Cobalt-based Fischer-Tropsch synthesis catalyst rich in surface defect sites and preparation method and application thereof

Abstract

The invention provides a cobalt-based Fischer-Tropsch synthesis catalyst rich in surface defect sites and a preparation method and application thereof, and the catalyst provided by the invention is applied to Fischer-Tropsch synthesis reaction and has excellent long-period stability and reaction activity. The cobalt-based Fischer-Tropsch synthesis catalyst rich in surface defect sites provided by the invention comprises a carrier, an active metal element Co and an auxiliary element, wherein the carrier is N-doped titanium dioxide, and the surface of the carrier comprises a Ti-O-N structure and / or a Ti-N-O structure; the atomic ratio of Ti to N is (8-40): 1, preferably (10-30): 1.

Description

Technical Field

[0001] This invention relates to the field of cobalt-based Fischer-Tropsch synthesis catalyst technology, specifically to a cobalt-based Fischer-Tropsch synthesis catalyst rich in surface defect sites, its preparation method, and its application. Background Technology

[0002] Fischer-Tropsch synthesis is one of the main technological routes for the catalytic conversion of syngas into high-value-added chemicals and fuels. Co-based catalysts have received widespread attention and application in this field due to their high reactivity and excellent selectivity for long-chain hydrocarbons. However, Co catalysts are prone to oxidation and sintering during the reaction, leading to deactivation. Designing highly active and stable Co catalysts is a key challenge in this research area.

[0003] CN 116726927 A provides a Fischer-Tropsch synthesis catalyst, wherein, based on the total weight of the catalyst, the Fischer-Tropsch synthesis catalyst comprises: 10 40wt% Co, 0.5 7wt% B and 53 The catalyst contains 89.5 wt% of a support; the support is TiO2, Co exists in the form of oxides, and B exists in the forms of boron oxide and titanium diboride. This catalyst is characterized by its simple preparation, high catalytic activity, and good stability.

[0004] CN 119897135 A provides a method for preparing a cobalt-based Fischer-Tropsch synthesis catalyst, comprising the following steps: (1) contacting a mixed solution containing an active metal precursor and an auxiliary precursor, a precipitant, and a dispersion containing a support for a deposition and precipitation reaction, followed by aging treatment; (2) filtering, washing, drying, and calcining the material obtained in step (1) to obtain a cobalt-based Fischer-Tropsch synthesis catalyst. The obtained cobalt-based Fischer-Tropsch synthesis catalyst exhibits less chlorine loss, low catalyst deactivation rate, and excellent stability during the Fischer-Tropsch synthesis reaction, making it particularly suitable for cobalt-based Fischer-Tropsch synthesis processes using fixed-bed reactors.

[0005] CN118751280A discloses a cobalt-based catalyst for Fischer-Tropsch synthesis, its preparation method, and its application. The catalyst comprises cobalt oxide, a supported molecular sieve, and a coupled molecular sieve; the mass ratio of the sum of the cobalt oxide and the supported molecular sieve to the coupled molecular sieve is 1:1 to 1:4; based on the total mass of the catalyst, the cobalt content in the cobalt oxide is 5-30 wt%. The catalyst provided by this technical solution exhibits high carbon monoxide conversion, high selectivity for aviation fuel fractions, and high heavy hydrocarbon C content in the Fischer-Tropsch synthesis reaction. 21 It has low selectivity, with low selectivity for the main byproduct methane, and good stability and low deactivation rate.

[0006] CN114797929B discloses a cobalt-based catalyst supported on a porous nitrogen-modified carbon material, its preparation, and its application. The catalyst support is ZIF. 7 is used as a precursor, which is pyrolyzed to generate nitrogen-modified carbon material, followed by impregnation with metallic Co and auxiliary metals. The catalyst uses Co as the active center and Fe, Cd, Cr, Ni, etc., as auxiliary dopants. The mass content of cobalt in the catalyst is 10.0%. 30.0 wt%, with an additive metal content of 0.1%. 5.0 wt%; The porous nitrogen-modified carbon material used as a catalyst support prepared by pyrolysis has a good pore structure, a large specific surface area, and a large pore volume and pore size. Metallic Co has good dispersibility and good reducibility under the action of promoters. It has excellent carbon monoxide hydrogenation catalytic performance, good catalyst stability, and good selectivity for C5+ hydrocarbons. Summary of the Invention

[0007] This invention provides a cobalt-based Fischer-Tropsch synthesis catalyst rich in surface defect sites, its preparation method, and its application. The catalyst provided by this invention exhibits excellent long-term stability and reactivity when applied in the Fischer-Tropsch synthesis reaction.

