Recycling of catalyst coated membrane components

Abstract

A method of recycling a spent catalyst coated membrane material, the membrane material comprising an ionomer, 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, wherein platinum, palladium and / or ruthenium are leached from the spent catalyst coated membrane material into the solution, the solution being 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 ionomers, wherein the dispersion of the ionomers is performed before or after the leaching of the platinum, palladium and / or ruthenium; and (c) treating the spent catalyst coated membrane material to extract iridium.

Description

Technical Field

[0001] The present description relates to methods for recycling components for catalyst coated membranes, such as those used in fuel cells and hydrogen producing water electrolyzers. Background Art

[0002] With the investment in the global hydrogen economy, the production of fuel cells and hydrogen-producing water electrolyzers will grow rapidly. Catalyst coated membranes (CCMs) are the main functional components of both fuel cells and electrolyzers. Such CCMs generally include a conductive polymer membrane coated with a catalyst layer on either side. CCMs are configured to drive oxidation and reduction reactions and support proton and electron transport, which are required for fuel cells and electrolysis technologies to function.

[0003] While variations in CCM component materials and configurations exist depending on functional performance requirements in end-use applications, they generally contain several valuable components including one or more platinum group metal (PGM) catalysts and one or more proton conducting polymers.

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

[0005] The CCM may contain two different catalysts, one for driving the oxidation reaction on one side of the CCM and one for driving the reduction reaction on the other side of the CCM. The CCM may also contain a recombination catalyst provided to catalyze the recombination of hydrogen and oxygen to form water, thereby reducing the amount of hydrogen that passes through the membrane and mixes with oxygen to form a potentially explosive mixture. The CCM may also contain a metal oxide (e.g., CeO2) as a peroxide scavenger.

[0006] The CCM catalyst may be based on a platinum group metal, such as platinum, ruthenium, iridium, palladium or mixtures thereof. The platinum group metal may be provided in elemental (metal) form, in compound form (e.g., oxide, such as iridium oxide catalyst) or as a PGM-based metal alloy (e.g., PtCo). In addition, the PGM catalyst material may be supported on a substrate material (e.g., carbon, such as a carbon-supported platinum catalyst comprising carbon particles with platinum disposed thereon or carbon-supported PtCo).

[0007] Catalyst coated membranes (CCMs) can also be provided in combination with additional functional layers to form multilayer membrane electrode assemblies (MEAs). Such MEAs can have, for example, 3, 5 or 7 layers.

[0008] With the increase in the manufacture of CCMs for fuel cells and electrolyzers, there has been an associated increase in CCM waste, including large amounts of waste formed during CCM manufacture (e.g., due to quality control failures) and 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 the membrane and catalyst layers), there is a growing need for methods to recycle such components from spent CCM materials.

[0009] A current method for recovering PGMs from production waste and end-of-life CCM materials involves incineration. The incineration process produces an ash rich in PGMs (typically Pt and Ir), which is processed via conventional PGM refining routes. However, the incineration process releases harmful and toxic gases, such as CO2 and HF, from the polymer that is part of the membrane. Both of these gases have negative effects because they pollute the atmospheric environment, increase the greenhouse effect and / or have harmful effects on the human body. Therefore, a clean process that reduces or eliminates the emission of these gases is needed.

[0010] In addition to the above, the incineration method destroys the ionomer component, which is also of great value. Therefore, it is also desirable to provide a process that can recycle both PGM and ionomer components and to provide a cleaner, safer and more environmentally friendly process. The process for recovering perfluorosulfonic acid ionomers is known. See, for example, WO2016 / 156815 and US7255798. In addition, the process for recovering each PGM catalyst component is known. For example, see US7709135. However, in order to enable fuel cells and electrolyzers to become more sustainable technologies, commercially viable and environmentally friendly routes are needed to recover, separate and recycle both PGM and ionomer components from waste CCM materials (including production waste and end-of-life materials).

[0011] The purpose of this specification is to solve this problem. Summary of the invention

[0012] According to one aspect of the present specification, there is provided a method of 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:

[0013] (a) treating the spent catalyst coated membrane material with a heated solution comprising an acid and an oxidant, wherein platinum, palladium and / or ruthenium is 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;

[0014] (b) treating the spent catalyst coated membrane material with a solvent to disperse the ionomer membrane and recovering a dispersion of the ionomer, wherein the dispersion of the ionomer is performed before or after leaching of the platinum, palladium and / or ruthenium; and

[0015] (c) treating the spent catalyst coated membrane material to extract iridium by one or both of the following:

[0016] (i) after leaching of the platinum, palladium and / or ruthenium and dispersion of the ionomer, separating the remaining solid iridium-containing catalyst material from the dispersion of ionomer; and

[0017] (ii) leaching iridium from the spent catalyst coated membrane material using a heated solution comprising an acid and a reducing agent, and separating the solution comprising the leached iridium from the remaining solid components of the spent catalyst coated membrane material, wherein the leaching of iridium is performed before or after the leaching of platinum, palladium and / or ruthenium.

