Carbon recycling method and co2 adsorption / conversion catalyst

Abstract

To provide a carbon recycling method capable of separating CO2 from a CO2-containing gas and performing a reduction reaction of CO2 in a low temperature atmosphere of about 100 to 200°C.SOLUTION: A carbon recycling method comprises a CO2 adsorption step, using a catalyst in which a platinum compound selected from platinum (Pt), platinum salts, platinum complexes, or platinum oxides and either an alkali metal salt or an alkaline earth metal salt are supported on the surface of titanium oxide (TiO2) particles as a catalyst that adsorbs CO2 in a CO2-containing gas for its conversion into a CO-containing gas, of adsorbing CO2 by passing the CO2-containing gas through the catalyst while keeping the catalyst heated at 100 to 200°C, and a conversion and desorption step of passing a reducing gas through the catalyst having adsorbed CO2, applying an electric charge as an external stimulus to the catalyst to convert the CO2 adsorbed on the catalyst into a CO-containing gas, and desorbing the CO-containing gas from the catalyst.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention is 2 CO in the gas 2 Carbon recycling method for converting CO into CO-containing gas and CO used in the carbon recycling method 2 This paper is concerned with the adsorption and conversion catalysts. [Background technology]

[0002] In recent years, carbon dioxide (CO), a type of greenhouse gas, has 2 ) into carbon monoxide (CO) and methane (CH 4 ) for effective use, carbon recycling methods have been studied. For example, the following Patent Document 1 proposes a gas production method in which an oxygen carrier used for producing a product gas containing carbon monoxide by contacting a raw material gas containing carbon dioxide with the oxygen carrier to reduce the carbon dioxide, the oxygen carrier containing a metal oxide containing copper (Cu) and a second element different from copper, the metal oxide having a copper oxide crystal phase and a crystal phase of an oxide of the second element, is brought into contact with a raw material gas containing carbon dioxide to reduce the carbon dioxide and produce a product gas containing carbon monoxide. In this production method, a high temperature of 300° C. or more is required to proceed with the reduction reaction of carbon dioxide.

[0003] In addition, the following Patent Document 2 proposes a method for producing carbon monoxide / methanol, which includes a step of carrying out a deoxygenation reaction of carbon dioxide in the presence of hydrogen using a platinum-supported Mo oxide catalyst comprising Mo oxide containing molybdenum trioxide and platinum particles supported on the Mo oxide to produce at least one of carbon monoxide and methanol. In this production method, the deoxygenation reaction of carbon dioxide can proceed at 200 to 300°C.

[0004] By the way, it is important that the carbon recycling method can be carried out industrially. 2 The source of CO in the atmosphere is the problem. 2Low concentration CO from industrial carbon recycling methods 2 On the other hand, CO in the exhaust gas from factories such as coal-fired power plants 2 The concentration is higher than that in the atmosphere, and the effective CO 2 However, nitrogen (N 2 ) concentration of CO 2 First, CO 2 It is necessary to separate NO from the exhaust gas. In addition, it is important to utilize the heat contained in the exhaust gas from factories such as coal-fired power plants in the carbon recycling method for industrial use. However, the exhaust gas from factories requires dust removal and NO X The exhaust gas temperature drops to around 100-200°C, so it is important that the carbon recycling method can be carried out even at such low temperatures. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2022-53181 [Patent Document 2] Patent Publication No. 2021-186732 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made to solve the above problems, and 2 CO from contained gas 2 and CO in a low-temperature atmosphere of about 100 to 200°C. 2 A carbon recycling method capable of carrying out a reduction reaction of CO 2 The present invention aims to provide an adsorption and conversion catalyst for [Means for solving the problem]

[0007] In order to achieve the above objectives,2 CO in the gas 2 The carbon recycling method for converting the CO 2 Titanium oxide (TiO) was used as a catalyst to adsorb CO and convert it into a CO-containing gas. 2 ) A catalyst having a platinum compound selected from platinum (Pt), platinum salts, platinum complexes, and platinum oxide, and an alkali metal salt or an alkaline earth metal salt supported on the surface of the particles is used, and the catalyst is heated to 100 to 200° C. while being maintained in a heated state. 2 The CO 2 Adsorbs CO 2 adsorption step; 2 A reducing gas is passed through the catalyst on which CO is adsorbed, and an electric charge is applied to the catalyst as an external stimulus to reduce the amount of CO adsorbed on the catalyst. 2 and a conversion / desorption step of converting the CO-containing gas into a CO-containing gas and desorbing the CO-containing gas from the catalyst.

[0008] The alkali metal salt is at least one of a salt of Li, Na, K, Rb, and Cs, so that methane (CH 4 ) concentration of CO in the resulting gas.

[0009] Since the alkaline earth metal salt is at least one of Mg, Ca, Sr, and Ba, a high concentration of methane (CH 4 ) can be obtained as a CO-containing gas.

[0010] The catalyst is titanium oxide (TiO 2 The surface of the platinum (Pt) and sodium (Na) salts are supported on the particles, which makes it possible to reduce CO 2 A large amount of adsorption and a high concentration of CO-containing gas can be obtained.

[0011] It is preferable to use hydrogen gas as the reducing gas.

[0012] Two CO tubes filled with the catalyst 2 The adsorption and conversion tube is installed, and the two CO 2 The CO in each of the adsorption and conversion columns 2 The adsorption process and the conversion / desorption process are performed alternately, and the CO 2 One of the adsorption and conversion columns is 2 During the adsorption step, the other CO 2 By adjusting the adsorption / conversion column to perform the conversion / desorption process, it is possible to continuously obtain CO-containing gas from exhaust gases from factories, etc.

[0013] CO made to achieve the above objectives 2 The adsorption and conversion catalyst for CO 2 CO in the gas 2 The CO adsorbed in the reducing gas is 2 A catalyst for converting a gas containing CO into a gas containing CO, comprising titanium oxide (TiO 2 ) platinum (Pt) and an alkali metal salt or an alkaline earth metal salt are supported on the surface of the particles.