[0008] To achieve its objective, the present invention provides the following technical solution: The present invention provides a cobalt-based Fischer-Tropsch synthesis catalyst rich in surface defect sites, the catalyst comprising a support, an active metal element Co, and an auxiliary element; The support is N-doped titanium dioxide, and the surface of the support contains Ti-ON and / or Ti-NO structures; the atomic ratio of Ti to N is 8-40:1, preferably 10-30:1.

[0009] Preferably, the mass ratio between the N-doped titanium dioxide and the active metal element Co is 2-4:1; And / or, the atomic molar ratio of the active metal element Co to the auxiliary element is 5-50:1; And / or, the auxiliary element is selected from one or more of Mn, Zr, Zn, K, Cu, Mg, Ca, Fe, B, Pt, Ru, and Pb, preferably one or more of Mn, Zr, Zn, K, and B.

[0010] Another aspect of the present invention provides a method for preparing the cobalt-based Fischer-Tropsch synthesis catalyst described above, wherein the catalyst is prepared by one or a combination of two of the following methods: impregnation, deposition precipitation, kneading, and mechanical mixing.

[0011] Preferably, the step of preparing the catalyst by impregnation includes: The catalyst is obtained by impregnating titanium dioxide with a mixed aqueous solution containing a Co source, an auxiliary source and a N-containing reagent, followed by drying and calcination. The N-containing reagent is selected from one or more of ammonia, ammonium carbonate, monoethanolamine, urea, and N,N-dimethylformamide.

[0012] Preferably, the step of preparing the catalyst using a deposition-precipitation method includes: In a precipitation vessel containing titanium dioxide, a mixed aqueous solution containing a Co source and an auxiliary source is added, along with an N-containing alkaline solution, to carry out a precipitation reaction. The resulting precipitate is then washed, dried, and calcined to obtain the catalyst. The N-containing alkaline solution is selected from one or more aqueous solutions of ammonia, ammonium carbonate, monoethanolamine, urea, and N,N-dimethylformamide.

[0013] Preferably, the step of preparing the catalyst using the kneading method includes: Titanium dioxide was mixed with a Co source, an auxiliary source, and an aqueous solution containing a N reagent, followed by drying and calcination to obtain the catalyst. The N-containing reagent is selected from one or more of nitric acid, ammonia, ammonium carbonate, monoethanolamine, urea, and N,N-dimethylformamide.

[0014] Preferably, the step of preparing the catalyst by mechanical mixing includes: Titanium dioxide was mechanically ball-milled with a Co source and an auxiliary agent source, then impregnated with an aqueous solution containing a N reagent, followed by drying and calcination to obtain the catalyst. Preferably, the N-containing reagent is selected from one or more of nitric acid, ammonia, ammonium carbonate, monoethanolamine, urea, and N,N-dimethylformamide.

[0015] Preferably, the step of preparing the catalyst using the precipitation-kneading method includes: An aqueous solution containing a Co source and an auxiliary source is subjected to a precipitation reaction with an alkaline solution. The resulting precipitate is washed and dried, then mixed with titanium dioxide and an aqueous solution containing a N reagent. After drying and calcination, the catalyst is obtained. The alkaline solution is selected from one or more aqueous solutions of ammonium carbonate, sodium carbonate, potassium carbonate, urea, and sodium hydroxide. The N-containing reagent is selected from one or more of nitric acid, ammonia, ammonium carbonate, monoethanolamine, urea, and N,N-dimethylformamide.

[0016] Preferably, the Co source is selected from one or more of Co nitrates, acetates, hydroxides, carbonates, and hydrochlorides; The auxiliary agent source is selected from one or more of the nitrates, hydroxides, carbonates, hydrochlorides, and acids of the auxiliary agent element.

[0017] In another aspect, the present invention provides the application of the catalyst described above or the catalyst prepared by the method described above in the Fischer-Tropsch synthesis reaction.

