KR20150131651A - Cobalt Based Catalyst Supported Silica Carrier Modified with Transition Metal and SiC for Fischer-Tropsch Synthesis - Google Patents

Abstract

The present invention relates to a catalyst for Fischer-Tropsch synthesis, wherein a cobalt-based active metal is supported in a mesoporous silica carrier (SiC-X-silica) which is improved by silicon carbide (SiC) and transition metals (X) such as aluminum, iron, etc., at the same time. The cobalt-based catalyst of the present invention maximizes a conversion rate of carbon monoxide and a yield of liquid hydrocarbon (C5+) by applying the improved mesoporous silica carrier manufactured with a suitable mole ratio to a Fischer-Tropsch synthesis reaction.

Description

[0001] The present invention relates to a cobalt-based catalyst for Fischer-Tropsch synthesis supported on a silica support simultaneously modified by transition metals and silicon carbide,

The present invention relates to a catalyst for Fischer-Tropsch synthesis in which a cobalt active metal is supported on a mesoporous silica support which is simultaneously improved by transition metals such as aluminum and iron and silicon carbide (SiC) Is used in the Fischer-Tropsch synthesis reaction to maximize the conversion of carbon monoxide and the selectivity and yield of liquid hydrocarbons (C ₅ +).

The Fischer-Tropsch synthesis (FTS) reaction is a synthesis of hydrocarbons using synthesis gas (CO + H ₂ ) obtained from various routes as a raw material, and research has been conducted for a relatively long time. The FTS reaction is also commonly referred to as a " hydrocarbon synthesis reaction ". Hydrocarbons produced by the FTS reaction are clean fuels containing no impurities such as sulfur, nitrogen, and aromatics, and also exhibit fuel characteristics with a high cetane number because of a large amount of linear paraffin. Therefore, the FTS reaction has attracted considerable attention from the energy-related industries such as natural gas, petroleum and oil, in terms of environment-friendlyness.

In reactions for producing liquid hydrocarbons (C ₅ +) from synthesis gas by FTS reaction, mainly cobalt-based catalysts are used. Cobalt-based catalysts are known to have excellent selectivity for hydrocarbons due to their high carbon monoxide conversion, long life and low CO ₂ production rates. However, since the cobalt-based catalyst predominantly generates methane (CH ₄ ) in the high temperature region of 300 ° C or higher, it is important to design the catalyst to control the local high temperature region through the temperature control of the catalyst layer. In the case of designing such a cobalt catalyst, alumina, silica, titania or the like having porous pores which are thermally and chemically stable are used as supports. These supports have a large specific surface area so that the active component is dispersed evenly on the support While the heat transfer efficiency is low.

In recent years, studies have been actively conducted on a method of performing FTS reaction using silicon carbide (SiC) having excellent heat transfer effect as a support. For example, U.S. Patent No. 5,710,093 discloses a catalyst for FTS reaction in which SiC is mixed with silica sol to form a support and then a cobalt-activated metal is supported thereon. Further, there is disclosed a catalyst for FTS reaction in which a surface of a silicon carbide (SiC) support is coated with alumina and then a cobalt active metal is supported. [Applied Catalysis A: General 397 (2011), pp. 62-72; Korean Patent Publication No. 2014-28503). However, silicon carbide (SiC) supports have a low specific surface area and a large pore size, and therefore, they are limited to use as a catalyst support for FTS reaction.

Accordingly, the inventors of the present invention have found that the support of a cobalt catalyst for FTS reaction is stable thermally and chemically, and has a high specific surface area, thereby enabling stable loading of active metals and excellent uniformity of heat transfer efficiency and uniform pore size required for FTS reaction We have made efforts to develop a support for the scaffold.

As a result, a hydrothermal reaction is carried out by simultaneously containing a transition metal such as aluminum or iron and silicon carbide (SiC) in the silica precursor, and the transition metal and silicon carbide (SiC) are uniformly distributed in the mesoporous silica inner structure And the resulting mesoporous silica was used as a support for a Fischer-Tropsch synthesis reaction, thereby completing the present invention.

It is an object of the present invention to provide a novel cobalt catalyst in a silica support improved by transition metals and silicon carbide.

