Catalyst structure, fixed-bed reactor, and method for manufacturing catalyst structure

Abstract

A catalyst structure (1) comprises an iron-based catalyst (2) containing an Fe5C2 phase and at least one of an Fe2O3 phase and an Fe3O4 phase, and a porous carrier (3) carrying the iron-based catalyst (2), and synthesizes a hydrocarbon including a lower olefin. A fixed-bed reactor (110) comprises the catalyst structure (1) and a reaction tube (112) that accommodates the catalyst structure (1).

Description

Catalyst structure, fixed bed reactor, and method for producing catalyst structure

[0001] The present disclosure relates to catalyst structures, fixed bed reactors and methods for making catalyst structures.

[0002] Conventionally, a method for synthesizing hydrocarbons by the Fischer-Tropsch reaction (FT reaction) has been known. The FT reaction proceeds as shown in the following reaction formula (1), and an iron-based catalyst and a cobalt-based catalyst are used as catalysts.

[0003] FT reaction: nCO + 2nH ２ →C ｎ H ２ｎ +nH ２ O (1)

[0004] Patent Document 1 discloses a catalyst for producing light hydrocarbons from synthesis gas. The catalyst contains a metal compound active in the FT synthesis reaction, and includes a catalyst for producing hydrocarbons from synthesis gas, and a catalyst for cracking the produced hydrocarbons to reduce their weight. Patent Document 1 also discloses that the metal compound contains cobalt.

[0005] International Publication No. 2014 / 142282

[0006] Carbon dioxide is considered a cause of global warming, and attempts have been made to synthesize hydrocarbons containing lower olefins from carbon dioxide. The reaction for synthesizing hydrocarbons from carbon dioxide proceeds in two steps as shown in the following reaction formulas (2) and (1), and an iron-based catalyst is used.

[0007] Reverse shift reaction: CO ２ +H ２ ⇔CO + H ２ O (2) FT reaction: nCO + 2nH ２ →C ｎ H ２ｎ +nH ２ O (1)

[0008] The active species in the above reaction formula (2) is Fe ２ O ３ phase (hematite phase) or Fe ３ O ４The active species in the reaction (1) is Fe, which is called Hegg carbide. ５ C ２ The iron-based catalyst is a catalyst containing Fe. ５ C ２ phase and Fe ２ O ３ phase and Fe ３ O ４ By including at least one of the phases, hydrocarbons can be produced from a feedstock containing carbon dioxide and hydrogen.

[0009] However, when the above iron-based catalyst is molded into pellets by a method such as extrusion molding, the Fe in the catalyst ２ O ３ or Fe ３ O ４ However, the catalyst pellets may react with CO in the gas phase to produce carbide components, which may result in powdering of the catalyst pellets. Therefore, when catalyst pellets are packed into a fixed-bed reactor, the catalyst pellets may powder, reducing the void space in the reaction tube and increasing the pressure loss during the reaction, and in the worst case, causing blockage of the reaction tube. In addition, in such cases, it may become difficult to remove the powdered catalyst from the reaction tube, which may make catalyst replacement maintenance difficult. This type of powdering of catalyst pellets has not been observed with cobalt-based catalysts and is a problem specific to iron-based catalysts.

[0010] Therefore, an object of the present disclosure is to provide a catalyst structure, a fixed-bed reactor, and a method for manufacturing a catalyst structure that can suppress powdering.

[0011] The catalyst structure according to the present disclosure comprises Fe ５ C ２ phase and Fe ２ O ３ phase and Fe ３ O ４ The present invention provides an iron-based catalyst containing at least one of the above phases and a porous carrier supporting the iron-based catalyst, and synthesizes hydrocarbons containing lower olefins.

[0012] The volume of the catalyst structure is 0.5 mm ３ More than 1000mm ３ It may be the following:

[0013] The porous carrier may be made of a metal.

[0014] The porous support may have a porosity of 85% to 95%.

[0015] A fixed bed reactor according to the present disclosure comprises a plurality of catalyst structures and a reactor tube containing the plurality of catalyst structures.

[0016] Hydrocarbons may be synthesized from feedstocks including carbon dioxide and hydrogen.

[0017] Hydrocarbons may be synthesized from feedstocks including carbon monoxide, carbon dioxide and hydrogen.

[0018] The method for producing a catalyst structure according to the present disclosure includes a supporting step of supporting an iron-based catalyst precursor on a porous support by impregnating the porous support with a slurry containing a binder and an iron-based catalyst precursor, followed by drying and calcination. The method for producing a catalyst structure also includes a reducing step of reducing the iron-based catalyst precursor supported on the porous support. The method for producing a catalyst structure further includes activating the reduced iron-based catalyst precursor with an activation gas containing at least one of carbon monoxide and carbon dioxide to form Fe. ５ C ２ phase and Fe ２ O ３ phase and Fe ３ O ４ The method further includes an activation step of producing an iron-based catalyst containing at least one of the iron-based catalyst and the porous support supporting the iron-based catalyst, and synthesizing hydrocarbons including lower olefins.

