WO2010143783A2

WO2010143783A2 - Iron-based catalyst for fischer-tropsch synthesis and preparation method thereof

Info

Publication number: WO2010143783A2
Application number: PCT/KR2009/005553
Authority: WO
Inventors: Suk Hwan Kang; Jong Wook Bae; Suk Jin Lee; Yun Jo Lee; Ki Won Jun
Original assignee: Korea Research Institute of Chemical Technology KRICT
Current assignee: Korea Research Institute of Chemical Technology KRICT
Priority date: 2009-06-12
Filing date: 2009-09-29
Publication date: 2010-12-16
Anticipated expiration: 2011-12-12
Also published as: KR20100133766A; KR101026536B1; WO2010143783A3

Abstract

Disclosed herein are an iron-based catalyst for Fischer- Tropsch synthesis (FTS) and a preparation method thereof. More specifically, disclosed are a novel catalyst wherein iron as a main catalytic component, one promoter metal selected from the group consisting of copper, manganese and cobalt, and if necessary, potassium, are incorporated as active components into a cerium-zirconium oxide prepared using a sol-gel process, and a preparation method thereof. When the iron-based catalyst is applied in Fischer- Tropsch synthesis reactions using synthetic gas, it can ensure stable catalytic activity for a long period of time while having the excellent effects of showing a high conversion of carbon monoxide and a low selectivity for main byproduct methane and increasing the yield of high-boiling-point hydrocarbons and C₂-C₄ light hydrocarbons.

Description

IRON-BASED CATALYST FOR FISCHER-TROPSCH SYNTHESIS AND PREPARATION METHOD THEREOF

The present invention relates to an iron-based catalyst for Fischer-Tropsch synthesis (FTS) and a preparation method thereof.

Technologies for converting synthesis gas to liquid hydrocarbons begin with the reforming of natural gas or the gasification of coal or biomass to produce synthesis gas. Generally, the Fischer-Tropsch synthesis (FTS) reaction transforms synthesis gas to hydrocarbons and involves the following main reactions taking place on iron-based catalysts or cobalt-based catalysts:

nCO +(2n+1)H₂ -> C_nH_2n+2+ nH₂O (1)

CO + H₂O -> CO₂+ H₂ (2)

2nCO + (n+1)H₂ -> C_nH_2n+2+ nCO₂ (3)

In the water-gas shift (WGS) reaction of equation (2) competing with the FTS reaction of equations (1) and (3), the carbon monoxide reacts with the water generated from equation (1), to form carbon dioxide and hydrogen. Thus, the water produced in equation (1) alters the ratio of hydrogen to carbon monoxide in the product in the Fischer-Tropsch synthesis reaction, and this alteration is known to occur particularly on iron-based catalysts having a high WGS reaction activity.

Catalysts used in the Fischer-Tropsch process vary in composition based upon the product mixture desired and reaction conditions employed. As a typical example, the Fischer-Tropsch catalyst comprises: at least one main catalytically active component selected from the elements of Group VIIIA of the Periodic Table, preferably Co, Ru, Fe or Ni; optionally, at least one promoter selected from the elements of Groups IIIA, IVA, VA, VIA or the like; and optionally, at least one promoter selected from the elements of Group IB [see US Patent No. 7067562 B2].

Although the main catalytically active component used in the Fischer-Tropsch synthesis reaction influences the distribution of products, the Fischer-Tropsch synthesis reaction generally shows high reaction activity at a H₂/CO ratio of 2.0, as explained by the Anderson-Schulz-Flory (ASF) mechanism. As is well known in the art, iron-based Fischer-Tropsch catalysts have high water-gas shift activity and tend to favor reaction (3) so as to additionally produce hydrogen during the reaction. Thus, the iron-based Fischer-Tropsch catalysts have high activity even in a wide H₂/CO molar ratio range (0.7-2.0). In contrast, cobalt-based Fischer-Tropsch catalysts tend to favor reaction (1) and have low water-gas shift activity, and thus show high a activity at a suitable H₂/CO molar ratio (about 2.0).　 Meanwhile, iron-based catalysts for Fischer-Tropsch synthesis have advantages in that they can be prepared at lower cost than cobalt-based catalysts and have inherently high catalytic activity for the WGS reaction. In addition, these catalysts allow the Fischer-Tropsch reaction to smoothly proceed due to their high water-gas shift activity, even when synthetic gas having a low H₂/CO molar ratio (H₂/CO < 1.0), produced from coal or biomass, is used, such that the need to introduce an additional process for controlling the H₂/CO molar ratio is eliminated. Thus, when iron-based catalysts having high water-gas shift activity are used to perform the Fischer-Tropsch reaction, a process for treating synthetic gas having a low H₂/CO molar ratio can be easily performed.

On the other hand, cobalt-based catalysts have the disadvantage of showing high catalytic activity only when the H₂/CO molar ratio of synthesis gas produced from natural gas is about 2.0. However, the use of the cobalt-based catalysts in the Fischer-Tropsch reaction is more advantageous for the production of liquid and waxy paraffinic hydrocarbons, because the reaction proceeds at a temperature lower than that used with the iron-based catalysts. Also, in the case of using the cobalt-based catalysts, a process of selectively producing required hydrocarbons (naphtha, diesel and wax) by additional hydrocracking or hydrogenation reaction is required. On the other hand, iron-based catalysts which are used at high temperature are advantageous for the direct production of mainly C₂-C₄ olefins, which can be used as raw materials for producing a variety of chemical or petrochemical products.

As is generally used in the art, iron-based catalysts for Fischer-Tropsch synthesis reaction are prepared by a fusion or precipitation method. When the precipitation method is used, the iron-based catalysts precipitated in an aqueous solution consist of iron hydroxides and iron oxides and are prepared through the precipitation, washing, drying and calcining processes. The iron-based catalysts prepared by the precipitation method as described above can provide liquid products of high viscosity in slurry-phase reactors. However, there is a disadvantage in that the activity of the catalysts is reduced due to the attrition of the catalysts. Meanwhile, iron-based catalysts prepared by fusion of iron ore are generally used together with promoters. Such iron-based catalysts prepared by the fusion method have excellent attrition resistance, but show activity lower than that of the iron-based catalysts prepared by precipitation. Indeed, the activity of the fused iron catalysts has been measured in slurry-phase reactors as half that of precipitated iron catalysts (See Fuel Processing Technology, Vol. 30, pp. 83, (1992)).

In addition, iron-based catalysts for Fischer-Tropsch synthesis can also be prepared by a spray-drying method, and in this case, the catalyst attrition resistance is improved. It was reported that the use of the spray-drying method improved the physical strength of iron-based Fischer-Tropsch catalysts without compromising the activity of the catalyst (see Industrial & Engineering Chemistry Research, vol. 40, pp. 1065, (2001)).

