Method for directionally regulating and controlling composite catalyst in lithium battery pyrolysis process

Abstract

The invention discloses a method for directionally regulating and controlling a composite catalyst in a lithium battery pyrolysis process, and relates to the technical field of lithium batteries, and the method comprises the following operation steps: S1, raw material selection: selecting one or more of cobalt nitrate, nickel sulfate and manganese chloride as a metal salt precursor, selecting a molecular sieve as a carrier raw material, and preparing a precursor; deionized water, ammonia water and citric acid are selected as auxiliary raw materials; s2, active component loading: weighing a metal salt precursor according to a preset proportion, adding the metal salt precursor into deionized water, and stirring under a constant-temperature water bath condition of 40-60 DEG C until the metal salt precursor is completely dissolved to form a precursor solution; according to the method for directionally regulating and controlling the composite catalyst in the lithium battery pyrolysis process, the transition metal oxide-molecular sieve composite catalyst is designed, and a catalytic regulation node is moved forwards to a lithium battery pyrolysis reaction stage, so that the limitation of tail end treatment of traditional pyrolysis tail gas is broken through; and the directional decomposition of the electrolyte and the binder and the in-situ adsorption of the harmful gas are synergistically carried out.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, and in particular to a method for the directional control of composite catalysts during the pyrolysis process of lithium batteries. Background Technology

[0002] With the rapid development of the new energy vehicle and electronic equipment industries, the number of retired lithium batteries has exploded, making their environmental treatment and resource recycling an urgent industry challenge. Currently, pyrolysis technology is widely used in the treatment of retired lithium batteries because it can effectively decompose organic components and separate valuable metals. However, in the traditional anaerobic pyrolysis process of lithium batteries, the decomposition efficiency of the electrolyte and binder is low, leading to complex pyrolysis products and the generation of large amounts of harmful gases. Among these, volatile organic compounds (VOCs) cause air pollution, and hydrogen fluoride (HF) gas is highly corrosive, damaging equipment and posing a serious threat to the ecological environment and human health.

[0003] In existing technologies, the treatment approaches for lithium battery pyrolysis are mostly focused on "passive resource utilization" or "end-of-pipe treatment of pyrolysis exhaust gas." Passive resource utilization lacks targeted control over the pyrolysis reaction, making it difficult to improve the conversion efficiency of organic components. End-of-pipe treatment requires significant additional investment in equipment and costs, and its effectiveness is limited, failing to reduce the generation of harmful gases at the source. Furthermore, the catalysts in traditional pyrolysis processes have limited functions, either only possessing catalytic decomposition capabilities or simple adsorption, making it difficult to simultaneously address the dual requirements of targeted conversion of organic components and in-situ removal of harmful gases. This hinders the industrial-scale promotion and upgrading of lithium battery pyrolysis technology.

[0004] Therefore, it is necessary to propose a method for the directional regulation of composite catalysts in the lithium battery pyrolysis process to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a method for the directional control of composite catalysts during the pyrolysis process of lithium batteries, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for directional control of composite catalysts during lithium battery pyrolysis, comprising the following steps:

[0007] S1. Raw material selection: One or more of cobalt nitrate, nickel sulfate, and manganese chloride are selected as metal salt precursors, molecular sieves are selected as carrier raw materials, and deionized water, ammonia water, and citric acid are selected as auxiliary raw materials.

[0008] S2. Active component loading: Weigh the metal salt precursor according to the preset ratio and add it to deionized water. Stir until completely dissolved under constant temperature water bath conditions of 40-60℃ to form a precursor solution. Then, calcine the molecular sieve and add it to the precursor solution after cooling to room temperature. At the same time, add 0.5%-1.0% of citric acid complexing agent according to the mass of the precursor solution. Stir at room temperature for 12-24 hours. During this period, add ammonia water dropwise to adjust the pH value of the solution to 6.0-8.0 to form an impregnation mixture.

[0009] S3. Drying and calcination: The impregnation mixture is placed in a vacuum drying oven and dried at a temperature of 80-100℃ and a vacuum degree of 0.05-0.08MPa for 8-12 hours to obtain a dried catalyst precursor; then the catalyst precursor is calcined at a constant temperature for 3-5 hours to obtain a transition metal oxide-molecular sieve composite catalyst.

[0010] S4. Lithium battery pretreatment: Discharge, crush and remove impurities from retired lithium-ion batteries to obtain lithium battery crushed material.

[0011] S5. Pyrolysis system construction and material loading: The composite catalyst is laid in the reaction tube of the horizontal tubular furnace to form a catalyst bed; then the crushed lithium battery material is evenly spread on the catalyst bed and the air in the reaction tube is discharged.

