Catalytic reaction method

Abstract

To provide a catalytic reaction method by which it is possible to further enhance a yield of an object in a competitive reaction in the presence of a catalyst.SOLUTION: A catalytic reaction method includes sequentially bringing a plurality of kinds of catalysts different in catalytic activity and a raw material into contact with each other so as to cause a catalytic reaction at a multistage when carrying out a competitive reaction in the presence of the catalysts, thereby obtaining an object at a higher generation rate than that of a single-stage catalytic reaction that brings one of the plurality of kinds of catalysts and the raw material into contact with each other.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a catalytic reaction method, and more particularly to a competitive reaction carried out in the presence of a catalyst. [Background technology]

[0002] Hydrogen is attracting increasing attention as a clean energy source amid the global trend toward decarbonization. Hydrogen can be obtained by subjecting hydrocarbons and oxygen-containing hydrocarbons to a reforming reaction using a catalyst.

[0003] Ethanol (EtOH) derived from biomass such as sugarcane, corn, and lignocellulose is expected to be a sustainable resource. Ethanol is low in toxicity, chemically stable, and easy to store and transport, so it is also considered a promising raw material for the above reforming reaction. The steam reforming reaction is known as a reforming reaction for ethanol. This steam reforming reaction is expressed by the following reaction formula. C2H5OH+3H2O→2CO2+6H2 In the steam reforming of ethanol, four reactions (a) to (d) are considered to occur, as shown in Figure 1 (Non-Patent Documents 1 and 2). The details of each reaction are as follows. [Reaction (a)] The production of acetaldehyde by the dehydrogenation reaction of ethanol, and the production of CH4 (methane) and CO (carbon monoxide) by the decarbonylation reaction of acetaldehyde. This reaction is an ethanol decomposition reaction (methane production reaction), and the reaction formula is shown below. CH3CH2OH→CH4+H2+CO [Reaction (b)] The production of acetaldehyde by dehydrogenation of ethanol, and the production of 3H2 (hydrogen) and 2CO by reaction of acetaldehyde with steam. This reaction is ethanol steam reforming, and the reaction formula is shown below. CH3CH2OH+H2O→4H2+2CO [Reaction (c)] The reaction of CH4 produced in reaction (a) with steam produces 3H2 and CO. This reaction is methane steam reforming, and the reaction formula is shown below. CH4+H2O→3H2+CO [Reaction (d)] The reaction of CO produced in reactions (a) to (c) with H2O (water vapor) produces H2 and CO2 (carbon dioxide). This reaction is the water-gas shift reaction, and the reaction formula is shown below. CO+H2O→CO2+H2

[0004] The above reactions (a) and (b) are collectively referred to as the ethanol conversion reaction.

[0005] Various catalysts for use in the above steam reforming reaction have been proposed. For example, Patent Document 1 describes an ethanol steam reforming catalyst in which ruthenium is supported on a support made of one or more metal oxides selected from the group consisting of zirconium oxide, cerium oxide, and cerium-zirconium composite oxide. According to the technology described in Patent Document 1, it is said that high catalytic activity and excellent hydrogen selectivity can be achieved by performing a steam reforming reaction of ethanol in the presence of this catalyst. Patent Document 2 describes a hydrogen production method in which an ethanol reforming catalyst, which is made of La2O3 as a carrier and Co supported on the carrier, is reduced with hydrogen at 500 to 600°C, and then ethanol is reacted with steam using the ethanol reforming catalyst to produce hydrogen. The technology described in Patent Document 2 is said to be able to improve hydrogen yield at a lower temperature than before. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2005-131468 A [Patent Document 2] JP 2009-102209 A [Non-patent literature]

[0007] [Non-Patent Document 1] S. Ogo, Y. Sekine, Fuel Processing Technology, 2020, Vol. 199, p. 1062383 [Non-Patent Document 2] Y.J.Wu,et al.,Chemical Engineering Journal,2013,Vol.231,pp.36-48 Summary of the Invention [Problem to be solved by the invention]

[0008] As described above, many catalysts for use in the steam reforming reaction of ethanol have already been proposed and are commercially available.

[0009] The above-mentioned steam reforming reaction of ethanol is a competitive reaction (competitive reaction, parallel reaction) that generates reactions (a) to (d) as described above. However, the inventors' investigations have revealed that CH4 generated in reaction (a) is a stable substance, while reaction (c) is less efficient, and CH4 generated in the steam reforming reaction of ethanol is not easily converted to H2, CO, or the like. Furthermore, CH4 as it is cannot be used as fuel for generating electricity in a hydrogen-powered fuel cell. Thus, the inventors have come up with the idea of ​​maximizing the production efficiency of the target product by controlling the balance of the multiple reactions (a) to (d) above. The target product can be, for example, H2. From the viewpoint of suppressing the production of methane, the target product can also be H2 and CO. The above-mentioned idea of ​​controlling the balance of each reaction that constitutes the competing reaction is not limited to the steam reforming reaction of ethanol, but can also be applied to maximizing the production efficiency of the target product in various competing reactions carried out in the presence of a catalyst. In various competitive reactions, the control of the balance of each reaction constituting the competitive reaction depends primarily on the properties of the catalyst. Currently, many catalyst species have already been proposed. However, in reality, there are limitations to the improvement of the efficiency of producing the target product in the competitive reaction by only improving the catalyst.

[0010] An object of the present invention is to provide a catalytic reaction method that makes it possible to increase the yield of a target product in a competitive reaction carried out in the presence of a catalyst. [Means for solving the problem]

[0011] The present inventors have conducted extensive research in light of the above problems. As a result, they have found that, when a competitive reaction is carried out in the presence of a catalyst, the yield of the target product can be increased to a high level that could not be achieved with a single catalyst by successively contacting the raw material with multiple catalysts having different catalytic activities to cause a catalytic reaction (changing the balance of each reaction constituting the competitive reaction over time). Based on this finding, the present inventors have conducted further research and have completed the present invention.