Iron-based catalysts generally contain at least one promoting component to assist in CO adsorption and/or iron reduction. Particularly, it is known that adding potassium to iron-based catalysts leads to an increase in the yield of high-boiling-point hydrocarbons which have a higher molecular weight. The effects of potassium on the behavior of iron-based catalysts may be summarized as follows:

1) potassium results in an increase in the average molecular weight of hydrocarbon products, leading to a higher α value and increases the olefin/paraffin ratio in the hydrocarbon products to increase the selectivity for olefins; and

2) potassium assists in the suppression of deactivation of the catalyst, and the optimum concentration of potassium increases the Fischer-Tropsch activity of the catalyst and decreases the selectivity for methane.

In addition, it is known that copper which is used as a promoter has the effect of facilitating the reduction of the iron. Copper tends to be more effective than potassium in increasing the rate of the Fischer-Tropsch reaction, but tends to attenuate water-gas shift activity, and for this reason, when synthetic gas having a low H₂/CO molar ratio (produced from coal or biomass) is used, copper makes it impossible to maintain the H₂/CO ratio suitable for the Fischer-Tropsch synthesis reaction. In order to overcome this shortcoming, unsupported single phase iron manganese spinels which are dual promoted with both copper and a Group IA or IIA metal may be used to selectively synthesize C₅₊ hydrocarbons at a high conversion of carbon monoxide (see US Patent No. 5118715).

A binder together with a promoter may be added as a structural stabilizer to an iron-based catalyst, because it is important to provide a large surface area in order to increase the dispersion of active component particles and the activity of iron as an active component. Silica is added as a binder to precipitated iron catalysts, especially for those used in fixed-bed reactors. However, because the use of silica in iron-based catalysts leads to an increase in the attrition of the catalysts, its usefulness in slurry-phase reactors has not yet been proven. It is known that, when silica is included in iron-based catalysts for Fischer-Tropsch synthesis, the concentration of iron in the catalyst is reduced due to an increase in the amount of supports in the catalyst, but the concentration of active metal sites is increased as a result of the metal being continuously in a highly dispersed state. Furthermore, it was reported that coprecipitation with cobalt in the preparation of iron-based catalysts for Fischer-Tropsch synthesis in slurry-phase reactors resulted in an increase in the selectivity for light olefins (see US Patent No. 4624967; and Applied Catalysis A: General, vol. 296, pp. 222 (2005)).　　It was reported that it is preferable to add potassium, copper and manganese as promoters to these iron-based catalysts in order to increase the reactivity of the catalysts and ensure a long-term performance of the catalysts.

Meanwhile, the present inventors previously developed an iron-based catalyst for Fischer-Tropsch synthesis, which contains a zeolite in order to increase the selectivity for high-boiling-point hydrocarbons and light olefins from synthetic gas, wherein the zeolite has a specific surface area of 200-500 ㎡/g and a Si/Al molar ratio of less than 50 is used in the catalyst after conversion into a hydrogen-type zeolite or after ion-exchange or impregnation with single or dual metal precursors of IA, IIA, Zr, P and lanthanide (Korean Patent Laid-Open Publication No. 2009-0038267).

It is an object of the present invention to provide a novel iron-based catalyst which ensures high catalytic activity and stability while having improved selectivity for high-boiling-point hydrocarbons and light hydrocarbons compared to iron-based catalysts which are generally known as catalysts for Fischer-Tropsch synthesis.

Another object of the present invention is to provide a method of preparing a cerium-zirconium oxide (Ce_xZr_1-xO₂) support for an iron catalyst and promoter metals using a sol-gel process.

Still another object of the present invention is to provide a method for preparing a novel iron-based catalyst for Fischer-Tropsch synthesis, which can increase the dispersion and activity of an iron catalyst and suppress the deactivation of the catalyst under the conditions of the Fischer-Tropsch synthesis reaction to ensure the effect of improving the long-term stability of the catalyst.

In order to accomplish the above objects, the present invention provides an iron-based catalyst for Fischer-Tropsch synthesis wherein 5-50 parts by weight of Fe, 0-15 parts by weight, preferably 0.5-15 parts by weight of K, and 0.25-10 parts by weight of a metal element selected from the group consisting of Cu, Co and Mn are incorporated into 100 parts by weight of a cerium-zirconium oxide support.

The present invention also provides a method of preparing a cerium-zirconium oxide for iron-based Fischer-Tropsch synthesis catalysts using a sol-gel reaction, the method comprising the steps of: adding an aqueous cerium precursor solution to a mixed solution of citric acid and ethylene glycol to prepare a cerium-containing solution; adding an aqueous zirconium precursor solution to a mixed solution of citric acid ethylene glycol to prepare a zirconium-containing solution; stirring a mixture of the cerium-containing solution and the zirconium-containing solution at a temperature between 50 ℃ and 100 ℃ and heating the stirred mixture at a temperature between 120 ℃ and 150 ℃ to completely remove water from the mixture, thereby preparing a sol; and calcining the sol by incrementally heating from 100 ℃ to 500 ℃ at a heating rate of 3 to 7 ℃/min.

The present invention also provides a method for manufacturing an iron-based catalyst for Fischer-Tropsch synthesis, the method comprising the steps of: adding an aqueous cerium precursor solution to a mixed solution of citric acid and ethylene glycol to prepare a cerium-containing solution; adding an aqueous zirconium precursor solution to a mixed solution of citric acid ethylene glycol to prepare a zirconium-containing solution; stirring a mixture of the cerium-containing solution and the zirconium-containing solution at a temperature between 50 ℃ to 100 ℃ and heating the stirred mixture at a temperature between 120 ℃ to 150 ℃ to completely remove water from the mixture, thereby preparing a sol; calcining the sol by incrementally heating from 100 ℃ to 500 ℃ at a heating rate of 3 to 7 ℃/min, thereby preparing a cerium-zirconium oxide support; and incorporating an Fe metal precursor, a precursor of a promoter metal selected from the group selected from the group consisting of Cu, Co and Mn, and if necessary, a K precursor, into the cerium-zirconium oxide precursor by impregnation or coprecipitation, thus obtaining a catalyst.

When an iron-based catalyst which comprises, as a support, a cerium-zirconium oxide prepared by a sol-gel process proposed in the present invention, is used in Fischer-Tropsch synthesis reactions, it has excellent effects of increasing the conversion of carbon monoxide and decreasing the selectivity for the main byproduct methane, thus increasing the yield of high-boiling-point hydrocarbons and light olefins.

FIG. 1 is a graphic diagram showing the conversion of carbon monoxide as a function of reaction time in Fischer-Tropsch synthesis reactions carried out using catalysts prepared in Examples 1 and 2 and Comparative Examples 1 and 4.

