Method for synthesizing aqueous methanol solution and apparatus for producing aqueous methanol solution

Abstract

Provided is a procedure for synthesizing an aqueous methanol solution from a mixed gas containing carbon dioxide and hydrogen under low-pressure conditions of less than 1 MPa. This method for synthesizing an aqueous methanol solution from a mixed gas containing hydrogen and CO2 is characterized by generating methanol and water vapor from a starting material gas containing CO2 and hydrogen by a catalytic reaction in a first reactor, then allowing 90% or more of both of the generated methanol and water vapor to permeate through to a membrane permeation side in a second reactor provided with a plurality of porous ceramic separation membranes that each have a separation layer including an MFI zeolite membrane body having a composition of Mn[AlnSi96-nO192] (2<n<8, M is a metal cation), and cooling and condensing the methanol and water vapor that have permeated through the membrane to obtain a 50 to 90 wt% aqueous methanol solution on the membrane permeation side.

Description

Method for synthesizing aqueous methanol solution and apparatus for producing aqueous methanol solution.

[0001] The present invention relates to a method for synthesizing an aqueous methanol solution from a mixed gas containing carbon dioxide (CO ２ ) and hydrogen under low-pressure conditions of less than 1 MPa, and an apparatus for producing an aqueous methanol solution therefor.

[0002] Aiming to achieve carbon neutrality by 2050, around 2020, global investment in green technology development towards carbon neutrality has accelerated, and the business environment has changed in almost all fields, from automobiles to chemistry, environment, energy, etc. Instead of fossil resources such as natural gas and coal, there is an urgent need to develop and improve new synthesis methods for chemicals and fuels derived from renewable biomass that are carbon neutral or recovered CO ２ as raw materials. Methanol is a very important compound in the industry as a raw material for manufacturing various chemicals and fuels. As shown in the following reactions, conventionally, synthesis via synthesis gas, which is a mixed gas of CO and hydrogen, from raw materials derived from fossil resources was the main method (Equation 1). Furthermore, when CO ２ is included in the raw materials, it is particularly necessary to consider Equations 2 and 3. CO + 2H ２ ⇔ MeOH (exothermic reaction) ··· (Equation 1) CO ２ + 2H ２ ⇔ CO + H ２ O (endothermic reaction) ··· (Equation 2) CO ２ + 3H ２ ⇔ MeOH + H ２ O (exothermic reaction) ··· (Equation 3) Equations 1 to 3 are equilibrium reactions, and the equilibrium composition that gives a higher methanol yield is more favorable at lower temperatures and higher pressures. However, industrially, a process of synthesizing under a temperature range of 200 to 300°C and high-pressure conditions of 5 to 10 MPa is generally used from the perspective of reaction rate.

[0003] In order to eliminate the equilibrium constraint in methanol synthesis, a method called a membrane reactor, which integrates a solid catalyst and a separation membrane, or a membrane reactor has been proposed. For example, in Patent Document 1, hydrogen and CO ２By using a type A zeolite membrane or a type T zeolite membrane that can selectively permeate and separate water vapor under reaction conditions of 200 °C and 3 MPa for a raw material gas containing [substance], it has been reported that methanol can be synthesized at a methanol conversion rate of 53.5% exceeding the equilibrium conversion rate (23.6%) with a methanol content of 97.5 wt%.

[0004] In addition, in Patent Document 2, a method is proposed in which by converting a part of the methanol produced using a membrane reactor into dimethyl ether, it is possible to achieve a high conversion rate of 90% or more at a combined yield of methanol and dimethyl ether under conditions of 250 °C and 5 MPa.

[0005] On the other hand, when the reaction conditions are 1 MPa or more, it becomes a regulated object as a high-pressure gas. To ensure safety and durability, the use of high-strength materials, strict design and manufacturing processes, strict safety inspections and quality control, addition of complex valves and safety devices, compliance with legal regulations, and safety environment preparation and operation costs require 3 to 5 times the cost compared to general low-pressure equipment. Therefore, for small-scale distributed methanol synthesis plants, the sites where economic efficiency can be obtained are extremely limited.

