Membrane reactor and reverse water-gas shift reaction system

Abstract

To provide a membrane reactor and a reverse water gas shift reaction system equipped with the same, the membrane reactor being equipped with a water vapor separation membrane for separating water vapor from a produced gas by molecular sieving and being configured to reduce hydrogen that is separated out of the reaction system by passing through the water vapor separation membrane.SOLUTION: A membrane reactor includes: a reaction chamber filled with a reverse water gas shift reaction catalyst and having a source gas inlet for introducing a source gas containing carbon dioxide and hydrogen; and a produced gas outlet for discharging a produced gas containing carbon monoxide and water vapor that is produced from the source gas by the reverse water gas shift reaction; a sweep gas flow path having a sweep gas inlet and a sweep gas outlet through which a sweep gas flows; and a water vapor separation membrane arranged so as to separate the reaction chamber from the sweep gas flow path and allowing permeation of water vapor and hydrogen by molecular sieving. The sweep gas is hydrogen or hydrogen-containing gas.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a reverse water gas shift reaction system and a membrane reactor included therein.

Background Art

[0002] In recent years, carbon recycling has been proposed to capture, recover, and reuse carbon dioxide (CO2), which is a type of greenhouse gas, as a carbon resource. Among them, there is a movement to reduce carbon dioxide to carbon monoxide (CO) and use it.

[0003] One method of converting carbon dioxide to carbon monoxide is known as the reverse water gas shift reaction. The reverse water gas shift reaction is a method of producing carbon monoxide and water (H2O) by adding hydrogen (H2) to carbon dioxide. Equation 1 shows the reaction formula of the reverse water gas shift reaction.

[0004]

Chemical

[0005] The reverse water gas shift reaction is known to be a reversible reaction. Therefore, in order to promote the forward reaction of the reverse water gas shift reaction, that is, to advance the reaction to the right in the reaction formula of Chemical Equation 1, it is desirable to separate the product carbon monoxide or water from the reaction system to disrupt the equilibrium.

[0006] Therefore, in Patent Document 1, a membrane reactor is proposed that is configured to promote a synthesis reaction by disposing a separation membrane element and a catalyst inside a casing and selectively separating the water vapor generated by the synthesis with the separation membrane element while advancing the synthesis reaction with the catalyst. Examples of this synthesis reaction include an esterification reaction, a methanol synthesis reaction, a dimethyl ether synthesis reaction, and the like.

Prior Art Documents

Patent Documents

[0007] [Patent Document 1] Japanese Patent Publication No. 2004-50129 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] When a reverse water-gas shift reaction is applied to the membrane reactor described in Patent Document 1, the reaction rate of the forward reaction is increased because water vapor is separated from the reaction system by a separation membrane element including a water vapor separation membrane. The water vapor separation membrane in Patent Document 1 is an inorganic porous material, and the permeation of water vapor is permitted due to the molecular sieving action of the pores of the inorganic porous material. By its properties, such a water vapor separation membrane also allows the permeation of hydrogen, which has a molecular size similar to that of water vapor. In a reverse water-gas shift reaction, if hydrogen, which is a reactant, permeates through the water vapor separation membrane and is separated from the reaction system, hydrogen from the raw material gas is lost from the reaction system, and the reaction rate of the reverse reaction increases. Therefore, in order to increase only the forward reaction rate of the reverse water-gas shift reaction, it is desirable to prevent the permeation of hydrogen from the reaction system through the water vapor separation membrane.

[0009] This disclosure has been made in view of the above circumstances, and its purpose is to provide a reverse water-gas shift reaction system and a membrane reactor therewith, which includes a water vapor separation membrane that separates water vapor from the product gas by molecular sieving action, and which reduces the amount of hydrogen separated out of the reaction system by permeating through the water vapor separation membrane. [Means for solving the problem]

[0010] To solve the above problems, a membrane reactor according to one aspect of this disclosure is provided. A reaction chamber filled with a reverse water-gas shift reaction catalyst, having a raw material gas inlet for introducing raw material gases containing carbon dioxide and hydrogen, and a product gas outlet for discharging product gases containing carbon monoxide and water vapor generated from the raw material gases by the reverse water-gas shift reaction, A sweep gas inlet for introducing sweep gas and a sweep gas outlet for discharging the sweep gas, and a sweep gas flow path through which the sweep gas flows, The device comprises a water vapor separation membrane positioned to separate the reaction chamber and the sweep gas flow path, which prevents the permeation of carbon dioxide and carbon monoxide through molecular sieving action while allowing the permeation of water vapor and hydrogen. The sweep gas is characterized by being hydrogen or a gas containing hydrogen.

