Method and apparatus for eluting platinum group metal

Abstract

One aspect of the present invention provides a method and apparatus for eluting platinum group metals from a catalyst by a simple process without the use of corrosive acids.SOLUTION: The platinum group metal is eluted from the catalyst by a contact step of bringing the catalyst into contact with an alkaline treatment agent containing an oxyanion-generating substance, a heating step of heating the catalyst after the contact step to 100 °C to 500 °C, and an elution step of bringing the catalyst after the heating step into contact with an eluent.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method and apparatus for eluting platinum group metals. [Background technology]

[0002] BACKGROUND ART Currently, catalysts comprising a substrate and a catalyst layer provided on the substrate are used for a variety of purposes in a variety of fields.

[0003] For example, a catalyst comprising a substrate having a honeycomb structure and a catalyst layer provided on the substrate and having exhaust gas purification performance is used to treat exhaust gas emitted from automobiles, etc. (See, for example, Patent Document 1.) The catalyst layer is composed of, for example, a support layer (e.g., alumina), promoter particles (e.g., particles of one or more types selected from alumina, zirconia, ceria, and silica, and composite oxide particles containing cerium and zirconium) supported on the support layer, and a precious metal (e.g., platinum, palladium, rhodium) supported on the promoter particles.

[0004] Since the catalyst layer contains valuable resources such as precious metals, attention is being focused on technologies for recovering the catalyst layer from discarded catalysts and technologies for further recovering precious metals and other resources from the recovered catalyst layer.

[0005] Techniques for recovering the catalyst layer from the catalyst include, for example, ultrasonic peeling, electric pulse crushing, and separation by combining heating, quenching, and physical treatment (see, for example, Non-Patent Document 1 and Non-Patent Document 2).

[0006] It is necessary to further recover precious metals and the like from the recovered catalyst layer. The technology for recovering precious metals from the recovered catalyst layer has a significant impact on the amount of precious metals and the like ultimately recovered, and is therefore an important technology in the field of catalyst recycling. One example of a technology for recovering precious metals from a recovered catalyst layer is a method in which the catalyst layer is reacted in a molten salt to solubilize the precious metals and the like contained in the catalyst or catalyst layer. More specifically, a technology is used in which the catalyst or catalyst layer is reacted with KHSO4 to produce water-soluble platinum group metals, and the water-soluble platinum group metals are recovered (see, for example, Non-Patent Document 3). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] WO2013 / 027531 A1 [Non-patent literature]

[0008] [Non-Patent Document 1] Gangfeng Liu et.al., "Concentration of PGMs from Automobile Catalyst by Combining Surface Grinding and Quenching" Proceedings of EMC(2013), p235-254 [Non-patent document 2] Shuji Owada, "A New Trend of Physical Concentration in Resources Recycling" ENGINEERING JOURNAL, Volume 20, Issue 4(2016), p129-136 [Non-patent document 3] Erik Prasetro et.al., "Platinum Group Elements Recovery from Used Catalytic Converters by Acidic Fusion and Leaching" Metals, 2020, 10(4), 485 Summary of the Invention [Problem to be solved by the invention]

[0009] However, the above-mentioned conventional techniques have the problems that the process for recovering platinum group metals is complicated and that a corrosive acid must be used in the process for recovering platinum group metals to improve the yield.

[0010] One aspect of the present invention is to provide a method and apparatus for eluting platinum group metals from a catalyst by a simple process that does not use corrosive acids. [Means for solving the problem]

[0011] The present inventors have discovered that platinum group metals can be eluted from catalysts by using an alkaline treating agent containing an oxyanion-generating substance, and have thus completed the present invention.

[0012] [1] A method for eluting a platinum group metal from a catalyst containing a platinum group metal, comprising: a contacting step of contacting the catalyst with an alkaline treating agent containing an oxyanion-generating substance; a heating step of heating the catalyst after the contacting step to 100°C to 500°C; and an eluting step of contacting the catalyst after the heating step with an eluent.

[0013] [2] The elution method according to [1], wherein the oxyanion-producing substance is at least one selected from the group consisting of B2O3, P2O5, SiO2, Al2O3, K2SiO3, K2MoO4, and transition metal oxides.

[0014] [3] The elution method according to [2], wherein the treatment agent has a concentration of the oxyanion-generating substance of 7% by mass or more.

[0015] [4] The elution method according to any one of [1] to [3], wherein the treatment agent includes a pH adjuster.

[0016] [5] The elution method according to [4], wherein the pH adjuster is at least one selected from the group consisting of KOH, NaOH, LiOH, K2CO3, Na2CO3, and Li2CO3.

[0017] [6] The elution method according to [5], wherein the treatment agent has a concentration of the pH adjuster of 30% by mass or more.

[0018] [7] The elution method according to any one of [1] to [6], wherein the eluent is at least one selected from the group consisting of water, hydrochloric acid, sulfuric acid, nitric acid, perchloric acid, phosphoric acid, acetic acid, and citric acid.

