A method and application for preparing doped porous cobalt-based nanomaterials using spent lithium cobalt oxide batteries

Abstract

This invention discloses a method and application for preparing doped-porous cobalt-based nanomaterials using spent lithium cobalt oxide batteries. The method is characterized by disassembling spent lithium cobalt oxide batteries, obtaining nano-precursor nanomaterials from the positive electrode sheets through a pretreatment-segmented stripping process, and then selectively recovering lithium to prepare doped-porous cobalt-based materials for catalytic oxidation of volatile organic compounds (VOCs) and mercury (HgO). This invention can selectively recover lithium while simultaneously preparing a low-cost doped-porous cobalt-based catalyst. The prepared material exhibits a porous rod-like structure and, as a catalyst, possesses high catalytic oxidation activity, high resistance, a wide active temperature range, and high selectivity. It can be used in fields such as simultaneous catalytic oxidation of VOCs and control of atmospheric pollutants such as mercury (HgO), and can also serve as a raw material for the synthesis of lithium cobalt oxide batteries.

Description

Technical Field

[0001] This invention belongs to the interdisciplinary field of solid waste treatment and resource utilization and environmental catalysis technology, specifically involving a method for preparing a doped-porous-cobalt-based nanomaterial / catalyst and its application in solid waste treatment and atmospheric environmental pollution control. Background Technology

[0002] As a high-performance energy storage source, lithium-ion batteries are widely used in portable electronic devices, electric vehicles, and renewable energy systems, with a projected capacity exceeding 3200 GWh by 2030. However, batteries inevitably face obsolescence after a few years of use. If not properly disposed of, discarded batteries will cause enormous resource waste and serious solid waste pollution.

[0003] Complex failure mechanisms in spent batteries, including changes in physical parameters, structural damage, interfacial phase transitions, and lithium loss, hinder the regeneration of lithium-ion battery electrode materials. The resource utilization of spent batteries, particularly their use as catalysts, is a forward-looking approach. Furthermore, in traditional processes, the plastics, metals, and their oxides mixed in the cathode material after battery crushing severely affect the quality of the recycled materials, making subsequent resource utilization difficult and increasing the complexity of subsequent processing. Therefore, appropriate pretreatment processes are crucial.

[0004] Mercury in flue gas, including HgO and volatile organic compounds (VOCs), poses a significant challenge to achieving carbon reduction and pollution control. Mercury exists in three forms: particulate mercury (HgO) and particulate mercury (VOCs). p ), mercury oxide (Hg) 2+ ) and elemental mercury (HgO). Hg p and Hg 2+ HgO can be captured by electrostatic precipitators or bag filters and absorbed in wet desulfurization processes. However, HgO is chemically stable and has poor solubility in water, making it difficult for existing flue gas purification devices to eliminate. Catalytic oxidation technology is a recognized method for converting HgO into soluble Hg. 2+ Catalytic oxidation is one of the effective methods for eliminating HgO. Simultaneously, catalytic oxidation is also a major process for removing volatile organic compounds (VOCs). Removing both HgO and VOCs simultaneously through catalytic oxidation in flue gas is a technically and economically sound choice in the field of atmospheric pollution control. The key to catalytic removal is the preparation of inexpensive, readily available, highly active, highly stable, and resistant catalysts.

[0005] In view of this, this invention proposes a classified recycling and "waste-to-treasure" strategy. High-value lithium and transition metals from waste lithium cobalt oxide battery cathode materials are classified, recycled, and recrystallized to form a main phase of porous rod-shaped cobalt tetroxide nanoparticles. During the high-temperature synthesis reaction, some lithium is sublimated. After pretreatment and lithium extraction, defects and oxygen vacancies are formed. The residual lithium has a doping effect in the cobalt tetroxide crystal lattice, increasing the material's specific surface area. The primary particles change from micrometer-scale to nanometer-scale, enhancing adsorption capacity and exhibiting high simultaneous catalytic oxidation activity for VOCs and HgO. In flue gas, it exhibits high catalytic activity, high resistance, a wide active temperature range, and high catalytic selectivity, demonstrating strong resistance to nitrogen oxides, sulfur, ammonia, and water. Simultaneously, due to the recrystallization of the nanomaterials, the lattice damage and defects of the original waste battery materials are repaired, making them suitable as high-performance raw materials for battery synthesis.

[0006] This invention provides new ideas and directions for the preparation of composite monolithic catalysts in solid waste treatment and air pollution control. Summary of the Invention

[0007] The purpose of this invention is to classify and recycle high-value lithium from waste lithium cobalt oxide battery cathode materials to prepare powdered / monolithic catalysts. These catalysts can efficiently catalyze the oxidation of VOCs and HgO, providing a simple preparation method and application of catalysts for solid waste treatment and atmospheric pollution control.

