JP2019188361A - Recovery method of supported metal from on-vehicle catalyst - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for recovering a supported metal from an on-vehicle catalyst which has a high recovery rate and is simple and low cost. SOLUTION: An acid solution is introduced into a hole of a honeycomb structure of an on-vehicle catalyst in which a supported metal is supported on a carrier, and the on-vehicle catalyst introduced with the acid solution is subjected to microwave irradiation to elute the supported metal. By, adding a reducing agent to the solution in which the supported metal is eluted, microwave irradiation to the solution containing the reducing agent, depositing the supported metal, and filtering the deposited supported metal, A method for recovering a supported metal from an on-vehicle catalyst, including recovering. [Selection diagram] Figure 1

Description

  The present disclosure relates to a method for recovering a supported metal from a vehicle-mounted catalyst.

  Precious metals such as Pd, Pt, and Rh are used in many products because of their excellent heat resistance and corrosion resistance. In particular, noble metals such as Pd, Pt, and Rh are used in large amounts as supported metals for in-vehicle catalysts (devices that purify exhaust gas), and it is desired to recycle them.

  Conventional methods for recovering precious metals in in-vehicle catalysts include a dry cracking method in which precious metals are recovered by a blast furnace using copper smelting and an electrolysis process, and a wet cracking method in which precious metals are recovered from scrap using aqua regia ( Non-patent document 1, Non-patent document 2).

Recovery of Platinum Group Metals from Spent Automotive Catalyst, 12th International Research / Expert Conference “Trends in the Development of Machinery and Associated Technology” TMT2008, Istanbul, Turkey, 26-30 August 2008. Recovery of Palladium from Spent Activated Carbon-Supported Palladium Catalysts, Platinum Metals Rev., 2013, 57 (4), 289-296.

  When recovering the noble metal from the vehicle-mounted catalyst by these conventional methods, pulverization is necessary. However, since the material other than the supported metal such as the carrier is recovered due to the pulverization step, the recovery rate of the supported metal is low. In addition to the pulverization process, a selection process of the supported metal and other materials is also necessary, which involves many processes and takes time and costs. Therefore, there is a need for a method for recovering a supported metal from a vehicle-mounted catalyst that has a high recovery rate and is simple and low cost.

  The present inventor has intensively studied in view of the above problems, and has found a method for recovering a supported metal in which microwave irradiation is performed using an oxidizing agent and a reducing agent without pulverizing a vehicle-mounted catalyst.

  In the present disclosure, an acid solution is introduced into the pores of a honeycomb structure of a vehicle-mounted catalyst having a supported metal supported on a carrier, and the vehicle-mounted catalyst into which the acid solution is introduced is irradiated with microwaves to elute the supported metal. Adding a reducing agent to the solution from which the supported metal is eluted, irradiating the solution containing the reducing agent with microwaves, precipitating the supported metal, and filtering the deposited supported metal, A method for recovering a supported metal from a vehicle-mounted catalyst, including recovery, is targeted.

  According to the recovery method of the present disclosure, the supported metal can be recovered from the vehicle-mounted catalyst at a high recovery rate with a simple cost reduction.

