KR102221053B1 - Preparation method of high performance iron/alumina catalysts and manufacturing method of synthetic liquid fuel using the iron/alumina catalyst - Google Patents

Abstract

The present invention relates to an iron/potassium/alumina composite catalyst for a Fischer-Tropsch synthesis reaction capable of obtaining a synthetic liquid fuel from a mixed gas containing carbon monoxide and hydrogen, and a manufacturing method and use thereof.
The catalyst manufacturing method according to the present invention is a melt-infiltration of hydrated iron hydrate salt in the pores of the alumina support so that the content of the supported iron salt is 0.4 to 1 gram (g) per unit gram (g) of the alumina support. The first step; And a second step of activating the ferrous metal hydrate supported in the pores of the alumina support with iron carbide by firing in an atmosphere of an activation gas to form a porous ferric carbide/alumina catalyst in which the iron carbide nanoparticles are supported in the pores of the alumina support. It is a feature.

Description

{Preparation method of high performance iron/alumina catalysts and manufacturing method of synthetic liquid fuel using the iron/alumina catalyst}

The present invention relates to an iron/potassium/alumina composite catalyst for a Fischer-Tropsch synthesis reaction capable of obtaining a synthetic liquid fuel from a mixed gas containing carbon monoxide and hydrogen, and a manufacturing method and use thereof.

_{Fischer-Tropsch (FT) synthesis reaction is a liquid synthetic fuel (C 5+} hydrocarbon) and chemical fuel obtained from synthesis gas (hydrogen and carbon monoxide) obtained through gasification and reforming of coal, natural gas, and biomass as shown in the formula below. It is a technology to manufacture (ethylene, propylene, etc.).

[Scheme 1]

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

In the Fischer-Tropsch Synthesis reaction, catalysts based on cobalt and iron are mainly used, and the reaction conditions such as reaction temperature, pressure, and gas composition depend on the type of catalyst applied. . The Fischer-Tropsch synthesis reaction is largely carried out between 200 and 250°C depending on the reaction temperature and the type of target product, and is a low temperature FT reaction (low temperature Fischer-Tropsch, which mainly obtains wax or diesel material). LTFT) and a high temperature FT reaction (high temperature Fischer-Tropsch, HTFT) in which light olefin gas (ethylene, propylene) or gasoline material is obtained by reacting at a temperature between 300 and 350°C. Traditionally, in the case of a low-temperature FT reaction that proceeds to produce paraffinic wax, a cobalt catalyst with a relatively long life of the catalyst is mainly used.The cobalt-based catalyst has an excellent advantage of having a high activity and a long lifespan, but due to sulfur compounds, etc. There is a disadvantage that the price is very expensive compared to easy poisoning or iron-based catalysts. In addition, since cobalt-based catalysts have little activity in water-gas-shift (WGS) reactions, the overall reaction depends on the ratio of the components of the synthesis gas (hydrogen: carbon monoxide = 2:1) during the FT synthesis reaction. It will be greatly affected. On the other hand, iron-based catalysts have activity in water gas transfer reactions, so they can be used in various gas compositions with a component ratio of hydrogen to carbon monoxide between 1 and 2, and can be used in the presence of carbon dioxide, which is an impure gas. Therefore, in the case of a large-scale commercial high-temperature FT reaction, iron-based catalysts, which are inexpensive and have strong resistance to skin toxicity by sulfur compounds, have been mainly used in the process. A representative example of a high-temperature Fischer-Tropsch reaction using an iron-based catalyst commercially available so far is the Synthol process using an iron-based catalyst made of fused Fe from Sasol. However, in the case of fused Fe, various impurities may be included during manufacture, and the catalytic activity is low.

Currently, in the case of iron catalysts used in commercial processes, various promoters such as potassium, copper, and silica have been used together to dramatically improve the catalytic performance. In particular, potassium is the reactivity of the catalyst in the Fischer-Tropsch reaction. It is well known to improve the chain growth selectivity of hydrocarbons, reduce the production of methane and increase the methane. The role of potassium is traditionally known to have an electronic effect as a base, and recently, it has been announced that potassium is partly involved in the formation of the active surface of iron particles. In U.S. Patent No. 4,340,503, an iron-based catalyst was prepared by supporting an iron component and a potassium component using a silicate carrier, and a method of synthesizing a _{C 2} -C _{4 fraction of olefin from a synthetic gas in a fluidized bed reactor is presented.} Has been.

In addition, in recent research, various carbon materials such as activated carbon, carbon tube (CNT), graphene, carbon fiber (CNF), and porous carbon support are used as a support for an iron catalyst.

