KR20140104636A - Cobalt catalyst for fischer tropsh synthesis, preparation method of the same, and method of liqiud hydrocarbon using the same - Google Patents

Abstract

The present invention relates to a cobalt catalyst for a Fischer-Tropsch synthesis to manufacture liquid hydrocarbon using synthetic gas generated from gasification of natural gas, coal, biomass, or the like; and a preparation method thereof. In the cobalt-based catalyst for the Fischer-Tropsch synthesis which is manufactured according to the present invention, cobalt nanoparticles are formed at low temperatures and thus chemical and physical changes in catalyst particles are prevented; and also since an oxygen deficiency is induced on the surface of the catalyst particles, reduction is triggered, and thus the conversion rate of carbon monoxide and selectivity of the liquid hydrocarbon are improved when applied to the Fischer-Tropsch synthesis.

Description

TECHNICAL FIELD [0001] The present invention relates to a cobalt catalyst for Fischer-Tropsch synthesis, a process for producing the same, and a process for producing a liquid hydrocarbon using the same,

The present invention relates to a cobalt catalyst for Fischer-Tropsch synthesis for producing liquid hydrocarbons using synthesis gas produced by gasification such as natural gas, coal or biomass, and a process for producing the same.

In the development of GTL technology, which is being watched as an alternative to cope with recent rapid changes in oil prices, the improvement of FT synthesis catalysts is directly related to the enhancement of GTL technology's competitiveness. In particular, according to the improvement of the catalyst for FT reaction, thermal efficiency and carbon utilization efficiency of the GTL process can be improved and the FT reaction process can be optimized and designed. In order for such FT reaction there is a catalyst, such as iron and cobalt-based mainly used, the characteristics of the cobalt-based catalyst but are expensive disadvantage, flew low, high activity and long life and CO ₂ generated the yield of liquid paraffinic hydrocarbon It has a high advantage. In addition, since it can be used only as a low-temperature catalyst because of the problem of producing a large amount of CH ₄ at a high temperature, it must be dispersed well on a stable support having a high surface area such as alumina, silica and titania because expensive cobalt is used. , Re, and the like are additionally added.

The GTL process consists of three main processes, such as reforming of natural gas, FT synthesis of syngas, and reforming of product. Among these processes, iron and cobalt are used as catalysts at 200 to 350 ° C And the FT reaction performed at a pressure of 10 atm to 30 atm can be explained by four main reactions as follows.

(a) Chain growth in F-T synthesis

CO + 2H ₂ --CH ₂ - + H ₂ OH (227 ° C) = -165 kJ / mol

(b) Methanation.

CO + 3H ₂ CH ₄ + H ₂ OH (227 ° C) = -215 kJ / mol

(c) Water gas shift reaction

CO + H ₂ O CO ₂ + H ₂ H (227 ° C) = -40 kJ / mol

(d) Boudouard reaction.

2CO C + CO ₂ H (227 ° C) = -134 kJ / mol

Generally, the catalyst for FT synthesis is an oxide catalyst. Therefore, the reducing property of the catalyst for FT synthesis is one of the most important factors for determining the catalytic reaction. The reducibility of the catalyst is related to the oxygen deficiency on the surface of the catalyst. The greater the oxygen deficiency on the surface, the better the reducibility and the lower the temperature. When such a highly reducible catalyst is used in the Fischer-Tropsch synthesis reaction, the conversion of carbon monoxide is increased and the selectivity to liquid hydrocarbons is improved.

Accordingly, the inventors of the present invention have been studying a process for producing cobalt-based catalyst particles for Fischer-Tropsch synthesis using a mesoporous carbon material as a template. When a cobalt-containing precursor which decomposes when an oxidizing gas is decomposed is used, cobalt- In addition, not only the chemical and physical changes of the cobalt-based catalyst particles can be prevented by the low-temperature heat treatment during the production of the catalyst, but also the oxygen deficiency is induced on the surface of the catalyst particles by the reduction action by the carbon material template, It was confirmed that high cobalt-based catalyst particles were produced. In addition, when the catalyst is applied to a Fischer-Tropsch synthesis reaction, the conversion of carbon monoxide is increased and the selectivity of liquid hydrocarbons is improved. Thus, the present invention has been completed.

A first aspect of the present invention is a method for preparing a porous carbon material, comprising the steps of: preparing a porous carbon material to which a cobalt-based precursor, The prepared porous carbon material is heat-treated at an decomposition temperature or higher of the cobalt-based precursor in an oxidizing atmosphere to form cobalt-based catalyst particles from the cobalt-based precursor using the pores of the porous carbon material as a template, Based catalyst for Fischer-Tropsch synthesis, which comprises a first step and a second step.

