Recycling of catalyst coating film components

Abstract

1. A method for recycling a spent catalyst coated membrane material comprising an ionomer membrane, at least one catalyst comprising platinum, palladium and / or ruthenium, and at least one catalyst comprising iridium, the method comprising: (a) treating the spent catalyst coated membrane material with a heated solution comprising an acid and an oxidizing agent, whereby the platinum, palladium and / or ruthenium are leached from the spent catalyst coated membrane material into the solution and the solution is separated from the remaining solid components of the spent catalyst coated membrane material; (b) treating the spent catalyst coated membrane material with a solvent to disperse the ionomer membrane and recover a dispersion of ionomer, whereby the dispersion of ionomer occurs before or after leaching of the platinum, palladium and / or ruthenium; and (c) treating the spent catalyst coated membrane material to extract iridium.

Description

Technical Field

[0001] This specification relates to a method for recycling components of a catalytic coating film, such as those used in fuel cells and hydrogen-producing water electrolyzers.

Background Art

[0002] As investments are made in a global hydrogen economy, the production of fuel cells and hydrogen-producing water electrolyzers is set to grow rapidly. Catalytic coating films (CCMs) are a major functional component of both fuel cells and electrolyzers. Such CCMs generally include a conductive polymer membrane coated on both sides by a catalyst-containing layer. The CCM is configured to drive oxidation and reduction reactions and carry proton and electron transport, and these processes are required for fuel cell and electrolyzer technologies to function.

[0003] The materials and configurations of CCM components vary according to the functional performance requirements in the end use, but they generally contain several useful components including one or more platinum group metal (PGM) catalysts and one or more proton-conductive polymers.

[0004] Typically, the membrane is formed from one or more ionomers such as perfluorosulfonic acid (PFSA) ionomers. The ionomer may also be provided on one or both of the catalyst layers. The ionomer in the catalyst layer may be the same as or different from the ionomer in the main membrane component and / or other catalyst layers.

[0005] The CCM can include two different catalysts, one for driving oxidation reactions on one side of the CCM and one for driving reduction reactions on the other side of the CCM. The CCM may also include a recombination catalyst provided to catalyze the recombination of hydrogen and oxygen to form water, reduce the amount of hydrogen passing through the membrane, and mix with oxygen to form a potentially explosive mixture. The CCM may also include a metal oxide (e.g., CeO2) as a peroxide scavenger.

[0006] CCM catalysts can be based on platinum group metals such as platinum, ruthenium, iridium, palladium, or mixtures thereof. Platinum group metals may be provided in elemental (metallic) form, compound form (e.g., oxides such as iridium oxide catalysts), or PGM-based metal alloys (e.g., PtCo). Furthermore, the PGM catalyst material may be supported on a substrate material (e.g., carbon such as a platinum-supported carbon catalyst or PtCo-supported carbon containing carbon particles on which platinum is arranged).

[0007] A catalyst coating (CCM) can also be provided in combination with additional functional layers to form a multilayer electrode assembly (MEA). Such an MEA may have, for example, 3, 5, or 7 layers.

[0008] With the increasing production of CCMs for fuel cells and electrolytic cells, there is also a corresponding increase in CCM waste material, including the large amount of scrap material generated during CCM production (e.g., due to quality control failures), as well as an increase in end-of-life (EoL) CCMs. Since CCMs contain several rare and / or valuable components, including platinum group metals (particularly Pt, Pd, Ir, and Ru) and ionomers (in both membrane and catalyst layers), there is a growing demand for methods to recycle such components from waste CCM materials.

[0009] One current method for recovering PGMs from production scrap and end-of-life CCM materials involves incineration. The incineration process produces PGM-rich (typically Pt and Ir) ash that is processed through conventional PGM refining routes. However, the incineration process releases harmful and toxic gases such as CO2 and HF from the polymers that are part of the membrane. Both of these gases have adverse effects as they pollute the atmosphere, increase the greenhouse effect, and / or have harmful effects on human health. Therefore, cleaner processes that reduce or eliminate the release of these gases are needed.

[0010] In addition to the above, incineration methods destroy ionomer components, which are of equally important value. Therefore, it is desirable to provide a process that can recover both PGMs and ionomer components, as well as a cleaner, safer, and more environmentally friendly process. Processes for recovering perfluorosulfonic acid ionomers are publicly known; see, for example, International Publication No. 2016 / 156815 and U.S. Patent No. 7255798. Furthermore, processes for recovering individual PGM catalyst components are known; see, for example, U.S. Patent No. 7709135. However, in order to enable fuel cells and electrolytic cells to become more sustainable technologies, there is a need for commercially viable and environmentally friendly routes for recovering, separating, and recycling both PGMs and ionomer components from waste CCM materials, including production scrap and end-of-life materials.

