Liquid fuel manufacturing method and liquid fuel synthesis system

Abstract

The main purpose of the present invention is to lessen the temperature difference between the gas temperature at the inlet and the gas temperature at the outlet of a reactor in a reaction that converts a raw material gas containing carbon oxides and hydrogen into a liquid fuel. The method for producing a liquid fuel according to an embodiment of the present invention includes allowing a raw material gas containing at least carbon oxides and hydrogen to flow into a reactor housing a catalyst and generating a liquid fuel from the raw material gas by a conversion reaction in the presence of the catalyst. The raw material gas also contains an inert gas, and the ratio of the carbon monoxide concentration to the carbon dioxide concentration in the carbon oxides is 0.9 or less.

Description

Technical Field

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

Background Art

[0002] In recent years, for the purpose of realizing a carbon-neutral society, it has been proposed to capture carbon oxides such as carbon monoxide and carbon dioxide as carbon resources and convert them into liquid fuels useful as industrial basic raw materials. For example, Patent Document 1 discloses a liquid fuel synthesis system that performs a conversion reaction of a raw material gas containing carbon dioxide (CO2) and hydrogen (H2) into methanol using a membrane reactor including a catalyst and a water vapor separation membrane.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the conversion reaction of a raw material gas containing carbon oxide and hydrogen into liquid fuel as described above, there has been a desire to reduce the temperature difference between the gas temperature at the inlet and the gas temperature at the outlet of the reactor.

[0005] The main object of the present invention is to reduce the temperature difference between the gas temperature at the inlet and the gas temperature at the outlet of the reactor in the conversion reaction of a raw material gas containing carbon oxide and hydrogen into liquid fuel.

Means for Solving the Problems

[0006] [1] A method for producing a liquid fuel according to one embodiment of the present invention comprises introducing a raw material gas containing at least carbon oxide and hydrogen into a reactor containing a catalyst, and producing a liquid fuel from the raw material gas by a conversion reaction in the presence of the catalyst, wherein the raw material gas further contains an inert gas, and the ratio of the carbon monoxide concentration to the carbon dioxide concentration in the carbon oxide is 0.9 or less. [2] In the manufacturing method described in [1] above, the concentration of the inert gas in the raw material gas may be 1% by volume or more and 55% by volume or less. [3] In the manufacturing method described in [1] or [2] above, the ratio of the inert gas concentration to the carbon dioxide concentration in the raw material gas may be 0.05 or more and 1.5 or less. [4] In the manufacturing method described in any of [1] to [3] above, the carbon oxide concentration in the raw material gas may be 5% by volume or more and 50% by volume or less. [5] In the manufacturing method described in any of [1] to [4] above, the hydrogen concentration in the raw material gas may be 20% by volume or more and 85% by volume or less. [6] In the manufacturing method described in any of [1] to [5] above, the temperature of the raw material gas when it is introduced into the reactor may be 40°C or higher and 350°C or lower. [7] The manufacturing method described in any of [1] to [6] above may include preparing the raw material gas using an inert gas and a gas containing carbon dioxide recovered from the atmosphere or biogas. [8] In the manufacturing method described in any of [1] to [7] above, the reactor may have a water vapor separation membrane that allows water vapor to pass through. [9] In the manufacturing method described in any of [1] to [7] above, the reactor may have at least a liquid fuel separation membrane that allows the liquid fuel to pass through.

[10] A method for producing a liquid fuel according to another embodiment of the present invention comprises: introducing a raw material gas containing at least carbon oxide and hydrogen into a reactor containing a catalyst; and producing a liquid fuel from the raw material gas by a conversion reaction in the presence of the catalyst; wherein the raw material gas further contains an inert gas; and the liquid fuel contains methanol, and based on the results of thermodynamic equilibrium calculations for the conversion reaction at 200°C and 4 MPa(G) when the ratio of carbon monoxide concentration (CO) to carbon dioxide concentration (CO2) and the ratio of the inert gas concentration (Inert) in the raw material gas are varied, the slope a of the approximate line prepared by linear approximation (Y=aX+b) for the plot with (Inert+CO) / CO2 in the raw material gas as the X axis and (percentage of suppressed calorific value) × (percentage of increased combustion energy obtained) as the Y axis is 1.4 or less; and the plot is such that for each CO / CO2 ratio of the raw material gas, Inert / C The study was conducted on 18 data points, including when the O2 ratio was varied in increments of 0.1 from 0 to 1.6, and when the Inert / CO2 ratio was 0.05. The percentage of suppressed calorific value and the percentage of increased combustion energy gained are calculated using the following formulas: Percentage of suppressed calorific value = (calorific value calculated under standard conditions - calorific value calculated when each raw material gas is used) / calorific value calculated under standard conditions, Percentage of increased combustion energy gained = (combustion energy of generated methanol calculated when each raw material gas is used - combustion energy of generated methanol calculated under standard conditions) / combustion energy of generated methanol calculated under standard conditions (where the standard conditions are when raw material gases containing only carbon dioxide and hydrogen in a ratio of CO2 / H2 = 1 / 3 are used, and the combustion energy of generated methanol is calculated using the formula: combustion energy of generated methanol = amount of methanol produced × higher heating value of methanol).

[11] In the manufacturing method described in

[10] above, the product of the proportion of the suppressed calorific value and the proportion of the increase in combustion energy obtained may be -3 or more.

[12] A liquid fuel synthesis system according to an embodiment of the present invention comprises: a reactor containing a catalyst that drives a conversion reaction from a raw material gas containing at least carbon oxide and hydrogen to a liquid fuel; and a raw material gas supply unit that supplies the reactor with a gas containing carbon oxide, hydrogen, and an inert gas as the raw material gas, wherein the ratio of the carbon monoxide concentration to the carbon dioxide concentration in the carbon oxide is 0.9 or less.

[13] In the liquid fuel synthesis system described in

[12] above, the concentration of the inert gas in the raw material gas may be 1 volume% or more and 55 volume% or less.

