A catalyst for preparing α-olefins from syngas, its preparation method and application

Abstract

The present invention discloses a catalyst for preparing α-olefins from syngas, a preparation method thereof, and an application thereof. Among them, the catalyst, in parts by weight, comprises A) 50 to 80 parts of a carrier; B) 20 to 50 parts of an active component, and the active component contains a composition with the following chemical formula in terms of atomic ratio: Co 100 Fe a B b Na 2c S c O x ; where B includes at least one of Mo, W, and V, the value range of a is 10 to 30; the value range of b is 1 to 10; the value range of c is 0.2 to 4; x is the total number of oxygen atoms required to satisfy the valence of each element in the catalyst. The catalyst is suitable for preparing α-olefins from syngas, and when applied in the reaction, it has the advantage of high α-olefin yield.

Description

Technical Field

[0001] The present invention belongs to the field of preparing α-olefins from syngas, and particularly relates to a catalyst for preparing α-olefins from syngas, a preparation method thereof, and an application thereof. Background Art

[0002] α-olefins refer to monoolefins with double bonds at the ends of the molecular chains. Industrially, they generally refer to straight-chain α-olefins with 4 or more carbon atoms. As industrial products, α-olefins are basically mixtures of straight-chain terminal olefins, with a wide carbon number range distribution (C4 - C40). The straight-chain α-olefins with a carbon number range of C6 - C20, which have wide uses, except for separating individual components such as C4 (1-butene), C6 (1-hexene), and C8 (1-octene), are separated into fractions within a certain carbon number range according to their uses.

[0003] There are many preparation methods for α-olefins. Commercialized technologies include ethylene oligomerization process, ethylene trimerization process, wax cracking method, mixed C4 separation process, Fischer-Tropsch synthesis method, and vegetable oil method, etc. Currently, except for separating 1-butene from mixed C4, more than 80% globally is produced through the ethylene trimerization process and the ethylene oligomerization process, followed by the Fischer-Tropsch synthesis method.

[0004] The Fischer-Tropsch synthesis was first industrialized by Sasol in South Africa. This technology is to process the intermediate products of indirect coal liquefaction containing α-olefins (based on the Fischer-Tropsch synthesis technology) through steps such as pre-separation, selective hydrogenation, water washing, etherification, methanol recovery, superfractionation extraction distillation, drying, and refining to obtain high-quality α-olefins. Currently, the production capacity of α-olefins in China is severely insufficient, and products mainly rely on imports. The Fischer-Tropsch synthesis technology can be divided into high-temperature Fischer-Tropsch technology (reaction temperature exceeding 300°C) and low-temperature Fischer-Tropsch technology (reaction temperature 200 - 280°C) according to the process. Among them, the high-temperature Fischer-Tropsch technology mostly uses iron-based catalysts to directly convert syngas into main products of olefins and alkanes with a carbon chain length less than 20. CN 106607059A introduced an Fe-Mn-based catalyst for directly synthesizing light olefins from syngas and its preparation method; the low-temperature Fischer-Tropsch technology uses cobalt-based or iron-based catalysts to convert syngas into main products of high-chain saturated oils and waxes. CN110252358A introduced a cobalt catalyst and its preparation method as well as a method for Fischer-Tropsch synthesis of Fischer-Tropsch wax. The amount of α-olefins in the products of the high-temperature Fischer-Tropsch technology is much larger than that in the low-temperature Fischer-Tropsch technology. Generally, the intermediate products based on the Fischer-Tropsch synthesis technology for subsequent separation and production of α-olefins mostly come from the high-temperature Fischer-Tropsch technology of iron-based catalysts.

[0005] In the prior art, the catalysts for preparing α-olefins from syngas generally have the problem of low olefin yield in the products. Therefore, it is of great significance to develop a catalyst suitable for preparing α-olefins from syngas. SUMMARY OF THE INVENTION

[0006] Aiming at the problem of low olefin yield in the Fischer-Tropsch synthesis products of cobalt-based catalysts in the prior art, the present invention provides a catalyst for preparing α-olefins from syngas, a preparation method thereof, and an application thereof. The catalyst is suitable for preparing α-olefins from syngas, and is particularly suitable for preparing α-olefins by a high-temperature Fischer-Tropsch process using syngas with a high hydrogen content, and has the advantage of high α-olefin yield.

