Catalyst, apparatus for producing carbon monoxide, method for producing carbon monoxide, and method for producing fuel

Abstract

To provide a catalyst having high selectivity of carbon monoxide even when the conversion rate of carbon dioxide becomes high.SOLUTION: The catalyst is used to reduce carbon dioxide. In the catalyst, alloy particles are supported on a metal oxide support. The alloy particles include a first metal and a second metal. The first metal is one or more selected from the group consisting of ruthenium, rhodium, palladium, osmium, iridium, and platinum. The second metal is one or more selected from the group consisting of vanadium, chromium, manganese, iron, and cobalt.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a catalyst used in the reduction of carbon dioxide, a carbon monoxide production apparatus, a carbon monoxide production method, and a fuel production method. [Background technology]

[0002] Traditionally, efforts have been made to mitigate or reduce the impact of climate change, and research and development into reducing carbon dioxide emissions has been carried out to achieve this.

[0003] Patent Document 1 describes a metal-containing nanoparticle-supported catalyst used for reducing carbon dioxide. The metal-containing nanoparticle-supported catalyst comprises metal-containing nanoparticles supported on semiconductor particles as a support. The metal-containing nanoparticles contain at least one metal atom (M) selected from gold, silver, copper, platinum, rhodium, palladium, nickel, cobalt, iron, manganese, chromium, iridium, zinc, titanium, and ruthenium. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-177094 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the metal-containing nanoparticle supported catalyst described in Patent Document 1 may have a low selectivity for carbon monoxide when the conversion rate of carbon dioxide increases.

[0006] An object of the present invention is to provide a catalyst that has high selectivity for carbon monoxide even when the conversion rate of carbon dioxide is increased. [Means for solving the problem]

[0007] (1) A catalyst used for the reduction of carbon dioxide, comprising alloy particles supported on a metal oxide support, the alloy particles comprising a first metal and a second metal, the first metal being one or more metals selected from the group consisting of ruthenium, rhodium, palladium, osmium, iridium, and platinum, and the second metal being one or more metals selected from the group consisting of vanadium, chromium, manganese, iron, and cobalt.

[0008] (2) The catalyst according to (1), wherein the first metal is palladium and the second metal is iron or cobalt.

[0009] (3) The catalyst according to (1) or (2), wherein the molar ratio of the first metal to the second metal is 1 / 4 or more and 4 or less.

[0010] (4) The catalyst according to (3), wherein the molar ratio of the first metal to the second metal is 11 / 9 or more and 4 or less.

[0011] (5) The catalyst according to any one of (1) to (4), wherein the metal oxide is titanium oxide.

[0012] (6) A carbon monoxide production apparatus comprising the catalyst according to any one of (1) to (5) and a carbon dioxide supply unit that supplies carbon dioxide to the catalyst.

[0013] (7) A method for producing carbon monoxide, comprising reducing carbon dioxide using the catalyst according to any one of (1) to (6).

[0014] (8) A method for producing fuel, comprising the steps of producing carbon monoxide by the method for producing carbon monoxide according to (7) above, and reacting the carbon monoxide with hydrogen by a Fischer-Tropsch process to synthesize fuel. [Effects of the Invention]

[0015] According to the present invention, it is possible to provide a catalyst that has high selectivity for carbon monoxide even when the conversion rate of carbon dioxide is increased. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a graph showing the relationship between CO selectivity and CO2 conversion rate for the catalysts of Examples 1 to 3 and Comparative Example 1. [Figure 2] 1 is a graph showing the relationship between CO selectivity and CO2 conversion rate for the catalysts of Examples 3 to 6. [Figure 3] 1 is a graph showing the relationship between CO selectivity and CO2 conversion rate for the catalysts of Example 7 and Comparative Example 1. [Figure 4] 1 is a diffuse reflectance infrared absorption spectrum of the catalyst of Example 3 on which CO is adsorbed. [Figure 5] 1 is a diffuse reflectance infrared absorption spectrum of the catalyst of Example 7 on which CO is adsorbed. [Figure 6] 1 is a diffuse reflectance infrared absorption spectrum of the catalyst of Comparative Example 1 on which CO is adsorbed. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, an embodiment of the present invention will be described.