[0018] The acid used in one or both of the iridium leaching and the platinum, palladium and / or ruthenium leaching is optionally hydrochloric acid and optionally does not contain nitric acid. In addition, it is preferred that one or both of the solutions used for the leaching of platinum, palladium and / or ruthenium and the leaching of iridium are heated to a temperature of at least 50°C, 60°C or 70°C; not more than 160°C, 100°C or 90°C; or within a range defined by any combination of the above lower and upper limits, wherein if the solution is heated to above 100°C, this is carried out in a pressurized vessel. Exemplary ranges include 50°C to 100°C or 70°C to 90°C. The solution is heated to increase the leaching rate of the PGM.

[0019] The oxidant may include, for example, a chlorate, such as a sodium chlorate solution or chlorine. According to a preferred option, the acid used in the leaching of platinum, palladium and / or ruthenium is hydrochloric acid, and the oxidant is chlorine generated in situ electrolysis from hydrochloric acid. The oxidant may be added to the hydrochloric acid solution or generated in situ after heating to the above temperature. Alternatively, the oxidant may be added in multiple aliquots during heating. For example, the oxidant may be added in a series of aliquots during heating to a total concentration in the range of 0.01 mol / l to 0.10 mol / l. The solution for leaching of platinum, palladium and / or ruthenium may have the following acid concentration: not less than 4M, 5M or 5.5M; not more than 7M, 6.5M or 6M; or within the range defined by any combination of the above lower and upper limits.

[0020] Separation of the solution containing the leached platinum, palladium and / or ruthenium can be achieved via filtration or centrifugation. The separated solution can be concentrated to a suitable platinum concentration for further processing by boiling the solution. Alternatively, the leachate can be recycled to leach platinum, palladium and / or ruthenium from additional spent catalyst coated membrane material, thereby repeating the recycling as needed until a suitable or target concentration of platinum is reached. The leachate containing platinum, palladium and / or ruthenium is then further processed using known techniques to extract platinum, palladium and / or ruthenium from the acidic solution. The remaining solid components of the spent catalyst coated membrane material can be processed separately.

[0021] One advantage of the above process is that it achieves high recovery rates for platinum, palladium and / or ruthenium. For example, at least 80 wt%, 85 wt%, 90 wt% or 95 wt% of the platinum in the spent catalyst coated membrane can be recovered.

[0022] Another advantage of the above process is that substantially no fluorine is leached from the fluoropolymer membrane into the leachate using these conditions. This is advantageous for two reasons. First, the ionomer remains intact and can be recycled separately. Second, fluorine leaching into the acidic leachate can result in the formation of HF, which can result in serious environmental health and safety risks and damage to downstream processing equipment. Therefore, avoiding HF formation provides a safer and more environmentally friendly process.

[0023] Another advantage of the above process 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 catalyst and anode catalyst, respectively, of a hydrogen-producing water electrolyzer, the leaching conditions are selective for platinum, palladium and / or ruthenium and do not leach iridium to any significant extent. Thus, the process represents an efficient way to separate platinum, palladium and / or ruthenium from other components of such spent CCMs while keeping the remaining CCM components intact for separate treatment.

[0024] Iridium (which may be in the form of iridium oxide, mixed iridium oxide or supported iridium oxide) may be extracted separately using a leaching solution or via dispersion of an ionomer and separation of the remaining solid iridium-containing catalyst material (e.g., via filtration or centrifugation). If a leacher is used, this is different from the leacher used for the leaching of platinum, palladium and / or ruthenium. In particular, a reducing agent (e.g., one selected from hydrazine, NaBH4 and ammonium oxalate) rather than an oxidant is used for iridium leaching. In addition, when compared with the leaching for platinum, palladium and / or ruthenium, an acid solution (e.g., HCl solution) may also be more concentrated for iridium leaching. For example, the acid used for iridium leaching may be: not less than 6M, 7M or 8M; not more than 15M, 12M or 10M; or within the range defined by any combination of the above lower and upper limits (e.g., within the range of 8M to 12M).