[14] In the liquid fuel synthesis system described in

[12] or

[13] above, the ratio of the inert gas concentration to the carbon dioxide concentration in the raw material gas may be 0.05 or more and 1.5 or less.

[15] The liquid fuel synthesis system described in any of

[12] to

[14] above may further include a gas recovery unit for recovering an inert gas and carbon dioxide from the atmosphere or biogas, and the gas containing the inert gas and carbon dioxide supplied from the gas recovery unit may be supplied to the reactor as a component of the raw material gas.

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

[12] to

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

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

[12] to

[15] above, the reactor may have at least a liquid fuel separation membrane that allows the liquid fuel to pass through. [Effects of the Invention]

[0007] In the liquid fuel production method according to an embodiment of the present invention, a gas containing carbon oxide, hydrogen, and an inert gas is used as the raw material gas. This makes it possible to reduce the temperature difference between the gas temperature at the reactor inlet and the gas temperature at the outlet. [Brief explanation of the drawing]

[0008] [Figure 1]Figure 1 is a schematic diagram illustrating a method for producing liquid fuel according to one embodiment of the present invention. [Figure 2] Figure 2 is a schematic diagram illustrating the configuration of an example reactor that may be used in a liquid fuel production method according to an embodiment of the present invention. [Figure 3] Figure 3 is a schematic diagram illustrating the configuration of an example reactor that may be used in a liquid fuel production method according to an embodiment of the present invention. [Figure 4] Figure 4 is a schematic diagram illustrating the configuration of an example reactor that may be used in a liquid fuel production method according to an embodiment of the present invention. [Figure 5] Figure 5 is a schematic diagram illustrating the configuration of an example reactor that may be used in a liquid fuel production method according to an embodiment of the present invention. [Figure 6] Figure 6 is a schematic diagram illustrating a liquid fuel synthesis system used in a liquid fuel production method according to one embodiment of the present invention. [Figure 7] Figures 7(a) and (b) are graphs created based on the results of thermodynamic equilibrium calculations for liquid fuel production when the ratio of N2 is varied for various CO / CO2 ratios of source gases. [Modes for carrying out the invention]

[0009] The embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to these embodiments. In addition, the drawings may be schematically represented in terms of the width, thickness, shape, etc. of each part compared to the embodiments in order to make the explanation clearer, but these are merely examples and do not limit the interpretation of the present invention.

[0010] A. Method of manufacturing liquid fuels The method for producing liquid fuel according to embodiments of the present invention is: Step I involves introducing a raw material gas containing at least carbon oxide and hydrogen into a reactor containing the catalyst, and The process includes generating liquid fuel from the raw material gas by a conversion reaction in the presence of the catalyst (Step II). Typically, the raw material gas further contains an inert gas. The ratio of the carbon monoxide concentration to the carbon dioxide concentration in the carbon oxides is, for example, 0.9 or less. The method for producing a liquid fuel according to an embodiment of the present invention typically further includes discharging a product gas containing the liquid fuel from the reactor (Step III).

[0011] In this specification, a liquid fuel is a fuel in a liquid state at normal temperature and normal pressure or a fuel that can be liquefied under normal temperature and pressurized conditions. Examples of fuels in a liquid state at normal temperature and normal pressure include methanol, ethanol, C n H 2(m-2n) (where m is an integer less than 90 and n is an integer less than 30), and mixtures thereof. Examples of fuels that can be liquefied under normal temperature and pressurized conditions include propane, butane, and mixtures thereof.

[0012] As an example of the conversion reaction, the reaction formula of a reaction that can 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 as a product and water as a by-product are generated. Regarding the calorific value, the calorific value when the reaction proceeds to the right side in each formula is described, where minus represents heat release and plus represents heat absorption.

[0013] CO + 2H2 ⇔ CH3OH :-90.8 kJ / mol (1) CO2 + 3H2 ⇔ CH3OH + H2O :-49.2 kJ / mol (2) CO + H2O ⇔ CO2 + H2 :-41.2 kJ / mol (3)

[0014] Figure 1 is a schematic diagram illustrating a method for producing liquid fuel according to one embodiment of the present invention. The method for producing liquid fuel according to the embodiment shown in Figure 1 is carried out using a liquid fuel synthesis system 1, which comprises a reactor 100 containing a catalyst and a raw material gas supply unit 200 that supplies raw material gas to the reactor 100. The liquid fuel synthesis system 1 further comprises a sweep gas supply unit 300 that supplies sweep gas to the reactor 100. The raw material gas supply unit 200 has a first gas storage unit 210 and a pressure boosting unit 220. The sweep gas supply unit 300 has a second gas storage unit 310 and a heating unit 320. The method for producing liquid fuel according to an embodiment of the present invention will be described below with reference to Figure 1.

[0015] A-1. Process (I) In step (I), a raw material gas containing carbon oxide, hydrogen, and an inert gas is introduced into a reactor containing the catalyst.

[0016] A reactor typically has a gas inlet for introducing raw material gas, a gas outlet for releasing product gas containing the products, and a space connecting these, in which the catalyst is contained.

[0017] The shape of the reactor is not particularly limited and can be, for example, monolithic, plate-shaped, tubular, cylindrical, columnar, or polygonal prism-shaped. A monolithic shape refers to a shape having multiple cells that penetrate in the longitudinal direction, and is a concept that includes honeycomb shapes.

[0018] In the embodiment shown in Figure 1, the reactor 100 is a so-called membrane reactor and includes a water vapor separation membrane 110, a catalyst 120, an impermeable space 100A, and a permeable space 100B. In the illustrated example, the water vapor separation membrane 110 is supported by a porous support 130. The reactor 100 further includes a first inlet s1 and a first outlet d1 communicating through the impermeable space 100A, and a second inlet s2 and a second outlet d2 communicating through the permeable space 100B. In the reactor 100, the impermeable space 100A is the space that houses the catalyst. Preferably, the reactor 100 has heat resistance and pressure resistance suitable for the synthesis conditions of the desired liquid fuel.

