KR101261124B1 - Iron-based fishcer-tropsch catalyst with high catalytic activity and olefin selectivity, preparation method thereof, and method for preparing heavy olefin using the same - Google Patents

Abstract

The present invention provides a Fischer-Tropsch iron-based catalyst and a method for preparing the olefin having high catalytic activity and olefin selectivity, excellent coke resistance, and improved catalyst life when preparing olefin from syngas, and syngas under the iron-based catalyst. The present invention relates to a method for producing light olefins, wherein the hydrocarbon containing a lot of olefins is prepared in a first reactor and cracking the olefins in a continuous secondary reactor to improve the selectivity of light olefins compared to the prior art.

Description

Fischer-Tropsch iron-based catalysts having high catalytic activity and olefin yield, and methods for preparing the same, and methods for preparing light olefins from syngas using the catalysts , AND METHOD FOR PREPARING HEAVY OLEFIN USING THE SAME}

The present invention is a fischer with improved catalytic activity, olefin selectivity and coke resistance, which is used to prepare light olefins from syngas produced by reforming natural gas or gasification such as coal or biomass. -Tropsch (Fischer-Tropsch, FT) iron-based catalyst and a method for preparing the same.

The present invention also relates to a process for producing light olefins from syngas using the iron catalyst of the present invention having high catalytic activity and olefin selectivity and excellent coke resistance.

FT synthesis, a key process in gas-to-liquid (GTL) technology, was first introduced in 1923 by German chemists Fischer and Tropsch to produce synthetic fuel from coal gasification. Started. FT synthesis refers to a process for converting syngas into linear paraffinic hydrocarbons through a chain growth reaction using iron or cobalt catalysts. In the FT synthesis reaction, linear paraffinic hydrocarbons are mainly formed, but side reactions also produce double-linked alpha-olefins or alcohols of C _n H _2n as by-products. Undesired side reactions can also result in methanation reactions that convert syngas to methane and carbon deposition reactions that lower the activity of the catalyst.

The FT synthesis reaction is carried out using iron-based and cobalt-based catalysts, generally at a reaction temperature of 200 to 350 ° C. and a pressure of 10 to 30 atmospheres (atm). FT synthesis reactions include the following main chemical reactions:

1) Methane Production Reaction

2) Heavy hydrocarbon production reaction

　　　　　

　　　　　

3) alcohol production reaction

　　　　　

　　　　　

4) Water gas shift (WGS) reaction

　　　　　

　　　　　

Among the above reactions, carbon monoxide reacts with hydrogen to generate methane, which proceeds rapidly when the activity of the catalyst is high and the temperature is high. The higher the temperature, the faster the desorption than the chain reaction on the catalyst surface, resulting in higher boiling point hydrocarbon and methane production. In addition, as the reaction pressure increases, the concentration of the reactants increases on the surface of the catalyst, thereby increasing the probability of the chain reaction, thereby increasing the production of high-boiling hydrocarbons and reducing the methane production. When the FT synthesis reaction is performed under a low ratio of carbon monoxide and hydrogen, the selectivity of high-boiling hydrocarbons decreases and the methane selectivity increases.

As an early iron-based catalyst used in the FT reaction, there is an iron-based catalyst developed by Ruhrchemie and used in the LTFT reaction of Sasol. In the iron catalyst used in the reaction, iron pieces and copper metal are dissolved in a nitric acid solution to form iron nitrate and copper nitrate. The solution is added to a sodium carbonate solution to adjust the pH to 7 and stirred to prepare a precipitate. Iron hydroxide and copper hydroxide were washed with hot water to remove the remaining sodium ions, and then water was added to the iron and copper precipitates to make a slurry, and potassium silicate solution was prepared. In order to use the iron catalyst thus prepared in a fixed bed reactor, the precursor mixture in the form of slurry must be extruded, dried, and calcined at 300 ° C. The catalyst for slurry reactor is prepared by firing at 400 ~ 500 ℃ through spray dry (spray dry).

