Fischer-Tropsch wax residue treatment method based on compound solvent and microwave coupling

Abstract

The invention discloses a Fischer-Tropsch wax residue treatment method based on compound solvent and microwave coupling. Belongs to the technical field of nonmetal waste treatment. The method comprises the following steps: crushing wax residue, and mixing the crushed wax residue with a compound solvent to obtain a primary mixture; placing the first-stage mixture in a microwave reactor for full treatment to obtain a second-stage mixture; carrying out gradient centrifugation on the secondary mixture to obtain a wax-containing solvent and solid residues; evaporating and recovering the wax-containing solvent to obtain wax and a compound solvent, and washing and drying the solid slag to obtain a catalyst; according to the method, the coupling effect of the compound solvent and the microwave field is utilized, gradient centrifugation is matched, efficient dissolution and recovery of wax and low-loss separation of the catalyst are achieved, and energy consumption is low; the problems that in the Fischer-Tropsch wax residue treatment process, wax and a catalyst are not thoroughly separated, and olefin impurities are generated are solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of non-metallic waste treatment, and specifically relates to a method for treating Fischer-Tropsch slag wax based on the coupling of compound solvent and microwave. Background Art

[0002] The gasification, liquefaction of coal and the production of hydrocarbon compounds are important parts of coal chemical industry. Fischer-Tropsch synthesis technology uses syngas (CO + H2) as raw material, and under suitable catalysts and reaction conditions, it generates hydrocarbons and oxygen-containing organic compounds. Through this reaction, not only can environmentally friendly products such as gasoline, diesel, and paraffin be obtained, but also high-value-added chemicals such as olefins and oxygen-containing compounds can be obtained, which has good economic efficiency and market prospects.

[0003] Fischer-Tropsch synthesis mainly conducts reactions in a slurry bed, and a large amount of iron-based catalysts are required for catalysis during the reaction process. After the catalysts complete their service cycles, they will be regularly discharged from the slurry bed. During the discharge process, part of the Fischer-Tropsch wax will be carried out and bonded together, becoming hazardous waste. The accumulation of a large amount of slag wax will cause serious environmental pollution and waste of resources, and it is necessary to classify and recycle it. Currently, the existing methods for treating slag wax include pyrolysis method, magnetic separation method, supercritical fluid extraction method, etc.

[0004] Patent CN111282574 A discloses a method for recovering iron-based catalysts for Fischer-Tropsch synthesis. This method uses a mixture of ethyl acetate, cyclohexane and morpholine to extract and separate the wax in the slag wax. After dissolving small molecule inorganic substances and organic substances in the extraction product with carboxylic acid, it is pyrolyzed at a high temperature of 100 - 250 °C and magnetically separated to recover the catalyst. Patent CN110607193 A discloses a method for resource recovery and utilization of Fischer-Tropsch slag wax. This method uses a mixture of hydrocarbon extractant, visbreaking agent and passivator to extract wax at 50 - 300 °C. After solid-liquid separation, a solid catalyst is obtained, and Fischer-Tropsch wax is recovered after evaporating the solvent.

[0005] It can be seen that the treatment temperatures of the existing extraction and pyrolysis methods are all above 100 °C, which will cause the small molecule hydrocarbons in the Fischer-Tropsch wax to vaporize or pyrolyze, generating olefin impurities, and the separation of wax and catalyst is not thorough. It is necessary to develop a non-high-temperature and rapid method for separating wax and catalyst to achieve rapid and efficient separation of wax and catalyst. Summary of the Invention

[0006] The present invention overcomes the deficiencies of the prior art, and proposes a method for treating Fischer-Tropsch slag wax based on the coupling of compound solvent and microwave; it solves the problems of incomplete separation of wax and catalyst and the generation of olefin impurities during the treatment process of Fischer-Tropsch slag wax.

