Catalyst for preparing low-carbon olefin from synthesis gas and preparation method thereof

Abstract

The invention provides a catalyst for preparing low-carbon olefin from synthesis gas and a preparation method of the catalyst. The catalyst has a shell-core structure; wherein the shell structure is prepared from a carbon material, and the core structure is prepared from an active phase and an auxiliary agent; the preparation method comprises the following steps: uniformly mixing a precursor corresponding to the activity, a precursor corresponding to the auxiliary agent and a carbon material to obtain a solid mixed material; and roasting the solid mixed material to obtain the catalyst, according to the preparation method of the catalyst provided by the invention, the catalyst can be obtained through one-step roasting treatment, the preparation process is greatly simplified, and the pretreatment energy consumption before reaction of the catalyst is reduced; moreover, through roasting treatment and sacrifice of a part of the carbon material, the formation of a metal active phase can be promoted, the grain size of the metal active phase can be regulated and controlled, the dispersity of the metal active phase and the alkaline additive can be increased, the obtained catalyst can catalyze the synthesis gas to be converted into the low-carbon olefin under relatively mild reaction conditions, and the catalytic performance is effectively improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of catalyst preparation, in particular to a catalyst for preparing low-carbon olefins from synthesis gas and a preparation method thereof. BACKGROUND

[0002] Olefins are indispensable key chemical raw materials, which can be converted into various downstream products through deep processing, and are widely used in plastics, rubber, fiber, paint, daily chemical industry, medicine and many other fields. The naphtha cracking technology not only has high energy consumption, but also has significantly decreased economic efficiency and market competitiveness when the price of raw materials rises. The coal-to-methanol-to-olefin and alkane deoxidation-to-olefin processes have complex equipment problems, and the reaction temperature is above 400℃, which not only causes high energy consumption, but also causes the active phase of the catalyst to easily agglomerate and reduce stability. At the same time, the reaction is accompanied by strong heat release, and the high temperature makes the reaction and mass and heat transfer processes form a strong coupling, increasing the difficulty of controlling the reaction conditions.

[0003] The one-step conversion of synthesis gas to olefins is a new technology. Since synthesis gas can be derived from coal chemical industry, natural gas chemical industry, biomass chemical industry and other fields, the development of this technology path has significant economic efficiency and competitiveness. Obviously, developing a catalyst with high activity and high product selectivity is a core challenge faced by this technology path.

[0004] Currently, the reaction temperature of the bifunctional catalyst composed of metal oxides and molecular sieves, and the structural catalyst combined with carbonides and basic additives is generally above 350℃, and the self-heating phenomenon is significant during the reaction, which makes the process control difficult. At the same time, the high reaction temperature causes the obtained olefin products to be easily further hydrogenated to generate low-value alkanes, or to be self-polymerized and coked to generate amorphous carbon. In addition, the high temperature also causes the active components of the catalyst to agglomerate and sinter, which is not conducive to long-term stable operation. SUMMARY

[0005] In view of the problems in the background art, the present application provides a catalyst for preparing low-carbon olefins from synthesis gas and a preparation method thereof. The present application obtains a catalyst for catalyzing the conversion of synthesis gas to low-carbon olefins under relatively mild reaction conditions by optimizing the preparation process.

[0006] The specific application content is as follows: In a first aspect, the present application provides a preparation method of a catalyst for preparing low-carbon olefins from synthesis gas, the composition of the catalyst comprising an active phase and an additive; the preparation method comprising: mixing a precursor corresponding to the active phase, a precursor corresponding to the additive and a carbon material uniformly to obtain a solid mixed material; partially burning and sacrificing the carbon material to form the catalyst by under-oxygen calcination on the solid mixed material. the active phase is selected from at least one of iron, cobalt, lanthanum, cerium, zirconium, manganese and zinc, and the assistant is selected from at least one of lithium, sodium, magnesium, calcium, potassium and strontium; the carbon material is selected from one or more of coconut shell carbon, carbon nanotube, activated carbon, mesoporous carbon, carbon black, graphite and graphene.

[0007] Optionally, in the solid mixed material, the mass ratio of the metal component in the precursor of the active phase to the metal component in the precursor of the assistant is 1:1-20:1. the mass ratio of the carbon material to the metal component in the precursor of the active phase is 1:0.5-1:10.

[0008] Optionally, the precursor salt of the active phase is a soluble nitrate salt, a soluble sulfate salt or a soluble carbonate salt containing an active metal. the precursor of the assistant is selected from a soluble nitrate salt, a soluble carbonate salt, a hydroxide or an oxide containing an assistant metal.

[0009] Optionally, the mixing of the precursor of the active phase, the precursor of the assistant and the carbon material includes: grinding and mixing after mixing the precursor of the active phase, the precursor of the assistant and the carbon material; or dissolving the precursor of the active phase and the precursor of the assistant into a proper amount of deionized water, then adding the carbon material, heating and stirring, and removing the liquid phase.

[0010] Optionally, the temperature of the calcination treatment is 350-700 ℃, and the time is 2-12 h. During the calcination treatment, the oxygen concentration in the calcination environment is 0.5-25%, and the rest is inert gas.

[0011] In a second aspect, the application provides a preparation method of a catalyst for preparing low-carbon olefins from synthesis gas, the composition of the catalyst including an active phase and an assistant; the preparation method including: mixing the precursor of the active phase and the carbon material to obtain a solid mixed material; performing under-oxygen calcination on the solid mixed material, and forming a catalyst precursor after partial combustion of the carbon material; mixing the catalyst precursor and the precursor of the assistant to obtain the catalyst; the active phase is selected from at least one of iron, cobalt, lanthanum, cerium, zirconium, manganese and zinc, and the assistant is selected from at least one of lithium, sodium, magnesium, calcium, potassium and strontium; The carbon material is selected from one or more of coconut shell carbon, carbon nanotubes, activated carbon, mesoporous carbon, carbon black, graphite and graphene.

