Hydrocarbon production catalyst, method for producing hydrocarbon production catalyst, and method for producing hydrocarbon

Abstract

To provide a highly active hydrocarbon production catalyst enabling an increased carbon dioxide conversion rate and enhanced productivity of hydrocarbons having 3 to 4 carbon atoms, a method for producing the hydrocarbon production catalyst, and a method for producing hydrocarbons using the hydrocarbon production catalyst.SOLUTION: The present invention provides a hydrocarbon production catalyst that includes iron as a main component, cobalt, at least one cocatalyst X selected from the group consisting of aluminum, chromium, gallium, and zinc, and sodium, a method for producing the hydrocarbon production catalyst, and a method for producing hydrocarbons using the hydrocarbon production catalyst.SELECTED DRAWING: None

Description

Technical Field

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

Background Art

[0002] In recent years, environmental problems such as global warming have become apparent. Compared with other hydrocarbon fuels and coal, natural gas has a high H / C ratio, can suppress the emission of carbon dioxide, which is a cause of global warming, and has rich reserves. Therefore, the importance of natural gas has been reevaluated, and its demand is expected to increase in the future. Under such circumstances, various efforts are being made to convert natural gas into synthesis gas and then produce hydrocarbons using the Fischer-Tropsch synthesis reaction from the synthesis gas.

[0003] For example, Patent Document 1 discloses "a hydrocarbon production catalyst comprising a compound having, as a metal component, iron, sodium, and at least one selected from the group consisting of zinc, manganese, and copper".

[0004] Further, Patent Document 2 discloses "a catalyst for obtaining a high-carbon α-olefin by carbon dioxide hydrogenation, characterized in that the catalyst contains Fe, and as a composite metal oxide catalyst of an alkali metal and other metals, the molar ratio of Fe to the metal is 1:1 to 1:0.05, so that the mass fraction in the alkali metal catalyst is 0.01% to 15%, and the alkali metal contains one or more of Na, K, and Rb, and the other metal contains one or more of Mn, Zn, Cu, and Co".

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

[0006] However, including Patent Documents 1 to 2, the production of hydrocarbons from carbon dioxide and hydrogen has a problem in that the one-pass conversion rate is low due to the stability of carbon dioxide. In particular, in the production of hydrocarbons, a catalyst is generally used, but there is room for improvement in the catalyst for producing hydrocarbons having 3 to 4 carbon atoms used as LPG with high efficiency.

[0007] Also, generally speaking, the higher the activity of the catalyst, the more preferable it is. This is because the productivity per unit weight of the catalyst increases, so that the size of the reactor can be reduced to suppress the equipment cost, and also because the amount of catalyst used can be reduced to suppress the catalyst cost. Therefore, the high activation of the catalyst is a very important factor.

[0008] Therefore, an object of the present invention is to provide a highly active hydrocarbon production catalyst capable of increasing the carbon dioxide conversion rate and also increasing the productivity of hydrocarbons having 3 to 4 carbon atoms in the production of hydrocarbons 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 Problems

[0009] The means for solving the problems include the following aspects. <1> A hydrocarbon production catalyst containing iron as a main component, cobalt, at least one promoter X selected from the group consisting of aluminum, chromium, gallium, and zinc, sodium, and. <2> The hydrocarbon production catalyst according to <1>, wherein the promoter X contains at least aluminum. <3> The hydrocarbon production catalyst according to <1> or <2>, wherein the molar percentage of sodium with respect to the iron is 0.01 to 0.30%. <4> The hydrocarbon production catalyst according to <1> or <2>, wherein the molar percentage of sodium with respect to the iron is 0.01 to 0.15%. <5> The hydrocarbon production catalyst according to any one of <1> to <4>, wherein the molar percentage of the promoter X with respect to the iron is 0.1 to 20.0%. <6> The hydrocarbon production catalyst according to any one of <1> to <4>, wherein the molar percentage of the promoter X with respect to the iron is 1.0 to 12.0%. <7> The hydrocarbon production catalyst according to any one of <1> to <6>, wherein the molar percentage of cobalt with respect to the iron is 1.0 to 120.0%. <8> A first step of obtaining a catalyst support containing iron, cobalt, and at least one promoter X selected from the group consisting of aluminum, chromium, gallium, and zinc by a precipitation method; A second step of supporting sodium on the surface of the catalyst support by an impregnation method; A method for producing a hydrocarbon production catalyst, comprising: <9> A method for producing a hydrocarbon using the hydrocarbon production catalyst according to any one of <1> to <7>, wherein a mixed gas having carbon dioxide and hydrogen is brought into contact with the hydrocarbon production catalyst to produce a hydrocarbon. <10> A method for producing a hydrocarbon using the hydrocarbon production catalyst according to any one of <1> to <7>, comprising a first step of bringing a mixed gas having carbon dioxide and hydrogen into contact with the hydrocarbon production catalyst; and a second step of decomposing a mixture containing the hydrocarbon obtained in the first step by bringing it into contact with a decomposition catalyst made of zeolite. A method for producing a hydrocarbon, comprising: <11> The method for producing a hydrocarbon according to <10>, wherein the zeolite is H-ZSM-5 zeolite.

