Synthesis gas production equipment

Abstract

To provide a synthesis gas production apparatus with improved CO2 conversion rate. [Solution] A synthesis gas production apparatus for producing synthesis gas containing carbon monoxide and hydrogen comprises: a reactor filled with a catalyst that functions as a stationary phase with a longer retention time for carbon dioxide than for oxygen, hydrogen, and carbon monoxide, while promoting a reverse water-gas shift reaction using carbon dioxide and hydrogen; a gas supply unit capable of supplying a first raw material gas containing carbon dioxide and oxygen and a second raw material gas containing hydrogen to the reactor; and a control unit that controls the gas supply unit. The control unit controls the gas supply unit to supply the second raw material gas to the reactor after supplying the first raw material gas, thereby discharging synthesis gas from the reactor.

Description

[Technical Field]

[0001] This invention relates to a synthesis gas production apparatus. [Background technology]

[0002] From the perspective of combating global warming, carbon dioxide separated from exhaust gases emitted from combustion equipment in factories and other facilities is being converted into carbon monoxide, which can be used for the synthesis of hydrocarbons and other applications. The reverse water-gas shift reaction is known as a reaction that converts carbon dioxide into carbon monoxide. Patent Document 1 discloses a reaction vessel having a catalyst for the reverse water-gas shift reaction and a water adsorbent inside. Patent Document 2 discloses a reactor filled with a catalyst that promotes the reverse water-gas shift reaction. Non-Patent Document 1 discloses a technology for producing carbon monoxide using a dual-function catalyst (DFM: Dual Function Material). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-171010 [Patent Document 2] Japanese Patent Publication No. 2018-202333 [Non-Patent Document 1] HYPERLINK "https: / / www.sciencedirect.com / journal / journal-of-co2-utilization" \o "Go to Journal of CO2 Utilization on ScienceDirect"Journal of CO2 Utilization, Volume 60, June 2022,“Integrated CO2 capture and selective conversion to syngas using transition-metal-free Na / Al2O3 dual-function material” [Overview of the project] [Problems that the invention aims to solve]

[0004] However, in both Patent Documents 1 and 2 and Non-Patent Document 1, there was room for improvement in improving the CO2 conversion rate, which represents the amount of carbon monoxide produced relative to the amount of carbon dioxide supplied.

[0005] The present invention has been made to solve at least some of the above-mentioned problems, and aims to provide a synthesis gas production apparatus with an improved CO2 conversion rate. [Means for solving the problem]

[0006] The present invention has been made to solve at least some of the above-mentioned problems and can be realized in the following forms.

[0007] (1) According to one embodiment of the present invention, a synthesis gas production apparatus is provided. This synthesis gas production apparatus is for producing synthesis gas containing carbon monoxide and hydrogen, and comprises a reactor filled with a catalyst that functions as a stationary phase with a retention time for carbon dioxide longer than the retention times for oxygen, hydrogen and carbon monoxide, and promotes a reverse water-gas shift reaction using carbon dioxide and hydrogen; a gas supply unit capable of supplying a first raw material gas containing carbon dioxide and oxygen and a second raw material gas containing hydrogen to the reactor; and a control unit that controls the gas supply unit, wherein the control unit controls the gas supply unit to supply the second raw material gas to the reactor after supplying the first raw material gas to the reactor, thereby discharging the synthesis gas from the reactor.

[0008] This configuration allows for an improvement in the CO2 conversion rate by supplying the first raw material gas to the reactor first, followed by the second raw material gas. In other words, by supplying the first raw material gas containing carbon dioxide and the second raw material gas containing hydrogen at different timings rather than simultaneously, the amount of carbon monoxide produced can be increased.

[0009] (2) In the syngas production apparatus of the above-described embodiment, the control unit may control the gas supply unit such that the supply time of the first raw material gas by the gas supply unit is within a range of 0.33 times to 3.00 times the time difference between the retention time of carbon dioxide by the catalyst and the retention time of oxygen by the catalyst. According to this configuration, the CO2 conversion rate can be further improved. Further, depending on the supply time of the first raw material gas within this range, it is also possible to produce carbon monoxide at a CO2 conversion rate exceeding the equilibrium conversion rate, which is the conversion rate at chemical equilibrium.

[0010] (3) In the syngas production apparatus of the above-described embodiment, the gas supply unit can supply an inert gas to the reactor in addition to the first raw material gas and the second raw material gas, and the control unit controls the gas supply unit to supply the inert gas to the reactor after supplying the first raw material gas to the reactor and then supply the second raw material gas to the reactor. According to this configuration, it is possible to prevent the oxygen contained in the first raw material gas from being mixed with the hydrogen contained in the second raw material gas. Therefore, the safety in the operation of the syngas production apparatus can be ensured.

[0011] Note that the present invention can be realized in various aspects. For example, it can be realized in the form of a system including a syngas production apparatus, a control method for the syngas production apparatus and the system, a computer program for causing the production of syngas in these apparatuses and systems, a server apparatus for distributing this computer program, a non-transitory storage medium storing the computer program, and the like.

Brief Description of the Drawings

[0012] [Figure 1] It is an explanatory diagram illustrating the configuration of the syngas production apparatus according to an embodiment of the present invention. [Figure 2] It is an explanatory diagram of the characteristics of the catalyst. [Figure 3] It is an explanatory diagram of the characteristics of the catalyst. [Figure 4]This diagram illustrates the retention times when various gases are supplied to a column under different temperature conditions. [Figure 5] This is an explanatory diagram showing the CO2 conversion rate when the raw material gas is supplied to the column. [Figure 6] This is an explanatory diagram showing the CO2 conversion rate when the raw material gas is supplied to the column. [Figure 7] This table shows the results of evaluation tests on the synthesis gas production capacity of the reactor. [Figure 8] This table shows the results of evaluation tests on the synthesis gas production capacity of the reactor. [Figure 9] This is an explanatory diagram showing the relationship between "Gas A supply time / ΔT" and "CO2 conversion rate". [Figure 10] This is an explanatory diagram showing the relationship between "Gas A supply time / ΔT" and "CO2 conversion rate". [Figure 11] This is an explanatory diagram that conceptually represents each gas. [Figure 12] This is an explanatory diagram that conceptually represents each gas. [Figure 13] This is an explanatory diagram that conceptually represents each gas. [Figure 14] This diagram illustrates the retention times when various gases are supplied to a column under different temperature conditions. [Figure 15] This table shows the results of evaluation tests on the synthesis gas production capacity of the reactor. [Figure 16] This table shows the results of evaluation tests on the synthesis gas production capacity of the reactor. [Figure 17] This is an explanatory diagram showing the spectra of various columns. [Figure 18] This is an explanatory diagram showing the spectra of various columns. [Figure 19] This is an explanatory diagram showing the spectra of various columns. [Figure 20] This is an explanatory diagram showing the spectra of various columns. [Figure 21] This is an explanatory diagram showing the amount of CO2 desorption in various temperature ranges for different types of columns. [Figure 22]This is an explanatory diagram showing the CO2 conversion rate when the raw material gas is supplied to the column. [Figure 23] This table shows the results of evaluation tests on the synthesis gas production capacity of the reactor. [Figure 24] This table shows the results of evaluation tests on the synthesis gas production capacity of the reactor. [Modes for carrying out the invention]

[0013] <Embodiment> Figure 1 is an explanatory diagram illustrating the configuration of a synthesis gas production apparatus 1 according to an embodiment of the present invention. The synthesis gas production apparatus 1 is a device that produces synthesis gas containing carbon monoxide and hydrogen. Synthesis gas is used in methanol synthesis, Fischer-Tropsch (FT) synthesis, and the like. The synthesis gas production apparatus 1 comprises a reactor 10, a gas supply unit 20, and a control unit 30.