[0006] Although the methanol synthesis process temperature at which a practical reaction rate can be obtained is 200 °C or higher, in the methanol synthesis methods proposed so far, under low-pressure conditions of less than 1 MPa, there is a problem that almost no methanol, which is the target product, can be obtained due to equilibrium constraints.

[0007] Furthermore, high-concentration methanol is highly toxic and highly flammable, making it difficult to handle for the general public who are not specialized in chemistry.

[0008] Japanese Patent Application Laid-Open No. 2007-55970, Patent No. 71,907,74

[0009] Derived from renewable biomass that becomes carbon neutral, or recovered CO ２Since much of the demand for methanol synthesis using this raw material is for small-scale, decentralized operations, a methanol synthesis system that can operate at less than 1 MPa is desirable for economic reasons. Furthermore, producing methanol as a safer aqueous solution rather than in the dangerous high-concentration state makes transportation and storage easier at small-scale, decentralized sites.

[0010] The object of this invention is hydrogen and CO ２ The objective is to provide a method for efficiently obtaining an aqueous methanol solution from a mixed gas containing [a specific substance] under low pressure conditions of less than 1 MPa.

[0011] To achieve the above objective, the first form is hydrogen and CO ２ A method for synthesizing an aqueous methanol solution from a mixed gas containing CO, wherein CO is used in the first reactor. ２ From a raw material gas containing hydrogen, methanol and water vapor are produced by a catalytic reaction, and then the separation layer is M ｎ [Al ｎ Si ９６－ｎ O １９２ In a second reactor equipped with multiple porous ceramic separation membranes containing a membrane body of MFI-type zeolite having the composition (2 < n < 8, M: metal cation), both the generated methanol and water vapor components are permeated to the membrane permeation side at a rate of 90% or more, and the permeated methanol and water vapor are cooled and condensed to obtain a 50-90 wt% methanol aqueous solution on the membrane permeation side.

[0012] The second embodiment is characterized in that the reaction temperature of the second reactor is in the range of 210 to 240°C, and the membrane permeation pressure of the porous ceramic separation membrane is in the range of 0.001 to 0.01 MPa in absolute pressure. The third embodiment is characterized in that M: the metal cation is sodium.

[0013] Furthermore, hydrogen and CO ２ In a methanol aqueous solution production apparatus that synthesizes a methanol aqueous solution from a mixed gas containing CO, ２ The first reactor generates methanol and water vapor from a hydrogen-containing raw material gas through a catalytic reaction, and the separation layer is M ｎ [Al ｎ Si ９６－ｎ O １９２The reactor comprises a second reactor equipped with multiple porous ceramic separation membranes containing MFI-type zeolite membranes having the composition (2 < n < 8, M: metal cation), and a heat exchanger for cooling and condensing the methanol and water vapor that have permeated the membrane. More than 90% of both methanol and water vapor components generated in the first reactor permeate to the membrane permeation side of the second reactor, and a 50-90 wt% methanol aqueous solution is produced on the membrane permeation side by cooling and condensing the methanol and water vapor that have permeated the membrane in the heat exchanger.

