CN109718783B

CN109718783B - A kind of stable ultrafine FT synthesis catalyst and its preparation method and application and Fischer-Tropsch synthesis method

Info

Publication number: CN109718783B
Application number: CN201711023990.0A
Authority: CN
Inventors: 吴玉; 晋超; 李学锋; 孙霞; 阎振楠; 侯朝鹏; 夏国富; 李明丰
Original assignee: Sinopec Research Institute of Petroleum Processing; China Petroleum and Chemical Corp
Current assignee: Sinopec Research Institute of Petroleum Processing; China Petroleum and Chemical Corp
Priority date: 2017-10-27
Filing date: 2017-10-27
Publication date: 2022-03-11
Anticipated expiration: 2037-10-27
Also published as: CN109718783A

Abstract

A catalyst, its preparation method and application, and a Fischer-Tropsch synthesis method. The catalyst is a core-shell nanostructure in which Co and stabilizers form a shell and oxides and/or hydroxides of Group IVB metal elements form a core. The catalyst provided by the invention greatly improves the utilization rate of cobalt, the stability and catalytic performance of the catalyst, and can be applied to reactors such as microchannels and slurry beds.

Description

Stable superfine FT synthesis catalyst, preparation method and application thereof, and Fischer-Tropsch synthesis method

Technical Field

The invention relates to a stable superfine Fischer-Tropsch synthesis catalyst, a preparation method and application thereof, and a Fischer-Tropsch synthesis method.

Background

Along with the increasing scarcity of global petroleum resources, people pay more and more attention to environmental protection, and the preparation of clean fuels and chemicals by using coal, natural gas and the like as raw materials is paid more and more attention by people. The Fischer-Tropsch synthesis technology is one of the key technologies for clean utilization of the coal and the natural gas.

The main products of the Fischer-Tropsch synthesis reaction for converting synthesis gas into hydrocarbons on a catalyst comprise alkane and olefin, and high-quality liquid fuel and high value-added chemicals can be obtained by deep processing of the products.

At present, the supported cobalt-based catalyst is a Fischer-Tropsch synthesis catalyst with industrial application value. The common supported cobalt-based catalyst is prepared by an impregnation method, the particle size of the active component Co is large, the distribution is wide, the utilization rate of the cobalt is low, and the inactivation phenomenon is obvious. In addition, in order to sufficiently reduce cobalt oxide to active metallic cobalt, a noble metal reduction aid is generally used, which results in a significant increase in catalyst cost. Therefore, how to improve the utilization rate of cobalt, reduce the utilization rate of noble metals, and improve the stability and catalytic performance of the catalyst has been the difficulty and direction of cobalt-based catalyst development.

Kouyuan et al (catalysis journal, 2013, No. 10, 1914-1925) disclose a method for aqueous phase synthesis of oil by Co nanoparticles, which comprises the step of adding CoCl₂And SB3-12 as a protective agent were dissolved in THF, then the reducing agent LiBEt was slowly injected with stirring₃H、NaBH₄And (3) rapidly changing the solution and the mixed solution from blue to black to indicate that Co is reduced, quenching the reaction by using ethanol after reacting for 10 minutes, then sequentially washing the reaction by using ethanol and water twice, and dispersing the obtained nano particles in the water to obtain the standby catalyst. The catalyst obtained by the method has high low-temperature activity, but has poor particle stability.

US20140039037 discloses a low-temperature (100-200 ℃) Fischer-Tropsch synthesis method by taking Ru, Fe and Co colloids with stable polymers as catalysts. The catalyst contains transition metal nanoparticles having a particle size of 1-10nm, preferably 1.4-2.2nm, and a polymer stabilizer capable of stabilizing the transition metal nanoparticles, the transition metal being selected from one or more of Ru, Co, Ni, Fe, and Rh. The preparation method of the catalyst comprises the steps of dispersing a transition metal salt and a polymer stabilizer in a liquid medium, and then reducing the transition metal salt by hydrogen at the temperature of 100-120 ℃. The stability of the colloidal catalyst under practical fischer-tropsch synthesis reaction conditions presents several problems.

Disclosure of Invention

The invention aims to solve the problem that the Fischer-Tropsch synthesis catalyst in the prior art is difficult to consider both catalytic activity and stability, and provides a novel Fischer-Tropsch synthesis catalyst which has high catalytic activity, selectivity and stability.

In a first aspect, the present invention provides a catalyst which is a core-shell type nanostructure in which Co and a stabilizer form a shell and an oxide and/or hydroxide of a group IVB metal element forms a core.

