion 21 has multiple openings that overlap with the multiple through holes 111 of the support 11, and therefore both longitudinal ends of each through hole 111 of the support 11 are not covered by the sealing portion 21. Therefore, liquid and the like can flow in and out of the through holes 111 from these ends.

[0059] The shape of the housing 22 is not particularly limited, and may be, for example, a substantially cylindrical tubular member. The housing 22 is formed of, for example, stainless steel or carbon steel. The longitudinal direction of the housing 22 is substantially parallel to the longitudinal direction of the zeolite membrane composite 1. A supply port 221 is provided at one longitudinal end of the housing 22 (i.e., the left end in FIG. 3 ), and a first discharge port 222 is provided at the other end. A second discharge port 223 is provided on a side surface of the housing 22. A supply unit 26 is connected to the supply port 221. A first collection unit 27 is connected to the first discharge port 222. A second collection unit 28 is connected to the second discharge port 223. The internal space of the housing 22 is a sealed space isolated from the space around the housing 22.

[0060] Two seal members 23 are disposed around the entire circumference between the outer circumferential surface of the zeolite membrane composite 1 and the inner circumferential surface of the housing 22 near both longitudinal ends of the zeolite membrane composite 1. Each seal member 23 is a substantially annular member made of a liquid-impermeable material. The seal members 23 are, for example, O-rings made of a flexible resin. The seal members 23 are in close contact with the outer circumferential surface of the zeolite membrane composite 1 and the inner circumferential surface of the housing 22 around the entire circumference. In the example shown in FIG. 3 , the seal member 23 is in close contact with the outer circumferential surface of the sealing portion 21 and indirectly with the outer circumferential surface of the zeolite membrane composite 1 via the sealing portion 21. A seal is formed between the seal member 23 and the outer circumferential surface of the zeolite membrane composite 1 and between the seal member 23 and the inner circumferential surface of the housing 22, so that liquids can hardly or completely pass through.

[0061] The supply unit 26 supplies the mixed liquid to the internal space of the housing 22 through the supply port 221. The supply unit 26 includes, for example, a pump that pressure-feeds the mixed liquid toward the housing 22. The pump includes a temperature regulator and a pressure regulator that regulate the temperature and pressure, respectively, of the mixed liquid supplied to the housing 22. The first recovery unit 27 includes, for example, a storage container that stores the liquid discharged from the housing 22, or a pump that transfers the liquid. The second recovery unit 28 includes, for example, a vacuum pump that reduces the pressure of the space outside the outer circumferential surface of the zeolite membrane composite 1 in the housing 22 (i.e., the space sandwiched between the two seal members 23), and a cooling chiller trap that cools and liquefies the gas that has vaporized and permeated the zeolite membrane composite 1.

[0062] When separating a mixed liquid, the above-described separation device 2 is provided, thereby preparing a zeolite membrane composite 1. Subsequently, a mixed liquid containing a plurality of liquids having different permeabilities to the zeolite membrane 12 is supplied by the supply unit 26 to the internal space of the housing 22. For example, the main components of the mixed liquid are water (H2O) and ethanol (C2H5OH). The mixed liquid may contain liquids other than water and ethanol. The pressure of the mixed liquid supplied from the supply unit 26 to the internal space of the housing 22 (i.e., the introduction pressure) is, for example, 0.1 MPa to 2 MPa, and the temperature of the mixed liquid is, for example, 10°C to 200°C.

[0063] The mixed liquid supplied from the supply unit 26 to the housing 22 is introduced into each of the through-holes 111 of the support 11 from the left end of the zeolite membrane composite 1 in the drawing, as indicated by arrow 251. A highly permeable substance, which is a liquid with high permeability in the mixed liquid, vaporizes and permeates through the zeolite membrane 12 provided on the inner circumferential surface of each through-hole 111 and the support 11, and is discharged from the outer circumferential surface of the support 11. In this way, the highly permeable substance (e.g., water) is separated from a less permeable substance (e.g., ethanol), which is a liquid with low permeability in the mixed liquid.