[0014] The alkali metal salt is at least one of a salt of Li, Na, K, Rb, and Cs, so that methane (CH 4 ) concentration of CO in the resulting gas.

[0015] Since the alkaline earth metal salt is at least one of Mg, Ca, Sr, and Ba, a high concentration of methane (CH 4 ) can be obtained as a CO-containing gas.

[0016] The catalyst is titanium oxide (TiO 2 The surface of the platinum (Pt) and sodium (Na) salts are supported on the particles, which makes it possible to reduce CO 2 A large amount of adsorption and a high concentration of CO-containing gas can be obtained. Effect of the Invention

[0017] According to the present invention, CO in the exhaust gas 2 and an adsorption process for adsorbing the adsorbed CO 2 The conversion and desorption process, in which CO is converted into CO and desorbed, can be carried out using one type of catalyst in an atmosphere at a temperature of 100 to 200°C, which can utilize exhaust heat emitted from exhaust gases from factories, etc. This makes it possible to implement the carbon recycling method industrially. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a schematic diagram showing an example of an apparatus for industrially implementing the carbon recycling method according to the present invention. [Diagram 2] 2 is a graph illustrating the CO2 adsorption conditions and adsorption amount of the catalyst according to the present invention. [Diagram 3] FIG. 1 is a schematic diagram of an experimental apparatus for experimenting with a carbon recycling method according to the present invention. [Figure 4] 4 is a graph showing the results of measuring the CO production rate and CH4 production rate converted from CO2 depending on the type of catalyst, obtained using the experimental apparatus shown in FIG. 3. [Diagram 5] 4 is a graph showing the results of measuring the CO production rate and the CH4 production rate when the type of TiO2 in the Pt-Na-TiO2 catalyst was changed, obtained using the experimental apparatus shown in FIG. [Figure 6] 4 is a graph showing the results of measuring the time-dependent changes in the cumulative amounts of CO, CH4, and CO2 produced in the adsorption process and the conversion / desorption process using the Pt-Na-TiO2-1 catalyst, obtained using the experimental apparatus shown in FIG. [Figure 7] 4 is a graph showing the results of measuring the time-dependent changes in the cumulative amounts of CO, CH4, and CO2 produced in the adsorption process and the conversion / desorption process using the Pt-Na-TiO2-2 catalyst, obtained using the experimental apparatus shown in FIG. [Figure 8] 4 is a graph showing the results of measuring the time-dependent changes in the cumulative amounts of CO, CH4, and CO2 produced in the adsorption process and the conversion / desorption process using the Pt-Na-TiO2-3 catalyst, obtained using the experimental apparatus shown in FIG. [Figure 9] 4 is a graph showing the results of measuring the change in the amount of CO and CO2 produced when the H2 concentration is changed in the conversion and desorption process using the Pt-Na-TiO2-2 catalyst, obtained using the experimental apparatus shown in FIG. 3. [Figure 10] 4 is a graph showing the results of measuring the change over time in the cumulative amounts of CO, CH4, and CO2 produced in the adsorption process and the conversion / desorption process using the Pt-TiO2 catalyst, obtained using the experimental apparatus shown in FIG. [Figure 11] 4 is a graph showing the results of measuring the change over time in the cumulative amounts of CO, CH4, and CO2 produced in the adsorption process and the conversion / desorption process using the Na-TiO2 catalyst, obtained using the experimental apparatus shown in FIG. [Figure 12] This is a graph showing the results of measuring the change over time in the accumulated amount of CO, CH4, and CO2 produced in the adsorption process and the conversion / desorption process using the Pt-Na-TiO2-2 catalyst when the application of electric charge was stopped in the experimental apparatus shown in Figure 3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] The catalyst used in the present invention is titanium oxide (TiO 2 ) A platinum compound selected from platinum (Pt), a platinum salt, a platinum complex, and platinum oxide, and an alkali metal salt and / or an alkaline earth metal salt are supported on the surface of the particles. Titanium dioxide (TiO 2 The TiO particles may be either rutile or anatase, or a mixture of rutile and anatase. 2 The particle size of the particles is preferably 8 to 15 μm. In particular, TiO 2 Within this particle size range, particles that are fine and have a large specific surface area are CO 2 This is preferable because it increases the amount of TiO adsorbed. 2 The surface of the particles is supported with any platinum compound selected from platinum (Pt), platinum salts, platinum complexes, and platinum oxide, and an alkali metal salt and / or an alkaline earth metal salt. Each of the platinum compound and the alkali metal salt and / or the alkaline earth metal salt is selected from TiO 2The TiO 2 An alkali metal salt and / or an alkaline earth metal salt may be supported on the platinum compound supported on the surface of the particles.

[0020] Here, TiO 2 When a catalyst in which a platinum compound and an alkali metal salt are supported on the surface of particles is used, the CO concentration is 4 A mixed gas having a significantly higher concentration than the concentration obtained by the method can be obtained. As the alkali metal salt, at least one salt of Li, Na, K, Rb, and Cs is preferable, and a Na salt is more preferable. As the alkali metal salt, a plurality of salts of Li, Na, K, Rb, and Cs may be used. In addition, TiO 2 When a catalyst in which a platinum compound and an alkaline earth metal salt are supported on the surface of the particles is used, the CH 4 A mixed gas with a high concentration can be obtained. As the alkaline earth metal salt, at least one of Mg, Ca, Sr, and Ba is suitable. In the category of alkaline earth metal salts, by using Ca salt, the CO concentration and CH 4 As the alkaline earth metal salt, a plurality of salts selected from the group consisting of Mg, Ca, Sr, and Ba may be used.

[0021] TiO 2 The amount of the platinum compound supported on the surface of the particles is preferably 0.1 to 10 mass % based on the total catalyst amount, more preferably 0.5 to 5 mass %, and particularly preferably 3 to 5 mass %. 2 In the case of an alkali metal salt supported on the particle surface, the amount supported is preferably 1 to 15 mass % relative to the total catalyst amount, more preferably 1 to 7 mass %, and particularly preferably 5 to 7 mass %, while in the case of an alkaline earth metal salt, the amount supported is preferably 1 to 15 mass %, more preferably 1 to 7 mass %, and particularly preferably 5 to 7 mass %, relative to the total catalyst amount.

