A method for recycling waste platinum catalyst

Abstract

The present invention relates to the technical field of recycling and regenerating key materials for hydrogen fuel cells, and specifically to a method for recycling and regenerating spent platinum catalysts. The method comprises the following steps: ball milling the spent platinum catalyst, adding a pore-forming agent, performing a hydrothermal reaction, calcining, and washing to remove the pore-forming agent to obtain a pretreated material. The material is then sand milled, added with chloroplatinic acid, and calcined to obtain a regenerated platinum catalyst that can be directly used in hydrogen fuel cell applications. The method features a short process flow, low carbon emissions, and is economical and environmentally friendly.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogen fuel cell key material recovery, and in particular to a method for recovering and regenerating waste platinum catalysts. Background Art

[0002] A hydrogen fuel cell consists of a fuel cell stack, a hydrogen supply and circulation system, an air supply system, a water and heat management system, and an electronic control system. The fuel cell stack, in turn, comprises bipolar plates, a proton exchange membrane, a catalyst, and a gas diffusion layer. The proton exchange membrane is a core component of a hydrogen fuel cell, currently primarily a perfluorosulfonic acid membrane. The catalyst is a key fuel cell material, currently primarily composed of platinum (Pt / C). The catalyst is bonded to the perfluorosulfonic acid membrane with an adhesive, and the gas diffusion layer, also known as a membrane electrode, is then used.

[0003] However, during hydrogen fuel cell service, platinum, due to its small particle size (~30nm), is susceptible to agglomeration, surface carbon accumulation, and poisoning, leading to catalyst deactivation and membrane electrode failure, ultimately causing the fuel cell to retire. The membrane electrode, a core component of retired hydrogen fuel cells, contains not only platinum but also various contaminants such as fluorine, sulfur, and carbon. Improper handling can lead to environmental pollution and resource waste. Therefore, the recycling of spent hydrogen fuel cell components, particularly the rare metal platinum, is imperative.

[0004] Currently, most platinum recovery technologies, both domestically and internationally, rely on hydrometallurgy, which involves dissolving the platinum metal using an acid and an oxidizing agent, followed by a series of processes such as impurity removal and precipitation to recover the platinum. For example, patent CN1114362A discloses a method for recovering platinum from platinum-containing catalysts. This method uses a platinum-based catalyst supported on a carrier such as γ-Al2O3 or SiO2-Al2O3 as the raw material. After calcination, oxidative leaching, anion separation, and purification, high-purity sponge platinum is obtained. Patent CN100348749C discloses a method for recovering platinum and rhenium from spent catalysts. This method uses spent catalysts containing platinum and rhenium on a porous carrier containing alumina as the raw material. A series of processes, including alkaline solution leaching, reduction with a reducing agent, filtration, and adsorption with anionic resins, allows for efficient recovery of platinum. Patent 200910133892.1 discloses a method for recovering platinum from nanostructured fuel cell catalysts. This method involves exposing the nanostructured fuel cell catalyst material to an acidic oxidizing solution to oxidize and dissolve the platinum metal particles. The platinum metal particles are then converted to platinum salts for leaching and calcination to obtain metallic platinum. The acidic oxidizing solution typically contains at least one acid and at least one oxidizing agent, and the curing agent can be, for example, hydrogen peroxide. Patent 201711313215.9 discloses a method for recycling spent fuel cells. This method involves disassembling the spent fuel cells to obtain membrane electrodes, which are then immersed in an organic solution to remove the membrane. Finally, the filter residue is roasted in air to dissolve and obtain platinum metal.

[0005] According to relevant literature, while platinum recovery can be achieved using the aforementioned methods, hydrometallurgical techniques require high acid consumption, multiple steps, and the recovered product is mostly platinum metal, with carbonaceous components converted to CO₂ or waste slag. Direct calcination in oxygen also yields platinum metal, but carbonaceous components are converted to CO₂, increasing carbon emissions. Platinum metal requires dissolution, impregnation, and calcination to produce a platinum-based catalyst, a complex process that undoubtedly increases catalyst preparation costs. Summary of the Invention

