CN110270334B - Cobalt-based Fischer-Tropsch synthesis catalyst and preparation method thereof - Google Patents

Cobalt-based Fischer-Tropsch synthesis catalyst and preparation method thereof Download PDF

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CN110270334B
CN110270334B CN201910589839.6A CN201910589839A CN110270334B CN 110270334 B CN110270334 B CN 110270334B CN 201910589839 A CN201910589839 A CN 201910589839A CN 110270334 B CN110270334 B CN 110270334B
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cobalt
catalyst
oxalate
tropsch synthesis
zirconium
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CN110270334A (en
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王计奎
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Tengzhou Jingtengxinhui New Material Technology Co ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/002—Mixed oxides other than spinels, e.g. perovskite
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
    • B01J23/74—Iron group metals
    • B01J23/75—Cobalt
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
    • C10G2/00—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon
    • C10G2/30—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen
    • C10G2/32—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen with the use of catalysts
    • C10G2/33—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen with the use of catalysts characterised by the catalyst used
    • C10G2/331—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen with the use of catalysts characterised by the catalyst used containing group VIII-metals
    • C10G2/332—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen with the use of catalysts characterised by the catalyst used containing group VIII-metals of the iron-group
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2523/00—Constitutive chemical elements of heterogeneous catalysts

Abstract

The invention belongs to the field of catalysts, and particularly relates to cobalt-based Fischer-Tropsch synthesis catalysisAn agent and a preparation method thereof. The catalyst comprises 10-30 wt% of metallic cobalt and the balance of oxide carrier, wherein the crystallite grain diameter of the metallic cobalt is 6.5-7.5nm, and the oxide carrier is made of Al2O3And ZrO2Composition of, wherein ZrO2The content of (B) is 5-10 wt% of the weight of the carrier. The catalyst is produced by a coprecipitation method, oxalic acid or oxalate and an alkaline precipitator are used as a precipitator system in the coprecipitation process, then the catalyst is roasted in an inert atmosphere, CO generated by oxalic acid decomposition in the roasting process is used as a reducing gas, the synchronous roasting and reduction is realized, the active component cobalt in the prepared cobalt-based catalyst is uniformly dispersed, the acting force between the cobalt and an oxide carrier is moderate, the catalyst has proper activity and C on the whole5+Selectivity and lifetime.

Description

Cobalt-based Fischer-Tropsch synthesis catalyst and preparation method thereof
Technical Field
The invention belongs to the field of catalysts, and particularly relates to a cobalt-based Fischer-Tropsch synthesis catalyst and a preparation method thereof.
Background
The general condition of the energy structure in China is rich coal, poor oil and less gas, the dependence of petroleum in China on the outside is continuously increased along with the continuous high-speed development of economy in China, and the dependence of petroleum in China is up to 67% in 2017, so that the method becomes one of the bottlenecks of the continuous and healthy development of the economy in China. Coal is used as main energy of China, synthesis gas is produced by taking coal as a raw material, and then liquid hydrocarbons are produced through a Fischer-Tropsch synthesis reaction, so that the method is one of important ways for solving the problem of insufficient supply of liquid fuel, and has important strategic significance for guaranteeing national energy safety and promoting social and economic sustainability and scientific development.
The Fischer-Tropsch synthesis reaction is synthesis gas (CO + H) obtained by converting coal, natural gas, biomass and the like2) Catalyzing and synthesizing the hydrocarbon liquid fuel in the presence of a Fischer-Tropsch synthesis catalyst. The gasoline prepared by Fischer-Tropsch synthesis is a high-quality clean fuel without sulfur, lead and other impurities and with high octane, which plays an important role in helping China to improve atmospheric conditions and realize green low carbon.
The fischer-tropsch synthesis catalyst generally includes an iron-based fischer-tropsch synthesis catalyst, a cobalt-based fischer-tropsch synthesis catalyst, and a ruthenium-based fischer-tropsch synthesis catalyst. Wherein, the cobalt-based Fischer-Tropsch synthesis catalyst has the characteristics of high activity, high linear chain saturated heavy hydrocarbon selectivity, low water gas change reaction and the like, has industrial application value, is one of the most suitable catalysts for synthesizing high-quality liquid fuel from coal, and is particularly suitable for the volume ratio H converted from natural gas2Syngas with/CO 2 is therefore widely used in industrial production.
