Fischer-Tropsch synthesis catalyst with iron loaded on modified silicon dioxide as well as preparation method and application of Fischer-Tropsch synthesis catalyst

Abstract

The invention provides a modified silicon dioxide loaded iron Fischer-Tropsch synthesis catalyst as well as a preparation method and application thereof, the preparation method comprises the following steps: (1) preparing a potassium permanganate solution, adding a certain amount of silicon dioxide carrier, fully stirring, and sequentially centrifuging, washing and drying to obtain a modified silicon dioxide carrier; (2) mixing soluble ferric salt, the modified silicon dioxide carrier and deionized water according to a certain proportion, fully stirring, and dropwise adding alkali liquor to obtain turbid liquid; (3) heating and stirring the turbid liquid in a water bath, cooling, centrifuging, washing to be neutral, and drying to obtain a precursor; and (4) calcining the precursor to obtain a powder sample, namely the catalyst. According to the present invention, the Mn auxiliary agent is introduced so as to easily form iron carbide, regulate and control the product distribution, improve the olefin selectivity, and reasonably regulate and control the ratio of the carrier to the Fe base, such that the problems of low olefin selectivity and high methane selectivity of the Fe-based catalyst in the traditional method are effectively solved.

Description

Technical Field

[0001] The present invention relates to the technical field of Fischer-Tropsch synthesis catalysts, and in particular to a modified silica-supported iron Fischer-Tropsch synthesis catalyst and a preparation method and application thereof. Background Art

[0002] Olefins occupy a very important position in the national economy. Olefins can be divided into low-carbon and high-carbon olefins according to the length of the carbon chain. Low-carbon olefins mainly refer to ethylene and propylene, which are the basic organic raw materials for synthetic plastics, fibers and other chemical products. High-carbon olefins generally refer to olefins with a carbon number of more than 4, especially alpha-olefins (alpha-olefins) that can be used to produce high-value-added fine chemicals. At present, both low-carbon olefins and high-carbon alpha-olefins are mainly produced by petroleum routes, and the shortage of petroleum resources is becoming an important factor restricting the economy and society. Finding an economical alternative process route to solve the problem of olefin supply and demand caused by rising oil demand, and exploring clean, efficient and low-cost olefin preparation processes are gradually becoming a hot topic of increasing concern.

[0003] In recent years, the one-step preparation of olefins by the Fischer-Tropsch route has become one of the important research areas of C1 chemistry. During the Fischer-Tropsch synthesis process, affected by the dynamic changes in the phase of the active components, main reactions including the synthesis of olefins and alkanes, the conversion of CO, and side reactions including methanation, the formation of oxygen-containing compounds, and carbon deposition reactions occur. Developers try to control the phase changes, control the formation pathway of olefins, and limit the occurrence of other side reactions. Research is conducted on the problems of the primary product olefins being prone to secondary hydrogenation reactions and the product selectivity being limited by Anderson-Schulz-Flory (ASF), resulting in a wide distribution of hydrocarbon products, low olefin selectivity, and high selectivity for by-products such as CH4.

[0004] The study found that single Fe-based catalysts have problems such as wide product distribution, low olefin selectivity, and high selectivity for byproducts such as CH4. Effective regulation of product distribution can be achieved through new catalyst design and process parameter adjustment. Supported catalysts can inhibit olefin re-adsorption to a certain extent, thereby reducing the secondary hydrogenation reaction of olefins and improving olefin selectivity.

[0005] Although traditional Fe-based catalysts have high activity in the Fischer-Tropsch reaction, they have high methane selectivity, low olefin selectivity, and unsatisfactory product distribution. Therefore, it is necessary to design a new preparation method for the Fischer-Tropsch synthesis catalyst of modified silica-supported iron to solve the above problems. Summary of the invention

[0006] The purpose of the present invention is to overcome the defects of the prior art and provide a modified silica-loaded iron Fischer-Tropsch synthesis catalyst and a preparation method and application thereof, which effectively solve the problems of poor catalytic activity, low olefin selectivity and high methane selectivity of traditionally prepared Fe-based catalysts.

