Hydrocarbon production catalyst and hydrocarbon production method

Abstract

To provide a highly active hydrocarbon production catalyst that can increase the productivity of LPG consisting of propane and butane in hydrocarbon production using carbon oxide and hydrogen as raw materials, a method for producing the hydrocarbon production catalyst, and a method for producing hydrocarbons using the hydrocarbon production catalyst. [Solution] A hydrocarbon production catalyst having a core containing catalyst A containing iron, cobalt, aluminum, and sodium, and an outer shell formed on the core containing zeolite, and a method for producing hydrocarbons using the hydrocarbon production catalyst.

Description

Technical Field

[0001] The present invention relates to a hydrocarbon production catalyst and a method for producing a hydrocarbon.

Background Art

[0002] In recent years, due to the emergence of environmental problems such as global warming, the reduction of carbon dioxide emissions has been demanded. Therefore, carbon recycling technology that separates and recovers carbon dioxide and effectively utilizes it as a resource can contribute to the reduction of carbon dioxide emissions. On the other hand, hydrocarbons can be utilized as various fuels. One of them, LPG (Liquefied Petroleum Gas) composed of propane and butane, has a lot of demand due to its high portability and storage properties.

[0003] Under such circumstances, research and development for producing LPG by Fischer-Tropsch (FT) synthesis reaction using carbon dioxide and hydrogen as raw materials has been actively conducted.

[0004] For example, Patent Document 1 discloses "a carbon dioxide reduction catalyst containing Na and Fe as catalytic metals and a porous solid catalyst having pores enlarged by alkali treatment". Non-Patent Document 1 discloses "a encapsulated catalyst in which a Na / Fe catalyst is encapsulated with HZSM-5 zeolite".

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Non-Patent Documents

[0006]

Non-Patent Document 1

[0007] In the production of hydrocarbons using carbon dioxide and hydrogen as raw materials, including in Patent Document 1, it is common to use iron-based catalysts due to the high conversion rate of carbon dioxide. However, a challenge with iron-based catalysts is that the proportion of olefins in the hydrocarbons produced is high, resulting in low productivity of LPG, which is a type of paraffin. In particular, the encapsulated catalyst evaluated in Non-Patent Document 1 exhibits relatively high paraffin selectivity, but has a low carbon dioxide conversion rate and low selectivity for hydrocarbons with 3 to 4 carbon atoms, resulting in low overall LPG productivity. Therefore, in hydrocarbon production using carbon dioxide and hydrogen as raw materials, there is room for improvement in hydrocarbon production catalysts that efficiently produce LPG.

[0008] Therefore, the object of the present invention is to provide a highly active hydrocarbon production catalyst that can increase the productivity of LPG consisting of propane and butane in hydrocarbon production using carbon dioxide and hydrogen as raw materials, a method for producing the hydrocarbon production catalyst, and a method for producing hydrocarbons using the hydrocarbon production catalyst. [Means for solving the problem]

[0009] The means for solving the problem include the following aspects: <1> A core containing catalyst A, which includes iron, cobalt, aluminum, and sodium, An outer shell portion formed on the aforementioned core portion and containing zeolite, A hydrocarbon production catalyst. <2> The zeolite is at least one of H-ZSM-5 zeolite and SAPO-11 zeolite, having a molar ratio of SiO2 to Al2O3 (SiO2 / Al2O3) of 200 or less. <1> A hydrocarbon manufacturing catalyst as described above. <3> The zeolite is an H-ZSM-5 zeolite with a molar ratio of SiO2 to Al2O3 (SiO2 / Al2O3) of 20 to 150. <1> A hydrocarbon manufacturing catalyst as described above. <4> The aforementioned zeolite is SAPO-11 zeolite. <1> A hydrocarbon manufacturing catalyst as described above. <5> The core portion and the outer shell portion are bonded together with colloidal silica. <1> ~ <4> A hydrocarbon production catalyst as described in any one of the items. <6> <1> ~ <5> A method for producing hydrocarbons using a hydrocarbon production catalyst described in any one of the items, A method for producing hydrocarbons, comprising contacting a mixed gas containing carbon dioxide and hydrogen with the hydrocarbon production catalyst to produce hydrocarbons. <7> <1> ~ <5> A method for producing hydrocarbons using a hydrocarbon production catalyst described in any one of the items, A first step involves contacting a mixed gas containing carbon dioxide and hydrogen with the hydrocarbon production catalyst, A second step involves contacting the hydrocarbon mixture obtained in the first step with a decomposition catalyst made of zeolite to decompose it, A method for producing hydrocarbons, comprising: [Effects of the Invention]

[0010] According to the present invention, in the production of hydrocarbons using carbon dioxide and hydrogen as raw materials, it is possible to provide a highly active hydrocarbon production catalyst capable of increasing the productivity of LPG composed of propane and butane, a method for producing the hydrocarbon production catalyst, and a method for producing hydrocarbons using the hydrocarbon production catalyst.

