Method for producing acetaldehyde and ethanol

Abstract

To provide a method for producing acetaldehyde and ethanol by reacting carbon dioxide and methane in a gas phase by applying a voltage to a catalyst, which is improved in at least one of an STY ratio (acetaldehyde STY / carbon monoxide STY) between acetaldehyde as an objective substance and carbon monoxide as an intermediate substance and an STY ratio (ethanol STY / carbon monoxide STY) between ethanol as an objective substance and carbon monoxide as an intermediate substance.SOLUTION: Provided is a method for producing acetaldehyde and ethanol by reacting a carbon dioxide and methane in a gas phase in the presence of a catalyst at a reaction temperature 80 to 400°C, while an electric current is applied to the catalyst in which rhodium (Rh) and an oxide of at least one element selected from the group consisting of titanium (Ti), vanadium (V), molybdenum (Mo), tungsten (W) and manganese (Mn) are supported on semiconductor carriers having a band gap of 3.3 to 6.0 eV.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The presently disclosed subject matter relates to a method for producing acetaldehyde and ethanol. [Background technology]

[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, which is also known as a greenhouse gas like carbon dioxide, as an alternative to using it as fuel. One such effective utilization method is to convert it into useful chemicals. However, because both carbon dioxide and methane are typically 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, characterized by applying voltage to a catalyst to cause the inert molecules to react.

[0003] For example, 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] Non-Patent Document 1 describes that carbon monoxide, hydrogen, ethane, and ethylene can be produced from carbon dioxide and methane by applying a voltage to a La2O3-based and ZrO2-based catalyst. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2019-206453 [Non-patent literature]

[0006] [Non-Patent Document 1] 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 Summary of the Invention [Problem to be solved by the invention]

[0007] The present disclosure provides a method for producing acetaldehyde and ethanol by reacting carbon dioxide and methane in the gas phase by applying a voltage to a catalyst, in which at least one of the STY ratios of the target product, acetaldehyde, and the intermediate product, carbon monoxide (acetaldehyde STY / carbon monoxide STY) and the STY ratio of the target product, ethanol, and the intermediate product, carbon monoxide (ethanol STY / carbon monoxide STY) is improved, and a catalyst used in the method is provided. [Means for solving the problem]

[0008] As a result of extensive research, the present inventors have discovered that in the reaction of carbon dioxide with methane, the production of at least one C2 compound selected from acetaldehyde and ethanol from the intermediate carbon monoxide is promoted by applying a voltage under heated conditions to a catalyst in which an oxide of at least one element selected from the group consisting of titanium (Ti), vanadium (V), molybdenum (Mo), tungsten (W), and manganese (Mn) and rhodium (Rh) are supported on a semiconductor support, and thus completed the present invention.

[0009] That is, the contents of the present disclosure relate to the following [1] to [9]. [1] A method for producing acetaldehyde and ethanol, comprising: passing an electric current through a catalyst in which an oxide of at least one element selected from the group consisting of titanium (Ti), vanadium (V), molybdenum (Mo), tungsten (W), and manganese (Mn), and rhodium (Rh) are 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 production method according to [1], wherein the total amount of at least one element selected from the group consisting of Ti, V, Mo, W, and Mn supported on the catalyst is 20 to 50 parts by mole per 100 parts by mole of the Rh. [3] The manufacturing method according to [1] or [2], wherein the semiconductor support is at least one selected from the group consisting of CeO2 and ZrO2. [4] The method according to any one of [1] to [3], wherein the amount of Rh supported on the catalyst is 0.05 to 10 parts by mass with respect to 100 parts by mass of the semiconductor support. [5] The reaction is 0.02 to 250 W / g 担持金属+半導体担体 The manufacturing method according to any one of [1] to [4], wherein the voltage is applied so that [6] The production method according to any one of [1] to [5], wherein the reaction temperature is 100 to 300°C. [7] The method according to any one of [1] to [6], wherein the space velocity of the reaction is 1,000 to 50,000 / h. [8] The method according to any one of [1] to [7], wherein the molar ratio of carbon dioxide to methane (CO2 / CH4 ratio) in the reaction is 0.05 to 20. [9] An electric field catalyst used in the production of acetaldehyde and ethanol using carbon dioxide and methane as raw materials, the electric field catalyst comprising an oxide of at least one element selected from the group consisting of Ti, V, Mo, W, and Mn, and Rh, supported on a semiconductor support having a band gap of 3.3 to 6.0 eV. [Effects of the Invention]

