WO2016060330A1

WO2016060330A1 - Method for preparing cobalt-silica egg-shell nanocatalyst for fischer-tropsch synthesis reaction, and the catalyst, and method for synthesizing liquid hydrocarbon using same, and the liquid hydrocarbon

Info

Publication number: WO2016060330A1
Application number: PCT/KR2014/012316
Authority: WO
Inventors: 박지찬; 양정일; 정헌; 이호태; 천동현; 홍성준; 권재인
Original assignee: 한국에너지기술연구원
Priority date: 2014-10-17
Filing date: 2014-12-15
Publication date: 2016-04-21
Also published as: KR101524574B1

Abstract

The present invention relates to a method for preparing a cobalt-silica egg-shell nanocatalyst for a Fischer-Tropsch synthesis reaction, and the catalyst, and a method for synthesizing liquid hydrocarbon using same, and the liquid hydrocarbon. Provided are a method for preparing a cobalt-silica egg-shell nanocatalyst, and the catalyst which has active cobalt particles that are thermally stable and adjusted by nano-size selectively and highly dispersed on a nano-sized porous silica support shell having pores developed thereon, the catalyst thereby exhibiting high activity in terms of the fast diffusion and contact of a reactant at the time of the Fischer-Tropsch reaction. Also provided are a method for preparing liquid hydrocarbon, and the liquid hydrocarbon, the method having effectiveness by using the cobalt-silica egg-shell nanocatalyst to exhibit a high CO conversion rate and selectivity at the time of the Fischer-Tropsch synthesis reaction.

Description

Method for preparing cobalt-silica egg-shell nanocatalyst for Fischer-Tropsch synthesis reaction and its catalyst, method for synthesizing liquid hydrocarbon using the same and liquid hydrocarbon

The present invention relates to a method for preparing a cobalt-silica egg-shell nanocatalyst for a Fischer-Tropsch synthesis reaction, a catalyst thereof, a method for synthesizing a liquid hydrocarbon using the same, and a liquid hydrocarbon thereof in detail. Manufacturing technology of cobalt / silica nanocatalyst in which particles are selectively dispersed in nanoporous silica support shell with small size of nanoscale, synthesis method of liquid hydrocarbon by Fischer-Tropsch synthesis reaction and liquid hydrocarbon technology It is about.

Fischer-Tropsch (FT) synthesis was developed by German chemists Franz Fischer and Hans Tropsch in the 1920s, a mixture of carbon monoxide and hydrogen obtained by converting coal, natural gas and biomass resources. It is a technique for producing a synthetic fuel (hydrocarbon) as shown in the following formula through a catalytic reaction under high temperature, high pressure using.

(2n + 1) H ₂ + nCO → C _n H _{(2n + 2)} + nH ₂ O

In the Fischer-Tropsch synthesis reaction, a catalyst including cobalt and iron is mainly used, and reaction conditions such as reaction temperature, pressure, and gas composition are determined according to the type of catalyst applied.

The Fischer-Tropsch synthesis reaction is a low temperature Fischer-Tropsch (LTFT) that mainly forms diesel and wax between 180 and 260 ° C, depending on the desired product to be obtained through the reaction and the reaction temperature conditions for obtaining it effectively. And high temperature Fischer-Tropsch (HTFT), which mainly synthesizes gasoline and light olefin gases (ethylene, propylene) under conditions of 300 ° C or higher (Andrei Y. Khodakov et al, Chem. Rev., 2007, 107, 1672).

In the CTL (coal-to-liquid) process, which is a process of obtaining a liquid hydrocarbon compound through synthesis gas obtained by using coal, traditionally, many iron-based catalysts are used as Fischer-Tropsch reaction catalysts. It is also active in the water gas shift reaction, and the ratio of hydrogen to carbon monoxide synthesis gas can be used in various compositions within 1 to 2, and it can be used even in the presence of carbon dioxide, which is an impure gas. However, the Fischer-Tropsch reaction using the iron-based catalyst also has the disadvantage of generating a large amount of carbon dioxide after the reaction, whereas the cobalt-based catalyst has a very low activity in the water gas transition reaction, and thus a long carbon chain chain with little generation of carbon dioxide. There is an advantage to obtain a hydrocarbon compound having. Although cobalt-based catalysts have a disadvantage of being expensive compared to iron-based catalysts, they have advantages of high activity and long life. Therefore, in the case of the Fischer-Tropsch synthesis reaction using such a cobalt catalyst, high dispersion, high support and high temperature stability of the supported cobalt catalyst particles are required in order to compactly design the reactor and secure economical efficiency.

In the case of metal / silica catalysts prepared using the known catalyst preparation co-precipitation or wetness impregnation, when the metal content is increased, the particles become larger and uneven due to the aggregation of the particles. In addition, sintering occurs easily during the high temperature firing process above 500 ° C. In order to secure such stability, hybrid structures have been developed between porous silica and an active metal used as a support in a supported catalyst, and various structures such as core-shell and yoke-shell structures have been attempted (Park, JC). et al., J. Mater. Chem., 2010, 20, 1239-1246.