[0019] The water vapor separation membrane 110 allows water vapor, a by-product of the conversion reaction from raw gas to liquid fuel, to permeate through. This allows the reaction equilibrium in equation (2) to be shifted towards the product side by utilizing the equilibrium shift effect.

[0020] The molecular diameter of water (0.26 nm) is close to that of hydrogen (0.296 nm). Therefore, not only water vapor, a by-product of the conversion reaction, but also some of the hydrogen contained in the raw material gas can permeate through the water vapor separation membrane 110. Furthermore, as will be described later, when helium is used as the inert gas, some of the helium contained in the raw material gas can also permeate through the water vapor separation membrane 110.

[0021] The water vapor separation membrane 110 has a vapor density of 100 nmol / (s·Pa·m). 2 It is preferable to have a water vapor permeability coefficient of ) or higher. The water vapor permeability coefficient can be determined by known methods (see Ind.Eng.Chem.Res.,40,163-175(2001)).

[0022] The water vapor separation membrane 110 preferably has a separation coefficient of 100 or more. The larger the separation coefficient, the easier it is for water vapor to permeate, and the less likely it is for components other than water vapor (such as hydrogen, carbon oxide, inert gases, and liquid fuels) to permeate. The separation coefficient can be determined by known methods (see Fig. 1 in "Separation and Purification Technology 239 (2020) 116533").

[0023] An inorganic membrane can be used as the water vapor separation membrane 110. Inorganic membranes are preferred because they have heat resistance, pressure resistance, and water vapor resistance. Examples of inorganic membranes include zeolite membranes, silica membranes, alumina membranes, and composite membranes thereof. For example, an LTA-type zeolite membrane in which the molar ratio of silicon element (Si) to aluminum element (Al) (Si / Al) is 1.0 or more and 3.0 or less is preferred because it has excellent water vapor permeability.

[0024] The zeolite membrane used as the water vapor separation membrane 110 can be obtained, for example, by the manufacturing method described in Japanese Patent Publication No. 2004-66188. The silica membrane used as the water vapor separation membrane 110 can be obtained, for example, by the manufacturing method described in International Publication No. 2008 / 050812.

[0025] The porous support 130 is composed of a porous material. As the porous material, ceramic materials, metal materials, resin materials, and composites thereof can be used, with ceramic materials being particularly preferred. As aggregates for the ceramic material, alumina (Al2O3), titania (TiO2), mullite (Al2O3·SiO2), celben, and cordierite (Mg2Al4Si5O) are used. 18 ), and composite materials containing two or more of these can be used, and alumina is preferred considering availability, soil stability, and corrosion resistance. As an inorganic binder for the ceramic material, at least one of titania, mullite, easily sintered alumina, silica, glass frit, clay minerals, and easily sintered cordierite can be used. The ceramic material does not need to contain an inorganic binder.

[0026] The average pore diameter of the porous support can be between 5 μm and 25 μm. The average pore diameter of the porous support can be measured by the mercury intrusion method. The porosity of the porous support can be between 25% and 50%. The average particle size of the porous material constituting the porous support can be between 1 μm and 100 μm. In this embodiment, the average particle size is the arithmetic mean of the maximum diameter of 30 measured target particles (randomly selected) measured by cross-sectional microstructure observation using a Scanning Electron Microscope (SEM).

[0027] The catalyst 120 facilitates the conversion reaction from the raw gas to the liquid fuel. The catalyst is placed in the impermeable space 100A. Preferably, the catalyst is filled in the impermeable space 100A, but it may also be arranged in layers or in islands on the surface of the water vapor separation membrane 110. If the catalyst is in the form of particles as shown in the illustrated example, the particle size (diameter) of the catalyst particles can be, for example, 0.5 mm or more and 10 mm or less. The catalyst particles may consist only of catalyst, or the catalyst may be supported on carrier particles. The carrier particles are preferably porous particles.

[0028] As a 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, zirconia, gallium oxide, etc.), and catalysts combining these (copper-zinc oxide, copper-zinc oxide-alumina, copper-zinc oxide-chromium oxide-alumina, copper-cobalt-titania, and catalysts modified with palladium, etc.) can be used.

[0029] The reactor is not limited to the illustrated example above. For example, as illustrated in Figure 2, the reactor 101 may be a flow-type reactor including a gas inlet s3, a gas outlet d3, a space 101A connecting them, and a catalyst (catalyst particles) 120 arranged (filled) in the space 101A. A raw material gas containing carbon oxide, hydrogen, and an inert gas is introduced into the reactor 101 from the gas inlet s3, and a product gas (product gas a) containing liquid fuel, by-products, and unreacted raw material gas (residual raw material gas) is discharged from the gas outlet d3.

[0030] As described above, the raw material gas contains carbon oxide, hydrogen, and an inert gas. At least carbon dioxide is used as the carbon oxide, and carbon monoxide may be used further within the range in which the effects of the present invention can be obtained. Preferably, the raw material gas contains carbon dioxide in a higher proportion than carbon monoxide. When the ratio of the carbon monoxide concentration to the carbon dioxide concentration in the raw material gas (CO volume% / CO2 volume%), sometimes referred to as the "CO / CO2 ratio", is large, the inert gas is activated. SexualWhen an inert gas is added, the effect of suppressing temperature unevenness in the reactor is weak, and the effects of the present invention may not be fully obtained. Specifically, the reaction of formula (1) generates more heat than the reaction of formula (2), and in addition, the equilibrium conversion rate of the reaction of formula (1) is larger than that of the reaction of formula (2), further increasing the amount of heat generated. Therefore, when the above CO / CO2 ratio is large, the effect of suppressing temperature unevenness in the reactor when an inert gas is added is weak. The above CO / CO2 ratio is typically 0.9 or less. Here, when the reactor inlet temperature decreases, the equilibrium conversion rate increases, and the temperature change due to heat generation becomes larger. Therefore, from the viewpoint of equilibrium conversion rate and temperature unevenness, when operating at an inlet temperature of 250°C or less, the CO / CO2 ratio is preferably 0.5 or less, and when operating at an inlet temperature of 230°C or less, the CO / CO2 ratio is preferably 0.2 or less. Since the reaction of equation (3) occurs after passing through the catalyst, there is no particular lower limit to the CO / CO2 ratio; however, from the viewpoint of ease of control, it is preferable to set the CO / CO2 ratio to 0.02 or higher. Note that the above CO / CO2 ratio is the CO / CO2 ratio of the raw material gas at the reactor inlet (specifically, the first inlet s1), and if the residual raw material gas is recycled, it is the CO / CO2 ratio of the raw material gas prepared using the residual raw material gas. Furthermore, other descriptions regarding the content ratio, proportion, etc. of each gas contained in the raw material gas also refer to the raw material gas at the reactor inlet.