[0019] [8] An apparatus for eluting a platinum group metal from a catalyst containing a platinum group metal, comprising: a contacting section that brings the catalyst into contact with an alkaline treating agent containing an oxyanion-generating substance; a heating section that heats the catalyst after contact with the treating agent to 100°C to 500°C; and an eluting section that brings the heated catalyst into contact with an eluent. [Effects of the Invention]

[0020] According to one aspect of the present invention, a method and apparatus for eluting platinum group metals from a catalyst can be realized by a simple process that does not use corrosive acids. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a flowchart showing the steps of a method for eluting platinum group metals according to one embodiment of the present invention. [Figure 2] 1 is a diagram showing the configuration of an apparatus for eluting platinum group metals according to one embodiment of the present invention. [Figure 3] 1 shows the EDS spectrum and elemental composition of a catalyst sample before elution treatment in an example of the present invention. [Figure 4] 1 shows the EDS spectrum and elemental composition of a substrate constituting a catalyst sample in an example of the present invention. [Figure 5] 1 is an image of a catalyst sample before and after an elution process in an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0022] One embodiment of the present invention will be described below, but the present invention is not limited thereto. The present invention is not limited to the respective configurations described below, and various modifications are possible within the scope of the claims. Embodiments and examples obtained by appropriately combining the technical means disclosed in different embodiments and examples are also included in the technical scope of the present invention. Furthermore, all academic literature and patent documents described in this specification are incorporated herein by reference. Furthermore, unless otherwise specified in this specification, "A to B" representing a numerical range means "greater than or equal to A and less than or equal to B."

[0023] 1. Platinum Group Metal Elution Method A method for eluting platinum group metals according to one embodiment of the present invention will be described with reference to FIG.

[0024] A method for eluting a platinum group metal according to one embodiment of the present invention is a method for eluting a platinum group metal from a catalyst containing a platinum group metal, and includes: a contacting step S1 in which the catalyst is contacted with an alkaline treating agent containing an oxyanion-generating substance; a heating step S2 in which the catalyst after the contacting step S1 is heated to 100°C to 500°C; and an eluting step S3 in which the catalyst after the heating step S2 is contacted with an eluent.

[0025] In a method for eluting platinum group metals according to one embodiment of the present invention, the platinum group metal contained in the catalyst can be converted into a soluble compound by the contacting step S1 and the heating step S2. In the eluting step S3, the compound is brought into contact with an eluent, whereby the platinum group metal constituting the compound is eluted from the catalyst into the eluent. The platinum group metal eluted into the eluent can be easily recovered and purified.

[0026] As an example, Pt contained in the catalyst is converted into "K m Pt x (BO β ) y (Al0 α ) z (OH) l n It is thought that the compound is converted into a compound such as ". The compound contains oxyanions and OH due to alkalinity. - In the elution step S3, the compound is brought into contact with an eluent, whereby Pt constituting the compound is eluted from the catalyst into the eluent. The Pt eluted into the eluent can be easily recovered and purified.

[0027] (Contact process S1) The contact step S1 is a step of contacting the catalyst with an alkaline treating agent containing an oxyanion-generating substance.

[0028] For example, the contacting step S1 may be (i) a step of contacting the catalyst with a treating agent, (ii) a step of contacting the catalyst with the treating agent and then removing excess treating agent from the catalyst, (iii) a step of contacting the catalyst with the treating agent to impregnate the catalyst with the treating agent, or (iv) a step of contacting the catalyst with the treating agent to impregnate the catalyst with the treating agent and then removing excess treating agent from the catalyst. The above-mentioned "removing excess treating agent from the catalyst" can be achieved, for example, by (v) introducing the catalyst into the treating agent in a container and then removing the treating agent from the container, or (vi) introducing the catalyst into the treating agent in a container and then recovering the catalyst from the treating agent.

[0029] The configuration of the catalyst is not limited, and may be, for example, a catalyst including a substrate and a catalyst layer provided on the substrate.

[0030] The components constituting the substrate are not limited. The components may be, for example, at least one selected from the group consisting of cordierite, SiC, zeolite, silica, and alumina. More specifically, the components may be at least one selected from the group consisting of MgO, Al2O3, and SiO2.

[0031] The components constituting the catalyst layer are not limited. The components can be, for example, at least one selected from the group consisting of ZrO2, CeO2, Al2O3, BaO, CaO, PO5, C, platinum group metals, Zr-Ce oxides, Zr-Nd oxides, and Zr-La oxides. The platinum group metals are not limited and can be, for example, at least one selected from the group consisting of Pd, Pt, Rh, Ir, Os, and Ru.

[0032] The structure of the catalyst is not limited, and may be, for example, a honeycomb structure or a porous structure.

[0033] The catalyst used in the contact step S1 may be either unpulverized or pulverized. The platinum group metal elution method according to one embodiment of the present invention can effectively elute platinum group metals from catalysts that have not undergone a pulverization treatment.

[0034] The upper limit of the mass of each catalyst used in the contacting step S1 is not limited. The upper limit may be, for example, 1000 kg or less, 100 kg or less, 10 kg or less, 1 kg or less, 500 g or less, 100 g or less, 50 g or less, or 10 g or less. The lower limit of the mass of each catalyst used in the contacting step S1 is not limited. The lower limit may be, for example, 0.01 g or more, 0.1 g or more, 1 g or more, or 5 g or more.

[0035] When the mass of the catalyst used in the contact step S1 is large, it is preferable to employ the recycling step S4 described below. By employing the recycling step S4 described below, platinum group metals can be effectively eluted even from a catalyst with a large mass.

