Method for producing liquid fuel and system for synthesizing liquid fuel

Abstract

The main purpose of the present invention is to suppress a decrease in reaction efficiency in the vicinity of a gas inlet of a reactor in a conversion reaction for converting a raw material gas containing a carbon oxide and hydrogen gas into a liquid fuel. A method for producing a liquid fuel according to an embodiment of the present invention comprises: a step in which a starting material gas containing at least a carbon oxide and hydrogen gas is introduced into a reactor in which a catalyst is housed; and a step for generating a liquid fuel from the raw material gas by a conversion reaction in the presence of the catalyst, the raw material gas further containing oxygen, and the ratio of the carbon monoxide concentration to the carbon dioxide concentration in the carbon oxide being 0.9 or less.

Description

Technical Field

[0001] The invention relates to a method for producing liquid fuel and a liquid fuel synthesis system. Background Art

[0002] In recent years, in order to achieve a carbon-neutral society, it has been proposed to treat carbon oxides such as carbon monoxide and carbon dioxide as carbon resources and convert them into liquid fuels that are useful as industrial basic raw materials. For example, Patent Document 1 discloses a liquid fuel synthesis system that uses a membrane reactor (Japanese: メンブレンリアタ) containing a catalyst and a water vapor separation membrane to perform a conversion reaction of a raw gas containing carbon dioxide (CO2) and hydrogen (H2) into methanol.

[0003] Prior art literature Patent Literature Patent Document 1: Japanese Patent Application Publication No. 2018-8940 Summary of the invention

[0004] Problems to be solved by the invention In the above-mentioned conversion reaction from the raw gas containing carbon oxides and hydrogen to the liquid fuel, there is a case where the reaction efficiency is reduced. Specifically, the above-mentioned conversion reaction is an exothermic reaction, and the heat generated is effective for maintaining the reaction temperature, but near the gas inlet of the reactor, the generated heat flows to the downstream side under the action of the gas flow, so there is a case where a sufficiently high reaction temperature cannot be obtained and the reaction efficiency is reduced.

[0005] A main object of the present invention is to suppress a decrease in reaction efficiency near a gas inlet of a reactor in a reforming reaction of reforming a raw gas containing carbon oxides and hydrogen into a liquid fuel.

[0006] Technical solutions to solve problems [1] According to an embodiment of the present invention, a method for producing a liquid fuel comprises: a step of allowing a raw gas containing at least carbon oxides and hydrogen to flow into a reactor containing a catalyst; and a step of generating a liquid fuel from the raw gas through a conversion reaction in the presence of the catalyst, wherein the raw gas also contains oxygen, and the ratio of the carbon monoxide concentration in the carbon oxides to the carbon dioxide concentration is less than 0.9.

[0007] [2] In the production method described in [1] above, the oxygen concentration in the raw material gas may be greater than or equal to 0.02% by volume and less than or equal to 4% by volume.

[0008] [3] In the production method described in [1] or [2] above, the ratio of the oxygen concentration in the raw material gas to the carbon dioxide concentration may be 0.05 or less.

[0009] [4] In the production method described in any one of [1] to [3] above, the carbon oxide concentration in the raw material gas may be greater than 9 volume % and less than 50 volume %.

[0010] [5] In the production method described in any one of [1] to [4] above, the hydrogen gas concentration in the raw material gas may be greater than 44% by volume and less than or equal to 90% by volume.

[0011] [6] In the production method described in any one of [1] to [5] above, the temperature of the raw material gas when flowing into the reactor may be 40° C. or higher and 350° C. or lower.

[0012] [7] The production method described in any one of [1] to [6] above may also include a step of preparing the raw material gas using a gas containing oxygen and carbon dioxide recovered from the atmosphere or biogas.

[0013] [8] In the production method described in any one of [1] to [7] above, the reactor may include a water vapor separation membrane that allows water vapor to pass through.

[0014] [9] In the production method described in any one of [1] to [7] above, the reactor may include a liquid fuel separation membrane that allows at least the liquid fuel to permeate.

[0015]

[10] A liquid fuel synthesis system according to an embodiment of the present invention comprises: a reactor which accommodates a catalyst, wherein the catalyst promotes a conversion reaction from a raw gas containing carbon oxides and hydrogen to a liquid fuel; and a raw gas supply unit which supplies a gas containing carbon oxides, hydrogen and oxygen and in which the ratio of the carbon monoxide concentration in the carbon oxides to the carbon dioxide concentration is less than 0.9 as the raw gas to the reactor.

[0016]

[11] In the liquid fuel synthesis system described in

[10] above, the oxygen concentration in the raw gas may be greater than or equal to 0.02% by volume and less than or equal to 4% by volume.

[0017]

[12] In the liquid fuel synthesis system described in

[10] or

[11] above, the ratio of the oxygen concentration in the raw gas to the carbon dioxide concentration may be 0.05 or less.