On the other hand, in the case of the FT reaction using an iron-based catalyst, it is important to make the active particles well in the form of iron carbide. Through this, the reaction introduction period can be minimized, and higher activity can be exhibited. In particular, among the reported various iron carbide phases, hagg carbide (χ-Fe ₅ C ₂ ) shows relatively excellent performance.

In the case of iron catalysts mainly used in the low-temperature Fischer-Tropsch synthesis reaction, catalysts made mainly through the co-precipitation method were widely used (Korean Patent Registration No. 10-1087165). Such a catalyst has an advantage of being able to support iron in a high content due to the high weight of iron occupied per the total weight of the catalyst. However, it has disadvantages in terms of the complexity of the manufacturing procedure and low reliability of the catalyst, as well as catalyst coking by carbon monoxide or high temperature stability.

On the other hand, in the case of the high-temperature Fischer-Tropsch Synthesis reaction, which is mainly aimed at producing light olefins or gasoline, fused Fe (melted iron) particles have been mainly used in commercial processes, and a research stage on a small laboratory scale. In, a supported catalyst using a support was applied a lot. Fused Fe, which is applied to a commercial process, has the advantage of having a high mechanical strength because it is melted at a very high temperature of 1000°C or higher, while the catalyst has a large crystal size and low activity.

In addition to the iron catalyst, copper was used to increase catalytic reducibility, or potassium was added to increase the activity of the catalyst. Recently, a lot of studies have been conducted on iron catalysts carrying potassium using carbon with well-developed pores as a support, and show high performance.

However, methods of uniformly supporting particles using an alumina support have not been well reported due to the relatively small pore development characteristics of alumina. In the case of a carbon support, it is stable against steam generated during high-temperature FT reactions, has an advantage of heat transfer, and the inside of the carbon support provides a more favorable atmosphere for reduction and activation of particles, and is advantageous for adsorption of CO, a reactant. Can work. However, there is a disadvantage in applying to a scale-up process because the obtained catalyst is easily crumbly to be used by granulating or molding it in another form. On the other hand, the silica support has a high porosity of carbon level and has an advantage of being advantageous for molding. However, silica has a poor stability against steam and is very vulnerable in structural stability during a high-temperature Fischer-Tropsch reaction.

It is an object of the present invention to provide a novel method for producing a catalyst capable of very effectively producing a liquid hydrocarbon compound at high temperature, and to provide suitable reaction conditions for such a catalyst.

Another object of the present invention is to efficiently produce liquid hydrocarbons based on high CO conversion and selectivity using the iron/potassium/alumina catalyst according to the present invention.

The first aspect of the present invention is a melt-infiltration agent for hydrated iron hydrate salt in the pores of the alumina support so that the content of the supported iron salt is 0.4 to 1 gram (g) per unit gram (g) of the alumina support. Step 1; It comprises a second step of activating the ferrous metal hydrate supported in the pores of the alumina support to iron carbide by firing in an atmosphere of an activation gas to form a porous ferric carbide/alumina catalyst in which the iron carbide nanoparticles are supported in the pores of the alumina support. It provides a method for producing a characteristic catalyst.

The second aspect of the present invention provides an iron/alumina complex catalyst prepared according to the first aspect and having an iron content of 5 to 13 wt% based on the total amount of catalyst including the alumina support.

A third aspect of the present invention is a method for producing a liquid hydrocarbon from syngas using a Fischer-Tropsch synthesis reaction, comprising: a step of applying the catalyst of the second aspect to a fixed bed reactor; And a step b of performing a Fischer-Tropsch reaction by injecting syngas into a reactor.

Hereinafter, the present invention will be described in detail.

Although the present inventors have difficulty in supporting catalytically active particles in the pores of alumina due to the relatively small pore characteristics of alumina, the present inventors first melted and impregnated a large amount of iron hydrate salt in alumina, followed by firing and activating, for the first time iron carbide nanoparticles. A porous iron carbide/alumina catalyst supported on the pores of the alumina support was prepared, and further, potassium could be additionally supported on the porous iron carbide/alumina catalyst by a wet impregnation method. As a result, it was possible to obtain results _{of improved catalytic reactivity, reduced methane selectivity, and increased productivity of liquid hydrocarbons (C 5+} ) through appropriate addition of potassium as a cocatalyst (1~3 wt%). The catalyst thus obtained was structurally stable to heat even in a high temperature Fischer-Tropsch reaction of 300° C. or higher, minimized agglomeration of particles, and selectively obtained liquid hydrocarbons in high yield. In particular, it exhibited much improved performance in terms of catalytic activity (FTY, Fe time yield) than previously reported catalysts based on carbon or silica support. The present invention is based on this.

