KR101644976B1 - Cesium promoter-containing iron-carbide/carbon composite catalyst for Fischer-Tropsch synthesis, preparation method thereof, and preparation method of liquid or soild hydrocarbon using the catalyst - Google Patents

Abstract

The present invention relates to an iron-carbide/carbon composite catalyst including cesium for fischer-tropsch (FT) synthesis, a manufacturing method thereof, and a method to manufacture liquid or sold hydrocarbon by using the catalyst. More specifically, the present invention relates to a high-vitality iron-carbide/cesium/carbon-based composite catalyst for FT synthesis in which an iron-carbide particle containing cesium with vitality is embodied in a porous carbon support; a manufacturing method of the composite catalyst by using a melting impregnation method, an external vitalizing process in a vitalizing gas atmosphere, and a wetting impregnation method of cesium salt; and a method to manufacture liquid or solid hydrocarbon by using the composite catalyst. The iron-carbide/carbon composite catalyst comprises the porous carbon support; and an iron carbide nano particle in which cesium embodied in an air hole of the porous carbon support is added.

Description

The present invention relates to an iron-carbide / carbon composite catalyst for Fischer-Tropsch synthesis containing cesium, a process for preparing the same, and a process for producing a liquid or solid hydrocarbon using the catalyst. synthesis, preparation method thereof, and preparation method of liquid or soild hydrocarbon using the catalyst}

The present invention relates to an iron-carbide / carbon composite catalyst for Fischer-Tropsch synthesis containing cesium, a process for producing the same, and a process for producing a liquid or solid hydrocarbon using the catalyst.

The Fischer-Tropsch synthesis reaction was developed by German chemists Franz Fischer and Hans Tropsch in the 1920s and is a technology for the production of synthetic fuels (hydrocarbons) from syngas (hydrogen and carbon monoxide) .

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

In such a Fischer-Tropsch synthesis reaction, cobalt or iron-containing catalysts are mainly used. Depending on the type of the catalyst to be used, reaction conditions such as reaction temperature, pressure, gas composition and the like are largely influenced.

In the FT reaction, the hydrocarbon product obtained in the presence of a cobalt-based and iron-based catalyst is generally classified into gaseous hydrocarbons (C ₁ -C ₄ ), liquid oils and solid waxes. In recent years, as a key building block of chemicals, low olefins have been used as FTOs using Fe / α-Al ₂ O ₃ or Fe / CNF (carbon-nanofiber) catalysts with Na and S added at low reaction pressure (Fischer-Tropsch to Olefins) process. However, under the low pressure feed gas, the CO hydrogenation reaction showed a much lower CO conversion level of ~ 1% compared to the CO conversion values of 70-80%, which can be obtained at high pressures (15-20 bar). Therefore, in order to obtain liquid hydrocarbons with higher productivity using an Fe-based catalyst, the FT synthesis reaction must be carried out under a high reaction pressure.

On the other hand, the hydrocarbon product distribution has been effectively controlled by changing the catalyst type and reaction conditions in consideration of the following applications. For example, it has been possible to obtain hydrocarbons in the gasoline range more selectively by using cobalt- and iron-zeolite hybride-based dual-acting catalysts. Microporous aluminosilicate materials such as ZSM-5 as an acid catalyst have been shown to enhance hydrocarbon product selectivity, but due to their limited surface area due to their small pore volume and size, the catalytic activity generally decreases, The reduction of the catalytic activity became severe.

The Fischer-Tropsch synthesis reaction consists mainly of a low-temperature Fischer-Tropsch (LTFT) reaction with a reaction between 200 and 250 ° C, and a high-temperature FT reaction with a reaction between 300 and 350 ° C high temperature Fischer-Tropsch, HTFT) (Andrei Y. Khodakov et al., Chem. Rev., 2007, 107, 1672).

Traditionally, low-temperature FT reactions use cobalt catalysts that have a relatively long catalyst lifetime. The cobalt catalysts have high activity and long service life. However, they are easily poisoned by sulfur compounds, It has a very expensive disadvantage. In addition, since the cobalt catalyst has little activity in the water gas shift (WGS) reaction, the ratio of the synthesis gas component (hydrogen: carbon monoxide = 2: 1) during the FT synthesis reaction greatly affects the reaction do.

On the other hand, in the case of the iron catalyst, the water gas field is active in the reaction, so that it can be used in various compositions within 1 to 2 ratio of hydrogen to carbon monoxide synthesis gas, and can also be used in the presence of carbon dioxide which is an impurity gas. Therefore, in the case of high-temperature FT reaction, which is being commercialized on a large scale, an iron-based catalyst having high endotoxicity due to sulfur compounds has been mainly used in the process. As a representative example of a high temperature Fischer-Tropsch reaction using a commercially available iron-based catalyst, there is a Synthol process using an iron-based catalyst composed of fused Fe in Sasol (Steynberg AP et al. Gen., 1999, 186, 41). However, in the case of fused Fe, there are disadvantages that various impurities may be contained in manufacturing and the catalytic activity is low.

At present, 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 has been used as a catalyst in the Fischer-Tropsch reaction To improve the selectivity of chain growth of hydrocarbons by reducing the production of methane. The role of potassium has traditionally been known to be electron effects as a base (DC Sorescu et al., Surf. Sci., 2011, 605, 401 .; ZP Liu et al., J. Am. , 2001, 123, 12596; SJ Jenkins et al., J. Am. Chem. Soc., 2000, 122, 10610.), recently it has been reported that this potassium is also involved in part of the formation of active surfaces of iron particles (C.-F. Huo et al, Angew. Chem. Int. Ed., 2011, 50, 7403).