A second aspect of the present invention is a method for preparing a porous carbon material, comprising: a first step of preparing a porous carbon material to which a cobalt-based precursor is applied in pores; Treating the prepared porous carbon material in an inert atmosphere at a temperature higher than a decomposition temperature of the cobalt precursor to a temperature lower than a pyrolysis temperature of the carbon material by using the pores of the porous carbon material as a template without removing the porous carbon material, And a second step of forming a cobalt-based catalyst particle from the precursor. The present invention also provides a method for producing a cobalt-based catalyst for Fischer-Tropsch synthesis.

A third aspect of the present invention provides a cobalt-based catalyst for Fischer-Tropsch synthesis prepared according to the present invention.

The catalyst may have a ratio of Co ^{3 +} / Co ^{2 +} peak by X-ray photoelectron spectroscopy to less than 3. In addition, the catalyst exhibits a first reduction peak at 180 ° C to 250 ° C and a second reduction peak at 260 ° C to 450 ° C in H ₂ -TPR analysis.

A fourth aspect of the present invention is a method for producing liquid hydrocarbons from a synthesis gas using a Fischer-Tropsch synthesis reaction, comprising the steps of: a) introducing a catalyst for Fischer-Tropsch synthesis according to the present invention into a Fischer- ) step; B) activating the catalyst with a catalyst for Fischer-Tropsch synthesis; And c) performing a Fischer-Tropsch synthesis reaction by the activated Fischer-Tropsch synthesis catalyst.

Hereinafter, the present invention will be described in detail.

When the cobalt-based precursor is decomposed and then heat-treated in an oxidizing atmosphere, an oxidizing gas generated from the cobalt precursor removes the carbon material at a temperature lower than the existing temperature, that is, the thermal decomposition temperature of the carbon material And that the generated cobalt particles have a high surface oxygen deficiency and therefore can easily be reduced.

In the present invention, "oxidizing gas" is a gas having an oxidizing power for oxidizing other substances. Non-limiting examples of oxidizing gases include oxygen or oxygen-containing materials as well as oxygen-containing materials, halogen gases such as F ₂ , Cl ₂ , Br ₂ , and I ₂ . Non-limiting examples of oxygen generating materials include HNO ₃ , H ₂ SO ₄ , KMnO ₄ , and H ₂ O ₂ . In addition, oxidizing gas can be formed by metal ions having a large valence such as FeCl ₃ and SnCl ₄ .

The cobalt-based precursor from which the oxidizing gas is generated when decomposed includes all cobalt-based water-soluble precursors or oil-soluble precursors capable of generating oxidizing gas upon decomposition. The cobalt-based precursor, which is decomposed when decomposed, is an oxide salt, an oxyhydroxide salt, a chloride salt, a carbonate salt, a nitrate salt, a citrate salt, a nitrosyl nitrate salt and a nitrate salt of cobalt. Firefighting. A water-soluble precursor selected from the group consisting of oxalates, carboxylates, sulfates and the like, or an alkoxy precursor containing hydrocarbons. Ammonium precursors, and the like. The non-limiting examples of cobalt-containing catalyst precursor is _{nitrate (NO 3), acetate (} CH 3 COO), chloride (Cl), carbonate (CO 3), sulfate (SO 4), nitrosylnitrate (NO (NO 3) 2) , Ammonium (NH ₄ ), and one or more precursors may be used as the cobalt precursor.

The porous material is divided into microporous and mesoporous materials depending on the pore size. Typically, when the pore size is 2 nm or less, micropores and when the pore size is between 2 and 50 nm, . The porous carbon material of the present invention is not limited to the pore size, but is preferably a mesoporous carbon material for producing a nano-level cobalt catalyst.

The porous carbon material of the present invention may have a pore average particle size of 1 to 50 nm and a surface area of 100 m ² g ^-1 to 2000 m ² g ^-1 , but the larger the surface area, the larger the content of cobalt particles.

In the present invention, the porous material may be carbon nanotubes, CMK-3, CMK-8, MSU-FC, activated carbon, graphite fiber, activated carbon fiber or a mixture thereof.

The "carbon nanotube" may be a cylindrical carbon crystal having a diameter of 0.5 nm to 10 nm, in which carbon atoms connected in a hexagonal ring are formed in a long dangle shape. The carbon nanotubes of the present invention may be single wall carbon nanotubes or multi wall carbon nanotubes.