Another object of the present invention is to provide a process for producing liquid hydrocarbons (C ₅ +) from a synthesis gas (CO + H ₂ ) at a high yield by using the novel cobalt-based catalyst.

In order to solve the above-described problems, the present invention provides a silica support having a modified cobalt-activated metal supported on a mesoporous silica containing a transition metal (X) and silicon carbide (SiC) And a cobalt catalyst for synthesis.

[Chemical Formula 1]

Co / SiC-X-silica

Wherein X is a transition metal selected from the group consisting of aluminum (Al) and iron (Fe)

The present invention also provides a process for preparing a precursor solution, comprising: i) dissolving a silica precursor, a precursor of a transition metal (X) and SiC in an aqueous solution containing a surfactant and hydrochloric acid to prepare a precursor solution; Ii) subjecting the precursor solution to a hydrothermal reaction at 30 to 60 ° C; Iii) aging the reaction solution at 90 to 120 ° C., followed by filtration washing, drying and calcination to prepare a modified silica support; And iv) supporting cobalt on the modified silica support to prepare a cobalt catalyst represented by Formula 1; Wherein the cobalt catalyst is a catalyst for synthesis of Fischer-Tropsch synthesis.

The present invention also provides a method for producing liquid hydrocarbons (C ₅ +) by a Fischer-Tropsch synthesis reaction using a synthesis gas as a raw material under a cobalt-based catalyst represented by the formula (1).

The support of the present invention is a mesoporous silica support improved at the same time by a transition metal and silicon carbide (SiC), which improves the reduction characteristics of the catalyst by a modification reaction by a transition metal, It is possible to suppress the deactivation effect of the catalyst.

The cobalt catalyst of the present invention is a catalyst supported on the above-mentioned improved silica support and is applied to the Fischer-Tropsch synthesis reaction to increase the conversion ratio of hydrogen and carbon monoxide and increase the selectivity of liquid hydrocarbons (C ₅ +) in the diesel range And exhibits catalytic activity. Therefore, the cobalt-based catalyst of the present invention has the effect of maximizing the production of eco-friendly diesel used as fuel for transportation.

FIG. 1 shows the results of TPR analysis for comparing the reduction characteristics of the cobalt catalysts prepared in Examples 1 to 3 and Comparative Examples 1 to 3.
Fig. 2 shows XRD analysis results of the catalysts of Examples 1 and 2 and Comparative Example 1. Fig.
FIG. 3 is a result of analysis of small angle X-ray scattering (SAXS) on the catalysts of Examples 1 and 2 and Comparative Example 1. FIG.

According to one aspect of the present invention, there is provided a method for producing a silica-based catalyst, which comprises adding a transition metal (X) and silicon carbide (SiC) to mesoporous silica, Based catalyst. That is, the present invention is characterized in that silica modified at the same time by a transition metal (X) and silicon carbide (SiC) is used as a support of a cobalt catalyst for Fischer-Tropsch synthesis.

The improved silica support may be referred to as 'SiC-X-silica'. The silica may be a mesoporous silica having a BET specific surface area of 500 to 700 m 2 / g, a pore volume of 0.5 to 1 cm 3 / g, and an average pore size of 5 to 10 nm. The mesoporous silica that can be obtained through synthesis may specifically include SBA-1, SBA-15, SBA-16, KIT-6, MCM-48, mesocellular silicaous foam (MCF), and MSU.

In addition, the improved silica support may have a physico-chemical property different from that of the siloxane group (SiO) constituting the silica due to the molar ratio of the transition metal (X) to silicon carbide (SiC) The transition metal (X) may be included in a range of 0.02 to 0.2 molar ratio and the silicon carbide (SiC) may be included in a range of 0.02 to 0.2 molar ratio based on 1 mol. If the content of the transition metal is less than 0.02 mol, the effect of improving the silica by the transition metal can not be obtained. If the content of the transition metal is more than 0.2 mol, the structure of the mesoporous silica can be broken down. If the content of silicon carbide (SiC) is less than 0.02 mol, the local heat removal effect is not exhibited. If the molar ratio exceeds 0.2 mol, excess SiC may interfere with silica modification by the transition metal. have.