[0011] Furthermore, the reverse water-gas shift reaction system according to one aspect of this disclosure is The above membrane reactor, A raw material gas line connected to the raw material gas inlet and supplying the raw material gas to the reaction chamber, A gas generation line is connected to the gas generation outlet and through which the gas generated from the reaction chamber flows, A sweep gas supply line connected to the sweep gas inlet and supplying the sweep gas to the sweep gas flow path, The system is characterized by comprising a sweep gas outlet connected to the sweep gas outlet, through which the sweep exhaust gas discharged from the sweep gas flow path flows. [Effects of the Invention]

[0012] According to one aspect of the present disclosure described above, a reverse water-gas shift reaction system and a membrane reactor comprising the same, which includes a water vapor separation membrane for separating water vapor from the product gas by molecular sieving action, can be provided that reduces the amount of hydrogen separated out of the reaction system by permeating the water vapor separation membrane. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 is a diagram showing a schematic configuration of a reverse water-gas shift reactor according to one aspect of the present disclosure. [Figure 2] Figure 2 shows a schematic configuration of a reverse water-gas shift reactor according to Modification 1. [Figure 3] Figure 3 shows a schematic configuration of a reverse water-gas shift reactor according to Modification 2. [Figure 4] Figure 4 is a chart showing the relationship between the pressure ratio pr and the evaluation value for each gas flow rate ratio. [Figure 5] FIG. 5 is a chart showing the relationship between the pressure ratio pr and the evaluation value for each gas flow rate ratio. [Figure 6] FIG. 6 is a chart showing the relationship between the pressure ratio pr and the evaluation value for each gas flow rate ratio. [Figure 7] FIG. 7 is a chart showing the relationship between the pressure ratio pr and the evaluation value for each gas flow rate ratio. [Figure 8] FIG. 8 is a chart showing the relationship between the pressure ratio pr and the evaluation value for each gas flow rate ratio. [Figure 9] FIG. 9 is a chart showing the relationship between the pressure ratio pr and the evaluation value for each gas flow rate ratio. [Figure 10] FIG. 10 is a diagram for explaining the analysis model. [Figure 11] FIG. 11 is a chart showing the analysis results.

MODE FOR CARRYING OUT THE INVENTION

[0014] Next, embodiments of the present disclosure will be described with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of a water-repellent gas shift reaction system 1 according to one aspect of the present disclosure. In the figure, the membrane reactor 2 is shown in a cross-sectional view. The water-repellent gas shift reaction system 1 generates a product gas composed of carbon monoxide and water vapor from a raw material gas composed of carbon dioxide and hydrogen by a water-repellent gas shift reaction, and is used for the production of carbon monoxide.

[0015] As shown in FIG. 1, the water-repellent gas shift reaction system 1 includes a membrane reactor 2, a raw material gas line 21, a product gas line 22, a sweep gas supply line 25, and a sweep gas discharge line 26. In the membrane reactor 2, by simultaneously performing the reaction and the separation of the product gas in the reaction system, a conversion rate exceeding the equilibrium conversion rate at the reaction temperature can be obtained.

[0016] The membrane reactor 2 has a reaction chamber 17 in which a water-repellent gas shift reaction is carried out and a sweep gas flow path 18 through which a sweep gas flows. The reaction chamber 17 and the sweep gas flow path 18 are separated by a separation membrane element 14.

[0017] The vessel body 10 of the membrane reactor 2 according to this embodiment has a cylindrical shape with both ends closed and extending in an arbitrary axial direction A. A raw material gas inlet 11, which is the entrance to the reaction chamber 17, is located at the first end of the vessel body 10, and a product gas outlet 12, which is the exit from the reaction chamber 17, is located at the second end of the vessel body 10, opposite to the first end. The raw material gas inlet 11 and the product gas outlet 12 are separated in the axial direction A. A raw material gas line 21 is connected to the raw material gas inlet 11. Raw material gas is supplied from the raw material gas line 21 to the reaction chamber 17 through the raw material gas inlet 11. The raw material gas contains carbon dioxide and hydrogen. The mixing ratio of hydrogen and carbon dioxide in the raw material gas is approximately 3:1 by volume. The temperature of the raw material gas is suitable for the reaction corresponding to the catalyst 13. A product gas line 22 is connected to the product gas outlet 12. Product gas is discharged from the reaction chamber 17 through the product gas outlet 12. However, the gas discharged outside the reaction system through the product gas outlet 12 includes not only the product gas but also unreacted raw material gas.

[0018] The separation membrane element 14 according to this embodiment is inserted into the container body 10 and has a hollow cylindrical shape that is arranged substantially coaxially with the container body 10. The hollow portion of the separation membrane element 14 becomes a sweep gas channel 18 through which the permeate gas and sweep gas that have permeated from the reaction chamber 17 through the separation membrane element 14 pass.