[0025] The leaching steps for platinum, palladium and / or ruthenium and the steps for extracting iridium and dispersing ionomer materials as described above can be integrated into many different process flows for recycling the various components of the spent CCM material. These various process flows are further described in the detailed description. The key feature of all process flows is that they can achieve the recovery of all PGM and ionomer components. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to better understand the invention and to show how it may be carried into effect, certain embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0027] Figure 1 The spent CCM recycling process is shown, including iridium leaching followed by platinum leaching;

[0028] Figure 2 The spent CCM recycling process is shown, including platinum leaching followed by iridium leaching;

[0029] Figure 3 A spent CCM recycling process is shown, wherein a platinum leaching step is performed before the ionomer dispersion step;

[0030] Figure 4 A spent CCM recycling process is shown wherein an ionomer dispersion step is performed prior to a platinum leaching step (and / or prior to an iridium leaching step); and

[0031] Figure 5 It shows that it can be Figure 3 or Figure 4 The waste CCM recycling process after the treatment process, but in which Figure 3 or Figure 4 The processing flow is to first separate the catalyst layer from the bulk polymer membrane by mechanical processes or chemical delamination before further processing the catalyst layer material. DETAILED DESCRIPTION

[0032] As described in the Summary of the Invention section, according to one aspect of the present specification, there is provided 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:

[0033] (a) treating the spent catalyst coated membrane material with a heated solution comprising an acid and an oxidant, wherein platinum, palladium and / or ruthenium is 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;

[0034] (b) treating the spent catalyst coated membrane material with a solvent to disperse the ionomer membrane and recovering a dispersion of the ionomer, wherein the dispersion of the ionomer is performed before or after leaching of the platinum, palladium and / or ruthenium; and

[0035] (c) treating the spent catalyst coated membrane material to extract iridium by one or both of the following:

[0036] (i) after leaching of the platinum, palladium and / or ruthenium and dispersion of the ionomer, separating the remaining solid iridium-containing catalyst material from the dispersion of ionomer; and

[0037] (ii) leaching iridium from the spent catalyst coated membrane material using a heated solution comprising an acid and a reducing agent, and separating the solution comprising the leached iridium from the remaining solid components of the spent catalyst coated membrane material, wherein the leaching of iridium is performed before or after the leaching of platinum, palladium and / or ruthenium.

[0038] The process steps may be performed in any order to recover Pt, Ir and ionomer. That is: Pt-Ir-ionomer; Ir-Pt-ionomer; ionomer-Pt-Ir; ionomer-Ir-Pt; Pt-ionomer-Ir; or Ir-ionomer-Pt.

[0039] The following description will focus on an example including a platinum catalyst and an iridium-based catalyst (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 comprising a combination of at least two of platinum, palladium, and ruthenium, or a catalyst comprising at least one PGM and at least one base metal (e.g., PtCo).

[0040] The acid used in one or both of the iridium leaching and the platinum leaching is optionally hydrochloric acid. In addition, it is preferred that one or both of the solutions used for the leaching of platinum and iridium are heated to the following temperatures: at least 50°C, 60°C or 70°C; not more than 160°C, 100°C or 90°C; or within the range defined by any combination of the above lower and upper limits, wherein if the solution is heated to above 100°C, this is carried out in a pressurized container. The oxidant used for the leaching of platinum may include, for example, chlorates, such as sodium chlorate solution or chlorine gas (e.g., generated by in situ electrolysis). The oxidant may be added to the hydrochloric acid solution after heating to the aforementioned temperature. The solution may contain concentrated HCl, for example, about 6M HCl.

[0041] Separation of the solution containing the leached platinum can be achieved via filtration. The separated solution can be concentrated to a suitable PGM concentration for further processing by boiling the solution. Alternatively, the leachate can be recycled to leach platinum from additional spent catalyst coated membrane material, repeating the recycling as needed until a target concentration of PGMs is reached. The PGM-containing leachate is then further processed using known techniques to extract platinum from the acidic solution. The remaining solid components of the spent catalyst coated membrane material can be processed separately.

[0042] The method also includes a step of extracting iridium from the spent catalyst coated membrane. This can be achieved by leaching Ir species from the spent catalyst coated membrane via a reductive dissolution process using an acid (such as 8M to 12M HCl) and a reducing agent (such as hydrazine, NaBH4 or ammonium oxalate), thereby producing an Ir-containing acidic liquid. WO2021083758 describes several examples of such processes for dissolving Ir in a reductive HCl environment. Since the aforementioned oxidative acidic platinum leaching does not leach iridium to any significant extent, such a reductive acidic leaching process step for iridium can be performed after the oxidative acidic leaching step for platinum. However, it is also envisioned that iridium leaching can be performed before platinum leaching. Therefore, the route proposed according to this example is as follows Figure 1 and Figure 2 The two-step process shown involves selective leaching of Ir and Pt species from spent CCM without the need for incineration or other destructive treatment. The steps are as follows and can be performed in any order:

[0043] 1. Leaching of Ir species via a reductive dissolution process using an acid (such as HCl) and a reducing agent (such as hydrazine), resulting in an Ir-containing acidic liquid and CCM / undissolved PGM residues.

