A method for recovering an iron-based catalyst from coal liquefaction residue

Abstract

The present application provides a method for recovering iron-based catalyst from coal liquefaction residue, which comprises the following steps: crushing the coal liquefaction residue, adding a solvent for dissolution, and performing solid-liquid separation, drying and crushing to obtain a solvent-insoluble powder; then mixing the powder with water and a demulsifier, adding an acid solution and stirring to react, performing solid-liquid separation on the reaction product to obtain an active metal solution; adding an oxygen source and an alkali source to the active metal solution to perform an oxidation reaction, and performing solid-liquid separation on the reaction product to obtain a nanoscale iron-based catalyst. The present application realizes the recovery, regeneration and high-value recycling of the iron-based catalyst used in the coal and heavy oil liquefaction process, which not only can reduce the discharge of industrial waste and environmental pollution, but also can avoid the waste of resources, and can also reduce the cost of purchasing catalyst in the coal-based raw material liquefaction process, and has high environmental value and economic value.

Description

Technical Field

[0001] This invention belongs to the field of coal chemical industry. Specifically, this invention relates to a method for recovering iron-based catalysts from coal liquefaction residues. Background Technology

[0002] Direct coal liquefaction, coal tar hydrogenation, and coal-oil co-refining are all technologies that convert coal and heavy oil into clean oil products with low sulfur and low nitrogen. Direct coal liquefaction was first invented by the Germans, but subsequent technological development in Germany, the United States, Japan, Russia, and other countries has led to the formation of various distinctive direct liquefaction processes. After screening and evaluating the performance of available coal types for direct liquefaction, my country has selected dozens of suitable coal types. In 2008, China built and put into operation a 1.08 million-ton / year coal direct liquefaction demonstration plant. Coal tar hydrogenation is a widely used technology for the clean processing of coal tar, with China already possessing a capacity of millions of tons. Suspended bed or slurry bed technologies capable of processing heavy coal tar are among the processing technologies used. Coal-oil co-refining technology is a technology that co-processes and converts coal and heavy oil. my country has built and successfully operated a 450,000-ton / year coal-oil co-refining demonstration plant.

[0003] Whether it's direct coal liquefaction, coal tar suspension bed or slurry bed hydrogenation, or coal-oil co-refining technology, all involve direct hydrocracking reactions with hydrogen under high temperature and pressure with the aid of catalysts, converting coal or heavy oil into light oil products. Catalysts play a crucial role in this process. One of the most commonly used catalysts in existing technologies is iron-based ore resources. However, the natural reserves of iron-based ore catalysts with good catalytic performance are relatively limited. Therefore, iron-based ore catalysts are a valuable natural resource. Furthermore, due to the high grinding cost and limited particle size of iron-based ore catalysts, their catalytic performance is insufficient, limiting their practical application in production. In recent years, the iron-based catalysts mainly used in industrial demonstration plants for direct coal liquefaction and coal-oil co-refining have been chemically synthesized FeOOH catalysts. For example, the catalyst used in the direct coal liquefaction industrial demonstration plant is a nano-catalyst prepared by a method for preparing a highly dispersed iron-based direct coal liquefaction catalyst disclosed in patent CN1579623A. The catalyst used in the coal-oil co-refining industrial demonstration plant is a composite iron-based catalyst prepared by a method for preparing a suspended bed hydrogenation multi-component composite iron-based catalyst disclosed in patent CN110465295. Patent CN104096563A also discloses an artificially synthesized FeOOH catalyst. Therefore, the industry generally recognizes FeOOH-type iron-based catalysts as nano-catalysts with good activity and dispersion. However, iron-based catalysts have long been considered disposable catalysts due to their relatively low price and environmental friendliness. That is, after being used once, they are removed from the reaction system along with the heavy products and are not recycled. However, this treatment method has the following problems:

[0004] (1) When mineral iron-based catalysts are widely used, they will not only cause environmental damage and high energy consumption, but also cause a series of problems such as serious waste of resources;

[0005] (2) When FeOOH type iron-based catalysts are used in large quantities, the raw materials for the current artificial synthesis of FeOOH catalysts are all commercially available ferrous salts. However, as other uses of these raw materials increase and consumption explodes, these raw materials will be unable to meet the market demand for the further development and increase in production capacity of industries such as direct coal liquefaction, coal tar hydrogenation and coal-oil co-refining. This will cause great obstacles and risks to the operation and industrial development of direct coal liquefaction, coal tar hydrogenation and coal-oil co-refining catalysts. Therefore, the industry urgently needs technologies for the supply, regeneration and recycling of high-performance iron-based catalyst raw materials. Summary of the Invention

[0006] This invention aims to at least partially address one of the technical problems in related technologies. To this end, embodiments of this invention propose a method for recovering iron-based catalysts from coal liquefaction residues.