[0012] S6. Pyrolysis reaction and directional control: The catalyst bed and lithium battery crushed material are pyrolyzed at a constant temperature in the reaction tube, and gaseous products are collected during the pyrolysis process. The VOCs and HF contents of the gaseous products are tested regularly.

[0013] S7. Post-reaction treatment: After the pyrolysis is completed and the reaction tube is cooled to room temperature, the pyrolysis residue and catalyst bed are removed. Valuable metals are extracted from the pyrolysis residue using an acid dissolution-extraction process, and the catalyst bed is analyzed and regenerated.

[0014] Preferably, in step S1, the specific surface area of ​​the molecular sieve is maintained at 300-500 m². 2 / g, with a pore size range of 0.5-1.0nm, and all auxiliary materials are of analytical purity.

[0015] Preferably, in step S2, the preset ratio is 5%-15% by mass of transition metal elements in the metal salt precursor to molecular sieves;

[0016] The molecular sieve calcination temperature is 500-600℃, and the calcination time is 2-3 hours.

[0017] Preferably, in step S3, when the catalyst precursor is calcined, it is heated to 400-550°C at a heating rate of 5-10°C / min, and then subjected to constant-temperature calcination.

[0018] Preferably, in step S4, the discharged lithium-ion battery is immersed in a 5% sodium chloride solution for 24 hours, then crushed into particles with a diameter of 5-10 mm, and the iron shell is removed by magnetic separation and impurities with excessive particle size are removed by sieving.

[0019] Preferably, in step S5, the thickness of the catalyst bed is 1-2 cm, and the amount of composite catalyst used is 5%-10% of the mass of the lithium battery crushed material.

[0020] Preferably, in step S5, the air in the reaction tube is discharged by introducing nitrogen gas with a purity of ≥99.99% into the reaction tube, with the nitrogen flow rate controlled at 50-100 mL / min and the aeration time being 30 minutes.

[0021] Preferably, in step S6, the isothermal pyrolysis temperature is 400-600℃, and the isothermal pyrolysis time is 2-4 hours.

[0022] Preferably, in step S7, the catalyst bed is analyzed for crystal structure by X-ray diffraction and catalytic activity by temperature-programmed reduction. If the activity retention rate is ≥80%, the catalyst is regenerated by calcining at 500°C for 2 hours.

[0023] Preferably, in step S7, the gaseous products collected during the pyrolysis reaction are also detected, including analyzing the volume fractions of CO2 and H2O in the collected gaseous products using gas chromatography, analyzing the content of HF using ion chromatography, and analyzing the types and concentrations of VOCs using gas chromatography-mass spectrometry.

[0024] The technical effects and advantages of this invention are as follows:

[0025] 1. This invention designs a transition metal oxide-molecular sieve composite catalyst, which moves the catalytic regulation node forward to the lithium battery pyrolysis reaction stage, breaking the limitations of traditional pyrolysis tail gas end treatment. It realizes the directional decomposition of electrolyte and binder and the in-situ adsorption of harmful gases in synergy, which greatly reduces the emission risk of harmful gases and improves the environmental friendliness of the pyrolysis process.

[0026] 2. Through precise selection of metal salt precursors and molecular sieves and optimized control of the preparation process, the composite catalyst obtained by this invention has stable dual-function characteristics. It can efficiently catalyze the conversion of target substances into harmless products and specifically capture harmful components generated by pyrolysis, which significantly improves the controllability and efficiency of lithium battery pyrolysis reaction.

[0027] 3. This invention achieves efficient resource recycling by recovering valuable metals from pyrolysis residue and regenerating and recycling the catalyst, thus constructing a resource-efficient recycling treatment mode, effectively reducing process costs, and balancing environmental and economic benefits. Attached Figure Description

[0028] Figure 1 This is a flowchart of the method for directional control of composite catalysts during the lithium battery pyrolysis process of the present invention. Detailed Implementation

