A pretreatment desulfurization and decarburization method for waste automobile catalyst recovery

Abstract

The application provides a pretreatment desulfurization and decarburization method for waste automobile catalyst recovery, and belongs to the technical field of catalyst recovery. The method comprises the following steps: pretreating waste automobile catalyst to obtain waste catalyst particles with water content less than or equal to 5%; low-temperature calcining the waste catalyst particles in an inert atmosphere and an oxygen-containing atmosphere containing ozone in sequence, wherein the temperature is 300 DEG C to 500 DEG C, and the calcined product is obtained after cooling to room temperature; performing oxidation washing on the calcined product, wherein the washing reagent for the oxidation washing comprises an oxidant and a washing aid, the oxidant is ozone and hydrogen peroxide, the washing aid comprises sodium dodecyl benzene sulfonate, fatty alcohol polyoxyethylene ether and sodium citrate, and a pH regulator is added in the oxidation washing process to gradually increase the pH of the system to 7.5 to 9.0; and obtaining the waste catalyst after desulfurization and decarburization through post-treatment. The low-temperature ozone calcining and dynamic pH oxidation washing combined process is adopted, high-efficiency desulfurization and decarburization of the waste catalyst are realized, and the activity of the noble metal is preserved.

Description

Technical Field

[0001] This invention belongs to the field of catalyst recycling technology, and specifically relates to a pretreatment desulfurization and decarbonization method for recycling waste automotive catalysts. Background Technology

[0002] During long-term use, automotive catalysts accumulate carbon deposits and sulfide impurities on their surfaces. Aromatic hydrocarbons and olefins in the fuel polymerize and dehydrogenate under high-temperature, oxygen-deficient conditions, forming carbon deposits. Some unburned fuel gas and lubricating oil vapors can seep into the exhaust system through piston ring gaps, depositing on the catalyst surface and forming carbon deposits. Simultaneously, sulfides in the exhaust gas (such as hydrogen sulfide and carbon disulfide) react with the active components and support in the catalyst, generating sulfide impurities (such as platinum sulfide and palladium sulfide). These carbon deposits and sulfides severely affect the subsequent leaching efficiency and separation effect of precious metals, and significantly increase the amount of acidic leachate required.

[0003] Currently, pretreatment methods for desulfurization and decarbonization of waste automotive catalysts are mainly divided into three categories: high-temperature calcination, chemical washing, and oxidation. High-temperature calcination requires temperatures of 800℃~1000℃, resulting in high energy consumption and a tendency for catalyst support sintering and precious metal oxidation and loss. Furthermore, the sulfur dioxide produced by sulfide combustion causes secondary pollution. Chemical washing uses strong acid or alkali solutions, which can remove some carbon deposits and sulfides, but it corrodes the catalyst support, causing precious metals to be encapsulated, reducing subsequent leaching rates, and generating large amounts of high-concentration acid and alkali wastewater, leading to high environmental treatment costs. Traditional oxidation methods use a single oxidant (such as oxygen or ozone), resulting in low desulfurization and decarbonization efficiency, making it difficult to completely remove stubborn carbon deposits and sulfides, especially for recalcitrant sulfides such as dibenzothiophene. The large amount of oxidant used also leads to resource waste and secondary pollution; for example, the desulfurization rate of ozone oxidation alone is difficult to exceed 90%, and ozone is unstable, easily decomposes, and has high operating costs.

[0004] Furthermore, existing pretreatment methods mostly involve single-stage desulfurization or single-stage decarbonization, making it difficult to achieve simultaneous desulfurization and decarbonization. These methods are cumbersome, have low pretreatment efficiency, and cannot meet the needs of large-scale industrial production. Therefore, developing a highly efficient, energy-saving, environmentally friendly pretreatment method that can simultaneously achieve desulfurization and decarbonization without damaging the catalyst support and precious metals is crucial for improving the recovery efficiency of precious metals from waste automotive catalysts. Summary of the Invention

[0005] In view of this, the present invention provides a pretreatment desulfurization and decarbonization method for recycling waste automotive catalysts, aiming to solve at least one of the technical problems in the background art.

[0006] This invention is implemented as follows: This invention provides a pretreatment method for desulfurization and decarbonization in the recycling of waste automotive catalysts, the method comprising the following steps: S1. Waste automotive catalysts are pretreated to obtain waste catalyst particles with a water content of ≤5%; S2. The spent catalyst particles were successively calcined at low temperatures in an inert atmosphere and an ozone-containing aerobic atmosphere, at temperatures of 300℃~500℃. After calcination, they were cooled to room temperature to initially remove carbon deposits and sulfides, and the calcined product was obtained. S3. The calcined product is subjected to oxidative washing. The washing reagent for oxidative washing includes an oxidant and a washing aid. The oxidant is ozone and hydrogen peroxide. The washing aid includes sodium dodecylbenzenesulfonate, fatty alcohol polyoxyethylene ether, and sodium citrate. During the oxidative washing process, a pH adjuster is added to gradually increase the pH of the system to 7.5~9.0. S4. Solid-liquid separation, cleaning, and drying are performed to obtain the desulfurized and decarbonized waste catalyst.

[0007] Furthermore, S3 specifically refers to: Hydrogen peroxide solution and detergent were added to the calcined product, and ozone was continuously introduced to adjust the initial pH of the system to 4.0~5.5 before washing began. During the washing process, the pH of the system is monitored online. When the pH of the system drops to 3.5-4, alkali is added every 10-20 minutes to raise the pH of the system by 0.5-1.0 until the pH of the system is 7.5-9.0.