[0012] Optionally, the mixing of the precursors corresponding to the active phase and the carbon material comprises: After mixing the precursors corresponding to the active phase and the carbon material, grinding is performed to mix them uniformly; or The precursor corresponding to the active phase is dissolved in a proper amount of deionized water, then the carbon material is added, heated and stirred, and the liquid phase is removed.

[0013] Optionally, the mixing of the precursors corresponding to the catalyst precursor and the additive comprises: After mixing the precursors corresponding to the catalyst precursor and the additive, grinding is performed to mix them uniformly; or The precursor corresponding to the additive is dissolved in a proper amount of deionized water, then the catalyst precursor is added, heated and stirred, and the liquid phase is removed.

[0014] In a third aspect, the present application provides a catalyst for preparing low-carbon olefins from synthesis gas, which is obtained by the preparation method of the first aspect or the preparation method of the second aspect, and has a shell-core structure; wherein the shell structure is composed of a carbon material, and the core structure is composed of an active phase and an additive.

[0015] Optionally, the catalyst is used in a process of preparing low-carbon olefins from synthesis gas, and the reaction pressure in the reactor is 1-5 MPa, the temperature is 250-350 ℃, and the catalyst volume space velocity is 3000-16000 ml / gcat / h.

[0016] Compared with the prior art, the present application has the following advantages: The present application provides a preparation method of a catalyst for preparing low-carbon olefins from synthesis gas, wherein the composition of the catalyst includes an active phase and an additive, the active phase is selected from at least one of iron, cobalt, lanthanum, cerium, zirconium, manganese and zinc, and the additive is selected from at least one of lithium, sodium, magnesium, calcium, potassium and strontium; the preparation method comprises: mixing a precursor corresponding to the active phase and a precursor corresponding to the additive with a carbon material to obtain a solid mixed material; and performing under-oxygen calcination on the solid mixed material, after partial combustion of the carbon material as a sacrifice, the catalyst is formed. The preparation method of the catalyst provided by the application is as follows: the active phase corresponding precursor, the additive corresponding precursor and the carbon material are uniformly mixed, and then a one-step calcination treatment is performed to obtain the catalyst, which greatly simplifies the preparation process and reduces the pretreatment energy consumption of the catalyst before reaction; and through the calcination treatment, part of the carbon material is sacrificed, which not only promotes the formation of the metal active phase, but also realizes the regulation and control of the grain size of the metal active phase, increases the dispersion degree of the metal active phase and the basic additive, and the obtained catalyst can catalyze the conversion of synthesis gas into low-carbon olefins under relatively mild reaction conditions, which not only has excellent catalytic performance, high selectivity of low-carbon olefins and few side reactions (such as methanation and carbon deposition), but also effectively improves the catalytic performance, reduces the equipment requirements and saves production costs. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0018] Figure 1 A flow chart of the preparation method of the catalyst for preparing low-carbon olefins from synthesis gas is shown; Figure 2 A flow chart of the preparation method of the catalyst for preparing low-carbon olefins from synthesis gas is shown; Figure 3 A TEM image of the catalyst for preparing low-carbon olefins obtained by the preparation method of Example 1 of the present application is shown; Figure 4 A TEM image of the catalyst for preparing low-carbon olefins obtained by the preparation method of Comparative Example 1 of the present application is shown; Figure 5 A characterization image of the catalyst after reduction in Example 1 of the present application is shown. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative, but not as any limitation on the present application and its application or use. Based on the embodiments in the present application, any person under the inspiration of the present application or by combining the present application with other prior art features can obtain any product same or similar to the present application, which falls within the protection scope of the present application. In addition, all other embodiments obtained by those skilled in the art without creative labor also fall within the protection scope of the present application.

[0020] Specific experimental steps or conditions are not specified in the embodiments; they can be performed according to the conventional experimental steps or conditions described in the prior art. Reagents and other instruments used, unless otherwise specified, are all commercially available conventional reagent products. Furthermore, the accompanying drawings are merely illustrative diagrams of the embodiments of the present invention and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore, repeated descriptions of them will be omitted. Some block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0021] Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of this specification.

[0022] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0023] This invention addresses the shortcomings of existing syngas-to-low-carbon olefin catalysts, including cumbersome preparation processes, high energy consumption, difficulty in precisely controlling the crystallite size of the metal active phase, and low dispersion of the active phase and basic promoters. These drawbacks necessitate high reaction pressures (>5 MPa) or high reaction temperatures (>350 °C) to achieve syngas conversion, resulting in demanding reaction conditions. The invention provides two highly efficient catalyst preparation methods (one-step mixing and calcination, and stepwise mixing and calcination) and the resulting catalysts. These methods simplify the preparation process, reduce energy consumption, improve the dispersion of the active phase and basic promoters, precisely control the active phase structure, and optimize catalytic performance. Specific implementation methods are as follows: In a first aspect, the present invention provides a method for preparing a catalyst for the synthesis of low-carbon olefins from syngas, wherein the catalyst is a catalyst having a shell-core structure; wherein the shell structure is composed of carbon material, and the core structure comprises an active phase and an auxiliary agent; the active phase is selected from at least one of iron, cobalt, lanthanum, cerium, zirconium, manganese and zinc, and the auxiliary agent is selected from at least one of lithium, sodium, magnesium, calcium, potassium and strontium; the carbon material is selected from one or more of coconut shell carbon, carbon nanotubes, activated carbon, mesoporous carbon, carbon black, graphite and graphene.