[0007] In a first aspect, embodiments of the present invention provide a method for recovering iron-based catalysts from coal liquefaction residues, comprising the following steps:

[0008] S1, after crushing the coal liquefaction residue, a solvent is added to dissolve it, forming solvent-soluble and solvent-insoluble substances, and a first solid-liquid separation is performed to obtain the solvent-insoluble substances; wherein, the coal liquefaction residue is obtained by liquefying coal-based raw materials under the action of an iron-based catalyst;

[0009] S2, the solvent-insoluble material is dried and crushed to obtain solvent-insoluble powder;

[0010] S3, the solvent-insoluble powder is mixed with water and demulsifier to form a first liquid-solid mixture;

[0011] S4, add acid solution to the first liquid-solid mixture, stir and react to obtain a second liquid-solid mixture;

[0012] S5, the second liquid-solid mixture is subjected to a second solid-liquid separation, and the filtrate is the active metal solution;

[0013] S6, add an oxygen source and an alkali source to the active metal solution to carry out an oxidation reaction. After the reaction is completed, perform a third solid-liquid separation on the reaction product to obtain a nano-sized iron-based catalyst.

[0014] This invention recovers iron from coal liquefaction residue and uses it to prepare highly active nanoscale iron-based catalysts, thereby achieving the regeneration and recycling of iron-based catalysts in the liquefaction process of coal-based raw materials, avoiding the waste of iron metal resources, and reducing the cost of coal liquefaction process.

[0015] In some embodiments, in step S1, the solvent includes at least one of toluene, xylene, tetrahydrofuran, and wash oil.

[0016] In some embodiments, in step S1, the iron-based catalyst is one or a mixture of two of the following: an unsupported iron-based catalyst and a supported iron-based catalyst.

[0017] Preferably, the unsupported iron-based catalyst includes at least one of iron ore, ferrous salt, and ferric salt; wherein the iron ore contains ≥10 wt% iron.

[0018] Preferably, the supported iron-based catalyst is a FeOOH-type iron-based catalyst supported on a support; wherein the support includes at least one of pulverized coal and inert carbon powder;

[0019] Preferably, the particle size of the unsupported iron-based catalyst is in the micrometer or nanometer range, and the particle size of the supported iron-based catalyst is in the nanometer range.

[0020] In some embodiments, in step S2, the particle size of the solvent-insoluble powder is <1 mm.

[0021] In some embodiments, in step S3, the demulsifier includes at least one of sodium hexametaphosphate, SP-type demulsifier, AP-type demulsifier, and AE-type demulsifier;

[0022] Preferably, the demulsifier has a mass content of 0.1% to 15% in the first liquid-solid mixture.

[0023] In some embodiments, in step S4, the acid solution includes at least one of formic acid, acetic acid, hydrochloric acid, nitric acid, phosphoric acid, and sulfuric acid; the mass concentration of the acid solution is 1-80%, preferably 5-50%.

[0024] And / or, the temperature of the stirring reaction is 20–300°C, preferably 20–200°C; the reaction time is 0.1–5 h.

[0025] In some embodiments, in step S5, the second solid-liquid separation method is centrifugal separation or pressure filtration separation.

[0026] In some embodiments, in step S6, the oxygen source includes at least one of hydrogen peroxide, air, and oxygen.

[0027] Preferably, the hydrogen peroxide has a mass concentration of 5-30%;

[0028] And / or, the alkali source includes an alkaline solution or an alkaline gas;

[0029] Preferably, the alkaline solution includes at least one of sodium hydroxide solution, calcium hydroxide solution, ammonia water, and Lewis alkaline solution;

[0030] Preferably, the alkaline gas is ammonia or ammonia-containing water vapor;

[0031] And / or, the amount of the alkali source is used to control the pH of the reaction system of the oxidation reaction to be 6.5 to 13, preferably 7 to 9;

[0032] And / or, the temperature of the oxidation reaction is 20–180°C, preferably 20–100°C; the reaction time is 0.1–4 h, preferably 0.2–2 h.