[0008] The objective of this invention is achieved through the following technical solution:

[0009] A method for preparing doped-porous cobalt-based nanomaterials using spent lithium cobalt oxide batteries is disclosed. The pretreatment process is environmentally friendly, simple, and low-cost. The cathode powder can be quickly and cleanly removed while the current collector remains intact. The resulting cathode material has high purity with extremely low levels of impurities such as PVDF and aluminum. The nanomaterial recrystallizes during a hydrothermal reaction and high-temperature phase transition to form lithium and aluminum-doped porous rod-shaped cobalt tetroxide nanoparticles, wherein the molar ratio of Co to Li is Co / Li = (10-100). After pretreatment and lithium extraction, defects and oxygen vacancies are formed. The residual metal has a doping effect in the cobalt tetroxide crystal lattice, which increases the specific surface area and oxygen vacancies of the material. The primary particles change from micron-sized to nano-sized, enhancing the adsorption capacity and exhibiting high catalytic oxidation activity and resistance to VOCs and mercury (HgO). The resistance includes resistance to nitrogen oxides, sulfur, ammonia, and water. At the same time, due to the recrystallization of the nanomaterials, the lattice damage and defects of the original waste battery materials are repaired. After predoping, it can be used as a high-performance cobalt-based raw material for synthesizing lithium batteries.

[0010] The method of preparing doped porous cobalt-based nanomaterials using waste lithium cobalt oxide batteries is applied to the fields of solid waste recycling and resource utilization as well as air pollution control.

[0011] A method for preparing doped-porous-cobalt-based nanomaterials using waste lithium cobalt oxide batteries involves dismantling the waste lithium cobalt oxide batteries, obtaining nano-precursor from the positive electrode sheet through a pretreatment-segmented stripping process, and then obtaining a doped-porous-cobalt-based powder / monolithic catalyst for catalytic oxidation of VOCs and HgO in coal-fired flue gas through selective lithium recovery and pretreatment-hydrothermal reaction-high-temperature phase change. This material can also be used as a raw material for synthesizing new batteries.

[0012] A method for preparing doped-porous cobalt-based nanomaterials using waste lithium cobalt oxide batteries, the method comprising the following steps:

[0013] (1) Pretreatment and preparation of defective cobalt-lithium particles:

[0014] The waste lithium cobalt oxide batteries were soaked in salt water and then disassembled to separate the positive electrode material for later use. The positive electrode sheet was placed in a mixed acid-organic solvent and ultrasonically soaked at a constant temperature. After drying, it was placed in a tube furnace for segmental calcination, and then ground and sieved to obtain defective lithium cobalt particles for later use.

[0015] The atmosphere of the tubular furnace is nitrogen with an oxygen content of 10-80 vol% or argon with an oxygen content of 10-80 vol%. The mixed acid includes two or more of acetic acid, sulfuric acid, phytic acid, tannic acid, oxalic acid and citric acid. The organic solvent includes one or more of toluene, xylene, benzyl nitrile, methanol, ethanol, chloroform, tetrahydrofuran and N,N-dimethylformamide.

[0016] (2) Lithium recovery and doping - preparation of porous cobalt-based materials:

[0017] The powder particles, additives, mixed acid, and deionized water prepared in step (1) are thoroughly mixed and placed in a rotary evaporator at a constant temperature with thorough stirring to dissolve them; after standing, the upper liquid is poured off, and sodium carbonate is added to recover the upper Li-containing solution; after recovering Li, the lower slurry is washed, filtered, centrifuged, dried, ground, subjected to hydrothermal reaction, and calcined in stages to obtain doped-porous-cobalt-based nanomaterials / powder catalysts; the mixed acid includes two or more of acetic acid, sulfuric acid, phytic acid, tannic acid, oxalic acid, and citric acid; the additives include glucose, fructose, and hydrogen peroxide;

[0018] (3) Preparation of doped-porous-cobalt-based monolithic catalysts:

[0019] The copper foam was soaked in a mixed acid for 3-5 hours, then washed with distilled water until the pH of the washing solution was neutral. It was then dried at 120-150℃ for 4-8 hours and transferred to a muffle furnace for calcination at 250-550℃ for 4-10 hours to remove various adsorbed impurities. The composite powder catalyst prepared in step (2) was ball-milled, and then ammonia and KOH were added and mixed. The pH was adjusted to 8-12 and the mixture was stirred at a constant temperature to dissolve it. The mixture was then directly impregnated or at least one of silica sol, boehmite, and hydroxycellulose was added. The pH was adjusted and the mixture was stirred to form a stable slurry. The copper foam was impregnated in the slurry and ultrasonically loaded. The residual suspension was then purged to form a uniform film on the substrate surface. The mixture was dried and the impregnation process was repeated until the appropriate loading was achieved. Finally, the mixture was calcined in stages with nitrogen as the balancing gas and an oxygen content of 5-80 vol% to obtain a doped-porous-cobalt-based monolithic catalyst with oxygen vacancies.

[0020] In the above method, in step (1), the concentration of the mixed acid is 1-10 mol / L, the concentration of organic matter in the organic solvent is 0.5-10 mol / L, the solid-liquid ratio of the electrode to the solvent is 10-100 g / L, the constant temperature soaking temperature is 20-90℃, the soaking time is 2-10 h, the drying temperature is 110-160℃, and the drying time is 3-15 h; the specific method of the calcination is as follows: first, using high-purity nitrogen as the atmosphere, the temperature is raised from room temperature to 250-360℃ at a rate of 1-35℃ / min and kept constant for 100-340 min; then, using high-purity nitrogen with an oxygen content of 5-90 vol%, the temperature is raised to 350-950℃ at a rate of 2-30℃ / min and kept constant for 5-15 h; finally, the temperature is lowered to room temperature at a rate of 1-10℃ / min.