[0014] Reactor 10 is a cylindrical container filled with catalyst CA, which promotes the reverse water-gas shift reaction using carbon dioxide and hydrogen. Catalyst CA is formed by filling the inside of reactor 10 with Na2CO3 / Al2O3 pellets. Na2CO3 / Al2O3 pellets are produced by impregnating alumina (Al2O3) pellets with an aqueous sodium carbonate (Na2CO3) solution, drying them in the air, and then calcining them at 550°C for 5 hours.

[0015] The gas supply unit 20 is a device capable of supplying a first raw material gas containing carbon dioxide and oxygen, and a second raw material gas containing hydrogen, to the reactor 10. The first raw material gas is a gas that mimics the exhaust gas discharged from the combustion device. In addition to the first and second raw material gases, the gas supply unit 20 can also supply an inert gas to the reactor 10. Examples of inert gases include nitrogen. The gas supply unit 20 may be composed of a collection of separate devices capable of supplying each of the first raw material gas, the second raw material gas, and the inert gas, or it may be composed of a single device capable of switching between supplying the first raw material gas, the second raw material gas, and the inert gas.

[0016] The control unit 30 is a computer comprising ROM, RAM, and CPU, and controls the gas supply unit 20. Specifically, the control unit 30 controls the supply of the first raw material gas, the second raw material gas, and the inert gas by the gas supply unit 20. In the synthesis gas production apparatus 1, the temperature of the reactor 10 is adjustable by a heater (not shown), etc. The upstream side U and downstream side D shown in Figure 1 are used in the explanation of Figure 2.

[0017] In the synthesis gas production apparatus 1, the control unit 30 controls the gas supply unit 20 to supply the reactor 10 with a first raw material gas, and then with a second raw material gas, thereby releasing synthesis gas from the reactor 10. Specifically, when the first raw material gas is supplied to the reactor 10, the carbon dioxide held in the catalyst CA is used in a reverse water-gas shift reaction together with the hydrogen contained in the second raw material gas supplied next, thereby generating carbon monoxide. Then, the carbon monoxide and the hydrogen contained in the second raw material gas are mixed, and synthesis gas is released from the reactor 10.

[0018] Furthermore, in the synthesis gas production apparatus 1, the control unit 30 controls the gas supply unit 20 so that after supplying the first raw material gas to the reactor 10, an inert gas is supplied to the reactor 10 before supplying the second raw material gas to the reactor 10. In other words, the control unit 30 controls the gas supply unit 20 so that an inert gas is supplied between the supply of the first raw material gas and the supply of the second raw material gas. This control prevents the oxygen contained in the first raw material gas and the hydrogen contained in the second raw material gas from mixing in the synthesis gas production apparatus 1. In the synthesis gas production apparatus 1, synthesis gas is produced by repeatedly supplying each gas in the order of first raw material gas → inert gas → second raw material gas → inert gas → first raw material gas →… For this reason, in the synthesis gas production apparatus 1, the control unit 30 controls the gas supply unit 20 so that an inert gas is supplied to the reactor 10 after the second raw material gas has been supplied to the reactor 10 and before the first raw material gas is supplied to the reactor 10.

[0019] Figure 2 is an explanatory diagram of the characteristics of catalyst CA. Figure 2 shows the results of gas chromatography with catalyst CA and reactor 10 considered as the stationary phase and column, respectively. The horizontal axis of Figure 2 shows the elapsed time since the carrier gas (inert gas) containing the target substance was supplied to catalyst CA. The thick line L1 in Figure 2 shows the change in carbon dioxide concentration detected downstream of catalyst CA (see Figure 1) after supplying a carrier gas containing 45% carbon dioxide from upstream of catalyst CA U (see Figure 1) at a flow rate of 270 ml / min to catalyst CA for 18 seconds. The retention time T1 shows the time from the start of supply of the carbon dioxide-containing carrier gas until the concentration of carbon dioxide detected downstream D reaches its peak.

[0020] The thin line L2 in Figure 2 shows the change in oxygen concentration detected at D downstream of catalyst CA after supplying a carrier gas containing 20% ​​oxygen to catalyst CA from U upstream of catalyst CA at a flow rate of 270 ml / min for 18 seconds. The retention time T2 indicates the time from when the supply of oxygen-containing carrier gas begins until the oxygen concentration detected at downstream D reaches its peak.

[0021] Figure 3 shows the gas chromatography results, similar to Figure 2, with catalyst CA and reactor 10 considered as the stationary phase and column, respectively. The thick line L3 in Figure 3 indicates the change in hydrogen concentration detected downstream of catalyst CA (D) after supplying a carrier gas containing 50% hydrogen from upstream of catalyst CA (U) at a flow rate of 270 ml / min to catalyst CA for 18 seconds. The retention time T3 indicates the time from the start of supplying the hydrogen-containing carrier gas until the hydrogen concentration detected downstream (D) reaches its peak.

[0022] The thin line L4 in Figure 3 shows the change in carbon monoxide concentration detected at D downstream of catalyst CA after supplying a carrier gas containing 35% carbon monoxide from U upstream of catalyst CA to catalyst CA at a flow rate of 270 ml / min for 18 seconds. The retention time T4 indicates the time from when the supply of the carbon monoxide-containing carrier gas begins until the carbon monoxide concentration detected at downstream D reaches its peak.

[0023] As shown in Figures 2 and 3, among the retention times T1 to T4, retention time T1 is the longest. That is, when carbon dioxide, oxygen, hydrogen, and carbon monoxide (hereinafter also referred to as various gases) are supplied to catalyst CA simultaneously, carbon dioxide reaches its peak the latest and can therefore be considered to be retained in catalyst CA for the longest time. Thus, catalyst CA not only promotes the reverse water-gas shift reaction but also functions as a stationary phase in which the retention time of carbon dioxide (exemplified as T1) is longer than that of oxygen, hydrogen, and carbon monoxide (exemplified as T2 to T4).

[0024] Figure 4 is an explanatory diagram showing the retention times when various gases are supplied to column A or column B under various temperature conditions. Column A is a reactor 10 packed with catalyst CA prepared using Mizusawa Chemical's Neobeat MSC#300 (particle size 90-425 μm) as alumina pellets impregnated with an aqueous sodium carbonate solution. Column B is a reactor 10 packed with catalyst CA prepared using Sumitomo Chemical's activated alumina KHO12 (particle size 1-2 mm) as alumina pellets impregnated with an aqueous sodium carbonate solution. Figure 4 shows the retention times of various gases in column A under temperature conditions of 500°C, 550°C, and 600°C, and the retention times of various gases in column B under temperature conditions of 600°C. As shown in Figure 4, under all temperature conditions for both column A and column B, carbon dioxide was retained in catalyst CA for the longest time among the various gases. In Figure 4, ΔT refers to the difference between the retention time of carbon dioxide and the retention time of oxygen in catalyst CA.