Also, the physico-chemical properties of the support can be changed by adjusting the molar ratio between the transition metal (X) and the silicon carbide (SiC) used for improving the mesoporous silica. The molar ratio of X / SiC ranges from 1 to 2 . If the molar ratio of X / SiC is less than 1, there is no reduction effect of the transition metal and local heat removal effect of SiC. If the molar ratio of X / SiC is more than 2, the mesoporous SBA-15 structure is not formed, Activity may be lowered.

Based on the above-described improved silica support, a cobalt-based active metal is supported to prepare a desired cobalt-based catalyst for Fischer-Tropsch synthesis according to the present invention. In the present invention, there is no particular limitation on the loading amount of the cobalt-active metal to be supported on the support, and it may be carried in a range of the usual supported amount. The amount of the cobalt-active metal to be supported may be specifically in the range of 0.1 to 30% by weight based on the weight of the support.

According to another aspect of the present invention, the present invention relates to a process for preparing a cobalt-based catalyst for Fischer-Tropsch synthesis, supported on a silica support simultaneously modified by transition metal (X) and silicon carbide (SiC). In the production process according to the present invention, a polymer surfactant is used as a template for mesoporous silica formation, and a sol-gel reaction of a silica precursor is performed.

The process for preparing a catalyst according to the present invention comprises the steps of: i) dissolving a precursor of a silica precursor, a precursor of a transition metal (X) and SiC in an aqueous solution containing a surfactant and hydrochloric acid to prepare a precursor solution; Ii) subjecting the precursor solution to a hydrothermal reaction at 30 to 60 ° C; Iii) aging the reaction solution at 90 to 120 ° C., followed by filtration, washing, drying and calcining to prepare an improved silica support; And iv) supporting the improved silica support with cobalt to prepare a cobalt catalyst represented by the above formula (1).

The process for preparing the catalyst according to the present invention will be described in more detail below.

Process i) is a process for preparing a precursor solution, in which a precursor solution is prepared by dissolving a silica precursor, a precursor of a transition metal (X) and SiC in an aqueous solution containing a surfactant and hydrochloric acid.

The surfactant is used as a template for preparing mesoporous silica, and polymer surfactants such as Pluronic F127, Pluronic P123, and Triton-X may be used. As the silica precursor, tetraalkoxyorthosilicate and the like can be used. Specifically, tetramethylorthosilicate, tetraethylorthosilicate and the like can be used. As the precursor of the transition metal, compounds such as alkoxide, halide, nitrate, sulfate, acetate and acetoacetonate salts including transition metals such as aluminum (Al) and iron (Fe) can be used.

(X) and silicon carbide (SiC) and the molar ratio of the transition metal (X) / silicon carbide (SiC) to the siloxyl group (SiO) It is preferable to maintain the X / SiO molar ratio, the SiC / SiO molar ratio, and the X / SiC molar ratio proposed by the present invention.

The process ii) is a process of sol-gelation through a hydrothermal reaction, and the hydrothermal reaction is carried out at 30 ° C to 60 ° C.

Iii) is a process for preparing a modified silica support by aging, filtering, washing, drying and calcining the hydrothermally treated solution. The aging is carried out at 80 to 120 ° C for 16 to 32 hours, followed by filtration washing and drying at 90 to 120 ° C. The firing is carried out at a temperature raising rate of 1 to 10 ° C / min, at a room temperature, in a temperature range of 500 to 600 ° C and for 5 to 20 hours.

The above processes (i), (ii) and (iii) are a process for synthesizing a mesoporous silica, and the transition metal (X) and SiC used for the improvement of the support are uniformly dispersed in the crystal structure or pores of the mesoporous silica. The mesoporous silica which can be produced by the above steps i), ii) and iii) is specifically SBA-1. SBA-15, SBA-16, KIT-6, MCM-48, mesocellular siliceous foam (MCF), and MSU.

The process iv) is a process for preparing a cobalt catalyst by supporting a cobalt active metal on a modified silica support. A cobalt precursor is used for supporting the cobalt active metal, and as the cobalt precursor, compounds such as alkoxide, halide, nitrate, sulfate, acetate and acetoacetate can be used.

