WO2025110346A1 - Carbon dioxide conversion system having improved liquid fuel yield by using zeolite, and carbon dioxide conversion reactor therefor - Google Patents

Abstract

The present invention relates to a carbon dioxide conversion system having improved liquid fuel yield by using zeolite, and a carbon dioxide conversion reactor therefor, and, specifically, to a carbon dioxide conversion system and a carbon dioxide conversion reactor therefor, the system using silicoaluminophosphate-34 (SAPO-34) zeolite so as to have an improved yield of naphtha and gasoline, which are produced through carbon dioxide hydrogenation.

Description

System for carbon dioxide conversion with improved liquid fuel yield utilizing zeolite and reactor for carbon dioxide conversion thereof

The present invention relates to a carbon dioxide conversion system and a carbon dioxide conversion reactor thereof, which utilize zeolite to improve the yield of liquid fuel, and more particularly, to a carbon dioxide conversion system and a carbon dioxide conversion reactor therefor, which utilize silicoaluminophosphate (SAPO-34) zeolite to improve the yield of naphtha and gasoline produced by the hydrogenation reaction of carbon dioxide.

Since the Industrial Revolution, the use of fossil fuels such as coal and oil has increased, resulting in excessive carbon dioxide ( _CO2 ) emissions. Carbon dioxide absorbs more radiant energy than necessary, increasing the temperature of the Earth, which is called global warming. Global warming is causing natural disasters such as rising temperatures, rising sea levels, droughts, floods, heat waves, heavy snowfalls, and earthquakes, and is also having a wide range of negative effects on our surroundings, including physical environmental changes such as ecosystem disruption, agriculture, livestock, and industrial activities in general, and human health and living environments.

Recently, as interest in low-carbon and eco-friendly economy including 'carbon neutrality' is increasing worldwide, technology to capture and process carbon dioxide emitted into the air is receiving attention from academia and industry. Accordingly, there is a lot of interest in the development of new technologies to separate and recover the generated carbon dioxide and recycle it into the current energy and chemical industry system. One of these is the reaction to convert carbon dioxide into petroleum substitute chemicals through hydrogenation, and through the hydrogenation reaction of carbon dioxide, large amounts of carbon dioxide can be effectively converted into base oil (C ₂ ~C ₄ ) and liquid transportation fuel (C ₅ ~C ₁₂ ).

In particular, since the flue gas discharged from the oil refining process contains an excessive amount of carbon dioxide, it can be utilized to produce chemicals such as olefin and paraffin, effectively reducing carbon dioxide. However, the optimal condition for carbon dioxide conversion is a H ₂ /CO ₂ molar ratio of 3, but since the H ₂ /CO ₂ molar ratio in the flue gas is less than 2, it is difficult to convert carbon dioxide. The carbon dioxide conversion rate can be improved by additionally supplying hydrogen to the flue gas in the oil refining process, but additionally supplying hydrogen at the current high price of hydrogen is not efficient in terms of process cost.

There is a method of utilizing zeolite to improve the yield of liquid fuel by converting carbon dioxide under these low hydrogen supply conditions. However, ZSM-5, a Si-Al zeolite that has been widely used in the past, has the disadvantage of producing a lot of _CH4 as a byproduct when converting carbon dioxide, and forming more aromatic hydrocarbons than linear hydrocarbons.

The present invention is intended to solve the problems of the prior art, and to improve the yield of liquid fuel by utilizing SAPO-34, which is widely known as a Si-P-Al zeolite catalyst for carbon dioxide hydrogenation reaction.

In addition, the present invention provides a reactor including a carbon dioxide hydrogenation reaction catalyst and a zeolite catalyst as dual beds within one reactor.

A system for converting carbon dioxide with improved liquid fuel yield utilizing the zeolite of the present invention may include a first catalyst section including an Fe-based catalyst and converting carbon dioxide to produce a reaction product; and a second catalyst section including a zeolite and producing a liquid fuel from the reaction product.

The above first catalyst section and second catalyst section can be operated as a single process including a dual bed in one reactor.

The above liquid fuel may have a carbon number of C ₅ to C ₁₂ .

The above Fe-based catalyst may be a compound represented by the following [chemical formula 1].

[Chemical Formula 1]

Fe _a Cu _b K _c Al _d (M) _e

The above M includes at least one selected from rare earth metals including Ce, La, and Pr,

The sum of the composition ratios of a, b, c, d, and e above is 1.

The above Fe-based catalyst may have a pore volume of 0.17 to 0.21 cm ³ /g in BET analysis.

The above Fe-based catalyst can have a S _BET of 80 to 200 m ² /g.

The above zeolite may include a Si-Al zeolite, a Si-P-Al zeolite, or a mixture thereof.

The above Si-P-Al zeolite may be a silicaluminophosphate-34 (SAPO-34) zeolite.

The pore size of the above SAPO-34 can be 1 to 5 Å.

The Acidity of the above SAPO-34 can be 1 to 1.5 mmol/g _cat .

The (Si+P)/Al ratio of the above SAPO-34 can be 0.6 to 0.65.