[0019] The binder may include at least one of an alumina binder and a silica binder.

[0020] According to the present disclosure, it is possible to provide a catalyst structure, a fixed-bed reactor, and a method for manufacturing a catalyst structure that can suppress powdering.

[0021] FIG. 1 is a schematic diagram showing a catalyst structure according to one embodiment. FIG. 2 is a schematic diagram showing a catalyst structure according to one embodiment. FIG. 3 is a schematic diagram showing a reaction system used in the examples and comparative examples. FIG. 4 is a photograph showing the appearance of the catalyst structure of Example 1 before and after activation when the catalyst structure was reacted under various conditions. FIG. 5 is a photograph showing the appearance of the catalyst structure of Comparative Example 1 before and after activation when the catalyst structure was reacted under various conditions. FIG. 6 is a photograph showing the appearance of the catalyst structure of Comparative Example 2 before and after activation when the catalyst structure was reacted under various conditions. FIG. 7 is a graph showing the relationship between activation time and pressure loss when the catalyst structure of Example 1 was reacted under the conditions of Run 4. FIG. 8 is a graph showing the relationship between activation time and pressure loss when the catalyst structure of Comparative Example 1 was reacted under the conditions of Run 4. FIG. 9 is a graph showing the relationship between activation time and pressure loss when the catalyst structure of Comparative Example 2 was reacted under the conditions of Run 4. Fig. 10 is an X-ray diffraction pattern of the iron-based catalyst after the catalyst structure of Example 1 was reacted under the conditions of Run 0. Fig. 11 is an X-ray diffraction pattern of the iron-based catalyst after the catalyst structure of Example 1 was reacted under the conditions of Run 1. Fig. 12 is an X-ray diffraction pattern of the iron-based catalyst after the catalyst structure of Example 1 was reacted under the conditions of Run 2. Fig. 13 is an X-ray diffraction pattern of the iron-based catalyst after the catalyst structure of Example 1 was reacted under the conditions of Run 3. Fig. 14 is an X-ray diffraction pattern of the iron-based catalyst after the catalyst structure of Example 1 was reacted under the conditions of Run 4.

[0022] Hereinafter, several exemplary embodiments will be described with reference to the drawings. Note that the dimensional proportions of the drawings are exaggerated for the convenience of explanation and may differ from the actual proportions.

[0023] [Catalyst Structure] First, a catalyst structure 1 according to this embodiment will be described. As shown in Fig. 1, the catalyst structure 1 according to this embodiment includes an iron-based catalyst 2 and a porous carrier 3.

[0024] The iron-based catalyst 2 is Fe ５ C ２ phase and Fe ２ O ３ phase and Fe ３ O４ The iron-based catalyst 2 contains at least one of the Fe ５ C ２ By including the iron-based catalyst 2, the FT reaction shown in the following reaction formula (1) can proceed. ２ O ３ phase and Fe ３ O ４ By including at least one of the phases, the reverse shift reaction shown in the following reaction formula (2) can proceed. ５ C ２ phase and Fe ２ O ３ phase and Fe ３ O ４ By including at least one of the phases, the following reaction formulas (1) and (2) can be promoted, and hydrocarbons including lower olefins can be synthesized from raw materials including carbon dioxide and hydrogen.

[0025] FT reaction: nCO + 2nH ２ →C ｎ H ２ｎ +nH ２ O (1) Reverse shift reaction: CO ２ +H ２ ⇔CO + H ２ O (2)

[0026] Here, Fe of the iron-based catalyst 2 ２ O ３ or Fe ３ O ４ Depending on the reaction conditions, Fe reacts with CO in the gas phase to generate carbide components, which progresses over time. ２ O ３ or Fe ３ O ４ The change of iron oxide to carbide components causes microscopic changes in the density and volume of the iron-based catalyst 2. That is, the iron oxide in the catalyst pellets is carbonized, and further, the pellets are pulverized. This tendency is particularly pronounced at high temperatures. For example, at temperatures higher than 300°C, the phase change to carbide vigorously progresses, causing excess carbon to precipitate and ultimately pulverizing the catalyst pellets.

[0027] Therefore, the porous carrier 3 supports the iron-based catalyst 2. When the iron-based catalyst 2 is formed into pellets by a method such as extrusion molding, there is a risk that the catalyst pellets will become powdered during use. However, by supporting the iron-based catalyst 2 on the porous carrier 3, it is possible to suppress this powdering. This reduces the pressure loss inside the reaction tube and suppresses clogging of the reaction tube with powdered catalyst. Furthermore, since it is possible to suppress the powdering of the iron-based catalyst 2, it is possible to easily replace the catalyst structure 1 inside the reaction tube.