[0011] The purpose of this specification is to address this problem. [Overview of the project]

[0012] According to one aspect of this specification, a method for recycling a waste catalyst coating material comprising an ionomer film, at least one catalyst comprising platinum, palladium and / or ruthenium, and at least one catalyst comprising iridium, wherein the method is (a) The spent catalyst coating material is treated with a heated solution containing an acid and an oxidizing agent, wherein platinum, palladium and / or ruthenium are leached from the spent catalyst coating material into the solution, and the solution is separated from the remaining solid components of the spent catalyst coating material. (b) Treating the spent catalyst coating material with a solvent to disperse an ionomer film and recovering the ionomer dispersion, wherein the ionomer dispersion is performed before or after the leaching of platinum, palladium, and / or ruthenium. (c) Below: (i) After leaching of platinum, palladium and / or ruthenium and dispersion of the ionomer, the remaining solid iridium-containing catalyst material is separated from the ionomer dispersion, and (ii) Extracting iridium by treating the spent catalyst coating material with iridium by using a heated solution containing an acid and a reducing agent to leach iridium from the spent catalyst coating material, separating the solution containing the leached iridium from the remaining solid components of the spent catalyst coating material, wherein the iridium leaching is performed either before or after the leaching of platinum, palladium and / or ruthenium, or both.

[0013] The acid used for iridium leaching and / or platinum, palladium, and / or ruthenium leaching, either or both, is optionally hydrochloric acid and optionally does not contain nitric acid. Furthermore, either or both of the solutions used for platinum, palladium, and / or ruthenium leaching and / or iridium leaching are preferably heated to a temperature within the range defined by at least 50°C, 60°C, or 70°C; 160°C, 100°C, or 90°C or less; or any combination of the aforementioned lower and upper limits, and if the solution is heated above 100°C, this is done in a pressurized vessel. Examples of ranges include 50-100°C or 70-90°C. The solution is heated to increase the leaching rate of the PGM.

[0014] The oxidizing agent may include, for example, a chlorate such as a sodium chlorate solution or chlorine gas. According to one preferred option, the acid used in the leaching of platinum, palladium, and / or ruthenium is hydrochloric acid, and the oxidizing agent is chlorine gas produced in situ from hydrochloric acid electrolytically. The oxidizing agent may be added to the hydrochloric acid solution or produced in situ after heating to the aforementioned temperature. Alternatively, the oxidizing agent may be added in multiple aliquots during heating. For example, the oxidizing agent may be added in a series of aliquots during heating up to a total concentration in the range of 0.01 to 0.10 mol / L. The solution for the leaching of platinum, palladium, and / or ruthenium may have an acid concentration of 4 M or more, 5 M or more, or 5.5 M or more, 7 M or less, 6.5 M or less, or 6 M or less; or within the range defined by any combination of the aforementioned lower and upper limits.

[0015] The separation of the leached solution containing platinum, palladium, and / or ruthenium can be achieved by filtration or centrifugation. The separated solution may be concentrated by boiling the solution to a suitable platinum concentration for further processing. Alternatively, the leachate can be recycled to leach platinum, palladium, and / or ruthenium from further spent catalyst coating material, and the recycling is repeated as needed until a suitable or target concentration of platinum is reached. The platinum, palladium, and / or ruthenium-containing leachate is then further processed to extract platinum, palladium, and / or ruthenium from the acidic solution using known techniques. The remaining solid components of the spent catalyst coating material can be processed separately.

[0016] One advantage of the aforementioned process is that it achieves high recovery yields for platinum, palladium, and / or ruthenium. For example, at least 80%, 85%, 90%, or 95% by weight of platinum in the spent catalyst coating can be recovered.

[0017] Another advantage of the aforementioned process is that, using these conditions, fluorine is not substantially leached from the fluoropolymer film into the leachate. This is advantageous for two reasons. Firstly, the ionomer remains intact and can be recycled separately. Secondly, fluorine leaching into an acidic leachate can lead to the formation of HF, which can pose serious environmental health and safety risks as well as damage to downstream processing equipment. Therefore, avoiding HF formation provides a safer and more environmentally friendly process.

[0018] Another advantage of the process described above is that, for CCMs containing both platinum, palladium, and / or ruthenium catalysts and iridium oxide catalysts (which are useful combinations of catalysts for the cathode and anode catalysts, respectively, in hydrogen-producing water electrolyzers), the leaching conditions are selective for platinum, palladium, and / or ruthenium, and do not leach iridium to a significant degree. Therefore, this process represents an efficient method for separating platinum, palladium, and / or ruthenium from other components of such waste CCMs, while leaving the remaining CCM components intact and processing them separately.

[0019] Iridium (which may be in the form of iridium oxide, mixed iridium oxide, or supported iridium oxide) can be extracted separately using a leaching solution or by either dispersing the ionomer and separating the remaining solid iridium-containing catalyst material (e.g., by filtration or centrifugation). When leaching is used, it differs from the leaching used for platinum, palladium, and / or ruthenium. In particular, a reducing agent (e.g., selected from one of hydrazine, NaBH4, and ammonium oxalate) rather than an oxidizing agent is used for iridium leaching. Furthermore, an acid solution, such as an HCl solution, may also be more concentrated for iridium leaching compared to leaching for platinum, palladium, and / or ruthenium. For example, the acid used for iridium leaching may be 6M, 7M, or 8M or higher, 15M or lower, 12M or lower, or 10M or lower, or within a range defined by any combination of the aforementioned lower and upper limits (e.g., in the range of 8M to 12M).