FIG. 1 is a schematic diagram showing a mode in which an acid solution is introduced into the pores of a honeycomb structure of a vehicle-mounted catalyst. FIG. 2 is a graph showing the relationship between the microwave irradiation time and the amount of elution of Pd in Examples 1 to 24. FIG. 3 is a graph showing the relationship between the microwave irradiation time and the elution amount of Pt in Examples 1 to 24. FIG. 4 is a graph showing the relationship between the microwave irradiation time and the Rh elution amount in Examples 1 to 24. FIG. 5 is a graph showing the relationship between the hot plate temperature and the elution amount of Pd in Comparative Examples 1-9. FIG. 6 is a graph showing the relationship between the hot plate temperature and the Pt elution amount in Comparative Examples 1-9. FIG. 7 is a graph showing the relationship between the hot plate temperature and the Rh elution amount in Comparative Examples 1-9. FIG. 8 is a graph showing the relationship between the microwave irradiation time and the atmospheric gas and the elution amount of Pd in Examples 25-33. FIG. 9 is a graph showing the relationship between the microwave irradiation time and atmospheric gas and the elution amount of Pt in Examples 25-33. FIG. 10 is a graph showing the relationship between the microwave irradiation time and the atmospheric gas and the elution amount of Rh in Examples 25-33. FIG. 11 is a graph showing the relationship between the atmospheric gas and the elution rate of Al and Mg when the microwave irradiation time in Examples 26, 29, and 32 is 10 seconds. FIG. 12 is a graph showing the relationship between the atmospheric gas and the elution rate of Al and Mg when the microwave irradiation time is 30 seconds in Examples 27, 30, and 33. FIG. 13 is a graph showing the relationship between the atmospheric gas and the elution rates of Al and Mg when the microwave irradiation time in Examples 25, 28, and 31 is 50 seconds. FIG. 14 is a graph showing the X-ray intensity of Pt, which is a supported metal, before and after the supported metal is eluted from the in-vehicle catalyst by the method of the present disclosure. FIG. 15 is a graph showing the X-ray intensities of Pd and Rh, which are supported metals, and Ce, which is a promoter metal, before and after the supported metals are eluted from the in-vehicle catalyst by the method of the present disclosure.

  The method for recovering a supported metal from a vehicle-mounted catalyst according to the present disclosure includes: introducing an acid solution into the pores of the honeycomb structure of the vehicle-mounted catalyst having a supported metal supported on a carrier; and introducing the acid solution into the vehicle-mounted catalyst Performing microwave irradiation to elute the supported metal, adding a reducing agent to the solution from which the supported metal is eluted, performing microwave irradiation on the solution to which the reducing agent is added, and depositing the supported metal; And filtering and recovering the deposited supported metal.

  According to the method of the present disclosure, the supported metal can be recovered without using an acid solution, a reducing agent, and microwave irradiation to elute and deposit the supported metal and pulverize the on-vehicle catalyst. The rate is high, and the supported metal can be recovered easily and at low cost. According to the method of the present disclosure, the recovery rate of the supported metal contained in the vehicle-mounted catalyst is preferably 97% or more, more preferably 99% or more.

  In addition, according to the method of the present disclosure, the pulverization process of the conventional method and the selection process of the supported metal and other materials are unnecessary, no special equipment is required, and the transportation cost is not increased. It is possible to quickly recover the supported metal in the vicinity.

  In addition, according to the method of the present disclosure, not only the in-vehicle catalyst does not need to be pulverized but also the supported metal existing on the inner wall surface of the honeycomb structure is selectively suppressed while suppressing the elution of the support portion of the in-vehicle catalyst. Can be dissolved. Therefore, it is possible not only to reuse the supported metal but also to reuse the carrier part.

  The in-vehicle catalyst has a function of converting harmful gas in exhaust gas of an automobile or the like into harmless gas. The vehicle-mounted catalyst used in the recovery method of the present disclosure is not particularly limited as long as it carries a supported metal on a carrier.

The following are mentioned as an example of a vehicle-mounted catalyst. For example, an in-vehicle catalyst has a cordierite honeycomb carrier structure mainly composed of silica, alumina _, and magnesia _, and cocatalyst particles (carrier part) such as ceria having a diameter of about 10 nm on the inner wall surface of the honeycomb structure. In addition, particles of supported metal such as Pd, Rh, and Pt, which are catalytic active points having a diameter of about 1 to 2 nm, are arranged in a dispersed manner.

The acid solution is preferably hydrochloric acid, aqua regia, nitric acid, or sulfuric acid, more preferably hydrochloric acid or aqua regia. In order to dissolve noble metals such as Pd, Pt, and Rh, hydrochloric acid or aqua regia containing Cl ^- ions is more preferred, and aqua regia is even more preferred.

  The acid solution is preferably heated to 50 to 100 ° C. By using the heated acid solution, the microwave irradiation time can be shortened.

  The hydrochloric acid is preferably concentrated hydrochloric acid, and the concentration is preferably substantially 35-36%. The aqua regia is composed of concentrated hydrochloric acid and concentrated nitric acid in a volume ratio of substantially 3: 1, and the concentration of concentrated hydrochloric acid is preferably substantially 35 to 36%. Is preferably substantially 60-70%. The nitric acid is preferably concentrated nitric acid, and the concentration is preferably substantially 60-70%. The sulfuric acid is preferably concentrated sulfuric acid, and the concentration is preferably substantially 90-98%.