[0007] The present invention is realized through the following technical solutions: A Fischer-Tropsch slag wax treatment method based on compound solvent and microwave coupling comprises the following steps: 1) The residual wax raw material and the compound solvent are fully mixed, and reacted under heating and stirring conditions to obtain a primary mixture; the liquid-solid ratio of the compound solvent to the residual wax raw material is 8-5:1; the compound solvent is composed of an extractant and a silane coupling agent; the extractant is a mixture of isopropanol and ethyl acetate, and the weight ratio of the extractant isopropanol to ethyl acetate is 4-5:3; 2) placing the primary mixture in a microwave reactor and treating it at 50° C. to 55° C. for 15 min to 30 min to obtain a secondary mixture; 3) performing gradient centrifugation on the secondary mixture to obtain a waxy solvent and solid residue; 4) heating and evaporating the wax-containing solvent to recover the wax and the compound solvent; washing and drying the solid residue to obtain the catalyst.

[0008] Preferably, the silane coupling agent is KH-500.

[0009] More preferably, the content of the silane coupling agent is 0.5-1 wt%.

[0010] Preferably, the residual wax raw material is first crushed into a powdery solid and then fully mixed with the compound solvent.

[0011] Preferably, the heating temperature in step 1) is 35°C to 45°C.

[0012] Preferably, the microwave frequency of the microwave reactor is 2-3 GHz.

[0013] Preferably, the gradient centrifugation speed is divided into three levels, the first level centrifugation speed is 2000~3000rpm, the time is 3~5 min, the second level centrifugation speed is 5000~6000rpm, the time is 5~6 min, and the third level centrifugation speed is 8000~9000rpm, the time is 8~9 min.

[0014] More preferably, the first stage centrifugation speed is 3000 rpm, the time is 3 min, the second stage centrifugation speed is 6000 rpm, the time is 5 min, and the third stage centrifugation speed is 8000 rpm, the time is 8 min.

[0015] Preferably, the evaporation temperature in step 4) is 70°C to 85°C.

[0016] Preferably, in step 4), the solid residue is treated by washing with water.

[0017] The reaction principle of the present invention is: The slag wax raw material is C 15 -C 30It is composed of Fischer-Tropsch wax and an iron-based catalyst, with the catalyst content being 8-15%. In order not to damage the original structures of the Fischer-Tropsch wax and the iron-based catalyst, in the present invention, a solvent is first used to dissolve and separate the Fischer-Tropsch wax in the slack wax raw material. In order to completely and thoroughly separate the wax from the iron-based catalyst and avoid the decomposition of the Fischer-Tropsch wax caused by high temperature, the mixture of the compound solvent and the wax is placed in a microwave reactor for reaction. Microwaves can break the bond between the wax molecules and the catalyst and accelerate the dissolution of the wax molecules into the extraction solvent. Since the particle sizes of the iron-based catalyst are different, in order to recover the small-particle iron-based catalyst as much as possible, gradient centrifugation is used to thoroughly recover the small-particle iron-based catalyst.

[0018] In step 1), the compound solvent consists of an extractant and a silane coupling agent. The extractant mainly plays the role of dissolving the wax, while the silane coupling agent plays a key role in interfacial modification and strengthening of selective separation. The silane coupling agent can chemically bond with the surface of the catalyst to form a monolayer, converting the high-surface-energy catalyst surface into a low-surface-energy wax-repellent interface. At the same time, the organic end of the silane coupling agent forms a link with the extractant, improving the penetration and dissolution of the extractant into the wax.

[0019] The beneficial effects of the present invention compared with the prior art are as follows: In the present invention, a solvent is first used to dissolve and separate the Fischer-Tropsch wax in the slack wax raw material, and then the mixture of the compound solvent and the wax is placed in a microwave reactor for reaction. Microwaves can break the bond between the wax molecules and the catalyst and accelerate the dissolution of the wax molecules into the extraction solvent; combined with gradient centrifugation, the small-particle iron-based catalyst is thoroughly recovered. The present invention utilizes the coupling effect of the solvent and the microwave field, combined with gradient centrifugation, to achieve efficient dissolution and recovery of the wax and low-loss separation of the catalyst, and has low energy consumption; the final wax recovery rate of the present invention can reach more than 85%. Description of the Drawings

[0020] Figure 1 is the operation flow chart of the Fischer-Tropsch slack wax treatment method based on the coupling of the compound solvent and the microwave according to the present invention. Detailed Embodiments

[0021] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer and more understandable, the present invention will be further described in detail in combination with embodiments and drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. The technical solutions of the present invention will be described in detail below in combination with embodiments and drawings, but the protection scope is not limited by this.