In a second aspect, the present invention provides a method for preparing a catalyst, comprising the steps of:

(1) preparing nano colloid of oxide and/or hydroxide of IVB group metal element;

(2) attaching Co to the surface of the nano colloid obtained in the step (1) to form a core-shell structure taking the nano colloid as a core and Co as a shell;

(3) and (3) stabilizing the core-shell structure obtained in the step (2).

The invention also provides the catalyst prepared by the method and application of the catalyst in Fischer-Tropsch synthesis reaction.

In yet another aspect, the invention provides a Fischer-Tropsch synthesis process comprising reacting CO and H in the presence of a catalyst under Fischer-Tropsch synthesis reaction conditions₂The catalyst is characterized in that the catalyst is the catalyst.

Compared with the prior art, the catalyst provided by the invention greatly improves the utilization rate of cobalt, the stability and the catalytic performance of the catalyst, and can be suitable for various reactors such as microchannels, slurry beds and the like. For example, the catalyst of example 1 of the present invention had a relative activity of 1.53 at 1 day of reaction, a methane selectivity of 6.0, a C5+ selectivity of 88.2%, and a relative activity of 1.39 after 10 days of reaction, whereas comparative example 1 of the prior art had an activity of 1 at the same Co content and under otherwise identical conditions, a methane selectivity of 8.1, and a C5+ selectivity of only 84.6%, and a relative activity of only 0.68 after 10 days of reaction. Therefore, compared with the prior art, the activity of the invention is improved, the selectivity of C5+ is improved, and the activity stability is obviously higher.

Drawings

FIG. 1 is a XPS-Co2p spectrum of a catalyst prepared in example 3 of the present invention;

FIG. 2 is a TEM of a colloid of titanium oxide obtained in example 3 of the present invention;

FIG. 3 is a TEM image of the catalyst colloid prepared in example 3 of the present invention.

Detailed Description

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

Preferably, the Co is present in an amount of 20 to 80 wt%, preferably 25 to 65 wt%, such as 21 wt%, 22 wt%, 23.2 wt%, 25 wt%, 30 wt%, 33.3 wt%, 39.5 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, and the total amount of stabilizer and group IVB metal element oxide and hydroxide is 20 to 80 wt%, preferably 35 to 75 wt%, such as 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, based on the total weight of the catalyst.

In the present invention, the total amount of the oxide and the hydroxide of the group IVB metal element means the total content of the oxide and the hydroxide of the group IVB metal element, and when the oxide or the hydroxide of the group IVB metal element is not contained, the content of the substance is 0.

Preferably, the catalyst has a particle size of 5-50nm, preferably 8-45nm, more preferably 10-35nm, such as 10, 12, 18, 20, 25, 26, 27, 28 nm. By controlling the particle size of the catalyst within the range, the catalytic activity, selectivity, stability and the utilization rate of the metal cobalt can be better provided, and the application range is wide in the using process.

It is further preferred that the average particle size of the oxide or hydroxide core of the group IVB metal element is from 1 to 40nm, preferably from 3 to 40nm, and more preferably from 3.5 to 30nm, such as 4, 4.5, 5, 8, 10, 15, 17, 20 nm. By controlling the particle size of the catalyst core within the above range, the structure and performance of the final catalyst can be ensured.

In the present invention, the particle size refers to the size of the particles. For spherical particles the particle size is expressed in diameter and cubic particles the particle size is expressed in side length. For an irregular particle, the equivalent diameter of the particle is taken as the diameter of a sphere that behaves the same as the particle. The particle size of the oxide or hydroxide core of the IVB group metal element refers to the particle size of the oxide or hydroxide colloid of the IVB group metal element, and is obtained by a Transmission Electron Microscope (TEM), specifically, a FEI FEI TECNAI G2F20S-TWIN type transmission electron microscope is adopted, the voltage is 200kV, 10-15 photos are taken by each sample with unequal resolution of 10-100nm, the particle size is obtained by measuring the pictures by using Nano Measure software, and the distribution calculation is carried out on the manual statistical results of the samples for more than 150 times. The core-shell structure is characterized by a Transmission Electron Microscope (TEM) and X-ray photoelectron spectroscopy (XPS). The measuring instrument for the X-ray photoelectron spectroscopy is an ESCALB 250 type instrument of Thermo Scientific company, and the measuring conditions are as follows: an excitation light source is a monochromator Al K alpha X ray of 150kW, and the combination energy is corrected by a peak (284.8eV) of C1 s; the measuring instrument for the X-ray fluorescence spectrum is a 3271 instrument of Nippon science and Motor industry Co., Ltd, and the measuring conditions are as follows: and (3) patterning the sample, wherein the rhodium target is arranged, the laser voltage is 50kV, and the laser current is 50 mA. And judging the structural characteristics of the sample through the change of the surface atomic ratio.