[0024] Figure 1 A flowchart illustrating the preparation method of the catalyst for the synthesis of low-carbon olefins from syngas provided in an embodiment of the present invention is shown, as follows: Figure 1 As shown, the preparation method includes: S11. Mix the precursor corresponding to the active agent, the precursor corresponding to the auxiliary agent, and the carbon material to obtain a solid mixed material. S12, performing under-oxygen calcination on the solid mixed material, and forming the catalyst after partial combustion of the carbon material.

[0025] The embodiment of the present application can use one or more carbon materials, and the active phase structure (metallic phase transformation promoter) is regulated by the carbon material sacrifice effect during the raw material calcination process. On the one hand, during the calcination process, the carbon material limits the growth rate of the active phase grain by slow combustion of itself, so as to control the active phase grain size to 5-20 nm (the traditional method is mostly 20-50 nm), and at the same time, the dispersion degree of the alkaline additive is improved (the dispersion degree is improved to more than 80 %), thereby avoiding active phase agglomeration and additive loss. On the other hand, the embodiment of the present application can also regulate the transformation process of the metallic compound phase by changing the type of the added carbon material, the calcination temperature, the calcination time, and the oxygen concentration (0.5-25 %) in the calcination atmosphere (the rest is N2, CO2 or Ar inert gas), so as to promote the generation of the metallic active phase; finally, the remaining carbon material after calcination is coated on the surface of the metallic active phase and the additive, and a catalyst with a shell-core structure is formed. In the application process, the surface shell structure composed of the carbon material has a large specific surface area, can better adsorb the reaction raw gas, so that the reaction raw gas can fully contact the metallic active phase, and the catalytic efficiency is improved; and due to the porous carbon material structure on the surface of the catalyst, the byproduct water formed in the catalyst can be quickly removed, and the service life of the catalyst is improved.

[0026] The embodiment of the present application completes the formation of the active phase and the loading of the additive by one-step mixing and calcination process, and the multi-step pretreatment (such as multiple calcination, impregnation) of the traditional catalyst is omitted, so that the process is greatly simplified, and the reaction pretreatment energy consumption is reduced (the energy consumption is actually reduced by 20 %-30 %).

[0027] In some embodiments, the content control of the carbon material in step 11 is one of the important factors for regulating the active phase structure. If the proportion of the carbon material in the solid mixed material is too low, the sacrifice effect is insufficient, the active phase grain is easily grown to 30-50 nm, and the active phase grain cannot be effectively regulated; if the proportion is too high, the active phase concentration is too low, and the catalytic conversion efficiency is reduced; in order to balance the regulation of the active phase grain structure and the active density, the present application confirms through a large number of experimental explorations that the mass ratio of the carbon material to the metal component in the precursor corresponding to the active phase in the solid mixed material is preferably 1:0.5-1:10. This ratio and the calcination condition control can ensure that the sacrifice amount of the carbon material is 10 %-60 %, and the active phase grain size is accurately regulated in the target range.

[0028] In some embodiments, the molar ratio of the active phase to the auxiliary agent directly affects the electron transfer efficiency (such as the transfer of electrons from K to Fe, improving the CO adsorption capacity), and the present application confirms through a large number of experiments that the mass ratio of the metal component in the precursor corresponding to the active phase to the metal component in the precursor corresponding to the auxiliary agent is preferably 1:1-20:1, which can avoid poisoning of the active phase caused by too much auxiliary agent and insufficient selectivity caused by too little auxiliary agent, and ensure stable catalytic performance.

[0029] In some embodiments, the precursor salt corresponding to the active phase is selected from a soluble nitrate salt, a soluble sulfate salt or a soluble carbonate salt containing an active metal; the precursor corresponding to the auxiliary agent is selected from a soluble nitrate salt, a soluble carbonate salt, a hydroxide or an oxide containing an auxiliary metal; the above soluble precursors can be mixed with the carbon material at the molecular level through dissolution and stirring to avoid local agglomeration caused by insoluble precursors. Moreover, the types of the precursor corresponding to the active phase and the precursor corresponding to the auxiliary agent are diverse, which can be flexibly selected according to the availability of raw materials to improve the industrial applicability. For example, when the active phase is iron and the auxiliary agent is magnesium, the corresponding precursors thereof can be iron nitrate nonahydrate and magnesium carbonate, respectively.

[0030] In some embodiments, the carbon material is selected from one or more of coconut shell carbon, carbon nanotubes, activated carbon, mesoporous carbon, carbon black, graphite and graphene with a specific surface area of 10-4000 m 2 / g.

[0031] In some embodiments, the mixing of the precursor corresponding to the active phase, the precursor corresponding to the auxiliary agent and the carbon material includes: After mixing the precursor corresponding to the active phase, the precursor corresponding to the auxiliary agent and the carbon material, grinding and mixing are performed; or The precursor corresponding to the active phase, the precursor corresponding to the auxiliary agent are dissolved in a proper amount of deionized water, then the carbon material is added, heated and stirred, and the liquid phase is removed.

[0032] In specific implementation, the present application explores two ways of mixing the two raw materials, i.e. dry grinding and wet dissolution, which can be flexibly selected according to the properties of different precursors; among them, the dry grinding realizes solid particle level mixing with particle size uniformity improved to more than 90%; the wet dissolution realizes molecular level mixing, and both ways can avoid local component enrichment.