[0014] According to the first form, hydrogen and CO ２ A method for synthesizing an aqueous methanol solution from a mixed gas containing CO, wherein CO is used in the first reactor. ２ From a raw material gas containing hydrogen, methanol and water vapor are produced by a catalytic reaction, and then the separation layer is M ｎ [Al ｎ Si ９６－ｎ O １９２ In a second reactor equipped with multiple porous ceramic separation membranes containing a membrane body of MFI-type zeolite having the composition (2 < n < 8, M: metal cation), both methanol and water vapor components generated are permeated to the membrane permeation side by more than 90%, and a 50-90 wt% methanol aqueous solution is obtained on the membrane permeation side by cooling and condensing the permeated methanol and water vapor. ２ It is characterized by having metal cations fixed to hydrogen that selectively adsorb methanol and water vapor, CO ２ This system allows for the selective permeation of methanol and water vapor from a mixed gas containing hydrogen at a reaction system of approximately equal moles at 200-300°C, while also providing high membrane durability. Furthermore, operation under low pressure conditions of less than 1 MPa significantly improves safety, and the membrane permeation side yields a 50-90 wt% methanol aqueous solution that is easy to transport and store. A methanol aqueous solution production apparatus equipped with this configuration provides similar effects.

[0015] According to the second embodiment, the reaction temperature of the second reactor is in the range of 210 to 240°C, and the membrane permeation pressure of the separation membrane is 0.001 to 0.01 MPa in absolute pressure. This has the effect of being able to produce methanol aqueous solution with high efficiency, achieving a methanol conversion rate of 75 to 95% per pass, even under low pressure conditions of less than 1 MPa. A methanol aqueous solution production apparatus equipped with this configuration also achieves the same effect.

[0016] According to the third form, M is characterized by the metal cation being sodium, and CO ２ This configuration allows for the selective permeation of methanol and water in approximately equimolar amounts from a mixed gas containing hydrogen through a membrane in a reaction system at 200-300°C, while also suppressing side reactions other than the methanol synthesis reaction, which is the target product derived from metal cations. A methanol aqueous solution production apparatus equipped with this configuration exhibits similar effects.

[0017] This is a flow sheet showing a method and apparatus configuration for synthesizing an aqueous methanol solution from a mixed gas containing carbon dioxide (CO2) and hydrogen under low pressure conditions of less than 1 MPa in the embodiment. This is a schematic diagram showing the second reactor (membrane reactor) of the embodiment. This is a schematic diagram showing the porous ceramic separation membrane of the embodiment.

[0018] Next, embodiments will be described based on the drawings, but the embodiments of the present invention are not limited to these.

[0019] Referring to Figure 1, the method for synthesizing a methanol aqueous solution under low pressure in the methanol aqueous solution production apparatus of the embodiment is as follows: raw material gas 1 (H ２ / CO ２ The mixed gas (H) is pressurized in compressor 2 to 0.6 to 1 MPa, not exceeding 1 MPa, and adjusted to a predetermined pressure and flow rate by gas pressure and flow rate control valve 3. The raw material gas temperature is adjusted in heat exchanger (heater) 4 to a predetermined temperature in the range of 200 to 250°C, preferably 210 to 240°C. In the first reactor 5, methanol and water vapor are generated near the equilibrium composition by catalytic reaction with the packed solid catalyst 6. The mixed gas (H) generated thereafter is increased in compressor 2 to 0.6 to 1 MPa, not exceeding 1 MPa, and adjusted to a predetermined pressure and flow rate by gas pressure and flow rate control valve 3. The raw material gas temperature is adjusted in heat exchanger (heat exchanger) 4 to a predetermined temperature in the range of 200 to 250°C, preferably 210 to 240°C. In the first reactor 5, methanol and water vapor are generated by catalytic reaction with the packed solid catalyst 6 until the equilibrium composition is reached. ２ / CO ２The methanol / water vapor (CO / methanol / water vapor) 7 is introduced into the second reactor (membrane reactor) 8 at a predetermined temperature in the range of 200 to 250°C, preferably 210 to 240°C. Simultaneously with the catalytic reaction by the packed solid catalyst 6, 90% or more, preferably 99% or more, of the methanol and water vapor components generated by the porous ceramic separation membrane 9 are permeated to the membrane permeate side. The methanol and water vapor 10 that have permeated the membrane are cooled and condensed by a heat exchanger (cooler / condenser) 11 to obtain a 50 to 90 wt% methanol aqueous solution in a collection tank 12 for the membrane-permeated methanol aqueous solution.