The pressure of the first catalyst section and the second catalyst section can be 1 to 50 bar.

The temperature of the first catalyst part and the second catalyst part can be 100 to 1000°C.

The H ₂ /CO ₂ molar ratio of the gas flowing into the first catalyst section and the second catalyst section may be 1 to 3.

The GHSV (Gas Hourly Space Velocity) of the first catalyst part and the second catalyst part may be 1,000 to 10,000 mL/g·h.

The yield of the above C ₅ to C ₁₂ can be 20 to 30%.

The carbon dioxide conversion reactor of the present invention comprises: a columnar body; an inlet formed in a first direction through which gas is introduced from the outside into the columnar body; an outlet formed in a direction opposite to the first direction; and a furnace for applying heat to the columnar body; wherein the interior of the columnar body is connected to the inlet and the outlet, and comprises a first catalyst section for converting carbon dioxide to produce a reaction product; and a second catalyst section for producing a liquid fuel from the reaction product; the rear ends of the first catalyst section and the second catalyst section may include silica gel for absorbing and removing moisture; and glass wool for blocking heat energy emission.

The above first direction may be from top to bottom.

The above first catalyst part may include an Fe-based catalyst of a carbon dioxide conversion system with improved liquid fuel yield utilizing the zeolite.

The above second catalyst part may include a zeolite of a carbon dioxide conversion system with improved liquid fuel yield by utilizing the zeolite.

The molar ratio of H ₂ /CO ₂ of the gas introduced from the outside may be 1 to 3.

The internal pressure of the above columnar body can be 1 to 50 bar.

The internal temperature of the above columnar body can be 100 to 1000°C.

The GHSV (Gas Hourly Space Velocity) of the above columnar body can be 1,000 to 10,000 mL/g·h.

The above liquid fuel may have a carbon number of C ₅ to C ₁₂ .

The yield of the above C ₅ to C ₁₂ can be 20 to 30%.

A carbon dioxide conversion system and a carbon dioxide conversion reactor thereof with improved liquid fuel yield utilizing the zeolite of the present invention utilize SAPO-34 zeolite in a carbon dioxide hydrogenation reaction, thereby oligomerizing base fractions (C ₂ to C ₄ ) produced by reverse water gas shift reaction (RWGS) and Fischer-Tropsch synthesis reaction, and cracking long-chain hydrocarbons (C ₁₃₊ ) to improve the yields of naphtha and gasoline (C ₅ to C ₁₂ ).

Figure 1 is a schematic diagram showing a reactor for carbon dioxide conversion according to one embodiment of the present invention.

Figure 2 shows a TEM image of an Fe-based catalyst according to the CeO ₂ content of the present invention.

Figure 3 shows the XRD results of the Fe-based catalyst according to the CeO ₂ content of the present invention.

Figure 4 shows the results of H ₂ -TPR, CO ₂ -TPD, and CO-TPD analyses of the Fe-based catalyst according to the CeO ₂ content of the present invention.

Figure 5 shows the results of H ₂ -TPR, CO ₂ -TPD, and CO-TPD analyses of an Fe-based catalyst according to the type of rare earth metal of the present invention.

Figure 6 shows the reaction activity according to the use of zeolite of the present invention.

Figure 7 shows the hydrocarbon distribution of a liquid product according to the zeolite of the present invention.

Figure 8 shows the carbon distribution of the liquid product according to the use of zeolite of the present invention.

The embodiments described in this specification may be modified in various different forms, and the technology according to one implementation example is not limited to the embodiments described below. In addition, the embodiments of one implementation example are provided to more completely explain the present disclosure to a person having average knowledge in the relevant technical field. In this case, if there is no other definition in the technical and scientific terms used, they have the meaning commonly understood by a person having ordinary knowledge in the technical field to which this invention belongs, and the description of well-known functions and configurations that may unnecessarily obscure the gist of the present invention in the following description and the attached drawings are omitted.

Additionally, as used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly dictates otherwise.

Additionally, the terms first, second, etc. in this specification and the appended claims are not used in a limiting sense but are used for the purpose of distinguishing one component from another.

Additionally, in this specification and the appended claims, when it is said that a part such as a film (layer), region or component is located “on,” “above,” “upper,” “below,” “lower,” or “below” another part, this includes not only cases where one part is in contact with another part, but also cases where another part exists between the two parts.

In addition, the terms “about,” “substantially,” and the like, as used in this specification and the appended claims, are used in a meaning at or close to the numerical value when manufacturing and material tolerances inherent in the stated meaning are presented, and are used to prevent unscrupulous infringers from unfairly utilizing the disclosure where exact or absolute values are mentioned in order to aid in the understanding of this specification and the appended claims.

Additionally, the numerical ranges used herein include lower and upper limits and all values within that range, increments logically derived from the shape and width of the defined range, all doubly defined values, and all possible combinations of upper and lower limits of numerical ranges defined in different shapes.

Furthermore, the terms “include” or “have” in this specification and the appended claims mean that a feature or component described in the specification is present, and unless specifically limited, do not preclude the possibility that one or more other features or components may be added.

