Method for producing carbon monoxide and hydrogen

Abstract

Provided is a method for producing carbon monoxide and hydrogen by reacting carbon dioxide and methane in a gas phase by applying a voltage to a catalyst, whereby the STY of carbon monoxide and hydrogen which are target objects is improved. The method for producing carbon monoxide and hydrogen involves reacting carbon dioxide and methane in a gas phase in the presence of a catalyst at a reaction temperature of 80-400 °C while causing a current to flow through a catalyst in which ruthenium (Ru) is supported on a semiconductor carrier having a band gap of 3.3-6.0 eV.

Description

Carbon monoxide and hydrogen production methods

[0001] The presently disclosed subject matter relates to a method for producing synthesis gas comprising carbon monoxide gas and hydrogen gas.

[0002] Efforts to capture and utilize carbon dioxide, a greenhouse gas, have been attracting attention. There is also a need to develop effective ways to utilize methane, another greenhouse gas known as carbon dioxide, instead of using it as fuel. One such effective utilization method is conversion into useful chemicals. However, because both carbon dioxide and methane are typical inert molecules, conversion using conventional catalytic technology is not easy. In recent years, electrocatalytic technology has been developed as a method for converting inert molecules, in which inert molecules are reacted using a catalyst with an applied voltage.

[0003] Patent Document 1 describes an electric field-applied catalytic reaction device that reacts a raw material gas consisting of methane contained in coke oven gas and carbon dioxide contained in steelworks by-product gas to produce carbon monoxide and hydrogen gas.

[0004] In Non-Patent Document 1, La ２ O ３ system and ZrO ２ It is described that carbon monoxide, hydrogen, ethane, and ethylene can be produced from carbon dioxide and methane by applying a voltage to the catalyst. ２ It is disclosed that carbon monoxide and hydrogen can be produced from carbon dioxide and methane by applying a voltage to a catalyst in which Pt is supported on a carrier.

[0005] Japanese Patent Application Laid-Open No. 2019-206453

[0006] Kazumasa Oshima et al., “Oxidative coupling of methane using carbon dioxide in an electric field over La-ZrO2 catalyst at low external temperature”, Fuel, 2013, vol. 107, pp. 879-881 Naoya Nakano et al., “Elucidation of the reaction mechanism on dry reforming of methane in an electric field by in in situ DRIFTs”, RSC Advances, 2022, vol. 12, pp. 9036-9043

[0007] The present disclosure relates to a method for producing carbon monoxide (CO) and hydrogen (H) by reacting carbon dioxide and methane in the gas phase by applying a voltage to a catalyst. ２ The present invention provides a method for producing carbon monoxide and hydrogen from ethanol, which has an improved STY for the target products, carbon monoxide and hydrogen, and a catalyst for use in the method.

[0008] As a result of extensive research, the present inventors have found that the production of carbon monoxide and hydrogen in a reaction between carbon dioxide and methane is promoted by applying a voltage under heated conditions to a catalyst in which ruthenium (Ru) is supported on a semiconductor support, and have completed the present invention.

[0009] That is, the contents of the present disclosure relate to the following [1] to [8]. [1] A method for producing carbon monoxide and hydrogen using carbon dioxide and methane as raw materials, comprising: passing an electric current through a catalyst in which ruthenium (Ru) is supported on a semiconductor support having a band gap of 3.3 to 6.0 eV; and reacting carbon dioxide and methane in the gas phase in the presence of the catalyst at a reaction temperature of 80 to 400°C. [2] The method according to [1], wherein the amount of Ru supported on the catalyst is 0.05 to 10 parts by mass per 100 parts by mass of the semiconductor support. [3] The semiconductor support is a catalyst in which the amount of Ru supported on the catalyst is 0.05 to 10 parts by mass per 100 parts by mass of the semiconductor support. ２[4] The manufacturing method according to any one of [1] to [3], wherein the reaction is carried out by applying a voltage to the catalyst so that the supported metal+semiconductor support is 0.02 to 250 W / g. [5] The manufacturing method according to any one of [1] to [4], wherein the reaction temperature is 100 to 300°C. [6] The manufacturing method according to any one of [1] to [5], wherein the space velocity of the reaction is 1000 to 50000 / h. [7] The manufacturing method according to any one of [1] to [5], wherein the molar ratio of carbon dioxide to methane (CO ２ / CH ４ [8] An electrocatalyst used in the production of carbon monoxide and hydrogen from carbon dioxide and methane as raw materials, wherein Ru is supported on a semiconductor support having a band gap of 3.3 to 6.0 eV.