[0064] The gas (hereinafter referred to as "permeate") discharged from the outer peripheral surface of the support 11 is led to the second collection section 28 via the second discharge port 223 as shown by the arrow 253, where it is cooled and collected as a liquid. The pressure of the gas collected by the second collection section 28 via the second discharge port 223 (i.e., permeate pressure) is, for example, about 6.67 kPa (about 50 Torr). The permeate may include low-permeate substances that have permeated the zeolite membrane 12 in addition to the high-permeate substances described above.

[0065] Furthermore, the liquid in the mixed liquid excluding the substances that have permeated the zeolite membrane 12 and the support 11 (hereinafter referred to as "impermeable substances") passes through each through-hole 111 of the support 11 from left to right in the figure and is recovered by the first recovery unit 27 via the first discharge port 222, as indicated by arrow 252. The pressure of the liquid recovered by the first recovery unit 27 via the first discharge port 222 is, for example, approximately the same as the introduction pressure. In addition to the low-permeability substances described above, the impermeable substances may also include highly permeable substances that did not permeate the zeolite membrane 12. The impermeable substances recovered by the first recovery unit 27 may be circulated to the supply unit 26 and supplied again into the housing 22, for example.

[0066] The separation apparatus 2 shown in FIG. 3 may be used, for example, as a membrane reactor. In this case, the housing 22 is used as a reactor. A catalyst that promotes a chemical reaction of the raw materials supplied from the supply unit 26 is accommodated inside the housing 22. The catalyst is disposed, for example, between the supply port 221 and the first discharge port 222. Preferably, the catalyst is disposed near the zeolite membrane 12 of the zeolite membrane composite 1. The catalyst is made of an appropriate material and shape depending on the type of raw material and the type of chemical reaction to be caused in the raw material. The raw material may include one type or two or more types of substances. The membrane reactor may further include a heating device for heating the reactor (i.e., the housing 22) and the raw material to promote the chemical reaction of the raw material.

[0067] In the separation device 2 used as a membrane reactor, a mixed substance containing a product substance produced by a chemical reaction of a raw material in the presence of a catalyst is supplied to the zeolite membrane 12 in the same manner as described above, and the highly permeable substance in the mixed substance permeates the zeolite membrane 12, thereby being separated from other substances having lower permeability than the highly permeable substance. For example, the mixed substance may be a fluid containing the product substance and unreacted raw material. The mixed substance may also contain two or more types of product substances. The highly permeable substance may be a product substance produced from the raw material, or may be a substance other than the product substance. Preferably, the highly permeable substance contains one or more types of product substances.

[0068] When the highly permeable substance is a product substance produced from a raw material, the yield of the product substance can be improved by separating the product substance from other substances using the zeolite membrane 12. When the mixed substance contains two or more types of product substances, the two or more types of product substances may be highly permeable substances, or some of the two or more types of product substances may be highly permeable substances.

[0069] Next, Examples 1 to 7 and Comparative Examples 1 to 4 of the zeolite membrane composite will be described. Table 1 shows the type of zeolite membrane, the composition of the raw material solution used to form the zeolite membrane, the synthesis temperature, synthesis time, firing temperature, and firing time in Examples 1 to 7 and Comparative Examples 1 to 4. In Examples 1, 3 to 5, and Comparative Example 1, an LTA zeolite membrane was formed, in Examples 2, 6, and Comparative Example 2, an RHO zeolite membrane was formed, in Example 7, an SOD zeolite membrane was formed, and in Comparative Examples 3 and 4, a CHA zeolite membrane was formed.