[0019] The separation membrane element 14 includes a water vapor separation membrane 14a, also known as a dehydration membrane, which prevents the passage of carbon dioxide and carbon monoxide through molecular sieving action while allowing the permeation of water vapor and hydrogen. However, the separation membrane element 14 does not strictly prevent the permeation of carbon dioxide and carbon monoxide, but may allow a small amount (for example, about one-tenth) of carbon dioxide and carbon monoxide to permeate relative to water vapor. The separation membrane element 14 has the water vapor separation membrane 14a supported on a porous support substrate. The water vapor separation membrane 14a is not particularly limited as long as it has the molecular sieving action described above, but a nanoporous zeolite separation membrane is an example. The separation membrane element 14 including the nanoporous zeolite separation membrane has the nanoporous zeolite separation membrane supported on the surface of a porous support substrate made of ceramic, alumina, carbonaceous, SiC, SiO2, or metallic material.

[0020] The outer wall of the separation membrane element 14 is exposed inside the membrane reactor 2. The space between the inner wall of the membrane reactor 2 and the outer wall of the separation membrane element 14 forms a reaction chamber 17 where a reverse water-gas shift reaction occurs, and this reaction chamber 17 is filled with a water-gas shift reaction catalyst (hereinafter simply referred to as "catalyst 13"). The catalyst 13 is not particularly limited as long as it is active in the reverse water-gas shift reaction. Known catalysts such as metal complex catalysts including group VIII catalysts such as Ni, Co, and Fe, group VI catalysts such as Mo, and Cu-based catalysts are examples of such catalysts 13.

[0021] A sweep gas inlet 15, which is the entrance to the sweep gas flow path 18, is located at the first end of the separation membrane element 14. A sweep gas outlet 16, which is the exit of the sweep gas flow path 18, is located at the second end of the separation membrane element 14, opposite to the first end. The sweep gas inlet 15 and the sweep gas outlet 16 are spaced apart in the axial direction A. A sweep gas supply line 25 is connected to the sweep gas inlet 15. Sweep gas is supplied to the sweep gas inlet 15 through the sweep gas supply line 25. The sweep gas supplied to the sweep gas inlet 15 passes through the sweep gas flow path 18, and is discharged from the sweep gas outlet 16, accompanied by the permeate gas that has permeated through the separation membrane element 14. A sweep gas discharge line 26 is connected to the sweep gas outlet 16.

[0022] The raw material gas inlet 11 and the sweep gas inlet 15 are located on the same side in axial direction A in the reverse water-gas shift reaction system 1, and the gas flow in the reaction chamber 17 and the sweep gas flow are approximately parallel. However, the membrane reactor 2 may be configured such that the gas flow in the reaction chamber 17 and the sweep gas flow are opposite each other.

[0023] The sweep gas is hydrogen or a gas containing hydrogen. Generally, the sweep gas is a gas that does not react with the raw material gas or the raw material gas. For example, nitrogen has been used as the sweep gas in the reverse water-gas shift reaction. In contrast, in this disclosure, hydrogen is used as the sweep gas in order to suppress the permeation of hydrogen through the separation membrane element 14 in the reaction chamber 17.

[0024] A method for producing carbon monoxide using the reverse water-gas shift reaction system 1 configured as described above will now be explained. When carbon dioxide and hydrogen, which are the raw material gases, are supplied from the raw material gas inlet 11 of the membrane reactor 2 to the reaction chamber 17, a reverse water-gas shift reaction occurs due to the action of the catalyst 13, producing carbon monoxide and water vapor, which are the product gases.

[0025] Most of the product gas is discharged from the reaction chamber 17 through the product gas outlet 12 and recovered as a product. Some of the water vapor in the reaction chamber 17 permeates through the separation membrane element 14 and moves to the sweep gas channel 18, where it is separated from the reaction chamber 17 (i.e., the reaction system). Although hydrogen in the reaction chamber 17 can permeate through the separation membrane element 14, the hydrogen contained in the sweep gas suppresses its permeation through the separation membrane element 14. In this way, the raw material gas, hydrogen, remains in the reaction chamber 17, while the product gas, water vapor, permeates through the separation membrane element 14, which includes the water vapor separation membrane 14a, and is separated from the reaction chamber 17. This improves the reaction rate of the forward reaction of the reverse water-gas shift reaction; in other words, the forward reaction is accelerated.

[0026] The water vapor that moves to the sweep gas passage 18 is carried along with the sweep gas and discharged from the sweep gas passage 18 through the sweep gas outlet 16. Therefore, the sweep exhaust gas discharged from the sweep gas passage 18 contains hydrogen and water vapor. A cold trap 31 is provided in the sweep gas discharge line 26 connected to the sweep gas outlet 16. The cold trap 31 cools the water vapor contained in the sweep exhaust gas and removes it in liquid form (i.e., water).

