A method for recycling and recycling of carbonaceous initiators in the production process of spinnable mesophase pitch

Abstract

The present application relates to a kind of carbonaceous initiator recycling and recycling method in the production process of spinnable mesophase pitch.The method is from the residue after liquid phase carbonization reaction, carbonaceous initiator is recovered by solvent extraction, high temperature treatment and fractional separation, and its pore structure and purity are restored by oxidation regeneration or acid washing regeneration, to realize the multiple recycling of initiator;When the number of cycle use is ≥5 times, the performance attenuation of initiator is ≤10%, and the use cost of initiator can be reduced by 30%-40% in single cycle.The present application solves the problems of initiator consumption and solid waste in large-scale production without changing the process advantages of "initiator exists throughout the process without separation", realizes cost reduction and environmental protection, and the process is simple, stable and suitable for continuous and large-scale production of spinnable mesophase pitch.

Description

Technical Field

[0001] This invention belongs to the field of carbon material preparation and resource recycling technology, specifically relating to a method for the recovery, regeneration and recycling of carbonaceous initiators in the production process of spinnable mesophase pitch. Background Technology

[0002] In the preparation of spinnable mesophase pitch based on carbonaceous initiators, the carbonaceous initiator exists throughout the system and does not require separation or removal after the reaction. This characteristic simplifies the process and avoids the problem of exogenous catalyst residue. However, "no removal required" does not mean "cannot be recycled." In large-scale continuous production, the carbonaceous initiator enters the pitch matrix with the product or is discharged with reaction residues, coke residue, and unspun materials. If it is not recycled, it will lead to continuous consumption of initiators, increased costs, and pressure on solid waste treatment and environmental protection.

[0003] For processes containing catalysts or functional additives, there are precedents for recycling and reuse. For example, CN101910375B discloses a catalyst recovery and recycling process in catalytic gasification; US10500563B2 discloses a method for cleaning, conditioning, and regenerating carbon-based adsorbents, which reuses the regenerated adsorbents after chemical cleaning and separation of pollutants in fluidized bed devices. However, existing recycling and regeneration efforts mainly focus on catalysts and adsorbents, addressing their activity decay and pollution issues, without addressing porous carbon-based initiators used as structure-inducing media in the production of spinnable mesophase pitch.

[0004] Existing technologies mostly focus on the preparation of spinnable mesophase pitch or carbon fibers themselves, with little dedicated research on the recycling and reuse of specific porous carbon-based additives such as carbonaceous initiators, and no corresponding patented methods. Since carbonaceous initiators are high-temperature and solvent-resistant carbon-based materials, they possess inherent feasibility for recycling and regeneration. Therefore, there is an urgent need to provide a method that can efficiently recover them from their residues, restore their pore structure and purity, and allow for multiple recycling.

[0005] Therefore, there is an urgent need to provide a method for the recovery, regeneration, and recycling of carbonaceous initiators in the production process of spinnable mesophase pitch, which can reduce costs and protect the environment while maintaining process continuity and not affecting the advantage of "initiator present throughout the process without separation". Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for the recovery, regeneration, and recycling of carbonaceous initiators in the production process of spinnable mesophase pitch. This method recovers the carbonaceous initiator through "solvent extraction—high-temperature treatment—gradual separation," and then restores its pore structure and purity through "oxidative regeneration or acid washing regeneration," achieving multiple recycling cycles.

[0007] A method for the recovery, regeneration, and recycling of carbonaceous initiators in the production process of spinnable mesophase asphalt is characterized by the following steps: (1) recovering carbonaceous initiators from the residue after liquid-phase carbonization reaction of spinnable mesophase asphalt, wherein the recovery adopts a process combining solvent extraction, high-temperature treatment, and graded separation, wherein the residue is separated into soluble asphalt / organic components by solvent extraction, the insoluble residue is subjected to high-temperature treatment to remove surface adsorbates, and then the recovered carbonaceous initiator is obtained by graded separation; (2) regenerating the recovered carbonaceous initiator, wherein the regeneration adopts one of oxidation regeneration or acid washing regeneration; (3) recycling the regenerated carbonaceous initiator for the preparation of spinnable mesophase asphalt.

[0008] In this invention, the solvent extraction uses aromatic and / or alkane solvents, with an extraction temperature of 30-120 °C, an extraction ratio (solvent / residue) of (2-6):1, and 1-3 extraction stages; the high-temperature treatment is carried out at 500-900 °C in an atmosphere of nitrogen, argon, water vapor, or CO2 for 1-4 h; the fractionation is performed by airflow fractionation or sieving, resulting in a particle size D50 of 1-30 μm and a particle size difference of no more than 1.2. The oxidative regeneration is carried out at 200-500 °C in an oxygen-containing gas atmosphere for 0.5-3 h; the acid washing regeneration is performed using 5%-20% hydrochloric acid or sulfuric acid at 40-90 °C for 1-3 h, followed by washing with water until neutral, and drying at 80-120 °C.

