JP2024139368A - SHORT-CHAIN PARAFFIN SYNTHESIS CATALYST, SHORT-CHAIN PARAFFIN SYNTHESIS APPARATUS, AND SHORT-CHAIN PARAFFIN PRODUCTION METHOD - Google Patents

Abstract

To provide: a catalyst for short-chain paraffin synthesis, which reacts CO and/or CO2 with hydrogen to produce methane and a significant amount of C2-4 short-chain paraffins; an apparatus for short-chain paraffin synthesis including the catalyst; and a method for producing short-chain paraffins using the apparatus.SOLUTION: Provided is a catalyst for producing C1-4 short-chain paraffins by reacting CO and/or CO2 with hydrogen, comprising a carrier and active metal. The carrier includes a stabilized zirconia carrier in which a stabilizing element is solid solubilized and has a tetragonal and/or cubic system crystal structure. The stabilizing element is at least one selected from the group consisting of Y, La, Ce, Pr, Nd, Sm, Gd, Dy, Ca, and Mg. The active metal includes Fe and/or Co and the ratio of atoms of Fe and/or Co exceeds 50 atom% relative to a total sum of the active metal.SELECTED DRAWING: None

Description

The present invention relates to a short-chain paraffin synthesis catalyst, a short-chain paraffin synthesis apparatus, and a short-chain paraffin production method.

Catalysts for reacting carbon dioxide with hydrogen to obtain methane have been known. For example, a methanation reaction catalyst in which Ni is supported on a stabilized zirconia carrier has been proposed as such a catalyst (see, for example, Patent Document 1).

International Publication No. 2016/013488

However, although the methanation catalyst in Patent Document 1 can produce methane from carbon dioxide at a high conversion rate, it is difficult to produce hydrocarbons with a higher carbon number.

The present invention provides a short-chain paraffin synthesis catalyst for producing methane and a relatively large amount of short-chain paraffins having 2 to 4 carbon atoms by reacting CO and/or _CO2 with hydrogen, a short-chain paraffin synthesis apparatus including the catalyst, and a short-chain paraffin production method using the apparatus.

The present invention [1] provides a short-chain paraffin synthesis catalyst for producing short-chain paraffins having 1 to 4 carbon atoms by reacting CO and/or _CO2 with hydrogen, the short-chain paraffin synthesis catalyst comprising a carrier and an active metal, the carrier comprising a stabilized zirconia carrier having a tetragonal and/or cubic crystal structure in which a stabilizing element is dissolved, the stabilizing element being at least one element selected from the group consisting of Y, La, Ce, Pr, Nd, Sm, Gd, Dy, Ca, and Mg, the active metal comprising Fe and/or Co, the atomic ratio of Fe and/or Co being more than 50 atomic % with respect to the total amount of the active metals.

The present invention [2] includes the short-chain paraffin synthesis catalyst according to [1], in which the atomic ratio of Zr is 0.40 atomic % or more and 65.0 atomic % or less, the atomic ratio of the stabilizing element is 0.20 atomic % or more and 35.0 atomic % or less, and the atomic ratio of Fe and/or Co is 9.0 atomic % or more and 99.4 atomic % or less, relative to the total of Zr and the stabilizing element constituting the stabilized zirconia carrier and Fe and/or Co contained in the active metal.

The present invention [3] includes the short-chain paraffin synthesis catalyst described in [1] or [2], which further contains at least one element selected from the group consisting of Na, K, Mo, Ca, Sr, Ba, Ra, and C.

The present invention [4] includes a short-chain paraffin synthesis catalyst according to any one of [1] to [3], which further includes at least one support selected from the group consisting of silica, alumina, titania, ceria, and zeolite.

The present invention [5] includes a short-chain paraffin synthesis catalyst according to any one of [1] to [4], in which the active metal is supported on the carrier and is dissolved in the stabilized zirconia carrier.

The present invention [6] includes the short-chain paraffin synthesis catalyst according to any one of [1] to [5], in which the short-chain paraffins include methane, ethane, propane, and butane, and the total amount of ethane, propane, and butane is 3 volume % or more relative to the total amount of the short-chain paraffins.

The present invention [7] includes a short-chain paraffin synthesis apparatus equipped with the short-chain paraffin synthesis catalyst described in any one of [1] to [6].

The present invention [8] includes a method for producing short-chain paraffins, comprising: a synthesis step of supplying CO and/or _CO2 and hydrogen to the short-chain paraffin synthesis apparatus described in [7] and reacting them to obtain a reaction product containing short-chain paraffins as a main product and _H2O as a by-product; a first separation step of cooling the reaction product and separating it into a gas containing short-chain paraffins and a liquid containing _H2O as water; and a second separation step of separating the gas containing short-chain paraffins into unreacted gas and short-chain paraffins.

The present invention [9] includes the method for producing short-chain paraffins according to [8], further comprising a third separation step, which is performed after the synthesis step and before the first separation step, and which separates H ₂ O from the reaction product as water vapor.

The present invention [10] includes the short-chain paraffin production method according to [8] or [9], further comprising a re-supply step of re-supplying the unreacted gas to the short-chain paraffin synthesis apparatus after the second separation step.

The short-chain paraffin synthesis catalyst of the present invention comprises a stabilized zirconia carrier having a tetragonal and/or cubic crystal structure in which a stabilizing element is dissolved, and an active metal containing Fe and/or Co supported on the stabilized zirconia carrier, in which the atomic ratio of Fe and/or Co to the total of the active metals is more than 50 atomic %. Therefore, it is possible to produce methane and a relatively large amount of short-chain paraffins having 2 to 4 carbon atoms by reacting CO and/or _CO2 with hydrogen.

The short-chain paraffin synthesis apparatus of the present invention is equipped with the short-chain paraffin synthesis catalyst of the present invention, and therefore, CO and/or _CO2 can be reacted with hydrogen to produce methane and a relatively large amount of short-chain paraffins having 2 to 4 carbon atoms.

The short chain paraffin production method of the present invention includes a synthesis step of supplying CO and/or _CO2 and hydrogen to the short chain paraffin synthesis apparatus of the present invention and reacting them to obtain a reaction product containing short chain paraffin as the main product. Therefore, by reacting CO and/or _CO2 with hydrogen, methane and a relatively large amount of short chain paraffin having 2 to 4 carbon atoms can be produced.

FIG. 1 is a schematic diagram showing an embodiment of a short-chain paraffin production system 1 in which the short-chain paraffin production method of the present invention is adopted.

1. Short-chain paraffin synthesis catalyst The short-chain paraffin synthesis catalyst is a catalyst for producing short-chain paraffin having 1 to 4 carbon atoms by reacting CO and/or _CO2 with hydrogen, and includes a carrier and an active metal.

<Carrier>
The support contains a stabilized zirconia support having a tetragonal and/or cubic crystal structure in which a stabilizing element is dissolved. The support may further contain particle components described below.

[Stabilized zirconia support]
The stabilized zirconia support contains at least a stabilizing element in a solid solution and has a tetragonal and/or cubic crystal structure (unit cell) mainly composed of Zr.

The crystal structure of the stabilized zirconia carrier is mainly composed of Zr (basic component), and Zr ions (Zr ⁴⁺ ) are mainly arranged at a plurality of lattice points of the crystal structure of the stabilized zirconia carrier.

The stabilizing element stabilizes the crystal structure of the stabilized zirconia support to be tetragonal and/or cubic.

The stabilizing element is at least one element selected from the group consisting of Y, La, Ce, Pr, Nd, Sm, Gd, Dy, Ca, and Mg. The stabilizing element is preferably Y, Sm, or Ca, and more preferably Y.

The stabilizing elements may be used alone or in combination of two or more.

In addition to the stabilizing element, the stabilized zirconia carrier may also contain an active metal, which will be described later.

When a stabilizing element or an active metal is dissolved in the crystal structure of a stabilized zirconia support, some of the lattice points of the crystal structure are replaced by Zr ions (Zr ⁴⁺ ) with either ions of the stabilizing element or ions of the active metal.

In other words, when a stabilizing element or active metal is dissolved in a stabilized zirconia carrier, the Zr ions located at the lattice points of the crystal structure are replaced by either the stabilizing element ions or the active metal ions. For example, when Fe is dissolved in a stabilized zirconia carrier, the Zr ions located at the lattice points of the crystal structure are replaced by Fe ions.