Mode for Carrying Out the Invention

[0011] Hereinafter, the present invention will be described. In this specification, a numerical range represented by "~" means a range including the numerical values described before and after "~" as the lower limit value and the upper limit value. In a numerical range described step by step, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the upper limit value or the lower limit value of the numerical range described in other step-by-step descriptions. In a numerical range, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the value shown in the examples. The amount of each component in the composition means the total amount of the plurality of substances present in the composition when there are a plurality of substances corresponding to each component in the composition, unless otherwise specified. The term "step" includes not only an independent step but also this term when the intended purpose of the step is achieved even when it cannot be clearly distinguished from other steps. "Combination of preferred embodiments" is a more preferred embodiment.

[0012] Also, "room temperature" means a temperature within the range of 23°C ± 3°C. Also, the "hydrocarbon production catalyst" is also simply referred to as the "catalyst".

[0013] <Hydrocarbon production catalyst> The hydrocarbon production catalyst of the present invention has a core portion containing a catalyst A containing iron, cobalt, aluminum and sodium, and an outer shell portion formed on the core portion and containing zeolite.

[0014] The catalyst of the present invention, with the above configuration, is a highly active catalyst that can increase the productivity of LPG (Large Propane and Butane) in hydrocarbon production using carbon dioxide and hydrogen as raw materials. The reason for this is presumed to be as follows.

[0015] By including cobalt, aluminum, and sodium as co-catalysts in addition to iron in the core catalyst A, the chain growth of hydrocarbons is promoted, and the yield of hydrocarbons with 3 to 4 carbon atoms is increased. In particular, cobalt, acting as a co-catalyst, promotes the reaction by acting as an active site not only on the iron but also on the cobalt itself, and the hydrocarbons produced by the highly hydrogenating cobalt shift to the shorter chain side. Furthermore, aluminum, acting as a co-catalyst, promotes the reaction of the raw materials by improving the dispersibility of iron, which is the active site. In addition, when cobalt, aluminum, and sodium are present as co-catalysts, the formation of iron carbide, which is the active species in the FT synthesis reaction, is promoted in a carbon dioxide and hydrogen atmosphere, improving the conversion rate of carbon dioxide and consequently increasing the yield of hydrocarbons with 3 to 4 carbon atoms. On the other hand, the zeolite, acting as a catalyst in the outer shell, converts the olefin produced by catalyst A into paraffin via acid sites, thereby increasing the paraffin selectivity of the product. Furthermore, by forming a capsule-shaped zeolite as an outer shell on the core containing catalyst A, the distance between the active sites of catalyst A and the zeolite is reduced, allowing for highly efficient conversion of the olefin produced by catalyst A into paraffin.

[0016] Therefore, it is presumed that the catalyst of the present invention will be a highly active catalyst that can increase the productivity of LPG, which consists of propane and butane, in hydrocarbon production using carbon dioxide and hydrogen as raw materials. Thus, while encapsulated catalysts, such as the one described in Non-Patent Document 1, which involves encapsulating a Na / Fe catalyst with HZSM-5 zeolite, increase the paraffin selectivity of the product, this comes at the cost of lowering the carbon dioxide conversion rate and the selectivity of C3-C4 hydrocarbons. In contrast, the catalyst of the present invention, by applying catalyst A as the core, increases both the carbon dioxide conversion rate and the selectivity of C3-C4 hydrocarbons, thereby improving overall LPG productivity.

[0017] The details of the catalyst of the present invention will be described below.

[0018] (core) -Catalyst A- The core contains catalyst A, which includes iron, cobalt, aluminum, and sodium. The core may contain components other than catalyst A. However, the proportion of catalyst A in the core is preferably 90% by mass or more, and more preferably 95% by mass or more. Other components besides catalyst A include the raw materials (precursors) of catalyst A.

[0019] Catalyst A, for example, has sodium supported on an iron, cobalt, and aluminum catalyst support. However, catalyst A may contain small amounts of impurities other than iron, cobalt, aluminum, and sodium. Here, in catalyst A, the iron content is, for example, 30% by mass or more (preferably 45% by mass or more, more preferably 60% by mass or more, and even more preferably 80% by mass or more) relative to the total components of the catalyst excluding oxygen. The number of moles or mass of each component (iron, cobalt, aluminum, sodium, and impurities) contained in the catalyst is measured by ICP-AES after pretreatment such as acid decomposition or alkali fusion of the catalyst.

[0020] The molar percentage of cobalt relative to iron is preferably 0.1 to 120.0%. When the molar percentage of cobalt is 0.1% or higher, the activity of cobalt itself as an active site increases, and the hydrocarbons produced by cobalt, which has high hydrogenation potential, shift to the shorter chain side, making it easier to produce hydrocarbons with 3 to 4 carbon atoms. When the molar percentage of cobalt is 120.0% or less, the relative decrease in the content of iron, which is an active species, is suppressed. In addition, stable iron-cobalt compounds are less likely to form, and the inhibition of FT reaction active site formation is suppressed. Therefore, when the molar percentage of cobalt is within the above range, the catalyst is more easily activated, and the carbon dioxide conversion rate and the productivity of hydrocarbons with 3 to 4 carbon atoms tend to improve. The lower limit of the molar percentage of cobalt relative to iron is 1.0%, 5.0%, 8.0%, and 10.0%, with the latter values ​​being more preferable. While a higher molar percentage of cobalt relative to iron improves the productivity of hydrocarbons with 3-4 carbon atoms, the increased cobalt content raises catalyst costs. Therefore, the upper limit for the molar percentage of cobalt is 55.0%, 50.0%, 20%, and 15%, with the latter being more preferable.