In particular, the egg-shell structure composed of cobalt and silica components, which are known to exhibit high activity in the Fischer-Tropsch reaction, has advantages in controlling heat of reaction or diffusion of reactants during the reaction, compared to general pellet type catalysts. (Gardezi, SA et. Al. Ind. Eng. Chem. Res. 2012, 51, 1703-1712).

However, since the total particle size is very large (1 to 2 mm) and the thickness of the shell portion on which the catalyst particles are supported is 0.2 to 0.5 mm, the surface of the cobalt particles actually supported has a high dispersibility and rapid diffusion and contact with the reactants. There are some disadvantages.

That is, the egg-shell catalyst manufactured in the conventional mm size region is mainly controlled by the metal salt impregnation time control or selective absorption technique using viscosity or affinity. The selective uptake of metal salts is not easy, which makes it nearly impossible to make egg-shell catalysts on nanosized silica supports (Iglesia, E. et. Al. J. Catal. 1995, 153, 108-122).

Therefore, there is a need to develop an egg-shell cobalt catalyst uniformly controlled at the nano level.

An object of the present invention for solving the above problems is that the thermally stable, cobalt nano-scaled active cobalt particles are selectively dispersed in the pores of the nano-sized porous silica support shell and reacted during the Fischer-Tropsch reaction The present invention provides a method for preparing a cobalt-silica egg-shell nanocatalyst having high activity in terms of fast diffusion and contact, and a catalyst thereof.

In addition, another object of the present invention to provide a liquid hydrocarbon and a method for producing a liquid hydrocarbon effectively by having a high CO conversion and selectivity during the Fischer-Tropsch synthesis reaction using the cobalt-silica egg-shell nanocatalyst have.

The present invention to achieve the object as described above and to solve the conventional drawbacks is to (i) the precursor of silica

Synthesizing silica structure particle powder using the method;

(ii) forming a porous silica shell through heat treatment after further coating the silica particle powder using CTAB (Cetyl trimethylammonium bromide);

(iii) then uniformly grinding the porous silica powder together with the cobalt hydrate salt, followed by melt impregnation near the melting point of the salt;

(iv) drying the mixed powder obtained after melt impregnation at room temperature and then heat-treating at high temperature in a hydrogen atmosphere;

(v) cooling the reduced cobalt / silica particles to room temperature to prevent oxidation through passivation using ethanol; and cobalt-silica egg-shell nanoparticles for the Fischer-Tropsch synthesis reaction comprising: It is achieved by providing a process for preparing the catalyst.

In a preferred embodiment, the step i) is to synthesize a silica structure having a spherical shape of 100 ~ 1000 nm size using the precursor TEOS (Tetraethyl orthosilicate) or TMOS (Tetramethyl orthosilicate) of silica in alcohol and water-based conditions It may be a step.

In a preferred embodiment, the step (iv) is a CTAB (Cetrimonium bromide, IUPAC Name: hexadecyl-trimethyl) having a long carbon chain of 16 carbons of step (ii) mixed with the silica precursor of step (i) -ammonium bromide) may be a step of forming pores by heat treatment to remove it.

In a preferred embodiment, the hydrated cobalt metal salt used by impregnating silica in step (iii) is Co (NO ₃ ) ₂ 6H ₂ O (mp = 55 ° C), CoCl ₂ 6H ₂ O having a melting point of 40 ~ 90 ℃ (mp = 86 ° C.), CoSO ₄ 7H ₂ O (mp = 74 ° C.).

In a preferred embodiment, the reaction time to melt-impregnated in step (iii) may be 4 to 48 hours.

In a preferred embodiment, the (iv) step is 400 ~ 700 ℃ to form a nanometer size cobalt particles by firing in a hydrogen atmosphere in the porous shell of the silica powder particles to be used as a support is optionally supported with a cobalt hydrate salt It can reduce in between.

In another embodiment, the present invention is prepared according to the method described above, and the active nano-cobalt particles are uniformly formed only in the porous silica shell in the nano-silica structure in which the porous shell is formed of a tightly packed silica and many pores are formed near the shell. It is achieved by providing a cobalt-silica egg-shell nanocatalyst for a Fischer-Tropsch synthesis reaction characterized in that it is selectively positioned.

In a preferred embodiment, the size of the cobalt nanoparticles supported on the porous silica shell is 2 ~ 20 nm, the size of the entire particle including the silica structure is 100 ~ 1000 nm, the thickness of the porous silica shell is 10 ~ 100 nm.