)(χ-Fe₅C₂) 종을 잘 형성시켜 주는 것이 중요하다고 볼 수 있다(Weckhuysen, B. M. et al. Chem. Soc. Rev., 2008, 37, 2758).
On the other hand, the FT reaction has been studied for almost 100 years since the 1920s, but it is still controversial whether the active species of the catalyst participating in the actual FT reaction is metallic iron surface, surface or bulk iron carbide or iron oxide, Comparing the activation energies, it is important to make iron carbide as well because it is characterized by low energy because the carbon is diffused and converted into iron carbide rather than the energy that the FT reaction proceeds on the metallic iron surface. This can minimize the induction period, and more preferably, among the various iron carbide phases reported, hag carbide

_{) (χ-Fe 5 C 2} ) it may be seen that it is important to form a species that well (Weckhuysen, BM et al. Chem . Soc. Rev., 2008, 37, 2758).

For the preparation of catalysts, some colloid methods for the synthesis of active Fe ₅ C ₂ nanoparticles having activity have been reported, but still have problems in mass production due to the high cost of the metal precursors and solvents and complex manufacturing methods .

An object of the present invention is to provide an iron-based catalyst for Fischer-Tropsch synthesis capable of enhancing the reactivity of a catalyst in a Fischer-Tropsch reaction, reducing the production of methane and improving the chain growth selectivity of a hydrocarbon, a method for producing the same, .

A first aspect of the present invention relates to a porous carbon support comprising: a porous carbon support; And cesium (Cs) added iron carbide nanoparticles supported in the pores of the porous carbon support.

In a second aspect of the present invention, a porous carbon support powder and an iron-containing compound having a melting point lower than that of the porous carbon support are mixed and mixed, and the mixture is melted and impregnated in a closed system at a temperature ranging from the melting point to the melting point + (Step 1); And a step (2) of wet-impregnating the composite powder obtained in the step 1 with a cesium-containing solution and then calcining (step 2), wherein the cesium (Cs) added iron-carbide is supported on the porous carbon support .

)(χ-Fe₅C₂) 종을 포함하는 것이 특징인, 피셔-트롭쉬 합성용 촉매를 제공한다.In a third aspect of the present invention, there is provided a catalyst for Fischer-Tropsch synthesis, which is produced according to the method of the second aspect, wherein cesium and iron are uniformly supported on a porous carbon support to be activated,

) (χ-Fe ₅ C ₂ ) species.

A fourth aspect of the present invention is a method for producing a liquid or solid hydrocarbon from a syngas using a Fischer-Tropsch synthesis reaction, comprising the steps of: i) mixing a Fischer-Tropsch synthesis catalyst according to the first or second aspect To a Fischer-Tropsch synthesis reactor; And ii) injecting a syngas into the Fischer-Tropsch synthesis reactor to perform a Fischer-Tropsch synthesis reaction with the Fischer-Tropsch synthesis catalyst.

Hereinafter, the present invention will be described in detail.

In the Fischer-Tropsch synthesis reaction, in the case of the iron-based catalyst, the water gas field is active in the reaction, so that it can be used in various compositions within the range of hydrogen to carbon monoxide synthesis gas composition ratio of 1 to 2, Can also be used. Therefore, in the case of high-temperature FT reaction, which is being commercialized on a large scale, an iron-based catalyst having high endotoxicity due to sulfur compounds has been mainly used in the process. However, iron-based catalysts still need to be improved in catalyst performance to be used in commercial processes. In the present invention, it has been found that when cesium is used as an additive (promoter) in an iron-based catalyst, the reactivity of the catalyst in the Fischer-Tropsch reaction can be enhanced, the production of methane can be reduced, and the selectivity of chain growth of hydrocarbons can be improved. Furthermore, the iron-based catalyst added as cesium as an additive has been devised as a method of easily synthesizing through a melt impregnation and a wet impregnation process using a porous carbon support. The present invention is based on this.

Specifically, in one embodiment of the present invention, Cs-added Fe ₅ C ₂ nanoparticle-type catalysts were easily synthesized through melt impregnation and wet impregnation using a porous activated carbon support (Example 1) In the case of using the cesium (Cs) added Fe ₅ C ₂ / activated carbon catalyst in the Lossh reaction, not only a higher total CO conversion rate as compared with the case of using an additive-free catalyst but also a shorter induction period, It was confirmed that the stable state could be quickly reached within 12 hours (Fig. 6).

In addition, in an embodiment of the present invention, when a cesium (Cs) added Fe ₅ C ₂ / activated carbon catalyst is used in a high temperature Fischer-Tropsch reaction, the methane selectivity is less than 10%, while the C _{5 +} selectivity is more than 30% (FIG. 7), it was confirmed that it is possible to continuously produce liquid oil in high-temperature FT synthesis (Table 1), as well as to improve the selectivity of chain growth of hydrocarbon by reducing the generation of methane.

Further, the Cs-added Fe ₅ C ₂ / activated carbon catalyst according to the present invention exhibited excellent stability without deactivation for 90 hours at a high temperature FT reaction condition of 320 ° C. and under 15 bar (Example 2).

The catalyst for Fischer-Tropsch synthesis according to the present invention comprises a porous carbon support; And cesium (Cs) added iron carbide nanoparticles supported in the pores of the porous carbon support.

)(χ-Fe₅C₂) 종을 포함하는 것일 수 있다. 철 카바이드가 해그 카바이드(

)(χ-Fe₅C₂) 종을 포함함으로써 반응도입시기(induction period), 즉 유도 기간을 최소화시킬 수 있다.
In the present invention, the iron carbide may be selected from the group consisting of Hag Carbide (

) (χ-Fe ₅ C ₂ ) species. Iron carbide is a mixture of Hag Carbide (

) (χ-Fe ₅ C ₂ ) species to minimize the induction period, ie, the induction period.