The iron catalyst prepared by the coprecipitation method is generally composed of Fe ₂ O ₃ / CuO / K ₂ O / Al ₂ O ₃ . As described above, the iron-based catalyst containing copper helps to reduce the iron oxide to the metal even at low temperatures by accelerating the reduction of the iron oxide. K ₂ O is used as chemical co-catalyst, Al ₂ O ₃ is is used as a structural promoter, where the cations of Al ₂ O ₃ is positioned into place of the cation positions of the iron Al ₂ O ₃ is iron oxide (Fe ₃ O ₄ ) spreads within the structure. As such, the structural promoter (Al ₂ O ₃ ) located in the iron oxide structure is located between the reduced iron structure when iron oxide is reduced by hydrogen, thereby suppressing the sintering phenomenon of the iron catalyst and increasing the surface area of the catalyst. do.

Iron-based catalysts have a greater change in FT product selectivity depending on the amount of potassium promoter than other promoters or supports. Alkali metals also interact with acidic supports to form aluminates with weak bases. Basic catalysts increase high boiling hydrocarbons by increasing the probability of chain growth. Low basic catalysts increase the hydrogenation reaction to increase the selectivity of methane and increase the selectivity of paraffinic hydrocarbons. In addition, potassium of the iron-based catalyst increases the rate of forming an active carbide compound, but also increases the carbon deposition of the catalyst.

If the FT synthesis reaction is operated below 240 ° C, carbon deposition hardly occurs in all cases of cobalt and iron catalysts. However, when the iron-based catalyst is operated at 280-350 ° C., coke caused by carbon is generated to affect the life of the catalyst and the selectivity of the product. The mechanism by which carbon is deposited in the FT synthesis reaction is due to chemical reactions as represented by the following schemes:

2CO → C + CO ₂ (Boardard reaction)

or

CO + H ₂ → C + H ₂ O

Among them, the doudouard reaction is known to act as a major factor. The activation energy of the voodoo reaction is 113 kJ / mol, which is greater than the activation energy of the FT synthesis reaction. Therefore, more carbon deposits are produced in the FT reaction as the temperature increases.

The rate at which carbon deposition of the catalyst is produced occurs much under relatively low hydrogen conditions. If the reaction pressure increases in FT synthesis, the hydrocarbon production rate increases and the carbon deposition rate decreases.

As a method for increasing the content of olefinic hydrocarbons in the product resulting from the FT synthesis reaction, potassium, a chemical promoter, may be added. However, if the potassium content is increased, there is a problem in that the lifetime of the catalyst is shortened by increasing the carbon deposition. Another method is to lower the FT synthesis reaction temperature. Since iron-based catalysts have lower activity than cobalt catalysts, if the FT synthesis reaction temperature is too low, the conversion of carbon monoxide decreases and the amount of desired product decreases. On the other hand, if the FT reaction temperature is too high, the conversion of carbon monoxide increases but the conversion to unwanted methane, there is a problem that the olefin hydrocarbon decreases.

The cracking phenomenon of the catalyst mainly includes chemical and physical causes. As a chemical cause, a structural change occurs when iron oxide, which is an active material of an iron-based catalyst, is converted into metal iron or iron carbide. Physical cracking is caused by friction and collision of catalyst particles. This catalyst cracking not only leads to catalyst deactivation but also interferes with normal and stable FT synthesis reaction operation, and also small broken catalyst particles can be included in the product and degrade the product. Therefore, long-term operation of the FT synthesis reaction requires stability of the catalyst life. To this end, it is necessary to develop a catalyst that generates less cracking and less coke.

WO 2009/100663 A1 discloses an iron-based catalyst having a Fe / Mn / Cu / K composition. A catalyst having high carbon monoxide conversion and low carbon dioxide selectivity was prepared by varying the composition ratios of Mn, Cu, and K. In the catalyst preparation method, NH ₄ OH or NH ₃ HCO ₃ is added to a solution of Fe (NO ₃ ) _{3 ·} 9H ₂ O and Mn (NO ₃ ) ₂ dissolved in water to form a precipitate. After drying for 16 hours at ℃, prepared by firing at 340 ℃ for 1 hour, impregnated with potassium dissolved in water and dried for 16 hours at 110 ℃, impregnated with Cu (NO ₃ ) ₂ solution, then again at 110 ℃ 16 After drying for an hour and calcined for 5 hours at 400 ℃. The reaction conditions were operated at a pressure of 2.0 MPa, H ₂ / CO 1.7, a reaction temperature of 240 ° C., and a space velocity (SV) 2000 h ⁻¹ . However, the prepared catalyst had a problem in that initial activity was rapidly dropped except for a catalyst composition having Fe / Mn = 6: 4, and in a composition having Fe / Mn = 6: 4, a low carbon monoxide conversion rate or a product was present. There was a problem in that the content of the olefinic hydrocarbons tends to be low.