[0009] Compared with the prior art, the beneficial effects of the present invention are: (1) The present invention takes into account the characteristics of carbon initiators as high-temperature resistant and solvent resistant carbon-based materials, and adopts a combination process of "solvent extraction - high-temperature treatment - graded separation", which can efficiently recover carbon initiators from reaction residues, coke residues and unspun materials, without affecting the process advantage of "initiator present throughout the process without separation". (2) By restoring the oxygen-containing functional groups on the surface and removing the weakly bound carbon layer on the surface through oxidation regeneration, or by removing the enriched ash and metal impurities through acid washing regeneration, the BET specific surface area, average pore size and purity of the regenerated initiator can be restored to the usable range. (3) When the regenerated carbon initiator is recycled ≥5 times, the performance decay is ≤10%, and the spinnable mesophase pitch mesophase prepared from it has a content of ≥98%, a softening point of 270~290 ℃ and a yield of ≥15%, maintaining process stability; the cost of a single cycle is reduced by 30%~40% compared with the newly prepared initiator, significantly reducing costs. (4) The process is simple, the cycle is stable and the recovery rate is high. It is suitable for continuous and large-scale production of spinnable mesophase pitch, which has both economic and environmental benefits. Detailed Implementation

[0010] The present invention will be further described below with reference to the embodiments. In the following embodiments, a freshly prepared carbonaceous initiator RO (BET specific surface area 1050 m² / g, average pore size 3.5 nm, ash content 0.06 wt%, D50 8 μm) was used as a reference and continuously recycled for the preparation of spinnable mesophase pitch, and the residues after each reaction were recycled and regenerated.

[0011] Example 1 (Cycle 1, Fresh Initiator)

[0012] 100 g of refined aromatic oil was mixed with 2 wt% fresh carbonaceous initiator R0 and carbonized in the liquid phase at 450 °C for 15 h under N2 atmosphere and 0.5 MPa to obtain spinnable mesophase pitch with a mesophase content of 98.6%, a softening point of 281 °C, and a yield of 18.5%. The residue (containing the initiator) after the reaction was extracted with mixed aromatics in two stages at 80 °C (extraction ratio 4:1) to separate the soluble components; the insoluble residue was treated with N2 atmosphere at 650 °C for 2 h to remove surface adsorbates; and then subjected to air classification to obtain the recovered carbonaceous initiator R1.

[0013] Example 2 (Second Cycle)

[0014] The recovered carbonaceous initiator R1 was oxidatively regenerated by treatment at 200 °C in air (15% oxygen by volume) for 1 h to obtain regenerated initiator R1', which has a BET specific surface area of ​​1035 m² / g, an average pore size of 3.5 nm, and an ash content of 0.07 wt%. 100 g of refined aromatic-rich oil was taken, and 2 wt% of the regenerated initiator R1' was added. The mixture was then carbonized in the liquid phase at 450 °C for 15 h to obtain spinnable mesophase pitch with a mesophase content of 98.4%, a softening point of 280 °C, and a yield of 18.2%. The residue was recovered according to Example 1 to obtain R2.

[0015] Example 3 (3rd cycle)

[0016] The recovered carbonaceous initiator R2 was oxidized and regenerated by treatment with CO2 atmosphere at 300 °C for 1.5 h to obtain regenerated initiator R2', which has a BET specific surface area of ​​1010 m² / g and an ash content of 0.08 wt%. Spinable mesophase pitch was prepared in the same manner, with a mesophase content of 98.3%, a softening point of 279 °C, and a yield of 17.9%.

[0017] Example 4 (4th cycle)

[0018] The recovered carbonaceous initiator R3 was acid-washed with 15% hydrochloric acid at 60 °C for 2 h, washed with water until neutral, and dried at 100 °C for acid regeneration to obtain regenerated initiator R3', which has a BET specific surface area of ​​990 m² / g and an ash content of 0.09 wt%. Spinizable mesophase pitch was prepared in the same manner, with a mesophase content of 98.1%, a softening point of 278 °C, and a yield of 17.6%.

[0019] Example 5 (5th cycle)

[0020] The recovered carbonaceous initiator R4 was oxidatively regenerated by treatment at 250 °C in air atmosphere (10% oxygen by volume) for 1 h to obtain regenerated initiator R4', which has a BET specific surface area of ​​970 m² / g, an average pore size of 3.4 nm, and an ash content of 0.10 wt%. Spinizable mesophase pitch was prepared in the same manner, with a mesophase content of 98.0%, a softening point of 277 °C, and a yield of 17.3%.

[0021] As can be seen from Examples 1-5, after five consecutive cycles of recycling and reuse, the BET specific surface area of ​​the carbonaceous initiator decreased from 1050 m² / g to 970 m² / g, a decrease of approximately 7.6%, while the ash content increased from 0.06 wt% to 0.10 wt%. The content of the spinnable mesophase pitch prepared from it decreased from 98.6% to 98.0%, and the yield decreased from 18.5% to 17.3%, with a total decrease of ≤10%. Furthermore, the softening point remained consistently within the range of 270-290 °C. Based on the purchase cost of fresh initiator, a single cycle can reduce the initiator usage cost by approximately 35%. The above data are exemplary representations of the implementation conditions of this invention; actual applications should be verified based on specific initiators, residue composition, and measured results.