[0018] The catalyst of this embodiment is used for reducing carbon dioxide and comprises alloy particles supported on a metal oxide support. The alloy particles include a first metal and a second metal. The first metal is at least one selected from the group consisting of ruthenium, rhodium, palladium, osmium, iridium, and platinum, and the second metal is at least one selected from the group consisting of vanadium, chromium, manganese, iron, and cobalt. Therefore, even if the carbon dioxide conversion rate is increased, the selectivity for carbon monoxide is also increased.

[0019] Here, the chemical bond between carbon monoxide and the metal is completed when an electron is donated (σ-donation) from the 5σ orbital, which is the highest occupied molecular orbital (HOMO) of carbon monoxide, to the vacant orbital of the metal, and at the same time, an electron is donated (π-backdonation) from the occupied orbital of the metal to the 2π orbital, which is the lowest unoccupied molecular orbital (LUMO) of carbon monoxide.

[0020] In the catalyst of this embodiment, it is believed that the ensemble effect of alloy particles containing a first metal and a second metal and the ligand effect in which electrons are donated from the second metal to the first metal, making the first metal electron-excessive, make it difficult for electrons to be donated, thereby suppressing the adsorption of carbon monoxide to the alloy particles. In particular, it is presumed that the suppression of the formation of bridged CO suppresses the formation of methane from bridged CO, resulting in high carbon monoxide selectivity even when the carbon dioxide conversion rate is high.

[0021] The first metal is preferably palladium from the viewpoint of catalytic activity for reducing carbon dioxide, and the second metal is preferably iron or cobalt from the viewpoint of selectivity for carbon monoxide.

[0022] The molar ratio of the first metal to the second metal is preferably 1 / 4 or more and 4 or less, and more preferably 11 / 9 or more and 4 or less. When the molar ratio of the first metal to the second metal is 1 / 4 or more and 4 or less, the selectivity to carbon monoxide is high even if the conversion rate of carbon dioxide is high.

[0023] The average particle size of the alloy particles is not particularly limited, but is, for example, 1 nm or more and 100 nm or less.

[0024] The method for producing the alloy particles is not particularly limited, but for example, a method in which a first metal salt and a second metal salt dissolved in water are reduced to precipitate the alloy particles can be mentioned.

[0025] The metal oxide is not particularly limited as long as it can support alloy particles, and examples thereof include titanium oxide, aluminum oxide, cerium oxide, and zirconium oxide. Among these, titanium oxide is preferred from the viewpoint of selectivity for carbon monoxide.

[0026] The average particle size of the metal oxide support is not particularly limited, but is, for example, 20 nm or more and 50 μm or less.

[0027] The catalyst of this embodiment has high carbon monoxide selectivity even when the carbon dioxide conversion rate is high, and therefore can be applied to, for example, a carbon monoxide production apparatus and a carbon monoxide production method. Here, the carbon monoxide production apparatus includes the catalyst of this embodiment and a carbon dioxide supply unit that supplies carbon dioxide to the catalyst of this embodiment. Furthermore, the carbon monoxide production method produces carbon monoxide by reducing carbon dioxide using the catalyst of this embodiment. In this case, because the carbon monoxide selectivity is high even when the carbon dioxide conversion rate is high, it is possible to synthesize fuel by reacting carbon monoxide with hydrogen using the Fischer-Tropsch process without purifying the carbon monoxide, and as a result, the cost of producing fuel is reduced.

[0028] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and the above-described embodiments may be modified as appropriate within the scope of the spirit of the present invention. [Example]

[0029] Examples of the present invention will be described below, but the present invention is not limited to these examples.

[0030] [Example 1] 0.55 g of sodium borohydride and 41.8 mL of ethanol were mixed to obtain an ethanol solution of sodium borohydride.

[0031] 0.8840 g of a 5% by mass aqueous solution of palladium(II) nitrate, 0.4195 g of a 10% by mass aqueous solution of iron(III) nitrate nonahydrate, 1.16 g of polyvinylpyrrolidone, and 23.9 mL of water were mixed to obtain an aqueous solution of metal salts. At this time, the molar ratio of palladium(II) to iron(III) in the aqueous solution of metal salts was 4.

[0032] An aqueous solution of the metal salt was added dropwise to an ethanol solution of sodium borohydride to reduce the metal salt, resulting in the precipitation of palladium-iron alloy particles, which were then centrifuged at 2500 rpm for 5 minutes. The palladium-iron alloy particles were then washed with a water / ethanol mixed solvent (volume ratio 1:1) and centrifuged at 2500 rpm for 5 minutes. The palladium-iron alloy particles were then washed with a water / ethanol mixed solvent (volume ratio 9:1) and centrifuged at 2500 rpm for 5 minutes. The palladium-iron alloy particles were then transferred to a beaker and ultrasonically dispersed in 150 mL of ethanol, yielding an ethanol dispersion of palladium-iron alloy particles.

