JP7246040B2 - Catalyst, method for producing catalyst, and method for producing synthesis gas - Google Patents

Description

The present invention relates to a catalyst, a method for producing a catalyst, and a method for producing synthesis gas.

Metals supported on zeolites are used as catalysts for various chemical reactions. Catalysts containing zeolites are used, for example, in petrochemical processes or in the purification of exhaust gases. As metals having catalytic activity, for example, transition metals such as nickel or noble metals such as platinum group elements are used. These metals are supported on the zeolite as a large number of metal particles with particle sizes on the order of nanometers. Due to the heat of reaction, the metal particles tend to move on the surface or inside the zeolite, and the metal particles tend to agglomerate. As a result, the particle size of the metal particles increases, the metal particles block the pores of the zeolite, and the specific surface area of the catalyst decreases. That is, the activity of the catalyst is lowered due to the sintering of the metal particles.

As a method of suppressing sintering of metal particles, a method of coating a catalyst with zeolite is known. (See Patent Documents 1 to 3 below.)

JP 2009-165941 A WO2010/101223 Pamphlet JP-A-2003-62466

However, the larger the size of the catalyst carrier, the more likely cracks are formed in the zeolite-coated catalyst, and the more difficult it is to uniformly coat the surface of the catalyst with zeolite. As a result, sintering of the metal particles tends to occur in a high-temperature environment, and the activity of the catalyst tends to decrease.

The present invention has been made in view of the above circumstances, and aims to provide a catalyst that suppresses sintering of metal particles, a method for producing the catalyst, and a method for producing synthesis gas using the catalyst. .

A catalyst according to one aspect of the present invention is a catalyst comprising a plurality of particles containing a metal and zeolite, wherein at least some of the particles are present inside the zeolite, and the particles present inside the zeolite The particle size is larger than the pore size of the zeolite, and the specific surface area of the catalyst is greater than 400 m ² /g and 700 m ² /g or less.

The specific surface area of the catalyst heated at 850° C. for 30 hours in air may be denoted as A1, and the specific surface area of the initial catalyst before heating may be denoted as A0, (A0-A1). /A0 may be 0% or more and 30% or less.

At least a portion of the metal may be nickel.

At least some of the zeolites may be MFI-type zeolites.

A method for producing a catalyst according to the first aspect of the present invention is a method for producing the above catalyst, comprising a step of forming micelles in a raw material liquid containing a metal element, a surfactant, and an organic solvent; By adding a silicon source to the raw material liquid containing and a surfactant coating the complex compound comprising particles and silica coating the particles.

A method for producing a catalyst according to the second aspect of the present invention is a method for producing the above catalyst, comprising the steps of preparing an aqueous solution containing metal ions and a silicon source, and heating the aqueous solution in an autoclave. , provided.

A method for producing a synthesis gas according to one aspect of the present invention comprises a step of obtaining a synthesis gas containing carbon monoxide and hydrogen by reacting hydrocarbons and carbon dioxide using a catalyst, wherein the catalyst is the above catalyst. .

At least some of the hydrocarbons may be methane.

ADVANTAGE OF THE INVENTION According to this invention, the catalyst which suppresses the sintering of a metal particle, the manufacturing method of the said catalyst, and the manufacturing method of synthesis gas using the said catalyst are provided.

FIG. 1 is a schematic cross-sectional view of a catalyst according to one embodiment of the invention. (a) in FIG. 2 shows the conversion rate of methane in the synthesis gas production method of Example 1 and Comparative Example 1, respectively, and (b) in FIG. 2 shows Example 1 and Comparative Example 1, respectively. (c) in FIG. 2 shows the yield of hydrogen in the synthesis gas production method of Example 1 and Comparative Example 1, and in FIG. (d) shows the yield of carbon monoxide in the synthesis gas production methods of Example 1 and Comparative Example 1, respectively. (a) in FIG. 3 shows the conversion rate of methane in the synthesis gas production methods of Example 2 and Comparative Example 2, respectively, and (b) in FIG. 3 shows Example 2 and Comparative Example 2, respectively. (c) in FIG. 3 shows the yield of hydrogen in the synthesis gas production method of Example 2 and Comparative Example 2, and in FIG. (d) shows the yield of carbon monoxide in the syngas production methods of Example 2 and Comparative Example 2, respectively. FIG. 4 shows the results of thermogravimetric analysis on the catalysts used in the synthesis gas production methods of Example 1 and Comparative Example 1, respectively.

Preferred embodiments of the present invention will be described below with reference to the drawings. In the drawings, similar components are provided with similar reference numerals. The present invention is not limited to the following embodiments.

As shown in FIG. 1 , the catalyst 3 according to this embodiment includes a plurality of metal-containing particles 1 and zeolite 2 . The zeolite 2 is a porous carrier, and the inside of the pores 2p of the zeolite 2 is a reaction field. Active sites of the catalyst 3 are present on the surface of the particles 1 . At least some of the particles 1 of the plurality of particles 1 exist inside the zeolite 2 . A plurality of particles 1 may be present inside the zeolite 2 . A plurality of particles 1 may be dispersed inside the zeolite 2 . All particles 1 of catalyst 3 may be present inside zeolite 2 . Some particles 1 may be present on the outer surface of the zeolite 2 . As long as the effects of the present invention can be obtained, the same metal or compound thereof as that of the particles 1 may be present on the outer surface of the zeolite 2 . The same metal or compound thereof as particles 1 may not be present on the outer surface of catalyst 3 at all. In the following, particles containing metal are referred to as "metal particles". In the following, the catalyst 3 having the structure shown in FIG. 1 is sometimes referred to as a "birdcage-type catalyst".

In the method for producing synthesis gas according to the present embodiment, synthesis gas containing carbon monoxide (CO) and hydrogen (H ₂ ) is produced by the reaction of hydrocarbons and carbon dioxide (CO ₂ ) due to the catalytic action of the catalyst 3. a step of obtaining. Hydrocarbon and carbon dioxide react via the surface of the metal particles 1 to produce carbon monoxide and hydrogen. Syngas is the primary feedstock in C1 chemistry. For example, synthesis gas is used in the production of lower alcohols or ethers. Syngas is also used as a feedstock in the production of fuels, lubricants (base oils) or waxes based on the Fischer-Tropsch process. Syngas production methods may be referred to as dry reforming of hydrocarbons. The catalyst 3 according to this embodiment may be rephrased as a reforming catalyst for dry reforming. However, the use of the catalyst 3 according to this embodiment is not limited to dry reforming.

