CN115254113A

CN115254113A - Fischer-Tropsch synthesis catalyst and preparation method and application thereof

Info

Publication number: CN115254113A
Application number: CN202110482631.1A
Authority: CN
Inventors: 孙霞; 侯朝鹏; 吴玉; 夏国富; 徐润; 汪天也; 栾学斌
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: 2021-04-30
Filing date: 2021-04-30
Publication date: 2022-11-01

Abstract

The invention relates to the technical field of catalysts, in particular to a Fischer-Tropsch synthesis catalyst and a preparation method and application thereof, wherein the catalyst comprises a carrier and an active component loaded on the carrier, the active component comprises cobalt and an auxiliary agent, and the auxiliary agent is selected from at least one of IA group metal elements, IIA group elements, IB group elements, IIB group elements, IIIB group elements, IVB group elements, VB group elements, VIB group elements, VIIB group elements and VIII group elements; the carrier is a raspberry type oxide microsphere, the surface of the carrier is provided with a macroporous hollow microsphere, a hollow structure is arranged in the hollow microsphere, and the macropores and the hollow structure are communicated to form a cavity with one open end; the active center number of the catalyst after the catalyst is subjected to re-reduction treatment is 0.06-0.3mmol of hydrogen per gram of catalyst. The catalyst provided by the invention has higher CO conversion rate and C5+ hydrocarbon selectivity when being used in the Fischer-Tropsch synthesis process.

Description

Fischer-Tropsch synthesis catalyst and preparation method and application thereof

Technical Field

The invention relates to the technical field of catalysts, in particular to a Fischer-Tropsch synthesis catalyst and a preparation method and application thereof.

Background

The microchannel reaction technology is one of new technologies of the chemical engineering subject of twenty-first century, and has obvious advantages compared with the conventional reactor: the reaction channel is in micron grade, the surface area is large, and the reactor has high mass transfer and heat transfer rates; the heat transfer coefficient is high, so that chemical reaction can occur under an isothermal condition, and the phenomenon of temperature runaway is avoided; the application of the high-activity and low-strength catalyst is realized; the modular form makes the project amplification simple; the reactor has high reaction load per unit volume, and the miniaturization of a large reactor is realized. The FT synthesis reaction is a strong exothermic reaction, the heat transfer of the catalyst layer is enhanced, and the control of the reaction temperature to be stable is the premise and guarantee of obtaining a good reaction effect. The micro-channel reaction technology is utilized, the reaction of the high-activity and fine-particle Fischer-Tropsch synthesis catalyst under the isothermal condition can be realized, the defects that a fixed bed has poor heat transfer and a small-particle-size catalyst cannot be applied are overcome, the problems of liquid phase mass transfer resistance of a slurry bed and the abrasion and separation of the catalyst are solved, and the Fischer-Tropsch synthesis catalyst is small in particle and large in macroscopic external surface area, so that wide channels and spaces are provided for the diffusion of reactants and products, and the reaction efficiency of the catalyst is greatly improved. The activity of the catalyst in the microchannel reactor can reach 4 times to 8 times of that of a fixed bed and a slurry bed. Therefore, the research on the high-efficiency FT synthetic microchannel reaction technology has very important significance.

The metal component of the metal hydrogenation catalyst is usually prepared in the form of an oxide, and the catalyst can only be made catalytically active by reduction treatment. The performance of the catalyst is directly affected by the reduction effect of the catalyst. The reduction pretreatment conditions of the catalyst are reasonably selected, so that the catalyst has higher activity in the reaction.

The catalyst reduction mode can adopt an ex-situ pre-reduction treatment or in-situ reduction treatment technology, the ex-situ pre-reduction technology can improve the utilization rate of the reducing agent and reduce the using amount of the reducing agent, the pre-reduction catalyst can recover the activity of the catalyst through simple reactivation at a lower temperature, the start-up time is reduced, the start-up cost is reduced, the start-up period is shortened, and the economic benefit of an enterprise is finally increased.

The same catalyst is subjected to different reduction and passivation treatment modes, and the activity and selectivity of the reaction are influenced differently. For different catalysts, different reduction and passivation treatments are also usually used to achieve better activity and selectivity. The pre-reduction passivation method in the prior art has long time, is not suitable for treating the micro-channel small-particle catalyst, and needs to develop a pre-reduction mode which is simple and convenient to operate, safe and reliable to pre-reduce the catalyst.

Disclosure of Invention

The invention aims to overcome the defects of low catalytic activity and harsh reduction and passivation conditions of a Fischer-Tropsch synthesis catalyst in the prior art, and provides the Fischer-Tropsch synthesis catalyst, and a preparation method and application thereof.

In order to achieve the above object, a first aspect of the present invention provides a fischer-tropsch synthesis catalyst, which includes a carrier and an active component supported on the carrier, wherein the active component includes cobalt and an auxiliary agent, the auxiliary agent is selected from at least one of group IA metal elements, group IIA elements, group IB elements, group IIB elements, group IIIB elements, group IVB elements, group VB elements, group VIB elements, group VIIB elements, and group VIII elements, and based on the total amount of the catalyst, the content of cobalt is 20 to 60 wt%, and the content of the auxiliary agent is 0.001 to 25 wt%;

the carrier is a raspberry type oxide microsphere, the raspberry type oxide microsphere is a hollow microsphere with a large hole on the surface, a hollow structure is arranged in the hollow microsphere, and the large hole is communicated with the hollow structure to form a cavity with an opening at one end; wherein the oxide in the raspberry type oxide microspheres is selected from one or more of alumina, silica, zirconia, magnesia, calcium oxide and titanium oxide;

wherein the active center number of the catalyst after the catalyst is subjected to re-reduction treatment is 0.06-0.3mmol of hydrogen per gram of catalyst, and the re-reduction treatment conditions comprise: the temperature was 200 ℃ and the time was 2 hours, and the atmosphere of hydrogen and argon was a reducing atmosphere having a hydrogen concentration of 10 vol%, and the gas-agent volume ratio was 15000.

In a second aspect, the present invention provides a method for preparing a fischer-tropsch synthesis catalyst, the method comprising:

(1) Preparing raspberry type oxide microspheres;

(2) Introducing active components to the raspberry type oxide microspheres by an impregnation method to obtain an oxidation state catalyst; the active component comprises cobalt and an auxiliary agent, wherein the auxiliary agent is selected from at least one of IA group metal elements, IIA group elements, IB group elements, IIB group elements, IIIB group elements, IVB group elements, VB group elements, VIB group elements, VIIB group elements and VIII group elements;

(3) Reducing the oxidation state catalyst in a hydrogen-containing atmosphere;

(4) And (3) passivating the catalyst obtained by the reduction in the step (3) when the temperature of the catalyst obtained by the reduction in the step (3) is reduced to below 60 ℃, wherein the passivation comprises the following steps: continuously introducing oxygen-containing gas below 60 ℃, and controlling the passivation temperature to be not higher than 90 ℃; wherein the oxygen concentration of the oxygen-containing gas is continuously increased;

wherein, the dosage of the raspberry type oxide microspheres and the active component ensures that the content of cobalt in the oxidation state catalyst is 20-60 wt% and the content of the auxiliary agent is 0.001-25 wt% in terms of oxide based on the total amount of the oxidation state catalyst.

In a third aspect, the invention provides a Fischer-Tropsch synthesis catalyst prepared by the preparation method of the second aspect.

In a fourth aspect, the invention provides use of a fischer-tropsch synthesis catalyst according to the first or third aspects as hereinbefore described in a fischer-tropsch synthesis reaction.

Through the technical scheme, the Fischer-Tropsch synthesis catalyst carrier provided by the invention is raspberry type oxide microspheres, the diffusion distance is short in the application process, the macroscopic surface area is large, in addition, the Fischer-Tropsch synthesis catalyst provided by the invention has more active centers, and the Fischer-Tropsch synthesis catalyst has better Fischer-Tropsch synthesis performance, especially higher CO conversion rate and C5+ hydrocarbon selectivity in the Fischer-Tropsch synthesis process.

Drawings

FIG. 1 is an SEM photograph of a catalyst prepared in example 1 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.

In the present invention, the gas-to-agent ratio refers to the ratio of the volume of gas passing through the catalyst bed per hour to the volume of the catalyst, the gas of the gas-to-agent ratio in the reduction process (or the re-reduction process) refers to the reducing gas (i.e., hydrogen-containing gas), and the gas of the gas-to-agent ratio in the passivation process refers to the passivation gas (i.e., oxygen-containing passivation gas, also referred to as oxygen-containing gas).

In the present invention, for the sake of distinction, reduction of a catalyst before passivation is referred to as "reduction", and reduction of a catalyst after passivation is referred to as "re-reduction".

The invention provides a Fischer-Tropsch synthesis catalyst, which comprises a carrier and an active component loaded on the carrier, wherein the active component comprises cobalt and an auxiliary agent, the auxiliary agent is selected from at least one of IA group metal elements, IIA group elements, IB group elements, IIB group elements, IIIB group elements, IVB group elements, VB group elements, VIB group elements, VIIB group elements and VIII group elements, the total amount of the catalyst is taken as a reference, the content of the cobalt is 20-60 wt% and the content of the auxiliary agent is 0.001-25 wt% in terms of oxide;

Preferably, the catalyst has an activity center number of 0.09 to 0.29mmol of hydrogen per g of catalyst after the catalyst is subjected to a re-reduction treatment, more preferably 0.1 to 0.29mmol of hydrogen per g of catalyst.