An object of the present invention is to provide a high olefin selectivity and superior catalyst resistance compared to conventional iron catalysts in FT synthesis reaction for producing light olefins from syngas by a continuous two-stage reaction. It is an object of the present invention to provide an iron-based catalyst suitable for the synthesis reaction and advantageous for long-term operation and a method for producing the same.

It is also an object of the present invention to provide a process for producing light olefins in high yield from syngas using the catalysts described above.

According to an aspect of the present invention,

An iron oxide catalyst for FT synthesis reaction (hereinafter referred to as "iron catalyst for FT") is further provided, which further comprises Al as a structural stabilizer and Mn as a structural stabilizer in the composition of K / Fe / Cu as an iron-based FT catalyst. .

More specifically, the iron-based catalyst for FT according to the present invention is iron, copper, manganese, potassium and aluminum K: Fe: Cu: Mn: Al = 1-6: 100: 1-6: 1-20: 5-40 It is characterized by including the molar ratio of.

In the iron-based catalyst composition for FT according to the present invention, the content of potassium (K) is in the range of 1 to 6 moles compared to 100 moles of iron (Fe), and when the content is less than 1 mole, the content of olefin in the reaction product is reduced, There is a problem that the production of methane, which is a by-product, which is not a by-product, increases, and in the case of more than 6 moles, heavy wax is generated too much, causing clogging of the catalyst pores by the wax, thereby degrading catalytic activity.

In the iron-based catalyst composition for FT according to the present invention, copper (Cu) serves as a co-catalyst to help reduce the iron at low temperatures, present in an amount ranging from 1 to 6 moles compared to 100 moles of iron in the catalyst, If the content is less than 1 mole has a problem that the activity of the catalyst is lowered, the catalyst activity is reduced, the fraction of the olefin is reduced, if more than 6 moles there is a disadvantage that the coke production increases.

In the iron-based catalyst composition for FT according to the present invention, Al serves as a structural stabilizer to prevent sintering of the Fe catalyst component, the content of Al is in the range of 5 to 40 moles compared to 100 moles of iron, the content If the amount is less than 5 moles, Fe catalyst particles are sintered to increase the size of the catalyst particles, thereby degrading the activity of the catalyst. If the content is more than 40 moles, the dispersion of the catalyst particles is excessively increased to reduce the particle size. Due to this, there is a lot of by-products of methane, while the selectivity of olefins is lowered.

In the iron-based catalyst composition for FT according to the present invention, manganese (Mn) serving as a promoter is evenly dispersed in the iron particles to reduce the size of the iron particles, or change the phase of the iron oxide to improve the activity of the catalyst It promotes, reduces coke formation, reduces catalyst deactivation, increases olefin selectivity, and is present in an amount ranging from 1 to 20 moles relative to 100 moles of iron in the catalyst. If the content of Mn is less than 1 mole, the function as a promoter is inferior, and if more than 20 moles, there is a disadvantage in that the activity of the catalyst is inferior.

According to the present invention, the iron oxide catalyst for FT synthesis reaction composed of the above composition is prepared by a production method comprising the following steps 1) to 4):

1) dissolving an acidic copper, iron and manganese compound, and an acidic or neutral Al ₂ O ₃ precursor compound in distilled water to prepare an acidic catalyst precursor solution, and dissolving a basic precipitant in distilled water to prepare a basic precipitant solution;

2) mixing the acidic catalyst precursor solution and the basic precipitant solution obtained in step 1) and coprecipitating to prepare a catalyst precursor slurry, and aging the same to prepare a catalyst precursor precipitate;

3) washing the catalyst precursor precipitate with water-forming-drying-firing to obtain a catalyst oxide; And

4) carrying a potassium compound aqueous solution on the obtained catalyst oxide, and drying-fired it.