Advantages of the Invention

[0010] According to the present invention, there can be provided a highly active hydrocarbon production catalyst capable of increasing the carbon dioxide conversion rate and also increasing the productivity of hydrocarbons having 3 to 4 carbon atoms in the production of hydrocarbons using carbon dioxide and hydrogen as raw materials, a method for producing the hydrocarbon production catalyst, and a method for producing a hydrocarbon using the hydrocarbon production catalyst.

Embodiments for Carrying Out the Invention

[0011] Hereinafter, the present invention will be described. In the present specification, a numerical range represented by "~" means a range including the numerical values described before and after "~" as a lower limit value and an upper limit value. In a numerically defined range described stepwise, 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 another numerically defined range described stepwise. 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 a step that cannot be clearly distinguished from other steps, as long as the intended purpose of the step is achieved. "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 "catalyst".

[0013] <Hydrocarbon production catalyst> The hydrocarbon production catalyst of the present invention contains iron as a main component, Cobalt, at least one promoter X selected from the group consisting of aluminum, chromium, gallium, and zinc, sodium, and contains.

[0014] Due to the above configuration, the catalyst of the present invention can be a highly active catalyst that increases the carbon dioxide conversion rate and also increases the productivity of hydrocarbons having 3 to 4 carbon atoms in the production of hydrocarbons using carbon dioxide and hydrogen as raw materials. The reason is presumed as follows. By including cobalt, sodium, and promoter X (at least one selected from the group consisting of aluminum, chromium, gallium, and zinc) as promoters in a catalyst mainly composed of iron, the chain growth of hydrocarbons is promoted, and the yield of hydrocarbons having 3 to 4 carbon atoms increases. In particular, cobalt as a promoter promotes the reaction by acting as an active site itself in addition to the active sites of iron, and the hydrocarbons produced by cobalt with high hydrogenation ability shift to the short-chain side. In addition, aluminum, chromium, gallium, and zinc as promoter X promote the reaction of raw materials by improving the dispersibility of iron, which is an active site. Further, when promoter X coexists in addition to cobalt and sodium as promoters, in an atmosphere of carbon dioxide and hydrogen, the formation of iron carbide, which is an active species of the Fischer-Tropsch synthesis reaction, is promoted, the conversion rate of carbon dioxide is improved, and as a result, the yield of hydrocarbons having 3 to 4 carbon atoms increases. Therefore, it is presumed that the catalyst of the present invention can be a highly active catalyst that increases the carbon dioxide conversion rate and also increases the productivity of hydrocarbons having 3 to 4 carbon atoms in the production of hydrocarbons using carbon dioxide and hydrogen as raw materials.

[0015] Hereinafter, the details of the catalyst of the present invention will be described.

[0016] (Components of the catalyst) The catalyst of the present invention contains iron as the main component, and in addition to cobalt and sodium, it contains a promoter X. Specifically, the catalyst of the present invention has sodium supported, for example, on a catalyst carrier containing iron, cobalt, and promoter X. However, the catalyst of the present invention may contain a small amount of impurities in addition to iron, cobalt, sodium, and promoter X. Here, the "catalyst containing iron as the main component" means that the iron content is 30% by mass or more (preferably 45% by mass or more, more preferably 60% by mass or more, even more preferably 80% by mass or more) with respect to all components of the catalyst excluding oxygen. The number of moles or mass of each component (iron, cobalt, promoter X, sodium, impurities) contained in the catalyst is measured by the ICP - AES method after subjecting the catalyst to pretreatment such as acid decomposition and alkali fusion.

[0017] The promoter X is selected from the group consisting of aluminum, chromium, gallium, and zinc. Since the effect of promoting the dispersion of iron, which is the active site, is highest in aluminum, aluminum is preferred. That is, the catalyst of the present invention preferably contains at least aluminum as the promoter X. Also, it is preferable that the promoter X contains only aluminum. Also, a plurality of types of promoter X may be mixed.

[0018] The molar percentage of promoter X with respect to iron is preferably 0.1 - 20.0%. When the molar percentage of promoter X is 0.1% or more, due to the action of promoter X as a promoter, the dispersion degree of iron, which is the active site, increases, and the reaction of the raw material is promoted. When the molar percentage of promoter X is 20.0% or less, the relative decrease in the content of iron, which is the active species, is suppressed. Therefore, when the molar percentage of promoter X is within the above range, the catalyst is easily highly activated, and the carbon dioxide conversion rate and the productivity of hydrocarbons having 3 to 4 carbon atoms are easily improved. The lower limit value of the molar percentage of promoter X with respect to iron is more preferably 1.0% or more, or 2.0% or more. The upper limit value of the molar percentage of promoter X with respect to iron is more preferably 15.0% or less, or 12.0% or less. In particular, the molar percentage of promoter X with respect to iron is preferably 1.0 to 12.0%, more preferably 2.0 to 12.0%.