Hereinafter, a carbon dioxide conversion system and a carbon dioxide conversion reactor thereof using the zeolite of the present invention with improved liquid fuel yield will be described in detail with reference to the attached drawings.

Hydrogenation is a reaction in which a hydrogen molecule is added to a compound with an unsaturated functional group, such as a double bond or triple bond, under a metal catalyst to obtain a product. For this reaction, an unsaturated compound, hydrogen, and a catalyst are required. Depending on the activity of the catalyst and the type of reactant (unsaturated compound), the reaction proceeds at various temperatures and pressures.

The hydrogenation reaction of carbon dioxide is as follows.

(1) reverse water gas shift reaction

CO ₂ + H ₂ → CO + H ₂ O

(2) Carbon chain extension reaction

nCO + (2n+1)H ₂ → C _n H _2n+2 + nH ₂ O (n > 1)

[Table 1] below shows the intended use according to the carbon number range of the product obtained through the hydrogenation reaction of carbon dioxide.

Carbon range classification Intended Uses C ₁ -C ₄ gas Gas fuel, plastic synthetic raw material C ₅ -C ₁₂ gasoline Automotive fuel C ₁₂ -C ₁₆ Kerosene Jet fuel, diesel oil C ₁₆ -C ₁₈ Viaduct Diesel fuel, pyrolysis raw material C ₁₈ -C ₂₀ lubricant Lubricants, thermal decomposition raw materials C ₂₀ -C ₄₀ paraffin wax Wax C over ₄₀ asphalt Asphalt, tar

One of the important elements in the hydrogenation reaction of carbon dioxide is the catalyst. Without a metal catalyst, hydrogen gas itself hardly reacts with organic compounds. Cobalt-based and iron-based catalysts are mainly used. Iron-based catalysts are relatively inexpensive, have a wide range of reactor operating conditions, and produce a large proportion of higher products such as branched hydrocarbons and lower olefins, so they are widely used.

In the case of FeCuKAl catalysts, which are conventionally known as Fe-based catalysts, there was a problem that carbon dioxide conversion was relatively low. Therefore, in the present invention, a rare earth metal was applied as a cocatalyst that facilitates carbon dioxide adsorption and desorption to the FeCuKAl catalyst.

Rare earth metals refer to 15 elements, from Lanthnum with atomic number 57 to Lutetium with atomic number 71. These elements are chemically very stable, do not change state even in dry air, and have the characteristic of conducting heat well. Also, since they can maximize the performance of devices even in small quantities, they are widely used in information technology (IT) electronic products such as liquid crystal displays (LCDs), light-emitting diodes (LEDs), and smartphones, as well as military supplies such as missile control devices and fighter jets. In addition, they are applied in various fields as core elements such as fluorescent substances, catalysts, abrasives, and alloying elements.

In particular, cerium (Ce), the most abundant element among rare earth metal elements, is a highly electropositive and chemically reactive metal that is easily oxidized to cerium(IV) oxide (CeO ₂ ) in the air. The surface of cerium oxide is highly hydrophobic, a characteristic unique to rare earth metals, so it adsorbs organic compounds well, and due to this characteristic, it is utilized as various catalysts. In particular, CeO ₂ forms oxygen vacancies at the interface, which not only has a higher oxygen storage capacity but also greatly increases the rate of redox reactions.

The Fe-based catalyst introducing a rare earth metal according to the present invention hydrogenates carbon dioxide contained in an externally introduced gas to produce a reaction product including a base fraction (C ₂ to C ₄ ) and a long-chain hydrocarbon (C ₁₃₊ ). The Fe-based catalyst includes a rare earth metal and Fe, and can be used without limitation on type as long as it can convert carbon dioxide into a hydrocarbon compound. As an example, it may be a compound represented by the following [Chemical Formula 1], but is not limited thereto.

[Chemical Formula 1]

Fe _a Cu _b K _c Al _d (M) _e

The above M includes at least one selected from rare earth metals including Ce, La, and Pr,

The sum of the composition ratios of a, b, c, d, and e above is 1.

The molar ratio of _H2 / _CO2 in the exhaust gas required for the hydrogenation reaction of carbon dioxide is 3, and the reaction pressure also requires 30 to 40 bar. The hydrogenation reaction activity of carbon dioxide at this time is the maximum carbon dioxide conversion rate of 40% and C5 ₊ yield of 20% according to the values reported so far.

In the hydrogenation reaction of carbon dioxide, the carbon dioxide conversion rate and product yield can be improved by additionally supplying hydrogen, but this is rather inefficient when considering the process cost issue. Therefore, it is necessary to develop a carbon dioxide conversion system to achieve the target yield without additional hydrogen supply.

Zeolite refers to natural and synthetic silicate minerals. Due to the porous structure of zeolite in which cavities large enough to adsorb molecules exist regularly inside the crystal, zeolites exhibit excellent interfacial activity and have excellent catalytic properties. The catalytic properties of zeolites vary depending on the structure of zeolite, the nature and structural position of cations, the Si/Al content ratio, and the presence of active metal elements. The catalytic properties of zeolites are utilized in the fields of petroleum refining and petrochemicals, and when long-chain hydrocarbons and light olefins are supplied as reactants, the carbon chain can be controlled through cracking and oligomerization to improve the yield of naphtha and gasoline.