[0044] 2. Leaching of Pt species via an oxidative dissolution process using an acid (such as HCl) and an oxidant (such as chlorate or Cl2), thereby producing a Pt-containing acidic liquid and a CCM / undissolved PGM residue.

[0045] The resulting liquids from step one and step two 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 undergo further leaching to remove remaining PGM species, and the resulting ionomer residue is then recycled.

[0046] The process selectively recycles PGM directly from waste CCM. The treated CCM also remains largely unchanged, allowing the remaining components (e.g., ionomers) of the waste CCM to be further simply recovered. Therefore, the process provides a complete recovery and recycling route for both PGM and ionomer. The two-step method involving Pt and Ir leaching realizes a simple and fast route to separate and recycle both Ir and Pt, and has the possibility of directly feeding the metal solution back into the catalyst manufacturing process. By 2040, the estimated demand for fuel cell and electrolyzer CCM is about 800kOzt Pt and 160kOzt Ir, and the compact, customized characteristics of the process will shorten the lead time and increase metal mobility. The process enables closed-loop circulation to be produced for waste CCM materials, not only PGM, but also ionomers. The process also realizes the open-loop recycling of end-of-life CCM.

[0047] As an alternative to leaching iridium from a 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 described, and then the remaining waste CCM containing solid ionomer and iridium material can be subjected to ionomer dispersion to produce a slurry comprising an ionomer dispersion in which a solid iridium material is disposed. The ionomer dispersion can be separated from the solid iridium material using solid / liquid separation (e.g., filtration or centrifugation) to produce an ionomer dispersion for recycling. The remaining solid iridium material can be directly reused in the CCM manufacturing process or can be refined before reuse. Alternatively, the ionomer can be dispersed before platinum leaching to produce a mixed PGM residue for further processing.

[0048] Figure 3Such a process is shown in . The CCM material may first need to be chopped into the size required for the process. The CCM material can then be subjected to HCl / oxidant (e.g., chlorine) treatment to leach platinum, and optionally also leaching ruthenium (if present in the CCM). The liquid from the treatment can then be treated to remove base metals such as nickel and cobalt (using, for example, a cation exchange resin), Ru removal occurs via distillation or other processes, and then directly enters the Pt refining process stream to recover Pt. The remaining CCM pieces from the leaching may undergo a process involving 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 via filtration or centrifugation. Further processing of the ionomer dispersion can then be continued to be recycled back to make new CCM as a pure material or a blended material. Examples of processes for recycling perfluorosulfonic acid ionomers are described in US7255798 and WO2016 / 156815. Due to its inherent stability, the Ir catalyst can be reused without further treatment, or the Ir solid can be refined to recover the Ir metal.

[0049] In the above process, the platinum leaching step is performed before the step of dispersing the ionomer. However, in an alternative method, the ionomer dispersion is performed before the platinum leaching step. Figure 4 Such an alternative method is shown in . As previously described, the waste CCM can first be shredded to the desired size. The CCM waste pieces can then be heated to an elevated temperature in a solvent (e.g., an alcohol solvent) and optionally autoclaved to disperse the CCM components. The resulting slurry is subjected to solid / liquid separation (e.g., by filtration or centrifugation). The solution will contain dispersed ionomers, which will then be further processed to be recycled back to make new CCM. The PGM residue can be dried to ensure that the organic solvent is completely removed before being subjected to the HCl / chlorine leaching treatment as previously described. The liquid from the leaching can be treated to remove base metals such as Ni and / or Co (e.g., cation exchange resin), Ru removal occurs (e.g., via a distillation process), and the remaining platinum-containing solution is then provided to the Pt refining process stream to recover Pt, as previously described. The residue from the leaching process still contains the Ir catalyst, which is largely unchanged due to its stability. It can be processed to directly reuse the Ir catalyst material (eg, IrOx), or the residue can be refined to recover the Ir.

[0050] As previously mentioned in the background section, the CCM may contain ionomers in one or both of the catalyst layers and in the membrane on which the catalyst layers are disposed. While the processing flow as previously described is applicable to the complete membrane and catalyst layer structure, it is also contemplated that the catalyst layer may be separated from the membrane so that the membrane may be processed separately from the catalyst layer. Figure 5Such a modified processing flow is shown in . The first stage of the modified process includes separating the catalyst layer from the ePTFE membrane, for example using a mechanical process such as sonication or electrohydraulic fragmentation or via chemical delamination. The sonication method can involve immersing the CCM material in an alcohol-water mixture and sonicating for a period of time, wherein the catalyst layer separates and disperses into the solvent. The ePTFE sheets can be separated and the solvent removed from the catalyst layer material. Once the membrane and catalyst layer are cleanly separated, the ePTFE membrane can be further processed to recover the ionomer component. In order to recover the PGM and ionomer in the catalyst layer, there are two options, such as Figure 5 As shown and discussed below.