[0036] The treating agent is alkaline and contains an oxyanion-producing substance. The treating agent may be in a liquid or solid form.

[0037] The oxyanion-generating substance is not limited as long as it can generate oxyanions. The oxyanion-generating substance is preferably at least one selected from the group consisting of BO, PO, SiO, AlO, KSiO, KMoO, and transition metal oxides. This configuration facilitates the generation of oxyanions capable of converting platinum group metals into soluble compounds.

[0038] The transition metal oxides are not limited to, and examples thereof include MoO3, WO3, MnO, FeO, CoO, NiO, CuO, and ZnO.

[0039] The lower limit of the concentration of the oxyanion-generating substance contained in the treatment agent is not limited. The concentration of the oxyanion-generating substance in the treatment agent may be, for example, 3% by mass or more, 5% by mass or more, 7% by mass or more, 10% by mass or more, 20% by mass or more, 30% by mass or more, 40% by mass or more, 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more. With this configuration, it is possible to easily generate oxyanions in an amount sufficient to convert the platinum group metal into a soluble compound.

[0040] The upper limit of the concentration of the oxyanion-generating substance contained in the treatment agent is not limited, and the concentration of the oxyanion-generating substance in the treatment agent may be, for example, 100% by mass or less, 90% by mass or less, 80% by mass or less, 70% by mass or less, 60% by mass or less, or 50% by mass or less.

[0041] The treatment agent may contain a pH adjuster. This configuration allows the pH of the treatment agent containing the oxyanion-generating substance to be easily adjusted to an alkaline state. If the pH of the treatment agent can be adjusted to an alkaline state using only the oxyanion-generating substance, the pH adjuster need not be used.

[0042] The pH adjuster is not limited as long as it can adjust the pH of the treatment agent to alkaline. Preferably, the pH adjuster is at least one selected from the group consisting of KOH, NaOH, LiOH, K2CO3, Na2CO3, and Li2CO3. This configuration allows the pH of the treatment agent containing the oxyanion-generating substance to be easily adjusted to alkaline.

[0043] The lower limit of the concentration of the pH adjuster contained in the treatment agent is not limited. The treatment agent may have a pH adjuster concentration of, for example, 10% by mass or more, 20% by mass or more, 30% by mass or more, or 40% by mass or more. In this configuration, the amount of OH capable of converting the platinum group metal into a soluble compound is 10% by mass or more, 20% by mass or more, 30% by mass or more, or 40% by mass or more. - can be easily generated.

[0044] The upper limit of the concentration of the pH adjuster contained in the treatment agent is not limited, and the concentration of the pH adjuster in the treatment agent may be, for example, 90% by mass or less, 80% by mass or less, 70% by mass or less, 60% by mass or less, or 50% by mass or less.

[0045] The treatment agent may contain a halogen-containing compound, which can further improve the effects of the present invention. Examples of the halogen-containing compound include LiF, NaF, KF, LiCl, NaCl, KCl, LiBr, NaBr, KBr, LiI, NaI, and KI.

[0046] (Heating process S2) The heating step S2 is a step of heating the catalyst after the contacting step S1 to 100°C to 500°C.

[0047] The temperature to which the catalyst is heated in the heating step S2 may be, for example, 150°C to 500°C, 180°C to 500°C, 200°C to 500°C, 250°C to 500°C, 300°C to 500°C, 350°C to 500°C, 400°C to 500°C, or 450°C to 500°C. Within each of these temperature ranges, the upper limit of the temperature is not limited to 500°C and may be, for example, 450°C, 400°C, or 350°C. A lower temperature to which the catalyst is heated has the advantage of reducing the amount of energy consumed. A method for eluting platinum group metals according to one embodiment of the present invention is capable of eluting platinum group metals even at low temperatures.

[0048] The time for heating the catalyst in the heating step S2 is not limited and can be set appropriately depending on the heating temperature, the size and / or the shape of the catalyst. The time can be, for example, 0.5 to 24 hours, 1 to 20 hours, 1 to 16 hours, 1 to 13 hours, 1 to 10 hours, 1 to 5 hours, or 2 to 5 hours. A shorter catalyst heating time has the advantage of reducing the amount of energy consumed. The platinum group metal elution method according to one embodiment of the present invention is capable of eluting platinum group metals even in a short time.

[0049] (Elution step S3) The elution step S3 is a step of contacting the catalyst with an eluent after the heating step S2.

[0050] The stripping solution is not limited as long as it can elute the platinum group metal from the catalyst after the heating step S2. The eluent is, for example, at least one selected from the group consisting of water, hydrochloric acid, sulfuric acid, nitric acid, perchloric acid, phosphoric acid, acetic acid, and citric acid. From the viewpoint of better eluting the platinum group metal, the solvent is preferably hydrochloric acid, sulfuric acid, or perchloric acid among the above-mentioned solvents.

[0051] In the elution step S3, for example, the catalyst heated to 100°C to 500°C in the heating step S2 may be brought into contact with the eluent while still at a temperature of approximately 100°C to 500°C, or the catalyst may be cooled to a temperature lower than the heating temperature (for example, room temperature) and then brought into contact with the eluent.