[0010] According to the present disclosure, it is possible to provide a method for producing acetaldehyde and ethanol by reacting carbon dioxide and methane in the gas phase by applying a voltage to a catalyst, in which at least one of the STY ratio between the target product acetaldehyde and the intermediate product carbon monoxide (acetaldehyde STY / carbon monoxide STY) and the STY ratio between the target product ethanol and the intermediate product carbon monoxide (ethanol STY / carbon monoxide STY) is improved, and a catalyst used in the method is provided. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram of an apparatus used for the reaction of carbon dioxide with methane in Examples 1 to 7 and Comparative Examples 1 to 4. [Figure 2] FIG. 1 is a diagram showing the relationship between the space-time yield (STY) of carbon monoxide obtained by the reaction of carbon dioxide with methane and the space-time yield of (a) acetaldehyde and (b) ethanol in Example 1, Examples 4 to 7, Comparative Example 1, and Comparative Example 3. DETAILED DESCRIPTION OF THE INVENTION

[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 "~" 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 from 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 upper and lower limits from those numerical ranges.

[0013] (Catalyst for use in the reaction of carbon dioxide and methane and its manufacturing method) The reaction between carbon dioxide and methane uses an electric field catalyst in which an oxide of at least one element (also called a second metal) selected from the group consisting of titanium (Ti), vanadium (V), molybdenum (Mo), tungsten (W), and manganese (Mn) and rhodium (Rh) are supported on a semiconductor support.

[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 acetaldehyde and ethanol can be increased. When the band gap is 6.0 eV or less, the influence of discharge and the like is reduced, 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. The semiconductor carrier preferably contains at least one selected from the group consisting of CeO2 (3.3 eV), ZrO2 (5.0 eV), and ZnO (3.4 eV), and more preferably contains at least one selected from the group consisting of CeO2 and ZrO2. 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 Rh (metallic rhodium) 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, and preferably 10 parts by mass or less, more preferably 7 parts by mass or less, and even more preferably 3.0 parts by mass or less, relative to 100 parts by mass of the semiconductor support. Any combination of these lower and upper limits is acceptable. For example, the amount of Rh 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 3.0 parts by mass, relative to 100 parts by mass of the semiconductor support. When the amount of Rh supported is 0.05 parts by mass or more, the activity per unit catalyst mass or volume can be increased. When the amount of Rh supported is 10 parts by mass or less, a decrease in catalytic activity due to aggregation of Rh can be suppressed.

[0018] The total amount of at least one element selected from the group consisting of Ti, V, Mo, W, and Mn supported is preferably 20 molar parts or more, more preferably 25 molar parts or more, even more preferably 30 molar parts or more, and preferably 50 molar parts or less, more preferably 45 molar parts or less, and even more preferably 40 molar parts or less, relative to 100 molar parts of Rh. Any combination of these lower and upper limits may be used. For example, the total amount of at least one element selected from the group consisting of Ti, V, Mo, W, and Mn supported is preferably 20 to 50 molar parts, more preferably 25 to 45 molar parts, and even more preferably 30 to 40 molar parts, relative to 100 molar parts of Rh. When the total amount of at least one element selected from the group consisting of Ti, V, Mo, W, and Mn supported is 20 molar parts or more, it can efficiently interact with Rh, thereby increasing the activity per unit catalyst mass or volume. When the total amount of at least one element selected from the group consisting of Ti, V, Mo, W, and Mn is 50 parts by mole or less, it is possible to prevent a decrease in catalytic activity due to excessive coating on Rh. Note that the amount of support is a value related to the number of moles of each element, not the number of moles of the oxide of each element.

[0019] Without being bound by any theory, oxides of Ti, V, Mo, W, and Mn have an electronic effect on Rh, changing the electron density of Rh, which in turn promotes the insertion reaction of carbon monoxide produced in the dry reforming of carbon dioxide and methane, thereby improving the activity of Rh in reactions that produce oxygen-containing organic compounds such as acetaldehyde and ethanol.