In the past, zeolites composed of Si-Al were widely used as catalysts. However, Si-Al zeolites have the disadvantages of producing a lot of _CH4 as a by-product during the cracking process due to strong acid sites, causing a decrease in catalytic activity due to coke, and forming more aromatic hydrocarbons than linear hydrocarbons due to the large pore size (5-6 Å).

As a means to improve the problems of such Si-Al zeolites, Si-P-Al zeolites, which are widely known as MTO (Methanol to Olefin) catalysts, can be utilized. The Si-P-Al zeolite may be, as an example, preferably silicon aluminophosphate (silicoaluminophosphate-34, SAPO-34), but is not limited thereto.

The above SAPO-34 is a molecular sieve with a unique shape structure and pore structure, appropriate acid properties, and excellent stability under various operating conditions. Unlike Si-Al zeolites, SAPO-34 is a molecular sieve in which the P element exists between Si-Al, and is characterized by a three-dimensional configuration of pores measuring 3.8 x 3.8 Å in size to form a unique framework (Chabazite type, CHA). Due to the nest having a diameter of 7.5 x 8.2 Å in the middle of the three-dimensional channel, it has the advantage of suppressing the production of aromatic compounds and heavy olefins, thereby increasing the yield of light olefins (C ₂ to C ₄ ). In addition, since the strength of the acid site is weaker than that of conventional zeolites, it can relatively suppress the production of by-products such as coke and CH ₄ .

Accordingly, the present invention aims to improve the yield of naphtha and gasoline (C ₅ to C ₁₂ ), which are liquid fuels, through carbon dioxide conversion by applying Si-P-Al zeolite as a dual bed to an Fe-based catalyst.

<Carbon Dioxide Conversion System with Improved Liquid Fuel Yield Using Zeolite>

The present invention relates to a carbon dioxide conversion system with improved liquid fuel yield utilizing zeolite, comprising: a first catalyst section including an Fe-based catalyst and converting carbon dioxide to produce a reaction product; and a second catalyst section including zeolite and producing a liquid fuel from the reaction product.

The above first catalyst section and second catalyst section are operated as a single process including a dual bed in one reactor.

The above first catalyst section comprises an Fe-based catalyst, which hydrogenates carbon dioxide contained in an externally introduced gas to produce a reaction product comprising a base fraction (C ₂ to C ₄ ) and a long-chain hydrocarbon (C ₁₃₊ ). The Fe-based catalyst comprises a rare earth metal and Fe, and any catalyst capable of converting carbon dioxide into a hydrocarbon compound may be used without limitation on type. As an example, the catalyst may preferably be a compound represented by the following [Chemical Formula 1], but is not limited thereto.

[Chemical Formula 1]

Fe _a Cu _b K _c Al _d (M) _e

The above M includes at least one selected from rare earth metals including Ce, La, and Pr,

The sum of the composition ratios of a, b, c, d, and e above is 1.

The Fe-based catalyst represented by the above [chemical formula 1] has a pore volume of 0.17 to 0.21 cm ³ /g in BET analysis and an S _BET of 80 to 200 m ² /g and 95 to 100 m ² /g.

The second catalyst part includes zeolite, and increases the carbon number by oligomerizing the base oil (C ₂ to C ₄ ) generated in the first catalyst part, and cracks long-chain hydrocarbons (C ₁₃₊ ) into molecules having a smaller carbon number, thereby improving the yield of liquid fuel (C ₅ to C ₁₂ ). The zeolite includes Si-Al zeolite, Si-P-Al zeolite, or a mixture thereof, and as an example, preferably, it may be silicon aluminophosphate (silicoaluminophosphate-34, SAPO-34).

The pore size of the above SAPO-34 may be 1 to 5 Å, the Acidity may be 1 to 1.5 mmol/g _cat , and the (Si+P)/Al ratio may be 0.6 to 0.65.

The pressure of the first catalyst section and the second catalyst section is 1 to 50 bar, and the temperature is 100 to 1000°C, preferably 20 bar and 300°C, but is not limited thereto. If the pressure and temperature inside the column-shaped body are too low, the conversion reaction of carbon dioxide is insufficient, resulting in a small amount of reaction product produced, and if the pressure and temperature of the reactor are too high, there is a problem that energy efficiency is reduced.

The H ₂ /CO ₂ molar ratio of the gas flowing into the first catalyst section and the second catalyst section is 1 to 3, preferably 1.5 to 2, but is not limited thereto.

In addition, the GHSV (Gas Hourly Space Velocity) of the first catalyst part and the second catalyst part is 1,000 to 10,000 mL/g·h, preferably 3,000 to 8,000 mL/g·h, more preferably 6,000 to 7,000 mL/g·h, but is not limited thereto.

<Reactor for carbon dioxide conversion>

Figure 1 is a schematic diagram showing a reactor for carbon dioxide conversion according to one embodiment of the present invention.