In order to solve the problem that it is difficult to uniformly support the particles on the alumina support due to the small pore characteristics of alumina, the present invention provides the pore volume of the alumina support through a melt-infiltration process of hydrated iron hydrate salt. It is characterized by suggesting a method of using it as much as possible and carrying it into the support very evenly. At this time, it is possible to uniformly support potassium together with the iron material.

In addition, in the case of the iron support catalyst containing potassium so far, in many cases, a catalyst in which a small amount of potassium is added in the state of iron oxide is used. In this case, in-situ to make the iron oxide into activated iron carbide or metallic iron inside the reactor. The long-term reduction/activation process is essential. In addition, since the catalyst performance varies greatly depending on this process, in the present invention, the catalyst activated in the form of iron carbide is obtained through an external activation process in a carbon monoxide atmosphere in a state in which the ferrous metal hydrate is supported on the support. It was found that the deviation of each reduction condition can be minimized.

The iron/potassium/alumina nanostructure catalyst obtained in the present invention has excellent thermal stability and can show high activity in a high-temperature Fischer-Tropsch reaction conducted at a high temperature around 340°C. While increasing the amount of liquid product, the overall catalytic activity can also be improved.

The method for producing a catalyst according to the present invention,

A first step of melt-infiltration of the hydrated iron hydrate salt in the pores of the alumina support so that the content of the supported iron salt is 0.4 to 1 gram (g) per unit gram (g) of the alumina support;

A second step of forming a porous iron carbide/alumina catalyst in which the iron carbide nanoparticles are supported on the pores of the alumina support by activating the ferrous metal hydrate supported in the pores of the alumina support with iron carbide by firing in an atmosphere of an activating gas.

At this time, after the second step, potassium salt is supported on the porous iron carbide/alumina catalyst by a wet supporting method using a potassium salt solution, and heat treatment is performed under an activation gas (pure carbon monoxide, carbon monoxide partially contained in hydrogen or nitrogen, etc.) to obtain alumina. A third step of highly dispersing potassium and iron carbide nanoparticles in the support may be further included.

In addition, in the first step, the potassium providing precursor may be supported in the pores of the alumina support together with the hydrated iron hydrate salt.

In addition, before the third step, the porous iron carbide/alumina catalyst formed in the second step may be passivated.

The iron, potassium, and alumina composite nanocatalyst for high-temperature Fischer-Tropsch synthesis reaction according to an embodiment of the present invention first obtains an iron carbide/alumina catalyst through a melt impregnation process and carbon monoxide activation as shown in FIG. The potassium salt solution can be prepared again on it through a wet supporting method. When the potassium salt is supported in this way, potassium and iron carbide nanoparticles can be highly dispersed in the alumina support through a sufficient activation process under continuous high temperature carbon monoxide conditions, and finally, the oxidation of active particles acting as a catalyst through the passivation process can be minimized. I can.

Hereinafter, a method of preparing an iron/potassium/alumina composite nanocatalyst according to the present invention will be described in more detail step by step.

Before the first step, the iron hydrate salt and the alumina support may be uniformly ground together to form a powder.

Non-limiting examples of iron hydrate salts may be Iron(III) chloride hexahydrate, Iron(II) chloride tetrahydrate, Iron(III) nitrate nonahydrate, Iron(II) perchlorate hydrate, and Iron(II) sulfate hydrate.

The iron hydrate salt used in the present invention is a hydrated iron compound having a melting point of about 30 to 100°C, and Fe(NO ₃ ) ₃ 9H ₂ O (d= 1.643 g/cm ³ , mp=47.2°C) , FeCl ₃ 6H ₂ O (d= 1.82 g/cm ³ , mp= 37°C), FeSO ₄ 7H ₂ O (1.898 g/cm ³ , mp=70°C) and the like are preferable. In the case of a compound having a melting point lower than this, it is difficult to handle it because it is in a liquid state at room temperature. In the case of a compound having a melting point higher than 100°C, a boiling problem may occur because water is impregnated at a higher temperature than the boiling temperature. In particular, each of these metal salts has a unique density value. If the impregnation amount of the metal salt is determined in consideration of the density of the metal salt and the pore volume of the porous carbon support, the salt can be impregnated more evenly.

As the alumina support that can be used with these salts, a gamma-phase porous support is suitable. In this case, the pore volume of the support is preferably 0.2 cm ³ /g or more for smooth support of the iron salt. In order to further increase the supported content of the particles, it is preferable to use an alumina material having a large pore volume and a constant pore size. The reason is that the alumina support can be molded, and the stability between particles can be improved by strong interaction between the particles and the support. In addition, while having advantageous properties for pelletization compared to carbon materials, it has higher steam stability compared to silica materials.