In the present invention, the number of active centers of the catalyst was determined by H on an Autochem2950 full-automatic high-pressure chemical adsorption apparatus manufactured by Micromeritics, USA₂Temperature programmed desorption (H)₂-TPD), the test method comprising: 0.2000g of a 40-60 mesh sample is weighed, and is firstly subjected to re-reduction activation under the following conditions: h having a hydrogen content of 10% by volume₂And (4) heating the mixed gas of-Ar at the flow rate of 50mL/min to 200 ℃ at the heating rate of 10 ℃/min, and reducing for 2h. The reduced catalyst was: h having a hydrogen content of 10% by volume₂Cooling in the-Ar mixed gas, switching to Ar gas for purging after the temperature is reduced to 55 DEG CAr flow 20mL/min until baseline stabilization, then H₂TPD experiments. H₂Experimental conditions and procedures for TPD were: ar is used as carrier gas, the flow rate of the carrier gas is 20mL/min, the heating rate is 10 ℃/min, the final temperature is 400 ℃, and a Thermal Conductivity Detector (TCD) detects signals to obtain a TPD curve.

According to a preferred embodiment of the invention, the catalyst is characterized by a TPR, in which the peak of the low temperature reduction peak with the largest area corresponds to a temperature of 140 to 270 ℃, preferably 150 to 260 ℃, more preferably 150 to 210 ℃. The temperature corresponding to the peak value of the low-temperature reduction peak with the largest area in the TPR map curve can be used as an index for evaluating the regeneration performance of the passivated catalyst, and the lower the temperature corresponding to the peak value of the low-temperature reduction peak with the largest area is, the easier the catalyst is to regenerate. The Fischer-Tropsch synthesis catalyst provided by the invention has good regenerability.

In the invention, the TPR (temperature programmed reduction) characterization is carried out on an Autochem2950 full-automatic high-pressure chemical adsorption instrument produced by Micromerics company in America, and the specific test conditions comprise: taking 0.20g of sample, firstly heating the sample to 120 ℃ at the heating rate of 10 ℃/min under 50mL/min Ar gas flow, dehydrating for 1 hour, and carrying out TPR (thermal Plastic rubber) experiment after the temperature is reduced to 50 ℃, wherein the experimental conditions and the procedures of the TPR are as follows: reducing gas 10 vol% H₂The flow rate of the Ar mixed gas is 50mL/min, and the temperature is increased to 900 ℃ at the temperature rising rate of 10 ℃/min; and detecting a signal through a Thermal Conductivity Detector (TCD) in the temperature rising process to obtain a TPR (thermal rubber pressure differential) spectrum curve.

According to the invention, the cobalt content is preferably 25 to 55 wt.% and the promoter content is preferably 0.001 to 10 wt.%, calculated as oxide, based on the total amount of catalyst.

According to the invention, the catalyst comprises, in particular, from 15 to 80% by weight, preferably from 35 to 75% by weight, of support, based on the total amount of catalyst.

The selection range of the auxiliary agent is wide, and the auxiliary agent is preferably one or more selected from La, zr, mn, V, cr, cu, ce, W, ti, zn, sc, mg, ca, be, na, K, ru, ag, au, re, pt and Pd, and more preferably one or more selected from La, zr, cu, ce, W, ti, ru, ag, au, re, pt and Pd. In a preferred aspect of the invention, the catalyst exhibits better CO conversion and C5+ hydrocarbon selectivity in a fischer-tropsch synthesis reaction.

In a preferred embodiment of the present invention, the active component may optionally include other components besides cobalt and the promoter, and those skilled in the art can select the components as required, so long as the catalytic performance of the catalyst in the fischer-tropsch synthesis reaction is favorably improved.

According to the Fischer-Tropsch synthesis catalyst provided by the invention, the oxide in the raspberry type oxide microspheres is an inorganic oxide, and can be selected from one or more of alumina, silica, zirconia, magnesia, calcium oxide and titanium oxide, and preferably is alumina and/or silica.

According to the Fischer-Tropsch synthesis catalyst provided by the invention, in the raspberry type oxide microspheres, the diameter of the hollow structure is 1-2000 μm, and preferably 1-400 μm.

According to the invention, in the raspberry type oxide microsphere, the pore diameter of the macropores is 0.2-1000 μm, preferably 0.5-200 μm.

According to the invention, in the raspberry type oxide microspheres, the shell thickness of the hollow microspheres is 0.2-1000 μm, preferably 0.5-200 μm.

According to the present invention, the appearance of the raspberry type oxide microspheres is close to spherical, and preferably, the sphericity of the raspberry type oxide microspheres is 0.5 to 0.99.

According to the Fischer-Tropsch synthesis catalyst provided by the invention, the particle size of the raspberry type oxide microspheres is preferably 3-2500 μm, and is preferably 10-500 μm.

The sphericity of the microsphere green body is represented by the formula sigma =4 pi A/L²And (5) calculating. In the formula: sigma is sphericity; a is the projected area of the microsphere in m²(ii) a L is the projection perimeter of the microsphere, and the unit is m; a and L are obtained from SEM pictures of microspheres and processed by Image processing software Image-ProPlus.

The raspberry type oxide microspheres of the invention are baked at 400-1300 ℃, preferably 450-1100 DEG CAfter firing, preferably at a temperature of 500-700 ℃ to give an oxide having a specific surface area of about 0.1-900m²A/g, preferably from 10 to 300m²A pore volume of about 0.01 to 3.6ml/g, preferably 0.1 to 0.9ml/g.

The breakage rate of the raspberry type oxide microspheres is preferably 0-1%, and the breakage rate is measured according to a method provided by a similar strength standard number Q/SH 3360-2010, and the specific method comprises the following steps:

firstly, selecting sieves S1 and S2 with the mesh numbers of M1 and M2 respectively, wherein M1 is less than M2, enabling microspheres to be detected to firstly pass through the sieve S1 with the mesh number of M1, then enabling the sieved microsphere powder to pass through the sieve S2 with the mesh number of M2, and finally enabling the microsphere powder intercepted by the sieve S2 to be used as a sample to be detected.

Adding a sample to be detected with a certain mass into a cylindrical steel container with the section diameter of 10mm, applying a certain pressure to microspheres through a cylinder for a certain time, screening the pressed microsphere powder by using a screen S2 with the mesh number of M2, recording the mass of the microsphere powder under the screen, and dividing the mass of the microsphere powder under the screen by the total mass of the added microspheres to obtain the breaking rate of the microspheres.

In the present invention, M1 may be 100 mesh, M2 may be 150 mesh, the pressure may be 100N, and the time may be 10s.

The strength of the microspheres can be evaluated by using the breakage rate; the strength of the microspheres is higher when the breakage rate is lower.

The raspberry type oxide microspheres of the invention have low breaking rate under the condition of pressurization, and the strength is obviously higher than that of the existing known oxide microspheres, such as the apple-shaped hollow molecular sieve microspheres disclosed in CN108404970A, which is determined by the difference of raw materials and preparation methods thereof. The higher strength enables the porosity of the raspberry type oxide microspheres to be larger, the pressure drop to be greatly reduced, and the raspberry type oxide microspheres have excellent processing performance and wear resistance.

The Fischer-Tropsch synthesis catalyst provided by the invention has the advantages of multiple active centers, high catalytic activity and good regenerability.

(1) preparing raspberry type oxide microspheres;

(3) Reducing the oxidation state catalyst in a hydrogen-containing atmosphere;

(4) And (3) passivating the catalyst obtained by the reduction in the step (3) when the temperature of the catalyst obtained by the reduction in the step (3) is reduced to below 50 ℃, wherein the passivation comprises the following steps: continuously introducing oxygen-containing gas below 50 ℃, and controlling the passivation temperature to be not higher than 70 ℃; wherein the oxygen concentration of the oxygen-containing gas is continuously increased;

wherein, the dosage of the raspberry type oxide microspheres and the active component is such that in the oxidation state catalyst, the content of cobalt is 20-60 wt%, preferably 25-55 wt%, and the content of the auxiliary agent is 0.001-25 wt%, preferably 0.001-10 wt%, calculated by the total amount of the oxidation state catalyst, calculated by oxide.

The specific selection and amounts of the active ingredients are as described above and will not be described in further detail herein.

The composition and structure of the raspberry-type oxide microspheres are as described above and are not described in detail herein.

Any method that can obtain raspberry-type oxide microspheres of the above composition and structure can be used for preparing raspberry-type oxide microspheres in step (1) of the present invention. Preferably, the preparing raspberry type oxide microspheres in step (1) comprises:

(1-1) adding nitrate, peptizing agent, pore-forming agent, and the oxide and/or precursor thereof into a dispersing agent and stirring to obtain dispersed slurry;

(1-2) subjecting the dispersion slurry to an aging treatment;

(1-3) feeding the aged dispersed slurry into a drying device, wherein the air inlet temperature is 400-1200 ℃, and preferably 450-700 ℃; drying and forming at the air outlet temperature of 50-300 ℃, preferably 120-200 ℃ to obtain the raspberry type oxide microspheres.