[0019] The molar percentage of cobalt with respect to iron is preferably 0.1 to 120.0%. When the molar percentage of cobalt is 0.1% or more, the function as an active site of cobalt itself is enhanced, and the hydrocarbons produced by cobalt with high hydrogenation ability shift to the short-chain side, and hydrocarbons having 3 to 4 carbon atoms are easily produced. When the molar percentage of cobalt is 120.0% or less, the relative decrease in the content of iron as an active species is suppressed. Further, it is difficult to form a stable iron-cobalt compound, and the inhibition of the formation of FT reaction active sites is suppressed. Therefore, when the molar percentage of cobalt is within the above range, the catalyst is easily highly activated, and the carbon dioxide conversion rate and the productivity of hydrocarbons having 3 to 4 carbon atoms are easily improved. The lower limit of the molar percentage of cobalt with respect to iron is more preferably 1.0% or more, 5.0% or more, 8.0%, or 10.0% or more. The higher the molar percentage of cobalt with respect to iron, the higher the productivity of hydrocarbons having 3 to 4 carbon atoms, but the catalyst cost increases due to the increase in the amount of cobalt. Therefore, the upper limit of the molar percentage of cobalt is more preferably 55.0% or less, 50.0% or less, 20% or less, or 15% or less.

[0020] The molar percentage of sodium with respect to iron is preferably 0.01 to 0.30%. When the molar percentage of sodium is 0.01% or more, the basicity of the catalyst surface is improved, and it is presumed that the formation of iron carbide presumed to be an active species of iron is promoted and the adsorption of carbon dioxide as a raw material gas to the catalyst surface is promoted. When the molar percentage of sodium is 0.30% or less, the relative decrease in the content of iron as an active species is suppressed. Therefore, when the molar percentage of sodium is within the above range, the catalyst is easily highly activated, and the carbon dioxide conversion rate and the productivity of hydrocarbons having 3 to 4 carbon atoms are easily improved. The lower limit of the molar percentage of sodium with respect to iron is more preferably 0.02% or more, or 0.03% or more. The upper limit of the molar percentage of sodium with respect to iron is preferably 0.20% or less, 0.15% or less, 0.8% or less, or more preferably 0.05%. In particular, the molar percentage of sodium with respect to iron is preferably 0.01 to 0.15%.

[0021] Here, although iron, cobalt, promoter X, and sodium are considered to be in the form of oxides in the catalyst, the number of moles of each component is calculated for each metal component obtained by summing up all chemical forms.

[0022] In the catalyst of the present invention, iron, cobalt, promoter X, and sodium mainly exist as oxides in the state where the catalyst is calcined (unreduced state) by the catalyst production method described below, but mainly exist in the metallic state in the state where the catalyst is reduced. Also, depending on the production conditions, use conditions, storage state, etc., the metal and the oxide are mixed and the ratio thereof also changes.

[0023] Even when iron, cobalt, promoter X, and sodium exist as oxides in the catalyst of the present invention, they are reduced and metallized during the reaction by the reducing atmosphere during the reaction, and exhibit the necessary catalytic function, so they do not have to exist only in the metallic state. Note that a small amount of the raw material (precursor) may remain in the catalyst.

[0024] (Properties of the catalyst) The average pore diameter of the catalyst of the present invention is preferably 5 to 50 nm. The smaller the average pore diameter, the larger the specific surface area can be. However, when the average pore diameter is 5 nm or more, gas diffusion in the pores is promoted, and hydrogen and carbon dioxide react efficiently. In addition, the diffusion rate of the generated hydrocarbons in the pores also increases, contributing to an increase in the reaction rate. On the other hand, when comparing with a certain pore volume, the larger the average pore diameter, the lower the specific surface area, and the tendency for the dispersion degree of the active metal in the catalyst to decrease. Therefore, the pore diameter is preferably 50 nm or less. The upper limit of the average pore diameter of the catalyst is more preferably 25 nm or less, 15 nm or less, or 10 nm or less.

[0025] To make the average pore diameter of the catalyst of the present invention fall within the above range, in the method for producing the catalyst, a method of obtaining a catalyst support containing iron, cobalt, and promoter X by a precipitation method (particularly the homogeneous precipitation method) can be mentioned.

[0026] The specific surface area of the catalyst of the present invention is preferably 20 to 200 m 2 / g. When the specific surface area of the catalyst is 20 m 2 / g or more, sufficient activity is likely to be exhibited in the reaction for producing hydrocarbons using carbon dioxide and hydrogen as raw materials. Further, the dispersion degree of iron increases, and the contribution efficiency to the reaction improves. When the specific surface area of the catalyst is 200 m 2 / g or less, it becomes easier to simultaneously satisfy the target ranges of the pore volume and the average pore diameter.

[0027] The total pore volume of the catalyst of the present invention is preferably 0.1 to 1.0 mL / g. When the total pore volume of the catalyst is 0.1 to 1.0 mL / g, it becomes easy to simultaneously satisfy the ranges of the average pore diameter and the specific surface area.

[0028] Here, the method for measuring the average pore diameter of the catalyst is to measure the specific surface area (S) and the total pore volume (V) of the catalyst, and use the formula: average pore diameter (nm) = 4 × 10 3 [total pore volume (cm 3 / g) / specific surface area (m 2 / g)] to calculate the average pore diameter. The specific surface area (S) of the catalyst is obtained by obtaining an adsorption isotherm by the nitrogen adsorption method, and calculated by analysis by the BET (Brunauer - Emmett - Teller) method from the obtained adsorption isotherm. The BET specific surface area is calculated by performing BET analysis in the range where the relative pressure of the isotherm during nitrogen gas adsorption is 0.10 to 0.25. The total pore volume (V) of the catalyst is the total volume of pores of all diameters, and the formula: total pore volume (cm 3 / g) = adsorption amount × molecular weight of the adsorbate / (22414 × density of the adsorbate (g / cm 3)(It is) calculated by (this method). The adsorption amount is obtained by linearly interpolating the adsorption data within the relative pressure range set above. As a pretreatment before performing the nitrogen adsorption method, in order to remove the moisture in the pores of the catalyst, the catalyst is heat-treated under vacuum at 150 °C for 2 hours. Also, the measurement temperature of the nitrogen adsorption method is set to 77 K.

