Method and apparatus for peeling catalyst layer from catalyst

Abstract

To achieve a novel method and apparatus for peeling a catalyst layer from a catalyst.SOLUTION: A peeling method is used which includes: a contact step (S1) of bringing a sulfuric acid solution (10) into contact with a catalyst (5) including a base material (6) and a catalyst layer (7); a heating step (S2) of heating the catalyst (5) after being subjected to the contact step (S1) to 180-260°C; and a peeling step (S3) of peeling the catalyst layer (7) from the base material (6) by causing the catalyst (5) after being subjected to the heating step (S2) and a peeling solution (11) to come into contact with each other.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method and an apparatus for peeling a catalyst layer from a catalyst.

Background Art

[0002] Currently, catalysts including a substrate and a catalyst layer provided on the substrate are used in various applications in various fields.

[0003] For example, a catalyst including a substrate having a honeycomb structure and a catalyst layer having a purification performance for exhaust gas provided on the substrate is used for treating exhaust gas discharged from automobiles and the like (see, for example, Patent Document 1). The catalyst layer is composed of, for example, a support layer (for example, alumina), promoter particles supported on the support layer (for example, one or more particles selected from alumina, zirconia, ceria, and silica, cerium, and composite oxide particles containing zirconium), and a noble metal (for example, platinum, palladium, rhodium) supported on the promoter particles.

[0004] Since the catalyst layer contains precious resources such as noble metals, attention has been focused on techniques for recovering the catalyst layer from the discarded catalyst and techniques for further recovering noble metals and the like from the recovered catalyst layer. In particular, the technique for recovering the catalyst layer from the discarded catalyst is an important technique in the field of catalyst recycling because it greatly affects the amount of noble metals and the like finally recovered. Examples of techniques for recovering the catalyst layer from the catalyst include ultrasonic peeling, electric pulse crushing, and separation combining heating, rapid cooling, and physical treatment (see, for example, Non-Patent Document 1 and Non-Patent Document 2).

[0005] In the ultrasonic peeling, ultrasonic treatment is performed on the waste containing a platinum group metal while the waste is immersed in water or an acidic solution. By this ultrasonic treatment, the catalyst layer is peeled off from the base material. At present, the peeling efficiency of the catalyst layer is low in the ultrasonic peeling. Further, if the ultrasonic peeling is to be carried out on an industrial scale, huge equipment (for example, an ultrasonic transmitter) commensurate with the industrial scale is required.

[0006] In the electric pulse crushing, while the waste containing a platinum group metal is immersed in water, an anode and a cathode are connected to the waste, and a high voltage is applied to the waste through these electrodes. At this time, a large current flows through the interface where different components in the waste come into contact (the interface between the base material and the catalyst layer), and as a result, a local temperature rise occurs at the interface. Due to the temperature rise, the catalyst layer is peeled off from the base material. If the electric pulse crushing is to be carried out on an industrial scale, high-cost equipment commensurate with the industrial scale is required.

[0007] In the separation combining the heating, rapid cooling, and physical treatment, the waste containing a platinum group metal is heated to 600°C to 800°C. Since the way of generating thermal stress is different between the base material and the catalyst layer, the difference between the thermal stress of the base material and the thermal stress of the catalyst layer becomes large due to the heating. By rapidly cooling the waste after heating, the crack propagation in the catalyst layer is promoted. Then, the waste is crushed and the crushed material is sorted, and the catalyst layer peeled off from the base material is recovered. The separation combining the heating, rapid cooling, and physical treatment has a large energy consumption and the process becomes complicated because it includes various treatments, and it is not suitable for industrialization.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Non-Patent Documents

[0009]

Non-Patent Document 1

Non-Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0010] As described above, there is room for improvement in the prior art, and a new peeling method and peeling device for peeling the catalyst layer from the catalyst are required.

[0011] One aspect of the present invention aims to realize a new peeling method and peeling device for peeling the catalyst layer from the catalyst.

Means for Solving the Problems

[0012] In order to solve the above problems, one aspect of the present invention may be the following aspect.

[0013] 〔1〕A contact step of bringing an aqueous sulfuric acid solution into contact with a catalyst including a substrate and a catalyst layer provided on the substrate; a heating step of heating the catalyst after the contact step to 180°C to 260°C; and a peeling step of peeling the catalyst layer from the substrate into the peeling liquid by bringing the catalyst after the heating step into contact with the peeling liquid. A method for peeling a catalyst layer from a catalyst, which has the above steps.

[0014] An aqueous sulfuric acid solution is safer and easier to handle than concentrated sulfuric acid. After bringing the aqueous sulfuric acid solution into contact with a catalyst and then heating the catalyst to 180°C to 260°C, the water contained in the aqueous sulfuric acid solution evaporates, increasing the concentration of sulfuric acid. The concentrated sulfuric acid generated by the evaporation of water can corrode the catalyst layer provided on the substrate. Further, if the corroded catalyst layer is brought into contact with a stripping solution, the catalyst layer can be stripped from the substrate into the stripping solution due to the interaction between the catalyst layer and the stripping solution.

[0015] 〔2〕The stripping method according to 〔1〕, wherein the aqueous sulfuric acid solution has a sulfuric acid concentration of 20% to 30% by mass.

[0016] With such a configuration, the aqueous sulfuric acid solution is safer and easier to handle than concentrated sulfuric acid, and concentrated sulfuric acid can be easily generated from the aqueous sulfuric acid solution by heating at 180°C to 260°C. Thereby, the catalyst layer can be easily stripped from the substrate into the stripping solution.

[0017] 〔3〕The stripping method according to 〔1〕 or 〔2〕, wherein in the stripping step, the catalyst is brought into contact with the stripping solution having a temperature lower than that of the catalyst.

[0018] With such a configuration, the catalyst can be cooled by the stripping solution. When the catalyst is cooled, the catalyst contracts, and due to the change in the shape of the catalyst at this time, etc., the catalyst layer can be efficiently stripped from the substrate into the stripping solution.

[0019] 〔4〕The stripping method according to any one of 〔1〕 to 〔3〕, wherein the heating step includes removing water vapor from the system for heating the catalyst.