[0018] The technical solution provided by this invention has the following beneficial effects: The catalyst provided by this invention is particularly suitable for use in Fischer-Tropsch synthesis reactions, exhibiting excellent catalytic performance and balancing superior long-term stability and reactivity. Attached Figure Description

[0019] Figure 1 The N1s XPS spectra of the catalysts obtained in Examples 1, 2 and 1 are shown.

[0020] Figure 2 The images show the Ti 2p XPS spectra of the catalysts obtained in Examples 1, 2, and 1. Detailed Implementation

[0021] To facilitate understanding of the present invention, the following description, in conjunction with embodiments, will further illustrate the invention. It should be understood that the following embodiments are merely for a better understanding of the invention and do not imply that the invention is limited to these embodiments.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The term "and / or" may be used herein to include any and all combinations of one or more of the associated listed items.

[0023] The present invention provides a cobalt-based Fischer-Tropsch synthesis catalyst rich in surface defect sites, the catalyst comprising a support, an active metal element Co, and an auxiliary element; The support is N-doped titanium dioxide, and the surface of the support contains Ti-ON and / or Ti-NO structures, and the atomic ratio of Ti to N is 8-40:1, such as 8:1, 9:1, 10:1, 15:1, 17:1, 20:1, 23:1, 25:1, 27:1, 30:1, 35:1, 40:1, etc., preferably 10-30:1.

[0024] The catalyst provided by this invention uses nitrogen-doped titanium dioxide as a support, and incorporates the active metal element Co and auxiliary elements. The support surface contains Ti-ON and / or Ti-NO structures, and the atomic ratio of Ti to N is 8-40:1, preferably 10-30:1. This catalyst exhibits excellent long-term stability and reactivity when applied in Fischer-Tropsch synthesis reactions.

[0025] Preferably, the mass ratio between the N-doped titanium dioxide and the active metal element Co is 2-4:1, for example 2:1, 3:1, or 4:1; Preferably, the atomic molar ratio of the active metal element Co to the auxiliary element is 5-50:1, such as 5:1, 10:1, 20:1, 30:1, 40:1, 50:1, etc. Preferably, the promoter element is selected from one or more of Mn, Zr, Zn, K, Cu, Mg, Ca, Fe, B, Pt, Ru, and Pb. More preferably, the promoter element is selected from one or more of Mn, Zr, Zn, K, and B, and the catalyst has better catalytic activity.

[0026] In the catalyst of the present invention, the atomic ratio of Ti to N is preferably 10-30:1. Under otherwise essentially the same conditions, the catalyst with this preferred atomic ratio has further improved reactivity and long-term stability in the Fischer-Tropsch synthesis reaction, higher CO conversion rate, and lower activity loss rate.

[0027] In a preferred embodiment, the atomic ratio of Ti to N in the catalyst is preferably 10-30:1, and the promoter element is selected from one or more of Mn, Zr, Zn, K, and B; this preferred catalyst has better catalytic performance and can achieve both higher CO conversion rate and lower activity loss rate.

[0028] Another aspect of the present invention provides a method for preparing the cobalt-based Fischer-Tropsch synthesis catalyst described above, wherein the catalyst is prepared by one or a combination of two of the following methods: impregnation, deposition precipitation, kneading, and mechanical mixing.

[0029] In some embodiments, the catalyst is prepared by impregnation, which can be carried out using existing impregnation processes in the art. Preferred preparation steps include: impregnating titanium dioxide with a mixed aqueous solution containing a Co source, an auxiliary agent source, and a nitrogen-containing reagent, followed by drying and calcination to obtain the catalyst; the nitrogen-containing reagent is selected from one or more of ammonia, ammonium carbonate, monoethanolamine, urea, and N,N-dimethylformamide. The drying temperature is, for example, 60-120°C, the calcination temperature is, for example, 350-600°C (e.g., 350, 400, 500, 600°C, etc.), and the calcination time is, for example, 2-6 hours. In some examples, in a mixed aqueous solution containing a Co source, an auxiliary source, and a N-containing reagent, the concentration of the Co source is, for example, 1-6 mol / L (e.g., 1, 2, 4, 6 mol / L, etc.), the concentration of the auxiliary source is, for example, 0.2-1 mol / L (e.g., 0.2, 0.5, 0.7, 1 mol / L, etc.), and the concentration of the N-containing reagent is, for example, 2-20 mol / L (e.g., 2, 4, 10, 15, 20 mol / L, etc.).