In the production method of the iron-based catalyst for FT synthesis reaction of the present invention, as the copper, iron and manganese compounds used in step 1), copper, iron and manganese compounds that can be used for preparing the catalyst can be used without particular limitation. For example, metal nitrate salts, halogen metal salts, metal oxides, organic acid metals and the like may be used for copper, iron and manganese.

The acidic or neutral Al ₂ O ₃ precursor compound used as the structural stabilizer in step 1) may be aluminum nitrate (Al (NO ₃ ) ₃ ), halogenated aluminum (eg, AlCl ₃ , AlBr _3, etc.), aluminum alkoxide ( As an example, aluminum isopropoxide, aluminum ethoxide, etc. may be used.

On the other hand, the above step 1), a structure stabilizer, an alkali aluminate (for example, instead of Al ₂ O ₃ precursor compounds of the acidic or neutral as described above, NaAlO _2, can also be used a basic Al ₂ O ₃ precursor compounds such as KAlO ₂₎ However, in this case, it is not mixed with copper, iron and manganese compounds, but mixed with a basic precipitant solution.

As a basic precipitating agent used in step 1), a basic carbonate selected from Na ₂ CO ₃ , NaHCO ₃ , KHCO ₃ , K ₂ CO ₃ , (NH ₄ ) ₂ CO ₃ , NH ₄ HCO ₃ or NaOH, KOH, A hydroxide selected from Ca (OH ₂ ) can be used.

Aging of the catalyst precursor slurry obtained in step 2) can be carried out by standing in the range of 20 ~ 100 ℃.

In step 3), the basic metal ions contained in excess in the aged catalyst precursor precipitate obtained in step 2) are washed with water and then molded. Molding may be used in any conventional method used in the manufacture of catalysts in the art, and is not particularly limited, but may be carried out by injection molding or spray drying, for example. Drying of the molded catalyst is carried out within 20 ~ 120 ℃, firing the catalyst is preferably carried out at 200 ~ 600 ℃, more preferably 300 ~ 500 ℃ in the air atmosphere.

If the calcination temperature is less than 200 ° C., the mixed metal carbonate hydroxide, which is a catalyst precursor, decomposes and conversion to a stable mixed metal oxide catalyst does not occur sufficiently. Thus, the stability of the catalyst is deteriorated. If the calcination temperature is more than 600 ° C., the catalyst component is excessive. The sintering phenomenon causes the catalyst particles to increase in size, resulting in separation of the catalytically active component and the cocatalyst, resulting in inferior catalytic activity.

In step 4), in order to satisfy 1 to 6 molar ratio of potassium to 100 moles of iron in the iron catalyst of the present invention, the catalyst oxide obtained in step 3) is further supported by an aqueous potassium compound solution to further introduce potassium ions into the catalyst. In the step of making, the potassium compound that can be used in this step is generally used in the art, and is not particularly limited, but potassium nitrate, potassium carbonate and the like can be used as an example.

Drying of the catalyst oxide supported on the aqueous potassium compound solution in step 4) is carried out at 50 ~ 120 ℃, firing is preferably carried out at 200 ~ 600 ℃, more preferably at 300 ~ 500 ℃ in the air atmosphere. The calcined catalyst may be activated at 250 to 350 ° C. under treatment with hydrogen or a synthesis gas which is a reaction gas.

On the other hand, in step 4), the compound containing potassium as a basic precipitant in step 1) is used, or in step 3) to partially remove the washing process of the precipitate so that potassium ions remain, from step 3) Of the catalyst oxides obtained, when 1 to 6 moles of potassium composition per 100 moles of iron are satisfied, they can be omitted.

According to the present invention there is provided a process for preparing light olefins in a syngas comprising H ₂ and CO comprising the following two successive steps:

(1) preparing a C2 to C4 hydrocarbon having a ratio of olefin of 60 vol% or more from syngas using the iron-based catalyst of the present invention as described above;

(2) increasing the content of light olefins by contacting the hydrocarbons produced by step (1) with an olefin cracking catalyst.

The method for preparing light olefins according to the present invention comprising the above two consecutive steps, unlike the conventional method, increases the total olefin yield as much as possible without using a separate separation process, and improves the selectivity of the light olefins in the range of C2 to C4. It has the advantage of letting.