Therefore, any one of Zr ⁴⁺ , stabilizing element ions, and active metal ions is arranged at a plurality of lattice points of the stabilized zirconia support. The crystal structure of such a stabilized zirconia support preferably includes a perovskite structure.

Such a stabilized zirconia carrier is represented by the following general formula (1):

General formula (1):

In general formula (1), x is, for example, more than 0, 0.10 or more, and, for example, less than 1, preferably 0.67 or less.

In general formula (1), y is, for example, 0 or more, preferably 0.01 or more, and, for example, less than 1, preferably 0.10 or less.

In addition, the crystal lattice spacing in the stabilized zirconia carrier varies depending on the amount of the stabilizing element dissolved in the stabilized zirconia carrier, since the ionic radii of Zr4 ⁺ , the stabilizing element ion, and the active metal ion are different from each other. For reference, the ionic radii of Zr4 ⁺ , Y3 ⁺ , Fe2 ⁺ , Fe3 ⁺ , Co2 ⁺ , and Co3 ⁺ are shown below.
Zr ⁴⁺ :0.079nm
Y ³⁺ :0.090nm
Fe ²⁺ :0.061 nm
Fe ³⁺ :0.055nm
Co2 ⁺ : 0.065nm
Co3 ⁺ : 0.055nm

More specifically, when a large amount of stabilizing element ions or active metal ions with a larger ionic radius than Zr ions are dissolved in the stabilized zirconia carrier, the crystal lattice spacing in the stabilized zirconia carrier increases (expands). On the other hand, when a large amount of stabilizing element ions or active metal ions with a smaller ionic radius than Zr ions are dissolved in the stabilized zirconia carrier, the crystal lattice spacing in the stabilized zirconia carrier decreases (shrinks).

The lattice spacing of the [111] plane in the crystal structure of the stabilized zirconia carrier is, for example, 0.2920 or more, preferably 0.2935 nm or more, and, for example, 0.2995 nm or less, preferably 0.2985 nm or less. The lattice spacing of the [111] plane in the crystal structure of stabilized zirconia in which the stabilizing element and the active metal are not dissolved is 0.2975 nm in the case of tetragonal zirconia and 0.2965 nm in the case of cubic zirconia.

The stabilized zirconia carrier has oxygen vacancies. When a stabilizing element and an active metal are dissolved in the stabilized zirconia carrier and stabilizing element ions or active metal ions having a valence of 3 or less (divalent or trivalent) are substituted for Zr ions, oxygen defects (missing ions) are generated in the crystal structure and oxygen vacancies are formed because the Zr ions (Zr ⁴⁺ ) are tetravalent and the stabilizing element ions or active metal ions are divalent or trivalent.

Specifically, when trivalent stabilizing element ions and/or active metal ions are substituted for Zr ions, oxygen vacancies are formed in the stabilized zirconia carrier according to the Kreger-Bink formula shown in the following general formula (2), and when divalent stabilizing element ions and/or active metal ions are substituted for Zr ions, oxygen vacancies are formed in the stabilized zirconia carrier according to the Kreger-Bink formula shown in the following general formula (3).

General formula (2):

General formula (3):

When tetravalent stabilizing element ions and/or active metal ions replace Zr ions, their valences are the same, so no oxygen vacancies are formed in the stabilized zirconia support.

The atomic percentage of each atom in such a short-chain paraffin synthesis catalyst is based on the elemental state and is calculated from the amount of raw materials (zirconia and/or Zr salt, stabilizing element salt, active metal salt, particle component salt, and additive salt) charged (same below).

In the following, the term "active metal containing Fe and/or Co" refers to the sum of the active metal containing Fe and/or Co supported on the carrier and the active metal containing Fe and/or Co dissolved in the stabilized zirconia carrier, and the term "Fe and/or Co contained in the active metal" refers to the sum of the Fe and/or Co supported on the carrier and the Fe and/or Co dissolved in the stabilized zirconia carrier. (The same applies below.)

The atomic ratio of Zr to the sum of Zr and the stabilizing element (= Zr/(Zr + stabilizing element) × 100) is, for example, 40 atomic % or more, preferably 50 atomic % or more, more preferably 60 atomic % or more, even more preferably 65 atomic % or more, and for example, 90 atomic % or less, preferably 80 atomic % or less, more preferably 70 atomic % or less.

The atomic ratio of Zr (=Zr/(Zr + stabilizing element + Fe and/or Co) x 100) to the sum of Zr and stabilizing elements constituting the stabilized zirconia carrier and Fe and/or Co contained in the active metal is, for example, 0.4 atomic % or more, preferably 1.0 atomic % or more, more preferably 5.0 atomic % or more, even more preferably 10.0 atomic % or more, particularly preferably 15 atomic % or more, and, for example, 65.0 atomic % or less, preferably 55.0 atomic % or less, more preferably 45.0 atomic % or less, even more preferably 35 atomic % or less, particularly preferably 30 atomic % or less.

If the atomic percentage of Zr relative to the sum of the Zr and stabilizing elements constituting the stabilized zirconia carrier and the Fe and/or Co contained in the active metal is equal to or greater than the lower limit, the tetragonal and/or cubic crystal structure can be reliably formed in the stabilized zirconia carrier, and if the atomic percentage of Zr is equal to or less than the upper limit, the mixing ratio of the active metal required for catalytic activity can be sufficiently ensured.

The atomic ratio of the stabilizing element to the sum of Zr and the stabilizing element (= stabilizing element/(Zr + stabilizing element) × 100) is, for example, 10 atomic % or more, preferably 20 atomic % or more, more preferably 30 atomic % or more, and, for example, 60 atomic % or less, preferably 50 atomic % or less, more preferably 40 atomic % or less, and even more preferably 35 atomic % or less.

When the atomic percentage of the stabilizing element relative to the total of Zr and the stabilizing element is within the above range, oxygen vacancies can be favorably formed in the stabilized zirconia support, and the stabilized zirconia support can reliably attract oxygen atoms (O) of carbon dioxide molecules (CO ₂ ) in the short-chain paraffin production method described below. Therefore, the catalytic activity can be reliably improved, and short-chain paraffins can be produced from carbon dioxide.

The atomic ratio of the stabilizing element (= stabilizing element/(Zr + stabilizing element + Fe and/or Co) x 100) to the sum of Zr and stabilizing elements constituting the stabilized zirconia carrier and Fe and/or Co contained in the active metal is, for example, 0.2 atomic % or more, preferably 1.0 atomic % or more, more preferably 3.0 atomic % or more, even more preferably 6.0 atomic % or more, and, for example, 35.0 atomic % or less, preferably 30.0 atomic % or less, more preferably 25.0 atomic % or less, even more preferably 20 atomic % or less.

If the atomic percentage of the stabilizing element relative to the sum of the Zr and stabilizing element constituting the stabilized zirconia carrier and the Fe and/or Co contained in the active metal is equal to or higher than the lower limit, the tetragonal and/or cubic crystal structure can be reliably stabilized, and if the atomic percentage of the stabilizing element is equal to or lower than the upper limit, the excess stabilizing element can be prevented from forming undesirable oxides and inhibiting catalytic activity.

[Other support materials]
The other support material is, for example, a support material for supporting an active metal other than the above-mentioned stabilized zirconia support, and is used by mixing with the stabilized zirconia support.

Other support materials include, for example, particle components, such as silica, alumina, titania, ceria, and monoclinic zirconia, and preferably silica, alumina, and titania.

The particle components may be used alone or in combination of two or more types.

In the following, the atom of the particle component refers to the atom other than oxygen contained in the particle component described below. For example, if the particle component is silica, the atom of the particle component is Si. (The same applies below.)

The atomic ratio of the particle components to the sum of the Zr and stabilizing elements constituting the stabilized zirconia carrier and the particle components (= (atoms of particle components)/(Zr + stabilizing elements + atoms of particle components) x 100) is, for example, 1.0 atomic % or more, preferably 10.0 atomic % or more, more preferably 30.0 atomic % or more, even more preferably 50.0 atomic % or more, particularly preferably 60 atomic % or more, and for example, less than 100.0 atomic %, preferably 90.0 atomic % or less, more preferably 80.0 atomic % or less, even more preferably 70.0 atomic % or less.