Claims

1. A method for the recovery, regeneration, and recycling of carbonaceous initiators in the production process of spinnable mesophase pitch, characterized in that, The process includes the following steps: (1) recovering carbonaceous initiator from the residue after liquid-phase carbonization reaction of spinnable mesophase pitch. The recovery adopts a process combining solvent extraction, high-temperature treatment and graded separation, in the following order: the residue is separated into soluble pitch / organic components by solvent extraction, the insoluble residue is subjected to high-temperature treatment to remove surface adsorbates, and then the recovered carbonaceous initiator is obtained by graded separation; (2) regenerating the recovered carbonaceous initiator, the regeneration adopts one of oxidation regeneration or acid washing regeneration; (3) recycling the regenerated carbonaceous initiator for the preparation of spinnable mesophase pitch.

2. The method for recycling and regenerating carbonaceous initiators in the production process of spinnable mesophase pitch according to claim 1, characterized in that: In step (1), the solvent extraction uses an extractant selected from aromatic solvents (one or more of mixed aromatics, methylnaphthalene, wash oil, and heavy aromatics) and alkane solvents (one or more of n-pentane, n-hexane, and isooctane); the extraction temperature is 30~120 ℃, the extraction ratio (solvent / residue) is (2~6):1, and the number of extraction stages is 1~3.

3. The method for recycling and regenerating carbonaceous initiators in the production process of spinnable mesophase pitch according to claim 1, characterized in that: In step (1), the high temperature treatment is 500~900 ℃, the atmosphere is one or more of nitrogen, argon, water vapor or CO2, and the treatment time is 1~4 h, in order to remove the asphalt, coke and light components adsorbed on the surface of the residue.

4. The method for recycling and regenerating carbonaceous initiators in the production process of spinnable mesophase pitch according to claim 1, characterized in that: In step (1), the classification and separation is air classification or sieving. After classification, the particle size D50 of the recovered carbonaceous initiator is 1~30 μm and the particle size distance is not greater than 1.2, removing fine powder and agglomerated large particles.

5. The method for recycling and regenerating carbonaceous initiators in the production process of spinnable mesophase pitch according to claim 1, characterized in that: In step (2), the oxidation regeneration is to treat the surface at 200~500 ℃ in air or oxygen-containing gas (oxygen volume fraction 5%~25%) for 0.5~3 h, in order to moderately oxidize, restore the oxygen-containing functional groups on the surface and remove the weakly bonded carbon layer on the surface.

6. The method for recycling and regenerating carbonaceous initiators in the production process of spinnable mesophase pitch according to claim 1, characterized in that: In step (2), the acid washing regeneration involves using a 5% to 20% hydrochloric acid or sulfuric acid solution at 40 to 90 °C for 1 to 3 hours, followed by water washing until neutral and drying at 80 to 120 °C to remove the ash and metal impurities accumulated in the regenerated sample.

7. The method for recycling and regenerating carbonaceous initiators in the production process of spinnable mesophase pitch according to claim 1, characterized in that: In step (2), the BET specific surface area, average pore size, ash content, sulfur content and total metal impurities of the regenerated carbonaceous initiator are tested. The BET specific surface area is required to be 200~1500 m² / g, the average pore size is 2~50 nm, the ash content is ≤0.1 wt%, the sulfur content is ≤0.05 wt%, and the total metal impurities are ≤10 ppm.

8. The method for recycling and regenerating carbonaceous initiators in the production process of spinnable mesophase pitch according to claim 1, characterized in that: In step (3), when the recycling is used to prepare spinnable mesophase pitch, the amount of regenerated carbonaceous initiator added is 0.1~5 wt% of the mass of refined aromatic oil, the reaction temperature is 430~460 ℃, and the liquid phase carbonization time is 10~25 h.

9. The method for recycling and regenerating carbonaceous initiators in the production process of spinnable mesophase pitch according to claim 8, characterized in that: The regenerated carbonaceous initiator is used ≥5 times, and after 5 cycles, its BET specific surface area, average pore size, and ash content decrease by ≤10%. The spinnable mesophase pitch prepared from it has a mesophase content of ≥98%, a softening point of 270~290 ℃, and a yield of ≥15%.

10. The method for recycling and regenerating carbonaceous initiators in the production process of spinnable mesophase pitch according to claim 1, characterized in that: The recycling and reuse method reduces the cost of a single cycle of carbonaceous initiator by 30% to 40% compared to newly prepared initiators; the method is applicable to the recovery of carbonaceous initiators from liquid-phase carbonization reaction residues, reactor coke residues, and unspun materials.