[0007] In the first aspect of the present invention, there is provided a catalyst for preparing α-olefins from syngas, wherein, based on parts by weight, the catalyst comprises

[0008] A) 50-80 parts of a carrier;

[0009] B) 20-50 parts of an active component, and the active component contains a composition with the following chemical formula in terms of atomic ratio: Co 100 Fe a B b Na 2c S c O x ;

[0010] wherein B includes at least one of Mo, W, and V,

[0011] the value range of a is 10-30;

[0012] the value range of b is 1-10;

[0013] the value range of c is 0.2-4;

[0014] x is the total number of oxygen atoms required to satisfy the valences of each element in the catalyst.

[0015] According to the present invention, the carrier includes at least one of oxides of Si and Ti.

[0016] According to the present invention, the catalyst is in the form of microspheres.

[0017] According to the present invention, based on the XPS characterization results, the molar ratio of Na to S on the surface of the catalyst is 8-16:1, preferably 10-14:1.

[0018] In the second aspect of the present invention, there is provided a preparation method of the above catalyst, and the method includes the following steps:

[0019] Mixing a mixed solution containing Co salt and Fe salt, a carrier, a B source, and Na2S for pulping, spray drying, and calcining to obtain the catalyst.

[0020] According to the present invention, the pH of the slurry can be adjusted during the mixed beating. Preferably, the pH is 1 to 5. Conventional acid-base regulators can be used to adjust the pH of the slurry. The acid-base regulator includes at least one of ammonia, ethylenediamine, and nitric acid.

[0021] According to the present invention, in the slurry obtained after the mixed beating, the solid content is 15 wt% to 45 wt%.

[0022] According to the present invention, the Co salt is a soluble Co salt. The Co salt includes at least one of cobalt nitrate, cobalt oxalate, and cobalt acetate. The iron salt includes at least one of iron nitrate and iron citrate. The carrier exists in the form of a sol. The B source includes at least one of ammonium molybdate, ammonium paratungstate, and ammonium metavanadate.

[0023] According to the present invention, the Co source solution and the Fe salt solution can be separately prepared and then mixed and then mixed with other raw materials of the catalyst.

[0024] According to the present invention, the spray drying is carried out in a spray dryer. The conditions for the spray drying are: the hot air temperature is 150 to 350 °C, and the hot air medium for the spray drying is air.

[0025] According to the present invention, the conditions for the calcination are: calcination at a temperature of 450 to 700 °C for 0.3 to 5 h. The calcination atmosphere is a mixed gas of air and an inert gas with a volume ratio of 1:0.2 to 1.2. The inert gas is preferably nitrogen.

[0026] According to the present invention, the temperature of the mixed beating is 80 to 95 °C. The time for the mixed beating is 0.5 to 5 h.

[0027] The third aspect of the present invention provides the application of the above catalyst or the catalyst prepared by the above method in the reaction of synthesizing syngas to prepare α-olefins.

[0028] According to the present invention, the syngas is a mixed gas of H2 and CO; preferably, the volume ratio of H2 and CO is 4 to 6.

[0029] According to the present invention, the conditions for the reaction are: the temperature of the reaction is 300 to 370 °C; the pressure of the reaction is 0.5 to 5 MPa; the catalyst load (standard volume space velocity) is 4000 to 10000 h -1 。

[0030] According to the invention, in the above application, the syngas rich in H2 can be efficiently converted into organic hydrocarbons rich in α-olefins, and at the same time, the problem that the cobalt-based catalyst is easily deactivated by carbon deposition under high-temperature Fischer-Tropsch conditions is solved.

[0031] Compared with the prior art, the main advantages of the present invention are as follows:

[0032] (1) In the catalyst of the present invention, based on parts by weight, it includes A) 50 to 80 parts of a carrier; B) 20 to 50 parts of an active component, and the active component contains a composition with the following chemical formula in terms of atomic ratio: Co 100 Fe a B b Na 2c S c O x . In the present invention, by doping specific proportions of Na and S elements in the composition of the Co-based catalyst, and further enabling Na and S on the catalyst surface to be distributed within a certain proportion range, this catalyst is particularly suitable for the reaction of converting syngas rich in H2 to prepare organic hydrocarbons. When this catalyst is used in this reaction, it has the advantages of high-efficiency conversion of syngas and a relatively high content of α-olefins in the product.

[0033] (2) In the preparation method of the catalyst of the present invention, by adding Na2S during the preparation of the Co-based catalyst, the doping of Na and S is achieved, and the preparation process is controlled, especially the selection of the calcination atmosphere, so that Na and S on the catalyst surface are distributed within a certain proportion range. This catalyst is particularly suitable for the reaction of converting syngas rich in H2 to prepare organic hydrocarbons. When this catalyst is used in this reaction, it has the advantages of high-efficiency conversion of syngas and a relatively high content of α-olefins in the product.