[0012] The above object of the present invention is achieved by the following means. [1] A catalytic reaction method comprising the steps of: carrying out a competitive reaction in the presence of a catalyst, successively contacting a raw material with a plurality of types of catalysts having different catalytic activities to generate a catalytic reaction in multiple stages, thereby obtaining a target product at a higher production rate than in a single-stage catalytic reaction in which the raw material is contacted with one of the plurality of types of catalysts. [2] The catalytic reaction method according to [1], which obtains a target product at a higher production rate than a single-stage catalytic reaction in which the raw material is contacted with a composition consisting of multiple catalysts having different catalytic activities. [3] The catalytic reaction method according to [1] or [2], wherein the raw material is in a gaseous state and the catalyst is in a solid state at a reaction temperature of the catalytic reaction, and the catalytic reaction is carried out by supplying the raw material from one side of a reactor containing the catalyst to the reactor and circulating the raw material to the other side of the reactor. [4] The catalytic reaction method according to any one of [1] to [3], wherein the reaction temperature of the catalytic reaction is 0 to 1000° C. [5] The catalytic reaction method according to any one of [1] to [4], wherein the competing reaction is a steam reforming reaction of ethanol. [6] The catalytic reaction method according to [5], wherein the multiple catalysts having different catalytic activities are two catalysts having different catalytic activities. [7] The catalytic reaction method according to [6], wherein, of the two catalysts, catalyst A which produces less methane when used alone as a catalyst for the steam reforming reaction of ethanol is used in the first-stage catalytic reaction. [8] The catalytic reaction method according to [6] or [7], wherein, of the two types of catalysts, the catalyst A used in the first-stage catalytic reaction has a relational expression r1 / (r1+r2) between a reaction rate r1 in the following reaction (a) constituting a steam reforming reaction of ethanol and a reaction rate r2 in the following reaction (b), of 0.5 or less when the catalytic reaction is performed with 3 mL of the catalyst A placed in a reactor, at a reaction temperature of 500°C, a molar ratio of ethanol to water in the raw materials of ethanol / water = 1 / 3, and an ethanol flow rate of 1630 ml-std / min. Reaction (a) CH3CH2OH → CH4 + H2 + CO Reaction (b) CH3CH2OH+H2O→4H2+2CO [9] The catalyst A is a catalytic reaction method according to [7] or [8], wherein the sum of the reaction rate r1 and the reaction rate r2 is 1.8 mol / (skg) or less when the catalytic reaction is carried out by disposing 0.3 mL of the catalyst A in a reactor, setting the reaction temperature to 500°C, setting the molar ratio of ethanol to water in the raw materials to ethanol / water = 1 / 3, and setting the ethanol flow rate to 1630 ml-std / min.

[10] The catalytic reaction method according to any one of [6] to [9], wherein, of the two types of catalysts, catalyst B used in the second-stage catalytic reaction has a relational expression r1 / (r1+r2) between a reaction rate r1 in the following reaction (a) constituting a steam reforming reaction of ethanol and a reaction rate r2 in the following reaction (b), of 0.5 or more when the catalytic reaction is performed with 3 mL of catalyst B placed in a reactor, at a reaction temperature of 500°C, a molar ratio of ethanol to water in the raw materials of ethanol / water = 1 / 3, and an ethanol flow rate of 1630 ml-std / min. Reaction (a) CH3CH2OH → CH4 + H2 + CO Reaction (b) CH3CH2OH+H2O→4H2+2CO

[11] The catalytic reaction method according to any one of [6] to

[10] , wherein the catalyst B used in the second-stage catalytic reaction, of the two types of catalysts, has a sum of the reaction rates r1 and r2 of 2.0 mol / (skg) or more when the catalytic reaction is carried out under the following conditions: 0.3 mL of catalyst B is placed in a reactor; the reaction temperature is 500° C.; the molar ratio of ethanol to water in the raw materials is ethanol / water=1 / 3; and the ethanol flow rate is 1630 ml-std / min.

[12] The catalytic reaction method according to any one of [6] to

[11] , further comprising disposing the reactor in a cavity resonator and forming a standing wave of microwaves in the cavity resonator to heat the catalyst.

[13] The catalytic reaction method according to any one of

[10] to

[12] , wherein the ratio by volume of the catalyst A and the catalyst B placed in the reactor is catalyst A / catalyst B=2 / 8 to 8 / 2.

[14] A method for producing hydrogen, comprising obtaining hydrogen by the catalytic reaction method according to any one of [5] to

[13] . Effect of the Invention

[0013] According to the catalytic reaction method of the present invention, it is possible to increase the yield of the target product in a competitive reaction carried out in the presence of a catalyst. [Brief description of the drawings]

[0014] [Figure 1] 1 is a diagram showing a reaction scheme of a steam reforming reaction of ethanol. [Diagram 2] This is a graph showing the simulation results of the flow rate profile of the fitted substance species (product gas). The test data points used for the fitting are also shown. H2O: thick black line (●), EtOH: thick gray line (◯), H2: solid black line (□), CO: solid gray line (◇), CO2: dotted black line (△), CH4: dotted gray line (×) [Diagram 3] 1 shows Arrhenius plots of catalysts (I) to (III). [Figure 4] 1 is a graph showing the results of a simulation of the relationship between the flow rate of a substance species (product gas) and the catalyst loading amount. H2O: thick black line, EtOH: thick gray line, H2: medium black line, CO: medium gray line, CO2: dotted black line, CH4: dotted gray line [Diagram 5] 1 is a graph showing the results of a simulation of the relationship between reaction rate and catalyst loading amount. r1: black thick line, r2: gray thick line, r3: gray dotted line, r4: black dotted line [Figure 6] Graph (1) shows the relationship between the ethanol conversion ability index r1+r2 and the amount of catalyst, and graph (2) shows the relationship between the methane production ability (inhibition ability) index r1 / (r1+r2) and the amount of catalyst. [Figure 7] 1 is a graph showing the results of a simulation of the relationship between the amount of various produced gases and the amount of catalyst in a steam reforming reaction of ethanol, in which Example 1 is shown by a solid line and Comparative Example 4 is shown by a dotted line. [Figure 8] 1 is a graph showing the results of a simulation of the relationship between the amount of various produced gases and the amount of catalyst in a steam reforming reaction of ethanol, in which Example 2 is shown by a solid line and Comparative Example 5 is shown by a dotted line. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] A preferred embodiment of the catalytic reaction method of the present invention will be described.