[0070] [Table 1]

[0071] (Preparation of LTA-type zeolite membrane) A raw material solution was obtained by mixing sodium aluminate (Sigma-Aldrich) as the Al source, colloidal silica (LUDOX AS-40, Sigma-Aldrich) as the Si source, sodium hydroxide (Sigma-Aldrich) as the Na source, and tetramethylammonium hydroxide solution (Fujifilm Wako Pure Chemical Industries, Ltd.) as SDA with pure water. Assuming that the Al, Si, and Na sources all exist as oxides, the molar ratios of SiO2 / Al2O3, HO / Na2O, Na2O / SiO2, SDA / Al2O3, and HO / Al2O3 in the raw material solution are as shown in Table 1.

[0072] A monolithic porous alumina support having LTA zeolite seed crystals attached to the cells (through holes) was immersed in the raw material solution, and the raw material solution was heated (hydrothermal synthesis). The synthesis temperature and synthesis time during the hydrothermal synthesis are shown in Table 1. As a result, an LTA zeolite membrane was formed on the support. After the hydrothermal synthesis, the support and the zeolite membrane were thoroughly washed with pure water and then dried at 80°C. Thereafter, in Example 3, the LTA zeolite membrane was heat-treated at 430°C for 15 hours, in Example 4, the LTA zeolite membrane was heat-treated at 400°C for 15 hours, and in Comparative Example 1, the LTA zeolite membrane was heat-treated at 450°C for 15 hours. As a result, part or all of the SDA contained in the LTA zeolite membrane was burned off. In Examples 1 and 5, SDA was not burned off. Through the above treatments, the zeolite membrane composites of Examples 1 and 3 to 5 and Comparative Example 1, each having an LTA zeolite membrane, were obtained.

[0073] (Preparation of RHO-type zeolite membrane) A raw material solution was obtained by mixing aluminum hydroxide (Sigma-Aldrich) as an Al source, colloidal silica (Snowtex S, Nissan Chemical Industries, Ltd.) as a Si source, sodium hydroxide (Sigma-Aldrich) as a Na source, cesium hydroxide (Sigma-Aldrich) as a Cs source, and 18-crown 6 (Tokyo Chemical Industry Co., Ltd.) as SDA with pure water. The molar ratios of SiO2 / Al2O3, HO / Na2O, Na2O / SiO2, CsOH / Al2O3, SDA / Al2O3, and HO / Al2O3 in the raw material solution are shown in Table 1.

[0074] A monolithic porous alumina support having separately prepared RHO zeolite seed crystals attached to its cells was immersed in the raw material solution, and the raw material solution was heated (hydrothermal synthesis). The synthesis temperature and synthesis time during hydrothermal synthesis are shown in Table 1. As a result, an RHO zeolite membrane was formed on the support. After hydrothermal synthesis, the support and zeolite membrane were thoroughly washed with pure water and then dried at 80°C. Thereafter, in Comparative Example 2, the RHO zeolite membrane was heat-treated at 450°C for 20 hours to burn off the SDA. In Examples 2 and 6, the SDA was not burned off. Through the above treatments, zeolite membrane composites having an RHO zeolite membrane were obtained for Examples 2 and 6 and Comparative Example 2.

[0075] (Preparation of SOD-type zeolite membrane) A raw material solution was obtained by mixing aluminum isopropoxide (Kanto Chemical Co., Ltd.) as an Al source, tetraethoxysilane (Kanto Chemical Co., Ltd.) as a Si source, and tetramethylammonium hydroxide solution (Fujifilm Wako Pure Chemical Industries, Ltd.) as SDA with pure water. The molar ratios of SiO2 / Al2O3, SDA / Al2O3, and H2O / Al2O3 in the raw material solution are shown in Table 1.

[0076] A monolithic porous alumina support having separately prepared SOD zeolite seed crystals attached to its cells was immersed in the raw material solution, and the raw material solution was heated (hydrothermal synthesis). The synthesis temperature and synthesis time during hydrothermal synthesis are shown in Table 1. As a result, an SOD zeolite membrane was formed on the support. After hydrothermal synthesis, the support and zeolite membrane were thoroughly washed with pure water and then dried at 80°C. Through the above treatments, the zeolite membrane composite of Example 7 having an SOD zeolite membrane was obtained. Note that SDA was not removed by combustion.