Metals contained in the metal particles 1 include iron (Fe), cobalt (Co), nickel (Ni), ruthenium (Ru), rhodium (Rh), palladium (Pd), platinum (Pt), gold (Au), and silver. (Ag), osmium (Os) and iridium (Ir). When the metal particles 1 contain the above-listed metals, the yield of syngas tends to increase. At least part of the metal contained in metal particles 1 may be nickel. All of the metal contained in metal particles 1 may be nickel. The metal particles 1 may consist of nickel only. When the metal particles 1 contain nickel, the synthesis gas yield is likely to be further increased. The metal particles 1 may consist of metal only. One metal particle 1 may contain multiple kinds of metals. The catalyst 3 may have a plurality of metal particles 1 with different compositions. A plurality of metal particles 1 with different compositions may be present inside the zeolite 2 . The content (supported amount) of the metal particles 1 in the catalyst 3 may be 0.1% by mass or more and 10% by mass or less with respect to the total mass of the catalyst 3 . In addition to the metals listed above, the metal particles 1 may contain other metals as long as the activity of the catalyst 3 is not impaired. For example, the catalyst 3 includes, in addition to the above metals, sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), calcium (Ca), strontium (Sr), barium (Ba), lanthanum ( La), Cesium (Ce), Praseodymium (Pr), Neodymium (Nd), Samarium (Sm), Europium (Eu), Gadolinium (Gd), Terbium (Tb), Dysprosium (Dy), Holmium (Ho), Erbium ( Er), yttrium (Yb), titanium (Ti), vanadium (V), chromium (Cr), copper (Cu), zirconium (Zr), niobium (Nb), molybdenum (Mo), technetium (Tc), hafnium ( Hf), tantalum (Ta), tungsten (W), rhenium (Re), zinc (Zn), cadmium (Cd), gallium (Ga), indium (In), tin (Sn), lead (Pb) and bismuth ( It may further contain at least one selected from the group consisting of Bi). As long as the activity of the catalyst 3 is not impaired, the metal particles 1 may contain nonmetallic elements in addition to the metal. For example, metal particles 1 may contain oxygen or silicon.

The particle diameter d1 (major diameter) of the metal particles 1 existing inside the zeolite 2 is larger than the pore diameter d2 of the zeolite 2 . The particle diameter d1 of the metal particles 1 may be an arithmetic mean diameter, and the pore diameter d2 of the zeolite 2 may also be an arithmetic mean diameter. That is, the arithmetic mean diameter of the particle diameters d1 of the plurality of metal particles 1 existing inside the zeolite 2 may be larger than the arithmetic mean diameter of the pore diameters d2 of the zeolite 2. Since the particle size d1 of the metal particles 1 is larger than the pore size d2 of the zeolite 2, it is difficult for the metal particles 1 to move through the pores of the zeolite 2. That is, the metal particles 1 are enclosed within the skeleton (crystal structure) of the zeolite 2 and physically restrained by the skeleton of the zeolite 2 . Since the metal particles 1 are restrained inside the zeolite 2, it is difficult for the metal particles 1 to move and agglomerate due to heat, and the specific surface area of the catalyst 3 is difficult to decrease. That is, since the metal particles 1 are constrained inside the zeolite 2, sintering between the metal particles 1 hardly occurs, and the activity of the catalyst 3 is easily maintained for a long time. Therefore, synthesis gas can be obtained in high yield.

The metal particles 1 may be spherical, acicular, or polyhedral, for example. The particle size d1 (major axis) of the metal particles 1 may be, for example, 1 nm or more and 10 nm or less, 1 nm or more and 5 nm or less, or 2 nm or more and 5 nm or less. The pore diameter d2 of the zeolite 2 may be, for example, 0.5 nm or more and 0.6 nm or less. The catalyst 3 may be a powder (multiple particles). In other words, each particle constituting the catalyst 3 may have the particulate zeolite 2 and the plurality of metal particles 1 present inside the particulate zeolite 2 . The number of metal particles 1 present inside one particle of the catalyst 3 may be, for example, 2 or more and 50 or less. The particle size of the catalyst 3 may be, for example, 50 nm or more and 1000 nm or less. However, the catalyst 3 does not have to be powder. For example, the catalyst 3 may be granular, cylindrical, cylindrical, spherical or lamellar. The particle size d1 of the metal particles 1 may be measured by a transmission electron microscope (TEM), a scanning transmission electron microscope (STEM), a scanning electron microscope (SEM) or a CO pulse method. The pore diameter d2 of the zeolite 2 may be measured by a nitrogen gas adsorption method or an argon gas adsorption method. The particle size of catalyst 3 may be measured by TEM, STEM, SEM or optical microscopy. The composition of the catalyst 3 may be determined, for example, by ICP emission spectroscopy (high frequency inductively coupled plasma emission spectroscopy).

The specific surface area of catalyst 3 is greater than 400 m ² /g and 700 m ² /g or less. When the specific surface area of the catalyst 3 is within the above range, the plurality of metal particles 1 are easily dispersed inside the catalyst 3, and the plurality of metal particles 1 are less likely to come into contact with each other. As a result, aggregation of metal particles 1 is suppressed. That is, the sintering of the metal particles 1 is suppressed when the specific surface area of the catalyst 3 is within the above range. For the same reason, the specific surface area of the catalyst 3 is 405 m ² /g or more and 700 m ² /g or less, 410 m ² /g or more and 700 m ² /g or less, 420 m ² /g or more and 700 m ² /g or less, 430 m ² /g or more. 700 m ² /g or less, 440 m ² /g or more and 700 m ² /g or less, 450 m ² /g or more and 700 m ² /g or less, 460 m ² /g or more and 700 m ² /g or less, 470 m ² /g or more and 700 m ² /g or less, It may be 470 m ² /g or more and 486 m ² /g or less, or 473 m ² /g or more and 486 m ² /g or less. The specific surface area of the catalyst 3 may be measured by the BET method based on the nitrogen gas adsorption method or the argon gas adsorption method.

The specific surface area of catalyst 3 heated at 850° C. for 30 hours in air is designated as A1. The initial specific surface area of the catalyst 3 before being heated is denoted as A0. (A0-A1)/A0 may be 0% or more and 30% or less. (A0-A1)/A0 can be rephrased as the reduction rate (ΔA) of the specific surface area due to the heat treatment. The specific surface area of catalyst 3 does not easily decrease with heat treatment, and the specific surface area reduction rate (ΔA) is 30% or less. That is, since a sufficient specific surface area of the catalyst 3 is easily maintained even after the heat treatment, the plurality of metal particles 1 are easily dispersed inside the catalyst 3, and the plurality of metal particles 1 are less likely to come into contact with each other. As a result, aggregation of the metal particles 1 is easily suppressed even after the heat treatment. For the same reason, the specific surface area reduction rate (ΔA) may be preferably 25% or less, more preferably 20% or less, and even more preferably 10% or less.