[0030] In some embodiments, the catalyst is prepared using a deposition-precipitation method, which can be carried out using existing deposition-precipitation processes in the art. Preferred preparation steps include: In a precipitation vessel containing titanium dioxide, a mixed aqueous solution containing a Co source and an auxiliary source is added, along with an N-containing alkaline solution (water as the solvent) to initiate a precipitation reaction. The resulting precipitate is washed, dried, and calcined to obtain the catalyst. The N-containing alkaline solution is selected from one or more aqueous solutions of ammonia, ammonium carbonate, monoethanolamine, urea, and N,N-dimethylformamide. The precipitation reaction is preferably carried out at a temperature of 20-60°C, and the pH is preferably controlled at 8±0.5. The drying temperature is, for example, 60-120°C, and the calcination temperature is, for example, 350-600°C (e.g., 350, 400, 500, 600°C, etc.), with a calcination time of, for example, 2-6 hours. In some examples, the concentration of the Co source in the mixed aqueous solution containing the Co source and the auxiliary source is, for example, 0.05-0.5 mol / L (e.g., 0.05, 0.1, 0.3, 0.5 mol / L, etc.), and the concentration of the auxiliary source is, for example, 0.001-0.01 mol / L (e.g., 0.001, 0.005, 0.01 mol / L, etc.). In some examples, the concentration of the N-based alkali solution is, for example, 0.1-1 mol / L (e.g., 0.1, 0.5, 0.7, 1 mol / L, etc.).

[0031] In some embodiments, the catalyst is prepared by a kneading method, which can be performed using existing kneading techniques in the art. A preferred preparation step includes: kneading titanium dioxide with a Co source, an auxiliary agent source, and an aqueous solution containing an N-containing reagent, followed by drying and calcination to obtain the catalyst; the N-containing reagent is selected from one or more of nitric acid, ammonia, ammonium carbonate, monoethanolamine, urea, and N,N-dimethylformamide, and the concentration of the aqueous solution containing the N-containing reagent is, for example, 20-40 wt% (e.g., 20, 30, 40 wt%). The drying temperature is, for example, 60-120°C, the calcination temperature is, for example, 350-600°C (e.g., 350, 400, 500, 600°C), and the calcination time is, for example, 2-6 hours.

[0032] In some embodiments, the catalyst is prepared by mechanical mixing, and the preferred preparation steps include: Titanium dioxide is mechanically ball-milled with a Co source and an additive source in the presence of grinding balls for a preferred time of 4-12 hours. Following this, the catalyst is impregnated with an aqueous solution containing a nitrogen-containing reagent, preferably selected from one or more of nitric acid, ammonia, ammonium carbonate, monoethanolamine, urea, and N,N-dimethylformamide, with a concentration of, for example, 2-20 mol / L. The catalyst is then dried and calcined to obtain the catalyst; the drying temperature is, for example, 60-120°C, and the calcination temperature is, for example, 350-600°C (e.g., 350, 400, 500, 600°C, etc.), for a calcination time of, for example, 2-6 hours.

[0033] In some embodiments, the catalyst is prepared using a precipitation-kneading method, and the preferred preparation steps include: A precipitation reaction is carried out by reacting an aqueous solution containing a Co source and an auxiliary source with an alkaline solution. The resulting precipitate is washed, dried, and then mixed with an aqueous solution containing titanium dioxide and a nitrogen-containing reagent. After drying and calcination, the catalyst is obtained. The alkaline solution is selected from one or more aqueous solutions of ammonia, ammonium carbonate, urea, sodium carbonate, and potassium carbonate, with a concentration of, for example, 0.1-1 mol / L (e.g., 0.1, 0.3, 0.5, 0.7, 1 mol / L). The nitrogen-containing reagent is selected from one or more of nitric acid, ammonia, ammonium carbonate, monoethanolamine, urea, and N,N-dimethylformamide. The precipitation reaction is preferably carried out at a temperature of 20-60°C, and the pH is preferably controlled at 8±0.5. The drying temperature is, for example, 60-120°C, and the calcination temperature is, for example, 350-600°C (e.g., 350, 400, 500, 600°C), with a calcination time of, for example, 2-6 hours. In the aqueous solution containing the Co source and the auxiliary agent source, the concentration of the Co source is, for example, 0.05-0.5 mol / L (e.g., 0.05, 0.1, 0.3, 0.5 mol / L, etc.), and the concentration of the auxiliary agent source is, for example, 0.001-0.01 mol / L (e.g., 0.001, 0.005, 0.01 mol / L, etc.); the concentration of the aqueous solution containing the N reagent is, for example, 20-40 wt% (e.g., 20, 30, 40 wt%, etc.).