[0022] Among these catalysts, titanium dioxide (TiO 2 The surface of the platinum (Pt) and sodium (Na) salts are supported on the particles, which makes it possible to reduce CO 2 This is preferable because it allows a large amount of adsorption and a high-concentration CO-containing gas to be obtained.

[0023] The catalyst used in the present invention is prepared by immersing titanium oxide powder in an aqueous solution of a water-soluble platinum complex such as tetraammine platinum nitrate and an alkali metal and / or alkaline earth metal nitrate, and evaporating the water on a hot plate while stirring. The resulting powder is then baked at 500°C for 3 hours to obtain a catalyst. In addition to this impregnation method, other methods may be used as long as they can support platinum and an alkali metal salt and / or an alkaline earth metal salt in a highly dispersed state on the surface of titanium oxide particles.

[0024] The carbon recycling method using the catalyst obtained in this way is 2 The gas is passed through a catalyst heated to 100-200℃, and CO 2 After the adsorption process, the catalyst is heated to 100-200°C to remove CO. 2 The catalyst adsorbed CO was then charged by applying an electric charge to the catalyst as an external stimulus while a reducing gas was passed through the catalyst. 2 This method converts the CO2-containing gas into a CO-containing gas and then desorbs the CO2-containing gas from the catalyst via a conversion and desorption process to obtain a CO2-containing gas.

[0025] In the adsorption step of the carbon recycling method according to the present invention, a catalyst and CO 2 The contact time with the gas containing the catalyst is about 5 to 10 minutes, and the temperature must be 100 to 200°C. If the temperature is less than 100°C, the reaction in the conversion and desorption process after the adsorption process becomes unfavorable, and the catalyst may become wet with the by-product water. If the temperature exceeds 200°C, the CO 2 This makes adsorption unfavorable, and is also unfavorable in terms of energy.

[0026] In this carbon recycling method, titanium oxide (TiO 2) When using a catalyst in which only platinum compounds are supported on the surface of the particles, CO 2 In the adsorption process, a small amount of CO 2 However, it is difficult to convert it to CO during the conversion and desorption process at 100 to 200 °C. In addition, titanium oxide (TiO 2 ) When using a catalyst in which only alkali metal salts and / or alkaline earth metal salts are supported on the surface of the particles, CO 2 In the adsorption process of CO 2 Although it can adsorb CO, it is easily desorbed, and is difficult to convert to CO in the conversion and desorption process at 100 to 200°C.

[0027] In the carbon recycling method according to the present invention, the CO 2 The gases contained are exhaust gases generated from coal-fired power plants, etc., and are used for dust removal and NO X The removal of CO 2 and N 2 In particular, exhaust gas having a temperature of 100 to 200°C is suitable because it is possible to omit or reduce the need for external heating of the space in which the catalyst is placed in the adsorption step. The gas that has passed through the adsorption step is 2 is adsorbed and N 2 Since the gas is composed only of CO, it may be released directly into the atmosphere or the remaining CO 2 In order to remove CO, commercially available CO 2 It may be passed through an adsorbent before being released into the atmosphere.

[0028] In this way, CO 2 The catalyst with adsorbed CO was fed to the conversion and desorption process, where it was heated to 100-200°C under a reducing gas atmosphere, and an electric charge was applied to the catalyst as an external stimulus to convert the CO adsorbed on the catalyst into CO. 2 is converted into a CO-containing gas and released from the catalyst. The reducing gas is preferably hydrogen gas, and hydrogen gas obtained using renewable energy such as solar power generation or wind power generation can be suitably used. The contact time between the reducing gas and the catalyst may be about 20 to 30 minutes. The charge applied to the catalyst is a direct current, and is preferably 3 to 15 mA and 0.1 to 1 kV. Here, if no charge is applied to the catalyst, the CO adsorbed on the catalyst 2 cannot be converted into a CO-containing gas. In the conversion and desorption process, the temperature of the atmosphere in which the catalyst is placed must be 100 to 200°C. If the temperature of the atmosphere is less than 100°C, the CO adsorbed on the catalyst 2 The reduction rate of CO becomes slower, and when the temperature exceeds 200°C, the reduction rate to CO becomes saturated, which is also unfavorable in terms of energy. In the conversion and desorption process, the catalyst that has passed through the adsorption process is heated to 100 to 200°C, and this heat can be utilized. However, since the temperature of the reducing gas introduced is less than 100°C, it may be necessary to heat the catalyst atmosphere to 100 to 200°C by external heating. In such a conversion and desorption process, when the reducing gas is first introduced, CO 2 is released, but gradually CO is produced and the released CO 2 ultimately resulting in CO and CH 4 The total amount of CO 2 The CO-containing gas discharged from the conversion and desorption process contains CO and CH 4 In addition to the CO released from the catalyst as mentioned above, 2 , CO 2 and H 2 H by reduction reaction with 2 O, H supplied as reducing gas 2 The remainder of the calculation is included.

[0029] In the carbon recycling method according to the present invention, TiO 2 When a catalyst in which a platinum compound and an alkali metal salt are supported on the surface of particles is used, the CO concentration is 4As the alkali metal salt, any of the salts of Li, Na, K, Rb, and Cs can be suitably used. In particular, TiO 2 By using a catalyst in which platinum compounds and sodium (Na) salts are supported on the surface of the particles, 2 The amount of adsorption is large and the amount of CO is CH 4 This is preferable because it allows obtaining a larger amount of CO-containing gas than the conventional method.

[0030] On the other hand, TiO 2 When a catalyst in which a platinum compound and an alkaline earth metal salt are supported on the surface of particles is used, CO and CH 4 However, the amount of CH is smaller than that when using a catalyst supported by an alkali metal salt. 4 As the alkaline earth metal salt, any of Mg, Ca, Sr, and Ba salts can be suitably used. In particular, by using a Ca salt, the amount of CO and CH 4 Therefore, a mixed gas having a large total amount can be obtained.