[0007] The present invention provides the following technical solutions:

[0008] The present invention provides a method for preparing a modified silica-supported iron Fischer-Tropsch synthesis catalyst, comprising the following steps:

[0009] (1) preparing a potassium permanganate solution, adding a certain amount of a silica carrier and fully stirring, and then centrifuging, washing, and drying in sequence to obtain a modified silica carrier;

[0010] (2) mixing a soluble iron salt, a modified silica carrier and deionized water in a certain proportion, stirring thoroughly and then dropping an alkali solution to obtain a suspension;

[0011] (3) placing the suspension in a water bath, heating and stirring for 1 h, allowing the mixture to cool naturally to room temperature, centrifuging, washing to neutrality, and then drying to obtain a precursor;

[0012] (4) calcining the precursor to obtain a powder sample, i.e., obtaining the catalyst;

[0013] The mass ratio of the active component Fe to the carrier Mn-SiO2 in the obtained catalyst is 0.1-0.5.

[0014] SiO2 has a large specific surface area, adjustable pore size and pore volume, and uniform pores, making it an ideal carrier material. In addition, SiO2 is hydrophilic and can effectively inhibit the re-adsorption of olefins, thereby reducing the secondary reaction of olefins.

[0015] The iron carbide phase in the Fe-based catalyst prepared by the traditional coprecipitation method is extremely unstable. Considering the influence of the phase on the product distribution, the surface groups of the silica carrier treated with potassium permanganate solution in step (1) of the present invention are more abundant, and the hydrophilic system can inhibit the re-adsorption of olefins, thereby reducing the secondary reaction of olefins. At the same time, by doping Mn elements in SiO2, the iron carbide phase is maintained, the methane selectivity is reduced and the olefin selectivity is improved, and SiO2 has a certain hydrophilicity, which can inhibit the re-adsorption of olefins, thereby reducing the secondary reaction of olefins and further improving the selectivity of olefins. However, excessive hydrophilicity is not conducive to the maintenance of the iron carbide phase. Iron carbide is easily oxidized by the byproduct water and loses its activity. Therefore, during the catalyst preparation process, the ratio of the carrier to the active metal should also be adjusted at the same time. The mass ratio of the active component Fe and the carrier Mn-SiO2 is 0.1-0.5, which is conducive to reducing the methane selectivity and improving the olefin selectivity.

[0016] Furthermore, in step (1), the concentration of the potassium permanganate solution is 0.1 mol / L, and the dosage ratio of the potassium permanganate solution to the silica carrier is (40-100) mL: (2-8) g.

[0017] Furthermore, in step (2), the ratio of the soluble iron salt, the modified silica carrier and the deionized water is (0.3-20) g: (1-2) g: (60-120) mL.

[0018] Furthermore, in step (2), the soluble iron salt is any one of ferric chloride hexahydrate, ferric nitrate nonahydrate or ferrous sulfate.

[0019] Furthermore, in step (2), the solute in the alkali solution is any one of ammonia water, potassium hydroxide, and calcium hydroxide.

[0020] Furthermore, in step (2), the ratio of the solute to the deionized water in the alkali solution is (5-10) g: (20-50) mL.

[0021] Furthermore, in step (2), after sufficient stirring, an alkali solution is added dropwise to obtain a suspension, and the pH value of the suspension is controlled to be 8-10.

[0022] Furthermore, in step (3), the suspension is preferably stirred in a water bath at a temperature of 80 to 120°C.

[0023] Furthermore, in step (3), the mixture is washed and then placed in an oven for drying, the oven temperature is controlled to be 60 to 100° C., and the drying time is 9 to 20 hours.

[0024] Furthermore, in step (4), the precursor is calcined at 400-500° C. in an air atmosphere for 3-6 hours. The purpose of calcination is to convert the precursor C into Fe2O3.

[0025] The present invention also provides a Fischer-Tropsch synthesis catalyst of modified silica loaded with iron prepared by the preparation method.

[0026] The present invention also provides the use of the prepared modified silica-supported iron Fischer-Tropsch synthesis catalyst in a Fischer-Tropsch synthesis reaction.