The present invention relates to an iron-based Fischer-Tropsch catalyst suitable for selective production of high-boiling-point hydrocarbons and light olefins from synthetic gas produced from natural gas, wherein iron, a promoter metal, and if necessary, potassium, are incorporated into a cerium-zirconium oxide support prepared by a sol-gel process.

Hereinafter, the present invention will be described in further detail.

The iron-based Fischer-Tropsch catalyst according to the present invention comprises 100 parts by weight of a cerium-zirconium oxide support, 5-50 parts by weight of Fe, 0-15 parts by weight (preferably 0.5-15 parts by weight) of K, and 0.25-10 parts by weight of a metal element selected from the group consisting of Cu, Co and Mn. Particularly, in the catalyst of the present invention, the weight ratio of the promoter metal (M) selected from among Cu, Co and Mn relative to the catalytic metal Fe, M/Fe, is maintained in the range from 0.05 to 0.20, and the weight ratio of the K metal to the iron (Fe) metal as a main active component, K/Fe, is maintained in the range from 0.0 to 0.3, and preferably from 0.01 to 0.30. In addition, the weight ratio of cesium (Ce) to zirconium, Ce/Zr, in the cerium-zirconium oxide (Ce_xZr_1-xO₂) which is used as a support for the above active components, is maintained in the range of from 0.05 to 0.50.

As is generally known in the art, the use of iron-based catalysts in Fischer-Tropsch reactions for the production of liquid hydrocarbons from synthetic gas shows a wide product distribution and low olefin selectivity because of the Fischer-Tropsch synthesis mechanism. Specifically, it is known that the selectivity for C₂-C₄ hydrocarbons is about 30% and the selectivity for olefins among the C₂-C₄ hydrocarbons is about 80%. Also, it is known that the maximum yield of C₂-C₄ hydrocarbons in Fischer-Tropsch reactions cannot exceed 56% as calculated according to Anderson-Schulz-Flory polymerization model due to the characteristics of CH₂ chain growth mechanism.

2009-0038267 and Korean Patent Application No. 2008-0058457, which were previously filed by the applicant, disclose processes for producing light olefins from synthesis gas, wherein the selectivity for olefins is improved either by the secondary thermal cracking of high-boiling-point hydrocarbons or by the catalytic cracking of high-boiling-point hydrocarbons using a hybrid catalyst comprising a zeolite-based acid catalyst. The inventions disclosed in said Korean patent applications suggest processes capable of increasing the production of light olefins while maximizing the utilization of byproducts by recycling reaction byproducts (methane and carbon dioxide) to a reforming process in order to improve the yield of C₂-C₄ hydrocarbons and increase carbon utilization efficiency on a catalyst prepared by impregnating or coprecipitating an iron catalyst into a zeolite or calcium oxide support. For example, Korean Patent Application No. 10-2008-0058457 discloses an Fe-Cu-K-based catalyst which contains, based on the weight of a zeolite support, 10-70 wt% of Fe, 1-10 wt% of Cu and 1-10 wt% of K, which are components showing activity in the hydrogenation of carbon monoxide.

The present invention suggests a novel catalyst system wherein an iron-based catalyst for Fischer-Tropsch synthesis is incorporated into a cerium-zirconium oxide support by impregnation or coprecipitation to minimize the selectivity for the byproduct methane, thus increasing the selectivity for high-boiling-point hydrocarbons and light hydrocarbons.

Examples of the iron precursor which can be used to prepare the catalyst according to the present invention include Fe (II) and Fe (III) precursors, such as iron nitrate hydrate (Fe(NO₃)₃ H₂O), iron acetate (Fe(CO₂CH₃)₂), iron oxalate hydrate (Fe(C₂O₄)₃ H₂O), iron acetylacetonate (Fe(C₅H₇O₂)₃) and iron chloride (FeCl₃). Also, the copper (Cu), cobalt (Co) or manganese (Mn) metallic elements serve as a promoter which is additionally used to improve the reduction and dispersion of iron (Fe), and may be one or a mixture of two or more selected from the group consisting of acetate-, nitrate- or chloride-based metal precursor compounds. In addition, potassium (K) may additionally be used as a component for increasing the selectivity for olefins, and the potassium (K) precursor may be selected from the group consisting of K₂CO₃, KOH and KHCO₃.

The Fe-Cu(or Co or Mn)-K-based catalyst prepared using the above-described iron precursor, promoter metal precursor and potassium precursor is incorporated into the cerium-zirconium oxide support by impregnation or coprecipitation to prepare the inventive catalyst. The prepared catalyst needs to be calcined in the temperature range from 300 to 700 ℃ in order to previously stabilize the structure of the catalytic active components.

The method for preparing the above-described iron-based catalyst according to the present invention will now be described in further detail.

First, the cerium-zirconium oxide support is prepared. The method for preparing the support comprises the steps of: adding an aqueous cerium precursor solution to a mixed solution of citric acid and ethylene glycol to prepare a cerium-containing solution; adding an aqueous zirconium precursor solution to a mixed solution of citric acid ethylene glycol to prepare a zirconium-containing solution; stirring a mixture of the cerium-containing solution and the zirconium-containing solution at a temperature of 50 to 100 ℃ and heating the stirred mixture at a temperature of 120 to 150 ℃ for 5-10 hours to completely remove water from the mixture, thereby preparing a sol; and performing stepwise calcination of the sol by maintaining the sol at temperatures of 100, 150, 200 and 300 ℃ for 0.5-2 hours for each temperature at a heating rate of 3 to 7 ℃/min, at a temperature of 350 to 450 ℃ for 2-10 hours, and finally at a temperature of 470 to 550 ℃ for 3-5 hours.