In the present invention, by controlling the surface basicity of the catalyst by adjusting the Cs / Fe atomic ratio, it is possible to change the selectivity to the desired hydrocarbon product by affecting the dissociative adsorption of CO and the adsorption of H ₂ . At this time, the larger the Cs / Fe atomic ratio, the higher the selectivity to heavier hydrocarbons, that is, the heavy chain hydrocarbon product.

In the present invention, the Cs / Fe atom ratio may preferably be 0.01 to 0.1, more preferably 0.025 to 0.050 on a molar basis. Preferably, the FT reaction at 320 ° C and 15 bar using a syngas (H ₂ / CO = 1.0, GHSV = 8.0 NL · g _cat ^-1 · h ^-1 ) yields a Cs / Fe atomic ratio of 0.01 to 0.04 case, the liquid oil productivity ^{_{0.3 g liq · g cat -1 ·}} h -1 or more can be excellent, and, in the case of Cs / Fe atomic ratio of 0.04 to 0.1, the solid wax productivity 0.1 g _sol · g ^-1 · _{c at} h ^-1 or more.

Specifically, in one embodiment of the present invention, the physicochemical properties and the Fischer-Tropsch synthesis reaction efficiency of the Cs-added Fe ₅ C ₂ / activated carbon nanocatalyst having a controlled Cs / Fe atomic ratio were analyzed , A catalyst with a Cs / Fe = 0.025, based on the small Fe ₅ C ₂ particle size (8.5 nm) promoted by appropriate Cs doping and the surface basicity, exhibited very high CO conversion (> 95%) and high oil productivity (~ 0.4 g _liq · g _cat ^-1 · h ^-1 ) (FIG. 3B, FIG. 6 and Table 1).

In the present invention, the iron content may be 5 to 30 wt% and the cesium content may be 0.5 to 5 wt% based on the weight of the total catalyst. When the content of iron is within the above range, it is advantageous in terms of uniform dispersion of the particles and size of the formed particles, and in the case where the content of cesium is in the above range, it is advantageous in improving the catalyst performance.

In the present invention, it is preferable that the pore volume of the porous carbon support used as a support is at least 0.2 cm 3 / g in order to uniformly carry the particles suitable for the Fischer-Tropsch reaction. In order to further increase the loading of the particles, It is preferable to use a large carbon material.

In the present invention, the porous carbon support may be selected from the group consisting of activated carbon, activated charcoal, acetylene carbon black, regular porous carbon supports such as CMK, CMK-3, CMK- 5 or CMK-8. Preferably, commercial activated carbon made from wood is used in the present invention. Commercial activated carbon is a superior carbon based support and is inexpensive, has thermal stability, high surface area (~ 1000 m < 2 > / g) and large pore volume (~ 0.8 cm < 3 > / g)

The method for preparing a catalyst in which cesium (Cs) added cesium (Cs) -contained iron-carbide is supported on a porous carbon support comprises grinding and mixing a porous carbon support powder and an iron- containing compound having a melting point lower than that of the porous carbon support, Containing compound at a temperature ranging from the melting point of the compound-containing compound to the melting point + 5 占 폚 and then calcining (step 1); And a step (step 2) of wet-impregnating the cesium-containing solution in the composite powder obtained in the step 1 and then firing it.

Step 1 is a step of performing melt infiltration of an iron-containing compound.

In the method for producing a catalyst according to the present invention, the iron-containing compound having a melting point lower than that of the porous carbon support may have a melting point in the range of 30 to 100 ° C, preferably iron hydrate. Compounds having a lower melting point are difficult to treat because they are liquid at room temperature. In the case of compounds having a high melting point of 100 ° C or higher, boiling may occur because the water is impregnated at a temperature higher than the boiling point. In particular, these metal salts have their respective density values. The amount of metal salt impregnation can be more uniformly determined by considering the density of the metal salt and the pore volume of the porous carbon support. Specifically, the iron hydrate salt is Fe (NO ₃ ) ₃ 9H ₂ O (d = 1.68 g / cm 3, mp = 47.2 ° C), FeCl ₃ 6H ₂ O (d = 1.82 g / FeSO ₄ 7H ₂ O (d = 1.898 g / cm 3, mp = 70 ° C) or a mixture thereof.

The reaction vessel can be selected according to the amount of metal hydrate salt and the reaction temperature applied in the melt infiltration process. The reaction vessel made of stainless steel or polypropylene or Teflon among the polymer plastics You can use the prepared container.

Further, in order to uniformly impregnate the iron-containing compound into the porous carbon support, it is important to control the temperature inside the reaction vessel and to maintain the pressure. In order to completely impregnate the iron-containing compound to be impregnated, More preferably 2 to 5 ° C higher than the melting point of the iron-containing compound, and the reaction is preferably 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 .

In the method for producing a catalyst according to the present invention, the type and pore volume of the porous carbon support are the same as those described in the above-mentioned Fischer-Tropsch synthesis catalyst.

Step 2 is a step of performing firing after wetness impregnation of the Cs solution.

In the method for producing a catalyst according to the present invention, the cesium-containing solution may be obtained by dissolving a cesium salt in water or an organic solvent. The present invention can add cesium metal onto iron carbide by doping a cesium salt onto the iron carbide particles through wet deposition, followed by activation and calcination. The cesium salts usable in the present invention include K ₂ CO ₃ , CsOH, CsI, CsCl, CsBr, Cs ₂ Cr ₂ O ₇ , CsNO ₃ , CsC ₂ H ₃ O ₂ , CsMnO ₄ , CsCN, CsIO ₃ , Cs ₂ S ₂ O ₈ , Cs ₂ SO ₄ , CsSCN, CsClO ₃ , CsF, CsH, CsH ₂ PO ₄ , C ₄ H ₉ CsO, and the like.

In the present invention, the firing of the step 1 and the firing step 2 is preferably carried out in an atmosphere of an activated gas.