[0022] Example 1 (1) Crush the waste wax raw material into a powdery solid, mix it with the compound solvent according to a liquid-solid ratio of 5:1, heat and stir at 40 °C to obtain a primary mixture; among them, the compound solvent is composed of an extractant and a silane coupling agent, the extractant is a mixture of isopropanol and ethyl acetate, and the weight ratio of isopropanol to ethyl acetate is 5:3; the silane coupling agent is KH-500, and the content is 1 wt%. (2) Place the primary mixture in the cavity of a microwave reactor, and treat it for 20 min under the heating condition of 50 °C to obtain a secondary mixture; the microwave frequency of the microwave reactor is 2.45 GHz. (3) Perform gradient centrifugation on the secondary mixture: the primary centrifugation speed is 3000 rpm, the time is 3 min, the secondary centrifugation speed is 6000 rpm, the time is 5 min, and the tertiary centrifugation speed is 8000 rpm, the time is 8 min; obtain a wax-containing solvent and solid slag. (4) Evaporate the wax-containing solvent at 75 °C to recover wax and the compound solvent. (5) Wash and dry the solid slag to obtain a catalyst.

[0023] Example 2 (1) Crush the waste wax raw material into a powdery solid, mix it with the compound solvent according to a liquid-solid ratio of 5:1, heat and stir at 40 °C to obtain a primary mixture; among them, the compound solvent is composed of an extractant and a silane coupling agent, the extractant is a mixture of isopropanol and ethyl acetate, and the weight ratio of isopropanol to ethyl acetate is 5:3, the silane coupling agent is KH-500, and the content is 0.5 wt%. (2) Place the primary mixture in the cavity of a microwave reactor, and treat it for 20 min under the heating condition of 50 °C to obtain a secondary mixture; the microwave frequency of the microwave reactor is 2.45 GHz. (3) Perform gradient centrifugation on the secondary mixture, the primary centrifugation speed is 3000 rpm, the time is 3 min, the secondary centrifugation speed is 6000 rpm, the time is 5 min, and the tertiary centrifugation speed is 8000 rpm, the time is 8 min. Obtain a wax-containing solvent and solid slag. (4) Evaporate the wax-containing solvent at 75 °C to recover wax and the compound solvent. (5) Wash and dry the solid slag to obtain a catalyst.

[0024] Example 3 (1) Crush the waste wax raw material into a powdery solid, mix it with the compound solvent at a liquid-solid ratio of 6:1, heat and stir at 40 °C to obtain a primary mixture; among them, the compound solvent is composed of an extractant and a silane coupling agent, the extractant is a mixture of isopropanol and ethyl acetate, the weight ratio of isopropanol to ethyl acetate is 5:3, the silane coupling agent is KH-500, and the content is 1 wt%. (2) Place the primary mixture in the cavity of a microwave reactor, and treat it for 20 min under the heating condition of 50 °C to obtain a secondary mixture; the microwave frequency of the microwave reactor is 2.45 GHz. (3) Perform gradient centrifugation on the secondary mixture, with the first centrifugation speed of 3000 rpm for 3 min, the second centrifugation speed of 6000 rpm for 5 min, and the third centrifugation speed of 8000 rpm for 8 min. Obtain a wax-containing solvent and solid slag. (4) Evaporate the wax-containing solvent at 75 °C to recover wax and the compound solvent. (5) Wash and dry the solid slag to obtain a catalyst.

[0025] Example 4 (1) Crush the waste wax raw material into a powdery solid, mix it with the compound solvent at a liquid-solid ratio of 7:1, heat and stir at 40 °C to obtain a primary mixture; among them, the compound solvent is composed of an extractant and a silane coupling agent, the extractant is a mixture of isopropanol and ethyl acetate, the weight ratio of isopropanol to ethyl acetate is 5:3, the silane coupling agent is KH-500, and the content is 1 wt%. (2) Place the primary mixture in the cavity of a microwave reactor, and treat it for 20 min under the heating condition of 50 °C to obtain a secondary mixture; the microwave frequency of the microwave reactor is 2.45 GHz. (3) Perform gradient centrifugation on the secondary mixture, with the first centrifugation speed of 3000 rpm for 3 min, the second centrifugation speed of 6000 rpm for 5 min, and the third centrifugation speed of 8000 rpm for 8 min; obtain a wax-containing solvent and solid slag. (4) Evaporate the wax-containing solvent at 75 °C to recover wax and the compound solvent. (5) Wash and dry the solid slag to obtain a catalyst.