[0021] In the above method, step (2) specifically involves the following steps: The lower layer slurry after lithium recovery is dried, ground, and mixed with ammonia to obtain solution A. Urea and water are then mixed to obtain solution B. Solutions A and B are simultaneously stirred at room temperature for 30-90 minutes. CTAB or polyethylene glycol is then added. Next, KOH solution is added dropwise to the mixed solution, the pH is adjusted to 9-12, and after stirring at room temperature, the mixture is transferred to the inner liner of a polytetrafluoroethylene (PTFE) reactor. Finally, the PTFE reactor inner liner is placed into a high-pressure reactor. The hydrothermal reaction is carried out at 20-220℃ for 6-48 hours. After natural cooling, the precipitate is centrifuged, washed, vacuum dried, and ground for later use. The specific calcination method is as follows: first, using high-purity nitrogen as the atmosphere, the temperature is raised from room temperature to 250-320℃ at a rate of 1-30℃ / min and held for 120-240 minutes. Then, using high-purity nitrogen with an oxygen content of 10-80 vol%, the temperature is raised to 350-900℃ at a rate of 10-30℃ / min and held for 5-15 hours. Finally, the temperature is lowered to room temperature at a rate of 1-10℃ / min.

[0022] In the above method, in step (2), the concentration of the mixed acid is 20-800 g / L, the stirring speed of the rotary evaporator is 120-450 rpm, the temperature is 30-95℃, and the ultrasonic time is 2-8 h; the drying temperature is 105-180℃, and the drying time is 6-18 h.

[0023] In the above method, in step (3), the mixed acid includes one or more of hydrochloric acid, acetic acid, sulfuric acid, oxalic acid and citric acid, and the pH of the slurry is maintained at 0.5 to 6.

[0024] In the above method, in step (3), the mass ratio of silica sol, pseudoboehmite, hydroxycellulose to carrier is 0.1-5%, the ultrasonic-assisted impregnation time is 10-60 min, the final loading of active material is 1-50%, and the drying temperature is 100-210℃.

[0025] In the above method, the specific method of segmented calcination in step (3) is as follows: first, using high-purity nitrogen as the atmosphere, the temperature is raised from room temperature to 280-380℃ at a rate of 5-15℃ / min, and held at a constant temperature for 360-660min; then, using high-purity nitrogen with an oxygen content of 10-90 vol%, the temperature is raised to 350-850℃ at a rate of 5-25℃ / min, and held at a constant temperature for 6-24h; finally, the temperature is lowered to room temperature.

[0026] The nanomaterial / catalyst of this invention recrystallizes while retaining some lithium, forming a main phase of porous rod-shaped cobalt tetroxide nanoparticles. During the high-temperature synthesis reaction, some lithium is sublimated and precipitated. After pretreatment and lithium removal, defects and oxygen vacancies are formed. The residual lithium has a doping effect in the cobalt tetroxide crystal lattice, increasing the specific surface area of ​​the material, transforming the primary particles from micrometer-scale to nanometer-scale, enhancing adsorption capacity, and exhibiting high catalytic activity, high resistance, and low-temperature activity. The resistance includes resistance to nitrogen oxides, sulfur, ammonia, and water. Simultaneously, due to the recrystallization of the nanomaterial, the lattice damage and defects of the original waste battery materials are repaired, making it a high-performance raw material for battery synthesis. The material is used as a catalyst for the catalytic oxidation of volatile organic compounds and in lithium recovery processes, applicable to solid waste recycling and resource utilization, as well as air pollution control. This catalyst exhibits high catalytic activity, high water resistance, a wide active temperature range, and high selectivity.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] (1) In all recycling processes, separating the active material from the current collector is one of the most important steps. Only after effective separation can the active material and aluminum foil be recycled. The preparation method used in this application is simple and easy to implement, employing organic acids and a segmented pretreatment process. This results in less environmental pollution, a simple process, and low cost. The pretreated cathode material has high purity, extremely low content of impurities such as PVDF and aluminum, and maintains good structural integrity, promoting the subsequent preparation of catalysts and efficient repair and regeneration. It is particularly noteworthy that after traditional simple heating treatment, the cathode powder has high aluminum chloride content (above 1%), residual PVDF binder, and difficulty in separating the current collector. Grinding and complex processes are required for the powder to detach, resulting in fragmented current collectors and complex, costly post-processing. Using the segmented pretreatment process of this patent, the electrode sheet detaches easily without grinding. The separated current collector is clean and intact, with low aluminum content in the powder (below 0.3%). PVDF and other binders in the powder are completely removed. The process is simple and low-cost, and new lithium cobalt oxide battery materials can be rapidly synthesized subsequently, resulting in high commercial value.