[0052] The eluate containing platinum group metals obtained in the elution step S3 may be subjected to, for example, precipitation, centrifugation, neutralization, coprecipitation, and / or adsorption. These processes allow the desired platinum group metals to be recovered in a highly concentrated state. Each of these processes can be carried out according to a known method. For example, neutralization can precipitate the platinum group metals eluted in the eluate, thereby increasing the recovery rate of the platinum group metals.

[0053] (Reuse process S4) A method for eluting platinum group metals according to one embodiment of the present invention preferably includes a reuse step S4 in which the catalyst obtained after the elution step S3 is reused as a catalyst in the contact step S1. This configuration makes it possible to elute platinum group metals that remain in the catalyst and cannot be eluted in a single elution treatment.

[0054] The number of times the recycling step S4 is performed is not limited, and may be once or multiple times (e.g., 2 to 10 times, 2 to 5 times, or 2 to 3 times). In other words, the treatment consisting of the contacting step S1, the heating step S2, and the elution step S3 may be performed twice or more times (e.g., 2 to 10 times, 2 to 5 times, or 2 to 3 times) for one catalyst. The number of times the recycling step S4 is performed may be determined depending on the size and shape of the catalyst, etc.

[0055] [2. Platinum Group Metals Elution Apparatus] An elution apparatus for platinum group metals according to one embodiment of the present invention will be described with reference to Fig. 2. Note that the configuration described above in [1. Platinum group metal elution method] will not be described below.

[0056] An elution apparatus 100 for platinum group metals according to one embodiment of the present invention is an apparatus for eluting platinum group metals from a platinum group metal-containing catalyst 15, and includes a contacting section 1 that brings the catalyst 15 into contact with an alkaline treating agent 10 containing an oxyanion-generating substance, a heating section 2 that heats the catalyst 15 after contact with the treating agent 10 to 100°C to 500°C, and an elution section 3 that brings the heated catalyst 15 into contact with an eluent 11. In the elution section 3, the catalyst 15 is brought into contact with the eluent 11, thereby producing an eluted catalyst 16 from the catalyst 15.

[0057] The contacting section 1, the heating section 2, and the eluting section 3 may each be configured separately. Alternatively, two or more (two or three) selected from the group consisting of the contacting section 1, the heating section 2, and the eluting section 3 may be configured as a single section. For example, (i) the contacting section 1 and the heating section 2 may be configured as a single section, (ii) the contacting section 1 and the eluting section 3 may be configured as a single section, (iii) the heating section 2 and the eluting section 3 may be configured as a single section, or (iv) the contacting section 1, the heating section 2, and the eluting section 3 may be configured as a single section.

[0058] (Contact part 1) The contacting section 1 brings the catalyst 15 into contact with the alkaline treating agent 10 containing an oxyanion-generating substance. The contacting section 1 is configured to carry out the above-mentioned contacting step S1.

[0059] The contact portion 1 may have any configuration (for example, a container) capable of accommodating the catalyst 15 therein, and there are no limitations on the shape and size thereof.

[0060] A treatment agent 10 can be supplied into the contacting section 1. The treatment agent 10 supplied into the contacting section 1 and the catalyst 15 contained in the contacting section 1 can come into contact with each other.

[0061] The amount of treatment agent 10 supplied into contact section 1 is not limited as long as it is an amount that allows the treatment agent 10 and catalyst 15 to come into contact with each other. A large amount of treatment agent 10 may be introduced into contact section 1, and catalyst 15 may be immersed in the treatment agent 10. Alternatively, a small amount of treatment agent 10 may be introduced into contact section 1, and part of catalyst 15 may be brought into contact with the treatment agent 10, thereby allowing catalyst 15 to be impregnated with the treatment agent 10. Alternatively, a small amount of treatment agent 10 may be sprayed into contact section 1, and the treatment agent 10 may be applied to the surface of catalyst 15.

[0062] The catalyst 15 and the alkaline treating agent 10 containing an oxyanion-generating substance have been explained above in [1. Platinum group metal elution method], so explanation thereof will be omitted here.

[0063] (Heating part 2) The heating section 2 heats the catalyst 15 after contact with the treatment agent 10 to a temperature of 100° C. to 500° C. The heating section 2 is configured to perform the heating step S2 described above.

[0064] Heat 21 (for example, hot air) is supplied to the heating unit 2 by a heater 20, and the heat 21 can heat the catalyst 15 in the heating unit 2. Note that the configuration for heating the catalyst 15 is not limited to the heater 20 as long as it is a configuration that can increase the temperature of the catalyst 15.

[0065] The heating unit 2 may be configured to remove water vapor from the system that heats the catalyst 15 (for example, the interior of the heating unit 2). When a liquid treatment agent 10 is used in the contact unit 1, water may evaporate from the catalyst 15 in the heating unit 2, and the water may fill the system that heats the catalyst 15 (for example, the interior of the heating unit 2). If the heating unit 2 has the above-described configuration, it is possible to prevent the system that heats the catalyst 15 from filling with water and / or prevent the pressure in the system that heats the catalyst 15 from increasing.

[0066] The configuration that can be provided in heating unit 2 is not limited as long as it is a configuration that can remove water vapor from the system that heats catalyst 15. The configuration may be, for example, (i) an air discharge path that discharges air from inside heating unit 2 to outside heating unit 2, (ii) an air inlet path that introduces air from outside heating unit 2 into heating unit 2 and an air discharge path that discharges air from inside heating unit 2 to outside heating unit 2, (iii) an air discharge hole that discharges air from inside heating unit 2 to outside heating unit 2, or (iv) an air inlet hole that introduces air from outside heating unit 2 into heating unit 2 and an air discharge hole that discharges air from inside heating unit 2 to outside heating unit 2.