[0033] And / or, the third solid-liquid separation method is static separation or centrifugal separation; wherein, the centrifugal separation speed is 500-5000 r / min.

[0034] In some embodiments, the particle size of the nanoscale iron-based catalyst is 10–500 nm.

[0035] Secondly, embodiments of the present invention also provide an iron-based catalyst, which is prepared by the method described in the first aspect.

[0036] The iron-based catalysts in the embodiments of this invention have excellent performance, which can not only ensure the high dispersion of the catalysts used in the hydrogenation conversion reaction system, but also ensure the high activity of the iron-based catalysts.

[0037] The advantages and beneficial effects of the embodiments of the present invention are as follows:

[0038] (1) The method for recovering iron-based catalysts from coal liquefaction residues in the embodiments of the present invention can truly realize the recovery, regeneration and high-value recycling of iron-based catalysts used in the coal and heavy oil liquefaction process.

[0039] (2) The embodiments of the present invention can reduce the emission of industrial waste and reduce environmental pollution by recovering, regenerating and recycling iron-based catalysts, while avoiding the waste of resources and reducing the cost of purchasing catalysts for coal-based raw material liquefaction processes.

[0040] (3) The method in the embodiments of the present invention can also effectively solve the risks of catalyst raw material shortage or unstable quality that may exist in large-scale projects such as direct coal liquefaction, coal tar hydrogenation and coal-oil co-refining; at the same time, it can significantly reduce the procurement and transportation costs of iron-based catalysts for enterprises, which is conducive to improving the economic benefits of enterprises.

[0041] (4) The performance of the nano-sized iron-based catalyst obtained by the regeneration in the embodiments of the present invention is comparable to or even better than that of the starting catalyst. It can not only ensure the high dispersion of the catalyst used in the hydrogenation conversion reaction system, but also ensure the high activity of the iron-based catalyst. Attached Figure Description

[0042] Figure 1 This is a process flow diagram of a method for recovering iron-based catalysts from coal liquefaction residue according to an embodiment of the present invention.

[0043] Figure 2 This is a particle size distribution diagram of the nanoscale iron-based catalyst prepared in Example 1 of the present invention. Detailed Implementation

[0044] The embodiments of the present invention are described in detail below. These embodiments are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0045] In this document, when values ​​are described as ranges, it should be understood that such disclosure includes disclosure of all possible subranges within that range, as well as the specific numerical values ​​that fall within that range, regardless of whether the specific numerical value or specific subrange is explicitly specified.

[0046] In this article, the words “contain” and “include” and their various variations mean that other elements or wholes may be included but not specifically described.

[0047] In this article, the term "and / or" is merely a description of the relationship between related objects, indicating that there can be three kinds of relationships. For example, A and / or B can represent three cases: A exists alone, A and B exist simultaneously, and B exists alone.

[0048] In this paper, the term "coal liquefaction residue" refers to heavy products such as solid residues or remnants remaining from the coal-based feedstock liquefaction process, including liquefaction residue, coal-based pitch precursors, and coal liquefaction pitch; wherein, coal-based feedstocks include lignite, low-rank bituminous coal, coal tar, or a mixture of coal and petroleum-based distillation byproducts and heavy oils such as coal tar.

[0049] Firstly, such as Figure 1 As shown in the figure, this invention provides a method for recovering iron-based catalysts from coal liquefaction residues, comprising the following steps:

[0050] S1, after crushing the coal liquefaction residue, a solvent is added to dissolve it, forming solvent-soluble and solvent-insoluble substances, and the first solid-liquid separation is performed to obtain the solvent-insoluble substances; wherein, the coal liquefaction residue is obtained by liquefying coal-based raw materials under the action of an iron-based catalyst;

[0051] S2, the solvent-insoluble material is dried and crushed to obtain solvent-insoluble powder;

[0052] S3, the solvent-insoluble powder is mixed with water and demulsifier to form a first liquid-solid mixture;

[0053] S4, add acid solution to the first liquid-solid mixture, stir and react to obtain the second liquid-solid mixture;

[0054] S5, the second liquid-solid mixture is subjected to a second solid-liquid separation, and the filtrate is the active metal solution;

[0055] S6. An oxygen source and an alkali source are added to the active metal solution to carry out an oxidation reaction. After the reaction is completed, the reaction product is subjected to a third solid-liquid separation to obtain a nano-sized iron-based catalyst.