[0018]

[13] In the liquid fuel synthesis system described in any one of

[10] to

[12] above, the liquid fuel synthesis system may also include a gas recovery unit, which recovers oxygen and carbon dioxide from the atmosphere or biogas, and the gas containing oxygen and carbon dioxide supplied from the gas recovery unit is supplied to the reactor as a component of the raw gas.

[0019]

[14] In the liquid fuel synthesis system described in any one of

[10] to

[13] above, the reactor may include a water vapor separation membrane that allows water vapor to pass through.

[0020]

[15] In the liquid fuel synthesis system described in any one of

[10] to

[13] above, the reactor may include a liquid fuel separation membrane that allows at least the liquid fuel to pass through.

[0021] Effects of the Invention In the method for producing liquid fuel according to an embodiment of the present invention, a gas containing carbon oxides, hydrogen and oxygen is used as a raw gas. Thus, water is generated from oxygen and hydrogen together with the generation of liquid fuel, and the heat generated at this time is used to suppress the temperature drop near the raw gas inlet of the reactor. As a result, the reaction efficiency reduction caused by the temperature drop near the raw gas inlet can be suppressed. It should be noted that as a prior art, there is the following autothermal reforming (ATR) method (for example, Japanese Patent Publication No. 2004-43195): two reactions, a partial oxidation reaction of a gas as an exothermic reaction and a modification (reforming) reaction of a gas as an endothermic reaction, occur sequentially in one reactor, and the heat generated by the partial oxidation reaction is used for the reforming reaction. The ATR method is a method of compensating the endothermic reaction of the endothermic reaction by the heat generated by the exothermic reaction, and its effect is exerted on the downstream side of the reactor. In contrast, the method for producing liquid fuel according to an embodiment of the present invention uses the heat generated in the exothermic reaction to suppress the temperature drop near the reactor inlet, thereby improving the reaction efficiency near the reactor inlet of the liquid fuel synthesis as an exothermic reaction, so the effect is different from the ATR method. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram for explaining a method for producing a liquid fuel according to one embodiment of the present invention.

[0023] Figure 2 This is a schematic diagram illustrating a structure of an example of a reactor that can be used in the method for producing a liquid fuel according to an embodiment of the present invention.

[0024] Figure 3 This is a schematic diagram illustrating a structure of an example of a reactor that can be used in the method for producing a liquid fuel according to an embodiment of the present invention.

[0025] Figure 4 This is a schematic diagram illustrating a structure of an example of a reactor that can be used in the method for producing a liquid fuel according to an embodiment of the present invention.

[0026] Figure 5 This is a schematic diagram illustrating a structure of an example of a reactor that can be used in the method for producing a liquid fuel according to an embodiment of the present invention.

[0027] Figure 6 Schematic diagram for explaining a liquid fuel synthesis system used in a method for producing a liquid fuel according to an embodiment of the present invention. DETAILED DESCRIPTION

[0028] Hereinafter, the embodiments of the present invention will be described with reference to the accompanying drawings, but the present invention is not limited to these embodiments. In addition, in order to make the description clearer, the accompanying drawings schematically show the width, thickness, shape, etc. of each part compared with the embodiments, but this is only an example and does not limit the interpretation of the present invention.

[0029] A. Methods for producing liquid fuel A method for producing a liquid fuel according to an embodiment of the present invention includes: a step of flowing a raw material gas containing at least carbon oxides and hydrogen into a reactor containing a catalyst (step I); and A step of producing a liquid fuel from the raw gas by a reforming reaction in the presence of the catalyst (step II).

[0030] Typically, the raw material gas further contains oxygen. The ratio of the carbon monoxide concentration in the carbon oxides to the carbon dioxide concentration is, for example, 0.9 or less.

[0031] The method for producing a liquid fuel according to the embodiment of the present invention typically further includes a step of causing a product gas containing the liquid fuel to flow out from the reactor (step III).

[0032] In this specification, liquid fuel refers to a fuel that is in a liquid state at room temperature and pressure, or a fuel that can be liquefied under room temperature and pressure. Examples of fuels that are in a liquid state at room temperature and pressure include methanol, ethanol, n H 2（m－2n） (m is an integer less than 90, n is an integer less than 30), and mixtures thereof. Examples of the fuel that can be liquefied under normal temperature and pressure include propane, butane, and mixtures thereof.

[0033] As an example of the above-mentioned conversion reaction, the reaction formula of a reaction that may occur when synthesizing methanol by catalytic hydrogenation of a raw material gas containing carbon monoxide, carbon dioxide and hydrogen in the presence of a catalyst is as follows. In the reaction of formula (2), methanol is generated as a product and water is generated as a by-product. It should be noted that regarding the calorific value, the calorific value when the reaction proceeds to the right side is recorded in each formula, and a negative sign indicates heat generation, and a positive sign indicates endothermicity.