[0026] Example 5 (1) Crush the waste wax raw material into a powdery solid, mix it with a compound solvent at a liquid-solid ratio of 8:1, heat and stir at 40 °C to obtain a primary mixture; wherein, the compound solvent is composed of an extractant and a silane coupling agent, the extractant is a mixture of isopropanol and ethyl acetate, the weight ratio of isopropanol to ethyl acetate is 5:3, the silane coupling agent is KH-500, and the content is 1 wt%; (2) Place the primary mixture in the cavity of a microwave reactor, and treat it for 20 min under heating conditions at 50 °C to obtain a secondary mixture; the microwave frequency of the microwave reactor is 2.45 GHz; (3) Perform gradient centrifugation on the secondary mixture, with the first centrifugation speed of 3000 rpm for 3 min, the second centrifugation speed of 6000 rpm for 5 min, and the third centrifugation speed of 8000 rpm for 8 min; obtain a wax-containing solvent and solid slag; (4) Evaporate the wax-containing solvent at 75 °C to recover wax and the compound solvent; (5) Wash and dry the solid slag to obtain a catalyst.

[0027] Example 6 (1) Crush the waste wax raw material into a powdery solid, mix it with a compound solvent at a liquid-solid ratio of 8:1, heat and stir at 40 °C to obtain a primary mixture; wherein, the compound solvent is composed of an extractant and a silane coupling agent, the extractant is a mixture of isopropanol and ethyl acetate, the weight ratio of isopropanol to ethyl acetate is 5:3, the silane coupling agent is KH-500, and the content is 0.8 wt%; (2) Place the primary mixture in the cavity of a microwave reactor, and treat it for 15 min under heating conditions at 50 °C to obtain a secondary mixture; the microwave frequency of the microwave reactor is 3 GHz; (3) Perform gradient centrifugation on the secondary mixture, with the first centrifugation speed of 3000 rpm for 3 min, the second centrifugation speed of 6000 rpm for 5 min, and the third centrifugation speed of 8000 rpm for 8 min; obtain a wax-containing solvent and solid slag; (4) Evaporate the wax-containing solvent at 75 °C to recover wax and the compound solvent; (5) Wash and dry the solid slag to obtain a catalyst.

[0028] Example 7 (1) Crush the waste wax raw material into a powdery solid, mix it with the compound solvent at a liquid-solid ratio of 8:1, heat and stir at 45 °C to obtain a primary mixture; among them, the compound solvent is composed of an extractant and a silane coupling agent, the extractant is a mixture of isopropanol and ethyl acetate, the weight ratio of isopropanol to ethyl acetate is 4:3, the silane coupling agent is KH-500, and the content is 0.8 wt%; (2) Place the primary mixture in the cavity of a microwave reactor, and treat it for 30 min under heating conditions at 50 °C to obtain a secondary mixture; the microwave frequency of the microwave reactor is 2 GHz; (3) Perform gradient centrifugation on the secondary mixture, with the first centrifugation speed of 3000 rpm for 3 min, the second centrifugation speed of 6000 rpm for 5 min, and the third centrifugation speed of 8000 rpm for 8 min; obtain a wax-containing solvent and solid slag; (4) Evaporate the wax-containing solvent at 75 °C to recover wax and the compound solvent; (5) Wash and dry the solid slag to obtain a catalyst.