[0006] To address the above technical issues, the present invention, based on practical industrial production and the resource recycling of waste materials, utilizes a combination of liquid-phase grinding and solid-phase calcination to rationally introduce and remove pore-forming factors, allowing the added platinum ions to enter the newly formed pore structure and be reduced to form platinum atoms, thereby regenerating and reusing waste platinum catalysts. Furthermore, the carbon-containing organic matter, such as the adhesive, in the waste materials described in the present invention exists as amorphous carbon under a protective atmosphere; the carbon material contained remains in its original state. Ball milling and sand milling before and after calcination reduce the interfacial bonding between particles of different materials, facilitating the preparation of the regenerated catalyst and the optimization of its catalytic performance. The entire process is short and amenable to industrial production, achieving economical and environmentally friendly recycling.

[0007] To achieve the above-mentioned purpose, an embodiment of the present invention provides a method for recycling and regenerating a waste platinum catalyst, the method comprising the following steps:

[0008] S1: The waste platinum catalyst is ball-milled, a pore-forming agent is added, and the catalyst is placed in a reactor for hydrothermal reaction. The catalyst is then dried, calcined, and washed to remove the pore-forming agent, thereby obtaining a pretreated material.

[0009] S2: sand-grinding the pretreated material to obtain a sand-grinding slurry; adding chloroplatinic acid to the sand-grinding slurry, and calcining to obtain a regenerated platinum catalyst.

[0010] Furthermore, in the method for recycling and regenerating a waste platinum catalyst, the waste platinum catalyst comes from one or a combination of two or more of the waste slurry generated when the platinum-carbon catalyst is mixed with the proton exchange membrane, the waste membrane electrode generated during the production process, and the waste hydrogen fuel cell.

[0011] Furthermore, in the method for recycling and regenerating waste platinum catalysts, the ball milling solvent is one or a mixture of two or more of water, methanol, ethanol, propanol, butanol, enol and derivatives of the above alcohols.

[0012] Furthermore, in the method for recovering and regenerating a waste platinum catalyst, the pore-forming agent is one of a metal salt, oxide, or hydroxide, preferably one of a salt, oxide, or hydroxide of sodium, potassium, aluminum, manganese, or magnesium; further preferably one of NaCl, KCl, Al2O3, Al(OH)3, AlCl3, MgCl2, Al(NO3)3, Al2(SO4)3, MnO2, and MnCO3.

[0013] Furthermore, in the method for recycling and regenerating waste platinum catalyst, the Al2O3, MnO2, and MnCO3 are preferably nanometer-sized.

[0014] Furthermore, in the method for recycling and regenerating waste platinum catalyst, the hydrothermal reaction temperature is 150-240° C., and the reaction time is 8-26 hours.

[0015] Furthermore, in the method for recycling and regenerating waste platinum catalyst, the calcination temperature is 300-800°C, the calcination time is 0.5-10h, and the calcination atmosphere is one or a combination of two or more of argon, nitrogen, hydrogen, and helium.

[0016] Furthermore, in the method for recovering and regenerating a waste platinum catalyst, the washing solvent is one of water and an acid; the acid is preferably one of HCl, H2SO4, HNO3, and H3PO4.

[0017] Furthermore, in the method for recycling and regenerating waste platinum catalyst, the sand milling solvent is one or a mixture of two or more of water, methanol, ethanol, propanol, butanol, and enol, the sand milling speed is 2000-20000 r / min, and the sand milling time is 1-12 h.

[0018] Furthermore, in the method for recycling and regenerating waste platinum catalyst, the solid content of the sand-grinding slurry is 5-40%.

[0019] Furthermore, in the method for recycling and regenerating waste platinum catalyst, the amount of chloroplatinic acid added is 0.01-10% of the solid content of the sand-grinding slurry.