  The acid solution can be introduced into the pores of the honeycomb structure of the vehicle-mounted catalyst by any method. For example, the vehicle-mounted catalyst may be immersed in the acid solution, the acid solution may be disposed on the opening of the honeycomb structure of the vehicle-mounted catalyst, or the acid solution may be injected into each hole.

  As shown in FIG. 1, since the acid solution enters the pores of the honeycomb structure of the vehicle-mounted catalyst by capillary action, the amount of the acid solution used may be small. The acid solution enters the pores of the honeycomb structure and reaches the supported metal attached to the inner wall surface by capillary action, so that the acid solution and the supported metal particles can be heated by microwave irradiation.

  The wavelength of the microwave irradiated to the vehicle-mounted catalyst into which the acid solution is introduced is preferably 300 MHz to 4 GHz, more preferably 2 to 3 GHz. By irradiating microwaves in the wavelength range in this way, the supported metal can be efficiently eluted from the on-vehicle catalyst.

  The output of the microwave applied to the vehicle-mounted catalyst into which the acid solution is introduced is preferably 500 W or more, more preferably 700 W or more, and further preferably 1000 W or more. The upper limit of the microwave output is not particularly limited, but may be, for example, 3000 W or less.

  The microwave irradiation time for irradiating the vehicle-mounted catalyst into which the acid solution is introduced is preferably 0.5 to 5 minutes. According to the method of the present disclosure, the supported metal can be eluted from the in-vehicle catalyst in a short time.

  The microwave irradiated to the vehicle-mounted catalyst into which the acid solution is introduced is irradiated by a device that can irradiate the microwave, and preferably can be irradiated using a microwave oven. Since a microwave oven can be used as a microwave irradiation device, the supported metal can be easily eluted from the vehicle-mounted catalyst quickly and at low cost without incurring transportation costs near the dismantling site of the automobile. .

  The microwave irradiation of the on-vehicle catalyst into which the acid solution is introduced is preferably performed in a nitrogen atmosphere or a rare gas atmosphere, more preferably in a rare gas atmosphere, and further preferably in an argon atmosphere. Is called.

  When an acid solution is introduced and microwave irradiation is performed to elute the supported metal, the solubility decreases if the supported metal becomes a metal oxide. By irradiating the vehicle-mounted catalyst introduced with the acid solution in the atmosphere with microwaves, the formation of oxide of the supported metal can be suppressed, and the dissolution rate of the supported metal from the vehicle-mounted catalyst can be further improved. it can.

  After the acid solution is introduced and microwave irradiation is performed to elute the supported metal from the in-vehicle catalyst, the in-vehicle catalyst is immersed in water or water is introduced into the in-vehicle catalyst to remove the eluted supported metal. As a solution containing, it can take out out of a vehicle-mounted catalyst.

  In the method of the present disclosure, a reducing agent is added to the solution from which the supported metal is eluted, and microwave irradiation is performed on the solution to which the reducing agent is added. By adding a reducing agent to the solution from which the supported metal is eluted and performing microwave irradiation, the dissolved supported metal can be precipitated in a short time.

  The reducing agent is preferably sodium borohydride (sodium tetraborate), lithium borohydride, triethylsilane, or a combination thereof, and is preferably used under alkaline conditions in which sodium hydroxide coexists.

  The amount of the reducing agent added to the solution from which the supported metal is eluted is preferably 0.1 to 10% by mass with respect to the mass of the solution.

  The wavelength of the microwave irradiated to the solution from which the supported metal added with the reducing agent is eluted is preferably 300 MHz to 4 GHz, more preferably 2 to 3 GHz. By irradiating microwaves in such a wavelength range, the dissolved supported metal can be deposited in a shorter time.

  The output of the microwave applied to the solution from which the supported metal added with the reducing agent is eluted is preferably 500 W or more, more preferably 700 W or more, and further preferably 1000 W or more. The upper limit of the microwave output is not particularly limited, but may be, for example, 3000 W or less.