A columnar body; an inlet formed in a first direction through which gas is introduced from the outside into the columnar body; an outlet formed in a direction opposite to the first direction; and a furnace for applying heat to the columnar body; wherein the interior of the columnar body is connected to the inlet and the outlet, and includes a first catalyst section which converts carbon dioxide to generate a reaction product; and a second catalyst section which generates liquid fuel from the reaction product; and the rear ends of the first catalyst section and the second catalyst section include silica gel which absorbs and removes moisture; and glass wool which blocks heat energy emission.

The above first direction is not particularly limited, and is preferably from the top to the bottom of the reactor.

Gas introduced from the outside through the inlet formed in the first direction in the columnar body is delivered to the first catalyst section. The first catalyst section includes an Fe-based catalyst to hydrogenate carbon dioxide to produce a reaction product including a base oil (C ₂ to C ₄ ) and a long-chain hydrocarbon (C ₁₃₊ ). The Fe-based catalyst includes a rare earth metal and Fe, and any catalyst capable of converting carbon dioxide into a hydrocarbon compound may be used without limitation on type. As an example, it may be a compound represented by the following [Chemical Formula 1], but is not limited thereto.

[Chemical Formula 1]

Fe _a Cu _b K _c Al _d (M) _e

The above M includes at least one selected from rare earth metals including Ce, La, and Pr,

The sum of the composition ratios of a, b, c, d, and e above is 1.

The Fe-based catalyst represented by the above [chemical formula 1] has a pore volume of 0.17 to 0.21 cm ³ /g in BET analysis and an S _BET of 80 to 200 m ² /g and 95 to 100 m ² /g.

The reaction product generated in the first catalyst unit is supplied to the second catalyst unit. The second catalyst unit includes zeolite to oligomerize the base oil (C ₂ to C ₄ ) generated in the first catalyst unit to increase the carbon number, and crack long-chain hydrocarbons (C ₁₃₊ ) to decompose them into molecules having a smaller carbon number, thereby improving the yield of liquid fuel (C ₅ to C ₁₂ ). The zeolite includes Si-Al zeolite, Si-P-Al zeolite or a mixture thereof, and as an example, preferably, it may be silicon aluminophosphate (silicoaluminophosphate-34, SAPO-34).

The pore size of the above SAPO-34 may be 1 to 5 Å, the Acidity may be 1 to 1.5 mmol/g _cat , and the (Si+P)/Al ratio may be 0.6 to 0.65.

The first catalyst section and the rear section of the first catalyst section include silica gel and glass wool. The silica gel removes moisture generated in the process reaction, and the glass wool prevents the release of heat energy of the reverse water gas shift reaction and the Fischer-Tropsch synthesis reaction.

The gas introduced from the outside contains carbon dioxide and hydrogen, and the molar ratio of H ₂ /CO ₂ is 1 to 3, preferably 1.5 to 2.

The internal pressure of the columnar body is 1 to 50 bar, and the temperature is 100 to 1000°C, preferably 20 bar and 300°C, but is not limited thereto. If the pressure and temperature inside the columnar body are too low, the conversion reaction of carbon dioxide is insufficient, resulting in a small amount of reaction product produced, and if the pressure and temperature of the reactor are too high, there is a problem that energy efficiency is reduced.

In addition, the GHSV (Gas Hourly Space Velocity) of the columnar body is 1,000 to 10,000 mL/g·h, preferably 3,000 to 8,000 mL/g·h, more preferably 6,000 to 7,000 mL/g·h, but is not limited thereto.

The liquid fuel produced in the second catalyst section is most preferably a hydrocarbon compound having a carbon number of C ₅ to C ₁₂ , and is delivered to the outside of the reactor or to another process through an outlet formed in the column-shaped body in a direction opposite to the first direction.

Hereinafter, specific examples of experiments will be given and explained. However, the experimental examples described below are only illustrative examples, and the technology described in this specification is not limited thereto.

<Experimental Example 1> CeO in Fe-based catalyst ₂ Effect according to content

The present invention introduces the characteristics of CeO ₂ into an Fe-based catalyst for the purpose of increasing the oxygen vacancy of the catalyst. Accordingly, the influence of the content of CeO ₂ in the Fe-based catalyst was confirmed.

Figure 2 shows TEM images of Fe-based catalysts according to the CeO ₂ content of the present invention. (Same magnification 100 nm, 5 nm) (a) is CeO ₂ 10 wt%, (b) is CeO ₂ 20 wt%, (c) is CeO ₂ 50 wt%, and (d) is CeO ₂ 100 wt%.

Looking at Fig. 2, CeO ₂ (111), (200), (220), (311) planes were confirmed. The average particle size was measured to be 89 nm for 10 wt% CeO ₂ , 250 nm for 20 wt% CeO ₂ , 410 nm for 50 wt% CeO ₂ , and over 500 nm for 100 wt% CeO _2. When the CeO ₂ lattice d-spacing value was calculated through the TEM image, it could be seen that as the CeO ₂ content increased, many CeO2 (111) and (220) planes were formed. In addition, it could be seen that the particles were clumped into round spherical shapes by CeO ₂ , and it could be seen that as the CeO ₂ content increased, the metal mixed particles clumped by CeO ₂ gradually grew larger.