Such as Chinese patent CN 104174398AThe method for producing the cobalt-based Fischer-Tropsch synthesis catalyst by self-reduction comprises the steps of preparing a cobalt oxide, an oxide carrier and a surface-passivated cobalt oxide; by introducing an organic carbon source in the process of preparing the catalyst carrier by a deposition precipitation method, and utilizing the characteristic that the organic carbon source is decomposed to generate a weak reduction component, namely simple substance carbon, in an inert atmosphere, the carbon-containing carrier is impregnated with cobalt and then roasted, so that the cobalt-based catalyst is roasted and self-reduced synchronously, and the self-reduced catalyst with the passivated surface is obtained, the online reduction temperature of the cobalt-based catalyst is greatly reduced, and the online reduction temperature can be basically equivalent to the temperature of the Fischer-Tropsch synthesis reaction; meanwhile, the organic carbon source can play a role in pore expansion of the catalyst in the processes of roasting, carbonizing and reducing cobalt, so that the prepared catalyst has a developed pore structure and a large specific surface area. But the catalyst is most commonly used in synthesis gas (H)22/CO (mol) ═ C) at 210 ℃ the CO conversion was only 75.6%, C5+The selectivity was only 78.3%.
In situ reduction process for the production of a cobalt based fischer-tropsch synthesis catalyst comprising cobalt oxide, an oxide support and surface passivated cobalt oxide, as disclosed in chinese patent CN 104174400A; by introducing hydroxy acid in the process of loading cobalt by an impregnation method and utilizing the characteristic that the hydroxy acid is decomposed in an inert atmosphere to generate reducing gas CO, the cobalt-based catalyst is roasted and self-reduced synchronously to obtain a self-reduced catalyst with a passivated surface, the online reduction temperature of the cobalt-based catalyst is greatly reduced, and the online reduction temperature can be basically equivalent to the temperature of the Fischer-Tropsch synthesis reaction; meanwhile, roasting decomposition of the hydroxy acid can also play a role in pore expansion of the catalyst, so that the prepared catalyst has a developed pore structure and a larger specific surface area. But the catalyst is most commonly used in synthesis gas (H)22/CO (mol) ═ C) at 210 ℃ the CO conversion was only 73.4%, C5+The selectivity was only 80.4%.
For example, the Chinese patent CN 1398669A discloses a cobalt zirconium Fischer-Tropsch synthesis catalyst, which comprises the following components in percentage by weight: 10.0-80.0% of cobalt, 15.0-85.0% of zirconium oxide and 0-5.0% of metal oxide auxiliary agent, wherein the metal oxide auxiliary agent is cerium oxide, manganese oxide and the like. The catalyst can be prepared by adopting a coprecipitation method or an impregnation method, and the catalyst utilizes zirconia as a carrier, so that under the reaction condition of Fischer-Tropsch synthesis, a compound cannot be formed between cobalt and the zirconia, and the catalyst has excellent stability, low inactivation rate, high reduction degree and high metal dispersion degree. However, the catalyst needs to be reduced at a conventional reduction temperature (about 420 ℃), so that the energy consumption required in the preparation process is increased, and the pore structure of the carrier is easily damaged.
For example, U.S. Pat. No. 5,573,3839A discloses a Pt-based additive and Al-based additive2O3A cobalt-based Fischer-Tropsch synthesis catalyst as a carrier, wherein the weight ratio of Pt to Co in the catalyst is (0.00005-0.1): 1. although the catalyst has higher catalytic activity, the noble metal Pt is introduced, so the production cost of the catalyst is increased.
For example, a compound made of TiO as disclosed in US 7851404A2A cobalt based fischer-tropsch synthesis catalyst supported on a cobalt based carrier, preferably having a cobalt content of from 3 to 75 wt%, and prepared by an impregnation process, preferably at a reduction temperature of 425 ℃. The catalyst has higher specific surface area of cobalt and better dispersity of cobalt, but the reduction temperature required in the preparation process is higher, so that the energy consumption is increased, and the pore channel structure of the carrier is easy to damage.
Generally, the catalytic performance and the production cost required by the preparation process of the existing cobalt-based catalyst for Fischer-Tropsch synthesis still have various defects, so that a new generation of cobalt-based catalyst with better performance for Fischer-Tropsch synthesis needs to be developed to provide more favorable support for the industrial production of synthetic gas-to-oil.
Disclosure of Invention
Therefore, the technical problem to be solved by the present application is how to increase the activity, C, of the cobalt-based Fischer-Tropsch synthesis catalyst as much as possible without increasing the production cost5+Selectivity and lifetime.