  The irradiation time of the microwave applied to the solution from which the supported metal to which the reducing agent is added is eluted is preferably within 15 minutes, more preferably within 12 minutes, and even more preferably within 9 minutes. According to the method of the present disclosure, the dissolved supported metal can be deposited in a short time.

  Without being bound by theory, it is considered that by adding a reducing agent and irradiating microwaves, the supported metal particles are locally heated, and the heated metal fine particles are aggregated to promote precipitation. Moreover, since the temperature of a solvent rises by irradiating a microwave, it is thought that the following metal precipitation reaction accelerates | stimulates, for example.

BH ⁴ + + 3H ₂ O → BO ₃ + 7H ⁺ + 8e ⁻
Pt ²⁺ + 2e ⁻ → Pt
Pd ²⁺ + 2e ⁻ → Pd
Rh ²⁺ + 2e ^- → Rh

  The microwave irradiated to the solution from which the supported metal to which the reducing agent is added is eluted is irradiated by a device that can irradiate the microwave, and can be preferably irradiated using a microwave oven. Since a microwave oven can be used as the microwave irradiation device, the dissolved supported metal can be easily deposited quickly and at low cost without incurring transportation costs near the dismantling site of the automobile.

  The microwave irradiation of the solution from which the supported metal added with the reducing agent is eluted is preferably performed in a nitrogen atmosphere or a rare gas atmosphere, more preferably in a rare gas atmosphere, and still more preferably an argon atmosphere. Done in.

  When adding a reducing agent and performing microwave irradiation to deposit the supported metal, if the supported metal becomes a metal oxide, the deposition property is lowered. By performing microwave irradiation on the solution from which the supported metal added with the reducing agent is eluted in the above atmosphere, oxide formation of the supported metal can be suppressed, and the deposition rate of the supported metal can be improved.

  After depositing the supported metal in the solution, the deposited supported metal is filtered and recovered. For the filtration, filter paper or suction filtration can be used.

  The supported metal is preferably a platinum group element, more preferably at least one metal selected from the group consisting of Pd, Rh, and Pt.

(Example 1)
(Analysis of components and content of automotive catalyst)
The used vehicle-mounted catalyst was pulverized, and 2.0 g of the crushed vehicle-mounted catalyst was further pulverized to 200 mesh or less using an agate mortar. About the sample grind | pulverized to 200 mesh or less, the qualitative analysis and quantitative analysis of the contained element were performed using the energy dispersive X-ray fluorescence analyzer (XRF, Rigaku, EDXL300). The in-vehicle catalyst was obtained by dismantling and taking out an automobile that had traveled 100,000 km, and as a result of qualification by XRF, it had a cordierite honeycomb carrier structure mainly composed of silica, alumina, magnesia, and ceria. Table 1 shows the components and contents of the in-vehicle catalyst.

(Elution of supported metal from in-vehicle catalyst)
Aqua regia was prepared by mixing a concentrated hydrochloric acid with a concentration of 36% (manufactured by Kanto Chemical Co., Ltd.) and concentrated nitric acid with a concentration of 61% (manufactured by Kanto Chemical Co., Ltd.) at a volume ratio of 3: 1. The above-mentioned used vehicle-mounted catalyst cut into a 1.0 g cube for the test, 10 mL of room temperature aqua regia, and a fluororesin container were placed in a glove box. The atmosphere in the glove box was replaced with Ar gas. In the glove box, the on-vehicle catalyst and 10 mL of aqua regia were placed in a fluororesin (polytetrafluoroethylene) container, aqua regia was introduced into the holes in the honeycomb structure of the on-vehicle catalyst, and the fluorine resin container was sealed. Remove the sealed fluororesin container from the glove box, put it in a microwave oven (manufactured by Panasonic, NE-EH224) with an output of 500 W and a wavelength of 2.45 GHz, and repeat microwave irradiation for 10 seconds and for 1 minute. went.

  In a fluororesin container subjected to microwave irradiation, pure water was introduced into the in-vehicle catalyst, and the eluted supported metal was taken out of the in-vehicle catalyst as a solution containing the eluted supported metal. The solution containing the eluted supported metal was filtered using 5C filter paper (ADVANTEC, 110 mm), and the concentrations of Pd, Pt, and Rh in the filtered solution were determined by inductively coupled plasma mass spectrometer (ICP-MS, manufactured by Perkin Elmer, ELAN DRCII) to determine the elution amount.