Reactors used in the method for preparing light olefins of the present invention are generally used in the art, and specifically, a fixed bed reactor, a fluidized bed reactor, or a liquid phase reactor may be used.

Synthesis gas, which is the reaction gas used in step (1) in the method, includes carbon monoxide and hydrogen, and hydrogen is used in the range of 1 to 4 volumes, preferably 1.5 to 3 volumes, with respect to 1 volume of carbon monoxide. If it is less than 1 volume ratio, the conversion of reaction will fall, and if it exceeds 4 volume ratios, the production | generation of methane and paraffin will increase and the volume of a reactant will arise.

The reaction in step (1) is 200 ~ 400 ℃, preferably 250 ~ 350 ℃, 5 ~ 25 atmospheric pressure (atm), preferably 10 to 20 atm, and gas space velocity (GHSV) 500 ~ 8000 hours ^{- 1} , preferably at a flow rate in the range of 1000 to 6000 hours ^-1 . If the reaction temperature is less than 200 ° C conversion and olefin production rate is lowered, if the reaction temperature exceeds 400 ° C, the production of methane increases, catalyst deactivation proceeds quickly. In addition, when the reaction pressure is less than 5 atm, the conversion rate is lowered, and when it exceeds 25 atm, there is a problem that the production of paraffin increases. In addition, when the flow rate is less than 500 hours ^-1 , the productivity is lowered, and when the flow rate exceeds 8000 hours ^-1 , there is a problem that the conversion rate is lowered.

The olefin prepared from step (1) as described above has a selectivity in the range of 50 to 90 carbon mol%, and the selectivity of methane is maintained at 20 carbon mol% or less, preferably 15 carbon mol% or less.

Step (1) is a step in which the synthesis gas as a raw material is converted into a hydrocarbon compound by a Fischer-Tropsch reaction, and the hydrocarbon compound includes an olefin compound which is an unsaturated hydrocarbon and a paraffin compound which is a saturated hydrocarbon. All the hydrocarbon compounds produced are transferred to step (2), where the cracking reaction is continuously performed without further purification, so that only the olefins in the hydrocarbon compounds included cause the reaction.

(2) above reaction in the step is 400 ~ 700 ℃, preferably 450 ~ 650 ℃, 0.1 ~ 5 atmospheres (atm), preferably from 0.5 to 3 atm, and gas space velocity (GHSV) 500 ~ 10000 Time ^{- 1} , preferably at a flow rate in the range of 1000 to 7000 hours ^-1 . If the reaction temperature is less than 400 ℃ olefin conversion falls, if it exceeds 700 ℃, the production of paraffins and aromatic compounds increases, the problem that the catalyst deactivation due to the formation of coke proceeds quickly.

The olefin cracking catalyst used in the step (2) is not particularly limited in kind, but is preferably a high content silica zeolite having an MFI structure excellent in reaction activity and excellent in selectivity of the light olefin, among which ZSM- having a MFI structure. 5 zeolite is good. ZSM-5 zeolite has a structure in which two 10-membered-ring pores intersect with each other, and is structurally stable and particularly resistant to coke formation, making it suitable as an olefin cracking catalyst. Since the olefin cracking catalyst has a low acid density and low coke production and high selectivity of light olefins, the use of ZSM-5 having a high Si / Al ratio of about 30 to 300 makes use of high hard selectivity and high coke formation. Catalyst stability can be ensured.

According to the catalyst for FT of the present invention and the method for preparing light olefin using the same, the carbon dioxide conversion rate is higher than that of the conventional iron catalyst, and the content of the olefin hydrocarbon is not only high in the product but also excellent in corrosion resistance and catalyst cracking phenomenon. It can be reduced to increase the life stability of the catalyst.

Hereinafter, the present invention is described in more detail by the following examples, but the present invention is not limited to these examples.