In order to solve the above technical problems, the inventors of the present application have earnestly studied and found that the above technical problems can be solved by producing a catalyst by a coprecipitation method in which oxalic acid or oxalate and an alkaline precipitant are used as a precipitant system during coprecipitation, then calcining the catalyst in an inert atmosphere, and simultaneously performing calcination and reduction by using CO generated by decomposition of oxalic acid during calcination as a reducing gas, so that cobalt as an active component in the prepared cobalt-based catalyst is uniformly dispersed and the crystallite particle size is concentrated in the range of 6.5 to 7.5 nm.
The technical scheme of the invention is as follows: the invention discloses a cobalt-based Fischer-Tropsch synthesis catalyst, which comprises 10-30 wt% of metal cobalt and the balance of an oxide carrier, wherein the crystallite diameter of the metal cobalt is 6.5-7.5 nm. The oxide carrier is made of Al2O3And ZrO2Composition of, wherein ZrO2The content of (B) is 5-10 wt% of the weight of the carrier.
The catalyst of the present application may contain optional auxiliary components such as rare earth oxides such as cerium oxide, lanthanum oxide, etc., transition metal oxides such as manganese oxide, chromium oxide, rhenium oxide, etc., and alkaline earth metal oxides such as magnesium oxide, etc., in addition to the active components of cobalt, alumina-zirconia support. The content of the auxiliary component is preferably from 0.5 to 5% by weight, based on the total weight of the catalyst.
It is considered that when alumina, silica or titania is used alone as a carrier of a cobalt-based fischer-tropsch synthesis catalyst, when the catalyst runs in a slurry bed or runs in a fixed bed for a long time, the hydrothermal action can promote the chemical action of active component cobalt and the carrier, and cobalt aluminate, cobalt silicate or cobalt titanate compounds which do not have reaction activity and can be reduced only at high temperature are formed respectively, and the reduction and activation at high temperature not only reduces the reaction efficiency, but also causes the severe agglomeration of cobalt metal and reduces the utilization rate of the active metal, thereby greatly shortening the service life of the catalyst, causing the cost of a ton oil catalyst to be high, and severely restricting the industrial application of the fischer-tropsch synthesis process.
The inventor of the application finds that in the catalyst, the proper amount of zirconia is introduced into the alumina carrier, which is helpful for adjusting the interaction between cobalt and alumina, so that the proper reduction degree and dispersion degree of the cobalt serving as an active component are realized, the cobalt aluminate compound which is difficult to reduce is prevented from being formed in the using process of the catalyst to a certain extent, and the cobalt can be prevented from sintering.
For Cobalt based Fischer-Tropsch synthesis catalysts, there are two perspectives in the art of optimum crystallite Size for metallic Co, one being that the Fischer-Tropsch catalyst has an optimum Cobalt crystallite Size in the 6nm range, because this provides a greater number of surface Cobalt sites than larger crystallites, and because crystallites below 6nm have a lower site activity than those of 6nm and larger sizes (see den Breejen et al, "On the Origin of the Cobalt Particle Effects in Fischer-Tropsch Catalysis", Journal of American Chemical Society, (2009), 131(20), 7197 and 7203). Secondly, the minimum grain size is required to be 8nm, and in order to effectively utilize a relatively expensive Co-based catalyst, the particle size distribution is required to be narrow and close to the minimum grain size (see "design and development of industrial catalysts", huang zhong tao et al, p 413, press of chemical industry, 9 months 2009).
However, the inventors of the present application have found, through studies, that, in the case of a cobalt-based Fischer-Tropsch synthesis catalyst, the catalytic activity of metallic Co is shown to be proportional to the surface cobalt sites when the minimum crystallite diameter is greater than 7nm, and the site activity begins to decrease when the minimum crystallite diameter is less than 7 nm. At the same time, it has also been found that metal crystallites of poor nanoscale homogeneity tend to aggregate severely more readily than those with a uniform nanoscale distribution. It is therefore believed that the cobalt based fischer-tropsch catalyst has an optimum cobalt crystallite size of 7nm, as it provides both more surface cobalt sites and higher site activity. Therefore, in order to effectively utilize a cobalt-based Fischer-Tropsch synthesis catalyst, it is required that the grain size distribution of the metal Co be narrow, close to the optimum cobalt crystallite size. By utilizing the preparation method, the grain size of the metal Co can be effectively controlled to be 6.5-7.5nm, and the cobalt microcrystal active component is loaded on the Al2O3-ZrO2On the carrier, the activity and C of the cobalt-based catalyst can be well improved5+Selectivity, and improves the stability and prevents sintering by adjusting the acting force between Co and the carrier.