[0008] Furthermore, the concentration of the hydrogen peroxide solution is 3%~15%, the ratio of hydrogen peroxide solution to calcined product is (2~6) mL: 1g calcined product; and the amount of ozone introduced is 3g / h~10g / h.

[0009] Furthermore, based on the calcined product mass, the amount of sodium dodecylbenzenesulfonate is 0.5%~1.5%, the amount of fatty alcohol polyoxyethylene ether is 0.2%~0.8%, and the amount of sodium citrate is 0.3%~0.8%; The mass ratio of sodium dodecylbenzenesulfonate to fatty alcohol polyoxyethylene ether is (2~4):1.

[0010] Furthermore, the oxidation washing is performed in an ultrasonic field with a frequency of 20kHz to 80kHz and a power density of 0.5W / cm². 2 ~5W / cm 2 .

[0011] Furthermore, during the oxidative washing process, once the system pH reaches 7.5~9.0, the washing continues for 1h~3h.

[0012] Furthermore, S2 specifically includes: S21. Place the waste catalyst particles in a calcination furnace and heat them to 300℃~500℃ under an inert atmosphere for 10min~30min; the inert atmosphere is nitrogen or argon. S22. Switch from an inert atmosphere to an ozone-containing aerobic atmosphere and continue calcining at 300℃~500℃ for 30min~60min. S23. After calcination, the ozone-containing aerobic atmosphere is switched to high-purity nitrogen for continuous purging, and the furnace is naturally cooled to room temperature.

[0013] Furthermore, the ozone-containing aerobic atmosphere is a mixture of ozone and air, wherein the ozone concentration is 50ppm to 200ppm.

[0014] Furthermore, the flow rates of the inert atmosphere in S21 and the ozone-containing aerobic atmosphere in S22 are 100 mL / min to 300 mL / min; the flow rate of high-purity nitrogen in S23 is 50 mL / min to 240 mL / min.

[0015] Furthermore, S1 specifically includes: S11. Collect waste automotive catalyst carriers; S12. Crush the carrier to 20mm~50mm, then remove impurities by magnetic separation and grind. Add deionized water during the grinding process. The mass ratio of particulate matter to water is 10:1~2. S13. Dry at 80℃~100℃ and sieve through 80-120 mesh to obtain waste catalyst particles with a moisture content ≤5%.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention employs a combination of low-temperature ozone calcination and dynamic pH oxidation washing process to achieve efficient desulfurization and decarbonization of waste automotive catalysts while preserving the activity of precious metals.

[0017] 2. The calcination section of this invention utilizes ozone for low-temperature carbonization, pre-opening channels and converting metal sulfides into easily soluble oxides; the pH-controlled oxidation and washing section allows the oxidation system to successively decarbonize using hydroxyl radical oxidation and desulfurize using alkaline ozone oxidation. Calcination and washing are deeply complementary in chemical function, forming a synergistic effect.

[0018] 3. This invention utilizes a pH-controlled oxidation washing stage, where highly active hydroxyl radicals in the acidic stage efficiently mineralize carbon deposits, while the alkaline stage utilizes the strong oxidizing properties of ozone to convert sulfides into soluble sulfates for complete stripping.

[0019] 4. In the process of the present invention, under mild conditions and in a chloride-free system, noble metals such as Pt, Pd, and Rh are in a passivated state and hardly dissolve or volatilize, thus avoiding high-temperature sintering and chemical loss.

[0020] 5. This invention uses a ternary compound detergent additive of SDBS + AEO-9 + sodium citrate, which improves the defect of easy hydrolysis and deposition of base metals in alkaline environment. AEO-9 and SDBS synergistically solubilize oil stains, while sodium citrate activates the chelation function in the alkaline section, preferentially combining with base metals to form soluble complexes, thus avoiding their enrichment in the catalyst. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0022] A pretreatment method for desulfurization and decarbonization for recycling waste automotive catalysts, comprising steps S1 to S4.

[0023] S1. Waste automotive catalysts are pretreated to obtain waste catalyst particles with a water content of ≤5%.

[0024] In specific implementation, S1 includes: mechanically dismantling the collected automotive catalyst waste to separate the outer shell from the internal carrier; crushing the carrier to 20mm~50mm in a crushing device; then magnetically separating the magnetic impurities mixed in the waste catalyst carrier (such as iron filings and equipment wear debris mixed in during the process) to avoid these impurities interfering with the purity of subsequent precious metal recovery; then grinding in a ball mill to process the waste catalyst blocks into uniform powder, increasing the contact area for subsequent calcination and oxidation washing, and improving reaction efficiency; adding a small amount of deionized water (solid to water mass ratio of 10:1~2) during the grinding process to prevent dust from flying, and at the same time initially loosening the surface carbon and sulfides; after grinding, filtering, drying, and sieving (passing through 80-120 mesh) at a drying temperature of 80℃~100℃ to obtain waste catalyst particles with a water content of ≤5%. Drying can avoid the generation of water vapor during subsequent roasting, which would affect the desulfurization and decarbonization effect.

[0025] S2. The spent catalyst particles were successively calcined at low temperatures of 300℃~500℃ in an inert atmosphere and an ozone-containing aerobic atmosphere. After calcination, they were cooled to room temperature to initially remove carbon deposits and sulfides, and the calcined product was obtained.