Other examples of carrier materials include zeolites.

The amount of zeolite to be blended is, for example, 0.3 parts by mass or more, preferably 0.5 parts by mass or more, and, for example, 10 parts by mass or less, preferably 5 parts by mass or less, more preferably 3 parts by mass or less, and even more preferably 1 part by mass or less, per 100 parts by mass of the catalyst components constituting the short-chain paraffin synthesis catalyst excluding zeolite (active metal, carrier (including stabilizing element), and additives described below).

<Active metals>
The active metal is supported on a carrier and may be further dissolved in a stabilized zirconia carrier.

The active metal may be, for example, in the form of a metal or a metal oxide. From the viewpoint of catalytic activity, the active metal is preferably in the form of a metal.

The active metals include Fe and/or Co.

The active metal may also include other active metals besides Fe and/or Co. Examples of other active metals include Ni, Cu, and Ru.

The active metals may be used alone or in combination of two or more.

When the active metal contains Fe and Co, the atomic ratio of Fe to the sum of Fe and Co (=Fe/(Fe+Co)×100) is, for example, more than 0 atomic %, preferably 10.0 atomic % or more, more preferably 20.0 atomic % or more, and for example, less than 100.0 atomic %, preferably 90.0 atomic % or less, more preferably 80.0 atomic % or less.

The atomic ratio of Fe and/or Co to the total of the active metals (= (Fe and/or Co)/(Fe and/or Co + other active metal atoms) x 100) is more than 50 atomic %, preferably 60 atomic % or more, more preferably 70 atomic % or more, even more preferably 80 atomic % or more, particularly preferably 90 atomic % or more, and most preferably 100 atomic %.

If the atomic ratio of Fe and/or Co to the total amount of active metals is equal to or greater than the lower limit, short-chain paraffins with 1 to 4 carbon atoms can be reliably produced, and methane and a relatively large amount of short-chain paraffins with 2 to 4 carbon atoms can be produced.

In other words, Fe and/or Co are the main active metals. Fe and/or Co being the main components means that the atomic ratio of Fe and/or Co (= (Fe and/or Co)/(Fe and/or Co + other active metal atoms) x 100) to the total active metals is 50 atomic % or more. In other words, Fe being the main component means that the atomic ratio of Fe to the total active metals is 50 atomic % or more, Co being the main component means that the atomic ratio of Co to the total active metals is 50 atomic % or more, and Fe and Co being the main components means that the atomic ratio of the sum of Fe and Co to the total active metals is 50 atomic % or more.

The atomic ratio of Fe and/or Co contained in the active metal to the sum of Zr and stabilizing elements constituting the stabilized zirconia carrier and Fe and/or Co contained in the active metal (=(Fe and/or Co)/(Zr + stabilizing element + Fe and/or Co) x 100) is, for example, 9.0 atomic % or more, preferably 15.0 atomic % or more, more preferably 25.0 atomic % or more, even more preferably 35 atomic % or more, particularly preferably 45 atomic % or more, most preferably 55 atomic % or more, and, for example, 99.4 atomic % or less, preferably 90 atomic % or less, more preferably 80.0 atomic % or less, even more preferably 75 atomic % or less.

When the atomic percentage of the total of Fe and/or Co contained in the active metal relative to the total of Zr and stabilizing elements constituting the stabilized zirconia carrier and Fe and/or Co contained in the active metal is equal to or higher than the lower limit, the catalytic activity can be improved, and when the atomic percentage of the total of Fe and/or Co contained in the active metal is equal to or lower than the upper limit, the aggregation of Fe and/or Co and the decrease in dispersibility of Fe and/or Co can be suppressed.

<Additives>
If necessary, an additive may be added to the short-chain paraffin synthesis catalyst.

Additives include, for example, reaction promoters, diluents, and binders.

[Reaction accelerator component]
Examples of the reaction-promoting component include a component that promotes the reaction of partially reducing _CO2 to CO, a component that promotes the reaction of synthesizing short-chain paraffin having 1 to 4 carbon atoms from CO, and a component that promotes the carbon-carbon bond of short-chain paraffin.

Examples of reaction-promoting components include alkali metals, alkaline earth metals, molybdenum (Mo), and carbon (C).

The reaction promoter may be used alone or in combination of two or more.

Examples of alkali metals include Na and K.

Examples of alkaline earth metals include Ca, Sr, Ba, and Ra.

When an alkali metal, alkaline earth metal, or molybdenum (Mo) is included as a reaction-promoting component, it can promote carbon-carbon bonds in the synthesized short-chain paraffin.

In addition, when the active metal is mainly composed of Fe, it is preferable that the catalyst contains carbon (C) as a reaction-promoting component. When the short-chain paraffin synthesis catalyst contains Fe and C, Fe ₅ C ₂ is generated, and the reaction of synthesizing short-chain paraffins having 1 to 4 carbon atoms from CO can be promoted.

The atomic ratio of the reaction-promoting component (= (atoms of reaction-promoting component)/(Zr + stabilizing element + Fe and/or Co + other active metal atoms + atoms of reaction-promoting component + atoms of particle component) x 100) to the total of Zr and stabilizing elements, active metals including Fe and/or Co, reaction-promoting components, and particle components that constitute the stabilized zirconia carrier is, for example, 1.0 atomic % or more, preferably 5.0 atomic % or more, more preferably 8.0 atomic % or more, and, for example, 30.0 atomic % or less, preferably 20.0 atomic % or less, more preferably 15.0 atomic % or less.

The atomic ratio of C to the sum of Fe and C (=C/(Fe+C)×100) is, for example, 1 atomic % or more, preferably 3 atomic % or more, more preferably 6 atomic % or more, and, for example, 40 atomic % or less, preferably 30 atomic % or less, more preferably 20 atomic % or less.

That is, the short-chain paraffin synthesis catalyst contains, for example, at least one element selected from the group consisting of Na, K, Mo, Ca, Sr, Ba, Ra, and C. The short-chain paraffin synthesis catalyst preferably contains at least one element selected from the group consisting of Na, K, and C, and more preferably contains K.

[Dilution components]
The diluent component is an inert substance in the short-chain paraffin synthesis reaction described below, and adding the diluent component to the short-chain paraffin synthesis catalyst can facilitate temperature control of the short-chain paraffin synthesis catalyst.

Examples of diluent components include alumina (e.g., α-alumina, θ-alumina, γ-alumina, etc.), titania (e.g., rutile-type titania, anatase-type titania, etc.), etc.

The diluent components may be used alone or in combination of two or more.

In the short-chain paraffin synthesis catalyst, the amount of the diluent component per 100 parts by mass of the short-chain paraffin synthesis catalyst is, for example, 100 parts by mass or more, preferably 1000 parts by mass or more, for example, 5000 parts by mass or less.

[binder]
The binder is a binding component for binding the short-chain paraffin synthesis catalyst together when the short-chain paraffin synthesis catalyst is used in a fluidized bed type reactor, for example.

Examples of binders include silicates, titanates, aluminates, zirconates, etc.

The binders may be used alone or in combination of two or more types.

The proportion of binder added is selected as desired depending on the application of the short-chain paraffin synthesis catalyst.

In the above-mentioned short-chain paraffin synthesis catalyst, the short-chain paraffin synthesis system described later, and the short-chain paraffin production method described later, by changing the formulation, reaction conditions, etc., the conversion rate of CO and/or _CO2 can be adjusted, and further, the proportions of methane, ethane, propane, and butane in the produced short-chain paraffin can be adjusted.

The conversion rate of CO and/or _CO2 is, for example, 20% or more, preferably 30% or more, more preferably 40% or more, even more preferably 50% or more, and particularly preferably 60% or more.

The volume ratio of the sum of ethane, propane, and butane to the sum of short-chain paraffins having 1 to 4 carbon atoms is, for example, 1 vol.% or more, preferably 3 vol.% or more, more preferably 5 vol.% or more, even more preferably 10 vol.% or more, and particularly preferably 15 vol.% or more.