[0031] According to this carbon recycling method, CO 2 The adsorbed CO is separated. 2 From CO and CH 4 This mixed gas contains CO and CH. 4 The carbon dioxide can be separated into two parts and used as raw materials for chemicals, fuel oil, etc. The catalyst used in the carbon recycling method is a series of 2 After the adsorption process of CO and the conversion and desorption process of the CO-containing gas in the reducing gas are completed, 2 The adsorption process and the conversion and desorption process of the CO-containing gas can be carried out.

[0032] The above-mentioned carbon recycling method can be industrially implemented by the apparatus shown in Fig. 1. In the apparatus shown in Fig. 1, two CO 2 The adsorption / conversion columns 10a and 10b are provided with heaters 12a and 12b, respectively.2 DC power sources 14a and 14b are provided to apply electric charges for stimulation to the catalysts filled in the adsorption / conversion columns 10a and 10b, respectively, and switches 16a and 16b are provided in the middle of the circuit connecting the electrodes in the catalyst layers to the DC power sources 14a and 14b. 2 Gas and CO 2 A four-way valve 18 is provided in the supply passage that supplies each of the adsorption / conversion columns 10a and 10b. As shown in FIG. 2 Exhaust gas is supplied to the adsorption / conversion column 10a, and CO 2 Adsorption and conversion tube 10b H 2 As shown in FIG. 1(b), the four-way valve 18 can be switched to supply CO 2 Exhaust gas is supplied to the adsorption / conversion column 10b, and CO 2 Adsorption and conversion tube 10a H 2 Gas can be supplied.

[0033] CO 2 A four-way valve 20 is provided in the flow path of the exhaust gas from each of the adsorption / conversion columns 10a and 10b. As shown in FIG. 2 The exhaust gas from the adsorption / conversion column 10a is treated with CO 2 The CO is exhausted into the atmosphere via an adsorption tower 22 filled with an adsorbent. 2 The adsorption / conversion column 10b discharges CO and CH 4 As shown in FIG. 1(b), the four-way valve 20 is switched to discharge the mixed gas containing CO. 2 The adsorption / conversion column 10a discharges CO and CH 4 A mixed gas containing CO is discharged. 2 The exhaust gas from the adsorption / conversion column 10b is exhausted to the atmosphere via the adsorption tower 22. 2 If the exhaust gas cannot be treated due to a malfunction of the adsorption / conversion columns 10a and 10b, or if the amount of exhaust gas is too low, 2A bypass 24 is provided to directly supply exhaust gas when the amount of exhaust gas to the adsorption column 22 exceeds the amount of exhaust gas to be treated by the adsorption / conversion columns 10a and 10b. An automatic valve 26 is provided in the bypass 24, and the amount of exhaust gas to the adsorption column 22 can be adjusted.

[0034] As shown in FIG. 1(a), CO 2 The adsorption / conversion column 10a (hereinafter referred to as column 10a) receives exhaust gas from a coal-fired power plant or the like through a four-way valve 18, and converts the CO 2 CO is adsorbed on the catalyst 2 In this case, if the internal temperature of the cylinder 10a can be kept at 100 to 200°C by the heat quantity of the exhaust gas, the heater 12a does not need to be used. However, if the internal temperature of the cylinder 10a cannot be kept at 100 to 200°C by the exhaust gas alone, the heater 12a is used to supplement the insufficient heat quantity and to keep the internal temperature of the cylinder 10a at 100 to 200°C. In the exhaust gas from the cylinder 10a, most of the CO in the exhaust gas is absorbed by the catalyst in the cylinder 10a. 2 Although the CO in the exhaust gas is adsorbed, 2 Since it is difficult to completely adsorb CO 2 Therefore, the exhaust gas from the column 10a passes through the four-way valve 20 and enters the adsorption tower 22 to remove the residual CO 2 The cylinder 10a shown in FIG. 1 is a cylinder for absorbing CO 2 Since the adsorption process is being carried out, there is no need to apply a stimulating charge to the catalyst, and switch 16a is in the OFF state.

[0035] In FIG. 1(a), CO 2 The CO 2 In the adsorption / conversion column 10b (hereinafter referred to as column 10b), CO 2 CO adsorbed on the catalyst during the adsorption process 2 The column 10b is a conversion / desorption process in which H is converted into a CO-containing gas and desorbed. 2 Gas is supplied through a four-way valve 18 to create a reducing atmosphere inside the tube 10b. Furthermore, the inside temperature of the tube 10b is heated by a heater 12b to be maintained at 100 to 200°C. 2In the adsorption process, the catalyst is heated to 100-200°C, but the H 2 This is because the gas is supplied at room temperature. In order to apply a stimulating charge to the catalyst in the tube 10b, a switch 16b in the middle of the circuit connecting the electrode in the catalyst in the tube 10b to the DC power source 14b is turned on. CO and CH 4 The resulting mixed gas containing the above is discharged and can be used as a feedstock for chemicals, fuel oil, etc.