[0033] It should be noted that after the two raw materials are mixed, the mixture is dried to remove excess water and easily decomposed impurities.

[0034] In some embodiments, the roasting treatment in step S12 has a temperature of 350-700 ℃ and a time of 2-12 h; during the roasting treatment, the oxygen concentration in the roasting environment is 0.5-25%, and the rest is inert gas.

[0035] In particular implementation, the carbon material combustion rate of the embodiment of the present application is controllable under a low-oxygen atmosphere (oxygen concentration of 0.5-25%), the sacrifice amount can be stabilized at 10-60%, and the active phase grain size is controlled at 5-20 nm; under a roasting temperature of 350-700 ℃, the precursor can be completely decomposed into the target active phase (such as Fe(NO3)3→Fe3O4, Co(NO3)2→CoO), and there is no undecomposed precursor residue.

[0036] In a second aspect, the present application provides a preparation method of a catalyst for preparing low-carbon olefins from synthesis gas, the catalyst being a catalyst with a shell-core structure; wherein the shell structure is composed of carbon material, and the core structure is composed of an active phase and an auxiliary agent; Figure 2 A flow chart of the preparation method of the catalyst for preparing low-carbon olefins from synthesis gas provided by another embodiment of the present application is shown in the figure, and the method comprises the following steps: Figure 2 S21, uniformly mixing a precursor corresponding to the active phase with carbon material to obtain a solid-state mixed material; S22, performing under-oxygen roasting on the solid-state mixed material, and after partial combustion and sacrifice of the carbon material, forming a catalyst precursor; S23, uniformly mixing the catalyst precursor with a precursor corresponding to the auxiliary agent to obtain the catalyst.

[0037] In particular implementation, the embodiment adopts a step-by-step mixing and roasting treatment mode of first roasting the active phase and carbon material to form a stable precursor (already having a shell-core structure) and then loading the auxiliary agent, which can avoid the problem of competition of the auxiliary agent and the active phase for adsorption of the carbon material in one-step mixing and roasting. The first roasting can make the active phase form a stable crystal structure (such as Fe3O4 spinel structure), avoiding disorder of the active phase crystal type caused by the auxiliary agent; the catalyst precursor obtained by roasting has formed a porous structure, and after partial sacrifice of the carbon material in the porous structure, the porosity of the carbon material in the shell structure is greatly improved; at this time, loading of the auxiliary agent precursor is performed, and the auxiliary agent precursor can more uniformly enter the inside of the shell structure and contact the core structure; avoiding agglomeration of the auxiliary agent on the surface of the catalyst, and effectively improving the dispersion degree.

[0038] In some embodiments, the uniformly mixing of the precursor corresponding to the active phase with the carbon material comprises: After mixing the precursor corresponding to the active phase with the carbon material, performing grinding and uniform mixing; or Dissolving the precursor corresponding to the active phase into a proper amount of deionized water, then adding the carbon material, heating and stirring, and removing the liquid phase.​

[0039] In the implementation, the active phase corresponding precursor and the carbon material are mixed uniformly, and dry grinding and wet dissolution are used, and the active phase corresponding precursor can be selected flexibly according to the properties of the active phase corresponding precursor.

[0040] In some embodiments, the mixing of the catalyst precursor and the precursor corresponding to the additive includes: After the mixing of the catalyst precursor and the precursor corresponding to the additive, grinding and mixing are performed; or The precursor corresponding to the additive is dissolved in a proper amount of deionized water, then the catalyst precursor is added, heated and stirred, and the liquid phase is removed.

[0041] In the implementation, the dry grinding and the wet dissolution are provided for the loading of the additive, the porous structure of the catalyst precursor can anchor the additive particles based on the sacrifice of part of the carbon material, the additive particles are prevented from agglomerating on the surface in the traditional impregnation method, and the two methods can well realize the uniform loading of the additive. After the mixing and removal of the liquid phase or the grinding, direct molding is performed, the secondary calcination step is omitted, and compared with the traditional step-by-step calcination method, the energy consumption is lower.

[0042] It should be noted that when the catalyst is prepared by using the preparation method (step-by-step mixing and calcination treatment method) of the embodiment, the types and dosages of the raw materials involved in the preparation, and the selection of the calcination conditions can be referred to the step-by-step mixing and calcination treatment method, and the details are not repeated here.

[0043] In a third aspect, the present application provides a catalyst for preparing low-carbon olefins from synthesis gas, wherein the catalyst is obtained by the preparation method of the first aspect or the preparation method of the second aspect, and the catalyst is a catalyst with a shell-core structure; wherein the shell structure is composed of a carbon material, and the core structure is composed of an active phase and an additive.

[0044] In the implementation, the catalyst obtained by the preparation method of the first aspect and the second aspect includes 30 %-90 % of the active phase, 1 %-35 % of the additive, and 0 %-65 % of the carbon shell structure; the particle size of the catalyst is 0.5 μm-400 μm; the particle size of the active phase is 1-30 nm, and the particle size of the additive is 1-30 nm.

[0045] In practice, the catalyst (after reduction treatment) is used in the process of catalytic synthesis of low carbon olefins from synthesis gas, the reaction pressure in the reactor is 1-5 MPa, the temperature is 250-350 ℃, and the catalyst volume space velocity is 3000-16000 ml / gcat / h; under this reaction condition, when the carbon monoxide conversion rate reaches 85 %-95 %, the carbon number of the hydrocarbon in the reaction product is 1-5, and the proportion of C2-C4 olefin is 73 %-85 %, and the product economy is enhanced.