"CMK-3" is a porous carbon material synthesized from mesoporous silica, SBA-15, having hexagonal pores and an axially long cylinder shape. "CMK-8" is a porous carbon material synthesized from silica-mesoporous silica, KIT-6, which has cubic structure in which two kinds of mesopores are three-dimensionally connected independently of each other. "MSU-FC" was synthesized from "MSU-F-silica" which is mesoporous silica. It has a mesocellular structure porous carbon having small pores of 4 to 8 nm between large pores of about 30 nm and pore structure Material.

"Activated carbon" is a substance having a strong adsorption property, and most constituent substances are carbonaceous substances. The graphite-shaped planar crystallizers are complex amorphous carbons and are porous and have an average pore radius of 1 mm to 2 mm and a specific surface area of 800 m ² / g to 1500 m ² / g.

In the present invention, the porous carbon material to which the cobalt-based catalyst precursor in which the oxidizing gas is decomposed is applied in the pores may be prepared by impregnating the cobalt-based catalyst precursor solution in the pores of the porous carbon material, followed by drying.

The solvent used for the cobalt precursor solution is not limited as long as it can evaporate below the temperature at which the oxidizing gas is decomposed from the cobalt precursor without chemical reaction with the cobalt precursor. Non-limiting examples of the solvent include C1-C6 alcohol (e.g., ethanol), water, ether series, ketones (e.g., acetone), and chain hydrocarbons (e.g., n-hexane).

At this time, the impregnation may be performed at room temperature. When the impregnation is carried out, the capillary force is utilized as much as possible. If the impregnation does not work well, a vacuum atmosphere may be applied or a method such as ultrasonic treatment may be performed in parallel. When the vacuum atmosphere is applied at the time of impregnation, the amount of impregnation can be increased since the air or moisture contained in the material is completely removed by the vacuum.

Upon impregnation, the cobalt precursor solution may have a mass ratio of cobalt to cobalt precursor of 1% to 500% relative to the porous carbon material. To impregnate at the desired mass ratio, impregnation may be carried out in one step or may be impregnated through more than one impregnation step, but is not limited thereto.

In the first step, the drying temperature after impregnation may be 100 to 150 ° C. The drying temperature depends on the solvent used in the cobalt precursor solution.

In the first step, the cobalt-based catalyst precursor is mixed with the cocatalyst component, so that the catalyst performance can be easily controlled. The cobalt-based precursor solution may include at least one metal selected from the group consisting of copper, ruthenium, rhodium, palladium, silver, and platinum as a co-catalyst component. At this time, one metal may be used alone, or two or more metals may be used in combination. The cocatalyst component preferably maintains the mole ratio of 0.001 to 0.999 relative to 1 mole of the cobalt-based catalyst precursor.

In the second step of the first embodiment, the prepared porous carbon material is heat-treated at a decomposition temperature or higher of the cobalt-based precursor in an oxidizing atmosphere to form porous cobalt oxide precursor And the carbon material is removed by catalytic oxidation by the residual gas generated by pyrolysis of the cobalt precursor and the oxidizing gas injected.

In the second step, the oxidizing atmosphere may be an oxidizing gas, or a mixed gas consisting of a combination of an oxidizing gas and an inert gas, but is not limited thereto. At this time, the oxidizing gas may be oxygen, nitrogen oxide (NO, NO ₂ ), air, or a combination thereof, but is not limited thereto. The injected oxidizing gas, together with the oxidizing gas resulting from the decomposition of the cobalt precursor, contributes to the removal of the carbon material at low temperatures.

The inert gas may be, but is not limited to, nitrogen, helium, argon, or combinations thereof. The inert gas serves as a carrier gas for promoting the movement of the mixed gas and also serves to adjust the concentration of the oxidizing gas.

In the second step, the heat treatment temperature may be 250 to 450 ° C. This is lower than the thermal decomposition temperature of general carbon material of 550 캜. Due to the interaction of the oxidizing gas and the injected oxidizing gas resulting from the decomposition of the cobalt precursor, the carbon material can be removed at a temperature lower than the conventional pyrolysis temperature of 250 ° C to 450 ° C. When the cobalt precursor is decomposed according to the present invention, the carbon material can be removed at a temperature lower than the pyrolysis temperature of the carbon when the cobalt precursor is used in an oxidizing atmosphere. Therefore, the cobalt particles Chemical and physical changes with the sintering and support of the catalyst. Also, the manufacturing method according to the present invention can reduce the cost and time by simultaneously performing the cobalt particle generating step and the carbon material removing step.