[0020] In one embodiment, a method for supporting an oxide of at least one element selected from the group consisting of Ti, V, Mo, W, and Mn, and Rh on a semiconductor support includes, in this order, an impregnation step in which the semiconductor support is absorbed or impregnated with a solution of a metal precursor of at least one element selected from the group consisting of Ti, V, Mo, W, and Mn, and a Rh salt (hereinafter referred to as an "impregnation solution"), a drying step, a calcination step, and a reduction step. Other steps may be included between each step. Examples of other steps include an air-drying step and a transfer step from an impregnation apparatus to a drying apparatus.

[0021] The Rh salt used in the impregnation step is not particularly limited, and examples thereof include commercially available rhodium chloride trihydrate, pentaamminechlororhodium dichloride, rhodium nitrate, or a combination thereof. The concentration of the Rh salt in the impregnation solution is determined based on the volume of the impregnation solution and the amount of Rh to be supported on the semiconductor support.

[0022] The metal precursor of at least one element selected from the group consisting of Ti, V, Mo, W, and Mn used in the impregnation step is not particularly limited, and examples include commercially available inorganic metal salts and metal complexes. Examples of Ti precursors include titanium complexes such as titanium tetraisopropoxide and titanium salts such as titanium(IV) chloride. Examples of V precursors include vanadates such as ammonium vanadate(V) and vanadium salts such as vanadium(III) chloride. Examples of Mo precursors include molybdates such as ammonium molybdate(VI) tetrahydrate and molybdenum salts such as molybdenum(V) chloride. Examples of W precursors include tungstates such as ammonium tungstate parapentahydrate and tungsten salts such as tungsten(VI) chloride. Examples of Mn precursors include manganese salts such as manganese(II) chloride tetrahydrate and manganese(II) nitrate hexahydrate. The concentration of the metal precursor of at least one element selected from the group consisting of Ti, V, Mo, W, and Mn in the impregnation solution is determined from the volume of the impregnation solution and the amount of oxide of at least one element selected from the group consisting of Ti, V, Mo, W, and Mn to be supported on the semiconductor support.

[0023] The solvent used in the impregnation step is not particularly limited as long as it can dissolve the metal precursor of at least one element selected from the group consisting of Ti, V, Mo, W, and Mn, and the Rh salt, etc. Examples of such solvents include water, ethanol, acetone, and hexane.

[0024] 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 150° C. A commercially available dryer can be used for the drying process.

[0025] The conditions for the calcination step are not particularly limited, but calcination can generally be performed 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 metal precursor of at least one element selected from the group consisting of Ti, V, Mo, W, and Mn, and the Rh salt, become the oxides of the respective elements.

[0026] The reduction step is carried out, for example, by adding hydrogen gas or a mixture of hydrogen gas and an inert gas such as nitrogen gas or helium to a catalyst precursor having an oxide of at least one element selected from the group consisting of Ti, V, Mo, W, and Mn and an oxide of Rh supported on a support at a space velocity (SV H2 The reduction step can be carried out by heating at 300 to 600°C for 1 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 + / H2: Compared to 0V, if the value is positive, the metal is easily reduced to the metal, but if the value is negative, the metal is not reduced to the metal. For example, Rh 3+ The standard redox potential of / Rh is 0.758 V, so it is easily reduced to the metal. However, Ti, V, Mo, W, and Mn are not reduced to the metal because the standard redox potential of the oxide / metal becomes negative from a low oxidation state, and they remain in the oxide state. (Ti 2+ / Ti:-1.630V, V 2+ / V:-1.175V, Mo 3+ / Mo:-0.200V, W 4+ / W:-0.119V, Mn 2+ / Mn:-1.185V, Source: HANDBOOK of CHEMISTRY and PHYSICS (1st Student Edition)

[0027] (Method for producing acetaldehyde and ethanol) Acetaldehyde and ethanol 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 an electric current flows.

[0028] This reaction is thought to proceed through the dry reforming reaction of carbon dioxide and methane (equation (1)), the formation reaction of acetaldehyde from carbon monoxide and hydrogen gas produced by the dry reforming reaction (equation (2)), and the formation reaction of ethanol (equation (3)). Therefore, it is necessary to set reaction conditions that allow both the reaction of equation (1) and the reactions of equations (2) and (3) to proceed.