As the cerium and zirconium precursors which are used to prepare the support, acetate-, nitrate- or chloride-based metal precursor compounds may be used. In an embodiment of the present invention, the cerium-zirconium oxide support is prepared by a sol-gel process using cerium nitrate (Ce(NO₃)₂ 6H₂O) and zirconium oxynitrate (ZrO(NO₃)₂ xH₂O). The method for preparing the support will now be described in further detail. First, a process of dissolving the metal precursors for 20-50 minutes while stirring citric acid and ethylene at 40 to 70 ℃ is required. Specifically, each of the cerium and zirconium precursors is completely dissolved in 10-30 mL of water, and then added slowly to the above-prepared mixed solution of citric acid and ethylene glycol to prepare a cerium-containing solution and a zirconium-containing solution. Subsequently, the cerium-containing solution is mixed with the zirconium-containing solution, and the mixture is stirred at 50 to 100 ℃ for 20-50 minutes, and then heated at 120 to 150 ℃ 2-5 hours to completely remove water from the stirred mixture, thereby preparing a sol solution. Herein, the mixture is preferably heated at a temperature of 120 to 150 ℃. If the heating temperature is lower than 120 ℃, it will be difficult to remove water, because the temperature is too low, and if the heating temperature is higher than 150 ℃, particles of cerium-zirconium hydroxide will not be uniformly synthesized due to the rapid evaporation of water at high temperature. The prepared sol solution is subjected to a stepwise calcination program wherein the sol maintained at temperatures of 100, 150, 200 and 300 ℃ for 0.5-2 hours for each temperature at a heating rate of 3 to 7 ℃, at a temperature of 350 to 450 ℃ 470 to 550 for 3-5 hours, thereby preparing the cerium-zirconium oxide support. If the calcination temperature of the sol solution is rapidly increased, a support having a large specific surface area cannot be obtained due to the agglomeration of the cerium-zirconium oxide precursors, but if the calcination temperature is increased in a stepwise fashion as proposed in the present invention, a cerium-zirconium oxide support having a large specific surface area can be obtained. The cerium-zirconium oxide support prepared according to the above-described method has a specific surface area ranging from 5 to 50 ㎡/g. The larger the specific surface area of the support is, the better the dispersion of the active component iron and the promoter is. However, if the surface area of the support is less than 5 ㎡/g, the dispersion of iron will be significantly reduced. If the specific surface area of the cerium-zirconium oxide support exceeds 50 ㎡/g, the strength of the catalyst will be reduced. For these reasons, the support of the present invention needs to be maintained in the above-described specific surface area range. Moreover, the weight ratio of metal components (Ce/Zr) in the cerium-zirconium oxide (Ce_xZr_1-xO₂) is preferably maintained in the range from 0.05 to 0.50. If the weight ratio of Ce/Zr metals is less than 0.05, the amount of acid sites of ZrO₂will be increased, leading to an increase in the selectivity for byproducts in addition to methane and CO₂, and if the weight ratio of Ce/Zr metals is more than 0.5, the production of base sites advantageous for the production of byproducts will be increased. For this reason, the weight ratio of Ce/Zr metals is maintained in the above-described range, such that the production of byproducts such as methane can be suppressed while the deactivation of the catalyst can be suppressed to the greatest possible extent.

Meanwhile, the present invention is characterized by a method of preparing an iron-based Fischer-Tropsch catalyst using the cerium-zirconium oxide support prepared according to the above-described method.

Specifically, the method of preparing an iron-based Fischer-Tropsch catalyst according to the present invention comprises the steps of: adding an aqueous cerium precursor solution to a mixed solution of citric acid and ethylene glycol to prepare a cerium-containing solution; adding an aqueous zirconium precursor solution to a mixed solution of citric acid ethylene glycol to prepare a zirconium-containing solution; stirring a mixture of the cerium-containing solution and the zirconium-containing solution at 50 to 100 ℃ and heating the stirred mixture at 120 to 150 ℃ for 5-10 hours to completely remove water from the mixture, thereby preparing a sol; performing stepwise calcination of the sol by maintaining the sol at temperatures of 100, 150, 200 and 300 ℃ for 0.5-2 hours for each temperature at a heating rate of 3 to 7 ℃/min, at a temperature of 350 to 450 ℃ for 2-10 hours, and finally at a temperature of 470 to 550 ℃ for 3-5 hours, thereby preparing a cerium-zirconium oxide support; and incorporating an Fe metal support, a precursor of a metal (M) selected from the group consisting of Cu, Co and Mn, and if necessary, a K metal precursor, into the cerium-zirconium oxide support by impregnation or coprecipitation.

The method for preparing the catalyst will now be described in further detail. First, a precursor of Fe metal as an active metal, a precursor of M metal (Cu, Co and/or Mn), and if necessary, a precursor of K metal, are incorporated into the cerium-zirconium support to prepare an iron-based catalyst for Fischer-Tropsch synthesis. The Fe metal precursor is used such that the amount of iron (Fe) metal incorporated is 5-50 parts by weight based on 100 parts by weight of the support. The M metal (Cu, Co and/or Mn) precursor is used such that the amount of metal (M) incorporated is 0.25-10 parts by weight based on 100 parts by weight of the support. The K metal precursor is used such that amount of potassium (K) incorporated is 0-15 parts by weight, and preferably 0.5-15 parts by weight, based on 100 parts by weight of the support. Herein, the weight ratio of the metal (M) selected from the group consisting of Cu, Co and Mn relative to the iron (Fe) metal as a main catalytically active component, M/Fe, is maintained in the range from 0.05 to 0.20, and the weight ratio of potassium (K) to iron (Fe), K/Fe, is maintained in the range from 0.0 to 0.3, and preferably from 0.01 to 0.3.

One method of preparing an iron-based catalyst by impregnation according to the present invention is performed in the following manner. Each of the iron precursor, the M metal (Cu, Co and/or Mn) serving as a promoter, and the potassium precursor is incorporated into the cerium-zirconium oxide support by simultaneous or sequential impregnation, thereby preparing a catalyst for Fischer-Tropsch synthesis. More specifically, the iron precursor may be one or a mixture of two or more selected from the group consisting of Fe (II) and Fe (III) precursors, including iron nitrate hydrate (Fe(NO₃)₃ 9H₂O), iron acetate (Fe(CO₂CH₃)₂), iron oxalate hydrate (Fe(C₂O₄)₃ 6H₂O), iron acetylacetonate (Fe(C₅H₇O₂)₃) and iron chloride (FeCl₃). The copper, cobalt or manganese precursor serving as a promoter may be a precursor compound such as acetate, oxalate, nitrate or chloride. The potassium precursor may be one or a mixture of two or more selected from the group consisting of K₂CO₃, KOH and KHCO₃.

The iron-based catalyst prepared according to the above-described method is dried in an oven at 100 ℃ or above for about one day, and then calcined in the temperature range from 300 to 700 ℃, and preferably from 400 to 600 ℃ in order to be used as a catalyst for Fischer-Tropsch synthesis. If the calcination temperature is lower than 300 ℃, the dispersion of the active component iron and the promoter will be reduced, leading to a decrease in the reactivity of the catalyst, and if the calcination temperature is higher than 700 ℃, active sites will be reduced due to the agglomeration of the active component. For this reason, the calcination temperature needs to be maintained in the above-described range.

An alternative method of preparing an iron-based catalyst by coprecipitation according to the present invention can be performed in the following manner. The iron precursor, the potassium precursor and the M metal (Cu, Co and/or Mn) serving as a promoter are mixed with each other on the slurry of the cerium-zirconium oxide prepared by the sol-gel process, and are coprecipitated into the slurry in an aqueous solution, such that the pH of the solution reaches the range from 7 to 8. Then, the coprecipitated solution is aged, and the precipitate is aged at the temperature range from 40 to 90 ℃, thereby preparing an iron-based catalyst. In order to maintain a pH of 7-8 during the coprecipitation, a basic precipitant may be used. Preferred examples of the basic precipitant which can be used in the present invention include sodium carbonate, calcium carbonate, ammonium carbonate and ammonia water.