[0020] In the heating step, water evaporates from the aqueous sulfuric acid solution, and the water fills the system for heating the catalyst. When the amount of water in the system increases, the evaporation of water from the aqueous sulfuric acid solution is suppressed. With such a configuration, by removing water vapor from the system for heating the catalyst, the evaporation of water from the aqueous sulfuric acid solution can be promoted (in other words, the generation of concentrated sulfuric acid from the aqueous sulfuric acid solution can be promoted).

[0021] [5] The peeling method according to any one of [1] to [4], further comprising a reuse step of reusing the catalyst after the peeling step as the catalyst in the contacting step.

[0022] With this configuration, the catalyst layer remaining on the substrate that could not be peeled off in a single peeling process can be peeled off. For example, when peeling a catalyst layer from a large catalyst or a catalyst with a complex shape, the amount of the catalyst layer remaining on the substrate without being peeled off tends to increase. With this configuration, the catalyst layer can be effectively peeled off from a large catalyst or a catalyst with a complex shape.

[0023] [6] The peeling method according to any one of [1] to [5], wherein the catalyst is unground.

[0024] In the case of the prior art, after the catalyst is ground, an attempt is made to peel off and recover the catalyst layer. In this case, there is a risk that the catalyst layer may be peeled off and lost due to the impact during grinding. According to this configuration, since the grinding process is not performed, the recovery rate of the catalyst layer can be increased.

[0025] [7] A catalyst layer peeling device from a catalyst, comprising: a contacting portion that brings an aqueous sulfuric acid solution into contact with a catalyst including a substrate and a catalyst layer provided on the substrate; a heating portion that heats the catalyst after bringing the aqueous sulfuric acid solution into contact therewith to 180°C to 260°C; and a peeling portion that peels the catalyst layer from the substrate into the peeling liquid by bringing the heated catalyst into contact with the peeling liquid.

[0026] The aqueous sulfuric acid solution is safer and easier to handle than concentrated sulfuric acid. After bringing the aqueous sulfuric acid solution into contact with the catalyst and heating the catalyst to 180°C to 260°C, the water contained in the aqueous sulfuric acid solution evaporates, increasing the concentration of sulfuric acid. The concentrated sulfuric acid generated by the evaporation of water can corrode the catalyst layer provided on the substrate. Further, if the corroded catalyst layer is brought into contact with the peeling liquid, the catalyst layer can be peeled off from the substrate into the peeling liquid due to the interaction between the catalyst layer and the peeling liquid.

[0027] 〔8〕The sulfuric acid aqueous solution in the peeling device according to [7] has a sulfuric acid concentration of 20% by mass to 30% by mass.

[0028] With such a configuration, the sulfuric acid aqueous solution is safer and easier to handle than concentrated sulfuric acid, and concentrated sulfuric acid can be easily generated from the sulfuric acid aqueous solution by heating at 180°C to 260°C. Thereby, the catalyst layer can be easily peeled from the substrate into the peeling liquid.

[0029] 〔9〕The peeling device according to [7] or [8], wherein the peeling portion brings the catalyst into contact with the peeling liquid having a temperature lower than that of the catalyst.

[0030] With such a configuration, the catalyst can be cooled by the peeling liquid. When the catalyst is cooled, the catalyst shrinks, and due to the change in the shape of the catalyst at this time, etc., the catalyst layer can be efficiently peeled from the substrate into the peeling liquid.

[0031] 〔10〕The peeling device according to any one of [7] to [9], wherein the heating portion includes a removing portion for removing water vapor from the system for heating the catalyst.

[0032] In the heating portion, moisture evaporates from the sulfuric acid aqueous solution, and the moisture fills the system for heating the catalyst. When the moisture in the system increases, the evaporation of moisture from the sulfuric acid aqueous solution is suppressed. With such a configuration, by removing water vapor from the system for heating the catalyst, the evaporation of moisture from the sulfuric acid aqueous solution (in other words, the generation of concentrated sulfuric acid from the sulfuric acid aqueous solution) can be promoted.

[0033] 〔11〕The peeling device according to any one of [7] to

[10] , further comprising a return path for returning the catalyst from which the catalyst layer has been peeled at the peeling portion to the contact portion.

[0034] With such a configuration, the catalyst layer remaining on the substrate that could not be peeled off in a single peeling process can be peeled off. For example, when peeling the catalyst layer from a large catalyst or a catalyst with a complex shape, the amount of the catalyst layer remaining on the substrate without being peeled off tends to increase. With such a configuration, the catalyst layer can be effectively peeled off from a large catalyst or a catalyst with a complex shape.

[0035] 〔12〕The catalyst is in an unground state, and the peeling device according to any one of 〔7〕~〔11〕.

[0036] In the case of the prior art, after pulverizing the catalyst, an attempt is made to peel and recover the catalyst layer. In this case, due to the impact during pulverization, etc., there is a risk that the catalyst layer is peeled off and lost. According to such a configuration, since the pulverization process is not performed, the recovery rate of the catalyst layer can be increased.

Advantages of the Invention

[0037] According to one aspect of the present invention, a new peeling method and a peeling device for peeling a catalyst layer from a catalyst can be realized.

Brief Description of the Drawings

[0038]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Mode for Carrying Out the Invention

[0039] 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 each configuration described below, and various modifications are possible within the scope shown in 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. In addition, all academic documents and patent documents described in this specification are incorporated herein by reference. Also, unless otherwise specified in this specification, "A~B" representing a numerical range is intended to mean "A or more and B or less".

[0040] 〔1. Method for Exfoliating Catalyst Layer from Catalyst〕 The method for exfoliating the catalyst layer from the catalyst according to one embodiment of the present invention will be described with reference to FIG. 1 and the like.

[0041] The method for exfoliating the catalyst layer from the catalyst according to one embodiment of the present invention includes a contact step S1 of bringing an aqueous sulfuric acid solution into contact with a catalyst including a substrate and a catalyst layer provided on the substrate, a heating step S2 of heating the catalyst after the contact step S1 to 180°C to 260°C, and an exfoliation step S3 of exfoliating the catalyst layer from the substrate into the stripping liquid by bringing the catalyst after the heating step S2 into contact with the stripping liquid.