Example  One

In 500 ml of distilled water, 100 g of Fe (NO ₃ ) ₃ .9H ₂ O, 2.39 g of Cu (NO ₃ ) ₂ , 6H ₂ O, 18.57 g of Al (NO ₃ ) _{3 ·} 6H ₂ O and Mn (NO ₃ ) ₂ 6H ₂ After dissolving 7.1 g of O, an aqueous metal solution was prepared, and an aqueous solution of 66.36 g of K ₂ CO ₃ was dissolved in 300 ml of distilled water, respectively, and then they were placed in a beaker with 1000 ml of distilled water heated to 70 ° C., mixed and co-precipitated with stirring at the same time. . After stirring for 3 hours at the same temperature, it was cooled to room temperature (20 ℃). The resulting precipitate was precipitated again by mixing distilled water corresponding to three times the precipitate slurry and discarded the filtrate, and the above process was repeated two more times and filtered. After filtration, washing with 1000 ml of water at 70 ° C., extrusion-molding the slurry with an extruder, dried for 12 hours at room temperature and 12 hours at 110 ° C., and calcined at 400 ° C. for 6 hours. The resulting catalyst precursor was impregnated with an aqueous solution of 1.25 g of KNO ₃ dissolved in 30 ml of distilled water, dried at 110 ° C. for 12 hours, and calcined at 400 ° C. for 6 hours to obtain a composition of 5K / 100Fe / 4Cu / 10Mn / 20AlOx molar ratio. Catalyst was prepared.

Using the prepared catalyst, the light olefin production reaction from the synthesis gas by the two-stage reaction of the following experimental example was carried out. Experimental results such as CO conversion and hydrocarbon selectivity carried out above are shown in Table 1 below.

Example  2

In the same manner as in Example 1, with respect to 100 mol of iron, a catalyst was prepared to contain 4 mol of copper, 10 mol of manganese, and 25 mol of alumina, and then 2K / of potassium nitrate was used as potassium compound to contain 2 mol of potassium. A catalyst having a composition of 100 Fe / 4Cu / 10Mn / 25AlOx molar ratio was prepared.

Using the prepared catalyst, the light olefin production reaction from the synthesis gas by the two-stage reaction of the following experimental example was carried out. Experimental results such as CO conversion and hydrocarbon selectivity carried out above are shown in Table 1 below.

Example  3

In the same manner as in Example 1, with respect to 100 mol of iron, a catalyst was prepared to contain 2 mol of copper, 4 mol of manganese, and 20 mol of alumina, and then 6K / of potassium nitrate as potassium compound to contain 6 mol of potassium. A catalyst having a composition of 100 Fe / 2Cu / 4Mn / 20AlOx molar ratio was prepared.

Using the prepared catalyst, the light olefin production reaction from the synthesis gas by the two-stage reaction of the following experimental example was carried out. Experimental results such as CO conversion and hydrocarbon selectivity carried out above are shown in Table 1 below.

Example  4

The catalyst was prepared in the same manner as in Example 1, but containing 5 mol of copper, 15 mol of manganese, and 15 mol of alumina, based on 100 mol of iron. At this time, sodium carbonate was used as a precipitating agent. A catalyst having a composition of 4K / 100Fe / 5Cu / 15Mn / 15AlOx molar ratio was prepared using potassium nitrate as a potassium compound so that 4 mol of potassium was contained in the prepared catalyst precursor.

Using the prepared catalyst, the light olefin production reaction from the synthesis gas by the two-stage reaction of the following experimental example was carried out. Experimental results such as CO conversion and hydrocarbon selectivity carried out above are shown in Table 1 below.

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Example 5

In the same manner as in Example 1, in the production of light olefins from the synthesis gas of the following experimental example, the temperature of the first stage reactor was performed at 260 ° C. instead of 280 ° C., and the experimental results such as CO conversion and hydrocarbon selectivity are shown in the following table. 1 is shown.

Example 6

In the same manner as in Example 1, in the production of light olefins from the synthesis gas of the following experimental example, the temperature of the first stage reactor was performed at 300 ° C. instead of 280 ° C., and the experimental results such as CO conversion and hydrocarbon selectivity are shown in the following table. 1 is shown.

Comparative example  One

In the same manner as in Example 1, with respect to 100 mol of iron, after preparing a catalyst to contain 4 mol of copper and 20 mol of alumina, 5K / 100Fe / 4Cu / using potassium nitrate as a potassium compound to contain 5 mol of potassium. A catalyst having a composition of 20 AlOx molar ratio was prepared.