The aging time of the catalyst is 0.1-10 hours, and preferably 0.5-8 hours, and this aging time range assists in the formation of an iron-based catalyst having high activity. If the aging time is shorter than 0.1 hours, the dispersion of the Fe-Cu (or Co and Mn) components will be decreased, thus causing a disadvantage in terms of the Fischer-Tropsch reaction, and if the aging time exceeds 10 hours, the size of the Fe-Cu (or Co and Mn) particles will be increased, leading to a decrease in active sites, and the synthesis time will be increased, leading to cost-ineffectiveness. In the Fe-Cu (or Co and Mn) catalyst prepared by coprecipitation, the weight ratio of potassium (K) to iron (Fe), K/Fe, is maintained in the range from 0.0 to 0.3.

The catalyst for Fischer-Tropsch synthesis prepared according to the above-described method is used in catalytic reactions, after it is reduced in a fixed-bed, fluidized-bed or slurry-phase reactor at a temperature ranging from 200 to 700 ℃ in a hydrogen atmosphere. The reduced catalyst is used in conditions similar to those of general Fischer-Tropsch reactions. Specifically, the Fischer-Tropsch synthesis catalyst is preferably used at a temperature between 250 and 400 ℃ at a pressure of 5-60 kg/㎠ at a space velocity of 500-10000 h^-1, but the scope of the present invention is not limited thereto.

The iron-based catalyst prepared according to the above-described method is useful as a catalyst for Fischer-Tropsch synthesis. Specifically, when a Fischer-Tropsch reaction is carried out in the presence of the iron-based catalyst at a fixed reactant molar ratio of carbon monoxide: hydrogen: argon (internal standard) of 31.7: 63.3: 5.0 under conditions of a temperature of 300 ℃, a pressure of 10 kg/㎠ and a space velocity of 2000 L/kg_cathr, the conversion of carbon monoxide is more than 90 carbon mole%, and the yield of C₅₊hydrocarbons, including naphtha, diesel, middle distillate, heavy oils and wax, is more than 30 mole%. Also, the selectivity of the catalyst to the main byproduct methane (C₁) is less than 10 mole%.

Hereinafter, the present invention will be described in further detail with reference to examples in connection with STO reaction, but the scope of the present invention is not limited only to these examples.

Example 1: Preparation of 20Fe-2Cu-4K/Ce _0.05 Zr _0.95 O ₂ catalyst

1) Preparation of cerium-zirconium oxide support

First, 12.1 g of citric acid and 14.3 g of ethylene glycol were dissolved with stirring at 60 ℃ for 30 minutes, and 2.5 g of cerium nitrate hexahydrate (Ce(NO₃)₂ 6H₂O) serving as a cerium precursor was completely dissolved in the minimum amount (less than 30 mL) of water, and was then added slowly to the above-prepared mixed solution (A) of citric acid and ethylene glycol. Herein, the citric acid was used in an amount 10 times the number of moles of cerium-zirconium metals, and the ethylene glycol was used in an amount 40 times the number of moles of cerium-zirconium metals. Similarly, 351.9 g of citric acid and 417.8 g of ethylene glycol were dissolved with stirring at 60 ℃ for 30 minutes, and 38.9 g of a zirconium (IV) oxychloride precursor (ZrCl₂O 8H₂O; zirconium (IV) oxychloride octahydrate) was completely dissolved in less than 38.9 g of water, and was then added slowly to the above-prepared mixed solution (B) of citric acid and ethylene glycol. The solutions (A) and (B) were mixed with each other and stirred at 60 ℃ for 30 minutes, and the stirred solution was heated at 120 to 130 ℃ for 5 hours to completely remove water therefrom.　　　The resulting sol-state material was calcined by maintaining it at 100, 150, 200 and 300 ℃ for 1 hour for each temperature at a heating rate of 5 ℃/min, at 400 ℃ for 2 hours in order to maximize the surface area of the support, and finally at 500 ℃ for 4 hours. The cerium-zirconium oxide prepared by the sol-gel process had a composition of 5 wt% Ce-95 wt% Zr on the basis of metal content and was expressed as Ce_0.05Zr_0.95O₂.

2) Preparation of 20Fe-2Cu-4K/Ce_0.05Zr_0.95O₂ catalyst

3 g of the above-prepared cerium-zirconium oxide support, 4.41 g of iron nitrate hydrate (Fe(NO₃)₃ H₂O) as an iron precursor, 0.29 g of copper nitrate hydrate (Cu(NO₃)₂ H₂O) as a copper precursor and 0.21 g of potassium carbonate (K₂CO₃) as a potassium precursor were dissolved in 60 ml of triple distilled water. The solution was stirred at 60 ℃ for at least 6 hours and distilled under reduced pressure to remove water. The remaining material was dried at 105 ℃ for at least 12 hours, and then calcined at 500 ℃ in an air atmosphere for 5 hours, thereby preparing a catalyst for Fischer-Tropsch synthesis comprising an iron-copper-potassium/cerium-zirconium oxide. The prepared catalyst for Fischer-Tropsch synthesis had a composition of 20Fe-2Cu-4K/Ce_0.05Zr_0.95O₂ comprising, based on 100 parts by weight of the cerium-zirconium oxide, 20 parts by weight of Fe, 2 parts by weight of Cu and 4 parts by weight of K.

A 1/2-inch stainless steel fixed-bed reactor was charged with 0.3 g of the prepared catalyst before the start of a reaction. The catalyst was reduced at 450 ℃ for 12 hours in a hydrogen atmosphere (5 vol% H₂/He), and then the reactants, carbon monoxide: hydrogen: argon (internal standard), were set at a molar ratio of 31. 7: 63.3: 5.0 under conditions of a temperature of 300 ℃, a pressure of 10 kg/cm² and a space velocity of 2000 L/kg_cathr and introduced into the reactor. Then, the reactants were subjected to a Fischer-Tropsch reaction. The catalytic activity was measured after 60 hours on stream at which the activity of the catalyst was stabilized and maintained. The CO conversion and selectivity after 60 hours on stream were averaged for 10 hours and summarized in Table 1 below.

Example 2: Preparation of 20Fe-2Cu-4K/Ce _0.08 Zr _0.92 O ₂ catalyst

A cerium-zirconium oxide support was prepared in the same manner as in Example 1, and the prepared support had a composition of 8 wt% Ce-92 wt% Zr on the basis of metal content and was expressed as Ce_0.08Zr_0.92O₂. A catalyst for Fischer-Tropsch synthesis was prepared using the above-prepared cerium-zirconium oxide according to the same method as the catalyst preparation method of Example 1. The prepared catalyst had a composition of 20Fe-2Cu-4K/Ce_0.08Zr_0.92O₂ comprising, based on 100 parts by weight of the cerium-zirconium oxide, 20 parts by weight of Fe, 2 parts by weight of Cu and 4 parts by weight of K.