[0025] Figures 5 and 6 show the CO2 conversion rates when a raw material gas containing carbon dioxide (25%) and hydrogen (75%) is supplied to column A or column B under various temperature conditions. The CO2 conversion rate is the amount of carbon monoxide produced from column A (column B) relative to the amount of carbon dioxide supplied to column A (column B). When the raw material gas is supplied to columns A and B, only carbon monoxide is observed as a product converted from carbon dioxide, so the CO2 conversion rate can also be considered as the CO yield. The solid line Ra in Figure 5 shows the CO2 conversion rate by column A supplied with the above-mentioned raw material gas. The solid line Rb in Figure 6 shows the CO2 conversion rate by column B supplied with the above-mentioned raw material gas. The dashed line Eq in Figures 5 and 6 shows the theoretical equilibrium conversion rate when the above-mentioned raw material gas is supplied under various temperature conditions. The equilibrium conversion rate is the conversion rate when the reverse water-gas shift reaction reaches equilibrium.

[0026] As shown in Figures 5 and 6, it was confirmed that the CO2 conversion rate increased with increasing temperature in both column A and column B. This confirms that catalyst CA, being packed in both column A and column B, possesses the activity for the reverse water-gas shift reaction using carbon dioxide and hydrogen. Furthermore, it was confirmed that the CO2 conversion rate reached the equilibrium conversion rate at temperatures above 500°C in both column A and column B. Therefore, catalyst CA was also confirmed to be a catalyst with high activity for the reverse water-gas shift reaction.

[0027] Figures 7 and 8 are tables showing the results of the synthesis gas production capacity evaluation tests in reactor 10. In the evaluation tests, each of the gases was repeatedly supplied to each of the reactors 10 under evaluation (Examples 1 to 28) in the order of gas A → gas B → gas C → gas D → gas A →… and the CO2 conversion rate was evaluated when the concentration pattern of the gases discharged from the reactor 10 for one cycle stabilized. Gas A is a carrier gas (inert gas) containing 10% carbon dioxide and 10% oxygen. Gases B and D are 100% carrier gases (inert gases). Gas C is 100% hydrogen gas. In the evaluation tests, each of gases A to D was supplied to the reactor 10 under evaluation at a flow rate of 270 ml / min.

[0028] Gases A to D correspond to the first raw material gas, inert gas, second raw material gas, and inert gas supplied from the gas supply unit 20 to the reactor 10 in the synthesis gas production apparatus 1 (see Figure 1). Specifically, gas A, a carrier gas containing 10% carbon dioxide and 10% oxygen, corresponds to the first raw material gas containing carbon dioxide and oxygen. Gas C, which is 100% hydrogen gas, corresponds to the second raw material gas containing hydrogen. Gases B and D, which are 100% carrier gases, correspond to inert gases. In other words, the process of repeatedly supplying each gas in the order of gas A → gas B → gas C → gas D → gas A →… in the evaluation test is the same as the process of repeatedly supplying each gas in the order of first raw material gas → inert gas → second raw material gas → inert gas → first raw material gas →… when synthesis gas is produced by the synthesis gas production apparatus 1.

[0029] As shown in the tables in Figures 7 and 8, Examples 1 to 28 differ in "column," "temperature," and "gas supply time." In the tables in Figures 7 and 8, "column" indicates whether each of Examples 1 to 28 uses column A or column B as described in Figure 4. In the tables in Figures 7 and 8, "temperature" is the temperature for each of Examples 1 to 28 when gases A to D are supplied, and the unit is °C. In the "gas supply time" column in Figures 7 and 8, "gas A," "gas B," "gas C," and "gas D" are the supply times for gases A to D in each of Examples 1 to 28, and the unit is min. "Gas A," "gas B," "gas C," and "gas D" indicate the supply time of each gas in one cycle.

[0030] In the tables in Figures 7 and 8, "ΔT" represents the difference between the retention time of carbon dioxide by catalyst CA and the retention time of oxygen by catalyst CA in each of Examples 1 to 28, and the unit is min. For example, in Example 1, "ΔT" is 0.47 min, so 0.47 (min) × 60 (seconds) = 28.2 seconds. The "ΔT" in each of Examples 1 to 28 was measured in advance using the same method as described in Figures 2 and 3. In the tables in Figures 7 and 8, "Gas A supply time / ΔT" is the value obtained by dividing the value of "Gas A" by the value of "ΔT" in each of Examples 1 to 28. For example, in Example 1, 0.47 min (value of "Gas A") / 0.47 min (value of "ΔT") = 1.00. In Examples 1 to 20, "Gas A supply time / ΔT" was set to a value within the range of 0.33 to 3.00, while in Examples 21 to 28, "Gas A supply time / ΔT" was set to a value less than 0.33 or greater than 3.00.

[0031] In the tables in Figures 7 and 8, the "Supply H2 / CO2 Ratio" is the value obtained by dividing the amount of hydrogen supplied by the amount of carbon dioxide supplied in each of Examples 1 to 28. For example, in Example 1, the amount of hydrogen supplied by gas C (100% hydrogen gas) in one cycle is 270 ml / min × 1 (100%) × 0.14 min = 37.8 ml, and the amount of carbon dioxide supplied by gas A (carrier gas containing 10% carbon dioxide) in one cycle is 270 ml / min × 0.1 (10%) × 0.47 min = 12.69 ml. Therefore, the "Supply H2 / CO2 Ratio" is 37.8 / 12.69 ≈ 3.0. Note that in all of Examples 1 to 27, except for Example 28, "Gas A" and "Gas C" were set so that the "Supply H2 / CO2 Ratio" was 3.0.

[0032] In the tables in Figures 7 and 8, "CO2 conversion rate" is the amount of carbon dioxide supplied to each of Examples 1 to 28 during one cycle, divided by the amount of carbon monoxide produced from each of Examples 1 to 28 during one cycle, and the unit is %. In the tables in Figures 7 and 8, "H2 / CO ratio produced" is the value obtained by dividing the hydrogen content in the gas discharged from each of Examples 1 to 28 when gas C is supplied by the carbon monoxide content in the same gas.

[0033] In the tables in Figures 7 and 8, examples with the same "column" and "temperature" were compared. Comparing the "CO2 conversion rate" of Example 1 and Example 21, where the "column" was column A and the "temperature" was 600°C, Example 1 had a higher conversion rate than Example 21. Comparing the "CO2 conversion rate" of Examples 2-10 and Examples 22-24, where the "column" was column A and the "temperature" was 550°C, Examples 2-10 generally had a higher conversion rate than Examples 22-24. Comparing the "CO2 conversion rate" of Examples 12-20 and Examples 25-28, where the "column" was column B and the "temperature" was 600°C, Examples 12-20 generally had a higher conversion rate than Examples 25-28.

[0034] Figure 9 is an explanatory diagram showing the relationship between "Gas A supply time / ΔT" and "CO2 conversion rate". Figure 9 shows the correspondence between "Gas A supply time / ΔT" and "CO2 conversion rate" in Examples 2-10 and Examples 22 and 23, where the "column" is Column A and the "temperature" is 550°C, as shown in the evaluation test results in Figures 7 and 8. The white circles in Figure 9 represent the data for Examples 2-10, and the black circles represent the data for Examples 22 and 23.