[0010] According to the present disclosure, it is possible to provide a method for producing carbon monoxide and hydrogen by reacting carbon dioxide and methane in the gas phase by applying a voltage to a catalyst, in which the STY of the target carbon monoxide and hydrogen is improved, and a catalyst used in the method.

[0011] FIG. 1 is a schematic diagram of an apparatus used for the reaction of carbon dioxide and methane in Examples 1 to 3 and Comparative Examples 1 to 3.

[0012] Hereinafter, embodiments of the present invention will be described, but it should be understood that the present invention is not limited to these embodiments and that various applications are possible within the spirit and scope of the present invention. In this disclosure, when "to" is used to describe a numerical range, the numerical values ​​at both ends are the upper and lower limits, respectively, and are included in the numerical range. When multiple upper or lower limits are listed, numerical ranges can be created using all combinations of the upper and lower limits. Similarly, when multiple numerical ranges are listed, separate numerical ranges can be created by individually selecting and combining the upper and lower limits from those numerical ranges.

[0013] (Catalyst for use in the reaction of carbon dioxide and methane and its manufacturing method) For the reaction of carbon dioxide and methane, an electric field catalyst in which ruthenium (Ru) is supported on a semiconductor carrier is used.

[0014] In the present disclosure, the semiconductor carrier refers to a semiconductor carrier having a band gap of 3.3 to 6.0 eV. By making the band gap 3.3 eV or more, the STY of carbon monoxide and hydrogen gas can be increased. If the band gap is 6.0 eV or less, the influence of discharge and the like is small, and voltage application is easy. The band gap of the semiconductor carrier is more preferably 3.3 to 5.0 eV, and even more preferably 3.3 to 4.0 eV.

[0015] The semiconductor carrier is not particularly limited as long as it has a band gap of 3.3 to 6.0 eV, but is preferably a metal oxide. ２ (3.3eV), ZrO ２ (5.0 eV) and ZnO (3.4 eV), and ２ The value in parentheses after the metal oxide is the band gap. The band gap value of the semiconductor carrier is measured by a conventionally known method such as a spectroscopic method.

[0016] The method for producing the semiconductor carrier is not particularly limited, and commercially available carriers can also be used as the semiconductor carrier.

[0017] The amount of Ru (metallic ruthenium) supported is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, even more preferably 1.0 parts by mass or more, preferably 10 parts by mass or less, more preferably 7 parts by mass or less, and even more preferably 5 parts by mass or less, relative to 100 parts by mass of the semiconductor support. Any combination of these lower and upper limits may be used. For example, the amount of Ru supported is preferably 0.05 to 10 parts by mass, more preferably 0.1 to 7 parts by mass, and even more preferably 1.0 to 5 parts by mass, relative to 100 parts by mass of the semiconductor support. When the amount of Ru supported is 0.05 parts by mass or more, the activity per unit catalyst mass or volume can be increased. When the amount of Ru supported is 10 parts by mass or less, the decrease in catalytic activity due to Ru aggregation can be suppressed. The amount of Ru supported is determined by elemental analysis such as ICP or X-ray fluorescence.

[0018] In one embodiment, the method for supporting Ru on a semiconductor carrier includes an impregnation step in which the semiconductor carrier is absorbed or impregnated with a Ru salt solution (hereinafter referred to as an "impregnation solution"), a drying step, a calcination step, and a reduction step, in this order. Other steps may be included between each step. Examples of such other steps include an air-drying step and a transfer step from an impregnation apparatus to a drying apparatus.

[0019] The Ru salt used in the impregnation step is not particularly limited, and examples thereof include ruthenium chloride, ruthenium acetate, tris(acetylacetonato)ruthenium(III), and combinations thereof. Commercially available Ru salts can also be used. The concentration of the Ru salt in the impregnation solution can be determined from the volume of the impregnation solution and the amount of Ru to be supported on the semiconductor support.