[0042] (Contact step S1) Contact step S1 is a step of bringing an aqueous sulfuric acid solution into contact with a catalyst comprising a substrate and a catalyst layer provided on the substrate. By this contact step S1, an aqueous sulfuric acid solution capable of removing moisture in the subsequent heating step S to produce concentrated sulfuric acid can be retained by the catalyst.

[0043] More specifically, contact step S1 may be (i) a step of removing excess aqueous sulfuric acid solution from the catalyst after bringing the aqueous sulfuric acid solution into contact with a catalyst comprising a substrate and a catalyst layer provided on the substrate, or (ii) a step of removing excess aqueous sulfuric acid solution from the catalyst after bringing the aqueous sulfuric acid solution into contact with a catalyst comprising a substrate and a catalyst layer provided on the substrate to impregnate the catalyst with the aqueous sulfuric acid solution. The above-mentioned "removing excess aqueous sulfuric acid solution from the catalyst" can be realized, for example, by (iii) removing the aqueous sulfuric acid solution from the container after introducing the catalyst into the aqueous sulfuric acid solution in the container, or (iv) recovering the catalyst from the aqueous sulfuric acid solution after introducing the catalyst into the aqueous sulfuric acid solution in the container.

[0044] The components constituting the substrate are not limited. The component may be, for example, at least one selected from the group consisting of cordierite, SiC, zeolite, silica, and alumina. More specifically, the component may be at least one selected from the group consisting of MgO, Al 2 O 3 , and SiO 2 selected from the group consisting of.

[0045] The components constituting the catalyst layer are not limited. The component may be, for example, ZrO 2 , CeO 2 , Al 2 O 3 , BaO, CaO, P 2 O 5, C, a platinum group metal, a Zr-Ce-based oxide, a Zr-Nd-based oxide, and / or a Zr-La-based oxide, and may be at least one selected from the group consisting of. The platinum group metal is not limited and may be, for example, at least one selected from the group consisting of Pd, Pt, Rh, Ir, Os, and Ru.

[0046] The structure of the catalyst is not limited and may be, for example, a honeycomb structure or a porous structure.

[0047] The catalyst used in the contacting step S1 may be unground or ground. With the method for peeling the catalyst layer from the catalyst according to an embodiment of the present invention, the catalyst layer can be effectively peeled even from a catalyst that has not undergone a grinding treatment.

[0048] The upper limit value of the mass per catalyst used in the contacting step S1 is not limited. The upper limit value 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 value of the mass per catalyst used in the contacting step S1 is not limited. The lower limit value may be, for example, 0.01 g or more, 0.1 g or more, 1 g or more, or 5 g or more.

[0049] When the mass of the catalyst used in the contacting step S1 is large, it is preferable to employ the recycling step S4 described later. By employing the recycling step S4 described later, the catalyst layer can be effectively peeled even from a catalyst with a large mass.

[0050] The sulfuric acid aqueous solution preferably has a sulfuric acid concentration of 20% by mass to 30% by mass, more preferably 22% by mass to 28% by mass, and even more preferably 24% by mass to 26% by mass. With such a configuration, the sulfuric acid aqueous solution is safer and easier to handle than concentrated sulfuric acid, and by heating at 180°C to 260°C, highly reactive concentrated sulfuric acid can be easily generated from the sulfuric acid aqueous solution. Thereby, the catalyst layer can be easily peeled from the substrate into the stripping solution.

[0051] The sulfuric acid aqueous solution may be (i) formed by mixing water and concentrated sulfuric acid, or (ii) formed by mixing water, concentrated sulfuric acid, and other components. The other components may be those that do not prevent the generation of concentrated sulfuric acid by heating and / or the corrosion of the catalyst layer by concentrated sulfuric acid, and the specific configuration is not limited. The other components are preferably those that promote the generation of concentrated sulfuric acid by heating and / or the corrosion of the catalyst layer by concentrated sulfuric acid (for example, phosphoric acid, phosphate).

[0052] (Heating step S2) The heating step S2 is a step of heating the catalyst after the contact step S1 to 180°C to 260°C. By this heating step S2, the water contained in the sulfuric acid aqueous solution held by the catalyst evaporates, and concentrated sulfuric acid is generated from the sulfuric acid aqueous solution. The concentrated sulfuric acid can corrode the catalyst layer provided on the substrate.

[0053] From the viewpoint of obtaining the advantage of locally generating concentrated sulfuric acid on the surface of the catalyst layer, the heating temperature is preferably 180°C to 260°C, and more preferably 200°C to 230°C.

[0054] The time for heating the catalyst in the heating step S2 is not limited and can be appropriately set according to the heating temperature, the size of the catalyst, and / or the shape of the catalyst, etc. The time can be, for example, 0.5 hours to 24 hours, 1 hour to 20 hours, 1 hour to 16 hours, 1 hour to 13 hours, 1 hour to 10 hours, or 1 hour to 5 hours. If the time is long, it tends to effectively corrode and peel the catalyst layer. On the other hand, if the time is short, the energy consumption can be reduced.

[0055] The heating step S2 preferably includes removing water vapor from the system that heats the catalyst. In the heating step S2, water evaporates from the aqueous sulfuric acid solution, and the water fills the system that heats the catalyst. When the amount of water in the system increases, the evaporation of water from the aqueous sulfuric acid solution is suppressed. With such a configuration, by removing water vapor from the system that heats the catalyst, the evaporation of water from the aqueous sulfuric acid solution (in other words, the production of concentrated sulfuric acid from the aqueous sulfuric acid solution) can be promoted.

[0056] The method for removing water vapor from the system that heats the catalyst is not limited. For example, air is introduced into the system (such as a heating furnace) that houses the catalyst and heats the catalyst, and the air in the system is discharged outside the system. Thereby, water vapor can be removed from the system that heats the catalyst.

[0057] (Peeling step S3) The peeling step S3 is a step of peeling the catalyst layer from the substrate to the peeling liquid by bringing the catalyst after the heating step S2 into contact with the peeling liquid. In the peeling step S3, the catalyst layer can be peeled from the substrate to the peeling liquid by the interaction between the catalyst layer and the peeling liquid.

