Method for producing hydrogen and carboxylic acid

Abstract

To provide a method for producing hydrogen and carboxylic acid, capable of producing hydrogen and carboxylic acid in a high yield or at a high purity from a primary alcohol and water in a short time and by simple operations.SOLUTION: In a method for producing hydrogen and carboxylic acid, a primary alcohol of 1 to 7 carbon atoms and water are reacted by continuously introducing the primary alcohol of 1 to 7 carbon atoms and water into a flow reactor packed with a solid catalyst consisting of an alloy of ruthenium and tin (Ru-Sn alloy) on a support and passed through the reactor under temperature and pressure conditions at which the water assumes a gaseous state.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing hydrogen and a carboxylic acid. [Background technology]

[0002] Biomass is an important resource that can be used as an alternative to fossil fuels such as petroleum and natural gas, reducing dependence on fossil fuels and contributing to the suppression of atmospheric carbon dioxide, which is believed to be a cause of global warming. Bioethanol, produced from cellulosic biomass, is currently primarily used as an alternative to fossil fuels. However, in order to promote the replacement of fossil fuels with biomass, it is desirable to develop methods for using it not only as a fuel but also as a chemical raw material. Furthermore, when using aqueous bioethanol solutions obtained by alcoholic fermentation, energy and cost are required for dehydration, such as by distillation and membrane separation of water from the azeotropic mixture. Therefore, it would be desirable to be able to use aqueous bioethanol solutions without removing water.

[0003] As an example of converting ethanol as a chemical raw material into useful chemicals, ethanol reforming, which produces hydrogen from ethanol and water, has been known. For example, a method using a Rh / CeO2-ZrO2 catalyst at 400-500°C has been reported (Catalysis Communications 3 (2002) 565-571 (Non-Patent Document 1)).

[0004] In ethanol reforming, a metal catalyst is reacted with ethanol and water, causing the water to act as an oxidant, oxidizing the ethanol to acetaldehyde, acetic acid, and finally to carbon dioxide, while producing hydrogen. The overall ethanol reforming reaction is expressed by the following equation (1). C2H5OH+3H2O→6H2+2CO2···(1)

[0005] Meanwhile, research is also being conducted on a method in which the carbon derived from ethanol is not released as carbon dioxide as in ethanol reforming, but is instead used as an intermediate in ethanol reforming, acetic acid, as shown in the following formula (2). In this reaction, two molecules of hydrogen and one molecule of acetic acid can be obtained from one molecule of ethanol and one molecule of water. C2H5OH+H2O→2H2+CH3COOH ···(2)

[0006] Hydrogen is widely used industrially in applications such as petroleum refining and chemical manufacturing. Its use as an energy source is expected to expand in the future as we move toward achieving carbon neutrality by 2050, i.e., toward the realization of a low-carbon society. When using hydrogen in fuel cells, it is necessary for the hydrogen to be highly pure to prevent carbon monoxide poisoning of the platinum catalyst. Furthermore, the current main method for producing hydrogen, the steam reforming method, uses fossil fuels such as natural gas and petroleum as raw materials and emits carbon dioxide. Therefore, there is a need for a hydrogen production method that uses renewable resources as raw materials and does not emit carbon dioxide. Acetic acid is also a useful chemical substance used industrially in many fields, including chemistry, food, and pharmaceuticals.

[0007] As a method for obtaining hydrogen and a carboxylic acid from a primary alcohol and water, for example, a method for producing hydrogen and a carbonyl compound in high yield by dehydrogenating alcohols under reflux conditions using an organic iridium complex having a nitrogen-containing ligand as a catalyst has been reported (WO 2013 / 125712 (Patent Document 1), ChemCatChem, 2018, 10, 3636-3640 (Non-Patent Document 2)). Another method for producing hydrogen and acetic acid from an aqueous ethanol solution using a Cu / ZnO-ZrO2-Al2O3 catalyst at atmospheric pressure and 250 to 300°C using a flow reactor has also been reported (Applied Catalysis A: General 458 (2013) 196-200 (Non-Patent Document 3)). Furthermore, a method for producing hydrogen and acetic acid from an aqueous ethanol solution using a flow reactor with a CuCr catalyst at 623 K (350°C) has also been reported (RSC Advances, 2017, 7, 38586-38593 (Non-Patent Document 4)). [Prior art documents] [Patent documents]

[0008] [Patent Document 1] International Publication No. 2013 / 125712

[0009] [Non-Patent Document 1] Catalysis Communications 3 (2002) 565-571 [Non-patent document 2] ChemCatChem, 2018, 10, 3636-3640 [Non-patent document 3] Applied Catalysis A: General 458 (2013) 196-200 [Non-patent document 4] RSC Advances, 2017, 7, 38586-38593 Summary of the Invention [Problem to be solved by the invention]

[0010] However, in Patent Document 1 and Non-Patent Document 2, for example, when ethanol is used as a raw material, a batch reaction requires a reaction time of 18 hours or more, leaving room for improvement in shortening the reaction time. Furthermore, in Non-Patent Document 2, the catalyst is recovered by drying the reaction solution under reduced pressure, extracting the catalyst with dichloromethane, and concentrating it, which requires a complicated procedure for recovering the catalyst. In addition, the catalyst used is an organometallic catalyst, and there are concerns about its stability and durability. Furthermore, the catalyst used is made from a complex of iridium, a precious metal, and a special nitrogen-containing ligand, both of which are expensive, and cost remains an issue from the perspective of industrialization.

[0011] Non-Patent Document 3 reports that acetic acid was obtained from an aqueous ethanol solution with a maximum yield of 73.3%, and that approximately 2 moles of hydrogen were produced per mole of acetic acid. Therefore, the hydrogen yield is estimated to be only approximately 150%, compared to a theoretical yield of 200%. Non-Patent Document 4 also reports that when argon was used as the carrier gas and an alloy consisting of 70 mass% copper and 30 mass% chromium was used as the catalyst, ethanol was almost completely converted, but the selectivity for acetic acid in the product was only 48%. Given the above, further improvements in the yields of both hydrogen and acetic acid are required.

[0012] Furthermore, in Non-Patent Document 3, even under the conditions described above that recorded the highest yield of acetic acid (73.3%), several percent of ethyl acetate, acetaldehyde, methyl ethyl ketone, and butanol were by-produced. Furthermore, in Non-Patent Document 4, under the conditions described above, the acetaldehyde content in the product reached approximately 50%. Given these facts, further improvements are needed in the purity of the resulting liquid. Additionally, in Non-Patent Document 3, the reaction is carried out at a high temperature of 250 to 300°C, while in Non-Patent Document 4, it is carried out at a high temperature of 350°C. When utilizing this reaction industrially, a lower reaction temperature is preferable because it allows the product to be obtained with less energy, so further improvements are needed in the reaction temperature as well.