[0034] In the method of the present invention, the Co source may be selected from one or more of Co nitrates, acetates, hydroxides, carbonates, and hydrochlorides; The auxiliary agent source may be selected from one or more of the nitrates, hydroxides, carbonates, hydrochlorides, and acids of the auxiliary agent element.

[0035] The present invention also provides the application of the catalyst described above or the catalyst prepared by the method described above in the Fischer-Tropsch synthesis reaction.

[0036] The present invention will be further illustrated by the following embodiments, but it should not be construed as the present invention being limited to these embodiments.

[0037] Where specific experimental steps or conditions are not specified in the examples, the corresponding conventional experimental steps or conditions in this technical field can be followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0038] Example 1 Take 800g of commercially available TiO2 powder, add 400g of Co(OH)2, 50g of Mn(NO3)2·4H2O and 100g of 25 wt% ammonia water, and mix thoroughly; dry the mixture at 120℃ for 12h, and then calcine at 350℃ for 4h to obtain nitrogen-doped Fischer-Tropsch synthesis catalyst.

[0039] XPS analysis showed that the catalyst had an atomic ratio of Ti to N of 22:1.

[0040] In this catalyst, the mass ratio between N-doped titanium dioxide and the metal element Co is 3.15:1, and the atomic molar ratio between the metal element Co and the auxiliary element Mn is 20:1.

[0041] Example 2 The same procedure was followed as in Example 1, except that the amount of ammonia was adjusted to 200g, and the atomic ratio of Ti to N in the final catalyst was 10:1.

[0042] Example 3 The same procedure was followed as in Example 1, except that the amount of ammonia was adjusted to 65g, and the atomic ratio of Ti to N in the final catalyst was 30:1.

[0043] Example 4 The same procedure was followed as in Example 1, except that the amount of ammonia was adjusted to 235g, and the atomic ratio of Ti to N in the final catalyst was 8:1.

[0044] Example 5 The same procedure was followed as in Example 1, except that the amount of ammonia was adjusted to 55g, and the atomic ratio of Ti to N in the final catalyst was 40:1.

[0045] Example 6 In a precipitation vessel containing 5g of commercially available TiO2 powder, a mixed aqueous solution containing 0.05mol / L Co(NO3)2·6H2O and 0.01mol / L Zn(NO3)2·6H2O, along with a 0.2mol / L urea aqueous solution, was added in a co-current flow to initiate a precipitation reaction. The temperature was controlled at 60℃, the pH at 8, and the reaction time was 2h. The resulting precipitate was washed with water, dried at 60℃ for 12h, and then calcined at 550℃ for 4h to obtain a nitrogen-doped Fischer-Tropsch synthesis catalyst.

[0046] In this catalyst, the atomic ratio of Ti to N is 32:1, the mass ratio between N-doped titanium dioxide and the metal element Co is 4:1, and the atomic molar ratio of the metal element Co and the auxiliary element Zn is 5:1.

[0047] Example 7 A precipitation reaction was carried out in a precipitation vessel by adding a mixed aqueous solution containing 0.1 mol / L Co(NO3)2·6H2O and 0.002 mol / L H3BO3, along with a 1 mol / L potassium carbonate aqueous solution, in a co-current flow. The pH was controlled at 8, the temperature at 30℃, and the reaction was carried out for 2 h. The resulting precipitate was washed with water and then dried at 80℃ for 12 h. Subsequently, 500 g of commercially available TiO2 powder and 100 g of a 25 wt% monoethanolamine aqueous solution were added and thoroughly mixed. The resulting mixture was dried at 120℃ for 12 h and then calcined at 450℃ for 2 h to obtain a nitrogen-doped Fischer-Tropsch synthesis catalyst.

[0048] In this catalyst, the atomic ratio of Ti to N is 21:1, the mass ratio between N-doped titanium dioxide and the metal element Co is 2:1, and the atomic molar ratio of the metal element Co to the auxiliary element B is 50:1.