[0026] In its specific implementation, S2 includes: S21. Place the spent catalyst particles in a calcination furnace and heat to 300℃~500℃ under an inert atmosphere (nitrogen or argon, flow rate 100mL / min~300mL / min), holding the temperature for calcination for 10min~30min. Avoid direct heating in an oxygen atmosphere, which can cause some organic matter to undergo condensation reactions, generating more difficult-to-oxidize graphitic carbon deposits. Pyrolysis under nitrogen first can avoid this unfavorable transformation, and heating under anaerobic conditions prevents precious metals such as Pt, Pd, and Rh from being oxidized by air at high temperatures.

[0027] S22. The inert atmosphere is switched to an ozone-containing aerobic atmosphere (a mixture of ozone and air, with an ozone concentration of 50ppm~200ppm and a flow rate of 100mL / min~300mL / min), and calcination continues at 300℃~500℃ for 30min~60min. This step performs deep removal of carbon deposits and preliminary desulfurization. Ordinary air requires temperatures above 600℃ to effectively burn carbon, which causes precious metal particles to sinter and grow, reducing the subsequent recovery rate. The strong oxidizing properties of ozone lower the carbon burning temperature. At a mild temperature of 300℃~500℃, ozone can oxidize the stubborn carbon deposits remaining on the catalyst surface and in the pores into CO2, achieving low-temperature carbon burning. At this temperature, some organic sulfides and metal sulfides can be oxidized by ozone, converting sulfur into SO2 or sulfate, reducing the load on subsequent oxidation washing. After burning off the carbon deposits, the blocked catalyst pores are re-exposed, providing favorable conditions for the oxidant and washing aid in the subsequent oxidation washing solution to enter the depth of the pores.

[0028] S23. After calcination, the ozone-containing aerobic atmosphere is switched to high-purity nitrogen (purity ≥99.9%, flow rate 50mL / min~240mL / min) for continuous purging, and the furnace is allowed to cool naturally to room temperature. During cooling, a slight positive pressure is maintained inside the furnace (gauge pressure +50Pa~+200Pa) to prevent air backflow. The calcined catalyst is in a high-temperature active state. If it is directly cooled by air, the precious metals (especially Pt and Pd) can be re-oxidized by oxygen in the air, increasing the difficulty of subsequent recovery.

[0029] During the low-temperature calcination stage (300℃~500℃), the removal / conversion process of carbon deposits and sulfides is as follows: (1) Under an inert atmosphere, the volatile organic compounds (VOCs), residual oils, unburned hydrocarbons, etc. adsorbed on the surface of the waste catalyst will volatilize or crack when heated. Some of the organic compounds with lower boiling points will directly detach from the catalyst surface in gaseous form during the heating process. For heavier organic compounds with larger molecular weights (such as tar and polymers), thermal decomposition will occur in a high-temperature oxygen-free environment, breaking down into smaller molecules.

[0030] (2) Ozone in an oxidizing atmosphere undergoes catalytic decomposition at active sites on the catalyst surface (such as noble metals like Pt and Pd or defect sites on the support surface) to generate active oxygen atoms, which attack the carbon-carbon double bonds on the carbon deposit surface, thus achieving oxidative cracking. The strong oxidizing properties of ozone can also oxidize some of the carbon deposits (mainly carbon and hydrocarbons) on the catalyst surface into CO2 and H2O.

[0031] (3) Heating under an oxidizing atmosphere oxidizes the water-insoluble and chemically stable metal sulfides on the catalyst surface into metal oxides, which are then removed during subsequent oxidation washing. In addition, high temperature can desorb some of the free sulfur adsorbed on the catalyst surface in physical or chemical form as gaseous SO2.

[0032] S3. The calcined product is subjected to oxidative washing. The washing reagents for oxidative washing include an oxidant and a washing aid. The oxidant is ozone and hydrogen peroxide. The washing aid includes sodium dodecylbenzenesulfonate, fatty alcohol polyoxyethylene ether, and sodium citrate. During the oxidative washing process, a pH adjuster is added to gradually increase the pH of the system from 4.5 to 5.5 to 7.5 to 9.0.

[0033] S3 specifically involves adding hydrogen peroxide solution and a washing aid to the calcined product and continuously introducing ozone to adjust the initial pH of the system to 4.0-5.5, and then starting the washing process. During the washing process, the pH of the system is monitored online. When the pH of the system drops to 3.5-4, alkali is added every 10-20 minutes to raise the pH of the system by 0.5-1.0 until the pH of the system is 7.5-9.0, and then the washing continues for 1-3 hours.

[0034] Low-temperature calcination is highly efficient at oxidizing and gasifying organic carbon deposits (hydrocarbons); however, high-temperature gasification is less effective for inorganic sulfides (such as PbS and NiS) and metal poisons like phosphorus, zinc, and calcium from lubricating oil. The washing stage specifically targets sulfides and heavy metal ions that calcination fails to completely remove. Calcination converts sulfides into oxides (such as PbO), and the ozone / hydrogen peroxide in the washing solution oxidizes them to soluble sulfates under alkaline conditions, dissolving them.