The invention also discloses a preparation method of the cobalt-based Fischer-Tropsch synthesis catalyst, which comprises the following steps:
1) weighing soluble cobalt salt, aluminum salt and zirconium salt according to the composition of the final catalyst, and adding deionized water to prepare a mixed solution;
2) adding the mixed solution obtained in the step 1) and oxalic acid or oxalate precipitant solution into a reaction kettle in a concurrent flow manner, then adding an alkaline precipitant, and keeping the pH value to be 7.5-8.5; heating to 30-50 ℃ in the coprecipitation process;
3) then aging at 65-85 deg.C for 2-10h, suction filtering or centrifuging to obtain filter cake, and washing;
4) drying the filter cake at 70-100 ℃ for 7-15h, then roasting at 350-600 ℃ for 3-7h under the protection of inert atmosphere, and then cooling to room temperature to obtain the catalyst product.
The soluble cobalt salt in the step 1) is selected from one or more of cobalt nitrate, cobalt acetate, cobalt sulfate, cobalt chloride and the like.
The soluble aluminum salt in the step 1) is one or more selected from aluminum nitrate, cobalt sulfate, aluminum chloride and the like.
The soluble zirconium salt in step 1) is selected from one or more of zirconium oxychloride, zirconium nitrate, zirconyl nitrate and the like.
The concentration of cobalt ions in the mixed solution in the step 1) is 0.1-0.4mol/L, the concentration of aluminum ions is 0.2-2mol/L, and the concentration of zirconium ions is 0.005-0.1 mol/L.
The oxalate precipitating agent in the step 2) is selected from one or more of ammonium oxalate, sodium oxalate, potassium oxalate and the like.
The alkaline precipitant in the step 2) is one or more selected from ammonium carbonate, potassium carbonate, sodium bicarbonate, sodium hydroxide, ammonia water, urea and the like.
The inert atmosphere in the step 4) is selected from one or more of nitrogen, argon, helium and the like.
In the preparation method of the present application, a forming step may be introduced after step 4), according to the requirements on the shape and mechanical strength of the catalyst in a specific use process, and a conventional forming manner, such as compression forming, extrusion forming, rotation forming, etc., may be adopted, and a proper amount of conventional forming aids, such as a binder such as methyl cellulose, a lubricant such as graphite, paraffin, an extrusion aid such as sesbania powder, etc., may be introduced during the forming process.
In order to prevent the catalyst produced from degrading the catalytic effect by oxidation during storage, transport or any period of time before use, corresponding measures may be taken to avoid exposing the catalyst to an oxidizing atmosphere during storage and transport. For example, the catalyst can be charged by placing the catalyst in an inert atmosphere (e.g., nitrogen), or by placing the catalyst in a reducing atmosphere (e.g., 5% H by volume)2，95％N2) Medium packing, or passivation by contacting the catalyst with a small amount of air to create a thin protective oxide layer on the catalyst surface, or coating the catalyst with wax to avoid contact of the catalyst with the oxidizing atmosphere. These measures can in particular be taken before any storage and/or transport.
The inventor of the present application has found that, in the preparation process of the present application, the active component cobalt is precipitated by using oxalic acid or oxalate first, since the solution contains a large amount of Al3+And a small amount of Zr2+Will be included in the colloidal precipitate, and will further make Al in the process of controlling the pH value of the solution to 7.5-8.5 by using alkaline precipitant3+And Zr2+The precipitate generates aluminum hydroxide and zirconium hydroxide, the mixed precipitate of the cobalt oxalate, the aluminum hydroxide and the zirconium hydroxide prepared in the way basically does not generate a cobalt-aluminum spinel structure in the roasting process, and the acting force of the active component cobalt and the oxide carrier is kept moderate.
The inventor of the present application has found that under the coprecipitation conditions of the present application, if oxalic acid or oxalate is used as a precipitant, and a basic precipitant is not introduced subsequently, only cobalt oxalate precipitate can be obtained, and aluminum oxalate and Zr do not form2+The precipitate of (4); if only an alkaline precipitant is used, or if an alkaline precipitant is introduced first, it is found that Al is caused3+、Co2+、Zr2+Simultaneously precipitating to obtain precipitates of cobalt hydroxide, aluminum hydroxide and zirconium hydroxide,the subsequent introduction of oxalic acid or oxalate precipitant is thus of no significance, even if the amount of basic precipitant is controlled such that a portion of the Co remains in solution2+Can generate cobalt oxalate precipitate when oxalic acid or oxalate precipitating agent is introduced subsequently, but Al often remains in the solution at the same time3+Thus, the production cost is obviously increased, and the method is also not environment-friendly; in addition, under the condition of simultaneously obtaining cobalt hydroxide precipitate and cobalt oxalate precipitate, when the cobalt hydroxide precipitate and cobalt oxalate precipitate are roasted in the following inert atmosphere, only the decomposed cobalt oxide part can be reduced into metal cobalt by CO reducing atmosphere, and other decomposed cobalt oxide also needs to be further introduced with H2Or a CO reducing atmosphere, thereby complicating the manufacturing process, and after stepwise reduction, the cobalt crystallites in the final catalyst are typically greater than 10nm, reducing its catalytic activity and C5+And (4) selectivity.