It is important that the sintering condition in which an iron-containing compound such as an iron hydrate salt is treated and then treated is an iron carbide phase in which the impregnated iron-containing compound is sufficiently decomposed to become active, It is preferably 300 to 400 ° C, more preferably about 350 ° C, which can exhibit activity without increasing.

The activation gas used in the present invention may be carbon monoxide, hydrogen, or a mixed gas (carbon monoxide + hydrogen), but it is more preferable to use pure carbon monoxide in terms of catalyst activation. The firing time is preferably 1 to 24 hours while allowing the activation gas to flow at least 100 mL per minute so that the activation can be sufficiently performed.

FIG. 1 is a schematic view showing an overall synthesis process of a Cs-added iron-carbide / activated carbon catalyst as one embodiment. The active iron-carbide nanoparticles doped with Cs were successfully inserted into the activated activated carbon support through the following simple two steps. That is, the first step of performing melt infiltration of the hydrated iron salt and the second step of performing firing after wetness impregnation of the Cs solution to form the Cs-added iron-carbide / An activated carbon catalyst can be produced.

In the first step, the Fe (NO ₃ ) ₃ .9H ₂ O salt is taken with the mesoporous activated carbon at room temperature and then aged in the oven at 50 ° C for 24 hours in an oven to form Fe (NO ₃ ) ₃ .9H ₂ O The salt may be melt-impregnated in the mesoporous activated carbon. The amorphous iron salt in activated carbon was then converted to small iron-carbide nanoparticles by pyrolysis at 350 DEG C under CO flow. In the second step, the iron-carbide nanoparticles supported on the porous activated carbon were impregnated with a Cs ₂ CO ₃ aqueous solution and doped with Cs by being thermally treated again at 350 ° C under a CO flow. The Cs / Fe atomic ratio in the Cs-added iron-carbide particles can be controlled by varying the concentration of the Cs ₂ CO ₃ aqueous solution.

Preferably, the method for preparing a catalyst according to the present invention comprises a step (step 3) of preventing oxidation and stabilizing the cesium-added iron-carbide / carbon composite catalyst with passivation through an organic solvent after the step 2, . ≪ / RTI >

The passivation process for stabilizing the activated catalyst in the high temperature activated gas atmosphere is an important step in the subsequent reaction application of the externally reduced catalyst and serves to block the reaction between the catalyst and oxygen by using an organic solvent.

As the organic solvent which can be used at this time, various solvents such as ethanol and mineral oil can be used, but water which can oxidize and change the catalyst can not be used. The passivation is carried out 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 it is preferable to use ethanol which is easy to volatilize as a solvent for further analysis or application to a fixed bed reactor .

Preferably, the method for preparing a catalyst according to the present invention may further comprise a step (step 4) of recovering and drying the iron-carbide / carbon composite catalyst to which cesium is added in the organic solvent after the step 3 .

In the case of the iron carbide / cesium / carbon supported catalyst, which is soaked in an organic solvent, the catalyst itself is magnetic, so it can be easily separated from the solvent by using a magnet. After separation, it is dried again by vacuum drying, Or nitrogen packaged.

)(χ-Fe₅C₂) 종을 포함하는 촉매 활성이 우수한 피셔-트롭쉬 합성용 촉매를 제공할 수 있다. 바람직하기로, 상기의 촉매 제조방법에 따라 제조된 촉매는 해그 카바이드 종이 전체 철 카바이드 종의 중량을 기준으로 바람직하기로 70 내지 100%일 수 있다.
In the present invention, cesium and iron are prepared by the above-mentioned catalyst production method and supported on the porous carbon support uniformly and activated, and the iron carbide formed after firing is activated with hag carbide

) (χ-Fe ₅ C ₂ ) species having high catalytic activity can be provided. Preferably, the catalyst prepared according to the above catalyst preparation process can be preferably 70-100%, based on the weight of the total iron carbide species of hagkabide species.

On the other hand, the present invention can effectively produce liquid or solid hydrocarbons based on high CO conversion and selectivity using the cesium (Cs) added iron-carbide / porous carbon support catalyst. That is, after injecting a cesium-containing iron carbide / carbon composite catalyst into a Fischer-Tropsch synthesis reactor and then activating it preferably, a synthesis gas is injected to produce liquid or solid hydrocarbons by Fischer-Tropsch synthesis reaction .

As a preferred embodiment, a method for producing a liquid or solid hydrocarbon from a syngas using a Fischer-Tropsch synthesis reaction according to the present invention comprises the steps of: i) preparing a Fischer-Tropsch synthesis catalyst according to the first or second aspect To a Fischer-Tropsch synthesis reactor; And ii) injecting a syngas into the Fischer-Tropsch synthesis reactor to perform a Fischer-Tropsch synthesis reaction with the Fischer-Tropsch synthesis catalyst.

Preferably, a method of producing a liquid or solid hydrocarbon from a syngas using a Fischer-Tropsch synthesis reaction according to the present invention is characterized in that i-1) between said step i) and step ii) Step < / RTI >

The synthesis gas used in the present invention may be selected from among carbon monoxide, hydrogen, carbon monoxide, and hydrogen mixed with any one of inert gas, methane and carbon dioxide as impurities. Preferably, carbon monoxide and hydrogen are mixed in a ratio of 1: 1 to 2, most preferably, carbon monoxide and hydrogen are used in a ratio of 1: 1 in terms of the yield of the product. Incidentally, Methane or other inert gas may be included. The ratio of carbon monoxide to hydrogen means the volume ratio. In addition, the ratio of syngas in the Fischer-Tropsch reaction throughout the present invention means the volume ratio.

The syngas can also be injected preferably within a range of space velocities of 6.0 to 24.0 NL / g _cat / hr. Even if the space velocity is less than the space velocity, there is no problem in the reaction progress, but the productivity of the liquid hydrocarbon is low, and the conversion rate of carbon monoxide can be reduced when the synthesis gas is injected at a rate higher than the space velocity.