[0035] In the initial acidic system, the complex oxidation system composed of ozone and hydrogen peroxide generates highly oxidizing hydroxyl radicals, which can attack the C-C and CH bonds in the carbon deposits, degrading stubborn polycyclic aromatic hydrocarbon deposits into small-molecule organic acids and ultimately mineralizing them into CO2. As the carbon deposits oxidize to produce organic acids (such as oxalic acid and acetic acid), the pH of the system naturally decreases. After the online pH sensor detects the pH decrease (e.g., 3.5~4), it automatically triggers the addition of dilute alkaline solution (NaOH) in a gradual gradient of 0.5~1.0 every 10~20 minutes until the pH of the system reaches 7.5~9.0, thus steadily raising the pH to the alkaline range. Sulfides are more efficiently oxidized and dissolved under alkaline conditions, and the system is washed for a period of time within this pH range.

[0036] Oxidants oxidize and decompose large molecular contaminants such as carbon deposits and sulfides on the catalyst surface into smaller fragments. However, some contaminants are tightly bound to the catalyst support surface and are not easily removed. In addition, base metal ions (Ni, Co, Pb, Zn, etc.) in the catalyst will immediately react with OH groups in the washing liquid. - The oxidation process generates insoluble hydroxide precipitates, which re-block the micropores of the high specific surface area coating that were just opened by the oxidation wash, making subsequent leaching difficult. To address the complexity of contaminants on the surface of waste automotive catalysts (containing carbon deposits, sulfides, metal deposits, etc.), a small amount of detergent is added to the oxidation wash to facilitate the detachment of the oxidized products from the waste catalyst carrier. Sodium dodecylbenzenesulfonate (SDBS) serves as the primary emulsifier; its amphiphilic properties (lipophilic and hydrophilic) promote the detachment of contaminants from the catalyst surface through emulsification, dispersing them into tiny particles suspended in the washing liquid. Fatty alcohol polyoxyethylene ether (AEO-9), as a synergist for sodium dodecylbenzenesulfonate (SDBS), significantly reduces the surface tension and critical micelle concentration of the system when combined with SDBS, improving detergency and controlling foaming while preventing redeposition of contaminants. Sodium citrate preferentially chelates base metal ions, preventing them from combining with SDBS to form water-insoluble compounds that reduce detergency. It also synergizes with SDBS / AEO-9 to enhance the suspension and dispersion of dirt in the washing liquid, preventing it from redepositing on the catalyst surface. Furthermore, the metal chelating ability of sodium citrate is pH-dependent: its chelating ability is weak under acidic conditions (not affecting the emulsifying function of SDBS / AEO-9), and its chelating ability gradually increases as the pH rises to alkaline conditions; therefore, its main effective stage is in an alkaline environment. Based on the calcined product mass, the dosage of sodium dodecylbenzenesulfonate is 0.5%–1.5%, the dosage of fatty alcohol polyoxyethylene ether is 0.2%–0.8%, and the dosage of sodium citrate is 0.3%–0.8%; the mass ratio of sodium dodecylbenzenesulfonate to fatty alcohol polyoxyethylene ether is (2–4):1.

[0037] In practical implementation, to improve the efficiency of oxidation washing, oxidation washing is performed in an ultrasonic field (frequency 20kHz~80kHz, power density 0.5W / cm²). 2 ~5W / cm 2 The process is carried out in the following steps. Ultrasonic cavitation assistance: When the cavitation bubbles generated by ultrasound collapse, they produce localized instantaneous high temperature and high pressure, which can physically impact the catalyst surface, promote the shedding of carbon deposits, and at the same time accelerate the generation and diffusion of hydroxyl radicals in the oxidation system.

[0038] S4. Solid-liquid separation, cleaning, and drying are performed to obtain the desulfurized and decarbonized waste catalyst.

[0039] After oxidation washing, a filter press is used for solid-liquid separation to obtain solid product and washing waste liquid. The solid product is washed with deionized water 2 to 3 times until the washing liquid is neutral (pH=6 to 8), and then dried at 80℃ to 100℃ for 2 to 3 hours to obtain the desulfurized and decarbonized waste catalyst. The washing waste liquid can be recycled for the preparation of oxidation washing liquid after neutralization, filtration and adsorption treatment, realizing the recycling of water resources and reagents and reducing costs. The sulfur dioxide gas generated during roasting and washing is absorbed by an alkaline absorption tower (sodium hydroxide solution) and converted into sodium sulfate, realizing resource recovery and avoiding environmental pollution.

[0040] The spent catalyst after the above desulfurization and decarbonization can be directly recycled for precious metals (Pd, Pt, Rh, etc.) using conventional leaching processes, without the need for complex activation steps, and the amount of masking agent required for subsequent precious metal separation is greatly reduced.

[0041] Example 1 A pretreatment method for desulfurization and decarbonization in the recycling of waste automotive catalysts includes the following steps: S1. The collected automotive catalyst waste is mechanically dismantled to separate the outer shell from the internal carrier. The carrier (carbon content approximately 2.5%, sulfur content approximately 0.3%, iron content approximately 0.89%) is placed in a crushing device and crushed to 20mm~50mm. Then, magnetic separation is used to remove magnetic impurities mixed in the waste catalyst carrier. The waste catalyst is then ground in a ball mill. Crushing and sieving process the waste catalyst blocks into uniform powder, increasing the contact area for subsequent calcination and oxidation washing, and improving the reaction efficiency. A small amount of deionized water (solid to water mass ratio 10:1) is added during the grinding process. After grinding, the powder is filtered, dried, and sieved (below 100 mesh). The drying temperature is 80℃~100℃. The resulting waste catalyst particles (moisture content 4%) are dried to avoid the generation of water vapor during subsequent roasting, which would affect the desulfurization and decarbonization effect.