[0056] In some embodiments, in step S1, the solvent includes at least one of toluene, xylene, tetrahydrofuran, and wash oil.

[0057] In some embodiments, in step S1, the iron-based catalyst is one or a mixture of two of the following: an unsupported iron-based catalyst and a supported iron-based catalyst.

[0058] Preferably, the unsupported iron-based catalyst includes at least one of iron ore (e.g., pyrite, ferrous ore, etc.), ferrous salts (e.g., ferrous sulfate, etc.), and ferric salts (e.g., ferric oxide, ferric chloride, ferric nitrate, ferric phosphate, etc.); wherein the iron content of the iron ore is ≥10wt%, and non-limiting examples include 10wt%, 15wt%, 40wt%, 60wt%, etc.

[0059] Preferably, the supported iron-based catalyst is a FeOOH-type iron-based catalyst supported on a support; wherein the support includes at least one of pulverized coal and inert carbon powder;

[0060] Preferably, the particle size of the unsupported iron-based catalyst is in the micrometer or nanometer range, and the particle size of the supported iron-based catalyst is in the nanometer range. That is, regardless of whether the original coal-based raw material liquefaction process uses a micrometer-sized or nanometer-sized iron-based catalyst, the final iron-based catalyst obtained after recovering the coal liquefaction residue using the method of the embodiments of the present invention has a particle size in the nanometer range.

[0061] In some embodiments, in step S2, the particle size of the solvent-insoluble powder is <1 mm, and non-limiting examples include: 0.5 mm, 0.2 mm, 0.1 mm, etc.

[0062] In some embodiments, in step S3, the demulsifier includes at least one of sodium hexametaphosphate, SP-type demulsifier (with polyoxyethylene polyoxypropylene octadecyl alcohol ether as the main component), AP-type demulsifier (with polyoxyethylene polyoxypropylene polyether as the main component with polyethylene polyamine as the initiator), and AE-type demulsifier (with polyoxyethylene polyoxypropylene polyether as the main component with polyethylene polyamine as the initiator). By introducing a demulsifier into the system, the dispersion rate of solid substances in water can be accelerated, thereby accelerating the entire reaction process.

[0063] Preferably, the demulsifier has a mass content of 0.1% to 15% in the first liquid-solid mixture, and non-limiting examples include: 0.1%, 0.3%, 0.5%, 1%, 1.5%, 5%, 8%, 10%, 12%, 15%, etc.

[0064] In some embodiments, in step S4, the acid solution includes at least one of formic acid, acetic acid, hydrochloric acid, nitric acid, phosphoric acid, and sulfuric acid; the mass concentration of the acid solution is 1% to 80%, with non-limiting examples such as 1%, 15%, 30%, 45%, 50%, 75%, 80%, etc.; preferably 5% to 50%, with non-limiting examples such as 5%, 15%, 20%, 30%, 45%, 50%, etc.; by introducing the acid solution into the reaction system, the selectivity of the target active metal can be improved, and the solubility of the metal compound after the reaction can be guaranteed;

[0065] And / or, the temperature of the stirred reaction is controlled at 20–300°C to improve the reaction efficiency and control the reaction rate. Non-limiting examples include: 20°C, 50°C, 100°C, 180°C, 200°C, 260°C, 300°C, etc.; preferably 20–200°C, non-limiting examples include: 20°C, 50°C, 100°C, 180°C, 200°C, etc.; the reaction time is 0.1–5 h, non-limiting examples include: 0.1 h, 1 h, 1.5 h, 2 h, 3 h, 4 h, 5 h, etc.

[0066] In some embodiments, in step S5, the second solid-liquid separation method is centrifugal separation or pressure filtration separation. By separating and removing excess water, a nano-scale highly active iron-based catalyst with low water content can be obtained. The recovered catalyst can be recycled for use in the liquefaction process of coal-based raw materials.

[0067] In some embodiments, in step S6, the oxygen source includes at least one of hydrogen peroxide, air, and oxygen.

[0068] Preferably, the mass concentration of hydrogen peroxide is controlled at 5% to 30%, thereby ensuring that the particle size of the reaction product meets the requirements and can reach the nanoscale. Non-limiting examples include: 5%, 10%, 18%, 20%, 25%, 30%, etc.