[0028] The porous carrier 3 has an open-cell structure and is composed of interconnected or through-pores. That is, the porous carrier 3 has open pores. As shown in FIGS. 1 and 2, the porous carrier 3 may have a network structure. As shown in FIG. 1, the iron-based catalyst 2 may cover the solid surface that forms the pores inside the porous carrier 3, and the catalyst structure 1 may have pores inside. Alternatively, as shown in FIG. 2, the iron-based catalyst 2 may be filled inside the porous carrier 3, and the catalyst structure 1 may have substantially no pores inside. The amount of the iron-based catalyst 2 supported may be 5 wt % to 45 wt %, 10 wt % to 40 wt %, 15 wt % to 35 wt %, or 20 wt % to 30 wt %. The amount of the iron-based catalyst 2 supported is the ratio of the weight of the iron-based catalyst 2 to the weight of the entire catalyst structure 1.

[0029] The porous support 3 may be formed of at least one material selected from the group consisting of metal, ceramic, and silicon carbide (SiC). For example, when the porous support 3 is formed of a metal, heat conduction within the catalyst structure 1 can be promoted. This makes the temperature distribution in the catalyst structure 1 uniform, and the generation of locally high-temperature hot spots can be suppressed. Therefore, excessive phase transition of the iron component of the iron-based catalyst 2 to carbide and carbon precipitation due to hot spots can be suppressed. Specifically, the porous support 3 may be a Ni alloy or an Fe alloy. More specifically, the porous support 3 may be a NiFeCr alloy. The porous support 3 may be an FeCrAl alloy.

[0030] The porosity of the porous carrier 3 may be 85% to 95%. By setting the porosity of the porous carrier 3 to 85% or more, it is possible to further suppress a decrease in pressure loss. By setting the porosity of the porous carrier 3 to 95% or less, it is possible to further improve the mechanical strength of the porous carrier 3. The porosity can be calculated by dividing the volume of the pores by the total volume of the porous carrier 3.

[0031] The average pore diameter of the porous carrier 3 may be 500 μm to 4000 μm. By setting the average pore diameter of the porous carrier 3 to 500 μm or more, it is possible to further suppress a decrease in pressure loss. By setting the average pore diameter of the porous carrier 3 to 4000 μm or less, it is possible to further improve the mechanical strength of the porous carrier 3. The average pore diameter can be determined by measuring the number of cells per predetermined length of the porous carrier 3 and calculating the reciprocal of the measured value.

[0032] The catalyst structure 1 synthesizes hydrocarbons including lower olefins. The lower olefins may include at least any hydrocarbon having 2 to 4 carbon atoms. The lower olefins may include at least one hydrocarbon selected from the group consisting of ethylene, propylene, 1-butene, 2-butene, and isobutene, for example. The lower olefins can be used, for example, as raw materials for plastics. Note that the catalyst structure 1 may synthesize hydrocarbons other than lower olefins in addition to lower olefins.

[0033] The catalyst structure 1 may be in the form of pellets. By forming the catalyst structure 1 into a pellet shape, when a plurality of catalyst structure 1 pellets are filled in a reaction tube, the reaction raw material gases are diffused, improving heat conduction. The shape of the catalyst structure 1 is not particularly limited, and may be a cube, a rectangular parallelepiped, a cylinder, a sphere, an ellipsoid, or an irregular shape. The size of the catalyst structure 1 may be 1 mm to 10 mm, 1.5 mm to 7 mm, or 2 mm to 5 mm. The size of the catalyst structure 1 is the value of the length of one side calculated from the volume of the catalyst structure 1, assuming that the catalyst structure 1 is a cube.

[0034] The volume of the catalyst structure 1 is 0.5 mm ３ More than 1000mm ３The volume of the catalyst structure 1 may be 0.5 mm or less. ３ By setting the volume of the catalyst structure 1 at 30 cm or more, it is possible to prevent the catalyst structure 1 from flowing out of the reaction tube during the reaction. ３ By setting the volume of the catalyst structure 1 to 5 mm or less, it is possible to improve the packing property into the reaction tube. ３ It may be 10 mm or more. ３ It may be 15 mm or more. ３ The volume of the catalyst structure 1 may be 500 mm or more. ３ It may be less than 200 mm ３ It may be less than 50 mm ３ It may be the following:

[0035] As described above, the catalyst structure 1 according to this embodiment is ５ C ２ phase and Fe ２ O ３ phase and Fe ３ O ４ The present invention provides an iron-based catalyst (2) containing at least one of the above phases and a porous carrier (3) supporting the iron-based catalyst (2), and synthesizes hydrocarbons containing lower olefins.