[0042] S2. Place the pretreated waste catalyst particles in a tubular calcination furnace; first, introduce high-purity nitrogen gas (purity ≥99.9%, flow rate 200 mL / min), and heat to 300℃ at 5℃ / min, holding for 20 min; then switch to ozone-containing air (prepared by an ozone generator using air as the gas source, ozone concentration 100 ppm, flow rate 200 mL / min), and continue to heat to 450℃ at 5℃ / min, holding for 50 min; after calcination, stop introducing ozone-containing air, switch to high-purity nitrogen gas (purity ≥99.9%, flow rate 150 mL / min), and allow the furnace to cool naturally to room temperature.

[0043] S3. Mix the cooled calcined product (1 kg) evenly and feed it into the oxidation washing reactor (equipped with an ozone aeration device, online pH monitoring and automatic alkali dripping device, and a stirrer). Add 5 L of hydrogen peroxide solution (concentration of 10%), then add 2.0 mol / L dilute sulfuric acid to adjust the initial pH of the system to 4.5. Add a washing aid (10 g SDBS + 3 g AEO-9 + 5 g sodium citrate). Continuously introduce ozone (flow rate of 5 g / h) for stirring and washing. Monitor the pH online. When the pH drops below 3.8, automatically add 1.0 mol / L NaOH solution. Increase the pH of the system by 0.5~1 every 15 min. Control the final pH at 8.0 and continue washing for 120 min.

[0044] S4. After washing, use deionized water to ultrasonically wash three times at 50℃~60℃ until neutral (pH≈7), and then dry at 100℃ for 4 hours to obtain the desulfurized and decarbonized waste catalyst.

[0045] Example 2 The difference between Example 2 and Example 1 is that the washing in S3 is performed in an ultrasonic field, while the other conditions and steps are the same as in Example 1.

[0046] In this embodiment 2, S3 specifically involves: uniformly mixing the cooled calcined product (1 kg) and feeding it into an oxidation washing reactor (equipped with an ultrasonic generator, ozone aeration device, online pH monitoring and automatic alkali dripping device, and stirrer); adding 5 L of hydrogen peroxide solution (concentration 10%); then adding 2.0 mol / L dilute sulfuric acid to adjust the initial pH of the system to 4.5; adding a washing aid (10 g SDBS + 3 g AEO-9 + 5 g sodium citrate); continuously introducing ozone (flow rate 5 g / h); and starting the ultrasonic generator (frequency 40 kHz, power density 2 W / cm³). 2 The system is stirred and washed, and the pH is monitored online. When the pH drops below 4, 1.0 mol / L NaOH solution is automatically added. The pH of the system is increased by 0.5~1 every 10 minutes. The final pH is controlled at 8.0, and then washing continues for another 60 minutes.

[0047] Example 3 The difference between Example 3 and Example 1 is that the conditions for S2 are the same as those for Example 1, while the other conditions and steps are the same.

[0048] In this embodiment 3, S2 specifically involves: placing the pretreated waste catalyst particles in a tubular calcination furnace; first, introducing high-purity argon gas (purity ≥99.9%, flow rate 200 mL / min), heating to 400°C at 10°C / min, and holding at that temperature for 30 min; then switching to ozone-containing air (prepared by an ozone generator using air as the gas source, ozone concentration 100 ppm, flow rate 200 mL / min), and continuing to heat to 500°C at 10°C / min, holding at that temperature for 50 min; after calcination, stopping the introduction of ozone-containing air, switching to high-purity nitrogen gas (flow rate 150 mL / min), and allowing the furnace to cool naturally to room temperature.

[0049] Example 4 The difference between Example 4 and Example 1 is that the amount of washing oxidant used in S3 is different, while other conditions and steps are the same as in Example 1.

[0050] In this embodiment 4, S3 specifically involves: uniformly mixing the cooled calcined product (1 kg) and feeding it into an oxidation washing reactor (equipped with an ozone aeration device, online pH monitoring and automatic alkali dripping device, and a stirrer). 5 L of hydrogen peroxide solution (concentration 15%) is added, followed by 2.0 mol / L dilute sulfuric acid to adjust the initial pH of the system to 4.5. A washing aid (10 g SDBS + 3 g AEO-9 + 5 g sodium citrate) is added, and ozone (flow rate 8 g / h) is continuously introduced for stirring and washing. The pH is monitored online. When the pH drops below 3.8, 1.0 mol / L NaOH solution is automatically added. The pH of the system increases by 0.5-1 every 15 minutes, and the final pH is controlled at 8.0. Washing continues for another 120 minutes.

[0051] Example 5 The difference between Example 5 and Example 1 is that the initial pH and the final pH of the washing in S3 are different, while the other conditions and steps are the same as in Example 1.

[0052] In this embodiment 5, S3 is as follows: S3, the cooled calcined product (1 kg) is mixed evenly and fed into an oxidation washing reactor (equipped with an ozone aeration device, online pH monitoring and automatic alkali dripping device, and a stirrer). 5 L of hydrogen peroxide solution (concentration of 10%) is added, followed by 2.0 mol / L dilute sulfuric acid to adjust the initial pH of the system to 4. A washing aid (10 g SDBS + 3 g AEO-9 + 5 g sodium citrate) is added, and ozone (flow rate of 5 g / h) is continuously introduced for stirring and washing. The pH is monitored online. When the pH drops to 3.5, 1.0 mol / L NaOH solution is automatically added. The pH of the system increases by 0.5 to 1 every 15 min. The final pH is controlled at 7.5, and washing continues for another 120 min.

