KR20110123051A - Structured mesoporous silica supported fischer-tropsch catalyst - Google Patents

Abstract

PURPOSE: A catalyst for a fischer-tropsch reaction using a mesoporous silica structure is provided to efficiently generate an intermediate distilled product in a liquid hydrocarbon range by manufacturing a stable catalyst support to the fischer-tropsch reaction. CONSTITUTION: An emulsion is generated by adding a surfactant to an organic solvent and an acidic aqueous solution. Silicon alkoxide is added to the emulsion to synthesize silica. The silica is aged and filtered. The filtered silica is dried and sintered to obtain mesoporous silica. A reactive metal for a fischer-tropsch catalyst is introduced to the mesoporous silica to obtain a fischer-tropsch catalyst. The reactive metal is the mixed metal of two or more selected from a group including cobalt, iron, ruthenium, nickel, palladium, platinum, and rhodium. The acidic aqueous solution is the aqueous solution of one or more selected from a group including hydrochloric acid, nitric acid, sulfuric acid, acetic acid, carbonic acid, and acetic acid.

Description

Structured Mesoporous Silica Supported Fischer-Tropsch Catalyst}

The present invention is directed to a process for preparing a Fischer-Tropsch process catalyst that contributes to an increase in the production of liquid hydrocarbons. A method for producing a hollow spherical mesoporous silica structure with a support of a cobalt catalyst and an invention for using the catalyst in the Fischer-Tropsch reaction.

The Fischer-Tropsch process is a method of synthesizing hydrocarbons from syngas, carbon monoxide and hydrogen, and was conceived by Franz Fischer and Hans Tropsch in 1923 as a method of producing synthetic fuel. It is a technology that has evolved. The synthesis reaction of carbon monoxide and hydrogen varies depending on the type of catalyst, the reaction temperature and the pressure of the reaction product such as paraffin, olefin hydrocarbon and alcohol. Catalytic metals commonly used in Fischer-Tropsch processes include cobalt, iron, ruthenium, and nickel. The active metal is dispersed in a support such as silica, alumina or zeolite in order to be highly dispersed in a small size and to be stably maintained during the reaction. Among them, silica is inexpensive and easily available, and has a high surface area and a fine pore structure, and is widely used as a support because it helps disperse active metals.

Conventional methods for producing silica are largely hydrolyzed water glass and condensation reaction to obtain colloidal silica, pyrolysis of silicon tetrachloride (Thermal Pyrolysis) to produce fumed silica (sol) based on TEOS, etc. Synthesis using Stover, a kind of gel method. Since this method produces irregularly sized silica particles, in order to control the average particle size to 1 ~ 10㎛, special additives such as surfactants or organic solvents should be used. In Korean Patent No. 10-2001-0013733, a method of preparing a nano-sized silica powder having a particle size distribution using a reverse micelle and a sol-gel method was described. Since the Fischer-Tropsch reaction product has a larger size than the microporous size of the conventional microporous silica, it is difficult to utilize the active metal inside the pores when the microporous silica is a support, and the product distribution of the liquid hydrocarbon size is low. Has disadvantages In order to improve this, studies have been made to increase the pore size to the range of mesopores.

Mesoporous material is a microporous material having a pore size of 1.5 nm or less, as in conventional zeolites, which extends the pore size in the range of 2 to 50 nm. Such mesoporous material is used for the application of molecular sieve material to the adsorption and separation of the material larger than the pore size of the existing microporous material, catalytic conversion reaction and the like. Regarding such mesoporous inorganic materials, materials named as M41 group were manufactured by Mobil in 1991 as a template for ionic surfactants, which are disclosed in US Pat. Nos. 5,057,296 and 5,102,643. In addition to one-dimensional mesopores, a method for producing mesoporous material using MCM-41, which forms a hexagonal array such as honeycomb, and an amphiphilic block copolymer, which is a neutral surfactant, is also described in US Pat. Nos. 6,027,706 and 6,054,111. It is listed on the back. In the synthesis of mesoporous silica, a method using a surfactant is mainly used. According to the interaction method between the surfactant and silica, acidity control is an important factor in the synthesis conditions. SBA-based mesoporous silica synthesized under acidic conditions is more widely used for catalytic reactions because of its superior thermal stability than other silicas. Unlike zeolite, mesoporous silica has no catalyst active point because aluminum is not added, and then metal is introduced after silica synthesis to introduce an active point. Silica has a problem of low thermal stability at high temperature while facilitating water absorption, and thus, a method for synthesizing under acidic conditions or making a structure has been studied to increase hydrothermal stability. There is a need for the invention of a catalyst which is effective in increasing the efficiency of the Fischer-Tropsch reaction and increasing the product in the range of liquid hydrocarbons, with less deactivation during the reaction.