Considering that the current process for preparing cobalt-based catalysts by means of co-precipitation methods is roughly of the following three types: firstly, precursor soluble salts of the carrier, the active component and the optional auxiliary component are co-precipitated together under the condition of an alkaline precipitator; secondly, preparing an oxide carrier, adding the oxide carrier into a solution of other components, and carrying out coprecipitation; thirdly, the other components are coprecipitated firstly and then mixed with the oxide carrier. The inventors of the present application compare the three processes with the process of the present application, and find that the performance of the catalyst product prepared by the three processes is significantly worse than that of the catalyst product of the present application, which is specifically described as follows:
catalyst product prepared by the method one3+、Co2+、Zr2+The cobalt and the oxide carrier in the product generated after roasting have strong acting force and generate more cobalt-aluminum spinel structures, so that the cobalt in the product is still difficult to reduce at the high temperature of more than 500 ℃, even if the cobalt is reduced at higher temperature, the cobalt crystallite is easy to sinter at the high temperature and then agglomerate, the cobalt crystallite is always as high as more than 20nm, and the catalytic activity and the C of the cobalt crystallite are seriously reduced5+And (4) selectivity.
The catalyst product prepared by the second method and the third method has low catalyst activity because the mixing uniformity of the carrier and the active component precursor is poor, the acting force between the roasted active component cobalt and the oxide carrier is weak, and the obtained cobalt microcrystal is large and is often more than 10 nm. And in the using process, the cobalt microcrystal is easy to sinter and grow up, so that the catalyst is poor in heat resistance, easy to inactivate and low in service life.
The application also discloses application of the cobalt-based Fischer-Tropsch synthesis catalyst in a Fischer-Tropsch synthesis hydrocarbon preparation process, wherein the used reactor can be a fixed bed reactor or a slurry bed reactor, and the reaction conditions are as follows: the reaction temperature is 180 ℃ and 230 ℃, H2The mol ratio of/CO is between 0.5 and 3.0, the pressure is between 1.0 and 5.0MPa, and the space velocity is 500--1。
In the reaction conditions, H2The mol ratio of/CO is preferably 1.0-2.0, the pressure is preferably 1.0-3.0MPa, and the space velocity is 500--1。
Compared with the prior art, the beneficial effect that this application has is:
1. the application overcomes the technical prejudice about the optimal cobalt microcrystal grain size in the cobalt-based Fischer-Tropsch synthesis catalyst in the prior art, and finds that the catalyst has extremely proper activity and C only by controlling the grain size of the cobalt microcrystal within 6.5-7.5nm5+Selectivity and lifetime.
2. The cobalt-based Fischer-Tropsch synthesis catalyst has the advantages that the acting force between the active component cobalt and the oxide carrier is moderate, the catalyst has good heat-resistant stability and chemical stability, the cobalt aluminate is basically not generated after the catalyst runs for a long time, and the cobalt microcrystal can be prevented from being sintered.
3. In the cobalt-based Fischer-Tropsch synthesis catalyst, a proper amount of zirconia is introduced into an alumina carrier, so that the interaction between cobalt and alumina is favorably adjusted, the proper reduction degree and dispersion degree of the active component cobalt are favorably realized, the cobalt aluminate compound which is difficult to reduce is prevented from being formed in the using process of the catalyst to a certain extent, and the cobalt-based Fischer-Tropsch synthesis catalyst can be favorably prevented from being sintered.
4. According to the preparation process of the cobalt-based Fischer-Tropsch synthesis catalyst, oxalic acid or oxalate and an alkaline precipitator are used as a precipitator system, then roasting is carried out in an inert atmosphere, CO generated by decomposition of the cobalt oxalate in the roasting process is used as a reducing gas, synchronous roasting and reduction are realized, the process is saved, the production time is shortened, the cobalt serving as an active component in the prepared cobalt-based catalyst is uniformly dispersed, and the crystallite grain size is concentrated at 6.5-7.5 nm.
5. In the preparation process of the cobalt-based Fischer-Tropsch synthesis catalyst, the co-precipitation process is controlled, so that the prepared mixed precipitate of cobalt oxalate, aluminum hydroxide and the like basically cannot generate a cobalt-aluminum spinel structure in the roasting process, and the acting force of the active component cobalt and an oxide carrier can be kept moderate.