[0035] Figure 10, like Figure 9, is an explanatory diagram showing the relationship between "Gas A supply time / ΔT" and "CO2 conversion rate". Figure 10 shows the correspondence between "Gas A supply time / ΔT" and "CO2 conversion rate" in Examples 12-20 and Examples 25 and 26, from the evaluation test results shown in Figures 7 and 8, where the "column" is column B and the "temperature" is 600°C. The white circles in Figure 10 represent the data for Examples 12-20, and the black circles in Figure 10 represent the data for Examples 25 and 26.

[0036] In both Figure 9 and Figure 10, the CO2 conversion rate was highest when "Gas A supply time / ΔT" was 1.00. In other words, the CO2 conversion rate was highest when "Gas A" (the supply time of Gas A) was equal to "ΔT" (the difference between the retention time of carbon dioxide by catalyst CA and the retention time of oxygen by catalyst CA). It was also confirmed that the CO2 conversion rate was relatively high when "Gas A supply time / ΔT" was within the range of 0.33 to 3.00, preferably within the range of 0.50 to 2.00. Therefore, in the synthesis gas production apparatus (see Figure 1), the control unit 30 controls the gas supply unit 20 so that the supply time of the first raw material gas by the gas supply unit 20 is within a range of 0.33 to 3.00 times the time difference (ΔT) between the retention time of carbon dioxide by catalyst CA and the retention time of oxygen by catalyst CA.

[0037] Using FIGS. 11 to 13, the reason why the CO2 conversion rate improves when the supply time of the first raw material gas (corresponding to gas A) is set near ΔT will be explained. FIGS. 11 to 13 are explanatory diagrams conceptually showing each gas passing through the catalyst CA. The upstream side U and the downstream side D shown in FIGS. 11 to 13 are the same as the upstream side U and the downstream side D shown in FIG. 1. The arrows shown in FIGS. 11 to 13 indicate the flow direction of each gas flowing from the upstream side U toward the downstream side D.

[0038] FIG. 11 is an explanatory diagram conceptually showing each gas when the second raw material gas is supplied for a time t after the first raw material gas is supplied for a length of ΔT. In the state of FIG. 11, the first raw material gas G CO2 , O2 is just before entering the catalyst CA, and the second raw material gas G H2 is upstream of the first raw material gas G1G CO 2, O2 . The area of each gas shown in FIGS. 11 to 13 represents the amount of each gas.

[0039] FIG. 12 is an explanatory diagram conceptually showing each gas at the point when the holding time of oxygen by the catalyst CA has elapsed after the first raw material gas is supplied. In the state of FIG. 12, the first raw material gas G1 (see FIG. 11) is not shown, and the carbon dioxide gas G CO2 and the oxygen gas G O2 are shown separately. This is because the difference between the holding time of carbon dioxide by the catalyst CA and the holding time of oxygen by the catalyst CA is relatively large, so that in the process of the first raw material gas G1 passing through the catalyst CA, the carbon dioxide gas G CO2 and the oxygen gas G O2 are separated. As shown in FIG. 12, at the point when the holding time of oxygen by the catalyst CA has elapsed, a part of the oxygen gas G O2 has begun to flow out of the catalyst CA, while the carbon dioxide gas G CO2 is held throughout the catalyst CA. The second raw material gas G H2 is such that the holding time of oxygen by the catalyst CA and the holding time of hydrogen by the catalyst CA are equal (see FIG. 4), so the oxygen gas G O2It is moving in pursuit of the second raw material gas G. H2 And the carbon dioxide gas G held in catalyst CA CO2 Through a reverse water-gas shift reaction with carbon monoxide gas G CO This is being generated. Meanwhile, this carbon monoxide gas G CO In response to the increase in the amount of production of the second raw material gas G H2 The amount is decreasing.

[0040] Figure 13 is a conceptual diagram illustrating each gas at the time after the carbon dioxide retention time by the catalyst CA has elapsed since the supply of the first raw material gas. As shown in Figure 13, at the time after the carbon dioxide retention time by the catalyst CA has elapsed, carbon dioxide gas G CO2 Some of it has begun to leak from the catalyst CA, as well as the second raw material gas G H2 It passes through almost the entire area of ​​catalyst CA. Also, in the state shown in Figure 13, the second raw material gas G H2 When the gas passed through the entire catalyst CA, the carbon dioxide gas G that was retained throughout the entire area was still present. CO2 As a result of the reverse water-gas shift reaction, more carbon monoxide gas G is present compared to the state shown in Figure 12. CO This is being generated. Therefore, the second raw material gas G H2 The amount has decreased even further compared to the state in Figure 12, and carbon monoxide gas G CO The amount produced has increased compared to the state shown in Figure 12.

[0041] As shown in Figure 13, when the supply time of the first raw material gas is set to around ΔT, the carbon dioxide gas G that was retained throughout the catalyst CA region CO2 The second raw material gas G H2 This allows for a reverse water-gas shift reaction, which is thought to improve the CO2 conversion rate. On the other hand, if the supply time of the first raw material gas becomes significantly longer than ΔT, the second raw material gas G H2 And carbon dioxide gas G flows out of catalyst CA without causing a reverse water-gas shift reaction. CO2As the amount increases, the CO2 conversion rate is expected to decrease. Also, if the supply time of the first raw material gas becomes significantly shorter than ΔT, the second raw material gas G H2 As the carbon dioxide gas G is passed through the entire catalyst CA, the carbon dioxide gas G held in the catalyst CA is CO2 Because the amount decreases, the CO2 conversion rate is thought to decrease.

[0042] As shown in the table in Figure 7, the CO2 conversion rates for Examples 5 and 6, where the column is column A and the temperature is 550°C, were 56.43% and 55.58%, respectively. In Examples 5 and 6, as described above, gas A and gas C are supplied to reactor 10 (column A) at different timings, meaning that carbon dioxide and hydrogen are supplied to reactor 10 (column A) at different timings. Also, the supply H2 / CO2 ratio in Examples 5 and 6 was 3.0. On the other hand, the equilibrium conversion rate (the conversion rate when the reverse water-gas shift reaction reaches equilibrium) when carbon dioxide and hydrogen are supplied simultaneously under a temperature condition of 550°C with a supply H2 / CO2 ratio of 3.0 is 55.2% (see dashed line Eq in Figures 5 and 6). In other words, the "CO2 conversion rate" in Examples 5 and 6 exceeds the equilibrium conversion rate under the same conditions as Examples 5 and 6 (temperature 550°C, "supply H2 / CO2 ratio" of 3.0).

[0043] As shown in the table in Figure 7, the CO2 conversion rates for Examples 12-17, where the "column" was column B and the "temperature" was 600°C, ranged from 60.73 to 73.59. In Examples 12-17, similar to Examples 5 and 6, carbon dioxide and hydrogen were supplied to reactor 10 (column B) at different timings, and the "supply H2 / CO2 ratio" was 3.0. On the other hand, the equilibrium conversion rate when carbon dioxide and hydrogen are supplied simultaneously under a temperature of 600°C with a "supply H2 / CO2 ratio" of 3.0 is 60.0% (see dashed line Eq in Figures 5 and 6). In other words, the CO2 conversion rates of Examples 12-17 exceed the equilibrium conversion rates under the same conditions as Examples 12-17 (temperature 600°C, "supply H2 / CO2 ratio" of 3.0).