In order to solve this problem, the present inventors have studied diligently to prepare a mesoporous silica having a spherical structure to prepare a catalyst support having a high thermal stability, and to examine the extent to which the support is involved in the Fischer-Tropsch reaction This invention was completed by confirming that the outstanding effect compared with the catalyst using the silica gel of can be obtained. That is, an object of the present invention is to provide a method for producing a catalyst containing mesoporous silica having high hydrothermal stability.

The present invention comprises the steps of generating an emulsion by adding a surfactant to an organic solvent and an acidic aqueous solution, synthesizing silica by adding a silicon alkoxide to the emulsion, aging and filtering the silica, drying the filtered silica and It relates to a method for preparing a Fischer-Tropsch catalyst comprising the step of preparing mesoporous silica by calcining and introducing the active metal for Fischer-Tropsch reaction into the mesoporous silica.

By producing mesoporous silica having a spherical structure according to the present invention, silica particles having high hydrothermal stability can be produced to prepare a catalyst support that is stable to the Fischer-Tropsch reaction, thereby preparing a catalyst that is beneficial to the reaction.

1 is an SEM image confirming the hydrothermal stability of mesoporous silica in Experimental Example 1.
2 is an SEM image of the catalyst prepared in Example 1 and Comparative Example 1.
3 is an XRD image of catalysts prepared in Example 1 and Comparative Example 1. FIG.
4 is a product distribution diagram of the Fischer-Tropsch reaction using the catalyst prepared in Experimental Example 3.

The present invention provides an emulsion by adding a surfactant to an organic solvent and an acidic aqueous solution, adding silicon alkoxide to the emulsion to synthesize silica, aging and filtering the silica, and drying and calcining the filtered silica to meso The present invention relates to a method for preparing a Fischer-Tropsch catalyst, comprising preparing a porous silica and introducing an active metal for Fischer-Tropsch reaction into the mesoporous silica.

In the present invention, hollow spherical mesoporous silica is prepared to increase the liquid hydrocarbon product, which is used as a catalyst support for the Fischer-Tropsch reaction. To this end, silica is prepared by a sol-gel method using silicon alkoxide. An emulsion solution obtained by dispersing a surfactant in an organic solvent and an acidic aqueous solution is used as a template material. The active metal for Fischer-Tropsch reaction is not particularly limited, but may be cobalt, iron, ruthenium, nickel, palladium, platinum or rhodium.

Fischer-Tropsch reaction for the active metal based on 100 parts by weight of the mesoporous silica may be used 1 to 50 parts by weight. If the Fisher-Tropsch reaction active metal is less than 1 part by weight, there may be a problem in that the efficiency of the Fischer-Tropsch reaction is low, and when it exceeds 50 parts by weight, the Fischer-Tropsch reaction active metal nano There may be a problem that the dispersion effect of the particles is lowered.

The organic solvent is not particularly limited as long as it can dissolve the surfactant and the silicon alkoxide, and may include a compound represented by the following Chemical Formula 1.

In Formula 1, x is 1 to 20, y is 4 to 42, and z is 0 to 20. More preferably, it may be isooctane (2,2,4-trimethyl pentane). The organic solvent may be used in an amount of 1 to 20 parts by weight based on 1 part by weight of the surfactant.