[0069] And / or, the alkali source includes an alkaline solution or an alkaline gas;

[0070] Preferably, the alkaline solution includes at least one of sodium hydroxide solution, calcium hydroxide solution, ammonia water, and Lewis alkaline solution;

[0071] Preferably, the alkaline gas is ammonia or ammonia-containing water vapor;

[0072] And / or, in order to control the crystal form of the metal compound, the amount of alkali source is determined by controlling the pH of the reaction system of the oxidation reaction to be 6.5 to 13, preferably 7 to 9;

[0073] And / or, similarly, in order to obtain a highly active metal catalyst crystal form for coal and heavy oil conversion, the temperature of the oxidation reaction is controlled at 20–180°C, with non-limiting examples such as 20°C, 50°C, 75°C, 100°C, 150°C, 180°C, etc.; preferably 20–100°C, with non-limiting examples such as 20°C, 50°C, 75°C, 100°C, etc.; the reaction time is 0.1–4 h, with non-limiting examples such as 0.1 h, 1 h, 2 h, 3.5 h, 4 h, etc.; preferably 0.2–2 h, with non-limiting examples such as 0.2 h, 1 h, 1.5 h, 2 h, etc.

[0074] And / or, the third solid-liquid separation method is static separation or centrifugal separation; wherein, the centrifugal separation speed is 500 to 5000 r / min, and non-limiting examples are: 500 r / min, 1000 r / min, 2000 r / min, 5000 r / min, etc.

[0075] In some embodiments, the particle size of the nanoscale iron-based catalyst is 10–500 nm, and non-limiting examples include: 10 nm, 80 nm, 100 nm, 120 nm, 150 nm, 180 nm, 200 nm, 300 nm, 450 nm, 500 nm, etc.

[0076] Secondly, embodiments of the present invention also provide an iron-based catalyst, which is prepared by the method described in the first aspect.

[0077] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. All raw materials used in the embodiments are conventional commercially available products, or can be prepared by known methods.

[0078] Example 1

[0079] A method for recovering iron-based catalysts from coal liquefaction residues includes the following steps:

[0080] S1, after crushing the coal liquefaction residue, toluene is added to dissolve it, forming toluene-soluble and toluene-insoluble substances, and then solid-liquid separation is performed to obtain the toluene-insoluble substances; wherein, the coal liquefaction residue is obtained by liquefying bituminous coal (dry basis) under the action of ferric oxide catalyst (added at 3wt% of dry coal weight);

[0081] S2, the toluene-insoluble matter is dried and crushed to obtain toluene-insoluble matter powder with a particle size of <1mm;

[0082] S3, add 100g of water and 0.5g of sodium hexametaphosphate to 30g of toluene-insoluble powder, mix well to form the first liquid-solid mixture;

[0083] S4, add 100g of a mixed solution of 15wt% sulfuric acid and phosphoric acid (prepared at a molar ratio of 2:3) to the first liquid-solid mixture, stir and react at 100℃ for 1h to obtain the second liquid-solid mixture;

[0084] S5, the second liquid-solid mixture is separated by pressure filtration, and the filtrate is the active metal solution;

[0085] S6. The active metal solution is transferred to a bubble reactor, and ammonia gas is introduced into the active metal solution. At the same time, 1 mL of 10 wt% hydrogen peroxide and air are added dropwise. The amount of ammonia gas introduced is adjusted to control the pH of the entire solution system to be 7-9, and the air flow rate is 500 mL / min. The oxidation reaction is carried out at 35°C. After 1 hour of reaction, the reaction product is separated by centrifugation, and the filter cake is the nano-sized iron-based catalyst.

[0086] The nano-sized iron-based catalyst recovered in this embodiment was recycled and reused in the liquefaction process of bituminous coal (wherein, the nano-sized iron-based catalyst was added at 1 wt% iron content of dry coal) to obtain liquefaction products. Then, steps S1-S6 were repeated to recover and regenerate the iron-based catalyst again. After repeating the experiment three times, the iron recovery rate and the results of direct liquefaction for each time are shown in Table 1 below.

[0087] Table 1

[0088]

[0089] Figure 2 The figure shows the particle size distribution of the iron-based catalyst recovered in this embodiment. As can be seen from the figure, the average particle size of the iron-based catalyst is about 150 nm.

[0090] Example 2

[0091] A method for recovering iron-based catalysts from coal liquefaction residues includes the following steps:

[0092] S1, after crushing the coal tar pitch by-product of direct coal liquefaction, add tetrahydrofuran to dissolve it, forming tetrahydrofuran soluble and tetrahydrofuran insoluble substances, and then perform solid-liquid separation to obtain tetrahydrofuran insoluble substances; among them, the coal tar pitch by-product of direct coal liquefaction refers to the coal tar pitch obtained by directly liquefying coal under the action of an iron-based catalyst, and its properties are shown in Table 2.