In the present invention, preferably, the mass ratio of the nitrate, the peptizing agent, the pore-forming agent, and the oxide and/or the precursor thereof is (10-500): (1-10): (10-500): (10-1000).

In the invention, the nitrate, the peptizing agent, the pore-forming agent and the oxide and/or the precursor thereof can be sequentially added into the dispersing agent or simultaneously added, and the adding sequence can be adjusted according to the dissolution condition of each raw material, and the nitrate, the peptizing agent, the pore-forming agent and the oxide and/or the precursor thereof are preferably stirred to be uniformly mixed while being added.

In the present invention, preferably, the nitrate is selected from one or more of zirconium nitrate, aluminum nitrate, lanthanum nitrate, and yttrium nitrate. Nitrate ions in the nitrate promote a self-propagating combustion reaction at high temperatures that can act as an oxidizer for the pore former, producing gases and vapors that form cavities in the oxide material.

In the present invention, preferably, the peptizing agent is selected from one or more of acids, alkalis, and salts. The acids can be selected from: inorganic acid (such as hydrochloric acid, sulfuric acid, nitric acid and the like), organic acid (formic acid, acetic acid, oxalic acid and the like) and one or more of inorganic acid or organic acid; alkalies can be selected from: inorganic bases (sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide, aluminum hydroxide, lithium hydroxide, magnesium hydroxide, zinc hydroxide, copper hydroxide, iron hydroxide, lead hydroxide, cobalt hydroxide, chromium hydroxide, zirconium hydroxide, nickel hydroxide, ammonium hydroxide, soda ash (anhydrous sodium carbonate), sodium carbonate (monohydrate, heptahydrate, decahydrate), sodium bicarbonate (baking soda), potassium carbonate, potassium bicarbonate, etc.), organic bases (such as amine compounds, alkali metal salts of alcohols, alkaloids, lithium alkyl metal compounds, etc.), and one or more of inorganic bases or organic bases; the salts can be selected from: inorganic acid salt (such as hydrochloric acid, sulfate, nitrate, etc.), organic acid salt (formate, acetate, oxalate, etc.), and one or more of inorganic acid salt or organic acid salt.

According to the present invention, preferably, the pore-forming agent is selected from one or more of synthetic cellulose, starch, polymeric alcohol and surfactant. Wherein the synthetic cellulose is preferably one or more of carboxymethyl cellulose, methyl cellulose, ethyl cellulose and hydroxy fiber fatty alcohol polyvinyl ether; the polymer alcohol is preferably one or more of polyethylene glycol, polypropylene alcohol, polyvinyl alcohol and polypropylene alcohol PPG; the surfactant is preferably one or more of fatty alcohol polyvinyl ether, fatty alcohol amide and derivatives thereof, acrylic acid copolymer with molecular weight of 200-2000000 and maleic acid copolymer.

According to the present invention, specifically, the oxide and/or its precursor may be directly used alumina, silica, zirconia and titania, and may also be used as a precursor for forming these oxides, and specifically, may be selected from one or more of a silicon source, an aluminum source, a zirconium source and a titanium source, wherein the aluminum source is preferably selected from one or more of pseudo-boehmite, aluminum alkoxide, aluminum sulfate, aluminum nitrate, aluminum chloride and sodium metaaluminate, the silicon source is preferably selected from one or more of sodium silicate, water glass and silica sol, the zirconium source is preferably selected from one or more of zirconium dioxide, zirconium tetrachloride, zirconium oxychloride, zirconium hydroxide, zirconium sulfate, zirconium phosphate, zirconyl nitrate, zirconium hydroxycarbonate and zirconium tetrabutoxide, and the titanium source is preferably selected from one or more of titanium dioxide, titanium nitrate, metatitanic acid, titanyl sulfate, titanium dichloride, titanium trichloride, titanium tetrachloride, titanium aluminide, tetraethyl titanate, tetrabutyl titanate, tetran-propyl titanate and tetraisopropyl titanate.

In the present invention, when the above-mentioned aluminum source, silicon source, zirconium source and titanium source are used, chemical agents for precipitating or gelling them, such as acids (e.g., inorganic acids such as hydrochloric acid, sulfuric acid and nitric acid, or organic acids such as acetic acid), and/or alkalis (e.g., sodium carbonate and sodium hydroxide) are also included.

When it is necessary to prepare an oxide composition containing other components, oxides such as vanadium oxide, chromium oxide, manganese oxide, iron oxide, cobalt oxide, molybdenum oxide, tungsten oxide, nickel oxide, and copper oxide may be added, and precursors that can form these oxides may also be added.

In the present invention, the dispersant is preferably one or more selected from water, alcohols, ketones and acids, wherein the alcohols are preferably methanol, ethanol, propanol and the like, the ketones are preferably acetone, butanone and the like, and the acids are preferably formic acid, acetic acid, propionic acid and the like. The preferable dispersing agent is a mixture of water and a small amount of ethanol, the small amount of ethanol can play a better dispersing effect in water and can be used as a boiling point regulator, and the water evaporation effect and the liquid drop shrinkage effect are matched and matched more through regulating the dispersing agent, so that the appearance effect of the microsphere is more regular and smooth.

According to a preferred embodiment of the present invention, the step (1-1) further comprises adding a blasting agent to the dispersing agent. The blasting agent may be added before or after the oxide. Preferably, the blasting agent is selected from one or more of picric acid, trinitrotoluene, digested glycerol, nitrocotton, dana explosive, hexogen and C4 plastic explosive. Preferably, the blasting agent is mixed with other materials before drying and forming. Preferably, the blasting agent is added in an amount of 0 to 1% by weight of the total dry basis of the nitrates, peptizers, porogens and oxides and/or precursors thereof.

According to a preferred embodiment of the invention, the nitrate, the peptizing agent, the pore-forming agent and the oxide precursor are sequentially added into the dispersant for pulping, and the slurry is pumped into a sand mill or a colloid mill for grinding after being uniformly stirred, so as to obtain the dispersed slurry. The slurry solids content during beating is preferably 5 to 60% by weight and the grinding time is preferably 1 to 30 minutes. After mixing and grinding, the average particle size of the aluminum source, silicon source, zirconium source and titanium source particles in the slurry can be ground to 0.01-10 μm.

After the raw materials are mixed and ground, the raw materials are fully dissolved and dispersed, so that the dispersed slurry is uniform. The milling equipment used may be a colloid mill, sand mill or other equipment, the criterion being selected such that the catalyst fines, after grinding thereof, reach the desired average particle size, preferably less than 10 μm.

In the present invention, the conditions for the aging treatment are selected in a wide range, and preferably, in the step (1-2), the temperature of the aging treatment is 0 to 90 ℃, preferably 20 to 60 ℃.

Preferably, the aging treatment is carried out for a treatment time of 0.1 to 24 hours, preferably 0.5 to 2 hours.

In the present invention, the drying apparatus used may be a flash drying apparatus and a spray drying apparatus, and is preferably a spray drying apparatus. Flash drying and spray drying are common methods applied for material drying. After the wet material is dispersed in a drying tower, the moisture is quickly vaporized in the contact with hot air, and a dry product is obtained. The spray drying method can directly dry the solution and emulsion into powder or granular products, and can omit the procedures of evaporation, pulverization and the like.

According to a preferred embodiment of the invention, the aged dispersion slurry is fed into a spray drying device, and is dried and formed at the air inlet temperature of 400-1200 ℃, preferably 450-700 ℃, and the air outlet temperature of 50-300 ℃, preferably 120-200 ℃. The pressure in the spraying tower is equivalent to that of the conventional spraying, and the raspberry type oxide microspheres can be obtained.

The working principle of spray drying in the invention is to disperse the material to be dried into fine particles like fog through mechanical action (such as pressure, centrifugation and air flow type spraying), increase the water evaporation area, accelerate the drying process, contact with hot air, remove most water in a short time and dry the solid matter in the material into powder.

The spray drying apparatus used in the present invention is a conventional apparatus in the existing flow path, and the present invention is not particularly limited thereto. The spray drying apparatus generally comprises: the device comprises a feeding system, a hot air system, a drying tower system, a receiving system and a sealing system. The feeding system is connected with the drying tower system in the middle of the top end, the hot air system is connected with the side face of the top end of the drying tower system, the receiving system is connected with the bottom end of the drying tower system, and the sealing system is connected with the hot air system. In the spray drying process, it is essentially necessary to have a spray of the stock solution; drying the tiny droplets in the spray; three functions of separating and recovering fine powder products. In the spray drying apparatus, an atomizer, a drying chamber, and a fine powder recoverer corresponding to the above functions are generally equipped.

Because the control parameters in the spray drying process are more and the factors are complex, the particle size and the particle shape after spray drying are very complex. The size range of the product is generally in micron order, and the product is generally a mixture of shapes including a sphere, a disc, an apple shape, a grape shape, a cavity shape, a meniscus shape and the like, and how to selectively form an ideal single shape, such as a cavity shape, is a difficulty in the formation of the product.

One method in the prior art is to form spherical emulsion under the action of surface tension of a surfactant, and then at the moment of spray forming at a lower temperature, a pore-forming agent is vaporized or pyrolyzed in the spherical emulsion, and gas generated by vaporization and pyrolysis can cause a cavity in the microsphere emulsion; and forming secondary stacking holes to become mesopores on the surface of the molecular sieve microspheres in the spray forming process of the molecular sieve particles, and combining the subsequent roasting process to obtain the large-particle hollow molecular sieve microspheres.