In the case of CeO ₂ 100 wt%, unlike other catalysts, it was confirmed that CuO (110) phase (CuO d = 0.264 nm) was widely distributed. This is thought to be because CeO ₂ itself has a relatively low specific surface area, so the dispersion of Fe, Cu, and K was low, and therefore it can be estimated that Cu metal exists in a state of being largely aggregated.

In the case of _CeO2 , the crystal growth state differs significantly depending on the electronic state of Ce, and is generally divided into Rod (110), Cube (100), and Octahedral (111) forms. Rod is formed when it is between Ce3 ⁺ and Ce4 ⁺ , Cube is formed a lot when it is Ce3 ⁺ , and Octahedral is formed when it is ^Ce4 +.

[Table 2] shows the specific surface analysis according to the CeO ₂ content of the Fe-based catalyst.

CeO ₂ addition amount Catalyst name catalyst S _BET (m ² /g) t-plot micropore area (m ² /g) pore volume (cm ³ /g) Pore size (nm) CeO ₂ 0 wt% FeCuKeAl Fe _0.38 Cu _0.04 K _0.09 Al _0.49 158 0 0.15 3.4 CeO ₂ 10 wt% FeCuK10CeAl Fe _0.37 Cu _0.04 K _0.09 Ce _0.02 Al _0.48 99 0 0.1 4.1 CeO ₂ 20 wt% FeCuK20CeAl Fe _0.37 Cu _0.04 K _0.09 Ce _0.03 Al _0.47 98.6 0 0.19 5.6 CeO ₂ 50 wt% FeCuK50CeAl Fe _0.35 Cu _0.04 K _0.09 Ce _0.08 Al _0.45 30 3.4 0.08 8.6 CeO ₂ 100 wt% FeCuKCeO ₂ Fe _0.5 Cu _0.06 K _0.14 Ce _0.26 9.3 2.6 0.06 21

As shown in [Table 2], the specific surface area and pore volume of the catalyst decreased as the CeO ₂ content increased through the BET analysis.

Fig. 3 shows the XRD results of the Fe-based catalyst according to the CeO ₂ content of the present invention. The XRD analysis according to the CeO ₂ content in the Fe-based catalyst was confirmed. As shown in Fig. 2, a peak corresponding to CeO ₂ was confirmed at 33.3 °, a peak corresponding to Fe ₂ O ₃ was confirmed at 35.9 °, and it was confirmed that the CeO ₂ peak grew as the CeO ₂ content increased. In addition, when approximately 32 to 43 of 2 theta/degree was magnified and confirmed, a phenomenon in which the Fe ₂ O ₃ peak shifted to a low angle was observed. It can be presumed that this was due to substitution by electron transfer between Fe and another transition metal.

FIG. 4 shows the results of H ₂ -TPR, CO ₂ -TPD, and CO-TPD analyses of the Fe-based catalyst according to the _{CeO 2} content of the present invention. Through thermal decomposition analysis (H ₂ -TPR, CO, and CO ₂ -TPD), the difference in the gas adsorption analysis results according to the CeO 2 content was confirmed. In the case of H ₂ -TPR, it was confirmed that H ₂ consumed by reduction gradually increased as the CeO ₂ content increased, and in particular, reduction was observed at high temperature. Since reduction is performed at 350 ℃ as a pretreatment in the actual CO ₂ hydrogenation reaction, the FeCuK20CeAl catalyst has the largest reduction amount in the actual reaction. Therefore, the higher the CeO ₂ content, the higher the temperature at which reduction is required. However, in the case of Fe catalyst, if reduction is performed above 400℃, the phase changes from Fe3 ⁺ to ^Fe0 , which causes deactivation in the _CO2 hydroxide reaction, so appropriate reduction conditions are required.

CO and _CO2 -TPD analysis showed that as _CeO2 increased, the amount of adsorbed CO and _CO2 increased, and the desorption phenomenon was confirmed at relatively high temperatures. This means that _CeO2 strongly adsorbs CO and _CO2 , which also contributes to the reaction activity. Although the amount of desorbed _CO2 was the largest at 20 wt% _CeO2 at the reaction temperature of 300 ℃, and the total CO and _CO2 adsorption amounts are not large, the fact that _CO2 is easily adsorbed/desorbed freely within the reaction temperature means that product formation is easier.

[Table 3] is a table showing the evaluation of reaction activity according to the CeO ₂ content of the Fe-based catalyst. Yield indicates the yield according to the conversion of CO+CO2.