In the step ii), the reaction temperature may be 250-350 ° C., but it is preferable to increase the conversion of carbon monoxide and increase the yield of liquid hydrocarbons to 300-350 ° C.

The reaction pressure in step ii) above may preferably be 10 to 30 bar, most preferably 15 bar, in order to increase the conversion of carbon monoxide and increase the yield of liquid hydrocarbons.

As described above, the cesium-added iron-carbide / porous carbon support catalyst according to the present invention has a high conversion of carbon monoxide at a high temperature of 300 ° C or higher in the Fischer-Tropsch synthesis reaction, _{5 +} or more liquid hydrocarbons, it can be applied to commercial processes as an excellent catalyst for high temperature Fischer-Tropsch reaction. In addition, the Cs-added Fe ₅ C ₂ / activated carbon nanocatalyst can serve as a commercially available catalyst platform enabling the continuous production of liquid oils in high temperature FT synthesis.

The present invention can provide a highly active iron-carbide / cesium / carbon-based composite catalyst for FT synthesis carrying cesium-containing iron-carbide particles activated on a porous carbon support, and also can provide a high activity iron- It is possible to provide a method for producing an active iron-carbide catalyst in a large amount by using a melt impregnation method, an external activation process in an activated gas atmosphere, and a wetting method of a cesium salt in a process of producing a cesium / have.

The high activity iron-carbide / cesium / carbon composite catalyst for FT synthesis provided by the present invention is structurally stable to heat even at a high temperature FT reaction of 300 ° C or higher and has the advantage of selectively obtaining liquid hydrocarbons with high yield.

FIG. 1 is a schematic view showing the overall synthesis process of Cs-added iron-carbide / activated carbon nanocatalyst.
Figure 2 shows TEM (a) and HADDF-STEM (b) images of a Cs-added Fe ₅ C ₂ / activated carbon catalyst with Cs / Fe = 0.025 and a Cs added Fe ₅ C ₂ XRD spectrum of a single HRTEM images of the particles (c), Cs / Fe = 0.050 Cs added Fe to ₅ C ₂ / activated carbon catalyst of the TEM image (d), and Cs doped Fe ₅ C ₂ / activated carbon catalyst ( e). At this time, the bars represent 50 nm (a, d), 20 nm (b), and 5 nm (c).
3 is a TEM image and particle size distribution diagram of Cs added Fe ₅ C ₂ / activated carbon with Cs / Fe = 0.025 (a, b) and Cs / Fe = 0.050 (c, d). At this time, more than 200 particles per sample were measured. Bar (a, c) represents 20 nm.
4 is an XPS spectrum of a Cs-added Fe ₅ C ₂ / activated carbon catalyst having Cs / Fe = 0.025.
FIG. 5 is (a) N ₂ adsorption / desorption isotherm and (b) pore size distribution diagram of Cs-added Fe ₅ C ₂ / activated carbon catalyst.
6 is a graph of the CO conversion of Cs-added Fe ₅ C ₂ / activated carbon catalyst with Cs / Fe = 0.025 (a) and Cs / Fe = 0.050 (b).
7 is a graph of CO ₂ and hydrocarbon product selectivity of Cs-added Fe ₅ C ₂ / activated carbon catalyst with Cs / Fe = 0.025 (a) and Cs / Fe = 0.050 (b)
8 is a graph showing the catalytic performance of Fe ₅ C ₂ / activated carbon catalyst added with Cs in high temperature FT synthesis.
Figure 9 is a hydrocarbon product distribution (a), and an ASF plot (b) of C _{5 +} hydrocarbon and chain growth potential.
10 is a hydrocarbon product distribution diagram. The hydrocarbon distribution (wt%) of each sample is calculated from the GC analysis of the gaseous product (C ₁ -C ₄ ) and the SIMDIS analysis of the separated liquid and solid product.

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

Example  1: Cesium ( Cs ) Added Fe ₅ C ₂ / Activated carbon catalyst production

First, 4.6 mmol of Fe (NO ₃ ) ₃ .9H ₂ O (Sigma-Aldrich, ACS reagent, ≥98%) was added to 1.0 g of commercially activated charcoal (Sigma-Aldrich, -100 mesh particle size) And the mixture was poured into a pest for several minutes under atmospheric conditions until the powder became uniformly black.

The mixture was stirred until it became sufficiently homogeneous. Then, black powder mixed with polypropylene was tightly tightened. The container was placed in a drying oven set at 50 ° C and stored for 24 hours. After aging for 24 hours, the mixed powder was cooled to room temperature and placed in an alumina boat in a tube-type furnace. Finally, the activated carbon powder containing iron obtained above was slowly heated in a firing oven at a rate of 2.7 DEG C / min up to 350 DEG C under a carbon monoxide gas atmosphere (normal pressure, flow rate of 200 mL / min) Lt; RTI ID = 0.0 > 350 C < / RTI > for 4 hours. After the heat treatment, the resulting black powder was cooled to room temperature and then immersed in 20 mL of anhydrous ethanol under an N ₂ flow of 500 mL / min. The immersed Fe / C powder was simply separated using a magnet and completely dried in a vacuum oven at 50 ° C.

Cs ₂ CO ₃ (Aldrich, ReagentPlus, 99%) dissolved in distilled water was then impregnated onto the dried Fe / C powder by an incipient wetness method. 0.057 mmol and 0.114 mmol of Cs ₂ CO ₃ salt were used to prepare Fe ₅ C ₂ catalyst added with Cs at a ratio of Cs / Fe = 0.025 and Cs / Fe = 0.050 on a molar basis. The Cs-added sample was reheated at 350 < 0 > C for 4 hours under continuous CO flow of 200 mL / min. Then, cooling the resulting powder to room temperature and was then immersed in absolute ethanol under N ₂ flow. Finally, the powder was separated and dried in a vacuum oven at 50 ° C.