[0036] In the catalyst structure 1 according to this embodiment, the porous support 3 supports the iron-based catalyst 2, and therefore, powdering can be suppressed compared to when extrusion-molded catalyst pellets are used. Therefore, by using the catalyst structure 1 according to this embodiment, an increase in pressure loss during reaction can be suppressed, and maintenance for catalyst replacement can also be facilitated.

[0037] [Fixed Bed Reactor] Next, the fixed bed reactor 110 according to this embodiment will be described with reference to Fig. 3. As shown in Fig. 3, the fixed bed reactor 110 according to this embodiment includes a catalyst structure 1 and a reaction tube 112 that houses the catalyst structure 1. The catalyst structure 1 is the same as the catalyst structure 1 described above, and a plurality of catalyst structures 1 are packed in the reaction tube 112. The fixed bed reactor 110 may include an electric furnace 113, and the reaction tube 112 may be installed in the electric furnace 113.

[0038] As described above, the catalyst structure 1 is made of Fe５ C ２ phase and Fe ２ O ３ phase and Fe ３ O ４ The reactor 110 is equipped with an iron-based catalyst 2 containing at least one of the above phases, and synthesizes hydrocarbons containing lower olefins. Therefore, the fixed-bed reactor 110 can synthesize hydrocarbons containing lower olefins from a raw material containing carbon dioxide and hydrogen. By synthesizing hydrocarbons containing lower olefins from carbon dioxide, it is possible to suppress the release of carbon dioxide, which causes global warming, into the atmosphere and to effectively utilize the carbon dioxide. The raw material may further contain carbon monoxide. In other words, the fixed-bed reactor 110 may synthesize hydrocarbons containing lower olefins from a raw material containing carbon monoxide, carbon dioxide, and hydrogen.

[0039] As described above, the fixed-bed reactor 110 according to this embodiment includes a plurality of catalyst structures 1 and a reaction tube 112 housing the plurality of catalyst structures 1. Housing a plurality of catalyst structures 1 within the reaction tube 112 allows the reaction raw material gas to diffuse, improving heat conduction. Furthermore, the fixed-bed reactor 110 can more easily remove reaction heat than a slurry reactor or a fluidized-bed reactor. Because the reaction represented by the above reaction formula (1) is an exothermic reaction, the fixed-bed reactor 110 can efficiently produce hydrocarbons from a raw material containing carbon dioxide. However, as described above, when conventional catalyst pellets are used in the fixed-bed reactor 110, if the catalyst becomes pulverized, the void space within the reaction tube 112 may decrease, potentially increasing pressure loss during the reaction. When a slurry reactor or a fluidized-bed reactor is used, the problem of increased pressure loss due to pulverization does not arise. However, the catalyst structure 1 according to this embodiment can suppress pulverization as described above. Therefore, by using the catalyst structure 1 according to this embodiment, it is possible to suppress an increase in pressure loss during the reaction, and it is also possible to facilitate maintenance such as catalyst replacement.

[0040] [Method for Manufacturing Catalyst Structure] Next, a method for manufacturing the catalyst structure 1 according to this embodiment will be described. The method for manufacturing the catalyst structure 1 includes a precursor preparation step, a supporting step, a reducing step, and an activating step.

[0041] (Precursor Preparation Step) The precursor preparation step is a step of preparing an iron-based catalyst precursor. The iron-based catalyst precursor may be produced, for example, by a coprecipitation method or an impregnation method together with a subcomponent and a cocatalyst as necessary. The step of producing the iron-based catalyst precursor may include, for example, an aqueous solution production step, a precipitate production step, and a first calcination step.

[0042] (Aqueous Solution Producing Step) The aqueous solution producing step is a step of producing an aqueous solution containing an iron salt and a surfactant. In the aqueous solution producing step, the aqueous solution can be produced by dissolving the iron salt and the surfactant in water such as ion-exchanged water.

[0043] The iron salt may be a divalent iron salt or a trivalent iron salt. The iron salt may contain at least one anion selected from the group consisting of nitrate, fluoride, chloride, bromide, iodide, phosphate, pyrophosphate, and perchlorate. The iron salt may contain, for example, iron nitrate.

[0044] The surfactant may be an ionic surfactant. The surfactant may contain at least one anion selected from the group consisting of halides, sulfonates, sulfates, phosphates, and carboxylates. The surfactant may contain, for example, a halide anion. The halide anion may contain a fluoride anion, a chloride anion, a bromide anion, or an iodide anion. The surfactant may contain, for example, a bromide anion. The surfactant may be a quaternary ammonium surfactant, such as cetrimonium bromide.

[0045] The molar ratio of iron to surfactant may be about 1:0.5 to 1:15, about 1:0.5 to 1:12, about 1:0.5 to 1:10, about 1:0.5 to 1:8, about 1:0.5 to 1:6, about 1:0.5 to 1:4, or about 1:0.5 to 1:2. The molar ratio of iron to surfactant may be, for example, about 1:1.