[0034] (3) In the application of the catalyst of the present invention, this catalyst is suitable for the reaction of converting syngas to prepare olefins, especially suitable for the reaction of converting syngas rich in H2 to prepare olefins. When this catalyst is applied to this reaction, it can efficiently convert syngas and the product contains a relatively high content of α-olefins, and at the same time solves the problem that the cobalt-based catalyst is prone to carbon deposition and deactivation under high-temperature Fischer-Tropsch conditions. Detailed implementation mode

[0035] In the present invention, XPS characterization of the elemental analysis on the catalyst surface is carried out using an EscalLab Xi+ X-ray photoelectron spectrometer.

[0036] In the present invention, C2 + hydrocarbons are hydrocarbons with 2 to 20 carbon atoms.

[0037] In the present invention, the catalyst evaluation methods for Examples 1 to 4 and Comparative Examples 1 to 4 are as follows:

[0038] The catalyst is reduced by in-situ reduction method. After the reduction is completed, the process conditions are directly switched to the synthesis reaction conditions in the reactor used for reduction to start the reaction;

[0039] Reactor specifications: Millimeter fluidized bed reactor;

[0040] Catalyst loading: 50 grams;

[0041] The reduction conditions are as follows: temperature 400 °C

[0042] pressure 0.1 MPa

[0043] catalyst loading (standard volume hourly space velocity) 6000 h⁻¹ -1

[0044] reducing gas H₂

[0045] reduction time 12 h

[0046] The synthesis reaction conditions are as follows: reaction temperature 320 °C

[0047] reaction pressure 2.5 MPa

[0048] catalyst loading (standard volume hourly space velocity) 6000 h⁻¹ -1

[0049] raw material ratio in syngas CO / H₂ = 1:5

[0050] The reaction runs for 100 h.

[0051] In the present invention, the reaction results of the catalyst evaluation test for the reaction running for 100 h are shown in Table 1; the test reaction results for the reaction running for 100 h and 200 h are shown in Table 2.

[0052] Example 1

[0053] Take 1 mol of Co(NO₃)₂·6H₂O and dissolve it in water to prepare a 0.5 mol / L Co element solution I. Take 0.3 mol of Fe(NO₃)₃·9H₂O and dissolve it in water to prepare a 0.5 mol / L Fe element solution II. Mix solution I and solution II to obtain solution III. Take a 0.5 mol / L aqueous solution of 0.01 mol of ammonium heptamolybdate, take a 40 wt% titanium sol containing 442 g of TiO₂, and a 0.5 mol / L aqueous solution of 0.02 mol of Na₂S, and add them to solution III in sequence, and then stir and beat the pulp at 90 °C for 1 h. Adjust the pH value of the mixture to 5 with 5 wt% dilute nitric acid, and adjust the solid content of the mixture to 35% with water to obtain a slurry. Spray-dry the slurry to form a shape, with the inlet temperature of the spray dryer being 350 °C and the outlet temperature being 200 °C, and the hot air medium of the spray dryer being air, to obtain a spray-dried material; then calcine it at 650 °C for 2 h in a low-oxygen atmosphere with a volume ratio of nitrogen to air of 0.5 to obtain a catalyst. The composition of the catalyst is: 20 wt% Co 100 Fe 30 Mo₇Na₄S₂O x +80 wt% TiO₂.

[0054] Detected by XPS, the molar ratio of surface Na to S of the prepared catalyst is 13:1.

[0055] The reaction results of the catalyst evaluation test are shown in Tables 1 and 2.

[0056] Example 2

[0057] Take 1 mol of Co(NO3)2·6H2O and dissolve it in water to prepare a 0.5 mol / L Co element solution I. Take 0.3 mol of Fe(NO3)3·9H2O and dissolve it in water to prepare a 0.5 mol / L Fe element solution II. Mix solution I and solution II to obtain solution III. Take a 0.5 mol / L aqueous solution of 0.005 mol of ammonium paratungstate, take a 40 wt% silica sol containing 110 g of SiO2, and a 0.5 mol / L aqueous solution of 0.01 mol of Na2S, and add them to solution III in sequence. Then stir and beat the pulp at 90 °C for 2 h. Adjust the pH value of the mixture to 5 with 5 wt% dilute nitric acid, and adjust the solid content of the mixture to 35% with water to obtain a slurry. Spray-dry the slurry to form a shape. The inlet temperature of the spray dryer is 330 °C, the outlet temperature is 195 °C, and the hot air medium of the spray dryer is air to obtain a spray-dried material; then calcine it at 650 °C for 2 h in a low-oxygen atmosphere with a volume ratio of nitrogen to air of 0.5 to obtain a catalyst. The composition of the catalyst is: 50 wt% 1Co 100 Fe 30 W6Na2SO x + 50 wt% SiO2.