In the invention, under the high temperature of the inlet air temperature of 400-1200 ℃, the oxide and the reducing agent in the slurry generate strong oxidation-reduction self-propagating combustion reaction to instantly generate a large amount of gas; meanwhile, the liquid drops enter a high-temperature area for spraying, the liquid drops are strongly evaporated, and the surface tension formed by the thickened slurry causes the liquid drops to shrink rapidly. The strong explosion of the inside and the strong contraction of the outside form a raspberry type hollow material with good strength. The prepared raspberry type oxide microspheres have high strength, high sphericity and high yield.

In the present invention, the raspberry-type oxide microspheres may be calcined before step (2) and then used as a carrier. Preferably, the temperature of calcination may be 400 ℃ to 1300 ℃, preferably 450 ℃ to 1100 ℃, and more preferably 500 ℃ to 700 ℃; the calcination time may be from 1 to 12 hours, preferably from 2 to 8 hours, and more preferably from 3 to 4 hours.

The present invention does not particularly limit the embodiment of step (2), as long as the active ingredient is introduced into the raspberry-type oxide microspheres by the dipping method. Preferably comprising formulating an impregnation solution of the compound containing the active metal component followed by impregnating the raspberry type oxide microspheres with the solution. The impregnation method is a conventional method, and for example, it may be an excess liquid impregnation, a pore saturation method impregnation. Wherein the concentration, amount or amount of the raspberry type oxide microspheres of the impregnation solution of the compound containing the active component can be adjusted and controlled to prepare the catalyst at the specified content, which is easily understood and realized by the skilled person.

In the invention, the number of the active components is more than 2, and the active components can be impregnated on the raspberry type oxide microspheres by co-impregnation or can be impregnated on the raspberry type oxide microspheres step by step, preferably co-impregnation. The specific operation is well known to those skilled in the art, and the present invention will not be described herein.

According to a preferred embodiment of the present invention, the raspberry type oxide microspheres are impregnated with an impregnation solution containing an active component precursor, and then dried and calcined. Preferably, the temperature for drying may be 80 ℃ to 200 ℃, further preferably 100 ℃ to 150 ℃. Preferably, the temperature of calcination is from 200 ℃ to 800 ℃, preferably from 300 ℃ to 600 ℃. The drying and calcining time is not limited in any way, and conventional drying and calcining time can be adopted. The roasting apparatus used and the operating conditions thereof are conventional equipment and operating parameters in the prior art roasting, and the present invention is not particularly limited thereto.

The kind of the precursor of the active component is not particularly limited in the present invention, and may be selected from water-soluble compounds corresponding to the active component, such as nitrate, acetate, chloride, and the like. For example, the precursor of cobalt may be at least one of cobalt nitrate, cobalt chloride, basic carbonate, and cobalt acetate, and the precursor of the auxiliary may be at least one of cobalt nitrate, cobalt chloride, basic cobalt carbonate, and cobalt acetate.

The invention adopts raspberry type oxide microspheres, which can reduce the waste of the carrier and the catalyst and save the materials; meanwhile, due to the improvement of the shape efficiency factor, the diffusion can be promoted, and the reaction efficiency and the selectivity of a target product are improved. In the reaction with larger heat effect, the hollow carrier can also reduce the generation of hot spots, and has good intrinsic safety.

According to the invention, the hydrogen-containing atmosphere contains hydrogen and optionally also a protective gas. The protective gas is a gas that does not participate in the reaction, and is preferably at least one selected from the group consisting of nitrogen, helium, argon, and neon, and more preferably nitrogen.

Preferably, the hydrogen gas concentration in the hydrogen-containing atmosphere is not less than 5% by volume, more preferably 5 to 90% by volume, and still more preferably 40 to 90% by volume.

In the present invention, specifically, before the reduction, the method further includes introducing a protective gas into the reduction apparatus for displacement, then introducing hydrogen to obtain the hydrogen-containing atmosphere, and then performing the reduction. According to the invention, in particular, the catalyst in the oxidized state is charged into the prereduction reactor with a protective gas (e.g. N)₂) Replacement system, preferably ensuring O in the system₂The volume percentage content of the catalyst is less than or equal to 0.5 percent, a compressor is started, the system pressure is kept at 0.0-2MPa (gauge pressure), and reduction is carried out according to the procedures of heating and hydrogen distribution.

Further preferably, the preparation method further comprises the step of heat exchange: the introduced hydrogen and optionally shielding gas are first heat exchanged with the reduced gas, then optionally heated, and then introduced into the reduction system. And the reduced tail gas is subjected to heat exchange and temperature reduction and then is subjected to gas-liquid separation preferentially, and the tail gas after water removal can be recycled for the reduction process.

In the present invention, the apparatus for carrying out the reduction is not particularly limited, and a rotary kiln reactor, a fluidized bed reactor or a rotary drum reactor is preferable, a fluidized bed reactor is more preferable, and a fluidized reactor with a riser is most preferable.

In the present invention, the amount of the reducing gas is not particularly limited, and is preferably selected so that the powder is in a fluidized state.

Preferably, the reducing conditions of step (3) include: the oxidation state catalyst is in a fluidized state and is contacted with a reducing gas; the temperature is 100 to 750 ℃ and more preferably 150 to 700 ℃.

Preferably, the reducing conditions of step (3) include: the time is not more than 2 hours, and the time is not more than 1.5 hours. The time refers to the residence time of the catalyst in the oxidized state at the highest reduction temperature in the apparatus in which the reduction is carried out.

Preferably, the reducing conditions of step (3) include: the reducing gas-agent ratio is 500-5000, more preferably 600-4500.

The pressure selection range of the invention for the reduction is wider, and the pressure selection range is preferably 0-2MPa. The pressure is a gauge pressure.

The oxidation state catalyst using raspberry type oxide microspheres as a carrier can be quickly reduced, and the obtained Fischer-Tropsch synthesis catalyst has good regenerability and a large number of active centers.

According to the invention, in the step (4), preferably, after the temperature of the catalyst obtained by the reduction in the step (3) is reduced to below 50 ℃, the catalyst obtained by the reduction in the step (3) is passivated by continuously introducing oxygen-containing gas below 50 ℃.

In the present invention, the method for reducing the temperature of the catalyst obtained by reduction in the step (3) is not limited at all, and the catalyst may be reduced to a desired temperature by, for example, heat exchange, cold exchange, water cooling, ammonia cooling, purging, or the like.

According to a preferred embodiment of the present invention, the method further comprises a step of replacing hydrogen in the system before the passivation. According to one embodiment of the invention, carbon dioxide or carbon dioxide and nitrogen are used to displace H in the system₂. The purging process not only can realize rapid cooling, but also can realize the replacement of hydrogen in the system.

Preferably, the catalyst obtained by the reduction in the step (3) is passivated when the temperature of the catalyst obtained by the reduction in the step (3) is reduced to 45 ℃ or lower (more preferably 35 ℃ or lower) and the hydrogen content in the system is less than or equal to 1 vol%.

In the production process of the present invention, it is understood that the deactivation temperature of not higher than 70 ℃ means that the deactivation temperature of the catalyst bed is not higher than 70 ℃. Preferably, the passivation temperature is controlled to be not higher than 65 ℃.

According to the method provided by the invention, as long as the concentration of the introduced oxygen-containing gas in the passivation process is in an increasing trend, the oxygen concentration of the oxygen-containing gas is in the range of the continuous increase of the oxygen concentration of the oxygen-containing gas. The oxygen concentration of the oxygen-containing gas may be constantly increased or irregularly increased, and the present invention is not particularly limited thereto.

According to an embodiment of the present invention, for convenience of operation, the oxygen-containing gas with a certain concentration may be introduced for a certain period of time, and then the oxygen-containing gas with a higher concentration may be introduced for a certain period of time, and so on. In this case, that is, the oxygen concentration increases in stages, for example, in a multi-stage, in one embodiment, the oxygen concentration in the subsequent stage is higher than that in the previous stage, and in another embodiment, the oxygen concentration in the previous stages is the same and lower than that in the subsequent stage, so that the whole of the oxygen concentration increases.

In the present invention, preferably, the oxygen concentration of the oxygen-containing gas is increased in stages, in this case, the duration of each stage in the present invention is wide enough to improve the performance of the obtained catalyst, and more preferably, in the passivation process, when the oxygen-containing gas introduced in the previous stage makes the oxygen concentration in the passivated outlet gas equal to the oxygen concentration of the introduced oxygen-containing gas, the operation of introducing the oxygen-containing gas in the subsequent stage is performed.

According to the present invention, preferably, during the passivation process, the oxygen concentration of the oxygen-containing gas is continuously increased in at least 2 stages, more preferably in 2-10 stages, and even more preferably in 3-8 stages, for example, the number of stages may be 3, 4, 5, 6, 7, and 8. By adopting the preferable scheme, the catalyst can be passivated more uniformly, so that the catalyst has more active centers after being subjected to reduction activation.