[0027] The method for preparing the modified silica-supported iron Fischer-Tropsch synthesis catalyst of the present invention can improve olefin selectivity while reducing methane selectivity by the following mechanism:

[0028] By doping SiO2 with Mn elements, the iron carbide phase is maintained, the methane selectivity is reduced and the olefin selectivity is improved. At the same time, SiO2 has a certain hydrophilicity, which can inhibit the re-adsorption of olefins, thereby reducing the secondary reaction of olefins and further improving the selectivity of olefins. However, excessive hydrophilicity is not conducive to the maintenance of the iron carbide phase. Iron carbide is easily oxidized by the byproduct water and loses its activity. Therefore, during the catalyst preparation process, the ratio of the carrier to the active metal should also be adjusted at the same time, which is conducive to reducing the methane selectivity and improving the olefin selectivity.

[0029] The present invention has the following beneficial effects:

[0030] 1. The modified silica-supported iron Fischer-Tropsch synthesis catalyst prepared by the present invention effectively solves the problem of high methane selectivity and low olefin selectivity in the Fischer-Tropsch synthesis reaction. The introduction of the silica carrier and the Mn element promotes the formation of the iron carbide phase, and the stable existence of the iron carbide phase is conducive to improving the olefin selectivity of the catalyst while reducing the methane selectivity.

[0031] 2. The present invention uses potassium permanganate to pretreat the silica carrier, and introduces a hydrophilic carrier into the catalytic system to inhibit the secondary hydrogenation of olefins; the introduction of the Mn element is conducive to the stable existence of the iron carbide phase, which is beneficial to improving the olefin selectivity.

[0032] 3. The modified silica-loaded iron Fischer-Tropsch synthesis catalyst prepared by the present invention has stable chemical properties, simple process, low cost, and is suitable for industrial production. DETAILED DESCRIPTION

[0033] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] The present invention provides a method for preparing a modified silica-supported iron Fischer-Tropsch synthesis catalyst, comprising the following steps:

[0035] (1) preparing a potassium permanganate solution, adding a certain amount of silica carrier and stirring sufficiently; centrifuging, washing and drying in sequence to obtain a modified silica carrier, which is recorded as A;

[0036] (2) mixing a soluble iron salt, a modified silica carrier and deionized water in a certain proportion, stirring thoroughly and then dropping an alkali solution to obtain a suspension B;

[0037] (3) placing suspension B in a water bath, heating and stirring for 1 h, allowing the mixture to cool naturally to room temperature, centrifuging, washing to neutrality, and then drying to obtain precursor C;

[0038] (4) calcining the precursor C to obtain the modified silica-supported iron Fischer-Tropsch synthesis catalyst;

[0039] The mass ratio of the active component Fe to the carrier Mn-SiO2 in the obtained catalyst is 0.1-0.5.

[0040] By doping SiO2 with Mn elements, the iron carbide phase is maintained, the methane selectivity is reduced and the olefin selectivity is improved. At the same time, SiO2 has a certain hydrophilicity, which can inhibit the re-adsorption of olefins, thereby reducing the secondary reaction of olefins and further improving the selectivity of olefins. However, excessive hydrophilicity is not conducive to the maintenance of the iron carbide phase. Iron carbide is easily oxidized by the byproduct water and loses its activity. Therefore, during the catalyst preparation process, the ratio of the carrier to the active metal should also be adjusted at the same time, which is conducive to reducing the methane selectivity and improving the olefin selectivity.

[0041] The iron carbide phase in the Fe-based catalyst prepared by the traditional coprecipitation method is extremely unstable. Considering the influence of the phase on the product distribution, the present invention maintains the iron carbide phase by doping Mn elements in SiO2, reduces the methane selectivity and improves the olefin selectivity. At the same time, SiO2 has a certain hydrophilicity, which can inhibit the re-adsorption of olefins, thereby reducing the secondary reaction of olefins and further improving the olefin selectivity. However, excessive hydrophilicity is not conducive to the maintenance of the iron carbide phase. Iron carbide is easily oxidized by the byproduct water and loses its activity. Therefore, during the catalyst preparation process, the ratio of the carrier to the active metal should also be adjusted at the same time, which is conducive to reducing the methane selectivity and improving the olefin selectivity.

[0042] Compared with the Fe-based catalyst prepared by the traditional co-precipitation method, the catalyst prepared in the present invention has a more stable iron carbide active phase, which can improve olefin selectivity while reducing methane selectivity.

[0043] The present invention will be further described below by means of the following specific embodiments.