[0044] Thus, the inventors have demonstrated that by supplying carbon dioxide and hydrogen at different timings, it is possible to reach a CO2 conversion rate that cannot be achieved when carbon dioxide and hydrogen are supplied simultaneously. Because the reverse water-gas shift reaction is constrained by chemical equilibrium, the CO2 conversion rate is usually limited to the equilibrium conversion rate, which is the conversion rate at chemical equilibrium. However, the inventors have demonstrated that by supplying carbon dioxide and hydrogen at different timings, it is possible to produce carbon monoxide at a CO2 conversion rate exceeding the equilibrium conversion rate. This is due to the carbon dioxide gas G CO2 Catalyst CA, in a state where it is maintained throughout the entire area, is used with the second raw material gas G H2 When it passes through, locally carbon dioxide gas G CO2 Against the second raw material gas G H2 This is thought to be because a large amount of this substance is present, causing the equilibrium to shift in the direction in which the reverse water-gas shift reaction proceeds (the direction in which carbon monoxide is produced).

[0045] In the reverse water-gas shift reaction, generally, a higher supply H2 / CO2 ratio tends to improve the CO2 conversion rate in equilibrium, but at the same time, the H2 / CO ratio in the resulting synthesis gas also tends to increase. Synthesis gas with a high H2 / CO ratio is unsuitable for use as a raw material gas for the Fischer-Tropsch reaction. In Examples 1 to 20 shown in the table in Figures 7 and 8, the supply H2 / CO2 ratio was set to a relatively low 3.0 in all cases, and the H2 / CO ratio in the resulting synthesis gas was in the range of 2.93 to 5.99, making it suitable for use as a raw material gas for the Fischer-Tropsch reaction. On the other hand, in Non-Patent Document 1 mentioned above, a large amount of hydrogen is supplied during the reverse water-gas shift reaction, resulting in an H2 / CO ratio of 100 or more in the resulting synthesis gas, making it unsuitable for use as a raw material gas for the Fischer-Tropsch reaction. Therefore, it can be said that the synthesis gas production apparatus 1 has higher practicality compared to the technology disclosed in Non-Patent Document 1.

[0046] According to the synthesis gas production apparatus 1 of the embodiment described above, the CO2 conversion rate can be improved by supplying a first raw material gas (containing carbon dioxide and oxygen) to the reactor 10, and then supplying a second raw material gas (containing hydrogen) to the reactor 10. In other words, by supplying the first raw material gas containing carbon dioxide and the second raw material gas containing hydrogen at different timings rather than simultaneously, the amount of carbon monoxide produced can be increased.

[0047] As described above, the first raw material gas is a gas that mimics the exhaust gas emitted from a combustion device. Even if we try to produce carbon monoxide by reacting hydrogen with carbon dioxide in the exhaust gas, the hydrogen is consumed by the oxygen in the exhaust gas, making it impossible to convert the carbon dioxide in the exhaust gas into carbon monoxide with high efficiency. Therefore, in order to separate carbon dioxide from the exhaust gas, the use of chemical absorption methods or physical adsorption methods using pressure swing (PSA) or temperature swing (TSA) is considered, but the equipment for implementing these methods tends to be large and complex. On the other hand, according to the synthesis gas production apparatus 1 of the embodiment described above, carbon dioxide can be retained by the catalyst CA packed in the reactor 10, so carbon dioxide can be separated from exhaust gas containing carbon dioxide and oxygen with a simple configuration.

[0048] Furthermore, in the synthesis gas production apparatus 1 of this embodiment, the control unit 30 controls the gas supply unit 20 so that the supply time of the first raw material gas by the gas supply unit 20 is within a range of 0.33 to 3.0 times the time difference (ΔT) between the retention time of carbon dioxide by catalyst CA and the retention time of oxygen by catalyst CA (see Figures 7 to 10). This makes it possible to further improve the CO2 conversion rate. In addition, depending on the supply time of the first raw material gas within this range, it is also possible to produce carbon monoxide at a CO2 conversion rate exceeding the equilibrium conversion rate (see Examples 5, 6, 12 to 17).

[0049] Furthermore, in the synthesis gas production apparatus 1 of this embodiment, the gas supply unit 20 is controlled to supply an inert gas between the supply of the first raw material gas and the supply of the second raw material gas. This prevents the mixing of oxygen contained in the first raw material gas and hydrogen contained in the second raw material gas. Thus, safety in the operation of the synthesis gas production apparatus 1 can be ensured.

[0050] <Another embodiment> Figure 14 is an explanatory diagram showing the retention times when various gases are supplied to various columns under various temperature conditions. The various gases refer to carbon dioxide, oxygen, hydrogen, and carbon monoxide, as mentioned above. The various columns shown in Figure 14 are reactors packed with catalyst CA, which is prepared by drying and calcining alumina pellets impregnated with one of the following: lithium carbonate (Li2CO3) aqueous solution, sodium carbonate (Na2CO3) aqueous solution, or potassium carbonate (K2CO3) aqueous solution. In other words, the catalyst CA packed into the various columns shown in Figure 14 contains an alkali metal compound selected from lithium, sodium, and potassium, and a carrier mainly composed of aluminum oxide that supports the compound. Here, "main component" refers to the component with the highest volume content. "Alumina particle size" in Figure 14 refers to the particle size of the alumina pellets used to prepare the various columns, in units of mm. "Alkali metal carbonate" in Figure 14 refers to the aqueous solution impregnated into the alumina pellets during the preparation of the various columns. In Figure 14, "Loaded Amount" refers to the amount of alkali metal carbonate loaded onto the alumina pellet, and the unit is mmol / g. The other items in Figure 14 are the same as in Figure 4.

[0051] As shown in Fig. 14, similar to Fig. 4, the retention times of various gases by various columns under the temperature conditions of 500 °C, 550 °C, and 600 °C are shown. As shown in Fig. 14, among the various columns under each temperature condition, the gas that was retained by the catalyst CA for the longest time among the various gases was carbon dioxide. Also, it was confirmed that the retention time of carbon dioxide by the catalyst CA increased as the loading amount of the "alkali metal carbonate" increased. Furthermore, when comparing Column D, Column H, and Column K with a "loading amount" of 0.75 mmol / g under the temperature condition of 600 °C, it was confirmed that the retention time of carbon dioxide by the catalyst CA increased in the order of Li2CO3 < Na2CO3 < K2CO3. That is, it was found that the retention time of carbon dioxide by the catalyst CA increased as the basic strength of the alkali metal increased. This is presumably because the higher the basic strength, the stronger the retention (adsorption) of carbon dioxide.

[0052] Figs. 15 and 16 are tables showing the results of the evaluation tests of the syngas production ability in the reactor 10. In Figs. 15 and 16, the results of the evaluation tests by the same method as the evaluation tests described in Figs. 7 and 8 are shown. In the tables of Fig. 15 and Fig. 16, "Column" indicates which of the columns A to L described in Fig. 14 each of the reactors 10 to be evaluated (Examples 29 to 63) is. Also, "Alkali Metal Carbonate" in the tables of Fig. 15 and Fig. 16 is the same as in Fig. 14. Although the "Supply H2 / CO2 ratio" shown in the tables of Figs. 7 and 8 is not shown in the tables of Fig. 15 and Fig. 16, "Gas A" and "Gas C" were set so that it would be 3.0 in any of Examples 29 to 63. Also, "Gas A Supply Time / ΔT" was set to a value within the range of 0.33 to 3.00 in any of Examples 29 to 63. In the table of Fig. 15, in addition to Examples 29 to 47, Examples 12 to 20 (see Fig. 7) were included to make the trend easier to understand.