[0031] The carbon oxide concentration in the raw material gas (total concentration if carbon monoxide and carbon dioxide are included) is, for example, 5% by volume or more and 50% by volume or less, preferably 10% by volume or more and 40% by volume or less. In one embodiment, the carbon dioxide concentration in the raw material gas is, for example, 5% by volume or more and 50% by volume or less, preferably 9% by volume or more and 35% by volume or less. In one embodiment, the carbon monoxide concentration in the raw material gas is, for example, 23% by volume or less, preferably 20% by volume or less. The hydrogen concentration in the raw material gas is, for example, 20% by volume or more and 85% by volume or less, preferably 30% by volume or more and 80% by volume or less.

[0032] Examples of inert gases include nitrogen, helium, and argon, and can be used individually or in combination of two or more. The inert gas concentration in the raw material gas is, for example, 1 volume% or more, preferably 2 volume% or more, more preferably 3 volume% or more, and even more preferably 5 volume% or more, and for example, 55 volume% or less, preferably 30 volume% or less, and more preferably 10 volume% or less. If the inert gas concentration is less than 1 volume%, temperature unevenness in the reactor cannot be sufficiently suppressed, and the effects of the present invention may not be fully obtained. If the inert gas concentration exceeds 55 volume%, the concentration of the reaction components becomes diluted, and the desired liquid fuel may not be sufficiently obtained. In one embodiment, the ratio of the inert gas concentration to the carbon dioxide concentration in the raw material gas (inert gas volume% / CO2 volume%), hereinafter sometimes referred to as the "Inert / CO2 ratio") is, for example, 0.05 or more, and preferably 0.15 or more. Setting the Inert / CO2 ratio to 0.15 or more is preferable because it simplifies the control of the Inert / CO2 ratio from the viewpoint of controlling the detector and mixing valve. The Inert / CO2 ratio in the raw material gas is, for example, 1.5 or less, preferably 1.1 or less. If the Inert / CO2 ratio is too low, temperature unevenness in the reactor cannot be sufficiently suppressed, and the effects of the present invention may not be fully obtained. If the Inert / CO2 ratio is too high, the concentration of the reaction components becomes low, and the amount of liquid fuel produced may be insufficient. Furthermore, if the Inert / CO2 ratio is 1.1 or less, the proportion of residual raw material gas discharged outside the system during purging when recycling can be suitably suppressed, which may be advantageous from the viewpoint of reducing raw material loss.

[0033] Similar to the Inert / CO2 ratio, from the viewpoint of achieving both the effect of suppressing temperature unevenness in the reactor and the amount of liquid fuel produced, the total ratio of the inert gas concentration and carbon monoxide concentration to the carbon dioxide concentration in the raw material gas ((inert gas volume% + CO volume%) / CO2 volume%) is, for example, 0.05 or more and, for example, 2.4 or less. From the viewpoint of ease of control, the above ratio is preferably 0.07 or more, and from the viewpoint of reducing raw material loss, it is preferably 2.2 or less. Furthermore, from the viewpoint of equilibrium conversion rate and temperature unevenness, for example, when operating at an inlet temperature of 250°C or less, the above ratio is preferably 2.2 or less.

[0034] The total concentration of carbon oxide, hydrogen, and inert gas in the raw material gas is, for example, 80% to 100% by volume, preferably 96% to 100% by volume. The raw material gas may consist substantially of only carbon oxide, hydrogen, and inert gas.

[0035] Figure 7(a) is a graph created in Excel based on the results of thermodynamic equilibrium calculations for the reactions of equations (1) to (3) when the ratio of N2 is changed for various CO / CO2 ratios of source gases. Figure 7(b) is an enlarged view of the graph in Figure 7(a) for the range Y = -0.3 to 0.1. In the graph, the X axis represents (N2 + CO) / CO2 in the source gas, and the Y axis represents (percentage of suppressed calorific value) × (percentage of increased combustion energy gained).

[0036] In creating the graph above, the reference condition is set to use a raw material gas containing only CO2 and H2 in a ratio of CO2 / H2 = 1 / 3 (CO2 volume% + H2 volume% = 100 volume%, CO / CO2 ratio = 0, (N2+CO) / CO2 ratio = 0). The "percentage of suppressed calorific value" is defined as "(calorific value calculated under reference conditions - calorific value calculated when using each raw material gas) / calorific value calculated under reference conditions," and the "percentage of increased combustion energy gained" is defined as "(combustion energy of methanol produced when using each raw material gas - combustion energy of methanol produced calculated under reference conditions) / combustion energy of methanol produced calculated under reference conditions." Here, the "combustion energy of methanol produced" is calculated by "amount of methanol produced × higher heating value (HHV) of methanol." The graph plots a total of 18 data points for each CO / CO2 ratio of source gas (i.e., when the N2 / CO2 ratio is varied in increments of 0.1 from 0 to 1.6, and when the N2 / CO2 ratio is 0.05).