[0029] (Method for producing catalyst) The method for producing the catalyst of the present invention is not particularly limited. For example, methods for producing the catalyst using sol-gel method, flux method, such as hydrothermal synthesis, coprecipitation method, homogeneous precipitation method, etc. can be exemplified. Among these, the method for producing the catalyst of the present invention preferably uses a precipitation method to produce the catalyst.

[0030] Specifically, the method for producing the catalyst of the present invention A first step of obtaining a catalyst support containing iron, cobalt, and promoter X (at least one selected from the group consisting of aluminum, chromium, gallium, and zinc) by a precipitation method, A second step of supporting sodium on the surface of the catalyst support by an impregnation method, A method for producing a hydrocarbon production catalyst having these steps can be mentioned. According to this method for producing the catalyst, in particular, a highly active hydrocarbon production catalyst with a high carbon dioxide conversion rate and high productivity of hydrocarbons having 3 to 4 carbon atoms can be obtained.

[0031] - First step - In the first step, a catalyst support containing iron, cobalt, and promoter X is obtained. Specifically, in the first step, a compound containing an iron compound, a cobalt compound, and promoter X (at least one selected from the group consisting of an aluminum compound, a chromium compound, a gallium compound, and a zinc compound) as a raw material (precursor) is brought into contact with a base to obtain a precipitate. The obtained precipitate is washed, dried, and calcined to obtain an iron-based oxide as the catalyst support.

[0032] As the precipitation method, either a homogeneous precipitation method or a coprecipitation method may be used. The homogeneous precipitation method is a precipitation method using urea as a precipitant. In the homogeneous precipitation method, an aqueous solution obtained by mixing a metal precursor and urea is heated, and ammonia gas generated by the hydrolysis of urea acts as a base to obtain a precipitate. In the homogeneous precipitation method, the average pore diameter is easily controlled within the above range, and the catalyst of the present invention is easily obtained. In the coprecipitation method, while dropping and contacting an aqueous solution of a metal precursor and an aqueous solution of a base, the pH is controlled to be constant to obtain a precipitate. Here, there is no limitation on the base, and examples thereof include sodium carbonate, potassium carbonate, sodium hydroxide, potassium hydroxide, and the like.

[0033] In the precipitation method, when the compounds containing an iron compound, a cobalt compound, and a promoter X (at least one of an aluminum compound, a chromium compound, a gallium compound, and a zinc compound) as raw materials (precursors) are each subjected to a drying treatment and a reduction treatment, or a drying treatment, a firing treatment, and a reduction treatment on the precipitate after precipitation, a counter ion (for example, (NO3) in Fe(NO3)2 if it is iron nitrate) - ) is a compound that volatilizes and is not particularly limited as long as it is a compound soluble in a solvent. Specifically, for the compounds containing an iron compound, a cobalt compound, and a promoter X (at least one of an aluminum compound, a chromium compound, a gallium compound, and a zinc compound), nitrates, carbonates, acetates, chlorides, acetylacetonates, etc. can each be used. As the compounds containing an iron compound, a cobalt compound, and a promoter X (at least one of an aluminum compound, a chromium compound, a gallium compound, and a zinc compound), hydrates of nitrates, carbonates, acetates, and chlorides may also be used. From the viewpoints of reducing production costs and ensuring a safe production working environment, it is preferable to use water-soluble compounds that can use an aqueous solution when performing the precipitation operation for the compounds containing an iron compound, a cobalt compound, and a promoter X (at least one of an aluminum compound, a chromium compound, a gallium compound, and a zinc compound), respectively. In particular, when using a ferric nitrate salt or an iron acetate salt as a compound containing an iron compound, a cobalt compound, and a promoter X (at least one of an aluminum compound, a chromium compound, a gallium compound, and a zinc compound), it easily changes to iron oxide during firing, and subsequent reduction treatment of the iron oxide, cobalt oxide, and the oxide of promoter X (at least one of an aluminum oxide, a chromium oxide, a gallium oxide, and a zinc oxide) is also easy, which is preferable.

[0034] -Second step- In the second step, sodium is supported on the surface of the catalyst support by an impregnation method. Specifically, in the second step, for example, the obtained catalyst support (oxide) is subjected to an impregnation treatment with an aqueous solution of a sodium compound as a raw material (precursor), and dried and fired in a vacuum atmosphere to support sodium on the surface of the catalyst support (oxide).

[0035] Here, the method for supporting sodium on the catalyst is not limited to the impregnation method, and well-known treatment methods such as the incipient wetness method, precipitation method, and ion exchange method may also be used. However, since it is preferable to support sodium on the surface of the catalyst (that is, sodium is supported on the surface of the oxide), as a method for supporting sodium on the catalyst support, the impregnation method and the ion exchange method are preferable, and the impregnation method is more preferable. When the impregnation method is adopted as a method for supporting sodium on the surface of the catalyst support (oxide), if ultrasonic waves are irradiated on the catalyst support (oxide) with sodium supported on the surface before drying or firing after the supporting operation, sodium can be uniformly supported on the catalyst support (oxide), which is preferable. Also, when drying after the supporting operation, drying in a vacuum atmosphere is preferable because sodium is dispersed into the pores of the catalyst support (oxide).