[0020] The solvent used in the impregnation step is not particularly limited as long as it can dissolve the Ru salt, and examples of such solvents include water, ethanol, and acetone.

[0021] The conditions for the drying step are not particularly limited, but generally the material can be dried in air for 1 to 24 hours at 100 to 200° C. A commercially available dryer can be used for the drying treatment.

[0022] The conditions for the calcination step are not particularly limited, but calcination can generally be carried out at 400 to 600°C for 0.5 to 12 hours under air flow. A commercially available calcination device such as a muffle furnace can be used for the calcination treatment. In the calcination step, the Ru salt is converted into ruthenium oxide (RuO ２ ) is converted into

[0023] In the reduction step, for example, hydrogen gas or a mixture of hydrogen gas and an inert gas such as nitrogen gas or helium is applied to a catalyst precursor in which ruthenium oxide is supported on a carrier at a space velocity (SV Ｈ２ The reduction step can be carried out by heating the catalyst at 300 to 600°C for 0.5 to 5 hours while passing the gas through at a flow rate of 4000 to 16000 / h. The reduction step is preferably carried out immediately before the reaction of carbon dioxide with methane in the reaction vessel. The oxidation state of the catalyst element after the reduction step with hydrogen gas is determined by the standard oxidation-reduction potential of the oxide / metal. That is, when the standard oxidation-reduction potential is H ＋ / H ２ Compared to 0 V, if the voltage is positive, the metal is easily reduced to the metal, but if the voltage is negative, the metal is not easily reduced to the metal. For example, Ru ３＋ Since the standard oxidation-reduction potential of Ce / Ru is 0.249 V, it is easily reduced to the metal, but since the standard oxidation-reduction potential of Ce, Zr, and Zn becomes negative from a low oxidation state, they are not reduced to the metal and remain in the oxide state. (Ce ３＋ / Ce: -2.483V, Zr ４＋ / Zr: -1.553V, Zn ２＋ / Zn: -0.762V, Source: HANDBOOK of CHEMISTRY and PHYSICS (1st Student Edition)

[0024] (Method for Producing Carbon Monoxide and Hydrogen) Carbon monoxide and hydrogen are produced by reacting carbon dioxide and methane in the gas phase under heated conditions in the presence of a catalyst through which a voltage is applied and a current flows.

[0025] In this reaction system, the dry reforming reaction of carbon dioxide and methane (Equation (1)) and the reverse water gas shift reaction of carbon dioxide and hydrogen (Equation (2)) proceed simultaneously. Therefore, in order to improve the STY of carbon monoxide and hydrogen, it is necessary to set reaction conditions that allow the reaction of Equation (1) to proceed while suppressing the reaction of Equation (2).

[0026] CH ４ +CO ２ → 2CO + 2H ２ (1) CO ２ +H ２ → CO + H ２ O (2)

[0027] Since a portion of the produced hydrogen is consumed by the reaction of formula (2), the proportion of carbon monoxide discharged from the reactor is greater than the proportion of hydrogen gas.

[0028] The reaction temperature is 80 to 400°C. In the present disclosure, the reaction temperature means the temperature downstream of the catalyst layer, near the center of the cross section of the flow path, during the reaction. The reaction temperature is preferably 100°C or higher, more preferably 150°C or higher, preferably 300°C or lower, and more preferably 270°C or lower. Any combination of these lower and upper limits may be used. For example, the reaction temperature is preferably 100 to 300°C, more preferably 150 to 270°C. If the reaction temperature is 80°C or higher, a sufficient current can be passed through the catalyst. If the reaction temperature is 400°C or lower, coke deposition or aggregation of Ru species, which can cause catalyst deterioration, is suppressed. Without being bound by any theory, it is believed that placing the electric field catalyst in a high-temperature environment allows protons (H ＋ ) is generated, and the generated protons are thought to form the conductive paths necessary for catalyst activation.