[0053] Example 6 The difference between Example 6 and Example 1 is that the initial pH and final pH of washing in S3 are different, while the other conditions and steps are the same as in Example 1.

[0054] In this embodiment 6, S3 is as follows: S3, the cooled calcined product (1 kg) is mixed evenly and fed into an oxidation washing reactor (equipped with an ozone aeration device, online pH monitoring and automatic alkali dripping device, and a stirrer). 5 L of hydrogen peroxide solution (concentration of 10%) is added, followed by 2.0 mol / L dilute sulfuric acid to adjust the initial pH of the system to 5.5. A washing aid (10 g SDBS + 3 g AEO-9 + 5 g sodium citrate) is added, and ozone (flow rate of 5 g / h) is continuously introduced for stirring and washing. The pH is monitored online. When the pH drops to 4, 1.0 mol / L NaOH solution is automatically added. The pH of the system increases by 0.5 to 1 every 15 min. The final pH is controlled at 9, and washing continues for another 120 min.

[0055] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the low-temperature calcination of S2 only uses oxygen-free calcination, while the other conditions and steps are the same as in Example 1.

[0056] Specifically, S2 of Comparative Example 1 was as follows: the pretreated waste catalyst particles were placed in a tubular calcination furnace; high-purity nitrogen gas (purity ≥99.9%, flow rate 200 mL / min) was first introduced, and the temperature was raised to 300℃ at 5℃ / min and held for 20 min; then the temperature was raised to 450℃ at 5℃ / min and held for 50 min; after calcination, the flow rate of high-purity nitrogen gas was reduced to 150 mL / min, and the furnace was allowed to cool naturally to room temperature.

[0057] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the low-temperature calcination of S2 only uses aerobic calcination, while the other conditions and steps are the same as in Example 1.

[0058] Specifically, S2 in Comparative Example 2 is: The pretreated waste catalyst particles were placed in a tubular calcination furnace; ozone-containing air (prepared by an ozone generator using air as the gas source, with an ozone concentration of 100 ppm and a flow rate of 200 mL / min) was introduced, and the temperature was increased to 300℃ at a rate of 5℃ / min and held for 20 min; then the temperature was increased to 450℃ at a rate of 5℃ / min and held for 50 min; after calcination, the ozone-containing air was stopped, and high-purity nitrogen (purity ≥99.9%, flow rate 150 mL / min) was introduced, and the furnace was allowed to cool naturally to room temperature.

[0059] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that the low-temperature calcination of S2 uses only air (without ozone) for aerobic calcination, while the other conditions and steps are the same as in Example 1.

[0060] In Comparative Example 3, S2 was specifically performed as follows: the pretreated waste catalyst particles were placed in a tubular calcination furnace; high-purity nitrogen (purity ≥99.9%, flow rate 200 mL / min) was first introduced, and the temperature was increased to 300℃ at 5℃ / min and held for 20 min; then air (flow rate 200 mL / min) was introduced, and the temperature was increased to 450℃ at 5℃ / min and held for 50 min; after calcination, the air supply was stopped, and high-purity nitrogen (purity ≥99.9%, flow rate 150 mL / min) was introduced, and the furnace was allowed to cool naturally to room temperature.

[0061] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that the calcination temperature of S2 is >500℃, while the other conditions and steps are the same as in Example 1.

[0062] In Comparative Example 4, S2 was specifically as follows: S2, the pretreated waste catalyst particles were placed in a tubular calcination furnace; high-purity nitrogen gas (purity ≥99.9%, flow rate 200 mL / min) was first introduced, and the temperature was increased to 550℃ at 5℃ / min and held for 20 min; then the temperature was switched to ozone-containing air (prepared by an ozone generator using air as the gas source, ozone concentration 100 ppm, flow rate 200 mL / min), and the temperature was increased to 600℃ at 5℃ / min and held for 50 min; after calcination, the ozone-containing air was stopped, and high-purity nitrogen gas (purity ≥99.9%, flow rate 150 mL / min) was switched to, and the furnace was allowed to cool naturally to room temperature.

[0063] Comparative Example 5 The difference between Comparative Example 5 and Example 1 is that the pH is not adjusted during the S3 washing process, while the other conditions and steps are the same as in Example 1.

[0064] Specifically, S3 of Comparative Example 5 was as follows: 1 kg of cooled calcined product was mixed evenly and fed into an oxidation washing reactor (equipped with an ozone aeration device, online pH monitoring and automatic alkali dripping device, and a stirrer). 5 L of hydrogen peroxide solution (concentration of 10%) was added, followed by the addition of 2.0 mol / L dilute sulfuric acid to adjust the initial pH of the system to 4.5. A washing aid (10 g SDBS + 3 g AEO-9 + 5 g sodium citrate) was added, and ozone (flow rate of 5 g / h) was continuously introduced for stirring and washing for 240 min.

[0065] Comparative Example 6 The difference between Comparative Example 6 and Example 1 is that no detergent is added during the S3 washing process, while the other conditions and steps are the same as in Example 1.