Additional advantages will be set forth in part in the description which follows and in part will be obvious from the description, or may be learned by practice of the invention. The following advantages are realized and attained, particularly in light of the chemical compositions, methods, and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive.
Supplemental definition
The materials, compounds, compositions, and components described herein can be used in, or can be used in combination with, the methods and compositions described herein, or can be used in the practice of the methods and in the preparation of the compositions, or as products obtained by the methods. It is to be understood that when combinations, subsets, interactions, groups, etc. of these materials are disclosed that while specific reference of each and every combination and permutation of these compounds may not be explicitly made, each is specifically contemplated and described herein. For example, if an adjunct component is disclosed and discussed, and a number of alternative actual forms of the component are discussed, each and every combination and permutation of the adjunct component and the actual forms that are possible is specifically contemplated unless specifically indicated to the contrary. This concept applies to all aspects of this application, including but not limited to steps in methods of making and using the disclosed compositions. Thus, if there are a plurality of additional steps that can be performed it is understood that each of these additional steps can be performed by any specific embodiment or combination of embodiments of the disclosed methods, and that each such combination is specifically contemplated and should be considered disclosed.
In this specification and in the claims which follow, reference will be made to a number of terms which shall be defined to have the following meanings:
it must be noted that, as used in this specification and the appended claims, the singular forms "a," "an," and "the" include both one and more than one (i.e., two, including two) unless the context clearly dictates otherwise. Thus, for example, reference to "a pH adjuster as described" can include a single pH adjuster, or a mixture of two or more pH adjusters, and the like.
"optional" or "optionally" means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where said event or circumstance occurs and instances where it does not. For example, the phrase "optional adjunct component" means that the adjunct component can or can not be present, and the description covers both situations where the adjunct component is included in the composition and where the adjunct component is not included in the composition.
Unless otherwise indicated, numerical ranges in this application are approximate and thus may include values outside of the ranges. Ranges of values can be expressed herein as from "about" one particular value, and/or to "about" another particular value. When such a range is expressed, it includes from the one particular value and/or to the other particular value. Similarly, when a particular value is expressed as an approximation by the use of the antecedent "about," it should be understood that it encompasses the particular value itself as well as the error ranges allowable in the art as a result of measurement or calculation. It will be further understood that the endpoints of each of the numerical ranges are significant both in relation to the other endpoint, and independently of the other endpoint.
Reference in the specification and concluding claims to parts by weight of a particular element or component in a composition or article refers to the weight relationship between that element or component and any other elements or components in the composition or article, expressed as parts by weight. Thus, in a composition comprising 2 parts by weight of component X and 5 parts by weight of component Y, X and Y are present in a weight ratio of 2:5 and are present in this ratio regardless of whether additional components are included in the composition.
Unless the context clearly dictates otherwise, or there is other meaning, or implicit based on the context or conventional manner in the art, all parts and percentages referred to herein are by weight and the weight percentages of a component are based on the total weight of the composition or product in which the component is included.
Reference throughout this application to "comprising," "including," "having," and similar language is not intended to exclude the presence of any optional components, steps or procedures, whether or not any optional components, steps or procedures are specifically disclosed. For the avoidance of any doubt, unless stated to the contrary, all methods claimed through use of the term "comprising" may include one or more additional steps, apparatus parts or components and/or materials. In contrast, the term "consisting of … …" excludes any component, step, or procedure not specifically recited or recited. Unless otherwise specified, the term "or" refers to the listed members individually as well as in any combination.
Furthermore, the contents of any referenced patent or non-patent document in this application are incorporated by reference in their entirety, especially with respect to definitions disclosed in the art (where not inconsistent with any definitions specifically provided herein) and general knowledge.
Detailed Description
The following examples are put forth so as to provide those of ordinary skill in the art with a complete disclosure and description of how the compounds, compositions, articles, devices, and/or methods described and claimed herein are made and evaluated, and are intended to be purely exemplary and are not intended to limit the scope of what applicants regard as their invention. Efforts have been made to ensure accuracy with respect to numbers (e.g., amounts, temperature, etc.) but some errors and deviations should be accounted for. Unless otherwise indicated, parts are parts by weight, temperatures are in degrees Celsius or at ambient temperature, and pressures are at or near atmospheric. There are many variations and combinations of reaction conditions (e.g., component concentrations, desired solvents, solvent mixtures, temperatures, pressures, and other reaction ranges) and conditions that can be used to optimize the purity and yield of the product obtained by the process. Only reasonable routine experimentation will be required to optimize such process conditions.