[0020] The pressure of the methanol and water vapor 10 that have permeated the membrane is adjusted by a depressurizing pump 13 so that it is in the range of 0.001 to 0.03 MPa, preferably 0.001 to 0.01 MPa, in absolute pressure. The non-permeable side of the separation membrane in the second reactor (membrane reactor) 8 may be closed, but if it is open, the methanol and water vapor are cooled and condensed by a heat exchanger (cooler / condenser) 11 and collected in a membrane-non-permeable methanol aqueous solution collection tank 14. For continuous operation, multiple methanol aqueous solution collection tanks can be installed so that when a predetermined amount of methanol aqueous solution has accumulated, the collection tank can be switched and used, enabling continuous operation. H discharged from the permeable and non-permeable sides of the membrane ２ / CO ２ The unreacted gas 15 consisting of CO may be recycled by recirculating it to the compressor 2 as needed. However, since there is energy loss due to repressurization, it is desirable to keep the recycling ratio as low as possible.

[0021] Here, known catalysts such as copper-zinc catalysts can be used as the solid catalyst 6 for methanol synthesis. As for the catalyst shape, granular or pellet-like catalysts in the range of 1 to 10 mm are preferred over powder, as they reduce pressure loss and are easier to handle.

[0022] For the second reactor (membrane reactor) 8, since the operating pressure is less than 1 MPa, it is possible to mount multiple tubular porous ceramic separation membranes 9 by using the multi-tube membrane module shape shown in Figure 2. Depending on the processing rate of the raw material gas, multiple second reactors (membrane reactors) 8 may be used by connecting them directly or in parallel, considering them as multi-tube membrane modules as shown in Figure 2. Since the methanol synthesis reaction is an exothermic reaction, it is common to install jackets for flowing a heat transfer medium to the multi-tube membrane module to remove heat and equalize the reaction temperature, or to divide the multi-tube membrane module into multiple units and install heat exchangers between each multi-tube membrane module to control the temperature, depending on the processing rate and heat generation of the raw material gas.

[0023] When the porous ceramic separation membrane 9 is tubular, it is common practice to attach a sealing plug to one end of the porous support and a connecting member to the other end, and then mount it on the module. For attaching and sealing the porous ceramic separation membrane 9 to the second reactor (membrane reactor) 8, it is common to use fluororesin-based heat shrink tubing and sealing tape such as Teflon (registered trademark). From the viewpoint of continuous operation, operation at 260°C or lower, preferably 230°C or lower, is preferable. Note that although the first reactor 5 and the first reactor 8 are shown separately in Figure 1, they may be integrated.

[0024] As shown in Figure 3, the porous ceramic separation membrane 9 is composed of a separation layer 16 and a porous support 17, and the separation layer 16 is generally formed on a porous support 17 with an average pore size of 0.1 to 5 μm. The separation layer 16 of the porous ceramic separation membrane 9 used in the present invention is M ｎ [Al ｎ Si ９６－ｎ O １９２ It is an essential requirement that the film body contain an MFI-type zeolite having the composition (2 < n < 8, M: metal cation). At the Al exchange cation sites in the zeolite skeleton, CO ２ Furthermore, metal cations such as Li, Na, and K that selectively adsorb methanol and water vapor onto hydrogen must be immobilized. If the Si / Al ratio is too low, the film durability will be poor, and if the Si / Al ratio is too high, CO ２Furthermore, the separation selectivity of methanol and water with respect to hydrogen is not exhibited. Also, if the metal cation is not immobilized at the Al exchange cation site in the zeolite skeleton, CO ２ Furthermore, the separation selectivity of methanol and water with respect to hydrogen is not exhibited. ２ The separation selectivity for methanol and water relative to hydrogen is preferably 100 or higher, more preferably 400 or higher. If the separation selectivity is lower than that, the CO2 used as the source gas will be used. ２ The hydrogen leakage becomes too large, making it difficult to achieve the desired effect.