[0027] The cold trap 31 is connected to the sweep gas supply line 25 by a recycling line 32. The sweep exhaust gas from which water vapor has been separated in the cold trap 31 is sent to the sweep gas supply line 25 via the recycling line 32 and reused as sweep gas. Alternatively, the recycling line 32 may be directly connected to the sweep gas inlet 15 without going through the sweep gas supply line 25. In this case, the sweep exhaust gas from which water vapor has been separated in the cold trap 31 is sent to the sweep gas inlet 15 via the recycling line 32 and reused as sweep gas.

[0028] Sweep exhaust gas may contain trace amounts of carbon monoxide and carbon dioxide in addition to hydrogen and water vapor. Therefore, as shown in Figure 2, the cold trap 31 may be connected to the raw material gas line 21 by a return line 33. The sweep exhaust gas from which water vapor has been separated in the cold trap 31 is sent to the raw material gas line 21 via the return line 33 and used as part of the raw material gas. Alternatively, the return line 33 may be directly connected to the raw material gas inlet 11 without going through the raw material gas line 21. In this case, the sweep exhaust gas from which water vapor has been separated in the cold trap 31 is sent to the raw material gas inlet 11 via the return line 33 and used as part of the raw material gas.

[0029] Furthermore, the reverse water-gas shift reaction system 1 may also include both a recycling line 32 and a return line 33. In this case, as shown in Figure 3, the cold trap 31 is connected to the raw material gas line 21 (or raw material gas inlet 11) via the return line 33, and the cold trap 31 is connected to the sweep gas supply line 25 (or sweep gas inlet 15) via the recycling line 32. The sweep exhaust gas from which water vapor has been separated in the cold trap 31 is, in principle, reused as sweep gas. Then, in order to remove trace amounts of carbon monoxide and carbon dioxide contained in the circulating sweep gas, the sweep exhaust gas may be periodically returned to the membrane reactor 2 as part of the raw material gas.

[0030] [Numerical analysis and results] Here, we will explain the numerical analysis and its results conducted to verify the hydrogen permeation suppression effect of the separation membrane element 14, which includes the water vapor separation membrane 14a using sweep gas.

[0031] [Numerical Analysis Example 1] First, let's explain numerical analysis example 1. In numerical analysis example 1, we search for a suitable range for the pressure ratio pr of the total sweep pressure / total raw material gas pressure. Equations 1 to 3 shown in the following [Equation 1] are the basic equations for numerical analysis. In equation (1) of these basic equations, the flow rate of component i in the raw material gas is defined as Fi (flow rate of component i in the raw material gas [mol / s]), and the change in Fi per unit length, dFi / dz, is calculated. Equation (3) is the equation for calculating R in equation (1). Also, in equation (2) of these basic equations, the flow rate of component i in the sweep gas is defined as Qi (flow rate of component i in the sweep gas [mol / s]), and the change in Qi per unit length of the separation membrane element 14, dQi / dz, is calculated. Table 1 explains the symbols used in equations 1 to 3.

[0032]

number

[0033] [Table 1]

[0034] The following equation [Equation 2] is the dimensionless form of the basic equation shown in [Equation 1]. In the dimensionless basic equation (Equation 4), fi (flow rate of the dimensionless component i in the source gas) is defined as the dimensionless flow rate of component i in the source gas, and the change in fi per unit dimensionless length, dfi / dζ, is calculated. In the dimensionless basic equation (Equation 5), qi (flow rate of the dimensionless component i in the sweep gas) is defined as the dimensionless flow rate of component i in the sweep gas, and the change in qi per unit dimensionless length, qi / dζ, is calculated. Equations (6) to (13) of the dimensionless basic equation are the equations for determining each element of (Equation 4) and (Equation 5). Tables [1] and [2] explain the symbols used in Equations 4 to 13.

[0035]

number

[0036] [Table 2]