The content of the supported iron salt is preferably 0.4 to 1 gram (g) per unit gram (g) of the alumina support for uniform support of the particles. In addition, the content of additionally added potassium is 0.5 ~ 5wt% based on the total amount of catalyst including the support, and the content of iron used as a catalyst is 5 ~ 13wt% in terms of uniform dispersibility of the particles and long-term stability of the catalyst. It is suitable to carry. The iron content exceeding 13wt% exceeds the capacity of the iron hydrate salt that can be uniformly impregnated in the pores of the alumina support.

In addition, it is possible to select a reaction vessel according to the amount of metal hydrate salt applied during the impregnation process and the reaction temperature, and the reactor is mainly made of stainless steel or made of polypropylene or Teflon among polymer plastics. You can use the old container.

In addition, in order to dissolve the iron hydrate salt and impregnate it evenly into the support, it is important to control the temperature and maintain pressure inside the reactor, and to allow complete impregnation of the salt to be impregnated, the melting point of the salt can be increased by about 2 to 5°C. In addition, the reaction must be carried out in a closed system so that the pressure due to the vapor pressure generated during the reaction does not disappear to the outside.

The melt-impregnation process can be performed in a general dry oven, but a rotary agitating oven can be used to obtain a more uniform and well-dispersed catalyst. The rotational speed can be used in the range of 1 to 60 rpm, and it is recommended to use it in the range of 20 to 40 rpm for proper stirring.

The second step may be performed after drying the mixed powder of the molten-impregnated iron hydrate salt and alumina formed in the first step at room temperature.

It is important to make the impregnated iron hydrate salt into an active iron carbide phase by sufficiently decomposing the impregnated iron hydrate salt as a sintering condition after the iron salt is supported, and the sintering temperature can exhibit activity without too large a particle size. It is possible between 300 ~ 400 ℃, more preferably about 350 ℃ is good.

Carbon monoxide and mixed gas (carbon monoxide + hydrogen, carbon monoxide + nitrogen) can be used as the activating gas, but pure carbon monoxide is more preferably used in terms of catalytic activation. The firing time is preferably 100 mL or more per minute for 2 to 10 hours so that activation is sufficiently possible.

Before the third step, the iron carbide nanoparticles formed in the second step may passivate the porous catalyst supported in the pores of the alumina support. At this time, the passivated catalyst can be dried and used in the third step.

The passivation process for stabilizing the activated catalyst in a high-temperature CO atmosphere is a very important step in the subsequent reaction application of the externally reduced catalyst, and serves to block the reaction between the catalyst and oxygen using an organic solvent. At this time, various solvents such as ethanol and mineral oil can be used as the organic solvent that can be used, but water that can oxidize and change the catalyst cannot be used. Passivation is performed by immersing the catalyst directly in an organic solvent so as not to be exposed to oxygen in an atmosphere of nitrogen or other inert gas, and for later analysis or application to a fixed bed reactor, it is preferable to use ethanol, which is easily volatilized, as a solvent. .

In the case of an iron carbide/alumina supported catalyst wetted in a solvent, since the catalyst itself is magnetic, it can be easily separated from the solvent using a magnet. After separation, re-dry it through a vacuum drying process and use it immediately, or use vacuum packaging or nitrogen packaging. It is desirable to keep it.

In the third step, potassium added through the wet supporting method can be used as a solution dissolved in water or an organic solvent, and available salts include KOH, KI, KCl, KBr, K ₂ CO ₃ , K ₂ Cr ₂ O ₇ , KNO ₃ , KC ₂ H ₃ O ₂ , KMnO ₄ , KCN, KIO ₃ , K ₂ S ₂ O ₈ , K ₂ SO ₄ , KSCN, KClO ₃ , KF, KH, KH ₂ PO ₄ , C ₄ H ₉ It can be KO, C ₆ H ₅ K ₃ O _{7 etc.}

The iron carbide/alumina catalyst on which potassium is supported, formed after the third step, may also be passivated and/or dried.

On the other hand, in accordance with the present invention, a method for producing a liquid hydrocarbon from syngas using a Fischer-Tropsch synthesis reaction,

A step of applying the catalyst prepared according to the present invention to a fixed bed reactor; And

Including step b of performing a Fischer-Tropsch reaction by injecting syngas into the reactor.