[0020] Beneficial Effects: The present invention achieves the recycling of platinum metal from waste platinum catalysts without requiring dissolution, impregnation, or calcination, and the entire process produces no wastewater or waste acid. Simply by adding the missing platinum element, waste materials can be recycled while ensuring perfect catalyst performance, resulting in a short process flow and high economic added value. The addition of a pore-forming agent causes the carbon in the waste to form a porous structure, providing storage space for the newly added platinum. Furthermore, the carbon materials and carbon-containing organic components in the waste are converted into carbon carriers through calcination and pore formation, enabling the recycling of carbon in the waste, reducing CO2 or waste residue emissions, and achieving environmentally friendly solid waste resource recycling. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a process flow of a waste platinum catalyst recovery and regeneration method of the present invention;

[0022] Figure 2 This is the SEM of the regenerated platinum / carbon catalyst obtained in Example 1;

[0023] Figure 3 The LSV diagram of hydrogen evolution of the regenerated platinum / carbon catalyst obtained for Example 1;

[0024] Figure 4 The hydrogen evolution LSV plot of the regenerated platinum / carbon catalyst was obtained for Example 6. DETAILED DESCRIPTION

[0025] To facilitate understanding of the present invention, the present invention will be described more fully below with reference to the accompanying drawings. The accompanying drawings illustrate preferred embodiments of the present invention. However, the present invention may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the present disclosure.

[0026] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly attached to the other element or there may be an intermediate element. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or there may be an intermediate element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only implementation methods.

[0027] An embodiment of the present invention provides a method for recycling and regenerating a waste platinum catalyst, the method comprising the following steps:

[0028] S1: The waste platinum catalyst is ball-milled, a pore-forming agent is added, and the catalyst is placed in a reactor for hydrothermal reaction. The catalyst is then dried, calcined, and washed to remove the pore-forming agent, thereby obtaining a pretreated material.

[0029] S2: sand-grinding the pretreated material to obtain a sand-grinding slurry; adding chloroplatinic acid to the sand-grinding slurry, and calcining to obtain a regenerated platinum catalyst.

[0030] Furthermore, in the method for recycling and regenerating a waste platinum catalyst, the waste platinum catalyst comes from one or a combination of two or more of the waste slurry generated when the platinum-carbon catalyst is mixed with the proton exchange membrane, the waste membrane electrode generated during the production process, and the waste hydrogen fuel cell.

[0031] Furthermore, in the method for recycling and regenerating waste platinum catalysts, the ball milling solvent is one or a mixture of two or more of water, methanol, ethanol, propanol, butanol, enol and derivatives of the above alcohols.

[0032] Furthermore, in the method for recovering and regenerating a waste platinum catalyst, the pore-forming agent is one of a metal salt, oxide, or hydroxide, preferably one of a salt, oxide, or hydroxide of sodium, potassium, aluminum, manganese, or magnesium; further preferably one of NaCl, KCl, Al2O3, Al(OH)3, AlCl3, MgCl2, Al(NO3)3, Al2(SO4)3, MnO2, and MnCO3.

[0033] Furthermore, in the method for recycling and regenerating waste platinum catalyst, the Al2O3, MnO2, and MnCO3 are preferably nanometer-sized.

[0034] Furthermore, in the method for recycling and regenerating waste platinum catalyst, the hydrothermal reaction temperature is 150-240° C., and the reaction time is 8-26 hours.

[0035] Furthermore, in the method for recycling and regenerating waste platinum catalyst, the calcination temperature is 300-800°C, the calcination time is 0.5-10h, and the calcination atmosphere is one or a combination of two or more of argon, nitrogen, hydrogen, and helium.

[0036] Furthermore, in the method for recovering and regenerating a waste platinum catalyst, the washing solvent is one of water and an acid; the acid is preferably one of HCl, H2SO4, HNO3, and H3PO4.

[0037] Furthermore, in the method for recycling and regenerating waste platinum catalyst, the sand milling solvent is one or a mixture of two or more of water, methanol, ethanol, propanol, butanol, and enol, the sand milling speed is 2000-20000 r / min, and the sand milling time is 1-12 h.

[0038] Furthermore, in the method for recycling and regenerating waste platinum catalyst, the solid content of the sand-grinding slurry is 5-40%.

[0039] Furthermore, in the method for recycling and regenerating waste platinum catalyst, the amount of chloroplatinic acid added is 0.01-10% of the solid content of the sand-grinding slurry.