[0025] Furthermore, the type A zeolite membrane used in Patent Document 1 is unsuitable as a separation membrane for use in the embodiment because it allows water to permeate but hardly allows methanol to permeate, and its membrane durability is insufficient. For example, Na cations can be immobilized at the exchange cation sites of Al in the zeolite skeleton. ｎ [Al ｎ Si ９６－ｎ O １９２ A MFI-type zeolite film having a composition (2 < n < 8) allows CO to be produced even at temperatures above 200°C under conditions of 1 MPa or less. ２ The separation selectivity of methanol to hydrogen is 100 or more, and 2 × 10 －７ It is possible to obtain permeability of methanol and water of [mol / (m²·s·Pa)] or higher.

[0026] For the porous support 17, for example, alumina (α-Al ２ O ３ (α-alumina), γ-Al ２ O ３Examples of ceramic supports include those made of (γ-alumina), mullite, zirconia, titania, or composites thereof, with porous α-alumina supports having an average pore size of 0.1 to 3 μm and a porosity of 25 to 55% being preferred. If the porosity is less than 25%, while the mechanical strength is excellent, the membrane permeability is reduced more than necessary. If the porosity is greater than 55%, the pressure resistance decreases, raising concerns that the porous ceramic separation membrane 9 may break due to the pressure difference across the membrane. The porous support 17 can be in the shape of a flat plate, tubular, or monolithic, but the tubular shape is common, and from the viewpoint of durability and economy, those with a diameter of 1 to 1.6 cm and a length of 40 to 120 cm are preferred.

[0027] Next, examples will be described together with comparative examples, but the embodiments of the present invention are not limited to these examples.

[0028] Membrane permeability (H ２ CO ２ CO, H ２ By varying the reaction temperature and operating conditions (absolute pressure on the non-permeable side of the porous ceramic separation membrane 9), MeOH and H2O are introduced into the membrane permeable side. ２ The recovery rate of oxygen (O), the methanol concentration of the membrane-permeated methanol aqueous solution, and the MeOH yield were calculated by process simulation. In the process simulation simulator, the target separation process was divided into 10,000 to 10 billion cells, and the reaction amount and membrane permeation amount in each divided cell were calculated sequentially. As a prerequisite for the analysis, the analysis was performed under isothermal and isobaric conditions relative to the flow direction in order to expedite (simplify) the analysis process. The reaction rate constants of the solid catalyst 6 packed into the first reactor 5 and the second reactor (membrane reactor) 8 were calculated using the reaction rate constants of commercially available copper-zinc catalysts.

[0029] As a model case, 0.6 kg of solid catalyst 6 is packed into the first reactor 5, 6.0 kg of solid catalyst 6 is packed into the second reactor (membrane reactor) 8, and the total effective surface area of ​​the porous ceramic separation membrane 9 in the second reactor is 0.4 m². ２The analysis was performed with 30 tubular separation membranes (each with a diameter of 1.2 cm and an effective length of 40 cm (effective length of 35 cm)) fixed in place. The absolute pressure on the non-permeable side of the porous ceramic separation membrane 9 in the first and second reactors was fixed at 0.98 MPa for comparison. Membrane permeability (H ２ CO ２ CO, H ２ System and operating conditions such as the reaction temperature (O, MeOH), absolute pressure on the membrane permeation side, and the flow of MeOH and H to the membrane permeation side. ２ Tables 1 and 2 summarize the analysis results of the permeability of O, the methanol concentration of the membrane-permeated methanol aqueous solution, and the methanol yield. In Table 1, the supply gas flow rate was H ２ : 3 NL / min, CO2: 1 NL / min, Table 2 shows that the supply gas flow rate is H ２ :2.5NL / min, CO ２ The results for the cases where 0.5 NL / min was used for both CO and 0.5 NL / min were summarized.