It is preferred that the ^first flow ^rate of the oxidizing gas in the second step, the heat treatment process is measured as the gas hourly space velocity (GHSV) is 0 hr ^-1 to about 10000 hr. At this time, 0 hr ^-1 means an atmosphere in a state in which there is no constant flow velocity and a static oxidizing gas atmosphere. Even in such a static atmosphere, it is possible to remove the oxidized cobalt particles and the carbon support.

In the second step, the oxidizing gas treatment is preferably performed for 30 minutes to 4 hours at a temperature ranging from 250 ° C to 450 ° C, but is not limited thereto. If the oxidizing gas treatment time is shorter than 30 minutes, the carbon material is incompletely removed and the remaining carbon material remains.

In the present invention, the cobalt precursor used in the second step has the greatest influence on the carbon material removal by the low temperature heat treatment. That is, the removal of the carbon material is caused by the thermal decomposition of the residual oxidizing gas (NO, NO ₂ , SO ₂ , SO ₃ ) generated by the thermal decomposition of the cobalt precursor in reaction with the carbon material.

In the present invention, the first step and the second step may be performed in different reactors, respectively. Even if the time elapses after the first step does not affect the reaction of the second step, it can be stored in the state of the first step. In addition, the step of applying the cobalt precursor in the pores of the porous carbon material in the first step and the step of heat-treating in the oxidizing atmosphere in the second step may be performed in the same reactor.

The particles formed in the second step may be cobalt oxide, and then the cobalt oxide may be reduced to form a cobalt catalyst. The reduction treatment may be an optional process, and the reduction may be performed by a conventional method known to those skilled in the art.

In the present invention, the produced cobalt-based catalyst is oxidized by an oxidizing gas, and the size thereof is determined by the pore size of the porous carbon material.

The second aspect of the present invention is also the same as the first aspect except that the second step is performed under an inert atmosphere instead of an oxidizing atmosphere. In this case, the cobalt oxide particles can be formed in the pores of the mold without removing the mesoporous carbon template.

The cobalt-based catalyst for Fischer-Tropsch synthesis prepared by the production method of the first or second aspect of the present invention can obtain a particle size determined by the pore size of the porous carbon material.

Meanwhile, the cobalt-based catalyst for Fischer-Tropsch synthesis prepared by the production method of the first or second aspect of the present invention may have a ratio of the peak of Co ^{3 +} / Co ^{2 +} by X-ray photoelectron spectroscopy to less than 3. The higher the ratio of the peak of Co ^{2 +,} the higher the surface oxygen deficiency of the catalyst. Compared to less than Co ^{3 +} / Co ^{2 +} ratio of cobalt catalyst 3 by a conventional known manufacturing method, a cobalt-containing catalyst of the present invention increases the surface anoxia Co ^{3 +} / Co ^{2 +} value appears more than 3. That is, the cobalt catalyst of the present invention has a higher ratio of surface adsorbed oxygen to lattice oxygen than that of the conventional cobalt catalyst obtained by impregnation, coprecipitation and vapor deposition, Is reduced. This reduction in the surface oxygen ratio improves the reducibility of the catalyst and enables the reduction of the catalyst at lower temperatures.

The cobalt-based catalyst according to the present invention may exhibit a primary reduction peak at 180 ° C to 250 ° C and a secondary reduction peak at 260 ° C to 450 ° C. The primary reduction peak is the peak that appears when reduction from Co ₃ O ₄ to CoO occurs, and the secondary reduction peak is the peak that appears when the reduction from CoO to cobalt metal occurs. These peaks can be confirmed at a heating-reduction test (H ₂ -TPR) with hydrogen. In the case of the cobalt catalyst supported on a general alumina support, the temperature at which the reduction peak appears is 300 ° C. to 560 ° C. at the first reduction peak and 700 ° C. or more at the second reduction peak, Reduction occurs at low temperatures. The high reducibility of these catalysts enables high conversion of carbon monoxide and high selectivity of liquid hydrocarbons when the catalyst is applied to the Fischer-Tropsch reaction.

A fourth aspect of the present invention relates to a process for the production of liquid hydrocarbons from syngas using a Fischer-Tropsch synthesis reaction, wherein the Fischer-Tropsch synthesis catalyst of the third aspect of the present invention is introduced into a Fischer- A) applying step; B) activating the catalyst with a catalyst for Fischer-Tropsch synthesis; And c) performing the Fischer-Tropsch synthesis reaction by the activated Fischer-Tropsch synthesis catalyst.