[0058] Detected by XPS, the molar ratio of Na to S on the surface of the prepared catalyst is 10:1.

[0059] The reaction results of the catalyst evaluation test are shown in Table 1.

[0060] Example 3

[0061] Dissolve 1 mol of Co(NO3)2·6H2O in water to prepare a 0.5 mol / L Co element solution I. Dissolve 0.3 mol of Fe(NO3)3·9H2O in water to prepare a 0.5 mol / L Fe element solution II. Mix solution I and solution II to obtain solution III. Prepare a 0.5 mol / L aqueous solution of V from 0.05 mol of ammonium metavanadate, take a 40 wt% titanium sol containing 166 g of TiO2, and a 0.5 mol / L aqueous solution of 0.005 mol of Na2S, and add them to solution III in sequence. Then stir and beat the slurry at 90 °C for 3.5 h. Adjust the pH value of the mixture to 5 with 5 wt% dilute nitric acid, and adjust the solid content of the mixture to 35% with water to obtain a slurry. Spray-dry the slurry to form a shape. The inlet temperature of the spray dryer is 320 °C, the outlet temperature is 180 °C, and the hot air medium of the spray dryer is air to obtain a spray-dried material; then calcine it at 650 °C for 2 h in a low-oxygen atmosphere with a volume ratio of nitrogen to air of 0.5 to obtain a catalyst. The composition of the catalyst is: 40 wt% Co 100 Fe 30 V5Na1S 0.5 O x + 60 wt% TiO2.

[0062] Detected by XPS, the molar ratio of Na to S on the surface of the prepared catalyst is 9:1.

[0063] The reaction results of the catalyst evaluation test are shown in Table 1.

[0064] Example 4

[0065] Dissolve 1 mol of Co(NO3)2·6H2O in water to prepare a 0.5 mol / L Co element solution I. Dissolve 0.3 mol of Fe(NO3)3·9H2O in water to prepare a 0.5 mol / L Fe element solution II. Mix solution I and solution II to obtain solution III. Prepare a 0.5 mol / L aqueous solution of V from 0.02 mol of ammonium metavanadate, prepare a 0.5 mol / L aqueous solution of Mo from 0.01 mol of ammonium heptamolybdate, take a 40 wt% titanium sol containing 442 g of TiO2, and a 0.5 mol / L aqueous solution of 0.02 mol of Na2S, and add them to solution III in sequence. Then stir and beat the slurry at 90 °C for 0.5 h. Adjust the pH value of the mixture to 5 with 5 wt% dilute nitric acid, and adjust the solid content of the mixture to 35% with water to obtain a slurry. Spray-dry the slurry to form a shape. The inlet temperature of the spray dryer is 350 °C, the outlet temperature is 200 °C, and the hot air medium of the spray dryer is air to obtain a spray-dried material; then calcine it at 650 °C for 2 h in a low-oxygen atmosphere with a volume ratio of nitrogen to air of 0.5 to obtain a catalyst. The composition of the catalyst is: 20 wt% Co 100 Fe30 V2Mo7Na4S2O x + 80 wt% TiO2.

[0066] The molar ratio of Na to S on the surface of the prepared catalyst was 12:1 as detected by XPS.

[0067] The reaction results of the catalyst evaluation test are shown in Table 1.

[0068] Example 5

[0069] The catalyst was prepared in the same manner as in Example 1, except that the raw material ratio in the synthesis gas for evaluation was CO / H2 = 1:4.

[0070] The reaction results of the catalyst evaluation test are shown in Table 1.

[0071] Example 6

[0072] The catalyst was prepared in the same manner as in Example 1, except that the raw material ratio in the synthesis gas for evaluation was CO / H2 = 1:6.

[0073] The reaction results of the catalyst evaluation test are shown in Table 1.