The acidic aqueous solution is not particularly limited, but may be at least one aqueous solution selected from the group consisting of hydrochloric acid, nitric acid, sulfuric acid, acetic acid, carbonic acid, and acetic acid, and the acidity is preferably pH 3-6. When the acidity exceeds pH 6, the dehydration polycondensation reaction of the silica may not be improved, and when the acidity is less than pH 3, there may be a problem that it is not easy to control the production rate of silica. Although the surfactant is not particularly limited, carboxylate, sulfonate, sulfate ester salt, phosphate ester salt, phosphonate salt, amine salt, quaternary ammonium salt, phosphonium salt, sulfonium salt, fatty acid monoglycerine ester, fatty acid polyglycol ester , Fatty acid sorbitan ester, fatty acid sucrose ester, fatty acid alkanolamide, polyethylene glycol condensation type nonionic surfactant, polyethylene glycol-polypropylene glycol copolymer may be any one or more selected from the group consisting of. The acidic aqueous solution may be used in an amount of 1 to 100 parts by weight based on 1 part by weight of the surfactant.

When silicon alkoxide is added to the emulsion, silica is synthesized by the sol-gel method through partial hydrolysis and condensation of silicon alkoxide. Synthesis of the silica may be prepared by mixing a mixture of an organic solvent and an acid catalyst in the presence of a template material emulsified using a cationic, anionic or nonionic surfactant. The silicon alkoxide is not particularly limited, but tetramethyoxysilane, tetraethyl orthosilicate, methyltrimethoxy silane, ethyltrimethoxysilane, and vinyltrier It may be any one or more selected from the group consisting of oxysilane (Vinyltriethoxy silane) and phenyltriethoxy silane (Phenyltriethoxy silane). The silicon alkoxide may be added in an amount of 0.1 to 10 parts by weight based on 1 part by weight of the surfactant. When the silicon alkoxide is less than 0.1 part by weight, there may be a problem in terms of low silica production rate, and when it exceeds 10 parts by weight, mesoporous silica may be difficult to form a shape, and thus may be difficult to obtain a silica having a specific structure. The type and acidity of the template material, the ratio of the additives, the aging time and the temperature can be adjusted so that the mesoporous silica forms a structure.

The cobalt-supported Fischer-Tropsch catalyst can be prepared by washing, drying, and calcining the prepared mesoporous silica, and then supporting the mesoporous silica on the support using a cobalt salt. Preferred cobalt precursors include, but are not limited to, cobalt nitrate, cobalt acetate, cobalt bromide, cobalt chloride, and cobalt iodide. Any one or more precursors selected from the group consisting of can be used.

The cobalt-mesoporous silica structure Fischer-Tropsch catalyst prepared as described above is sieved to a certain size and then charged in a fixed bed catalyst reactor and the Fischer-Tropsch reaction is performed. Fischer-Tropsch reaction conditions are not limited, but preferably the reaction temperature 100 ~ 300 ℃, the reaction pressure 10 ~ 50 bar and H ₂ / CO ratio can be carried out under the reaction conditions of 1-3.

Hereinafter, the present invention will be described in more detail with reference to examples, but the following examples are merely to illustrate the present invention, but it should be understood that the present invention is not limited thereto.

Manufacturing example  One : Mesoporous  Preparation of Silica Support

4 g of ethylene glycol-propylene glycol copolymer [Poly (ethylene glycol) -block-poly (propylene glycol) -block-poly (ethylene glycol)] was dissolved in 8.75 ml of 99.9 vol% ethanol and 112 ml of 0.6 M acetic acid aqueous solution. 24 g of 2,2,4-trimethylpentane was added and stirred to prepare a template. 8.52 g of tetramethoxysilane was added, stirred at room temperature, aged for 1-100 hours at a temperature in the range of 60-180 ° C, washed with distilled water and ethanol, and filtered. The filtered precipitate was calcined after drying. About 4.8 g of mesoporous silica support was obtained.