The method for producing liquid hydrocarbons according to the present invention may prepare a synthesis gas (CO / H ₂ ) by reforming natural gas at least before step c).

On the other hand, the Fischer-Tropsch synthesis reactor may be a fixed bed, fluidized bed or slurry reactor.

In the present invention, the step b) is a step of reducing the Fischer-Tropsch synthesis catalyst under a hydrogen atmosphere. The step b) may be performed in a hydrogen atmosphere at 100 to 500 ° C.

In the present invention, the Fischer-Tropsch synthesis reaction in the step c) may be carried out at a temperature of 200 to 350 ° C, a reaction pressure of 5 to 30 kg / cm ³ , and a space velocity of 1000 to 10000 h ^-1 .

The Fischer-Tropsch synthesis reaction is preferably carried out while maintaining the hydrogen / carbon monoxide reaction ratio at 1.5 to 2.5 molar ratio.

In addition, the method for producing a liquid hydrocarbon according to the present invention may further comprise a step of reforming the Fischer-Tropsch synthesis reaction product after step c).

When the Fischer-Tropsch synthesis reaction is carried out using the Fischer-Tropsch synthesis catalyst of the present invention as described above, the cobalt catalyst can be reduced at a low temperature due to the high reducibility due to the oxygen deficiency of the cobalt catalyst of the present invention , The carbon monoxide conversion of the Fischer-Tropsch synthesis reaction and the liquid hydrocarbon selectivity are increased. Further, since the cobalt catalyst for Fischer-Tropsch synthesis according to the present invention is produced at a relatively low temperature, it is possible to prevent physical and chemical changes due to high temperature when nanoparticles are formed.

The cobalt-based catalyst for Fischer-Tropsch synthesis prepared according to the present invention can prevent the chemical and physical changes of the catalyst particles due to the formation of cobalt nano-particles at low temperature, and the oxygen deficiency is induced on the surface of the catalyst particles, When applied to Fischer-Tropsch synthesis, the conversion of carbon monoxide and the selectivity of liquid hydrocarbons are improved.

1A is a scanning electron micrograph (TEM) of a cobalt nano catalyst (Example 1) using CMK-3 as a template and Fig. 1B is a scanning electron microphotograph of a cobalt nano catalyst (Example 2) using MSU-FC as a template (TEM).
2 is an X-ray diffraction analysis (top) of a cobalt nano catalyst (Example 1) using CMK-3 as a template and an X-ray diffraction analysis of a cobalt nano catalyst (Example 2) using MSU- Graph (below).
FIG. 3A shows a high resolution electron microscope (HRTEM) image of a cobalt nano catalyst (Example 1) using MK-3 as a template and FIG. 3B shows a high resolution electron injection (HRTEM) image of a cobalt nano catalyst using MSU- (HRTEM). ≪ / RTI >
FIG. 4 shows X-ray photoelectron spectroscopy (XPS) results of the cobalt nano catalysts (FIGS. 4A and 4B) prepared in Examples 1 and 2 and the cobalt supported catalyst (FIG. 4C) prepared in Comparative Example 1.
5A is a graph showing the results of the temperature increase and reduction experiments (H ₂ -TPR) using hydrogen of the cobalt nano catalyst (Example 1) using CMK-3 as a template, (H ₂ -TPR) test using hydrogen of hydrogen peroxide.
6 shows the results of the temperature raising and reducing test (H ₂ -TPR) using hydrogen of the cobalt catalyst supported on the alumina support (Comparative Example 1).

Hereinafter, the present invention will be described in more detail with reference to examples. These examples are for further illustrating the present invention, and the scope of the present invention is not limited by these examples.

Example  One: CMK -3 as Porous Carbon Material

As the mesoporous carbon material, CMK-3 synthesized from SBA-15 frame was used. The pore size is 3 to 6 nm and the BET surface area is 1496 m ² / g. CMK-3 has hexagonal pores and an axially long cylinder shape. Cobalt nitrate hexahydrate (Co (NO ₃ ) ₂ 6H ₂ O) was used as a cobalt precursor and ethanol was used as a solvent. Prior to using the CMK-3 carbon mold, it was dried in an oven at 150 ° C for 12 hours to remove moisture that might be present in the foreign materials and pores remaining on the surface. The mass of CMK-3 was 1.0 g and the cobalt precursor was 1.235 g (calculated as 20% of the mass of the cobalt metal). The CMK-3 and cobalt precursor solutions were thoroughly mixed, and then the solvent was sufficiently evaporated at an internal temperature of 70 to 90 DEG C for 2 hours or more in a vacuum evaporator. The resulting mixture was dried in an electric oven at < RTI ID = 0.0 > 110 C < / RTI > The dried mixture was heated at a reaction temperature of 400 DEG C for 5 hours in a firing furnace where air at a flow rate of 100 sccm was injected.