[0030]

[0031]

[0032] The supply gas flow rate is H ２ :3NL / min, CO ２ Regarding the results in Table 1 for a mixed gas of 1 NL / min, Examples 1 to 12 are embodiments of the method for synthesizing the methanol aqueous solution of the present invention shown in Figure 1, in which the separation layer is Na ｎ [Al ｎ Si ９６－ｎ O １９２ The results of an analysis of the typical membrane permeability of a porous ceramic separation membrane characterized by containing an MFI-type zeolite membrane having a composition of (2 < n < 8) are shown. The effect of reaction temperature was analyzed in Examples 1 to 7, and the effect of absolute pressure on the membrane permeation side was analyzed in Examples 8 to 12. In particular, the reaction temperature of the second reactor equipped with the separation membrane showed a remarkably high methanol yield in the range of 210 to 240°C. Furthermore, the membrane permeation side pressure of the separation membrane showed a remarkably high methanol yield in the range of 0.001 to 0.01 MPa in absolute pressure.

[0033] Comparative Examples 1 to 3 show methanol yields when the membrane permeation pressure of the separation membrane in Example 3 was operated in the range of 0.04 to 0.1 MPa in absolute pressure, and the permeation rate of both methanol and water vapor components to the membrane permeation side was less than 90%. However, the methanol yield was only 24.5%. Comparative Examples 4 to 6 show the results of analysis at typical membrane permeability with a type A zeolite membrane proposed in Patent Document 1, Comparative Examples 7 to 9 show the results of analysis at typical membrane permeability with a type T zeolite membrane and a type CHA zeolite membrane, and Comparative Examples 10 to 12 compare the analysis results when almost no methanol or water vapor permeated the membrane. Despite the reaction temperature and the absolute pressure on the membrane permeation side being the same as in the example, the results obtained in Examples 1 to 12 showed significantly higher methanol yields compared to the results obtained in Comparative Examples 4 to 12.

[0034] The supply gas flow rate is H ２ :2.5NL / min, CO ２ Table 2 shows the results for a mixed gas of 0.5 NL / min of : and 0.5 NL / min of CO. Examples 13 to 24 are embodiments of the method for synthesizing the methanol aqueous solution of the present invention shown in Figure 1, in which the separation layer is Na ｎ [Al ｎ Si ９６－ｎ O １９２ The results of an analysis of the typical membrane permeability of a porous ceramic separation membrane characterized by containing an MFI-type zeolite membrane having a composition of 2 < n < 8, with the effects of reaction temperature being analyzed in Examples 13 to 19 and the effects of absolute pressure on the membrane permeation side being analyzed in Examples 20 to 24. In particular, the reaction temperature of the second reactor equipped with the separation membrane showed a remarkably high methanol yield in the range of 210 to 240°C. Furthermore, the membrane permeation side pressure of the separation membrane showed a remarkably high methanol yield in the range of 0.001 to 0.01 MPa in absolute pressure.

[0035] Comparative Examples 13 to 15 show the methanol yield when the membrane permeation pressure of the separation membrane in Example 15 was operated in the range of 0.04 to 0.1 MPa in absolute pressure, and the permeation rate of both methanol and water vapor components to the membrane permeation side was less than 90%. However, the methanol yield was only 42.0%. Comparative Examples 16 to 18 show the results of analysis at typical membrane permeability with a type A zeolite membrane proposed in Patent Document 1, Comparative Examples 19 to 21 show the results of analysis at typical membrane permeability with a type T zeolite membrane and a type CHA zeolite membrane, and Comparative Examples 22 to 24 compare the analysis results when almost no methanol or water vapor permeated the membrane. Despite the reaction temperature and the absolute pressure on the membrane permeation side being the same as in the example, the results obtained in Examples 13 to 24 showed a significantly higher methanol yield compared to the results obtained in Comparative Examples 16 to 24. From the above, the usefulness of the embodiment of the present invention for synthesizing an aqueous methanol solution under low pressure conditions of less than 1 MPa has been confirmed.