(Examples 2 to 6)
In Examples 2 to 6, the same method as in Example 1 except that 10 seconds of irradiation and 1 minute of microwave irradiation were repeated once, twice, three times, ten times, and twenty times. The amount of elution was measured with

(Example 7)
The elution amount was measured in the same manner as in Example 1 except that concentrated hydrochloric acid having a concentration of 36% (manufactured by Kanto Chemical Co., Inc.) was used as the acid solution.

(Examples 8 to 12)
In Examples 8 to 12, the same method as in Example 7 except that 10 seconds of irradiation and 1 minute of microwave irradiation were repeated once, twice, three times, ten times, and twenty times. The amount of elution was measured with

(Example 13)
The amount of elution was measured in the same manner as in Example 1 except that concentrated nitric acid having a concentration of 61% (manufactured by Kanto Chemical Co., Inc.) was used as the acid solution.

(Examples 14 to 18)
In Examples 14 to 18, the same method as in Example 13 except that 10 second irradiation and 1 minute microwave irradiation were repeated once, twice, three times, ten times, and twenty times. The amount of elution was measured with

(Example 19)
The elution amount was measured in the same manner as in Example 1 except that 96% concentrated sulfuric acid (manufactured by Kanto Chemical Co., Inc.) was used as the acid solution.

(Examples 20 to 24)
In Examples 20 to 24, the same method as in Example 19 except that 10 second irradiation and 1 minute microwave irradiation were repeated once, twice, three times, ten times, and twenty times. The amount of elution was measured with

(Comparative Example 1)
The amount of elution was measured by elution of the supported metal from the supported metal using a wet decomposition method, which is a conventional method for recovering noble metals in the vehicle-mounted catalyst.

  Specifically, the following method was used. The in-vehicle catalyst was pulverized to obtain 1.0 g of a pulverized product. In air, aqua regia is placed in a fluororesin container placed on a hot plate and heated to 80 ° C. The crushed product is immersed in the heated aqua regia and allowed to stand for 1 hour to dissolve the crushed product. I let you. The solution in which the pulverized product was dissolved was filtered using 5C filter paper (ADVANTEC, 110 mm), and the concentrations of Pd, Pt, and Rh in the filtered solution were determined by inductively coupled plasma mass spectrometer (ICP-MS, manufactured by Perkin Elmer, ELAN DRCII) to determine the elution amount.

(Comparative Examples 2-3)
In Comparative Examples 2-3, the amount of elution was measured by the same method as Comparative Example 1 except that the aqua regia was heated to 100 ° C and 150 ° C.

(Comparative Example 4)
The elution amount of the supported metal was measured in the same manner as in Comparative Example 1 except that concentrated hydrochloric acid having a concentration of 36% (manufactured by Kanto Chemical Co., Ltd.) was used as the acid solution.

(Comparative Examples 5-6)
In Comparative Examples 5-6, the elution amount was measured by the same method as Comparative Example 4 except that concentrated hydrochloric acid was heated to 100 ° C and 150 ° C.

(Comparative Example 7)
The amount of elution was measured by the same method as in Comparative Example 1 except that concentrated nitric acid having a concentration of 61% (manufactured by Kanto Chemical Co., Inc.) was used as the acid solution.

(Comparative Examples 8-9)
In Comparative Examples 8 to 9, the amount of elution was measured by the same method as Comparative Example 7 except that concentrated nitric acid was heated to 100 ° C. and 150 ° C.

(Comparative Example 10)
The amount of elution was measured in the same manner as in Comparative Example 1 except that 96% concentrated sulfuric acid (manufactured by Kanto Chemical Co., Inc.) was used as the acid solution.

(Comparative Examples 11-12)
In Comparative Examples 11-12, the elution amount was measured by the same method as Comparative Example 10 except that concentrated sulfuric acid was heated to 100 ° C. and 150 ° C.