[0020] The leaching steps for platinum, palladium, and / or ruthenium, as well as the extraction of iridium and the dispersion of the ionomer material as described above, can be integrated into several different process flows for recycling various components of waste CCM material. These various process flows will be further described in the detailed description. A key feature of all process flows is that they can achieve the recovery of all PGM and ionomer components. [Brief explanation of the drawing]

[0021] For a better understanding of the present invention and to show how the present invention can be implemented, specific embodiments of the present invention are described by way of example only with reference to the accompanying drawings. [Figure 1] Shows a waste CCM recycling process including iridium leaching followed by platinum leaching. [Figure 2] Shows a waste CCM recycling process including platinum leaching followed by iridium leaching. [Figure 3] Shows a waste CCM recycling process in which the platinum leaching step is carried out before the ionomer dispersion step. [Figure 4] Shows a waste CCM recycling process in which an ionomer dispersion step is carried out before the platinum leaching step (and / or before the iridium leaching step). [Figure 5-1] Shows a waste CCM recycling process that can follow the process flow of FIG. 3 or FIG. 4, where the catalyst layer is first separated from the bulk polymer membrane by mechanical means or chemical delamination before further treatment of the catalyst layer material by the process flow of FIG. 3 or FIG. 4. [Figure 5-2] Shows a waste CCM recycling process that can follow the process flow of FIG. 3 or FIG. 4, where the catalyst layer is first separated from the bulk polymer membrane by mechanical means or chemical delamination before further treatment of the catalyst layer material by the process flow of FIG. 3 or FIG. 4. [Figure 5-3] Shows a waste CCM recycling process that can follow the process flow of FIG. 3 or FIG. 4, where the catalyst layer is first separated from the bulk polymer membrane by mechanical means or chemical delamination before further treatment of the catalyst layer material by the process flow of FIG. 3 or FIG. 4.

Embodiments for Carrying Out the Invention

[0022] As described in the Summary of the Invention section, according to one aspect of the present specification, a method for recycling a waste catalyst-coated film material including an ionomer film, at least one catalyst including platinum, palladium and / or ruthenium, and at least one catalyst including iridium, the method comprises (a) treating the waste catalyst-coated film material with a heated solution containing an acid and an oxidizing agent, wherein platinum, palladium and / or ruthenium are leached from the waste catalyst-coated film material into the solution and the solution is separated from the remaining solid components of the waste catalyst-coated film material, (b) treating the waste catalyst-coated film material with a solvent to disperse the ionomer film and recovering a dispersion of the ionomer, wherein the dispersion of the ionomer is carried out before or after the leaching of platinum, palladium, and / or ruthenium, (c) the following: (i) separating the remaining solid iridium-containing catalyst material from the dispersion of the ionomer after the leaching of platinum, palladium and / or ruthenium and the dispersion of the ionomer, and (ii) using a heated solution containing an acid and a reducing agent to leach iridium from the waste catalyst-coated film material, separating the solution containing the leached iridium from the remaining solid components of the waste catalyst-coated film material, and treating the waste catalyst-coated film material to extract iridium by one or both of the iridium leaching being carried out before or after the leaching of platinum, palladium and / or ruthenium.

[0023] The steps of the method can be performed in any order to recover Pt, Ir, and the ionomer. That is, Pt-Ir-ionomer; Ir-Pt-ionomer; ionomer-Pt-Ir; ionomer-Ir-Pt; Pt-ionomer-Ir; or Ir-ionomer-Pt.

[0024] The following explanation will focus on examples involving platinum catalysts and iridium-based catalysts (e.g., IrOx). However, the same method can be used if the platinum catalyst is replaced with a palladium catalyst, a ruthenium catalyst, a mixed PGM catalyst containing at least two combinations of platinum, palladium, and ruthenium, or a catalyst containing at least one PGM and at least one base metal (e.g., PtCo).

[0025] The acid used for iridium leaching and / or platinum leaching is optionally hydrochloric acid. Furthermore, one or both of the solutions used for platinum and iridium leaching are preferably heated to a temperature within the range defined by at least 50°C, 60°C, or 70°C; 160°C, 100°C, or 90°C or lower; or any combination of the aforementioned lower and upper limits, and if the solution is heated above 100°C, this is done in a pressurized vessel. The oxidizing agent for platinum leaching may include, for example, a chlorate such as a sodium chlorate solution or chlorine gas (e.g., produced electrolytically in situ). The oxidizing agent can be added to the hydrochloric acid solution after it has been heated to the above temperatures. The solution may contain concentrated HCl, for example, about 6 M HCl.

[0026] The separation of the solution containing leached platinum can be achieved by filtration. The separated solution may be concentrated by boiling the solution to a suitable PGM concentration for further processing. Alternatively, the leachate can be recycled to leach platinum from further spent catalyst coating material, and the recycling is repeated as needed until the target concentration of PGM is reached. The PGM-containing leachate is then further processed to extract platinum from the acidic solution using known techniques. The remaining solid components of the spent catalyst coating material can be processed separately.