[0016] The catalytic reaction method of the present invention includes, in carrying out a competitive reaction in the presence of a catalyst, sequentially contacting a raw material with a plurality of catalysts having different catalytic activities to generate a multi-stage (multiple-stage) catalytic reaction, thereby obtaining a target product at a higher production rate than a single-stage catalytic reaction in which the raw material is contacted with one of the plurality of catalysts. Note that this comparison is performed assuming that the amount of catalyst (bulk volume) in the single-stage catalytic reaction is the same as the total amount of catalyst (bulk volume) in the multi-stage catalytic reaction. The catalytic reaction method of the present invention is preferably a reaction that obtains the target product at a higher production rate than a single-stage catalytic reaction in which the raw material is contacted with a composition consisting of multiple types of catalysts with different catalytic activities (a homogeneous mixture of the multiple types of catalysts with different catalytic activities). This composition is a composition in which the catalysts used in the multi-stage catalytic reaction are mixed in the amounts (bulk volumes) used in the multi-stage catalytic reaction.

[0017] [Catalysis] The catalytic reaction in the present invention is not particularly limited as long as it is a competitive reaction carried out in the presence of a catalyst, and examples thereof include steam reforming of ethanol, steam reforming of methane, carbon dioxide reforming of methane, partial oxidation of methane, Fischer-Tropsch (FT) synthesis reaction, catalytic cracking reaction, steam reforming of propane, reforming reaction of liquefied petroleum gas, reforming reaction of hydrocarbon compounds, CC bond formation reaction, oxidation reaction, hydrogenation reaction, esterification reaction, amidation reaction, cross-coupling reaction, polymerization reaction, and cracking reaction. In the catalytic reaction of the present invention, it is preferable to bring the raw material and the catalyst into contact with each other and react them while the raw material is in a gaseous state and the catalyst is in a solid state at the reaction temperature. For example, since the steam reforming reaction of ethanol is carried out at a high temperature of several hundred degrees Celsius, the raw material ethanol and water are in a gaseous state at the reaction temperature, and this mixed gas of gaseous ethanol and steam is usually brought into contact with a solid catalyst (solid catalyst) at the reaction temperature. The ratio of the amounts of ethanol and water in the raw materials is determined by a stoichiometric ratio. For example, the ratio of the amounts of ethanol and water in the raw materials is appropriately adjusted based on a molar ratio of ethanol / water = 1 / 3.

[0018] The catalytic reaction in the present invention is preferably carried out while flowing the gaseous raw material from one side (inlet) to the other side (outlet) of a reactor in which a solid catalyst is arranged at a reaction temperature. In this way, the reaction product (product gas) can be taken out from the outlet. For example, in the case of using two types of catalysts, the two types of catalysts are arranged in sequence from one side (inlet) to the other side (outlet) of the reactor, forming a catalyst A region (inlet side region) in which catalyst A is arranged and a catalyst B region (outlet side region) in contact with the catalyst A region and in which catalyst B is arranged. By introducing the raw material from the inlet side of this reactor and flowing the raw material toward the outlet side, the catalytic reaction proceeding due to the action of catalyst A and the catalytic reaction proceeding due to the action of catalyst B proceed in sequence, and the reaction product can be taken out from the outlet. The catalyst A region and the catalyst B region may be in contact with each other as described above, or may not be in contact with each other. When the catalyst A region and the catalyst B region are not in contact with each other, the catalyst A region and the catalyst B region may be separated by a space, or the catalyst A region and the catalyst B region may be stacked via a separator or the like. Similarly, when three or more types of catalysts are used, the catalysts are sequentially arranged in the reactor, and the raw material is introduced from the inlet and circulated toward the outlet side, so that the reaction product can be taken out from the outlet. Examples of the reactor include a cylindrical reactor, a plate reactor, a multi-tube reactor, and a stacked reactor.

[0019] In the catalytic reaction of the present invention, multiple types of catalysts are used. Each of these multiple types of catalysts can catalyze the same reaction, but they have different catalytic activities (degree to increase the reaction rate) for the reaction they catalyze. In the present invention, the catalytic reaction is carried out by contacting these multiple types of catalysts with the raw material sequentially in multiple stages (two stages if there are two types of catalysts, three stages if there are three types, and four stages if there are four types). As described above, the catalytic reaction in the present invention is a multi-stage reaction using multiple types of catalysts. As a result, the target product is obtained at a higher production rate than in a single-stage catalytic reaction in which one of the multiple types of catalysts is contacted with the raw material. That is, the catalytic reaction in the present invention obtains the target product at a higher production rate than in any case in which the catalytic reaction is performed using each of the multiple types of catalysts used in the catalytic reaction alone. In addition, it is preferable that the target product is obtained at a higher production rate than in any case in which the catalytic reaction is performed using a composition (a uniform mixture of multiple types of catalysts) consisting of the multiple types of catalysts used in the catalytic reaction. The number of types of catalysts used is preferably 2 to 5, more preferably 2 to 4, even more preferably 2 or 3, and even more preferably 2. That is, the catalytic reaction is preferably a 2 to 5-stage reaction, more preferably a 2 to 4-stage reaction, even more preferably a 2 or 3-stage reaction, and even more preferably a 2-stage reaction.