[0034] CO+2H2 CH3OH: -90.8 kJ / mol (1) CO2+3H2 CH3OH+H2O:-49.2kJ / mol (2) CO+H2O CO2+H2: -41.2kJ / mol (3) H2+1 / 2O2 H2O: -241.8 kJ / mol (4) CO+1 / 2O2 CO2: -283.0 kJ / mol (5) Figure 1 Schematic diagram for explaining a method for producing a liquid fuel according to one embodiment of the present invention. Figure 1 The method for producing a liquid fuel according to the embodiment shown is performed using a liquid fuel synthesis system 1, which includes a reactor 100 that accommodates a catalyst, and a raw gas supply unit 200 that supplies a raw gas to the reactor 100. The liquid fuel synthesis system 1 also includes a purge gas supply unit 300 that supplies a purge gas to the reactor 100. The raw gas supply unit 200 includes a first gas storage unit 210 and a pressurizing unit 220. The purge gas supply unit 300 includes a second gas storage unit 310 and a heating unit 320. Figure 1 A method for producing a liquid fuel according to an embodiment of the present invention will be described.

[0035] A-1. Process (I) In step (I), a raw material gas containing carbon oxides, hydrogen, and oxygen is flowed into a reactor containing a catalyst.

[0036] The reactor typically includes a gas inlet for allowing a raw material gas to flow in, a gas outlet for allowing a product gas containing a product to flow out, and a space connecting these, and a catalyst is accommodated in the space.

[0037] The shape of the reactor is not particularly limited, and may be, for example, monolithic, flat, tubular, cylindrical, cylindrical, polygonal, etc. The monolithic shape refers to a shape having a plurality of cells penetrating in the longitudinal direction, and is a concept including a honeycomb shape.

[0038] exist Figure 1 In the illustrated embodiment, the reactor 100 is a so-called membrane reactor, and includes a water vapor separation membrane 110, a catalyst 120, a non-permeable side space 100A, and a permeable side space 100B. In the illustrated example, the water vapor separation membrane 110 is supported by a porous support 130. The reactor 100 also includes a first inlet s1 and a first outlet d1 communicated via the non-permeable side space 100A, and a second inlet s2 and a second outlet d2 communicated via the permeable side space 100B. In the reactor 100, the non-permeable side space 100A is a space for accommodating a catalyst. The reactor 100 preferably has heat resistance and pressure resistance suitable for the desired synthesis conditions of the liquid fuel.

[0039] The water vapor separation membrane 110 allows water vapor, which is a byproduct of the conversion reaction from the raw material gas to the liquid fuel, to pass therethrough, thereby shifting the reaction equilibrium of the above formula (2) to the product side by utilizing the equilibrium shift effect.

[0040] The molecular diameter of water (0.26 nm) is close to the molecular diameter of hydrogen (0.296 nm). Therefore, not only water vapor as a byproduct of the reforming reaction but also part of the hydrogen contained in the raw gas may permeate the water vapor separation membrane 110 .

[0041] The water vapor separation membrane 110 preferably has a relative humidity of 100 nmol / (s·Pa·m 2 ) or more. The water vapor permeability coefficient can be obtained by a known method (see Ind. Eng. Chem. Res., 40, 163-175 (2001)).

[0042] The water vapor separation membrane 110 preferably has a separation factor of 100 or more. The larger the separation factor, the easier it is for water vapor to pass through, and the harder it is for components other than water vapor (hydrogen, carbon oxides, oxygen, and liquid fuel, etc.) to pass through. The separation factor can be obtained by a known method (see Fig. 1 of "Separation and Purification Technology 239 (2020) 116533").

[0043] As the water vapor separation membrane 110, an inorganic membrane can be used. The inorganic membrane has heat resistance, pressure resistance, and water vapor resistance, so it is preferred. As the inorganic membrane, zeolite membrane, silica membrane, alumina membrane, and composite membranes thereof can be cited. For example, an LTA type zeolite membrane having a molar ratio (Si / Al) of silicon element (Si) to aluminum element (Al) of 1.0 or more and 3.0 or less is preferred because it has excellent water vapor permeability.

[0044] The zeolite membrane used as the water vapor separation membrane 110 can be obtained by the production method described in, for example, Japanese Patent Application Publication No. 2004-66188. The silica membrane used as the water vapor separation membrane 110 can be obtained by the production method described in, for example, International Publication No. 2008 / 050812.

[0045] The porous support 130 is made of a porous material. As the porous material, ceramic materials, metal materials, resin materials, and composite members thereof can be used, and ceramic materials are particularly preferred. As the aggregate of the ceramic material, alumina (Al2O3), titanium dioxide (TiO2), mullite (Al2O3·SiO2), ceramic granules, cordierite (Mg2Al4Si5O 18 ), and composite materials containing two or more of them, etc., if the availability, clay stability and corrosion resistance are taken into consideration, alumina is preferred. As an inorganic binder for the ceramic material, at least one of titanium dioxide, mullite, sinterable alumina, silicon dioxide, glass powder, clay mineral, and sinterable cordierite can be used. The ceramic material may not contain an inorganic binder.