[0033] The ethanol dispersion of palladium-iron alloy particles was washed into a recovery flask containing 4.950 g of titanium oxide particles with 50 mL of ethanol, followed by ultrasonic dispersion. Next, the ethanol was removed using an evaporator, and the resulting mixture was calcined at 500°C for 2 hours to obtain a catalyst in which 1% by mass of palladium-iron alloy particles were supported on titanium oxide particles.

[0034] [Example 2] A catalyst was obtained in the same manner as in Example 1, except that the amounts of a 5 mass% aqueous solution of palladium (II) nitrate and a 10 mass% aqueous solution of iron (III) nitrate nonahydrate added when preparing the aqueous solution of metal salts were changed to 0.3227 g and 2.450 g, respectively, so that the molar ratio of palladium (II) to iron (III) was 1 / 4.

[0035] [Example 3] A catalyst was obtained in the same manner as in Example 1, except that the amounts of a 5 mass% aqueous solution of palladium (II) nitrate and a 10 mass% aqueous solution of iron (III) nitrate nonahydrate added when preparing the aqueous solution of metal salts were changed to 0.6996 g and 1.0865 g, respectively, so that the molar ratio of palladium (II) to iron (III) was 11 / 9.

[0036] [Comparative Example 1] 200 mL of pure water was added to a recovery flask containing 1.000 g of a 5% by mass aqueous solution of palladium (II) nitrate and 4.950 g of titanium oxide particles. Next, the mixture was degassed, stirred, and dried using an evaporator, and then calcined at 500°C for 2 hours to obtain a catalyst in which 1% by mass of palladium particles were supported on titanium oxide particles.

[0037] [CO2 Conversion Rate and CO Selectivity] A simulated gas was passed through the catalytic activity evaluation device, and the CO2 conversion rate and CO selectivity were evaluated under the following conditions. At this time, the CO2 conversion rate increased when the flow rate of the simulated gas was reduced. Catalyst amount: 100mg Flow rate of simulated gas: 200 mL / min → 100 mL / min → 50 mL / min → 15 mL / min Simulated gas pressure: 0.1 MPa Partial pressure of simulated gas: CO2 (10 kPa), H2 (60 kPa), Ar (balance) Temperature: 400℃

[0038] Specifically, the CO2 conversion rate is calculated using the formula [(CO2 concentration at the inlet) - (CO2 concentration at the outlet)] / (CO2 concentration at the inlet) x 100 The CO selectivity was calculated using the formula (CO concentration at outlet) / [(CO2 concentration at outlet) + (CO concentration at outlet) + (CH4 concentration at outlet)] x 100 The concentrations of CO2, CO, and CH4 were analyzed by FID and TCD.

[0039] Before evaluating the CO conversion rate and CO selectivity, the catalyst was pretreated by reducing it at 500 °C for 1 hour while flowing a 10% H / 90% Ar mixed gas at a flow rate of 20 mL / min.

[0040] FIG. 1 shows the relationship between CO2 conversion rate and CO selectivity for the catalysts of Examples 1 to 3 and Comparative Example 1.

[0041] 1 shows that the catalysts of Examples 1 to 3 have high CO selectivity even when the CO2 conversion rate is high. In contrast, the catalyst of Comparative Example 1 supports palladium particles, and therefore, as the CO2 conversion rate increases, the CO selectivity decreases.

[0042] [Example 4] A catalyst was obtained in the same manner as in Example 3, except that aluminum oxide particles were used instead of titanium oxide particles.

[0043] [Example 5] A catalyst was obtained in the same manner as in Example 3, except that cerium oxide particles were used instead of titanium oxide particles.

[0044] [Example 6] A catalyst was obtained in the same manner as in Example 3, except that zirconium oxide particles were used instead of titanium oxide particles.

[0045] FIG. 2 shows the relationship between CO2 conversion rate and CO selectivity for the catalysts of Examples 3 to 6.

[0046] 2, it can be seen that the catalyst of Example 3 has high selectivity to CO compared to the catalysts of Examples 4 to 6, even when the conversion rate of CO2 is high.