[0036] As the sodium compound as a raw material (precursor), when performing a drying treatment and / or a firing treatment after loading, a counter ion (for example, (NO3) in NaNO3 if it is sodium nitrate) -) is a compound that volatilizes, and there is no particular limitation as long as it is a compound soluble in a solvent. Specifically, as the sodium compound, nitrates, carbonates, acetates, chlorides, acetylacetonates, etc. can be used. From the viewpoint of reducing manufacturing costs and ensuring a safe manufacturing working environment, it is preferable to use a water-soluble compound for sodium that can use an aqueous solution when performing the supporting operation. In particular, when using sodium nitrate or sodium acetate as sodium, it is preferable because it easily changes to iron oxide during firing and the subsequent reduction treatment of sodium oxide is also easy.

[0037] Through the above steps, the catalyst of the present invention is obtained. Through the above steps, the obtained catalyst of the present invention is a compound mainly composed of an oxide, but a reduction treatment may be performed as a post-treatment. If the reduction conditions are made severe by increasing the temperature or prolonging the time of the reduction treatment, after the reduction treatment, the ratio of the metal-based compound in the catalyst being reduced from the oxide state to the metal state increases, and it is possible to make it into a state of only the active metal by performing an extremely severe reduction treatment. However, under general reduction conditions, the catalyst of the present invention often becomes a chemical state containing iron oxide, cobalt oxide, an oxide of the promoter X (at least one of aluminum oxide, chromium oxide, gallium oxide, and zinc oxide), and sodium oxide.

[0038] The catalyst after the reduction treatment should be handled so as not to be oxidized and deactivated by contact with the atmosphere. Performing a stabilization treatment that blocks the surface of the iron metal on the catalyst surface from the atmosphere makes it possible to handle the catalyst in the atmosphere, which is preferable. For the stabilization treatment, there is a so-called passivation (passivation treatment) in which nitrogen, carbon dioxide, or an inert gas containing low-concentration oxygen is brought into contact with a catalyst to oxidize only the outermost layer of the active metal on the catalyst surface, and when a reaction for producing hydrocarbons using carbon dioxide and hydrogen as raw materials is carried out in a liquid phase, there is a treatment of immersing in a reaction solvent, molten wax, etc. to cut off from the atmosphere. However, for the stabilization treatment, an appropriate stabilization treatment may be carried out according to the situation.

[0039] (Method for producing hydrocarbons) Next, a method for producing hydrocarbons by reacting carbon dioxide and hydrogen using the catalyst of the present invention will be described. The method for producing hydrocarbons of the present invention produces hydrocarbons by bringing a mixed gas having carbon dioxide and hydrogen into contact with a hydrocarbon production catalyst.

[0040] The method for producing hydrocarbons of the present invention may be a method having, in addition to a first step (hereinafter, also referred to as "FT synthesis step") of bringing a mixed gas having carbon dioxide and hydrogen into contact with a hydrocarbon production catalyst, a second step (hereinafter, referred to as "cracking reaction step") of bringing the mixture containing hydrocarbons obtained in the first step into contact with a cracking catalyst made of zeolite and decomposing it.

[0041] -FT synthesis step- In the FT synthesis step, the reaction conditions are not particularly limited, but favorable results are easily obtained when the reaction temperature is 250 to 400°C and the reaction pressure is 1.0 to 6.0 MPa.

[0042] When the reaction temperature is 250°C or higher, sufficient catalyst activity is likely to be exhibited. When the reaction temperature is 400°C or lower, an increase in the selectivity of by-products such as methane and a decrease in the catalyst life are suppressed, and the productivity of hydrocarbons having 3 to 4 carbon atoms is likely to be improved. Therefore, the reaction temperature is preferably set in the range of 250 to 400°C, more preferably 280 to 330°C.

[0043] When the reaction temperature is low or the reaction pressure is low, the catalytic reaction proceeds gently, so the carbon dioxide conversion rate tends to be low. Since the chain growth of hydrocarbons proceeds slowly, hydrocarbons with short carbon chains are likely to be produced, and the selectivity of hydrocarbons with 3 to 4 carbon atoms tends to be high. When the reaction temperature is high or the reaction pressure is high, the catalytic reaction proceeds violently, so the carbon dioxide conversion rate tends to be high. Since the chain growth of hydrocarbons proceeds rapidly, hydrocarbons with long carbon chains are likely to be produced, and the selectivity of hydrocarbons with 3 to 4 carbon atoms tends to be low. In addition, when the reaction temperature is high, the decomposition reaction of hydrocarbons also proceeds, and by-products such as methane are likely to be produced.

[0044] Therefore, the carbon dioxide conversion rate and the selectivity of hydrocarbons with 3 to 4 carbon atoms are in a trade-off relationship. By controlling within a certain reaction temperature range or reaction pressure range, hydrocarbons with 3 to 4 carbon atoms can be obtained highly productively.

[0045] 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 more, sufficient catalytic activity is likely to be exhibited. When the reaction pressure is 6.0 MPa or less, it is possible to suppress setting the pressure resistance design of the plant high, and it is easy to reduce the equipment cost. Therefore, the reaction pressure is preferably set within the above range.