According to the catalyst provided by the invention, preferably, the IVB group metal element is one or more of Ti, Zr and Hf.

According to the invention, the catalyst also contains a stabilizer which forms a shell of core-shell structure together with Co. The stabilizer is preferably one or more of Zr, W, Ta, La, Ce and oxides and/or hydroxides thereof. In the invention, the stabilizer is used for stabilizing and modifying the surface of metal Co and the interface of Co and a carrier.

Preferably, the molar ratio of stabilizer to Co, calculated as metal element, is from 1:2 to 500, preferably from 1:3 to 300, more preferably from 1:4 to 200, even more preferably from 1:4 to 30, such as 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:15, 1:18, 1:20, 1:25, 1: 30.

when the catalyst contains the oxide and/or hydroxide of the IVB group metal element, cobalt and the stabilizer, the structural relationship of the three is that the oxide and/or hydroxide of the IVB group metal element is at the innermost side to form a core with a core-shell structure, the cobalt is coated on the surface of the oxide and/or hydroxide of the IVB group metal element, and the stabilizer is further coated on the surface of the oxide and/or hydroxide of the IVB group metal element.

In the invention, the content of each metal component in the catalyst is measured by an ICP method.

According to the catalyst provided by the invention, the active metal component is attached to the surface of the oxide or hydroxide of the IVB group metal element to form a core-shell structure, so that the activity and the catalytic stability of the catalyst can be greatly improved. By further adding the stabilizer on the surface of the core-shell structure, the stability and the regulation and control selectivity can be further improved.

According to the method, the nano Co particle layer is formed on the surface of the nano colloid in situ, so that the Co catalyst with the core-shell structure is obtained.

According to the present invention, the nanocolloid of the oxide and/or hydroxide of the group IVB metal element can be prepared by a conventional method. Examples of the method include precipitation, hydrothermal method and solvothermal method. The group IVB metal precursor used to prepare the nanocolloid of the oxide and/or hydroxide of the group IVB metal element may be an inorganic or organic salt thereof, such as a nitrate, a chloride, or the like. For example, the zirconium hydroxide nanocolloid may be prepared by any one of the following methods: (1) mixing a zirconium oxychloride solution with urea and/or ammonia water, reacting at 0-90 ℃ for 0.5-10 hours, aging at 20-90 ℃ for 5-10 hours, filtering and washing to obtain a nano colloid, wherein the concentration of zirconium oxychloride can be 0.01-0.5 mol/L, and the dosage of zirconium oxychloride and urea and/or ammonia water is based on the maintenance of the pH of a reaction system at 8-11; (2) mixing a titanium tetrachloride solution with urea and/or ammonia water, reacting at-10 ℃ to 10 ℃ for 4-10 hours, aging at 0-40 ℃ for 5-10 hours, filtering and washing to obtain the nano colloid, wherein the concentration of the titanium tetrachloride solution is preferably 0.05-0.5 mol/L, the use amount of the urea and the ammonia water is based on the maintenance of the pH of a reaction system at 9-11, and the concentration of the ammonia water can be 0.5-2 wt%. Aging was performed by standing.

The titanium oxide colloid can be prepared by the following method: slowly adding titanium tetrachloride into acetone at the temperature of between 10 ℃ below zero and 10 ℃, then carrying out solvothermal reaction for 8 to 20 hours at the temperature of between 80 and 120 ℃, and then filtering and washing to obtain the nano colloid.

Preferably, the average particle size of the nanocolloid obtained in step (1) is 1 to 50nm, preferably 3 to 45nm, and more preferably 3.5 to 30nm such as 4, 4.5, 5, 8, 10, 15, 17, 20 nm.

According to the catalyst provided by the invention, the synthesis method for in-situ synthesis of the nano cobalt is not limited. In the presence of IVB group metal element oxide or hydroxide colloid, the cobalt oxide can be prepared by adopting a controlled reduction method, namely, in the presence of a protective agent, cobalt salt is reduced by using a reducing agent to obtain the cobalt oxide; hydrothermal or solvothermal methods may also be employed.

According to a preferred embodiment of the present invention, step (2) is achieved by: under the protection of inert gas, the nano colloid and the protective agent are dispersed in Co salt solution and then contacted with a reducing agent.

The inert gas may be nitrogen gas and a gas of group zero element of the periodic table.

In the invention, the protective agent can be various polymers, amines, phosphines and surfactants, and is preferably one or more of polyvinylpyrrolidone, polyethylene glycol, linoleic acid, sodium oleate, oleylamine, trihydroxymethyl phosphine, trimethyl hexadecyl ammonium bromide, tetraoctyl ammonium bromide, polyether and polymethoxy aniline. Wherein the polyvinylpyrrolidone is preferably PVP-30 k. The polyethylene glycol is preferably PEG4000 or PEG 6000. The methoxy groups in the polymethoxyaniline may be in one or more of the ortho, meta, or para positions.