[0029] (2) The material prepared in this application is a porous rod-shaped cobalt tetroxide material doped with metal lattices such as lithium, aluminum, and copper, which is completely different from the previously reported cobalt tetroxide. After lithium is extracted, defects and oxygen vacancies are formed, and the residual lithium, aluminum, copper, etc. have a doping effect in the cobalt tetroxide crystal lattice. The specific surface area of ​​the material increases, the primary particles change from micron to nanometer scale, and the adsorption capacity is enhanced, thus exhibiting high simultaneous catalytic oxidation activity of VOCs and HgO. At the same time, the unique pretreated material, the acid-treated material, and the cobalt tetroxide material doped with metal lattices such as lithium, aluminum, and copper can all be used as precursors for preparing high-capacity lithium cobalt oxide batteries, and can be used to prepare or repair high-performance lithium cobalt oxide batteries.

[0030] (3) This invention proposes a classification and recycling strategy and “turning waste into treasure” to classify and recycle high-value lithium and transition metals in waste lithium battery materials. Pre-treatment materials, intermediate products and catalysts can all be used as new lithium cobalt oxide synthesis materials. After classification and recycling, the commercial value is high. Attached Figure Description

[0031] Figure 1 This is the process for recovering the precursor cathode material of the catalyst of the present invention;

[0032] Figure 2 This is the XRD pattern of the catalyst of the present invention;

[0033] Figure 3 This is a SEM image of the pretreated precursor of the present invention;

[0034] Figure 4 This is a SEM image of the catalyst of the present invention;

[0035] Figure 5 This is the EPR diagram of the catalyst of the present invention;

[0036] Figure 6 This is the XRD pattern of lithium cobalt oxide synthesized according to the present invention.

[0037] Figure 7 This refers to the removal rate of propylene by the catalyst of this invention during catalytic oxidation;

[0038] Figure 8 The removal rate of propylene by the catalyst of this invention compared with other catalysts;

[0039] Figure 9 The removal rates of propylene by the catalyst of this invention and commercial catalysts are shown.

[0040] Figure 10 This is an evaluation diagram of the catalytic oxidation of a mixture of toluene and propylene using the catalyst of this invention.

[0041] Figure 11 The stability of the propylene removal rate catalytically oxidized by the catalyst of this invention.

[0042] Figure 12 The stability of the total hydrocarbon removal rate of the catalyst for catalytic oxidation of propylene in this invention.

[0043] Figure 13 The stability of the toluene removal rate catalytically oxidized by the catalyst of this invention.

[0044] Figure 14 The stability of the propylene removal rate catalytically oxidized by the catalyst of this invention.

[0045] Figure 15 The catalyst of this invention achieves the removal rate of total hydrocarbons from a mixture of toluene and propylene.

[0046] Figure 16 This refers to the Hg removal rate of the catalyst of this invention.

[0047] Figure 17 This invention relates to the water-resistant activity of the catalyst. Detailed Implementation

[0048] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto. For process parameters not specifically noted, conventional techniques can be referred to.

[0049] Example 1

[0050] Preparation of doped porous cobalt-based nanomaterials / powder catalysts

[0051] Discarded lithium cobalt oxide batteries were disassembled after being soaked in brine, and the positive electrode material was separated for later use. The positive electrode sheets were ultrasonically soaked in a mixture of oxalic acid and citric acid, and a mixture of toluene and tetrahydrofuran (1:1). The concentrations of oxalic acid and citric acid were 7 mol / L, the solid-liquid ratio was 80 g / L, the soaking temperatures were 50°C and 20°C, and the soaking times were 0.5 h and 2 h, respectively. The drying temperature was 125°C, and the drying time was 10 h. The batteries were then calcined in stages. Specifically, the temperature was first raised from room temperature to 310°C at a rate of 2°C / min under a high-purity nitrogen atmosphere and held for 210 min. Then, the temperature was raised to 580°C at a rate of 2.5°C / min under a high-purity nitrogen atmosphere with an oxygen content of 28 vol% and held for 15 h. Finally, the temperature was lowered to room temperature at a rate of 1.5°C / min, and the resulting powder particles were obtained by grinding.

[0052] Oxalic acid and citric acid were added to deionized water in a 4:1 ratio, resulting in a total concentration of 350 g / L. Cobalt-lithium powder particles were added, and the mixture was sonicated for 2.5 h. The mixture was then placed in a rotary evaporator and stirred at a constant temperature of 150 rpm at 75 °C. After standing, the upper liquid was poured off. Sodium carbonate was added to recover the Li-containing solution from the upper layer. The lower slurry was dried at 105 °C for 12 h, ground, and mixed with ammonia water to obtain solution A. Urea and water were mixed to obtain solution B. Solutions A and B were simultaneously stirred at room temperature for 60 min, and 0.11% CTAB was added. 3 mol / L KOH was added dropwise to the mixed solution to adjust the pH to 10. After stirring at room temperature, the mixture was transferred to a PTFE reactor liner and placed in a high-pressure reactor. The reaction was carried out hydrothermally at 150 °C for 15 h. After natural cooling, the precipitate was centrifuged, washed, vacuum dried at 120 °C, ground, and calcined. During calcination, the temperature was increased from room temperature to 275°C at a rate of 6°C / min and held for 180 min. Then, using high-purity nitrogen with an oxygen content of 30 vol%, the temperature was increased to 390°C at a rate of 6°C / min and held for 12 h. Finally, the temperature was decreased to room temperature at a rate of 3°C / min to obtain doped porous cobalt-based nanomaterial / powder catalyst-A (catalyst A of this patent).