[0036] The CO 2 When the adsorption step in column 10a and the conversion / desorption step in column 10b are completed, column 10a is put into the conversion / desorption step, and column 10b is put into the CO 2 In order to carry out the adsorption process, the four-way valves 18 and 20 are switched as shown in FIG. 1(b) to supply H 2 Gas is supplied to create a reducing gas atmosphere in the tube 10a, and CO is supplied to the tube 10b. 2 1(b), exhaust gas containing CO2 is supplied to the adsorption tower 22 through the four-way valve 20. At the same time, the heater 12a of the tube 10a is turned ON to maintain the internal temperature of the tube 10a at 100 to 200°C, and a switch 16a in the circuit connecting the electrode in the catalyst in the tube 10a to the DC power supply 14a is turned ON. In the tube 10b, the heater 12b is turned OFF, and a switch 16b in the circuit connecting the electrode in the catalyst in the tube 10b to the DC power supply 14b is turned OFF. In the state shown in FIG. 1(b), the exhaust gas from the tube 10b passes through the four-way valve 20 and is adsorbed to the adsorption tower 22 to remove residual CO2. 2 is adsorbed and then released into the atmosphere, and CO and CH 4 A gas mixture containing

[0037] As shown in FIG. 1(a), the tube 10a is 2 During the adsorption process, column 10b is in the conversion / desorption process, and column 10a is in the CO 2 When the adsorption process and the conversion / desorption process of column 10b are completed, column 10a starts the conversion / desorption process as shown in FIG. 1(b), and at the same time, column 10b starts the CO 2 The adsorption process is then started. In this way, the CO 2By alternately performing the adsorption process and the conversion / desorption process, it is possible to continuously treat exhaust gas from a coal-fired power plant, etc. When the amount of exhaust gas fluctuates and the exhaust gas treatment capacity of the columns 10a and 10b becomes insufficient, the automatic valve 26 is opened to directly supply part of the exhaust gas to the adsorption tower 22, and the CO in the exhaust gas is removed. 2 is absorbed onto an adsorbent and then released into the atmosphere. EXAMPLES

[0038] Examples of the present invention will be described in detail below, but the scope of the present invention is not limited to these examples.

[0039] (Catalyst Preparation) Pt-M-TiO 2 The following catalysts were prepared:

[0040] (I) M: Alkali metal (1) Pt-Na-TiO 2 catalyst (a) Pt-Na-TiO 2 -1 Titanium oxide (JRC-TIO-17 (mixture of anatase and rutile, specific surface area: 50 m) provided by the Reference Catalyst Division of the Catalysis Society of Japan 2 Using titanium dioxide as a support, Pt and Na were co-supported by impregnation so that the Pt and Na concentrations were 3% by mass and 5% by mass, respectively. A solution in which a given amount of tetraammine platinum nitrate and sodium nitrate were dissolved was added to the titanium oxide powder, and the mixture was evaporated to dryness on a hot plate while stirring. The powder obtained was then dried overnight at 70°C, and then calcined in air at 500°C for 3 hours in a calcination furnace.

[0041] (b) Pt-Na-TiO 2 -2 Titanium oxide provided by the Reference Catalyst Division of the Catalysis Society of Japan (JRC-TIO-7 (anatase only, specific surface area: 270 m 2 In addition to the above, Pt-Na-TiO 2 -1 was prepared in the same manner.

[0042] (c) Pt-Na-TiO 2 -3 Titanium oxide provided by the Reference Catalyst Division of the Catalysis Society (JRC-TIO-16 (rutile only, specific surface area: 110 m 2 In addition to the above, Pt-Na-TiO 2 -1 was prepared in the same manner.

[0043] (2) Pt-Li-TiO 2 catalyst Titanium oxide (JRC-TIO-17) provided by the Reference Catalyst Committee of the Catalysis Society was used as the support, and Pt and Li were co-supported by impregnation so that the Pt and Li were 3% by mass and 5% by mass, respectively. A solution in which a specified amount of tetraammine platinum nitrate and lithium nitrate were dissolved was added to the titanium oxide powder, and the mixture was evaporated to dryness on a hot plate while stirring. The resulting powder was then dried overnight at 70°C, and then calcined in air at 500°C for 3 hours using a calcination furnace.

[0044] (3) Pt-K-TiO 2 catalyst Titanium oxide (JRC-TIO-17) provided by the Reference Catalyst Committee of the Catalysis Society was used as the support, and Pt and K were co-supported by impregnation so that the Pt and K were 3% by mass and 5% by mass, respectively. A solution in which a specified amount of tetraammine platinum nitrate and potassium nitrate were dissolved was added to the titanium oxide powder, and the mixture was evaporated to dryness on a hot plate while stirring. The resulting powder was then dried overnight at 70°C, and then calcined in air at 500°C for 3 hours using a calcination furnace.

[0045] (4) Pt-Rb-TiO 2 catalyst Titanium oxide (JRC-TIO-17) provided by the Reference Catalyst Committee of the Catalysis Society was used as the support, and Pt and Rb were co-supported by impregnation so that they were 3% by mass and 5% by mass, respectively. An aqueous solution in which a specified amount of tetraammine platinum nitrate and rubidium nitrate were dissolved was added to the titanium oxide powder, and the mixture was evaporated to dryness on a hot plate while stirring. The resulting powder was then dried overnight at 70°C, and then calcined in air at 500°C for 3 hours in a calcination furnace.

[0046] (5) Pt-Cs-TiO 2 catalyst Titanium oxide (JRC-TIO-17) provided by the Reference Catalyst Committee of the Catalysis Society was used as the support, and Pt and Cs were co-supported by impregnation so that the Pt and Cs amounts were 3% by mass and 5% by mass, respectively. A solution in which a specified amount of tetraammine platinum nitrate and cesium nitrate were dissolved was added to the titanium oxide powder, and the mixture was evaporated to dryness on a hot plate while stirring. The resulting powder was then dried overnight at 70°C, and then calcined in air at 500°C for 3 hours using a calcination furnace.

[0047] (II) M: alkaline earth metal (1) Pt-Mg-TiO 2 catalyst Titanium oxide (JRC-TIO-17) provided by the Reference Catalyst Committee of the Catalysis Society was used as the support, and Pt and Mg were co-supported by impregnation so that the Pt and Mg were 3% by mass and 5% by mass, respectively. A solution in which a specified amount of tetraammine platinum nitrate and magnesium nitrate were dissolved was added to the titanium oxide powder, and the mixture was evaporated to dryness on a hot plate while stirring. The resulting powder was then dried overnight at 70°C, and then calcined in air at 500°C for 3 hours using a calcination furnace.