The amount of the protective agent is based on the amount of the stable dispersion colloid particles, and preferably, the ratio of the nano colloid: a protective agent: the weight ratio of the Co salt is 0.2-5: 2-200: 1, preferably 0.5 to 3: 5-20: 1, wherein the amount of the Co salt is calculated by Co element. The Co salt may be an inorganic salt and/or carboxylate of cobalt, for example, may be one or more of cobalt acetate, cobalt nitrate, cobalt chloride and hydrates thereof such as cobalt chloride hexahydrate, cobalt acetate tetrahydrate.

The reducing agent can be various substances capable of reducing Co salt into Co simple substance, and can be one or more of sodium borohydride, potassium borohydride, organic amine borohydride and hydrazine hydrate. The organic ammonium borohydride is, for example, one or more of tetrabutylammonium borohydride, tetramethylammonium borohydride and tetraethylammonium borohydride.

The dosage of the reducing agent is based on that Co element in the Co salt is fully reduced into Co simple substance.

The conditions for the reduction reaction are determined by the kind of the reducing agent, and are known to those skilled in the art, and the present invention is not described herein.

The nano-colloid of the oxide or hydroxide of the group IVB metal element may be dispersed in a liquid medium such as water or an organic solvent, for example, one or more of ethanol, propanol, ethylene glycol, and glycerol, and preferably, the liquid medium is one or more of water, ethanol, and ethylene glycol.

The amount of the liquid medium is 10-1000ml, preferably 100-500ml, relative to 1g of the nano-colloid.

According to a preferred embodiment of the present invention, the method further comprises stabilizing the core-shell structure product obtained in step (2), wherein the stabilizing treatment comprises dispersing the core-shell structure product in a liquid medium, and contacting the core-shell structure product with a soluble salt of a stabilizer and a non-metallic alkaline substance under stabilizing conditions.

According to this embodiment, a colloid of nano-oxide or hydroxide of group IVB metal element is prepared, and then nano-cobalt is synthesized in situ outside the colloid to form a core-shell type nanostructure with cobalt as the shell and oxide or hydroxide of group IVB metal element as the core, and finally stabilization is performed.

The stabilization reaction is preferably carried out under a reducing atmosphere containing 5-60% by volume of hydrogen and/or CO, wherein the concentration of hydrogen and/or CO may be any concentration in the range of 5% to 60% by volume, such as about 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50% by volume. The rest of the reducing atmosphere is inert gas such as nitrogen.

The stabilization conditions may include a temperature of from 0 to 400 deg.C, preferably from 0 deg.C to 350 deg.C, more preferably from room temperature to 300 deg.C, still more preferably from 150 deg.C to 250 deg.C, a pressure of from 0.1 to 4MPa, preferably from 0.1 to 3.5MPa, more preferably from 1.5 to 3MPa, and a time of from 0.01 to 144 hours, preferably from 0.01 to 96 hours, more preferably from 20 to 50 hours.

The stabilizer is preferably one or more of Zr, W, Ta, La, Ce and oxides and/or hydroxides thereof.

The non-metallic alkaline substance may be, for example, one or more of urea, ammonia, and organic amine. In the stabilization reaction, the non-metallic basic substance acts to precipitate the stabilizer onto the surface of the catalyst.

Preferably, the molar ratio of the soluble salt of the stabilizer to the core-shell structure product is 1:2 to 500, preferably 1:3 to 300, more preferably 1:4 to 200, the core-shell structure product: the weight ratio of the non-metallic alkaline substances is 1: 1-20, the core-shell structure product is calculated by Co element, and the soluble salt of the stabilizer is calculated by metal element.

The liquid medium for the stabilization reaction can be various liquid substances which do not dissolve the nano core-shell structure but can disperse the nano core-shell structure, and can be one or more of ethanol, propanol, ethylene glycol and glycerol, for example.

The amount of liquid medium used for the stabilization reaction may be between 10 and 1000ml per gram of the nano core-shell structure.

In the present invention, the substance of the stabilizing treatment is to wash or leave the product obtained in step (2) under the above-mentioned atmosphere and conditions without washing. The stabilization treatment is preferably carried out under gas agitation.

According to a preferred embodiment of the present invention, the method further comprises washing the core-shell structure product obtained in step (2) so that the content of impurities of the metal elements other than cobalt and the group IVB metal elements is not more than 100 ppm. Rinsing or rinsing can be carried out directly using water or an organic solvent. The organic solvent may be, for example, one or more of ethanol, propanol, ethylene glycol, glycerol.