[0020] The reaction temperature of the catalytic reaction in the present invention can be appropriately set depending on the type of reaction. For example, the reaction temperature can be 0 to 1000°C, 20 to 1000°C, 40 to 1000°C, or 60 to 1000°C. Taking the steam reforming reaction of ethanol as an example, the reaction temperature is preferably 300 to 700°C. In addition, in consideration of energy efficiency, the reaction temperature is preferably as low as possible within the range in which the target reaction occurs. In addition, since the suitable temperature range may differ depending on the catalyst type and gas composition, the temperature may be changed for each stage. The reaction temperature can be controlled (heated) by using, for example, an electric furnace or the like, or by irradiating the catalyst with microwaves. In terms of energy efficiency, it is preferable to apply catalyst heating by microwave irradiation. Microwaves may be multi-mode or single-mode, and single-mode is preferable. For example, a cavity resonator can be used to form a single-mode standing wave inside the resonator, and a catalyst can be placed at or around a portion where the energy intensity of this standing wave is maximized. This allows the catalyst to be heated to a desired high temperature quickly with excellent energy efficiency. The portion where the energy intensity is maximized may be a portion where the electric field energy intensity is maximized, or may be a portion where the magnetic field energy intensity is maximized, as long as the desired heating can be achieved. The reaction is not limited to being driven by heating, and may be driven by electricity or light. That is, the present invention may be applied to electrochemical reactions, photoreactions, and the like.

[0021] <Catalyst> The catalyst used in the above catalytic reaction can be used without any particular limitation as long as it catalyzes the target competing reaction and satisfies the requirement of the present invention (obtaining the target product at a higher production rate than in a single-stage catalytic reaction in which one of the multiple catalysts is brought into contact with the raw material) when the multiple-stage reaction system is constructed by combining it with another catalyst that catalyzes the same competing reaction. For example, multiple types of known catalysts or their improved products can be selected. As an example, a catalyst used in the steam reforming reaction of ethanol includes a catalyst containing a metal having catalytic activity. The metal having catalytic activity may be an alloy. Catalysts containing these metals are usually in a state in which the metal having catalytic activity is supported on a metal oxide, a carbon support, or the like, and are used as catalysts in this state. Note that when the term "catalyst" is used simply in the present invention, it is used as a concept including the support. From the viewpoint of further increasing the heating efficiency (particularly the electric field heating efficiency) by microwave irradiation, it is preferable that the catalyst contains a substance having high microwave absorption efficiency as a support. For example, β-alumina, silicon carbide, other specific ceramics, zeolites, and carbon materials can be mentioned. A preferred example of the catalyst used in the steam reforming reaction of ethanol is a catalyst containing a ceramic support and catalytic metal particles supported on the ceramic support. The catalytic metal particles are not particularly limited as long as the effect of the present invention can be obtained, and include catalysts containing ruthenium, catalysts containing cobalt, catalysts containing platinum, and catalysts containing nickel, and catalysts containing at least one of ruthenium, cobalt, platinum, and nickel are preferred. The form of the present catalyst to be contacted with the raw material is not particularly limited as long as the effect of the present invention can be obtained, and may be, for example, a powder, granules, pellets, a structure such as a honeycomb structure, or a filter containing the present catalyst. The catalyst is preferably particulate (also called catalyst particles), and more preferably the catalyst particles are porous particles. The particle size of the catalyst particles is not particularly limited, and is usually 50 to 5000 μm, and preferably 100 to 3000 μm. In the present invention, the particle size of the catalyst including the ceramic carrier and the catalytic metal particles supported on the ceramic carrier is determined by observing 50 catalyst particles (primary particles) at random using an optical microscope or an electron microscope, and calculating the arithmetic mean value of the maximum diameter of each catalyst particle in planar observation (the distance from one point to another point on the outer periphery of the catalyst particle at the maximum).

[0022] Another example of the catalyst in the present invention is a catalyst including a carbon carrier and catalytic metal particles supported on the carbon carrier. The carbon carrier is preferably a porous carbon material. The carbon carrier can include pores having interconnection. The carbon carrier can include a carbon catalyst that itself has catalytic activity. The carbon carrier can be, for example, particulate. In this case, the particle size of the carbon carrier is not particularly limited, and the median diameter (volume basis) of the carbon carrier may be, for example, 0.05 μm or more and 1.00 μm or less. In the present invention, the median diameter of the catalyst including the carbon carrier and the catalytic metal particles supported on the carbon carrier is obtained by using a laser diffraction type particle size distribution measuring device to obtain particle size distribution data in which the horizontal axis indicates the particle size (μm) and the vertical axis indicates the cumulative relative particle amount (%), and the particle diameter at which the cumulative relative particle amount becomes 50% in the particle distribution data is used as the median diameter (μm). The carbon carrier may be a powder, granules, pellets, a structure such as a honeycomb structure, or a filter. The catalytic metal particles supported on the carbon carrier preferably contain a precious metal. The precious metal contained in the catalytic metal particles is not particularly limited as long as the effect of the present invention is obtained, and may be one or more selected from ruthenium, palladium, rhodium, silver, osmium, iridium, platinum, and gold. The form of the present catalyst to be contacted with the raw material is not particularly limited as long as the effect of the present invention is obtained, and may be, for example, a powder, granules, pellets, a structure such as a honeycomb structure, or a filter containing the present catalyst. In this case, the particle size of the granules or pellets is not particularly limited, but may be, for example, 0.1 mm or more and 10 mm or less. In the present invention, the particle size of the carbon carrier or the granules or pellets containing the catalyst containing the catalytic metal particles supported on the carbon carrier is determined by randomly observing 50 catalyst particles (primary particles) using an optical microscope or an electron microscope, etc., and taking the arithmetic average value of the maximum diameter of each catalyst particle in planar observation (the distance from one point to another point on the outer periphery of the catalyst particle at the maximum).

[0023] Taking the steam reforming reaction of ethanol, which is a preferred embodiment of the catalytic reaction of the present invention, as an example, the catalytic reaction of the present invention will be described in more detail based on a simulation model and simulation results. EXAMPLES

[0024] (Steam reforming of ethanol) -Simulation model- A catalyst is generally defined as a substance that accelerates the reaction rate of a specific chemical reaction and does not change before or after the reaction. Catalysts for competing reactions have different degrees of acceleration of the reaction rate of each reaction in the competing reaction (reaction selectivity) depending on the catalyst type. The catalytic reaction of the present invention utilizes the difference in reaction selectivity depending on the catalyst type to effectively increase the production efficiency of the target product.