[0029] This invention provides, for example Figure 1 This invention discloses a method for the targeted regulation of composite catalysts during lithium battery pyrolysis, designed to address the problems of low electrolyte and binder decomposition efficiency and high levels of harmful gases (VOCs, HF) during anaerobic pyrolysis of lithium batteries. Unlike conventional approaches such as "passive resource utilization of waste lithium battery materials" and "end-of-pipe treatment of pyrolysis tail gas," this method designs a "transition metal oxide-molecular sieve" composite catalyst. By precisely selecting high-purity metal salt precursors and molecular sieves with specific parameters, and preparing a composite catalyst with dual functions of "targeted catalysis + in-situ adsorption" through equal-volume impregnation, drying, and calcination, a pyrolysis system is constructed using this catalyst and pretreated retired lithium batteries. Under anaerobic conditions, temperature and reaction time are controlled to allow the catalyst to participate in the pyrolysis reaction stage, simultaneously achieving the targeted decomposition of electrolyte and binder into CO2 and H2O, and in-situ adsorption of harmful gases. Furthermore, the residue after pyrolysis can recover valuable metals, and the catalyst can be recycled, ultimately achieving a balance between efficient regulation of lithium battery pyrolysis and environmentally friendly resource utilization. The specific operation steps are as follows:

[0030] (I) Raw material selection

[0031] Transition metal oxide active component raw materials: at least one metal salt selected from cobalt, nickel, and manganese is selected as the precursor of transition metal oxide (hereinafter referred to as "metal salt precursor"). Specifically, cobalt nitrate, nickel sulfate, manganese chloride, etc. can be selected, and the purity of the selected metal salt precursor is not less than 99.0%.

[0032] Using high-purity metal salt precursors can avoid impurities interfering with subsequent catalytic reactions, ensuring that the final transition metal oxide can effectively catalyze the directional decomposition of lithium battery electrolyte and binder into CO2 and H2O.

[0033] Molecular sieve support material: Select zeolite molecular sieves with regular pore structure, such as ZSM-5 or Beta type, with a specific surface area controlled between 300-500 m². 2 / g, with a pore size range of 0.5-1.0nm.

[0034] Sufficient specific surface area and suitable pore size can provide a large number of sites for subsequent adsorption, ensuring efficient capture of HF and small molecule VOCs generated during pyrolysis.

[0035] Auxiliary materials: Deionized water is prepared as a dissolving solvent, ammonia is prepared as a pH adjuster, and citric acid is prepared as a complexing agent. All three auxiliary materials must reach analytical grade.

[0036] (II) Loading of active components

[0037] Precursor solution preparation: Based on the "mass of transition metal elements in the metal salt precursor" and the "mass of molecular sieve", weigh the corresponding mass of metal salt precursor according to the mass ratio of transition metal elements to molecular sieve of 5%-15%; add the weighed metal salt precursor to deionized water, place it in a constant temperature water bath at 40-60℃ and stir for 30-60 minutes until the metal salt precursor is completely dissolved and a homogeneous precursor solution is formed.

[0038] Molecular sieve pretreatment: The selected molecular sieve is placed in a muffle furnace and calcined at a temperature of 500-600℃ for 2-3 hours to remove the moisture and impurities adsorbed on the surface of the molecular sieve. After calcination, the molecular sieve is cooled to room temperature for later use.

[0039] Impregnation loading: The pretreated molecular sieve is slowly added to the prepared precursor solution, and an appropriate amount of citric acid complexing agent is added at the same time; the mixture is stirred continuously at room temperature for 12-24 hours. During the stirring process, the pH value of the solution is adjusted by adding ammonia dropwise to stabilize the pH value at 6.0-8.0; during this process, the transition metal ions dissociated from the metal salt precursor gradually combine with the molecular sieve to eventually form an impregnation mixture.

[0040] (III) Drying and Calcination Curing

[0041] Drying treatment: The impregnation mixture is placed in a vacuum drying oven and dried at a temperature of 80-100℃ and a vacuum degree of 0.05-0.08MPa for 8-12 hours to remove moisture and obtain a dried catalyst precursor.

[0042] Calcination and activation: The dried catalyst precursor is transferred to a muffle furnace and heated to 400-550℃ at a rate of 5-10℃ / min, and then calcined at this temperature for 3-5 hours. During the calcination process, two key reactions occur simultaneously: firstly, the components in the dried catalyst precursor originally derived from the metal salt decompose and transform, ultimately forming catalytically active transition metal oxides; secondly, the generated transition metal oxides tightly bind with the molecular sieve support, forming a structurally stable whole, ultimately yielding the desired transition metal oxide-molecular sieve composite catalyst.

[0043] II. Lithium-ion battery pyrolysis and catalyst-directed regulation operation

[0044] (I) Lithium-ion battery pretreatment

[0045] Thorough discharge treatment: Select retired lithium-ion batteries, such as ternary lithium batteries and lithium iron phosphate batteries, and immerse them in a 5% sodium chloride solution for 24 hours to ensure that the batteries are completely depleted and to avoid safety accidents caused by residual charge during the subsequent crushing process.