[0037] In the graph, the X-axis is an index that takes into account both the ratio of N2, which is related to the suppression of calorific value, and the ratio of CO, which is related to the amount of liquid fuel produced. In the graph created using the above method based on the results of thermodynamic equilibrium calculations performed under the following conditions, the value of the slope a when an approximate line is created by linear approximation (Y=aX+b) for the 18 points plotted for each CO / CO2 ratio of the raw material gas is preferably 1.4 or less. The lower limit of the value a is not particularly limited, but it may be, for example, -0.2 or more. If the value a exceeds 1.4, it may become difficult to achieve both the effect of suppressing temperature unevenness in the reactor and the amount of liquid fuel produced. Furthermore, from the viewpoint of making it easier to achieve both the effect of suppressing temperature unevenness in the reactor and the amount of liquid fuel produced, the value a is preferably 0.7 or less.

[0038] Temperature variations within the reactor can be caused by the heat generated during the synthesis reaction of liquid fuels. Therefore, diluting the raw material gas with an inert gas to suppress the synthesis reaction of liquid fuels (and consequently suppressing the amount of heat generated) can help reduce temperature variations within the reactor. On the other hand, suppressing the synthesis reaction of liquid fuels can reduce the amount of liquid fuel produced. Thus, the Y-axis of the graph can be used as an indicator of the balance between the effect of suppressing temperature variations and the amount of liquid fuel produced. Specifically, there is a trade-off relationship between the effect of suppressing temperature variations and the amount of liquid fuel produced. If one is a large positive value, the other will be a large negative value, and their product tends to move away from zero. Therefore, if the value of the Y-axis is close to 0, it can be considered that the two are in balance. In the graph prepared using the above method based on the results of thermodynamic equilibrium calculations performed under the following conditions, the value of the Y-axis is preferably -3 or higher, more preferably -1.5 or higher, and there is no particular upper limit, but it may be, for example, 0.1 or lower. If the Y-axis value is less than -3, it may be difficult to achieve a balance between suppressing temperature unevenness within the reactor and the amount of liquid fuel produced.

[0039] As described above, when liquid fuel is produced using a raw material gas with a composition such that the slope value a of the approximate straight line in the above graph is preferably 1.4 or less, preferably 0.7 or less, and preferably a raw material gas with a composition such that the slope value a is preferably 1.4 or less or 0.7 or less and the value of the Y axis is -3 or more, a good balance can be maintained between the effect of suppressing temperature unevenness and the amount of liquid fuel produced. For example, according to the above graph, when the CO / CO2 ratio in the raw material gas is 0.9 or less, the value of the Y axis is within the range of -3 or more, and it is possible to produce liquid fuel with a good balance between the effect of suppressing temperature unevenness and the amount of liquid fuel produced. Furthermore, it can be seen that this balance can be improved by blending N2 into the raw material gas. Moreover, when the CO / CO2 ratio is 0.9 or less, the slope value a of the approximate straight line is 1.4 or less, and it can be seen that a good balance can be maintained between the effect of suppressing temperature unevenness and the amount of liquid fuel produced. Note that the reaction conditions for the liquid fuel production method according to the embodiment of the present invention are not limited to the reaction conditions used in the thermodynamic equilibrium calculation below.

[0040] The above thermodynamic equilibrium calculations were performed using the thermodynamic data database built into the chemical equilibrium calculation software "MALT" under the following conditions. However, the thermodynamic data used is not limited to this; for example, the NIST Chemistry web book database published by the National Institute of Standards and Technology (NIST) may also be used. Reaction temperature: 200℃ • Reaction pressure: 4 MPa (G) • Raw gas composition: H2 / CO2=3 :N2 / CO2 = 0 to 1.6 in increments of 0.1, and 0.05 :CO / CO2=0.02, 0.1, 0.3, 0.5, 0.6, 0.9, 1.0

[0041] The raw material gas is prepared by mixing its components to achieve a desired composition. In one embodiment, the raw material gas is prepared using concentrated carbon dioxide gas recovered from the atmosphere by direct air recovery (DAC) technology. The concentrated carbon dioxide gas obtained by DAC contains inert gas (typically nitrogen) and carbon dioxide recovered from the atmosphere. Specifically, the concentrated carbon dioxide gas obtained by DAC may contain a high concentration (e.g., 30% to 99.9% by volume) of carbon dioxide, in addition to a small amount (e.g., 0.05% to 60% by volume) of nitrogen derived from the atmosphere. It also has a low concentration of carbon monoxide. Therefore, when preparing the raw material gas using concentrated carbon dioxide gas obtained by DAC, there is an advantage that it is not necessary to prepare and mix inert gas separately, or the amount of inert gas prepared separately can be reduced. In another embodiment, the raw material gas is prepared using concentrated carbon dioxide gas recovered from biogas. Biogas is a gas produced by fermentation (methane fermentation) using biomass such as food waste, paper waste, and livestock manure as raw materials. The main components of biogas are methane and carbon dioxide, and it may also contain nitrogen and other elements. By using a separation membrane, carbon dioxide can be recovered from biogas to obtain concentrated carbon dioxide gas. The concentrated carbon dioxide gas recovered from biogas may contain inert gas (typically nitrogen) in addition to carbon dioxide, and has a low concentration of carbon monoxide. Therefore, when preparing a raw material gas using concentrated carbon dioxide gas recovered from biogas, there is an advantage that it is not necessary to separately prepare and mix inert gas, or the amount of inert gas to be prepared separately can be reduced. In one embodiment, the liquid fuel synthesis system 1 may further include a gas recovery unit that recovers inert gas (typically nitrogen) and carbon dioxide from the atmosphere using a DAC, or a gas recovery unit that recovers inert gas (typically nitrogen) and carbon dioxide from biogas using a separation membrane, and the gas recovery unit may be configured to supply concentrated carbon dioxide gas (gas containing inert gas and carbon dioxide recovered from the atmosphere or biogas) to the raw material gas supply unit.The concentrated carbon dioxide gas may be supplied directly from the gas recovery unit to the raw material gas supply unit, or it may be supplied to the raw material gas supply unit after passing through the reactor as a component of the sweep gas. The gas recovery unit includes, for example, a carbon dioxide adsorbent (e.g., an amine compound) that adsorbs carbon dioxide upon contact with a carbon dioxide-containing gas and desorbs carbon dioxide by heating, depressurization, etc., and using this carbon dioxide adsorbent, an inert gas and a gas containing a high concentration of carbon dioxide can be recovered from the atmosphere. Alternatively, for example, the gas recovery unit may include a separation membrane such as a carbon dioxide permeable membrane, and a concentrated carbon dioxide gas containing an inert gas and a high concentration of carbon dioxide can be recovered from a carbon dioxide-containing gas such as biogas.