[0046] The average pore size of the porous support can be set to be greater than 5 μm and less than 25 μm. The average pore size of the porous support can be measured by mercury intrusion. The porosity of the porous support can be set to be greater than 25% and less than 50%. The average particle size of the porous material constituting the porous support can be set to be greater than 1 μm and less than 100 μm. In this embodiment, the average particle size refers to the arithmetic mean of the maximum diameters of 30 particles (randomly selected) measured by cross-sectional microstructure observation using a SEM (Scanning Electron Microscope).

[0047] The catalyst 120 promotes the conversion reaction from the raw gas to the liquid fuel. The catalyst is arranged in the non-permeable side space 100A. The catalyst is preferably filled in the non-permeable side space 100A, but can also be arranged on the surface of the water vapor separation membrane 110 in a layered or island shape. In the case where the catalyst is in a particle shape as shown in the example, the particle size (diameter) of the catalyst particles can be set to, for example, 0.5 mm or more and 10 mm or less. The catalyst particles can be composed of only the catalyst, or can be a structure in which the catalyst is supported on the carrier particles. The carrier particles are preferably porous particles.

[0048] As the catalyst, any catalyst suitable for the conversion reaction to the desired liquid fuel can be used. Specifically, metal catalysts (copper, palladium, etc.), oxide catalysts (zinc oxide, zirconium oxide, gallium oxide, etc.), and composite catalysts thereof (copper-zinc oxide, copper-zinc oxide-alumina, copper-zinc oxide-chromium oxide-alumina, copper-cobalt-titanium dioxide, and catalysts obtained by modifying these with palladium, etc.) can be used.

[0049] The reactor is not limited to the above-mentioned examples. Figure 2 As illustrated, the reactor 101 may be a flow reactor including a gas inlet s3, a gas outlet d3, a space 101A connecting the gas inlet s3, and a catalyst (catalyst particles) 120 disposed (filled) in the space 101A. In the reactor 101, a raw gas containing carbon oxides, hydrogen, and oxygen flows in from the gas inlet s3, and a product gas (product gas a) containing liquid fuel, by-products, and unreacted raw gas (residual raw gas) flows out from the gas outlet d3.

[0050] As described above, the raw gas contains carbon oxides, hydrogen and oxygen. As the carbon oxide, at least carbon dioxide is used, and carbon monoxide can be further used within the range in which the effect of the present invention can be obtained. The raw gas preferably contains carbon dioxide at a higher ratio than carbon monoxide. When the ratio of the carbon monoxide concentration in the carbon oxide in the raw gas to the carbon dioxide concentration (CO volume % / CO2 volume %, hereinafter sometimes referred to as "CO / CO2 ratio") is large, there is a situation where the effect of the present invention cannot be fully obtained by mixing oxygen. Specifically, the calorific value of the reaction of formula (1) and the reaction of formula (2) is large. In addition, the reaction of formula (1) has a large equilibrium conversion rate compared with the reaction of formula (2), and the calorific value is further increased. Therefore, when the above-mentioned CO / CO2 ratio is large, the effect of suppressing the temperature drop near the raw gas inlet of the reactor by mixing oxygen becomes weak. The above-mentioned CO / CO2 ratio is typically less than 0.9. Here, when the inlet temperature of the reactor decreases, the equilibrium conversion rate increases, and therefore the temperature change caused by heat generation increases. Therefore, from the viewpoint of balanced conversion rate and temperature unevenness, when operating at an inlet temperature of less than 250°C, the CO / CO2 ratio is preferably less than 0.5, and when operating at an inlet temperature of less than 230°C, the CO / CO2 ratio is preferably less than 0.2. It should be noted that the reaction of formula (3) occurs after passing through the catalyst, so the lower limit of the CO / CO2 ratio is not particularly limited. From the viewpoint of easy control, the CO / CO2 ratio is preferably set to 0.02 or more. It should be noted that the above CO / CO2 ratio is the CO / CO2 ratio in the raw gas at the reactor inlet (specifically, the first inlet s1). In the case of recycling the remaining raw gas, it is the CO / CO2 ratio in the raw gas prepared using the remaining raw gas. In addition, other records related to the content ratio, ratio, etc. of each gas contained in the raw gas are also records about the raw gas at the reactor inlet.

[0051] The carbon oxide concentration in the raw gas (the total concentration in the case of including carbon monoxide and carbon dioxide) may be greater than 9% by volume and less than 50% by volume, for example, greater than 10% by volume and less than 50% by volume, preferably greater than 20% by volume and less than 40% by volume. In one embodiment, the carbon dioxide concentration in the raw gas is, for example, greater than 10% by volume and less than 50% by volume, preferably greater than 15% by volume and less than 35% by volume. In one embodiment, the carbon monoxide concentration in the raw gas is, for example, less than 23% by volume, preferably less than 20% by volume. The hydrogen concentration in the raw gas may be greater than 44% by volume and less than 90% by volume, for example, greater than 45% by volume and less than 90% by volume, preferably greater than 60% by volume and less than 80% by volume.