A Fischer-Tropsch reaction was carried out on the catalyst under the same conditions as in Example 1. The catalytic activity was measured after 60 hours on stream at which the activity of the catalyst was stabilized and maintained. The CO conversion and below.

Example 3: Preparation of 20Fe-2Cu-4K/Ce _0.15 Zr _0.85 O ₂ catalyst

A cerium-zirconium oxide support was prepared in the same manner as in Example 1, and the prepared support had a composition of 15 wt% Ce-85 wt% Zr on the basis of metal content and was expressed as Ce_0.15Zr_0.85O₂. A catalyst for Fischer-Tropsch synthesis was prepared using the above-prepared cerium-zirconium oxide according to the same method as the catalyst preparation method of Example 1. The prepared catalyst had a composition of 20Fe-2Cu-4K/Ce_0.15Zr_0.85O₂comprising, based on 100 parts by weight of the cerium-zirconium oxide, 20 parts by weight of Fe, 2 parts by weight of Cu and 4 parts by weight of K.

Example 4: Preparation of 20Fe-2Cu-4K/Ce _0.50 Zr _0.50 O ₂ catalyst

A cerium-zirconium oxide support was prepared in the same manner as in Example 1, and the prepared support had a composition of 50 wt% Ce-50 wt% Zr on the basis of metal content and was expressed as Ce_0.50Zr_0.50O₂. A catalyst for Fischer-Tropsch synthesis was prepared using the above-prepared cerium-zirconium oxide according to the same method as the catalyst preparation method of Example 1. The prepared catalyst had a composition of 20Fe-2Cu-4K/Ce_0.50Zr_0.50O₂comprising, based on 100 parts by weight of the cerium-zirconium oxide, 20 parts by weight of Fe, 2 parts by weight of Cu and 4 parts by weight of K.

A Fischer-Tropsch reaction was carried out on the catalyst under the same conditions as in Example 1. The catalytic activity was measured after 60 hours on stream at which the activity of the catalyst was stabilized and maintained. The CO 1 below.

Example 5: Preparation of 5Fe-0.5Cu-1K/Ce _0.08 Zr _0.92 O ₂ catalyst

A cerium-zirconium oxide support was prepared in the same manner as in Example 1, and the prepared support had a composition of 8 wt% Ce-92 wt% Zr on the basis of metal content and was expressed as Ce_0.08Zr_0.92O₂. A catalyst for Fischer-Tropsch synthesis was prepared using the above-prepared cerium-zirconium oxide according to the same method as the catalyst preparation method of Example 1, except that the contents of Fe, Cu and K as active metal components were changed. The prepared catalyst had a composition of 5Fe-0.5Cu-1K/Ce_0.08Zr_0.92O₂comprising, based on 100 parts by weight of the cerium-zirconium oxide, 5 parts by weight of Fe, 0.5 parts by weight of Cu and 4 parts by weight of K. Also, the prepared catalyst had a specific surface area of 35.6 ㎡/g and an average pore size of 13.2 nm.

A Fischer-Tropsch reaction was carried out on the catalyst under the same conditions as in Example 1. The catalytic activity was measured after 60 hours on stream at which the activity of the

Example 6: Preparation of 30Fe-3Cu-6K/Ce _0.08 Zr _0.92 O ₂ catalyst

A cerium-zirconium oxide support was prepared in the same manner as in Example 1, and the prepared support had a composition of 8 wt% Ce-92 wt% Zr on the basis of metal content and was expressed as Ce_0.08Zr_0.92O₂. A catalyst for Fischer-Tropsch synthesis was prepared using the above-prepared cerium-zirconium oxide according to the same method as the catalyst preparation method of Example 1, except that the contents of Fe, Cu and K as active metal components were changed. The prepared catalyst had a composition of 30Fe-3Cu-6K/Ce_0.08Zr_0.92O₂comprising, based on 100 parts by weight of the cerium-zirconium oxide, 30 parts by weight of Fe, 3 parts by weight of Cu and 6 parts by weight of K. Also, the prepared catalyst had a specific surface area of 29.6 ㎡/g and an average pore size of 12.9 nm.

A Fischer-Tropsch reaction was carried out on the catalyst under the same conditions as in Example 1. The catalytic activity was measured after 60 hours on stream at which the activity of the catalyst was stabilized and maintained. The CO

Example 7: Preparation of 40Fe-4Cu-8K/Ce _0.08 Zr _0.92 O ₂ catalyst

A cerium-zirconium oxide support was prepared in the same manner as in Example 1, and the prepared support had a composition of 8 wt% Ce-92 wt% Zr on the basis of metal content and was expressed as Ce_0.08Zr_0.92O₂. A catalyst for Fischer-Tropsch synthesis was prepared using the above-prepared cerium-zirconium oxide according to the same method as the catalyst preparation method of Example 1, except that the contents of Fe, Cu and K as active metal components were changed. The prepared catalyst had a composition of 40Fe-4Cu-6K/Ce_0.08Zr_0.92O₂comprising, based on 100 parts by weight of the cerium-zirconium oxide, 40 parts by weight of Fe, 4 parts by weight of Cu and 8 parts by weight of K. Also, the prepared catalyst had a specific surface area of 35.6 ㎡/g and an average pore size of 13.2 nm.

A Fischer-Tropsch reaction was carried out on the catalyst under the same conditions as in Example 1. The catalytic activity was measured after 60 hours on stream at which the activity of the catalyst was stabilized and maintained. The CO below.

Example 8: Preparation of 20Fe-2Cu/Ce _0.08 Zr _0.92 O ₂ catalyst

A cerium-zirconium oxide support was prepared in the same manner as in Example 1, and the prepared support had a composition of 8 wt% Ce-92 wt% Zr on the basis of metal content and was expressed as Ce_0.08Zr_0.92O₂. A catalyst for Fischer-Tropsch synthesis was prepared using the above-prepared cerium-zirconium oxide according to the same method as the catalyst preparation method of Example 1, except that the catalyst contained only Fe and Cu as active metal components without containing the potassium (K) metal. The prepared catalyst had a composition of 20Fe-2Cu/Ce_0.08Zr_0.92O₂comprising, based on 100 parts by weight of the cerium-zirconium oxide, 20 parts by weight of Fe and 2 parts by weight of Cu. Also, the prepared catalyst had a specific surface area of 24.6 ㎡/g and an average pore size of 15.5 nm.