[0042] The raw material gas is introduced into the reactor at a desired temperature and pressure. In the embodiment shown in Figure 1, the gas containing carbon oxide, hydrogen, and inert gas stored in the first gas storage unit 210 is mixed with the remaining raw material gas, pressurized and heated in the pressure boosting unit 220, and then introduced as the raw material gas into the impermeable side space 100A of the reactor 100 via line L1. The pressure boosting unit 220 is composed of a compressor, a pressure intensifier, etc. In the illustrated example, the raw material gas, which has been prepared in advance to a desired composition, is supplied to the reactor from the first gas storage unit 210, but the raw material gas only needs to be introduced into the reactor at a desired composition, and is not limited to the embodiment shown. For example, carbon oxide, hydrogen, and inert gas may be introduced into the reactor separately from their respective sources.

[0043] The temperature of the raw material gas when it is introduced into the reactor (in other words, the temperature of the raw material gas at the reactor's gas inlet) is, for example, 40°C to 350°C, preferably 180°C to 330°C.

[0044] The pressure of the raw material gas when it is introduced into the reactor (in other words, the pressure at the gas inlet of the reactor) is, for example, 1.0 MPa(G) or more and 6.0 MPa(G) or less, preferably 2.0 MPa(G) or more and 6.0 MPa(G) or less.

[0045] The flow rate of the raw material gas introduced into the reactor is, for example, 1,000 / h or more and 50,000 / h or less in space velocity GHSV, preferably 2,000 / h or more and 20,000 / h or less, and more preferably 3,000 / h or more and 12,000 / h or less.

[0046] A-2. Process (II) In step (II), liquid fuel is produced from the raw material gas by a conversion reaction in the presence of a catalyst. For example, as shown in reaction equations (1) to (2), methanol is produced by catalytic hydrogenation of carbon oxide and hydrogen in the presence of a catalyst. Both the produced liquid fuel and by-products (typically water) are in a gaseous state at the time of synthesis and remain in a gaseous state at least until they are discharged from the reactor.

[0047] According to the embodiment shown in Figure 1, the raw material gas flows into the impermeable space 100A through the first inlet s1, and the conversion reaction from the raw material gas to liquid fuel proceeds in the catalyst 120, synthesizing liquid fuel. In addition, water vapor, which is a by-product, and hydrogen (and inert gas depending on the type) in the raw material gas permeate through the water vapor separation membrane 110 and flow into the permeable space 100B. A sweep gas to sweep these substances flows into the permeable space 100B from the second inlet s2 via line L3. Specifically, the sweep gas stored in the second gas storage section 310 is heated to a desired temperature (e.g., 150°C to 350°C) in the heating section 320, and then flows into the permeable space 100B of the reactor 100 via line L3. Any suitable gas can be used as the sweep gas, such as nitrogen, carbon oxide, hydrogen, and mixtures thereof.

[0048] The reactions in reaction equations (1) to (3) are all equilibrium reactions, and it is preferable to carry out the reaction under high temperature and high pressure in order to increase both the conversion rate and the reaction rate. The reaction temperature (in other words, the temperature of the space in the reactor where the catalyst is contained) is, for example, 180°C or higher, preferably 200°C to 350°C, and more preferably 200°C to 300°C. The reaction pressure (in other words, the pressure in the space in the reactor where the catalyst is contained) is, for example, 1 MPa(G) or higher, preferably 2.0 MPa(G) to 6.0 MPa(G), and more preferably 2.5 MPa(G) to 4.0 MPa(G).

[0049] In the reactions of equations (1) and (2), methanol production is an exothermic reaction, which can cause temperature differences (temperature variations) inside the reactor due to the generated heat and gas flow. When such temperature differences occur, the equilibrium conversion rate decreases in the higher-temperature areas, which can lead to a decrease in the reaction yield. In contrast, according to the manufacturing method of the embodiment of the present invention, by diluting the raw material gas with an inert gas, excessive temperature rise inside the reactor can be suppressed, and the temperature difference between the gas temperature at the reactor inlet and the gas temperature at the outlet can be reduced. This makes it possible to improve the uniformity of the reactor temperature and suppress the decrease in the conversion rate.

[0050] A-3.Process (III) In step (III), the product gas containing liquid fuel is discharged from the reactor. The product gas typically contains liquid fuel and residual raw material gas. Therefore, preferably, the liquid fuel is separated and recovered from the product gas.

[0051] The temperature of the product gas when it is discharged from the reactor (in other words, the temperature of the product gas at the reactor's gas outlet) is, for example, between 200°C and 350°C, preferably between 200°C and 300°C.

[0052] The difference between the gas temperature at the gas inlet and the gas temperature at the gas outlet (gas temperature at the gas outlet - gas temperature at the gas inlet) is, for example, 10°C or more and 100°C or less, preferably 20°C or more and 50°C or less. Here, the gas temperature at the gas inlet is the gas temperature at a point where the gas enters 20% of the total length of the reactor from the gas inlet. , The gas temperature at the outlet refers to the gas temperature immediately after the outlet.

[0053] In the embodiment shown in Figure 1, the product gas flows out of the reactor 100 (more specifically, the impermeable space 100A) to line L2 through the first outlet d1. Furthermore, water vapor and hydrogen that have permeated the water vapor separation membrane 110 and entered the permeable space 100B, along with the sweep gas, flow out of the reactor 100 (more specifically, the permeable space 100B) to line L4 as a water vapor-containing gas through the second outlet d2.