[0052] The oxygen concentration in the raw gas is, for example, 0.02% by volume or more, preferably 0.03% by volume or more, more preferably 0.1% by volume or more, for example, 4% by volume or less, preferably 3% by volume or less, and more preferably 2% by volume or less. If the oxygen concentration is less than 0.02% by volume, there is a situation where the effect of the present invention cannot be fully obtained. If the oxygen concentration exceeds 4% by volume, there is a situation where the reaction yield of the liquid fuel is reduced due to the consumption of hydrogen that should react with carbon dioxide, and a situation where the reaction yield is reduced due to the decrease in equilibrium conversion rate due to the increase in reaction temperature compared to the assumption. In this way, if there is oxygen in the raw gas, it is predicted that: due to the reaction of oxygen and hydrogen, hydrogen is consumed and does not contribute to the generation of liquid fuel. In addition, due to the water generated by the reaction, the reaction equilibrium of the above formula (2) moves to the raw gas side, and the reaction yield is reduced. However, according to an embodiment of the present invention, by utilizing the reaction heat of the reaction, contrary to these predictions, the effect of suppressing the reduction in reaction efficiency can be obtained. In one embodiment, the ratio of the oxygen concentration in the raw gas to the carbon dioxide concentration (O2 volume % / CO2 volume %, hereinafter sometimes referred to as "O2 / CO2 ratio") is, for example, less than 0.05. If the O2 / CO2 ratio increases, there is a possibility that the equilibrium conversion rate decreases with the increase in heat generation, in addition to the hydrogen gas as the raw material being consumed and the reaction yield decreasing. For example, when operating at an inlet temperature of less than 250°C, it is preferred to set the O2 / CO2 ratio to less than 0.02. In addition, since the reaction of formula (5) occurs after the catalyst passes through, from the perspective of controlling the detector and the mixing valve, it is preferred to set the O2 / CO2 ratio to more than 0.0015 because it is easy to control on the basis of stable operation.

[0053] The total concentration of carbon oxides, hydrogen and oxygen in the raw material gas is, for example, 80% by volume to 100% by volume, preferably 96% by volume to 100% by volume. The raw material gas may consist essentially of only carbon oxides, hydrogen and oxygen.

[0054] The raw gas is prepared by mixing the components to form the desired composition. In one embodiment, the raw gas is prepared using carbon dioxide concentrated gas recovered from the atmosphere by direct air recovery technology (DAC). The carbon dioxide concentrated gas obtained by DAC contains oxygen and carbon dioxide recovered from the atmosphere. Specifically, the carbon dioxide concentrated gas obtained by DAC may contain a trace amount of oxygen (for example, 0.02% by volume and 15% by volume) from the atmosphere in addition to high concentrations of carbon dioxide (for example, 30% by volume or more and 99.9% by volume or less). In addition, the concentration of carbon monoxide is low. Therefore, when the raw gas is prepared using the carbon dioxide concentrated gas obtained by DAC, there is no need to prepare oxygen separately and mix it, or the amount of oxygen prepared separately can be reduced. In another embodiment, the raw gas is prepared using carbon dioxide concentrated gas recovered from biogas. Biogas is a gas produced by fermentation (methane fermentation) using biomass such as kitchen waste, paper waste, and livestock feces as raw materials. The main components of biogas are methane and carbon dioxide, and can further contain oxygen, etc. By using a separation membrane, carbon dioxide can be recovered from biogas to obtain a carbon dioxide concentrated gas. The carbon dioxide concentrated gas recovered from the biogas may contain oxygen in addition to carbon dioxide, and the concentration of carbon monoxide is low. Therefore, when using the carbon dioxide concentrated gas recovered from the biogas to prepare the raw gas, there is an advantage that there is no need to prepare and mix oxygen separately, or the amount of oxygen prepared separately can be reduced. In one embodiment, the liquid fuel synthesis system 1 can also be configured as follows: it also has a gas recovery unit that recovers oxygen and carbon dioxide from the atmosphere through DAC, or a gas recovery unit that recovers oxygen and carbon dioxide from the biogas using a separation membrane, and supplies carbon dioxide concentrated gas (gas containing oxygen and carbon dioxide recovered from the atmosphere or biogas) from the gas recovery unit to the raw gas supply unit. The carbon dioxide concentrated gas can be directly supplied to the raw gas supply unit from the gas recovery unit, or it can be supplied to the raw gas supply unit as a component of the purge gas after passing through the reactor. The gas recovery unit includes, for example, a carbon dioxide adsorbing material (e.g., an amine compound) that adsorbs carbon dioxide by contact with a gas containing carbon dioxide and releases the carbon dioxide by heating, reducing pressure, etc., and the carbon dioxide adsorbing material can be used to recover a gas containing oxygen and high-concentration carbon dioxide from the atmosphere. In addition, for example, the gas recovery unit includes a separation membrane such as a carbon dioxide permeable membrane, and can recover a carbon dioxide-enriched gas containing oxygen and high-concentration carbon dioxide from a gas containing carbon dioxide such as biogas.