[0029] CH4 + CO2 → 2CO + 2H2(1) 2CO+3H2→ CH3CHO +H2O (2) 2CO+4H2→ C2H5OH +H2O (3)

[0030] It should be noted that not all of the carbon monoxide and hydrogen gas produced in the reaction of formula (1) are always consumed by the reaction of formula (2) or formula (3). Therefore, unreacted carbon monoxide or hydrogen gas that was produced in the reaction of formula (1) but did not react in the reaction of formula (2) or formula (3) may be discharged from the reactor. Furthermore, the reaction of formula (2) or formula (3) requires more H2 than the H2 produced in the reaction of formula (1). Therefore, the proportion of unreacted carbon monoxide discharged from the reactor is greater than the proportion of unreacted hydrogen gas.

[0031] The reaction temperature is 80 to 400°C. 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, side reactions are suppressed, or aggregation of Rh species 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.

[0032] The reaction pressure is preferably 0 to 5 MPaG (gauge pressure), more preferably 0.2 to 3 MPaG (gauge pressure), and even more preferably 0.5 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.

[0033] 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.

[0034] (Reactant gas) The forms of the reactant gases carbon dioxide and methane are not particularly limited, and commercially available gases can be used. A mixed gas of the reactant gas and an inert gas such as nitrogen gas or argon can also be used in 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.

[0035] The molar ratio of raw materials in the above reaction, i.e., the molar ratio of carbon dioxide to methane (CO2 / CH4 ratio), 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 and upper limits 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 it is possible to prevent carbon dioxide or methane from reacting alone.

[0036] (Reaction Apparatus) 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. Figure 1 shows a schematic diagram of a reactor used for the reaction of carbon dioxide and methane. 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. A catalyst is packed 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.

[0037] 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.

[0038] 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 1 g of the total mass of the supported metal and semiconductor support. That is, the applied voltage is preferably 0.02 W / g 担持金属+半導体担体 More than 0.1 W / g, preferably 0.1 W / g 担持金属+半導体担体 More preferably 0.5 W / g or more 担持金属+半導体担体 More than 250W / g, preferably 担持金属+半導体担体 Less than or equal to 150W / g, more preferably 担持金属+半導体担体 or less, more preferably 30 W / g 担持金属+半導体担体 For example, the voltage is preferably applied in the range of 0.02 to 250 W / g. 担持金属+半導体担体 , more preferably 0.1 to 150 W / g 担持金属+半導体担体 , and more preferably 0.5 to 30 W / g 担持金属+半導体担体 The value should be 0.02~250W / g. 担持金属+半導体担体 If so, it is possible to apply a voltage to the catalyst with a moderate amount of power, and the reaction between carbon dioxide and methane can be effectively promoted. [Example]

[0039] 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.

[0040] (Preparation of catalyst precursor A) 5.3 g of an ethanol solution containing 0.255 g of rhodium chloride trihydrate (to make the Rh loading 1 part by mass per 100 parts by mass of the support) and 0.0921 g of titanium tetraisopropoxide (to make the Ti loading 33 parts by mole per 100 parts by mole of Rh) was added to a commercially available CeO support (BET specific surface area: 93 m). 2 The mixture was dropped into 10 g of 100% ethanol (100% ethanol / g) at room temperature. After kneading for 5 minutes, it was dried at 120°C for 5 hours using a dryer. It was then pulverized in an agate mortar for 5 minutes and calcined in air at 500°C for 3 hours using a muffle furnace. The resulting powder was sized to a mesh size of 300 to 500 μm to obtain catalyst precursor A.

[0041] (Preparation of catalyst precursor B) Catalyst precursor B was prepared in the same manner as catalyst precursor A, except that the ethanol solution was changed to 10.6 g of an aqueous solution containing 0.255 g of rhodium chloride trihydrate and 0.0379 g of ammonium vanadate (V).

[0042] (Preparation of catalyst precursor C) Catalyst precursor C was prepared in the same manner as catalyst precursor B, except that 0.0572 g of ammonium molybdate (VI) tetrahydrate was used instead of ammonium vanadate (V), and the amount of the aqueous solution was changed to 3.7 g.