[0029] The reaction pressure is preferably 0 to 5 MPaG (gauge pressure), more preferably 0 to 3 MPaG (gauge pressure), and even more preferably 0 to 1.5 MPaG (gauge pressure). If the reaction pressure is 0 to 5 MPaG (gauge pressure), side reactions are less likely to proceed and the catalyst is highly stable, allowing the reaction of carbon dioxide and methane to proceed efficiently.

[0030] The space velocity (gas flow rate (mL / h) / catalyst volume (mL) = 1 / h) of the gas containing the reactant gas supplied to the reactor is preferably 1000 / h or more, more preferably 1500 / h or more, even more preferably 2000 / h or more, preferably 50,000 / h or less, more preferably 30,000 / h or less, and even more preferably 15,000 / h or less. Any combination of these lower and upper limits may be used. For example, the space velocity of the gas containing the reactant gas is preferably 1000 to 50,000 / h, more preferably 1500 to 30,000 / h, and even more preferably 2000 to 15,000 / h. A space velocity of 1000 to 50,000 / h ensures sufficient time for the reactant gas to contact the catalyst, allowing the reaction between carbon dioxide and methane to proceed efficiently. The reaction between carbon dioxide and methane can proceed without problems even when an inert gas such as nitrogen or helium is simultaneously passed through.

[0031] (Reaction Raw Material Gas) The form of the reaction raw material gases carbon dioxide and methane is not particularly limited, and commercially available gases can be used. A mixed gas of the reaction raw material gas and an inert gas such as nitrogen gas or argon can also be used for the reaction. In this case, from the viewpoint of efficient reaction progress, it is preferable that the ratio of the volume of the inert gas to the total volume of carbon dioxide and methane (volume of inert gas / volume of (carbon dioxide + methane)) is 0.9 or less.

[0032] The molar ratio of raw materials in the above reaction, i.e., the molar ratio of carbon dioxide to methane (CO ２ / CH ４ The molar ratio of the raw materials is preferably 0.05 or more, more preferably 0.1 or more, even more preferably 0.5 or more, and preferably 20 or less, more preferably 8 or less, and even more preferably 4 or less. Any combination of these lower limit and upper limit values ​​may be used. For example, the raw material molar ratio is preferably 0.05 to 20, more preferably 0.1 to 8, and even more preferably 0.5 to 4. When the raw material molar ratio is 0.05 to 20, the reaction of carbon dioxide and methane can be efficiently promoted, and the reaction of carbon dioxide or methane alone can be suppressed.

[0033] (Reactor) A carbon dioxide and methane reaction apparatus includes a reactor vessel for containing a catalyst and for bringing the catalyst into contact with carbon dioxide and methane, and a means for generating an electric field in the catalyst layer. A schematic diagram of a reactor used for the reaction of carbon dioxide and methane is shown in Figure 1. Figure 1 shows an example of a carbon dioxide and methane reaction apparatus, and usable reactors are not limited to this structure. In Figure 1, the carbon dioxide and methane reaction apparatus 1 includes two spaced electrodes 4 and 5 inside a reaction tube 3, with a catalyst filled between the electrodes to form a catalyst layer 2. The two electrodes 4 and 5 consist of a high-voltage electrode 4 to which a voltage is applied from a power source 6 and a grounded electrode 5. The electrodes 4 and 5 are made of a metal mesh, such as stainless steel, to hold the catalyst and allow the flow of the reactant gas. The reaction tube 3 is made of a non-conductive material to prevent electrical conduction between the electrodes. The reaction apparatus 1 also includes a heating means, such as a heater 7, for heating the catalyst layer 2 and maintaining a predetermined reaction temperature.

[0034] The reaction tube 3 is generally made of a material that is non-conductive and does not affect the reaction between carbon dioxide and methane. A preferred material for the reaction tube 3 is, for example, quartz. The shape of the reaction tube 3 may be a shape other than the cylindrical shape shown in FIG. 1 . The size of the reaction tube 3 may be appropriately set depending on the required processing amount, etc., and is not particularly limited. Various conditions such as the sizes of the high-voltage side electrode 4 and the ground side electrode 5, and the amount of the catalyst layer 2 in the reaction tube 3 may be appropriately set depending on the size of the reaction tube 3, etc., and are not particularly limited.