It will be appreciated that in this preferred embodiment, the oxygen concentration of the oxygen-containing gas in the first stage is lower than the oxygen concentration of the oxygen-containing gas in the second stage, and the oxygen concentration of the oxygen-containing gas in the second stage is lower than the oxygen concentration of the oxygen-containing gas in the third stage, so that the oxygen concentration increases. Further, it is understood that the relative multiple of the oxygen concentration of the oxygen-containing gas of each of the adjacent two stages may be the same or different, for example, the relative multiple of the oxygen concentration of the oxygen-containing gas of the first stage and the second stage is 1.5, and the relative multiple of the oxygen concentration of the oxygen-containing gas of the second stage and the third stage may be 1.5 or 2.

Preferably, the passivating gas to agent ratio is from 200 to 4500, more preferably from 300 to 4000.

In the passivation process of the invention, the gas-to-agent ratios of passivation in each stage can be respectively and independently the same or different, so long as the uniform passivation process of the catalyst is promoted and the passivation efficiency is improved, and the person skilled in the art can freely select the gas-to-agent ratios according to the requirements.

According to a preferred embodiment of the invention, the passivation time is not more than 5h, preferably not more than 1.5h, and may for example be between 0.5 and 1.5h. The method provided by the invention can complete passivation in a short time and has a good passivation effect.

In the present invention, preferably, the oxygen concentration of the oxygen-containing gas is increased in stages, in this case, the duration of each stage in the present invention is wide enough to improve the performance of the obtained catalyst, and more preferably, in the passivation process, when the oxygen-containing gas introduced in the previous stage makes the oxygen concentration in the passivated outlet gas equal to the oxygen concentration of the introduced oxygen-containing gas, the oxygen-containing gas is introduced in the next stage.

In the present invention, the oxygen-containing gas is preferably a mixed gas of a shielding gas selected from one or more of helium, argon, carbon dioxide and nitrogen, and oxygen.

Preferably, the concentration of the oxygen-containing gas is from 0.05 to 21% by volume, preferably from 0.1 to 21% by volume.

According to a preferred embodiment of the invention, the initial oxygen concentration of the oxygen-containing gas fed during the passivation is between 0.05 and 0.2% by volume. The adoption of the oxygen-containing gas with lower initial oxygen concentration can lead the passivation to be uniform and controllable, and is more beneficial to obtaining the catalyst with good reproducibility.

According to a preferred embodiment of the invention, the oxygen concentration of the oxygen-containing gas fed in the second stage during the passivation is between 0.1 and 1% by volume.

According to a preferred embodiment of the present invention, the oxygen concentration of the oxygen-containing gas introduced in the latter stage is 1 to 8 times higher than the oxygen concentration of the oxygen-containing gas introduced in the former stage during the passivation. Under the preferable scheme, the catalyst can be passivated more uniformly and controllably, so that the obtained catalyst has more active centers after re-reduction treatment, and the passivation efficiency is high.

The apparatus for carrying out the passivation is not particularly limited, and the apparatus may be used together with the reduction apparatus or may be provided separately, and the type thereof may be referred to an apparatus used in the reduction process, for example, a fluidized bed reactor, in which the catalyst is in a fluidized state.

In the present invention, when the same apparatus is used for the reduction and the passivation, the method further comprises: before the passivation, protective gas (preferably carbon dioxide and N in a volume ratio of 10-20) is introduced₂) Replacement of H in the System₂Quick cooling, as H in the system₂Is less than or equal to 1 percent by volume, then introducing oxygen so that the oxygen content in the passivated atmosphere meets the required oxygen concentration, and then carrying out the passivation. And the passivated gas is recycled or directly discharged. Preferably, the passivation temperature is ensured not to be higher than 70 ℃ by adjusting the pumping amount of the protective gas (preferably carbon dioxide).

In the invention, the reducing gas (namely the hydrogen-containing atmosphere) and the passivating gas (namely the oxygen-containing gas) can be used once or recycled by adopting the circulating gas; preferably, the hydrogen-containing gas is recycled, and the passivation gas is not recycled.

According to a preferred embodiment of the present invention, before the reduction in step (3), the method further comprises: the reducing gas (i.e., hydrogen-containing gas) is preheated while the oxidation state catalyst is preheated, and then the preheated reducing gas is brought into contact with the oxidation state catalyst to perform the reduction. Further, the product obtained after reduction is preferably subjected to gas-solid separation, and the gas-solid separation is preferably realized in a cyclone dust collector.

In the present invention, the reduction and passivation are preferably carried out in the form of a double reactor, for example, after the oxidation state catalyst is reduced in the first stage rapid reduction reactor, the reduced material is transferred to a tundish, cooled and then transferred to the second reactor for passivation. The matched equipment can comprise a powder preheating furnace, a gas preheating furnace, a feeding device, a powder reduction device, a middle tank, a powder passivation device and the like.

Compared with the prior art, the invention has the advantages of improving the reduction speed and the equipment utilization coefficient, having high efficiency and realizing low energy consumption and low production cost. The advantages are as follows: when the particle size of the powder is ground to less than 2000 μm, the fine powder can be used in a fast circulating fluidized bed or a transport reactor, the required gas velocity is lower than the fluidizing gas velocity of the coarse powder, and the reaction velocity of the fine powder is high, so the efficiency of the reactor is high.

In a third aspect, the invention provides a Fischer-Tropsch synthesis catalyst prepared by the preparation method of the second aspect. The fischer-tropsch synthesis catalyst has the composition and structure of the fischer-tropsch synthesis catalyst of the first aspect described above and will not be described in further detail herein.

According to the invention, the degree of reduction of the fischer-tropsch synthesis catalyst, characterized by TPR, is preferably comprised between 50 and 98%. The Fischer-Tropsch synthesis catalyst provided by the invention has a proper reduction degree and higher activity. The pre-reduction catalyst in the prior art has high reduction degree (close to 100 percent) and low activity.

In the invention, the reduction degree test method comprises the following steps: the reduction degree test method comprises the following steps: firstly testing a TPR (thermal Plastic rubber) spectrum curve of the pre-reduction catalyst; then 0.2g of the pre-reduction catalyst is roasted for 2h at 450 ℃ in the air atmosphere to obtain the oxidation state catalyst, the TPR map curve of the oxidation state catalyst is tested according to the TPR test method of the first aspect, and the reduction degree of the pre-reduction catalyst is calculated. Wherein, the reduction degree = (oxidized state catalyst direct reduction TPR peak area-pre-reduction catalyst high temperature unreduced peak area)/oxidized state catalyst direct reduction TPR peak area is 100%.

The Fischer-Tropsch synthesis catalyst provided by the invention can be activated by hydrogen again at the temperature of below 300 ℃.

The Fischer-Tropsch synthesis catalyst provided by the invention adopts raspberry type oxide microspheres as a carrier, so that the diffusion distance is short, the macroscopic surface area is large, better reduction passivation can be carried out in the reduction passivation process, the efficiency is high, and better Fischer-Tropsch synthesis performance is achieved. In addition, the preparation method of the invention has lower cost and can be applied in large-scale industry.

According to the invention, by quickly reducing smaller particles, on one hand, oxides in the catalyst are fully reduced, the reduction degree of the catalyst is improved, and the crystal grains can be kept smaller. Thereby efficiently reducing the catalyst in an oxidized state to a catalyst precursor having high activity. On the other hand, the process of the invention has the advantage of high efficiency, giving catalysts which are very homogeneous and easy to regenerate and have a large number of active centers. Thereby improving the reactivity of the catalyst as a whole. Has good industrial application prospect.

The present invention will be described in detail below by way of examples. In the following examples, the test methods are as follows:

the temperature corresponding to the peak value of the maximum low temperature reduction peak in the TPR map curve is used as a measure for evaluating the regenerability of the passivated catalyst: the lower the temperature corresponding to the peak of the low-temperature reduction peak having the largest area, the easier the catalyst is to regenerate. Temperature Programmed Reduction (TPR) was carried out on an Autochem2950 full-automatic high-pressure chemisorption apparatus manufactured by Micromeritics, USA under the following test conditions: firstly, heating a 0.20g sample to 120 ℃ under 50mL/min Ar gas flow at the heating rate of 10 ℃/min, dehydrating for 1 hour, and carrying out a TPR (thermal Plastic rubber) experiment after the temperature is reduced to 50 ℃, wherein the experimental conditions and the procedures of the TPR are as follows: the reducing gas was H with a hydrogen content of 10% by volume₂Ar mixed gas, the flow rate of reducing gas is 50mL/min, and the temperature is increased to 900 ℃ at the temperature increasing rate of 10 ℃/min; and detecting signals through a Thermal Conductivity Detector (TCD) in the temperature rising process to obtain a TPR spectrum curve.

The degree of reduction of the catalyst was characterized by TPR. The test method comprises the following steps: the reduction degree test method comprises the following steps: firstly testing a TPR (thermal Plastic rubber) spectrum curve of the pre-reduction catalyst; and then 0.2g of the pre-reduction catalyst is roasted for 2h at 450 ℃ in the air atmosphere to obtain the oxidation state catalyst, the TPR map curve of the oxidation state catalyst is tested according to the TPR test method, and the reduction degree of the pre-reduction catalyst is calculated. Wherein, the reduction degree = (oxidation state catalyst direct reduction TPR peak area-pre-reduction catalyst high temperature unreduced peak area)/oxidation state catalyst direct reduction TPR peak area 100%.