[0053] As shown in the tables in Figures 15 and 16, a high CO2 conversion rate could be obtained in any column impregnated with an alkali metal carbonate by setting the gas A supply time / ΔT to a value within the range of 0.33 to 3.00, and the maximum CO2 conversion rate could be selected from among them. Next, comparing columns C to E (Examples 29 to 32) impregnated with Li2CO3 as the alkali metal carbonate, column E (Example 32) showed the highest CO2 conversion rate. According to Figure 14, column E (Example 32) has a loading amount of 1.5 mmol / g. On the other hand, comparing columns B, F to H (Examples 12 to 20, 33 to 47) impregnated with Na2CO3 as the alkali metal carbonate, column H (Example 41) showed the highest CO2 conversion rate. According to Figure 14, column H (Example 41) has a loading amount of 0.75 mmol / g. Furthermore, comparing columns I-L (Examples 48-63) impregnated with K2CO3 as the alkali metal carbonate, column J (Example 50) showed the highest CO2 conversion rate. According to Figure 14, column J (Example 50) had a loading capacity of 0.50 mmol / g. This clearly demonstrated that an optimal loading capacity exists for each column impregnated with the alkali metal carbonate. Additionally, it was found that the higher the basicity of the alkali metal (K > Na > Li), the lower the optimal loading capacity for each alkali metal carbonate. Thus, the results shown in the tables of Figure 15 and Figure 16 suggest the existence of a CO2 adsorption capacity that is effective in improving the CO2 conversion rate.

[0054] Figures 17 to 20 are explanatory diagrams showing the measurement results of various columns using the carbon dioxide thermal desorption method. The carbon dioxide thermal desorption method was used to investigate the CO2 adsorption capacity of catalyst CA packed into various columns. The procedure for the carbon dioxide thermal desorption method used to obtain the measurement results shown in Figures 17 to 20 is described below. First, 0.50 g of catalyst CA was heated at 600°C for 30 minutes while supplying a 2% O2 / He mixed gas as a pretreatment, and then cooled to 100°C while supplying He gas. Next, a 5% CO2 / He mixed gas was supplied under a temperature of 100°C until carbon dioxide was considered to be saturated adsorbed on the catalyst CA (15 minutes in this case), and then the carbon dioxide that could be removed from the catalyst CA was removed by supplying an inert gas (He gas in this case) for 10 minutes under the same temperature conditions. Finally, carbon dioxide was desorbed from the catalyst CA by raising the temperature while supplying an inert gas (He gas in this case) at a rate of 30 mL / min. At this time, the amount of carbon dioxide desorbed from catalyst CA when the temperature was increased from 100°C to 800°C at a rate of 10°C / min was measured using a mass spectrometer. The time until carbon dioxide is considered to be saturated adsorbed onto catalyst CA is assumed to be determined in advance by measuring the CO2 concentration downstream of catalyst CA while supplying a 5% CO2 / He mixed gas, or by observing the weight change of catalyst CA when the 5% CO2 / He mixed gas is supplied.

[0055] Figures 17 to 20 each show the spectra of various columns measured by the carbon dioxide thermal desorption method. The horizontal axis of Figures 17 to 20 represents the temperature of catalyst CA, and the vertical axis represents the concentration of carbon dioxide desorbed from catalyst CA. Figure 17 shows the spectra of columns C to E. Figure 18 shows the spectra of columns B, F to H. Figure 19 shows the spectra of columns I to L. In addition, each of Figures 17 to 19 also shows the spectra of a catalyst packed with alumina pellets that are not impregnated with alkali metal carbonates. Furthermore, Figure 20 corresponds to an enlarged vertical axis scale (upper limit 0.5) of Figure 19, displaying up to an upper limit of 2.0.

[0056] Figure 21 is an explanatory diagram showing the amount of CO2 desorption in each temperature range calculated from the spectra of various columns shown in Figures 17 to 20. Figure 21 shows the amount of CO2 desorption in three temperature ranges: 100-500°C, 500-650°C, and 650-800°C.

[0057] As shown in Figures 17-19, in all columns impregnated with alkali metal carbonate, as the amount of alkali metal carbonate increased (see Figure 21), the temperature characteristics did not change, and the spectrum did not become higher overall; rather, the spectrum in the higher temperature range increased. Furthermore, in columns H, B, K, and L, which had a large amount of alkali metal carbonate, two spectra were observed, one with a peak in the low temperature range of 200-300°C and the other in the high temperature range around 750°C. The higher the amount of alkali metal carbonate, the greater the peak in the high temperature range. Generally, spectra measured by the carbon dioxide thermal desorption method (CO2-TPD spectra) show the amount of basic sites and the basicity intensity. Therefore, it became clear that as the amount of alkali metal carbonate increased, not only did the number of basic sites adsorbing CO2 increase, but the basicity intensity also increased. Basicity intensity here can be said to be the degree of CO2 adsorption.

[0058] Referring to Figure 15, the "CO2 conversion rates" for columns C, D, and F were 20.33%, 41.55%, and 28.44%, respectively, making them the three columns with the lowest "CO2 conversion rates." Furthermore, referring to Figures 17 and 18, CO2 desorption was completed up to 500°C in columns C, D, and F. Basic sites that cannot adsorb CO2 at 500°C are considered non-functional in the synthesis gas production apparatus 1. In other words, basic sites capable of adsorbing CO2 even above 500°C are necessary.

[0059] As described above, the "CO2 conversion rates" of columns C, D, and F were all low, less than 42% (similar to Examples 21-28 shown in Figure 8), and according to Figure 21, the amount of CO2 desorbed in the temperature range of 500-650°C was less than 0.0010 mmol / g. On the other hand, the "CO2 conversion rates" of columns E, G, H, B, and I-L were all 45% or higher (depending on the conditions for column G), and according to Figure 21, the amount of CO2 desorbed in the temperature range of 500-650°C was 0.0030 mmol / g or higher. From the above, it was determined that in order to obtain a high "CO2 conversion rate," it is preferable that the amount of CO2 desorbed from catalyst CA when the temperature is raised from 500°C to 650°C by the carbon dioxide heating desorption method (hereinafter sometimes referred to as the first desorption amount) be 0.0030 mmol / g or higher. This is likely because synthesis gas production apparatus 1 requires a certain level of CO2 adsorption capacity at temperatures above 500°C.

[0060] Furthermore, in columns E, H, and J, which showed the highest "CO2 conversion rate" among the columns impregnated with Li2CO3, Na2CO3, and K2CO3 respectively, the spectra in the high-temperature range were very small or almost not observed. In other words, in these columns, the amount of CO2 desorbed from catalyst CA when the temperature is raised from 650°C to 800°C (second desorption amount) is less than the first desorption amount (the amount of CO2 desorbed from catalyst CA when the temperature is raised from 500°C to 650°C). This is thought to be because the basic sites that do not desorb CO2 even above 650°C stabilize the CO2 too much, so it is not reduced by H2 and remains adsorbed, making it difficult for the synthesis gas production apparatus 1 to function. From the above, it was confirmed that in order to obtain a high "CO2 conversion rate" using the synthesis gas production apparatus 1, it is preferable that the first desorption amount (the amount of CO2 desorbed from catalyst CA when the temperature is raised from 500°C to 650°C) is 0.0030 mmol / g or more, and that the second desorption amount (the amount of CO2 desorbed from catalyst CA when the temperature is raised from 650°C to 800°C) is less than the first desorption amount. In other words, it was confirmed that it is preferable for catalyst CA packed into reactor 10 to be catalyst CA in which the second desorption amount is less than the first desorption amount.