[0021] The molar percentage of aluminum relative to iron is preferably 0.1 to 20.0%. When the molar percentage of aluminum is 0.1% or higher, the aluminum acts as a co-catalyst, increasing the dispersion of iron, which is the active site, and thus accelerating the reaction of the raw materials. When the molar percentage of aluminum is 20.0% or less, the relative decrease in the content of iron, which is an active species, is suppressed. Therefore, when the molar percentage of aluminum is within the above range, the catalyst is more easily activated, and the carbon dioxide conversion rate and the productivity of hydrocarbons with 3 to 4 carbon atoms tend to improve. The lower limit of the molar percentage of aluminum relative to iron is more preferably 1.0%, and even more preferably 2.0%. The upper limit for the molar percentage of aluminum relative to iron is more preferably 15.0%, and even more preferably 12.0%.

[0022] The molar percentage of sodium relative to iron is preferably 0.01 to 0.30%. It is estimated that when the molar percentage of sodium is 0.01% or higher, the basicity of the catalyst surface improves, promoting the formation of iron carbide, which is presumed to be an active species of iron, and promoting the adsorption of carbon dioxide, the raw material gas, onto the catalyst surface. When the molar percentage of sodium is 0.30% or less, the relative decrease in the content of iron, which is an active species, is suppressed. Therefore, when the molar percentage of sodium is within the above range, the catalyst is more easily activated, and the carbon dioxide conversion rate and the productivity of hydrocarbons with 3 to 4 carbon atoms tend to improve. The lower limit of the molar percentage of sodium relative to iron is preferably 0.02%, and more preferably 0.03%. The upper limits for the molar percentage of sodium relative to iron are 0.20%, 0.15%, 0.8%, and 0.05%, with the latter values ​​being more preferable.

[0023] Here, iron, cobalt, aluminum, and sodium are considered to exist in the form of oxides in catalyst A, but the number of moles of each component is calculated based on the total amount of each metal component in all chemical forms.

[0024] In catalyst A, iron, cobalt, aluminum, and sodium exist mainly as oxides when the catalyst is calcined (unreduced) using the catalyst manufacturing method described later, but mainly as metallics when the catalyst is reduced. Furthermore, depending on the manufacturing conditions, usage conditions, and storage conditions, metals and oxides may be mixed and their proportions may change.

[0025] Catalyst A does not need to exist solely in a metallic state, as iron, cobalt, aluminum, and sodium are reduced to metallization during the reaction by the reducing atmosphere, even if they are present as oxides, and thus perform the necessary catalytic function. Note that trace amounts of raw materials (precursors) may remain in catalyst A.

[0026] -Method for producing catalyst A- The method for producing catalyst A is not particularly limited, but examples include hydrothermal synthesis, coprecipitation, homogeneous precipitation, sol-gel method, and flux method. Among these, the method for producing catalyst A using a precipitation method is preferred.

[0027] Specifically, the method for manufacturing catalyst A is: The first step involves obtaining a catalyst support containing iron, cobalt, and aluminum by precipitation, The second step involves supporting sodium on the surface of the catalyst support by impregnation, A method for producing hydrocarbon catalysts is provided, which includes having the above characteristics. This method for producing catalyst A yields a highly active hydrocarbon production catalyst that can significantly increase the productivity of LPG, particularly LPG composed of propane and butane.

[0028] --First step-- In the first step, a catalyst support containing iron, cobalt, and aluminum is obtained. Specifically, in the first step, a mixture of iron compounds, cobalt compounds, and aluminum compounds, which serve as raw materials (precursors), is brought into contact with a base to obtain a precipitate. The obtained precipitate is then washed, dried, and calcined to obtain a metal oxide to serve as a catalyst support.

[0029] Either homogeneous precipitation or coprecipitation is acceptable as the precipitation method. The homogeneous precipitation method is a precipitation method that uses urea as a precipitant. In the homogeneous precipitation method, an aqueous solution of a metal precursor and urea is heated, and the ammonia gas generated by the hydrolysis of urea acts as a base to obtain a precipitate. In the coprecipitation method, a precipitate is obtained by dropwise contact between an aqueous solution of a metal precursor and an aqueous solution of a base, while maintaining a constant pH. There are no restrictions on the base, but examples include sodium carbonate, potassium carbonate, sodium hydroxide, and potassium hydroxide.