[0074] Comparative Example 1:

[0075] 1 mol of Co(NO3)2·6H2O was dissolved in water to prepare a 0.5 mol / L Co element solution I. 0.3 mol of Fe(NO3)3·9H2O was dissolved in water to prepare a 0.5 mol / L Fe element solution II. Solution I and solution II were mixed to obtain solution III. 0.01 mol of ammonium heptamolybdate was prepared into a 0.5 mol / L Mo aqueous solution. A 40 wt% titanium sol containing 442 g of TiO2 and a 0.5 mol / L aqueous solution of 0.04 mol of NaOH were successively added to solution III, and then stirred and slurried at 90 °C for 1 h. The pH value of the mixture was adjusted to 5 with 5 wt% dilute nitric acid, and the solid content of the mixture was adjusted to 35% with water to obtain a slurry; the slurry was spray-dried and formed, the inlet temperature of the spray dryer was 350 °C, the outlet temperature was 200 °C, and the hot air medium of the spray dryer was air, to obtain a spray-dried material; then it was calcined at 650 °C for 2 h in a low-oxygen atmosphere with a volume ratio of nitrogen to air of 0.5 to obtain a catalyst. The composition of the catalyst is: 20 wt% Co 100 Fe 30 Mo7Na4O x + 80 wt% TiO2.

[0076] The evaluation conditions of the catalyst were the same as in Example 1. The reaction results of the evaluation test are shown in Tables 1 and 2.

[0077] Comparative Example 2

[0078] Dissolve 1 mol of Co(NO3)2·6H2O in water to prepare a 0.5 mol / L Co element solution I. Dissolve 0.3 mol of Fe(NO3)3·9H2O in water to prepare a 0.5 mol / L Fe element solution II. Mix solution I and solution II to obtain solution III. Prepare a 0.5 mol / L aqueous solution of Mo from 0.01 mol of ammonium heptamolybdate. Take a 40 wt% titanium sol containing 442 g of TiO2, as well as a 0.5 mol / L aqueous solution of 0.04 mol of NaOH and a 0.05 mol / L solution containing 0.02 mol of H2S, and add them to solution III in sequence. Then stir and beat the mixture at 90 °C for 1 h. Adjust the pH value of the mixture to 5 with 5 wt% dilute nitric acid, and adjust the solid content of the mixture to 35% with water to obtain a slurry; Spray-dry the slurry to form a shape. The inlet temperature of the spray dryer is 350 °C, the outlet temperature is 200 °C, and the hot air medium of the spray dryer is air to obtain a spray-dried material; Then calcine at 650 °C for 2 h in a low-oxygen atmosphere with a volume ratio of nitrogen to air of 0.5 to obtain a catalyst. The composition of the catalyst is: 20 wt% Co 100 Fe 30 Mo7Na4S2O x + 80 wt% TiO2.

[0079] By XPS detection, the molar ratio of Na to S on the surface of the prepared catalyst is 2:1.

[0080] The evaluation conditions of the catalyst are the same as those in Example 1. The reaction results of the catalyst evaluation test are shown in Table 1.

[0081] Comparative Example 3:

[0082] Dissolve 1 mol of Co(NO3)2·6H2O in water to prepare a 0.5 mol / L Co element solution I. Dissolve 0.3 mol of Fe(NO3)3·9H2O in water to prepare a 0.5 mol / L Fe element solution II. Mix solution I and solution II to obtain solution III. Prepare a 0.5 mol / L aqueous solution of Mo from 0.01 mol of ammonium heptamolybdate. Take a 40 wt% titanium sol containing 442 g of TiO2, as well as a 0.5 mol / L aqueous solution of 0.02 mol of Na2S, and add them to solution III in sequence. Then stir and beat the mixture at 90 °C for 1 h. Adjust the pH value of the mixture to 5 with 5 wt% dilute nitric acid, and adjust the solid content of the mixture to 35% with water to obtain a slurry; Spray-dry the slurry to form a shape. The inlet temperature of the spray dryer is 350 °C, the outlet temperature is 200 °C, and the hot air medium of the spray dryer is air to obtain a spray-dried material; Then calcine at 650 °C for 2 h in an air atmosphere to obtain a catalyst. The composition of the catalyst is: 20 wt% Co 100 Fe 30 Mo7Na4S2Ox +80 wt% TiO2.

[0083] Detected by XPS, the molar ratio of Na to S on the surface of the prepared catalyst is 4:1.

[0084] The evaluation conditions of the catalyst are the same as those in Example 1. The reaction results of the catalyst evaluation test are shown in Table 1.