The number of active centers was H on an Autochem2950 fully automatic high pressure chemical adsorption apparatus manufactured by Micromeritics, USA₂Temperature programmed desorption (H)₂TPD) test, test method: 0.2000g of a 40-60 mesh sample was weighed, and first, re-reduction activation was performed under the following conditions: h having a hydrogen content of 10% by volume₂And (4) Ar mixed gas, wherein the flow rate of the mixed gas is 50mL/min, and the temperature is increased to 200 ℃ at the heating rate of 10 ℃/min for reduction for 2h. Reduced catalyst has a hydrogen content of 10% by volume H₂Cooling in the-Ar mixed gas, switching to Ar gas for purging when the temperature is reduced to 55 ℃, wherein the Ar flow is 20mL/min until the base line is stable, and then carrying out H₂TPD experiments. H₂Experimental conditions and procedures for TPD were: ar is carrier gas, the flow rate of the carrier gas is 20mL/min, the heating rate is 10 ℃/min, the final temperature is 400 ℃, and a Thermal Conductivity Detector (TCD) detects signals to obtain a TPD curve.

In the following examples, preparations and comparative examples, some of the raw material specifications used were as follows:

pseudo-boehmite powder (produced by Changling catalyst plant, solid content 69.5 wt%; gamma-Al)₂O₃Content of not less than 98 wt%);

alumina sol (produced by Zhou village catalyst works, containing 22 wt% Al)₂O₃)；

Sodium silicate (Jinan Yifengda chemical Co., ltd., modulus 3.1-3.4, insoluble matter less than 0.4%);

ammonia, hydrochloric acid, nitric acid, sulfuric acid, aluminum sulfate, aluminum chloride, zirconium hydroxide, zirconium oxychloride, titanium tetrachloride, titanium dioxide (national chemical group, ltd., industrial grade);

polyethylene glycol PEG4000 powder (Wenzhou Shuanghoi rubber and plastic materials Co., ltd.);

methylcellulose (Hubei Jiangtiantai chemical Co., ltd.);

tetraethoxysilane (TEOS, johnwa chemical limited, content about 99%);

cobalt nitrate, aluminum nitrate, titanium nitrate, zirconium nitrate, yttrium nitrate, magnesium nitrate (yutai qixin chemical limited, industrial grade).

The breakage of the support and the catalyst can be measured according to the following method:

the microspheres to be measured firstly pass through a 100-mesh sieve, then the sieved microsphere powder passes through a 150-mesh sieve, and finally the microsphere powder intercepted by the 150-mesh sieve is used as a sample to be measured. Adding microspheres with a certain mass (the granularity is 100-150 meshes) into a cylindrical steel container with the section diameter of 10mm, applying a certain pressure (100N) to the microspheres through a cylinder for a certain time (10 seconds), screening the pressed microsphere powder by using a 150-mesh screen, recording the mass of the microsphere powder under the screen, and dividing the mass of the microsphere powder under the screen by the mass of the total added microspheres to obtain the breaking rate of the microspheres.

The following preparation examples are provided to illustrate the preparation of raspberry-type oxide microspheres.

Preparation example 1

20kg of water is added into a reaction kettle, 1.2kg of aluminum nitrate is added into the reaction kettle, 200g of concentrated nitric acid is added into the reaction kettle, 2.3kg of PEG4000 is added into the reaction kettle, and finally 4.0kg of pseudo-boehmite powder is added into the reaction kettle, and the mixture is stirred uniformly and ground to obtain dispersed slurry.

The dispersion slurry was aged at 35 ℃ for 1.5 hours with stirring.

Feeding the aged dispersed slurry into a spray drying device for drying and forming to obtain raspberry type oxide microspheres, wherein the atomization pressure of spray drying is 0.3-3.0 MPa, and the pressure in a tower is-0.0010-0.0090 MPa; the initial air inlet temperature of drying is 580 ℃, and the air outlet temperature of drying termination is 160 ℃.

According to the SEM picture of the raspberry type oxide microsphere, the surface of the microsphere is provided with a macroporous hollow microsphere, a hollow structure is arranged in the hollow microsphere, and the macropore is communicated with the hollow structure to form a cavity with an opening at one end.

Preparation example 2

20kg of water is added into a reaction kettle, 0.5kg of zirconium nitrate is added into the reaction kettle, 175g of concentrated nitric acid is added into the reaction kettle, 2kg of PEG4000 is added into the reaction kettle, and finally 4.6kg of pseudo-boehmite powder is added into the reaction kettle, and the mixture is stirred uniformly and ground to obtain dispersed slurry.

The dispersion slurry was aged at 25 ℃ for 1 hour with stirring.

Feeding the aged dispersed slurry into a spray drying device for drying and forming to obtain raspberry type oxide microspheres, wherein the atomization pressure of spray drying is 0.3-3.0 MPa, and the pressure in a tower is-0.0010-0.0090 MPa; the initial air inlet temperature of drying is 600 ℃, and the air outlet temperature of drying termination is 180 ℃.

The SEM of the resulting raspberry-type oxide microspheres was similar to that of preparation example 1.

Preparation example 3

30kg of water is added into a reaction kettle, 0.7kg of zirconium nitrate is added into the reaction kettle, then 2L of concentrated ammonia water is added, 1.5kg of PEG4000 and 8g of picric acid are added, finally 7kg of zirconium hydroxide is added, and the mixture is stirred uniformly and ground to obtain dispersed slurry.

The dispersion slurry was aged at 25 ℃ for 2 hours with stirring.

Feeding the aged dispersed slurry into a spray drying device for drying and forming to obtain raspberry type oxide microspheres, wherein the atomization pressure of spray drying is 0.3-3.0 MPa, and the pressure in a tower is-0.0010-0.0090 MPa; the initial air inlet temperature of drying is 560 ℃, and the air outlet temperature of drying termination is 140 ℃.

Preparation example 4

30kg of water is added into a reaction kettle, 0.7kg of titanium nitrate is added into the reaction kettle, then 2.6L of concentrated ammonia water is added, 1.5kg of PEG4000 and 6g of picric acid are added, and finally 500g of concentrated nitric acid and 7kg of titanium nitrate are added, stirred uniformly and ground to obtain dispersed slurry.

The dispersion slurry was aged at 25 ℃ for 2 hours with stirring.

Feeding the aged dispersed slurry into a spray drying device for drying and forming to obtain raspberry type oxide microspheres, wherein the atomization pressure of spray drying is 0.3-3.0 MPa, and the pressure in a tower is-0.0010-0.0090 MPa; the initial air inlet temperature of the drying is 560 ℃, and the air outlet temperature of the drying is 141 ℃.

The following examples are provided to illustrate Fischer-Tropsch synthesis catalysts provided by the present invention.

Example 1

The raspberry type oxide microspheres obtained in preparation example 1 were calcined at 600 ℃ for 3 hours to obtain a carrier ZT1, and the physical properties thereof are shown in table 1.

The carrier ZT1 is dipped in a solution of cobalt nitrate and zirconium nitrate for a plurality of times to prepare a catalyst with the Co content of 35 wt% and the Zr content of 1 wt%, and the catalyst is dried for 2 hours at the temperature of 120 ℃ and roasted for 2 hours at the temperature of 420 ℃ to obtain the catalyst CAT1.

And (3) conveying the roasted powder into a fluidized bed reduction system, and firstly introducing a nitrogen replacement system into the reactor to an oxygenation grid (the oxygen content is less than or equal to 0.5 vol%). Then the hydrogen content in the mixed gas of hydrogen and nitrogen is made to be 40 volume percent by supplementing hydrogen, and then a one-step reduction process is started: introducing the mixed gas with the gas-to-agent ratio of 2000 to enable the catalyst to be in a fluidized state, raising the temperature of the catalyst to 400 ℃ at the temperature raising rate of 80 ℃/h, and keeping the temperature for 1 h; and finishing the reduction step.

Then introducing hydrogen in a nitrogen replacement system, cooling the reduced catalyst to below 45 ℃, and introducing oxygen-containing gas with the oxygen concentration of 0.2-21 vol% prepared by air and nitrogen below 45 ℃ under normal pressure. Introducing oxygen-containing gas with oxygen concentration of 0.2 vol%, 0.6 vol%, 1.0 vol%, 3.0 vol%, 8.0 vol% and 21 vol% into 6 sections in sequence, wherein after the oxygen-containing gas in the previous stage is introduced, when the oxygen concentration at the gas outlet is equal to the oxygen concentration at the gas inlet, the oxygen-containing gas in the next stage is introduced, and the oxygen concentration is gradually increased in such a way to carry out passivation until the passivation is finished. The passivation gas-agent ratio is 2000, the passivation temperature of the catalyst bed layer is controlled to be less than 65 ℃ in the period, and the total passivation time is 1 hour. Obtaining the Fischer-Tropsch synthesis catalyst.

The SEM photograph of the catalyst prepared in example 1 is shown in FIG. 1.

Comparative example 1

According to the method of embodiment 1, except that the passivation is not segmented, specifically comprising: introducing oxygen-containing gas with the oxygen concentration of 21 volume percent below 55 ℃ under normal pressure, wherein the gas-agent ratio is 500, the passivation time is 0.5 hour, and the passivation temperature of a catalyst bed layer is controlled to be less than 150 ℃.