Example  2: MSU -Cobalt-based catalyst using -F-C as a porous carbon material

A cobalt-based catalyst was prepared in the same manner as in Example 1 except that MSU-FC synthesized from a MSU-F-silica framework was used as a mesoporous carbon material. The pore size of MSU-FC is 3-6 nm and the BET surface area is 1496 m ² / g. The MSU-FC has hexagonal pores and an axially long cylinder shape.

Comparative Example  1: Catalyst preparation using alumina support

For comparison with the cobalt-based catalyst prepared in the above example, a catalyst was prepared by carrying an alumina support, which is a widely used method, on a cobalt precursor solution. The alumina support used was PURALOX manufactured by Sasol Corporation and used for heat treatment at 500 ° C for 5 hours before the catalyst was produced. The support was fabricated using the incipient wetness impregnation method. Cobalt nitrate hexahydrate (Co (NO ₃ ) ₂ 6H ₂ O) was used as a cobalt precursor and ethanol was used as a solvent. 1.0 g of alumina support and 1.235 g of cobalt precursor were used. After sufficiently mixing the alumina support and cobalt precursor solution, the solvent was sufficiently evaporated at an internal temperature of 70 to 90 DEG C for 2 hours or more in a vacuum evaporator. The resulting mixture was dried in an electric oven at < RTI ID = 0.0 > 110 C < / RTI > The dried mixture was heated at a reaction temperature of 400 DEG C for 5 hours in a firing furnace where air at a flow rate of 100 sccm was injected.

Experimental Example  1: Analysis of catalyst size and structure

Transmission electron microscopic (TEM) photographs of the cobalt-based catalyst particles prepared in Examples 1 and 2 are shown in FIG. The size of the cobalt oxide of Example 1 shown in FIG. 1A was 6-10 nm, and the size of the cobalt oxide of Example 2 shown in FIG. 1B was 10-16 nm.

The X-ray diffraction analysis (XRD) of the cobalt nanoparticles prepared above is shown in FIG. It was confirmed from the XRD pattern of FIG. 2 that cobalt oxide nanoparticles having a composition of Co ₃ O ₄ were produced.

The high-resolution TEM (HRTEM) of the cobalt nanoparticles prepared above is shown in Fig. 3 (Fig. 3A: Example 1, Fig. 3B: Example 2). As a result, it was confirmed that particles having crystal structures of (311) and (220) which are typical crystal planes of Co ₃ O ₄ were produced.

Experimental Example  2: Measurement of surface oxygen deficiency of catalyst

In order to measure the degree of surface oxygen deficiency of the prepared catalyst particles, each catalyst particle was analyzed by X-ray photoelectron spectroscopy (XPS) and the results are shown in FIG.

Figure 4 (a) In the case of Co 2p _3/2 peak, when the two peaks 779.8 eV, 782.2 eV. 779.8 eV, 782.2 eV means that each Co ^{+ 3,} a peak caused by Co ^{2 +,} the more the more surface anoxia higher the ratio of Co ^{2 +} peak. CMK-3 The cobalt oxide produced by the mold shown in Co2p _3/2 ^{+ 3} peaks to Co / Co ^{+ 2} ratio is 2.45. Further, Co ^{3 +} / ^{2 +} Co ratio was 2.43 in the oxidized cobalt Co2p _3/2 peak produced by the MSU-FC mold. Whereas in Co2p _3/2 peak of Co ₃ O ₄ / γ-Alumina catalyst Co ^{3 +} / Co ^{2 +} ratio was in 3.07. Compared with the results of Examples 1 and 2, it can be seen that the relative intensity of the Co ^{2 +} peak is small. In the case of Co ₃ O ₄ / γ-Alumina, The degree of oxygen deficiency was low.

In addition, the intensities of Examples 1 and 2 were low at 531.3 eV peaks related to surface oxygen at the O 1s peak, while the intensity of Comparative Example 1 was higher than that of the nano catalysts of Examples 1 and 2 there was. It was also confirmed that the degree of oxygen deficiency of the cobalt-based nanoparticles of Examples 1 and 2 was higher than that of the existing Co ₃ O ₄ / γ-Alumina.