[0049] Example 8 10 g of commercially available TiO2 powder, 5 g of Co(OH)2, 0.5 g of RuCl3, and grinding balls were placed together in a ball mill and mechanically ball-milled at 800 rpm with a cycle of 5 minutes of grinding followed by 5 minutes of rest, for a total milling time of 8 hours. After ball milling, the obtained powder was impregnated with a 2 mol / L aqueous solution of N,N-dimethylformamide, and then placed in a drying oven and dried at 120 °C for 12 h, followed by calcination at 550 °C for 4 h. This yielded a nitrogen-doped Fischer-Tropsch synthesis catalyst.

[0050] In this catalyst, the atomic ratio of Ti to N is 14:1, the mass ratio between N-doped titanium dioxide and the metal element Co is 3.15:1, and the atomic molar ratio of the metal element Co and the auxiliary element Ru is 22:1.

[0051] Example 9 Take 10 g of commercially available TiO2 powder and impregnate it with a mixed aqueous solution containing 4 mol / L Co(NO3)2·6H2O, 0.5 mol / L Mg(NO3)2, and 3 mol / L monoethanolamine. Then place it in a drying oven and dry at 100 °C for 6 h, followed by calcination at 400 °C for 2 h. Nitrogen-doped Fischer-Tropsch synthesis catalyst is obtained.

[0052] In this catalyst, the atomic ratio of Ti to N is 18:1, the mass ratio between N-doped titanium dioxide and the metal element Co is 4:1, and the atomic molar ratio of the metal element Co and the auxiliary element Mg is 8:1.

[0053] The N1s XPS spectra of the catalysts prepared in Examples 1 and 2 are shown below. Figure 1 ,from Figure 1 As can be seen, the catalyst exhibits a distinct Ti-ON peak at 400.1 eV, indicating that the O element in the TiO2 support has been partially replaced by N element, forming nitrogen-doped titanium dioxide. The Ti 2p XPS spectra of the catalysts in Examples 1 and 2 are shown below. Figure 2 ,from Figure 2 It is evident that the catalyst peaks all shift towards lower binding energies, indicating the presence of defects on the support surface. The detection results of the catalysts prepared in Examples 3-9 are basically consistent with those in Examples 1 and 2, and will not be repeated here.

[0054] Comparative Example 1 The procedure is the same as in Example 1, except that the ammonia is replaced with the same amount of water. The specific steps are as follows: Take 800g of commercially available TiO2 powder, add 400g of Co(OH)2, 50g of Mn(NO3)2·4H2O and 100g of water, and mix thoroughly. Dry the resulting mixture at 120℃ for 12h, then calcine it at 350℃ for 4h to obtain a conventional Fischer-Tropsch synthesis catalyst. The N1s XPS spectrum of this catalyst is shown below. Figure 1 .from Figure 1 It is evident that the catalyst has no obvious peaks, indicating that there is no nitrogen element in the TiO2 support.

[0055] Comparative Example 2 The same procedure was followed as in Example 1, except that the amount of ammonia was adjusted to 800 g, and the atomic ratio of Ti to N in the resulting catalyst was 7.0:1.

[0056] Comparative Example 3 The same procedure was followed as in Example 1, except that the amount of ammonia was adjusted to 10g, and the atomic ratio of Ti to N in the resulting catalyst was 45:1.

[0057] Performance testing of catalysts prepared in the examples and comparative examples: The catalyst was loaded into a 10 mL fixed-bed reactor at a loading rate of 0.5 g. It was then incubated at 300 °C under a H2 atmosphere. The catalyst was reduced at 400℃ for 12 hours. After the reduction was completed, the temperature was lowered to 120℃, and the reaction gas was switched to H2 / CO = 2 (volume ratio). The catalyst performance was evaluated after the reaction temperature and pressure were increased.

[0058] Catalyst performance evaluation conditions: 230℃, 1.5 MPa, space velocity of 5000 ml / (g) cat ·h).

[0059] The evaluation results are shown in Table 1 below: Table 1

[0060] In Table 1, "Activeness Loss Rate" refers to the decrease in CO conversion rate at 500 hours relative to CO conversion rate at 5 hours.

[0061] As can be seen from the above experimental results, the catalyst provided in this embodiment of the invention has a higher CO conversion rate and a lower activity loss rate compared with the comparative example, and has better reaction activity and long-term stability.

[0062] A comparison of Examples 1-3 and Examples 4-5 shows that, under essentially the same conditions, a Ti to N atomic ratio of 10-30:1 in the catalyst exhibits superior catalytic performance compared to lower or higher atomic ratios, resulting in further improved CO conversion and further reduced activity loss.