Wherein the operation and conditions of the fischer-tropsch synthesis reaction may be carried out with reference to the prior art. Preferably, the Fischer-Tropsch synthesis reaction conditions comprise a temperature of 160-300 ℃, preferably 190-280 ℃, a pressure of 1-8MPa, preferably 1-5MPa, a molar ratio of hydrogen to carbon monoxide of 0.4-2.5, preferably 1-2.5, and a gas volume space velocity of 200-40000h^-1Preferably 500-30000h^-1。

In the present invention, the pressure is a gauge pressure unless otherwise specified.

The present invention will be described in detail below by way of examples. In the following examples, the average particle size of the Nano-cobalt in the Nano-colloids and catalysts is obtained by Transmission Electron Microscopy (TEM), specifically, FEI FEI TECNAI G2F20S-TWIN transmission electron microscopy is adopted, the voltage is 200kV, 10-15 photographs are taken at different resolutions of 10-100nm for each sample, Nano Measure software is used to Measure the photographs, and the average particle size is obtained by performing distribution calculation on the manual statistics results of the samples for more than 150 times. The composition of the catalyst was measured using the ICP method. The measuring instrument for the X-ray photoelectron spectroscopy is an ESCALB 250 type instrument of Thermo Scientific company, and the measuring conditions are as follows: an excitation light source is a monochromator Al K alpha X ray of 150kW, and the combination energy is corrected by a peak (284.8eV) of C1 s; the measuring instrument for the X-ray fluorescence spectrum is a 3271 instrument of Nippon science and Motor industry Co., Ltd, and the measuring conditions are as follows: and (3) patterning the sample, wherein the rhodium target is arranged, the laser voltage is 50kV, and the laser current is 50 mA. And judging the structural characteristics of the sample through the change of the surface atomic ratio.

Example 1

(1) Preparation of zirconium hydroxide colloid

Mixing 268mL of zirconium oxychloride aqueous solution with the concentration of 0.05mol/L and 3.84g of urea, heating to 85 ℃ for reaction for 1h, cooling to 30 ℃, aging for 8h, performing centrifugal filtration, washing for 3 times by using deionized water until no precipitate is generated when the filtrate is detected by using a silver nitrate solution. TEM showed an average particle size of 15nm for the zirconium hydroxide colloid.

(2)Co/Zr(OH)₄Preparation of core-shell structures

Under the protection of inert gas, the zirconium hydroxide colloid is dispersed in 350ml of distilled water in a three-mouth bottle, then 30.8g of PVP-30k (national drug group, analytical purity) and 6.69g of cobalt chloride hexahydrate (carbofuran, analytical purity) are added, the mixture is kept for 15 minutes at normal temperature, after the solid is slowly dissolved, 80g of aqueous solution containing 5.8g of potassium borohydride (Beijing reagent, analytical purity) is rapidly injected into the three-mouth bottle by using an injector, and the reaction is continued for 15 minutes under the condition of normal-temperature stirring.

(3) Washing machine

After the reaction, the reaction solution was transferred to a centrifuge tube for high-speed centrifugation (1000 rpm), and then the solid was subjected to centrifugation-ultrasonic washing 5 times with distilled water in an amount of 400mL each time. To obtain the nano-particles.

(4) Stabilization treatment

Dispersing the nanoparticles in 500mL of absolute ethanol, adding 2.41g of zirconium nitrate pentahydrate and 1.2g of urea, 50% H at 180 DEG C₂Under a pressure of 2MPa in nitrogen for 40h, and the molar ratio of the stabilizing agent to the cobalt is 1/5 calculated by the metal element. The catalyst obtained is designated C1 and its composition is shown in Table 1.

Example 2

(1) Titanium hydroxide colloid

623mL of TiCl with the concentration of 0.1mol/L under the protection of ice-water bath₄Precipitating the solution with 1.0 wt% ammonia water solution, maintaining pH at 9-11, aging for 8 hr, centrifuging, filtering, and washing for 3 times until no precipitate is formed in the filtrate detected with silver nitrate solution. TEM showed the average particle size of the titanium hydroxide colloid to be 17 nm.

(2)Co/Ti(OH)₄Core-shell structure

Under the protection of inert gas, the titanium hydroxide colloid is dispersed in 410ml of distilled water, 30.8g of protective agent PVP-30k (national drug group, analytical purity) and 7.0g of cobalt acetate tetrahydrate (carbofuran, analytical purity), the mixture is kept for 15 minutes at normal temperature, after the solid is slowly dissolved, 80g of aqueous solution containing 5.6g of sodium borohydride (Beijing reagent, analytical purity) is quickly injected into a three-mouth bottle by using an injector, and the mixture is continuously reacted for 15 minutes under the condition of normal-temperature stirring.