[0046] (Precipitation Step) The precipitation step is a step of adding a solution of a basic salt to the aqueous solution produced in the aqueous solution production step to produce a precipitate.

[0047] The salt contained in the basic salt solution may contain at least one specific element selected from the group consisting of alkali metals, alkaline earth metals, transition metal elements from Groups 3 to 7 or 9 to 11 in the periodic table, and lanthanides. The alkali metal may contain at least one element selected from the group consisting of lithium, sodium, potassium, rubidium, and cesium. The alkaline earth metal may contain at least one element selected from the group consisting of beryllium, magnesium, calcium, strontium, and barium. The Group 3 element may contain at least one element selected from the group consisting of scandium and yttrium. The Group 4 element may contain at least one element selected from the group consisting of titanium, zirconium, and hafnium. The Group 5 element may contain at least one element selected from the group consisting of vanadium, niobium, and tantalum. The Group 6 element may contain at least one element selected from the group consisting of chromium, molybdenum, and tungsten. The Group 7 element may include at least one element selected from the group consisting of manganese, technetium, and rhenium. The Group 9 element may include at least one element selected from the group consisting of cobalt, rhodium, and iridium. The Group 10 element may include at least one element selected from the group consisting of nickel, palladium, and platinum. The Group 11 element may include at least one element selected from the group consisting of copper, silver, and gold. The lanthanoid may include at least one element selected from the group consisting of lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium.

[0048] The basic salt solution may include hydroxide anions, carbonate anions, or bicarbonate anions. The basic salt may be sodium hydroxide, lithium hydroxide, potassium hydroxide, cesium hydroxide, or a combination thereof. The basic salt solution may be an aqueous solution.

[0049] The precursor preparation step may include a recovery step of recovering the precipitate by at least one of centrifugation and filtration. The precursor preparation step may also include a step of drying the recovered precipitate before the first firing step. The drying may be performed in the atmosphere at a temperature of 80° C. or higher and 120° C. or lower. Washing of the precipitate is not required.

[0050] (First Calcination Step) The first calcination step is a step of calcining the precipitate produced in the precipitation step. The first calcination step may be carried out at a temperature of about 300°C to 600°C, about 350°C to 600°C, about 400°C to 600°C, or about 400°C to 550°C. The first calcination step may be carried out for about 1 to 10 hours, about 1 to 8 hours, about 1 to 6 hours, about 1 to 5 hours, about 1 to 4 hours, about 1 to 3 hours, or about 1 to 2 hours.

[0051] (Supporting Step) The supporting step is a step of impregnating the porous support 3 with the slurry, drying, and calcining the porous support 3, thereby supporting the iron-based catalyst precursor on the porous support 3. The supporting step may include an impregnation step, a drying step, and a second calcination step.

[0052] (Impregnation Step) The impregnation step is a step of impregnating the porous carrier 3 with the slurry. In the impregnation step, the porous carrier 3 may be immersed in the slurry to impregnate the porous carrier 3 with the slurry. The porous carrier 3 impregnated with the slurry may be stirred under reduced pressure.

[0053] The slurry contains an iron-based catalyst precursor. The slurry may contain a binder. The binder may contain at least one of an alumina binder and a silica binder. By using these binders, the iron-based catalysts 2 are firmly bound to each other, and peeling of the iron-based catalyst 2 from the porous support 3 can be suppressed. The slurry may contain water in addition to the iron-based catalyst precursor and binder. The weight ratio of water to the iron-based catalyst precursor in the slurry may be 0.1 to 20, 3 to 14, or 5 to 7. The weight ratio of binder to the iron-based catalyst precursor in the slurry may be 0.1 to 2, 0.15 to 1, or 0.3 to 0.5.

[0054] The porous support 3 may be any of those described above. For the purpose of improving the adhesion of the iron-based catalyst precursor, the porous support 3 may be heated in the atmosphere. The heating temperature of the porous support 3 may be 500°C or higher and 700°C or lower, or 550°C or higher and 650°C or lower. The heating time of the porous support 3 may be, for example, 1 hour or higher and 3 hours or lower.

[0055] (Drying Step) The drying step is a step of drying the porous carrier 3 impregnated with the slurry. After the liquid of the slurry impregnated into the porous carrier 3 is sucked out, the porous carrier 3 may be dried. The drying temperature of the porous carrier 3 may be 110°C to 190°C, or 130°C to 170°C.

[0056] The impregnation step and the drying step may be performed only once, or these steps may be performed repeatedly in this order. These steps may be repeated 1 to 7 times, 2 to 5 times, or 3 to 4 times. By increasing the number of repetitions, the amount of iron-based catalyst precursor supported on the porous support 3 can be increased.