[0025] In order to clarify the reaction selectivity that characterizes the catalyst, a reaction kinetics analysis was performed using the following procedure. Note that this analysis assumes a configuration in which the raw material (a mixture of ethanol and steam) is supplied from one side of a reactor containing a solid catalyst and the raw material is circulated to the other side of the reactor to perform the catalytic reaction.

[0026] As described above, reactions (a) to (d) occur in the steam reforming of ethanol (Non-Patent Documents 1 and 2). Therefore, the equilibrium reactions of reactions (a) to (d) were assumed. ΔH 298 is the reaction enthalpy under standard conditions (25°C (298K), 1 atm), and is customarily written in the reaction equation. 1-298 is the ΔH of reaction (a) 298 , ΔH 2-298 is the ΔH of reaction (b) 298 , ΔH 3-298 is the ΔH of reaction (c) 298 , ΔH 4-298 is the ΔH of reaction (d) 298 means... Reaction (a) CH3CH2OH⇔CH4+H2+CO ΔH 1-298 =49.6kJ / mol Reaction (b) CH3CH2OH+H2O⇔4H2+2CO ΔH 2-298 =255.6kJ / mol Reaction (c) CH4+H2O⇔3H2+CO ΔH 3-298 =205.9kJ / mol Reaction (d) CO+H2O⇔CO2+H2 ΔH 4-298 =-41.4kJ / mol

[0027] From the above reactions (a) to (d), the following simple reaction rate equation was assumed. Although a more realistic reaction rate equation that takes into account the adsorption of substances onto the catalyst surface could be considered, the following reaction rate equation is valid because the plots of all reactions tend to be close to linear in the Arrhenius plot described below. Note that EtOH means ethanol. Reaction (a): r1=k1C EtOH -k1 / K eq1 C CH4 C H2 C CO K eq1 =(y CH4 y H2 y CO / y EtOH ) eq =exp(-6452.1 / T+29.249) Reaction (b): r2=k2C EtOH C H2O -k2 / K eq2 C H2 4 C CO 2 K eq2 =(y H2 4 y CO 2 / y EtOH y H2O )eq =exp(-37371.1 / T+62.9988) Reaction (c): r3=k3C CH4 C H2O -k3 / K eq3 C H2 3 C CO K eq3 =(y H2 3 y CO / y CH4 y H2O ) eq =exp(-26337 / T+29.518) Reaction (d): r4=k4C CO C H2O -k4 / K eq4 C CO2 C H2 K eq4 =(y CO2 y H2 / y CO y H2O ) eq =exp(4582 / T-4.2311) Here, "r" is the reaction rate, and r1 to r4 correspond to reaction equations (a) to (d), respectively. "k" is the reaction rate constant, and k1 to k4 correspond to reaction equations (a) to (d), respectively. "K eq " is the equilibrium constant, K eq1 ~K eq4 correspond to reaction equations (a) to (d), respectively. "y" is the mole fraction, and "C" is the concentration of the substance species (mol / m 3 ), "T" stands for temperature (Kelvin). eqis a value that can be theoretically estimated using thermodynamic property values, and is a value that does not depend on the catalyst. The formula expressed as exp( ) is an approximation derived from a group of values ​​obtained using the calculation method described below (it is a device for simplifying complicated formulas while maintaining approximate estimation accuracy, and it is not always necessary to use an approximation). "C" and "T" are variables that can be specified by the person implementing the initial conditions. "k" is a parameter specific to the catalyst, and the value is determined so that the reaction model is consistent with the reaction test results.

[0028] K eq The calculation method of K eq can be calculated from the thermodynamic properties of each substance. The thermodynamic properties were calculated based on the descriptions in Reference 1 below. Reference 1: Carl Yaws,Chemical Properties Handbook:Physical,Thermodynamic,Environmental Transport,Safety and Health Related Properties for Organic and Inorganic Chemicals 1st Edition,1st edition,McGraw Hill,New York,United States(October 22,1998) The equilibrium constant K is eq The formula required to calculate is shown below. a, b, c, d, and e are parameters for estimation that are linked to the substance type and the estimation formula. If the Gibbs energy change of the reaction can be estimated, the equilibrium constant can also be estimated. C p =a+bT+cT 2 +dT 3 +eT 4

number

number

[0029] The following three catalysts (I) to (III) were prepared. (I) 5wt% Ru / Al2O3 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., particle size 250-500μm, packing density 1.0g / ml) (II) 10wt%Pt / Al2O3+β alumina ([10wt%Pt / Al2O3] / β alumina (mass ratio) = 4 / 6, particle size 250-500μm. Packing density 0.50g / ml) (III) Ru / Co / Fe / CA (Ru 5wt%, Co 19wt%, Fe 1wt%, CA is a carrier made of carbon material, the catalyst obtained was mixed with a binder and formed into pellets with a particle diameter of 1 to 2 mm. Packing density 0.333g / ml) Here, using catalyst (I) as an example, a method for determining the reaction rate constants k1 to k4 of each of reactions (a) to (d) from the results of reaction tests actually performed under the reaction test conditions below will be described.