[0036] The examples demonstrate that methanol aqueous solution can be efficiently produced from a mixed gas containing carbon dioxide and hydrogen under low-pressure conditions of less than 1 MPa. The produced methanol aqueous solution can be used industrially, for example, directly as a fuel such as direct methanol fuel (DMFC), or as a transport medium for safely transporting methanol raw materials to various chemical manufacturing sites. In particular, it is carbon neutral and derived from renewable biomass or recovered CO2. ２ Since much of the demand for methanol synthesis using this raw material is small-scale and decentralized, it can be industrially utilized as an on-site process.

[0037] 1. Raw material gas (H ２ / CO ２ 1. Compressor (CO) 2. Gas pressure / flow control valve 3. Heat exchanger (heater) 5. First reactor 6. Solid catalyst 7. Mixed gas (H ２ / CO ２ / CO / methanol / water vapor) 8 Second reactor (membrane reactor) 9 Porous ceramic separation membrane 10 Methanol and water vapor permeated through the membrane 11 Heat exchanger (cooling / condenser) 12 Methanol aqueous solution collection tank permeated through the membrane 13 Vacuum pump 14 Methanol aqueous solution collection tank not permeated through the membrane 15 Unreacted gas (H ２ / CO ２ / CO) 16 Separation layer 17 Porous support

Claims

1. Hydrogen and CO ２ A method for synthesizing an aqueous methanol solution from a mixed gas containing CO2, wherein CO2 is used in the first reactor. ２ From a raw material gas containing hydrogen, methanol and water vapor are produced by a catalytic reaction, and then the separation layer is M ｎ [Al ｎ Si ９６－ｎ O １９２ A method for synthesizing an aqueous methanol solution, characterized in that a second reactor is equipped with multiple porous ceramic separation membranes containing a membrane body of MFI-type zeolite having the composition (2 < n < 8, M: metal cation), 90% or more of both the generated methanol and water vapor components are permeated to the membrane permeation side, and the permeated methanol and water vapor are cooled and condensed to obtain an aqueous methanol solution of 50 to 90 wt% on the membrane permeation side.

2. The method for synthesizing an aqueous methanol solution according to claim 1, wherein the reaction temperature of the second reactor is in the range of 210 to 240°C, and the membrane permeation pressure of the porous ceramic separation membrane is in the range of 0.001 to 0.01 MPa in absolute pressure.

3. The method for synthesizing an aqueous methanol solution according to claim 1 or 2, wherein the metal cation M is sodium.

4. Hydrogen and CO ２ A methanol aqueous solution production apparatus for synthesizing a methanol aqueous solution from a mixed gas containing ２ CO and hydrogen, comprising a first reactor that generates methanol and steam by a catalytic reaction from a raw material gas containing ｎ CO and hydrogen, a second reactor having a plurality of porous ceramic separation membranes each including a membrane body of an MFI-type zeolite having a composition of M ｎ [Al ９６－ｎ Si １９２ O](2 < n < 8, M: metal cation), and a heat exchanger that cools and condenses the methanol and steam that have permeated through the membrane. Both components of the methanol and steam generated in the first reactor permeate to the membrane permeation side of the second reactor by 90% or more, and the methanol and steam that have permeated through the membrane are cooled and condensed by the heat exchanger, and a methanol aqueous solution of 50 to 90 wt% is generated on the membrane permeation side. A methanol aqueous solution production apparatus characterized by this.

5. The methanol aqueous solution production apparatus according to claim 4, wherein the reaction temperature of the second reactor is in the range of 210 to 240°C, and the membrane permeation pressure of the porous ceramic separation membrane is in the range of 0.001 to 0.01 MPa in absolute pressure.

6. The methanol aqueous solution production apparatus according to claim 4 or 5, wherein the metal cation M is sodium.

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