[0048] (2) Pt-Ca-TiO 2 catalyst Titanium oxide (JRC-TIO-17) provided by the Reference Catalyst Committee of the Catalysis Society was used as the support, and Pt and Ca were co-supported by impregnation so that the Pt and Ca contents were 3% by mass and 5% by mass, respectively. A solution in which a specified amount of tetraammine platinum nitrate and calcium nitrate were dissolved was added to the titanium oxide powder, and the mixture was evaporated to dryness on a hot plate while stirring. The resulting powder was then dried overnight at 70°C, and then calcined in air at 500°C for 3 hours using a calcination furnace.

[0049] (3) Pt-Sr-TiO 2 catalyst Titanium oxide (JRC-TIO-17) provided by the Reference Catalyst Committee of the Catalysis Society was used as the support, and Pt and Sr were co-supported by impregnation so that the Pt and Sr were 3% by mass and 5% by mass, respectively. An aqueous solution in which a specified amount of tetraammine platinum nitrate and strontium nitrate were dissolved was added to the titanium oxide powder, and the mixture was evaporated to dryness on a hot plate while stirring. The resulting powder was then dried overnight at 70°C, and then calcined in air at 500°C for 3 hours using a calcination furnace.

[0050] (4) Pt-Ba-TiO 2 catalyst Titanium oxide (JRC-TIO-17) provided by the Reference Catalyst Committee of the Catalysis Society was used as the support, and Pt and Ba were co-supported by impregnation so that the Pt and Ba were 3% by mass and 5% by mass, respectively. A solution in which a given amount of tetraammine platinum nitrate and barium nitrate were dissolved was added to the titanium oxide powder, and the mixture was evaporated to dryness on a hot plate while stirring. The resulting powder was then dried overnight at 70°C, and then calcined in air at 500°C for 3 hours using a calcination furnace.

[0051] (III) Comparative example (1) Pt-TiO 2 catalyst Titanium oxide (JRC-TIO-7) provided by the Reference Catalyst Committee of the Catalysis Society was used as the support, and Pt was supported by impregnation so that the Pt content was 3 mass%. An aqueous solution in which a specified amount of tetraammine platinum nitrate and barium nitrate were dissolved was added to the titanium oxide powder, and the mixture was evaporated to dryness on a hot plate while stirring. The resulting powder was then dried overnight at 70°C, and then calcined in air at 500°C for 3 hours in a calcination furnace.

[0052] (2) Na-TiO 2 catalyst Titanium oxide (JRC-TIO-7) provided by the Reference Catalyst Committee of the Catalysis Society was used as the support, and Na was supported by impregnation so that the content was 5 mass%. An aqueous solution in which a specified amount of sodium nitrate was dissolved was added to the titanium oxide powder, and the mixture was evaporated to dryness on a hot plate while stirring. The resulting powder was then dried overnight at 70°C, and then calcined in air at 500°C for 3 hours using a calcination furnace.

[0053] Example 1 (CO 2 adsorption amount) Using a differential thermal-thermogravimetric analyzer, 2 The amount of adsorption was measured. 5 mg of the prepared catalyst was packed in the device, and N 2 While flowing gas at 1000ml / min, the temperature was increased from room temperature 30℃ to 400℃ and held for 30 minutes to remove organic matter from the catalyst. After that, the temperature was held at 150℃ to remove CO. 2 CO mixed with 5 vol% 2 mixed N 2 Gas (flow rate: 400 ml / min) was passed through the catalyst for 60 minutes to detect CO 2 After adsorption, N 2 Switched to gas. CO 2 The weight change before and after the introduction of the mixed gas was used to determine the CO 2 The amount of CO adsorption on the catalyst calculated from the weight change is shown in Figure 2(b). 2 The change in adsorption amount over time is shown. 2 mixed N 2 When gas is flowed, CO 2 The amount of adsorption increases rapidly and remains constant (shown as "Adsorption capacity" in Figure 2(b)). After that, the amount of CO 2 mixed N 2 Stop the gas and turn on N. 2 As soon as the gas started to flow, CO 2 The amount of adsorption gradually decreased and reached a constant value (Fig. 2(b) shows “Desorbed CO 2 The CO that was attached to the catalyst 2 Therefore, it is assumed that the CO adsorbed on the catalyst is desorbed. 2 The true amount of adsorption is calculated by subtracting "Adsorption capacity" from "Desorbed CO 2 " (Figure 2(b) shows the difference between "RemainingCO 2 " is indicated.)

[0054] For each of the prepared catalysts, CO 2The actual amount of adsorption was measured, and the results are shown in Table 1 below.

[0055] [Table 1] As is clear from Table 1, Pt-Na-TiO 2 The catalyst is the most CO 2 The amount of adsorption was large. In addition, Pt-Na-TiO 2 As a catalyst, TiO with a large specific surface area 2 Supported catalyst (Pt-Na-TiO 2 -2, Pt-Na-TiO 2 -3) CO 2 The amount of adsorption increased. In addition, Pt-TiO 2 Catalyst and Na-TiO 2 The catalyst is CO 2 Although CO is adsorbed, CO desorbs. 2 The quantity is large.

[0056] Example 2 Using the experimental apparatus shown in the schematic diagram of FIG. 3, the catalyst prepared in Example 1 was subjected to CO 2 The mixture gas discharged from the conversion / desorption process was measured.

[0057] (Experimental Equipment) As shown in Figure 3, electrodes were inserted into the catalyst packed in a cylinder that could be heated by a heater, and a DC power supply was applied from a power supply V. A switch was installed in the middle of the wiring from the power supply to the electrodes, and when a stimulus was to be applied to the catalyst, the switch was turned on to apply an electric charge to the catalyst. CO 2 , H 2 The gas discharged from the other end of the cylinder was collected as a sample and analyzed.

[0058] (Experimental conditions) Using the experimental apparatus shown in Figure 3, the inside of the cylinder was heated with a heater to maintain the temperature at 150°C, and CO 2The adsorption process and the conversion and desorption process were carried out. Between the adsorption process and the conversion and desorption process, only argon (Ar) was flowed, and in the conversion and desorption process, the switch was turned on and a charge of 5 mA and 0.15 kV was applied to the catalyst as an external stimulus. The experimental conditions are shown in Table 2 below, and the results are shown in Figure 4.