2. Method for Producing the Short-Chain Paraffin Synthesis Catalyst Next, a method for producing the short-chain paraffin synthesis catalyst will be described.

The method for producing a short-chain paraffin synthesis catalyst includes a step of mixing the raw material components to prepare a mixture (mixing step), and a step of calcining the mixture to prepare a stabilized zirconia support that supports an active metal (calcining step). If necessary, the method may also include a step of reducing the active metal (reduction step).

In the mixing step, zirconia ( _ZrO2 ) and/or a salt of Zr as the carrier component, the salt of the stabilizing element, and the salt of the active metal are mixed, for example, so that the atomic ratio of each atom (Zr, the stabilizing element, and the active metal) is within the above-mentioned range.

The zirconia may be, for example, low-crystalline _ZrO2 fine particles.

Examples of Zr salts include Zr nitrates (e.g., zirconium nitrate (Zr( _NO3 ) ₄ ), zirconium oxide nitrate (ZrO( _NO3 ) ₂ ), etc.), Zr hydrochlorides (e.g., zirconium oxide chloride ( _ZrCl2O ), etc.), Zr acetates (e.g., zirconium oxide acetate ( _ZrO ( _C2H3O2 ) ₂ ) _, etc.).

Zr salts may be used alone or in combination of two or more.

Such Zr salts can be commercially available products, such as zirconium nitrate pentahydrate (manufactured by BOC Sciences), zirconium oxide nitrate dihydrate (manufactured by Kanto Chemical), zirconium oxide chloride octahydrate (manufactured by Kanto Chemical), and zirconium oxide acetate (manufactured by Daiichi Kigenso Kogyo Co., Ltd.).

As the Zr salt, preferably, Zr acetate is used, and more preferably, zirconium oxide acetate is used.

Examples of salts of stabilizing elements include nitrates of stabilizing elements and chlorides of stabilizing elements, and preferably nitrates of stabilizing elements, and more preferably nitrates of Y, Sm, and Ca.

The salts of the stabilizing elements may be used alone or in combination of two or more.

Note that commercially available salts of stabilizing elements can also be used.

Examples of active metal salts include nitrates of active metals and chlorides of active metals, and preferably nitrates of active metals, and more preferably nitrates of Fe and/or Co.

The active metal salts may be used alone or in combination of two or more.

In addition, commercially available active metal salts can also be used.

To mix the raw material components, for example, a salt of a stabilizing element and a salt of an active metal are added to an aqueous solution of zirconia sol and/or a salt of Zr so that the atomic ratio of each atom (Zr, stabilizing element, and active metal) falls within the above-mentioned range, and then the mixture is stirred and mixed.

More specifically, a salt of a stabilizing element is added to an aqueous solution of zirconia sol and/or a Zr salt, and the solution is stirred and mixed to form a homogeneous solution, after which an active metal salt is added and the solution is stirred and mixed for, for example, 1 hour or more and, for example, 30 hours or less.

This produces a mixed solution (slurry) containing zirconia and/or Zr salts, stabilizing element salts, and active metal salts.

The mixed solution is then heated, for example in a thermostatic drying oven, to evaporate excess water.

The heating temperature of the mixed solution is, for example, 100° C. or higher, preferably 150° C. or higher, and for example, 200° C. or lower, preferably 170° C. or lower. The heating time of the mixed solution is, for example, 30 minutes or longer, preferably 1 hour or longer, and for example, 10 hours or lower, preferably 3 hours or lower.

This produces a mixture (hard slurry) containing salts of zirconia and/or Zr, salts of stabilizing elements, and salts of active metals.

Next, the mixture is stirred if necessary, and then fired in a firing process, for example, in a heating furnace such as an electric furnace.

The firing temperature is, for example, 550°C or higher, preferably 600°C or higher, and, for example, 800°C or lower.

If the calcination temperature is equal to or higher than the lower limit, the crystal structure of the stabilized zirconia carrier can be reliably made tetragonal and/or cubic, and if the calcination temperature is equal to or lower than the upper limit, the specific surface area of the stabilized zirconia carrier can be prevented from decreasing excessively, which would otherwise cause a decrease in catalytic activity.

The baking time is, for example, 1 hour or more, preferably 3 hours or more, and, for example, 24 hours or less.

The mixture is thereby calcined to form the stabilized zirconia support shown in the above general formula (1), and the oxide of the active metal is supported on the stabilized zirconia support, preparing the short-chain paraffin synthesis catalyst.

Next, if a reduction step is included, the short-chain paraffin synthesis catalyst is reduced, for example, using a hydrogen stream.

More specifically, the short-chain paraffin synthesis catalyst is crushed in a mortar or the like if necessary, sieved, and then filled into a specified cylindrical tube.

The sieve openings are, for example, 100 μm or less, preferably 75 μm or less.

Then, the inside of the tube is heated using a heater such as an electric tubular furnace so that the inside of the tube reaches the reduction temperature described below, and hydrogen is passed through the tube.

The reduction temperature is, for example, 200°C or higher, preferably 300°C or higher, and for example, 600°C or lower. The reduction time is, for example, 2 hours or higher, preferably 3 hours or higher, and for example, 10 hours or lower, preferably 5 hours or lower.

The flow rate of hydrogen is, for example, 50 mL·min ⁻¹ ·g ⁻¹ or more, preferably 100 mL·min −1 ·g ⁻¹ or more, and for example, 500 mL·min ⁻¹ ·g ⁻¹ or less, per gram of the short ^-chain paraffin synthesis catalyst.

As a result, the oxide of the active metal supported on the stabilized zirconia carrier is reduced to its metallic state.

The short-chain paraffin synthesis catalyst may also be reduced using carbon monoxide as a reducing agent.

The stabilizing elements and active metals dissolved in the stabilized zirconia carrier are covered by the active metals in the metallic state supported on the stabilized zirconia carrier, and therefore are not reduced in this reduction process and remain in an oxidized state.

Such short-chain paraffin synthesis catalysts are particulate, but may be formed into a specific shape (e.g., a cylindrical shape, a rectangular prism shape, a hollow cylinder shape, etc.) by, for example, applying pressure.

In addition, the short-chain paraffin synthesis catalyst may be prepared by adding the above-mentioned particulate components during the process of mixing the raw materials, and the active metal may be supported on the particulate components.

Furthermore, the short-chain paraffin synthesis catalyst may contain the above-mentioned reaction-promoting components, diluent components, and binders during the process of mixing the raw materials.

3. Short chain paraffin synthesis system One embodiment of a short chain paraffin synthesis system 1 using the short chain paraffin synthesis catalyst of the present invention will be described with reference to Fig. 1. The short chain paraffin synthesis system 1 is a short chain paraffin production facility that produces short chain paraffins by reacting CO and/or _CO2 with hydrogen.

The short-chain paraffin synthesis system 1 includes, for example, a short-chain paraffin synthesis device 2, a cooling device 3, a first separation device 4, a second separation device 5, a raw material gas supply line 10, a first line 11, a second line 12, a third line 13, a drainage line 14, and a short-chain paraffin discharge line 15. If necessary, a third separation device 6 may be interposed in the first line 11, and a circulation line 16 may also be provided.

In the following description, the upstream and downstream sides refer to the upstream and downstream sides in the gas flow direction.

The raw material gas supply line 10 is located upstream of the short chain paraffin synthesis apparatus 2, has one end connected to the short chain paraffin synthesis apparatus 2, and is a pipe for supplying raw material gas to the short chain paraffin synthesis apparatus 2. More specifically, the raw material gas supply line 10 supplies a mixed gas containing CO and/or _CO2 and hydrogen to the short chain paraffin synthesis apparatus 2. Note that CO and/or _CO2 and hydrogen may be supplied from different pipes, in which case the raw material gas supply line 10 is composed of two pipes. Note that the mixed gas may be heated before being supplied.

The short-chain paraffin synthesis unit 2 is a unit that reacts CO and/or _CO2 with hydrogen to generate a reaction product containing short-chain paraffins as a main product. The short-chain paraffin synthesis unit 2 includes, for example, a reactor and a short-chain paraffin synthesis catalyst (not shown), and a jacket as necessary.