[0046] In the FT synthesis process, as the reaction form, it may be selected according to the reaction conditions such as a fixed bed, a slurry bed, a moving bed, etc., and there is no particular limitation. However, from the viewpoint of catalytic activity, it is preferable to set the reaction temperature above 250 °C, and it is preferable to adopt a fixed bed. In the slurry bed, it is preferable that a solvent that becomes a liquid under the reaction conditions is generated by the reaction. However, at a reaction temperature above 250 °C, most hydrocarbons are gaseous, and it becomes difficult to maintain the reaction in the slurry bed. Therefore, it is preferable to use a fixed bed as the reaction form and react carbon dioxide and hydrogen under a catalyst to produce hydrocarbons.

[0047] When using a fixed bed, it is preferable to mold the catalyst into a pellet shape in consideration of the pressure loss in the reactor.

[0048] In the case of a relatively small-scale plant equipped with a hydrocarbon conversion plant at a carbon dioxide emission source, a microchannel reactor may be advantageous. However, considering filling the catalyst in channels below the millimeter order, the catalyst particle size is preferably about 20 to 250 μm.

[0049] In the cracking reaction step, a mixture containing hydrocarbons obtained in the FT synthesis step is brought into contact with a cracking catalyst composed of zeolite and subjected to catalytic cracking. In the cracking reaction step, since the cracking catalyst does not convert carbon dioxide, the carbon dioxide conversion rate hardly changes between after the FT synthesis step and after the cracking reaction step. On the other hand, in the cracking reaction step, by performing catalytic cracking, the selectivity of hydrocarbons having 3 to 4 carbon atoms is improved, and the productivity of hydrocarbons having 3 to 4 carbon atoms is improved.

[0050] In the cracking reaction step, as the cracking catalyst, either natural zeolite or synthetic zeolite can be used. However, from the viewpoint of improving the productivity of hydrocarbons having 3 to 4 carbon atoms, it is preferable to use H-ZSM-5 zeolite obtained by ion-exchanging ZSM-5 type zeolite with protons. Here, H-ZSM-5 zeolite refers to an aluminosilicate zeolite having a framework structure code of ZSM-5 (Zeolite Socony Mobil-5) type and proton-exchanged. An aluminosilicate zeolite having a framework structure code of ZSM-5 (Zeolite Socony Mobil-5) type that is not proton-exchanged is "ZSM-5 zeolite". For ZSM-5 type zeolite, the molar ratio of SiO2 to Al2O3 (SiO2 / Al2O3) is preferably 20 or more and 1500 or less, more preferably 50 or more and 300 or less, and still more preferably 100 or more and 300 or less.

[0051] In the cracking reaction step, the reaction conditions are not particularly limited, but the reaction temperature is preferably 300 to 600 °C, and the reaction pressure is preferably normal pressure (0.1 MPa).

[0052] When the reaction temperature is 300 °C or higher, sufficient decomposition catalyst activity is likely to be exhibited. When the reaction temperature is 600 °C or lower, an increase in the selectivity of by-products such as methane and a decrease in the catalyst life are suppressed, and the productivity of hydrocarbons having 3 to 4 carbon atoms is likely to be improved. Therefore, the reaction temperature is preferably set in the range of 300 to 600 °C.

[0053] When the reaction pressure is normal pressure (0.1 MPa), sufficient catalyst activity is likely to be exhibited, and the pressure-resistant design of the plant can be simplified, so that the equipment cost is likely to be reduced. Therefore, the reaction pressure is preferably set in the normal pressure range.

[0054] In the cracking reaction step, as the reaction mode, it may be selected according to the reaction conditions such as a fixed bed, a slurry bed, a moving bed, etc., and is not particularly limited. However, from the viewpoint of catalyst activity, it is preferable to set the reaction temperature above 300 °C, and it is preferable to adopt a fixed bed. In the slurry bed, it is preferable that a solvent that becomes a liquid under the reaction conditions is generated by the reaction. However, at a reaction temperature above 300 °C, most hydrocarbons are gases, and it becomes difficult to maintain the reaction in the slurry bed. Therefore, it is preferable to use a fixed bed as the reaction mode and perform catalytic cracking under a catalyst.

[0055] When adopting a fixed bed, in consideration of the pressure loss in the reactor, the catalyst is preferably formed into a pellet shape.

[0056] Here, in the method for producing the catalyst of the present invention, when the mass ratio (mass of hydrocarbon production catalyst / mass of decomposition catalyst) between the hydrocarbon production catalyst in the FT synthesis step and the decomposition catalyst in the cracking reaction step is 0.1 to 10.0, good results are likely to be obtained. When the mass ratio of the hydrocarbon production catalyst to the decomposition catalyst is 0.1 or more, the catalytic cracking activity is likely to be sufficiently exhibited, and the selectivity of hydrocarbons having 3 to 4 carbon atoms is likely to be improved. When the mass ratio of the hydrocarbon production catalyst to the decomposition catalyst is 10.0 or less, it is easy 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.