[0051] Process Option A: The catalyst layer material is subjected to an HCl / oxidant (e.g., chlorine) treatment to leach out the platinum. The liquid from this treatment can then be purified from the base metal (using, for example, a cation exchange resin), Ru removal occurs via distillation or other processes, and then directly enters the Pt refining stream. The remaining Ir-containing residue from the leaching can undergo a process involving heating / autoclaving the material in an alcohol solvent to dissolve / disperse the ionomer. The ionomer dispersion is separated from the Ir-containing solution via filtration or centrifugation (as an alternative, the Ir can be leached before or after the ionomer dispersion). Further processing of the ionomer dispersion then proceeds for recycling back to the manufacture of new CCM. The Ir-containing residue can be processed for direct reuse of the Ir catalyst, or the residue can be refined to recover the Ir metal. This process route is similar to Figure 3 The process routes shown are similar.

[0052] Process Option B: Alternatively, the catalyst layer material can be heated to elevated temperatures in an alcohol solvent and optionally autoclaved to disperse the CCM components. The resulting slurry is then subjected to solid / liquid separation by filtration or centrifugation. The supernatant / filtrate contains the dispersed ionomer which can then be further processed for recycling back into the manufacture of 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 can then be purified from the base metals (using, for example, a cation exchange resin), Ru removal occurs via a distillation process, and then directly into a Pt refining stream. The residue from the leaching process still contains the Ir catalyst, which is largely unchanged due to its stability. It can be processed for direct reuse of the Ir catalyst, or the residue can be refined to recover the Ir metal. This process route is similar to Figure 4 The process routes shown are similar.

[0053] The common feature of all the above CCM recycling processes is the use of oxidative acid leaching to extract the platinum (and / or palladium and / or ruthenium) material with ionomer dispersion, and the extraction of iridium via reductive leaching or solid-liquid separation after the extraction of the platinum and ionomer dispersion. Pt leaching can be performed before or after the dispersion of the ionomer and before or after the leaching of the iridium. Figure 1 In the process sequence: (i) iridium leaching; (ii) platinum leaching; (iii) treatment of the remaining ionomer membrane. Figure 2 In the process sequence: (i) platinum leaching; (ii) iridium leaching; (iii) treatment of the remaining ionomer membrane. Figure 3 , Figure 4 and Figure 5 In the present invention, iridium leaching is not required to separate iridium from ionomer. Instead, the iridium-containing material is separated from the ionomer material by dispersing the ionomer material and using solid / solution separation to remove the ionomer. Figure 3 As shown, the platinum leaching step can be performed before the step of dispersing the ionomer. Alternatively, the ionomer dispersion step can be performed before the platinum leaching step, such as Figure 4 shown. Figure 5 Two options in the process of first separating the catalyst layer from the bulk polymer membrane are shown.

[0054] The specific method utilized will depend on operator requirements, the demand for the component, and the desired form of the material recovered by the process. For example, if it is desired to extract a certain component early in the recycling process, such as due to a shortage of that particular component, then an appropriate processing flow may be selected to obtain the desired component early in the process, rather than retaining a large amount of the component for a long time during the recycling process. For example, if it is desired to recover platinum quickly, then a process flow may be selected. Figure 2 Alternatively, if it is desired to recover the bulk of the ionomer early in the process, one may choose Figure 5 The process is simple because the initial step of removing the catalyst layer from the bulk ionomer membrane ensures that the bulk ionomer membrane can be quickly recovered and processed, while the ionomer and PGM in the catalyst layer are further processed for various separation steps. Alternatively still, if it is desired to recover a specific form of material, such as an iridium oxide catalyst material for reuse rather than an iridium-containing leachate, then an appropriate processing flow can be selected to obtain the material in the desired form. For example, where it is desired to directly recover an iridium-based / derived catalyst for reuse, then the process of Figure 1 and Figure 2 The iridium leaching process during the Figures 3 to 5 One of the routes can be used to directly recover solid iridium-based catalyst materials (e.g., IrO x ).

[0055] Processes for recycling ionomers have been described in US7255798 and WO2016 / 156815, and such processes can be integrated into the process flow of the present specification as described above. As discussed in the background section, it is often the case that a different ionomer can be used in one or both of the catalyst layers compared to the ionomer in the bulk membrane. The different ionomers can be selected to provide improved performance in the final application. Blends of ionomers or layers of different ionomers within the bulk polymer membrane can also be used. In this case, Figure 5 The process flow can be used to separate the bulk polymer membrane from the catalyst layer at the beginning of the process flow. If different ionomers are used in the catalyst layer compared to the bulk membrane, such separation can be used to separate the different ionomers before further processing.