[0058] The peeling liquid may be any liquid that can peel the catalyst layer from the substrate by the interaction with the catalyst layer, and the specific configuration is not limited. Examples of the peeling liquid include water, NaOH solution, KOH solution, aqueous ammonia, and mixtures thereof. From the viewpoint of generating heat of hydration or heat of neutralization by the contact between the peeling liquid and the catalyst layer, thereby obtaining the advantage of promoting the crack propagation of the catalyst layer, the peeling liquid is preferably water and more preferably NaOH solution.

[0059] In the peeling step S3, it is preferable to bring the catalyst into contact with the peeling liquid whose temperature is lower than that of the catalyst. With such a configuration, the catalyst can be cooled by the peeling liquid. When the catalyst is cooled, the catalyst contracts, and due to the change in the shape of the catalyst at this time, the catalyst layer can be efficiently peeled from the substrate to the peeling liquid.

[0060] In the peeling step S3, for example, it is preferable to bring the catalyst heated to 180°C to 260°C in the heating step S2 into contact with the peeling liquid whose temperature is lower than that of the catalyst. With such a configuration, the catalyst layer can be more efficiently peeled from the substrate to the peeling liquid. The upper limit value of the temperature of the peeling liquid in this case can be, for example, 100°C or lower, 80°C or lower, 60°C or lower, 40°C or lower, 30°C or lower, or 20°C or lower. The lower limit value of the temperature of the peeling liquid in this case can be, for example, 0°C or higher, 3°C or higher, 5°C or higher, or 10°C or higher.

[0061] The greater the difference between the temperature of the catalyst and the temperature of the peeling liquid in contact with the catalyst, the greater the contraction of the catalyst, and the greater the change in the shape of the catalyst at this time. As a result, the catalyst layer can be more efficiently peeled from the substrate to the peeling liquid.

[0062] The peeling liquid containing the catalyst layer obtained in the peeling step S3 may be subjected to, for example, precipitation treatment, centrifugation treatment, neutralization treatment, coprecipitation treatment, and / or adsorption treatment. By these treatments, a desired resource (for example, a platinum group) can be recovered in a high-concentration state. Each of these treatments can be performed according to a known method. For example, by performing neutralization treatment, the recovery rate of the resource (for example, a platinum group) dissolved and eluted in the peeling liquid can be increased by precipitating the resource.

[0063] (Reuse step S4) The method for peeling the catalyst layer from the catalyst according to an embodiment of the present invention preferably has a reuse step S4 of reusing the catalyst after the peeling step S3 as the catalyst in the contact step S1. With such a configuration, the catalyst layer remaining on the substrate that could not be peeled in one peeling treatment can be peeled off.

[0064] The number of times the reuse process S4 is performed is not limited and may be once or multiple times (for example, 2 to 10 times, 2 to 5 times, or 2 to 3 times). In other words, the process consisting of the contact step S1, the heating step S2, and the peeling step S3 may be performed twice or more (for example, 2 to 10 times, 2 to 5 times, or 2 to 3 times) on one catalyst. The number of times the reuse process S4 is performed may be determined according to the size and shape of the catalyst, etc.

[0065] [2. Catalyst layer peeling device from catalyst] The catalyst layer peeling device from the catalyst according to an embodiment of the present invention will be described with reference to FIGS. 2 to 5, etc. Note that the description of the configuration described in the above [1. Catalyst layer peeling method from catalyst] will be omitted below.

[0066] [2-1. Aspect 1 of the peeling device] As shown in FIG. 2, the catalyst layer peeling device 100 from the catalyst according to an embodiment of the present invention contacts a catalyst 5 including a substrate 6 and a catalyst layer 7 provided on the substrate 6 with an aqueous sulfuric acid solution 10, a contact part 1, heats the catalyst 5 after contacting with the aqueous sulfuric acid solution 10 to 180°C to 260°C, a heating part 2, and contacts the heated catalyst 5 with a peeling liquid 11 to peel the catalyst layer 7 from the substrate 6 to the peeling liquid 11, and includes a peeling part 3.

[0067] The contact part 1, the heating part 2, and the peeling part 3 may each have a separate configuration. Alternatively, two or more (two or three) selected from the group consisting of the contact part 1, the heating part 2, and the peeling part 3 may have one configuration. For example, (i) the contact part 1 and the heating part 2 may have one configuration, (ii) the contact part 1 and the peeling part 3 may have one configuration, (iii) the heating part 2 and the peeling part 3 may have one configuration, or (iv) the contact part 1, the heating part 2, and the peeling part 3 may have one configuration.

[0068] (Contact part 1) The contact part 1 is configured to bring the sulfuric acid aqueous solution 10 into contact with a catalyst 5 including a base material 6 and a catalyst layer 7 provided on the base material 6. In the contact part 1, the above-described contact step S1 can be performed.

[0069] The contact part 1 only needs to be configured (for example, a container) that can accommodate the catalyst 5 therein, and its shape and size are not limited.

[0070] The sulfuric acid aqueous solution 10 can be supplied into the contact part 1 via a sulfuric acid supply path 20 (for example, a pipe). The sulfuric acid aqueous solution 10 supplied into the contact part 1 and the catalyst 5 accommodated in the contact part 1 can contact each other.

[0071] The amount of the sulfuric acid aqueous solution 10 supplied into the contact part 1 only needs to be an amount that allows the sulfuric acid aqueous solution 10 and the catalyst 5 accommodated in the contact part 1 to contact each other, and is not limited. A large amount of the sulfuric acid aqueous solution 10 can be introduced into the contact part 1, and the catalyst 5 can be immersed in the sulfuric acid aqueous solution 10. Alternatively, a small amount of the sulfuric acid aqueous solution 10 can be sprayed into the contact part 1, and the sulfuric acid aqueous solution 10 can be applied to the surface of the catalyst 5 accommodated in the contact part 1.