Synthetic gas may be carbon monoxide, hydrogen, other inert gas, methane, or a material composed of carbon dioxide. More preferably, it is good in terms of product yield to use carbon monoxide and hydrogen in a ratio of 1:1. In addition, synthesis gas space velocity ^{_{6 ~ 30 NL · g cat -1}} · h - is preferably injected into the fixed bed reactor in the ^first range. Even if it is less than the space velocity, there is no great difficulty in the progress of the reaction, but there is a problem that the productivity per unit time of the liquid hydrocarbon is low, and when a synthesis gas greater than the space velocity is injected, the conversion rate of carbon monoxide may be reduced. The reaction temperature can be carried out at 250 to 350°C, but it is preferable to proceed between 300 to 350°C in order to increase the conversion rate of carbon monoxide and increase the yield of liquid hydrocarbons.

Step a may further include reducing to 300 to 400° C. in an in-situ state inside the reactor for reduction and reactivation of some oxidized particles during the catalyst loading process.

In the iron carbide/potassium/alumina catalyst according to an embodiment of the present invention, potassium pushes electrons to the surface of the iron carbide when carbon monoxide is adsorbed, helps carbon monoxide to fall well, and has excellent catalytic activity even when using a small amount of iron. Do. In addition, it improves catalyst stability by suppressing the sintering phenomenon of iron carbide particles on alumina.

Accordingly, iron carbide / potassium / alumina composite catalyst according to the invention for using Fischer-Tropsch synthesis reaction at the time of, or more high conversion rate of carbon monoxide in the high temperature condition over 300 ℃, eumyeonseodo generate the methane is low, the liquid C ₅₊ hydrocarbon Since it has the advantage of increasing selectivity, it can be applied to commercial processes as an excellent catalyst for high-temperature Fischer-Tropsch reactions.

Furthermore, the alumina support can be easily molded, unlike the activated carbon support, so that the alumina support carrying iron carbide nanoparticles can be processed and used in various shapes as desired, such as pellets, which makes it easy to scale-up the reactor.

If the catalyst prepared in the present invention is used, it is possible to obtain results _{of improvement in catalytic reactivity, decrease in methane selectivity, and increase in productivity of liquid hydrocarbons (C 5+} ) through appropriate addition of potassium as a cocatalyst (1~3 wt%). there was. The catalyst thus obtained has the advantage of being structurally stable to heat even in a high temperature Fischer-Tropsch reaction of 300° C. or higher, minimizing agglomeration of particles, and selectively obtaining liquid hydrocarbons in high yield. In particular, it is possible to achieve much improved performance in terms of catalytic activity (FTY, Fe time yield) than previously reported catalysts based on carbon or silica support.

1 is a schematic diagram of the preparation of an iron carbide/alumina nanocomposite catalyst containing potassium.
2 is a low magnification (a) and high magnification (b) TEM image (a = 98,000 magnification, b = 490,000 magnification) of the iron carbide/alumina nanocomposite catalyst obtained through the melt-impregnation process of Example 1.
3 is an XRD spectrum of the iron carbide/alumina composite catalyst obtained by the melt-impregnation process of Example 1. FIG.
4 is a graph of nitrogen adsorption and desorption of the iron carbide/alumina composite catalyst obtained by the melt impregnation process of Example 1. FIG.
5 is a pore distribution diagram of the iron carbide/alumina composite catalyst of Example 1 obtained from a nitrogen desorption curve.
6 is a low magnification (a) and high magnification (b) TEM image (a=98,000 magnification, b=490) of an iron carbide/potassium/alumina nanocomposite catalyst (potassium content: 0.8 wt%) after addition of potassium according to Example 2 , 000 magnification).
7 is a low magnification (a) and high magnification (b) TEM image (a=98,000 magnification, b=490) of an iron carbide/potassium/alumina nanocomposite catalyst (potassium content: 1.6 wt%) after addition of potassium according to Example 2 , 000 magnification).
8 is a low magnification (a) and high magnification (b) TEM image (a=98,000 magnification, b=490,000) of an iron carbide/potassium/alumina nanocomposite catalyst (potassium content: 3.2 wt%) after addition of potassium according to Example 2 Magnification).
9 is an XRD analysis result of the iron-carbide/potassium/alumina nanocomposite catalyst of Example 2.
10 is a graph of nitrogen adsorption and desorption of an iron carbide/potassium/alumina composite catalyst to which 1.6wt% of potassium is added according to Example 2.
11 is a pore distribution diagram of an iron carbide/potassium/alumina catalyst to which 1.6 wt% of potassium is added according to Example 2 obtained from a nitrogen desorption curve.
12 is a graph of (a) conversion, (b) selectivity, (c) Fischer-Tropsch activity, and (d) hydrocarbon product productivity of an iron carbide/alumina catalyst containing no potassium according to Example 3. FIG.
13 shows the (a) conversion rate, (b) selectivity, (c) Fischer-Tropsch activity, (d) hydrocarbon product productivity of the iron carbide/potassium/alumina catalyst containing 0.8 wt% of potassium according to Example 3 It is a graph.
14 shows (a) conversion, (b) selectivity, (c) Fischer-Tropsch activity, (d) hydrocarbon product productivity of an iron carbide/potassium/alumina catalyst containing 1.6 wt% of potassium according to Example 3 It is a graph.
FIG. 15 shows the (a) conversion rate, (b) selectivity, (c) Fischer-Tropsch activity, (d) hydrocarbon product productivity of the iron carbide/potassium/alumina catalyst containing 3.2 wt% of potassium according to Example 3 It is a graph.
16 is a graph of (a) conversion, (b) selectivity, (c) Fischer-Tropsch activity, and (d) hydrocarbon product productivity of an iron carbide/activated carbon catalyst containing no potassium according to Comparative Example 1. FIG.
FIG. 17 is a graph of (a) conversion, (b) selectivity, (c) Fischer-Tropsch activity, and (d) hydrocarbon product productivity of the iron carbide/porous silica SBA-15 catalyst containing no potassium.