[0054] The product gas discharged from reactor 100 flows into a drain trap 400 located downstream of reactor 100. The drain trap 400 liquefies the gaseous liquid fuel and separates the residual raw material gas from the liquid fuel. This recovers the liquid fuel. Meanwhile, the separated residual raw material gas is returned upstream by line L5 and mixed with the gas discharged from the first gas storage unit to obtain the raw material gas. From the viewpoint of adjusting the composition of the raw material gas, the residual raw material gas may be purged as needed. The recycling rate of residual raw material gas in the raw material gas (volume %) may be, for example, 15% to 85%. The obtained raw material gas is pressurized and heated in the pressure boosting unit 220 and then flows into reactor 100 via line L1. As described above, in the embodiment of the present invention, since the concentration ratio of each gas in the raw material gas is suitably controlled, even when recycling residual raw material gas, liquid fuel can be continuously produced while achieving both the effect of suppressing temperature unevenness in the reactor and the amount of liquid fuel produced.

[0055] Similarly, in the water vapor-containing gas discharged from reactor 100, condensable by-products (typically water vapor) are liquefied by the drain trap 500, and separated and recovered from the remaining gas. If necessary, hydrogen or other substances may be recovered from the separated gas and reused as part of the raw material gas.

[0056] B. Variations The present invention is not limited to the embodiments described above, and various modifications are possible. For example, the configurations shown in the embodiments above can be replaced with configurations that are substantially the same, configurations that produce the same effects, or configurations that can achieve the same purpose.

[0057] B-1. Variation 1 The reactor may be a combination of multiple reactors. For example, as shown in Figure 3, the reactor may be configured with a flow-type reactor 101, shown in Figure 2, positioned upstream of reactor 100, which is a membrane reactor. Reactor 100 has a water vapor separation membrane 110, a catalyst 120, an impermeable side space 100A, and a permeable side space 100B. The water vapor separation membrane 110 is typically supported by a porous support (not shown). With a reactor of this configuration, product gas a, which includes liquid fuel, water vapor, and residual raw material gas flowing out of reactor 101, is released into reactor 100. Non The gas flows into the permeate space 100A, where the conversion reaction from the residual raw material gas to liquid fuel proceeds. Product gas b, containing the liquid fuel produced in reactors 101 and 100, flows out from the non-permeate space 100A. Water vapor and swept gas that have permeated through the water vapor separation membrane 110 flow out as water vapor-containing gas from the permeate space 100B.

[0058] There is no limit to the number of reactors 100 placed downstream of the flow-type reactor 101, and two or more reactors 100 can be connected in series and / or parallel, as shown in Figure 4. Note that in the figure, only the flow of product gas is shown downstream of reactor 101.

[0059] B-2. Variation 2 The reactor in the above embodiment uses a water vapor separation membrane that allows water vapor to pass through as a separation membrane to separate water vapor and liquid fuel. Non Transmissive side space ra The system was configured to separate by permeating water vapor into the transient space, but instead used a liquid fuel separation membrane that permeates liquid fuel. Non Transmissive side space ra The configuration may also involve separating the liquid fuel by allowing it to permeate into the permeable space. For example, the reactor 102 shown in Figure 5 has a liquid fuel separation membrane 150, a catalyst 120, an impermeable space 102A, and a permeable space 102B. The liquid fuel separation membrane 150 may typically be supported by a porous support (not shown). With such a configuration, since the liquid fuel permeates from the impermeable space 102A to the permeable space 102B, the reaction equilibrium of the above equations (1) and (2) can be shifted to the product side. As a separation membrane that selectively permeates liquid fuel, one described in Japanese Patent Application Publication No. 2020-23488 can be used. In this invention, the separation membrane that separates water vapor and liquid fuel has higher selective permeability to one than to the other, and does not need to completely separate the two as long as the effects of the present invention are obtained. For example, the liquid fuel separation membrane permeates liquid fuel with higher selectivity than water vapor, and does not completely separate the two.

[0060] B-3. ​​Modification 3 As described above, the raw material gas can be prepared using concentrated carbon dioxide gas (for example, gas containing inert gas and carbon dioxide recovered from the atmosphere or biogas using a separation membrane) recovered from the atmosphere by a DAC. Therefore, the liquid fuel synthesis system used in the liquid fuel production method according to the embodiment of the present invention may further include a gas recovery unit that recovers inert gas and carbon dioxide from the atmosphere by a DAC or from biogas using a separation membrane, and may be configured so that the concentrated carbon dioxide gas supplied from the gas recovery unit is supplied to the reactor as a component of the raw material gas. For example, as shown in the liquid fuel synthesis system 2 in Figure 6, the sweep gas supply unit 300 may include a gas recovery unit 340 and a hydrogen production unit 360, and the sweep gas prepared by mixing the concentrated carbon dioxide gas supplied from the gas recovery unit 340 and the hydrogen supplied from the hydrogen production unit 360 may be supplied to the reactor 100 as a component of the raw material gas. In the modified example 3, the carbon dioxide contained in the raw material gas may be entirely derived from the concentrated carbon dioxide gas recovered in the gas recovery unit 340, or only a portion may be derived from the concentrated carbon dioxide gas.