[0066] Specifically, in Comparative Example 6, S3 was as follows: 1 kg of cooled calcined product was mixed evenly and fed into an oxidation washing reactor (equipped with an ozone aeration device, online pH monitoring and automatic alkali dripping device, and a stirrer). 5 L of hydrogen peroxide solution (10% concentration) was added, followed by 2.0 mol / L dilute sulfuric acid to adjust the initial pH of the system to 4.5. Ozone (flow rate of 5 g / h) was continuously introduced for stirring and washing. The pH was monitored online. When the pH dropped below 3.8, 1.0 mol / L NaOH solution was automatically added. The pH of the system increased by 0.5-1 every 15 min, and the final pH was controlled at 8.0. Washing continued for another 120 min.

[0067] Comparative Example 7 The difference between Comparative Example 7 and Example 1 is that the detergent in the S3 washing process does not contain AEO-9, while the other conditions and steps are the same as in Example 1.

[0068] Specifically, in Comparative Example 67, S3 was as follows: 1 kg of cooled calcined product was mixed evenly and fed into an oxidation washing reactor (equipped with an ozone aeration device, online pH monitoring and automatic alkali dripping device, and a stirrer). 5 L of hydrogen peroxide solution (10% concentration) was added, followed by 2.0 mol / L dilute sulfuric acid to adjust the initial pH of the system to 4.5. A washing aid (10 g SDBS + 5 g sodium citrate) was added, and ozone (flow rate of 5 g / h) was continuously introduced for stirring and washing. The pH was monitored online. When the pH dropped below 3.8, 1.0 mol / L NaOH solution was automatically added. The pH of the system increased by 0.5-1 every 15 min, and the final pH was controlled at 8.0. Washing continued for another 120 min.

[0069] Comparative Example 8 The difference between Comparative Example 8 and Example 1 is that the detergent in the S3 washing process does not contain sodium citrate, while the other conditions and steps are the same as in Example 1.

[0070] Specifically, in Comparative Example 8, S3 was as follows: 1 kg of cooled calcined product was mixed evenly and fed into an oxidative washing reactor (equipped with an ozone aeration device, online pH monitoring and automatic alkali dripping device, and a stirrer). 5 L of hydrogen peroxide solution (10% concentration) was added, followed by 2.0 mol / L dilute sulfuric acid to adjust the initial pH of the system to 4.5. A washing aid (10 g SDBS + 3 g AEO-9) was added, and ozone (flow rate of 5 g / h) was continuously introduced for stirring and washing. The pH was monitored online. When the pH dropped below 3.8, 1.0 mol / L NaOH solution was automatically added. The pH of the system increased by 0.5-1 every 15 min, and the final pH was controlled at 8.0. Washing continued for another 120 min.

[0071] The carbon removal rate, sulfur removal rate, base metal (taking iron as an example) removal rate, and precious metal loss rate of the methods in Examples 1 to 6 and Comparative Examples 1 to 8 were measured. The results are shown in Table 1. Five parallel replicates were set up for each example. The data are in the form of mean ± standard deviation.

[0072] Carbon removal rate (%) = (carbon content before treatment - carbon content after treatment) / carbon content before treatment × 100%; Sulfur removal rate (%) = (Sulfur content before treatment - Sulfur content after treatment) / Sulfur content before treatment × 100%; Base metal iron removal rate (%) = (Iron content before treatment - Iron content after treatment) / Iron content before treatment × 100%; Precious metal loss rate (%) = (1 - precious metal content after treatment / precious metal content before treatment) × 100% The carbon content was determined by elemental analysis, the sulfur content by inductively coupled plasma atomic emission spectrometry, and the content of precious metals (Pd, Pt, Rh, etc.) was determined by inductively coupled plasma mass spectrometry.

[0073] Table 1

[0074] Note: If the precious metal loss rate is ≤0.1%, it will be marked as " / ".

[0075] Table 1 shows that the decarbonization and desulfurization treatment of waste automotive catalysts in this embodiment of the invention achieved a carbon removal rate >95% and a sulfur removal rate >90%, indicating significant decarbonization and desulfurization effects, while the loss rate of precious metals was ≤0.1%. In addition, the removal rate of base metals (taking iron as an example) was >80%, which greatly reduced the adverse effects of base metals on subsequent precious metal recovery. It is foreseeable that the process flow and steps for recovering precious metals from waste automotive catalysts treated by this invention alone are greatly simplified, effectively reducing costs.

[0076] Compared with Example 1, the low-temperature calcination in Comparative Example 1 was carried out in an oxygen-free environment. The results showed that although the precious metal loss rate was ≤0.1%, the carbon removal rate, sulfur removal rate and iron removal rate were all reduced, especially the carbon removal rate and sulfur removal rate dropped sharply.

[0077] Compared with Example 1, the low-temperature calcination in Comparative Example 2 only used ozone-containing air for aerobic calcination. The results showed that although the sulfur removal rate and iron removal rate only decreased slightly, the carbon removal rate decreased significantly, and the precious metal loss rate was >1.5%.

[0078] Compared with Example 1, the aerobic calcination in Comparative Example 3 used only air. The results showed that although the iron removal rate decreased only slightly, the carbon removal rate and sulfur removal rate decreased significantly, and the precious metal loss rate was >1.0%.