Hereinafter, the present invention will be described in more detail through examples. However, these examples are for illustrative purposes only, and the scope of the present invention is not limited to these examples.

Example One. Iron carbide /Alumina nano catalyst manufacturing

For uniform and high support of the hydrated iron metal salt in the alumina support, the ratio of the salt compared to the support alumina when the metal salt is melt-impregnated into the support material [F/A ratio= Fe salt (amount of iron salt (g))/A( Alumina amount (g))] was set to 0.8. First, Fe(NO ₃ ) ₃ 9H ₂ O (Aldrich, 98+%, fw= 404 g·mol ^-1 , mp = 47.2℃) 0.8 g and gamma-alumina (STREM, fw= 102 g·mol ^-1 , surface Area:~185m ² ·g ^-1 ) 1.0g was put in a mortar and changed with a mortar until the color became even. After grinding until it becomes sufficiently uniform, put the mixed powder in a polypropylene container, tighten the cap of the container, and place it in a rotary stirring oven set at 50°C for 24 hours while rotating at 30 rpm. Kept for a while. After aging for 24 hours, the hybrid powder was immediately dried at room temperature. Finally, an iron carbide/gamma alumina catalyst was obtained by performing heat treatment at 350 for 4 hours in a carbon monoxide gas atmosphere (normal pressure, flow rate 200 mL min ^{- 1) using a tube furnace.} Since the obtained catalyst powder is easily oxidized when exposed to air as it is, immediately after it is activated, passivation is performed through a process of soaking in ethanol while creating an atmosphere that is blocked from air using an inert gas such as nitrogen or helium. After drying the wet ethanol in a vacuum oven, it was stably stored through final vacuum packaging.

Formation analysis of iron carbide particles was carried out through transmission electron microscopy (TEM), and as shown in FIG. 2, it was confirmed that the crystal size of the iron carbide particles formed as a result of TEM analysis was very small, ranging from 5 to 10 nm. . The catalyst obtained through the XRD analysis of FIG. 3 may be matched with alumina and iron carbide structures, respectively, and the BET surface area value through the nitrogen adsorption and desorption experiment of FIG. 4 was 169m ² ·g ^-1 . In the case of the pore volume, it was 0.345cm ³ ·g ^-1 , which showed a high level even after the particles were loaded, and as shown in FIG. 5, the pore size analysis result showed uniformity at the level of 6 nm.

Example 2. Preparation of iron carbide/potassium/alumina catalyst

To obtain a catalyst containing 0.8 wt% of potassium (K) relative to the total catalyst, 1 mL of K ₂ CO ₃ (Aldrich, powder, fw=139.205 g·mol ^-1 ) aqueous solution (12 mM) was added in Example 1 using a micropipette. The obtained iron carbide/alumina catalyst powder was divided and impregnated in 20 or more tens of times. After impregnation, the naturally dried powder was subjected to heat treatment at 350 for 4 hours in a carbon monoxide gas atmosphere (normal pressure, flow rate 200 mL min ^{- 1) using a tube calciner again to obtain an iron carbide/potassium/alumina catalyst.}

Using the same method as above, _{only the concentration of K 2} CO ₃ used together is changed to 23.9mM, 47.8mM, 95.5mM, respectively, and each 1mL is used to make iron containing potassium in 1.6wt%, 3.2wt%, and 6.3wt%. A carbide/potassium/alumina composite catalyst could be obtained.