[0030] In the precipitation method, iron compounds, cobalt compounds, and aluminum compounds used as raw materials (precursors) are all subjected to drying and reduction treatment of the precipitate after precipitation, or drying, calcination and reduction treatment, when counterions (for example, in the case of iron nitrate, (NO3) in Fe(NO3)2) - There are no particular restrictions on the compound as long as it is a compound that volatilizes and is soluble in a solvent. Specifically, iron compounds, cobalt compounds, and aluminum compounds can be used in the form of nitrates, carbonates, acetates, chlorides, acetylacetonates, etc. Alternatively, hydrates of nitrates, carbonates, acetates, and chlorides may be used for iron compounds, cobalt compounds, and aluminum compounds. From the viewpoint of reducing manufacturing costs and ensuring a safe manufacturing environment, it is preferable to use water-soluble compounds for the iron, cobalt, and aluminum compounds, which can be used in aqueous solutions during the precipitation process. In particular, using iron nitrate or iron acetate as the iron compound, cobalt compound, and aluminum compound is preferable because they readily convert to iron oxide during calcination, and subsequent reduction treatment of iron oxide, cobalt oxide, and aluminum oxide is also easy.

[0031] --Second step-- In the second step, sodium is supported on the surface of the catalyst support obtained in the first step by impregnation. Specifically, in the second step, for example, the obtained catalyst support (oxide) is impregnated with an aqueous solution of a sodium compound as a raw material (precursor), dried and calcined in a vacuum atmosphere, and sodium is supported on the surface of the catalyst support (oxide).

[0032] Here, the method for supporting sodium on the catalyst is not limited to the impregnation method, but may also be well-known treatment methods such as the incipient wetness method, precipitation method, or ion exchange method. However, since it is preferable to support sodium on the surface of the catalyst (i.e., to support sodium on the surface of the oxide), the impregnation method and the ion exchange method are preferred as methods for supporting sodium on the catalyst support, with the impregnation method being more preferable. When employing the impregnation method to support sodium on the surface of a catalyst support (oxide), it is preferable to irradiate the catalyst support (oxide) with ultrasound after the support operation and before drying or calcination, as this allows the sodium to be uniformly supported on the catalyst support (oxide). Furthermore, during drying after the support operation, drying under a vacuum atmosphere is preferable because it allows the sodium to disperse into the pores of the catalyst support (oxide).

[0033] As for sodium compounds used as raw materials (precursors), when drying and / or calcining treatments are performed after loading, counterions (for example, in the case of sodium nitrate, (NO3) in NaNO3) - There are no particular restrictions on the compound as long as it is a compound that volatilizes and is soluble in a solvent. Specifically, suitable sodium compounds include nitrates, carbonates, acetates, chlorides, and acetylacetonates. From the perspective of reducing manufacturing costs and ensuring a safe manufacturing environment, it is preferable to use a water-soluble compound of sodium that can be used in aqueous solution during the loading operation. In particular, using sodium nitrate or sodium acetate as the sodium is preferable because it readily changes to iron oxide during calcination, and the subsequent reduction treatment of sodium oxide is also easy.

[0034] Catalyst A is obtained through the above process. The catalyst A obtained through the above process is an oxide-based compound, but it may be subjected to a reduction treatment as a post-treatment. By increasing the temperature or duration of the reduction process, the reduction conditions become more stringent. This increases the proportion of metal compounds in catalyst A that are reduced from oxide to metallic after the reduction process. With extremely stringent reduction treatment, it is even possible to reduce the catalyst to a state consisting solely of active metals. However, under typical reduction conditions, catalyst A often ends up in a chemical state containing some iron oxide, cobalt oxide, aluminum oxide, and sodium oxide.

[0035] Catalyst A, after the reduction treatment, should be handled in a way that prevents it from being exposed to air and subsequently oxidized and deactivated. A stabilization treatment that isolates the iron metal surface of the catalyst from the atmosphere is preferable, as it allows for handling of catalyst A in the atmosphere. Stabilization treatments include passivation, which involves exposing the catalyst to nitrogen, carbon dioxide, or an inert gas containing low concentrations of oxygen to oxidize only the outermost layer of the active metal on the catalyst surface; and, in the case of reactions producing hydrocarbons using carbon dioxide and hydrogen as raw materials, which are carried out in the liquid phase, treatments such as immersion in a reaction solvent or molten wax to isolate the catalyst from the atmosphere. However, the appropriate stabilization treatment should be performed depending on the situation.

[0036] (Outer shell) The outer shell contains zeolite. The outer shell may contain components other than zeolite. However, the proportion of zeolite in the outer shell is preferably 90% by mass or more, and more preferably 95% by mass or more. Other components besides zeolite include silica, alumina, and zirconia.

[0037] Both natural and synthetic zeolites can be used. Examples of zeolites include H-ZSM-5 zeolite, SAPO-11 zeolite, NaY zeolite, and MCM-22 zeolite. Among these, from the viewpoint of improving the productivity of saturated hydrocarbons having 3 to 4 carbon atoms, the zeolite is preferably one in which the molar ratio of SiO2 to Al2O3 (SiO2 / Al2O3) is 200 or less (preferably 20 to 150), and SAPO-11 zeolite is preferred, with SAPO-11 zeolite being more preferred.