[0056] Example

[0057] CCM - HCl / Chlorate Leaching - Single Use of Leaching Solution

[0058] Processes have been developed to leach PGMs from CCM production waste. The recovered PGM material is subsequently refined using existing PGM refining processes. For such processes, there are strict restrictions on the fluorine content (<1%) of the PGM material introduced into the PGM refining process. This is considered a potential problem in leaching PGMs from spent CCM material because CCM is primarily made of fluoropolymers. The leaching process of the present invention allows PGMs to be leached without introducing significant amounts of fluorine in the leachate.

[0059] An HCl / chlorate solution was used to dissolve Pt from the CCM. Ir was in the form of an oxide in the CCM and no significant amount of Ir was leached, enabling separation of Pt and Ir. Chlorate was introduced in the form of a sodium chlorate solution added using a peristaltic pump.

[0060] 8.56 g of fuel cell CCM (cut into pieces of about 2 cm x 3 cm) were loaded into the container. 400 mL of 6M HCl (a solution prepared from concentrated HCl and distilled H2O) was loaded into the flask and the stirring speed was set to 250 rpm. The reaction mixture was heated to 70°C. During the heating period, a pale yellow color of the solution could be seen.

[0061] With the speed of about 0.09mL / min, add 4mL of NaClO solution (450g / L).After the addition of NaClO solution finishes, the reaction mixture is cooled to room temperature.By 0.45 μm filter paper, filter the reaction mixture, obtain yellow solution (365mL).Collect liquid, and use distilled H o (86mL) to wash the remaining CCM sheet.Choose the CCM sheet and arrange on the watch glass to dry overnight in air.

[0062] In 8.56g CCM, there were about 931mg Pt and 136mg Ir. IC / ICP analysis indicated that there were minimal traces of Ir in the leachate, indicating that the leaching conditions did not leach Ir to any significant extent. 926mg Pt was leached into the liquid and an additional 27mg was leached into the wash liquid. A total of about 953mg of Pt was recovered. This gave a recovery of 102%. However, there was an error of + / -10% in the initial Pt loading and there was also an error in the analysis, so the results are reasonable. Analysis of the untreated CCM indicated that about 11mg of Pt remained. Therefore, the Pt recovery was 98% by weight. The liquid also showed an undetectable amount of fluoride, indicating that the leaching conditions were not destructive to the ionomers in the CCM.

[0063] CCM - HCl / Chlorate Leaching - Multiple Uses of Leaching Solutions

[0064] This example uses a leaching process corresponding to that described in the previous example. However, in this case, the liquor from the leaching was reused multiple times with the addition of fresh batches of CCM and chlorate to demonstrate that the liquor can 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 refining step.

[0065] For each leaching cycle, the initial CCM weight, the liquor volume before and after leaching, the wash volume and the residual CCM weight were measured.

[0066] The general method for each cycle is to load the CCM pieces (cut into 2cm×3cm pieces) into a container with HCl / recirculating liquid. Before cycles 3 and 5, the liquid is replenished with fresh 6M HCl (a solution prepared from concentrated HCl and distilled H2O). The mixture is stirred at 250rpm and heated to 70°C. 3mL of NaClO3 solution (450g / L) is added at a rate of about 0.09mL / min. 45 minutes after the start of the addition, the reaction mixture is cooled to <30°C. The reaction mixture is filtered through 0.45μm cellulose filter paper to obtain a yellow liquid that deepens in color during the cycle. The remaining CCM pieces are washed with distilled H2O and dried overnight in air before recording the weight. An overview of each leaching cycle is provided below.

[0067] Loop 1:

[0068] CCM tablets before leaching: 9.96g

[0069] HCl / liquid before leaching: 400mL (fresh 6M HCl)

[0070] Liquid after leaching: 385mL

[0071] Washing liquid: 89mL

[0072] Remaining CCM flakes: 9.00 g

[0073] Loop 2:

[0074] CCM tablets before leaching: 9.98g

[0075] HCl / liquid before leaching: 375mL

[0076] Liquid after leaching: 365mL

[0077] Washing liquid: 88mL

[0078] Remaining CCM flakes: 9.06 g

[0079] Loop 3:

[0080] CCM tablets before leaching: 10.00g

[0081] HCl / liquid before leaching: 400 mL (355 mL is supplemented to 400 mL with fresh 6M HCl)

[0082] Liquid after leaching: 390mL

[0083] Washing liquid: 115mL

[0084] Remaining CCM flakes: 9.06 g

[0085] Loop 4:

[0086] CCM tablets before leaching: 9.98g

[0087] HCl / liquid before leaching: 375mL

[0088] Liquid after leaching: 365mL

[0089] Washing liquid: 87mL

[0090] Remaining CCM flakes: 9.04 g

[0091] Loop 5:

[0092] CCM tablets before leaching: 9.98g

[0093] HCl / liquid before leaching: 460 mL (360 mL of liquid was supplemented with fresh 6M HCl)

[0094] Liquid after leaching: 445mL

[0095] Washing liquid: 85mL

[0096] Remaining CCM flakes: 9.04 g

[0097] Loop 6:

[0098] CCM tablets before leaching: 9.98g

[0099] HCl / liquid before leaching: 435mL

[0100] Liquid after leaching: 425mL

[0101] Washing liquid: 102mL

[0102] Remaining CCM flakes: 8.90 g

[0103] Loop 7:

[0104] CCM tablets before leaching: 9.99g

[0105] HCl / liquid before leaching: 415mL

[0106] Liquid after leaching: 405mL

[0107] Washing liquid: 99mL

[0108] Remaining CCM flakes: 8.97 g

[0109] Loop 8:

[0110] CCM tablets before leaching: 10.00g

[0111] HCl / liquid before leaching: 395mL

[0112] Liquid after leaching: 385mL

[0113] Washing liquid: 77mL

[0114] Remaining CCM flakes: 9.05 g

[0115] Between each cycle, a 10 mL liquid sample was taken for analysis, thus reducing the liquid between cycles.

[0116] The results are indicated in the table below. Although the weight percent of Pt recovered in the liquor decreased during the multiple cycles from the initial 95 weight percent value, it is noteworthy that even after eight cycles of reusing the same leach liquor, the Pt recovery was still 83 weight percent.

[0117]

[0118]

[0119] batch Liquid determination (mg / L) Liquid (mL) Pt-liquid (mg) Pt-per batch (mg) 1 2686 385 1034 1034 2 5570 365 2033 999 3 7433 390 2899 866 4 10166 370 3761 863 5 10511 445 4677 916 6 12022 425 5109 432 7 14313 405 5797 687 8 17393 385 6696 900

[0120] batch Washing determination (mg / L) Washing liquid (mL) Pt-washing liquid (mg) 1 393 89 35 2 780 88 69 3 899 115 103 4 1329 87 116 5 1625 85 138 6 1536 102 157 7 2043 99 202 8 2657 77 205

[0121]

[0122] batch %Pt recovered in liquid 1 95％ 2 92％ 3 80％ 4 79％ 5 84％ 6 40％ 7 63％ 8 83％

[0123] Thus, it has been shown that this method can be used to recover Pt from spent CCM material without damaging the ionomer material of the CCM or introducing fluorine into the Pt processing stream for subsequent Pt refining. It has also been shown that Pt can be leached from spent CCM material without leaching iridium, thus enabling the separation and recovery of Pt and Ir for reuse. Thus, using this method, Pt, Ir and ionomer components (and optionally ruthenium if present) can be recovered.

[0124] Iridium Recovery

[0125] Iridium can be recovered using a reductive leaching process. For example, it has been demonstrated that iridium can be leached from an IrOx catalyst material using a leaching solution comprising a hydrazine reducing agent and 8M to 12M HCl at reflux for about 5 hours. It should be noted that the iridium leaching process is not as efficient as the aforementioned platinum leaching. Therefore, repeated leaching cycles can be used to increase the recovery of iridium.

[0126] A reducing agent may be provided in the acidic leaching solution. Alternatively, the spent catalyst coated membrane material may be pretreated with a reducing agent prior to leaching with an acidic leaching solution to extract iridium. In this method, CCM waste or PGM residues from a CCM recycling process are subjected to treatment with a reducing agent (such as hydrazine, sodium borohydride, ammonium oxalate, etc.) in water as a solvent. This reduces the Ir catalyst to a lower oxidation state, which is then subjected to highly concentrated HCl (e.g., 12M HCl) at an elevated temperature (e.g., 70°C to 105°C for 5 to 6 hours) to produce an Ir solution. The mixture is cooled to room temperature, and the remaining CCM and fine particles are filtered, washed with water and dried for further processing to recover the remaining components, such as other PGM catalysts and ionomers.

[0127] To increase the recovery of Ir, the residue can be subjected to the above reaction conditions in an iterative process. The resulting Ir liquid can then be evaluated to determine if any separation methods are required to separate the Ir species via conventional refining methods and / or to separate the desired form of Ir (e.g., iridium chloride salt, Ir metal).

[0128] This process leaves the CCM residue largely intact to allow further processing to recover other components, such as ionomers and other catalysts for recycle.

[0129] The above method can be carried out on pure IrOx material, PGM residue that has been formed by a recycling process of CCM aimed at first recovering ionomer, or alternative PGM residue containing a mixture of IrOx with other PGM catalysts and impurities. The method can also be carried out in a sealed container (i.e. under pressure).