[0029] Example 8 (1) Crush the waste wax raw material into a powdery solid, mix it with the compound solvent at a liquid-solid ratio of 8:1, heat and stir at 35 °C to obtain a primary mixture; among them, the compound solvent is composed of an extractant and a silane coupling agent, the extractant is a mixture of isopropanol and ethyl acetate, the weight ratio of isopropanol to ethyl acetate is 5:3, the silane coupling agent is KH-500, and the content is 0.8 wt%; (2) Place the primary mixture in the cavity of a microwave reactor, and treat it for 25 min under heating conditions at 55 °C to obtain a secondary mixture; the microwave frequency of the microwave reactor is 2.45 GHz; (3) Perform gradient centrifugation on the secondary mixture, with the first centrifugation speed of 3000 rpm for 4 min, the second centrifugation speed of 6000 rpm for 6 min, and the third centrifugation speed of 8000 rpm for 6 min; obtain a wax-containing solvent and solid slag; (4) Evaporate the wax-containing solvent at 85 °C to recover wax and the compound solvent; (5) Wash and dry the solid slag to obtain a catalyst.

[0030] Example 9 (1) Crush the waste wax raw material into a powdery solid, mix it with a compound solvent at a liquid-solid ratio of 8:1, heat and stir at 35 °C to obtain a primary mixture; wherein, the compound solvent is composed of an extractant and a silane coupling agent, the extractant is a mixture of isopropanol and ethyl acetate, the weight ratio of isopropanol to ethyl acetate is 5:3, and the silane coupling agent is KH-500 with a content of 0.8 wt%. (2) Place the primary mixture in the cavity of a microwave reactor, and under the heating condition of 45 °C, process it for 25 min to obtain a secondary mixture; the microwave frequency of the microwave reactor is 2.45 GHz. (3) Perform gradient centrifugation on the secondary mixture, with the primary centrifugation speed of 2000 rpm for 5 min, the secondary centrifugation speed of 5000 rpm for 6 min, and the tertiary centrifugation speed of 9000 rpm for 9 min; obtain a wax-containing solvent and solid residue. (4) Evaporate the wax-containing solvent at 70 °C to recover wax and the compound solvent. (5) Wash and dry the solid residue to obtain a catalyst.

[0031] Comparative Example 1 (1) Crush the waste wax raw material into a powdery solid, mix it with single isopropanol at a liquid-solid ratio of 8:1, heat and stir at 40 °C to obtain a primary mixture. (2) Place the primary mixture in the cavity of a microwave reactor, and under the heating condition of 50 °C, process it for 20 min to obtain a secondary mixture; the microwave frequency of the microwave reactor is 2.45 GHz. (3) Perform gradient centrifugation on the secondary mixture, with the primary centrifugation speed of 3000 rpm for 3 min, the secondary centrifugation speed of 6000 rpm for 5 min, and the tertiary centrifugation speed of 8000 rpm for 8 min. Obtain a wax-containing solvent and solid residue. (4) Evaporate the wax-containing solvent at 75 °C to recover wax and the compound solvent. (5) Wash and dry the solid residue to obtain a catalyst.

[0032] Comparative Example 2 (1) Crush the waste wax raw material into a powdery solid, mix it with ethyl acetate at a liquid-solid ratio of 8:1, heat and stir at 40 °C to obtain a primary mixture. (2) Place the primary mixture in the cavity of a microwave reactor, and under the heating condition of 50 °C, process it for 20 min to obtain a secondary mixture; the microwave frequency of the microwave reactor is 2.45 GHz. (3) Perform gradient centrifugation on the secondary mixture. The primary centrifugation speed is 3000 rpm for 3 min, the secondary centrifugation speed is 6000 rpm for 5 min, and the tertiary centrifugation speed is 8000 rpm for 8 min. A wax-containing solvent and solid residue are obtained; (4) Evaporate the wax-containing solvent at 75 °C to recover wax and the compound solvent; (5) Wash and dry the solid residue to obtain a catalyst.

[0033] Comparative Example 3 (1) Crush the residue wax raw material into a powdery solid and mix it with the compound solvent at a liquid-solid ratio of 1:1; heat and stir at 40 °C to obtain a primary mixture; among them, the compound solvent consists of an extractant and a silane coupling agent. The extractant is a mixture of isopropanol and ethyl acetate, the weight ratio of isopropanol to ethyl acetate is 1:1, and the silane coupling agent is KH-500 with a content of 0.1 wt%; (2) Place the primary mixture in the cavity of a microwave reactor and treat it at 50 °C for 20 min to obtain a secondary mixture; the microwave frequency of the microwave reactor is 2.45 GHz; (3) Perform gradient centrifugation on the secondary mixture. The primary centrifugation speed is 3000 rpm for 3 min, the secondary centrifugation speed is 6000 rpm for 5 min, and the tertiary centrifugation speed is 8000 rpm for 8 min. A wax-containing solvent and solid residue are obtained; (4) Evaporate the wax-containing solvent at 75 °C to recover wax and the compound solvent; (5) Wash and dry the solid residue to obtain a catalyst.