CeO ₂ addition amount Catalyst name X _CO+CO2 (%) X _CO2 (%) Yield (%) CH ₄ C _2~4 C _5~12 C ₁₃₊ CeO ₂ 0 wt% FeCuKeAl 24.9 18.1 1.4 4.0 11.8 7.7 CeO ₂ 3 wt% FeCuK3CeAl 26.5 18.4 1.6 4.4 12.9 7.6 CeO ₂ 10 wt% FeCuK10CeAl 28 18.3 1.5 6.0 13.0 4.0 CeO ₂ 20 wt% FeCuK20CeAl 36.8 25.9 1.5 10.6 18.0 6.0 CeO ₂ 30 wt% FeCuK30CeAl 30.4 16.7 3.1 7.3 13.0 3.2 CeO ₂ 50 wt% FeCuK50CeAl 29 15.5 2.8 7.0 14.5 4.7 CeO ₂ 100 wt% FeCuKCeO ₂ 29.4 16.8 1.2 5.8 15.3 7.1

As shown in [Table 3], it was confirmed that the _CO2 conversion rate increased as the _CeO2 content increased. In particular, when _CeO2 was 20 wt%, the yields of _C2 ~ _C4 and _C5 ~ _C12 were the highest at 10.7% and 18.0%, respectively.

<Experimental Example 2> Screening of rare earth metal types in Fe-based catalysts

The present invention confirmed the same oxygen vacancy effect by adding a rare earth metal along with Ce to an Fe-based catalyst, and also added La and Pr to confirm the catalytic activity.

[Table 4] is a table showing a comparison of the reaction activity evaluation according to the type of rare earth metal of the Fe-based catalyst. Yield indicates the yield according to the conversion of CO+ _CO2 .

Rare earth metal types Catalyst name X _CO+CO2 (%) X _CO2 (%) Yield (%) CH ₄ C _2~4 C _5~12 C ₁₃₊ Ce FeCuK20CeAl 36.8 25.9 1.5 10.6 18.0 6.0 La FeCuK20LaAl 32.7 24.8 2.2 10.8 16.9 6.3 Pr FeCuK20PrAl 31.1 24.1 2.6 4.8 17.1 6.6

As shown in [Table 4], the _CO2 conversion rate of Ce was measured as 25.9%, La as 24.8%, and Pr as 24.1%.

FIG. 5 shows the results of H ₂ -TPR, CO ₂ -TPD, and CO-TPD analyses of the Fe-based catalyst according to the type of rare earth metal of the present invention. While La exists as La ₂ O ₃ oxide, Pr exists as Pr ⁶⁺ or Pr ⁵⁺ , so relatively many reducing sites can be expected. However, in reality, due to the high oxidation number, the number of sites adjacent to Al and Fe increases, so the number of sites for CO or CO ₂ to be adsorbed is relatively reduced, resulting in a lower adsorption amount than Ce in CO ₂ -TPD and CO-TPD.

<Experimental Example 3> Comparison by Zeolite Type

The present invention compares SAPO-34, a Si-P-Al zeolite, with ZSM-5, the most widely used conventional Si-Al zeolite. The average pore size of SAPO-34 is 3.8 Å, and the average pore size of ZSM-5 is 5.5 Å.

The reaction activity was evaluated when only an Fe-based catalyst (FeCuK20CeAl) was used and when an Fe-based catalyst and zeolite (SAPO-34 or ZSM-5) were used as a dual bed. The reaction conditions were as follows.

- Catalyst: Fe-based catalyst 0.6 g, zeolite 0.6 g (weight ratio 1:1)

- Reduction conditions: _H2 50 sccm, atmospheric pressure, 350 ℃, 5 h

- Reaction conditions: _H2 / _CO2 =1.6, 20 bar, 300℃

[Table 5] and Fig. 6 show the reaction activity according to the use of zeolite of the present invention. Yield represents the yield according to CO+CO ₂ conversion.

catalyst X _CO+CO2 (% X _CO2 (%) Selectivity C ₁ C _2~4 ⁼ C _2~4 C ₅ ⁼ C ₅ C ₆₊ Fe-based catalyst 36.8 25.9 4.1 24.4 4.7 0.3 0.6 64.5 Fe-based catalyst + ZSM-5 27.0 17.3 11.5 6.0 9.3 0.6 0.3 69.6 Fe-based catalyst + SAPO-34 36.3 28.9 6.8 6.6 8.2 0.2 0.4 77.8

It was confirmed that the selectivity of C6 ₊ increased when the Fe-based catalyst and zeolite were used as a dual bed compared to when only the Fe-based catalyst was used. However, when the zeolite was ZSM-5, there was a problem that the selectivity of _CH4 increased by about 2.5 times due to the effect of cracking by acid sites. Therefore, it was confirmed that the reaction activity was the best when the Fe-based catalyst and SAPO-34 were used as a dual bed.

Figure 7 shows the hydrocarbon distribution of the liquid product according to the zeolite of the present invention. The hydrocarbon distribution of the liquid product (C ₄ ~C ₁₀ ) was analyzed by Reformulyzer. (a) is Fe-based catalyst + ZSM-5, and (b) is Fe-based catalyst + SAPO-34. (a) shows 17% of the produced aromatic compound, while (b) shows 4.2%, which is significantly less than ZSM-5. This is thought to be because the aromatic compound was not formed during the oligomerization process due to the pore specificity of SAPO-34.