[0077] (Preparation of CHA-type zeolite membrane) A raw material solution was obtained by mixing aluminum hydroxide (Sigma-Aldrich) as the Al source, colloidal silica (Snowtex S, Nissan Chemical Industries, Ltd.) as the Si source, sodium hydroxide (Sigma-Aldrich) as the Na source, and trimethyladamantylammonium hydroxide solution (SACHEM) as SDA with pure water. The molar ratios of SiO2 / Al2O3, HO / Na2O, Na2O / SiO2, SDA / Al2O3, and HO / Al2O3 in the raw material solution are shown in Table 1.

[0078] A monolithic porous alumina support with separately prepared CHA-type zeolite seed crystals attached to the cells was immersed in the raw material solution, and the raw material solution was heated (hydrothermal synthesis). The synthesis temperature and synthesis time during hydrothermal synthesis are as shown in Table 1. As a result, a CHA-type zeolite membrane was formed on the support. After hydrothermal synthesis, the support and zeolite membrane were thoroughly washed with pure water and then dried at 80°C. Thereafter, in Comparative Example 4, the CHA-type zeolite membrane was heat-treated at 400°C for 40 hours to burn off the SDA. In Comparative Example 3, the SDA was not burned off. Through the above treatments, zeolite membrane composites having a CHA-type zeolite membrane were obtained for Comparative Examples 3 and 4.

[0079] Table 2 shows the membrane composition, water / ethanol separation performance, and hydrothermal durability of the zeolite membranes of Examples 1 to 7 and Comparative Examples 1 to 4.

[0080] [Table 2]

[0081] (Membrane composition measurement) The C / (Al+Si) molar ratio, Si / Al molar ratio, and presence or absence of N in the cross section of the zeolite membrane (referred to as "C / (Al+Si)," "Si / Al," and "N-containing," respectively, in Table 2) were measured using a scanning electron microscope (SEM)-energy dispersive X-ray spectroscopy (EDX). The acceleration voltage was 15 kV. Regarding the presence or absence of N, the zeolite membrane was determined to contain N when the molar ratio of nitrogen to the sum of aluminum and silicon (i.e., the N / (Al+Si) molar ratio) was 0.03 or higher. In Table 2, "◯" indicates that the zeolite membrane contained N, and "×" indicates that the zeolite membrane did not contain N. The zeolite membranes of Examples 1 to 7 and Comparative Example 3 all had a C / (Al+Si) molar ratio of 0.1 or higher.

[0082] (Water / ethanol separation test) The water / ethanol separation test was carried out by pervaporation using the above-mentioned separation apparatus 2. In the separation apparatus 2, a zeolite membrane composite is housed in the housing 22. In this test, a mixed liquid containing 50 mass % water and 50 mass % ethanol at 60°C was supplied from the supply section 26 to the housing 22 through the supply port 221 at atmospheric pressure. The second discharge port 223, which is the permeation side of the zeolite membrane composite, was depressurized to -94.66 kPaG (approximately 50 Torr). The gas that permeated the zeolite membrane and was discharged from the outer peripheral surface of the support 11 was cooled in the second recovery section 28 and recovered as a liquid. From the mass of the liquid recovered in the second recovery section 28, the total permeation flux (kg / m), which is the amount of fluid that permeated the membrane per unit area per unit time, was calculated. 2 h) was calculated. In addition, the concentrations (mass%) of water and ethanol in the liquid were measured, and the water concentration / ethanol concentration was obtained as the separation factor.