[0043] (Preparation of catalyst precursor D) Catalyst precursor D was prepared in the same manner as catalyst precursor B, except that 0.0846 g of ammonium tungstate parapentahydrate was used instead of ammonium vanadate (V), and the amount of the aqueous solution was changed to 7.1 g.

[0044] (Preparation of catalyst precursor E) Catalyst precursor E was prepared in the same manner as catalyst precursor B, except that 0.0640 g of manganese(II) chloride tetrahydrate was used instead of ammonium vanadate(V), and the amount of the aqueous solution was changed to 3.5 g.

[0045] (Preparation of Comparative Catalyst Precursor F) Comparative catalyst precursor F was prepared in the same manner as catalyst precursor A, except that the ethanol solution was changed to 3.3 g of an aqueous solution containing only 0.255 g of rhodium chloride trihydrate.

[0046] (Preparation of Comparative Catalyst Precursor G) Comparative catalyst precursor G was prepared using a commercially available TiO2 support (P-25, Sigma-Aldrich, BET specific surface area: 54 m 2 The catalyst precursor was prepared in the same manner as Comparative Catalyst Precursor F, except that the amount of the catalyst precursor was 10 g ( / g).

[0047] (Comparative catalyst H) Comparative catalyst H used a commercially available TiO2 support (P-25, Sigma-Aldrich).

[0048] (Reaction of carbon dioxide and methane) The reaction between carbon dioxide and methane was carried out using the reactor 1 shown in Figure 1. A cylindrical quartz reactor with 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. 0.38 mL of a granulated catalyst precursor (or comparative catalyst precursor or comparative catalyst; the same applies below) was packed on top of a stainless steel mesh ground electrode 5 installed in the reaction tube 3, and a stainless steel mesh high-voltage electrode 4 was placed in contact with the top of the catalyst precursor to form a catalyst layer 2. The thickness of the catalyst layer 2 was 6 mm. The conductive wire connecting the high-voltage electrode 4 to the power supply 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 supply 6 (DC high-voltage power supply: HAR-10N30, Matsusada Precision Co., Ltd.).

[0049] In the reactor 1, 3 NL / h of hydrogen gas and 12 NL / h of nitrogen gas were supplied from the top of the reaction tube 3, and the heater temperature was adjusted so that the temperature of the catalyst layer 2 was 450°C. The catalyst precursor was reduced with hydrogen gas and the reduction step was carried out to convert rhodium oxide to metallic rhodium by flowing the gas for 1 hour. Note that, for the reasons mentioned above, the oxides of Ti, V, Mo, W, and Mn supported on the support together with rhodium oxide remained as oxides even after the reduction step. The temperature of the catalyst layer 2 was measured using a thermocouple placed below the catalyst layer 2.

[0050] 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 applied from the power supply 6 between the high-voltage electrode 4 and the ground electrode 5 to generate an electric field within the catalyst layer 2, thereby allowing the reaction of carbon dioxide and methane. The carbon dioxide gas supply rate was 0.57 NL / h, and the methane gas supply rate was also 0.57 NL / h (raw material molar ratio: 1.0), and the space velocity was 3000 / h. 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 supply 6.

[0051] The reaction product gas discharged from the bottom of the reaction tube 3 was collected using a trap tube containing 70 g of pure water, and the products contained in the liquid product collected in the pure water and the gas product after passing through the trap tube were analyzed by gas chromatography.

[0052] (Method for analyzing liquid products) 1. Acetaldehyde and ethanol Using the internal standard method, 0.1 g of 1,4-dioxane was added as an internal standard to 10 g of the solution in the trap tube that collected the liquid product, and 0.5 μL of this was injected into a gas chromatography analyzer and analyzed under the following conditions. Gas chromatograph: 7890A (Agilent Technology) Column: DB-WAX (Agilent Technology, Ltd., length 30 m, inner diameter 0.32 mm, film thickness 0.5 μm) Carrier gas: Helium (split ratio: 11.8, column flow rate: 3 mL / min) Temperature conditions: the detector temperature was 200°C, the vaporizer temperature was 220°C, and the column temperature was raised from 60°C to 200°C at a rate of 10°C / min and held at 200°C for 1 min. Detector: FID

[0053] (Method of analyzing gas products) 1. Acetaldehyde and ethanol Using the absolute calibration curve method, 0.5 mL of gas components were sampled and the entire volume was injected into a gas chromatograph for analysis. The gas chromatographic conditions were the same as those for the analysis of the liquid product described above.