[0093] S2, the tetrahydrofuran insoluble matter is dried and crushed to obtain tetrahydrofuran insoluble matter powder with a particle size <0.175mm;

[0094] S3, add 500g of water and 2g of SP-type demulsifier with polyoxyethylene polyoxypropylene octadecyl alcohol ether as the main component to 30g of tetrahydrofuran insoluble powder, mix evenly to form the first liquid-solid mixture;

[0095] S4, add 100g of a 30wt% mixed solution of phosphoric acid and acetic acid (prepared at a molar ratio of 2:4) to the first liquid-solid mixture, stir and react at 100℃ for 1.5h to obtain the second liquid-solid mixture;

[0096] S5, the second liquid-solid mixture is separated by pressure filtration, and the filtrate is the active metal solution;

[0097] S6. The active metal solution is transferred to a bubbling reactor, and ammonia gas is introduced into the active metal solution. At the same time, 5 mL of 10 wt% hydrogen peroxide and air are added dropwise. The amount of ammonia gas introduced is adjusted to control the pH of the entire solution system to be 7-9, and the air flow rate is 1000 mL / min. The oxidation reaction is carried out at 28°C. After 1 hour of reaction, the reaction product is centrifuged, and the filter cake is the nano-sized iron-based catalyst with an average particle size of about 80 nm.

[0098] The nanoscale iron-based catalyst recovered in this embodiment was recycled and reused in the coal liquefaction process (wherein, the nanoscale iron-based catalyst was added at 1 wt% iron content of dry coal) to obtain liquefaction products. Then, steps S1-S6 were repeated to recover and regenerate the iron-based catalyst again. After repeating the experiment four times, the iron recovery rate and the results of direct liquefaction for each time are shown in Table 3 below.

[0099] Table 2

[0100]

[0101] Table 3

[0102]

[0103] Example 3

[0104] A method for recovering iron-based catalysts from coal liquefaction residues includes the following steps:

[0105] S1, after crushing the coal tar pitch by-product of direct coal liquefaction, add tetrahydrofuran to dissolve it, forming tetrahydrofuran soluble and tetrahydrofuran insoluble substances, and then perform solid-liquid separation to obtain tetrahydrofuran insoluble substances; among them, the coal tar pitch by-product of direct coal liquefaction refers to the coal tar pitch obtained by directly liquefying coal under the action of an iron-based catalyst, and its properties are shown in Table 4.

[0106] S2, the tetrahydrofuran insoluble matter is dried and crushed to obtain tetrahydrofuran insoluble matter powder with a particle size of <1mm;

[0107] S3, add 1000g of water and 2g of SP-type demulsifier with polyoxyethylene polyoxypropylene octadecyl alcohol ether as the main component to 30g of tetrahydrofuran insoluble powder, mix evenly to form the first liquid-solid mixture;

[0108] S4, add 180g of a 30wt% mixed solution of phosphoric acid and sulfuric acid (prepared at a molar ratio of 2:4) to the first liquid-solid mixture, stir and react at 100℃ for 1.5h to obtain the second liquid-solid mixture;

[0109] S5, the second liquid-solid mixture is separated by pressure filtration, and the filtrate is the active metal solution;

[0110] S6. The active metal solution is transferred to a bubbling reactor, and ammonia gas is introduced into the active metal solution. At the same time, 5 mL of 10 wt% hydrogen peroxide and air are added dropwise. The amount of ammonia gas introduced is adjusted to control the pH of the entire solution system to be 7-9, and the air flow rate is 1000 mL / min. The oxidation reaction is carried out at 24℃. After 1 hour of reaction, the reaction product is centrifuged, and the filter cake is the nano-sized iron-based catalyst with an average particle size of about 120 nm.

[0111] The nanoscale iron-based catalyst recovered in this embodiment was recycled and reused in the coal liquefaction process (wherein, the nanoscale iron-based catalyst was added at 1 wt% iron content of dry coal) to obtain liquefaction products. Then, steps S1-S6 were repeated to recover and regenerate the iron-based catalyst again. After repeating the experiment four times, the iron recovery rate and the results of direct liquefaction for each time are shown in Table 5 below.