Experimental Example  1: Cesium ( Cs ) Added Fe ₅ C ₂ / Characterization of Activated Carbon Catalysts

The sample obtained in Example 1 was analyzed using HRTEM (Tecnai G2 F30 operated at 300 kV, KAIST). For TEM analysis, a sample was prepared by dropping a few drops of the corresponding colloidal solution on a formvar-carbon copper grid (Ted Pellar, Inc). For analysis, high power powder-XRD (Rigaku D / MAX-2500, 18 kW) was used.

The results are shown in Fig. 2 and Fig.

Figure 2 shows the TEM (a) and HADDF-STEM (b) images of Fe ₅ C ₂ / activated carbon catalysts with Cs / Fe atomic ratios of 0.025 and the Cs addition shown with the corresponding FT pattern the Fe ₅ C ₂ XRD of the HRTEM image (c), Cs / Fe = the Cs was added as 0.050 Fe ₅ C ₂ / TEM images of the activated carbon catalyst (d), and Cs doped Fe ₅ C ₂ / activated carbon catalyst in a single particle Spectrum (e). At this time, the bars represent 50 nm (a, d), 20 nm (b), and 5 nm (c).

3 is a TEM image and particle size distribution diagram of Cs added Fe ₅ C ₂ / activated carbon with Cs / Fe = 0.025 (a, b) and Cs / Fe = 0.050 (c, d). At this time, more than 200 particles per sample were measured. Bar (a, c) represents 20 nm.

It can be seen from FIGS. 2A and 3A that the small iron-carbide nanoparticles are well dispersed in the activated carbon support. These nanoparticles were observed to have an average particle size of 8.5 +/- 1.4 nm (Figure 3b). High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images show bright spots and relatively dark areas representing iron-carbide nanoparticles and carbon support structures, respectively (FIG. Through high-resolution TEM (HRTEM) and corresponding Fourier-transform pattern analysis, the final Cs-added iron-carbide particles were spherical in shape, single crystal with a distance of 0.208 nm between neighboring boundaries , And the (021) plane of the iron-carbide (FIG. 2C).

(χ-Fe₅C₂) 상과 매치됨을 보여주었다 (도 2e, JCPDS No. 36-1248 및 No. 51-0997). 2θ = 26.5°의 날카로운 피크는 활성화된 활성탄의 결정질 탄소 구조에 해당한다 (JCPDS No. 26-1077). XRD 스펙트럼에서, 임의의 결정질 세슘 화합물에 관련된 유의적인 피크는 관찰되지 않았다.
The Cs-added iron-carbide particles with a Cs / Fe atomic ratio of 0.050 were slightly irregular and showed a large particle size and an average particle size of 13.8. + -. 2.8 nm (FIGS. 2d and 3c-d). 2 X-ray diffraction (XRD) spectrum showing broad peaks at ? = 43-45 ° shows that the Cs-added iron-carbide particles in both Cs / Fe = 0.025 and Cs / Fe =

(χ-Fe ₅ C ₂ ) phase (FIG. 2e, JCPDS No. 36-1248 and No. 51-0997). 2 A sharp peak at θ = 26.5 ° corresponds to the crystalline carbon structure of activated carbon (JCPDS No. 26-1077). In the XRD spectrum, no significant peak related to any crystalline cesium compound was observed.

On the other hand, X-ray photoelectron spectroscopy (XPS) analysis was performed using a Thermo VG Multilab 2000 spectrometer equipped with a monochromatic Al K? Light source. N ₂ adsorption isotherms were measured at 77 K (-196 ° C) with a TriStar II 3020 surface area analyzer. Prior to measurement, the sample was degassed in a vacuum of 300 DEG C for 4 hours.

Core-level X-ray photoelectron spectroscopy (XPS) spectra of Fe and Cs were measured to confirm the surface state of the Cs-added Fe ₅ C ₂ particles as described above. The XPS spectrum of the energy region of the Fe and Cs bands shows two sets of assigned sharp peaks, namely iron carbide (Fe (0)) peaks at 707.9 eV and 721.0 eV and cesium at 725.7 and 739.5 eV (0)) peak (Fig. 4). Another weak peak at 710.8 eV showed that the iron oxide phase (Fe (3+)) was due to the slightly oxidized surface of Fe ₅ C ₂ during the sampling process.

All Fe loading of Cs-added Fe ₅ C ₂ / activated carbon catalyst was calculated and confirmed to be approximately 20 wt% based on Fe converted from iron nitrate after pyrolysis. The Cs content of the total catalyst weight combined Fe ₅ C ₂ , Cs and activated carbon was calculated to be about 1 wt% at Cs / Fe = 0.025 and 2 wt% at Cs / Fe = 0.050 based on Cs converted from cesium carbonate precursor, . N ₂ adsorption experiments at 77 K on Cs-added Fe ₅ C ₂ / activated carbon catalysts showed type IV adsorption-desorption hysteresis with delayed capillary evaporation at a relative pressure of 0.5 (FIG. 5A). The BET (Brunauer-Emmett-Teller) surface area of the Cs-added Fe ₅ C ₂ / activated carbon catalyst was calculated to be 541.1 m 2 / g at Cs / Fe = 0.025 and 516.2 m 2 / g at Cs / Fe = 0.050. Also, the total pore volume was measured to be 0.42 cm 3 / g at Cs / Fe = 0.025 and 0.37 cm 3 / g at Cs / Fe = 0.050. The slight decrease in the BET surface area and pore volume at Cs / Fe = 0.050 may be due to the fact that the Fe ₅ C ₂ particle size is larger at 13.8 nm than at Cs / Fe = 0.025 (8.5 nm). Using the BJH (Barrett-Joyner-Halenda) method for the desorption branch, it was confirmed that the small pore size of the Cs-added Fe ₅ C ₂ / activated carbon catalyst was 3.8 nm (FIG.