[0027] This method further includes a step of extracting iridium from the spent catalyst coating. This can be achieved by leaching Ir species from the spent catalyst coating via a reductive dissolution process using an acid (such as 8-12 M HCl) and a reducing agent (such as hydrazine, NaBH4, or ammonium oxalate) to obtain an Ir-containing acidic solution. International Publication No. 2021083758 describes several examples of such processes for the dissolution of Ir in a reducing HCl environment. Since the aforementioned oxidative acidic platinum leaching does not leach iridium to a significant degree, such a reductive acidic leaching process step for iridium can be carried out after the oxidative acidic leaching step for platinum. However, it is also conceivable that iridium leaching can be carried out before platinum leaching. Therefore, the route proposed according to this embodiment is a two-step process, as shown in Figures 1 and 2, which includes the selective leaching of Ir and Pt species from waste CCM without requiring incineration or other destructive treatment. The steps are as follows and can be carried out in any order. 1. Ir species are leached out through a reduction and dissolution process using an acid (such as HCl) and a reducing agent (such as hydrazine), yielding an Ir-containing acidic solution and CCM / undissolved PGM residue. 2. By leaching of Pt species through an oxidative dissolution process using an acid (such as HCl) and an oxidizing agent (such as chlorate or Cl2), a Pt-containing acidic solution and CCM / undissolved PGM residue are obtained.

[0028] The liquids produced from steps 1 and 2 can then be directed to their respective purification processes (if significant impurities are present) or used directly as precursors for new catalyst materials. The CCM residue can then be further leached to remove any remaining PGM species, and the resulting ionomer residue can then be recycled.

[0029] This process selectively recovers PGMs directly from waste CCM. The treated CCM also remains largely unchanged, allowing for a further simple recovery process for the remaining components of the waste CCM (e.g., ionomers). Thus, this process provides a complete recovery and recycling route for both PGMs and ionomers. The two-step process, including Pt and Ir leaching, allows for a simple and rapid route to separate and recover both Ir and Pt, with the possibility of directly feeding the metal solution back into the catalyst manufacturing process. Since it is estimated that approximately 800 kOzt Pt and 160 kOzt Ir will be needed for fuel cell and electrolytic cell CCM by 2040, the compact and bespoke nature of the process reduces lead times and increases metal fluidity. This process enables the creation of a closed-loop cycle for scrap CCM material, not only PGMs but also ionomers. This process also enables open-loop recycling of end-of-life CCM.

[0030] Instead of leaching iridium from the solid ionomer material as described above, the iridium (or iridium oxide) material can be separated from the ionomer by dispersing the ionomer. In this case, platinum can be leached from the waste CCM as previously mentioned, and then the remaining waste CCM containing the solid ionomer and iridium species can be subjected to the ionomer dispersion to obtain a slurry containing the ionomer dispersion with the solid iridium species present. The ionomer dispersion can be separated from the solid iridium species using solid / liquid separation (e.g., filtration or centrifugation) to obtain an ionomer dispersion for recycling. The remaining solid iridium material may be reused directly in the CCM manufacturing process or purified before reuse. Alternatively, the ionomer can be dispersed before platinum leaching to obtain a mixed PGM residue for further processing.

[0031] Such a process is shown in Figure 3. The CCM material may first need to be shredded to the size required for the process. The CCM material can then be subjected to an HCl / oxidizing agent (e.g., chlorine) treatment to leach platinum and, optionally, ruthenium if present in the CCM. The liquid from this treatment can then be processed to remove base metals such as nickel and cobalt (e.g., using a cation exchange resin), and Ru can be removed via distillation or other processes, and then Pt can be recovered by directly adding it to the Pt purification process stream. The remaining CCM pieces from the leaching can undergo a process that includes heating / autoclaving the material in a solvent (e.g., an alcohol solvent) to disperse the ionomer. The ionomer dispersion can then be separated from the Ir-containing solid by filtration or centrifugation. The ionomer dispersion can then proceed to further processing, be recycled and returned to produce new CCM as either pure or blended material. Examples of processes for recycling perfluorosulfonic acid ionomers are described in U.S. Patent No. 7,255,798 and International Publication No. 2016 / 156815. Due to its inherent stability, the Ir catalyst can be reused without further processing, or the Ir solid can be purified to recover the Ir metal.