In the present invention, as a method of supporting the cobalt-active metal on the support, repetitive drying impregnation is performed. That is, a cobalt solution prepared by dissolving a cobalt precursor in distilled water is impregnated into a support and dried, thereby carrying cobalt on a support.

The cobalt catalyst prepared by the above process has a BET specific surface area of 500 to 700 m 2 / g, a pore volume of 0.5 to 1 cm 3 / g, and an average pore size of 5 to 10 nm.

According to another aspect of the present invention, the present invention relates to a method for producing liquid hydrocarbons by performing a Fischer-Tropsch synthesis reaction using a synthesis gas as a raw material under the above-mentioned cobalt catalyst.

The FTS reaction performed by the present invention is carried out by a conventional method, and the present invention does not have any particular limitation on the FTS reaction conditions. Typical FTS reaction conditions are reaction conditions using a synthesis gas at a reaction temperature of 200 to 300 ° C, a reaction pressure of 10 to 50 bar and a H ₂ / CO = _{2 to} 2.3.

The FTS reaction using the cobalt catalyst according to the present invention has an effect of maximizing the conversion of carbon monoxide and the yield of liquid hydrocarbon (C ₅ +).

The present invention as described above will be described in more detail based on the following examples and experimental examples. It is to be understood, however, that the following Examples and Experiments are presented only for the understanding of the contents of the present invention, and the scope of the present invention is not limited to these Examples and Experimental Examples.

[Examples] Preparation of Catalyst

Example 1. Preparation of Co / SiC-Al-silica catalyst (Al / SiC mole ratio = 1)

An SiC-Al-silica support was prepared according to the preparation method of SBA-15 ( J Porous Mater 13 , 187 (2006)) proposed by Q. Yang's group as a mesoporous silica support preparation method.

I.e., Pluronic P123 as a surfactant (Sigma-Aldrich; [Poly ( EO) - b -poly (PO) - b -poly (EO)) 4 g of distilled water then placed in a 130 mL stirred until complete dissolution, 38 % HCl aqueous solution was added thereto, followed by stirring for about 1 hour. To this solution, tetraethylorthosilicate (TEOS), aluminum isopropoxide and silicon carbide were added as precursors, and the mixture was stirred at 50 DEG C for 8 hours. At this time, the content ratio of the precursor was adjusted so that the molar ratio of aluminum (Al) and SiC was 1: 0.11: 0.11 based on the silane (Si) element of the silica precursor.

After the reaction was completed, the reaction product was aged at 80 DEG C for 24 hours, and then the product was filtered and dried. (SiC-Al-SBA-15) containing aluminum (Al) and SiC inside the mesoporous silica (SBA-15) was obtained by raising the temperature from room temperature to 550 ° C at a heating rate of 1 ° C / min and calcining at 550 ° C for 5 hours. 15 'support.

The SiC-Al-SBA-15 support prepared above was fired at 200 ° C for 24 hours to remove moisture contained in the support. Cobalt nitrate (Co (NO ₃ ) ₂ 6H ₂ O) is weighed so that the content of the cobalt-based active metal is 20 wt% based on the weight of the support, and dissolved in distilled water to prepare a cobalt solution. 2.5 volume times the pore volume was used. The cobalt solution was stirred for 3 hours. 0.2 mL of the cobalt solution was impregnated into the supporter in which moisture was completely removed by an impregnation method using osmotic pressure, and then dried in a 60 ° C. vacuum oven for 1 hour. The impregnation and drying were repeated until all the cobalt solution was exhausted. This impregnation process was referred to as Repeated Drying Impregnation in the present invention.

The cobalt supported catalyst prepared through the repeated dry impregnation process was dried in a vacuum oven at 80 ° C. for 24 hours and then calcined at 500 ° C. under atmospheric pressure and air atmosphere for 12 hours to obtain the desired Co / SiC-Al-SBA-15 catalyst .