[0035] In the carbon dioxide and methane reactor 1, carbon dioxide and methane are supplied downward from the top of the reaction tube 3. At this time, a voltage is applied from a power source 6 between a high-voltage electrode 4 and a ground electrode 5, which are spaced apart, to generate an electric field, and by passing a current, the reactant gas can be brought into contact with the catalyst layer 2 in the electric field. The applied voltage is preferably adjusted so that the power (W) applied to the catalyst layer 2 is 0.02 to 250 W per gram of the total mass of Ru, which is the supported metal, and the semiconductor support. That is, the voltage is preferably applied at 0.02 W / g or more of the supported metal + semiconductor carrier, more preferably 0.1 W / g or more of the supported metal + semiconductor carrier, even more preferably 0.5 W / g or more of the supported metal + semiconductor carrier, particularly preferably 1.0 W / g or more of the supported metal + semiconductor carrier, preferably 250 W / g or less of the supported metal + semiconductor carrier, more preferably 150 W / g or less of the supported metal + semiconductor carrier, even more preferably 30 W / g or less of the supported metal + semiconductor carrier, particularly preferably 10 W / g or less of the supported metal + semiconductor carrier. For example, the voltage is preferably applied at 0.02 to 250 W / g of the supported metal + semiconductor carrier, more preferably 0.1 to 150 W / g of the supported metal + semiconductor carrier, even more preferably 0.5 to 30 W / g of the supported metal + semiconductor carrier, particularly preferably 1.0 to 10 W / g of the supported metal + semiconductor carrier. If the supported metal+semiconductor carrier has a loading of 0.02 to 250 W / g, a voltage can be applied to the catalyst with an appropriate power, and the reaction between carbon dioxide and methane can be effectively promoted.

[0036] The present invention will be further described with reference to the following examples and comparative examples, but the present invention is not limited to these examples.

[0037] (Preparation of catalyst precursor A) 15 g of an ethanol solution containing 0.0788 g of tris(acetylacetonato)ruthenium(III) was mixed so that the amount of Ru supported was 1 part by mass per 100 parts by mass of the support, and commercially available CeO ２ Carrier (BET specific surface area: 93 m ２2 g of ruthenium salt-supported carrier (100%) was mixed with 2 g of ruthenium salt (100%). After distilling off the ethanol using an evaporator, the mixture was dried in a dryer at 120°C for 5 hours. The resulting Ru salt-supported carrier was then pulverized in an agate mortar for 5 minutes and calcined in air at 450°C for 2 hours using a muffle furnace. The resulting powder was sized to a mesh size of 300 to 500 μm to obtain catalyst precursor A.

[0038] (Preparation of Catalyst Precursor B) Catalyst precursor B was prepared in the same manner as catalyst precursor A, except that the amount of tris(acetylacetonato)ruthenium(III) was changed to 0.3941 g so that the amount of Ru supported was 5 parts by mass per 100 parts by mass of the support.

[0039] (Preparation of Comparative Catalyst Precursor C) Comparative catalyst precursor C was prepared in the same manner as catalyst precursor A, except that 0.0632 g of rhodium(III) nitrate was used instead of tris(acetylacetonato)ruthenium(III) so that the amount of Rh supported was 1 part by mass per 100 parts by mass of the support.

[0040] (Preparation of Comparative Catalyst Precursor D) Comparative catalyst precursor D was prepared in the same manner as catalyst precursor A, except that 0.0422 g of palladium acetate (II) was used instead of tris(acetylacetonato)ruthenium (III) so that the amount of Pd supported was 1 part by mass per 100 parts by mass of the support.

[0041] (Preparation of Comparative Catalyst Precursor E) Comparative catalyst precursor E was prepared in the same manner as catalyst precursor A, except that 0.0397 g of tetraamineplatinum(II) nitrate was used instead of tris(acetylacetonato)ruthenium(III) so that the amount of Pt supported was 1 part by mass per 100 parts by mass of the support.