[0032] In the process described above, the platinum leaching step is performed before the ionomer dispersion step. However, alternatively, ionomer dispersion is performed before the platinum leaching step. Such an alternative configuration is illustrated in Figure 4. As previously mentioned, waste CCM can first be shredded to the required size. The CCM scrap pieces can then be heated to a high temperature in a solvent (e.g., an alcohol solvent) and optionally autoclaved to disperse the CCM components. Solid / liquid separation is performed on the resulting slurry (e.g., by filtration or centrifugation). The solution contains the dispersed ionomer, which is then further processed and recycled back to produce new CCM. The PGM residue may be dried to ensure complete removal of the organic solvent before undergoing the HCl / chlorine leaching treatment as described above. The liquid from the leaching can be processed to remove base metals such as Ni and / or Co (e.g., cation exchange resins), and Ru can be removed (e.g., via a distillation process), and then the remaining platinum-containing solution can be fed into the Pt purification process stream to recover Pt as described above. The residue from the leaching process still contains the Ir catalyst, which remains largely unchanged due to its stability. This allows the Ir catalyst material (e.g., IrOx) to be processed for direct reuse, or the residue can be purified to recover the Ir.

[0033] As mentioned in the background section, the CCM may contain ionomers in one or both of the catalyst layers, as well as in the membrane on which the catalyst layers are arranged. While the process flow described above can be applied to intact membrane and catalyst layer structures, it is also conceivable that the catalyst layers can be separated from the membrane so that the membrane can be separated from the catalyst layers for processing. Such a modified process flow is shown in Figure 5. The first step of this modified process includes separating the catalyst layers from the ePTFE membrane using mechanical means such as sonication or electrostatic fracturing, or by chemical exfoliation. The sonication method may include immersing the CCM material in an alcohol-water mixture and sonicating it for a period of time that the catalyst layers are separated and dispersed in the solvent. The ePTFE pieces can be separated and the solvent removed from the catalyst layer material. Once the membrane and catalyst layers are cleanly separated, the ePTFE membrane can be further processed to recover the ionomer components. There are two options for recovering the PGM and ionomers in the catalyst layer, as shown in Figure 5 and described below.

[0034] Process Option A: The catalyst layer material can be subjected to HCl / oxidizing agent (e.g., chlorine) treatment to leach platinum. The liquid from this treatment can then be purified from base metals (e.g., using cation exchange resin), undergo Ru removal via distillation or other processes, and then enter directly into the Pt purification stream. The remaining Ir-containing residue from leaching can undergo a process including heating / autoclaving the material in an alcohol solvent to dissolve / disperse the ionomer. The ionomer dispersion is separated from the Ir-containing solution by filtration or centrifugation (alternatively, Ir can be leached before or after ionomer dispersion). The ionomer dispersion then proceeds to further processing, is recycled and returned to produce a new CCM. The Ir-containing residue can be processed for direct reuse of the Ir catalyst, or the residue can be purified to recover the Ir metal. This process route is similar to that shown in Figure 3.

[0035] Process Option B: Alternatively, the catalyst layer material can be heated to a high temperature in an alcohol solvent and optionally autoclaved to disperse the CCM components. The resulting slurry then undergoes solid / liquid separation by either filtration or centrifugation. The supernatant / filtrate, containing the dispersed ionomer, can then be further processed and recycled to produce new CCM. The PGM residue is dried to ensure complete removal of the organic solvent before being subjected to an HCl / chlorine leaching treatment. The liquid from this leaching treatment is then purified from base metals (e.g., using a cation exchange resin), undergoes Ru removal via a distillation process, and can then be directly entered into the Pt purification stream. The residue from the leaching process still contains the Ir catalyst, which remains largely unchanged due to its stability. This can then be processed for direct reuse of the Ir catalyst, or the residue can be purified to recover the Ir metal. This process route is similar to that shown in Figure 4.

[0036] A common feature of all the CCM recycling processes described above is the use of oxidative acid leaching to extract platinum (and / or palladium and / or ruthenium) material from the ionomer dispersion, and the extraction of iridium via either reductive leaching or solid-liquid separation after extraction of the platinum and ionomer dispersions. Pt leaching can be applied before or after dispersing the ionomer, and before or after iridium leaching. In Figure 1, the process sequence is: (i) iridium leaching; (ii) platinum leaching; (iii) processing of the remaining ionomer film. In Figure 2, the process sequence is: (i) platinum leaching; (ii) iridium leaching; (iii) processing of the remaining ionomer film. In Figures 3, 4 and 5, iridium leaching is not required to separate iridium from the ionomer. Rather, the iridium-containing material is separated from the ionomer material by dispersing the ionomer material and removing the ionomer using solid / solution separation. The platinum leaching step can be performed before the ionomer dispersion step, as shown in Figure 3. Alternatively, the ionomer dispersion step can be performed before the platinum leaching step, as shown in Figure 4. Figure 5 shows both options in the process of initially separating the catalyst layer from the bulk polymer film.