In the conventional method of syngas production using a reforming catalyst, the activity of the reforming catalyst is reduced by coking, and the yield of syngas may decrease. That is, coke (carbon) is deposited on the surface of the reforming catalyst as the synthesis gas is generated, and the metal (active sites) is covered with coke, making it difficult for the catalytic reaction to occur on the surface of the reforming catalyst. Moreover, when the reforming catalyst is porous like zeolite, the open pores on the surface of the carrier are clogged with coke. As a result, it becomes difficult for hydrocarbons and carbon dioxide to enter the inside of the reforming catalyst through the pores, and catalytic reaction within the reforming catalyst hardly occurs.

In the production of conventional reforming catalysts with zeolites, metals are loaded onto the zeolites by impregnation or ion exchange techniques. Therefore, in the case of conventional reforming catalysts, metals are likely to be supported on the surface (outer surface) of zeolite. As the amount of metal supported on the surface of the zeolite increases, coke tends to deposit on the surface of the reforming catalyst as synthesis gas is generated, and the metal tends to be covered with coke. As a result, the catalytic reaction on the surface of the reforming catalyst is less likely to occur. In addition, the larger the amount of metal supported on the surface of the zeolite, the more easily the open pores on the surface of the zeolite are clogged with coke, and the more difficult it is for hydrocarbons and carbon dioxide to enter the reforming catalyst through the pores. . As a result, the catalytic reaction within the reforming catalyst is less likely to occur.

In contrast to conventional reforming catalysts, the birdcage-type catalyst according to the present embodiment is synthesized by growing zeolite 2 so as to cover metal particles 1 . As a result, the metal particles 1 tend to exist inside the zeolite 2 and hardly exist on the outer surface of the zeolite 2 . In other words, the active sites of the birdcage-type catalyst tend to exist inside the zeolite 2 and hardly exist on the outer surface of the zeolite 2 . Therefore, coking on the surface of the birdcage-type catalyst is less likely to occur, and pores 2p open on the surface of the zeolite 2 are less likely to be clogged with coke, as compared with conventional reforming catalysts. Therefore, synthesis gas can be obtained in high yield.

The hydrocarbon that is the raw material of synthesis gas may be, for example, at least one selected from the group consisting of methane, ethane, propane, butane, pentane, ethylene and propylene. Multiple types of hydrocarbons may be used as feedstock. The hydrocarbon may be an alkane. Since alkanes having no double bond are easily decomposed by the catalyst 3, synthesis gas is easily generated from alkanes and carbon dioxide. Part or all of the hydrocarbon may be methane. The use of methane tends to increase the yield of synthesis gas.

Zeolite 2 may be, for example, at least one selected from the group consisting of MFI-type zeolite, MEL-type zeolite, MTW-type zeolite, BEA-type zeolite, and FAU-type zeolite. Each of the above three letters of the alphabet is the zeolite structure code defined by the Structure Commission of the International Zeolite Association (IZA-SC). The MFI-type zeolite may be, for example, ZSM-5 and/or silicalite.

Silica-alumina ratio of zeolite 2 is, for example, 5 to 1000000, 5 to 100000, 100 to 1000000, 100 to 100000, 1000 to 1000000, 1000 to 100000, 10000 to 1000000, Or it may be 10000 or more and 100000 or less. The higher the Keiban ratio of the zeolite 2, the more easily the metal particles 1 exist inside the zeolite 2, and the more easily the particle diameter d1 of the metal particles 1 existing inside the zeolite 2 becomes larger than the pore diameter d2 of the zeolite 2. As a result, coking is easily suppressed. In other words, the larger the number of moles of silica constituting the zeolite 2 than the number of moles of alumina constituting the zeolite 2, the easier it is to obtain a birdcage-type catalyst structure and to suppress coking. For example, the MFI zeolite (Silicalite-1) has a significantly higher Silicon ratio, and MFI zeolites are substantially free of aluminum. In other words, substantially no aluminum is contained in the framework (crystal structure) of MFI-type zeolite. Therefore, when the zeolite 2 is an MFI-type zeolite, a birdcage-type catalyst structure is likely to be obtained. A portion of the zeolite 2 may be MFI-type zeolite. The entire zeolite 2 may be MFI zeolite. The MFI-type zeolite may contain a trace amount of alumina as an impurity derived from raw materials.

Dry reforming may be a gas phase reaction. That is, the raw material gas containing hydrocarbons and carbon dioxide should contact the catalyst 3 in the reactor. Dry reforming may be a continuous reaction (flow reaction). The reaction temperature for dry reforming may be, for example, 500° C. or higher and 900° C. or lower. The reaction temperature may be rephrased as the temperature of the catalyst. The reaction time may be adjusted according to the amount of feed gas (hydrocarbon and carbon dioxide) supplied and the reaction temperature. The reaction time may be, for example, 5.0 hours or more and 100 hours or less. The pressure inside the reactor may be, for example, 0.01 MPaG or more and 3.0 MPaG or less. The feed rate of the raw material gas per unit mass (1 g) of the catalyst 3 is, for example, 3000 L _SATP ·g _cat . ^-1 · h ^-1 or more 10000L _SATP · g _cat . ⁻¹ ·h ⁻¹ or less. L _SATP is the volume of source gas at standard conditions. When the number of moles of hydrocarbon in the source gas is denoted as M _CH and the number of moles of carbon dioxide in the source gas is denoted as M _CO2 , M _CO2 /M _CH is adjusted according to the number of carbon atoms in the hydrocarbon molecule. may be For example, when the hydrocarbon is methane, M _CO2 /M _CH may be from 0.5 to 2.0. The raw material gas may further contain a rare gas in addition to hydrocarbons and carbon dioxide.

Before using the catalyst 3 for chemical reactions, the metal particles 1 of the catalyst 3 may be reduced. For example, the metal particles 1 may be reduced by heating the catalyst 3 in gas containing hydrogen. The catalyst 3 may be heated at a temperature of 850° C. or higher in a gas containing hydrogen. This pretreatment may improve the activity of the catalyst 3 .

(Method for producing catalyst)
The method for producing the catalyst 3 according to the present embodiment comprises a step of forming micelles in a raw material solution containing a metal element, a surfactant and an organic solvent, and a step of adding a silicon source to the raw material solution containing the micelles. It comprises a step of forming a compound and a step of heating water containing the complex compound in an autoclave (hydrothermal synthesis step). A micelle has particles containing a metallic element and a surfactant coating the particles. The composite compound has particles containing a metal element and silica covering the particles. The details of the manufacturing method are as follows. In the following description of the production method, particles containing a metal element are referred to as "metal particles". Metal particles include fine particles of simple metal, fine particles of metal hydroxide, and fine particles of complex metal ions.