(3) Washing machine

After the reaction is finished, the reaction solution is transferred to a centrifuge tube for high-speed centrifugal separation, and then the sample is subjected to centrifugal-ultrasonic washing 6 times with distilled water, wherein the dosage is 500mL each time.

(4) Stabilization treatment

The nanoparticles were dispersed in 500mL of ethanol and 1.22g of cerous nitrate hexahydrate and 0.67g of urea were added at 200 ℃ with 10 vol.% H₂Under the pressure of 2.5MPa in nitrogen for 24 hours, and the molar ratio of the stabilizing agent to the cobalt is 1/10. The catalyst was designated C2 and the composition is given in Table 1.

Example 3

(1) Titanium oxide colloid

Under the protection of an ice-water bath, 7.24g of TiCl₄Slowly dropwise adding the mixture into 750mL of acetone solution, carrying out solvothermal reaction for 12h at 100 ℃, and washing the separated sample with deionized water for 3 times, 400mL each time. So that no precipitate is formed when the filtrate is tested with silver nitrate solution. TEM (as shown in FIG. 2) showed a titania colloid average particle size of 4.5 nm.

(2)Co/TiO₂Core-shell structure

Under the protection of inert gas, the titanium oxide colloid is dispersed in 120mL of absolute ethyl alcohol, 8g of sodium oleate and 15mL of linoleic acid are added simultaneously, 7.0g of cobalt acetate tetrahydrate (carbofuran, analytically pure) and 14.4g of tetrabutyl borohydride amine are added, and the solvent thermal reaction is carried out for 8 hours at the temperature of 120 ℃.

(3) Washing machine

(4) Stabilization treatment

Dispersing the nanoparticles in 400mL of water-ethanol-ethylene glycol mixed solution (volume ratio 50:40:10), adding 0.308g of ammonium metatungstate and 0.5g of urea, and adding 10 vol% of H at 220 DEG C₂Under a pressure of 2.5MPa in nitrogenAnd the molar ratio of the stabilizer to the cobalt is 1/20 after 24 hours. The catalyst was designated as C3. The TEM of the resulting product is shown in FIG. 3, and the composition of the catalyst is shown in Table 1 below. The X-ray photoelectron spectrum of the catalyst is shown in FIG. 1. As can be seen from the XPS-Co2P diagram of FIG. 1 and the Transmission Electron Microscope (TEM) and X-ray photoelectron spectroscopy (XPS) diagrams of FIGS. 2-3, the catalyst has a core-shell structure.

Example 4

(1) Zirconium hydroxide colloid

The zirconium hydroxide colloid was prepared in the same manner as in example 1.

(2)Co/Zr(OH)₄Core-shell structure

Co/Zr(OH)₄The core-shell structure was prepared as in example 1.

(3) Washing machine

The washing method was the same as in example 1.

(4) Stabilization treatment

The procedure is as in step (4) of example 1, except that the above nanoparticles are dispersed in 500mL of anhydrous ethanol, followed by 50 vol% H at 180 ℃ without adding 2.41g of zirconium nitrate pentahydrate and 1.2g of urea₂Under 2MPa pressure in nitrogen for 40h, and the molar ratio of the stabilizing agent to the cobalt is 1/5. The catalyst obtained is designated C4 and its composition is shown in Table 1.

Example 5

A supported catalyst was prepared by following the procedure of example 1 except that the temperature for reductive activation in step (2) was 500 ℃ to obtain catalyst C5 having the composition shown in Table 1.

Example 6

A supported catalyst was prepared by following the procedure of example 1 except that the temperature of the stabilization treatment in step (4) was 500 ℃ to obtain catalyst C6 having the composition shown in Table 1.

Comparative example 1

(1) Catalyst preparation

6.69g of cobalt chloride hexahydrate (carbofuran, analytical pure) and 4.32g of zirconium oxychloride octahydrate (Beijing reagent, analytical pure) are dissolved in 300mL of deionized water, 7.6g of urea is added, the temperature is increased to 85 ℃, the reaction is carried out for 1h, and the mixture is cooled to 40 ℃ and aged for 8 h. The solution was centrifuged and washed 3 times until no precipitate was formed when the filtrate was checked with silver nitrate solution.

(2) Catalyst activation

The powder is dried for 4h at 120 ℃, reduced for 4h at 400 ℃ under normal pressure in pure hydrogen atmosphere to complete catalyst activation, the obtained catalyst is marked as R1, and the composition is shown in Table 1. TEM showed the average particle size of the catalyst to be 32 nm.