[0083] In Examples 1 to 7 and Comparative Examples 1 and 2, the total permeation flux was 1.0 kg / m2 h or more, and the separation factor was more than 1000. On the other hand, for the CHA-type zeolite membrane, in Comparative Example 3 where SDA was not removed by combustion, water did not permeate (i.e., the mixed liquid was not separated), and in Comparative Example 4 where SDA was removed by combustion, the separation factor was 420, which was significantly smaller.

[0084] (Hydrothermal durability evaluation) To evaluate hydrothermal durability, the zeolite membrane composite was immersed in pure water at 100°C for 6 hours and then dried at 80°C for 12 hours or more. The "water / ethanol separation test" was then repeated to measure the separation factor, and the ratio of the separation factor after immersion to the separation factor before immersion ("Separation factor after hot water immersion / Separation factor before hot water immersion" in Table 2) was used as an index of hydrothermal durability. In Comparative Examples 3 and 4, the hydrothermal durability was not evaluated.

[0085] In Comparative Examples 1 and 2, where the detected carbon was close to zero and the C / (Al+Si) molar ratio was 0, the hydrothermal durability value (the ratio of the separation factor after immersion to the separation factor before immersion) was 0.3 or less. In contrast, in Examples 1 to 7, where the C / (Al+Si) molar ratio was 0.1 or more, the hydrothermal durability value was 0.7 or more, which was significantly higher. When comparing Examples 1, 3, and 4, which used the same type of zeolite and the same Si / Al molar ratio, the hydrothermal durability value increased with the increase in the C / (Al+Si) molar ratio. Specifically, in Examples 1 and 4, where the C / (Al+Si) molar ratio was 0.3 or more, the hydrothermal durability value was 0.95 or more.

[0086] As described above, the zeolite membrane composite 1 comprises a porous support 11 and a zeolite membrane 12 containing aluminum, silicon, and carbon, provided on the support 11. The zeolite membrane 12 has a stabilized crystal structure due to the presence of SDA, an organic substance (a substance containing carbon), in the pores, and therefore has improved hydrothermal durability compared to zeolite membranes in which SDA is not present in the pores. Furthermore, when a mixed liquid containing 50 mass % water and 50 mass % ethanol at 60°C is supplied to the permeate side at -94.66 kPaG, the zeolite membrane composite 1 has a total permeation flux of 1.0 kg / m 2 h or more, and the separation factor between water and ethanol is greater than or equal to 1000. Thus, the zeolite membrane composite 1 can achieve high water separation performance even when SDA is present in the pores.

[0087] The amount of SDA contained in the zeolite membrane 12 can be expressed by the molar ratio of carbon to the sum of aluminum and silicon in the zeolite membrane 12. In the zeolite membrane 12, the molar ratio of carbon to the sum of aluminum and silicon is 0.1 or more, preferably 0.3 or more. This allows SDA to be present in most of the pores of the zeolite membrane 12, thereby more reliably improving hydrothermal durability. The molar ratio of carbon to the sum of aluminum and silicon is, for example, 5.0 or less, preferably 4.0 or less, and more preferably 3.0 or less. Preferably, the zeolite membrane 12 further contains nitrogen. In such a zeolite membrane composite 1, nitrogen-containing SDA is present in the pores of the zeolite membrane 12, more reliably improving hydrothermal durability.

[0088] The silicon / aluminum molar ratio in the zeolite membrane 12 is preferably 1 or more and 10 or less, more preferably 1 or more and 6 or less. This increases the hydrophilicity of the zeolite membrane 12, thereby further improving the water separation performance. Normally, a zeolite membrane with a low silicon / aluminum molar ratio has reduced durability, but the zeolite membrane 12 containing SDA can achieve high hydrothermal durability even when the silicon / aluminum molar ratio is low.