Using the prepared catalyst, the light olefin production reaction from the synthesis gas by the two-stage reaction of the following experimental example was carried out. Experimental results such as CO conversion and hydrocarbon selectivity carried out above are shown in Table 1 below.

Comparative example  2

In the same manner as in Example 1, with respect to 100 mol of iron, after preparing the catalyst to contain 4 mol of copper, Mg (NO ₃ ) ₂ instead of manganese 6 mol, 20 mol of alumina, containing 5 mol of potassium A catalyst having a composition of 5K / 100Fe / 4Cu / 6Mg / 20AlOx molar ratio was prepared using potassium nitrate as the potassium compound.

Using the prepared catalyst, the light olefin production reaction from the synthesis gas by the two-stage reaction of the following experimental example was carried out. Experimental results such as CO conversion and hydrocarbon selectivity carried out above are shown in Table 1 below.

Comparative example  3

In the same manner as in Example 1, but with respect to 100 mol of iron, after preparing a catalyst to contain 8 mol of nickel and 20 mol of alumina using 4 mol of copper and Ni (NO ₃ ) ₂ instead of manganese, it contained 5 mol of potassium. A catalyst having a composition of 5K / 100Fe / 4Cu / 8Ni / 20AlOx molar ratio was prepared using potassium nitrate as the potassium compound.

Using the prepared catalyst, the light olefin production reaction from the synthesis gas by the two-stage reaction of the following experimental example was carried out. Experimental results such as CO conversion and hydrocarbon selectivity carried out above are shown in Table 1 below.

Comparative example  4

Performed in the same manner as in Comparative Example 1, in the light olefin production reaction from the synthesis gas of the experimental example was carried out at the temperature of the reactor in 260 ℃ instead of 280 ℃, the experimental results such as CO conversion and hydrocarbon selectivity 1 is shown.

Comparative example  5

Performed in the same manner as in Comparative Example 1, in the production of light olefins from the synthesis gas of the following experimental example, the temperature of the first stage reactor was carried out at 300 ℃ instead of 280 ℃, the experimental results such as CO conversion and hydrocarbon selectivity 1 is shown.

Experimental Example

The iron-based catalyst prepared in Examples and Comparative Examples was crushed and classified into about 1 mm size, 1 g of the catalyst was charged, and charged into a one-stage fixed bed reactor, and the activation process was carried out at atmospheric pressure at 450 ° C. for 12 hours. To reduce. Subsequently, under the conditions of a reaction temperature of 280 ° C. and a reaction pressure of 10 atm, a reaction was carried out while flowing a synthesis gas having a CO / H ₂ ratio of 2 at a flow rate of 3600 cc / g catalyst and h to prepare a hydrocarbon compound. . At this time, the hydrocarbon compound prepared above was moved to a high temperature trap, and the temperature of the trap was maintained at 200 ° C. The hydrocarbon compound prepared above is transferred directly to a two-stage reactor filled with a zeolite catalyst (HZSM-5, Si / Al = 140, 250-850 μm pellets), the reaction temperature is 500 ° C., and the reaction pressure is a cracking reaction at atmospheric pressure. The light olefin was prepared by the following procedure.

The composition of the product was analyzed by gas chromatograph (GC).

division CO conversion after 5 hours (%) 5 hours after reaction time
Hydrocarbon selectivity (%) CO conversion after 170 hours (%) Carbon deposit (%) after 170 hours of reaction time * CH ₄ C2 ~ C4 C5 + C2 ~ C4
Olefin Example 1 92.5 6.7 55.7 37.6 84.4 92.3 13.6 Example 2 80.6 5.9 56.3 37.8 83.2 80.2 15.6 Example 3 84.5 6.2 56 37.8 83.7 83.9 14.0 Example 4 92.5 6.8 55.5 37.7 83.9 92.3 13.4 Example 5 68.3 3.1 53.6 43.3 78.6 68.4 9.5 Example 6 95.2 7.9 57.4 34.7 84.6 92.8 19.8 Comparative Example 1 64.5 6.3 54.8 38.9 84.3 54.7 17.0 Comparative Example 2 60.1 9.2 37.2 53.6 67.3 51.2 16.7 Comparative Example 3 62.3 7.8 41.5 50.7 72.4 58.4 16.1 Comparative Example 4 42.5 4.3 43.5 52.2 78.8 38.9 11.6 Comparative Example 5 81.5 9.4 45.7 44.9 83.6 67.8 36.1 * After 170 hours of reaction in a one-step FT reaction, the catalyst was taken out and the amount of carbon deposition relative to the catalyst weight was shown by thermal analysis (TGA).