[0013] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for producing hydrogen and a carboxylic acid from a primary alcohol and water in a short time, by a simple operation, in high yield, and a method for producing hydrogen and a carboxylic acid from a primary alcohol and water in a short time, by a simple operation, and a method for producing hydrogen and a carboxylic acid with high purity from a primary alcohol and water. [Means for solving the problem]

[0014] As a result of extensive research into achieving the above object, the present inventors have found that hydrogen and a carboxylic acid can be obtained in high yield from a primary alcohol and water, or hydrogen and a carboxylic acid can be obtained in high purity from a primary alcohol and water, by carrying out a reaction in a flow reactor using a solid catalyst in which an alloy of ruthenium and tin is supported on a carrier, and have thus completed the present invention.

[0015] That is, the present invention provides a method for producing hydrogen and a carboxylic acid. 1. A method for producing hydrogen and a carboxylic acid, comprising continuously introducing a primary alcohol having 1 to 7 carbon atoms and water into a flow reactor packed with a solid catalyst made of a support carrying an alloy of ruthenium and tin (Ru-Sn alloy), and passing the primary alcohol and water through the flow reactor under temperature and pressure conditions that cause the water to enter a gas phase, thereby reacting the primary alcohol and water. 2. 2. The method for producing hydrogen and a carboxylic acid according to 1, wherein the temperature inside the flow reactor is 185 to 350° C. and the pressure inside the flow reactor is 0.1 to 15 MPa. 3. 3. The method for producing hydrogen and a carboxylic acid according to 1 or 2, wherein the content of ruthenium in the Ru—Sn alloy is 25 to 200 parts by mass per 100 parts by mass of tin. 4. 4. The method for producing hydrogen and a carboxylic acid according to any one of 1 to 3, wherein the primary alcohol is ethanol and acetic acid is produced as the carboxylic acid. 5. 5. The method for producing hydrogen and a carboxylic acid according to any one of 1 to 4, wherein the residence time of the introduced primary alcohol having 1 to 7 carbon atoms and water in the flow reactor is 60 seconds or less. 6. 6. The method for producing hydrogen and a carboxylic acid according to any one of 1 to 5, wherein the solid catalyst is composed of particles made of a metal oxide or a carbon material supporting a Ru—Sn alloy. [Effects of the Invention]

[0016] According to the present invention, the residence time of the introduced raw materials, a primary alcohol having 1 to 7 carbon atoms and water, in a flow reactor (catalyst-packed section) packed with a solid catalyst, i.e., the reaction time, can be shortened to 60 seconds or less, and hydrogen and a carboxylic acid having 1 to 7 carbon atoms can be easily obtained in high yield or with high purity. Furthermore, since the solid catalyst made of a support carrying an alloy of ruthenium and tin is an inorganic catalyst, it has excellent stability and durability and can be easily reused. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a schematic diagram showing an example of the configuration of a flow reactor used in the method for producing hydrogen and a carboxylic acid according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] [Method of producing hydrogen and carboxylic acid] The configuration of the method for producing hydrogen and carboxylic acid according to the present invention will be described below. The method for producing hydrogen and carboxylic acid according to the present invention is a production method in which a raw material consisting of a primary alcohol having 1 to 7 carbon atoms and water is subjected to a dehydrogenation reaction in a flow reactor (column), characterized in that the primary alcohol having 1 to 7 carbon atoms and water are continuously introduced into a flow reactor packed with a solid catalyst made of a support carrying an alloy of ruthenium and tin (Ru—Sn alloy), and are passed through the flow reactor under temperature and pressure conditions that cause the water to be in a gas phase, thereby reacting the primary alcohol having 1 to 7 carbon atoms with the water. Note that the phase state of the primary alcohol having 1 to 7 carbon atoms and water when introduced into the flow reactor packed with the solid catalyst may be any of a liquid phase, a gas phase, or a liquid and gas phase (i.e., a gas-liquid mixed state).

[0019] ·Raw materials In the present invention, a primary alcohol and water are used. The primary alcohol has 1 to 7 carbon atoms, preferably 1 to 3 carbon atoms. The primary alcohol is not particularly limited as long as it is soluble in water, since the reaction is carried out by contacting an aqueous solution of the primary alcohol with a solid catalyst. Examples include linear saturated aliphatic primary alcohols such as methanol, ethanol, 1-propanol, 1-butanol, and 1-pentanol; branched saturated aliphatic primary alcohols such as isobutyl alcohol and isopentyl alcohol; unsaturated aliphatic primary alcohols such as allyl alcohol; and aromatic primary alcohols such as benzyl alcohol. One or more of these may be used in combination. Among these, ethanol is preferred because it can be produced from biomass, which is utilized to reduce dependence on fossil resources and suppress the increase in carbon dioxide. Furthermore, ethanol is not particularly limited as long as it is industrially available with a certain degree of purity (e.g., impurities other than water are 3% or less). Either synthetic ethanol or fermented ethanol (also known as bioethanol or biomass ethanol) can be used. When ethanol is used as a raw material, acetic acid is produced as the carboxylic acid in the present invention. The water is water that does not contain ions or organic substances as impurities, and is preferably pure water such as distilled water, ion-exchanged water, or purified water.

[0020] The primary alcohol and water may be in either a liquid or gas phase when introduced into a flow reactor filled with a solid catalyst. That is, the primary alcohol and water may be vaporized inside the flow reactor or before being introduced into the flow reactor.

[0021] When the primary alcohol and water are introduced in a liquid phase into a flow reactor filled with a solid catalyst, the primary alcohol and water are mixed and introduced into the flow reactor. The timing of mixing the primary alcohol and water is not particularly limited, and the primary alcohol and water may be mixed in advance to form an aqueous primary alcohol solution which is then passed through the flow reactor, or they may be mixed immediately before or inside the flow reactor before being brought into contact with the solid catalyst.

[0022] When introducing primary alcohol and water in a gaseous state into a flow reactor packed with a solid catalyst, an empty column may be inserted before the inlet of the flow reactor, the temperature and pressure inside the empty column may be adjusted to a level at which water is in a gaseous phase, and an aqueous primary alcohol solution prepared by premixing the primary alcohol and water may be introduced into the empty column, or the primary alcohol and water may be introduced separately. Furthermore, primary alcohol and water in a gaseous state that have been vaporized by a known method other than the method using the empty column may also be introduced into the flow reactor.

[0023] Inside the flow reactor, the primary alcohol and water in the vapor phase come into contact with the solid catalyst and react.

[0024] The amount of water per mole of the primary alcohol as a raw material is preferably 1 to 25,000 moles, more preferably 2.5 to 5,000 moles, and even more preferably 20 to 2,500 moles. When the primary alcohol is distributed as an aqueous solution, the concentration of the aqueous solution of primary alcohol is preferably 0.1 to 700 g / L, more preferably 0.5 to 500 g / L, and even more preferably 1 to 100 g / L, from the viewpoint of producing the product in a high yield.

[0025] Flow reactor The flow reactor is a column incorporated in a flow reaction apparatus described below, and is a flow-type reaction vessel in which a solid catalyst made of a support carrying an alloy of ruthenium and tin (Ru-Sn alloy) is packed inside, and primary alcohol and water (aqueous primary alcohol solution) introduced as raw materials pass through the inside of the reactor in a vaporized state while coming into contact with the solid catalyst, and the reaction product can be discharged.