[0079] Compared with Example 1, the calcination temperature in Comparative Example 4 was increased. The results showed that although the carbon removal rate, sulfur removal rate and iron removal rate decreased very little, the carbon removal rate and sulfur removal rate decreased significantly, and the precious metal loss rate was >2.0%.

[0080] Compared with Example 1, the oxidation washing process in Comparative Example 5 was carried out in an acidic environment. The results showed that although the loss rate of precious metals was ≤0.1%, the carbon removal rate was almost unchanged, and the iron removal rate increased slightly, the sulfur removal rate dropped sharply.

[0081] Compared with Example 1, the detergent additives or some components were removed in Comparative Examples 6 to 8. The results showed that although the loss rate of precious metals was ≤0.1%, the removal rates of carbon deposits and sulfur were reduced to a certain extent, and the removal rate of some iron dropped sharply.

[0082] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A pretreatment method for desulfurization and decarbonization in the recycling of waste automotive catalysts, characterized in that, The method includes the following steps: S1. Waste automotive catalysts are pretreated to obtain waste catalyst particles with a water content of ≤5%; S2. The spent catalyst particles were successively calcined at low temperatures in an inert atmosphere and an ozone-containing aerobic atmosphere, at temperatures of 300℃~500℃. After calcination, they were cooled to room temperature to initially remove carbon deposits and sulfides, and the calcined product was obtained. S3. The calcined product is subjected to oxidative washing. The washing reagent for oxidative washing includes an oxidant and a washing aid. The oxidant is ozone and hydrogen peroxide. The washing aid includes sodium dodecylbenzenesulfonate, fatty alcohol polyoxyethylene ether, and sodium citrate. During the oxidative washing process, a pH adjuster is added to gradually increase the pH of the system to 7.5~9.

0. S4. Solid-liquid separation, cleaning, and drying are performed to obtain the desulfurized and decarbonized waste catalyst.

2. The pretreatment desulfurization and decarbonization method for recycling waste automotive catalysts according to claim 1, characterized in that, Specifically, S3 is: Hydrogen peroxide solution and detergent were added to the calcined product, and ozone was continuously introduced to adjust the initial pH of the system to 4.0~5.5 before washing began. During the washing process, the pH of the system is monitored online. When the pH of the system drops to 3.5-4, alkali is added every 10-20 minutes to raise the pH of the system by 0.5-1.0 until the pH of the system is 7.5-9.

0.

3. The pretreatment desulfurization and decarbonization method for recycling waste automotive catalysts according to claim 2, characterized in that, The concentration of the hydrogen peroxide solution is 3%~15%, and the ratio of hydrogen peroxide solution to calcined product is (2~6) mL: 1g calcined product; the amount of ozone introduced is 3g / h~10g / h.

4. The pretreatment desulfurization and decarbonization method for recycling waste automotive catalysts according to claim 2, characterized in that, Based on the mass of the calcined product, the amount of sodium dodecylbenzenesulfonate is 0.5%~1.5%, the amount of fatty alcohol polyoxyethylene ether is 0.2%~0.8%, and the amount of sodium citrate is 0.3%~0.8%. The mass ratio of sodium dodecylbenzenesulfonate to fatty alcohol polyoxyethylene ether is (2~4):

1.

5. The pretreatment desulfurization and decarbonization method for recycling waste automotive catalysts according to claim 2, characterized in that, The oxidation washing is performed in an ultrasonic field with a frequency of 20kHz to 80kHz and a power density of 0.5W / cm². 2 ~5W / cm 2 .

6. A pretreatment desulfurization and decarbonization method for recycling waste automotive catalysts according to claim 2 or 5, characterized in that, During the oxidation washing process, once the system pH reaches 7.5~9.0, the washing continues for 1h~3h.

7. The pretreatment desulfurization and decarbonization method for recycling waste automotive catalysts according to claim 1, characterized in that, S2 specifically includes: S21. Place the waste catalyst particles in a calcination furnace and heat them to 300℃~500℃ under an inert atmosphere for 10min~30min; the inert atmosphere is nitrogen or argon. S22. Switch from an inert atmosphere to an ozone-containing aerobic atmosphere and continue calcining at 300℃~500℃ for 30min~60min. S23. After calcination, the ozone-containing aerobic atmosphere is switched to high-purity nitrogen for continuous purging, and the furnace is naturally cooled to room temperature.

8. The pretreatment desulfurization and decarbonization method for recycling waste automotive catalysts according to claim 7, characterized in that, An ozone-containing aerobic atmosphere is a mixture of ozone and air, with an ozone concentration of 50 ppm to 200 ppm.

9. The pretreatment desulfurization and decarbonization method for recycling waste automotive catalysts according to claim 7, characterized in that, The flow rates of the inert atmosphere in S21 and the ozone-containing aerobic atmosphere in S22 are 100 mL / min to 300 mL / min; the flow rate of the high-purity nitrogen in S23 is 50 mL / min to 240 mL / min.

10. The pretreatment desulfurization and decarbonization method for recycling waste automotive catalysts according to claim 1, characterized in that, S1 specifically includes: S11. Collect waste automotive catalyst carriers; S12. Crush the carrier to 20mm~50mm, then remove impurities by magnetic separation and grind. Add deionized water during the grinding process. The mass ratio of particulate matter to water is 10:1~2. S13. Dry at 80℃~100℃ and sieve through 80-120 mesh to obtain waste catalyst particles with a moisture content ≤5%.

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