In another embodiment, the present invention comprises the steps of injecting the cobalt-silica egg-shell nanocatalyst for the Fischer-Tropsch synthesis reaction;

Then injecting syngas into the reactor;

After charging the cobalt-silica egg-shell nanocatalyst at a high reaction temperature in the reactor and proceeding with the Fischer-Tropsch synthesis reaction to prepare a liquid hydrocarbon; Fischer-Tropsch synthesis reaction comprising the It is achieved by providing a process for the preparation of liquid hydrocarbons using cobalt-silica egg-shell nanocatalysts.

In a preferred embodiment, the synthesis gas may be a mixture of one or two of a volume ratio of carbon monoxide and hydrogen, or a gas in which any one of an inert gas, methane, and carbon dioxide is mixed as impurities in carbon monoxide and hydrogen.

In a preferred embodiment, the syngas may be injected into the reactor within a gas hourly space velocity (GHSV) of 2.0 to 24.0 NL / g _cat / hr.

In a preferred embodiment, the reaction temperature may be carried out between 180 ~ 260 ℃.

The present invention is also achieved in another embodiment by providing a liquid hydrocarbon prepared according to the method for preparing a liquid hydrocarbon using the cobalt-silica egg-shell nanocatalyst for the Fischer-Tropsch synthesis reaction.

The cobalt / silica egg-shell nanocatalyst of the present invention having the above characteristics is made of a porous silica structure formed of solid dense silica in the inside and many pores in the vicinity of the shell. While the active cobalt particles are uniformly supported, they can also be selectively positioned only inside large silica shells.

In addition, the cobalt / silica egg-shell nano-catalyst is a structure that is advantageous for the diffusion and heat dissipation of the reactant when used to obtain a stable and excellent reaction results in the Fischer-Tropsch synthesis reaction proceeds at a high temperature of more than 180 degrees It is a useful invention having the advantage of being able to effectively obtain a hydrocarbon compound from a mixed gas of carbon monoxide and hydrogen is an invention that is expected to be greatly utilized in industry.

1 is a schematic diagram of the production of egg-shell type high dispersion cobalt / silica nanocatalyst according to an embodiment of the present invention,

2 is a flow chart showing an egg-shell type highly dispersed cobalt / silica nanocatalyst manufacturing process according to one embodiment of the present invention;

3 is a SEM image of silica particles according to Example 1 of the present invention, (b) TEM image of a silica structure coated with a porous silica shell, and (c) egg-shell cobalt / cobalt-containing cobalt particles 10wt% / TEM image of silica nanoparticles, (d) HADDF-STEM image of egg-shell cobalt / silica nanoparticles, high-magnification TEM image of egg-shell cobalt / silica nanoparticle shell portion,

4 is a TEM image of silica particles according to Example 2 of the present invention, (b) TEM image of a silica structure coated with a porous silica shell, and (c) an egg-shell cobalt containing 10 wt% of cobalt particles. XRD spectrum of the silica nanoparticles,

5 is (a) a graph of nitrogen adsorption and desorption of a silica structure coated with a porous silica shell and (b) nitrogen of an egg-shell cobalt / silica nanoparticle in which 10 wt% of cobalt particles are loaded. Adsorption and desorption experiment graph,

6 is a TEM image of (a) an egg-shell cobalt / silica nanoparticle having 20 wt% of cobalt particles according to Example 3 of the present invention, (b) a high magnification TEM image, (c) an XRD spectrum,

FIG. 7 is a time-phase FT activity of hydrocarbon production of an egg-shell cobalt / silica nano catalyst having 10 wt% of cobalt particles according to Example 4 of the present invention.

FIG. 8 is a time-phase FT activity of hydrocarbon production of an egg-shell cobalt / silica nano catalyst having 20 wt% of cobalt particles according to Example 5 of the present invention.

9 is a liquid hydrocarbon compound photograph, a) oil, b) wax, actually produced for 90 hours using an egg-shell cobalt / silica nano catalyst having 20 wt% of cobalt particles according to Example 5 of the present invention.

Hereinafter, the configuration and the operation of the embodiments of the present invention will be described in detail with reference to the accompanying drawings. In describing the present invention, when it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

1 is a schematic view of the production of egg-shell high dispersion cobalt / silica nanocatalyst according to an embodiment of the present invention, Figure 2 is an egg-shell high dispersion cobalt / silica nanocatalyst according to an embodiment of the present invention It is a flowchart showing a manufacturing process.

The present invention relates to the production of a cobalt / silica nanostructure catalyst selectively dispersed in the shell of the porous silica structure particles in which the cobalt particles are used as a support at a small size of 2 to 20 nm while thermally stable. As the supporting method of the cobalt salt, the procedure is easy, and a melt impregnation method which is advantageous for high dispersion of particles is used.

At this time, the silica structure particles used as a support is a conventionally known method

Silica spherical particles prepared by the method have a porous shell obtained through heat treatment after the silica coating again with a compound having a long carbon chain.