[0063] It is readily understood that the above embodiments are merely illustrative examples for clear explanation and do not imply that the invention is limited thereto. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A cobalt-based Fischer-Tropsch synthesis catalyst rich in surface defect sites, characterized in that, The catalyst comprises a support, an active metal element Co, and auxiliary elements; The support is N-doped titanium dioxide, and the surface of the support contains Ti-ON and / or Ti-NO structures; the atomic ratio of Ti to N is 8-40:1, preferably 10-30:

1.

2. The cobalt-based Fischer-Tropsch synthesis catalyst according to claim 1, characterized in that, The mass ratio between the N-doped titanium dioxide and the active metal element Co is 2-4:1; And / or, the atomic molar ratio of the active metal element Co to the auxiliary element is 5-50:1; And / or, the auxiliary element is selected from one or more of Mn, Zr, Zn, K, Cu, Mg, Ca, Fe, B, Pt, Ru, and Pb, preferably one or more of Mn, Zr, Zn, K, and B.

3. The method for preparing the cobalt-based Fischer-Tropsch synthesis catalyst according to claim 1 or 2, characterized in that, The catalyst is prepared by one or a combination of two of the following methods: impregnation, deposition and precipitation, kneading, and mechanical mixing.

4. The preparation method according to claim 3, characterized in that, The steps for preparing the catalyst using the impregnation method include: The catalyst is obtained by impregnating titanium dioxide with a mixed aqueous solution containing a Co source, an auxiliary source and a N-containing reagent, followed by drying and calcination. The N-containing reagent is selected from one or more of ammonia, ammonium carbonate, monoethanolamine, urea, and N,N-dimethylformamide.

5. The preparation method according to claim 3, characterized in that, The steps for preparing the catalyst using the deposition-precipitation method include: In a precipitation vessel containing titanium dioxide, a mixed aqueous solution containing a Co source and an auxiliary source is added, along with an N-containing alkaline solution, to carry out a precipitation reaction. The resulting precipitate is then washed, dried, and calcined to obtain the catalyst. The N-containing alkaline solution is selected from one or more aqueous solutions of ammonia, ammonium carbonate, monoethanolamine, urea, and N,N-dimethylformamide.

6. The preparation method according to claim 3, characterized in that, The steps for preparing the catalyst using the kneading method include: Titanium dioxide was mixed with a Co source, an auxiliary source, and an aqueous solution containing a N reagent, followed by drying and calcination to obtain the catalyst. The N-containing reagent is selected from one or more of nitric acid, ammonia, ammonium carbonate, monoethanolamine, urea, and N,N-dimethylformamide.

7. The preparation method according to claim 3, characterized in that, The steps for preparing the catalyst by mechanical mixing include: Titanium dioxide was mechanically ball-milled with a Co source and an auxiliary agent source, then impregnated with an aqueous solution containing a N reagent, followed by drying and calcination to obtain the catalyst. Preferably, the N-containing reagent is selected from one or more of nitric acid, ammonia, ammonium carbonate, monoethanolamine, urea, and N,N-dimethylformamide.

8. The preparation method according to claim 3, characterized in that, The steps for preparing the catalyst using the precipitation-kneading method include: An aqueous solution containing a Co source and an auxiliary source is subjected to a precipitation reaction with an alkaline solution. The resulting precipitate is washed and dried, then mixed with titanium dioxide and an aqueous solution containing a N reagent. After drying and calcination, the catalyst is obtained. The alkaline solution is selected from one or more aqueous solutions of ammonium carbonate, sodium carbonate, potassium carbonate, urea, and sodium hydroxide. The N-containing reagent is selected from one or more of nitric acid, ammonia, ammonium carbonate, monoethanolamine, urea, and N,N-dimethylformamide.

9. The preparation method according to any one of claims 4-8, characterized in that: The Co source is selected from one or more of the following: nitrate, acetate, hydroxide, carbonate, and hydrochloride of Co. The auxiliary agent source is selected from one or more of the nitrates, hydroxides, carbonates, hydrochlorides, and acids of the auxiliary agent element.

10. The use of the catalyst according to any one of claims 1-2 or the catalyst prepared by any one of claims 3-9 in the Fischer-Tropsch synthesis reaction.

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