[0055] The feed gas flows into the reactor at the desired temperature and pressure. Figure 1In the embodiment shown, the gas containing carbon oxides, hydrogen and oxygen stored in the first gas storage unit 210 is mixed with the remaining raw gas, and after being pressurized and heated by the booster unit 220, it flows into the non-permeable side space 100A of the reactor 100 through the pipeline L1 as the raw gas. The booster unit 220 is composed of a compressor, a supercharger, etc. It should be noted that in the example shown in the figure, the raw gas prepared in advance to a desired composition is supplied to the reactor from the first gas storage unit 210, but the raw gas can flow into the reactor with a desired composition, and is not limited to the embodiment shown in the figure. For example, carbon oxides, hydrogen and oxygen can also be made to flow into the reactor separately from their respective supply sources.

[0056] The temperature of the raw material gas when flowing into the reactor (in other words, the temperature of the raw material gas at the gas inlet of the reactor) is, for example, 40°C to 350°C, preferably 180°C to 330°C.

[0057] The pressure of the raw material gas when flowing into the reactor (in other words, the pressure at the gas inlet of the reactor) is, for example, 1.0 MPa(G) to 6.0 MPa(G), preferably 2.0 MPa(G) to 6.0 MPa(G).

[0058] The flow rate of the raw material gas flowing into the reactor is, for example, 1000 / h to 50000 / h, preferably 2000 / h to 20000 / h, and more preferably 3000 / h to 12000 / h in terms of space velocity GHSV.

[0059] A-2. Step (II) In step (II), liquid fuel is generated from raw gas by a conversion reaction in the presence of a catalyst. For example, as shown in reaction formulas (1) to (2), methanol is generated by catalytic hydrogenation of carbon oxides and hydrogen in the presence of a catalyst. The generated liquid fuel and byproduct (representatively water) are both in a gaseous state at the time of synthesis and remain in a gaseous state at least until they flow out of the reactor.

[0060] according to Figure 1In the embodiment shown, the raw gas flows into the non-permeable side space 100A through the first inlet s1, and the conversion reaction from the raw gas to the liquid fuel is promoted by the catalyst 120 to synthesize the liquid fuel. In addition, water vapor as a by-product and hydrogen in the raw gas pass through the water vapor separation membrane 110 and flow into the permeable side space 100B. The purge gas for purging them flows from the second inlet s2 to the permeable side space 100B through the pipeline L3. Specifically, the purge gas stored in the second gas storage unit 310 is heated to a desired temperature (for example, 150° C. or more and 350° C. or less) in the heating unit 320, and then flows into the permeable side space 100B of the reactor 100 through the pipeline L3. As the purge gas, any appropriate gas such as nitrogen, carbon oxides, hydrogen, and a mixed gas thereof can be used.

[0061] The reactions of reaction formulas (1) to (5) are all equilibrium reactions. In order to improve both the conversion rate and the reaction rate, it is preferred to react them under high temperature and high pressure conditions. The reaction temperature (in other words, the temperature of the space containing the catalyst in the reactor) is, for example, 180°C or more, preferably 200°C or more and 350°C or less, and more preferably 200°C or more and 300°C or less. The reaction pressure (in other words, the pressure of the space containing the catalyst in the reactor) is, for example, 1 MPa (G) or more, preferably 2.0 MPa (G) or more and 6.0 MPa (G) or less, and more preferably 2.5 MPa (G) or more and 4.0 MPa (G) or less.

[0062] In reaction equations (1) and (2), the generation of methanol is an exothermic reaction, so the heat generated is effective for maintaining the reaction temperature. However, near the gas inlet of the reactor, the heat generated flows to the downstream side under the action of the gas flow, so there is a situation where a sufficiently high reaction temperature cannot be obtained. In contrast, according to an embodiment of the present invention, the raw gas contains oxygen, so water is generated from oxygen and hydrogen under the condition of the presence of the above-mentioned catalyst, and the calorific value in the generation of this water is greater than the calorific value in the generation of methanol. Therefore, compared with an embodiment in which the raw gas does not contain oxygen, even if the heat generated near the gas inlet flows to the downstream side under the action of the gas flow, the temperature near the gas inlet can be increased. As a result, the effect of suppressing the reduction of the reaction efficiency near the gas inlet can be obtained.

[0063] A-3. Step (III) In step (III), a product gas containing liquid fuel is discharged from the reactor. The product gas typically contains liquid fuel and residual raw material gas. Therefore, it is preferred to separate and recover the liquid fuel from the product gas.

[0064] The temperature of the product gas when flowing out of the reactor (in other words, the temperature of the product gas at the gas outlet of the reactor) is, for example, 200° C. to 350° C., preferably 200° C. to 300° C.