[0072] The sulfuric acid aqueous solution 10 can be recovered from the contact part 1 via a sulfuric acid recovery path 21 (for example, a pipe). Thereby, excess sulfuric acid aqueous solution 10 can be removed from the catalyst 5. The removal of the excess sulfuric acid aqueous solution 10 from the catalyst 5 can also be performed, for example, by tilting the contact part 1 to discharge the sulfuric acid aqueous solution 10 from the inside of the contact part 1 to the outside of the contact part 1. The recovered or discharged sulfuric acid aqueous solution 10 may be supplied into the contact part 1 again and reused.

[0073] The catalyst 5 accommodated in the contact part 1 may be uncrushed or crushed. For the catalyst layer peeling device 100 according to an embodiment of the present invention, the catalyst layer 7 can be effectively peeled off even from a large catalyst 5 that has not undergone a crushing process. Details of the catalyst 5 have been described in the above-mentioned [1. Method for Peeling Catalyst Layer from Catalyst], and the description thereof will be omitted.

[0074] The sulfuric acid aqueous solution 10 preferably has a sulfuric acid concentration of 20% to 30% by mass, more preferably 22% to 28% by mass, and even more preferably 24% to 26% by mass. Details of the sulfuric acid aqueous solution 10 have been described in the above [1. Method for peeling the catalyst layer from the catalyst], so the description thereof will be omitted.

[0075] (Heating unit 2) The heating unit 2 is a configuration (for example, a container equipped with a heater) for heating the catalyst 5 after contacting it with the sulfuric acid aqueous solution 10 to 180°C to 260°C. From the viewpoint of obtaining the advantage of being able to locally generate concentrated sulfuric acid on the surface of the catalyst layer, the heating temperature is preferably 180°C to 260°C, and more preferably 200°C to 230°C. In the heating unit 2, the above-described heating step S2 can be performed.

[0076] In the heating unit 2, heat 16 (for example, hot air) is supplied by the heater 15, and the catalyst 5 in the heating unit 2 can be heated by the heat 16. Note that the configuration for heating the catalyst 5 may be any configuration that can increase the temperature of the catalyst 5, and is not limited to the heater 15.

[0077] The heating unit 2 preferably includes a removal unit 17 for removing water vapor from the system (for example, the inside of the heating unit 2) that heats the catalyst 5. In the heating unit 2, moisture evaporates from the sulfuric acid aqueous solution 10, and the moisture fills the system (for example, the inside of the heating unit 2) that heats the catalyst 5. When the moisture in the system increases, the evaporation of moisture from the sulfuric acid aqueous solution 10 is suppressed (in other words, the generation of concentrated sulfuric acid from the sulfuric acid aqueous solution 10 is suppressed). With this configuration, by removing water vapor from the system that heats the catalyst 5, the evaporation of moisture from the sulfuric acid aqueous solution 10 can be promoted (in other words, the generation of concentrated sulfuric acid from the sulfuric acid aqueous solution 10 can be promoted).

[0078] The method for removing water vapor from the system that heats the catalyst 5 is not limited. For example, air is introduced into the heating section 2 and the air in the heating section 2 is discharged outside the heating section 2. Thereby, water vapor can be removed from the system that heats the catalyst 5.

[0079] The removal section 17 may have any configuration as long as it can remove water vapor from the system that heats the catalyst 5, and the specific configuration is not limited. The removal section 17 may be constituted by, for example, (i) an air introduction passage that introduces air from outside the heating section 2 into the heating section 2 and an air discharge passage that discharges air from inside the heating section 2 to outside the heating section 2, or (ii) an air introduction hole that introduces air from outside the heating section 2 into the heating section 2 and an air discharge hole that discharges air from inside the heating section 2 to outside the heating section 2.

[0080] Another embodiment of the heating section 2 will be described with reference to FIG. 3.

[0081] As shown in FIG. 3, the heating section 2 is covered by a tubular furnace 52 (for example, an electric tubular furnace), and the temperature of the tubular furnace 52 can be controlled to a desired temperature (for example, 180°C to 260°C) by the control section 53. Thereby, the catalyst 5 disposed inside the heating section 2 can be efficiently and evenly heated.

[0082] The two ends of the heating section 2 are each closed by a flange 51, whereby the inside of the heating section 2 is substantially sealed.

[0083] An air introduction passage as the removal section 17 is connected to one of the flanges 51. Air can be introduced into the heating section 2 from the pump 50 through the air introduction passage. An air discharge passage as the removal section 17 is connected to the other flange 51. The air containing water vapor inside the heating section 2 can be discharged outside the heating section 2 through the air discharge passage. The amount of air introduced into the heating section 2 may be appropriately set based on the capacity of the heating section 2 and / or the size of the catalyst 5, etc. (for example, 8 L / min).

[0084] (Peeling section 3) The peeling section 3 is configured to peel the catalyst layer 7 from the base material 6 into the peeling liquid 11 by bringing the heated catalyst 5 into contact with the peeling liquid 11. In the peeling section 3, the catalyst layer 7 can be peeled from the base material 6 into the peeling liquid 11 due to the interaction between the catalyst layer 7 and the peeling liquid 11. In the peeling section 3, the above-described peeling step S3 can be performed.

[0085] The peeling section 3 may have a configuration (for example, a container) capable of accommodating the catalyst 5 therein, and its shape and size are not limited.

[0086] The peeling liquid 11 can be supplied into the peeling section 3 through a peeling liquid supply path (not shown). The peeling liquid 11 supplied into the peeling section 3 and the catalyst 5 accommodated in the peeling section 3 can come into contact with each other.

[0087] The amount of the peeling liquid 11 supplied into the peeling section 3 may be any amount as long as the peeling liquid 11 and the catalyst 5 accommodated in the peeling section 3 can come into contact with each other, and is not limited. A large amount of the peeling liquid 11 may be introduced into the peeling section 3 and the catalyst 5 may be immersed in the peeling liquid 11. At least one treatment selected from the group consisting of bubbling (for example, air bubbling), stirring treatment, shaking treatment, ultrasonic treatment, and heat treatment may be performed on the peeling liquid 11 in the peeling section 3. With such a configuration, the effect of peeling the catalyst layer 7 from the base material 6 into the peeling liquid 11 can be enhanced.