[0046] In order to enable those skilled in the art to more clearly understand the present application, the synthesis gas preparation low carbon olefin catalyst and preparation method described in the present application will be described in detail through the following examples.

[0047] Example 1 12 g of iron nitrate nonahydrate, 5 g of anhydrous sodium carbonate and 4 g of coconut shell carbon with a specific surface area of 150 m 2 / g are physically mixed and ground for 2 h; the obtained solid powder is dried at 80 ℃ for 18 h to remove water, and a solid mixed material is obtained; wherein the mass of the sodium component is 2.13 g, and the mass of the iron component is 1.66 g; The obtained solid mixed material is calcined at 600 ℃ (atmosphere: 0.5 %O2, the rest is N2) for 6 h to prepare the catalyst.

[0048] The mass ratio of the auxiliary agent (sodium) and the active phase metal component (iron) in the obtained catalyst is 1:1.529 detected by inductively coupled plasma emission spectrometer. The carbon material sacrifice amount is 27 % detected by elemental carbon. The composition of the obtained catalyst includes 45 % active component, 35 % basic auxiliary agent and 20 % carbon material on a mass basis.

[0049] The prepared catalyst is placed in a fixed bed reactor and reduced at 400 ℃ for 8 h using a reducing gas (24 % CO, 72 % H2, 4 %N2). The reaction pressure is increased to 2 MPa by passing in synthesis gas, and the temperature is reduced to 250 ℃ for reaction, and the space velocity is 6000 ml / gcat / h. At this time, the CO conversion rate can reach 92 %, the carbon number of the hydrocarbon product is 1-5, and the proportion of C2-C4 olefin can reach 80 %.

[0050] Example 2 20 g of iron nitrate nonahydrate, 8 g of zirconium nitrate pentahydrate, 1 g of anhydrous sodium carbonate, 4 g of graphite with a specific surface area of 8 m 2 / g and 2 g of graphite with a specific surface area of 200 m 2g of carbon nanotubes were physically mixed and thoroughly ground for 4 h. The obtained solid powder was dried at 60 °C for 24 h to remove water, obtaining a solid mixed material; wherein the mass of the sodium component was 0.43 g, the mass of the zirconium component was 3.24 g, and the mass of the iron component was 5.45 g; The obtained solid mixed material was calcined at 400 °C (atmosphere of 25% 02, balance N2) for 12 h to prepare a catalyst. The mass ratio of the auxiliary additive (sodium), the metal component (zirconium), and the metal component (iron) in the obtained catalyst was 1 : 7.47: 12.75, as detected by inductively coupled plasma emission spectrometer. The amount of carbon material sacrificed was 55%, as detected by elemental carbon. On a mass basis, the composition of the obtained catalyst included 87% active component, 5% basic additive, and 8% carbon material.

[0051] The prepared catalyst was placed in a fixed bed reactor and reduced at 550 °C for 12 h using a reducing gas (24% CO, 72% H2, 4% N2). The reaction pressure was increased to 1 MPa by passing in synthesis gas, and the temperature was reduced to 300 °C for reaction at a space velocity of 12000 ml / gcat / h. At this time, the CO conversion rate could reach 98%, and the carbon number of the hydrocarbon product was 1-5, of which the proportion of C2-C4 olefins could reach 82%.

[0052] Example 3 4 g of graphene with a specific surface area of 2630 m 2 / g and 4 g of mesoporous carbon with a specific surface area of 1600 m 2 / g were immersed in a mixed solution containing 16 g of iron nitrate nonahydrate and 6 g of zinc nitrate hexahydrate, stirred at room temperature for 3 h, and evaporated at 80 °C to remove water, obtaining a solid mixed material; wherein the mass of the zinc component was 1.30 g, and the mass of the iron component was 2.18 g; The obtained solid mixed material was calcined at 350 °C (atmosphere of 5% 02, balance Ar) for 5 h to obtain a solid particulate precursor, which was physically mixed with 2 g of magnesium carbonate at room temperature, thoroughly ground, and dried at 70 °C for 12 h to prepare a catalyst. The mass ratio of the auxiliary additive (magnesium), the auxiliary additive (zinc), and the metal component (iron) in the obtained catalyst was 1 : 2.39: 4.03, as detected by inductively coupled plasma emission spectrometer. The amount of carbon material sacrificed was 10%, as detected by elemental carbon. On a mass basis, the composition of the obtained catalyst included 32% active component, 5% basic additive, and 63% carbon material.

[0053] The prepared catalyst was placed in a fixed bed reactor and reduced at 550 °C for 8 h using a reducing gas (48% CO, 48% H2, 4% N2). The reaction was carried out by passing synthesis gas (24% CO, 72% H2, 4% N2) to increase the reaction pressure to 1 MPa and reduce the temperature to 270 °C, with a space velocity of 7000 ml / gcat / h. At this time, the CO conversion rate can reach 94%, and the carbon number of the hydrocarbon product is 1-5, of which the proportion of C2-C4 olefins can reach 79%.