Comparative example 2

According to the method of the embodiment 1, except that the passivation process is different, specifically, oxygen-containing gas with the oxygen concentration of 1.5-21 vol% below 55 ℃ is introduced under normal pressure, the passivation is divided into two sections, the gas-to-agent ratio is 500, and the oxygen concentration of the oxygen-containing gas adopted in the first-stage passivation is 1.5 vol%; the oxygen concentration of the oxygen-containing gas used in the second stage passivation was 21 vol%, wherein after the oxygen-containing gas in the first stage was introduced, when the oxygen concentration at the gas outlet was equal to that at the gas inlet, the oxygen-containing gas in the second stage was introduced for a total passivation time of 1 hour. During which the deactivation temperature of the catalyst bed is controlled to be less than 150 ℃.

Example 2

The raspberry type oxide microspheres obtained in preparation example 2 were calcined at 500 ℃ for 3 hours to obtain a carrier ZT2, and the physical properties thereof are shown in table 1.

The carrier ZT2 was immersed in a solution containing cobalt nitrate and zirconium nitrate several times to prepare a catalyst having a Co content of 35 wt% and a Zr content of 2 wt%, dried at 110 ℃ for 4 hours, and calcined at 350 ℃ for 3 hours to obtain a catalyst CAT2.

Catalyst CAT2 was reduced and passivated according to the procedure of example 1, except that the oxygen concentration of the oxygen-containing gas used in the first stage of passivation was 0.1% by volume, the oxygen concentration of the oxygen-containing gas used in the second stage was 0.8% by volume, and the total passivation time in the third and subsequent stages was 1.5 hours as in example 1. Obtaining the Fischer-Tropsch synthesis catalyst.

Example 3

The raspberry type oxide microspheres obtained in preparation example 3 were calcined at 550 ℃ for 3 hours to obtain a carrier ZT3, and the physical properties thereof are shown in table 1.

Impregnating the carrier ZT3 with cobalt nitrate and Re (NO) for multiple times₃)₃The catalyst (2) was dried at 120 ℃ for 2 hours and calcined at 420 ℃ for 2 hours to obtain CAT3.

The catalyst CAT3 was reduced in the same manner as in example 1, except that the reduction temperature was 450 ℃ and the temperature was maintained for 1.5 hours; then, passivation was carried out in the same manner as in example 1 except that the oxygen concentration of the oxygen-containing gas used in the first stage of passivation was 0.15 vol%, the oxygen concentration of the oxygen-containing gas used in the second stage was 0.9 vol%, and the total time of passivation in the third and subsequent stages was 1 hour as in example 1. Obtaining the Fischer-Tropsch synthesis catalyst.

Example 4

The raspberry type oxide microspheres obtained in preparation example 4 were calcined at 700 ℃ for 3 hours to obtain a carrier ZT4, and the physical properties thereof are shown in table 1.

The carrier ZT4 is dipped in cobalt nitrate and copper nitrate solution for a plurality of times to prepare a catalyst with the Co content of 35.0 wt% and the Cu content of 1.0 wt%, and the catalyst is dried for 2 hours at the temperature of 130 ℃ and roasted for 4 hours at the temperature of 370 ℃ to obtain a catalyst CAT4.

The CAT4 catalyst was reduced and passivated according to the method of example 3, except that the reduction temperature was 450 ℃ and the temperature was kept constant for 1.5 hours during the reduction; in the passivation process, the oxygen concentration of the oxygen-containing gas used in the first stage passivation is 0.2 volume percent, the oxygen concentration of the oxygen-containing gas used in the second stage passivation is 1 volume percent, and the total passivation time of the third stage and the subsequent stages is 2 hours as in example 1. Obtaining the Fischer-Tropsch synthesis catalyst.

TABLE 1 physical Properties of the support

As can be seen from Table 1, when the raspberry-type oxide microspheres of the inventive preparation were used as the carrier, the sphericity and strength were greatly improved, although the specific surface, pore volume and average pore diameter were similar to those of the comparative example, which is significantly better than those of the oxide microspheres of the comparative preparation. The possibility is provided for the use of these vectors.

Example 5

The method of example 1 was followed except that the reduction process specifically included: firstly, a nitrogen replacement system is introduced into a reactor until oxygen content is less than or equal to 0.5 volume percent, and hydrogen-containing gas (70 volume percent of mixed gas of hydrogen and nitrogen) is adopted to reduce for 1 hour at 410 ℃, wherein the gas-to-agent ratio is 2200. Obtaining the catalyst CAT5 for Fischer-Tropsch synthesis.

Example 6

According to the method of embodiment 1, except that the passivation process specifically includes: the temperature of the reduced catalyst is reduced to below 40 ℃, and oxygen-containing gas with the oxygen concentration of 0.05-21 volume percent, which is prepared by air and nitrogen and is below 40 ℃, is introduced under normal pressure. Introducing oxygen-containing gas with oxygen concentration of 0.05 vol%, 0.2 vol%, 0.4 vol%, 0.8 vol%, 1.2 vol%, 3.0 vol%, 8.0 vol% and 21 vol% into 8 stages in sequence, wherein after the oxygen-containing gas in the previous stage is introduced, when the oxygen concentration at the gas outlet is equal to the oxygen concentration at the gas inlet, the oxygen-containing gas in the next stage is introduced, and the oxygen concentration is gradually increased to carry out passivation until the passivation is finished. The gas-agent ratio of the first two segments of passivation is 1000, and the gas-agent ratio of the last six segments of passivation is 500. During the period, the passivation temperature of the catalyst bed layer is controlled to be less than 55 ℃, and the total passivation time is 1 hour. Obtaining the catalyst CAT6 for Fischer-Tropsch synthesis.

Example 7

According to the method of embodiment 1, except that the passivation process specifically includes: cooling the reduced catalyst to below 45 ℃, introducing oxygen-containing gas with the oxygen concentration of 0.15-21 vol% under normal pressure, and sequentially introducing the oxygen-containing gas with the oxygen concentrations of 0.15 vol%, 0.3 vol%, 1.0 vol%, 6 vol%, 12 vol% and 21.0 vol% in 6 sections; the gas-agent ratio of the first 2 sections of the passivation is 2000, the gas-agent ratio of the second 4 sections of the passivation is 1000, the passivation temperature of the catalyst bed layer is controlled to be less than 55 ℃, and the total passivation time is 1 hour. Obtaining the Fischer-Tropsch synthesis catalyst CAT7.

Example 8

According to the method of the embodiment 1, except that the passivation process is different, specifically: introducing oxygen-containing gas with oxygen concentration of 1-21 vol% prepared from air and nitrogen at 45 deg.C or below under normal pressure. Introducing oxygen-containing gas with oxygen concentration of 1.0 vol%, 3.0 vol%, 8.0 vol% and 21 vol% into the reactor in 4 stages, introducing oxygen-containing gas in the former stage when the oxygen concentration in the gas outlet is equal to that in the gas inlet, and gradually raising the oxygen concentration for passivation until the passivation is finished. During the period, the passivation temperature of the catalyst bed layer is controlled to be less than 65 ℃, and the total passivation time is 2 hours. Obtaining the Fischer-Tropsch synthesis catalyst CAT8.

The catalysts prepared in the above examples and comparative examples were subjected to characterization analysis, and the number of active centers of the catalysts after re-reduction treatment, the temperature corresponding to the peak of the maximum low-temperature reduction peak in the TPR spectrum curve, the degree of reduction, and the like are shown in table 2.

TABLE 2

As can be seen from Table 2, the Fischer-Tropsch synthesis catalyst obtained by the method of the invention has higher active center number, and the temperature corresponding to the peak value of the low-temperature reduction peak with the largest area is lower, so that the catalyst is easier to regenerate.

Test example 1

The catalyst prepared in the above way is subjected to a reaction performance test in a small-sized microchannel reactor (the minimum dimension of the cross section of the channel is 1000 μm), the small-sized microchannel reactor module is provided with 16 reaction channels and 36 cooling channels, the reaction channels are 200mm long, and the maximum loading of the catalyst is 6mL.

The pre-reduced catalysts obtained in the above examples and comparative examples were each tested by filling 4.0ml of the above catalyst in the constant temperature zone of a mini microchannel reactor. Before the catalyst is used, the catalyst needs to be reduced again. Reducing the atmosphere to hydrogen; the conditions of the re-reduction reaction are as follows: the pressure is normal pressure, the heating rate is 5 ℃/min, and the air speed of hydrogen is 600h^-1The re-reduction temperature was 200 ℃ and the re-reduction time was 2 hours.

After the re-reduction, a reaction performance test is carried out, and the specific reaction conditions are as follows: the feed gas is a synthesis gas in which H₂The mol ratio of/CO is =2/1, the pressure is 2.5MPa, the temperature is 220 ℃, and the volume space velocity of the raw material gas is 24000h^-1. After the reaction was carried out for 12 hours, a gas sample was taken for chromatography.

The reactivity indicators are: CO conversion, methane selectivity and C5+ hydrocarbon selectivity and CO₂And (4) selectivity. The results of the reaction performance test are shown in table 3.

Wherein, the calculation formula of the methane selectivity is as follows:

wherein n is_CH4Moles of CO to methane, n_conIs the total moles of CO converted.