[0067] If water vapor is present in the system for heating the catalyst 15 (for example, inside the heating unit 2), the water vapor may promote solubilization of the platinum group metal or an unwanted reaction. Therefore, the heating unit 2 may be provided with a configuration for controlling the water vapor partial pressure in the system for heating the catalyst 15 (for example, inside the heating unit 2). This configuration may be composed of, for example, (i) an air inlet path for introducing air into the heating unit 2 from outside, an air outlet path for discharging air from inside the heating unit 2 to outside, and a blower for introducing air into the heating unit 2 from outside, or (ii) an air inlet hole for introducing air into the heating unit 2 from outside, an air outlet hole for discharging air from inside the heating unit 2 to outside, and a blower for introducing air into the heating unit 2 from outside.

[0068] (Elution section 3) The elution section 3 brings the heated catalyst 15 into contact with the eluent 11. The elution section 3 is configured to perform the elution step S3 described above.

[0069] The elution section 3 may have any configuration (for example, a container) capable of containing the catalyst 15 therein, and there are no limitations on the shape and size thereof.

[0070] An eluent 11 can be supplied into the elution section 3. The eluent 11 supplied into the elution section 3 and the catalyst 15 contained in the elution section 3 can come into contact with each other.

[0071] The amount of eluent 11 supplied into the elution section 3 is not limited as long as it is an amount that allows the eluent 11 and the catalyst 15 to come into contact with each other. A large amount of eluent 11 may be introduced into the elution section 3, and the catalyst 15 may be immersed in the eluent 11. Alternatively, a small amount of eluent 11 may be introduced into the elution section 3, and a portion of the catalyst 15 may be brought into contact with the eluent 11, thereby allowing the eluent 11 to permeate the catalyst 15. Alternatively, a small amount of eluent 11 may be sprayed into the elution section 3, and the eluent 11 may be applied to the surface of the catalyst 15.

[0072] The eluent 11 in the elution section 3 may be subjected to at least one treatment selected from the group consisting of bubbling (e.g., air bubbling), stirring, shaking, ultrasonic treatment, and heating. With this configuration, platinum group metals can be efficiently eluted from the catalyst 15 layer into the eluent 11.

[0073] An eluent 11 containing platinum group metals can be recovered from the elution section 3 via an eluent recovery path (not shown). The recovery of the eluent 11 containing platinum group metals can also be performed by, for example, tilting the elution section 3 to discharge the eluent 11 containing platinum group metals from inside the elution section 3 to outside the elution section 3.

[0074] The eluent 11 containing the recovered platinum group metals may be subjected to, for example, precipitation, centrifugation, neutralization, coprecipitation, and / or adsorption. These processes allow the desired platinum group metals to be recovered in a highly concentrated state. Each of these processes can be carried out according to known methods. For example, neutralization can be carried out to precipitate the platinum group metals eluted in the eluent, thereby increasing the recovery rate of the platinum group metals.

[0075] (Return Route 30) The platinum group metal elution apparatus 100 according to one embodiment of the present invention preferably includes a return path 30 for returning the eluted catalyst 16 after contact with the eluent 11 in the elution section 3 to the contact section 1. This configuration makes it possible to elute platinum group metals that cannot be eluted in a single elution treatment and remain in the catalyst. The return path 30 is configured for carrying out the above-mentioned recycling step S4.

[0076] The return path 30 may have any configuration as long as it can return the eluted catalyst 16 after contact with the eluent 11 in the elution section 3 to the contact section 1, and the configuration is not limited thereto.

[0077] One embodiment of the present invention can purify exhaust gases emitted from power sources and reuse discarded resources, and therefore has the potential to contribute to the achievement of Goal 7 "Affordable and clean energy" and Goal 9 "Build resilient infrastructure, promote inclusive and sustainable industrialization," among the Sustainable Development Goals (SDGs) advocated by the United Nations. [Example]

[0078] The present invention will be described in more detail below based on examples, but the present invention is not limited to the following examples.

[0079] <1. Measurement of components in spent catalyst before elution treatment> A catalyst comprising a substrate having a honeycomb structure and a catalyst layer provided on the substrate was cut into a size of approximately 5 to 10 mm square to form a catalyst sample, and the following tests were carried out using this catalyst sample.

[0080] First, a secondary electron image of the cross section of the catalyst sample before the elution treatment was acquired. From the secondary electron image, it was confirmed that the catalyst sample had a catalyst layer formed on a substrate (not shown).

[0081] Next, the EDS spectrum and elemental composition of each of the catalyst layer and the substrate in the catalyst sample before the elution treatment were analyzed using an EDS instrument manufactured by Bruker Corp. The specific analysis method followed the protocol attached to the instrument.

[0082] Figure 3 shows the EDS spectrum and elemental composition of the catalyst layer in the catalyst sample before elution, and Figure 4 shows the EDS spectrum and elemental composition of the substrate. In the images of the catalyst sample in each of Figures 3 and 4, the areas marked with circles are the areas where the EDS spectrum and elemental composition were analyzed.