As such, the porous silica structure is made of solid dense silica inside and many pores are formed near the shell, so that the active cobalt particles are uniformly supported when the particles are supported by the melt impregnation method. Will be located.

In particular, when applied to the catalytic reaction may have an advantageous advantage in the diffusion of the reactant, and furthermore, in the Fischer-Tropsch synthesis reaction, which is a big problem because the exotherm during the reaction is very severe, a local hot spot is formed during the reaction. do.

As such, when cobalt / silica nanostructures in which cobalt nanoparticles are monodispersed inside a porous silica shell are used as catalysts, stable and excellent reaction results can be obtained in Fischer-Tropsch synthesis reactions in which the reaction proceeds at a high temperature of 200 ° C or higher. .

The cobalt / silica egg-shell catalyst of the present invention is formed at the nano level by selectively impregnating the cobalt salt only in the nanometer-level porous silica shell portion with pores.

In the highly dispersed cobalt / silica egg-shell catalyst proposed in the present invention, the size of the cobalt nanoparticles supported on the porous silica shell is preferably between 2 and 20 nm in consideration of its dispersibility and optimal activity. The total particle size, including, may include from 100 nm to 1000 nm. The reason is that if the size of the spherical particles is too small, the loading of the cobalt particles becomes difficult, and if they are too large, they may be disadvantageous in reactant diffusion and heat dissipation.

At this time, the thickness of the stacked porous silica shell may be between 10 nm and 100 nm that can support the active cobalt particles well.

The present invention is well known

Highly dispersed nano cobalt / silica egg-shell hybrid nanocatalysts are obtained through melt impregnation and thermal reduction of hydrated cobalt salt using nano-sized silica particles synthesized through the process.

The method for preparing the cobalt / silica egg-shell catalyst is (i)

Synthesizing silica structure particles using the method, (ii) further coating silica using a CTAB (Cetyl trimethylammonium bromide) reagent to form a porous silica shell through heat treatment, and (iii) heat treating the porous silica powder. Uniformly grind together with the cobalt hydrate salt and then melt impregnating near the melting point of the salt; (iv) drying the mixed powder obtained after melt impregnation at room temperature and heat-treating it under a hydrogen atmosphere at high temperature, (v) reduced cobalt / The silica particles are cooled to room temperature and then oxidized to prevent oxidation through passivation.

Specifically, the silica structure synthesized in step (i) has a spherical shape and uses TEOS (Tetraethyl orthosilicate) as a precursor of silica under alcohol and water-based conditions.

It can be synthesized through the method, and the particle size of the silica can be about 100 ~ 1000 nm.

Alcohol used in the method may be methanol, ethanol, propanol (2-propanol) and the like, and the use of ethanol is more preferable to obtain a silica of uniform shape.

The silica precursor can be used not only in TEOS (Tetraethyl orthosilicate) but also in TMOS (Tetramethyl orthosilicate). It is disadvantageous.

Cetrimonium bromide ((C ₁₆ H ₃₃ ) N (CH ₃ ) ₃ Br, cetyltrimethylammonium bromide, IUPAC Name: hexadecyl-trimethyl-ammonium bromide, CTAB) compound used in step (ii) is a long carbon chain consisting of 16 carbons Since it remains together when mixed with the silica precursor, it is removed during subsequent heat treatment to form pores.

In the CTAB used here, that is, (CnH _{2n + 1} ) N (CH ₃ ) ₃ Br) (n = 12, 14, 16, 18) can all be used, but considering its uniform shape and pore formation, n More preferred is the use of CTAB ((C ₁₆ H ₃₃ ) N (CH ₃ ) ₃ Br) = 16.

In the case of the hydrated cobalt metal salt used by impregnating silica in step (iii), the melting point belongs to 40 ~ 90 ℃ Co (NO ₃ ) ₂ 6H ₂ O (mp = 55 ℃), CoCl ₂ 6H ₂ O (mp = 86 ° C.), CoSO ₄ 7H ₂ O (mp = 74 ° C.) and the like may be used, but the use of Co (NO ₃ ) ₂ 6H ₂ O with a low melting point is preferred for more convenient and stable production.

The reaction time is preferably about 4 to 48 hours so that the cobalt salts are sufficiently dissolved to enter the pores of the silica shell.

In the step (iv), when the cobalt hydrate salt is selectively supported on the porous shell of the silica support, baking in a hydrogen atmosphere causes cobalt particles having a size of several nanometers due to decomposition and reduction of the supported salt. At this time, the reduction temperature is preferably between 400 ~ 700 ℃ to achieve a sufficient reduction. This is because reduction may not be performed completely at a temperature below 400 ° C., and aggregation of particles may occur at a temperature of 700 ° C. or more.

Cobalt particles located in the cobalt / silica structure obtained through high temperature heat treatment in a hydrogen atmosphere may easily be oxidized when exposed to air, so a passivation process is required immediately after the heat treatment.