Example  1: Preparation of Catalyst

4 g of ethylene glycol-propylene glycol copolymer [Poly (ethylene glycol) -block-poly (propylene glycol) -block-poly (ethylene glycol)] was dissolved in 8.75 ml of 99.9 vol% ethanol and 112 ml of 0.6 M acetic acid aqueous solution. 24 g of 2,2,4-trimethylpentane was added and stirred to prepare a template. 8.52 g of tetramethoxysilane was added, stirred at room temperature, aged for 1-100 hours at a temperature in the range of 60-180 ° C, washed with distilled water and ethanol, and filtered. The filtered precipitate was dried and then calcined at a temperature of 550 ° C. to obtain about 4.8 g of mesoporous silica support. 1 g of the support was impregnated with 20 wt% of cobalt using an aqueous solution of cobalt nitrate (Co (NO ₃ ) ₂ 6H ₂ O). The impregnated catalyst was dried and then calcined at a temperature of 550 ° C. for 5 hours. The resulting catalyst was prepared in a 20-40 mesh range for use in a fixed bed Fischer-Tropsch reaction.

Comparative example  One

The catalyst was prepared using silica gel instead of the support prepared in Preparation Example 1. 1 g of commercial silica gel was impregnated with 20 wt% cobalt using an aqueous solution of cobalt nitrate (Co (NO ₃ ) ₂ 6H ₂ O). The impregnated catalyst was dried and then calcined at a temperature of 550 ° C. for 5 hours. The resulting catalyst was prepared in a 20-40 mesh range for use in a fixed bed Fischer-Tropsch reaction.

Experimental Example  1: Measurement of the thermal durability of the support

As mentioned above, since the silica support has a problem of low hydrothermal stability, a mesoporous silica having a structure has been prepared to improve it. To confirm this, 1 g of mesoporous silica of Preparation Example 1 was mixed with 200 ml of distilled water and maintained at a temperature of 300 ° C. for 3 days in a hydrothermal synthesizer. The catalyst heat-treated for 3 days in the hydrothermal synthesizer was dried and confirmed by the electron microscope for the deformation of the structure.

Experimental Example  2: Measurement of Structure and Structure Characteristics of Catalyst

The particle size, BET surface area, pore volume, and pore size of the support and the catalyst of Example 1 and Comparative Example 1 were measured by the following method. The particle size of the catalyst was measured using XRD (X-ray Diffrentiation, Shimazdu Co., XRD-6000). The average size of the catalyst particles by XRD was calculated by substituting the full width at half maximum of the peak [311] into the Debye-Scherrer Equation. The BET surface area of the catalyst was derived from N ₂ adsorption isotherm (N ₂ -adsorption Isotherm; Quantachrome Co., Autosorb-1C). The SEM image is shown in FIG. 2 and the XRD image in FIG. 3.

Table 1 shows BET surface area, pore volume, pore size and average size of catalyst particles by XRD of Preparation Example 1, Example 1, Comparative Example 1 and silica gel.

BET surface area
(m ² / g) Pore volume
(cm < ³ > / g) Pore size
(nm) Cobalt Particle Size
(nm) Preparation Example 1 Mesoporous Silica 721.56 2.1752 12.0580 - - Silica gel 620.45 0.3441 2.2185 - Example 1 Cobalt / Mesoporous Silica Catalyst 296.98 0.7856 10.5810 19.85 Comparative Example 1 Cobalt / Silica Gel Catalyst 367.19 0.3010 3.2790 19.23

As shown in Table 1, although the catalyst prepared in Example 1 had a small BET surface area, the pore volume and pore size were significantly higher than those of the cobalt / silica gel catalyst (Comparative Example 1). The efficiency at

Experimental Example  3: Comparison of the Effects of Catalysts

0.5 g of the catalyst of Example 1 was charged onto a Fischer-Tropsch fixed bed reactor, and then the Fischer-Tropsch synthesis reaction was performed for 120 hours. The synthesis reaction was carried out at 250 ℃, 25 bar, H ₂ / CO = 2 molar ratio conditions. The produced reaction gas product was analyzed using On-line GC (TCD, FID), and the resulting liquid product was analyzed using Off-line GC (FID).

Similarly, the catalyst prepared in Comparative Example 1 was reacted with Fischer-Tropsch by the above method. 5 shows the molar amount of the product according to the carbon number according to Example 1 and Comparative Example 1, and summarized by calculating the CO conversion rate, H ₂ conversion rate, hydrocarbon selectivity and liquid product in Table 2 below.