Example 9: Preparation of 20Fe-2Mn-4K/Ce _0.08 Zr _0.92 O ₂ catalyst

A cerium-zirconium oxide support was prepared in the same manner as in Example 1, and the prepared support had a composition of 8 wt% Ce-92 wt% Zr on the basis of metal content and was expressed as Ce_0.08Zr_0.92O₂. A catalyst for Fischer-Tropsch synthesis was prepared using the above-prepared cerium-zirconium oxide according to the same method as the catalyst preparation method of Example 1, except that the catalyst contained only Fe and K as active metals and that manganese nitrate hydrate (Mn(NO₃)₂ H₂O) was used as the promoter precursor. The prepared catalyst had a composition of 20Fe-2Mn-4K/Ce_0.08Zr_0.92O₂comprising, based on 100 parts by weight of the cerium-zirconium oxide, 20 parts by weight of Fe and 2 parts by weight of Mn and 4 parts by weight of K.

A Fischer-Tropsch reaction was carried out on the catalyst under the same conditions as in Example 1. The catalytic activity was measured after 60 hours on stream at which the activity of the catalyst was stabilized and maintained. The CO conversion Example 10: Preparation of 20Fe-2Co-4K/Ce _0.08 Zr _0.92 O ₂ catalyst

A cerium-zirconium oxide support was prepared in the same manner as in Example 1, and the prepared support had a composition of 8 wt% Ce-92 wt% Zr on the basis of metal content and was expressed as Ce_0.08Zr_0.92O₂. A catalyst for Fischer-Tropsch synthesis was prepared using the above-prepared cerium-zirconium oxide according to the same method as the catalyst preparation method of Example 1, except that the catalyst contained only Fe and K as active metals and that cobalt nitrate hydrate (Co(NO₃)₂ H₂O) was used as the promoter precursor. The prepared catalyst had a composition of 20Fe-2Co-4K/Ce_0.08Zr_0.92O₂comprising, based on 100 parts by weight of the cerium-zirconium oxide, 20 parts by weight of Fe, 2 parts by weight of Co and 4 parts by weight of K.

A Fischer-Tropsch reaction was carried out on the catalyst under the same conditions as in Example 1. The catalytic activity was measured after 60 hours on stream at which the activity of the catalyst was stabilized and maintained. The CO conversion and

Comparative Example 1: Preparation of 20Fe-2Cu-4K/ZrO ₂ catalyst

Zirconia (ZrO₂) available from Kanto Chemical Co., Inc. was used as a metal oxide support, unlike Example 1. A catalyst for Fischer-Tropsch synthesis was prepared using the zirconia support according to the same method as the catalyst preparation method of Example 1. The prepared catalyst had a composition of 20Fe-2Cu-4K/ZrO₂comprising, based on 100 parts by weight of the zirconia support, 20 parts by weight of Fe, 2 parts by weight of Cu and 4 parts by weight of K.

A Fischer-Tropsch reaction was carried out on the catalyst under the same conditions as in Example 1. The catalytic activity was measured after 60 hours on stream at which the activity of the catalyst was stabilized and maintained. The CO conversion

Comparative Example 2: Preparation of 20Fe/Ce _0.08 Zr _0.92 O ₂ catalyst

A cerium-zirconium oxide support was prepared in the same manner as in Example 1, and the prepared support had a composition of 8 wt% Ce-92 wt% Zr on the basis of metal content and was expressed as Ce_0.08Zr_0.92O₂. A catalyst for Fischer-Tropsch synthesis was prepared using the above-prepared cerium-zirconium oxide according to the same method as the catalyst preparation method of Example 1, except that the catalyst contained only Fe as an active component. The prepared catalyst had a composition of 20Fe/Ce_0.08Zr_0.92O₂comprising, based on 100 parts by weight of the cerium-zirconium oxide, 20 parts by weight of Fe. Also, the prepared catalyst had a specific surface area of 37.8 ㎡/g and an average pore size of 13.8 nm.

A Fischer-Tropsch reaction was carried out on the catalyst under the same conditions as in Example 1. The catalytic activity was measured after 60 hours on stream at which the activity of

Comparative Example 3: Preparation of 20Fe-4K/Ce _0.08 Zr _0.92 O ₂ catalyst

A cerium-zirconium oxide support was prepared in the same manner as in Example 1, and the prepared support had a composition of 8 wt% Ce-92 wt% Zr on the basis of metal content and was expressed as Ce_0.08Zr_0.92O₂. A catalyst for Fischer-Tropsch synthesis was prepared using the above-prepared cerium-zirconium oxide according to the same method as the catalyst preparation method of Example 1, except that the catalyst contained only Fe and K as active components. The prepared catalyst had a composition of 20Fe-4K/Ce_0.08Zr_0.92O₂comprising, based on 100 parts by weight of the cerium-zirconium oxide, 20 parts by weight of Fe and 4 parts by weight of K. Also, the prepared catalyst had a specific surface area of 42.4 ㎡/g and an average pore size of 14.8 nm.

Comparative Example 4: Preparation of 20Fe-2Cu-4K/Ce _0.92 Zr _0.08 O ₂ catalyst

A cerium-zirconium oxide support was prepared in the same manner as in Example 1, except that the Ce/Zr ratio of the support was changed. The prepared support had a composition of 92 wt% Ce-8 wt% Zr on the basis of metal content and was expressed as Ce_0.92Zr_0.08O₂. A catalyst for Fischer-Tropsch synthesis was prepared using the above-prepared cerium-zirconium oxide according to the same method as the catalyst preparation method of Example 1. The prepared catalyst had a composition of 20Fe-2Cu-4K/Ce_0.92Zr_0.08O₂comprising, based on 100 parts by weight of the cerium-zirconium oxide, 20 parts by weight of Fe, 2 parts by weight of Cu and 4 parts by weight of K.

A Fischer-Tropsch reaction was carried out on the catalyst under the same conditions as in Example 1. The catalytic activity was measured after 60 hours on stream at which the activity of the 1 below.

[Table 1]

As can be seen in Table 1 above, the iron-based catalysts include the cerium-zirconium oxide (Ce_xZr_1-xO₂) support prepared by the sol-gel process according to the present invention, the support having a Ce/Zr weight ratio ranging from 0.05 to 0.50, and comprise, based on 100 parts by weight of the support, 5-50 parts by weight of Fe, 0-15 parts by weight of K and 0.25-10 parts by weight of one promoter metal selected from the group consisting of Cu, Co and Mn (Examples 1 to 10). When the iron-based catalysts of Examples 1 to 10 were used in the Fischer-Tropsch synthesis reactions, they showed excellent catalytic activities, including a carbon monoxide conversion of more than 90.4 carbon mole %, a C₅₊hydrocarbon yield of more than 32.3 carbon mole%, and a selectivity of less than 9.6 carbon mole% for byproduct methane. On the contrary, in the case in which the cerium-zirconium oxide support was not used (Comparative Example 1) and in the case in which one promoter metal selected from the group consisting of Cu, Co and Mn was not contained therein (Comparative Examples 2 and 3), the C₅₊hydrocarbon yield was shown to be low, and in the case in which the weight ratio of Ce/Zr in the cerium-zirconium oxide (Ce_xZr_1-xO₂) was 0.92 (Comparative Example 4), low catalytic activity was also observed.