[0065] exist Figure 1 In the illustrated embodiment, the product gas flows out from the reactor 100 (more specifically, the non-permeable side space 100A) to the line L2 through the first outlet d1. In addition, the water vapor and hydrogen gas that have passed through the water vapor separation membrane 110 and flowed into the permeable side space 100B flow out from the reactor 100 (more specifically, the permeable side space 100B) to the line L4 as a gas containing water vapor together with the purge gas through the second outlet d2.

[0066] The product gas flowing out of the reactor 100 flows into the drain elbow 400 arranged downstream of the reactor 100. The drain elbow 400 liquefies the liquid fuel in the gas state and separates the remaining raw gas from the liquid fuel. Thus, the liquid fuel is recovered. On the other hand, the remaining raw gas after separation returns to the upstream through the pipeline L5 and mixes with the gas flowing out of the first gas storage unit, thereby obtaining the raw gas. From the perspective of adjusting the composition of the raw gas, the residual raw gas can be purified as needed. The recycling rate of the residual raw gas in the raw gas (the volume % of the residual raw gas in the raw gas) can be, for example, 15% or more and 85% or less. The obtained raw gas is pressurized and heated in the booster 220 and flows into the reactor 100 via the pipeline L1. As described above, in the embodiment of the present invention, since the concentration ratio of each gas in the raw gas is appropriately controlled, it is possible to continuously produce liquid fuel while maintaining the effect of the present invention even when the residual raw gas is recycled.

[0067] Similarly, the gas containing water vapor flowing out of the reactor 100 is liquefied by the condensable byproduct (representatively water vapor) by using the drain elbow 500, and is separated and recovered from the purge gas and hydrogen. If necessary, hydrogen gas and the like can be recovered from the separated gas and reused as part of the raw material gas.

[0068] B. Modification The present invention is not limited to the above-described embodiment, and various modifications are possible. For example, the structure shown in the above-described embodiment may be replaced with a structure that is substantially the same as the structure shown in the above-described embodiment, a structure that has the same function and effect, or a structure that can achieve the same purpose.

[0069] B-1. Modification 1 The reactor can be a combination of multiple reactors. Figure 3 As shown, the reactor may be configured as follows: a reactor 100 as a membrane reactor is disposed upstream of the reactor 100. Figure 2 The structure of the flow-type reactor 101 shown in FIG. The reactor 100 includes a water vapor separation membrane 110, a catalyst 120, a non-permeable side space 100A, and a permeable side space 100B. The water vapor separation membrane 110 is typically supported by a porous support (not shown). According to the reactor with such a structure, the product gas a containing liquid fuel, water vapor, and excess raw gas flowing out of the reactor 101 flows into the permeable side space 100A of the reactor 100, and the conversion reaction from the excess raw gas to the liquid fuel is promoted. The product gas b containing the liquid fuel generated in the reactors 101 and 100 flows out from the non-permeable side space 100A. The water vapor and the purge gas that have passed through the water vapor separation membrane 110 flow out from the permeable side space 100B as a gas containing water vapor.

[0070] There is no limit to the number of reactors 100 disposed downstream of the flow-type reactor 101. Figure 4 As shown, two or more reactors 100 can be connected in series and / or in parallel. It should be noted that in the figure, only the flow of the product gas is shown downstream of the reactor 101.

[0071] B-2. Modification 2 The reactor of the above embodiment uses a water vapor separation membrane that allows water vapor to pass as a separation membrane for separating water vapor from liquid fuel, so that water vapor passes from the permeation side space to the non-permeation side space for separation, but it may also be a structure that uses a liquid fuel separation membrane that allows liquid fuel to pass from the permeation side space to the non-permeation side space for separation. For example, Figure 5 The reactor 102 shown has a liquid fuel separation membrane 150, a catalyst 120, a non-permeable side space 102A, and a permeable side space 102B. The liquid fuel separation membrane 150 can be supported by a porous support body (not shown). According to such a structure, the liquid fuel permeates from the non-permeable side space 102A to the permeable side space 102B, so that the reaction equilibrium of the above formulas (1) and (2) can be shifted to the product side. As a separation membrane that selectively allows liquid fuel to pass through, a separation membrane described in Japanese Patent Gazette No. 2020-23488 can be used. It should be noted that in the present invention, as a separation membrane that separates water vapor and liquid fuel, it has a higher selective permeability to one side than to the other side, and as long as the effect of the present invention can be obtained, the two may not be completely separated. For example, the liquid fuel separation membrane allows liquid fuel to pass through with a higher selectivity than water vapor, and does not completely separate the two.