[0054] Example 4 The 24 g of cobalt nitrate hexahydrate, 5 g of carbon black with a specific surface area of 50 m 2 / g, 1 g of lanthanum nitrate hexahydrate, 2 g of cerium nitrate hexahydrate, 2 g of calcium carbonate, and 2 g of potassium carbonate were physically mixed and ground for 30 min. The obtained solid powder was dried at 90 °C for 24 h to remove water, and a solid mixed material was obtained. The mass of the calcium component was 0.79 g, the mass of the potassium component was 1.12 g, the mass of the cerium component was 0.64 g, the mass of the lanthanum component was 0.42 g, and the mass of the cobalt component was 4.83 g. The obtained solid mixed material was calcined at 450 °C (atmosphere of 15% O2, the rest being 50% N2, 35% CO2) for 2 h and then calcined at 550 °C for 3 h to prepare a catalyst. The mass ratio of the auxiliary auxiliary agent (calcium), the auxiliary auxiliary agent (potassium), the metal component (cerium), the metal component (lanthanum), and the metal component (cobalt) in the obtained catalyst was 1.86:2.64:1.51:1:11.37, as detected by an inductively coupled plasma emission spectrometer. The amount of carbon material sacrificed was 15%, as detected by elemental carbon. On a mass basis, the composition of the obtained catalyst included 49% active component, 15% basic auxiliary agent, and 36% carbon material.

[0055] The prepared catalyst was placed in a fixed bed reactor and reduced at 650 °C for 4 h using a reducing gas (24% CO, 72% H2, 4% N2). The reaction was carried out by passing synthesis gas to increase the reaction pressure to 3 MPa and reduce the temperature to 260 °C, with a space velocity of 6000 ml / gcat / h. At this time, the CO conversion rate can reach 87%, and the carbon number of the hydrocarbon product is 1-5, of which the proportion of C2-C4 olefins can reach 76%.

[0056] Example 5 The 24 g of iron nitrate nonahydrate, 5 g of carbon black with a specific surface area of 150 m 2g of coconut shell charcoal, 1 g of lanthanum nitrate, 1 g of zirconium nitrate and 1 g of cerium nitrate were physically mixed and thoroughly ground for 1 h. The obtained solid powder was dried at 90 °C for 24 h to remove water, to obtain a solid mixed material; wherein the mass of the cerium component was 0.65 g, the mass of the zirconium component was 0.43 g, the mass of the lanthanum component was 0.86 g, and the mass of the iron component was 6.65 g; The obtained solid mixed material was calcined at 450 °C (atmosphere of 7.5% 02, balance N2) for 2 h to obtain a catalyst precursor; The catalyst precursor powder was immersed in a solution of 2 g of sodium carbonate and 2 g of lithium carbonate for 5 h, and then the system was evaporated at 80 °C to obtain a catalyst. The mass ratio of the auxiliary agent (sodium), the auxiliary agent (lithium) to the metal component (zirconium), the metal component (cerium), the metal component (lanthanum), the metal component (iron) in the obtained catalyst was 2.04:1.77:1:1.52:2.01:15.60, as determined by inductively coupled plasma emission spectrometer. The amount of carbon material sacrificed was 13 %, as determined by elemental carbon detection. On a mass basis, the composition of the obtained catalyst included 53 % active component, 17 % basic auxiliary agent, and 30 % carbon material.

[0057] The prepared catalyst was placed in a fixed bed reactor and reduced at 650 °C for 4 h using a reducing gas (24% CO, 72% H2, 4% N2). Synthetic gas was introduced, the reaction pressure was increased to 1.5 MPa, and the temperature was decreased to 350 °C for reaction at a space velocity of 6000 ml / gcat / h. At this time, the CO conversion rate could reach 94%, and the carbon number of the hydrocarbon product was 1-5, of which the proportion of C2-C4 olefins could reach 84%.

[0058] Example 6 15 g of cobalt nitrate hexahydrate, 5 g of iron nitrate nonahydrate, 8 g of activated carbon with a specific surface area of 1300 m 2 / g, 1 g of cerium nitrate hexahydrate and 1 g of strontium carbonate were physically mixed and thoroughly ground for 1 h. The solid powder was dried at 100 °C for 10 h to remove water, to obtain a solid mixed material; wherein the mass of the cobalt component was 4 g, the mass of the iron component was 0.91 g, the mass of the cerium component was 0.43 g, and the mass of the strontium component was 0.78 g; The obtained solid mixed material was placed in a furnace and calcined at 500 °C (atmosphere of 20% O2, balance Ar) for 8 h to prepare the catalyst. The mass ratio of the auxiliary additive (strontium) to the metal component (cerium), the metal component (iron), and the metal component (cobalt) in the obtained catalyst was 1.84:1:2.14:9.41, detected by an inductively coupled plasma emission spectrometer. The amount of carbon material sacrificed was 40%, detected by elemental carbon. The composition of the obtained catalyst included 45% active component, 11% basic additive, and 44% carbon material, on a mass basis.

[0059] The catalyst was loaded into a fixed bed reactor and reduced by passing a reducing gas (30% CO, 66% H2, 4% N2) at 450 °C for 4 h. A synthesis gas (20% CO, 76% H2, 4% N2) was passed through the reactor, and the reaction pressure was controlled at 3 MPa, the temperature was 320 °C, and the space velocity was 5000 ml / gcat / h. The reaction results were as follows: the CO conversion rate was 91%, and the carbon number of the hydrocarbon product was 1-5, of which C2-C4 olefins accounted for 78%.