[0040] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0041] Example 1

[0042] Waste hydrogen fuel cells are disassembled and separated to obtain waste membrane electrodes. A mixture of water and methanol in a mass ratio of 1:1 is added to the waste membrane electrodes, filtered, dried, and then ball-milled in a ball mill for 6 hours. The mixture is then removed, Al(OH)3 added, and placed in a reactor, heated, and held at 240°C for 8 hours. The mixture is filtered and dried to obtain a calcined material. The calcined material is placed in a tubular furnace and held at 300°C for 6 hours under a high-purity argon atmosphere to obtain a calcined material. The calcined material is placed in an HCl solution, stirred, filtered, and dried. A slurry with a solid content of 40% is prepared using water as the solvent and sand-milled at a speed of 20,000 r / min to obtain a calcined sand-milled slurry. Chloroplatinic acid, at 10% of the solid content of the sand-milled slurry, is added to the calcined sand-milled slurry, and calcined to obtain a regenerated platinum catalyst.

[0043] Example 2

[0044] The waste slurry generated when the platinum-carbon catalyst is mixed with the proton exchange membrane is added with water, stirred, filtered, dried, and then placed in a ball mill for 2 hours. Then, it is taken out and placed in a reactor after adding NaCl, heated, kept warm at 220°C for 10 hours, filtered, and dried to obtain the material to be calcined. The material to be calcined is placed in a tubular furnace and kept warm at 400°C for 2 hours under a high-purity argon atmosphere to obtain the calcined material. The calcined material is placed in water, stirred, filtered, and dried. Then, water and methanol are used as a mixed solvent to prepare a slurry with a solid content of 25%, which is sand-milled at a speed of 12,000 r / min to obtain the sand-milled slurry to be calcined. Chloroplatinic acid at 0.01% of the solid content of the sand-milled slurry is added to the sand-milled slurry to be calcined, and calcined to obtain a regenerated platinum catalyst.

[0045] Example 3

[0046] Waste hydrogen fuel cells are disassembled and separated to obtain spent membrane electrodes. A mixture of water and anhydrous ethanol at a mass ratio of 5:1 is added to the spent membrane electrodes, filtered, dried, and then ball-milled in a ball mill for 10 hours. The mixture is then removed, added with MnCO₃, placed in a reactor, heated, and held at 200°C for 12 hours. The mixture is then filtered and dried to obtain a calcined material. The calcined material is placed in a tube furnace and held at 400°C for 1 hour under a high-purity argon atmosphere to obtain a calcined material. The calcined material is then placed in an H₃PO₄ solution, stirred, filtered, and dried. A 30% solids slurry is then prepared using butanol as a solvent and sand-milled at 13,000 rpm to obtain a calcined slurry. Chloroplatinic acid, equivalent to 8% of the slurry's solids content, is added to the calcined slurry, and calcined to obtain a regenerated platinum catalyst.

[0047] Example 4

[0048] The waste slurry generated when the platinum-carbon catalyst is mixed with the proton exchange membrane is added with ethanol, stirred, filtered, dried, and then placed in a ball mill for 2 hours. Then, it is taken out and placed in a reactor after adding Al(OH)3, heated, kept warm at 180°C for 20 hours, filtered, and dried to obtain the material to be calcined. The material to be calcined is placed in a tubular furnace and kept warm at 300°C for 10 hours under a high-purity argon atmosphere to obtain the calcined material. The calcined material is placed in an H2SO4 solution, stirred, filtered, and dried. Then, using enol as a solvent, a slurry with a solid content of 15% is prepared and sand-milled at a speed of 8000 r / min to obtain the sand-milled slurry to be calcined. Chloroplatinic acid at 0.5% of the solid content of the sand-milled slurry is added to the sand-milled slurry to be calcined, and calcined to obtain a regenerated platinum catalyst.

[0049] Example 5

[0050] The waste membrane electrodes generated during the production process are shredded, mixed with butanol, stirred, filtered, dried, and then ball-milled in a ball mill for 1 hour. The mixture is then removed, Al(OH)3 added, and placed in a reactor, heated, and held at 150°C for 26 hours. The mixture is then filtered and dried to obtain the calcined material. The calcined material is placed in a tube furnace and held at 350°C for 3 hours under a high-purity argon atmosphere to obtain the calcined material. The calcined material is then placed in an H2SO4 solution, stirred, filtered, and dried. A 20% solids slurry is prepared using ethanol as the solvent and sand-milled at 10,000 rpm to obtain the calcined slurry. Chloroplatinic acid, at a concentration of 4% of the slurry's solids, is added to the calcined slurry, and calcined to obtain the regenerated platinum catalyst.