Example 2. Preparation of Co / SiC-Al-SBA-15 catalyst (Al / SiC molar ratio = 2)

(Al) and SiC in a ratio of 1: 0.11: 0.056 to the silane (Si) element of the silica precursor in the preparation of a Co / SiC-Al- The content ratio of the precursors was adjusted.

Example 3. Preparation of Co / SiC-Fe-SBA-15 catalyst (Al / SiC molar ratio = 1)

A Co / SiC-Fe-silica catalyst was prepared in the same manner as in Example 1, except that iron nitrate was used as an iron precursor. However, the precursor content ratio was adjusted so that the molar ratio of iron (Fe) and SiC to the silane (Si) element of the silica precursor was 1: 0.11: 0.11.

Comparative Preparation Example 1. Preparation of Co / SBA-15 catalyst

Co / SBA-15 catalyst was prepared in the same manner as in Example 1 except that tetraethylorthosilicate (TEOS) alone was used as a precursor.

Comparative Preparation Example 2. Preparation of Co / Al-SBA-15 catalyst

Co / Al-SBA-15 catalyst was prepared in the same manner as in Example 1 except that the ratio of the precursor was adjusted so that the molar ratio of the aluminum (Al) to the silane (Si) element of the silica precursor was 1: Respectively.

Comparative Preparation Example 3. Preparation of Co / SiC-silica catalyst

A Co / SiC-silica catalyst was prepared in the same manner as in Example 1 except that the ratio of the precursors was controlled so that the molar ratio of SiC to the silane (Si) in the silica precursor was 1: 0.11.

The molar ratio of Al / SiC, the molar ratio of SiC / SiO 2, the molar ratio of Al / SiO 2, the BET specific surface area, the pore volume, and the average pore size of the respective catalysts prepared in Examples 1 to 3 and Comparative Examples 1 to 3 Table 1 summarizes the results.

catalyst Mole ratio Nitrogen physical adsorption Transition metal / SiC Al / SiO SiC / SiO BET surface area
(m ² g ^-1 ) Pore volume
(cm ³ g ^-1 ) Average pore size (nm) Co / SiC-Al-SBA-15
(Example 1) One 0.11 0.11 680 0.85 5 Co / SiC-Al-SBA-15
(Example 2) 2 0.11 0.056 537 0.80 5 Co / SiC-Fe-SBA-15
(Example 3) One 0.11 0.11 511 0.82 5.1 Co / SBA-15
(Comparative Example 1) - - - 750 0.93 4 Co / Al-SBA-15
(Comparative Example 2) - 0.11 - 653 0.78 4.5 Co / SiC-SBA-15
(Comparative Example 3) - - 0.11 629 0.80 4.8

[Experimental Example]

Experimental Example 1. Fischer-Tropsch synthesis reaction

The following experiments were carried out to confirm the effect of each of the cobalt-based catalysts prepared in Examples 1 to 3 and Comparative Examples 1 to 3 in the Fischer-Tropsch synthesis reaction.

A fixed bed reactor of 3/8 inch stainless steel was filled with 0.2 g of a cobalt-based catalyst and hydrogen gas (10 mL / min) at 450 ° C was injected at a space velocity of 1200 mL / g cat / hr. Pretreatment was carried out. Fischer-Tropsch synthesis reaction to a stability test of the catalyst takes place in the reaction, at a comparatively which is the extreme conditions of reaction temperature 230 ℃, a reaction pressure of 20 bar, the conditions of a space velocity of 5000 mL / g cat / hr H 2 / CO = 2 molar ratio. The reaction was run for 100 hours. The product obtained by the Fischer-Tropsch synthesis reaction was subjected to qualitative / quantitative analysis by gas chromatography using a Carbon-Sphere column and an HP-5 column. The results are shown in Table 2 below.

catalyst CO conversion (%) Selectivity (% by weight) CH ₄ C _2-4 C ₅ + Co / SiC-Al-SBA-15
(Example 1) 30.7 17.5 10.1 72.4 Co / SiC-Al-SBA-15
(Example 2) 26.5 15.2 8.4 76.4 Co / SiC-Fe-SBA-15
(Example 3) 29.1 16.9 9.7 73.4 Co / SBA-15
(Comparative Example 1) 15.5 21.4 10.5 68.1 Co / Al-SBA-15
(Comparative Example 2) 18.8 22.7 12.1 65.2 Co / SiC-SBA-15
(Comparative Example 3) 16.4 20.1 11.3 68.6