As shown in Figs. 6 to 8, it can be seen that the crystal size of the iron carbide particles in the iron carbide/potassium/alumina composite catalyst to which 0.8 to 3.2 wt% of potassium is added is mostly obtained at a level of around 10 nm as a result of TEM analysis. there was.

The obtained sample was first subjected to XRD analysis as shown in FIG. 9, and as a result, it was found that there was no obvious change in the shape of the particle phase according to the K content change.

The BET surface area value of the iron carbide/potassium/alumina composite catalyst to which 1.6 wt% of potassium was added obtained through the nitrogen adsorption and desorption experiment of FIG. 10 was 175 m ² g ^-1 , which was slightly higher than that of the iron carbide/alumina catalyst without potassium. It turned out to be a large value. In the case of the pore volume, it was 0.347cm ³ ·g ^-1 , which showed a high level even after the addition of potassium, and as shown in FIG. 11, the pore size analysis obtained by the desorption curve showed a uniform value at the level of 6 nm.

Example 3. Fischer-Tropsch reaction using iron carbide/potassium/alumina catalyst

Based on the catalyst obtained in Example 2, the Fischer-Tropsch synthesis reaction was carried out. In order to compare the performance, the catalyst prepared by the same method but did not contain any potassium obtained in Example 1 was compared under the same conditions.

A reactor applied to check the catalyst characteristics was a fixed-bed reactor, and an automated system capable of operating with a personal computer (PC) was used for the reaction process. 0.3 g of the catalyst obtained in a reactor having an inner diameter of 5 mm was dried, pelletized, and loaded at a constant size (300-600 μm) and used. An additional 3.5 g of glass bead was added together to prevent hot spots from being generated due to severe heat generation from the catalyst during the reaction. Prior to this reaction, in order to reduce and reactivate some oxidized particles during the catalyst loading process, the reactor was sufficiently reduced to 350 degrees for 4 hours or more in an in-situ state.

In the Fischer-Tropsch reaction, synthesis gas with a volume ratio of hydrogen to carbon monoxide maintained at a ratio of 1:1 was injected, the reaction pressure was 15 atm, and the gas hourly space velocity (GHSV) was 14 NL·g _cat. Fischer-Tropsch synthesis reaction was performed at 340°C by injecting into the reactor under the conditions of ^-1 ·h ^-1. The reaction results for each type of catalyst for 90 hours are shown in Figs. 12, 13, 14, and 15, respectively.

As a result of the reaction, even though only a very small amount of catalyst was used compared to the flow rate of the reactant, in the case of iron carbide/potassium/alumina catalyst to which 1.6 wt% of potassium was added, the conversion rate of carbon monoxide was very high, 95% or more, as shown in FIG. In the product selectivity graph in FIG. 14B, the selectivity for liquid hydrocarbon (C ₅₊ ) also showed very excellent properties approaching 40%. In addition, the FTY (Iron Time Yield) value, which indicates the degree of conversion of hydrocarbons over time per gram of iron (g), showed a very high value as in FIG. 14C.

Comparative Example 1. Fischer-Tropsch reaction using iron carbide / activated carbon catalyst

After preparing a catalyst using activated carbon instead of porous gamma alumina in the same manner as in Example 1, the Fischer-Tropsch synthesis reaction was carried out under the same pretreatment as in Example 3, the same reaction temperature, and the same flow rate. I did.

As in Example 3, 0.3 g of the catalyst obtained in a reactor having an inner diameter of 5 mm was dried and loaded immediately after being used. An additional 3.5 g of glass bead was added together to prevent hot spots from being generated due to severe heat generation from the catalyst during the reaction. Prior to this reaction, in order to reduce and reactivate some oxidized particles during the catalyst loading process, the reactor was sufficiently reduced to 350 degrees in-situ for 4 hours or more. Fischer-bit progression Tropsch reaction is the volume ratio of hydrogen to carbon monoxide, 1: injecting a synthesis gas maintained at a ratio of 1: 1 and the reaction pressure was 15 atm, a space velocity (GHSV, gas hourly space velocity) is 14 NL · gcat ^{- 1} · h ^- injected into the reactor under the conditions of ¹ to Fischer at 340 ℃ - it was performed Tropsch synthesis reaction. The result of the catalytic reaction for 90 hours is shown in FIG. 16. As a result of the reaction, the iron carbide/activated carbon catalyst showed somewhat lower results _{in terms of CO conversion and C 5+ product selectivity than the iron carbide/alumina catalyst.}

Comparative Example 2 Fischer-Tropsch reaction using iron carbide/porous silica SBA-15 catalyst

In the same manner as in Example 1, a catalyst was prepared using the well-known porous silica SBA-15 instead of porous gamma alumina, and then the Fischer-Tropsch synthesis reaction under the same pretreatment, the same reaction temperature, and the same flow rate as in Example 3. Proceeded.