[0038] Here, H-ZSM-5 zeolite refers to a proton-exchange aluminosilicate zeolite whose skeletal structure code is ZSM-5 (Zeolite Socony Mobil-5). Aluminosilicate zeolite with a skeleton structure code of type ZSM-5 (Zeolite Socony Mobil-5) that has not undergone proton exchange is called "ZSM-5 zeolite". SAPO-11 zeolite is a porous silicoaluminophosphate molecular sieve composed of AlO4, PO4, and SiO4. NaY zeolite is a sodium-type aluminosilicate zeolite composed of NaO, Al2O3, and SiO2. MCM-22 zeolite is an aluminosilicate zeolite whose skeletal structure code is of the MCM-22 type.

[0039] The mass ratio of zeolite to catalyst A is preferably 0.1 to 2.0. It is presumed that if the mass ratio of zeolite is 0.1 or higher, the olefin produced by catalyst A will be effectively converted to paraffin by the acid sites of the zeolite, and sufficient LPG productivity will be obtained. When the mass ratio of zeolite is 2.0 or less, the excess zeolite suppresses the progression of side reactions and the relative decrease in the selectivity of hydrocarbons with 3 to 4 carbon atoms. Furthermore, the coating process on catalyst A is more likely to succeed. Therefore, when the mass ratio of zeolite is within the above range, the olefin produced by catalyst A is more easily converted to paraffin, and the productivity of LPG tends to improve. The lower limit of the zeolite mass ratio is more preferably 0.2, and even more preferably 0.3. The upper limit of the zeolite mass ratio is more preferably 1.0, and even more preferably 0.8 or less.

[0040] The mass ratio of zeolite to catalyst A is calculated from the proportion of each crystalline phase, determined by Rietveld analysis using XRD measurement data.

[0041] (Adhesive part) Preferably, the core and the outer shell (i.e., catalyst A and zeolite) are bonded together by an adhesive portion interposed between the core and the outer shell. Specifically, for example, it is preferable that the core and the outer shell (i.e., catalyst A and zeolite) are bonded together with colloidal silica. Colloidal silica includes, for example, amorphous silica particles having an average primary particle size of 1 to 300 nm (preferably 1 to 300 nm).

[0042] The mass ratio of colloidal silica to catalyst A is preferably 0.1 to 1.0. When the mass ratio of colloidal silica is 0.1 or higher, it acts appropriately as an adhesive, making it easier for the zeolite to coat the surface of catalyst A. When the mass ratio of colloidal silica is 1.0 or less, the excess colloidal silica suppresses the uneven adhesion of zeolite to the surface of catalyst A, or the formation of areas that are not covered, making it easier to successfully coat catalyst A. Therefore, when the mass ratio of colloidal silica is within the above range, the olefin produced by catalyst A is more easily converted to paraffin, and the productivity of saturated hydrocarbons with 3 to 4 carbon atoms (LPG) is more easily improved. The lower limit of the mass ratio of colloidal silica is more preferably 0.2, and even more preferably 0.4 or higher. The upper limit of the mass ratio of colloidal silica is more preferably 0.8, and even more preferably 0.6 or less.

[0043] (Catalyst composition) The catalyst of the present invention includes, for example, a catalyst in which granular zeolite with an average particle size of 1 to 20 μm is attached to the surface of a core with an average particle size of 5 to 100 μm, either directly or via an adhesive portion (for example, colloidal silica with an average primary particle size of 1 to 300 nm), thereby forming an outer shell. The core portion may be composed of a single granular catalyst A, or it may be composed of aggregates of multiple granular catalysts A. Here, the average particle size of the core, the average particle size of the zeolite, and the average primary particle size of the colloidal silica are determined by measuring the equivalent circle diameters of 100 circles of the core and zeolite, and the equivalent circle diameters of 100 primary particles of colloidal silica, when observed with a scanning electron microscope, and taking the arithmetic mean of the obtained equivalent circle diameters.

[0044] (Method of manufacturing a catalyst) One method for producing the catalyst of the present invention is to coat the catalyst A, which will be the core, with a zeolite, which will be the outer shell. The method of coating is not particularly limited, but examples include hydrothermal synthesis and physical coating. Among these, the preferred method for producing the catalyst of the present invention is a method in which a zeolite forming the outer shell is coated onto the catalyst A forming the core by a physical coating method. In a method for producing catalysts by physical coating, one example is the use of colloidal silica as the adhesive (i.e., bonding agent) between catalyst A and zeolite. Specifically, for example, a colloidal silica aqueous dispersion is added to a mixture of granular catalyst A and granular zeolite and stirred. The resulting dispersion is then dried and calcined to obtain the catalyst of the present invention, in which catalyst A is coated with zeolite via colloidal silica. In other words, the catalyst of the present invention is obtained in which a zeolite-containing outer shell is bonded to a core containing catalyst A by an adhesive portion made of colloidal silica.

[0045] (Method of manufacturing hydrocarbons) Next, a method for producing hydrocarbons by reacting carbon dioxide and hydrogen using the catalyst of the present invention will be described. The present invention provides a method for producing hydrocarbons by contacting a mixed gas containing carbon dioxide and hydrogen with a hydrocarbon production catalyst.