[0061] Next, we will explain the results of further investigations regarding the operating conditions applied to the synthesis gas production apparatus 1. In the synthesis gas production apparatus 1, in addition to the CO2-O2 separation performance when the first raw material gas is supplied, the reverse water-gas shift (RWGS) reaction activity between the CO2 retained in the catalyst CA from the first raw material gas and the H2 supplied as the second raw material gas is considered to be an important factor.

[0062] Figure 22 shows the CO2 conversion rate when a raw material gas containing carbon dioxide (25%) and hydrogen (75%) is supplied to column F under various temperature conditions. Figures 5 and 6 showed that the CO2 conversion rate reached the equilibrium conversion rate at temperatures above 500°C. However, the results shown in Figures 5 and 6 may not have yielded sufficient RWGS reaction activity because the space velocity was high, i.e., the contact time between the catalyst and the reaction gas was short. Therefore, the CO2 conversion rate was measured when the contact time of the raw material gas containing carbon dioxide (25%) and hydrogen (75%) was tripled compared to when the results shown in Figures 5 and 6 were obtained, i.e., the space velocity was reduced to 1 / 3 and supplied to column F. Figure 22 shows the measurement results. In addition, the flow rate of the raw material gas when obtaining the results shown in Figures 5 and 6 was 270 mL / min, while the flow rate of the raw material gas when obtaining the results shown in Figure 22 was 90 mL / min. As shown in Figure 22, it was confirmed that reducing the flow rate of the raw material gas improved the CO2 conversion rate around 360-460°C. Based on these results, it is expected that reducing the flow rate of the raw material gas will also improve the RWGS reaction activity around 550°C.

[0063] Figures 23 and 24 are tables showing the results of evaluation tests of the synthesis gas production capacity in reactor 10. Figures 23 and 24 show the results of evaluation tests conducted using the same method as the evaluation tests described in Figures 7 and 8. The results shown in Figure 23 are based on Examples 64 to 73, where gas C was supplied at a flow rate of 270 ml / min. In Examples 74 to 83, gas C was supplied at a flow rate of 90 ml / min for three times the supply time of gas C in Examples 64 to 73. The results shown in Figure 24 are based on Examples 84 to 93, where gas C was supplied at a flow rate of 270 ml / min. In Examples 94 to 103, gas C was supplied at a flow rate of 90 ml / min for three times the supply time of gas C in Examples 84 to 93. Referring to the combinations of examples where "Gas A" (and the supply time of Gas A) is the same, such as Examples 66 and 76, 67 and 77, 68 and 78, 86 and 96, 87 and 97, and 88 and 98, it was confirmed that the "CO2 conversion rate" improved by approximately 1% by tripling the "Gas C" (and the supply time of Gas C) while reducing the flow rate of Gas C to 1 / 3. From these results, it was confirmed that in order to obtain a high "CO2 conversion rate" using the synthesis gas production apparatus 1, it is preferable to reduce the flow rate when supplying the second raw material gas (raw material gas containing hydrogen) while extending the supply time of the second raw material gas. Furthermore, compared to the evaluation tests in Figures 7, 8 and 15, 16, where the flow rates of the first raw material gas (270 ml / min) and the second raw material gas (270 ml / min) were the same, in the evaluation tests in Figures 23, 24, the flow rate of the second raw material gas (90 ml / min) was smaller than the flow rate of the first raw material gas (270 ml / min). Therefore, it can be said that it is preferable for the gas supply unit 20 (see Figure 1) to set the second supply flow rate, which is the flow rate when supplying the second raw material gas to the reactor 10 (see Figure 1), to be smaller than the first supply flow rate, which is the flow rate when supplying the first raw material gas to the reactor 10 (see Figure 1).

[0064] Based on the results of the evaluation tests described above, in a synthesis gas production apparatus 1 equipped with a reactor 10 filled with catalyst CA, it is preferable that the amount of CO2 desorbed from catalyst CA when the temperature is raised from 500°C to 650°C by the carbon dioxide heating desorption method (hereinafter sometimes referred to as the first desorption amount) is 0.0030 mmol / g or more. It has been confirmed from Figures 15, 16, and 21 that a high "CO2 conversion rate" can be obtained in such a case.

[0065] Based on the results of the evaluation tests described above, in a synthesis gas production apparatus 1 equipped with a reactor 10 filled with catalyst CA, it is preferable that the second desorption amount (the amount of CO2 desorbed from catalyst CA when the temperature is raised from 650°C to 800°C) is less than the first desorption amount (the amount of CO2 desorbed from catalyst CA when the temperature is raised from 500°C to 650°C). Figures 15, 16, and 21 confirm that a high "CO2 conversion rate" can be obtained in this case.

[0066] Based on the results of the evaluation tests described above, in a synthesis gas production apparatus 1 equipped with a reactor 10 filled with catalyst CA, it is preferable for the gas supply unit 20 (see Figure 1) to set the second supply flow rate, which is the flow rate when supplying the second raw material gas to the reactor 10 (see Figure 1), to be smaller than the first supply flow rate, which is the flow rate when supplying the first raw material gas to the reactor 10 (see Figure 1). As can be seen from Figures 23 and 24, a high "CO2 conversion rate" can be obtained in this case.

[0067] <Modified form of this embodiment> The present invention is not limited to the embodiments described above, and can be implemented in various forms without departing from its spirit, for example, the following modifications are also possible.

[0068] In the evaluation tests shown in Figures 7 and 8, the supply time of gas B in one cycle was set to 0.30 min or longer in all embodiments. Similarly, in the evaluation tests shown in Figures 23 and 24, the supply time of gas B in one cycle was set to 0.20 min or longer in all embodiments. However, in the synthesis gas production apparatus 1, the supply time of the inert gas may be shorter than 0.20 min, as long as mixing of oxygen contained in the first raw material gas and hydrogen contained in the second raw material gas is prevented.

[0069] In the above embodiment, the supply time of the first raw material gas was controlled to be within a range of 0.33 to 3.0 times ΔT, but is not limited to this. The supply time of the first raw material gas may be controlled to be less than 0.33 times ΔT or longer than 3.00 times ΔT. Of course, from the viewpoint of improving the CO2 conversion rate, it is preferable that the supply time of the first raw material gas is controlled to be within a range of 0.33 to 3.0 times ΔT.

[0070] In the above embodiment, when saturating carbon dioxide adsorption onto the catalyst CA in the carbon dioxide thermal desorption method, a 5% CO2 / He mixed gas (gas containing carbon dioxide) was supplied under a temperature of 100°C, but this is not limited to this. The temperature conditions when saturating carbon dioxide adsorption onto the catalyst CA in the carbon dioxide thermal desorption method may be 100°C ± 20°C. Even with the first and second desorption amounts measured under such temperature conditions, a high "CO2 conversion rate" can be obtained as long as the catalyst CA has a first desorption amount of 0.0030 mmol / g or more, or a second desorption amount less than the first desorption amount.