[0026] Solid catalyst The solid catalyst used in the present invention is a catalyst for reacting a primary alcohol having 1 to 7 carbon atoms with water, and is made of a carrier carrying an alloy of ruthenium and tin (Ru—Sn alloy).

[0027] The material constituting the support is not particularly limited as long as it can support an alloy of ruthenium and tin (Ru—Sn alloy) and does not adversely affect the reaction between the primary alcohol having 1 to 7 carbon atoms and water, and examples thereof include metal oxides such as titanium dioxide (TiO), silica (SiO), and alumina (AlO), and carbon materials such as activated carbon, carbon black, and graphite, with titanium dioxide being preferred because it is expected to act as a Lewis acid catalyst. These materials may be used alone or in combination as the material constituting the support.

[0028] The content of ruthenium in the Ru—Sn alloy is preferably 25 to 200 parts by mass, more preferably 50 to 150 parts by mass, and particularly preferably 90 to 110 parts by mass, per 100 parts by mass of tin, from the viewpoint of producing hydrogen and carboxylic acid from primary alcohol and water in high yield.

[0029] The content of elemental tin in the solid catalyst is not particularly limited. However, when titanium dioxide particles are used as a support, for example, from the viewpoint of suppressing by-products in the reaction of a primary alcohol having 1 to 7 carbon atoms with water, increasing the purity of hydrogen, and improving the yield of carboxylic acid, the tin content is preferably 1 to 20 parts by mass, and more preferably 1 to 10 parts by mass, per 100 parts by mass of the support.

[0030] The shape of the solid catalyst, i.e., the shape of the support, is not particularly limited, but a particulate form is preferred in consideration of the ease of filling into a flow reactor and the fact that a larger contact area with the raw material is better for catalytic activity. Therefore, it is particularly preferred that the solid catalyst be composed of particles made of the above-mentioned metal oxide or carbon material supporting a Ru-Sn alloy. The support may be prepared by an alkoxide method or the like, as described below, or a commercially available powder such as a prepared reagent may be used as is.

[0031] When the carrier is particulate, a powdered solid catalyst obtained by sieving the carrier through a sieve having an opening of preferably 30 to 180 μm, more preferably 40 to 130 μm, and even more preferably 50 to 90 μm is preferred. The finer the opening of the sieve used, the smaller the particle size of the solid catalyst becomes, and the larger the contact area with the raw material becomes, which is preferable.

[0032] The specific surface area of ​​the carrier is not particularly limited, but is preferably 30 to 1,000 m 2 / g is preferred, and 50 to 300m 2 / g is more preferable. The larger the specific surface area of ​​the support, the larger the contact area between the solid catalyst and the raw material, which is therefore preferable. The specific surface area is the value determined by the nitrogen adsorption method.

[0033] The solid catalyst used in the present invention may be prepared by a conventionally known method. Here, the method for supporting the ruthenium-tin alloy (Ru-Sn alloy) on a support is not particularly limited, and known methods can be used. However, from the viewpoint of dispersing ruthenium and tin and supporting them on a support to enhance the activity of the solid catalyst, a coprecipitation method is preferred. The coprecipitation method is a method in which a precipitant is added to a solution of a metal salt containing multiple target metals to obtain a precipitate of a poorly soluble salt. For example, adding a base as a precipitant to an aqueous solution of multiple metal salts results in a precipitate of a metal hydroxide, which is a poorly soluble salt. To support a poorly soluble salt on a support, the support can be coexisted in a solution of the metal salt. The obtained poorly soluble salt precipitate is washed and dried as necessary, and then calcined to form a metal oxide, which can then be further reduced with hydrogen or the like to obtain an alloy.

[0034] The solid catalyst used in the present invention may be prepared by the following method (1) or (2). (Method for preparing solid catalyst (1)) The method for preparing the solid catalyst used in the present invention is as follows: (i) adding an alkoxide solution of at least one selected from titanium, silicon, and aluminum to an aqueous solution containing (a) ruthenium ions and (b) tin ions to generate a precipitate containing at least one selected from titanium, silicon, and aluminum; (ii) further adding a precipitant to co-precipitate components (a) and (b); (iii) The method is characterized by comprising a step of separating and collecting the precipitate obtained in (ii) above by filtration or centrifugation, heating and drying, calcining the precipitate at 300 to 1,000°C in an oxygen-containing atmosphere, and then reducing the calcined precipitate at 300 to 800°C in a reducing atmosphere to obtain a solid catalyst comprising a support carrying an alloy of ruthenium and tin (Ru-Sn alloy).

[0035] The raw material for component (a) is not particularly limited as long as it generates ruthenium ions and dissolves in a solvent. Examples include ruthenium compounds such as ruthenium chloride, ruthenium nitrate, and ruthenium nitrosyl nitrate. These may be used alone or in combination. From the standpoints of availability and economy, ruthenium chloride (RuCl3·nH2O) is preferred. Its purity is preferably 95% by mass or higher, and more preferably 97% by mass or higher.

[0036] The raw material for component (b) is not particularly limited as long as it generates tin ions and dissolves in the solvent, but examples include tin compounds such as tin chloride, tin sulfate, sodium stannate, and tin acetate. These may be used alone or in combination. From the standpoints of availability and economy, tin chloride (SnCl2·2H2O) is preferred. Its purity is preferably 95% by mass or higher, and more preferably 97% by mass or higher.

[0037] These raw materials are weighed out in amounts corresponding to the composition of the final ruthenium-tin alloy (Ru-Sn alloy) to be produced and the amount to be supported on the carrier, and then dissolved in a solvent (neutral or acidic aqueous solution). That is, the raw materials for component (a) and component (b) are weighed out in amounts corresponding to the predetermined alloy composition of the ruthenium-tin alloy (Ru-Sn alloy) to be produced and the predetermined amount to be supported on the carrier.

[0038] The weighed raw materials for components (a) and (b) can be dissolved by mixing the raw materials and then dissolving the mixed powder in a solvent (neutral or acidic aqueous solution), or by dissolving each raw material sequentially.

[0039] The solvent to be used is not particularly limited as long as it can dissolve the raw materials for the components (a) and (b) without forming complex ions and can contain the ions of the components (a) and (b). Examples of the solvent include pure water, a 5N aqueous solution of nitric acid, an aqueous solution of sulfuric acid, and an aqueous solution of hydrochloric acid, and among these, pure water is preferred.

[0040] The solution of at least one alkoxide selected from titanium, silicon, and aluminum is a solution in which at least one alkoxide (metal alkoxide) selected from titanium, silicon, and aluminum is dissolved in an organic solvent such as alcohols.