In the reactor, a mixed gas is supplied from a raw material gas supply line 10, and CO and/or CO ₂ are reacted with hydrogen to generate a reaction product containing short-chain paraffins having 1 to 4 carbon atoms as the main product and H ₂ O as a by-product. The reaction product is supplied to a cooling device 3 via a first line 11.

The short-chain paraffin synthesis catalyst is filled in the reactor. It promotes the short-chain paraffin synthesis reaction between CO and/or _CO2 and hydrogen. As described above, examples of the short-chain paraffin synthesis catalyst include a short-chain paraffin synthesis catalyst mainly composed of Fe as an active metal, a short-chain paraffin synthesis catalyst mainly composed of Co, and a short-chain paraffin synthesis catalyst mainly composed of Fe and Co.

Short-chain paraffin synthesis catalysts may be used alone or in combination of two or more types.

In other words, examples of the short-chain paraffin synthesis catalyst include a short-chain paraffin synthesis catalyst whose main component is Fe, a short-chain paraffin synthesis catalyst whose main component is Co, and a short-chain paraffin synthesis catalyst whose main components are Fe and Co. Examples of the short-chain paraffin synthesis catalyst include a short-chain paraffin synthesis catalyst whose main component is Fe and a short-chain paraffin synthesis catalyst whose main component is Co.

When using a short-chain paraffin synthesis catalyst whose main component is Fe and a short-chain paraffin synthesis catalyst whose main component is Co in combination, methods for filling the reactor include, for example, a method of separately filling the short-chain paraffin synthesis catalyst whose main component is Fe and a short-chain paraffin synthesis catalyst whose main component is Co, and a method of mixing and filling them.

As an example of a method of packing separately, a method of packing the upper part of the reactor with a short-chain paraffin synthesis catalyst mainly composed of Fe and packing the lower part of the reactor with a short-chain paraffin synthesis catalyst mainly composed of Co can be given.

Examples of methods for mixing and filling include a method of uniformly mixing and filling a short-chain paraffin synthesis catalyst whose main component is Fe and a short-chain paraffin synthesis catalyst whose main component is Co, and a method of adjusting the mixing ratio of the short-chain paraffin synthesis catalyst whose main component is Fe and the short-chain paraffin synthesis catalyst whose main component is Co, and filling the reactor with a gradation so that the Fe mixing ratio is high at the upper end and the Co mixing ratio is high at the lower end. When filling the reactor with a gradation like this, a raw material gas supply line 10 is arranged so that the raw material gas is supplied from the upper end side of the reactor, and a first line 11, described later, is arranged so that the raw material gas is discharged from the lower end side of the reactor.

When a short-chain paraffin synthesis catalyst whose main component is Fe and a short-chain paraffin synthesis catalyst whose main component is Co are used in combination, the mixing ratio of the short-chain paraffin synthesis catalyst whose main component is Fe and the short-chain paraffin synthesis catalyst whose main component is Co is not particularly limited.

The short-chain paraffin synthesis unit 2 is also equipped with a jacket for cooling the reactor as necessary. More specifically, the reactor can be cooled by circulating a refrigerant through the jacket.

The jacket helps prevent excessive temperature rise in the reactor due to the reaction heat generated during the synthesis of short-chain paraffins.

The first line 11 is a pipe located between the short chain paraffin synthesis apparatus 2 and the cooling apparatus 3, one end of which is connected to the short chain paraffin synthesis apparatus 2 and the other end of which is connected to the cooling apparatus 3. More specifically, the first line 11 supplies the reaction product containing short chain paraffin as the main product and H ₂ O as a by-product from the short chain paraffin synthesis apparatus 2 to the cooling apparatus 3. When the third separation apparatus 6 is provided, the reaction product is supplied from the short chain paraffin synthesis apparatus 2 to the cooling apparatus 3 via the third separation apparatus 6.

The third separation device 6 is disposed between the first lines 11, and separates H ₂ O as water vapor from the reaction product. The reaction product after H ₂ O has been separated as water vapor by the third separation device 6 is supplied to the cooling device 4 via the first line 11. On the other hand, the separated water vapor and unreacted gas may be supplied again to the short chain paraffin synthesis device 2, may be supplied to a reactor filled with another catalyst described later, or may be discharged. The path of the water vapor separated by the third separation device 6 is not shown.

The third separation device 6 may be, for example, a porous membrane (filter) made of zeolite, silica, and/or carbon. More specifically, a porous membrane with pores slightly smaller than the molecular diameter of methane (0.38 nm) is used to separate short-chain paraffins with molecular diameters equal to or larger than that of methane, and unreacted gas and water vapor with molecular diameters smaller than that of methane.

By passing the reaction product discharged from the short-chain paraffin synthesis unit 2 through the third separation unit 6, H ₂ O in the reaction product can be separated while still at a high temperature, so that the energy required for cooling by the cooling unit 3 can be reduced.

The cooling device 3 is located downstream of the short-chain paraffin synthesis device 2, and is a device for cooling the reaction product containing the main product short-chain paraffin and the by-product H ₂ O. When the reaction product containing the main product short-chain paraffin and the by-product H ₂ O supplied via the first line 11 is cooled by the cooling device 3, the H ₂ O as water vapor in the reaction product is condensed to water. Then, the reaction product containing a liquid containing H ₂ O as water and a gas containing short-chain paraffin is supplied to the first separation device 4 via the second line 12.

In the cooling device 3, examples of the refrigerant include water for cooling and a brine liquid. In addition, for example, a mixed gas containing CO and/or _CO2 and hydrogen supplied from the raw material gas supply line 10 may be used as the refrigerant for heat exchange.

The second line 12 is a pipe located between the cooling device 3 and the first separation device 4, one end of which is connected to the cooling device 3 and the other end of which is connected to the first separation device 4. More specifically, the second line 12 supplies the reaction product from the cooling device 3 to the first separation device 4, the reaction product including a liquid containing H ₂ O as water and a gas containing short-chain paraffin and unreacted gas.

The first separation device 4 is located downstream of the cooling device 3 and separates the reaction product, which contains a liquid containing H ₂ O as water and a gas containing short-chain paraffins and unreacted gas, into liquid and gas. The reaction product, which is supplied via the second line 12 and contains a liquid containing H ₂ O as water and a gas containing short-chain paraffins and unreacted gas, is separated into liquid and gas by the first separation device 4, the liquid is recovered from the drainage line 14, and the gas is supplied to the second separation device 5 via the third line 13.

Examples of the first separation device 4 include a known distillation device and an extraction device.

The drain line 14 is a pipe connected at one end to the first separation device 4 and used to recover the liquid separated by the first separation device 4 and containing H ₂ O as water.

The third line 13 is a pipe located between the first separation device 4 and the second separation device 5, with one end connected to the first separation device 4 and the other end connected to the second separation device 5. More specifically, the third line 13 supplies gas containing short-chain paraffins and unreacted gas from the first separation device 4 to the second separation device 5.

The second separation device 5 is located downstream of the first separation device 4 and separates the gas containing short-chain paraffins and unreacted gas into short-chain paraffins and unreacted gas. The gas containing short-chain paraffins and unreacted gas supplied via the third line 13 is separated into short-chain paraffins and unreacted gas by the second separation device 5, the short-chain paraffins are recovered from the short-chain paraffin discharge line 15, and the unreacted gas is supplied again to the short-chain paraffin synthesis device 2 via the circulation line 16 as necessary.

Examples of the second separation device 5 include a known distillation device and an extraction device.

The short-chain paraffin discharge line 15 is a pipe connected at one end to the second separation device 5 and used to recover the short-chain paraffin separated by the second separation device 5.

The circulation line 16 is a pipe having one end connected to the second separation device 5 and the other end connected to the short-chain paraffin synthesis device 2. The other end may be connected to the raw material gas supply line 10. More specifically, the circulation line 16 supplies the unreacted gas from the second separation device 5 again to the short-chain paraffin synthesis device 2.

4. Short-Chain Paraffin Production Method Next, an embodiment of the short-chain paraffin production method of the present invention using the above-mentioned short-chain paraffin synthesis system 1 will be described.