  FIGS. 2-4 shows the graph showing the relationship between the microwave irradiation time in Examples 1-24, and the elution amount of Pd, Pt, and Rh. The graph showing the relationship between the hot-plate temperature in Comparative Examples 1-12 and the elution amount of Pd, Pt, and Rh in Comparative Examples 1-12 is shown in FIGS.

(Example 25)
The elution amounts of Pd, Pt, and Rh were measured in the same manner as in Example 1 except that 10 mL of aqua regia warmed to 60 ° C. was used as the acid solution. In addition, the elution rates of Al and Mg as carrier components were also measured.

(Examples 26 to 27)
In Examples 26 to 27, the elution amount and elution rate were measured in the same manner as in Example 25 except that 10 seconds of irradiation and 1 minute of microwave irradiation were repeated once and three times.

(Example 28)
The elution amount and elution rate were measured in the same manner as in Example 25 except that the atmosphere in the glove box was changed to air.

(Examples 29 to 30)
In Examples 29 to 30, the elution amount and elution rate were measured in the same manner as in Example 28 except that 10 seconds of irradiation and 1 minute of microwave irradiation were repeated once and three times.

(Example 31)
Except that the atmosphere in the glove box was N _2, was measured elution amount and dissolution rate in the same manner as in Example 25.

(Examples 32-33)
In Examples 32-33, the elution amount and elution rate were measured in the same manner as in Example 31 except that 10 seconds of irradiation and 1 minute of microwave irradiation were repeated once and three times.

  The graph showing the relationship between the microwave irradiation time in Examples 25-33, atmospheric gas, and the elution amount of Pd, Pt, and Rh in FIGS. 8-10 is shown.

  In FIGS. 11-13, the graph showing the relationship between the microwave irradiation time in Example 25-33, atmospheric gas, and the elution rate of Al and Mg is shown.

(Elution of palladium black powder and platinum black powder by microwave irradiation method)
In order to obtain an accurate dissolution rate and recovery rate, dissolution experiments were performed using platinum black powder and palladium black powder.

(Example 34)
Fluorine resin (polytetrafluoroethylene) containing palladium black powder (manufactured by Wako Pure Chemical Industries, purity 97% or more) and aqua regia 10 mL heated to 60 ° C. in a glove box substituted with Ar gas as in Example 1. Sealed in a container. Then, using a microwave oven (manufactured by Panasonic, NE-EH224) having an output of 500 W and a wavelength of 2.45 GHz, microwave irradiation was performed 5 times for 10 seconds and 1 minute. The solution containing dissolved Pd is filtered using 5C filter paper (ADVANTEC, 110 mm), and the concentration of Pd in the filtered solution is measured with an inductively coupled plasma mass spectrometer (ICP-MS, manufactured by Perkin Elmer, ELAN DRCII). The dissolution rate was determined.

(Example 35)
The dissolution rate was measured in the same manner as in Example 34, except that 10 seconds of irradiation and 1 minute of microwave irradiation were repeated 10 times.

(Example 36)
The dissolution rate was measured in the same manner as in Example 34 except that platinum black powder (made by Tanaka Kikinzoku, purity 98% or more, particle size 74 μm or less) was dissolved instead of palladium black powder.

(Example 37)
The dissolution rate was measured in the same manner as in Example 36 except that 10 seconds of irradiation and 1 minute of microwave irradiation were repeated 10 times.

  Table 2 shows the dissolution rates of palladium black powder and platinum black powder in an Ar atmosphere when the microwaves of Examples 34 and 36 were irradiated for 50 seconds.

  Table 3 shows the dissolution rates of palladium black powder and platinum black powder in an Ar atmosphere when the microwaves of Examples 35 and 37 were irradiated for 100 seconds.

  (Recovery of palladium black powder and platinum black powder by microwave irradiation method)

(Example 38)
A mixed solution of 1.25 M sodium hydroxide and 1 M sodium tetrahydroborate as a reducing agent was added to 20 mL of a palladium black powder solution obtained by dissolving palladium black powder in aqua regia in the same manner as in Example 34. 5 mL was dropped, and microwave irradiation was performed 5 times by using a microwave oven (manufactured by Panasonic, NE-EH224) having an output of 500 W and a wavelength of 2.45 GHz to deposit Pd. .