[0054] 2. Hydrogen (H2) 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 the gas chromatography analyzer, and analysis was carried out under the following conditions. Gas chromatograph: 7890A (Agilent Technology) Column: 8ft Molecular Sieve 5A 60 / 80 mesh (Agilent Technologies, length 2.4m, inner diameter 2mm) Carrier gas: Nitrogen gas (split ratio: 80, column flow rate: 2 mL / min) Temperature conditions: The detector and vaporizer temperatures were set to 250°C, and the column temperature was maintained at 50°C for 7 minutes after the start of analysis. The temperature was then increased to 75°C at a rate of 10°C / min and maintained at 75°C for 1 minute. The temperature was then increased to 145°C at a rate of 20°C / min and maintained at 145°C for 3 minutes. Detector:TCD

[0055] 3. 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 chromatograph: 7890A (Agilent Technology) Column: 6 ft HayeSep Q 80 / 100 mesh in Nickel (Agilent Technology, length 1.8 m, inner diameter 2 mm) and 8 ft Molecular Sieve 5A 60 / 80 mesh (Agilent Technology, 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 above. Detector:TCD

[0056] From the above analytical results, the space-time yield (STY) of each product was calculated as follows. Product STY (g / L h) = Amount of product produced (g) / [Catalyst (supported metal + support) volume (L) × Reaction time (h)]

[0057] Example 1 0.38 mL of catalyst precursor A was loaded into the reaction tube 3, and after the reduction step, carbon dioxide and methane were reacted. After the reaction was carried out for 5 hours, the liquid product collected in the purified water and the gas product after passing through the trap tube were analyzed, and the space-time yields of carbon monoxide, hydrogen, acetaldehyde, and ethanol were calculated. The reaction conditions and results are shown in Table 1. In Table 1, ALD stands for acetaldehyde, and EOH stands for ethanol. Figure 2 shows the relationship between the space-time yield of acetaldehyde and the space-time yield of ethanol and the space-time yield of carbon monoxide. Note that a volume change occurs when the catalytic metal salt is reduced to the catalytic metal. However, since the mass of the catalytic metal is approximately 1.3 parts by mass per 100 parts by mass of the support, which does not change in volume during the reduction step, this volume change was ignored when calculating the STY.

[0058] <Example 2> The reaction of carbon dioxide and methane was carried out in the same manner as in Example 1, except that the catalyst layer temperature was set to 150° C., and analysis was carried out in the same manner as in Example 1. The results are shown in Table 1.

[0059] Example 3 The reaction of carbon dioxide and methane was carried out in the same manner as in Example 1, except that the catalyst layer temperature was set to 250° C., and analysis was carried out in the same manner as in Example 1. The results are shown in Table 1.

[0060] <Examples 4 to 7> Carbon dioxide and methane were reacted and analyzed in the same manner as in Example 1, except that catalyst precursors B to E were packed instead of catalyst precursor A. The results are shown in Table 1 and FIG.

[0061] <Comparative Example 1> The reaction of carbon dioxide and methane was carried out in the same manner as in Example 1, except that comparative catalyst precursor F 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 and FIG.

[0062] <Comparative Example 2> Carbon dioxide and methane were reacted in the same manner as in Comparative Example 1, except that the catalyst layer temperature was set to 250° C., and analysis was carried out in the same manner as in Example 1. The results are shown in Table 1.

[0063] <Comparative Example 3> The reaction of carbon dioxide and methane was carried out in the same manner as in Example 1, except that comparative catalyst precursor G 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 and FIG.

[0064] <Comparative Example 4> The reaction of carbon dioxide and methane was carried out in the same manner as in Example 1, except that comparative catalyst H was packed in place of catalyst precursor A and the reduction treatment step was not carried out, and analysis was carried out in the same manner as in Example 1. The results are shown in Table 1.