[0072] B-3. ​​Modification 3 As described above, the raw gas can be prepared using carbon dioxide concentrated gas recovered from the atmosphere by DAC or carbon dioxide concentrated gas recovered from biogas by separation membrane (for example, gas containing oxygen and carbon dioxide recovered from the atmosphere or biogas). Therefore, the liquid fuel synthesis system used in the method for producing liquid fuel according to an embodiment of the present invention may also be configured as follows: it also includes a gas recovery unit that recovers oxygen and carbon dioxide from the atmosphere by DAC or recovers oxygen and carbon dioxide from biogas by separation membrane, and the carbon dioxide concentrated gas supplied from the gas recovery unit is supplied to the reactor as a constituent component of the raw gas. For example, it may also be as follows Figure 6 The liquid fuel synthesis system 2 shown in FIG. 1 is configured as follows: the purge gas supply unit 300 includes a gas recovery unit 340 and a hydrogen generation unit 360, and the purge gas prepared by mixing the carbon dioxide concentrated gas supplied from the gas recovery unit 340 and the hydrogen supplied from the hydrogen generation unit 360 is supplied to the reactor 100 as a constituent component of the raw gas. In the modification 3, the carbon dioxide contained in the raw gas may all be derived from the carbon dioxide concentrated gas recovered by the gas recovery unit 340, or only a part thereof may be derived from the carbon dioxide concentrated gas.

[0073] The gas recovery unit 340 typically includes a carbon dioxide adsorbent (e.g., an amine compound), which adsorbs carbon dioxide by contact with a gas containing carbon dioxide, and removes carbon dioxide by heating, reducing pressure, etc., and uses the carbon dioxide adsorbent to recover a carbon dioxide-concentrated gas containing oxygen and high-concentration carbon dioxide from the atmosphere. Alternatively, the gas recovery unit 340 includes a separation membrane such as a carbon dioxide permeable membrane, and can recover a carbon dioxide-concentrated gas containing oxygen and high-concentration carbon dioxide from a gas containing carbon dioxide such as biogas. The hydrogen generation unit 360 is, for example, a hydrogen production device using water electrolysis technology.

[0074] Industrial Applicability The method for producing a liquid fuel according to the embodiment of the present invention can be applied to producing a liquid fuel such as methanol.

[0075] Explanation of symbols 100: Reactor 100A: Non-permeable side space 100B: Through side space 110: Water vapor separation membrane 120: Catalyst 200: Raw gas supply unit 300: Purge gas supply unit.

Claims

1. A method for producing a liquid fuel, comprising: A step of flowing a raw material gas containing at least carbon oxides and hydrogen into a reactor containing a catalyst; as well as a step of generating liquid fuel from the raw gas through a reforming reaction in the presence of the catalyst, The raw material gas also contains oxygen, The ratio of the carbon monoxide concentration in the carbon oxides to the carbon dioxide concentration is 0.9 or less.

2. The manufacturing method according to claim 1, wherein: The oxygen concentration in the raw material gas is greater than or equal to 0.02 volume % and less than or equal to 4 volume %.

3. The manufacturing method according to claim 1, wherein: A ratio of the oxygen concentration to the carbon dioxide concentration in the raw material gas is 0.05 or less.

4. The manufacturing method according to claim 1, wherein: The carbon oxide concentration in the raw material gas exceeds 9 volume % and is 50 volume % or less.

5. The manufacturing method according to claim 1, wherein: The hydrogen concentration in the raw material gas exceeds 44 volume % and is 90 volume % or less.

6. The manufacturing method according to claim 1, wherein: The temperature of the raw material gas when flowing into the reactor is 40° C. or higher and 350° C. or lower.

7. The production method according to claim 1, comprising a step of preparing the raw material gas using a gas containing oxygen and carbon dioxide recovered from the atmosphere or biogas.

8. The manufacturing method according to any one of claims 1 to 7, wherein: The reactor has a water vapor separation membrane that allows water vapor to permeate.

9. The manufacturing method according to any one of claims 1 to 7, wherein: The reactor has a liquid fuel separation membrane that allows at least the liquid fuel to permeate.

10. A liquid fuel synthesis system comprising: A reactor containing a catalyst for promoting a conversion reaction of a raw gas containing at least carbon oxides and hydrogen into a liquid fuel; and A raw material gas supply unit supplies a gas containing carbon oxides, hydrogen and oxygen, wherein the ratio of the carbon monoxide concentration in the carbon oxides to the carbon dioxide concentration is 0.9 or less, as the raw material gas, to the reactor.

11. The liquid fuel synthesis system according to claim 10, wherein: The oxygen concentration in the raw material gas is greater than or equal to 0.02 volume % and less than or equal to 4 volume %.

12. The liquid fuel synthesis system according to claim 10, wherein: A ratio of the oxygen concentration to the carbon dioxide concentration in the raw material gas is 0.05 or less.

13. The liquid fuel synthesis system according to claim 10, wherein: The liquid fuel synthesis system further includes a gas recovery unit that recovers oxygen and carbon dioxide from the atmosphere or biogas. The gas containing oxygen and carbon dioxide supplied from the gas recovery unit is supplied to the reactor as a constituent component of the raw material gas.

14. The liquid fuel synthesis system according to any one of claims 10 to 13, wherein: The reactor has a water vapor separation membrane that allows water vapor to permeate.

15. The liquid fuel synthesis system according to any one of claims 10 to 13, wherein: The reactor has a liquid fuel separation membrane that allows at least the liquid fuel to permeate.

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