[0041] At least one alkoxide (metal alkoxide) selected from titanium, silicon, and aluminum is a compound in which at least one metal selected from titanium, silicon, and aluminum (preferably titanium, silicon, or aluminum) is bonded to an alkoxy group, and may be a compound in which hydrogen atoms of a hydroxy group of an alcohol are substituted with at least one metal selected from titanium, silicon, and aluminum (preferably titanium, silicon, or aluminum). The specific structure is not particularly limited, but is preferably one represented by the formula M(OR)n (M is titanium, silicon, or aluminum, OR is a single or different alkoxy group (R is an alkyl group having 1 to 4 carbon atoms), and n is an integer of 2 to 4).

[0042] As the alcohols used as the organic solvent, ethanol, methanol, butanol, 2-propanol and ethoxyethanol are preferred, and ethanol, methanol and 2-propanol are more preferred.

[0043] In step (i) of the solid catalyst preparation method (1), when an alkoxide solution of at least one selected from titanium, silicon, and aluminum is added to an aqueous solution containing (a) ruthenium ions and (b) tin ions, the metal alkoxide contained in the alkoxide solution undergoes hydrolysis and polycondensation reaction to produce a precipitate containing at least one selected from titanium, silicon, and aluminum (a sol- and / or gel-like precipitate consisting of a polymeric alkoxide or colloidal polymer containing a metal-oxygen-metal bond derived from the metal alkoxide).

[0044] The precipitant used in step (ii) of the solid catalyst preparation method (1) is not particularly limited as long as it can raise the pH of the aqueous solution containing the above components (a) and (b) to cause precipitation of a poorly soluble salt, and examples thereof include sodium hydroxide, potassium hydroxide, sodium carbonate, ammonia, urea, etc. These may be used alone or in combination, or may be added in the form of an aqueous solution.

[0045] In step (ii) of the solid catalyst preparation method (1), a precipitate containing at least one selected from titanium, silicon, and aluminum is formed, and then a precipitant (base) is added to the aqueous solution containing components (a) and (b) to precipitate (co-precipitate) components (a) and (b) as poorly soluble salts. The method is not particularly limited, but for example, the aqueous solution containing components (a) and (b) is maintained at 10 to 35°C and the precipitant is added while stirring. After adding the precipitant, it is preferable to allow the solution to stand and age in order to complete the precipitation (co-precipitation). The ageing temperature is preferably 10 to 35°C, and the ageing time is preferably 1 to 24 hours.

[0046] In step (iii) of the solid catalyst preparation method (1), the precipitate obtained in step (ii) is separated and collected by filtration or centrifugation, heated and dried, and then calcined at 300 to 1,000°C in an oxygen-containing atmosphere. For example, the heated and dried precipitate may be placed in a furnace and heated while circulating air. The calcination temperature is preferably 300 to 1,000°C, more preferably 350 to 600°C, and the calcination time is preferably 0.5 to 5 hours. In this case, the Ru—Sn composite oxide is supported on particles made of at least one metal oxide selected from titanium, silicon, and aluminum.

[0047] Next, the Ru—Sn composite oxide obtained by the above-mentioned firing is reduced at 300 to 800° C. For example, the metal oxide may be heated while passing hydrogen through it. The reduction temperature is preferably 300 to 800° C., more preferably 350 to 500° C., and the reduction time is preferably 1 to 10 hours. This yields a solid catalyst comprising particles of an oxide of at least one metal selected from titanium, silicon, and aluminum, carrying an alloy of ruthenium and tin (Ru—Sn alloy).

[0048] (Method for preparing solid catalyst (2)) The method for preparing the solid catalyst used in the present invention is as follows: (ii') adding particles of at least one metal oxide selected from titanium, silicon, and aluminum or a carbon material to an aqueous solution containing (a) ruthenium ions and (b) tin ions, and then adding a precipitating agent to co-precipitate the components (a) and (b); (iii') The method is characterized by comprising a step of separating and collecting the particles containing the coprecipitate obtained in (ii') above by filtration or centrifugation, heating and drying, calcining the particles at 300 to 1,000°C in an oxygen-containing atmosphere, and then reducing the particles at 300 to 800°C in a reducing atmosphere to obtain a solid catalyst comprising a support carrying an alloy of ruthenium and tin (Ru-Sn alloy).

[0049] The particles used here may be those mentioned above, i.e., particles made of metal oxides such as titanium dioxide, silica, and alumina, or carbon materials such as activated carbon, carbon black, and graphite, which are obtained by sieving through a sieve with an opening size of preferably 30 to 180 μm, more preferably 40 to 130 μm, and even more preferably 50 to 90 μm, and which have a specific surface area of ​​preferably 30 to 1,000 m 2 / g, more preferably 50 to 300m 2 It is recommended to use one with a saturation of 0.15 to 0.25 g.

[0050] The method and conditions in step (ii') of the solid catalyst preparation method (2) may be the same as those in step (ii) of the solid catalyst preparation method (1).

[0051] The method and conditions in step (iii') of the solid catalyst preparation method (2) may be the same as those in step (iii) of the solid catalyst preparation method (1). This produces a solid catalyst that supports an alloy of ruthenium and tin (Ru—Sn alloy) and is made of particles of a metal oxide such as titanium dioxide, silica, or alumina, or a carbon material such as activated carbon, carbon black, or graphite.

[0052] In the method for producing hydrogen and a carboxylic acid of the present invention, it is necessary to set the temperature and pressure conditions inside the flow reactor so that water becomes a gas phase. Here, the pressure inside the flow reactor, i.e., the pressure when the primary alcohol and water introduced as raw materials are brought into contact with the solid catalyst, is a pressure at which water becomes gaseous at a temperature described below, and from the viewpoint of producing a reaction product in a high yield, it is preferably 0.1 to 20 MPa, more preferably 0.1 to 18 MPa, even more preferably 0.1 to 15 MPa, and most preferably 0.1 to 10 MPa, and from the viewpoint of producing a reaction product with a high purity, it is preferably 0.1 to 20 MPa, more preferably 0.1 to 10 MPa, even more preferably 0.2 to 6 MPa, and most preferably 0.5 to 4 MPa.

[0053] Furthermore, the temperature inside the flow reactor, i.e., the temperature at which the primary alcohol and water introduced as raw materials are brought into contact with the solid catalyst, is set to a temperature at which water becomes gaseous at the above pressure, i.e., a temperature at which the water boils according to the pressure, from the viewpoint of producing a reaction product in a high yield. The boiling point of water is, for example, 312°C at a pressure of 10 MPa, 297°C at a pressure of 8.2 MPa, 276°C at a pressure of 6 MPa, 251°C at a pressure of 4 MPa, 212°C at a pressure of 2 MPa, 152°C at a pressure of 0.5 MPa, and 100°C at a pressure of 0.1 MPa. On the other hand, if the temperature is too high, the intermediate aldehyde or the product carboxylic acid will decompose, producing carbon monoxide, carbon dioxide, methane, etc. Therefore, the preferred range of temperature inside the flow reactor varies depending on the pressure: 312 to 340°C when the pressure is 10 MPa, 297 to 340°C when the pressure is 8.2 MPa, 276 to 320°C when the pressure is 6 MPa, 251 to 320°C when the pressure is 4 MPa, 212 to 300°C when the pressure is 2 MPa, 152 to 290°C when the pressure is 0.5 MPa, and 100 to 280°C when the pressure is 0.1 MPa. The boiling point of water at each pressure can be determined using the steady-state process simulator Pro / II Version 10.1 (manufactured by Schneider Electric).