[0071] In the above embodiment, it was explained that in order to obtain a high "CO2 conversion rate" using the synthesis gas production apparatus 1, it is preferable that the first desorption amount (the amount of CO2 desorbed from catalyst CA when the temperature is raised from 500°C to 650°C) is 0.0030 mmol / g or more, and that the second desorption amount (the amount of CO2 desorbed from catalyst CA when the temperature is raised from 650°C to 800°C) is less than the first desorption amount. However, it is not limited to this. A high "CO2 conversion rate" can be obtained even if at least one of the following conditions is met: the first desorption amount is 0.0030 mmol / g or more, and the second desorption amount is less than the first desorption amount.

[0072] The embodiments of this specification have been described above based on the embodiments and modifications described above. The embodiments described above are for the purpose of facilitating understanding of this specification and do not limit it. This specification may be modified and improved without departing from its spirit and the scope of the claims, and equivalents thereof are included in this specification. Furthermore, any technical features that are not described as essential in this specification may be deleted as appropriate.

[0073] This disclosure can also be implemented in the following forms: [Application Example 1] A synthesis gas production apparatus that produces synthesis gas containing carbon monoxide and hydrogen, A reactor filled with a catalyst that functions as a stationary phase, where the retention time of carbon dioxide is longer than that of oxygen, hydrogen, and carbon monoxide, and which promotes a reverse water-gas shift reaction using carbon dioxide and hydrogen, A gas supply unit capable of supplying a first raw material gas containing carbon dioxide and oxygen and a second raw material gas containing hydrogen to the reactor, The system includes a control unit for controlling the gas supply unit, A synthesis gas production apparatus in which the control unit controls the gas supply unit to supply the second raw material gas to the reactor after supplying the first raw material gas to the reactor, thereby discharging the synthesis gas from the reactor. [Application Example 2] The synthesis gas production apparatus described in Application Example 1, Synthesis gas production apparatus, wherein the control unit controls the gas supply unit so that the supply time of the first raw material gas by the gas supply unit is within a range of 0.33 to 3.00 times the time difference between the retention time of carbon dioxide by the catalyst and the retention time of oxygen by the catalyst. [Application Example 3] A synthesis gas production apparatus as described in Application Example 1 or Application Example 2, The gas supply unit is capable of supplying an inert gas to the reactor in addition to the first raw material gas and the second raw material gas. Synthesis gas production apparatus, wherein the control unit controls the gas supply unit to supply the first raw material gas to the reactor, then the inert gas to the reactor, and then the second raw material gas to the reactor. [Application Example 4] A synthesis gas production apparatus described in any of Application Examples 1 to 3, A synthesis gas production apparatus comprising a carbon dioxide heating desorption method in which a gas containing carbon dioxide is supplied under a temperature condition of 100°C ± 20°C until it is considered that carbon dioxide has been saturated adsorbed onto the catalyst, then carbon dioxide that can be removed from the catalyst is removed by supplying an inert gas under the same temperature conditions, and then carbon dioxide is desorbed from the catalyst by raising the temperature while supplying an inert gas, wherein the first desorption amount, which is the amount of carbon dioxide desorbed from the catalyst when the temperature is raised from 500°C to 650°C, is 0.0030 mmol / g or more. [Application Example 5] A synthesis gas production apparatus described in any of Application Examples 1 to 4, A synthesis gas production apparatus wherein, by the carbon dioxide heating desorption method described above, the second desorption amount, which is the amount of carbon dioxide desorbed from the catalyst when the temperature is raised from 650°C to 800°C, is less than the first desorption amount, which is the amount of carbon dioxide desorbed from the catalyst when the temperature is raised from 500°C to 650°C. [Application Example 6] A synthesis gas production apparatus described in any of Application Examples 1 to 5, The synthesis gas production apparatus wherein the gas supply unit reduces the second supply flow rate, which is the flow rate when supplying the second raw material gas to the reactor, to a lower value than the first supply flow rate, which is the flow rate when supplying the first raw material gas to the reactor. [Application Example 7] A synthesis gas production apparatus described in any of Application Examples 1 to 6, The catalyst comprises an alkali metal compound selected from lithium, sodium, and potassium, and a carrier mainly composed of aluminum oxide that supports the compound, in a synthesis gas production apparatus. [Explanation of symbols]

[0074] 1...Synthesis gas production equipment 10… Reactor 20... Gas Supply Department 30…Control Unit CA... Catalyst

Claims

1. A synthesis gas production apparatus that produces synthesis gas containing carbon monoxide and hydrogen, A reactor filled with a catalyst that functions as a stationary phase, where the retention time of carbon dioxide is longer than that of oxygen, hydrogen, and carbon monoxide, and which promotes a reverse water-gas shift reaction using carbon dioxide and hydrogen, A gas supply unit capable of supplying a first raw material gas containing carbon dioxide and oxygen and a second raw material gas containing hydrogen to the reactor, The system includes a control unit for controlling the gas supply unit, A synthesis gas production apparatus in which the control unit controls the gas supply unit to supply the second raw material gas to the reactor after supplying the first raw material gas to the reactor, thereby discharging the synthesis gas from the reactor.

2. A synthesis gas production apparatus according to claim 1, Synthesis gas production apparatus, wherein the control unit controls the gas supply unit so that the supply time of the first raw material gas by the gas supply unit is within a range of 0.33 to 3.00 times the time difference between the time difference between the time of retention of carbon dioxide by the catalyst and the time of retention of oxygen by the catalyst.

3. A synthesis gas production apparatus according to claim 1 or claim 2, The gas supply unit is capable of supplying an inert gas to the reactor in addition to the first raw material gas and the second raw material gas. Synthesis gas production apparatus, wherein the control unit controls the gas supply unit to supply the first raw material gas to the reactor, then the inert gas to the reactor, and then the second raw material gas to the reactor.

4. A synthesis gas production apparatus according to claim 1, A synthesis gas production apparatus comprising a carbon dioxide heating desorption method in which a gas containing carbon dioxide is supplied under a temperature condition of 100°C ± 20°C until it is considered that carbon dioxide has been saturated adsorbed onto the catalyst, then carbon dioxide that can be removed from the catalyst is removed by supplying an inert gas under the same temperature conditions, and then carbon dioxide is desorbed from the catalyst by raising the temperature while supplying an inert gas, wherein the first desorption amount, which is the amount of carbon dioxide desorbed from the catalyst when the temperature is raised from 500°C to 650°C, is 0.0030 mmol / g or more.

5. A synthesis gas production apparatus according to claim 1, A synthesis gas production apparatus wherein, by the carbon dioxide heating desorption method described above, the second desorption amount, which is the amount of carbon dioxide desorbed from the catalyst when the temperature is raised from 650°C to 800°C, is less than the first desorption amount, which is the amount of carbon dioxide desorbed from the catalyst when the temperature is raised from 500°C to 650°C.

6. A synthesis gas production apparatus according to claim 1, The synthesis gas production apparatus wherein the gas supply unit reduces the second supply flow rate, which is the flow rate when supplying the second raw material gas to the reactor, to a first supply flow rate, which is the flow rate when supplying the first raw material gas to the reactor.

7. A synthesis gas production apparatus according to any one of claims 4 to 6, The catalyst comprises an alkali metal compound selected from lithium, sodium, and potassium, and a carrier mainly composed of aluminum oxide that supports the compound, in a synthesis gas production apparatus.

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