[0060] Example 7 20 g of cobalt nitrate hexahydrate, 4 g of zirconium nitrate hexahydrate, 6 g of carbon nanotubes with a specific surface area of 700 m 2 / g, 2 g of potassium nitrate, and 1 g of magnesium nitrate were physically mixed and ground for 20 min. The solid powder was dried at 80 °C for 24 h to remove water, and a solid mixed material was obtained; the mass of the cobalt component was 5.32 g, the mass of the zirconium component was 1.12 g, the mass of the potassium component was 0.50 g, and the mass of the magnesium component was 0.21 g; The obtained solid mixed material was placed in a furnace and calcined at 450 °C (atmosphere of 4.5% O2, balance CO2) for 10 h to prepare the catalyst. The mass ratio of the auxiliary additive (potassium) and the auxiliary additive (magnesium) to the metal component (zirconium) and the metal component (cobalt) in the obtained catalyst was 2.37:1:5.25:24.97, detected by an inductively coupled plasma emission spectrometer. The amount of carbon material sacrificed was 11%, detected by elemental carbon. The composition of the obtained catalyst included 52% active component, 6% basic additive, and 42% carbon material, on a mass basis.

[0061] The catalyst was loaded into a fluidized bed reactor and reduced by passing a reducing gas (40% CO, 56% H2, 4% N2) at 500 °C for 3 h. A synthesis gas (25% CO, 71% H2, 4% N2) was passed through the reactor, and the reaction pressure was controlled at 4 MPa, the temperature was 260 °C, and the space velocity was 8000 ml / gcat / h. The reaction results were as follows: the CO conversion rate was 89%, and the carbon number of the hydrocarbon product was 1-5, of which C2-C4 olefins accounted for 81%.

[0062] Example 8 10 g of cobalt nitrate hexahydrate, 10 g of iron nitrate nonahydrate, 4 g of coconut shell carbon with a specific surface area of 150 m 2 / g, 4 g of carbon nanotubes with a specific surface area of 700 m 2 / g, 3 g of manganese nitrate, 2 g of sodium carbonate, and 1 g of potassium carbonate were physically mixed and thoroughly ground. The solid powder was dried at 120 °C for 5 h to remove water, obtaining a solid mixed material; wherein the mass of the cobalt component was 2.66 g, the mass of the iron component was 1.82 g, the mass of the manganese component was 1.21 g, the mass of the sodium component was 0.29 g, and the mass of the potassium component was 0.74 g; The obtained solid mixed material was calcined at 600 °C (atmosphere of 10 % O2, the rest being 50 % N2, 40 % Ar) for 5 h to prepare the catalyst. The mass ratio of the auxiliary additive (potassium), the auxiliary additive (sodium), the metal component (manganese), the metal component (iron), and the metal component (cobalt) in the obtained catalyst was 2.61:1:4.25:6.37:9.33, detected by inductively coupled plasma emission spectrometer. The amount of carbon material sacrificed was 60 %, detected by elemental carbon. On a mass basis, the composition of the obtained catalyst included 45 % active component, 23 % basic additive, and 32 % carbon material.

[0063] The catalyst was loaded into a moving bed reactor, and reducing gas (20 % CO, 76 % H2, 4 % N2) was introduced to reduce it at 350 °C for 8 h. Synthesis gas (30 % CO, 66 % H2, 4 % N2) was introduced, and the reaction pressure was controlled at 5 MPa, the temperature was 300 °C, and the space velocity was 3000 ml / gcat / h. The reaction results were as follows: the CO conversion rate was 93 %, and the carbon number of the hydrocarbon product was 1-5, of which C2-C4 olefins accounted for 77 %.

[0064] Comparative Example 1 12 g of iron nitrate nonahydrate was dissolved in 20 ml of water (concentration of 1.23 mol / L), and 5 g of anhydrous sodium carbonate was dissolved in 10 ml of water. An iron nitrate solution with a concentration of 1.23 mol / L was added to a three-necked flask, and then sodium carbonate solution was added dropwise to the three-necked flask to perform a precipitation reaction. After filtration, the slurry was dried at 100-150 °C for 12 hours. The obtained solid mixed material was calcined at 600 °C (atmosphere of 0.5 % O2, the rest being N2) for 6 h to prepare a catalyst. The mass ratio of the auxiliary additive (sodium) to the metal component (iron) in the obtained catalyst was 1:1.529, detected by inductively coupled plasma emission spectrometer. On a mass basis, the composition of the obtained catalyst included 56 % active component and 44 % basic additive.

[0065] The prepared catalyst was placed in a fixed bed reactor, and reduced with a reducing gas (24% CO, 72% H2, 4% N2) at 400 ℃ for 8 h. The synthesis gas was introduced, the reaction pressure was increased to 2 MPa, and the temperature was decreased to 250 ℃ for reaction, with a space velocity of 6000 ml / gcat / h. At this time, the CO conversion rate can reach 50%, and the carbon number of the hydrocarbon product is 1-5, of which the proportion of C2-C4 olefins can reach 60%.

[0066] Figure 3 A TEM image of the catalyst for preparing low-carbon olefins obtained by the preparation method provided in Embodiment 1 of the present application is shown, Figure 4 A TEM image of the catalyst for preparing low-carbon olefins obtained by the preparation method provided in Comparative Example 1 of the present application is shown; the comparison Figure 3 、 Figure 4 It can be seen that the dispersity of the metal active phase and the basic auxiliary agent in the catalyst prepared by the preparation method of sacrificing part of the carbon carrier (10-60%) is obviously higher than that of the catalyst obtained by the traditional preparation method, and the active phase grain size is controlled in 5-20 nm, which is obviously smaller than the active phase grain size in the catalyst obtained by the traditional preparation method.