[0037] The specific method used depends on the operator's requirements, the demand for components, and the desired form of the material recovered by the process. For example, if it is desirable to extract a certain component early in the recycling process, for example, due to a shortage of that particular component, an appropriate process flow can be selected to obtain the desired component early in the process rather than retaining a significant amount of the component for a long period of time within the recycling process. For example, if it is desirable to recover platinum rapidly, the process in Figure 2, in which platinum leaching is performed first, may be selected. Alternatively, if it is desirable to recover the bulk ionomer early in the process, the process in Figure 5 may be selected, as the initial step of removing the catalyst layer from the bulk ionomer film ensures that the bulk ionomer film can be rapidly recovered and processed, while the ionomer and PGM in the catalyst layer are subjected to further processing for various separation steps. Or, if it is desirable to recover a specific form of material, such as iridium oxide catalyst material, for reuse rather than iridium-containing leaching, an appropriate process flow can be selected to obtain the material in the desired form. For example, if you want to directly recover iridium-based / inducible catalysts for reuse, you can avoid iridium leaching processes like those in Figures 1 and 2, and directly recover solid iridium-based catalyst material (e.g., IrOx) using one of the routes shown in Figures 3 to 5.

[0038] Methods for recovering ionomers are described in U.S. Patent No. 7,255,798 and International Publication No. 2016 / 156815, and such methods can be incorporated into the process flow of this specification as described above. As described in the background art section, different ionomers can often be used in one or both of the catalyst layers compared to the ionomer in the bulk film. The selection of different ionomers can provide improved performance in the end application. It is also possible to use a blend of ionomers or to have layers of different ionomers within the bulk polymer film. In such cases, the process flow in Figure 5 may be useful for separating the bulk polymer film from the catalyst layer at the start of the process flow. When different ionomers are used in the catalyst layer compared to the bulk film, such separation may be useful for separating the different ionomers before further processing. [Examples]

[0039] CCM-HCl / chlorate leachate - single-use leachate solution A method has been developed to leach PGMs from CCM manufacturing scrap. The recovered PGM material is then purified using existing PGM purification processes. Such processes have strict limitations on the fluorine content (<1%) of the PGM material introduced into the PGM purification process. Since CCM is made primarily from fluoropolymers, this has been identified as a potential problem for leaching PGMs from waste CCM material. The leaching process of the present invention is such that PGMs can be leached without introducing a significant amount of fluorine into the leachate.

[0040] Pt was dissolved from CCM using an HCl / chlorate solution. Ir was in oxide form in CCM, and no significant amount of Ir leached out, allowing for the separation of Pt and Ir. Chlorates were introduced in the form of a sodium chlorate solution added using a peristaltic pump.

[0041] 8.56 g of fuel cell CCM (cut into approximately 2 cm x 3 cm pieces) was placed in a container. 400 mL of 6 M HCl (a solution prepared from concentrated HCl and distilled H2O) was added to the flask, and the stirring speed was set to 250 rpm. The reaction mixture was heated to 70°C. A slight yellow color was observed in the solution during heating.

[0042] 4 mL of NaClO3 solution (450 g / L) was added at a rate of approximately 0.09 mL / min. After the addition of the NaClO3 solution was complete, the reaction mixture was cooled to room temperature. The reaction mixture was filtered through 0.45 μm filter paper. This yielded a yellow solution (365 mL). The liquid was collected, and the remaining CCM fragments were washed with distilled H2O (86 mL). The CCM fragments were removed and dried in the air overnight on a watch glass.

[0043] Approximately 931 mg of Pt and 136 mg of Ir were present in 8.56 g of CCM. IC / ICP analysis showed the presence of trace amounts of Ir in the leachate, indicating that the leaching conditions did not cause significant leaching of Ir. 926 mg of Pt leached into the solution, and an additional 27 mg leached into the washing solution. A total of approximately 953 mg of Pt was recovered, giving a recovery rate of 102%. However, the results are reasonable due to a + / - 10% error in the initial Pt addition amount and errors in the analysis. Analysis of the untreated CCM showed that approximately 11 mg of Pt remained. Therefore, the Pt recovery rate was 98% by weight. The solution also showed undetectable amounts of fluoride, indicating that the leaching conditions did not destroy the ionomers in the CCM.

[0044] CCM-HCl / chlorate leaching - multiple uses of the leaching solution This embodiment uses the leaching process corresponding to that described in the previous embodiment. However, in this case, the liquid from the leaching was reused multiple times with a fresh batch of CCM and the addition of chlorate, and it was shown that the liquid could be concentrated in this manner. In this regard, it should be noted that a more concentrated Pt solution is advantageous for improving the efficiency of the subsequent Pt purification process.

[0045] For each leaching cycle, the initial CCM weight, liquid volume before and after leaching, washing volume, and residual CCM weight were measured.

[0046] The general method for each cycle was to load CCM pieces (cut into 2cm x 3cm pieces) into a container with HCl / recycle solution. Before cycles 3 and 5, the solution was filled with fresh 6M HCl (a solution made from concentrated HCl and distilled H2O). The mixture was stirred at 250 rpm and heated to 70°C. 3 mL of NaClO3 solution (450 g / L) was added at a rate of approximately 0.09 mL / min. 45 minutes after the start of addition, the reaction mixture was cooled to <30°C. The reaction mixture was filtered through 0.45 μm cellulose filter paper to obtain a yellow liquid, which became darker in color over the cycles. The remaining CCM pieces were washed with distilled H2O, dried in air overnight, and then recorded by weight. A summary of each leaching cycle is shown below.