[0053] The process of separating the current collector from the active powder is as follows: Figure 1 As shown, after simple heat treatment, the aluminum content of the electrode sheet is high (visible white spots, higher than 1%), and there is a large amount of residual PVDF and other binders. Figure 3 Previously, grinding was required to remove the electrode from the powder, resulting in fragmented electrodes after separation. However, using the method described in this application, the electrode detaches easily without grinding, leaving a clean and intact electrode with a low aluminum content (below 0.3%) and complete removal of the PVDF binder. Figure 3 The process is economical and has low cost.

[0054] X-ray diffraction pattern and SEM image of the prepared catalyst are shown below. Figure 2 and Figure 4 As shown, this demonstrates the successful preparation of Li-doped porous cobalt-based nanomaterials / powder catalysts. From... Figure 5 and Figure 8 As can be seen, compared with simple acid-treated catalysts B and C, the catalyst synthesized by hydrothermal reaction-high temperature phase change in this application greatly increases the oxygen vacancy concentration and enhances catalytic activity. The T90 temperature of catalytic oxidation can be increased by more than 113 degrees, which greatly improves catalytic activity and efficiency, and has extremely high commercial value.

[0055] Example 2

[0056] Preparation of cobalt-based catalysts by simple acid treatment:

[0057] Discarded lithium cobalt oxide batteries were disassembled after being soaked in brine, and the positive electrode material was separated for later use. The positive electrode sheets were soaked in oxalic acid and citric acid respectively, with an oxalic acid to citric acid ratio of 1:1 at 7 mol / L and a solid-liquid ratio of 80 g / L. The soaking temperatures were 50°C and 20°C, and the soaking times were 0.5 h and 2 h, respectively. The drying temperature was 125°C, and the drying time was 10 h. The batteries were then calcined in stages. The specific method was as follows: first, the temperature was raised from room temperature to 310°C at a rate of 2°C / min under a high-purity nitrogen atmosphere and held for 210 min; then, the temperature was raised to 650°C at a rate of 2.5°C / min under a high-purity nitrogen atmosphere with an oxygen content of 20 vol% and held for 15 h; finally, the temperature was lowered to room temperature at a rate of 1.5°C / min, and the resulting powder particles were obtained by grinding.

[0058] Oxalic acid was added to deionized water to a total concentration of 350 g / L. Cobalt-lithium powder particles were added, and the mixture was sonicated for 2.5 h. The mixture was then placed in a rotary evaporator and stirred at a constant temperature of 150 rpm at 85 °C. The supernatant was poured off after standing. Sodium carbonate was added to recover the Li-containing solution from the supernatant. The lower slurry was dried at 105 °C for 12 h, ground, and then calcined. During calcination, the temperature was increased from room temperature to 275 °C at a rate of 6 °C / min and held for 180 min. Then, under a high-purity nitrogen atmosphere with an oxygen content of 30 vol%, the temperature was increased to 390 °C at a rate of 6 °C / min and held for 12 h. Finally, the temperature was decreased to room temperature at a rate of 3 °C / min to obtain catalysts B and C. Catalytic activity tests were performed as follows: Figure 8 As shown.

[0059] Example 3

[0060] Preparation of doped-porous-cobalt-based monolithic copper foam catalyst

[0061] Copper foam was immersed in oxalic acid for 4 hours, then washed with distilled water until the pH of the washing solution was neutral. It was then dried at 125°C for 6 hours and calcined in a muffle furnace at 450°C for 7 hours to remove adsorbed impurities. The prepared doped-porous-cobalt-based nanomaterials were ball-milled, and ammonia was added to adjust the pH to 10. The mixture was then dissolved by constant-temperature ultrasonic stirring. Silica sol was added, and a stable slurry was formed. Copper foam was then immersed in this slurry and ultrasonically loaded. Residual suspension was then purged, forming a uniform film on the substrate surface. The film was dried. The mass ratio of silica sol to copper foam was 0.25%, the ultrasonic-assisted impregnation time was 20 minutes, and the drying temperature was 115°C. The impregnation process was repeated until the loading reached 18%. Finally, the temperature was first raised from room temperature to 290°C at a rate of 6°C / min using high-purity nitrogen as the atmosphere, and held for 420 min. Then, the temperature was raised to 450°C at a rate of 5.5°C / min using high-purity nitrogen with an oxygen content of 25 vol%, and held for 18 h. Finally, the temperature was lowered to room temperature to obtain a doped-porous-cobalt-based monolithic catalyst with oxygen vacancies.

[0062] Example 4

[0063] Synthesis of lithium cobalt oxide

[0064] The nanomaterials were tested using ICP to determine the Co content. Lithium carbonate was added, and the molar ratio of Li to Co was calculated to be 1.07. The mixture was ball-milled for 36 hours. The heating program was as follows: annealing at 1.5℃ / min from 30℃ to 360℃, holding for 12.5 hours; then annealing at 1℃ / min to 860℃, holding for 13.5 hours, and finally cooling to 50℃ at 3℃ / min. The specific method for the atmosphere during the calcination was as follows: in the first stage, an atmosphere with an oxygen content of 25 vol% was used; in the second stage, a high-purity nitrogen atmosphere with an oxygen content of 35 vol% was used. The X-ray diffraction pattern of the prepared repaired lithium cobalt oxide is shown below. Figure 6 As shown.