[0044] Example 1

[0045] The modified silica-supported iron Fischer-Tropsch synthesis catalyst was prepared by the following steps:

[0046] (1) 0.6 g of potassium permanganate was added to 80 mL of deionized water to prepare a potassium permanganate solution, and 3 g of a silica carrier was added and stirred thoroughly; the modified silica carrier was obtained after centrifugation, washing, and drying in an oven at 80° C. for 12 h, which was recorded as A.

[0047] (2) 0.8 g of ferric nitrate nonahydrate was added to 50 mL of deionized water to fully dissolve, 1 g of the modified silica carrier was added, and after sufficient stirring, 1.2 mL of ammonia water was added dropwise to obtain a suspension B;

[0048] (3) placing the suspension B in a water bath, heating at 80°C with stirring for 1 h, allowing the mixture to cool naturally to room temperature, centrifuging, washing until neutral, and then drying in an oven at 80°C for 12 h to obtain a precursor C;

[0049] (4) The precursor C is calcined at 450° C. for 4 h in an air atmosphere to obtain the modified silica-supported iron Fischer-Tropsch synthesis catalyst, which is recorded as 0.1Fe / Mn-SiO2.

[0050] Example 2

[0051] The preparation method of the modified silica-supported iron Fischer-Tropsch synthesis catalyst in this example is basically the same as that in Example 1, except that 2.4 g of ferric nitrate nonahydrate and 2.8 mL of ammonia water are added in step (2). Therefore, the modified silica-supported iron Fischer-Tropsch synthesis catalyst prepared in this example is marked as 0.25Fe / Mn-SiO2.

[0052] Example 3

[0053] The preparation method of the modified silica-supported iron Fischer-Tropsch synthesis catalyst in this example is basically the same as that in Example 1, except that 7.2 g of ferric nitrate nonahydrate and 11.7 mL of ammonia water are added in step (2). Therefore, the modified silica-supported iron Fischer-Tropsch synthesis catalyst prepared in this example is marked as 0.5Fe / Mn-SiO2.

[0054] Example 4

[0055] The preparation method of the modified silica-supported iron Fischer-Tropsch synthesis catalyst in this example is basically the same as that in Example 1, except that 2.4 g of ferric nitrate nonahydrate is added in step (2) instead of 1.59 g of ferric chloride hexahydrate. Therefore, the modified silica-supported iron Fischer-Tropsch synthesis catalyst prepared in this example is labeled as ferric chloride hexahydrate-0.25Fe / Mn-SiO2.

[0056] Comparative Example 1

[0057] Preparation of silica-supported iron catalyst without Mn modification:

[0058] (1) 80 mL of deionized water was weighed, 3 g of a silica carrier was added and stirred thoroughly; the washed silica carrier was centrifuged, washed and dried in an oven at 80° C. for 12 h to obtain a washed silica carrier, which was recorded as A.

[0059] (2) 2.4 g of ferric nitrate nonahydrate was added to 50 mL of deionized water to fully dissolve, 1 g of the silica support washed in step (1) was added, and after sufficient stirring, 2.8 mL of ammonia water was added dropwise to obtain a suspension B;

[0060] (3) placing the suspension B in a water bath, heating at 80°C with stirring for 1 h, allowing the mixture to cool naturally to room temperature, centrifuging, washing until neutral, and then drying in an oven at 80°C for 12 h to obtain a precursor C;

[0061] (4) The precursor C is calcined at 450° C. for 4 h in an air atmosphere to obtain the supported Fe-based Fischer-Tropsch synthesis catalyst, which is recorded as 0.25Fe / SiO2.

[0062] Comparative Example 2

[0063] Preparation of Fe-based catalysts:

[0064] (1) Take 2.4 g of ferric nitrate nonahydrate and add it to 50 mL of deionized water to fully dissolve it, and then add 2.8 mL of ammonia water dropwise to obtain suspension B;

[0065] (3) placing the suspension B in a water bath, heating at 80°C with stirring for 1 h, allowing the mixture to cool naturally to room temperature, centrifuging, washing until neutral, and then drying in an oven at 80°C for 12 h to obtain a precursor C;

[0066] (4) The precursor C is calcined at 450° C. for 4 h in an air atmosphere to obtain the Fe-based Fischer-Tropsch synthesis catalyst, which is denoted as Fe2O3.