[0047] Cycle 1 CCM fragment before exudation: 9.96g HCl / solution before leaching: 400 mL (fresh 6M HCl) Extract after exudation: 385 mL Washing solution: 89 mL Residual CCM piece: 9.00g

[0048] Cycle 2 CCM fragment before exudation: 9.98g HCl / solution before leaching: 375 mL Extract after exudation: 365 mL Washing solution: 88mL Residual CCM piece: 9.06g

[0049] Cycle 3 CCM fragment before exudation: 10.00g HCl / solution before leaching: 400 mL (355 mL is refilled with fresh 6M HCl up to 400 mL) Extracted liquid: 390 mL Washing solution: 115 mL Residual CCM piece: 9.06g

[0050] Cycle 4 CCM fragment before exudation: 9.98g HCl / solution before leaching: 375 mL Extract after exudation: 365 mL Washing solution: 87mL Residual CCM piece: 9.04g

[0051] Cycle 5 CCM fragment before exudation: 9.98g HCl / solution before leaching: 460 mL (360 mL solution is replenished with fresh 6M HCl) Extract after exudation: 445 mL Washing solution: 85mL Residual CCM piece: 9.04g

[0052] Cycle 6 CCM fragment before exudation: 9.98g HCl / solution before leaching: 435 mL Extract after exudation: 425 mL Washing solution: 102 mL Residual CCM piece: 8.90g

[0053] Cycle 7 CCM fragment before exudation: 9.99g HCl / solution before leaching: 415 mL Extract after exudation: 405 mL Washing solution: 99 mL Residual CCM piece: 8.97g

[0054] Cycle 8 CCM fragment before exudation: 10.00g HCl / solution before leaching: 395 mL Extract after exudation: 385 mL Washing solution: 77 mL Residual CCM piece: 9.05g

[0055] Between each cycle, a 10 mL sample of the liquid was taken for analysis, thus measuring the decrease in liquid volume between cycles.

[0056] The results are shown in the table below. It is noteworthy that while the weight percentage of Pt recovered in the liquid decreased from the initial value of 95% by weight over multiple cycles, the Pt recovery rate remained at 83% by weight even after reusing the same leachate for 8 cycles.

[0057] [Table 1]

[0058] [Table 2]

[0059] [Table 3]

[0060] [Table 4]

[0061] [Table 5]

[0062] Therefore, it has been shown that this method can be used to recover Pt from waste CCM material without damaging the ionomer material of the CCM or without introducing fluorine into the Pt treatment stream for subsequent Pt purification. It has also been shown that Pt can be leached from waste CCM material without also leaching iridium, and thus Pt and Ir can be separated and recovered for reuse. Thus, it is possible to recover Pt, Ir, and ionomer components (and optionally ruthenium, if present) using this method.

[0063] Iridium recovery Iridium can be recovered using a reductive leaching process. For example, it has been demonstrated that iridium can be leached from IrOx catalyst materials by refluxing a leaching solution containing a hydrazine reducing agent and 8-12 M HCl for approximately 5 hours. It should be noted that the iridium leaching process is not as efficient as the platinum leaching process described above. Thus, the recovery rate of iridium can be increased by utilizing repeated leaching cycles.

[0064] The reducing agent can be provided in an acidic leaching solution. Alternatively, the spent catalyst coating material can be pre-treated with a reducing agent before being leached in an acidic leaching solution for iridium extraction. In this method, CCM scrap, or PGM residue from a CCM recycling process, is subjected to treatment with a reducing agent (such as hydrazine, sodium borohydride, or ammonium oxalate) in water as a solvent. This reduces the Ir catalyst to a lower oxidation state, which is then subjected to high-temperature (e.g., 70-105°C for 5-6 hours) high-concentration HCl (e.g., 12M HCl) to obtain an Ir solution. The mixture is cooled to room temperature, the residual CCM and fine particles are filtered out, washed with water, and dried for further processing to recover other PGM catalysts and residual components such as ionomers.

[0065] To increase the recovery rate of Ir, the residue may be subjected to the above reaction conditions in a repeated process. The resulting Ir solution can then be evaluated to determine whether any separation method is necessary to isolate the Ir species via conventional purification methods and / or to isolate Ir in a desired form (e.g., Ir chloride salt, Ir metal).

[0066] This process leaves the majority of the CCM residue unchanged, allowing for further processing to recover other components such as ionomers and other catalysts for recycling.

[0067] The above method can be applied to pure IrOx material, PGM residue formed from a CCM recycling process aimed at recovering the ionomer first, or alternative PGM residue containing a mixture of IrOx with other PGM catalysts and impurities. This method can also be carried out in a sealed container (i.e., under pressure).

[0068] Additionally or alternatively, residual IrOx catalyst can be recovered after dispersing the ionomer via a liquid-solid extraction process. Combining the two methods (Ir leaching and solid / liquid Ir-catalyst separation) can ensure that virtually all iridium is recovered.

[0069] Various different process flows, including this leaching method, can be used to recover the Pt, Ir, and ionomer components described herein. Although the present invention has been specifically illustrated and described with reference to certain examples, it will be understood by those skilled in the art that various modifications in form and detail can be made without departing from the scope of the invention as defined by the appended claims.