[0065] Example 5

[0066] Evaluation of the catalytic oxidation activity of propylene alone:

[0067] The catalytic oxidation of toluene was carried out in a self-made reactor under the following conditions: propylene concentration of 50 ppm, catalyst dosage of 200 mg, reaction temperature of 125℃~390℃, reaction flow rate of 100 mL / min, and space velocity of 30000 h⁻¹. -1 20 vol% O2, N2 as equilibrium gas; toluene, total hydrocarbons and CO were detected by gas chromatography. x The concentration value. Figure 7The graph shows the evaluation of the catalytic oxidation removal rate of the catalyst prepared in this invention. The results indicate that the reaction temperature (T) at which the catalytic oxidation removal rate of toluene by the catalyst prepared in this invention reaches 90% is [missing information]. 90 The T90 of the catalyst prepared in this invention is 200℃, while that of the commercial Mn-based catalyst under the same conditions is 263℃. This indicates that the catalyst exhibits excellent low-temperature activity for the catalytic oxidation of VOCs. Meanwhile, as... Figure 8 As shown, this patent's pretreatment-segmented exfoliation process yields a nano-precursor, which is then selectively recovered for lithium and undergoes a pretreatment-hydrothermal reaction-high-temperature phase transition to obtain a doped-porous-cobalt-based powder / monolithic catalyst for the catalytic oxidation of volatile organic compounds. Compared to simple acid-treated catalysts B and C, the T90 temperature can be increased by 113 degrees Celsius, significantly improving catalytic activity and efficiency. Simultaneously, as... Figure 9 As shown, compared with existing commercial MnCu and vanadium-based catalysts, the doped-porous-cobalt-based powder / monolithic catalyst exhibits a significantly lower T90 temperature.

[0068] Example 6

[0069] Evaluation of the catalytic oxidation activity of a mixture of toluene and propylene:

[0070] The catalytic oxidation degradation reaction of propylene was carried out in a self-made reactor. The test conditions were as follows: toluene and propylene concentrations were both 50 ppm, catalyst dosage was 200 mg, reaction temperature was 125℃~390℃, reaction flow rate was 100 mL / min, and space velocity was 30000 h⁻¹. -1 20 vol% O2 and N2 were used as the equilibrium gases; the concentrations of toluene and CO2 were detected by a gas chromatograph equipped with a flame ionization (FID) detector and connected to a nickel conversion furnace. Figure 10 This is an activity evaluation diagram of the catalyst prepared in this invention for the catalytic oxidation degradation of a mixture of toluene and propylene. The results show that the reaction temperature (T) at which the catalytic oxidation removal rate of the catalyst prepared in this invention reaches 90% for the mixture of toluene and propylene is [missing information]. 90 The temperature was 250℃, which indicates that the catalyst prepared in this invention exhibits excellent catalytic activity against mixed multi-component VOCs.

[0071] Example 7

[0072] Catalyst stability test for propylene oxidation alone

[0073] Propylene (C3H6) was used as a probe molecule to investigate the catalytic oxidation stability of the catalyst prepared in this invention. The catalytic oxidation reaction was carried out in a self-made reactor under the following conditions: propylene concentration of 100 ppm, catalyst dosage of 200 mg, reaction temperature of 250 °C, reaction flow rate of 100 mL / min, and space velocity of 30000 h⁻¹. -1The reaction atmosphere was a simulated gas, with 20 vol% O2 and N2 as the equilibrium gas; the concentrations of propylene and CO2 were detected by a gas chromatograph equipped with a flame ionization (FID) detector and a nickel conversion furnace. Figure 11 and Figure 12 To assess the stability of the catalyst prepared in this invention for the catalytic oxidation degradation of propylene, experimental results showed that after 65 hours of reaction, the removal rates of both propylene and total hydrocarbons remained above 99%, indicating that the catalyst prepared in this invention exhibits excellent stability for the catalytic oxidation of VOCs and high CO2 selectivity.

[0074] Example 8

[0075] Catalytic oxidation stability test of catalyst for mixed VOCs of toluene and propylene

[0076] Propylene (C3H6) was used as a probe molecule to investigate the catalytic oxidation stability of the catalyst prepared in this invention. The catalytic oxidation reaction was carried out in a self-made reactor under the following conditions: toluene and propylene concentrations were both 50 ppm, catalyst dosage was 200 mg, reaction temperature was 300 °C, reaction flow rate was 100 mL / min, and space velocity was 30000 h⁻¹. -1 The reaction atmosphere was a simulated gas, with 20 vol% O2 and N2 as the equilibrium gas; the concentrations of propylene and CO2 were detected by a gas chromatograph equipped with a flame ionization (FID) detector and a nickel conversion furnace. Figure 13 , Figure 14 and Figure 15 To assess the stability of the catalyst prepared in this invention for the catalytic oxidation degradation of mixed VOCs of toluene and propylene, experimental results showed that after 105 hours of reaction, the removal rates of toluene, propylene, and total hydrocarbons remained above 99%, indicating that the catalyst prepared in this invention exhibits excellent catalytic oxidation stability of VOCs and high CO2 selectivity.