[0037] Numerical analysis used dimensionless fundamental equations. The parameters of the dimensionless fundamental equations are Da, θ, Pr, and the inlet gas flow rate ratio (sweep gas / raw material gas). Da represents the relative reaction rate, and θ represents the relative membrane permeation rate. Of the parameters, Da, θ, and the flow rate ratio were assumed to be sufficiently large values ​​to represent an actual process, and Pr was set to a variable of 1 or less. Furthermore, the composition ratio of the raw material gas, the composition of the sweep gas, and the analytical conditions for the selectivity of the separation membrane element 14 were set to represent an actual process. The specific analytical conditions are as follows. The gas flow rate ratio at the inlet (sweep gas / raw material gas) is varied as follows: (a) 1, (b) 3, (c) 5, (d) 7.5, (e) 10. Da=1. θ=10. The composition ratio (volume ratio) of H2 and CO2 in the raw material gas at the raw material gas inlet is varied between (a) 1:1 and (b) 3:1. The composition of the sweep gas at the sweep gas inlet is varied as follows: (a) 100% H2, (b) 75% H2-25% N2, (c) 50% H2-50% N2, and (d) 100% N2. • Selectivity of H2O / H2 is αH2 = 2 The selectivity αX for H2O / X is 50 (X = CO2, CO, N2). *Selectivity is the ratio of the permeability of gas α to gas β, and [permeability of gas α / permeability of gas β] represents the selectivity of gas α for gas β.

[0038] In the numerical analysis, under the above analysis conditions, the CO2 reaction rate was determined by varying the pressure ratio pr of the total sweep gas pressure / total raw material gas pressure (0.05, 0.1, 0.25, 0.5, 0.75, 1) for both cases where the sweep gas composition at the sweep gas inlet was 100% H2 and 100% N2. The CO2 reaction rate is expressed as [CO2 in the gas discharged from the generated gas outlet 12 / CO2 in the raw material gas supplied to the raw material gas inlet 11 (by volume)].

[0039] The analysis results are shown in Table 3-8 and Figures 5 to 9. In Table 3-8, the columns represent the inlet gas flow rate ratio (sweep gas / raw material gas), and the rows represent the pressure ratio pr, showing the evaluation values ​​when the gas flow rate ratio and pressure ratio pr are changed. Similarly, in Figures 5 to 9, the horizontal axis represents the pressure ratio pr (= total pressure of the inlet sweep gas / total pressure of the raw material gas), and the vertical axis represents the evaluation value. The evaluation value is [CO2 reaction rate when the sweep gas is of a predetermined composition / CO2 reaction rate when the sweep gas is 100% N2] at each pressure ratio pr.

[0040] [Table 3]

[0041] [Table 4]

[0042] [Table 5]

[0043] [Table 6]

[0044] [Table 7]

[0045] [Table 8]

[0046] The analysis results showed that when the sweep gas contained 25% or more hydrogen, all evaluation values ​​were greater than 1, indicating that a higher CO2 reaction rate was obtained compared to when the sweep gas was 100% N2. Here, an evaluation value exceeding 1.30 is considered to indicate that the reverse water-gas shift reaction is being promoted well, and an evaluation value exceeding 1.50 is considered to indicate that the reverse water-gas shift reaction is being promoted significantly. When the pressure ratio pr was 0.25 or higher, an evaluation value of 1.30 or higher was obtained regardless of the composition of the raw material gas or the sweep gas. In other words, a CO2 reaction rate of 1.3 times or more was obtained compared to when the sweep gas composition was 100% N2. Therefore, in the range of pressure ratio pr of 0.25 or higher, it can be said that the permeation of hydrogen gas from the reaction chamber 17 to the sweep gas flow path 18 is effectively suppressed by using hydrogen gas as the sweep gas. Furthermore, when the pressure ratio pr is 0.5 or higher, an evaluation value of 1.50 or higher is obtained regardless of the composition of the raw material gas or the sweep gas. In other words, a CO2 reaction rate of 1.5 times or more is obtained compared to the case where the sweep gas composition is 100% N2. Therefore, in the range where the pressure ratio pr is 0.5 or higher, the use of hydrogen gas as the sweep gas significantly and effectively suppresses the permeation of hydrogen gas from the reaction chamber 17 to the sweep gas flow path 18.

[0047] [Numerical Analysis Example 2] Next, we will explain numerical analysis example 2. In numerical analysis 2, we explore the hydrogen partial pressure of the sweep gas at the sweep gas inlet relative to the hydrogen partial pressure of the source gas at the source gas inlet.

[0048] Figure 10 shows the analytical model of the reverse water-gas shift reaction system 1, and the analytical conditions are as follows. <Membrane reactor 2 of the analytical model> The length L in the axial direction A is 100 mm. The inner diameter D is 25.4 mm. <Separation membrane element 14 of the analysis model> • The water vapor separation membrane 14a is a nanoporous zeolite separation membrane. • The diameter d is 10 mm. The transparency of H2O is 5000 GPU. *Permeability is a physical property value that represents the gas permeation rate per unit area and unit partial pressure difference. The gas permeation rate is determined by membrane area × gas permeability × gas partial pressure difference. The selectivity for H2O / H2 is 2. The selectivity of H2O / X is 50 (X = CO2, CO, N2). *Selectivity is the ratio of the permeability of gas α to gas β, and [permeability of gas α / permeability of gas β] represents the selectivity of gas α for gas β. <Raw material gas> The composition ratio of H2 to CO2 at the raw material gas inlet 11 is 3:1 (by volume). • Flow rate is 1.0 × 10 -3 Nm 3 / min. The total pressure at the raw material gas inlet 11 is 1 MPaA (i.e., the partial pressure of hydrogen is 0.75 MPaA). <Sweep gas> The composition at the sweep gas inlet 15 is 100% H2 or 100% N2. The total pressure at the sweep gas inlet 15 is a parameter. • Flow rate is parameter (1.0 × 10 -3 ,3.0×10 -3 ,5.0×10 -3 ,7.0×10 -3 ,10.0×10 -3 [Units are Nm] 3 [ / min]).