Claims

1. A method for recycling a waste catalyst coating material comprising an ionomer film, at least one catalyst containing platinum, palladium and / or ruthenium, and at least one catalyst containing iridium, wherein the method is: (a) The spent catalyst coating material is treated with a heated solution containing an acid and an oxidizing agent, wherein platinum, palladium and / or ruthenium are leached from the spent catalyst coating material into the solution, the solution is separated from the remaining solid components of the spent catalyst coating material, and the remaining solid components contain iridium-containing catalyst material. (b) Treating the waste catalyst coating material with a solvent to disperse the ionomer film and recovering the ionomer dispersion, wherein the dispersion of the ionomer is performed before or after the leaching of the platinum, palladium, and / or ruthenium. (c) Below: (i) After the leaching of platinum, palladium and / or ruthenium and the dispersion of the ionomer, the iridium-containing catalyst material contained in the remaining solid components is separated from the dispersion of the ionomer, and (ii) Leaving iridium from the waste catalyst coating material using a heated solution containing an acid and a reducing agent, and separating the solution containing the leached iridium from the remaining solid components of the waste catalyst coating material, wherein the iridium leaching is performed before or after the leaching of platinum, palladium and / or ruthenium. A method comprising treating the waste catalyst coating material with one or both of the following to extract iridium.

2. The method according to claim 1, wherein the acid used in either or both of the iridium leaching and the platinum, palladium, and / or ruthenium leaching is hydrochloric acid.

3. The method according to claim 1, wherein one or both of the solutions used for the leaching of platinum, palladium and / or ruthenium and the solutions used for the leaching of iridium are heated to a temperature within the range defined by at least 50°C, 60°C, or 70°C; 160°C, 100°C, or 90°C or less; or any combination of the aforementioned lower and upper limits, and if the solutions are heated above 100°C, this is done in a pressurized vessel.

4. The method according to claim 1, wherein the oxidizing agent comprises a chlorate or chlorine gas.

5. The method according to claim 1, wherein the acid used for the leaching of platinum, palladium and / or ruthenium is hydrochloric acid, and the oxidizing agent is chlorine gas electrolytically generated in situ from the hydrochloric acid.

6. The method according to claim 1, wherein the oxidizing agent is added to the acid, or generated in the acid after heating the acid, to form the heated solution containing the acid and the oxidizing agent.

7. The method according to claim 1, wherein the oxidizing agent is added to the acid or generated in the acid in multiple aliquots during heating to form the heated solution containing the acid and the oxidizing agent.

8. The method according to claim 1, wherein the oxidizing agent is added to the acid or generated within the acid in the heated solution containing the acid and the oxidizing agent, so that the total concentration of the oxidizing agent in the heated solution is in the range of 0.01 to 0.10 mol / L.

9. The method according to claim 1, wherein the solution for leaching platinum, palladium and / or ruthenium may have an acid concentration of 4 M or more, 5 M or more, or 5.5 M or more, 7 M or less, 6.5 M or less, or 6 M or less; or any combination of the aforementioned lower and upper limits.

10. The method according to claim 1, wherein the solution containing the leached platinum, palladium, and / or ruthenium is separated from the remaining solid components of the waste catalyst coating material, and the solution is concentrated by boiling.

11. The method according to claim 1, wherein the solution containing the leached platinum, palladium, and / or ruthenium is separated from the remaining solid components of the waste catalyst coating material, and the solution is reused to leach platinum, palladium, and / or ruthenium from further waste catalyst coating material.

12. The method according to claim 1, wherein the platinum, palladium and / or ruthenium are leached from the waste catalyst coating material before the ionomer is dispersed.

13. The method according to claim 1, wherein the platinum, palladium and / or ruthenium disperse the ionomer and leach out of the spent catalyst coating material after separating the solvent containing the ionomer from the remaining solid components of the spent catalyst coating material.

14. The method according to claim 1, wherein the spent catalyst coating material comprises a film and two catalyst layers disposed on both sides of the film, and the spent catalyst coating material is treated to remove the catalyst layers from the film before further processing the catalyst layers according to the method according to any one of claims 1 to 13.

15. The method according to claim 1, wherein the catalyst containing iridium is iridium oxide or mixed iridium oxide.

16. The reducing agent is hydrazine, NaBH ４ The method according to claim 1, wherein one of the following is selected: and ammonium oxalate.

17. The method according to claim 1, wherein the heated solution containing the acid and the reducing agent may have an acid concentration within the range defined by 6 M, 7 M, or 8 M or more; 15 M or less, 12 M or less, or 10 M or less; or any combination of the aforementioned lower and upper limits.

18. The method according to claim 1, wherein the reducing agent is provided in the acid to form the heated solution containing the acid and the reducing agent for extracting iridium, or the spent catalyst coating material is pretreated with the reducing agent before being leached with the acid to form the heated solution containing the acid and the reducing agent for extracting iridium.

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