[0030] Reaction test conditions ================== Heating method: Microwave electric field heating Catalyst amount: 0.03g Reaction tube: Quartz, cylindrical, outer diameter 6.0 mm x inner diameter 4.0 mm Raw material: ethanol aqueous solution 0.10 ml / min (ethanol:water = 1:3 (molar ratio), gas volume flow rate at standard conditions (0°C, 1 atm) is ethanol: 20.7 ml-std / min, water: 62.0 ml-std / min) Carrier gas: Argon, gas volume flow rate at standard conditions: 250ml-std / min Reaction temperature (control temperature): 600℃ ================== The reaction rate r is a differential value with respect to the substance species, and can be expressed as r = dF / dW. Here, F represents the flow rate of the substance species, and W represents the volume of the reaction field. In this analysis, F is the molar flow rate [mol / s], and W is the catalyst weight [kg]. The unit of the associated reaction rate r is [mol / (skg)]. For details, please refer to Reference 2. Reference 2: Kenji Hashimoto, Reaction Engineering, Revised and Expanded Edition, Baifukan (2019) The variables related to each substance were integrated numerically on a computer to determine their values, i.e., F was updated for each step size ΔW. F+ΔF(=ΣrΔW)→F The reaction rate constants k1 to k4 were determined by parameter fitting using the least squares method so that F at W was consistent with the value calculated from the results of the reaction test. The ΔF for each substance type is expressed using r as follows: ΔF EtOH =(-r1-r2)ΔW ΔF H2O =(-r2-r3-r4)ΔW ΔF H2 =(r1+4r2+3r3+r4)ΔW ΔF CO =(r1+2r2+r3-r4)ΔW ΔF CO2 =(r4)ΔW ΔF CH4 =(r1-r3)ΔW The determined k1 to k4 values ​​are as follows: The fitting results are shown in FIG. k1=0.2002, k2=0.1654, k3=2.836×10 -5 , k4=0.7271

[0031] In the analysis up to this point, the initial concentration and amount of catalyst can be arbitrarily specified and calculated, but the temperature is 600°C (1 / T = 0.001145K (Kelvin)). -1 ) is limited to Here, by analyzing k at other temperatures in the same manner as above and expressing it as a function of temperature, it becomes possible to specify any temperature. In other words, the frequency factor k0 and activation energy E can be determined from parameter fitting of an Arrhenius plot in which k at multiple temperatures is plotted on the 1 / T axis, and expressed in the form k = k0exp(-E / (RT)). The Arrhenius plot (Figure 3) and the equation for the analyzed reaction rate constant are shown. The Arrhenius plots for catalysts (II) and (III) are also shown.

[0032] The following equation can be derived from the Arrhenius plot above. Catalyst (I): k1=1486exp(-63341[J / mol] / (RT)) k2=7744exp(-79514[J / mol] / (RT)) k3=18.5exp(-23701[J / mol] / (RT)) k4=4.03×10 -5 exp(-2725[J / mol] / (RT)) Catalyst (II): k1=54268exp(-68642[J / mol] / (RT)) k2=1385519exp(-107309[J / mol] / (RT)) k3=8.21×10 -5 exp(-8391[J / mol] / (RT)) k4=0.3047exp(-10550[J / mol] / (RT)) Catalyst (III): k1=8.503exp(-32008[J / mol] / (RT)) k2=11.9exp(-37505[J / mol] / (RT)) k3=19.97×10 -5 exp(-14998[J / mol] / (RT)) k4=0.00899exp(1223[J / mol] / (RT)) In this way, the reaction selectivity that characterizes the catalyst could be quantified by the reaction rate constant.

[0033] Since the units of reaction rate constants vary depending on their definition, it is difficult to compare reaction selectivities as they are. For example, if the reaction rate were an indicator, comparisons would be possible. As an example, the flow rate profile and reaction rate profile up to the position where the catalyst loading amount is 3 ml under the following conditions are shown in FIGS. 4 and 5 for each of catalysts (I) to (III). conditions ================== Catalyst filling volume: 3.0ml (Catalyst (I): 3.0g, Catalyst (II): 1.5g, Catalyst (III): 1.0g) Raw material: Ethanol aqueous solution equivalent to 8ml / min (ethanol:water molar ratio 1:3, ethanol: 1630ml-std / min, water: 4890ml-std / min) Dilution gas: 250ml-std / min Reaction temperature: 500℃, uniform temperature distribution ==================

[0034] Ethanol conversion potential can be evaluated using r1+r2 (the higher the r1+r2, the higher the ethanol conversion potential), and methane production potential can be evaluated using r1 / (r1+r2) (the higher the r1 / (r1+r2), the higher the methane production potential). From Figure 6(1), the order of integral values ​​of ethanol conversion capacity r1+r2 from 0 to 3 ml of catalyst (where the horizontal axis in Figure 6(1) is converted to kg using the packing density) is "Catalyst (II) > Catalyst (I) > Catalyst (III)" (12.0>9.64>6.72, unit is ×10 -4 mol / s). From Figure 6 (2), the ranking of methane production potential r1 / (r1+r2) is "Catalyst (II) > Catalyst (I) > Catalyst (III)". Generally, methane is a stable substance and is not easily converted to H2, CO, etc. at temperatures around 500°C. It is also not suitable as a power generating fuel for hydrogen fuel cells. Therefore, in the steam reforming reaction of ethanol, a catalyst with high ethanol conversion ability and low methane production ability is preferred. However, the above results show that catalyst (II), which has excellent ethanol conversion ability, also has high methane production ability, while catalysts (I) and (III), which have low methane production ability, have poor ethanol conversion ability. Incidentally, catalysts (II) and (III) are catalysts designed for microwave heating, and have the advantage of being more efficient at absorbing microwaves than catalyst (I).

[0035] The present inventors have now changed their perspective and focused on the possibility of combining catalysts to compensate for each other's shortcomings, and have come up with the idea of ​​using a hybrid catalyst to increase the amount of hydrogen (H2) or the total amount of hydrogen and carbon monoxide (H2+CO). That is, the reactor is filled with catalyst (I) or catalyst (III) (low methane production ability, or in other words, excellent methane suppression ability) in the first stage and catalyst (II) (excellent ethanol conversion ability) in the second stage, and the raw material ethanol is first brought into contact with catalyst (I) or (III) for catalytic reaction, and then brought into contact with catalyst (II) to form a sequential catalytic reaction system, which leads to the idea of ​​obtaining the target product H2 with high efficiency, or obtaining the total amount of H2 and CO with high efficiency. Here, CO is produced by the water gas shift reaction (reaction (d)) to produce H2. This idea was verified by the following reaction simulation.