[0046] Crushing and impurity removal: The discharged battery is mechanically crushed to particles with a diameter of 5-10mm. Then, the iron shell is removed by magnetic separation and impurities with excessive particle size are removed by sieving to obtain lithium battery crushed material. This crushed material mainly contains electrode materials, electrolyte and binder.

[0047] (II) Construction of the pyrolysis system and material loading

[0048] Reactor and Catalyst Bed Preparation: A horizontal tubular furnace was selected as the pyrolysis reactor. This furnace is equipped with a heating system, a temperature control system (error ±1℃), an atmosphere control system (adjustable inert gas flow rate), and a tail gas collection system. A composite catalyst was uniformly laid inside the reaction tube of the horizontal tubular furnace to form a composite catalyst bed with a thickness of 1-2 cm. The amount of composite catalyst used was 5%-10% of the mass of the lithium battery crushed material.

[0049] Filling and atmosphere replacement of lithium battery crushed material: The pretreated lithium battery crushed material is evenly spread on the top of the composite catalyst bed. After sealing the reaction tube, nitrogen gas with a purity of ≥99.99% is introduced into the reaction tube as a protective gas through the atmosphere control system. The nitrogen flow rate is controlled at 50-100mL / min and the gas is continuously introduced for 30 minutes to remove the air in the reaction tube.

[0050] (III) Pyrolysis Reaction and Directional Control

[0051] Temperature program control and reaction heat preservation: Start the temperature control system of the tube furnace and heat the reaction system to 400-600℃ at a heating rate of 10-20℃ / min. Maintain constant temperature pyrolysis at this temperature for 2-4 hours. The constant temperature time can be adjusted according to the amount and composition of the lithium battery crushed material.

[0052] Synergistic effect of dual-function catalysts: During pyrolysis, the active sites on the transition metal oxide surface of the composite catalyst (such as Co) 3+ Ni 2+ The composite catalyst adsorbs carbonate organic molecules in the electrolyte, promoting their directional decomposition into CO2 and H2O. At the same time, the regular pore structure of the molecular sieve in the composite catalyst physically and chemically adsorbs HF generated by pyrolysis (generated by the decomposition of LiPF6 in the electrolyte) and incompletely decomposed small molecule VOCs.

[0053] Process monitoring and gas collection: During pyrolysis, the reaction temperature is monitored in real time through a temperature control system, and gaseous products are continuously collected through a tail gas collection system. Products are collected using gas bags or online gas analyzers, and VOCs content is detected periodically using gas chromatography-mass spectrometry and HF content is detected by ion chromatography.

[0054] (iv) Post-reaction treatment

[0055] System cooling and material removal: After the pyrolysis reaction is completed, the heating system of the pyrolysis reaction device is turned off, and nitrogen is continuously introduced to allow the reaction system to cool naturally to room temperature for 2-3 hours. Then, the pyrolysis residue and catalyst bed are removed in sequence. The pyrolysis residue mainly contains electrode active materials, such as LiCoO2 and LiFePO4.

[0056] Residue and catalyst recycling: Valuable metals such as lithium, cobalt and nickel are extracted from the pyrolysis residue using an acid dissolution-extraction process; the extracted catalyst bed is analyzed for its crystal structure by X-ray diffraction and its catalytic activity by programmed temperature reduction. If the activity retention rate is ≥80%, the catalyst is regenerated by calcining at 500℃ for 2 hours. After regeneration, it can be recycled.

[0057] Gas product analysis and effect verification: Gas chromatography was used to analyze the volume fraction of CO2 and H2O in the gas products, ion chromatography was used to analyze the HF content, and gas chromatography-mass spectrometry was used to analyze the types and concentrations of VOCs to confirm the electrolyte decomposition efficiency and the removal effect of harmful gases.

[0058] By designing a transition metal oxide-molecular sieve composite catalyst, the catalytic regulation node is moved forward to the lithium battery pyrolysis reaction stage, breaking the limitations of traditional end-of-pipe treatment of pyrolysis tail gas. This enables the synergistic effect of directional decomposition of electrolyte and binder and in-situ adsorption of harmful gases, significantly reducing the emission risk of harmful gases and improving the environmental friendliness of the pyrolysis process.

[0059] By precisely selecting metal salt precursors and molecular sieves and optimizing the preparation process, the obtained composite catalyst possesses stable dual-functional properties. It can efficiently catalyze the conversion of target substances into harmless products and specifically capture harmful components generated by pyrolysis, significantly improving the controllability and efficiency of lithium battery pyrolysis reactions.