Comparative example 2

(1) Preparation of colloidal catalyst

Under the protection of inert gas, 30.8g of protective agent PVP-30k (national drug group, analytically pure) and 6.69g of cobalt chloride hexahydrate (carbofuran, analytically pure) are added into 350ml of distilled water, the mixture is kept for 15 minutes at normal temperature until the solid is slowly dissolved, 80g of aqueous solution containing 5.8g of potassium borohydride (Beijing reagent, analytically pure) is rapidly injected into a three-mouth bottle by using an injector, and the reaction is continued for 15 minutes under the condition of normal temperature stirring, so that the colloidal catalyst is obtained. TEM showed the average particle size of the colloidal catalyst to be 10 nm.

(2) Washing with colloidal catalyst

After the reaction is finished, the reaction solution is transferred to a centrifuge tube for high-speed centrifugal separation, and then the sample is subjected to centrifugal-ultrasonic washing for 5 times by using distilled water, wherein the dosage is 400mL each time. The resulting colloidal catalyst was designated as R2 and the composition is shown in Table 1.

Comparative example 3

A supported catalyst was prepared by following the procedure of example 1 except for excluding the step of stabilization treatment of step (4), to obtain catalyst R3 having the composition shown in Table 1.

TABLE 1

Evaluation of catalyst Performance

The method is carried out in a continuous stirring kettle, and comprises the following specific operations: transferring the activated catalyst into an autoclave containing 150 g of squalane (Mobil, 4#) under an oxygen-free condition in a glove box, replacing the catalyst with nitrogen after checking the airtightness, and introducing synthesis gas when the temperature is raised to 110 ℃, wherein the synthesis gas comprises the following components: h₂:CO:N₂56:28:16, control pressureThe force is 2.5MPa, the reaction temperature is 200-.

The catalyst performance indexes comprise relative catalytic activity, methane selectivity and C₅+ selectivity and stability, wherein the catalytic relative activity is defined as: taking the catalytic activity of R1 as a reference, and obtaining a value compared with the catalytic activity of the other catalysts as the relative activity of the corresponding catalysts, wherein the catalytic activity refers to the volume (milliliter) of CO converted per gram of catalyst in unit time (hour); methane selectivity is defined as: the mole percent of CO converted to methane based on the converted CO; c5+ selectivity is defined as: generation of C₅+ CO of the hydrocarbons as a mole percentage of converted CO; the stability means the degree of decrease in catalytic activity of the catalyst after a long-term continuous reaction, and the less the decrease, the higher the stability, and conversely, the worse the stability. The results of the evaluation are shown in tables 2, 3 and 4, and Table 4 shows the distribution of the product obtained after the reaction for 10 days.

TABLE 2

Catalyst and process for preparing same	Relative activity	Methane selectivity/%	C5+ Selectivity/%)
				C1	1.53	6.0	88.2
C2	1.66	6.5	87.5
				C3	2.56	7.0	86.5
C4	1.51	6.9	87.4
				C5	1.16	6.9	86.9
C6	1.23	6.8	87.1
				R1	1.00	8.1	84.6
R2	0.1	14.5	77.1
				R3	0.15	13.6	77.8

TABLE 3

The deactivation rate is defined as the percent of the initial activity lost by the catalyst activity per unit time, i.e. (relative activity of 1 day-10 days relative activity)/1 day relative activity/9X 100%.

TABLE 4

As can be seen from the results in table 2, compared with the catalyst obtained in the prior art, the catalyst provided by the invention has high catalytic activity, low methane selectivity and high C5+ selectivity; the results in table 3 show that the catalysts provided by the present invention have higher stability; the results in Table 4 show that the catalyst provided by the invention can obtain C5-C20 products and C5-C35 products in higher yield, and C36+ products in lower yield, so that the product distribution is narrower.

The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.

Claims

1. A Fischer-Tropsch synthesis catalyst is characterized in that the catalyst is a core-shell type nano structure, wherein Co and a stabilizer form a shell, and oxides and/or hydroxides of IVB group metal elements form a core; the stabilizer is one or more of Zr, W, Ta, La, Ce and oxides and/or hydroxides thereof, and the molar ratio of the stabilizer to Co is 1:2-500 calculated by metal elements;

the catalyst is prepared by the following method, and comprises the following steps:

(3) stabilizing the core-shell structure product obtained in the step (2);

the stabilizing treatment mode comprises the steps of dispersing the core-shell structure product in a liquid medium, and then contacting the core-shell structure product with soluble salt of a stabilizer and a non-metallic alkaline substance under a stabilizing condition;

wherein the contacting is carried out in a reducing atmosphere containing 5 to 60 vol% of hydrogen and/or CO, and the stabilizing conditions include a temperature of 0 to 400 ℃, a pressure of 0.1 to 4MPa, and a time of 0.01 to 144 hours;

the soluble salt of the stabilizer is one or more of acetate, nitrate and chloride of one or more of Zr, W, Ta, La and Ce; the mol ratio of the soluble salt of the stabilizer to the core-shell structure product is 1:2-500 calculated by metal elements.