[0083] As shown in Figure 4, the substrate contained Mg, Al, Si, O, and other substances derived from cordierite. On the other hand, as shown in Figure 3, the catalyst layer contained platinum group metals (Pd, etc.) derived from the catalyst in addition to substances derived from the promoter.

[0084] <2. Elution treatment of platinum group metals from spent catalysts - 1> <2-1. Test method> Predetermined amounts of a pH adjuster (e.g., KOH), an oxyanion-generating substance (e.g., BO, PO, KSiO, KMoO), and ion-exchanged water were mixed to prepare alkaline treatment agents containing the oxyanion-generating substance. Table 1 below shows the composition of the treatment agents. The pH of these treatment agents was approximately 14. In Examples 1 to 3 and 5 to 10, the mass ratio of KOH to BO (KOH / BO) was adjusted to approximately 4, and in Example 12, the mass ratio of KOH to BO (KOH / BO) was adjusted to approximately 6.7.

[0085] In Table 1, in Example 13, the catalyst sample (catalyst layer) contained Al2O3, an oxyanion-producing substance, so no oxyanion-producing substance was added to the treatment agent.

[0086] In Table 1, in Comparative Example 1, the catalyst sample was treated directly with water and 1M hydrochloric acid without being brought into contact with a treating agent or heated.

[0087] [Table 1]

[0088] The resulting treating agent was added to a glass container, and then the catalyst sample was placed in the container, with the treating agent contacting only the bottom of the catalyst sample.

[0089] The catalyst sample was left in this state for about 1 minute, which allowed the treating agent to permeate the entire catalyst sample from the bottom, and also coated the inside of the honeycomb structure of the catalyst sample with the treating agent.

[0090] The catalyst sample, now entirely wet with the treatment agent, was removed from the glass container and placed in a 30 mL alumina crucible. The alumina crucible containing the catalyst sample was placed in an electric furnace, and the catalyst sample was heated for a predetermined time under the conditions shown in Table 1. Thereafter, the power of the electric furnace was turned off, and the catalyst sample was allowed to cool naturally within the electric furnace.

[0091] 6 mL of ion-exchanged water was added to the alumina crucible taken out of the electric furnace, and the catalyst sample in the alumina crucible was subjected to water treatment for 30 minutes.

[0092] The suspension in the alumina crucible was then suction filtered using 5C filter paper to perform solid-liquid separation. The liquid obtained by solid-liquid separation is called the "treated water liquid."

[0093] Meanwhile, the solid residue obtained by solid-liquid separation was returned to the alumina crucible, and 10 mL of a 1 M aqueous hydrochloric acid solution was added to the alumina crucible, and the catalyst sample was subjected to an acid treatment for 30 minutes.

[0094] The suspension in the alumina crucible was then suction filtered using 5C filter paper to perform solid-liquid separation. The liquid obtained by solid-liquid separation is referred to as the "1M hydrochloric acid-treated liquid."

[0095] The concentrations of the components contained in the water treatment solution and the 1M hydrochloric acid treatment solution were examined by ICP emission spectroscopy.

[0096] The weight of the catalyst sample was measured before and after the elution treatment, and the weight loss rate of the catalyst sample was calculated using the measured weight values ​​according to the following formula (1): In the following formula (1), W0 is the weight of the catalyst sample before the elution treatment, and W is the weight of the catalyst sample after the elution treatment: Weight reduction rate (%)=(1-W / W0)×100 Equation (1).

[0097] In a previous study, the relationship between the catalyst layer peeling rate and the weight loss rate was investigated from the cross-section of the substrate, and the predicted weight loss rate when the catalyst layer peeling rate is 100% was 35%. Therefore, in this test, when the weight loss rate was 35%, the catalyst layer peeling rate was converted to 100%.

[0098] As a comparative test, the following test was carried out.

[0099] A catalyst sample (approximately 10 mm square) was immersed in 6 mL of dilute sulfuric acid (water: 98% concentrated sulfuric acid = 5:1 (volume ratio)) and kept in this state for 1 hour.

[0100] The catalyst sample was then removed from the dilute sulfuric acid and placed in a quartz crucible. The quartz crucible containing the catalyst sample was placed in an electric furnace and heated at 200°C for 1 hour. After that, 6 mL of ion-exchanged water was added to the quartz crucible removed from the electric furnace. At this time, the catalyst layer peeled off from the substrate in the catalyst sample, and the ion-exchanged water became suspended.

[0101] The substrate remaining after the catalyst layer was peeled off was removed from the ion-exchanged water, and the resulting ion-exchanged water was subjected to suction filtration to perform solid-liquid separation. The resulting liquid is referred to as the "peeling treatment liquid."

[0102] The concentrations of the components contained in the stripping treatment solution were examined by ICP emission spectroscopy.

[0103] <2-2. Test Results> <2-2-1. Visual confirmation of elution> FIG. 5 shows an image of the catalyst sample before elution treatment ("Before Treatment" in FIG. 5) and an image of the catalyst sample after acid treatment with 1 M aqueous hydrochloric acid solution ("After Treatment" in FIG. 5) for Example 1.