The results are summarized as follows.

template Particle Size (nm) Co ^{3 +} / Co ^{2 +} ratio (XPS) Example 1 CMK-3 6 to 10 2.45 Example 2 MSU-f-C 10-16 2.43 Comparative Example 1 Co ₃ O ₄ / γ-Alumina > 15 3.07

Depletion of surface oxygen affects the reducibility of the catalyst, and the greater the surface oxygen deficiency, the better the reduction of the catalyst. Therefore, it can be confirmed that the reduction of the nanoparticle catalyst of Examples 1 and 2, in which surface oxygen deficiency is high, is better.

Experimental Example  3: Evaluation of reducing property of catalyst

In order to measure the reducibility of the prepared catalysts, the catalysts prepared in the above Examples and Comparative Examples were subjected to a temperature raising reduction test (H ₂ -TPR) using hydrogen and the results are shown in FIG. 5 (Examples 1 and 2) and 6 (Comparative Example 1). In the case of Fig. 5, in the cobalt nanoparticles (a) of Example 1 and the cobalt nanoparticles (b) of Example 2, two peaks at 233-235 ° C and 260-450 ° C were observed. The first peak is a peak that appears when the lead to reduced to CoO in the Co ₃ O _4, the second peak is the peak consumption of hydrogen that is consumed when reduction occur from CoO to Co metal. The temperature at which the reduction occurred was generally low, which is consistent with the tendency of the Co ^{3 +} / Co ^{2 +} ratio in the XPS of Experimental Example 2.

On the other hand, in the case of the Co ₃ O ₄ / γ-Alumina of Comparative Example 1, two peaks at 300-560 ° C and above 700 ° C were observed. It was confirmed that this was generally higher than the peak temperature of the examples and that the reduction did not occur well. Cobalt aluminate compounds appear to be due to the formation because the reduction is not likely to occur. Comparative Co ₃ O high reduction temperature of ₄ / γ-Alumina of Example 1 is consistent with the tendency of the ^{3 +} Co / Co ^{+ 2} in the ratio shown in the XPS Experiment 2.

Experimental Example  4: Evaluation of catalytic activity

The synthesis gas composition H ₂ / CO / CO ₂ / Ar = 57.3 / 28.4 / 9.3 / 5 (volume%), reaction temperature 220 ° C., reaction pressure 2.0 MPa, The space velocity was more than 50 hours at 2000 h ^-1 , and the Fischer-Tropsch synthesis reaction proceeded. % H ₂ (He balance) prior to initiating the Fischer-Tropsch synthesis reaction at 100 sccm at 400 ° C for 5 hours. CO conversion, FT activity, and hydrocarbon selectivity were measured after the reaction had proceeded for a certain period of time and the activity of the catalyst was stabilized. The results are shown in Table 2.

template
CO conversion rate
(%) FT activity
(10 ^-5 molg ^-1 s ^-1 ) Hydrocarbon selectivity (%) CH ₄ C ₂ -C ₄ C ₅ Example 1 CMK-3 91.0 3.20 10.5 11.5 78.0 Example 2 MSU-F-C 64.5 2.27 15.7 11.3 73.0 Comparative Example 1 Co ₃ O ₄ / γ-Alumina 43.2 1.32 10.8 9.9 79.2

As a result, the catalyst prepared in Example 1 showed the highest CO conversion (91.0%) and Fischer-Tropsch activity (3.20). In the case of the catalyst prepared in Example 2, the CO conversion was 64.5% and the Fischer-Tropsch activity was 2.27, indicating that the activity of the catalyst of Example 1 was different. This seems to be due to the size difference of the catalyst particles. The optimal activity of the cobalt nanoparticles in the Fischer-Tropsch reaction is 6-8 nm, which is the optimal activity point for nanoparticles of this size. Therefore, it is judged that the activity of the cobalt nano-catalyst is larger in Example 1 close to the above-mentioned size.

In the case of Comparative Example 1, the CO conversion and the Fischer-Tropsch activity were lower than those of Examples 1 and 2. The selectivity of the product was somewhat improved, but it was confirmed that the Co ₃ O ₄ / γ-Alumina catalyst was lower overall than the nanocatalyst in terms of the yield per catalyst mass. This is because, in the case of the catalyst prepared by the conventional method, a substance which is difficult to be reduced by the chemical bonding between the catalytic active material and the support is generated, and the reduction activity is lowered, and the activity of the catalyst is lowered.