[0042] (Reaction of Carbon Dioxide and Methane) The reaction of carbon dioxide and methane was carried out using the reactor 1 shown in FIG. 1 . A cylindrical quartz reactor having an outer diameter of 20 mm, an inner diameter of 9 mm, and a length of 260 mm was used as the reaction tube 3. 0.18 mL of a granulated catalyst precursor (or comparative catalyst precursor; the same applies hereinafter) was packed on a stainless steel mesh ground electrode 5 provided in the reaction tube 3, and a stainless steel mesh high-voltage electrode 4 was brought into contact with the top of the catalyst precursor to form a catalyst layer 2. The thickness of the catalyst layer 2 was 3 mm. The conductive wire connecting the high-voltage electrode 4 to the power source 6 and the conductive wire connecting the ground electrode 5 to earth were both stainless steel rods with a diameter of 3.2 mm. The high-voltage electrode 4 was electrically connected to the power source 6 (DC high-voltage power supply: HAR-10N30, Matsusada Precision Co., Ltd.).

[0043] In the reactor 1, hydrogen gas was supplied from the top of the reaction tube 3 at a rate of 1.2 NL / h and argon gas at a rate of 4.8 NL / h. The heater temperature was adjusted so that the temperature of the catalyst layer 2 was 400°C, and the mixture was allowed to flow for 0.5 hours. This carried out a reduction step in which the catalyst precursor was reduced with hydrogen gas to convert ruthenium oxide to metallic ruthenium (or rhodium oxide to metallic rhodium, palladium oxide to metallic palladium, or platinum oxide to metallic platinum). The space velocity of the hydrogen gas was 6700 / h. The temperature of the catalyst layer 2 was measured using a thermocouple located below the catalyst layer 2.

[0044] In the reactor 1, carbon dioxide gas and methane gas were supplied as reaction feed gases from the top of the reaction tube 3. The pressure inside the reaction tube 3 was increased from atmospheric pressure to 0.8 MPaG (gauge pressure). The temperature of the catalyst layer 2 was then increased to 180°C using the heater 7. Then, a current was passed from the power source 6 between the high-voltage electrode 4 and the ground electrode 5 to generate an electric field within the catalyst layer 2, thereby carrying out a reaction between carbon dioxide and methane. The carbon dioxide gas supply rate was 0.6 NL / h, and the methane gas supply rate was also 0.6 NL / h (raw material molar ratio: 1.0). The space velocity of the reaction feed gas was 6700 / h. During the reaction, a constant current was applied at the value determined for each example and comparative example listed in Table 1, and the temperature of the heater 7 was adjusted so that the temperature of the catalyst layer 2 was the temperature listed in Table 1. The corresponding voltage was measured using the power source 6.

[0045] The reaction product gas discharged from the bottom of the reaction tube 3 was analyzed by gas chromatography.

[0046] (Method of Analyzing Gas Products) 1. Hydrogen (H ２ ) Using the absolute calibration curve method, 40 mL of gas components were collected and the entire amount was passed through a 1 mL gas sampler attached to a gas chromatography analyzer, and analysis was performed under the following conditions. Gas chromatography analyzer: 7890A (Agilent Technology Co., Ltd.) Column: 8 Ft Molecular Sieve 5A 60 / 80 mesh (Agilent Technology Co., Ltd., length 2.4 m, inner diameter 2 mm) Carrier gas: nitrogen gas (split ratio: 80, column flow rate 2 mL / min) Temperature conditions: The temperature of the detector and vaporizer was set to 250°C, and the column temperature was maintained at 50°C for 7 minutes from the start of analysis, and then the temperature was increased to 75°C at a rate of 10°C / min and maintained at 75°C for 1 minute. Thereafter, the temperature was increased to 145°C at a rate of 20°C / min and maintained at 145°C for 3 minutes. Detector: TCD

[0047] 2. Carbon monoxide (CO) The gas sample was introduced into the gas chromatography apparatus in the same manner as in the hydrogen analysis described above. The gas chromatography analysis was carried out under the following conditions. Gas chromatography analyzer: 7890A (Agilent Technology Co., Ltd.) Column: 6 ft HayeSep Q 80 / 100 mesh in Nickel (Agilent Technology Co., Ltd., length 1.8 m, inner diameter 2 mm) and 8 ft Molecular Sieve 5A 60 / 80 mesh (Agilent Technology Co., Ltd., length 2.4 m, inner diameter 2 mm) Carrier gas: Helium (split ratio: 80, column flow rate 2 mL / min) Temperature conditions: The same as in the hydrogen analysis described above. Detector: TCD