[0077] Example 9

[0078] Catalytic oxidation performance test of HgO

[0079] HgO was used as a probe molecule to investigate the catalytic oxidation performance of the catalyst prepared in this invention. The test conditions were: HgO concentration of 80 μg / m³. 3 The catalyst dosage was 200 mg, the reaction temperature was 250 °C, the flow rate was 100 mL / min, and the space velocity was 30,000 h⁻¹. -1 The concentration of Hg0 was continuously determined online using a cold vapor atomic absorption spectrophotometer (CVAAS, Lumex RA915M). The results are as follows: Figure 16 As shown in the experimental results, the catalyst prepared in this application has a removal rate of HgO close to 100% or more, exhibiting excellent catalytic oxidation activity and stability for HgO.

[0080] Example 10

[0081] Water resistance test of catalyst

[0082] Propylene (C3H6) was used as a probe molecule to investigate the water resistance of the catalyst prepared in this invention. The test conditions were: propylene concentration of 100 ppm, catalyst dosage of 200 mg, reaction temperature of 300 °C, reaction flow rate of 100 mL / min, and space velocity of 30000 h⁻¹. -1 The reaction atmosphere was a simulated gas, with 20 vol% O2 and N2 as the equilibrium gas. The real-time concentrations of propylene, CO, CO2, and H2O were simultaneously measured online using a MultiGas2030 infrared Fourier transform spectrometer from MKS (USA), with values ​​for each gas component taken every 5 seconds. Figure 17 As shown, the experimental results indicate that after adding H2O, the catalyst prepared in this invention achieves a propylene removal rate of nearly 100%, exhibiting excellent water resistance and stability.

[0083] The above embodiments are only used to illustrate the technical solutions of the present invention and are not strict limitations. Those skilled in the art should understand that various changes can be made to the details or form without departing from the spirit and scope of the present invention as defined in the claims.

Claims

1. A method for preparing a doped-porous-cobalt-based nanomaterial using a waste lithium cobalt oxide battery, characterized by, The nanomaterial is re-crystallized in a hydrothermal reaction-high temperature phase change to form lithium and aluminum doped porous rod-shaped cobalt trioxide nanoparticles, wherein the mole ratio of Co and Li is Co / Li=(10-100), defects and oxygen vacancies are formed after pretreatment and lithium extraction, the residual metal has a doping effect in the cobalt trioxide crystal lattice, the specific surface area and oxygen vacancies of the material are increased, the primary particles change from microns to nanometers, the adsorption capacity is enhanced, and high catalytic oxidation VOCs and mercury Hg0 activity and resistance are exhibited; the resistance includes resistance to nitrogen oxides, resistance to sulfur, resistance to ammonia, and resistance to water; at the same time, due to the re-crystallization of the nanomaterial, the lattice damage and defects of the original waste battery material are repaired, and after pre-doping, the material is used as a high-performance cobalt-based raw material for synthesizing lithium batteries; After the waste lithium cobalt oxide battery is disassembled, the positive electrode sheet is obtained by pretreatment-subsection stripping process to obtain a nanometer precursor, and then selective recovery of lithium and pretreatment-hydrothermal reaction-high temperature phase change are carried out to obtain a doped-porous cobalt-based powder / monolithic catalyst for catalytic oxidation of VOCs and Hg0 in coal-fired flue gas; the method comprises the following steps: (1) Preparation of pretreated and defect type cobalt lithium particles: After the waste lithium cobalt oxide battery is soaked in brine and disassembled, the positive electrode material is separated and reserved, the positive electrode sheet is placed in a mixed acid-organic solvent for constant temperature ultrasonic immersion, dried, and then placed in a tube furnace for subsection calcination, ground and sieved to obtain defect type cobalt lithium particles, which are reserved; The atmosphere of the tube furnace is nitrogen with an oxygen content of 10-80vol% or argon with an oxygen content of 10-80vol%, and the mixed acid includes two or more of acetic acid, sulfuric acid, phytic acid, tannic acid, oxalic acid and citric acid; the organic solvent includes one or more of toluene, xylene, benzonitrile, methanol, ethanol, chloroform, tetrahydrofuran and N,N-dimethylformamide; (2) Recovery of lithium and preparation of doped-porous cobalt-based material: The powder particles prepared in step (1), additives, mixed acid and deionized water are fully mixed, placed in a rotary evaporator for constant temperature and sufficient stirring to dissolve them; after standing, the upper liquid is poured out, sodium carbonate is added to recover the Li-containing solution in the upper layer; after recovering Li, the lower slurry is washed, filtered, centrifuged, dried, ground, subjected to hydrothermal reaction and subsection calcination to obtain a doped-porous cobalt-based nanomaterial / powder catalyst; the mixed acid includes two or more of acetic acid, sulfuric acid, phytic acid, tannic acid, oxalic acid and citric acid; the additives include glucose, fructose and hydrogen peroxide; (3) Preparation of doped-porous cobalt-based monolithic catalyst: The foamed copper is soaked in mixed acid for 3-5 h, washed with distilled water until the washing liquid is neutral after being taken out, then dried at a temperature of 120-150 DEG C for 4-8 h, transferred to a muffle furnace and calcined at a temperature of 250-550 DEG C for 4-10 h to remove the adsorbed various impurities; the composite powder catalyst prepared in step (2) is ball milled by a ball mill, mixed with ammonia water and KOH, the pH is adjusted to 8-12, and is fully stirred under constant temperature ultrasonic to be dissolved, directly immersed or at least one of silica sol, pseudo-boehmite and hydroxyl cellulose is added, the pH is adjusted, and a stable slurry is formed after stirring, the foamed copper is immersed in the slurry and loaded under ultrasonic, then the residual suspension is blown, a uniform film is formed on the surface of the substrate, dried, and the immersion process is repeated until the appropriate loading amount; finally, the doped-porous-cobalt-based monolithic catalyst with oxygen vacancies is obtained by sub-step calcination in nitrogen as the balance gas and in 5-80 vol% oxygen content.