The raw material liquid may be a microemulsion. Microemulsions are prepared by mixing surfactants and organic solvents. The surfactant may be any compound that binds to metal particles to form micelles. The surfactant may be, for example, polyoxyethylene (15) olein ether or polyoxyethylene (15) cetyl ether. By using polyoxyethylene (15) olein ether or polyoxyethylene (15) cetyl ether, the growth of metal particles in the raw material solution is moderately suppressed, and small metal particles are easily obtained. The organic solvent is not limited as long as micelles are formed in the organic solvent. The organic solvent can be, for example, cyclohexane. The number of moles of the surfactant contained in the raw material liquid may be represented by Ms, the volume of the surfactant contained in the raw material liquid may be represented by Ls liters, and the volume of the organic solvent contained in the raw material liquid may be represented by Ls liters. and Ms/(Ls+Los) may be 0.1 or more and 0.75 or less, or 0.3 or more and 0.6 or less.

The metal element contained in the raw material liquid may be derived from the metal salt contained in the raw material liquid. The metal salt is not limited as long as the metal salt is soluble in water. The metal salt may be, for example, at least one selected from the group consisting of chlorides, nitrates, sulfates, and ammonium salts. Metal salts may be complexes. The metal salt may contain at least one metal selected from the group consisting of iron, cobalt, nickel, ruthenium, rhodium, palladium, platinum, gold, silver, osmium and iridium. A plurality of kinds of metal salts may be contained in the raw material liquid. The metal salt may be added to the raw material liquid (microemulsion) as an aqueous solution. A metal salt is likely to be contained in an aqueous phase (for example, water droplets) in a raw material liquid (microemulsion).

Metal elements (ions) may be reduced in the raw material liquid by adding the reducing agent to the raw material liquid. The reducing agent can be, for example, an aqueous solution of ammonia. Hydrazine having excellent reducing power or sodium borohydride may be added to the raw material liquid as a reducing agent. The temperature of the raw material liquid when the reducing agent is added may be 0° C. or higher and 60° C. or lower, or 40° C. or higher and 50° C. or lower. The higher the temperature of the raw material liquid, the easier the reduction of metal ions. If the temperature of the raw material liquid is too high, the metal particles generated in the raw material liquid tend to agglomerate. Also, if the temperature of the raw material liquid is too high, the reducing agent is likely to react with the organic solvent in the raw material liquid, and the raw material liquid may ignite. When the raw material liquid contains metal elements that are difficult to reduce, such as Ni, Fe, Co, and Cu, it is possible to form micelles without reducing the metal elements. For example, a hydroxide may be formed from a metal element in the raw material solution, and fine particles of this hydroxide may be contained in the micelles. A complex ion may be formed from the metal element in the raw material liquid, and fine particles of this complex ion may be contained in the micelles.

After micelles are formed in the raw material liquid, a complex compound is formed in the raw material liquid by adding a silicon source to the raw material liquid containing micelles. The composite compound has metal particles and silica (SiO ₂ ) covering the surfaces of the metal particles. In other words, a composite compound is formed by bonding the metal constituting the metal particles and the silicon derived from the silicon source. The composite compound may have metal particles and amorphous silica coating the surfaces of the metal particles. The silicon source may be an alkoxide of silicon. A hydrolysis reaction and a polycondensation reaction occur between the alkoxides of silicon in the water droplets that form the micelles, whereby silica is likely to be formed on the surface of the metal particles. The alkoxide of silicon may be, for example, at least one selected from the group consisting of tetramethyl orthosilicate (TMOS), tetraethyl orthosilicate (TEOS), and tetrapropyl orthosilicate. The shorter the alkoxy group, the more easily the alkoxide of silicon is hydrolyzed, and the more easily the thickness of the silica layer covering the metal particles becomes uniform. Therefore, the silicon alkoxide is preferably at least one of tetramethyl orthosilicate and tetraethyl orthosilicate. The silicon source may be a silane coupling agent. In addition to the silicon source, an aluminum source (eg, an aluminosilicate) may be added to the stock solution. The content of the silicon source in the raw material liquid may be, for example, 2% by mass or more and 40% by mass or less.

Water may be added together with the silicon source to the raw material solution containing micelles. Addition of water tends to hydrolyze the silicon source and form complex compounds. For example, the addition of water hydrolyzes the alkoxide of silicon and tends to form silica on the surface of the metal particles. The water may contain acids or bases. Acids or bases act as catalysts to promote hydrolysis of the silicon source. The acid can be, for example, hydrochloric acid. The base can be, for example, ammonia.

During the hydrolysis of the silicon source, the pH of the raw material liquid may be 7 or more and 11 or less. After hydrolysis of the silicon source, the raw material liquid may have a pH of 7 or more and 11 or less. When the pH of the raw material solution is lower than 7, the SiO ₂ layers of each composite compound tend to react with each other, and the composite compounds tend to aggregate. This unfavorable reaction may cause the raw material liquid to solidify. Moreover, when the aggregated composite compound is used in the hydrothermal synthesis step, the particle size of the finally obtained zeolite is too large, and the specific surface area of the catalyst is small. On the other hand, when the pH of the raw material solution is higher than 11, the SiO ₂ layer of the composite compound is easily dissolved.

During the hydrolysis of the silicon source, the temperature of the raw material liquid may be 0°C or higher and 50°C or lower. After hydrolysis of the silicon source, the temperature of the raw material liquid may be 0° C. or higher and 50° C. or lower. When the temperature of the raw material liquid is lower than 0° C., the reaction between the SiO ₂ layers is suppressed, but the hydrolysis of the silicon source is difficult to proceed, and the time required to form the SiO ₂ layer is extremely long. On the other hand, when the temperature of the raw material liquid is higher than 50° C., hydrolysis of the silicon source tends to proceed, but the SiO ₂ layers of each composite compound tend to react with each other, and the composite compounds tend to aggregate.

Complex compounds may be formed in the source liquid in parallel with the formation of micelles in the source liquid. In other words, a source of silicon may be formed in the source liquid concurrently with the reduction of metal ions in the source liquid.

A complex compound is separated from the raw material liquid that has undergone the above steps. The method for separating the complex compound from the raw material liquid may be, for example, at least one selected from the group consisting of filtration, centrifugation, and evaporation of the organic solvent by heating or reduced pressure.

The complex compound separated from the microemulsion is added to water. Water containing complex compounds is heated in a closed autoclave. As a result, a hydrothermal synthesis reaction proceeds to produce zeolite containing metal particles in water.

A silicon source as described above may be added to the water along with the complex compound. A template agent may be added to the water along with the complex compound. Both the silicon source and template agent may be added to the water along with the complex compound. A templating agent is a compound that defines the structure of a zeolite. A template agent may be selected according to the structure of the zeolite, and the template agent is not limited. When the zeolite is an MFI-type zeolite, the template agent may be tetrapropylammonium hydroxide. The mass of the template agent added to water may be 0.1 to 0.5 times the mass of silica contained in the composite compound.

The temperature of the water in the autoclave may be, for example, 80° C. or higher and 180° C. or lower, or 80° C. or higher and 120° C. or lower. The hydrothermal synthesis time may be, for example, 24 hours or more and 120 hours or less.