[0057] In the method for producing hydrocarbons of the present invention, as the reaction gas (that is, the raw material gas), a mixed gas of carbon dioxide and hydrogen is preferably a gas in which the total of carbon dioxide and hydrogen is 50% by volume or more of the whole from the viewpoint of productivity. 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 more, the amount of hydrogen present in the raw material gas is sufficient, so the hydrogenation reaction of carbon dioxide easily proceeds and the productivity is high. On the other hand, when the molar ratio of hydrogen to carbon dioxide is 4.0 or less, the amount of carbon dioxide present in the raw material gas is sufficient, so that the productivity of hydrocarbons is high in combination with the high activity of the catalyst according to the present invention.

Examples

[0058] Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. Since the carbon dioxide conversion rate increases with an increase in the reaction temperature and the reaction pressure in this reaction, it is necessary to compare at the same reaction temperature and the same reaction pressure when comparing the catalyst performance.

[0059] (Catalyst preparation using the co-precipitation method: Examples 1 to 3, 5 to 7, 15, 21) An aqueous solution obtained by mixing iron nitrate hydrate, cobalt nitrate hydrate, and nitrate hydrate of promoter X (aluminum nitrate hydrate, chromium nitrate hydrate, gallium nitrate hydrate, or zinc nitrate hydrate) as raw materials (precursors) with urea as a precipitant is heated at 90 °C for 4 hours to obtain a precipitate. The obtained precipitate is washed, dried at 120 °C for 12 hours, and calcined at 400 °C for 4 hours to obtain an oxide. The obtained oxide was impregnated with an aqueous sodium nitrate solution, and after ultrasonic treatment, it was dried at 120 °C for 12 hours and calcined at 400 °C for 4 hours in a vacuum atmosphere to obtain a catalyst. However, the amounts of iron nitrate hydrate, cobalt nitrate hydrate, nitrate hydrate of promoter X (aluminum nitrate hydrate, chromium nitrate hydrate, gallium nitrate hydrate, or zinc nitrate hydrate), and sodium nitrate were adjusted so that the molar percentages of cobalt, promoter X (aluminum, chromium, gallium, or zinc), and sodium with respect to iron in the resulting catalyst were the values shown in Tables 1 to 10.

[0060] (Catalyst preparation using the coprecipitation method: Examples 4, 8 - 14, 16 - 20, 22 - 32, Comparative Examples 1 - 4) Oxides containing iron, cobalt, and promoter X (aluminum, chromium, gallium, or zinc) were synthesized using the coprecipitation method, and then sodium was supported on the above oxides by the impregnation method to obtain a catalyst. Specifically, it is as follows. Iron nitrate hydrate, cobalt nitrate hydrate, and nitrate hydrate of promoter X (aluminum nitrate hydrate, chromium nitrate hydrate, gallium nitrate hydrate, or zinc nitrate hydrate) as raw materials (precursors) were dissolved in an aqueous solution, and an aqueous sodium carbonate solution was added as a precipitant to precipitate a composite hydroxide of iron, cobalt, and promoter X (aluminum, chromium, gallium, or zinc). Then, aging treatment was performed at 80 °C for 4 hours in a state where the composite oxide had precipitated, followed by drying at 120 °C for 12 hours and calcining at 400 °C for 4 hours to obtain a composite oxide. Thereafter, the composite oxide was impregnated with sodium hydroxide or a solution containing sodium hydroxide, and dried at 120 °C for 12 hours and calcined at 400 °C for 4 hours to obtain a catalyst. However, the amounts of iron nitrate hydrate, cobalt nitrate hydrate, nitrate hydrate of promoter X (aluminum nitrate hydrate, chromium nitrate hydrate, gallium nitrate hydrate, or zinc nitrate hydrate), and sodium nitrate were adjusted so that the molar percentages of cobalt, promoter X (aluminum, chromium, gallium, or zinc), and sodium to iron in the resulting catalyst would be the values shown in Tables 1 to 10. In Comparative Examples 1 to 4, catalysts not containing promoter X (aluminum, chromium, gallium, or zinc) were prepared.

[0061] (Catalyst evaluation in the FT synthesis process: Examples 1 to 20, Comparative Example 1) The catalysts shown in Tables 1 to 6 were evaluated for their catalytic performance using a fixed-bed flow reactor. Specifically, it was as follows. The catalysts shown in Tables 1 to 6 were sized to a particle diameter of 300 to 500 μm and filled into the reaction tube. Pure hydrogen was passed through the reaction tube filled with the catalyst, and reduction treatment was carried out at normal pressure and 400 °C for 6 hours. Thereafter, the reaction gas (H2 / CO2 = 3.0) was passed at W (catalyst mass) / F (synthesis gas flow rate); (g·h / mol) = 5.0 and held at 330 °C and 3.0 MPa for 6 to 24 hours. The gas after the reaction was analyzed using gas chromatography (GC).

[0062] (Catalyst evaluation in the FT synthesis process and the cracking reaction process: Examples 21 to 31, Comparative Examples 2 to 4) The catalysts shown in Tables 6 to 10 (FT synthesis catalysts) were evaluated for their catalytic performance using a fixed-bed flow reactor. Specifically, it was as follows. The catalysts for FT synthesis and the catalysts for cracking reaction (decomposition catalysts) shown in Tables 6 to 10 were sized to a particle diameter of 300 to 500 μm and then filled into their respective reaction tubes. The reaction tubes for the FT synthesis step and the cracking reaction step were connected in series, and the reaction temperature and reaction pressure were controlled separately. The catalyst for FT synthesis was pre-treated by flowing pure hydrogen through the reaction tube and performing a reduction treatment at normal pressure and 400 °C for 6 hours. The reaction gas (H2 / CO2 = 3.0) was passed at W (catalyst mass) / F (synthesis gas flow rate); (g·h / mol) = 7.5. The FT synthesis step was maintained at 285 to 340 °C and 0.1 to 3.0 MPa, and the cracking reaction step was maintained at 500 °C and 0.1 MPa for 6 to 24 hours. The gas after the reaction was analyzed using gas chromatography (GC).