[0059] [Table 2]

[0060] Figure 4(a) shows Pt-M-TiO 2 TiO as a catalyst and support 2 JRC-TIO-17 (mixture of anatase and rutile, specific surface area: 50 m 2 The CO formation rate and CH formation rate in the mixed gas discharged after 2 minutes in the conversion and desorption process were measured using a 1000-milliliter (1000-milliliter) 100-milliliter (1000-milliliter) / g and an alkali metal (Li, Na, K, Rb, Cs) as M. 4 The formation rate of Pt-M-TiO is shown in Fig. 4(b). 2 TiO as a catalyst and support 2 JRC-TIO-17 (mixture of anatase and rutile, specific surface area: 50 m 2 The CO formation rate and CH formation rate in the mixed gas discharged after 2 minutes in the conversion and desorption process were measured using a 1000-milliliter (1000-milliliter) sintered gas (1000-milliliter) / g and alkaline earth metals (Mg, Ca, Sr, Ba) as M. 4 As is clear from Fig. 4(a) and (b), the CO production rate in the mixed gas when alkali metals (Li, Na, K, Rb, Cs) were used was 100%. 4 On the other hand, in the mixed gas using alkaline earth metals (Mg, Ca, Sr, Ba), the production rate of CH 4 The rate of CO production in the mixed gas is higher than that when an alkali metal is used. In particular, the rate of CO production in the mixed gas is the highest when Na is used as the alkali metal.

[0061] Example 3 Pt-Na-TiO 2 TiO as a catalyst and support 2 The specific surface area is 50m2 / g of titanium oxide powder (JRC-TIO-17: a mixture of anatase and rutile) 2 -1, specific surface area is 270m 2 / g of titanium oxide powder (JRC-TIO-7: anatase only) 2 -2, specific surface area is 110m 2 / g of titanium oxide powder (JRC-TIO-16: rutile only) 2 The CO formation rate and CH formation rate in the mixed gas discharged after 2 minutes in the conversion and desorption process were measured using 300-3 in the same manner as in Example 2. 4 The production rates of CO and CH were calculated and are shown in Figure 5. As is clear from Figure 5, 4 The rate of formation of Pt-Na-TiO 2 -1 Catalyst <Pt-Na-TiO 2 -2 catalyst ≒ Pt-Na-TiO 2 -3, and by using titanium oxide powder with a large specific surface area, CO and CH 4 As shown in Table 1 above, the rate of Pt-Na-TiO 2 -2 catalyst and Pt-Na-TiO 2 -3 Catalytic CO 2 The adsorption amount is Pt-Na-TiO 2 -1 catalyst than CO 2 It is presumed that this is because the amount of adsorption increases.

[0062] Example 4 Using the experimental apparatus shown in Fig. 3, Pt-Na-TiO 2 -1 catalyst (TiO 2 : Mixture of anatase and rutile, specific surface area 50m 2 / g), Pt-Na-TiO 2 -2 catalyst (TiO 2 Anatase alone, specific surface area 270m 2 / g), or Pt-Na-TiO 2 -3 catalyst (TiO 2 : Rutile alone, specific surface area: 110m 2 The cylinder filled with 100g of ethanol was heated to 150°C with a heater while CO 2The adsorption process and the conversion / desorption process were carried out twice. Between the adsorption process and the conversion / desorption process, only argon (Ar) was flowed, and in the conversion / desorption process, the switch was turned on and a charge of 5 mA and 0.15 kV was applied to the catalyst as an external stimulus. The experimental conditions are shown in Table 3 below. 2 CO, CH in the adsorption process and the conversion and desorption process 4 ,CO 2 The time-dependent change in the cumulative amount of CO generated was measured, and the results are shown in Figures 6 to 8. In addition, for each catalyst, the amount of CO generated and the amount of CO 2 The amount of desorption is also shown in Table 4 below. 4 was not generated.

[0063] [Table 3]

[0064] [Table 4]

[0065] (a) in each of Figures 6 to 8 is a graph showing the time-dependent change in the cumulative amount of CO produced in the first adsorption step, and almost no CO was produced. (b) in each of Figures 6 to 8 is a graph showing the time-dependent change in the cumulative amount of CO, CH 4 ,CO 2 FIG. 7(b) is a graph showing the change over time in the cumulative amount of CO generated. 2 The amount of CO generated is about the same as that of CO, but in the latter half, the cumulative amount of CO generated is 2 The cumulative amount of CO generated will be greater than the cumulative amount of CO generated. 2 The cumulative amount of CO generated is approximately constant from the middle of the conversion and desorption process. 2 The formation of CO adhered to the catalyst 2 It is presumed that this is because CH is desorbed from the catalyst. 4(c) in each of Figures 6 to 8 is a graph showing the time-dependent change in the integrated amount of CO produced in the second adsorption step, which is approximately the same as that in the first step shown in (a) in each of Figures 6 to 8. (d) in each of Figures 6 to 8 shows the changes in the integrated amount of CO produced in the second conversion and desorption step. 4 ,CO 2 This is a graph showing the change over time in the cumulative amount of CO generated, which is almost the same as the first test. As shown in Table 4, the cumulative amount of CO generated and the cumulative amount of CO 2 The desorption amounts are almost the same. In this way, CO 2 Even if the adsorption process and the conversion / desorption process of Pt-Na-TiO 2 -1 catalyst, Pt-Na-TiO 2 -2 catalyst, Pt-Na-TiO 2 The -3 catalysts all exhibited roughly the same performance in the first and second runs. In addition, the TiO 2 The specific surface area of ​​Pt-Na-TiO 2 -1 catalyst than Pt-Na-TiO 2 -2 catalyst and Pt-Na-TiO 2 -3 catalyst absorbed CO 2 The amount of CO converted to Pt-Na-TiO 2 -1 catalyst. In particular, the TiO 2 The Pt-Na-TiO has the largest specific surface area. 2 -2 Catalyst adsorbed CO 2 is converted to CO by 100%.