[0034] The wax recovery rates of Examples 1-5 and Comparative Examples 1-3 are shown in Table 1.

[0035] When the compound solvent is single isopropanol or single ethyl acetate and no silane coupling agent is added, the wax recovery rate is much lower than that of Examples 1-5; under the preferred conditions of Examples 1-5, the wax recovery rate is above 85%.

[0036] The above content is a further detailed description of the present invention in combination with specific preferred embodiments. It cannot be determined that the specific embodiments of the present invention are limited to this. For those of ordinary skill in the technical field to which the present invention belongs, without departing from the premise of the present invention, several simple deductions or substitutions can still be made, which should all be regarded as belonging to the patent protection scope determined by the claims submitted for the present invention.

Claims

1. A method for treating Fischer-Tropsch slag wax based on a composite solvent and microwave coupling, characterized in that: The following steps are involved: 1) The residual wax raw material and the compound solvent are fully mixed, and reacted under heating and stirring conditions to obtain a primary mixture; the liquid-solid ratio of the compound solvent to the residual wax raw material is 8-5:1; the compound solvent is composed of an extractant and a silane coupling agent; the extractant is a mixture of isopropanol and ethyl acetate, and the weight ratio of the extractant isopropanol to ethyl acetate is 4-5:3; 2) placing the primary mixture in a microwave reactor and treating it at 50° C. to 55° C. for 15 min to 30 min to obtain a secondary mixture; 3) performing gradient centrifugation on the secondary mixture to obtain a waxy solvent and solid residue; 4) heating and evaporating the wax-containing solvent to recover the wax and the compound solvent; washing and drying the solid residue to obtain the catalyst.

2. The method for treating Fischer-Tropsch slag wax based on composite solvent and microwave coupling according to claim 1, characterized in that: The silane coupling agent is KH-500.

3. The method for treating Fischer-Tropsch slag wax based on composite solvent and microwave coupling according to claim 2, characterized in that: The content of the silane coupling agent is 0.5-1 wt%.

4. The method for treating Fischer-Tropsch slag wax based on compound solvent and microwave coupling according to claim 1, characterized in that: Firstly, the slag wax raw material is crushed into powdery solid, and then fully mixed with the compound solvent.

5. The method for treating Fischer-Tropsch slag wax based on compound solvent and microwave coupling according to claim 1, characterized in that: The heating temperature in step 1) is 35°C to 45°C.

6. The method for treating Fischer-Tropsch slag wax based on compound solvent and microwave coupling according to claim 1, characterized in that: The microwave frequency of the microwave reactor is 2-3 GHz.

7. The method for treating Fischer-Tropsch slag wax based on compound solvent and microwave coupling according to claim 1, characterized in that: The gradient centrifugation speed is divided into three levels: the first level centrifugation speed is 2000-3000 rpm, the time is 3-5 min, the second level centrifugation speed is 5000-6000 rpm, the time is 5-6 min, and the third level centrifugation speed is 8000-9000 rpm, the time is 8-9 min.

8. The method for treating Fischer-Tropsch slag wax based on compound solvent and microwave coupling according to claim 7, characterized in that: The first stage centrifugation speed is 3000 rpm, the time is 3 min, the second stage centrifugation speed is 6000 rpm, the time is 5 min, and the third stage centrifugation speed is 8000 rpm, the time is 8 min.

9. The method for treating Fischer-Tropsch slag wax based on compound solvent and microwave coupling according to claim 1, characterized in that: The evaporation temperature of step 4) is 70°C to 85°C.

10. The method for treating Fischer-Tropsch slag wax based on compound solvent and microwave coupling according to claim 1, characterized in that: In the step 4), the solid residue is treated by washing with water.

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