The product (precipitate) obtained by the hydrothermal synthesis step is separated from the water. The method of separating the product from water may be, for example, at least one selected from the group consisting of filtration, centrifugation, and evaporation of water by heating or reduced pressure. The product may be dried in a reduced pressure or vacuum atmosphere. Heating may dry the product. The catalyst according to the present embodiment is obtained by calcining the dried product. If a templating agent is used, calcining the product burns off the templating agent. The firing temperature may be, for example, 400° C. or higher and 600° C. or lower. The firing time may be, for example, 1 hour or more and 48 hours or less. The firing atmosphere may be air or an oxidizing atmosphere. When the firing temperature and firing time are within the above ranges, the template agent is sufficiently burnt off, and excessive growth and agglomeration of metal particles and zeolite are suppressed.

Hereinafter, the above manufacturing method is referred to as a "two-step method". A feature of the two-step method is to separate the complex compound from the raw material liquid (microemulsion) prior to hydrothermal synthesis.

In the above two-step method, metal particles (metal particles 1 shown in FIG. 1) are formed from the metal salt in the process of forming the composite compound in the raw material solution or in the process of hydrothermal synthesis. Then, the zeolite 2 grows around the metal particles 1 in the process of hydrothermal synthesis. As a result, the metal particles 1 are included in the zeolite 2 and physically constrained by the skeleton of the zeolite 2 . In other words, since the zeolite 2 grows around the metal particles 1, the metal particles 1 having a particle size d1 larger than the pore size d2 of the zeolite 2 are enclosed in the zeolite 2 without damaging the skeleton of the zeolite 2. touched. Further, according to the two-step method, the specific surface area of the catalyst 3 can be controlled within a range of more than 400 m ² /g and 700 m ² /g or less. The particle size of the metal particles 1 and the specific surface area of the catalyst 3 are determined by the amount and compounding ratio of each raw material such as the metal salt and the silicon source, conditions for reduction of metal ions, conditions for hydrolysis of the silicon source, and hydrothermal synthesis. It may be controlled by process conditions, product firing conditions, and the like.

In the conventional impregnation method or ion exchange method, after the zeolite is synthesized, metal particles or metal ions are supported on the zeolite. Therefore, it is difficult for metal particles having a particle size larger than the zeolite pore size to enter the zeolite pores. If the metal particles or metal ions penetrate into the pores of the zeolite and the metal particles grow inside the zeolite, the particle size of the metal particles becomes larger than the pore size of the zeolite, thereby forming the skeleton of the zeolite 2 is destroyed. For the above reasons, it is difficult to produce the catalyst 3 (birdcage type catalyst) according to the present embodiment by the conventional impregnation method or ion exchange method.

The "one-pot method" (One-Pot method), which is a comparison target of the two-step method, is as follows.

In the one-pot method, complex compounds are not separated from the raw material liquid (microemulsion). In the hydrothermal synthesis step of the one-pot method, a mixture of a raw material liquid containing a complex compound and water is heated in an autoclave.

The catalyst obtained by the one-pot method comprises a plurality of metal particles and zeolite, at least some of the metal particles are present inside the zeolite, and the particle size of the metal particles present inside the zeolite is Larger than the zeolite pore size. However, it is difficult for the specific surface area of the catalyst obtained by the one-pot method to exceed 400 m ² /g. Catalysts obtained by the one-pot method are inferior in dry reforming activity to catalysts obtained by the two-step method.

Although the preferred embodiments of the present invention have been described above, the present invention is not necessarily limited to the above-described embodiments.

For example, the catalyst according to the present invention can also be produced by the following "one-step method" (One-step method).

The one-step method comprises the steps of preparing an aqueous solution containing metal ions and a silicon source, and heating the aqueous solution in an autoclave (hydrothermal synthesis step). In the one-step method, surfactants and organic solvents are not used as raw materials, and micelles are not formed in the raw material solution. That is, the aqueous solution prepared in the one-step method does not contain surfactants and organic solvents. In the one-step method, catalysts are synthesized without going through micelle formation. The one-step method does not include the step of separating the silica-coated metal particles (complex compound) from the raw liquid.

Also for the one-step method, the metal ions in the aqueous solution may originate from the metal salt. That is, the aqueous solution prepared in the one-step method may contain metal salts. The metal salt used in the one-step method may be the same as the metal salt used in the two-step method. The silicon source used in the one-step process can be the same as the silicon source used in the two-step process. The aqueous solution prepared in the one-step method may contain a template agent. The template agent used in the one-step method can be the same as the template agent used in the two-step method. All ingredients used in the two-step process, with the exception of surfactants and organic solvents, may be included in the aqueous solution prepared in the one-step process. The blending ratio of each raw material used in the one-step method may be the same as the blending ratio of each raw material used in the two-step method. The conditions for the one-step hydrothermal synthesis process may be the same as the conditions for the two-step hydrothermal synthesis process.

The catalyst according to the invention may be used for fluid catalytic cracking, hydrogenation of unsaturated hydrocarbons, dehydrogenation of hydrocarbons or purification of exhaust gases.

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

(Example 1)
[Preparation of reforming catalyst]
The catalyst of Example 1 was made by the following two-step method.

A raw material liquid (microemulsion) was obtained by mixing the surfactant and the organic solvent. Polyoxyethylene (15) cetyl ether was used as the surfactant. Cyclohexane was used as an organic solvent. The surfactant content in the raw material solution was adjusted to 0.5 mol/liter.

After an aqueous solution of nickel nitrate (Ni(NO ₃ ) ₂ ) was added dropwise to the above raw material solution, hydrazine monohydrate was added to the raw material solution to form a nickel-hydrazine complex. The concentration of the nickel nitrate aqueous solution (the content of nickel nitrate) was 18% by mass. The amount of the nickel nitrate aqueous solution added was 5 cc. The amount of hydrazine monohydrate added was 6 cc. The temperature of the stock solution was adjusted to 50°C when hydrazine monohydrate was added.

After formation of the nickel-hydrazine complex, further tetraethyl orthosilicate (TEOS) and aqueous ammonia solution were added to the stock solution. As a result, the nickel ions were reduced, and a composite compound containing metal particles made of nickel and amorphous silica surrounding the metal particles was formed in the raw material liquid. The mass of tetraethyl orthosilicate added to the raw material liquid was 20 g. The concentration of the aqueous ammonia solution was 1 mol/liter. The amount of the aqueous ammonia solution added was 18 cc. The temperature of the raw material liquid was adjusted to 50° C. when the tetraethyl orthosilicate and the aqueous ammonia solution were added.

A composite compound was separated from the raw material solution that had undergone the above steps. The separation method was centrifugation.

The above complex compound separated from the raw material liquid was added to water. Further aqueous solutions of tetrapropylammonium hydroxide and tetraethyl orthosilicate were added to the water. The concentration of the aqueous solution of tetrapropylammonium hydroxide (content of tetrapropylammonium hydroxide) was 10% by mass. The mass of the aqueous solution of tetrapropylammonium hydroxide added to water was 41.5 g. The mass of tetraethyl orthosilicate added to the water was 10.9 g.