FIG. 1 is a graphical diagram showing the conversion of carbon monoxide as a function of reaction time in Fischer-Tropsch synthesis reactions carried out in the presence of each of the catalysts of Examples 1 and 2 and Comparative Examples 1 and 4 at a fixed reactant molar ratio of carbon monoxide: hydrogen: argon (internal standard) under conditions of a temperature of 300 ℃, a pressure of 10 kg/㎠ and a space velocity of 2000 L/kg_cathr.　　As can be seen in FIG. 1, the deactivation of the inventive catalysts employing the cerium-zirconium oxide support (Examples 1 and 2) was remarkably suppressed compared to the catalyst of Comparative Example 1 employing the zirconium oxide.

Accordingly, it can be seen that, in the case of the inventive iron-based catalysts prepared using the cerium-zirconium oxide support in which the weight of Ce/Zr metals was limited and which was prepared by the sol-gel process, when the catalysts were used as catalysts for Fischer-Tropsch synthesis reactions, the deactivation of the catalysts with the passage of reaction time was very low while the production of the byproduct methane was suppressed. This suggests that the use of the catalysts can assist in ensuring a stable process.

The development of catalyst technologies for selectively producing high-boiling-point hydrocarbons for the production of light olefins and clean fuels, which are basic raw materials in the petrochemical industry, while coping with skyrocketing oil prices, can become an important factor in ensuring competitiveness in the development of efficient Fischer-Tropsch processes. Particularly, as a result of the improvement of iron-based Fischer-Tropsch catalysts, the thermal efficiency and carbon utilization efficiency of the entire process can be improved.

The iron-based Fischer-Tropsch catalyst employing the cerium-zirconium support according to the present invention has the excellent effects of increasing the conversion of carbon monoxide and decreasing the selectivity for methane as a major byproduct, thus increasing the yield of high-boiling-point hydrocarbons and light olefins. Thus, it is considered that the iron-based Fischer-Tropsch catalyst of the present invention can greatly contribute to the development of economical Fischer-Tropsch processes in future.

Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims

An iron-based catalyst for Fischer-Tropsch synthesis wherein 5-50 parts by weight of Fe and 0.25-10 parts by weight of a metal element selected from the group consisting of Cu, Co and Mn are incorporated into 100 parts by weight of a cerium-zirconium oxide support.
The iron-based catalyst of Claim 1, wherein 0.0-15 parts by weight of potassium is additionally incorporated into 100 parts by weight of the cerium-zirconium oxide support.
The iron-based catalyst of Claim 1 or 2, wherein the cerium-zirconium oxide support is prepared using a sol-gel process.
The iron-based catalyst of Claim 1 or 2, wherein the cerium-zirconium oxide support has a specific surface area of 5-50 ㎡/g.
The iron-based catalyst of Claim 1 or 2, wherein the weight ratio of the promoter metal (M) selected from among Cu, Co and Mn relative to the iron (Fe) metal, M/Fe, is maintained in the range from 0.05 to 0.20, and the weight ratio of the potassium (K) metal to the iron (Fe) metal, K/Fe, is maintained in a range of from 0.0 to 0.3.
The iron-based catalyst of Claim 1 or 2, wherein the weight ratio of cesium (Ce) to zirconium (Zr), Ce/Zr, is maintained in a range of from 0.05 to 0.50.
A method of preparing a cerium-zirconium oxide for an iron-based Fischer-Tropsch synthesis catalyst using a sol-gel reaction, the method comprising the steps of:

adding an aqueous cerium precursor solution to a mixed solution of citric acid and ethylene glycol to prepare a cerium-containing solution;

adding an aqueous zirconium precursor solution to a mixed solution of citric acid ethylene glycol to prepare a zirconium-containing solution;

stirring a mixture of the cerium-containing solution and the zirconium-containing solution at a temperature of 50 to 100 ℃ and heating the stirred mixture at a temperature of 120 to 150 ℃ to completely remove water from the mixture, thereby preparing a sol; and

calcining the sol by stepwise heating from 100 ℃ to 500 ℃ at a heating rate of 3 to 7 ℃/min.
The method of Claim 7, wherein the cerium precursor is cerium nitrate, and the zirconium precursor is zirconium oxynitrate.
The method of Claim 7, wherein the cerium-zirconium oxide support has a specific surface area of 5-50 ㎡/g.
The method of Claim 7, wherein the weight ratio of Ce/Zr in the cerium-zirconium oxide is maintained in a range of from 0.05 to 0.50.
A method for manufacturing an iron-based based catalyst for Fischer-Tropsch synthesis, the method comprising the steps of:

adding an aqueous cerium precursor solution to a mixed solution of citric acid and ethylene glycol to prepare a cerium-containing solution;

adding an aqueous zirconium precursor solution to a mixed solution of citric acid ethylene glycol to prepare a zirconium-containing solution;

stirring a mixture of the cerium-containing solution and the zirconium-containing solution at a temperature of 50 to 100 ℃ and heating the stirred mixture at a temperature of 120 to 150 ℃ to completely remove water from the mixture, thereby preparing a sol;

calcining the sol by stepwise heating from 100 ℃ to 500 ℃ at a heating rate of 3 to 7 ℃/min, thereby preparing a cerium-zirconium oxide support; and

incorporating an Fe metal precursor, a precursor of a promoter metal selected from the group selected from the group consisting of Cu, Co and Mn, and if necessary, a K precursor, into the cerium-zirconium oxide precursor by impregnation or coprecipitation, thus obtaining a catalyst.
The method of Claim 11, wherein a potassium precursor is further incorporated into the cerium-zirconium oxide support.
The method of Claim 11, wherein the Fe metal precursor is selected from the group consisting of Fe (II) and Fe (III) precursors, including iron nitrate hydrate (Fe(NO₃)₃ H₂O), iron acetate (Fe(CO₂CH₃)₂), iron oxalate hydrate (Fe(C₂O₄)₃ H₂O), iron acetylacetonate (Fe(C₅H₇O₂)₃) and iron chloride (FeCl₃).
The method of Claim 11 or 12, wherein the weight ratio of the promoter metal (M) selected from among Cu, Co and Mn relative to the iron (Fe) metal, M/Fe, is maintained in a range of from 0.05 to 0.20, and the weight ratio of the potassium (K) metal to the iron (Fe) metal, K/Fe, is maintained in a range of from 0.0 to 0.3.
The method of Claim 11 or 12, further comprising a step of calcining the prepared catalyst at a temperature between 300 ℃ and 700 ℃.