Example  2: Cesium ( Cs ) Added Fe ₅ C ₂ / High Temperature Fisher with Activated Carbon Catalyst - Tropsch  reaction

The Fischer-Tropsch (FT) reaction was carried out in a fixed-bed stainless steel reactor with an internal diameter of 5 mm and a length of 180 mm. 0.3 g of the catalyst was diluted with glass beads (3.5 g, 425-600 mm size) to inhibit hot spot formation and then placed in a fixed bed reactor. The catalyst was reactivated in situ under a CO flow of 40 mL / min at 350 < 0 > C for 4 hours. The FT reaction was then carried out at 320 ° C and 15 bar for 90 hours using syngas (H ₂ / CO = 1.0, GHSV = 8.0 NL · g _cat ^-1 · h ^-1 ). The flow rate of the outlet gas was measured with a wet-gas flow meter (Shinagawa Co.) and the gas was analyzed using an on-line gas chromatograph equipped with a molecular sieve and a Plot Q column (Agilent, 3000A Micro-GC) Respectively. After performing the FT synthesis reaction for 90 hours, the solid hydrocarbon product was collected in a hot trap at 230 ° C, and the liquid hydrocarbon product and water were collected in a cold trap at 0 ° C. The composition of wax and liquid oil was analyzed by offline GC (Agilent, 6890 N) using the simulated distillation method (ASTM D2887).

As described above, the high temperature FT synthesis was carried out at 15 bar, 320 ° C, H ₂ / CO = 1 and the CO conversion and selectivity of the Cs-added Fe ₅ C ₂ / activated carbon catalyst were measured over the reaction stream for 90 hours. The results were obtained by gas chromatography (GC) analysis of the exit gas containing unreacted CO, H ₂ , CH ₄ , C ₂ -C ₄ hydrocarbons and CO ₂ . The liquid hydrocarbons obtained in the cold trap and the solid hydrocarbons obtained in the hot trap were analyzed by a simulated distillation method (SIMDIS) as described above.

Hydrocarbon formation proceeds as follows by FT synthesis.

nCO + (2n + 1) H ₂ ? C _n H _{2n + 2} + _n H ₂ O: paraffin

_{nCO + 2nH 2 → C n H} 2n + nH 2 O: olefin

In addition, CO ₂ can be produced by the accompanying WGS reaction as follows.

CO + H ₂ O? CO ₂ + H ₂

6, it can be seen that the CO conversion quickly reached a steady-state within 12 hours of the reaction. All Cs-added Fe ₅ C ₂ / activated carbon catalysts showed very high total CO conversion without deactivation. Specifically, the total CO conversion was 96.9% at Cs / Fe = 0.025 and 95.5% at Cs / Fe = 0.050. On the other hand, the promoter-free Fe ₅ C ₂ / activated carbon catalyst showed a relatively low CO conversion of 90.8% during the FT reaction and a very long reaction induction period (~66 h). The conversion of CO to HC and CO to CO ₂ for 90 hours of time-on-stream was 56.4% and 40.5% at Cs / Fe = 0.025, respectively (Fig. 6a) % And 36.8% (Fig. 6b).

In the selectivity data, the graph of Cs / Fe = 0.025 shows that at TOS 90 h CH _{4 (8.3%), C 2 -C} 4 (16.9%), and C _{5 +} (33.1%) (Fig. 7A). On the other hand, Cs / Fe = 0.050 shown in the lower CH ₄ selectivity (6.2%) and higher C _{5 +} selectivity (38.2%) (Fig. 7b). The higher selectivity for heavier hydrocarbons appearing at Cs / Fe = 0.050 may be mainly due to the higher surface basicity of the catalyst. The surface basicity controlled by the Cs / Fe atomic ratio can affect the dissociative adsorption of CO and the adsorption of H ₂ to change the selectivity to the desired hydrocarbon product.

The catalytic activity was recorded as CO moles converted to hydrocarbons per gram of iron per second (FTY), ie, per second, reflecting CO conversion and hydrocarbon selectivity of the catalyst during the FT reaction (Figure 8) . If the Cs / Cs = Fe the Fe ₅ C ₂ / active carbon catalyst is added at 0.050 Cs / Fe = 0.025 1.454 × 10 slightly higher than _{^{(1.398 × 10 -4 mol CO ·}} g Fe -1 · s -1) - ^And an FTY value of ⁴ mol _CO · g _Fe ^-1 · s ^-1 . This is because the selectivity from CO to CO ₂ is 38.6% when Cs / Fe = 0.050 is lower than 40.4% at Cs / Fe = 0.025.

The productivity of FTY, liquid and solid hydrocarbons of Cs-added Fe ₅ C ₂ / activated carbon catalysts is shown in Table 1 below.

Cs / Fe = 0.025 Cs / Fe = 0.050 FTY (10 ^-4 mol _CO · g _Fe ^-1 · s ^-1 ) 1.398 1.454 Liquid oil productivity (g _liq · g _cat ^-1 · h ^-1 ) 0.401 0.296 Solid wax productivity (g _sol · g _cat ^-1 · h ^-1 ) 0.026 0.164 [Note] g _cat is the total weight of Fe and activated carbon support, g _liq and g _sol are the weight of liquid oil and solid wax separated after reaction, respectively.

Interestingly, the Cs / Fe = 0.025 Cs-added Fe ₅ C ₂ / activated carbon catalyst has a Cs / Fe = 0.050 Cs-added Fe ₅ C ₂ / activated carbon catalyst (0.296 g _liq · g _cat ^-1 · h ^-1 ) After 90 hours of FT reaction, it showed very high liquid oil productivity of 0.401 g _liq · g _cat ^-1 · h ^-1 (Table 1). Conversely, the solid wax productivity of the Cs-added Fe ₅ C ₂ / activated carbon catalyst was very low compared to the high liquid oil productivity. Specifically, Cs / Fe = 0.025 In ^{_{0.026 g sol · g cat -1 ·}} h - indicated by ^1, a much lower value than Cs / Fe = 0.050 representing ^{_{0.164 g sol · g cat -1 ·}} h -1 It looked.