The C5+ hydrocarbon selectivity is calculated as: (total moles of CO converted-moles of carbon monoxide converted to carbon dioxide and C1-C4 hydrocarbons)/total moles of CO converted.

CO₂The selectivity is calculated as: conversion to CO₂Mole of C/total moles of CO converted.

TABLE 3

The test results in Table 3 show that the catalyst provided by the invention has better FT synthesis performance, namely higher CO conversion rate and C5+ hydrocarbon selectivity, and lower methane selectivity and CO₂And (4) selectivity. Furthermore, the methane selectivity of the catalyst of the invention is not obviously increased due to the temperature rise,the diffusion problem of the FT synthesis reaction is obviously solved.

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 comprises a carrier and an active component loaded on the carrier, wherein the active component comprises cobalt and an auxiliary agent, the auxiliary agent is selected from at least one of IA group metal elements, IIA group elements, IB group elements, IIB group elements, IIIB group elements, IVB group elements, VB group elements, VIB group elements, VIIB group elements and VIII group elements, the total amount of the catalyst is taken as a reference, the content of the cobalt is 20-60 wt% and the content of the auxiliary agent is 0.001-25 wt% in terms of oxide;

wherein the active center number of the catalyst after the catalyst is subjected to re-reduction treatment is 0.06-0.3mmol of hydrogen per gram of catalyst, and the re-reduction treatment conditions comprise: the temperature was 200 ℃ and the time was 2 hours, and the reducing atmosphere was an atmosphere containing hydrogen and argon at a hydrogen concentration of 10 vol%, and the gas-agent volume ratio was 15000.

2. The catalyst according to claim 1, wherein the catalyst has an activity center number of 0.09 to 0.29mmol of hydrogen per g of catalyst after the catalyst is subjected to a re-reduction treatment;

preferably, the catalyst is characterized by TPR, and the peak of the low temperature reduction peak with the largest area in the TPR curve corresponds to a temperature of 140-270 ℃, preferably 150-260 ℃.

3. The catalyst according to claim 1 or 2, wherein the cobalt content is 25-55 wt% and the promoter content is 0.001-10 wt%, calculated as oxide, based on the total amount of the catalyst;

preferably, the auxiliary agent is selected from one or more of La, zr, mn, V, cr, cu, ce, W, ti, zn, sc, mg, ca, be, na, K, ru, ag, au, re, pt and Pd, more preferably from one or more of La, zr, cu, ce, W, ti, ru, ag, au, re, pt and Pd;

preferably, the oxide in the raspberry-type oxide microspheres is aluminum oxide and/or silicon oxide.

4. A catalyst as claimed in any one of claims 1 to 3, wherein the raspberry type oxide microspheres have a particle size of 3 to 2500 μm, preferably 10 to 500 μm; and/or the presence of a gas in the gas,

the diameter of the hollow structure is 1-2000 μm, preferably 1-400 μm; and/or the presence of a gas in the gas,

the pore diameter of the macropores is 0.2-1000 μm, preferably 0.5-200 μm; and/or the presence of a gas in the gas,

the shell thickness of the hollow microsphere is 0.2-1000 μm, preferably 0.5-200 μm.

5. The catalyst of any one of claims 1-4, wherein the raspberry-type oxide microspheres have a sphericity of 0.5-0.99; and/or

The breakage rate of the raspberry type oxide microspheres is 0-1%.

6. A method of preparing a fischer-tropsch synthesis catalyst, the method comprising:

(1) Preparing raspberry type oxide microspheres;

(3) Reducing the oxidation state catalyst in a hydrogen-containing atmosphere;

7. The production method according to claim 6, wherein the auxiliary is selected from one or more of La, zr, mn, V, cr, cu, ce, W, ti, zn, sc, mg, ca, be, na, K, ru, ag, au, re, pt and Pd, more preferably from one or more of La, zr, cu, ce, W, ti, ru, ag, au, re, pt and Pd; and/or the presence of a gas in the atmosphere,

the oxides in the raspberry type oxide microspheres are selected from one or more of aluminum oxide, silicon oxide, zirconium oxide, magnesium oxide, calcium oxide and titanium oxide, and preferably aluminum oxide and/or silicon oxide;

preferably, the raspberry type oxide microspheres have a particle size of 3 to 2500 μm, preferably 10 to 500 μm.

8. The production method according to claim 6 or 7, wherein the step (1) of producing raspberry-type oxide microspheres comprises:

(1-1) adding nitrate, peptizing agent, pore-forming agent, the oxide and/or precursor thereof into a dispersing agent and stirring to obtain dispersed slurry;

(1-2) subjecting the dispersion slurry to an aging treatment;

(1-3) conveying the aged dispersed slurry into a drying device, wherein the air inlet temperature is 400-1200 ℃, and preferably 450-700 ℃; drying and forming at the air outlet temperature of 50-300 ℃, preferably 120-200 ℃ to obtain the raspberry type oxide microspheres.

9. The preparation method according to claim 8, wherein the mass ratio of the nitrate, the peptizing agent, the pore-forming agent and the oxide and/or precursor thereof is (10-500): (1-10): (10-500): (10-1000);

preferably, the nitrate is selected from one or more of aluminum nitrate, zirconium nitrate, lanthanum nitrate, and yttrium nitrate; and/or the presence of a gas in the atmosphere,

the peptizing agent is selected from one or more of acids, alkalis and salts; and/or the presence of a gas in the gas,

the pore-forming agent is selected from one or more of starch, synthetic cellulose, polymeric alcohol and surfactant; and/or the presence of a gas in the atmosphere,

the oxide and/or a precursor thereof is selected from one or more of an aluminum source, a silicon source, a zirconium source and a titanium source, wherein the aluminum source is selected from one or more of pseudo-boehmite, aluminum alkoxide, aluminum nitrate, aluminum sulfate, aluminum chloride and sodium metaaluminate, the silicon source is selected from one or more of silicate, sodium silicate, water glass and silica sol, the zirconium source is selected from one or more of zirconium dioxide, zirconium tetrachloride, zirconium oxychloride, zirconium hydroxide, zirconium sulfate, zirconium phosphate, zirconyl nitrate, zirconium hydroxycarbonate and tetrabutoxyzirconium, and the titanium source is selected from one or more of titanium dioxide, metatitanic acid, titanium nitrate, titanyl sulfate, titanium dichloride, titanium trichloride, titanium tetrachloride, titanium aluminum chloride, tetraethyl titanate, tetrabutyl titanate, tetra-n-propyl titanate and tetra-isopropyl titanate; and/or the presence of a gas in the gas,

the dispersant is selected from one or more of water, alcohols, ketones and acids.

10. The preparation method according to claim 8 or 9, wherein the step (1-1) further comprises adding a blasting agent to the dispersing agent, wherein the blasting agent is selected from one or more of picric acid, trinitrotoluene, digested glycerol, nitrocotton, dana explosive, hexogen and C4 plastic explosive;

preferably, the addition amount of the blasting agent is 0-1% of the total dry basis weight of the nitrate, the peptizing agent, the pore-forming agent and the oxide and/or the precursor thereof.

11. The production method according to claim 8 or 9, wherein, in the step (1-2), the temperature of the aging treatment is 0 to 90 ℃, preferably 20 to 60 ℃; and/or the presence of a gas in the gas,

in the step (1-3), the drying device is a flash evaporation drying device or a spray drying device.

12. The production method according to any one of claims 6 to 11, wherein the reducing conditions of step (3) include: the oxidation state catalyst is in a fluidized state and is contacted with a reducing gas; the temperature is 100-750 ℃, the time is not more than 2h, and the reducing gas-agent ratio is 500-5000;

preferably, the temperature is 150-700 ℃, the time is not more than 1.5h, and the reducing gas-agent ratio is 600-4500;

preferably, the hydrogen-containing atmosphere contains hydrogen and optionally a shielding gas, and the hydrogen concentration in the hydrogen-containing atmosphere is not less than 5% by volume, preferably 5-90% by volume;

preferably, the reduction is carried out in a fluidized bed reactor.

13. The preparation method according to any one of claims 6 to 12, wherein the passivation time is not more than 5h, preferably not more than 1.5h;

preferably, during the passivation process, the oxygen concentration of the oxygen-containing gas is continuously increased in at least 2 stages, more preferably in 2-10 stages, and even more preferably in 3-8 stages;

preferably, the passivating gas to agent ratio is from 200 to 4500, more preferably from 300 to 4000;

preferably, the passivation is carried out in a fluidized bed reactor, the catalyst being in a fluidized state.

14. The production process according to any one of claims 6 to 13, wherein the concentration of the oxygen-containing gas is 0.05 to 21% by volume, preferably 0.1 to 21% by volume;

preferably, during the passivation process, the initial oxygen concentration of the introduced oxygen-containing gas is 0.05-0.2 vol%;

preferably, during the passivation process, the oxygen concentration of the oxygen-containing gas introduced in the second stage is 0.1-1% by volume;

preferably, during the passivation process, the oxygen concentration of the oxygen-containing gas introduced in the later stage is 1-8 times higher than that of the oxygen-containing gas introduced in the previous stage.

15. A fischer-tropsch synthesis catalyst prepared according to the process of any one of claims 6 to 14.

16. Use of a fischer-tropsch synthesis catalyst as claimed in any one of claims 1 to 5 and 15 in a fischer-tropsch synthesis reaction.