  The solution in which Pd was precipitated was suction filtered with a membrane filter (ADVANTEC, 0.45 μm, 25 mm), and a mixed acid of hydrochloric acid: nitric acid = 1: 1 was added to the remaining filtrate, and dissolved on the hot plate until the total amount became 25 mL. Thereafter, measurement was performed by ICP-MS, and the residual amount was subtracted to measure the recovery rate of Pd.

(Examples 39 to 41)
The recovery rate was measured in the same manner as in Example 38, except that 10 seconds of irradiation and 1 minute of microwave irradiation were repeated 0 times, 3 times, and 10 times.

(Example 42)
The recovery rate was measured in the same manner as in Example 38 except that the output of the microwave oven was set to 700 W.

(Examples 43 to 44)
The recovery rate was measured in the same manner as in Example 42, except that 10 seconds of irradiation and 1 minute of microwave irradiation were repeated 3 times and 7 times.

(Example 45)
The recovery rate of Pt was measured in the same manner as in Example 38 except that a platinum black powder solution obtained by dissolving platinum black powder was used.

(Examples 46 to 47)
The recovery rate was measured in the same manner as in Example 45, except that 10 seconds of irradiation and 1 minute of microwave irradiation were repeated 0 times and 3 times.

(Examples 48 to 49)
The recovery rate was measured in the same manner as in Example 45 except that the output of the microwave oven was 700 W, and the microwave irradiation was allowed to stand for 10 seconds and left for 1 minute, once and twice.

  Table 4 shows the recovery rate of palladium black powder in Examples 38 to 41 when using a microwave with an output of 500 W and a reducing agent.

  Table 5 shows the recovery rate of palladium black powder in Examples 42 to 44 when using a microwave with an output of 700 W and a reducing agent.

  Table 6 shows the recovery rate of platinum black powder in Examples 45 to 47 when a microwave with an output of 500 W and a reducing agent are used.

  Table 7 shows the recovery rate of platinum black powder in Examples 48 to 49 when a microwave with an output of 700 W and a reducing agent were used.

(Recovery of palladium black powder and platinum powder by conventional method)
(Comparative Example 13)
The recovery rate of Pd was measured in the same manner as in Example 38 except that the palladium black powder solution to which the reducing agent was added without microwave irradiation was allowed to stand at room temperature for 24 hours.

(Comparative Example 14)
The recovery rate of Pt was measured in the same manner as in Example 45 except that the platinum black powder solution to which the reducing agent was added without microwave irradiation was allowed to stand at room temperature for 24 hours.

  Table 8 shows the recovery rate of Pd in Comparative Example 13.

  Table 9 shows the recovery rate of Pt in Comparative Example 14.

  FIG. 14 shows a graph representing the X-ray intensity of Pt, which is a supported metal, before and after the supported metal is eluted from the in-vehicle catalyst by the method of the present disclosure. FIG. 15 is a graph showing the X-ray intensity of Pd and Rh, which are supported metals, and Ce, which is a promoter metal, before and after the supported metals are eluted from the vehicle-mounted catalyst by the method of the present disclosure. According to the method of the present disclosure, it was shown that the supported metal can be selectively dissolved while suppressing the elution of Ce, which is the carrier portion of the vehicle-mounted catalyst, to a small amount.

Claims (4)

Introducing an acid solution into the pores of the honeycomb structure of an in-vehicle catalyst carrying a supported metal on a carrier;
Performing microwave irradiation on the vehicle-mounted catalyst into which the acid solution is introduced, and eluting the supported metal;
Adding a reducing agent to the solution from which the supported metal is eluted;
A method for recovering a supported metal from an in-vehicle catalyst, comprising: irradiating a solution containing the reducing agent with microwaves to precipitate the supported metal; and filtering and recovering the deposited supported metal.   The recovery method according to claim 1, wherein the acid solution is hydrochloric acid or aqua regia.   The collection method according to claim 1 or 2, wherein the microwave irradiation is performed in a nitrogen atmosphere or a rare gas atmosphere on the vehicle-mounted catalyst into which the acid solution is introduced.   The recovery method according to claim 3, wherein the microwave irradiation is performed in an argon atmosphere on the vehicle-mounted catalyst into which the acid solution is introduced.