Example 1:
the catalyst contains Co 12 wt% and ZrO in the carrier2The content of (B) is 5 wt%, and Co (NO) is weighed3)2·6H2O，Al(NO3)3·9H2O，Zr(NO3)4·5H2Adding deionized water into the O to prepare a mixed solution; the concentration of cobalt ions in the mixed solution was 0.15mol/L, the concentration of aluminum ions was 1.8mol/L, and the concentration of zirconium ions was 0.01 mol/L.
Adding the mixed solution and ammonium oxalate precipitator solution into a reaction kettle in a concurrent flow manner, then adding sodium carbonate, and keeping the pH value at 7.5; heating to 35 ℃ in the coprecipitation process; after the coprecipitation is finished, aging for 8 hours at 70 ℃, then performing suction filtration to obtain a filter cake, and washing; and drying the filter cake at 80 ℃ for 12h, then roasting at 400 ℃ for 6h under the protection of nitrogen atmosphere, and then cooling to room temperature to obtain the catalyst product.
The particle size of the cobalt microcrystal in the catalyst is 6.8-7.2nm through TEM determination.
Example 2
The catalyst Co accounts for 18 wt% of the catalyst weight, and the carrier ZrO2The content of (B) was 7.5 wt%, and Co (NO) was weighed3)2·6H2O，Al(NO3)3·9H2O，Zr(NO3)4·5H2Adding deionized water into the O to prepare a mixed solution; the concentration of cobalt ions in the mixed solution is 0.3mol/L, the concentration of aluminum ions is 1.2mol/L, and the concentration of zirconium ions is 0.02 mol/L.
Adding the mixed solution and ammonium oxalate precipitator solution into a reaction kettle in a concurrent flow manner, then adding sodium carbonate, and keeping the pH value at 8.0; heating to 40 ℃ in the coprecipitation process; after the coprecipitation is finished, aging for 6 hours at 75 ℃, then performing suction filtration to obtain a filter cake, and washing; and drying the filter cake at 100 ℃ for 7h, then roasting at 350 ℃ for 7h under the protection of nitrogen atmosphere, and then cooling to room temperature to obtain the catalyst product.
The particle size of the cobalt microcrystal in the catalyst is 6.5-7.0nm through TEM determination.
Example 3
The amount of Co in the catalyst was 26 wt% based on the weight of the catalyst, and ZrO in the carrier2The content of (B) was 9.5 wt%, and Co (NO) was weighed3)2·6H2O，Al(NO3)3·9H2O，Zr(NO3)4·5H2Adding deionized water into the O to prepare a mixed solution; the concentration of cobalt ions in the mixed solution is 0.35mol/L, the concentration of aluminum ions is 0.8mol/L, and the concentration of zirconium ions is 0.07 mol/L.
Adding the mixed solution and ammonium oxalate precipitator solution into a reaction kettle in a concurrent flow manner, then adding sodium carbonate, and keeping the pH value at 8.3; heating to 45 ℃ in the coprecipitation process; after the coprecipitation is finished, aging for 4 hours at 80 ℃, then performing suction filtration to obtain a filter cake, and washing; and drying the filter cake at 90 ℃ for 8h, then roasting at 450 ℃ for 5h under the protection of nitrogen atmosphere, and then cooling to room temperature to obtain the catalyst product.
The particle size of the cobalt microcrystal in the catalyst is 6.8-7.3nm through TEM determination.
Comparative example 1
The preparation process is basically the same as that of example 2, except that: the used precipitant is only sodium carbonate; after roasting, reducing the mixture in a hydrogen atmosphere under the following reducing conditions: 750 ℃, 1.0MPa and the airspeed of 1000h-1And keeping the temperature constant for 18 h.
The particle size of the cobalt microcrystal in the catalyst is 25-40nm through TEM determination.
Comparative example 2
The catalyst composition was the same as in example 2, but Al was first obtained2O3-ZrO2Carrier, then preparing aqueous solution of cobalt nitrate with cobalt ion concentration of 0.3mol/L, impregnating the carrier, washing,drying at 100 deg.C for 7h, then calcining at 350 deg.C for 7h under air atmosphere, and then reducing under hydrogen atmosphere: 350 ℃, 1.0MPa and airspeed of 1000h-1And keeping the temperature constant for 7 hours.
The particle size of the cobalt microcrystal in the catalyst is 12-20nm through TEM determination.
Comparative example 3
The catalyst composition was identical to that of example 2, the preparation being essentially as described in example 1 of CN104174400A (hydroxy acid to obtain reducing gas CO), except that the final passivation and reduction steps were omitted.