[0047] [Example 7] 0.46 g of sodium borohydride and 42.3 mL of ethanol were mixed to obtain an ethanol solution of sodium borohydride.

[0048] 0.6436 g of a 5% by mass aqueous solution of palladium(II) nitrate, 0.4195 g of a 10% by mass aqueous solution of cobalt(II) nitrate hexahydrate, 1.18 g of polyvinylpyrrolidone, and 24.2 mL of water were mixed to obtain an aqueous solution of metal salts. At this time, the molar ratio of palladium(II) to cobalt(II) in the aqueous solution of metal salts was 1.

[0049] A catalyst in which 1 mass % of palladium-cobalt alloy particles were supported on titanium oxide particles was obtained in the same manner as in Example 1, except that the obtained aqueous solution of metal salt was used.

[0050] FIG. 3 shows the relationship between CO selectivity and CO2 conversion rate for the catalysts of Example 7 and Comparative Example 1.

[0051] 3, it can be seen that the catalyst of Example 7 has high CO selectivity even when the CO2 conversion rate is high. In contrast, the catalyst of Comparative Example 1, which supports palladium particles, has low CO selectivity as the CO2 conversion rate increases.

[0052] Next, the CO adsorption amounts of the catalysts of Examples 3 and 7 and Comparative Example 1 were measured at a pulse temperature of 50°C using a metal dispersion measuring device BELMETAL3 (manufactured by MicrotrackBell).

[0053] Table 1 shows the measurement results of the CO adsorption amounts of the catalysts of Examples 3 and 7 and Comparative Example 1.

[0054] [Table 1]

[0055] It can be seen from Table 1 that the catalysts of Examples 3 and 7 suppressed CO adsorption compared to the catalyst of Comparative Example 1. This is presumably due to electrons being donated from Fe or Co to Pd.

[0056] Next, CO was adsorbed onto the catalysts of Examples 3 and 7 and Comparative Example 1 in an environment of 50°C and a CO concentration of 1000 ppm, and then the diffuse reflectance infrared absorption spectra were measured. Before adsorbing CO onto the catalyst, the catalyst was subjected to an oxidation treatment in an oxygen atmosphere at 500°C for 15 minutes, and then to a reduction treatment in a hydrogen atmosphere at 500°C for 15 minutes.

[0057] 4 to 6 show the diffuse reflectance infrared absorption spectra of the catalysts of Examples 3 and 7 and Comparative Example 1 on which CO was adsorbed.

[0058] 4 to 6, it can be seen that the catalysts of Examples 3 and 7 have suppressed CO adsorption compared to the catalyst of Comparative Example 1. Here, FIG. 6 shows the on-top CO (2082 cm) peak due to CO adsorption on Pd. -1 ) and Bridged CO (1972cm -1 ) peak can be seen.

[0059] From the above, it is presumed that the catalysts of Examples 3 and 7 suppress CO adsorption compared to the catalyst of Comparative Example 1, thereby suppressing the reduction of CO to CH by H, and as a result, even if the CO conversion rate is high, the CO selectivity is high.

Claims

1. A catalyst for use in the reduction of carbon dioxide, The alloy particles are supported on a metal oxide support, the alloy particles include a first metal and a second metal; the first metal is at least one selected from the group consisting of ruthenium, rhodium, palladium, osmium, iridium, and platinum; The catalyst, wherein the second metal is one or more selected from the group consisting of vanadium, chromium, manganese, iron and cobalt.

2. the first metal is palladium; 10. The catalyst of claim 1, wherein the second metal is iron or cobalt.

3. 3. The catalyst according to claim 1, wherein the molar ratio of the first metal to the second metal is 1 / 4 or more and 4 or less.

4. 4. The catalyst of claim 3, wherein the molar ratio of the first metal to the second metal is 11 / 9 or greater and 4 or less.

5. 3. The catalyst according to claim 1, wherein the metal oxide is titanium oxide.

6. The catalyst according to claim 1 or 2; a carbon dioxide supply unit that supplies carbon dioxide to the catalyst.

7. A method for producing carbon monoxide, comprising reducing carbon dioxide using the catalyst according to claim 1 or 2 to produce carbon monoxide.

8. a step of producing carbon monoxide by the method for producing carbon monoxide according to claim 7; and reacting the carbon monoxide with hydrogen by a Fischer-Tropsch process to synthesize a fuel.

Images