The method for producing short-chain paraffins includes, for example, a synthesis step of supplying CO and/or _CO2 and hydrogen to the short-chain paraffin synthesis unit 2 and reacting them to obtain a reaction product containing short-chain paraffins as a main product and _H2O as a by-product, a first separation step of cooling the reaction product and separating it into a gas containing short-chain paraffins and a liquid containing _H2O as water, and a second separation step of separating the gas containing short-chain paraffins separated in the first separation step into unreacted gas and short-chain paraffins. If necessary, the method may include a third separation step after the synthesis step and before the first separation step of separating _H2O as water vapor from the reaction product, and may further include a re-supply step after the second separation step of re-supplying the unreacted gas to the short-chain paraffin synthesis unit 2.

<Synthesis process>
The synthesis step is a step in which a mixed gas is supplied from a raw gas supply line 10 to the short-chain paraffin synthesis device 2 and reacted to obtain a reaction product containing short-chain paraffin as a main product and H ₂ O as a by-product.

To produce short-chain paraffins with carbon numbers of 1 to 4 using the short-chain paraffin production device 2, a short-chain paraffin synthesis catalyst is brought into contact with the mixed gas.

More specifically, after the short-chain paraffin synthesis catalyst is loaded into the reactor using the loading method described above, the reactor is maintained at the reaction temperature described below under normal pressure, and the mixed gas is supplied to the reactor.

The reaction temperature is, for example, 100°C or higher, preferably 150°C or higher, and, for example, 500°C or lower, preferably 450°C or lower.

When a short-chain paraffin synthesis catalyst mainly composed of Fe is used alone as the short-chain paraffin synthesis catalyst, the reaction temperature is, for example, 200°C or higher, preferably 300°C or higher, more preferably 350°C or higher, and, for example, 500°C or lower, preferably 450°C or lower.

When a short-chain paraffin synthesis catalyst mainly composed of Co is used alone as the short-chain paraffin synthesis catalyst, the reaction temperature is, for example, 100°C or higher, preferably 150°C or higher, and, for example, 400°C or lower, preferably 300°C or lower, more preferably 250°C or lower.

When the mixed gas contains _CO2 and hydrogen gas, the molar ratio of _CO2 to hydrogen gas is not particularly limited, and is, for example, 1: 4. When the mixed gas contains CO and hydrogen gas, the molar ratio of CO to hydrogen gas is not particularly limited, and is, for example, 1: 3.

The flow rate of the mixed gas is, per gram of the short-chain paraffin synthesis catalyst, for example, 30 mL·min ⁻¹ ·g ⁻¹ or more, preferably 50 mL·min ⁻¹ ·g ⁻¹ or more, and for example, 500 mL·min ⁻¹ ·g ⁻¹ or less, preferably 100 mL·min ⁻¹ ·g ⁻¹ or less.

In this way, when the short-chain paraffin synthesis catalyst is brought into contact with the mixed gas, even if the carrier supports a metal oxide, the metal oxide is reduced to its metallic state by the hydrogen in the mixed gas.

Then, the oxygen vacancies in the stabilized zirconia carrier attract the oxygen atoms of CO and/or _CO2 , and the active metal in a metallic state supported on the carrier attracts hydrogen, so that CO and/or _CO2 react efficiently with hydrogen on the surface of the short-chain paraffin synthesis catalyst to produce reaction products containing short-chain paraffins as the main product and _H2O as a by-product.

More specifically, the short-chain paraffin yield per 1 g of the short-chain paraffin synthesis catalyst is, for example, 0.010 mmol·s ⁻¹ ·g ⁻¹ or more, preferably 0.250 mmol·s ⁻¹ ·g ⁻¹ or more, further preferably 0.400 mmol·s ⁻¹ ·g ⁻¹ or more, and particularly preferably 0.500 mmol·s ⁻¹ ·g ⁻¹ or more.

In addition, in such a method for producing short-chain paraffins, the active metal in a metallic state supported on the surface of the short-chain paraffin synthesis catalyst may peel off and become detached from the short-chain paraffin synthesis catalyst due to the supply of the mixed gas. In this case, the active metal ions of the stabilized zirconia support exposed from the peeled portion are reduced to a metallic state and act as catalytic active sites.

<Third separation step>
The third separation step is performed after the synthesis step and before the first separation step, and is a step of separating H ₂ O as water vapor from the reaction product produced in the synthesis step.

The reaction product produced in the synthesis process can be separated into H ₂ O as water vapor by passing through the third separation device 6 midway through the first line 11. The reaction product after H ₂ O has been separated into water vapor by the third separation device 6 is supplied to the cooling device 3 via the first line 11.

An example of a method for the third separation step is membrane separation using a porous membrane.

<First separation step>
The first separation step is a step of removing H ₂ O as water from a reaction product containing short-chain paraffins as the main product and H ₂ O as the by-product produced in the synthesis step.

The reaction product, which contains short-chain paraffins as the main product and H ₂ O as the by-product produced in the synthesis step, is supplied to the cooling device 3 via a first line 11 and cooled.

The temperature of the reaction product before cooling is, for example, 100°C or more, preferably 120°C or more, and, for example, 400°C or less, preferably 380°C or less.

By cooling the generated reaction product, the H ₂ O vapor is condensed to generate water.

The cooling temperature in the cooling device is, for example, 25°C or higher, preferably 85°C or higher, and, for example, 150°C or lower, preferably 100°C or lower.

That is, the temperature of the reaction product after cooling is, for example, 20°C or higher, preferably 30°C or higher, and, for example, 100°C or lower, preferably 80°C or lower.

The pressure in the cooling device is not particularly limited as long as it is a pressure at which H ₂ O as water vapor exists in the form of liquid (water) at the temperature of the reaction product after cooling described above.

Next, H ₂ O condensed by cooling is removed as water. More specifically, the reaction product containing a gas containing short-chain paraffins and unreacted gas and a liquid containing H ₂ O as water is supplied from the cooling device 3 to the first separation device 4 via the second line 12, and the gas containing short-chain paraffins and unreacted gas and the liquid containing H ₂ O as water are separated. The separated liquid containing H ₂ O as water is recovered from the drainage line 14.

The separation method for the first separation step is not particularly limited, and may be any known method. Known separation methods include, for example, distillation and extraction.

<Second separation step>
The second separation step is a step of separating the gas containing short-chain paraffins and unreacted gas into the short-chain paraffins and the unreacted gas. More specifically, the gas containing short-chain paraffins and unreacted gas separated by the first separation device 4 is supplied to the second separation device 5 via the third line 13, and separated into the short-chain paraffins and the unreacted gas. The separated short-chain paraffins are recovered from the short-chain paraffin discharge line 15.

The separation method for the second separation step is not particularly limited, and may be any known method. Examples of known separation methods include distillation and extraction. In addition, if it is a laboratory scale method, gel filtration chromatography may also be used.

<Resupply process>
The re-supply step is a step that occurs after the second separation step, and is for re-supplying the unreacted gas separated by the second separation step to the short chain paraffin synthesis unit 2. More specifically, the unreacted gas separated by the second separation unit 5 is re-supplied to the short chain paraffin synthesis unit 2 via the circulation line 16. As described above, the unreacted gas may be directly supplied to the short chain paraffin synthesis unit 2 from the circulation line 16, or may be supplied to the short chain paraffin synthesis unit 2 via the raw material gas supply line 10.

The unreacted gas can be reused as a reaction raw material by supplying it again to the short-chain paraffin synthesis unit 2.

If necessary, the unreacted gas can be pressurized using a compressor or the like and supplied to the short-chain paraffin synthesis unit 2.

(Variation 1)
The above-described short-chain paraffin synthesis system 1 includes a single short-chain paraffin synthesis apparatus 2, but may include a plurality of short-chain paraffin synthesis apparatuses 2 (multi-stage system of modified example 1). Note that the multi-stage system of modified example 1 is not shown.

The multi-stage system of the first modified example is not particularly limited as long as it has multiple short-chain paraffin synthesis units 2. Specifically, there are systems that have a second short-chain paraffin synthesis unit downstream of the first separation unit 4 and supply the gas containing short-chain paraffins separated by the first separation unit to the second short-chain paraffin synthesis unit, and systems that have a second short-chain paraffin synthesis unit downstream of the second separation unit 5 and supply the unreacted gas separated by the second separation unit 5 to the second short-chain paraffin synthesis unit.