[0046] The present invention may also be a method for producing hydrocarbons, comprising a first step (hereinafter also referred to as the "FT synthesis step") in which a mixed gas containing carbon dioxide and hydrogen is brought into contact with a hydrocarbon production catalyst, and a second step (hereinafter referred to as the "cracking reaction step") in which the mixture containing the hydrocarbons obtained in the first step is brought into contact with a decomposition catalyst made of zeolite to decompose it.

[0047] -FT synthesis process- In the FT synthesis process, there are no particular restrictions on the reaction conditions, but good results tend to be obtained when the reaction temperature is 250-400°C and the reaction pressure is 1.0-6.0 MPa.

[0048] When the reaction temperature is 250°C or higher, sufficient catalytic activity is more likely to be exhibited. When the reaction temperature is below 400°C, the selectivity of by-products such as methane increases, the decrease in catalyst life is suppressed, and the productivity of hydrocarbons with 3 to 4 carbon atoms tends to improve. Therefore, the reaction temperature is preferably set in the range of 250 to 400°C, and more preferably in the range of 280 to 330°C.

[0049] When the reaction temperature or pressure is low, the catalytic reaction proceeds slowly, resulting in a tendency for a low carbon dioxide conversion rate. Because the hydrocarbon chain growth proceeds slowly, short-chain hydrocarbons are more easily produced, and the selectivity for hydrocarbons with 3 to 4 carbon atoms tends to be high. Higher reaction temperatures or pressures tend to result in more vigorous catalytic reactions and thus a higher carbon dioxide conversion rate. Rapid hydrocarbon chain growth also facilitates the formation of long-chain hydrocarbons, while the selectivity for hydrocarbons with 3-4 carbon atoms tends to be lower. Furthermore, high reaction temperatures promote hydrocarbon decomposition, leading to the formation of by-products such as methane.

[0050] Therefore, there is a trade-off between the carbon dioxide conversion rate and the selectivity of hydrocarbons with 3 to 4 carbon atoms. By controlling the reaction temperature or pressure within a certain range, hydrocarbons with 3 to 4 carbon atoms can be obtained with high productivity.

[0051] In the FT synthesis process, the reaction pressure is preferably 1.0 to 6.0 MPa. When the reaction pressure is 1.0 MPa or higher, sufficient catalytic activity is more likely to be exhibited. If the reaction pressure is 6.0 MPa or less, it becomes possible to avoid setting a high pressure resistance design for the plant, which helps to reduce equipment costs. Therefore, it is preferable to set the reaction pressure within the above range.

[0052] In the FT synthesis process, the reaction mode can be selected from fixed bed, slurry bed, moving bed, etc., depending on the reaction conditions, and is not particularly limited. However, from the viewpoint of catalytic activity, it is preferable to set the reaction temperature above 250°C, and therefore a fixed bed is preferable. In a slurry bed, it is preferable that a solvent that becomes liquid under the reaction conditions is produced by the reaction, but at reaction temperatures above 250°C, most hydrocarbons are gaseous, making it difficult to maintain the reaction in a slurry bed. Therefore, it is preferable to use a fixed bed as the reaction method and react carbon dioxide and hydrogen under a catalyst to produce hydrocarbons.

[0053] When a fixed bed reactor is used, it is preferable to mold the catalyst into a pellet shape, taking into account the pressure loss within the reactor.

[0054] In the case of relatively small-scale plants that have a hydrocarbon conversion plant attached to a carbon dioxide emission source, microchannel reactors may be advantageous. However, considering that the catalyst is packed into a channel on the order of millimeters or less, a catalyst particle size of about 20 to 250 μm is preferable.

[0055] In the cracking reaction step, the hydrocarbon mixture obtained in the FT synthesis step is brought into contact with a decomposition catalyst made of zeolite and undergoes catalytic decomposition. In the cracking reaction step, the decomposition catalyst does not convert carbon dioxide, so the carbon dioxide conversion rate remains almost unchanged between the FT synthesis step and the cracking reaction step. On the other hand, by performing catalytic cracking in the cracking reaction process, the selectivity of hydrocarbons having 3 to 4 carbon atoms is improved, and the productivity of hydrocarbons having 3 to 4 carbon atoms is increased.

[0056] In the cracking reaction process, both natural and synthetic zeolites can be used as the decomposition catalyst. However, from the viewpoint of improving the productivity of hydrocarbons with 3 to 4 carbon atoms, it is preferable to use H-ZSM-5 zeolite, which is obtained by ion exchange of ZSM-5 type zeolite with protons. Here, H-ZSM-5 zeolite refers to a proton-exchange aluminosilicate zeolite whose skeletal structure code is ZSM-5 (Zeolite Socony Mobil-5). Aluminosilicate zeolite with a skeleton structure code of type ZSM-5 (Zeolite Socony Mobil-5) that has not undergone proton exchange is called "ZSM-5 zeolite". The ZSM-5 type zeolite has a molar ratio of SiO2 to Al2O3 (SiO2 / Al2O3) that is preferably 20 to 1500, more preferably 50 to 300, and even more preferably 100 to 300.

[0057] In the cracking reaction process, the reaction conditions are not particularly limited, but it is preferable that the reaction temperature be 300 to 600°C and the reaction pressure be atmospheric pressure (0.1 MPa).