[0036] conditions ================== Catalyst filling volume: 3.0ml Raw material: Ethanol aqueous solution equivalent to 8.0 ml / min (ethanol:water = 1:3 (molar ratio), ethanol: 1630 ml-std / min, water: 4890 ml-std / min) Dilution gas: 250ml-std / min Reaction temperature: 500℃, uniform temperature distribution ==================

[0037] Example 1: From the inlet side, catalyst (I) was packed first, followed by catalyst (II), with the ratio of each catalyst being changed. As shown by the solid line in Figure 7, the amount of H2+CO reached a maximum value when 1.95 ml of catalyst (I) and 1.05 ml of catalyst (II) were packed, and the amount of H2+CO was calculated to be 6631 ml-std / min (H2 amount 5684 ml-std / min, CO amount 947 ml-std / min).

[0038] Example 2: From the inlet side, catalyst (III) and catalyst (II) were packed in this order, with the ratio of each catalyst being changed. As shown by the solid line in Figure 8, the amount of H2+CO reached a maximum value when 1.68 ml of catalyst (III) and 1.32 ml of catalyst (II) were packed, and the amount of H2+CO was calculated to be 6222 ml-std / min (H2 amount 4618 ml-std / min, CO amount 1604 ml-std / min).

[0039] Comparative Example 1: Only catalyst (I) was packed. As shown in Figure 7, the amount of gas produced when the catalyst packing amount was 3 mL was calculated to be 6284 ml-std / min of H2 + CO (5605 ml-std / min of H2, 679 ml-std / min of CO).

[0040] Comparative Example 2: Only catalyst (II) was packed. As shown in Figures 7 and 8, when the packed amount of catalysts (I) and (III) was 0 mL, the amount of gas generated was calculated to be 5366 ml-std / min of H2 + CO (4329 ml-std / min of H2, 1037 ml-std / min of CO).

[0041] Comparative Example 3: Only catalyst (III) was packed in the reactor. As shown in Figure 8, the amount of gas produced when the catalyst was packed in 3 mL was calculated to be 4813 ml-std / min of H2+CO (3336 ml-std / min of H2, 1477 ml-std / min of CO).

[0042] Comparative Example 4: Catalyst (I) and catalyst (II) were mixed uniformly and packed at different ratios. Regardless of the ratio, the amount of H2, CO, or H2+CO was calculated to be intermediate between those in Comparative Example 1 and Comparative Example 2, and no maximization was observed as in Example 1 (dotted line in FIG. 7).

[0043] Comparative Example 5: Catalyst (III) and catalyst (II) were mixed uniformly at different ratios and packed. The amount of H2+CO reached a maximum value when 1.62 ml of catalyst (III) and 1.38 ml of catalyst (II) were packed, and the amount of H2+CO was calculated to be 5479 ml-std / min (H2 amount 4068 ml-std / min, CO amount 1411 ml-std / min). However, compared to Example 2, these amounts were significantly smaller (dotted line in FIG. 8).

[0044] In this way, it was demonstrated that in Examples 1 and 2, which satisfy the provisions of the present invention, the target product, H2 or H2+CO, can be obtained with high efficiency.

[0045] In relation to the above-mentioned embodiment, the following embodiments can be mentioned as preferred embodiments in the case where the catalytic reaction method of the present invention is a steam reforming reaction of ethanol.

[0046] Embodiment 1: A catalytic reaction method, wherein the multiple types of catalysts having different catalytic activities are two types of catalysts having different catalytic activities.

[0047] Embodiment 2: A catalytic reaction method in which, of the two catalysts, catalyst A which produces less methane when used alone as a catalyst for the steam reforming reaction of ethanol is used in a first-stage catalytic reaction. In the second embodiment, the volumes of the catalysts used are the same, and other reaction conditions are the same, and the amounts of methane produced are compared to determine catalyst A. The "volume" of the catalyst refers to the volume of the packed area when the catalyst is packed (i.e., the bulk volume).

[0048] Embodiment 3: The catalyst A has a relationship formula r1 / (r1+r2) between a reaction rate r1 in the following reaction (a) constituting a steam reforming reaction of ethanol and a reaction rate r2 in the following reaction (b), which is 0.5 or less, and preferably 0.45 or less, when the catalytic reaction is performed with 3 mL of catalyst A placed in a reactor (3 mL placed in terms of bulk volume), at a reaction temperature of 500°C, a molar ratio of ethanol to water in the raw materials of ethanol / water = 1 / 3, and an ethanol flow rate of 1630 ml-std / min. Reaction (a) CH3CH2OH → CH4 + H2 + CO Reaction (b) CH3CH2OH+H2O→4H2+2CO

[0049] Embodiment 4: The catalyst A has a catalytic reaction method in which the sum of the reaction rates r1 and r2 is 1.8 mol / (skg) or less, and preferably 1.5 mol / (skg) or less, when the catalytic reaction is carried out with 0.3 mL of the catalyst placed in a reactor (0.3 mL placed in terms of bulk volume), at a reaction temperature of 500°C, a molar ratio of ethanol to water in the raw materials of ethanol / water = 1 / 3, and an ethanol flow rate of 1630 ml-std / min.

[0050] Embodiment 5: A catalytic reaction method in which, of the two catalysts, catalyst B used in the second-stage catalytic reaction has a relationship r1 / (r1+r2) between a reaction rate r1 in the following reaction (a) constituting a steam reforming reaction of ethanol and a reaction rate r2 in the following reaction (b) of 0.5 or more, preferably 0.6 or more, and more preferably 0.7 or more, when the catalytic reaction is performed with 3 mL of catalyst placed in a reactor (3 mL placed in terms of bulk volume), at a reaction temperature of 500°C, a molar ratio of ethanol to water in the raw materials of ethanol / water = 1 / 3, and an ethanol flow rate of 1630 ml-std / min. Reaction (a) CH3CH2OH → CH4 + H2 + CO Reaction (b) CH3CH2OH+H2O→4H2+2CO

[0051] Embodiment 6: The catalyst B has a catalytic reaction method in which the sum of the reaction rates r1 and r2 is 2.0 mol / (skg) or more, and preferably 2.4 mol / (skg) or more, when the catalytic reaction is carried out with 0.3 mL of the catalyst placed in a reactor (0.3 mL placed in terms of bulk volume), at a reaction temperature of 500°C, a molar ratio of ethanol to water in the raw materials of ethanol / water = 1 / 3, and an ethanol flow rate of 1630 ml-std / min.