In addition, when multiple short-chain paraffin synthesis devices 2 are provided, multiple cooling devices 3, first separation devices 4, second separation devices 5, and third separation devices 6 may also be provided.

(Variation 2)
The above-described short-chain paraffin synthesis system 1 includes the short-chain paraffin synthesis device 2 alone, but can also use a reaction device filled with another catalyst (multi-stage system of modified example 2). Note that the multi-stage system of modified example 2 is not shown.

Other catalysts include, for example, the methanation catalysts described in JP 2011-206770 A and JP 2013-119526 A.

The multi-stage system of the second modification is not particularly limited as long as it includes a reactor filled with another catalyst in addition to the short-chain paraffin synthesis unit 2. Specifically, there are systems including a reactor filled with another catalyst downstream of the first separation unit 4, and a gas containing short-chain paraffins separated by the first separation unit 4, which is supplied to the reactor filled with another catalyst, and a system including a reactor filled with another catalyst downstream of the second separation unit 5, and a gas containing short-chain paraffins separated by the second separation unit 5, which is supplied to the reactor filled with another catalyst.

In addition, when a reaction device filled with another catalyst is provided, the cooling device 3, the first separation device 4, the second separation device 5, and the third separation device 6 described above may also be provided separately.

(Variation 3)
The above-described short-chain paraffin synthesis system 1 includes a plurality of separation devices (the first separation device 4, the second separation device 5, and further, if necessary, the third separation device 6), but may include a single separation device (the system of the modified example 3).

An example of the system of the third modification is a system including only the short chain paraffin synthesis apparatus 2 and the third separation apparatus 6. The reaction product generated by the short chain paraffin synthesis apparatus 2, which contains the short chain paraffin as the main product and H ₂ O as the by-product, is supplied to the third separation apparatus 6, and the reaction product is separated into short chain paraffin and non-short chain paraffin by the third separation apparatus, and the short chain paraffin can be recovered.

In the third modification, the third separation device 6 can be, for example, a porous membrane (filter) made of zeolite, silica, and/or carbon. In this case, if a porous membrane with pores slightly smaller than the molecular diameter of methane (0.38 nm) is used, short-chain paraffins with molecular diameters equal to or larger than the molecular diameter of methane and unreacted gas and water vapor with molecular diameters smaller than the molecular diameter of methane can be separated. In addition, if a porous membrane with pores slightly larger than the molecular diameter of methane and slightly smaller than the molecular diameter of ethane is used, short-chain paraffins with molecular diameters equal to or larger than the molecular diameter of ethane and methane, unreacted gas, and water vapor with molecular diameters smaller than the molecular diameter of ethane can be separated.

When a porous membrane having pores slightly larger than the molecular diameter of methane and slightly smaller than the molecular diameter of ethane is used, the methane, unreacted gas and steam separated from the short-chain paraffins (excluding methane) can be supplied to a separate device for decomposing methane, whereby the methane can be decomposed into CO and/or _CO2 and hydrogen, and can be reused for the synthesis of short-chain paraffins. This allows the proportion of short-chain paraffins other than methane to be increased.

<Action and effect>
The short-chain paraffin synthesis catalyst of the present invention is a short-chain paraffin synthesis catalyst for producing short-chain paraffins having 1 to 4 carbon atoms by reacting CO and/or _CO2 with hydrogen, and includes a support and an active metal, the support includes a stabilized zirconia support having a tetragonal and/or cubic crystal structure in which a stabilizing element is solid-dissolved, the stabilizing element is at least one element selected from the group consisting of Y, La, Ce, Pr, Nd, Sm, Gd, Dy, Ca, and Mg, the active metal includes Fe and/or Co, and the atomic ratio of Fe and/or Co to the total amount of the active metals exceeds 50 atomic %. Therefore, methane, ethane, propane, and butane can be produced by reacting CO and/or _CO2 with hydrogen, and the volume ratio of the total of ethane, propane, and butane to the total of short-chain paraffins having 1 to 4 carbon atoms is 1 vol% or more, preferably 2 vol% or more, and more preferably 3 vol% or more.

More specifically, the short-chain paraffin synthesis catalyst of the present invention includes a stabilized zirconia carrier having a tetragonal and/or cubic crystal structure as a carrier. The oxygen vacancies of the stabilized zirconia carrier attract oxygen atoms of CO and/or _CO2 , and the active metal in a metallic state supported on the stabilized zirconia carrier attracts hydrogen, so that CO and/or _CO2 react with hydrogen efficiently on the surface of the short-chain paraffin synthesis catalyst to produce methane, ethane, propane, and butane, and the volume ratio of the total of ethane, propane, and butane to the total of short-chain paraffins having 1 to 4 carbon atoms is 1 volume % or more.

The short-chain paraffin synthesis catalyst of the present invention contains an active metal, the active metal contains Fe and/or Co, and the atomic ratio of Fe and/or Co to the total of the active metals is more than 50 atomic %. Therefore, _CO2 is produced, and further, methane, ethane, propane, and butane can be produced from CO, and the volume ratio of the total of ethane, propane, and butane to the total of the short-chain paraffins having 1 to 4 carbon atoms is 1 volume % or more.

The present invention will be described in more detail below with reference to examples and comparative examples. Note that the present invention is in no way limited to the examples and comparative examples. Furthermore, the specific numerical values of the compounding amounts (contents), physical property values, parameters, etc. used in the following description can be replaced with the upper limit (a numerical value defined as "equal to or less than") or lower limit (a numerical value defined as "equal to or more than" or "exceeding") of the corresponding compounding amounts (contents), physical property values, parameters, etc. described in the above "Form for carrying out the invention."

<Preparation of short-chain paraffin synthesis catalyst>
Example 1
100 g of zirconia hydrosol "ZSL-10A" (manufactured by Daiichi Kigenso Kagaku Kogyo, Zr: 10 mass percent, pH = 7.2) was taken, and nitrates of each raw material (manufactured by Fujifilm Wako Pure Chemical Industries, purity 99% or more) were mixed according to the atomic percentage of the formulation shown in Table 1. A mixture of zirconia hydrosol and nitrates of each raw material was mixed in a SiC crucible to obtain a uniform slurry. The slurry was placed in a muffle furnace and heated and dried at 170 ° C. for 2 hours to produce a hard slurry in which excess moisture was evaporated. Furthermore, with the hard slurry placed in the muffle furnace, the temperature of the muffle furnace was raised to 650 ° C. under the condition of 20 ° C. / min, and the hard slurry was fired at 650 ° C. for 4 hours. The gray-black bulk oxide obtained after firing was ground in a mortar and sieved with a 75 μm mesh to obtain a fine powder short-chain paraffin synthesis catalyst precursor.

A 1/2-inch SUS tube was filled with a predetermined amount of 0.5 g of glass wool, and the fine powder short-chain paraffin synthesis catalyst precursor was filled on top of it, and the tube was surrounded by a tubular furnace. The temperature of the furnace was adjusted so that the temperature of the fine powder short-chain paraffin synthesis catalyst precursor filled in the tube was 400°C or higher. After the temperature reached 400°C or higher, hydrogen was continuously supplied from the top of the tube at a flow rate of 500 mL/min for 4 hours to activate the fine powder short-chain paraffin synthesis catalyst precursor and obtain a short-chain paraffin synthesis catalyst. Next, the supply of hydrogen was stopped, the temperature of the short-chain paraffin synthesis catalyst was lowered to about room temperature, nitrogen was flowed at a flow rate of 100 mL/min for 1 hour, and air was supplied from another port at a flow rate of 5 mL/min so that the air-nitrogen ratio was 1/20, and the mixed gas of nitrogen and air was continued to flow at a total flow rate of 105 mL/min for 30 minutes. Furthermore, the air flow rate was increased to 10 mL/min, and the mixed gas was allowed to flow continuously for 60 minutes. During this time, it was confirmed that the temperature of the short-chain paraffin synthesis catalyst temporarily rose to around 40-50°C, then returned to room temperature, and the short-chain paraffin synthesis catalyst was obtained from the tube.