[0058] When the reaction temperature is 300°C or higher, sufficient decomposition catalytic activity is more likely to be exhibited. When the reaction temperature is below 600°C, the selectivity of by-products such as methane increases, the decrease in catalyst life is suppressed, and the productivity of hydrocarbons with 3 to 4 carbon atoms tends to improve. Therefore, it is preferable to set the reaction temperature in the range of 300 to 600°C.

[0059] When the reaction pressure is atmospheric pressure (0.1 MPa), sufficient catalytic activity is easily achieved, and the pressure resistance design of the plant can be simplified, thus reducing equipment costs. Therefore, it is preferable to set the reaction pressure within the atmospheric pressure range.

[0060] In the cracking reaction process, the reaction method can be selected from a fixed bed, slurry bed, moving bed, etc., depending on the reaction conditions, and is not particularly limited. However, from the viewpoint of catalytic activity, it is preferable to set the reaction temperature above 300°C, and a fixed bed is preferable. In a slurry bed, it is preferable that a solvent that becomes liquid under the reaction conditions is produced by the reaction, but at reaction temperatures above 300°C, most hydrocarbons are gaseous, making it difficult to maintain the reaction in a slurry bed. Therefore, it is preferable to use a fixed bed and catalytic decomposition as the reaction method.

[0061] When a fixed bed reactor is used, it is preferable to mold the catalyst into a pellet shape, taking into account the pressure loss within the reactor.

[0062] In the catalyst production method of the present invention, favorable results are likely to be obtained when the mass ratio (mass of hydrocarbon production catalyst / mass of decomposition catalyst) of the hydrocarbon production catalyst in the FT synthesis step to the decomposition catalyst in the cracking reaction step is 0.1 to 10.0. When the hydrocarbon production catalyst and the decomposition catalyst have a ratio of 0.1 or higher, catalytic decomposition activity is more likely to be sufficiently expressed, and the selectivity of hydrocarbons with 3 to 4 carbon atoms tends to improve. When the hydrocarbon production catalyst and decomposition catalyst are below 10.0, it becomes easier to suppress the increase of by-products such as methane due to excessive catalytic cracking. Therefore, it is preferable to set the mass ratio of the hydrocarbon production catalyst to the decomposition catalyst within the above range.

[0063] In the hydrocarbon production method of the present invention, the mixed gas of carbon dioxide and hydrogen used as the reaction gas (i.e., raw material gas) is preferably a gas in which the total amount of carbon dioxide and hydrogen is 50% or more by volume, from the viewpoint of productivity, and in particular, the molar ratio of hydrogen to carbon dioxide (hydrogen / carbon dioxide) is preferably in the range of 0.5 to 4.0. This is because when the molar ratio of hydrogen to carbon dioxide is 0.5 or higher, the amount of hydrogen present in the raw material gas is sufficient, so the hydrogenation reaction of carbon dioxide proceeds easily and productivity is high. On the other hand, when the molar ratio of hydrogen to carbon dioxide is 4.0 or lower, the amount of carbon dioxide present in the raw material gas is sufficient, so in combination with the high activity of the catalyst according to the present invention, hydrocarbon productivity is high. [Examples]

[0064] (Comparative Examples 1 and 2) Using a coprecipitation method, an oxide containing iron, cobalt, and aluminum was synthesized, and then, by impregnation, sodium was supported on the oxide to obtain catalyst A. Specifically, the procedure is as follows. As raw materials (precursors), iron nitrate hydrate, cobalt nitrate hydrate, and aluminum nitrate hydrate were dissolved in aqueous solutions, and a sodium carbonate aqueous solution was added as a precipitating agent to precipitate the complex hydroxide. After that, with the complex oxide settled, it was aged at 80°C for 4 hours, dried at 120°C for 12 hours, and calcined at 400°C for 4 hours to obtain iron oxide. Subsequently, catalyst A was obtained by impregnating the iron oxide with a solution containing sodium nitrate, drying at 120°C for 12 hours, and calcining at 400°C for 4 hours. However, the amounts of cobalt nitrate hydrate, aluminum nitrate hydrate, and sodium nitrate were adjusted so that the molar percentages of cobalt, aluminum, and sodium relative to iron in the resulting catalyst were as shown in Table 1.

[0065] (Examples 1-12) The surface of catalyst A, prepared as described above, was coated with one of the following zeolites—H-ZSM-5 zeolite (SiO2 / Al2O3=24, 105, or 1100), MCM-22 zeolite, NaY zeolite, or SAPO-11 zeolite—by physical coating, according to Table 1. Specifically, the following was performed. With a mass ratio of zeolite to catalyst A of 0.4 and a mass ratio of colloidal silica to catalyst A of 0.4, a 40% by mass aqueous solution of colloidal silica was added to a mixture of catalyst A and zeolite and stirred. Subsequently, the catalyst was obtained by drying at 120°C for 12 hours and calcining at 400°C for 4 hours. Upon examination, it was found that the obtained catalyst consisted of a core containing catalyst A, with an outer shell containing zeolite attached to the core surface via an adhesive portion made of colloidal silica.