The autoclave was sealed after the water passed through the above steps was placed in the autoclave. Hydrothermal synthesis proceeded in the autoclave by heating the water in the autoclave. The temperature of hydrothermal synthesis was adjusted to 100°C. The hydrothermal synthesis time was 72 hours.

The product (precipitate) obtained by the above hydrothermal synthesis was separated from water by centrifugation. After washing and drying the product of hydrothermal synthesis, the product was calcined. The firing temperature was adjusted to 550°C. The firing time was 12 hours. The firing atmosphere was air.

The catalyst of Example 1 was obtained by the above method. The catalyst of Example 1 was a powder. The amount of nickel supported in the catalyst was adjusted to 1.0% by mass.

[Analysis of catalyst]
The X-diffraction pattern of the catalyst was measured by powder X-ray diffractometry. The X-diffraction pattern had diffraction line peaks unique to MFI-type zeolite. The catalyst was observed by transmission electron microscopy (TEM). As a result of observation by TEM, it was confirmed that a plurality of metal particles (nickel particles) containing nickel existed inside the zeolite. As a result of TEM observation, it was confirmed that the particle size d1 of the nickel particles present inside the zeolite was about 2 nm or more and 6 nm or less. The pore diameter of the MFI zeolite is 0.5 nm or more and 0.6 nm or less. Therefore, it was confirmed that the particle size of the nickel particles present inside the zeolite is larger than the pore size of the MFI zeolite. That is, the catalyst of Example 1 was a birdcage type catalyst.

[Dry reforming]
Dry reforming of methane with the catalyst of Example 1 was performed. Dry reforming is represented by Chemical Reaction Formula 1 below. In the following, dry reforming is sometimes denoted as "DRM". The details of the dry reforming were as follows.
_CH4 + _CO2 →2CO+ _2H2 (1)

270 mg of catalyst was placed in a fixed bed flow reactor. In the pretreatment, hydrogen gas and nitrogen gas were continuously supplied into the reactor for 1 hour while maintaining the temperature of the catalyst in the reactor at 800°C. The flow rate of hydrogen gas supplied into the reactor was 30 mL _SATP /min. The flow rate of nitrogen gas supplied into the reactor was 30 mL _SATP /min. After the pretreatment, the raw material gas was continuously supplied into the reactor while maintaining the temperature of the catalyst in the reactor at 600°C. The product (gas) discharged from the reactor was intermittently analyzed by GC-TCD. GC-TCD means Gas Chromatography-Thermal Conductivity Detector (GC-TCD). The source gas was a mixed gas consisting of methane ( _CH4 ), carbon dioxide ( _CO2 ), argon (Ar) and helium (He). The feed rate of the raw material gas per unit mass (1 g) of the catalyst was 20 L _SATP ·g _cat . ^-1 ·h was maintained at ^-1 . The flow rate of methane fed into the reactor was 20 mL _SATP /min. The flow rate of carbon dioxide fed into the reactor was 20 mL _SATP /min. The flow rate of argon supplied into the reactor was 40 mL _SATP /min. The flow rate of helium fed into the reactor was 10 mL _SATP /min. The above dry reforming was continued for 5 hours.

Analysis of the product using GC-TCD confirmed that the product contained carbon monoxide (CO) and hydrogen ( _H2 ). Based on the analysis of the products using GC-TCD, the methane conversion R _CH4 , carbon dioxide conversion R _CO2 , carbon monoxide yield Y _CO , and hydrogen yield Y _H2 were calculated. The definitions of R _CH4 , R _CO2 , Y _CO and Y _H2 are defined by the following equations. R _CH4 , R _CO2 , Y _H2 and Y _CO at each reaction time are shown in Table 1 below.
R _CH4 (mol %) = 100 × {[CH ₄ ] ₀ - [CH ₄ ] ₁ }/[CH ₄ ] ₀ (1)
[CH ₄ ] ₀ in Equation 1 is the number of moles of methane supplied to the reactor as the raw material gas within a unit time. [CH ₄ ] ₁ in Equation 1 is the number of moles of methane discharged from the reactor as an unreacted product per unit time.
R _CO2 (mol%) = 100 × {[CO ₂ ] ₀ - [CO ₂ ] ₁ }/[CO ₂ ] ₀ (2)
[CO ₂ ] ₀ in Equation 2 is the number of moles of carbon dioxide supplied to the reactor as a raw material gas within a unit time. [CO ₂ ] ₁ in Equation 2 is the number of moles of carbon dioxide discharged from the reactor as an unreacted product within a unit time.
_YH2 (mol%) = 100 x [ _H2 ] _1/2 [ _CH4 ] ₀ (3)
[CH ₄ ] ₀ in Equation 3 is the number of moles per unit time of methane supplied to the reactor as the raw material gas within the unit time. [H ₂ ] ₁ in Equation 3 is the number of moles of hydrogen discharged from the reactor as a product in unit time.
Y _CO (mol%) = 100 x [CO] _1/2 [CH ₄ ] ₀ (4)
[CH ₄ ] ₀ in Equation 4 is the number of moles of methane supplied to the reactor as a raw material gas within a unit time. [CO] ₁ in Equation 4 is the number of moles of carbon monoxide discharged from the reactor as a product in unit time.

The change over time in the methane conversion rate R _CH4 is shown in FIG. 2(a). The horizontal axis (Time stream) of (a) in FIG. 2 is the reaction time, and the vertical axis (Methane conversion) of (a) in FIG. 2 is the methane conversion rate _RCH4 .

The change over time of the carbon dioxide conversion rate R _CO2 is shown in FIG. 2(b). The horizontal axis (Time stream) of (b) in FIG. 2 is the reaction time, and the vertical axis (CO ₂ conversion) of (b) in FIG. 2 is the carbon dioxide conversion rate R _CO2 .

The time course of the hydrogen yield _YH2 is shown in FIG. 2(c). The horizontal axis (Time stream) of (c) in FIG. 2 is the reaction time, and the vertical axis (Hydrogen yield) of (c) in FIG. 2 is the hydrogen yield _YH2 .

The time course of the carbon monoxide yield _YCO is shown in FIG. 2(d). The horizontal axis (Time stream) of (d) in FIG. 2 is the reaction time, and the vertical axis (CO yield) of (d) in FIG. 2 is the yield _YCO of carbon monoxide.

[Analysis of catalyst after dry reforming]
The catalyst after dry reforming was observed by TEM. As a result of observation by TEM, it was confirmed that a plurality of metal particles (nickel particles) containing nickel existed inside the zeolite. As a result of TEM observation, it was confirmed that the particle size d1 of the nickel particles present inside the zeolite was about 2 nm or more and 6 nm or less. That is, the particle size d1 of the nickel particles present inside the zeolite did not change even after the dry reforming.