[0104] As is clear from Figure 5, the catalyst sample before the elution treatment exhibited a dark color that was thought to be derived from the catalytic layer present on the catalyst surface. On the other hand, the catalyst sample after the acid treatment with 1 M hydrochloric acid aqueous solution lost its dark color and assumed a white color. This color change is thought to be the result of the elution of platinum group metals from the catalyst.

[0105] <2-2-2. Elution of platinum group metals into the eluent> Table 2 below shows the amount of platinum group metals transferred to the "water treatment solution," the amount of platinum group metals transferred to the "1M hydrochloric acid treatment solution," and the total amount of platinum group metals transferred to the "water treatment solution" and the "1M hydrochloric acid treatment solution."

[0106] From a comparison of Examples 5, 10, 6 and 1 in Table 2-1 below, the effect of the amount of oxyanion-generating substance contained in the treatment agent can be primarily understood.

[0107] The effect of the heating temperature can be primarily understood from a comparison of Examples 3, 2, 7, 8 and 9 in Table 2-1 below.

[0108] From Examples 2, 4, and 11 to 13 in Table 2-2 below, the effect of the type of oxyanion-generating substance contained in the treatment agent can be primarily understood.

[0109] Regarding the amount of oxyanion-generating substance contained in the treatment agent, a small amount of oxyanion-generating substance tended to increase the amount of Pt eluted, and a large amount of oxyanion-generating substance tended to increase the amount of Pd eluted. The Examples eluted a larger amount of platinum group metals than the Comparative Examples.

[0110] With respect to the heating temperature, the amount of platinum group metal eluted was greater in the Examples than in the Comparative Examples.

[0111] Regarding the type of oxyanion-generating substance contained in the treatment agent, even when only KOH was added to the treatment agent and only Al2O3 contained in the catalyst itself was used as the oxyanion-generating substance, as in Example 13, the elution amount of platinum group metals (Pt + Pd + Rh) was high. When P2O3 was added to the treatment agent as an oxyanion-generating substance, as in Example 4, the elution amount of Pt increased compared to Example 13. Furthermore, when B2O3 or K2SiO3 was added to the treatment agent, as in Examples 2 and 11, the elution amount of Rh increased compared to Example 13. This also shows that the addition of a separate oxyanion-generating substance to the treatment agent significantly increases the elution amount of certain types of platinum group metals.

[0112] Example 12, in which the mass ratio of KOH to B2O3 (KOH / B2O3) was approximately 6.7, had a greater amount of eluted platinum group metals (Pt + Pd + Rh) than Example 2, in which the mass ratio of KOH to B2O3 (KOH / B2O3) was approximately 4. Also, Example 12, in which the mass ratio of KOH to B2O3 (KOH / B2O3) was approximately 6.7, had a greater amount of eluted Pd than Example 13, in which no B2O3 was added. These results demonstrate that the elution of platinum group metals can be promoted by appropriately adjusting the mass ratio of KOH to B2O3 (KOH / B2O3) contained in the treatment agent.

[0113] [Table 2] JPEG2026012109000003.jpg87166

[0114] In the elution process, it is desirable to selectively elute the platinum group metals to be recovered and suppress the elution of other components contained in the catalyst layer (e.g., Ce, Zr, Al, Ca). This allows the platinum group metals to be concentrated in the "water treatment liquid" and "1M hydrochloric acid treatment liquid," reducing the load on the subsequent purification process.

[0115] The mass ratios of the components contained in the "1M hydrochloric acid treatment solution" are shown in Table 3 below. As a comparative test, the mass ratios of the components contained in the "stripping treatment solution" obtained by treatment with dilute sulfuric acid are also shown.

[0116] The ratio of other components (Ce, Zr, Al, Ca) to the amount of platinum group metals was calculated by the formula "(Ce + Zr + Al + Ca) / (Pt + Pd + Rh)." The smaller this value, the more selectively platinum group metals were eluted.

[0117] As shown in Table 3, it was revealed that the present invention can selectively elute the platinum group metals that are the target of recovery.

[0118] [Table 3] JPEG2026012109000005.jpg87152JPEG2026012109000006.jpg32152

[0119] <2-2-3. Weight loss rate due to elution treatment> The weight loss rates of the catalyst samples are shown in Table 4. As shown in Table 4, in the present invention, the weight loss rate due to the elution treatment was large. This indicates that platinum group metals were efficiently eluted from the catalyst samples.

[0120] [Table 4]

[0121] <3. Elution treatment of platinum group metals from spent catalysts - 2> <3-1. Test method> The spent catalyst used in Examples 1 to 13 was designated "Catalyst 1." A different type of automobile exhaust gas purification catalyst from Catalyst 1 was prepared and designated "Catalyst 2." Catalyst 1 and Catalyst 2 were the same in that both had a coating layer on the surface of a cordierite substrate. Catalyst 2 was cut into pieces approximately 5 to 10 mm square to prepare catalyst samples.

[0122] The EDS spectrum and elemental composition of the catalyst layer in the catalyst sample before elution were analyzed using an EDS instrument manufactured by Bruker Corp. As a result, in addition to palladium, rhodium was also detected in the catalyst sample derived from catalyst 2.

[0123] Potassium hydroxide, boron oxide, and ion-exchanged water were mixed to prepare a treatment agent. The composition of the treatment agent is shown in Table 5 below.