That is, the passivation process for the stabilization of the activated catalyst under reducing conditions at a high temperature of 300 ° C. or higher in step (v) is a very important step in the subsequent catalytic reaction application of the nanoparticle powder. It will block the reaction of the. At this time, as the organic solvent can be used a variety of solvents such as ethanol, mineral oil, but can not use water or other oxidizing agents that can oxidize and change the catalyst.

Passivation is carried out by dipping the catalyst directly in an organic solvent so as not to be exposed to oxygen in nitrogen or other inert gas atmosphere. It is preferable to use volatile ethanol as a solvent for further analysis or reaction. Especially in the case of transition metal / silica nanostructures, the catalyst itself is magnetic, so it can be easily separated from the solvent using a magnet. desirable.

The highly dispersed cobalt / silica supported catalyst prepared as described above is a structure in which small cobalt particles are uniformly embedded in the silica shell, as well as the Fischer-Tropsch reaction, as well as the Pauson-Kand reaction or Carbo. It can be usefully applied to various liquid catalyst reactions such as phenoxycarbonyl reactions.

In particular, the cobalt / silica egg-shell nanocatalyst prepared by the method for preparing the catalyst may be used in the preparation of liquid hydrocarbons using Fischer-Tropsch synthesis reaction, which includes the step of putting the synthesis gas into a tubular fixed bed reactor. have.

The method for producing liquid hydrocarbon using Fischer-Tropsch synthesis reaction according to the present invention is as follows.

Syngas may be carbon monoxide, hydrogen, inert gas or methane, or a material composed of carbon dioxide. More preferably, the volume ratio of carbon monoxide and hydrogen is used in a ratio of 1: 2 in terms of yield of the product.

In addition, the synthesis gas is preferably injected into the fixed bed reactor in the range of the space velocity is 2.0 ~ 24.0 NL / gcat / hr.

Even if it is less than the space velocity, there is no big problem in the reaction progress, but there is a problem of low productivity per unit time of liquid hydrocarbon, and when more synthesis gas is injected, the conversion rate of carbon monoxide may be reduced.

In addition, the reaction temperature can be used at 180 ~ 260 ℃ but if the high temperature stability of the catalyst is secured, the reaction may be suitable between 220 ~ 240 ℃ to increase the conversion of carbon monoxide and increase the yield of liquid hydrocarbon.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following examples are merely to illustrate the invention, but the content of the present invention is not limited by the following examples.

Example 1 Preparation of Cobalt / Silica Egg-Shell Nanocatalyst Supported by 10wt% Cobalt Particles

Silica nanoparticles that can be used as silica supports are well known

It was prepared using the method.

To obtain silica spherical particles, add 8 mL of ammonium hydroxide solution (28 wt%) and 20 mL of tetraethyl orthosilicate (TEOS) in a 1 L beaker containing 200 mL of ethanol and 32 mL of distilled water. Put and stirred for 2 hours.

The silica particles obtained after 2 hours were used after being precipitated through centrifugation and dispersed in ethanol. In order to minimize ammonia that may remain even after washing, the dispersion-precipitation process was repeated two or more times using ethanol.

Ahead of

Porous silica shells were further coated with a silica solution dispersed in ethanol obtained by the method.

First, 1.2 g of Cetrimonium bromide ((C ₁₆ H ₃₃ ) N (CH ₃ ) ₃ Br, cetyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, CTAB) reagent was dissolved in a solution containing 20 mL of distilled water and 10 mL of ethanol. Here, 60 mL of 0.3 M silica colloidal solution obtained above with 200 mL of distilled water was added thereto, followed by stirring for 30 minutes.

After that, 2.15 mL of tetraethylorthosilicate reagent was added and reacted again for 21 hours.

After 21 hours of reaction, the precipitate was precipitated by centrifugation, followed by water, ethanol, acetone, and washed again by repeating the dispersion-precipitation process. Finally, the powder obtained was sufficiently dried in an oven set at 100 ° C., and then heat-treated at 500 ° C. for 8 hours using an calcination apparatus.

Thereafter, 0.349 g of Co (NO ₃ ) ₂ 6H ₂ O (mp = 55 ° C.) salt was uniformly ground using a mortar and pestle together with 0.636 g of silica nanoparticles having a porous silica shell obtained through heat treatment. After sufficiently grinding, mixed powder was placed in a 30 mL polypropylene container, the container was capped tightly, and put in a drying oven having a temperature set at 60 ° C., and aged for 24 hours.

After 24 hours, the powder was cooled at room temperature, and then calcined at 400 ° C. for 4 hours in a hydrogen atmosphere using a baking oven to obtain an egg-shell cobalt / silica hybrid nanocatalyst having 10 wt% of cobalt.