[0057] (Second Calcination Step) The second calcination step is a step of calcining the dried porous support 3. The second calcination step may be carried out at a temperature of about 300°C to 600°C, about 350°C to 600°C, about 400°C to 600°C, about 400°C to 550°C, or about 400°C to 550°C. The second calcination step may be carried out for about 1 to 10 hours, about 1 to 8 hours, about 1 to 6 hours, about 1 to 5 hours, about 1 to 4 hours, about 1 to 3 hours, or about 1 to 2 hours.

[0058] (Reduction Step) The reduction step is a step of reducing the iron-based catalyst precursor supported on the porous support 3. In the reduction step, the iron-based catalyst precursor is reacted with a reducing gas. The reducing gas is a gas capable of reducing iron oxide, and may be, for example, hydrogen gas or carbon monoxide gas. The reaction temperature may be 200°C to 500°C or 300°C to 400°C. The reaction time may be, for example, 1 hour to 12 hours, 3 hours to 10 hours, or 5 hours to 8 hours.

[0059] (Activation step) In the activation step, the reduced iron-based catalyst precursor is activated with an activation gas to form Fe ５ C ２ phase and Fe ２ O ３ phase and Fe ３ O ４ This is a process for producing an iron-based catalyst 2 containing at least one of the above phases. The activation gas contains at least one of carbon monoxide and carbon dioxide. The activation gas may be, for example, a mixed gas containing hydrogen and at least one of carbon monoxide and carbon dioxide. The activation pressure may be 0.7 MPa to 1.1 MPa, or 0.8 MPa to 1 MPa. The activation temperature may be 250°C to 370°C or 300°C to 350°C. The activation time may be, for example, 1 hour or more, 2 hours or more, 3 hours or more, or 5 hours or more. The activation time may also be, for example, 100 hours or less, 50 hours or less, 25 hours or less, 10 hours or less, or 5 hours or less.

[0060] Through the above steps, a catalyst structure 1 can be produced which comprises an iron-based catalyst 2 and a porous carrier 3 supporting the iron-based catalyst 2 and which synthesizes hydrocarbons containing lower olefins.

[0061] As described above, the method for producing the catalyst structure 1 according to this embodiment is a method for producing a catalyst structure including a supporting step, a reducing step, and an activating step. In the supporting step, the porous support 3 is impregnated with a slurry containing a binder and an iron-based catalyst precursor, followed by drying and firing, thereby supporting the iron-based catalyst precursor on the porous support 3. In the reducing step, the iron-based catalyst precursor supported on the porous support 3 is reduced. In the activating step, the reduced iron-based catalyst precursor is activated with an activation gas containing at least one of carbon monoxide and carbon dioxide to form Fe. ５ C ２ phase and Fe ２ O ３ phase and Fe ３ O ４ The catalyst structure 1 includes the iron-based catalyst 2 and a porous carrier 3 supporting the iron-based catalyst 2, and synthesizes hydrocarbons including lower olefins.

[0062] According to the method for producing the catalyst structure 1 according to this embodiment, as described above, it is possible to produce the catalyst structure 1 that can be prevented from being pulverized.

[0063] Hereinafter, the present embodiment will be described in more detail with reference to examples and comparative examples, but the present embodiment is not limited to these examples.

[0064] Example 1 First, a catalyst structure according to this example was fabricated using an iron-based catalyst precursor and a porous support prepared as follows.

[0065] (Iron-based catalyst precursor) Iron nitrate (Fe(NO ３ ) ２ ・9H ２ An iron salt (O) and a surfactant were dissolved in ion-exchanged water to prepare a homogeneous aqueous solution. An aqueous solution of an alkali metal salt, i.e., an aqueous NaOH solution, was added dropwise to this aqueous solution to form a precipitate containing the iron salt and the alkali metal. After aging at room temperature, the precipitate was filtered to separate the solid and liquid, and the solid was recovered. The recovered solid was not washed, and was then dried at 100°C and calcined in air at 450°C. The calcined oxide was pulverized in a mortar to obtain a test sample of an iron-based catalyst precursor.

[0066] (Porous Support) A cubic NiFeCr alloy with a length of 3 mm, a width of 3 mm, and a height of 3 mm was used as the support. The cell size (pore diameter) of the support was 800 μm, and the porosity was 90% to 95%. In order to improve the adhesion of the iron-based catalyst powder, the porous support was heated to 600°C at a heating rate of 10°C / min in the atmosphere, heated at 600°C for 2 hours, and then allowed to cool in a furnace to obtain a pretreated porous support.