As in Example 3, 0.3 g of the catalyst obtained in a reactor having an inner diameter of 5 mm was dried, pelletized, and loaded to a constant size (300-600 μm) and used. An additional 3.5 g of glass bead was added together to prevent hot spots from being generated due to severe heat generation from the catalyst during the reaction. Prior to this reaction, in order to reduce and reactivate some oxidized particles during the catalyst loading process, the reactor was sufficiently reduced to 350 degrees in-situ for 4 hours or more. Fischer-bit progression Tropsch reaction is the volume ratio of hydrogen to carbon monoxide, 1: injecting a synthesis gas maintained at a ratio of 1: 1 and the reaction pressure was 15 atm, a space velocity (GHSV, gas hourly space velocity) is 14 NL · gcat ^{- 1} · h ^- injected into the reactor under the conditions of ¹ to Fischer at 340 ℃ - it was performed Tropsch synthesis reaction. The result of the catalytic reaction for 90 hours after that is shown in FIG. 17.

As a result of the reaction, the iron carbide/porous silica SBA-15 catalyst showed very low results _{in terms of CO conversion and C 5+ product selectivity compared to the iron carbide/alumina catalyst and the iron carbide/activated carbon catalyst.}

Claims (11)

In a tumbling oven, hydrated iron hydrate salt is melt-infiltration into the pores of the alumina support so that the content of the supported iron salt is 0.4 to 1 gram (g) per unit gram (g) of the alumina support. A first step of letting go;
Iron carbide nanoparticles of a size capable of exerting catalytic activity by activating ferrous metal hydrate salts supported in the pores of the alumina support into iron carbide by firing in an activating gas atmosphere to form a porous iron carbide/alumina catalyst supported in the pores of the alumina support. A second step of letting go;
Potassium salt is supported on a porous iron carbide/alumina catalyst by a wet supporting method using a potassium salt solution, and high temperature heat treatment in the range of 300 to 400°C in an activated gas condition containing carbon monoxide to collect potassium and iron carbide nanoparticles in the pores of the alumina support. A third step of dispersing; And
Forming the catalyst powder prepared in the previous step or the powder obtained by passivating the same
It is characterized by including,
In the catalyst, the crystal size of the iron carbide nanoparticles is 5 to 10 nm, and the content of potassium is 1 to 5 wt% based on the total amount of catalyst including the support. The method of claim 1, wherein a hydrated iron hydrate salt having a melting point of 30 to 100°C is used. The method of claim 1, wherein the first step is performed in a closed system so that the pressure due to the vapor pressure generated during the reaction does not disappear to the outside at a temperature about 2 to 5 °C higher than the melting point of the hydrated iron hydrate salt. Phosphorus catalyst manufacturing method. The method of claim 1, wherein in the first step, the alumina support is a gamma-phase porous support. The method of claim 1, wherein in the first step, the potassium providing precursor is supported in the pores of the alumina support together with the hydrated iron hydrate salt. The method of claim 1, wherein the second step is performed at a sintering temperature at which the impregnated iron hydrate salt is decomposed to form an active iron carbide phase. ◈ Claim 7 was abandoned upon payment of the set registration fee. The method of claim 6, wherein the firing temperature for activation in the form of iron carbide in the second step is 300 to 400°C. The method of claim 1, wherein the activation gas in the second step is carbon monoxide, hydrogen, or a mixture gas thereof. The method of claim 1, wherein the porous iron carbide/alumina catalyst formed in the second step is passivated before the third step. It is prepared according to any one of claims 1 to 9, and potassium and iron carbide nanoparticles having a size capable of exerting catalytic activity are supported in the pores of the alumina support, and the crystal size of the iron carbide nanoparticles is 5 to 10. nm, iron/alumina molding complex catalyst containing potassium with an iron content of 5 to 13 wt% based on the total amount of catalyst including the alumina support, and potassium content of 1 to 5 wt% based on the total catalyst amount including the support . In the method for producing a liquid hydrocarbon from syngas using a Fischer-Tropsch synthesis reaction,
A step of applying the catalyst according to claim 10 to a fixed bed reactor; And
A method for producing a liquid hydrocarbon comprising step b of performing a Fischer-Tropsch reaction by injecting syngas into the reactor.

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