[0063] Here, the catalyst for FT synthesis (hydrocarbon production catalyst) and the catalyst for cracking reaction (decomposition catalyst) were used in the mass ratios shown in Tables 6 to 10. Also, the details of the cracking reaction catalyst (decomposition catalyst) used are as follows. · H-ZSM-5: H-ZSM-5 zeolite with the molar ratio (SiO2 / Al2O3) shown in Tables 6 to 10 · SAPO-11: SAPO-11 phosphate-based zeolite

[0064] (Properties) [Specific surface area, total pore volume, and average pore diameter of the catalyst] The specific surface area, total pore volume, and average pore diameter of the catalysts in each example were measured according to the method described above.

[0065] Then, the compositions of the feed gas and the autoclave outlet gas were determined by gas chromatography, and the following reaction characteristics were calculated. · CO2 conversion rate · CO selectivity · Selectivity of hydrocarbons with 1 carbon atom (methane) (referred to as "C1 selectivity") · Selectivity of hydrocarbons with 2 carbon atoms (referred to as "C2 selectivity") · Selectivity of hydrocarbons with 3 to 4 carbon atoms (referred to as "C 3-4 selectivity") · Selectivity of hydrocarbons with 5 or more carbon atoms (referred to as "C5+ (denoted as "selectivity") · Yield of hydrocarbons having 3 to 4 carbon atoms ("C 3-4 yield" is denoted)

[0066] The CO2 conversion rate and each selectivity were calculated based on the following formula.

Equation

[0067] In addition, the selectivity of hydrocarbons having 3 to 4 carbon atoms (denoted as "C 3-4 yield") was calculated based on the following formula.

[0068]

Equation

[0069] In Tables 1 to 10, the notation with X indicates at least one promoter X selected from the group consisting of aluminum, chromium, gallium, and zinc, and corresponds to the element shown at the end of the catalyst composition indicated in the catalyst species column.

[0070]

Table 1A

[0071]

Table 1B

[0072]

Table 2A

[0073]

Table 2B

[0074]

Table 3A

[0075]

Table 3B

[0076]

Table 4A

[0077]

Table 4B

[0078]

Table 5A

[0079]

Table 5B

[0080]

Table 6A

[0081]

Table 6B

[0082]

Table 7A

[0083]

Table 7B

[0084]

Table 8A

[0085]

Table 8B

[0086]

Table 9A

[0087]

Table 9B

[0088]

Table 10A

[0089]

Table 10B

[0090] From the above results, it can be seen that the catalyst of this example is a highly active hydrocarbon production catalyst with a higher carbon dioxide conversion rate and a higher productivity of hydrocarbons having 3 to 4 carbon atoms compared to the catalysts of the comparative examples at the same reaction temperature and the same reaction pressure.

Claims

1. A hydrocarbon production catalyst containing iron as a main component, cobalt, at least one promoter X selected from the group consisting of aluminum, chromium, gallium, and zinc, sodium, and.

2. The hydrocarbon production catalyst according to claim 1, wherein the promoter X contains at least aluminum.

3. The hydrocarbon production catalyst according to claim 1, wherein the molar percentage of sodium with respect to the iron is 0.01 to 0.30%.

4. The hydrocarbon production catalyst according to claim 1, wherein the molar percentage of sodium with respect to the iron is 0.01 to 0.15%.

5. The hydrocarbon production catalyst according to claim 1, wherein the molar percentage of the promoter X with respect to the iron is 0.1 to 20.0%.

6. The hydrocarbon production catalyst according to claim 1, wherein the molar percentage of the promoter X with respect to the iron is 1.0 to 12.0%.

7. The hydrocarbon production catalyst according to claim 1, wherein the molar percentage of cobalt with respect to the iron is 1.0 to 120.0%.

8. A first step of obtaining a catalyst carrier containing iron, cobalt, and at least one promoter X selected from the group consisting of aluminum, chromium, gallium, and zinc by a precipitation method, A second step of supporting sodium on the surface of the catalyst carrier by an impregnation method, And a method for producing a hydrocarbon production catalyst.

9. A method for producing a hydrocarbon using the hydrocarbon production catalyst according to any one of claims 1 to 7, A method for producing a hydrocarbon, comprising bringing a mixed gas having carbon dioxide and hydrogen into contact with the hydrocarbon production catalyst to produce a hydrocarbon.

10. A method for producing a hydrocarbon using the hydrocarbon production catalyst according to any one of claims 1 to 7, A first step of bringing a mixed gas having carbon dioxide and hydrogen into contact with the hydrocarbon production catalyst, A second step of decomposing a mixture containing the hydrocarbon obtained in the first step by contacting it with a decomposition catalyst made of zeolite, And a method for producing a hydrocarbon.

11. The method for producing a hydrocarbon according to claim 10, wherein the zeolite is H-ZSM-5 zeolite.

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