[0067] Comparative Example 3

[0068] The preparation method of the modified silica-supported iron Fischer-Tropsch synthesis catalyst in this example is basically the same as that in Example 1, except that 0.38 g of ferric nitrate nonahydrate and 0.5 mL of ammonia water are added in step (2). Therefore, the modified silica-supported iron Fischer-Tropsch synthesis catalyst prepared in this example is marked as 0.05Fe / Mn-SiO2.

[0069] Comparative Example 4

[0070] The preparation method of the modified silica-supported iron Fischer-Tropsch synthesis catalyst in this example is basically the same as that in Example 1, except that 15.1 g of ferric nitrate nonahydrate and 18.8 mL of ammonia water are added in step (2). Therefore, the modified silica-supported iron Fischer-Tropsch synthesis catalyst prepared in this example is marked as 0.75Fe / Mn-SiO2.

[0071] Test example

[0072] The catalyst performance tests and characterizations were performed on the catalysts prepared in the above Examples 1 to 4 and Comparative Examples 1 to 4:

[0073] When evaluating the performance of the catalyst, in order to make the catalyst particles uniform in size and not to block the reaction tube, the catalysts prepared in the above Examples 1 to 4 and Comparative Examples 1 to 4 of the present invention should all be made into catalyst particles of 20 to 40 meshes.

[0074] The catalysts prepared in Examples 1 to 4 and Comparative Examples 1 to 4 were evaluated in a micro fixed reactor. The process conditions were: 0.5 to 3 mL of 20 to 40 mesh catalyst, reaction temperature 250 to 400°C, reaction pressure 0.5 to 3 MPa, raw gas H2 / CO=1 or 2, and space velocity 500 to 5000·h -1 .

[0075] For example, the performance of the 0.1Fe / SiO2 catalyst prepared in Example 1 was evaluated in a fixed bed reactor. The specific operation steps are as follows: 1 mL of the modified silica-loaded iron Fischer-Tropsch synthesis catalyst prepared in Example 1 was weighed and loaded into the constant temperature zone in the middle of the reaction tube. The raw gas H2 / CO=2, the temperature was 280°C, the pressure was 1.5 MPa, and the space velocity (GHSV) was 1000 h -1 After reaching a stable state, sampling and analysis were carried out at intervals of 3 hours. Gas chromatography was used to perform quantitative and qualitative analysis on the raw gas and products. The CO conversion rate and the selectivity of each component were calculated using the methane correlation method of "Determination and gas chromatography of H2, N2, CO, CO2 and C1-C8 hydrocarbons in coal-based Fischer-Tropsch synthesis tail gas". The specific results are shown in Table 1.

[0076] Table 1 Comparison of process parameters and performance test results of Fischer-Tropsch synthesis of olefins using catalysts prepared in Examples 1 to 4 and Comparative Examples 1 to 4

[0077]

[0078] As can be seen from Table 1, in the product distribution of the modified silica-supported iron Fischer-Tropsch synthesis catalyst, the CH4 selectivity is maintained at about 10%. Compared with the Fe-based catalyst prepared by the traditional precipitation method, the modified silica-supported iron Fischer-Tropsch synthesis catalyst prepared by this method has a smaller particle size, which is conducive to the dispersion of the active components. Compared with the unmodified Fe / SiO2, the methane selectivity of the modified 0.1Fe / SiO2, 0.25Fe / SiO2 and 0.5Fe / SiO2 catalysts is reduced, C 2+ ＝ The selectivity and O / P value were improved. Compared with the Fe / SiO2 catalyst loaded with silica only, the catalytic performance of the series of catalysts introduced with Mn was more obvious. 2+ ＝The selectivity is significantly improved, which is attributed to the fact that Mn metal doping promotes the formation of more iron carbide phases on the catalyst. Although SiO2 is hydrophilic and can effectively inhibit the re-adsorption of olefins, thereby reducing the secondary reaction of olefins, the iron carbide phase is easily oxidized, which is not conducive to the formation of olefins. Therefore, the stability of iron carbide can be maintained by adding the additive Mn, and a catalyst with low methane selectivity and high C 2+ ＝ Selective catalyst.