[0112] Table 4

[0113]

[0114] Table 5

[0115]

[0116]

[0117] Example 4

[0118] A method for recovering iron-based catalysts from coal liquefaction residues includes the following steps:

[0119] S1, after crushing the coal tar pitch by-product of kerosene co-refining, add tetrahydrofuran to dissolve it, forming tetrahydrofuran soluble and tetrahydrofuran insoluble substances, and then perform solid-liquid separation to obtain tetrahydrofuran insoluble substances; among them, the coal tar pitch by-product of kerosene co-refining refers to the coal tar pitch by-product obtained by co-processing and converting coal and heavy oil under the action of iron-based catalysts, and its properties are shown in Table 6.

[0120] S2, the tetrahydrofuran insoluble matter is dried and crushed to obtain tetrahydrofuran insoluble matter powder with a particle size <0.175mm;

[0121] S3, add 100g of water and 2g of SP type demulsifier with polyoxyethylene polyoxypropylene octadecyl alcohol ether as the main component to 30g of tetrahydrofuran insoluble powder, mix evenly to form the first liquid-solid mixture;

[0122] S4, 100g of 15wt% sulfuric acid was added to the first liquid-solid mixture, and the mixture was stirred at 100℃ for 1.5h to obtain the second liquid-solid mixture;

[0123] S5, the second liquid-solid mixture is separated by pressure filtration, and the filtrate is the active metal solution;

[0124] S6. The active metal solution is transferred to a bubbling reactor, and ammonia gas is introduced into the active metal solution. At the same time, 2 mL of 10 wt% hydrogen peroxide and air are added dropwise. The amount of ammonia gas introduced is adjusted to control the pH of the entire solution system to be 7-9, and the air flow rate is 500 mL / min. The oxidation reaction is carried out at 35°C. After 1 hour of reaction, the reaction product is centrifuged, and the filter cake is the nano-sized iron-based catalyst with an average particle size of about 160 nm.

[0125] The nano-sized iron-based catalyst recovered in this embodiment was recycled and reused in the liquefaction process of bituminous coal and Tarim heavy oil in Shaanxi Province (where the mass ratio of coal to Tarim heavy oil was 3:7, and the nano-sized iron-based catalyst was added at 1 wt% iron of the total amount of raw materials to be liquefied) to obtain liquefied products. Then, steps S1-S6 were repeated to recover and regenerate the iron-based catalyst again. After repeating the experiment three times, the iron recovery rate and the results of direct liquefaction for each time are shown in Table 7 below.

[0126] Table 6

[0127]

[0128]

[0129] Table 7

[0130]

[0131] Example 5

[0132] A method for recovering iron-based catalysts from coal liquefaction residues includes the following steps:

[0133] S1, after crushing the coal liquefaction residue, tetrahydrofuran is added for dissolution to form tetrahydrofuran soluble and tetrahydrofuran insoluble substances, and solid-liquid separation is performed to obtain tetrahydrofuran insoluble substances; wherein, the coal liquefaction residue is obtained by liquefying coal tar heavy distillate oil under the action of iron ore powder catalyst (added at 3wt% of tar material), and its properties are shown in Table 8;

[0134] S2, the tetrahydrofuran insoluble matter is dried and crushed to obtain tetrahydrofuran insoluble matter powder with a particle size of <1mm;

[0135] S3, add 100g of water and 1g of SP-type demulsifier with polyoxyethylene polyoxypropylene octadecyl alcohol ether as the main component to 30g of tetrahydrofuran insoluble powder, mix evenly to form the first liquid-solid mixture;

[0136] S4, add 100g of a mixed solution of 15wt% sulfuric acid and phosphoric acid (prepared at a molar ratio of 2:3) to the first liquid-solid mixture, stir and react at 100℃ for 1h to obtain the second liquid-solid mixture;

[0137] S5, the second liquid-solid mixture is separated by pressure filtration, and the filtrate is the active metal solution;

[0138] S6. The active metal solution is transferred to a bubbling reactor, and 10wt% dilute ammonia is added to the active metal solution. At the same time, 2mL of 10wt% hydrogen peroxide is added dropwise, and air is introduced. The amount of ammonia added is adjusted to control the pH of the entire solution system to be 7-9. The air flow rate is 500mL / min. The oxidation reaction is carried out at 26℃. After 1 hour of reaction, the reaction product is centrifuged. The filter cake is the nano-sized iron-based catalyst with an average particle size of about 180nm.