[0088] The peeling liquid 11 containing the catalyst layer 7 can be recovered from inside the peeling section 3 through a peeling liquid recovery path (not shown). The recovery of the peeling liquid 11 containing the catalyst layer 7 can also be performed, for example, by tilting the peeling section 3 to discharge the peeling liquid 11 containing the catalyst layer 7 from inside the peeling section 3 to the outside of the peeling section 3.

[0089] The stripping solution 11 containing the recovered catalyst layer 7 can be further subjected to precipitation treatment, centrifugation treatment, neutralization treatment, coprecipitation treatment, and / or adsorption treatment. By these treatments, desired resources (for example, platinum group) can be recovered. These treatments can be carried out according to known methods. Note that these treatments may be carried out using the stripping section 3 or may be carried out using a configuration different from the stripping section 3. For example, by performing neutralization treatment, the recovery rate of the resource (for example, platinum group) dissolved and eluted in the stripping solution 11 can be increased by precipitating it.

[0090] On the other hand, the substrate 6 left in the stripping section 3 may be reused, recovered, or discarded. The method of using the substrate 6 left in the stripping section 3 is not limited.

[0091] The catalyst layer stripping device 100 from the catalyst according to an embodiment of the present invention preferably includes a return path 25 (for example, a pipe) that returns the catalyst 5 from which the catalyst layer 7 has been stripped in the stripping section 3 (in other words, the substrate 6 having a part of the catalyst layer 7 remaining thereon) to the contact section 1. With this configuration, the catalyst layer 7 remaining on the substrate 6 that could not be stripped in one stripping process can be stripped. The reuse process S4 described above can be performed by the return path 25.

[0092] The stripping section 3 preferably brings the catalyst 5 into contact with the stripping solution 11 having a temperature lower than that of the catalyst 5. With this configuration, the catalyst 5 can be cooled by the stripping solution 11. When the catalyst 5 is cooled, the catalyst 5 contracts, and due to the change in the shape of the catalyst 5 at this time, the catalyst layer 7 can be efficiently stripped from the substrate 6 into the stripping solution 11. The stripping section 3 may include a heating device and / or a cooling device (not shown) for adjusting the temperature of the stripping solution 11 in the stripping section 3.

[0093] The configuration of the stripping solution 11 and the relationship between the temperature of the stripping solution 11 and the temperature of the catalyst 5 have been described in the above [1. Catalyst layer stripping method from catalyst], so the description thereof is omitted.

[0094] 〔2-2. Mode 2 of the peeling device〕 Using FIGS. 4 and 5, another mode of the catalyst layer peeling device 100 according to an embodiment of the present invention will be described.

[0095] As shown in FIG. 4, in the peeling device 100, the contact portion 1 is disposed on the conveyor 60, and the catalyst 5 is disposed within the contact portion 1. An aqueous sulfuric acid solution is supplied into the contact portion 1, and the catalyst 5 is immersed in the aqueous sulfuric acid solution. The aqueous sulfuric acid solution within the contact portion 1 can be discharged from within the contact portion 1 to outside the contact portion 1 while the contact portion 1 is being conveyed by the conveyor 60.

[0096] Next, the contact portion 1 is conveyed into the hot blast stove 61 equipped with the heater 15 by the conveyor 60. Here, the contact portion 1 functions as the heating portion 2. Heat 16 (for example, hot air) is supplied into the interior of the heating portion 2 by the heater 15, and the catalyst 5 within the heating portion 2 is heated by the heat 16. At this time, moisture evaporates from the aqueous sulfuric acid solution, and concentrated sulfuric acid is generated from the aqueous sulfuric acid solution. The air containing water vapor within the hot blast stove 61 is introduced from within the hot blast stove 61 to the heater 15, and as a result, the water vapor within the hot blast stove 61 is removed.

[0097] Next, the heating portion 2 is conveyed outside the hot blast stove 61 by the conveyor 60. Here, the heating portion 2 functions as the peeling portion 3. A peeling liquid (for example, dilute NaOH solution) is added into the peeling portion 3, and bubbling (for example, air bubbling) is performed with respect to the peeling liquid within the peeling portion 3. By the bubbling, the effect of peeling the catalyst layer from the substrate into the peeling liquid can be enhanced. Regarding the peeling liquid within the peeling portion 3, adjustment of the pH (for example, pH 8) may be performed. According to the said structure, resources (for example, platinum group) dissolved in the peeling liquid can be precipitated. If a dilute NaOH solution or the like is used as the peeling liquid, not only the effect of peeling the catalyst layer from the substrate into the peeling liquid but also the effect of precipitating the resources dissolved in the peeling liquid (the effect corresponding to the neutralization treatment) can be obtained.

[0098] Next, by tilting the peeling section 3, the peeling liquid containing the catalyst layer is discharged from inside the peeling section 3 to the outside of the peeling section 3, and the substrate 6 is recovered inside the peeling section 3. The substrate 6 left inside the peeling section 3 may be reused, recovered, or discarded. For example, the peeling section 3 containing the substrate 6 may be transported to a predetermined position by a conveyor 60, and an aqueous sulfuric acid solution may be supplied into the peeling section 3, and the peeling process of the catalyst layer from the catalyst described above may be performed again.

[0099] The above processing steps are taken as Processing Step 1. FIG. 5 is a diagram showing the configuration of the peeling apparatus 100 for performing Processing Step 1 in a planar manner. In the peeling apparatus 100 shown in FIG. 5, one or more (for example, five) contact portions 1 are arranged in the dilute sulfuric acid immersion region where the catalyst is immersed in the aqueous sulfuric acid solution, one or more (for example, five) heating portions 2 are arranged in the heating region where the catalyst is heated, and one or more (for example, five) peeling portions 3 are arranged in the dilute NaOH solution leaching region where the catalyst layer is peeled from the substrate to the peeling liquid. The contact portion 1, the heating portion 2, and the peeling portion 3 are transported so as to draw an ellipse or a circle by a conveyor 60. With such a configuration, the peeling process of the catalyst layer from the catalyst can be continuously performed.