[0051] Example 6

[0052] Scrapped membrane electrodes from decommissioned hydrogen fuel cells were shredded and mixed with water and anhydrous ethanol in a mass ratio of 1:2. The mixture was then added to the shredded membrane electrodes, filtered, and dried to obtain a calcined material. The calcined material was placed in a tube furnace and heated at 800°C for 0.5 hours under a high-purity argon atmosphere to obtain a calcined material. The calcined material was then ball-milled in a jar for 2 hours. The calcined material was then removed, added with AlCl₃, and placed in a reactor. The mixture was heated and held at 200°C for 8 hours, filtered, dried, and then placed in H₂O, stirred, filtered, and dried. A 10% solids slurry was then prepared using ethanol as the solvent and sand-milled at 6000 rpm to obtain a calcined slurry. Chloroplatinic acid (1% of the slurry's solids content) was added to the calcined slurry and calcined to obtain a regenerated platinum catalyst.

[0053] Example 7

[0054] Scrapped membrane electrodes from discarded hydrogen fuel cells are shredded and mixed with water and propanol in a mass ratio of 1:5. The mixture is then added to the shredded membrane electrodes, filtered, and dried to obtain a calcined material. The calcined material is placed in a tube furnace and kept at 300°C for 5 hours under a high-purity argon atmosphere to obtain a calcined material. The calcined material is then ball-milled in a jar for 2 hours, removed, added with KCl, and placed in a reactor. The mixture is heated and kept at 180°C for 15 hours, filtered, dried, and then placed in HNO3, stirred, filtered, and dried. A 5% solids slurry is then prepared using water as the solvent and sand-milled at 20,000 rpm to obtain a sand-milled slurry to be calcined. Chloroplatinic acid, equivalent to 2% of the sand-milled slurry solids content, is added to the calcined sand-milled slurry and calcined to obtain a regenerated platinum catalyst.

[0055] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0056] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A method for recycling and regenerating waste platinum catalyst, characterized in that: The method comprises the following steps S1: liquid-phase ball milling the waste platinum catalyst, adding a pore-forming agent, and placing the waste platinum catalyst in a reactor for hydrothermal reaction, drying, roasting, and washing to remove the pore-forming agent to obtain a pretreated material; S2: sand-milling the pretreated material in liquid phase to obtain a sand-milled slurry; adding chloroplatinic acid to the sand-milled slurry and calcining the slurry to obtain a regenerated platinum catalyst; By combining liquid-phase grinding with solid-phase calcination, pore-forming factors are rationally introduced and removed, allowing the added platinum ions to enter the new pore-forming structure and be reduced to form platinum atoms; The waste platinum catalyst comes from one or a combination of two or more of the waste slurry generated when the platinum-carbon catalyst is mixed with the proton exchange membrane, the waste membrane electrode generated during the production process, and the waste hydrogen fuel cell.

2. The method according to claim 1, characterized in that The ball milling solvent is one of water, methanol, ethanol, propanol, butanol, or a mixture of two or more thereof.

3. The method according to claim 1, characterized in that The pore-forming agent is one of metal salts, oxides and hydroxides.

4. The method according to claim 1, characterized in that The hydrothermal reaction temperature is 150-240°C, and the reaction time is 8-26h.

5. The method according to claim 1, characterized in that The calcination temperature in step S1 is 300-800°C, the calcination time is 0.5-10h, and the calcination atmosphere is one or a combination of two or more of argon, nitrogen, hydrogen, and helium.

6. The method according to claim 1, wherein The washing solvent is one of water and acid; the acid is one of HCl, H2SO4, HNO3, and H3PO4.

7. The method according to claim 1, characterized in that The sand milling solvent is one of water, methanol, ethanol, propanol, butanol, or a mixture of two or more thereof; the sand milling speed is 2000-20000 r / min; and the sand milling time is 1-12 h.

8. The method according to claim 1, characterized in that , the solid content of the sand grinding slurry is 5-40%.

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