As shown in Table 1, the catalyst prepared in Examples 1 to 4 has a high initial CO conversion rate, it can be seen that the CO conversion rate does not significantly decrease even after the reaction time 170 hours. On the other hand, the catalyst prepared in Comparative Example 1 without a manganese promoter or the catalysts of Comparative Examples 2 and 3 in which magnesium or nickel were used as a promoter instead of manganese had a low CO conversion and a large CO conversion after 170 hours. You can see the decrease.

In general, it is known that the main reason for deactivation of the iron-based FT catalyst is due to coke formation in the catalyst. After the FT reaction for 170 hours, the catalysts of Examples and Comparative Examples were taken out and the amount of carbon deposited was analyzed by thermal analysis. It can be seen that this is relatively small, which is consistent with the tendency of catalyst deactivation.

As shown in Examples 1, 5, and 6, as the reaction temperature increases to 260, 280, and 300 ° C., the CO conversion rate increases, and after 170 hours of reaction time, the CO conversion rate increases and the decrease rate of the CO conversion rate increases. However, it can be seen that the catalysts of Comparative Examples 1, 4, and 5 are more carbon deposited after 170 hours of reaction time at the same reaction temperature, and have a higher activity deactivation than those of manganese-added catalysts.

Claims (10)

Iron (Fe), copper (Cu), manganese (Mn), potassium (K), and aluminum (Al) are converted into K: Fe: Cu: Mn: Al = 1-6: 100: 1-6: 1-20: 5 Fischer-Tropsch iron-based catalyst, characterized in that it comprises a molar ratio of ~ 40. A method for preparing an iron catalyst for Fischer-Tropsch synthesis reaction according to claim 1, comprising the following steps 1) to 4):
1) dissolving an acidic copper, iron and manganese compound, and an acidic or neutral Al ₂ O ₃ precursor compound in distilled water to prepare an acidic catalyst precursor solution, and dissolving a basic precipitant in distilled water to prepare a basic precipitant solution;
2) mixing the acidic catalyst precursor solution and the basic precipitant solution obtained in step 1) and coprecipitating to prepare a catalyst precursor slurry, and aging the same to prepare a catalyst precursor precipitate;
3) washing the catalyst precursor precipitate with water-forming-drying-firing to obtain a catalyst oxide; And
4) supporting an aqueous potassium compound solution on the obtained catalyst oxide, and drying-fired it. The method according to claim 2, wherein the acidic or neutral Al ₂ O ₃ precursor compound is selected from the group consisting of aluminum nitrate, aluminum halide and aluminum alkoxide. The method of claim 2, wherein the basic precipitant is Na ₂ CO ₃ , NaHCO ₃ , KHCO ₃ , K ₂ CO ₃ , (NH ₄ ) ₂ CO ₃ and NH ₄ HCO ₃ selected from a basic carbonate or NaOH, KOH and Ca ( It is a hydroxide selected from OH ₂ ). delete A process for preparing light olefins from syngas comprising H ₂ and CO, comprising the following steps:
(1) preparing a C2 to C4 hydrocarbon having a proportion of olefin of 60 vol% or more from syngas using the iron-based catalyst according to claim 1;
(2) increasing the content of light olefins by contacting the hydrocarbons produced by step (1) with an olefin cracking catalyst. The method of claim 6, wherein the ratio of the olefin in the C2 ~ C4 hydrocarbon prepared from the synthesis gas in the step (1) is 70% or more. The method according to claim 6, wherein the ratio of olefins in the C2 to C4 hydrocarbons prepared from the synthesis gas in the step (1) is 80% or more. The method of claim 6, wherein the olefin cracking catalyst is a zeolite having an MFI structure. 10. The method of claim 9, wherein the zeolite having the MFI structure is characterized in that the molar ratio of Si / Al 30 ~ 300.