[0100] In the dilute sulfuric acid immersion region, the introduction of the catalyst (for example, crushed waste catalyst) and the aqueous sulfuric acid solution (for example, dilute sulfuric acid) into the contact portion 1 and the discharge of the aqueous sulfuric acid solution (for example, dilute sulfuric acid) from the contact portion 1 can be performed. In the heating region, the heating of the catalyst arranged in the heating portion 2 can be performed. In the dilute NaOH solution leaching region, the introduction of the peeling liquid (for example, dilute NaOH solution) into the peeling portion 3 can be performed. On the downstream side of the dilute NaOH solution leaching region with respect to the rotation direction of the conveyor 60, by tilting the peeling portion 3, the peeling liquid containing the catalyst layer is discharged from inside the peeling portion 3 to the outside of the peeling portion 3, and the substrate can be recovered inside the peeling portion 3.

[0101] Hereinafter, with reference to FIG. 4, any configuration of the peeling apparatus 100 for performing the processing after Processing Step 1 will be further described.

[0102] The stripping liquid containing the catalyst layer discharged from the inside of the stripping section 3 to the outside of the stripping section 3 is supplied to a sieve separator 62, and substances derived from the base material contained in the stripping liquid (for example, cordierite substrates) are removed by the sieve separator 62.

[0103] The stripping liquid discharged from the sieve separator 62 is supplied to a stirring tank 63 and then to a filter separation tank 64. Thereby, unnecessary substances are further removed from the stripping liquid.

[0104] The stripping liquid from which unnecessary substances have been removed can be supplied to a process for separating and purifying a desired resource (for example, platinum group). Known processes can be employed for the separation and purification process.

[0105] The above describes one embodiment of the present invention. In one embodiment of the present invention, for example, exhaust gas discharged from a power source can be purified. Therefore, one embodiment of the present invention may contribute to the achievement of Sustainable Development Goals (SDGs) proposed by the United Nations, such as Goal 7, "Ensure access to affordable, reliable, sustainable and modern energy for all", and Goal 9, "Build resilient infrastructure, promote inclusive and sustainable industrialization and foster innovation".

Examples

[0106] Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to the following examples.

[0107] <1. Measurement methods for various parameters> <1-1. Weight loss rate> Let the weight of the catalyst before the stripping treatment of the catalyst layer be A [g], and the weight of the catalyst after the stripping treatment of the catalyst layer be B [g]. The weight loss rate of the catalyst was determined according to the following formula 1: (Weight loss rate of catalyst) = (1 - B / A) × 100 ··· (Formula 1).

[0108] <1-2. Stripping rate of catalyst layer> The weight loss rate of the catalyst was calculated based on the following formula 2: Weight reduction rate (%) = (0.127×3.1×θ×w) / (0.115×2.58 + 0.127×3.1×θ)×100 ··· (Equation 2).

[0109] Each parameter used in the above (Equation 2) is as follows: · Cross-sectional area of the substrate (based on observation data): 0.115 mm 2 , · Cross-sectional area of the catalyst layer (based on observation data): 0.127 mm 2 , · Specific gravity of the substrate (based on data of the catalyst used): 2.58, · Specific gravity of the catalyst layer (based on data of the catalyst used): 3.1 · θ (value obtained from the porosity of the catalyst coating layer described in the literature): particle filling rate, · w (value obtained by substituting the above θ and the weight reduction rate measured experimentally into Equation (2)): peeling rate, Note that it is assumed that the specific gravity of the substrate and the specific gravity of the catalyst layer are the same before and after peeling. Also, with θ = 0.4, while arbitrarily changing the value of w, the value of the weight reduction rate under specific conditions was calculated.

[0110] Figure 10 shows a function indicating the relationship between the peeling rate of the catalyst layer and the weight reduction rate (weight reduction rate = 0.3462×peeling rate). By substituting the value of the actually measured weight reduction rate into the function, the value of the peeling rate of the catalyst layer can be calculated.

[0111] <2. Consideration of the peeling conditions of the catalyst layer> Under various conditions, the catalyst layer was peeled from the catalyst. As the catalyst, a sample obtained by cutting out a catalyst having a honeycomb structure substrate and a catalyst layer provided on the substrate into a dice shape (10 mm×10 mm×10 mm) was used.

[0112] The main components of the catalyst from which the sample was cut out are described in Table 1 below:

[0113]

Table 1

[0114] As specific tests, the following Tests 1 to 6 with different conditions and Control Tests 1 to 2 were conducted.

[0115] Test 1: A sample whose weight had been measured in advance was immersed in an aqueous sulfuric acid solution (a mixed solution of water (volume 5) and 98% concentrated sulfuric acid (volume 1), H 2 SO 4 with a concentration of 20 to 30% by mass) for 1 hour. Then, the sample was taken out from the aqueous sulfuric acid solution, and the sample was heated at 200°C for 1 hour. The heated sample was immersed in normal-temperature water. Then, the sample was taken out from the water, and after the sample was air-dried, its weight was measured.

[0116] Test 2: A sample whose weight had been measured in advance was immersed in an aqueous sulfuric acid solution (a mixed solution of water (volume 5) and 98% concentrated sulfuric acid (volume 1), H 2 SO 4 with a concentration of 20 to 30% by mass) for 12.5 hours. Then, the sample was taken out from the aqueous sulfuric acid solution, and the sample was heated at 200°C for 1 hour. The heated sample was immersed in normal-temperature water at the heating temperature. Then, the sample was taken out from the water, and after the sample was air-dried, its weight was measured.

[0117] Test 3: A sample whose weight had been measured in advance was immersed in an aqueous sulfuric acid solution (a mixed solution of water (volume 5) and 98% concentrated sulfuric acid (volume 1), H 2 SO 4 with a concentration of 20 to 30% by mass) for 16 hours. Then, the sample was taken out from the aqueous sulfuric acid solution, and the sample was heated at 200°C for 1 hour. The heated sample was immersed in normal-temperature water. Then, the sample was taken out from the water, and after the sample was air-dried, its weight was measured.