[0065] 2, comparing Example 1 and Comparative Example 1, it can be seen that the ratio of acetaldehyde STY to carbon monoxide STY and the ratio of ethanol STY increased by using a catalyst in which Rh and Ti oxides were supported on a semiconductor support CeO2, thereby promoting the production of acetaldehyde and ethanol from carbon monoxide and hydrogen gas. In other words, by using a catalyst in which Rh and Ti oxides were supported on a semiconductor support CeO2, it is possible to increase the yield of the target products, acetaldehyde and ethanol.

[0066] From Examples 2 and 3, it can be seen that acetaldehyde and ethanol were produced even under different temperature conditions.

[0067] In addition, when Example 3 is compared with Comparative Example 2, it is found that the ratio of acetaldehyde STY to carbon monoxide STY and the ratio of ethanol STY are higher even under temperature conditions different from those in Example 1, and that the production rates of acetaldehyde and ethanol from carbon monoxide and hydrogen gas are higher.

[0068] Comparing Example 4 with Comparative Example 1, it can be seen that the use of a catalyst in which oxides of Rh and V are supported on a semiconductor support CeO2 increases the ratio of acetaldehyde STY to carbon monoxide STY, thereby promoting the production of acetaldehyde from carbon monoxide and hydrogen gas.

[0069] Comparing Example 5 with Comparative Example 1, it can be seen that the use of a catalyst in which oxides of Rh and Mo are supported on a semiconductor support CeO2 increases the ratio of acetaldehyde STY to carbon monoxide STY and the ratio of ethanol STY, thereby promoting the production of acetaldehyde and ethanol from carbon monoxide and hydrogen gas.

[0070] Comparing Example 6 with Comparative Example 1, it can be seen that the ratio of ethanol STY to carbon monoxide STY increased when a catalyst in which oxides of Rh and W were supported on a semiconductor support CeO2 was used, and the production of ethanol from carbon monoxide and hydrogen gas was promoted.

[0071] Comparing Example 7 with Comparative Example 1, it can be seen that the use of a catalyst in which oxides of Rh and Mn are supported on a semiconductor support CeO2 increases the ratio of acetaldehyde STY to carbon monoxide STY and the ratio of ethanol STY, thereby promoting the production of acetaldehyde and ethanol from carbon monoxide and hydrogen gas.

[0072] From Comparative Example 3, it can be seen that in the catalyst in which only Rh is supported on the semiconductor support TiO2, the ratio of acetaldehyde STY to carbon monoxide STY is high, but the absolute amount of acetaldehyde STY is low, and ethanol is not produced.

[0073] Comparative Example 4 shows that acetaldehyde and ethanol are not produced when only the TiO2 carrier is used.

[0074] [Table 1-1] [Table 1-2] [Explanation of symbols]

[0075] 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 acetaldehyde and ethanol, comprising: passing an electric current through a catalyst comprising a semiconductor support having a band gap of 3.3 to 6.0 eV, the semiconductor support carrying an oxide of at least one element selected from the group consisting of titanium (Ti), vanadium (V), molybdenum (Mo), tungsten (W), and manganese (Mn), and rhodium (Rh); 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. 2. The production method according to claim 1, wherein the total amount of the at least one element selected from the group consisting of Ti, V, Mo, W, and Mn supported on the catalyst is 20 to 50 parts by mole per 100 parts by mole of the Rh.

3. The semiconductor support is CeO ２ and ZrO ２ 3. The method according to claim 1, wherein the compound is at least one selected from the group consisting of:

4. 3. The method according to claim 1, wherein the amount of Rh supported on the catalyst is 0.05 to 10 parts by mass per 100 parts by mass of the semiconductor support.

5. The reaction is 0.02 to 250 W / g 担持金属＋半導体担体 The method according to claim 1 or 2, wherein the method is carried out by applying a voltage so that

6. 3. The method according to claim 1, wherein the reaction temperature is 100 to 300°C.

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

8. 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 is 0.05 to 20.

9. An electric field catalyst used in the production of acetaldehyde and ethanol using carbon dioxide and methane as raw materials, the electric field catalyst comprising an oxide of at least one element selected from the group consisting of Ti, V, Mo, W, and Mn, and Rh, supported on a semiconductor support having a band gap of 3.3 to 6.0 eV.

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