In the case of the cobalt / silica hybrid catalyst finally obtained here, since oxidation proceeds rapidly when exposed to air, the cobalt / silica hybrid catalyst was stored in ethanol which is effective for passivation under a nitrogen atmosphere after firing. At this time, it is important to blow nitrogen strongly at 500cc / min so as not to introduce external air that may cause oxidation, and to put it instantaneously into a container containing ethanol under a prepared nitrogen atmosphere.

Scanning electron microscope (SEM) and transmission electron microscopy (TEM) images and high angle annular dark field-scanning transmission electron microscopy (HADDF-STEM) images of the samples thus obtained are shown in FIG. 3. It was.

As can be observed in the SEM image of Figure 3 a) spherical silica nanoparticles obtained by the above method was uniformly formed in the size of 300 ~ 400 nm level.

3 b) through the TEM image, it could be seen that the porous silica shell was formed through silica coating and heat treatment using CTAB.

In c) TEM image of Figure 3 it can be seen that the small cobalt particles of 5 ~ 10 nm level inside the silica shell through a reduction heat treatment under a hydrogen atmosphere. Through HADDF-STEM analysis for clearer confirmation, bright small dots representing cobalt particles as shown in d) of FIG. 3 were found to exist on the surface of the spherical silica particles.

In addition, the lattice shape of the cobalt particles was seen through e) high magnification TEM photograph of FIG.

Example 2 Preparation of Cobalt / Silica Egg-Shell Nanocatalyst Supported by 10wt% Cobalt Particles

Silica particles

The method can be adjusted to various sizes depending on various conditions, such as the amount of water, ethanol or ammonia used in the synthesis. Accordingly, the overall size of the egg-shell particles can also be controlled. As an example, 4 mL of ammonium hydroxide solution (28 wt%) and 10 mL of tetraethyl orthosilicate (TEOS) were further added to an Erlenmeyer flask containing 50 mL of ethanol and 8 mL of distilled water, followed by stirring for 2 hours. .

The SEM image of the silica particles thus obtained is shown in Figure 4 a), the average size of the particles was about 450 nm level.

Ahead of

Porous silica shells were further coated with a colloidal silica solution dispersed in ethanol obtained by the method. First, 1.2 g of CTAB reagent was dissolved in a solution of 20 mL of distilled water and 10 mL of ethanol. Here, 100 mL of the 0.181 M silica solution obtained above with 200 mL of distilled water was added and stirred well for 30 minutes.

Then, 2.15 mL of tetraethylorthosilicate reagent was added and reacted again for 12 hours. The TEM image for this is shown in b) of FIG. 4, and it can be seen that the porous silica shell is formed very uniformly on the silica particles obtained above.

After the reaction for 12 hours, the silica particles were precipitated by centrifugation, followed by water, ethanol and acetone, followed by washing again by dispersing-precipitation. Finally, the powder obtained was sufficiently dried in an oven set at 100 ° C., and then heat-treated at 500 ° C. for 8 hours using a firing apparatus.

Thereafter, 0.274 g of Co (NO ₃ ) ₂ 6H ₂ O (mp = 55 ° C.) salt was uniformly ground using a mortar and pestle together with 0.5 g of silica nanoparticles having a porous silica shell obtained through heat treatment. After sufficiently grinding, mixed powder was placed in a 30 mL polypropylene container, the container was capped tightly, and put in a drying oven having a temperature set at 60 ° C., and aged for 24 hours.

After 24 hours, the powder is cooled at room temperature, and then fired at 500 ° C. for 4 hours in a hydrogen atmosphere flowing at 200 ml per minute using a tube-type baking oven to obtain an egg-shell cobalt / silica hybrid catalyst containing 10 wt% of cobalt. there was.

Immediately after the heat treatment, cobalt / silica mixed powder was stored in ethanol, which is effective for passivation under nitrogen atmosphere, in order to prevent rapid oxidation upon exposure to air.

X-ray diffraction (XRD) analysis for qualitative analysis showed that the crystal phase of the particles was metallic cobalt species, as shown in FIG.

In addition, nitrogen adsorption and desorption experiments were carried out for pore formation and surface area analysis of the silica particles having the porous silica shell obtained, and the analysis graph is shown in FIG. As a result, the surface area of Brunauer-Emmett-Teller (BET) was 383.3 m ² / g and the pore volume was 0.30 cm ³ / g.

Similarly, in the case of cobalt / silica egg-shell loaded with 10wt% of cobalt, the nitrogen adsorption and desorption test results are shown in b) of FIG. 5, and the BET surface area value was obtained as 355.9 m ² / g. Was 0.20 cm ³ / g.

Example 3 Preparation of Cobalt / Silica Egg-Shell Nanocatalyst Carrying 20wt% Cobalt Particles

An egg-shell nanocatalyst carrying 20 wt% of cobalt particles was prepared using silica particles coated with a porous silica shell prepared in the same manner as in Example 2.