[0067] (Supporting Step) Next, an iron-based catalyst precursor, purified water, and an alumina binder were mixed in a container at a weight ratio of iron-based catalyst precursor:purified water:alumina binder = 1:6.2:0.32 to prepare a slurry. The pretreated porous support was immersed in the prepared slurry, and the pressure was reduced while stirring the slurry using a vacuum degassing device equipped with a stirrer. After stirring the slurry, the liquid was sucked using a suction dryer, and the porous support was dried at 150°C. The impregnation and drying were repeated a total of three times. The weight of the iron-based catalyst precursor relative to the supported support (the amount of supported iron-based catalyst precursor) was measured and found to be 26.4 wt%. Note that the amount of supported iron-based catalyst precursor is calculated by subtracting the amount of supported alumina from the material supported on the porous support. The catalyst precursor-supported support thus obtained was heated at a rate of 5°C / min in the atmosphere and calcined at 450°C for 2 hours.

[0068] (Reaction System) Next, in order to reduce and activate the calcined catalyst precursor-supported carrier, a reaction system 100 including a fixed-bed reactor 110 was prepared as shown in FIG. 3 . Specifically, the calcined catalyst precursor-supported carrier 111 prepared as described above was packed into a reaction tube 112 having an outer diameter of ¼ inch, and the reaction tube 112 was placed in an electric furnace 113. In addition, a hydrogen tank 121, a nitrogen tank 122, and an activation mixed gas tank 123 were prepared as gases to be supplied to the reaction tube 112. The supply of hydrogen gas from the hydrogen tank 121 to the reaction tube 112 was controlled by a solenoid valve 124 and an MFC 125 (mass flow controller). The supply of nitrogen gas from the nitrogen tank 122 to the reaction tube 112 was controlled by an MFC 126. The supply of the activation mixed gas from the activation mixed gas tank 123 to the reaction tube 112 was controlled by a high-pressure MFC 127. These gases were mixed in a mixer 128 as required.

[0069] An inlet back pressure valve 131 and a safety valve 132 were installed on the inlet side of the reaction tube 112, and an outlet back pressure valve 133 was installed on the outlet side of the reaction tube 112. The temperature on the inlet side of the catalyst precursor-supported carrier 111 was measured with an inlet thermometer 141 of a thermocouple, and the temperature on the outlet side of the catalyst precursor-supported carrier 111 was measured with an outlet thermometer 142 of a thermocouple. Furthermore, the pressure on the inlet side of the reaction tube 112 was measured with an inlet pressure gauge 143, and the pressure on the outlet side of the reaction tube 112 was measured with an outlet pressure gauge 144. When the pressure loss increased, the apertures of the inlet back pressure valve 131 and the outlet back pressure valve 133 were adjusted so that the pressure on the inlet pressure gauge 143 became constant and the pressure on the outlet pressure gauge 144 decreased.

[0070] Next, the catalyst precursor was reduced and activated under the test conditions shown in Table 1 as follows.

[0071] (Reduction) The supply of nitrogen gas (28 NmL / min) to the reaction tube 112 was started. Next, heating of the reaction tube 112 was started, and the temperature was increased from room temperature to 400°C. After the temperature of the reaction tube 112 reached 400°C, the supply gas was switched from nitrogen to hydrogen (28 NmL / min), and reduction was started. Six hours after the start of the supply of hydrogen, the supply gas to the reaction tube 112 was switched from hydrogen to nitrogen. The heating of the reaction tube 112 was stopped, and the reaction tube 112 was allowed to cool naturally.

[0072] (Activation) The supply of nitrogen gas to the reaction tube 112 was started. Next, the pressure in the reaction tube 112 was increased to about 0.65 MPaG. Next, the temperature of the reaction tube 112 was increased from room temperature to 325°C at 10°C / min. The supply of nitrogen gas to the reaction tube 112 was stopped, and the pressure was increased to 0.9 MPaG with activation gas (28 NmL / min). After the time shown in Table 1 had elapsed, the supply of activation gas was stopped. The reaction tube 112 was allowed to cool naturally, and the pressure was reduced to normal pressure. O ２ -0.5% / N ２ The catalyst was then switched to a gas and the catalyst surface was oxidized for at least one hour, after which the catalyst was taken out.

[0073] Comparative Example 1 A test sample prepared in the same manner as in Example 1 was extruded to prepare pellets having a diameter of 3 mm, and the pellets were filled into the reaction tube 112. Except for this, reduction and activation were carried out in the same manner as in Example 1.

[0074] Comparative Example 2 Reduction and activation were carried out in the same manner as in Comparative Example 1, except that the calcination time of the test sample was changed from 450°C to 550°C.

[0075] [Evaluation] The state of powdering, pressure loss and XRD of the catalyst structure after the activation treatment were evaluated.

[0076] 4 to 6 are photographs showing the appearance of the catalyst structures according to Example 1, Comparative Example 1, and Comparative Example 2 before and after the reaction and activation in Runs 1 to 4. As shown in FIGS. 4 to 6, no pulverization was observed in the catalyst structure according to Example 1, even after activation in Run 4. On the other hand, pulverization was observed in the catalyst structure according to Comparative Example 1 at least after activation in Run 4. Furthermore, pulverization was also observed in the catalyst structure according to Comparative Example 2, which is thought to have been made stronger by using a higher calcination temperature than Comparative Example 1, at least after activation in Run 4.