Example 1 Comparative Example 1 Conversion rate
(%) CO 46.37 11.58 H ₂ 57.94 42.49 Selectivity
(mole%) CH ₄ 28.11 32.73 C ₂ ~ C ₄ 20.57 17.61 C ₅ ~ C ₁₁ (gasoline) 26.32 23.07 C ₁₂ -C ₁₈ (diesel) 16.69 25.66 C ₁₉ or higher 3.70 5.48 Productivity of Liquid Products (g / kg_cat.h) 73.14 57.25

As summarized in Table 2, the catalyst (Example 1) characterized by the present invention was confirmed that the liquid product is produced significantly more than in Comparative Example 1.

Looking more specifically, it was confirmed that the catalyst containing mesoporous silica as a support component (Example 1) the hydrogen and carbon monoxide conversion rate is significantly higher than in Comparative Example 1.

In addition, as shown in Figure 4 it was confirmed that the selectivity of the carbon product of the wax size is low and the amount of the carbon product in the gasoline range is higher than in Comparative Example 1. This may be due to the molecular sieve role of the product according to the pore size of the mesoporous silica used in Example 1.

Claims (10)

Generating an emulsion by adding a surfactant to the organic solvent and the acidic aqueous solution;
Adding silica alkoxide to the emulsion to synthesize silica;
Aging and filtering the silica;
Drying and calcining the filtered silica to prepare mesoporous silica; And
Preparing a Fischer-Tropsch catalyst by introducing an active metal for Fischer-Tropsch reaction into the mesoporous silica;
Fischer-Tropsch catalyst production method comprising a.
According to claim 1, wherein the fischer-Tropsch reaction active metal is Fischer-Trop, characterized in that a single metal or a mixed metal selected from the group consisting of cobalt, iron, ruthenium, nickel, palladium, platinum and rhodium. Process for preparing a catalyst
The method of claim 1, wherein the Fischer-Tropsch catalyst is prepared by introducing 1 to 50 parts by weight of the active metal for Fischer-Tropsch reaction based on 100 parts by weight of the mesoporous silica.
The method of claim 1, wherein the silicon alkoxide is tetramethoxysilane, tetraethyl orthosilicate, methyltrimethoxy silane, ethyltrimethoxysilane, vinyltri Fischer-Tropsch catalyst, characterized in that any one or more selected from the group consisting of ethoxysilane (Vinyltriethoxy silane) and phenyltriethoxy silane (Phenyltriethoxy silane).
The method of claim 1, wherein the surfactant is a carboxylate, sulfonate, sulfate ester salt, phosphate ester salt, phosphonate salt, amine salt, quaternary ammonium salt, phosphonium salt, sulfonium salt, fatty acid monoglycerine ester, fatty acid poly Fischer-Tropsch, characterized in that any one or more selected from the group consisting of glycol esters, fatty acid sorbitan esters, fatty acid sucrose esters, fatty acid alkanolamides, polyethylene glycol condensed nonionic surfactants and polyethylene glycol-polypropylene glycol copolymers Method for preparing a catalyst.
The method of claim 1, wherein the acidic aqueous solution is at least one aqueous solution selected from the group consisting of hydrochloric acid, nitric acid, sulfuric acid, acetic acid, carbonic acid, and acetic acid.
The method of claim 1, wherein the acidic aqueous solution has a pH of 3 to 6. 6.
The method of claim 1, wherein the organic solvent comprises a compound represented by the following Chemical Formula 1. Fischer-Tropsch catalyst.
[Formula 1]

In Formula 1, x is 1 to 20, y is 4 to 42, and z is 0 to 20.
Fischer-Tropsch catalyst according to claim 1, wherein 1 to 20 parts by weight of the organic solvent, 0.1 to 10 parts by weight of silicon alkoxide, and 1 to 100 parts by weight of an acidic aqueous solution are added to 1 part by weight of the surfactant. Manufacturing method.
The cobalt nitrate, cobalt acetate, cobalt bromide, cobalt chloride and cobalt iodide according to claim 1, wherein the active metal is cobalt nitrate. Fischer-Tropsch reaction catalyst production method characterized in that using at least one cobalt precursor selected from the group consisting of.

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