[0061] The gas recovery unit 340 typically includes a carbon dioxide adsorbent (e.g., an amine compound) that adsorbs carbon dioxide upon contact with a carbon dioxide-containing gas and desorbs it by heating, depressurization, etc. Using this carbon dioxide adsorbent, a concentrated carbon dioxide gas containing an inert gas and a high concentration of carbon dioxide can be recovered from the atmosphere. Alternatively, the gas recovery unit 340 includes a separation membrane such as a carbon dioxide permeable membrane, and can recover a concentrated carbon dioxide gas containing an inert gas and a high concentration of carbon dioxide from a carbon dioxide-containing gas such as biogas. The hydrogen production unit 360 is, for example, a hydrogen production facility utilizing water electrolysis technology. [Industrial applicability]

[0062] The liquid fuel production method according to the embodiment of the present invention can be suitably used for the production of liquid fuels such as methanol. [Explanation of Symbols]

[0063] 100 reactors 100A Non-transparent side space 100B Transmission side space 110 Water vapor separation membrane 120 Catalyst 200 Raw Gas Supply Department 300 Sweeping Gas Supply Unit

Claims

1. Introducing a raw material gas containing at least carbon oxide and hydrogen into the reactor containing the catalyst, and This includes generating a liquid fuel from the raw material gas by a conversion reaction in the presence of the catalyst, The aforementioned raw material gas is selected from nitrogen, helium, and argon, and further contains an inert gas containing at least nitrogen. The ratio of carbon monoxide concentration to carbon dioxide concentration in the aforementioned carbon oxide is 0.9 or less. The concentration of the inert gas in the raw material gas is 1% by volume or more and 55% by volume or less. A method for producing a liquid fuel, further comprising preparing the raw material gas using a gas containing nitrogen and carbon dioxide recovered from the atmosphere or biogas.

2. The manufacturing method according to claim 1, wherein the concentration of the inert gas in the raw material gas is 3% by volume or more and 30% by volume or less.

3. The manufacturing method according to claim 1, wherein the ratio of the inert gas concentration to the carbon dioxide concentration in the raw material gas is 0.05 or more and 1.5 or less.

4. The manufacturing method according to claim 1, wherein the carbon oxide concentration in the raw material gas is 5% by volume or more and 50% by volume or less.

5. The manufacturing method according to claim 1, wherein the hydrogen concentration in the raw material gas is 20% by volume or more and 85% by volume or less.

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

7. The manufacturing method according to any one of claims 1 to 6, wherein the reactor has a water vapor separation membrane that allows water vapor to pass through.

8. The manufacturing method according to any one of claims 1 to 6, wherein the reactor has at least a liquid fuel separation membrane that allows the liquid fuel to pass through.

9. Introducing a raw material gas containing at least carbon oxide and hydrogen into the reactor containing the catalyst, and A method for producing a liquid fuel, comprising generating a liquid fuel from a raw material gas by a conversion reaction in the presence of the catalyst; The aforementioned raw material gas is selected from nitrogen, helium, and argon, and further contains an inert gas containing at least nitrogen. The concentration of the inert gas in the raw material gas is 1% by volume or more and 55% by volume or less. The preparation of the source gas using a gas containing nitrogen and carbon dioxide recovered from the atmosphere or biogas, The liquid fuel comprises methanol, The carbon dioxide concentration (CO) in the carbon oxide in the raw material gas ２ Based on the thermodynamic equilibrium calculation results for the conversion reaction at 200°C and 4 MPa (G) when the ratio of carbon monoxide concentration (CO) to the raw material gas and the ratio of the inert gas concentration (Inert) are changed, the (Inert + CO) / CO ratio in the raw material gas is calculated. ２ The slope a of the approximate line created by linear approximation (Y = aX + b) for a point plotted with (percentage of suppressed heat generation) × (percentage of increased combustion energy gained) as the x-axis and (y-axis) as the x-axis is 1.4 or less; The above plot shows each CO / CO ２ Regarding the case where the above-mentioned raw material gas ratio is used, Inert / CO ２ When the ratio is changed in increments of 0.1 within the range of 0 to 1.6, and when Inert / CO ２ The analysis was performed on a total of 18 data points when the ratio was 0.

05. The proportion of the suppressed calorific value and the proportion of the increased combustion energy gained are values ​​calculated from the following formulas, respectively: Percentage of suppressed calorific value = (calorific value calculated under standard conditions - calorific value calculated when each raw material gas is used) / calorific value calculated under standard conditions The percentage increase in combustion energy gained = (combustion energy of methanol produced calculated when each raw material gas is used - combustion energy of methanol produced calculated under standard conditions) / combustion energy of methanol produced calculated under standard conditions. (Here, The aforementioned standard conditions are that only carbon dioxide and hydrogen are CO2 ２ / H ２ = This is the case when using a raw material gas containing it in a ratio of 1 / 3. The combustion energy of the methanol produced is calculated using the formula: "Combustion energy of the methanol produced = Amount of methanol produced × Higher heating value of methanol"; Manufacturing method.

10. The manufacturing method according to claim 9, wherein the product of the proportion of the suppressed calorific value and the proportion of the increase in combustion energy obtained is -3 or more.

11. A reactor containing a catalyst that facilitates the conversion reaction from a source gas containing at least carbon oxide and hydrogen into a liquid fuel; The reactor is supplied with a raw material gas supply unit that provides a gas containing carbon oxide, hydrogen, and an inert gas as the raw material gas, wherein the ratio of carbon monoxide concentration to carbon dioxide concentration in the carbon oxide is 0.9 or less; A liquid fuel synthesis system comprising, The inert gas is selected from nitrogen, helium, and argon, and includes at least nitrogen. The concentration of the inert gas in the raw material gas is 1% by volume or more and 55% by volume or less. It further includes a gas recovery unit that recovers nitrogen and carbon dioxide from the atmosphere or biogas, A liquid fuel synthesis system in which a gas containing nitrogen and carbon dioxide supplied from the gas recovery unit is supplied to the reactor as a component of the raw material gas.

12. The liquid fuel synthesis system according to claim 11, wherein the concentration of the inert gas in the raw material gas is 3% by volume or more and 30% by volume or less.

13. The liquid fuel synthesis system according to claim 11, wherein the ratio of the inert gas concentration to the carbon dioxide concentration in the raw material gas is 0.05 or more and 1.5 or less.

14. The liquid fuel synthesis system according to any one of claims 11 to 13, wherein the reactor has a water vapor separation membrane that allows water vapor to pass through.

15. The liquid fuel synthesis system according to any one of claims 11 to 13, wherein the reactor has at least a liquid fuel separation membrane that allows the liquid fuel to pass through.

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