[0060] By recovering valuable metals from pyrolysis residue and simultaneously regenerating and recycling the catalyst, a resource-efficient recycling treatment model has been constructed, effectively reducing process costs and balancing environmental and economic benefits, thus providing a superior technical solution for lithium battery pyrolysis treatment.

[0061] In addition, the method for directional control of composite catalysts during lithium battery pyrolysis includes the following embodiments:

[0062] Example 1

[0063] I. Preparation of Composite Catalysts

[0064] Raw material selection: Cobalt nitrate was selected as the metal salt precursor, with a purity of 99.0%; ZSM-5 type zeolite molecular sieve with a specific surface area of ​​300 m² was used. 2 / g, pore size 0.5nm.

[0065] Active component loading: Cobalt nitrate was weighed at a mass ratio of 5% of the transition metal element in the metal salt precursor to the molecular sieve, added to deionized water, and stirred in a constant temperature water bath at 40℃ for 30 minutes until completely dissolved to form a precursor solution. The molecular sieve was placed in a muffle furnace and calcined at 500℃ for 2 hours, then cooled to room temperature for later use. The pretreated molecular sieve was slowly added to the precursor solution, along with citric acid complexing agent at a mass of 0.5% of the precursor solution. The mixture was stirred at room temperature for 12 hours, during which ammonia was added dropwise to adjust the pH of the solution to 6.0, forming an impregnation mixture.

[0066] Drying and calcination: The impregnation mixture was placed in a vacuum drying oven and dried at 80℃ and 0.05MPa for 8 hours to obtain a dried catalyst precursor. The precursor was then transferred to a muffle furnace and heated to 400℃ at a rate of 5℃ / min, and calcined at a constant temperature for 3 hours to obtain a transition metal oxide-molecular sieve composite catalyst.

[0067] II. Lithium-ion Battery Pyrolysis and Regulation Operation

[0068] Lithium battery pretreatment: Select retired ternary lithium batteries, soak them in a 5% sodium chloride solution for 24 hours until they are completely de-energized, mechanically crush them to a particle size of 5mm, remove iron by magnetic separation and remove impurities by sieving to obtain lithium battery crushed material.

[0069] Pyrolysis system setup: A horizontal tubular furnace was selected as the pyrolysis device. A composite catalyst was uniformly laid inside the reaction tube of the horizontal tubular furnace to form a catalyst bed with a thickness of 1 cm. The amount of catalyst used was 5% of the mass of the lithium battery crushed material. The lithium battery crushed material was spread on top of the catalyst bed. After sealing the reaction tube, nitrogen gas with a purity ≥99.99% was introduced at a flow rate of 50 mL / min for 30 minutes, after which the air was discharged.

[0070] The pyrolysis reaction was carried out by heating the temperature to 400℃ at a rate of 10℃ / min, maintaining the temperature for 2 hours, and collecting the gaseous products. The VOCs content was detected periodically using gas chromatography-mass spectrometry and the HF content was detected using ion chromatography.

[0071] Post-reaction processing and detection: After the reaction is completed, stop heating, keep nitrogen gas flowing through until the system cools to room temperature, and remove the pyrolysis residue and catalyst bed.

[0072] Lithium, cobalt, and nickel were extracted from the pyrolysis residue using an acid-dissolution-extraction process. 2 mol / L hydrochloric acid was used as the acid dissolution reagent. The pyrolysis residue and hydrochloric acid were mixed at a liquid-to-solid ratio of 10:1 (mL / g), and leaching was carried out with stirring at 80℃ for 2 hours. Subsequently, P204 extractant was added, and the volume ratio of the organic phase to the aqueous phase was controlled at 1:2. Extraction was carried out with stirring at room temperature for 30 minutes. After back-extraction, concentration, and crystallization, the recovery rates of lithium, cobalt, and nickel reached 91%, 93%, and 92%, respectively.

[0073] X-ray diffraction analysis of the catalyst bed crystal structure and temperature-programmed reduction analysis of catalytic activity showed no significant distortion of the catalyst crystal structure and a catalytic activity retention rate of 82%. Regeneration was performed by calcination at 500℃ for 2 hours, after which the catalytic activity recovered to over 95% of that of fresh catalyst, allowing for recycling. Gas chromatography analysis of the CO2 and H2O volume fractions in the gaseous products showed a CO2 volume fraction of 18% and an H2O volume fraction of 12%, while ion chromatography detected a reduction in HF content to 5 mg / m³. 3 The following data shows that the total concentration of VOCs detected by gas chromatography-mass spectrometry has decreased to 10 mg / m³. 3 the following.