Figure 8 shows the carbon distribution of the liquid product according to the utilization of zeolite of the present invention. (a) is when only an Fe-based catalyst is used, and (b) is when an Fe-based catalyst and SAPO-34 are used as a dual bed. The specific gravity of C ₅ ~ C ₁₂ in the liquid product of (a) is 74.6%, and the specific gravity of C ₅ ~ C ₁₂ in the liquid product of (b) is 81.5%, confirming that the specific gravity of C ₅ ~ C ₁₂ in the liquid product increased by about 7% compared to (a).

Although the present invention has been described in this specification with reference to specific matters and limited embodiments, this has only been provided to help a more general understanding of the present invention, and the present invention is not limited to the embodiments described above, and those skilled in the art to which the present invention pertains can make various modifications and variations based on this description. Therefore, the ideas described in this specification should not be limited to the described embodiments, and all things that are equivalent or equivalent to the claims below, as well as the claims, are considered to fall within the scope of the ideas described in this specification.

Claims (26)

A first catalyst section including an Fe-based catalyst and converting carbon dioxide to generate a reaction product; and A second catalyst section comprising zeolite and generating a liquid fuel from the reaction product; A system for converting carbon dioxide, comprising: In paragraph 1, A system for converting carbon dioxide, wherein the first catalyst section and the second catalyst section are operated as a single process, including a dual bed in one reactor. In paragraph 1, The above liquid fuel is a system for converting carbon dioxide with a carbon number of C ₅ to C ₁₂ . In paragraph 1, The above Fe-based catalyst is a carbon dioxide conversion system represented by the following [chemical formula 1]. [Chemical Formula 1] Fe _a Cu _b K _c Al _d (M) _e The above M includes at least one selected from rare earth metals including Ce, La, and Pr, The sum of the composition ratios of a, b, c, d, and e above is 1. In paragraph 4, The above Fe-based catalyst is a carbon dioxide conversion system having a pore volume of 0.17 to 0.21 cm ³ /g as determined by BET analysis. In paragraph 4, The above Fe-based catalyst is a system for carbon dioxide conversion having a S _BET of 80 to 200 m ² /g. In paragraph 1, The above zeolite is a system for carbon dioxide conversion including Si-Al zeolite, Si-P-Al zeolite or a mixture thereof. In Article 7, The above Si-P-Al zeolite is a carbon dioxide conversion system that is a silicon aluminophosphate (SAPO-34) zeolite. In Article 8, The above SAPO-34 is a carbon dioxide conversion system with a pore size of 1 to 5 Å. In Article 8, The acidity of the above SAPO-34 is 1 to 1.5 mmol/g _cat , a system for carbon dioxide conversion. In Article 8, A system for carbon dioxide conversion having a (Si+P)/Al ratio of the above SAPO-34 of 0.6 to 0.65. In paragraph 1, A system for converting carbon dioxide, wherein the pressure of the first catalyst section and the second catalyst section is 1 to 50 bar. In paragraph 1, A system for converting carbon dioxide, wherein the temperature of the first catalyst section and the second catalyst section is 100 to 1000°C. In paragraph 1, A system for converting carbon dioxide, wherein the molar ratio of H ₂ /CO ₂ of the gas flowing into the first catalyst section and the second catalyst section is 1 to 3. In paragraph 1, A system for converting carbon dioxide, wherein the GHSV (Gas Hourly Space Velocity) of the first catalyst section and the second catalyst section is 1,000 to 10,000 mL/g·h. In the third paragraph, A system for converting carbon dioxide having a yield of C ₅ to C ₁₂ of 20 to 30%. A columnar body; an inlet formed in a first direction through which gas is introduced from the outside into the columnar body; an outlet formed in a direction opposite to the first direction; and a furnace for applying heat to the columnar body; The interior of the columnar body is connected to the inlet and outlet, and includes a first catalyst section that converts carbon dioxide to generate a reaction product; and a second catalyst section that generates liquid fuel from the reaction product; as a dual bed. A reactor for converting carbon dioxide, comprising: a rear end of the first catalyst section and the second catalyst section; silica gel for absorbing and removing moisture; and glass wool for preventing heat energy release. In Article 17, The above first direction is a reactor for converting carbon dioxide from top to bottom. In Article 17, A reactor for converting carbon dioxide, wherein the first catalyst section comprises a catalyst according to any one of claims 4 to 6. In Article 17, A reactor for converting carbon dioxide, wherein the second catalyst section comprises a catalyst according to any one of claims 7 to 10. In Article 17, A reactor for converting carbon dioxide, wherein the molar ratio of H ₂ /CO ₂ of the gas introduced from the outside is 1 to 3. In Article 17, A reactor for carbon dioxide conversion having an internal pressure of the columnar body of 1 to 50 bar. In Article 17, A reactor for carbon dioxide conversion having an internal temperature of the columnar body of 100 to 1000°C. In Article 17, A reactor for carbon dioxide conversion, wherein the GHSV (Gas Hourly Space Velocity) of the column-shaped body is 1,000 to 10,000 mL/g·h. In Article 17, The above liquid fuel is a reactor for converting carbon dioxide with a carbon number of C ₅ to C ₁₂ . In Article 25, A reactor for converting carbon dioxide having a yield of C ₅ to C ₁₂ of 20 to 30%.

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