[0079] Comparing three different modified silica-loaded iron Fischer-Tropsch synthesis catalysts, the catalytic effect of the 0.25Fe / SiO2 catalyst is the best, with methane selectivity reduced to 9.8%, total olefin selectivity up to 62.5%, and olefin ratio (O / P) of 5.25. When the loaded Fe content is too high (0.75Fe / Mn-SiO2 of Comparative Example 4) or the modified silica carrier content is too high (0.05Fe / Mn-SiO2 of Comparative Example 3), the catalytic effect is not improved well. This shows that the ratio of the carrier to the active metal is adjusted (the mass ratio of the active component Fe and the carrier Mn-SiO2 is 0.1 to 0.5), and the modified silica carrier and the active component Fe in the appropriate ratio are conducive to the formation of the iron carbide phase, which is conducive to improving the olefin selectivity while reducing the methane selectivity.

[0080] The modified silica-supported iron Fischer-Tropsch synthesis catalyst prepared by the present invention effectively solves the problems of high methane conversion rate and low olefin selectivity in the Fischer-Tropsch synthesis reaction process. By introducing silica carrier and Mn element and adjusting the ratio of carrier to active metal, a stable iron carbide phase is formed. The stable existence of the iron carbide phase is beneficial to improving the olefin selectivity of the catalyst.

[0081] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a Fischer-Tropsch synthesis catalyst of modified silica-supported iron, characterized in that: The following steps are involved: (1) preparing a potassium permanganate solution, adding a certain amount of a silica carrier and fully stirring, and then centrifuging, washing, and drying in sequence to obtain a modified silica carrier; (2) mixing a soluble iron salt, a modified silica carrier and deionized water in a certain proportion, stirring thoroughly and then dropping an alkali solution to obtain a suspension; (3) placing the suspension in a water bath, heating and stirring for 1 h, allowing the mixture to cool naturally to room temperature, centrifuging, washing to neutrality, and then drying to obtain a precursor; (4) calcining the precursor to obtain a powder sample, i.e., obtaining the catalyst; The mass ratio of the active component Fe to the carrier Mn-SiO2 in the obtained catalyst is 0.1-0.

5.

2. The method for preparing a Fischer-Tropsch synthesis catalyst of modified silica supported iron according to claim 1, characterized in that: In step (1), the concentration of potassium permanganate solution is 0.1 mol / L, and the dosage ratio of potassium permanganate solution to silica carrier is (40-100) mL: (2-8) g.

3. The method for preparing the Fischer-Tropsch synthesis catalyst of modified silica supported iron according to claim 1, characterized in that: In step (2), the ratio of the soluble iron salt, the modified silica carrier and the deionized water is (0.3-20) g: (1-2) g: (60-120) mL.

4. The method for preparing a Fischer-Tropsch synthesis catalyst of modified silica supported iron according to claim 3, characterized in that: In step (2), the soluble iron salt is any one of ferric chloride hexahydrate, ferric nitrate nonahydrate or ferrous sulfate.

5. The method for preparing the Fischer-Tropsch synthesis catalyst of modified silica supported iron according to claim 3, characterized in that: In step (2), the solute in the alkali solution is any one of ammonia water, potassium hydroxide and calcium hydroxide.

6. The method for preparing the Fischer-Tropsch synthesis catalyst of modified silica supported iron according to claim 3, characterized in that: In step (2), the ratio of solute to deionized water in the alkali solution is (5-10) g: (20-50) mL.

7. The method for preparing a Fischer-Tropsch synthesis catalyst of modified silica supported iron according to claim 1, characterized in that: In step (2), after sufficient stirring, an alkali solution is added dropwise to obtain a suspension, and the pH value of the suspension is controlled to be 8-10.

8. The method for preparing a Fischer-Tropsch synthesis catalyst of modified silica supported iron according to claim 1, characterized in that: In step (4), the precursor is calcined at 400-500° C. in an air atmosphere for 3-6 hours.

9. A Fischer-Tropsch synthesis catalyst containing iron supported on modified silica prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the modified silica-supported iron Fischer-Tropsch synthesis catalyst according to claim 9 in catalyzing CO hydrogenation to olefins synthesis reaction.

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