FIG. 1 shows the results of TPR analysis for comparing the reduction characteristics of the cobalt catalysts prepared in Examples 1 to 3 and Comparative Examples 1 to 3. 1 shows that the catalysts of Examples 1 to 3 carried on a silica support modified with a transition metal and silicon carbide are more reducible than the catalysts of Comparative Examples 1 to 3 because the maximum reduction temperature is lowered It can be confirmed that it is excellent.

Fig. 2 shows XRD analysis results of the catalysts of Examples 1 and 2 and Comparative Example 1. Fig. FIG. 2 shows that the catalysts of Examples 1 and 2 have no significant difference in crystallinity as compared with the catalyst of Comparative Example 1. It can be seen that the transition metal and silicon carbide (SiC) are stably contained in the mesoporous silica (SBA-15) support without any influence on the SBA-15 crystal structure.

In order to grasp the crystal structure more accurately, FIG. 3 shows the results of SAXS (Small Angle Xray Scattering) analysis of the catalysts prepared in Example 1, Example 2 and Comparative Example 1. FIG. 3 shows that the catalysts of Examples 1 and 2 have the same crystal structure of the catalyst of Comparative Example 1, and that the mesoporous pore size varies depending on the molar ratio of Al / SiC. In addition, it can be seen that the SBA-15 structure (100) is decreased in Example 2 than in Example 1. As shown in FIG. 1, in order to maintain the structure (100) having SBA-15 characteristics, the optimum molar ratio range of Al / SiC is 1 ~ 2.

According to the above experimental results, the cobalt catalyst of the present invention can be obtained by selectively using a transition metal and a silica support modified with silicon carbide (SiC) to select the conversion of carbon monoxide and the concentration of liquid hydrocarbon (C ₅ +) in the Fischer- The effect of improving the selectivity can be obtained.

Claims (7)

A cobalt catalyst for Fischer-Tropsch synthesis represented by the following formula (1) wherein a cobalt-based active metal is supported on an improved silica support containing a transition metal (X) and silicon carbide (SiC) in mesoporous silica.
[Chemical Formula 1]
Co / SiC-X-silica
Wherein X is a transition metal selected from the group consisting of aluminum (Al) and iron (Fe)
The method according to claim 1,
Characterized in that the improved silica support comprises 0.01 to 0.2 mole ratio of transition metal (X) and 0.01 to 0.2 mole ratio of silicon carbide (SiC) based on 1 mole of siloxy group (SiO) Cobalt catalyst.
The method according to claim 1,
Wherein the modified silica support has a molar ratio of transition metal (X) / silicon carbide (SiC) of 1 to 2.
The method according to claim 1,
Wherein the cobalt catalyst has a BET specific surface area of 500 to 700 m 2 / g, a pore volume of 0.5 to 1 cm 3 / g, and an average pore size of 5 to 10 nm.
The method according to claim 1,
And 0.1 to 30% by weight of a cobalt active metal is supported on the basis of the weight of the modified silica support.
I) dissolving a silica precursor, a precursor of a transition metal (X) and SiC in an aqueous solution containing a surfactant and hydrochloric acid to prepare a precursor solution;
Ii) subjecting the precursor solution to a hydrothermal reaction at 30 to 60 ° C;
Iii) aging the reaction solution at 90 to 120 ° C., followed by filtration washing, drying and calcination to prepare a modified silica support; And
(Iv) supporting cobalt on the modified silica support to prepare a cobalt-based catalyst represented by Formula 1;
Wherein the cobalt catalyst is selected from the group consisting of:
[Chemical Formula 1]
Co / SiC-X-silica
Wherein X is a transition metal selected from the group consisting of aluminum (Al) and iron (Fe)
A process for the production of liquid hydrocarbons, characterized by subjecting to a Fischer-Tropsch synthesis reaction using a synthesis gas as a raw material under a cobalt catalyst according to any one of claims 1 to 5.

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