[0054] From the above, the temperature and pressure conditions inside the flow reactor are those at which water is in a gas phase. From the viewpoint of producing the reaction product in a high yield, the temperature is preferably 200 to 350°C and the pressure is preferably 0.1 to 15 MPa, and more preferably 251 to 340°C and the pressure is 0.1 to 10 MPa. From the viewpoint of producing the reaction product with a high purity, the temperature is preferably 185 to 300°C and the pressure is 0.1 to 4 MPa, and more preferably 185 to 250°C and the pressure is 0.1 to 2 MPa.

[0055] The residence time t (seconds) of the reaction solution, i.e., the primary alcohol and water introduced as raw materials, inside the flow reactor (catalyst-packed section) means the reaction time and is expressed by the following formula (3): t=φV / (Fρ / ρ')×60 (3) In the formula, φ is the void fraction inside the flow reactor (catalyst packed section), V is the volume (mL) inside the flow reactor (catalyst packed section), F is the flow rate (mL / min) at standard ambient temperature and pressure (SATP), and ρ is the density (g / cm) of the reaction solution at SATP. 3 ), ρ' is the density of the reaction solution (g / cm) under the reaction conditions (temperature and pressure inside the flow reactor). 3 The void fraction φ of the inside of the flow reactor (catalyst packed section) is the ratio of the volume of water that can be packed inside the flow reactor (catalyst packed section) to the volume of the inside of the flow reactor (catalyst packed section).

[0056] The densities ρ and ρ′ can be estimated by the Soave-Redlich-Kwong model using, for example, a steady-state process simulator Pro / II version 10.1 (manufactured by Schneider Electric).

[0057] The residence time t is preferably within 60 seconds, more preferably 0.03 to 30 seconds, even more preferably 0.04 to 20 seconds, and particularly preferably 0.05 to 10 seconds, from the viewpoint of suppressing the generation of carbon dioxide or methane due to decomposition of the intermediate aldehyde or the product carboxylic acid.

[0058] The residence time t can be set to a desired time by appropriately adjusting the flow rate of the reaction solution at standard ambient temperature and pressure (SATP) and the inner diameter and length of the inside of the flow reactor (catalyst-packed section).

[0059] Here, in the method for producing hydrogen and a carboxylic acid of the present invention, there are no particular limitations on the flow-type reaction apparatus, as long as it is a flow-type reaction system in which raw materials (reaction solution) are continuously introduced into a high-temperature and high-pressure system and the reaction product is discharged, and it is capable of continuously flowing the raw materials (reaction solution) at a predetermined temperature and pressure through a flow-type reactor filled with a solid catalyst, and any known flow-type reaction apparatus can be used.

[0060] For example, in the method for producing hydrogen and a carboxylic acid of the present invention, a flow reactor as shown in FIG. 1 may be used. In FIG. 1, reference numeral 1 denotes a raw material tank that stores a primary alcohol having 1 to 7 carbon atoms and water (here, an aqueous primary alcohol solution), 2 denotes a high-pressure pump that transfers the primary alcohol having 1 to 7 carbon atoms and water in raw material tank 1 to flow reactor 4, 3 denotes a heat exchanger that exchanges heat between the primary alcohol having 1 to 7 carbon atoms and water from raw material tank 1 and the post-reaction mixture (reaction product) from flow reactor 4, 4 denotes a flow reactor (column) packed with a solid catalyst made of a support carrying an alloy of ruthenium and tin (Ru—Sn alloy), 5 denotes an aluminum block for heat insulation, 6 denotes an electric furnace that heats flow reactor 4, 7 denotes a pressure gauge, 8 denotes a back pressure valve, 9 denotes a gas-liquid separator, 10 denotes a gas recovery unit made of a gas bag or the like, and 11 denotes a liquid recovery unit made of a glass bottle or the like.

[0061] Here, the suction side of the high-pressure pump 2 is connected to a raw material tank 1 containing a primary alcohol having 1 to 7 carbon atoms and water (a primary alcohol aqueous solution) through piping so that the liquid can pass through, and the discharge side is connected to an inlet side of a flow reactor 4 through a heat exchanger 3 through piping so that the liquid can be sent. The pump used is a high-pressure liquid-sending pump that can discharge the raw material primary alcohol having 1 to 7 carbon atoms and water (a primary alcohol aqueous solution) at high pressure.

[0062] The flow reactor 4 is, for example, a cylindrical vessel, and is provided at both ends in the longitudinal direction with an inlet for introducing the raw material primary alcohol having 1 to 7 carbon atoms and water (aqueous primary alcohol solution), and an outlet for discharging the reaction product, and is filled inside with a solid catalyst made of a support carrying the above-mentioned alloy of ruthenium and tin (Ru—Sn alloy) so as to have voids large enough to allow the introduced raw material primary alcohol having 1 to 7 carbon atoms and water (aqueous primary alcohol solution) to vaporize and pass through. The inside of the flow reactor 4 is also referred to as the catalyst-filled section.

[0063] Piping is connected from the discharge side of the flow reactor 4 to the gas-liquid separator 9 via the heat exchanger 3 and the back pressure valve 8 so that the reaction product discharged from the flow reactor 4 can pass through. The gas-liquid separator 9 separates the reaction product that has been discharged from the flow reactor 4 and cooled by the heat exchanger 3 into gas and liquid. The gas discharge part of the gas-liquid separator 9 is connected to a gas recovery part (gas bag) 10, and the liquid discharge part is connected to a liquid recovery part (glass bottle) 11.

[0064] The pressure gauge 7 measures the pressure in the system from the high-pressure pump 2 to the back-pressure valve 8. Based on the measured pressure, the pressure at which the high-pressure pump 2 delivers the liquid and the pressure at which the back-pressure valve 8 releases the liquid are adjusted, and the pressure inside the flow reactor 4 is set to the predetermined pressure described above. The inside of the flow reactor 4 is heated by the electric furnace 6 and adjusted to the above-mentioned temperature.