[0066] (Catalyst evaluation in the FT synthesis process: Examples 1-6, Comparative Example 1) The catalysts shown in Table 1 were evaluated for their catalytic performance using a fixed-bed flow reactor. Specifically, the results are as follows: The catalysts shown in Table 1 were packed into a reaction tube. Pure hydrogen was passed through the reaction tube packed with catalysts, and reduction treatment was carried out at atmospheric pressure and 400°C for 6 hours. Subsequently, the reaction gas (H2 / CO2=3.0) was passed through at W (catalyst mass) / F (synthesis gas flow rate); (g·h / mol)=5.0, and the reaction was held at 330°C and 3.0 MPa for 6 to 24 hours. The gas after the reaction was analyzed using gas chromatography (GC).

[0067] (Catalyst evaluation for FT synthesis and cracking reaction steps: Examples 7-12, Comparative Example 2) The catalysts shown in Table 1 (catalysts for FT synthesis) were evaluated for their catalytic performance using a fixed-bed flow reactor. Specifically, the results are as follows: The catalysts shown in Table 1 (catalyst for FT synthesis) and the catalyst for the cracking reaction (decomposition catalyst) were packed into their respective reaction tubes. The reaction tubes for the FT synthesis process and the cracking reaction process were connected in series, and the reaction temperature and pressure were controlled separately for each. The FT synthesis catalyst was pre-treated by flowing pure hydrogen through the reaction tube and reducing it at atmospheric pressure and 400°C for 6 hours. The reaction gas (H2 / CO2=3.0) was flowed at W (catalyst mass) / F (synthesis gas flow rate); (g·h / mol)=7.5, and the FT synthesis process was maintained at 285~340°C and 0.1~3.0 MPa, while the cracking reaction process was maintained at 500°C and 0.1 MPa for 6~24 hours. The gases after the reaction were analyzed using gas chromatography (GC).

[0068] (Reaction characteristics) [CO2 conversion rate, CO selectivity, selectivity for each hydrocarbon, olefin / paraffin ratio of C3-C4 hydrocarbons, LPG yield] In catalyst evaluation, the composition of the supply gas and the reaction gas (outlet gas) was determined by gas chromatography, and the following reaction characteristics were calculated. CO2 conversion rate • CO selection rate • Selectivity for hydrocarbons with one carbon atom (methane) (referred to as "C1 selectivity") • Selectivity of hydrocarbons with 2 carbon atoms (denoted as "C2 selectivity") • Selectivity of hydrocarbons with 3-4 carbon atoms ("C 3-4 (Represented as "selection rate") • Selectivity of hydrocarbons with 5 or more carbon atoms ("C 5+ (Represented as "selection rate") • Olefin / paraffin ratio of hydrocarbons with 3-4 carbon atoms ("C 3-4 (Written as "OP / P") • Paraffin yield of hydrocarbons with 3-4 carbon atoms (indicated as "LPG yield")

[0069] The CO2 conversion rate, selectivity, olefin / paraffin ratio, and LPG yield were calculated based on the following formula. In the formula, C 3-4 The selectivity (%) of paraffin indicates the olefin / paraffin ratio.

[0070]

number

[0071] [Table 1-1]

[0072] [Table 1-2]

[0073] From the above results, it can be seen that the catalyst of this example is a highly active hydrocarbon production catalyst that can increase the productivity of LPG composed of propane and butane compared to the catalyst of the comparative example.

Claims

1. A core containing catalyst A, which includes iron, cobalt, aluminum, and sodium, An outer shell portion formed on the core portion and containing zeolite, A hydrocarbon production catalyst.

2. The aforementioned zeolite is Al ２ O ３ SiO ２ Molar ratio (SiO ２ / Al ２ O ３ The hydrocarbon production catalyst according to claim 1, wherein the ) is at least one of H-ZSM-5 zeolite and SAPO-11 zeolite with a value of 200 or less.

3. The zeolite is Al ２ O ３ The molar ratio of SiO to Al ２ (SiO ２ / Al ２ O ３ ) is 20 to 150 H-ZSM-5 zeolite, and the hydrocarbon production catalyst according to claim 1.

4. The hydrocarbon production catalyst according to claim 1, wherein the zeolite is SAPO-11 zeolite.

5. The hydrocarbon production catalyst according to claim 1, wherein the core portion and the outer shell portion are bonded together with colloidal silica.

6. A method for producing hydrocarbons using a hydrocarbon production catalyst according to any one of claims 1 to 5, A method for producing hydrocarbons, comprising contacting a mixed gas containing carbon dioxide and hydrogen with the hydrocarbon production catalyst to produce hydrocarbons.

7. A method for producing hydrocarbons using a hydrocarbon production catalyst according to any one of claims 1 to 5, A first step involves contacting a mixed gas containing carbon dioxide and hydrogen with the hydrocarbon production catalyst, A second step involves contacting the hydrocarbon mixture obtained in the first step with a decomposition catalyst made of zeolite to decompose it, A method for producing hydrocarbons, comprising the same characteristics.

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