[0066] Example 5 Pt-Na-TiO 2 The first conversion and removal step (H 2 -1) and the second conversion / removal step (H 2 In Example 4, except that the hydrogen concentration was changed as shown in Table 5, CO 2 The adsorption process and the conversion / desorption process were carried out twice. 2 -2) CO,CO 2 The cumulative amount of generated water was measured and the results are shown in Figure 9.

[0067] [Table 5]

[0068] As is clear from Figure 9, the amount of CO produced increases as the hydrogen concentration increases in the conversion and desorption process. 2 is presumably converted to CO.

[0069] Comparative Example 1 In Example 4, the catalyst was Pt-TiO 2 Catalyst or Na-TiO 2 The same procedure as in Example 4 was used except that the catalyst was changed to a sintered catalyst. The inside of the packed cylinder was heated with a heater to maintain it at 150°C, and CO 2 The adsorption process and the conversion / desorption process were carried out twice. Between the adsorption process and the conversion / desorption process, only argon (Ar) was flowed, and in the conversion / desorption process, the switch was turned on and a charge of 5 mA and 0.15 kV was applied to the catalyst as an external stimulus. 2 CO, CH in the adsorption process and the conversion and desorption process 4 ,CO 2 The time-dependent change in the cumulative amount of Pt-TiO 2 The results for the catalyst are shown in Figure 10. 2 The results for the catalyst are shown in Figure 11. The amount of CO produced and CO 2 The amount of desorption is shown in Table 6 below.

[0070] [Table 6]

[0071] Pt-TiO 2 Catalyst and Na-TiO 2 The catalyst was CO as shown in Table 1. 2 Although it adsorbs CO, it does not have the ability to convert it to CO.

[0072] Comparative Example 2 Pt-Na-TiO2 The same procedure as in Example 4 was used with the Catalyst 1-2, except that the switch shown in FIG. 3 was turned off and no charge was applied to the catalyst as an external stimulus. The inside of the packed cylinder was heated with a heater to maintain the temperature at 150° C., and CO 2 The adsorption step and the conversion / desorption step were carried out twice. Between the adsorption step and the conversion / desorption step, only argon (Ar) was flowed. 2 CO, CH in the adsorption process and the conversion and desorption process 4 ,CO 2 The time course of the cumulative amount of CO generated was measured, and the results are shown in Figure 12. 2 The amounts of desorbed are shown in Table 7 below.

[0073] [Table 7]

[0074] When no charge is applied to the catalyst as an external stimulus, the CO adsorbed on the catalyst 2 was not converted to CO at all. [Industrial Applicability]

[0075] According to the present invention, CO 2 CO from contained gas 2 and CO in a low-temperature atmosphere of about 100 to 200°C. 2 This makes it possible to carry out the reduction reaction of the above, thereby making the carbon recycling method commercially feasible. [Explanation of symbols]

[0076] 10a, 10b:CO 2 Adsorption / conversion cylinder, 12a, 12b: heater, 14a, 14b: DC power supply, 16a, 16b: switch, 18, 20: four-way valve, 22: adsorption tower, 24: bypass, 26: automatic valve

Claims

1. CO ２ CO in the gas ２ A carbon recycling method for converting a carbon dioxide gas into a CO-containing gas, comprising the steps of: The CO ２ Titanium oxide (TiO ２ ) A catalyst having a platinum compound selected from platinum (Pt), a platinum salt, a platinum complex, and platinum oxide, and an alkali metal salt or an alkaline earth metal salt supported on the surface of particles is used, and the catalyst is heated to 100 to 200° C. while being maintained in a heated state. The catalyst is ２ The CO ２ CO absorbs ２ An adsorption step; The CO ２ A reducing gas is passed through the catalyst on which CO is adsorbed, and an electric charge is applied to the catalyst as an external stimulus to reduce the amount of CO adsorbed on the catalyst. ２ a conversion / desorption step of converting the carbon dioxide gas into a CO-containing gas and desorbing the CO-containing gas from the catalyst.

2. 2. The carbon recycling method according to claim 1, wherein the alkali metal salt is at least one salt of Li, Na, K, Rb, or Cs.

3. 2. The carbon recycling method according to claim 1, wherein the alkaline earth metal salt is at least one salt of Mg, Ca, Sr, or Ba.

4. The catalyst is titanium oxide (TiO ２ 2. The carbon recycling method according to claim 1, characterized in that platinum (Pt) and sodium (Na) salt are supported on the surface of the carbon particles.

5. 2. The carbon recycling method according to claim 1, wherein hydrogen gas is used as the reducing gas.

6. Two CO ２ An adsorption / conversion tube is provided, and the two CO ２ The CO in each of the adsorption / conversion columns ２ The adsorption step and the conversion / desorption step are performed alternately, and the CO ２ One of the adsorption and conversion cylinders is ２ During the adsorption step, the other CO ２ 2. The carbon recycling method according to claim 1, wherein the adsorption / conversion column is adjusted to perform the conversion / separation process.

7. CO ２ CO in the gas ２ and the CO adsorbed in the reducing gas is adsorbed. ２ The catalyst for converting the CO-containing gas into the CO-containing gas is titanium oxide (TiO ２ ) A CO catalyst comprising platinum (Pt) and an alkali metal salt or an alkaline earth metal salt supported on the surface of the particles. ２ Adsorption and conversion catalyst.

8. 8. The CO according to claim 7, wherein the alkali metal salt is at least one of a salt of Li, Na, K, Rb, and Cs. ２ Adsorption and conversion catalyst.

9. 8. The CO composition according to claim 7, wherein the alkaline earth metal salt is at least one of Mg, Ca, Sr, and Ba. ２ Adsorption and conversion catalyst.

10. The catalyst is titanium oxide (TiO ２ 8. The CO 2 catalyst according to claim 7, characterized in that platinum (Pt) and sodium (Na) salts are supported on the surface of the particles. ２ Adsorption and conversion catalyst.

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