[0065] In the flow reactor of FIG. 1, hydrogen and a carboxylic acid are produced as follows. First, a primary alcohol having 1 to 7 carbon atoms and water (aqueous primary alcohol solution) are continuously introduced from raw material tank 1 into flow reactor 4. At this time, the primary alcohol having 1 to 7 carbon atoms and water (aqueous primary alcohol solution) sent from high-pressure pump 2 are heated to some extent in heat exchanger 3 and introduced into flow reactor 4 in an easily vaporizable state. Next, since the temperature and pressure inside the flow reactor 4 are such that water is in a gas phase, the introduced primary alcohol having 1 to 7 carbon atoms and water (aqueous solution of the primary alcohol) are vaporized and pass through the inside of the flow reactor 4 while coming into contact with the solid catalyst. At this time, the vaporized primary alcohol having 1 to 7 carbon atoms and water (aqueous primary alcohol solution) come into contact with the solid catalyst, whereby the primary alcohol having 1 to 7 carbon atoms reacts with the water to produce a mixture (reaction product) containing hydrogen and a carboxylic acid having 1 to 7 carbon atoms. The produced mixture (reaction product) is discharged from the flow reactor 4, cooled in the heat exchanger 3, and then separated into gas and liquid in the gas-liquid separator 9. The separated gas is hydrogen and is recovered in the gas recovery section (gas bag) 10, and the separated liquid is mainly carboxylic acid and is recovered in the liquid recovery section (glass bottle) 11.

[0066] 1 shows a configuration in which the primary alcohol and water are introduced into the flow reactor 4 in a liquid phase state. When the primary alcohol and water are introduced into the flow reactor 4 in a gas phase state, an empty column is inserted before the inlet of the flow reactor 4, the temperature and pressure inside the empty column are adjusted to such a level that water is in the gas phase (for example, the same temperature and pressure as those inside the flow reactor 4), the primary alcohol and water are introduced into the empty column, vaporized, and introduced into the flow reactor 4 as is.

[0067] Furthermore, the solid catalyst packed in the flow reactor 4 after being used in the reaction of the primary alcohol with water can be reused by rinsing it with water. The solid catalyst can be washed with water while still packed in the flow reactor 4, so there is no need for a recovery operation for the solid catalyst. When reusing the solid catalyst packed in the flow reactor 4, it is preferable to perform a test reaction under certain conditions to confirm that the catalytic activity is maintained. If the catalytic activity has decreased, the solid catalyst can be removed from the flow reactor 4 and regenerated by heat treatment under a hydrogen atmosphere.

[0068] As described above, the method for producing hydrogen and carboxylic acid of the present invention allows the residence time (reaction time) in the flow reactor (catalyst-packed section) to be as short as 60 seconds or less, and easily produces hydrogen and a carboxylic acid having 1 to 7 carbon atoms in high yield or high purity from the raw materials, a primary alcohol having 1 to 7 carbon atoms and water. Here, "high yield" means that the yield of the product recovered as a liquid other than the carboxylic acid is preferably 9% or less, more preferably 5.5% or less, even more preferably less than 5%, and particularly preferably less than 2%. Furthermore, "high purity" means that the purity of hydrogen in the recovered gaseous product is preferably 95 mol% or more, more preferably 98 mol% or more, and even more preferably 98.5 mol% or more. [Example]

[0069] EXAMPLES The present invention will be explained in more detail below with reference to examples and comparative examples, but the present invention is not limited to these.

[0070] The reaction products were quantified by the following method. (Quantitative determination of acetic acid, acetaldehyde and ethanol) Acetic acid, acetaldehyde and ethanol were quantified by high performance liquid chromatography under the following conditions. Equipment: High-performance liquid chromatograph, Shimadzu Corporation, Prominence Column: Bio-Rad Laboratories, Inc., Aminex HPX-87H, inner diameter 7.8 mm, length 300 mm ·Mobile phase: 5mmol / L sulfuric acid aqueous solution ·Flow rate: 0.6mL / min Column temperature: 45℃ Detector: Differential refractive index detector, Shimadzu Corporation, RID-20A

[0071] (Quantitative determination of hydrogen, CH4, CO, CO2, C2H4 and C2H6) Hydrogen, CH4, CO, CO2, C2H4 and C2H6 were quantified by gas chromatography under the following conditions. Equipment: Gas chromatograph, Varian Medical Systems, Inc., CP-4900 Micro GC Column: Agilent Technologies, Inc., CP-Molsieve 5Å, inner diameter 0.32 mm, length 10 m, film thickness 0.12 μm Carrier gas: Argon Column inlet pressure: 170kPa Column temperature: 100℃ Detector: Thermal conductivity detector Internal standard: Neon, Imamura Oxygen Co., Ltd., purity >99.999%

[0072] <Preparation of solid catalyst (titanium dioxide-supported ruthenium-tin catalyst)> Ruthenium(III) chloride (Tokyo Chemical Industry Co., Ltd., purity >97%, 0.821 g) and tin(II) chloride dihydrate (Nacalai Tesque, Inc., purity >97%, 0.76 g) were dissolved in 100 mL of distilled water at 60°C to obtain an aqueous solution. This aqueous solution was kept at 60°C and stirred, and a mixture of titanium(IV) isopropoxide (Nacalai Tesque, Inc., purity >95%, 37.2 mL) and 2-propanol (Nacalai Tesque, Inc., purity >99%, 20 mL) was added dropwise over 7 minutes. The mixture was further stirred at 25°C for 30 minutes, and a precipitate was formed. Next, 100 mL of a 0.1475 mol / L aqueous sodium hydroxide solution was added, and the mixture was stirred at 25°C for 30 minutes, and then allowed to stand at 25°C for 12 hours. The resulting precipitate was collected by centrifugation, washed by suspending in 100 mL of distilled water, and this was repeated five times, and then dried in an oven set at 105°C for 12 hours. The amounts of tin(II) chloride dihydrate and titanium(IV) isopropoxide used were such that the mass of elemental tin was 4 parts by mass per 100 parts by mass of titanium dioxide produced, and the amount of ruthenium(III) chloride used was such that the mass of elemental ruthenium was 100 parts by mass per 100 parts by mass of elemental tin. The precipitate was then placed on a quartz boat and calcined in a glass tube at 450°C for 1 hour while air was circulated at 100 mL / min, and then reduced at 400°C for 5 hours while hydrogen (purity >99.9%) was circulated at 100 mL / min. Finally, the mixture was sieved through a sieve with 75 μm openings to obtain a titanium dioxide-supported ruthenium-tin catalyst (Ru-Sn / TiO2 catalyst). The specific surface area of ​​the obtained catalyst was 80±5m 2 The specific surface area was determined by a nitrogen adsorption method using a specific surface area measuring device (manufactured by Micromeritics Instruments Corporation, product name Gemini VII 2390).