[0049] As shown in Table 1 below, in Examples 1-3 and Comparative Examples 1-3, the total pressure of the sweep gas was applied to each, and the flow rate of the sweep gas was varied. In Comparative Example 4, the permeability of all gases in the separation membrane element 14 of the analytical model was set to zero, and the separation membrane element 14 and the sweep gas flow path 18 were considered to be absent, thereby excluding the influence of the separation membrane element 14 and the sweep gas.

[0050] [Table 9]

[0051] In the analysis, the CO2 reaction rate was determined under the above-described analysis model and conditions. The CO2 reaction rate is expressed as [CO2 in the gas discharged from the generated gas outlet 12 / CO2 in the raw material gas supplied to the raw material gas inlet 11 (by volume)]. The analysis results are shown in the table in Figure 11. In this table, the vertical axis represents the CO2 reaction rate, and the horizontal axis represents the sweep gas flow rate.

[0052] As shown in Figure 11, in the reverse water-gas shift reaction system 1, the CO2 reaction rate is higher when the sweep gas is H2 (Examples 1-3) compared to when the separation membrane element 14 is not provided (Comparative Example 4) and when the sweep gas is N2 (Comparative Examples 1-3). The high CO2 reaction rate means that the forward reaction of the reverse water-gas shift reaction was accelerated.

[0053] Furthermore, the analysis results from Examples 1 to 3 clearly show that the smaller the difference between the hydrogen partial pressure of the sweep gas and the hydrogen partial pressure of the source gas, the higher the CO2 reaction rate.

[0054] Based on the analysis results of Examples 1 to 3, it is desirable that the hydrogen partial pressure of the sweep gas at the sweep gas inlet 15 be 0.1 times or more and 1.0 times or less of the hydrogen partial pressure of the raw material gas at the raw material gas inlet 11, more preferably 0.5 times or more and 1.0 times or less of the hydrogen partial pressure of the raw material gas at the raw material gas inlet 11, and especially desirable that it be approximately the same as the hydrogen partial pressure of the raw material gas at the raw material gas inlet 11. Note that, since the hydrogen partial pressure in the reaction chamber 17 is assumed to decrease from the raw material gas inlet 11 towards the product gas outlet 12, the hydrogen partial pressure of the raw material gas at the raw material gas inlet 11 is used as the reference; however, the hydrogen partial pressure at a predetermined position near the raw material gas inlet 11 in the reaction chamber 17 may also be used as the reference.

[0055] If the hydrogen partial pressure of the sweep gas is higher than the hydrogen partial pressure of the raw material gas, hydrogen in the sweep gas permeates through the separation membrane element 14 and moves to the reaction chamber 17. When hydrogen in the sweep gas moves to the reaction chamber 17, the amount of hydrogen in the reaction chamber 17 increases, promoting the forward reaction of the reverse water-gas shift reaction. For this reason, the hydrogen partial pressure of the sweep gas may be higher than the hydrogen partial pressure of the raw material gas. For example, the hydrogen partial pressure of the sweep gas at the sweep gas inlet 15 may be 1.3 times or less the hydrogen partial pressure of the raw material gas at the raw material gas inlet 11. However, as the total pressure of the sweep gas increases, the permeation of water vapor through the separation membrane element 14 in the reaction chamber 17 is inhibited. Therefore, the total pressure of the sweep gas must be lower than the total pressure of the raw material gas at the raw material gas inlet 11.

[0056] Furthermore, the analysis results from Examples 1 to 3 clearly show that the CO2 reaction rate is higher when the sweep gas flow rate is higher. However, since it is presumed that the CO2 reaction rate will converge to a certain value even if the sweep gas flow rate increases, it is desirable to determine the sweep gas flow rate while considering the balance between the CO2 reaction rate and economic efficiency.