[0124] [Table 5]

[0125] The resulting treating agent was added to a glass container, and then the catalyst sample was placed in the glass container, with the treating agent contacting only the bottom of the catalyst sample.

[0126] The catalyst sample was left in this state for about 1 minute, which allowed the treating agent to permeate the entire catalyst sample from the bottom, and also coated the inside of the honeycomb structure of the catalyst sample with the treating agent.

[0127] The catalyst sample, now completely wet with the treating agent, was removed from the glass container and placed in a 30 mL alumina crucible. The alumina crucible containing the catalyst sample was placed in an electric furnace, and the catalyst sample was heated at 350°C for 120 minutes (see Table 5). Thereafter, the power to the electric furnace was turned off, and the catalyst sample was allowed to cool naturally within the alumina crucible in the electric furnace.

[0128] 6 mL of ion-exchanged water was added to the alumina crucible taken out of the electric furnace, and the catalyst sample having a honeycomb structure in the alumina crucible was subjected to water treatment for 30 minutes.

[0129] The suspension in the alumina crucible was then suction filtered using 5C filter paper to perform solid-liquid separation. The liquid obtained by solid-liquid separation is called the "treated water liquid."

[0130] Meanwhile, the solid residue obtained by solid-liquid separation was returned to the alumina crucible, and 10 mL of a 1 M aqueous hydrochloric acid solution was added to the alumina crucible, and the catalyst sample was subjected to an acid treatment for 30 minutes.

[0131] The suspension in the alumina crucible was then suction filtered using 5C filter paper to perform solid-liquid separation. The liquid obtained by solid-liquid separation is referred to as the "1M hydrochloric acid-treated liquid."

[0132] The concentrations of components contained in the 1M hydrochloric acid treatment solution were examined by ICP emission spectroscopy.

[0133] <3-2. Test Results> Table 6 shows the amount of platinum group metal transferred to the 1M hydrochloric acid treatment solution. In the test results for catalyst 1 in Examples 1 to 13, the majority of the platinum group metal was contained in the 1M hydrochloric acid treatment solution. Therefore, in the test results for catalyst 2 in Example 14, the test results are shown focusing on the 1M hydrochloric acid treatment solution.

[0134] From Table 6, it can be seen that for catalyst 2 in Example 14, rhodium was also detected in addition to platinum and palladium in the 1M acid-treated solution.

[0135] Table 7 shows the mass ratios of the components contained in the "1M acid treatment solution" in tests using catalyst samples derived from catalyst 2. The value of "(Ce + Zr + Al + Ca) / (Pt + Pd + Rh)" was used as an index showing the ratio of the amount of other components (Ce, Zr, Al, Ca) to the amount of platinum group metals. The smaller this value, the more selectively the platinum group metals are eluted.

[0136] As can be seen from Table 7, compared to Comparative Examples 1 and 2, Example 14 had a smaller value of (Ce+Zr+Al+Ca) / (Pt+Pd+Rh).

[0137] [Table 6]

[0138] [Table 7] [Industrial Applicability]

[0139] The present invention can be used in the field of recovering platinum group metals from catalysts. More specifically, the present invention can be used in the field of recycling, where platinum group metals are recovered from discarded catalysts (e.g., catalysts for engine exhaust gases, honeycomb catalysts for engine exhaust gases) and reused. [Explanation of symbols]

[0140] 1 Contact part 2 Heating section 3 Elution section 10 Treatment Agent 11 Eluent 15 Catalyst 16 Eluted catalyst 20 Heater 21 fever 30 Return Route 100 Elution device S1 Contact process S2 heating process S3 elution step S4 Reuse process

Claims

1. 1. A method for eluting platinum group metals from a catalyst containing platinum group metals, comprising: a contacting step of contacting the catalyst with an alkaline treating agent containing an oxyanion-generating substance; a heating step of heating the catalyst after the contacting step to 100°C to 500°C; an elution step of contacting the catalyst with an eluent after the heating step.

2. The oxyanion-producing substance is B ２ O ３ , P ２ O ５ , SiO ２ , Al ２ O ３ , K. ２ SiO ３ , K. ２ MoO ４ 2. The elution method according to claim 1, wherein the catalyst is at least one selected from the group consisting of:

3. 3. The elution method according to claim 2, wherein the treatment agent has a concentration of the oxyanion-producing substance of 7% by mass or more.

4. The elution method of claim 1 , wherein the treatment agent comprises a pH adjuster.

5. The pH adjuster may be KOH, NaOH, LiOH, K ２ CO ３ , Na ２ CO ３ , and Li ２ CO ３ The elution method according to claim 4, wherein the elution method is at least one selected from the group consisting of:

6. The elution method according to claim 5 , wherein the treatment agent contains the pH adjuster at a concentration of 30% by mass or more.

7. 2. The elution method according to claim 1, wherein the eluent is at least one selected from the group consisting of water, hydrochloric acid, sulfuric acid, nitric acid, perchloric acid, phosphoric acid, acetic acid, and citric acid.

8. 1. An apparatus for eluting platinum group metals from a catalyst containing platinum group metals, comprising: a contact section for contacting the catalyst with an alkaline treating agent containing an oxyanion-generating substance; a heating section that heats the catalyst after contact with the treating agent to 100°C to 500°C; an elution section that brings the heated catalyst into contact with an eluent.

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