[0074] Example 2

[0075] I. Preparation of Composite Catalysts

[0076] Raw material selection: Nickel sulfate with a purity of 99.5% was selected as the metal salt precursor; Beta-type zeolite molecular sieves with a specific surface area of ​​400 m² were used. 2 / g, pore size 0.7nm; auxiliary raw materials deionized water, ammonia water and citric acid are all analytical grade.

[0077] Active component loading: Nickel sulfate was weighed at a mass ratio of 10% of the transition metal element in the metal salt precursor to the molecular sieve, added to deionized water, and stirred in a constant temperature water bath at 50℃ for 45 minutes until completely dissolved to form a precursor solution. The molecular sieve was placed in a muffle furnace and calcined at 550℃ for 2.5 hours, then cooled to room temperature for later use. The pretreated molecular sieve was slowly added to the precursor solution, along with citric acid complexing agent at a mass of 0.8% of the precursor solution mass. The mixture was stirred at room temperature for 18 hours, during which ammonia was added dropwise to adjust the pH of the solution to 7.0, forming an impregnation mixture.

[0078] Drying and calcination: The impregnation mixture was placed in a vacuum drying oven and dried at 90℃ and 0.06MPa for 10 hours to obtain a dried catalyst precursor. The precursor was then transferred to a muffle furnace and heated to 475℃ at a rate of 7℃ / min, and calcined at this temperature for 4 hours to obtain a transition metal oxide-molecular sieve composite catalyst.

[0079] II. Lithium-ion Battery Pyrolysis and Regulation Operation

[0080] Lithium battery pretreatment: Select retired lithium iron phosphate batteries, soak them in a 5% sodium chloride solution for 24 hours until they are completely de-energized, mechanically crush them to a particle size of 8mm, remove iron by magnetic separation and remove impurities by sieving to obtain lithium battery crushed material.

[0081] Pyrolysis system setup: A horizontal tubular furnace was selected as the pyrolysis device. A composite catalyst was uniformly laid inside the reaction tube of the horizontal tubular furnace to form a catalyst bed with a thickness of 1.5 cm. The amount of catalyst used was 7.5% of the mass of the lithium battery crushed material. The lithium battery crushed material was spread on top of the catalyst bed. After sealing the reaction tube, nitrogen gas with a purity ≥99.99% was introduced at a flow rate of 75 mL / min for 30 minutes, after which the air was discharged.

[0082] The pyrolysis reaction was carried out by heating the temperature to 500℃ at a rate of 15℃ / min, maintaining the temperature for 3 hours, and collecting the gaseous products. The VOCs content was detected periodically using gas chromatography-mass spectrometry and the HF content was detected using ion chromatography.

[0083] Post-reaction processing and detection: After the reaction is completed, stop heating, keep nitrogen gas flowing through until the system cools to room temperature, and remove the pyrolysis residue and catalyst bed.

[0084] Lithium and iron were extracted from the pyrolysis residue using an acid-dissolution-extraction process. 3 mol / L sulfuric acid was used as the acid dissolution reagent, and the liquid-to-solid ratio of the pyrolysis residue to sulfuric acid was controlled at 8:1 (mL / g). Leaching was carried out at 90℃ with stirring for 1.5 hours. P507 extractant was selected, and the organic and aqueous phases were mixed at a volume ratio of 1:1.5. Extraction was carried out at room temperature with stirring for 40 minutes. After subsequent back-extraction and purification, the recovery rate of lithium reached 94%, and the recovery rate of iron reached 95%.

[0085] Structural and activity analyses of the catalyst bed were performed. X-ray diffraction patterns showed that the crystal structure remained intact. Temperature-programmed reduction tests indicated a catalytic activity retention rate of 85%. After regeneration at 500℃ for 2 hours, the catalytic activity recovered to over 96% of that of fresh catalyst, making it recyclable. Gas chromatography analysis of the volume fractions of CO2 and H2O in the gaseous products showed that the CO2 volume fraction reached 22% and the H2O volume fraction reached 15%. Ion chromatography detected a decrease in HF content to 3 mg / m³. 3 The following data shows that the total concentration of VOCs detected by gas chromatography-mass spectrometry has decreased to 8 mg / m³. 3 the following.

[0086] Example 3

[0087] I. Preparation of Composite Catalysts

[0088] Raw material selection: Manganese chloride was selected as the metal salt precursor, with a purity of 99.9%; ZSM-5 type zeolite molecular sieve with a specific surface area of ​​500 m² was used. 2 / g, pore size 1.0nm; auxiliary raw materials deionized water, ammonia water and citric acid are all analytical grade.