[0067] Figure 5 A characterization image of the catalyst after reduction in Embodiment 1 of the present application is shown, wherein, Figure 5 (a) shows an EDS mapping image of the catalyst after reduction, Figure 5 (b) further shows Figure 5 (a) shows a TEM image of a certain local part of the catalyst, Figure 5 (c) further shows Figure 5 (b) shows a TEM image of a certain local part of the catalyst; as Figure 5 shown, through the element distribution information in the EDS mapping image and combined with lattice analysis, it is found that the catalyst prepared in the embodiment of the present application has a shell-core structure, wherein the composition of the outermost shell structure is carbon, and the composition of the core structure is iron carbide, triiron tetroxide from outside to inside.

[0068] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in the present specification.

[0069] For method embodiments, the steps recited in any combination are not necessarily meant to be performed in the order written, as some steps can be performed in other orders or even at the same time with the present application. Also, those skilled in the art will appreciate that embodiments described in the specification are preferred embodiments only and that steps recited in the specification are not necessarily meant to be the only steps in which the present application could operate.

[0070] The above describes in detail the catalyst for preparing low-carbon olefins from synthesis gas and the preparation method. The principles and implementation manners of the present application are described by using specific examples. The above examples are only used to help understand the method and core idea of the present application. Meanwhile, for those skilled in the art, the specific implementation manners and application ranges can be changed according to the idea of the present application. In summary, the content of the specification should not be understood as a limitation on the present application.

Claims

1. A method for preparing a catalyst for the synthesis of low-carbon olefins from syngas, characterized in that, The catalyst comprises an active phase and an auxiliary agent; the preparation method includes: The precursor corresponding to the active agent and the precursor corresponding to the auxiliary agent are mixed with the carbon material to obtain a solid mixed material. The solid mixture is subjected to oxygen-deficient calcination, and after some of the carbon material is burned off, the catalyst is formed. The active phase is selected from at least one of iron, cobalt, lanthanum, cerium, zirconium, manganese and zinc, and the auxiliary is selected from at least one of lithium, sodium, magnesium, calcium, potassium and strontium; The carbon material is selected from one or more of coconut shell carbon, carbon nanotubes, activated carbon, mesoporous carbon, carbon black, graphite and graphene.

2. The preparation method according to claim 1, characterized in that, The mass ratio of the metal component in the precursor corresponding to the activity to the metal component in the precursor corresponding to the auxiliary agent is 1:1-20:

1. The mass ratio of the carbon material to the metal component in the precursor corresponding to the active material is 1:0.5-1:

10.

3. The preparation method according to claim 1, characterized in that, The precursor salt corresponding to the activity is a soluble nitrate, soluble sulfate, or soluble carbonate containing an active metal. The precursors corresponding to the additives are selected from soluble nitrates, soluble carbonates, hydroxides, or oxides containing additive metals.

4. The preparation method according to claim 1, characterized in that, The step of mixing the precursor corresponding to the active agent, the precursor corresponding to the auxiliary agent, and the carbon material includes: The precursors corresponding to the active agents and the precursors corresponding to the additives are mixed with the carbon material and then ground and mixed evenly; or The precursors corresponding to the active agent and the precursors corresponding to the auxiliary agent are dissolved in an appropriate amount of deionized water, and then the carbon material is added. The mixture is heated and stirred to remove the liquid phase.

5. The preparation method according to claim 1, characterized in that, The calcination treatment is performed at a temperature of 350-700 ℃ for 2-12 h. During the roasting process, the oxygen concentration in the roasting environment is 0.5-25%, with the remainder being inert gases.

6. A method for preparing a catalyst for the synthesis of low-carbon olefins from syngas, characterized in that, The catalyst comprises an active phase and an auxiliary agent; the preparation method includes: The active precursor is mixed with carbon material to obtain a solid mixed material. The solid mixed material is subjected to oxygen-deficient calcination, and after part of the carbon material is burned off, a catalyst precursor is formed. The catalyst precursor is mixed with the precursor corresponding to the auxiliary agent to obtain the catalyst; The active phase is selected from at least one of iron, cobalt, lanthanum, cerium, zirconium, manganese and zinc, and the auxiliary is selected from at least one of lithium, sodium, magnesium, calcium, potassium and strontium; The carbon material is selected from one or more of coconut shell carbon, carbon nanotubes, activated carbon, mesoporous carbon, carbon black, graphite and graphene.

7. The preparation method according to claim 6, characterized in that, The step of mixing the active precursor with the carbon material includes: The precursor corresponding to the active material is mixed with the carbon material and then ground and mixed evenly; or The precursor corresponding to the active ingredient is dissolved in an appropriate amount of deionized water, and then the carbon material is added. The mixture is heated and stirred to remove the liquid phase.

8. The preparation method according to claim 6, characterized in that, The step of mixing the catalyst precursor with the precursor corresponding to the auxiliary agent includes: The catalyst precursor and the precursor corresponding to the auxiliary agent are mixed and then ground to achieve homogeneity; or The precursor corresponding to the auxiliary agent is dissolved in an appropriate amount of deionized water, and then the catalyst precursor is added. The mixture is heated and stirred to remove the liquid phase.

9. A catalyst for the synthesis of low-carbon olefins from syngas, characterized in that, The catalyst is obtained by the preparation method according to any one of claims 1-5 or any one of claims 6-8, and the catalyst is a catalyst with a shell-core structure; wherein the shell structure is composed of carbon material and the core structure includes an active phase and an auxiliary agent.

10. The catalyst for producing low-carbon olefins from syngas according to claim 9, characterized in that, The catalyst is used in the process of catalytic synthesis of low-carbon olefins from syngas, where the reaction pressure in the reactor is 1-5 MPa, the temperature is 250-350 ℃, and the catalyst volume hourly space velocity is 3000-16000 ml / gcat / h.

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