First, 0.617 g of Co (NO ₃ ) ₂ 6H ₂ O (mp = 55 ° C.) salt was uniformly ground using a mortar and pestle together with 0.5 g of silica nanoparticles having a porous silica shell obtained through heat treatment.

After sufficiently grinding, mixed powder was placed in a 30 mL polypropylene container, the container was capped tightly, and put in a drying oven having a temperature set at 60 ° C., and aged for 24 hours.

After 24 hours, the powder was cooled to room temperature, and then calcined at 500 ° C. for 4 hours using a baking oven to obtain an egg-shell cobalt / silica hybrid catalyst having 20 wt% of cobalt.

Immediately after heat treatment, cobalt / silica hybrid powder was stored in ethanol under nitrogen atmosphere to prevent rapid oxidation upon exposure to air.

As a result of the TEM analysis on the obtained sample, it can be seen that the particle size was formed at a level of 5 to 20 nm as shown in FIGS. 6A and 6B), and peaks indicating metallic cobalt were identified in the XRD analysis for qualitative analysis. Could. Nitrogen adsorption and desorption experiments were carried out for pore formation and surface area analysis of silica particles, and the results showed that the BET (Brunauer-Emmett-Teller) surface area value was 287.1 m ² / g, and the pore volume was 0.16 cm ³ /. g.

Example 4 Fischer-Tropsch Synthesis Reaction Using Cobalt / Silica Egg-Shell Nanocatalysts Supported with 10wt% Cobalt Particles

The Fischer-Tropsch synthesis reaction was carried out based on the cobalt / silica egg-shell catalyst containing 10 wt% of cobalt metal obtained in Example 2.

The reactor used a fixed-bed reactor, and the reaction process used an automated system that can be operated by a personal computer (PC).

0.5 g of the catalyst obtained in a reactor having an inner diameter of 5 mm was dried and pelletized to load a constant size (300-600 µm). In order to prevent hot spots from being severely exothermic in the catalyst, 2.5 g of glass beads having a size of 425 to 600 μm were added together.

In addition, after the catalyst was loaded in the reactor prior to the reaction, an additional reduction process was performed for 2 hours in an atmospheric hydrogen atmosphere (80 mL / min) at 500 ° C. for 4 hours, thereby partially purifying the partially oxidized portion on the surface of the catalyst. Made with cobalt.

Thereafter, a synthetic gas maintained at a ratio of hydrogen to carbon monoxide at a ratio of 2: 1 was introduced into the reactor under a reaction pressure of 20 atm and a gas hourly space velocity (GHSV) 7.2 NL / G (cat) -h. Fischer-Tropsch synthesis was performed at. After the reaction for 90 hours is shown in FIG. As a result, as shown in FIG. 7, 6 * 10 ^-5 mol _co / g _Co -s at CTY (Cobalt Time Yield, FT activity) value indicating the degree of conversion of CO to hydrocarbons per unit second per cobalt g as shown in FIG. Showed very high values.

[Example 5] Fischer-Tropsch synthesis reaction using cobalt / silica egg-shell nanocatalyst loaded with 20wt% cobalt particles

The Fischer-Tropsch synthesis reaction was carried out on the basis of the cobalt / silica egg-shell catalyst containing 20 wt% of the cobalt metal obtained in Example 3. As in Example 4, 0.5 g of a cobalt / silica egg-shell catalyst was dried and immediately loaded into a reactor having an inner diameter of 5 mm.

In order to prevent hot spots from being severely exothermic in the catalyst during the reaction, 2.5 g of glass beads were added together and the reduction process was carried out under a hydrogen atmosphere of normal pressure (flow rate 80 mL / min) at 500 ° C. for 4 hours. This resulted in part of the oxidized portion of the catalyst surface made of pure metallic cobalt.

Thereafter, a synthesis gas maintained at a ratio of hydrogen to carbon monoxide at a ratio of 2: 1 was introduced into the reactor under a reaction pressure of 20 atm and a space velocity of 7.2 NL / G (cat) -h to carry out Fischer-Tropsch synthesis reaction at 230 ° C. Was performed.

The reaction results for 90 hours thereafter are shown in FIG. 8. As a result, as shown in FIG. 8, a high value of 5 * 10 ^-5 mol _co / g _Co -s or more at the Cobalt Time Yield (CTY) value indicating the degree of conversion of CO to hydrocarbons per unit second of cobalt as shown in FIG. Showed.

After the actual reaction, the product was recovered from the trap to identify oil and wax formation components as shown in FIG. 9.

The present invention is not limited to the above-described specific preferred embodiments, and various modifications can be made by any person having ordinary skill in the art without departing from the gist of the present invention claimed in the claims. Of course, such changes will fall within the scope of the claims.