[0048] From the above analytical results, the space-time yield (STY) of each product was calculated. The calculation method is as follows: Product STY (g / L h) = Amount of product produced (g) / [Volume of catalyst (supported metal + support) (L) × Reaction time (h)]

[0049] Example 1 0.18 mL of catalyst precursor A was packed into the reaction tube 3, and after carrying out the reduction step, carbon dioxide and methane were reacted. After carrying out the reaction for 1 hour, the gas product was analyzed and the space-time yields of carbon monoxide and hydrogen were calculated. The reaction conditions and results are shown in Table 1. Note that a volume change occurs when ruthenium oxide is reduced to metallic ruthenium. However, since the mass of metallic ruthenium is about 1 part by mass per 100 parts by mass of the support, which does not change in volume during the reduction step, the volume change was ignored when calculating the STY.

[0050] Example 2 A reaction between carbon dioxide and methane was carried out in the same manner as in Example 1, except that the applied current was set to 10 mA, and analysis was carried out in the same manner as in Example 1. The results are shown in Table 1.

[0051] Example 3 A reaction between carbon dioxide and methane was carried out in the same manner as in Example 1, except that catalyst precursor B was packed instead of catalyst precursor A, and analysis was carried out in the same manner as in Example 1. The results are shown in Table 1.

[0052] Comparative Examples 1 to 3 Carbon dioxide and methane were reacted and analyzed in the same manner as in Example 1, except that comparative catalyst precursors C to E were packed instead of catalyst precursor A. The results are shown in Table 1.

[0053] As shown in Table 1, in Example 1, the semiconductor carrier CeO ２ It can be seen that the reaction was carried out while passing an electric current through the catalyst on which Ru was supported, and the target products, carbon monoxide and hydrogen, were produced.

[0054] From Example 2, it can be seen that carbon monoxide and hydrogen were produced even under conditions of different current values.

[0055] From Example 3, it can be seen that carbon monoxide and hydrogen were produced even under conditions where the amount of supported metal was different.

[0056] Comparing Example 1 with Comparative Examples 1 to 3, the semiconductor carrier CeO ２ It can be seen that the catalyst supporting Ru on the catalyst has higher STY for carbon monoxide and hydrogen than the catalysts supporting other metals.

[0057]

[0058] 1: Carbon dioxide and methane reactor 2: Catalyst layer 3: Reaction tube 4: High-voltage electrode 5: Ground electrode 6: Power supply 7: Heater

Claims

1. A method for producing carbon monoxide and hydrogen using carbon dioxide and methane as raw materials, which comprises passing an electric current through a catalyst comprising ruthenium (Ru) supported on a semiconductor carrier having a band gap of 3.3 to 6.0 eV, and reacting carbon dioxide and methane in the gas phase in the presence of the catalyst at a reaction temperature of 80 to 400°C.

2. The method according to claim 1, wherein the amount of Ru supported in the catalyst is 0.05 to 10 parts by mass per 100 parts by mass of the semiconductor support.

3. The semiconductor support is CeO ２ The method according to claim 1 or 2, wherein 4. The method according to claim 1 or 2, wherein the reaction is carried out by applying a voltage to the catalyst so that the loaded metal+semiconductor support is 0.02 to 250 W / g.

5. The method according to claim 1 or 2, wherein the reaction temperature is 100 to 300°C.

6. The production method according to claim 1 or 2, wherein the space velocity of the reaction is 1,000 to 50,000 / h.

7. The molar ratio of carbon dioxide to methane in the reaction (CO ２ / CH ４ The method according to claim 1 or 2, wherein the ratio (R) is 0.05 to 20.

8. An electrocatalyst used for producing carbon monoxide and hydrogen from carbon dioxide and methane as raw materials, the electrocatalyst comprising Ru supported on a semiconductor support having a band gap of 3.3 to 6.0 eV.

Images