2. The method for preparing doped-porous cobalt-based nanomaterials using waste lithium cobalt oxide batteries according to claim 1, characterized in that, In step (1), the concentration of the mixed acid is 1-10 mol / L, the concentration of the organic matter in the organic solvent is 0.5-10 mol / L, the solid-liquid ratio of the pole and the solvent is 10-100 g / L, the constant temperature soaking temperature is 20-90 DEG C, the soaking time is 2-10 h, and the drying temperature is 110-160 DEG C.

3. The method for preparing doped-porous-cobalt-based nanomaterials using waste lithium cobalt oxide batteries according to claim 1, characterized in that, In step (1), the sub-step calcination is specifically as follows: first, the high-purity nitrogen gas is used as the atmosphere, the temperature is increased from room temperature to 250-360 DEG C at a rate of 1-35 DEG C / min, and the temperature is kept constant for 100-340 min; then, the nitrogen gas with 5-90 vol% oxygen content is used as the atmosphere, the temperature is increased to 350-950 DEG C at a rate of 2-30 DEG C / min, and the temperature is kept constant for 5-15 h; finally, the temperature is decreased to room temperature at a rate of 1-10 DEG C / min.

4. The method for preparing doped-porous-cobalt-based nanomaterials using waste lithium cobalt oxide batteries according to claim 1, characterized in that, In step (2), the hydrothermal reaction is specifically as follows: the lower slurry liquid after recovering lithium is mixed with ammonia water after drying and grinding to obtain solution A, urea and water are mixed to obtain solution B, solution A and solution B are stirred at room temperature for 30-90 min, and then CTAB or polyethylene glycol is added; then, solution KOH is added dropwise into the mixed solution, the pH is adjusted to 9-12, and the solution is stirred at room temperature and then transferred into a polytetrafluoroethylene reaction kettle inner container; finally, the polytetrafluoroethylene reaction kettle inner container is placed in a high-pressure reaction kettle, and hydrothermal reaction is carried out at 120-220 DEG C for 6-48 h; after natural cooling, the precipitate is centrifuged, washed, vacuum dried and ground for standby use; the calcination is specifically as follows: first, the nitrogen gas is used as the atmosphere, the temperature is increased from room temperature to 250-320 DEG C at a rate of 1-30 DEG C / min, and the temperature is kept constant for 120-240 min; then, the nitrogen gas with 10-80 vol% oxygen content is used as the atmosphere, the temperature is increased to 350-900 DEG C at a rate of 10-30 DEG C / min, and the temperature is kept constant for 5-15 h; finally, the temperature is decreased to room temperature at a rate of 1-10 DEG C / min.

5. The method for preparing doped-porous-cobalt-based nanomaterials using waste lithium cobalt oxide batteries according to claim 1, characterized in that, In step (2), the concentration of the mixed acid is 20-800 g / L, the stirring rate of the rotary evaporator is 120-450 rpm, and the temperature is 30-95 ℃; the drying temperature is 105-180 ℃, and the drying time is 6-18 h. 6.The method of claim 1, wherein the method further comprises: washing the porous cobalt-based nanomaterial with deionized water; and drying the porous cobalt-based nanomaterial. In step (3), the mixed acid comprises one or more of hydrochloric acid, acetic acid, sulfuric acid, oxalic acid and citric acid, and the pH of the slurry is maintained at 0.5-6.

7. The method for preparing doped-porous-cobalt-based nanomaterials using waste lithium cobalt oxide batteries according to claim 1, characterized in that, In step (3), the mass ratio of the silica sol, pseudo-boehmite and hydroxyl cellulose to the carrier is 0.1-5%, the ultrasonic-assisted impregnation time is 10-60 min, the final loading amount of the active substance is 1-50%, and the drying temperature is 100-210 ℃.

8. The method for preparing doped-porous-cobalt-based nanomaterials using waste lithium cobalt oxide batteries according to claim 1, characterized in that, In step (3), the specific method of the staged calcination is as follows: first, the temperature is raised from room temperature to 280-380 ℃ at a rate of 5-15 ℃ / min in a high-purity nitrogen atmosphere, and then the temperature is kept constant for 360-660 min; second, the temperature is raised to 350-850 ℃ at a rate of 5-25 ℃ / min in a nitrogen atmosphere with an oxygen content of 10-90 vol%, and then the temperature is kept constant for 6-24 h; finally, the temperature is lowered to room temperature.

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