[Thermogravimetry]
A thermogravimetry (TG) measurement was performed on the catalyst used in the above dry reforming. For TG measurements, the temperature of the catalyst was raised from 119° C. to 900° C. over 2.5 hours by heating in the atmosphere of the catalyst. Then, the mass of the catalyst at each temperature was measured. The results of the TG measurement of Example 1 are indicated by the solid line in FIG. The horizontal axis of FIG. 4 is the catalyst temperature (unit: ° C.), and the vertical axis Δw (unit: mass %) of FIG. 4 is defined by Equation 5 below.
Δw=100×(w−w _dry )/w _dry (5)
w in Equation 5 is the mass of the catalyst at each temperature. w _dry in Equation 5 is the mass of the catalyst at 120°C.

The mass of the catalyst before TG measurement was 11.2 mg. The mass w _dry of the catalyst at 120°C was 11.0 mg. The mass w ₀ of the catalyst at 900° C. was 10.9 mg. It is assumed that all of the coke that adhered to the catalyst during dry reforming was burned off at 900°C and removed from the catalyst. Therefore, the mass w ₀ of the catalyst at 900° C. is taken as the true mass of the decoked catalyst. On the other hand, it is presumed that the coke attached to the catalyst during dry reforming was not burned at all at 120°C. Therefore, the mass of the catalyst at 120° C. w _dry is taken to be equal to the sum of the true mass of the catalyst w ₀ and the mass of coke deposited on the catalyst during dry reforming w _COKE (w ₀ +w _COKE ). That is, the mass of coke attached to the catalyst during dry reforming, w _COKE , is equal to w _dry - w ₀ . w _COKE calculated from w _dry and w ₀ was 0.1 g. 100×w _COKE /w ₀ was about 0.92 wt%. In the following, 100×w _COKE /w ₀ is sometimes referred to as the “coke amount”.

[Measurement of specific surface area]
The specific surface area A0 of the unused catalyst of Example 1 was measured by the BET method based on the nitrogen gas adsorption method. The fresh Example 1 catalyst was heated at 850° C. for 30 hours in air. The specific surface area A1 of the catalyst 3 after heating was measured by the same method as A0. (A0-A1)/A0 of Example 1 was calculated. A0, A1 and (A0-A1)/A0 of Example 1 are shown in Table 5 below. ΔA in Table 5 below means (A0-A1)/A0.

(Comparative example 1)
A powder consisting of MFI-type zeolite (silicalite-1) was immersed in an aqueous solution of nickel nitrate. After the MFI zeolite was immersed in an aqueous solution of nickel nitrate, the MFI zeolite was dried. The dried MFI-type zeolite was calcined at 550° C. for 12 hours. A catalyst of Comparative Example 1 was produced by the impregnation method described above. The catalyst of Comparative Example 1 was powder. The amount of nickel supported in the catalyst of Comparative Example 1 was adjusted to 1.0% by mass.

Analyzes and measurements on the catalyst of Comparative Example 1 were carried out in the same manner as in Example 1. The analysis and measurement results are shown in Table 5 below. It was confirmed that a large number of metal particles made of nickel were supported on the surface of the catalyst of Comparative Example 1. Therefore, many nickel particles were present on the outer surface of the catalyst. That is, the catalyst of Comparative Example 1 was not a birdcage type catalyst.

Dry reforming of methane using the catalyst of Comparative Example 1 was performed. The dry reforming of Comparative Example 1 continued for 2.5 hours. The dry reforming of Comparative Example 1 was carried out in the same manner as in Example 1, except for the difference in catalyst and duration. The dry reforming results of Comparative Example 1 are shown in Table 2 below, (a) in FIG. 2, (b) in FIG. 2, (c) in FIG. 2, and (d) in FIG.

TG measurement of the catalyst of Comparative Example 1 used for dry reforming was performed in the same manner as in Example 1. The results of the TG measurement of Comparative Example 1 are indicated by the dashed line in FIG. The mass of the catalyst of Comparative Example 1 before TG measurement was 9.8 mg. The mass w _dry of the catalyst of Comparative Example 1 at 120° C. was 9.6 mg. The mass w ₀ of the catalyst at 900° C. was 6.2 mg. The w _COKE of Comparative Example 1 calculated from w _dry and w ₀ was 3.4. 100×w _COKE /w ₀ was about 54.84 wt%.

The conversion rate of carbon dioxide and the yield of hydrogen and carbon monoxide in Example 1 were higher than those in Comparative Example 1, regardless of the difference in the reaction time of dry reforming. w _COKE of Example 1 was significantly less than w _COKE of Comparative Example 1, and 100×w _COKE /w ₀ of Example 1 was also significantly less than 100×w _COKE /w ₀ of Comparative Example 1. That is, it was confirmed that the catalyst of Example 1 is superior to the catalyst of Comparative Example 1 in suppressing coking.

(Example 2)
In the dry reforming of Example 2, the catalyst of Example 1 was used. For the dry reforming of Example 2, 50 mg of catalyst was placed in the fixed bed flow reactor. In the pretreatment of Example 2, hydrogen gas and nitrogen gas were continuously supplied into the reactor for 1 hour while maintaining the temperature of the catalyst in the reactor at 850°C. In the dry reforming of Example 2, the raw material gas was continuously supplied into the reactor while maintaining the temperature of the catalyst in the reactor at 850°C. In the dry reforming of Example 2, the feed rate of the raw material gas per unit mass (1 g) of the catalyst was 108 L _SATP ·g _cat . ^-1 ·h was maintained at ^-1 .

The dry reforming of Example 2 was carried out in the same manner as in Example 1 except for the above items. The dry reforming results of Example 2 are shown in Table 3 below, (a) in FIG. 3, (b) in FIG. 3, (c) in FIG. 3, and (d) in FIG.

(Comparative example 2)
In the dry reforming of Comparative Example 2, the catalyst of Comparative Example 1 was used. Dry reforming of Comparative Example 2 was carried out in the same manner as in Example 2 except for the difference in catalyst. The dry reforming results of Comparative Example 2 are shown in Table 4 below, (a) in FIG. 3, (b) in FIG. 3, (c) in FIG. 3, and (d) in FIG.

Both the methane and carbon dioxide conversion rates and the hydrogen and carbon monoxide yields of Example 2 were higher than those of Comparative Example 2, regardless of the difference in dry reforming reaction time. In the TG measurement of Example 2, the mass of the catalyst hardly changed. Also in the TG measurement of Comparative Example 2, the mass of the catalyst hardly changed. These TG measurement results are presumed to be due to the high reaction temperatures of dry reforming in Example 2 and Comparative Example 2, respectively.

(Example 3)
The catalyst of Example 3 was made by the following one-step method.