[0089] Active component loading: Manganese chloride was weighed at a mass ratio of 15% of the transition metal element in the metal salt precursor to the molecular sieve, added to deionized water, and stirred in a constant temperature water bath at 60℃ for 60 minutes until completely dissolved to form a precursor solution. The molecular sieve was placed in a muffle furnace and calcined at 600℃ for 3 hours, then cooled to room temperature for later use. The pretreated molecular sieve was slowly added to the precursor solution, along with citric acid complexing agent at a mass of 1.0% of the precursor solution. The mixture was stirred at room temperature for 24 hours, during which ammonia was added dropwise to adjust the pH of the solution to 8.0, forming an impregnation mixture.

[0090] Drying and calcination: The impregnation mixture was placed in a vacuum drying oven and dried at 100℃ and 0.08MPa for 12 hours to obtain a dried catalyst precursor. The precursor was then transferred to a muffle furnace and heated to 550℃ at a rate of 10℃ / min, and calcined at this temperature for 5 hours to obtain a transition metal oxide-molecular sieve composite catalyst.

[0091] II. Lithium-ion Battery Pyrolysis and Regulation Operation

[0092] Lithium battery pretreatment: Select retired ternary lithium batteries, soak them in a 5% sodium chloride solution for 24 hours until they are completely de-energized, mechanically crush them to a particle size of 10mm, remove iron by magnetic separation and remove impurities by sieving to obtain lithium battery crushed material.

[0093] Pyrolysis system setup: A horizontal tubular furnace was selected as the pyrolysis device. A composite catalyst was uniformly laid inside the reaction tube of the horizontal tubular furnace to form a catalyst bed with a thickness of 2 cm. The amount of catalyst used was 10% of the mass of the lithium battery crushed material. The lithium battery crushed material was spread on top of the catalyst bed. After sealing the reaction tube, nitrogen gas with a purity ≥99.99% was introduced at a flow rate of 100 mL / min for 30 minutes, after which the air was discharged.

[0094] The pyrolysis reaction was carried out by heating the temperature to 600℃ at a rate of 20℃ / min, maintaining the temperature for 4 hours, and collecting the gaseous products. The VOCs content was detected periodically using gas chromatography-mass spectrometry and the HF content was detected using ion chromatography.

[0095] Post-reaction processing and detection: After the reaction is completed, stop heating, keep nitrogen gas flowing through until the system cools to room temperature, and remove the pyrolysis residue and catalyst bed.

[0096] Valuable metals such as lithium, cobalt, nickel, and manganese were extracted from the pyrolysis residue using an acid-dissolution-extraction process. A 2.5 mol / L mixed acid (hydrochloric acid and sulfuric acid, volume ratio 1:1) was used as the acid dissolution reagent, with a liquid-to-solid ratio of 9:1 (mL / g) between the pyrolysis residue and the mixed acid. The leaching was carried out with stirring at 85℃ for 1.8 hours. A composite extractant of P204 and P507 (volume ratio 2:1) was used, with the organic phase and aqueous phase volume ratio controlled at 1:1.8. The extraction was carried out with stirring at room temperature for 35 minutes. The lithium, cobalt, nickel, and manganese were separated stepwise. After back-extraction and crystallization purification, the recovery rates of lithium, cobalt, nickel, and manganese reached 93%, 95%, 94%, and 92%, respectively.

[0097] Analysis of the catalyst bed showed that its crystal structure was stable and the catalytic activity retention rate was 88%. After calcination and regeneration at 500℃ for 2 hours, the catalytic activity recovered to more than 97% of that of the fresh catalyst, and it can still be used in lithium battery pyrolysis reactions. Gas chromatography analysis of the volume fractions of CO2 and H2O in the gaseous products showed that the CO2 volume fraction reached 25% and the H2O volume fraction reached 18%, while ion chromatography detected that the HF content decreased to 2 mg / m³. 3 The following data shows that the total concentration of VOCs detected by gas chromatography-mass spectrometry has decreased to 5 mg / m³. 3 the following.