[0052] Embodiment 7: A catalytic reaction method comprising: disposing the reactor in a cavity resonator; and forming a standing microwave wave in the cavity to heat the catalyst.

[0053] Embodiment 8: The catalytic reaction method, in which the ratio of the amount of the catalyst A and the amount of the catalyst B placed in the reactor is, in terms of volume ratio (bulk volume ratio), catalyst A / catalyst B=2 / 8 to 8 / 2, preferably catalyst A / catalyst B=3 / 7 to 7 / 3, more preferably catalyst A / catalyst B=4 / 6 to 7 / 3, and further preferably catalyst A / catalyst B=5 / 5 to 7 / 3.

[0054] As explained above, it has been demonstrated that when a competitive reaction is carried out in the presence of a catalyst, multiple types of catalysts having different catalytic activities are contacted with the raw material in succession to cause a catalytic reaction in multiple stages, thereby making it possible to obtain the target product at a higher production rate than a single-stage catalytic reaction in which the raw material is contacted with one of the multiple types of catalysts, and further, it makes it possible to obtain the target product at a higher production rate than a single-stage catalytic reaction in which the raw material is contacted with a composition consisting of the multiple types of catalysts having different catalytic activities.

Claims

1. A catalytic reaction method comprising: in a competitive reaction in the presence of a catalyst, successively contacting a raw material with a plurality of types of catalysts having different catalytic activities to generate a catalytic reaction in multiple stages, thereby obtaining a target product at a higher production rate than in a single-stage catalytic reaction in which the raw material is contacted with one of the plurality of types of catalysts.

2. 2. The catalytic reaction method according to claim 1, wherein the catalytic reaction method obtains the target product at a higher production rate than a single-stage catalytic reaction in which the raw material is contacted with a composition consisting of multiple types of catalysts having different catalytic activities.

3. 3. The catalytic reaction method according to claim 2, wherein the raw material is in a gaseous state and the catalyst is in a solid state at a reaction temperature of the catalytic reaction, and the catalytic reaction is carried out by supplying the raw material from one side of a reactor containing the catalyst to the reactor and circulating the raw material to the other side of the reactor.

4. The catalytic reaction method according to claim 3, wherein the reaction temperature of the catalytic reaction is 0 to 1000° C.

5. 5. The catalytic reaction method according to claim 4, wherein the competing reaction is a steam reforming reaction of ethanol.

6. 6. The catalytic reaction method according to claim 5, wherein the plurality of catalysts having different catalytic activities are two catalysts having different catalytic activities.

7. 7. The catalytic reaction method according to claim 6, wherein, of the two catalysts, catalyst A which produces a smaller amount of methane when used alone as a catalyst for the steam reforming reaction of ethanol is used in the first stage catalytic reaction.

8. The catalyst A has a reaction rate r １ and the reaction rate r in the following reaction (b) ２ The relation r １ / (r １ +r ２ 8. The catalytic reaction method according to claim 7, wherein the catalytic reaction is carried out with 3 mL of catalyst A in a reactor, at a reaction temperature of 500° C., a molar ratio of ethanol to water in the raw materials of ethanol / water=1 / 3, and an ethanol flow rate of 1630 ml-std / min, and the catalytic reaction is carried out in such a manner that the catalytic reaction temperature is 500° C., the molar ratio of ethanol to water in the raw materials is ethanol / water=1 / 3, and an ethanol flow rate of 1630 ml-std / min. Reaction (a) CH ３ CH ２ OH → CH ４ +H ２ +CO Reaction (b) CH ３ CH ２ OH+H ２ O → 4H ２ +2CO

9. The catalyst A is a catalyst having a reaction rate r １ and reaction rate r ２ is 1.8 mol / (skg) or less when the catalytic reaction is carried out with 0.3 mL of catalyst A placed in a reactor, the reaction temperature set to 500° C., the molar ratio of ethanol to water in the raw materials set to ethanol / water=1 / 3, and the ethanol flow rate set to 1630 ml-std / min.

10. Of the two catalysts, the catalyst B used in the second stage catalytic reaction has a reaction rate r １ and the reaction rate r in the following reaction (b) ２ The relation r １ / (r １ +r ２ 10. The catalytic reaction method according to claim 9, wherein the catalytic reaction is carried out with 3 mL of catalyst B in a reactor, at a reaction temperature of 500° C., a molar ratio of ethanol to water in the raw materials of ethanol / water=1 / 3, and an ethanol flow rate of 1630 ml-std / min, and the catalytic reaction is carried out in this condition. Reaction (a) CH ３ CH ２ OH → CH ４ +H ２ +CO Reaction (b) CH ３ CH ２ OH+H ２ O → 4H ２ +2CO

11. The catalyst B is a catalyst having a reaction rate r １ and reaction rate r ２ is 2.0 mol / (skg) or more when the catalytic reaction is carried out with 0.3 mL of catalyst B placed in a reactor, the reaction temperature set to 500° C., the molar ratio of ethanol to water in the raw materials set to ethanol / water=1 / 3, and the ethanol flow rate set to 1630 ml-std / min.

12. 12. The catalytic reaction method according to claim 11, further comprising disposing the reactor in a cavity resonator and forming a standing microwave wave in the cavity to heat the catalyst.

13. The catalytic reaction method according to claim 12, wherein the volume ratio of the catalyst A to the catalyst B placed in the reactor is catalyst A / catalyst B=2 / 8 to 8 / 2.

14. A method for producing hydrogen, comprising obtaining hydrogen by the catalytic reaction method according to any one of claims 5 to 13.

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