Claims

(i) the precursor of silica
Synthesizing silica structure particle powder using the method;

(ii) forming a porous silica shell through heat treatment after further coating the silica particle powder using CTAB (Cetyl trimethylammonium bromide);

(iii) then uniformly grinding the porous silica powder together with the cobalt hydrate salt, followed by melt impregnation near the melting point of the salt;

(iv) drying the mixed powder obtained after melt impregnation at room temperature and then heat-treating at high temperature in a hydrogen atmosphere;

(v) cooling the reduced cobalt / silica particles to room temperature to prevent oxidation through passivation using ethanol; and cobalt-silica egg-shell nanoparticles for the Fischer-Tropsch synthesis reaction comprising: Method for preparing a catalyst.
The method according to claim 1,

Step i) is a step of synthesizing a silica structure having a spherical shape of 100 ~ 1000 nm size using the precursor TEOS (Tetraethyl orthosilicate) or TMOS (Tetramethyl orthosilicate) of silica under alcohol and water-based conditions Method for preparing a cobalt-silica egg-shell nanocatalyst for Fischer-Tropsch synthesis reaction.
The method according to claim 1,

Step (iv) is a CTAB (Cetrimonium bromide, IUPAC Name: hexadecyl-trimethyl-ammonium bromide) having a long carbon chain of 16 carbons of step (ii) mixed with the silica precursor of step (i) Method of producing a cobalt-silica egg-shell nanocatalyst for Fischer-Tropsch synthesis reaction, characterized in that the step of removing the heat treatment to form pores.
The method according to claim 1,

The hydrated cobalt metal salt used by impregnating silica in step (iii) has a melting point of 40 to 90 ° C. Co (NO 3 ) 2 6H 2 O (mp = 55 ° C.), CoCl 2 6H 2 O (mp = 86 ° C.) ), CoSO 4 7H 2 O (mp = 74 ℃) method for producing a cobalt-silica egg-shell nanocatalyst for Fischer-Tropsch synthesis reaction, characterized in that at least one.
The method according to claim 1,

The reaction time of the melt impregnation in step (iii) is 4 ~ 48 hours, characterized in that the cobalt-silica egg-shell nanocatalyst for Fischer-Tropsch synthesis reaction.
The method according to claim 1,

In step (iv), the porous shell of silica powder particles used as a support is calcined under hydrogen atmosphere in a state in which cobalt hydrate salts are selectively supported, and reduced at 400 to 700 ° C. to form nanometer-sized cobalt particles. A method for preparing a cobalt-silica egg-shell nanocatalyst for a Fischer-Tropsch synthesis reaction.
The active nano-cobalt particles are uniformly selected only inside the porous silica shell in the nano silica structure formed according to the method of any one of claims 1 to 6 and formed of a porous shell in which the porous shell is made of solid dense silica inside and many pores are formed near the shell. Cobalt-silica egg-shell nanocatalyst for the Fischer-Tropsch synthesis reaction, characterized in that it is configured to.
The method according to claim 7,

The size of the cobalt nanoparticles supported on the porous silica shell is 2 ~ 20 nm, the size of the entire particle including the silica structure is 100 ~ 1000 nm, the thickness of the porous silica shell is 10 ~ 100 nm Cobalt-silica egg-shell nanocatalysts for Fischer-Tropsch synthesis reactions.
Injecting a cobalt-silica egg-shell nanocatalyst for the Fischer-Tropsch synthesis reaction according to claim 8 into the reactor;

Then injecting syngas into the reactor;

After charging the cobalt-silica egg-shell nanocatalyst at a high reaction temperature in the reactor and proceeding with the Fischer-Tropsch synthesis reaction to prepare a liquid hydrocarbon; Fischer-Tropsch synthesis reaction comprising the Process for preparing liquid hydrocarbons using cobalt-silica egg-shell nanocatalysts.
The method according to claim 9,

The synthesis gas is a Fischer-Tropsch, characterized in that the volume ratio of carbon monoxide and hydrogen 1: 1 or a mixture of any one of an inert gas, methane, carbon dioxide mixed with carbon monoxide and hydrogen in 1: 2: Method for preparing liquid hydrocarbon using cobalt-silica egg-shell nanocatalyst for synthesis reaction.
The method according to claim 9,

The synthesis gas is injected into the reactor within the gas hourly space velocity (GHSV, gas hourly space velocity) of 2.0 ~ 24.0 NL / g cat / h, cobalt-silica egg-shell nanoparticles for Fischer-Tropsch synthesis reaction Method for producing a liquid hydrocarbon using a catalyst.
The method according to claim 9,

The reaction temperature is a method for producing a liquid hydrocarbon using a cobalt-silica egg-shell nanocatalyst for Fischer-Tropsch synthesis reaction, characterized in that proceeding between 180 ~ 260 ℃
Liquid hydrocarbon prepared according to the method for preparing a liquid hydrocarbon using the cobalt-silica egg-shell nanocatalyst for the Fischer-Tropsch synthesis reaction according to claim 9.