The particle size of the cobalt microcrystal in the catalyst is 18-25nm through TEM determination.
Test for catalytic Performance
The catalysts obtained in examples 1 to 3 and comparative examples 1 to 3 were each tested for their catalytic performance, and the results are shown in table 1, where the lifetime is the time period during which the catalyst can be continuously used with its activity and selectivity substantially unchanged.
Taking 10g of the catalyst to react in a fixed bed reactor, wherein the specific conditions are as follows: 210 ℃ under 1.5MPa for 1000h-1(V/V)，H2/CO(mol)＝2。
TABLE 1 catalyst Performance test results
Figure BDA0002115635160000131
As can be seen from the test results of Table 1, the catalyst of the present application realizes high activity and high C due to cobalt crystallites having a suitable particle size5+Selectivity, and good stability due to moderate acting force of Co microcrystal and oxide carrier, thereby obtaining longer service life.
Throughout this application, various publications are referenced. The disclosures of these publications in their entireties are hereby incorporated by reference into this application in order to more fully describe the compounds, compositions, and methods described herein.
Various modifications and changes can be made to the compounds, compositions, and methods described herein. Other aspects of the compounds, compositions, and methods described herein will be apparent from consideration of the specification and practice of the compounds, compositions, and methods disclosed herein. It is intended that the specification and examples be considered as exemplary.
It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.

Claims (9)

1. A preparation method of a cobalt-based Fischer-Tropsch synthesis catalyst comprises the following steps:
1) weighing soluble cobalt salt, aluminum salt, zirconium salt and optional soluble salt of an auxiliary agent component according to the composition of the final catalyst, and adding deionized water to prepare a mixed solution;
2) adding the mixed solution obtained in the step 1) and oxalic acid or oxalate precipitant solution into a reaction kettle in a concurrent flow manner, then adding an alkaline precipitant, and keeping the pH value to be 7.5-8.5; heating to 30-50 ℃ in the coprecipitation process;
3) then aging at 65-85 deg.C for 2-10h, suction filtering or centrifuging to obtain filter cake, and washing;
4) drying the filter cake at 70-100 ℃ for 7-15h, then roasting at 350-600 ℃ for 3-7h under the protection of inert atmosphere, and then cooling to room temperature to obtain a catalyst product;
the catalyst comprises 10-30 wt% of metallic cobalt and the balance of oxide carrier, wherein the crystallite grain diameter of the metallic cobalt is 6.5-7.5 nm.
2. The production method according to claim 1, wherein the oxide support is made of Al2O3And ZrO2Composition of, wherein ZrO2The content of (B) is 5-10 wt% of the weight of the carrier.
3. The process of claim 1 wherein the catalyst further comprises an auxiliary component in an amount of from 0.5 to 5 wt%, based on the total weight of the catalyst.
4. The method according to any one of claims 1 to 3, wherein the soluble cobalt salt in step 1) is selected from one or more of cobalt nitrate, cobalt acetate, cobalt sulfate and cobalt chloride; the soluble aluminum salt is selected from one or more of aluminum nitrate, cobalt sulfate and aluminum chloride; the soluble zirconium salt is selected from one or more of zirconium oxychloride, zirconium nitrate and zirconium oxynitrate.
5. The production method according to any one of claims 1 to 3, wherein the mixed solution in the step 1) has a cobalt ion concentration of 0.1 to 0.4mol/L, an aluminum ion concentration of 0.2 to 2mol/L, and a zirconium ion concentration of 0.005 to 0.1 mol/L.
6. The method according to any one of claims 1 to 3, wherein the oxalate precipitating agent in step 2) is selected from one or more of ammonium oxalate, sodium oxalate and potassium oxalate; the alkaline precipitant is selected from one or more of ammonium carbonate, potassium carbonate, sodium bicarbonate, sodium hydroxide, ammonia water, and urea.
7. The production method according to any one of claims 1 to 3, wherein a molding step is introduced after step 4).
8. The use of the catalyst prepared by the preparation method according to any one of claims 1 to 7 in a Fischer-Tropsch synthesis hydrocarbon preparation process, wherein the reactor is a fixed bed reactor or a slurry bed reactor, and the reaction conditions are as follows: the reaction temperature is 180 ℃ and 230 ℃, H2The mol ratio of/CO is between 0.5 and 3.0, the pressure is between 1.0 and 5.0MPa, and the space velocity is 500--1。
9. The use according to claim 8, wherein, under the reaction conditions, H2The mol ratio of/CO is 1.0-2.0, the pressure is 1.0-3.0MPa, and the space velocity is 500--1。
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