As described above, the detailed composition of the liquid and solid hydrocarbons was analyzed by ASTM D2887, and the result is shown in FIG. 9A. The chain growth potential (α) of the hydrocarbons was calculated using the ASF (Anderson-Schulz-Flory) chain growth mechanism of the following equation (FIG.

[Equation 1]

_{log (W n / n) =} log (ln 2 α) + n · logα

Where W _n is the weight fraction of hydrocarbon having n carbon atoms.

Two α value (the C ₅ to C ₁₈ of the α ₁ and C ₁₉ to C ₄ α ₂₎ was obtained by fitting the slope of the graph by means of two linear regression. The high values of 0.744 at Cs / Fe = 0.025 and 0.762 at Cs / Fe = 0.050 and 0.852 at Cs / Fe = 0.025 and 0.877 at Cs / Fe = And Cs-enriched position. (? ₁ = 0.762 and? ₂ = 0.877) at Cs / Fe = 0.050 were higher than the? Value at Cs / Fe = 0.025. This indicates that a larger Cs doped Fe ₅ C ₂ surface can provide a more favorable condition for growth of carbon chains during FT synthesis.

The yield of hydrocarbon products (grams of hydrocarbons produced per gram of iron per second) for the gaseous hydrocarbon product (C ₁ -C ₄ gas) is shown in Table 2 below.

catalyst Gas product yield (10 ^-4 g _HC · g _Fe ^-1 s ^-1 ) CH ₄ C ₂ -C ₄ olefins C ₂ -C ₄ paraffin all Cs / Fe = 0.025 2.95 1.94 3.67 8.56 Cs / Fe = 0.050 2.42 3.62 1.99 8.03

Cs / Fe = 0.025 is added to the Cs Fe ₅ C ₂ / For the activated carbon catalyst, the total gas product yields _{^{8.56 × 10 -4 g HC · g}} Fe -1 · s - 1 to 8.03 in the case of Cs / Fe = 0.050 X 10 ^-4 g _HC · g _Fe ^-1 s ^-1 . However, the product yield ratio (0.53) of C ₂ -C ₄ olefin / C ₂ -C ₄ paraffins at Cs / Fe = 0.025 was much lower than that for Cs / Fe = 0.050 (1.82). Cs In the total parts by weight of the CH ₄ , C ₂ -C ₄ olefins, C ₂ -C ₄ paraffins, C ₅ -C ₁₂ , C ₁₃ -C ₁₈ , and C _{19 +} of the Fe ₅ C ₂ / activated carbon catalyst added, The weight fraction of heavy hydrocarbons (C ₁₉₊ ) was significantly lower at Cs / Fe = 0.025. This was due to the relatively low surface basicity of the catalyst (FIG. 10). Thus, in high temperature FT synthesis, this combination can increase the CO conversion and reduce the formation of solid wax, so a combination of the appropriate reaction temperature (320 DEG C) and the reaction pressure (15 bar) and the combination of Cs / Fe = 0.025 The use of an activated Fe ₅ C ₂ / activated carbon catalyst may be the best way to produce liquid oils with high productivity and selective production.

Claims (20)

A porous carbon support; And cesium (Cs) added iron carbide nanoparticles supported in the pores of the porous carbon support,
(G _liq · g _cat ^-1 · h ^-1 ) relative to solid wax productivity (g _sol · g _cat ^-1 · h ^-1 ), with a Cs / Fe atomic ratio of 0.01 to 0.04 on a molar basis Wherein the ratio is 0.401 / 0.026 or more.
delete The method of claim 1, wherein the iron carbide is selected from the group consisting of Hag Carbide

) (χ-Fe ₅ C ₂ ) species.
The catalyst according to claim 1, wherein the content of iron is 5 to 30 wt% and the content of cesium is 0.5 to 5 wt% based on the weight of the total catalyst.
The catalyst according to claim 1, wherein the porous carbon support has a pore volume of 0.2 cm 3 / g or more.
The catalyst according to claim 1, wherein the porous carbon support is selected from CMK as activated carbon, activated charcoal, acetylene carbon black and ordered porous carbon support.
delete delete delete delete delete delete delete delete The ratio of liquid oil productivity (g _liq · g _cat ^-1 · h ^-1 ) to the solid wax productivity (g _sol · g _cat ^-1 · h ^-1 ) from the syngas using a Fischer-Tropsch synthesis reaction was 0.401 / 0.026 < / RTI > or more,
i) applying the catalyst for Fischer-Tropsch synthesis according to claim 1 to a Fischer-Tropsch synthesis reactor; And
ii) injecting a syngas into the Fischer-Tropsch synthesis reactor to perform a Fischer-Tropsch synthesis reaction with the Fischer-Tropsch synthesis catalyst.
16. The method of claim 15, further comprising: i-1) reducing and activating the catalyst between step i) and step ii).
16. The production method according to claim 15, wherein the synthesis gas is one selected from the group consisting of carbon monoxide, hydrogen, carbon monoxide, and hydrogen mixed with any one of inert gas, methane and carbon dioxide.
16. The method according to claim 15, wherein the synthesis gas is a mixture of carbon monoxide and hydrogen in a volume ratio of 1: 1 to 2: 1.
16. The method of claim 15, wherein the synthesis gas is injected at a space velocity in the range of 6.0 to 24.0 NL / g _cat / hr.
The process according to claim 15, wherein said step ii) is carried out at 250 to 350 ° C.

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