Claims

1. A method for the directional control of composite catalysts during lithium battery pyrolysis, characterized in that: The following steps are included: S1. Raw material selection: One or more of cobalt nitrate, nickel sulfate, and manganese chloride are selected as metal salt precursors, molecular sieves are selected as carrier raw materials, and deionized water, ammonia water, and citric acid are selected as auxiliary raw materials. S2. Active component loading: Weigh the metal salt precursor according to the preset ratio and add it to deionized water. Stir until completely dissolved under constant temperature water bath conditions of 40-60℃ to form a precursor solution. Then, calcine the molecular sieve and add it to the precursor solution after cooling to room temperature. At the same time, add 0.5%-1.0% of citric acid complexing agent according to the mass of the precursor solution. Stir at room temperature for 12-24 hours. During this period, add ammonia water dropwise to adjust the pH value of the solution to 6.0-8.0 to form an impregnation mixture. S3. Drying and calcination: The impregnation mixture is placed in a vacuum drying oven and dried at a temperature of 80-100℃ and a vacuum degree of 0.05-0.08MPa for 8-12 hours to obtain a dried catalyst precursor; then the catalyst precursor is calcined at a constant temperature for 3-5 hours to obtain a transition metal oxide-molecular sieve composite catalyst. S4. Lithium battery pretreatment: Discharge, crush and remove impurities from retired lithium-ion batteries to obtain lithium battery crushed material. S5. Pyrolysis system construction and material loading: The composite catalyst is laid in the reaction tube of the horizontal tubular furnace to form a catalyst bed; then the crushed lithium battery material is evenly spread on the catalyst bed and the air in the reaction tube is discharged. S6. Pyrolysis reaction and directional control: The catalyst bed and lithium battery crushed material are pyrolyzed at a constant temperature in the reaction tube, and gaseous products are collected during the pyrolysis process. The VOCs and HF contents of the gaseous products are tested regularly. S7. Post-reaction treatment: After the pyrolysis is completed and the reaction tube is cooled to room temperature, the pyrolysis residue and catalyst bed are removed. Valuable metals are extracted from the pyrolysis residue using an acid dissolution-extraction process, and the catalyst bed is analyzed and regenerated.

2. The method for directional control of composite catalysts during lithium battery pyrolysis according to claim 1, characterized in that: In S1, the specific surface area of ​​the molecular sieve is maintained at 300-500 m². 2 / g, with a pore size range of 0.5-1.0nm, and all auxiliary materials are of analytical purity.

3. The method for directional control of composite catalysts during lithium battery pyrolysis according to claim 1, characterized in that: In S2, the preset ratio is 5%-15% of the mass ratio of the transition metal element in the metal salt precursor to the molecular sieve. The molecular sieve calcination temperature is 500-600℃, and the calcination time is 2-3 hours.

4. The method for directional control of composite catalysts during lithium battery pyrolysis according to claim 1, characterized in that: In S3, when the catalyst precursor is calcined, it is heated to 400-550℃ at a heating rate of 5-10℃ / min, and then subjected to isothermal calcination.

5. The method for directional control of composite catalysts during lithium battery pyrolysis according to claim 1, characterized in that: In S4, the discharge method of the retired lithium-ion battery is to soak it in a sodium chloride solution with a mass fraction of 5% for 24 hours, then crush it into particles with a particle size of 5-10mm, and remove the iron shell through magnetic separation and remove impurities with excessive particle size through sieving.

6. The method for directional control of composite catalysts during lithium battery pyrolysis according to claim 1, characterized in that: In step S5, the thickness of the catalyst bed is 1-2 cm, and the amount of composite catalyst used is 5%-10% of the mass of the lithium battery crushed material.

7. The method for directional control of composite catalysts during lithium battery pyrolysis according to claim 1, characterized in that: In step S5, the air inside the reaction tube is vented by introducing nitrogen gas with a purity of ≥99.99% into the reaction tube. The nitrogen gas flow rate is controlled at 50-100 mL / min, and the venting time is 30 minutes.

8. The method for directional control of composite catalysts during lithium battery pyrolysis according to claim 1, characterized in that: In step S6, the isothermal pyrolysis temperature is 400-600℃, and the isothermal pyrolysis time is 2-4 hours.

9. The method for directional control of composite catalysts during lithium battery pyrolysis according to claim 1, characterized in that: In step S7, the catalyst bed is analyzed for crystal structure by X-ray diffraction and catalytic activity by temperature-programmed reduction. If the activity retention rate is ≥80%, the catalyst is regenerated by calcining at 500°C for 2 hours.

10. The method for directional control of composite catalysts during lithium battery pyrolysis according to claim 1, characterized in that: In step S7, the gaseous products collected during the pyrolysis reaction also need to be detected, including analyzing the volume fractions of CO2 and H2O in the collected gaseous products using gas chromatography, analyzing the content of HF using ion chromatography, and analyzing the types and concentrations of VOCs using gas chromatography-mass spectrometry.

Images