[0077] 7 to 9 are graphs showing the relationship between activation time and pressure loss when the catalyst structures of Example 1, Comparative Example 1, and Comparative Example 2 were reacted under the conditions of Run 4. As shown in Fig. 7, the catalyst structure of Example 1 maintained constant pressures at the inlet and outlet of the reaction tube until the activation of Run 4 was completed, and no pressure loss was observed. On the other hand, as shown in Figs. 8 and 9, the catalyst structures of Comparative Examples 1 and 2 showed that the pressure at the outlet of the reaction tube continued to decrease relative to the pressure at the inlet of the reaction tube during the activation of Run 4, and it was confirmed that a pressure loss occurred.

[0078] From the results of Figures 4 to 9, it can be seen that the catalyst structure of Example 1 can suppress powdering compared to catalyst pellets molded by extrusion molding, and as a result, can suppress the occurrence of pressure loss.

[0079] 10 to 14 show X-ray diffraction patterns of the iron-based catalyst after the catalyst structure of Example 1 was reacted under the conditions of Run 0, Run 1, Run 2, Run 3, and Run 4, respectively. As shown in FIG. 10, the main component of the iron-based catalyst after calcination was iron oxide. As shown in FIG. 11, the main component of the iron-based catalyst after reduction was iron. As shown in FIGS. 12 to 14, the iron-based catalyst after activation contained Fe. ５ C２ phase and Fe ２ O ３ phase and Fe ３ O ４ It was found that at least one of the phases was contained, but carbon was also produced.

[0080] The iron-based catalyst according to Example 1 is Fe ２ O ３ phase and Fe ３ O ４ Since the iron-based catalyst according to Example 1 contains at least one of the phases, the reverse shift reaction shown in the above-mentioned reaction formula (2) can proceed, and carbon monoxide can be produced from a raw material containing carbon dioxide and hydrogen. ５ C ２ Since the catalyst contains a phase, the FT reaction shown in the above-mentioned reaction formula (1) can proceed, and hydrocarbons containing lower olefins can be produced from a raw material containing carbon monoxide and hydrogen.

[0081] The entire contents of Japanese Patent Application No. 2023-088819 (filing date: May 30, 2023) are incorporated herein by reference.

[0082] Although several embodiments have been described, the embodiments can be modified or varied based on the above disclosure. All components of the above embodiments and all features described in the claims may be individually extracted and combined, unless they are mutually inconsistent.

[0083] The present disclosure can contribute, for example, to Goal 13 of the United Nations-led Sustainable Development Goals (SDGs), "Take urgent action to combat climate change and its impacts."

[0084] REFERENCE SIGNS LIST 1 catalyst structure 2 iron-based catalyst 3 porous carrier 110 fixed-bed reactor 112 reaction tube

Claims

1. Fe ５ C ２ phase and Fe ２ O ３ phase and Fe ３ O ４ an iron-based catalyst containing at least one of the phases; a porous carrier that supports the iron-based catalyst; Equipped with A catalyst structure for synthesizing hydrocarbons including lower olefins.

2. The volume of the catalyst structure is 0.5 mm ３ More than 1000mm ３ 2. The catalyst structure of claim 1, wherein:

3. 3. The catalyst structure according to claim 1, wherein the porous support is made of a metal.

4. 3. The catalyst structure according to claim 1, wherein the porosity of the porous support is 85% to 95%.

5. A plurality of catalyst structures according to claim 1 or 2; a reaction tube containing the plurality of catalyst structures; A fixed bed reactor comprising:

6. 6. The fixed-bed reactor according to claim 5, wherein the hydrocarbons are synthesized from a feedstock containing carbon dioxide and hydrogen.

7. 6. The fixed-bed reactor according to claim 5, wherein the hydrocarbons are synthesized from a feedstock containing carbon monoxide, carbon dioxide, and hydrogen.

8. a supporting step of impregnating a porous support with a slurry containing a binder and an iron-based catalyst precursor, followed by drying and calcining the porous support to support the iron-based catalyst precursor on the porous support; a reduction step of reducing the iron-based catalyst precursor supported on the porous support; The reduced iron-based catalyst precursor is activated with an activation gas containing at least one of carbon monoxide and carbon dioxide to produce Fe. ５ C ２ phase and Fe ２ O ３ phase and Fe ３ O ４ an activation step to produce an iron-based catalyst comprising at least one of the phases; A method for producing a catalyst structure comprising: The catalyst structure comprises the iron-based catalyst and the porous carrier supporting the iron-based catalyst, and is used to synthesize hydrocarbons containing lower olefins.

9. The method for producing a catalyst structure according to claim 8 , wherein the binder includes at least one of an alumina binder and a silica binder.