[0139] The nano-sized iron-based catalyst recovered in this embodiment is recycled again in the liquefaction process of heavy coal tar distillate (wherein, the nano-sized iron-based catalyst is added at 1.5 wt% iron content of the feedstock to be liquefied) to obtain liquefied products. Then, steps S1-S6 are repeated to recover and regenerate the iron-based catalyst again. After repeating the experiment twice, the iron recovery rate and the results of direct liquefaction are shown in Table 9 below.

[0140] Table 8

[0141]

[0142] Table 9

[0143]

[0144] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0145] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for recovering an iron-based catalyst from coal liquefaction residue, characterized by, The method comprises the following steps: S1, after crushing coal liquefaction residue, a solvent is added for dissolution, forming solvent-soluble and solvent-insoluble, and first solid-liquid separation is performed to obtain solvent-insoluble; S2, the solvent-insoluble is dried and crushed to obtain solvent-insoluble powder with particle size <1mm; S3, the solvent-insoluble powder is mixed with water and demulsifier to form a first liquid-solid mixture; S4, an acid solution is added to the first liquid-solid mixture, and stirring reaction is performed to obtain a second liquid-solid mixture; S5, the second liquid-solid mixture is subjected to second solid-liquid separation, and the filtrate is an active metal solution; S6, an oxygen source and an alkali source are added to the active metal solution for oxidation reaction, and after the reaction is completed, the reaction product is subjected to third solid-liquid separation to obtain a nanoscale iron-based catalyst; wherein the oxygen source comprises hydrogen peroxide and air, and the mass concentration of the hydrogen peroxide is 5-30%.

2. The method of recovering an iron-based catalyst from coal liquefaction residue according to claim 1, characterized by, In the step S1, the solvent comprises at least one of toluene, xylene, tetrahydrofuran, and wash oil.

3. The method of recovering an iron-based catalyst from coal liquefaction residue according to claim 1, characterized by, In the step S1, the iron-based catalyst is one or a mixture of both of a non-supported iron-based catalyst and a supported iron-based catalyst; the non-supported iron-based catalyst comprises at least one of iron ore, divalent iron salt, and trivalent iron salt; wherein the iron ore has an iron content ≥10wt%; the supported iron-based catalyst is a FeOOH type iron-based catalyst supported by a carrier; wherein the carrier comprises at least one of coal powder and inert carbon powder; the particle size of the non-supported iron-based catalyst is micron level or nanometer level, and the particle size of the supported iron-based catalyst is nanometer level.

4. The method of recovering an iron-based catalyst from coal liquefaction residue according to claim 1, characterized by, In the step S3, the demulsifier comprises at least one of sodium hexametaphosphate, SP type demulsifier, AP type demulsifier, and AE type demulsifier; the mass content of the demulsifier in the first liquid-solid mixture is 0.1-15%.

5. The method of recovering an iron-based catalyst from coal liquefaction residue according to claim 1, characterized by, In the step S4, the acid solution comprises at least one of formic acid, acetic acid, hydrochloric acid, nitric acid, phosphoric acid, and sulfuric acid; the mass concentration of the acid solution is 1-80%; And / or, the temperature of the stirring reaction is 20-300℃, and the reaction time is 0.1-5h.

6. The method of recovering an iron-based catalyst from coal liquefaction residue according to claim 1, characterized by, In the step S5, the second solid-liquid separation is performed by centrifugal separation or pressure filtration separation.

7. The method of recovering an iron-based catalyst from coal liquefaction residue according to claim 1, characterized by, In the step S6, the alkali source comprises an alkali solution or an alkaline gas; the alkali solution comprises at least one of sodium hydroxide solution, calcium hydroxide solution, ammonia water, and Lewis base solution; the alkaline gas is ammonia gas or ammonia water vapor; And / or, the amount of the alkali source is determined according to the pH of the reaction system of the oxidation reaction, which is 6.5-13; And / or, the temperature of the oxidation reaction is 20-180℃, and the reaction time is 0.1-4h; And / or, the third solid-liquid separation is performed by standing separation or centrifugal separation; wherein the rotation speed of the centrifugal separation is 500-5000r / min.

8. The method of recovering an iron-based catalyst from coal liquefaction residue according to claim 1, characterized by, The particle size of the nanoscale iron-based catalyst is 10-500nm.

9. An iron-based catalyst, characterized by The iron-based catalyst is prepared by the method of any one of claims 1-8.

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