[0073] [Example 1] Hydrogen and acetic acid were produced using the flow reactor shown in Figure 1. In the flow reactor shown in FIG. 1, the high-pressure pump 2, heat exchanger 3, flow reactor (column) 4, aluminum block 5, electric furnace 6, pressure gauge 7, and back pressure valve 8 are manufactured by ThalesNano Inc., and Phoenix Flow Reactor TM The reactor (column) 4 was packed with 0.8±0.05 g of the titanium dioxide-supported ruthenium-tin catalyst prepared above. The inside of the reactor (column) 4 (catalyst-packed section) was cylindrical with an inner diameter of 3.9 mm and a length of 100 mm, and the porosity measured by filling it with water was 0.66. A 10 g / L aqueous ethanol solution placed in a raw material tank 1 was pumped at a flow rate of 0.3 mL / min by a high-pressure pump 2 and introduced into a flow reactor (column) 4 heated to 320°C by an electric furnace 6. The aqueous ethanol solution was in a liquid state until it was introduced into the flow reactor (column) 4. That is, the phase state of the ethanol and water when introduced into the flow reactor (column) 4 was liquid. The pressure in the system from the high-pressure pump 2 to the back-pressure valve 8 (i.e., the pressure inside the flow reactor (column) 4) was maintained at 10 MPa. The reaction mixture was cooled to 25°C in heat exchanger 3, the pressure was returned to normal pressure using backpressure valve 8, and gas-liquid separation was performed using gas-liquid separator 9. The gas was collected in gas collection section (gas bag) 10 and the liquid in liquid collection section (glass bottle) 11. The gas was collected for 10 minutes and the liquid for 5 minutes. The product yield (% (mol / mol)) relative to the ethanol (mol) introduced into flow reactor (column) 4 was calculated from the yield (mol) of each substance (component) contained in each. The hydrogen purity was also calculated from the yield (mol) of each substance (component) contained in the collected gas. Analysis of the collected liquid by high-performance liquid chromatography confirmed the presence of no substances other than ethanol, acetic acid, and acetaldehyde. Analysis of the collected gas by gas chromatography confirmed the presence of no substances (components) other than hydrogen, CH4, CO, CO2, CH4, and CH6. The residence time of the reaction solution in the catalyst-packed section of the flow reactor (column) 4, calculated by the above formula (3), was 8.23 ​​seconds. The densities ρ and ρ' in formula (3) were estimated by the Soave-Redlich-Kwong model using a steady-state process simulator Pro / II Version 10.1 (manufactured by Schneider Electric). The results are shown in Table 1.

[0074] [Example 2] The same operations as in Example 1 were carried out, except that the internal pressure from the high-pressure pump 2 to the back-pressure valve 8 was set to 6 MPa, and the yield (% (mol / mol)) of the product relative to the ethanol introduced into the flow reactor (column) 4 was determined. The results are shown in Table 1. Analysis of the recovered liquid confirmed the production of no substances other than those shown in Table 1.

[0075] [Example 3] The same operations as in Example 1 were carried out, except that the internal pressure from the high-pressure pump 2 to the back-pressure valve 8 was set to 6 MPa and the temperature of the flow reactor (column) 4 was set to 300°C, and the product yield (% (mol / mol)) relative to the ethanol introduced into the flow reactor (column) 4 was determined. The results are shown in Table 1. Analysis of the recovered liquid confirmed the production of no substances other than those shown in Table 1.

[0076] [Example 4] The same operations as in Example 1 were carried out, except that the internal pressure from the high-pressure pump 2 to the back-pressure valve 8 was set to 6 MPa and the temperature of the flow reactor (column) 4 was set to 280°C, and the product yield (% (mol / mol)) relative to the ethanol introduced into the flow reactor (column) 4 was determined. The results are shown in Table 1. Analysis of the recovered liquid confirmed the production of no substances other than those shown in Table 1.

[0077] [Example 5] The same operations as in Example 1 were carried out, except that the internal pressure from the high-pressure pump 2 to the back-pressure valve 8 was set to 4 MPa and the temperature of the flow reactor (column) 4 was set to 260°C, and the product yield (% (mol / mol)) relative to the ethanol introduced into the flow reactor (column) 4 was determined. The results are shown in Table 1. Analysis of the recovered liquid confirmed the production of no substances other than those shown in Table 1.

[0078] [Example 6] The same operations as in Example 1 were carried out, except that the internal pressure from the high-pressure pump 2 to the back-pressure valve 8 was set to 2.5 MPa and the temperature of the flow reactor (column) 4 was set to 240°C, and the product yield (% (mol / mol)) relative to the ethanol introduced into the flow reactor (column) 4 was determined. The results are shown in Table 1. Analysis of the recovered liquid confirmed the production of no substances other than those shown in Table 1.

[0079] [Example 7] The same operations as in Example 1 were carried out, except that the internal pressure from the high-pressure pump 2 to the back-pressure valve 8 was set to 0.5 MPa and the temperature of the flow reactor (column) 4 was set to 260°C, and the product yield (% (mol / mol)) relative to the ethanol introduced into the flow reactor (column) 4 was determined. The results are shown in Table 1. Analysis of the recovered liquid confirmed the production of no substances other than those shown in Table 1.

[0080] [Example 8] The same operations as in Example 1 were carried out, except that the internal pressure from the high-pressure pump 2 to the back-pressure valve 8 was set to 4 MPa, the temperature of the flow reactor (column) 4 was set to 260°C, and an empty column was inserted before the inlet of the flow reactor (column) 4 to set the temperature inside the empty column to 260°C, so that the ethanol and water were in the gas phase when introduced into the flow reactor (column) 4. The product yield (% (mol / mol)) relative to the ethanol introduced into the flow reactor (column) 4 was determined. The results are shown in Table 1. Analysis of the recovered liquid confirmed the production of no substances other than those shown in Table 1.

[0081] [Example 9] The same operations as in Example 8 were carried out, except that the internal pressure from the high-pressure pump 2 to the back-pressure valve 8 was set to 2 MPa, and the yield (% (mol / mol)) of the product relative to the ethanol introduced into the flow reactor (column) 4 was determined. The results are shown in Table 1. Analysis of the recovered liquid confirmed the production of no substances other than those shown in Table 1.

[0082] [Example 10] The same operations as in Example 8 were carried out, except that the internal pressure from the high-pressure pump 2 to the back-pressure valve 8 was set to 0.5 MPa, and the yield (% (mol / mol)) of the product relative to the ethanol introduced into the flow reactor (column) 4 was determined. The results are shown in Table 1. Analysis of the recovered liquid confirmed the production of no substances other than those shown in Table 1.

[0083] [Example 11] The same operations as in Example 8 were carried out, except that the internal pressure from the high-pressure pump 2 to the back-pressure valve 8 was set to 0.1 MPa, and the yield (% (mol / mol)) of the product relative to the ethanol introduced into the flow reactor (column) 4 was determined. The results are shown in Table 1. Analysis of the recovered liquid confirmed the production of no substances other than those shown in Table 1.

[0084] [Example 12] The same operations as in Example 8 were carried out, except that the internal pressure from the high-pressure pump 2 to the back-pressure valve 8 was set to 0.1 MPa, the temperature of the flow reactor (column) 4 was set to 240°C, and an empty column was inserted before the inlet of the flow reactor (column) 4 to set the temperature inside the empty column to 240°C, so that the ethanol and water were in the gas phase when introduced into the flow reactor (column) 4. The product yield (% (mol / mol)) relative to the ethanol introduced into the flow reactor (column) 4 was determined. The results are shown in Table 1. Analysis of the recovered liquid confirmed the production of no substances other than those shown in Table 1.