Examples 2 to 9 and Comparative Examples 1 to 14
Based on the formulations in Tables 1 and 3, each short-chain paraffin synthesis catalyst was prepared in the same manner as the short-chain paraffin synthesis catalyst of Example 1, except that the types of each raw material and the blending ratio of each raw material were changed.

Examples 10 and 11
The type of each raw material and the blending ratio of each raw material were changed based on the recipe in Table 1, and the process was the same as in Example 1 until a uniform slurry was obtained. Mesoporous alumina "MCM-41" (Sigma-Aldrich) powder (zeolite) was added to the obtained slurry according to the blending ratio (parts by mass) relative to 100 parts by mass of the catalyst components other than zeolite shown in Table 1, and after stirring for 24 hours, it was left to stand for another 12 hours. The slurry was placed in a muffle furnace and heated at 170°C for 1 hour, once removed from the muffle furnace and stirred again with a glass rod. Thereafter, the slurry was placed in the muffle furnace again, the temperature of the muffle furnace was raised to 650°C at a condition of 20°C/min, and the hard slurry was fired at 650°C for 4 hours. The subsequent process was the same as that of the short-chain paraffin synthesis catalyst in Example 1 to prepare each short-chain paraffin synthesis catalyst.

Examples 12 to 27
100 g of zirconia hydrosol "ZSL-10A" was taken, and either silica sol "Snowtex OS" (Nissan Chemical Industries, Ltd., SiO ₂ : 20 mass percent, pH = 4.0), alumina sol "AS-520A" (Nissan Chemical Industries, Ltd., Al ₂ O ₃ : 20 mass percent, pH = 4.0), or titania sol "Tainoc AM-15, Taki Chemical Industries, Ltd., TiO ₂ : 15 mass percent, pH = 4.0) was added according to the atomic ratio of the recipe shown in Table 2, and after initial mixing, each short-chain paraffin synthesis catalyst was prepared in the same manner as the short-chain paraffin synthesis catalyst of Example 1. Note that the type of each raw material and the mixing ratio of each raw material were changed based on the recipe in Table 2.

<Evaluation>
[Production of short-chain paraffins]
In a small reactor with a total length of 10 cm made of a 3/8 inch tube, 0.5 g of glass wool was laid on the lower end side of the tube, and 3 g of the short-chain paraffin synthesis catalyst of each Example and each Comparative Example was gently filled on top of it. A tubular furnace was placed around the reactor, and the catalyst temperature in the reactor was heated until it reached the reaction temperature of each Example or each Comparative Example. After reaching a predetermined temperature, hydrogen was flowed at 156 mL/min for 2 hours as a pretreatment. Thereafter, while hydrogen was supplied at 156 mL/min, nitrogen was supplied as a calibration gas at 5 mL/min and _CO2 gas was supplied as a reaction raw material at 39 mL/min. Furthermore, the pressure at the reactor inlet was adjusted to 0.98 MPaG, and the reaction was started under the condition of 4 L/g_cat·h. After the reaction started, the reaction was continued for 14 hours, and the gas at the reactor outlet was sampled at regular intervals and the composition was analyzed using a gas chromatograph (Agilent Micro GC990). Tables 1 to 7 show the composition ratio of short-chain paraffin oxides in the gas at the reactor outlet after 14 hours and the _CO2 conversion rates before and after the reaction. The conversion rates were calculated based on the following formula.

_CO2 conversion rate (%) = (volume of short chain paraffins + volume of carbon monoxide) / volume of raw _CO2

<Considerations>
In Examples 1 to 27, the carrier includes a stabilized zirconia carrier having a tetragonal and/or cubic crystal structure in which a stabilizing element is dissolved, the stabilizing element being at least one element selected from the group consisting of Y, La, Ce, Pr, Nd, Sm, Gd, Dy, Ca, and Mg, the active metal includes Fe and/or Co, and the atomic ratio of Fe and/or Co to the total of the active metals is more than 50 atomic %. Therefore, short-chain paraffins having 1 to 4 carbon atoms can be produced by reacting CO and/or CO ₂ with hydrogen, and the ratio of short-chain paraffins having 2 to 4 carbon atoms is higher than that of the comparative example, specifically, the volume ratio of the total of ethane, propane, and butane to the total of the short-chain paraffins having 1 to 4 carbon atoms is 3 volume % or more, and is up to 29.7 volume %.

In Comparative Examples 1 to 14, the carrier includes a stabilized zirconia carrier having a tetragonal and/or cubic crystal structure in which a stabilizing element is dissolved, and the stabilizing element is at least one element selected from the group consisting of Y, La, Ce, Pr, Nd, Sm, Gd, Dy, Ca, and Mg, but the active metal does not include Fe and/or Co, or the atomic ratio of Fe and/or Co to the total of the active metal is 50 atomic % or less. Therefore, in Comparative Examples 1 to 4, 6, 7, and 9 to 14, it is not possible to produce propane and/or butane by reacting CO and/or CO ₂ with hydrogen, and in Comparative Examples 1 to 14, the ratio of short-chain paraffins having 2 to 4 carbon atoms is lower than in the Examples, and specifically, the volume ratio of the total of ethane, propane, and butane to the total of short-chain paraffins having 1 to 4 carbon atoms is 0.8 volume % or less.

REFERENCE SIGNS LIST 1 Short-chain paraffin synthesis system 2 Short-chain paraffin synthesis device 3 Cooling device 4 First separation device 5 Second separation device 6 Third separation device 10 Raw material gas supply line 11 First line 12 Second line 13 Third line 14 Drainage line 15 Short-chain paraffin discharge line 16 Circulation line

Claims (10)

A short chain paraffin synthesis catalyst for producing short chain paraffins having 1 to 4 carbon atoms by reacting CO and/or _CO2 with hydrogen,
A carrier;
and an active metal;
The support includes a stabilized zirconia support having a stabilizing element dissolved therein and a tetragonal and/or cubic crystal structure,
The stabilizing element is at least one element selected from the group consisting of Y, La, Ce, Pr, Nd, Sm, Gd, Dy, Ca, and Mg;
The active metal comprises Fe and/or Co;
A short-chain paraffin synthesis catalyst, wherein the atomic ratio of Fe and/or Co to the total amount of the active metals is more than 50 atomic %. With respect to the sum of Zr and the stabilizing element constituting the stabilized zirconia support and Fe and/or Co contained in the active metal,
The atomic ratio of Zr is 0.40 atomic % or more and 65.0 atomic % or less,
The atomic ratio of the stabilizing element is 0.20 atomic % or more and 35.0 atomic % or less,
2. The short-chain paraffin synthesis catalyst according to claim 1, wherein the atomic ratio of Fe and/or Co is 9.0 atomic % or more and 99.4 atomic % or less. The short-chain paraffin synthesis catalyst according to claim 1, further comprising at least one element selected from the group consisting of Na, K, Mo, Ca, Sr, Ba, Ra, and C. The short-chain paraffin synthesis catalyst according to claim 1, further comprising at least one support selected from the group consisting of silica, alumina, titania, ceria, and zeolite. The short-chain paraffin synthesis catalyst according to claim 1, wherein the active metal is supported on the carrier and is dissolved in the stabilized zirconia carrier. The short chain paraffins include methane, ethane, propane, and butane;
2. The short-chain paraffin synthesis catalyst according to claim 1, wherein the total amount of ethane, propane, and butane is 3% by volume or more based on the total amount of the short-chain paraffins. A short-chain paraffin synthesis apparatus equipped with the short-chain paraffin synthesis catalyst according to any one of claims 1 to 6. A synthesis step of supplying CO and/or _CO2 and hydrogen to the short chain paraffin synthesis apparatus according to claim 7 and reacting them to obtain a reaction product containing short chain paraffin as a main product and _H2O as a by-product;
A first separation step of cooling the reaction product and separating it into a gas containing short-chain paraffins and a liquid containing H ₂ O as water;
a second separation step of separating the gas containing the short-chain paraffins into unreacted gas and the short-chain paraffins. The method for producing short-chain paraffins according to claim 8, further comprising a third separation step, which is performed after the synthesis step and before the first separation step, and which separates H ₂ O from the reaction product in the form of water vapor. The short-chain paraffin production method according to claim 8, further comprising a re-supply step of re-supplying the unreacted gas to the short-chain paraffin synthesis device after the second separation step.