[0130] Additionally or alternatively, the remaining IrOx catalyst may be recovered via a liquid-solid extraction process after dispersing the ionomer.These two methods (Ir leaching and solid / liquid Ir catalyst separation) may be combined to ensure that substantially all of the iridium is recovered.

[0131] Various different processing schemes including this leaching method can be used to recover Pt, Ir and ionomer components as described herein. While the invention has been particularly shown and described with reference to certain examples, it will be understood by those skilled in the art that various changes in form and details may be made without departing from the scope of the invention as defined by the appended claims.

Claims

1. A method of 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 oxidant, wherein platinum, palladium and / or ruthenium is 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 recovering a dispersion of ionomer, wherein the dispersion of the ionomer is in the platinum, palladium and and / or before or after said leaching of ruthenium; and (c) treating the spent catalyst coated membrane material to extract iridium by one or both of the following: (i) between said leaching of said platinum, palladium and / or ruthenium and said dispersion of said ionomer After that, the remaining solid iridium-containing catalyst material is mixed with the ionomer Dispersion separation; as well as (ii) leaching the iridium from the spent catalyst coated membrane material using a heated solution comprising an acid and a reducing agent, and mixing the solution comprising the leached iridium with the spent catalyst coated membrane material; The remaining solid components of the spent catalyst coated membrane material are separated, wherein the iridium impregnated The leaching may be carried out before or after said leaching of said platinum, palladium and / or ruthenium.

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

3. The method according to claim 1 or 2, wherein one or both of said solution for said leaching of platinum, palladium and / or ruthenium and said solution for said leaching of iridium are heated to a temperature of at least 50°C, 60°C or 70°C; not more than 160°C, 100°C or 90°C; or within a range defined by any combination of the above lower and upper limits, wherein if said solution is heated to above 100°C, this is carried out in a pressurized vessel.

4. A method according to any preceding claim, The oxidant comprises chlorate or chlorine gas.

5. A method according to any preceding claim, wherein the acid used in the leaching of platinum, palladium and / or ruthenium is hydrochloric acid, and the oxidant is chlorine gas generated in situ electrolysis from the hydrochloric acid.

6. A method according to any preceding claim, The oxidizing agent is added to the acid solution or generated in the acid solution after heating the hydrochloric acid solution.

7. The method according to any one of claims 1 to 5, The oxidizing agent is either added to the acid solution or generated in multiple aliquots during heating.

8. A method according to any preceding claim, The oxidant is added to the acid solution or generated to a total oxidant concentration in the range of 0.01 mol / l to 0.10 mol / l.

9. A method according to any preceding claim, The solution used for leaching platinum, palladium and / or ruthenium has the following acid concentration: not less than 4M, 5M or 5.5M; not more than 7M, 6.5M or 6M; or within the range defined by any combination of the above lower limit and upper limit.

10. A method according to any preceding claim, wherein after separation of the solution containing the leached platinum, palladium and / or ruthenium from the remaining solid components of the spent catalyst-coated membrane material, the solution is concentrated by boiling the solution.

11. A method according to any preceding claim, wherein after separating the solution containing the leached platinum, palladium and / or ruthenium from the remaining solid components of the spent catalyst coated membrane material, the solution is reused to leach platinum, palladium and / or ruthenium from further spent catalyst coated membrane material.

12. A method according to any preceding claim, wherein the platinum, palladium and / or ruthenium is leached from the spent catalyst coated membrane material prior to dispersing the ionomer.

13. The method according to any one of claims 1 to 11, wherein the platinum, palladium and / or ruthenium is leached from the spent catalyst coated membrane material after dispersing the ionomer and separating the solvent containing the ionomer from the remaining solid components of the spent catalyst coated membrane material.

14. A method according to any preceding claim, wherein the spent catalyst coated membrane material comprises a membrane and two catalyst layers disposed on either side of the membrane, and wherein the spent catalyst coated membrane material is treated to remove the catalyst layers from the membrane prior to further processing the catalyst layers according to the method of any preceding claim.

15. A method according to any preceding claim, The catalyst comprising iridium is iridium oxide or mixed iridium oxide.

16. A method according to any preceding claim, wherein the reducing agent is selected from one of hydrazine, NaBH4 and ammonium oxalate.

17. A method according to any preceding claim, wherein the iridium leaching solution has an acid concentration of: not less than 6M, 7M or 8M; not more than 15M, 12M or 10M; or Within the range defined by any combination of the above lower limits and upper limits.

18. A method according to any preceding claim, wherein the reducing agent is provided in an acidic leaching solution to extract iridium, or wherein the spent catalyst coated membrane material is pre-treated with the reducing agent prior to leaching with the acidic leaching solution to extract iridium.

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