[0089] Preferably, the zeolite membrane 12 contains an AEI, AFT, AFX, ANA, CHA, ETL, ERI, FER, KFI, LTA, MER, RHO, SOD, MOR, FAU, BEA, or HEU zeolite. More preferably, the zeolite membrane 12 contains an AEI, AFT, AFX, ANA, CHA, ETL, ERI, KFI, LTA, MER, RHO, or SOD zeolite. This more reliably achieves a zeolite membrane composite 1 with high water separation performance and improved hydrothermal durability. Of course, the zeolite membrane 12 may contain other types of zeolite.

[0090] The above-mentioned zeolite membrane composite 1 and membrane reactor can be modified in various ways.

[0091] Depending on the hydrothermal durability required for the zeolite membrane composite 1, the molar ratio of carbon to the sum of aluminum and silicon in the zeolite membrane 12 may be greater than 3.0. Depending on the strength and water separation performance required for the zeolite membrane composite 1, the molar ratio of silicon / aluminum in the zeolite membrane 12 may be less than 1 or greater than 6.

[0092] In the production of the zeolite membrane 12, a nitrogen-free SDA may be used, and in this case, the zeolite membrane 12 may not contain nitrogen.

[0093] In addition to the support 11 and the zeolite membrane 12, the zeolite membrane composite 1 may further include a functional membrane or a protective membrane laminated on the zeolite membrane 12. Such a functional membrane or protective membrane may be an inorganic membrane such as a zeolite membrane, a silica membrane, or a carbon membrane, or an organic membrane such as a polyimide membrane or a silicone membrane. Furthermore, a substance that easily adsorbs water may be added to the functional membrane or protective membrane laminated on the zeolite membrane 12.

[0094] In the separation device 2, the membrane reactor and the separation method, the mixed substances may be separated by vapor permeation, reverse osmosis, gas permeation or the like, in addition to the pervaporation method exemplified in the above description.

[0095] In the separation device 2, the membrane reactor, and the separation method, substances other than those exemplified in the above description may be separated from the mixed substance.

[0096] The configurations in the above-described embodiment and each modification may be combined as appropriate as long as they are not mutually contradictory.

[0097] While the invention has been particularly illustrated and described, it should be understood that the foregoing description is illustrative and not restrictive, and that numerous modifications and variations are possible without departing from the scope of the invention. [Industrial Applicability]

[0098] The zeolite membrane composite of the present invention can be used, for example, as a dehydration membrane, and further, can be used in various fields in which zeolites are used, such as separation membranes for various substances other than water and adsorption membranes for various substances. [Explanation of symbols]

[0099] 1 Zeolite membrane composite 11 Support 12 Zeolite membrane

Claims

1. A zeolite membrane composite, a porous support; a zeolite membrane provided on the support and containing aluminum, silicon, and carbon; Equipped with In the zeolite membrane, a molar ratio of carbon to the sum of aluminum and silicon is 0.1 or more and 3.0 or less; the zeolite membrane contains an LTA-type, an RHO-type, or an SOD-type zeolite; When a mixed liquid containing 50% by mass of water and 50% by mass of ethanol at 60 ° C. was supplied to the permeation side at −94.66 kPaG, the total permeation flux was 1.0 kg / m ２ h or more, and the separation factor between water and ethanol is 1000 or more.

2. The zeolite membrane composite according to claim 1, In the zeolite membrane, the molar ratio of carbon to the sum of aluminum and silicon is 0.3 or more and 3.0 or less.

3. The zeolite membrane composite according to claim 1, The zeolite membrane further contains nitrogen.

4. The zeolite membrane composite according to claim 1, The zeolite membrane has a silicon / aluminum molar ratio of 1 or more and 6 or less.

5. A membrane reactor comprising: The zeolite composite membrane according to any one of claims 1 to 4, a catalyst that promotes a chemical reaction of the raw materials; a reactor containing the zeolite membrane composite and the catalyst; a supply unit that supplies the raw material to the reactor; Equipped with The zeolite membrane composite separates the highly permeable substance from the other substances in the mixture containing the product substance produced by the chemical reaction of the raw material in the presence of the catalyst by allowing the highly permeable substance to pass through.

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