2. The catalyst of claim 1, wherein the Co content is 20 to 80 wt% and the total amount of the stabilizer and the oxide and hydroxide of the group IVB metal element is 20 to 80 wt%, based on the total weight of the catalyst.

3. The catalyst of claim 2, wherein the Co content is 25 to 65 wt% based on the total weight of the catalyst, the molar ratio of the stabilizer to Co is 1:3 to 300, calculated as the metal element, and the total amount of the stabilizer to the oxides and hydroxides of the group IVB metal elements is 35 to 75 wt%.

4. The catalyst of claim 3, wherein the molar ratio of stabilizer to Co, calculated as the metal element, is from 1:4 to 200, based on the total weight of the catalyst.

5. The catalyst of claim 2, wherein the catalyst has a particle size of 5-50 nm.

6. The catalyst of claim 5, wherein the catalyst has a particle size of 8-45 nm.

7. The catalyst according to any one of claims 1 to 6, wherein the average particle size of the oxide and/or hydroxide core of the group IVB metal element is 1 to 40 nm.

8. The catalyst according to claim 7, wherein the average particle size of the oxide and/or hydroxide core of the group IVB metal element is 3 to 40 nm.

9. The catalyst of any one of claims 1-6, wherein the group IVB metal element is one or more of Ti, Zr, Hf.

10. A preparation method of a Fischer-Tropsch synthesis catalyst comprises the following steps:

(3) stabilizing the core-shell structure product obtained in the step (2);

11. The method of claim 10, wherein step (2) is achieved by: under the protection of inert gas, the nano colloid and the protective agent are dispersed in Co salt solution and then contacted with a reducing agent.

12. The method of claim 11, wherein the protective agent is one or more of polyvinylpyrrolidone, polyethylene glycol, linoleic acid, sodium oleate, oleylamine, trishydroxymethyl phosphine, trimethylhexadecylammonium bromide, tetraoctylammonium bromide, polyether, polymethoxyaniline.

13. The method of claim 11 or 12, wherein the ratio of nanocolloid: a protective agent: the weight ratio of the Co salt is 0.2-5: 2-200: 1, wherein the amount of the Co salt is calculated by Co element.

14. The method of claim 10, wherein the nanocolloid has a particle size of 1-40 nm.

15. The method of claim 14, wherein the nanocolloid has a particle size of 3-40 nm.

16. The method of claim 15, wherein the nanocolloid has a particle size of 5-40 nm.

17. The method of claim 10, wherein the stabilizing conditions comprise a temperature of room temperature to 300 ℃, a pressure of 1-3.5MPa, and a time of 0.01-96 hours.

18. The method as claimed in claim 17, wherein the stabilizing conditions include a temperature of 150 ℃ and 250 ℃, a pressure of 1.5 to 3MPa and a time of 20 to 50 hours.

19. The method of claim 10, wherein the non-metallic alkaline substance is one or more of urea, ammonia, and an organic amine.

20. The method of claim 10, wherein the core-shell structure product: the weight ratio of the non-metallic alkaline substances is 1: 1-20, and the core-shell structure product is calculated by Co element.

21. The method of claim 10, wherein the molar ratio of soluble salt of the stabilizer to core-shell structure product is 1:3 to 300, calculated as metal element.

22. The method of claim 21, wherein the molar ratio of soluble salt of the stabilizer to core-shell structure product is 1:4 to 200, calculated as metal element.

23. A catalyst made by the process of any one of claims 10-22.

24. Use of a catalyst as claimed in any one of claims 1 to 9 and 23 in a fischer-tropsch synthesis reaction.

25. A Fischer-Tropsch synthesis method comprises the step of enabling CO and H to react in the presence of a catalyst under Fischer-Tropsch synthesis reaction conditions₂A fischer-tropsch synthesis reaction occurring in contact, wherein the catalyst is as claimed in any one of claims 1 to 9 and 23.

26. The Fischer-Tropsch synthesis process of claim 25, wherein the Fischer-Tropsch synthesis reaction conditions include a temperature of 160-^-1。

27. The Fischer-Tropsch synthesis method of claim 26, wherein the Fischer-Tropsch synthesis reaction conditions comprise a temperature of 190 ℃ and a pressure of 1-5MPa, a molar ratio of hydrogen to carbon monoxide of 1-2.5, and a gas volume space velocity of 500 ℃ and 30000h^-1。