[0057] [Summary] As explained above, the membrane reactor 2 relating to item 1 of this disclosure is A reaction chamber 17 is filled with a reverse water-gas shift reaction catalyst 13 and has a raw material gas inlet 11 for introducing raw material gas containing carbon dioxide and hydrogen, and a product gas outlet 12 for discharging product gas containing carbon monoxide and water vapor generated from the raw material gas by the reverse water-gas shift reaction. It has a sweep gas inlet 15 for introducing sweep gas and a sweep gas outlet 16 for discharging sweep gas, and a sweep gas flow path 18 through which the sweep gas flows, The system includes a water vapor separation membrane 14a positioned to separate the reaction chamber 17 from the sweep gas flow path 18, which prevents the permeation of carbon dioxide and carbon monoxide through molecular sieving action while allowing the permeation of water vapor and hydrogen. The sweep gas is characterized by being hydrogen or a hydrogen-containing gas. Here, the water vapor separation membrane 14a may be provided in the membrane reactor 2 supported on a porous support substrate.

[0058] The membrane reactor 2 relating to item 2 of this disclosure is the same as the membrane reactor 2 relating to item 1, wherein the sweep gas contains hydrogen in the range of 25% to 100%, and the total pressure of the sweep gas at the sweep gas inlet 15 is 0.25 times to 1.0 times the total pressure of the raw material gas at the raw material gas inlet 11.

[0059] The membrane reactor 2 relating to item 3 of this disclosure is the same as the membrane reactor 2 relating to item 1, wherein the sweep gas contains hydrogen in the range of 25% to 100%, and the total pressure of the sweep gas at the sweep gas inlet 15 is 0.5 times to 1.0 times the total pressure of the raw material gas at the raw material gas inlet 11.

[0060] In the membrane reactor 2 with the above configuration, the hydrogen flowing as sweep gas in the sweep gas channel 18 suppresses the movement of hydrogen from the reaction chamber 17 through the water vapor separation membrane 14a to the sweep gas channel 18. In this way, the water vapor selectivity of the water vapor separation membrane 14a is increased, the source gas hydrogen remains in the reaction chamber 17, and the product gas water vapor is separated from the reaction chamber 17 by permeating through the water vapor separation membrane 14a. As a result, the reaction rate of the forward reaction of the reverse water-gas shift reaction in the membrane reactor 2 is improved, or in other words, the forward reaction is accelerated.

[0061] The membrane reactor 2 relating to item 4 of this disclosure is the same as the membrane reactor 2 relating to item 1, wherein the hydrogen partial pressure of the sweep gas at the sweep gas inlet 15 of the sweep gas flow path 18 is 0.1 times or more and 1.0 times or less than the hydrogen partial pressure of the raw material gas at the raw material gas inlet 11 of the reaction chamber 17.

[0062] The membrane reactor 2 relating to item 5 of this disclosure is the same as the membrane reactor 2 relating to item 1, wherein the hydrogen partial pressure of the sweep gas at the sweep gas inlet 15 of the sweep gas flow path 18 is 0.5 times or more and 1.0 times or less of the hydrogen partial pressure of the raw material gas at the raw material gas inlet 11 of the reaction chamber 17.

[0063] The membrane reactor 2 relating to item 6 of this disclosure is a membrane reactor 2 relating to item 1 in which the partial pressure of hydrogen in the sweep gas at the sweep gas inlet 15 of the sweep gas flow path 18 is substantially the same as the partial pressure of hydrogen in the raw material gas at the raw material gas inlet 11 of the reaction chamber 17.

[0064] Furthermore, the reverse water-gas shift reaction system 1 relating to item 7 of this disclosure is A membrane reactor 2 relating to one of items 1 to 6, A raw material gas line 21 is connected to the raw material gas inlet 11 and supplies raw material gas to the reaction chamber 17, A product gas line 22 is connected to the product gas outlet 12, and the product gas discharged from the reaction chamber 17 flows through it. A sweep gas supply line 25 is connected to the sweep gas inlet 15 and supplies sweep gas to the sweep gas flow path 18, The system includes a sweep gas outlet 16 and a sweep gas discharge line 26 through which the sweep exhaust gas discharged from the sweep gas flow path 18 flows.

[0065] The membrane reactor 2 according to item 8 of this disclosure is a reverse water-gas shift reaction system 1 according to item 7, wherein the sweep gas discharge line 26 has a cold trap 31 that cools and separates the water vapor contained in the sweep exhaust gas discharged from the sweep gas flow path 18, and further comprises a recycling line 32 that sends the sweep exhaust gas from which the water vapor has been separated to the sweep gas supply line 25.

[0066] According to the reverse water-gas shift reaction system 1 with the above configuration, the sweep gas can be recycled, making it economical.