[0085] [Example 13] The same operations as in Example 1 were carried out, except that the raw material was a 100 g / L aqueous ethanol solution, and the yield (% (mol / mol)) of the product relative to the ethanol introduced into the flow reactor (column) 4 was determined. The results are shown in Table 1. Analysis of the recovered liquid confirmed the production of no substances other than those shown in Table 1.

[0086] [Example 14] The same operations as in Example 8 were carried out, except that the internal pressure from the high-pressure pump 2 to the back-pressure valve 8 was set to 0.1 MPa, the temperature of the flow reactor (column) 4 was set to 190°C, and an empty column was inserted before the inlet of the flow reactor (column) 4 to set the temperature inside the empty column to 190°C, so that the ethanol and water were in the gas phase when introduced into the flow reactor (column) 4. The product yield (% (mol / mol)) relative to the ethanol introduced into the flow reactor (column) 4 was determined. The results are shown in Table 1. Analysis of the recovered liquid confirmed the production of no substances other than those shown in Table 1.

[0087] [Example 15] The same operations as in Example 1 were carried out, except that the internal pressure from the high-pressure pump 2 to the back-pressure valve 8 was set to 0.7 MPa and the temperature of the flow reactor (column) 4 was set to 190°C, and the product yield (% (mol / mol)) relative to the ethanol introduced into the flow reactor (column) 4 was determined. The results are shown in Table 1. Analysis of the recovered liquid confirmed the production of no substances other than those shown in Table 1.

[0088] [Example 16] The same operations as in Example 1 were carried out, except that the internal pressure from the high-pressure pump 2 to the back-pressure valve 8 was set to 1.2 MPa and the temperature of the flow reactor (column) 4 was set to 200°C, and the product yield (% (mol / mol)) relative to the ethanol introduced into the flow reactor (column) 4 was determined. The results are shown in Table 1. Analysis of the recovered liquid confirmed the production of no substances other than those shown in Table 1.

[0089] [Example 17] The same operations as in Example 1 were carried out, except that the internal pressure from the high-pressure pump 2 to the back-pressure valve 8 was set to 2 MPa and the temperature of the flow reactor (column) 4 was set to 220°C, and the product yield (% (mol / mol)) relative to the ethanol introduced into the flow reactor (column) 4 was determined. The results are shown in Table 1. Analysis of the recovered liquid confirmed the production of no substances other than those shown in Table 1.

[0090] [Comparative Example 1] The same operation as in Example 1 was carried out, except that the temperature of the flow reactor (column) 4 was set to 300°C, at which point water becomes liquid at a pressure of 10 MPa, and the yield (% (mol / mol)) of the product relative to the ethanol introduced into the flow reactor (column) 4 was determined. The results are shown in Table 1. Analysis of the recovered liquid confirmed the production of no substances other than those shown in Table 1.

[0091] Comparative Example 2 The same operation as in Example 1 was carried out, except that the temperature of the flow reactor (column) 4 was set to 280°C, at which point water becomes liquid at a pressure of 10 MPa, and the product yield (% (mol / mol)) relative to the ethanol introduced into the flow reactor (column) 4 was determined. The results are shown in Table 1. Analysis of the recovered liquid confirmed the production of no substances other than those shown in Table 1.

[0092] Comparative Example 3 The same operations as in Example 8 were carried out, except that the temperature of flow reactor (column) 4 was set to 260°C, at which point water becomes liquid at a pressure of 6 MPa, and an empty column was inserted before the inlet of flow reactor (column) 4, so that the temperature inside the empty column was set to 260°C, and the yield (% (mol / mol)) of the product relative to the ethanol introduced into flow reactor (column) 4 was determined. The results are shown in Table 1. Analysis of the recovered liquid confirmed the production of no substances other than those shown in Table 1.

[0093] In this example and comparative example, the same solid catalyst was washed with water and reused. When the solid catalyst was reused, the reaction was carried out under certain conditions to confirm that the catalytic activity was maintained. As a result, it was confirmed that the same catalyst could be used for a cumulative total of 60 hours or more. Furthermore, when the catalytic activity decreased, the solid catalyst could be easily regenerated by heat treatment under a hydrogen atmosphere.

[0094] [Table 1]

[0095] From the above results, when a solid catalyst carrying a ruthenium-tin alloy (Ru-Sn alloy) on a carrier was used and the reaction was carried out at a temperature of 240°C or higher under temperature and pressure conditions where water was in the gas phase (i.e., when the temperature of the flow reactor (column) 4 was 240°C or higher), hydrogen and carboxylic acid could be obtained in high yield from primary alcohol and water. Furthermore, when the reaction was carried out at a temperature of 190°C or higher and 220°C or lower (i.e., when the temperature of the flow reactor (column) 4 was 190°C or higher and 220°C or lower), hydrogen and carboxylic acid could be obtained in high purity from primary alcohol and water. Furthermore, the product could be obtained in a short residence time of 10 seconds or less in the flow reactor (catalyst-packed section). Furthermore, the solid catalyst used in the present invention was stable and durable, and could be easily reused by simply washing with water.

[0096] Although the present invention has been described above using the above-mentioned embodiments, the present invention is not limited to these embodiments, and can be modified within the scope of what a person skilled in the art can conceive, such as other embodiments, additions, changes, deletions, etc., and any aspect is included in the scope of the present invention as long as it achieves the effects of the present invention. [Explanation of symbols]

[0097] 1 Raw material tank 2. High-pressure pump 3 Heat exchanger 4. Flow reactor (column) 5 Aluminum Block 6. Electric furnace 7. Pressure gauge 8 Back Pressure Valve 9 Gas-liquid separator 10 Gas recovery section (gas bag) 11 Liquid collection section (glass bottle)

Claims

1. A method for producing hydrogen and a carboxylic acid, comprising continuously introducing a primary alcohol having 1 to 7 carbon atoms and water into a flow reactor packed with a solid catalyst made of a support carrying an alloy of ruthenium and tin (Ru—Sn alloy), and passing the primary alcohol and water through the flow reactor under temperature and pressure conditions that convert the water into a gas phase, thereby reacting the primary alcohol and water.

2. 2. The method for producing hydrogen and a carboxylic acid according to claim 1, wherein the temperature inside the flow reactor is 185 to 350° C. and the pressure inside the flow reactor is 0.1 to 15 MPa.

3. 3. The method for producing hydrogen and a carboxylic acid according to claim 1, wherein the content of ruthenium in the Ru—Sn alloy is 25 to 200 parts by mass per 100 parts by mass of tin.

4. The method for producing hydrogen and a carboxylic acid according to any one of claims 1 to 3, wherein the primary alcohol is ethanol and acetic acid is produced as the carboxylic acid.

5. 5. The method for producing hydrogen and a carboxylic acid according to claim 1, wherein the residence time of the introduced primary alcohol having 1 to 7 carbon atoms and water in the flow reactor is 60 seconds or less.

6. 6. The method for producing hydrogen and a carboxylic acid according to claim 1, wherein the solid catalyst is composed of particles made of a metal oxide or a carbon material supporting a Ru—Sn alloy.

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