Claims (18)

A first step of preparing a porous carbon material to which a cobalt-based precursor in which an oxidizing gas is decomposed is applied in pores;
The prepared porous carbon material is heat-treated at an decomposition temperature or higher of the cobalt-based precursor in an oxidizing atmosphere to form cobalt-based catalyst particles from the cobalt-based precursor using the pores of the porous carbon material as a template, Comprising a second step,
A method for preparing a cobalt-based catalyst for Fischer-Tropsch synthesis.
The method according to claim 1, wherein the heat treatment temperature in the second step is 250 to 450 ° C.
The manufacturing method according to claim 1, wherein the oxidizing atmosphere in the second step is heat treatment with an oxidizing gas, or a mixed gas composed of an oxidizing gas and an inert gas.
The production method according to claim 1, wherein the porous carbon material to which the cobalt-based catalyst precursor in which the oxidizing gas is decomposed is applied in the pores is prepared by impregnating the cobalt-based catalyst precursor solution in the pores of the porous carbon material, followed by drying.
The method of claim 1, wherein the cobalt-based catalyst precursor is selected from the group consisting of oxide salts of cobalt, oxyhydroxide salts, chloride salts, carbonates, nitrates, citrates, nitrosyl nitrates and nitrates. Firefighting. A water-soluble precursor selected from the group consisting of oxalates, carboxylates, sulfates and the like, or an alkoxy precursor containing hydrocarbons. An ammonium precursor, and the like.
5. The method of claim 4, wherein the cobalt precursor solution comprises at least one metal selected from the group consisting of copper, ruthenium, rhodium, palladium, silver, and platinum as a co-catalyst.
The method according to claim 1, wherein the porous carbon material is a mesoporous carbon material, and the cobalt-based catalyst particles are nano-sized particles.
The method of claim 1, wherein the porous carbon material has pores having an average particle size of 1 ~ 50nm, and the specific surface area of ^{100 m 2 g -1 ~ 2000 m} 2 g - 1 of the production method is characterized.
The method according to claim 1, wherein the porous carbon material is a carbon nanotube, CMK-3, CMK-8, MSU-FC, activated carbon, graphite fiber, activated carbon fiber or a mixture thereof.
The method according to claim 2, wherein the oxidizing gas is oxygen, nitrogen oxide (NO, NO ₂ ), air, or a combination thereof.
A first step of preparing a porous carbon material to which a cobalt precursor is applied in pores;
Treating the prepared porous carbon material in an inert atmosphere at a temperature higher than a decomposition temperature of the cobalt precursor to a temperature lower than a pyrolysis temperature of the carbon material by using the pores of the porous carbon material as a template without removing the porous carbon material, And a second step of forming cobalt-based catalyst particles from the precursor.
A method for preparing a cobalt-based catalyst for Fischer-Tropsch synthesis.
A cobalt-based catalyst for Fischer-Tropsch synthesis prepared by the method of any one of claims 1 to 11.
The method of claim 12, wherein the catalyst has X-ray photoelectron spectroscopy according to the Co ^{3 +} / ^{2 +} Co is characterized by the Fischer Tropsch synthesis cobalt catalyst for the ratio of the peak is less than 3.
The catalyst for synthesis of Fischer-Tropsch synthesis according to claim 12, wherein the catalyst exhibits a first reduction peak at 180 ° C to 250 ° C and a second reduction peak at 260 ° C to 450 ° C in H ₂ -TPR analysis.
A method for producing liquid hydrocarbons from syngas using a Fischer-Tropsch synthesis reaction,
A) applying the Fischer-Tropsch synthesis catalyst of claim 12 to a Fischer-Tropsch synthesis reactor;
B) activating the catalyst with a catalyst for Fischer-Tropsch synthesis; And
And performing the Fischer-Tropsch synthesis reaction by the activated Fischer-Tropsch synthesis catalyst.
16. The process according to claim 15, wherein step b) comprises reducing the catalyst for Fischer-Tropsch synthesis in a hydrogen atmosphere.
16. The process according to claim 15, wherein step b) is carried out in a hydrogen atmosphere at 100 to 500 캜.
16. The method of claim 15, c) steps 200 ℃ to 350 ℃, a reaction pressure of 5 to 30 kg / cm ^3, a space velocity of 1000 - The method is characterized in that is carried out at 10000 h ^-1.

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