[0067] The membrane reactor 2 according to item 9 of this disclosure is a reverse water-gas shift reaction system 1 according to item 7, wherein the sweep gas discharge line 26 has a cold trap 31 that cools and separates water vapor contained in the sweep exhaust gas discharged from the sweep gas flow path 18, and further comprises a return line 33 that sends the sweep exhaust gas from which water vapor has been separated in the cold trap 31 to the raw material gas line 21.

[0068] According to the reverse water-gas shift reaction system 1 with the above configuration, hydrogen and carbon dioxide contained in the sweep exhaust gas can be used as part of the raw material gas, thereby enabling effective use of the raw material gas.

[0069] While preferred embodiments (and modifications) of the present disclosure have been described above, the present invention may also include modifications to the specific structure and / or functional details of the above embodiments, without departing from the spirit of the present disclosure. The above configuration can be modified, for example, as follows:

[0070] For example, in the reverse water-gas shift reaction system 1 according to the above embodiment, both the membrane reactor 2 and the separation membrane element 14 are cylindrical, but their shapes are not limited to cylindrical. The membrane reactor 2 may have a reaction chamber 17 and a sweep gas flow path 18 separated from the reaction chamber 17 by the separation membrane element 14. [Explanation of Symbols]

[0071] 1: Reverse water-gas shift reaction system 2: Membrane reactor 10: Container body 11: Raw material gas inlet 12: Gas outlet 13: Reverse water-gas shift reaction catalyst 13: Catalyst 14: Separation membrane element 14a: Water vapor separation membrane 15: Sweep gas inlet 16: Sweep gas outlet 17: Reaction Room 18: Sweep gas flow path 21: Raw material gas line 22: Gas generation line 25: Sweep gas supply line 26: Sweep gas discharge line 31: Cold trap 32: Recycling Line 33: Return Line

Claims

1. A reaction chamber filled with a reverse water-gas shift reaction catalyst, having a raw material gas inlet for introducing raw material gases containing carbon dioxide and hydrogen, and a product gas outlet for discharging product gases containing carbon monoxide and water vapor generated from the raw material gases by the reverse water-gas shift reaction, A sweep gas inlet for introducing sweep gas and a sweep gas outlet for discharging the sweep gas, and a sweep gas flow path through which the sweep gas flows, The system comprises a water vapor separation membrane positioned to separate the reaction chamber and the sweep gas flow path, which prevents the permeation of carbon dioxide and carbon monoxide through molecular sieving action while allowing the permeation of water vapor and hydrogen. The sweep gas is hydrogen or a gas containing hydrogen. Membrane reactor.

2. The sweep gas contains hydrogen in a range of 25% to 100%, The total pressure of the sweep gas at the sweep gas inlet is 0.25 times or more and 1.0 times or less the total pressure of the raw material gas at the raw material gas inlet. The membrane reactor according to claim 1.

3. The sweep gas contains hydrogen in a range of 25% to 100%, The total pressure of the sweep gas at the sweep gas inlet is 0.5 times or more and 1.0 times or less the total pressure of the raw material gas at the raw material gas inlet. The membrane reactor according to claim 1.

4. The hydrogen partial pressure of the sweep gas at the sweep gas inlet is between 0.1 and 1.0 times the hydrogen partial pressure of the raw material gas at the raw material gas inlet. The membrane reactor according to claim 1.

5. The hydrogen partial pressure of the sweep gas at the sweep gas inlet is 0.5 times or more and 1.0 times or less the hydrogen partial pressure of the raw material gas at the raw material gas inlet. The membrane reactor according to claim 1.

6. The hydrogen partial pressure of the sweep gas at the sweep gas inlet is substantially the same as the hydrogen partial pressure of the raw material gas at the raw material gas inlet. The membrane reactor according to claim 1.

7. The membrane reactor according to claim 1, A raw material gas line connected to the raw material gas inlet and supplying the raw material gas to the reaction chamber, A gas generation line is connected to the gas generation outlet and through which the gas generated from the reaction chamber flows, A sweep gas supply line connected to the sweep gas inlet and supplying the sweep gas to the sweep gas flow path, The system includes a sweep gas outlet connected to the sweep gas outlet, through which the sweep exhaust gas discharged from the sweep gas flow path flows. Reverse water-gas shift reaction system.

8. The sweep gas discharge line further includes a cold trap for cooling and separating water vapor contained in the sweep exhaust gas, and a recycling line for sending the sweep exhaust gas, from which water vapor has been separated in the cold trap, to the sweep gas supply line. The reverse water-gas shift reaction system according to claim 7.

9. The sweep gas discharge line further includes a cold trap for cooling and separating water vapor contained in the sweep exhaust gas, and a return line for sending the sweep exhaust gas, from which the water vapor has been separated by the cold trap, to the raw material gas line. The reverse water-gas shift reaction system according to claim 7.

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