[0085] Comparative Example 4:

[0086] Dissolve 1 mol of Co(NO3)2·6H2O in water to prepare a 0.5 mol / L Co element solution I. Dissolve 0.3 mol of Fe(NO3)3·9H2O in water to prepare a 0.5 mol / L Fe element solution II. Mix solution I and solution II to obtain solution III. Take a 0.5 mol / L aqueous solution of Mo prepared from 0.01 mol of ammonium heptamolybdate, a 40 wt% titanium sol containing 442 g of TiO2, and a 0.05 mol / L solution containing 0.02 mol of H2S, and add them to solution III in sequence. Then stir and beat the mixture at 90 °C for 1 h. Adjust the pH value of the mixture to 5 with 5 wt% dilute nitric acid, and adjust the solid content of the mixture to 35% with water to obtain a slurry; spray-dry the slurry to form a shape. The inlet temperature of the spray dryer is 350 °C, the outlet temperature is 200 °C, and the hot air medium of the spray dryer is air to obtain a spray-dried material; then calcine it at 650 °C for 2 h in a low-oxygen atmosphere with a volume ratio of nitrogen to air of 0.5 to obtain a catalyst. The composition of the catalyst is: 20 wt% Co 100 Fe 30 Mo7S2O x +80 wt% TiO2.

[0087] The evaluation conditions of the catalyst are the same as those in Example 1. The reaction results of the catalyst evaluation test are shown in Table 1.

[0088] Comparative Example 5:

[0089] The catalyst is prepared in the same way as in Example 1, except that the raw material ratio in the synthesis gas for evaluation is CO / H2 = 1:3.

[0090] The reaction results of the catalyst evaluation test are shown in Table 1.

[0091] Table 1 Reaction results of the catalyst evaluation test for 100 h

[0092]

[0093]

[0094] Table 2 Reaction results of the catalyst evaluation test for 100 h and 200 h

[0095]

[0096] The specific embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A catalyst for preparing α-olefins from syngas, wherein, The catalyst, by weight, comprises A) 50 to 80 parts of a carrier; B) 20 to 50 parts of an active component, the active component containing, in atomic ratio, a composition having the following chemical formula: Co 100 Fe a B b Na 2c S c O x ; wherein B comprises at least one of Mo, W, and V, the value range of a is 10 to 30; the value range of b is 1 to 10; the value range of c is 0.2 to 4; x is the total number of oxygen atoms required to satisfy the valence of each element in the catalyst; the molar ratio of Na to S on the catalyst surface is 8 to 16:1; the synthesis gas is a mixture of H2 and CO; the volume ratio of H2 to CO is 4 to 6.

2. The catalyst according to claim 1, characterized in that, The carrier comprises at least one of oxides of Si and Ti.

3. The catalyst according to claim 1, wherein The molar ratio of Na to S on the catalyst surface is 10 to 14:

1.

4. The preparation method of the catalyst according to any one of claims 1 to 3, comprising the following steps: Mixing a mixed solution containing a Co salt and an Fe salt, a carrier, a B source, and Na2S into a slurry, spray-drying, and calcining to obtain the catalyst; The calcination atmosphere is a mixed gas with a volume ratio of air to inert gas of 1:0.2 to 1.

2.

5. The preparation method according to claim 4, characterized in that, In the slurry obtained after mixing into a slurry, the solid content is 15wt% to 45wt%.

6. According to the preparation method described in claim 4, characterized in that, Adjust the pH of the slurry during mixing; the pH is 1 to 5.

7. According to the preparation method described in claim 4, characterized in that, The Co salt is a soluble Co salt; and / or, the iron salt comprises at least one of iron nitrate and iron citrate; and / or, the carrier exists in the form of a sol; and / or, the B source comprises at least one of ammonium molybdate, ammonium paratungstate, and ammonium metavanadate.

8. The preparation method according to claim 7, wherein The Co salt comprises at least one of cobalt nitrate, cobalt oxalate, and cobalt acetate.

9. The preparation method according to claim 4, characterized in that, The conditions for spray drying are: the hot air temperature is 150 to 350°C; and / or, the hot air medium for spray drying is air.

10. According to the preparation method described in claim 4, characterized in that, The conditions for calcination are: calcining at 450 to 700°C for 0.3 to 5 h; and / or, the inert gas is nitrogen.

11. The application of the catalyst according to any one of claims 1 to 3 or the catalyst prepared by the preparation method according to any one of claims 4 to 10 in the reaction of synthesizing syngas to prepare α-olefins.

12. The application according to claim 11, wherein, The temperature of the reaction is 300 to 370 °C; the pressure of the reaction is 0.5 to 5 MPa; the standard volume hourly space velocity of the catalyst load is 4000 to 10000 h -1 .

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