An aqueous solution of tetrapropylammonium hydroxide and tetraethyl orthosilicate were added to the water. The concentration of the aqueous solution of tetrapropylammonium hydroxide (content of tetrapropylammonium hydroxide) was 10% by mass. The mass of the aqueous solution of tetrapropylammonium hydroxide added to water was 37.5 g. The mass of tetraethyl orthosilicate added to the water was 12 g.

Subsequently, an aqueous solution of nickel nitrate was added to the above water. The concentration of the nickel nitrate aqueous solution (the content of nickel nitrate) was 18% by mass. The amount of the nickel nitrate aqueous solution added was 0.64 cc.

An aqueous solution containing nickel nitrate, tetraethyl orthosilicate, and tetrapropylammonium hydroxide was prepared by the above procedure. This aqueous solution was placed in an autoclave and then the autoclave was sealed. Hydrothermal synthesis proceeded in the autoclave by heating the water in the autoclave. The temperature of hydrothermal synthesis was adjusted to 100°C. The hydrothermal synthesis time was 72 hours.

The product (precipitate) obtained by the above hydrothermal synthesis was separated from water by centrifugation. After washing and drying the product of hydrothermal synthesis, the product was calcined. The firing temperature, firing time and firing atmosphere were the same as in Example 1.

A catalyst of Example 3 was obtained by the above method. The catalyst of Example 3 was a powder. The amount of nickel supported in the catalyst of Example 3 was adjusted to 1.0% by mass.

Analyzes and measurements on the catalyst of Example 3 were carried out in the same manner as in Example 1. The analysis and measurement results are shown in Table 5 below. In the case of Example 3 as well, a plurality of metal particles containing nickel (nickel particles) are present inside the MFI zeolite, and the particle size of the nickel particles present inside the zeolite is larger than the pore size of the MFI zeolite. was also big. That is, the catalyst of Example 3 was a birdcage type catalyst.

Dry reforming using the catalyst of Example 3 was carried out in the same manner as in Example 1. The dry reforming results of Example 3 are shown in Table 5 below.

(Example 4)
In the dry reforming of Example 4, the catalyst of Example 3 was used. Dry reforming using the catalyst of Example 4 was carried out in the same manner as in Example 2 except for the difference in catalyst. The dry reforming results of Example 4 are shown in Table 5 below.

(Comparative Example 3)
A catalyst of Comparative Example 3 was produced by the following one-pot method.

A raw material liquid of Comparative Example 3 was prepared in the same manner as in Example 1. A composite compound was formed in the raw material liquid of Comparative Example 3 in the same manner as in Example 1.

However, in the case of Comparative Example 3, the complex compound was not separated from the raw material liquid, and an aqueous solution of tetrapropylammonium hydroxide and tetraethyl orthosilicate were further added to the raw material liquid of Comparative Example 3 containing the complex compound. The amounts of tetrapropylammonium hydroxide and tetraethyl orthosilicate used in Comparative Example 3 were the same as in Example 1.

The autoclave was sealed after putting the raw material liquid which passed through the above process into the autoclave. Hydrothermal synthesis was advanced in the autoclave by heating the raw material liquid in the autoclave. The temperature of hydrothermal synthesis was adjusted to 100°C. The hydrothermal synthesis time was 72 hours.

The product (precipitate) obtained by the above hydrothermal synthesis was separated from the raw material liquid by centrifugation. After washing and drying the product of hydrothermal synthesis, the product was calcined. The firing temperature, firing time and firing atmosphere were the same as in Example 1.

A catalyst of Comparative Example 3 was obtained by the above method. The catalyst of Comparative Example 3 was powder. The amount of nickel supported in the catalyst of Comparative Example 3 was adjusted to 1.0% by mass.

Analysis and measurement of the catalyst of Comparative Example 3 were carried out in the same manner as in Example 1. The analysis and measurement results are shown in Table 5 below. In the case of Comparative Example 3 as well, a plurality of metal particles containing nickel (nickel particles) are present inside the MFI zeolite, and the particle size of the nickel particles present inside the zeolite is larger than the pore size of the MFI zeolite. was also big. That is, the catalyst of Comparative Example 3 was a birdcage type catalyst. However, the specific surface area of the catalyst of Comparative Example 3 was much smaller than 400 m ² /g.

Dry reforming using the catalyst of Comparative Example 3 was carried out in the same manner as in Example 1. The dry reforming results of Comparative Example 3 are shown in Table 5 below.

(Comparative Example 4)
In the dry reforming of Comparative Example 4, the catalyst of Comparative Example 3 was used. Dry reforming using the catalyst of Comparative Example 4 was carried out in the same manner as in Example 2 except for the difference in catalyst. The dry reforming results of Comparative Example 4 are shown in Table 5 below.

The conversion rate of methane shown in Table 5 below is the average value of the conversion rate at each reaction time.

According to the present invention, sintering of metal particles contained in a catalyst can be suppressed.

1 Particles containing metal, 2 Zeolite, 2p Pores of zeolite, 3 Reforming catalyst, d1 Particle diameter of particles present inside zeolite, d2 Pore diameter of zeolite.

Claims (6)

A catalyst comprising a plurality of particles containing a metal and a zeolite,
at least a portion of said metal is nickel,
at least some of the particles are inside the zeolite;
The particle size of the particles present inside the zeolite is larger than the pore size of the zeolite,
The specific surface area of the catalyst is greater than 400 m ² /g and 700 m ² /g or less,
The catalyst is used in a method for producing synthesis gas,
The method for producing the synthesis gas comprises obtaining a synthesis gas containing carbon monoxide and hydrogen by reaction of hydrocarbons and carbon dioxide using the catalyst ,
at least some of said hydrocarbons are methane;
catalyst. the specific surface area of the catalyst heated at 850° C. for 30 hours in air is A1;
The initial specific surface area of the catalyst before heating is A0,
(A0-A1)/A0 is 0% or more and 30% or less,
Catalyst according to claim 1. at least some of the zeolites are MFI-type zeolites;
A catalyst according to claim 1 or 2 . A method for producing the catalyst according to any one of claims 1 to 3 ,
forming micelles in a raw material solution containing a metal element, a surfactant and an organic solvent;
forming a complex compound by adding a silicon source to the raw material solution containing the micelles;
a step of heating water containing the complex compound in an autoclave;
with
the metal element is nickel,
The micelle has particles containing the metal element and the surfactant covering the particles,
wherein the composite compound comprises the particles and silica covering the particles;
A method for producing a catalyst. A method for producing the catalyst according to any one of claims 1 to 3 ,
preparing an aqueous solution containing ions of the metal and a silicon source;
heating the aqueous solution in an autoclave;
comprising
A method for producing a catalyst. catalyzed reaction of hydrocarbons and carbon dioxide to obtain synthesis gas comprising carbon monoxide and hydrogen;
The catalyst is the catalyst according to any one of claims 1 to 3 ,
at least some of said hydrocarbons are methane;
A method for producing synthesis gas.

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