[0118] Test 4: A sample whose weight had been measured in advance was immersed in an aqueous sulfuric acid solution (a mixed solution of water (volume 5) and 98% concentrated sulfuric acid (volume 1), H 2 SO 4It was immersed in a sulfuric acid aqueous solution with a concentration of 20 to 30% by mass for 1 hour. Then, the sample was taken out from the sulfuric acid aqueous solution, and the sample was heated at 260 °C for 1 hour. The heated sample was immersed in normal-temperature water while maintaining the heating temperature. Then, the sample was taken out from the water, air-dried, and then weighed.

[0119] Test 5: A sample whose weight had been measured in advance was immersed in a sulfuric acid aqueous solution (a mixed solution of water (volume 5) and 98% concentrated sulfuric acid (volume 1), H 2 SO 4 with a concentration of 20 to 30% by mass for 1 hour. Then, the sample was taken out from the sulfuric acid aqueous solution, and the sample was heated at 180 °C for 1 hour. The heated sample was immersed in normal-temperature water while maintaining the heating temperature. Then, the sample was taken out from the water, air-dried, and then weighed.

[0120] Test 6: A sample whose weight had been measured in advance was immersed in a sulfuric acid aqueous solution (a mixed solution of water (volume 5) and 98% concentrated sulfuric acid (volume 1), H 2 SO 4 with a concentration of 20 to 30% by mass for 1 hour. Then, the sample was taken out from the sulfuric acid aqueous solution, and the sample was heated at 200 °C for 1 hour. After the heated sample was cooled to normal temperature (about 25 °C), the sample was immersed in normal-temperature water. Then, the sample was taken out from the water, air-dried, and then weighed.

[0121] Control Test 1: A sample whose weight had been measured in advance was immersed in a sulfuric acid aqueous solution (a mixed solution of water (volume 5) and 98% concentrated sulfuric acid (volume 1), H 2 SO 4 with a concentration of 20 to 30% by mass for 1 hour. Then, the sample was taken out from the sulfuric acid aqueous solution, and the sample was heated at 120 °C for 1 hour. The heated sample was immersed in normal-temperature water while maintaining the heating temperature. Then, the sample was taken out from the water, air-dried, and then weighed.

[0122] Control Test 2: A sample whose weight had been measured in advance was immersed in a nitric acid aqueous solution (a mixed solution of water (volume 5) and 61% concentrated nitric acid (volume 1), HNO3 It was immersed in a nitric acid aqueous solution with a concentration of about 10% by mass for 5 hours. Then, the sample was taken out from the nitric acid aqueous solution, and the sample was heated at 200°C for 1 hour. The heated sample was immersed in water at room temperature. Then, the sample was taken out from the water, air-dried, and its weight was measured.

[0123] The test results of the weight loss rate and the catalyst layer peeling rate for Tests 1 to 6 and Control Tests 1 to 2 are shown in Table 1 below.

[0124]

Table 2

[0125] The value of the catalyst layer peeling rate calculated based on Equation 2 of <1-2. Peeling rate of the catalyst layer> described above may include the influence of measurement errors of numerical values of various parameters substituted into Equation 2. Therefore, the value of the catalyst layer peeling rate calculated based on Equation 2 may exceed 100%. In Table 2, when the calculated value of the catalyst layer peeling rate exceeded 100%, the value of the catalyst layer peeling rate was described as 100%, and the calculated value of the catalyst layer peeling rate was described in parentheses. In addition, the same description was used for the subsequent test results.

[0126] From Test 1 and Control Test 2, etc., it was clarified that the catalyst layer can be efficiently peeled off by a sulfuric acid aqueous solution.

[0127] From Test 4, Test 5, and Control Test 1, etc., it was clarified that the catalyst layer can be efficiently peeled off at a heating temperature of 180°C or higher, and that most of the catalyst layer can be peeled off at a heating temperature of about 200°C.

[0128] From Test 5 and Test 6, etc., it was clarified that the catalyst layer can be efficiently peeled off by quenching the heated catalyst.

[0129] <3. Component measurement of the peeled product and the neutralization precipitate> Similar to the <2. Catalyst layer peeling test> described above, as the catalyst, a sample obtained by cutting out a catalyst having a honeycomb structure substrate and a catalyst layer provided on the substrate into a die shape (10 mm × 10 mm × 10 mm) was used.

[0130] A sample whose weight was measured in advance was immersed in an aqueous sulfuric acid solution (a mixed solution of water (volume 5) and 98% concentrated sulfuric acid (volume 1), H 2 SO 4 with a concentration of 20 to 30 mass%) for 20 to 140 hours. Then, the sample was taken out from the aqueous sulfuric acid solution, and the sample was heated at 200 °C for 1 hour. The heated sample was immersed in water at room temperature.

[0131] After removing the die-shaped sample from the water, an aqueous NaOH solution was added to the water. As a result, the pH of the water was adjusted to about 7, and the water was neutralized. The water contained the peeled-off matter of the catalyst layer and the precipitate (neutralization precipitate) generated by neutralization.

[0132] The water containing the peeled-off matter and the neutralization precipitate was subjected to centrifugal separation to separate it into water, and the peeled-off matter and the neutralization precipitate. The separated water was filtered through a filter with a pore size of 0.2 μm, and the residue remaining on the filter without passing through the filter was recovered.

[0133] The peeled-off matter and the neutralization precipitate were washed away into a beaker with water. The beaker was heated to 200 °C to evaporate the water until the amount of water became about 20 mL. The peeled-off matter, the neutralization precipitate, and the water in the beaker were transferred into a crucible made of alumina with a purity of 95%. The crucible was heated at 200 °C for 1 hour to completely evaporate the water, and the peeled-off matter and the neutralization precipitate were recovered.

[0134] The above-described test was performed a total of 2 times. The test results such as the weight loss rate in the 2 tests (Test A, Test B) are as shown in Table 3 below.

[0135]

Table 3

[0136] The EDS spectrum and elemental composition of the mixture of the recovered exfoliated material and the neutralization precipitate were analyzed using an EDS device manufactured by Bruker Corporation. The specific analysis method followed the protocol attached to the device.

[0137] Figure 6 shows the test results of the EDS spectrum and elemental composition of the mixture of the exfoliated material and the neutralization precipitate. As is clear from Figure 6, the exfoliated material and the neutralization precipitate contained the elements constituting the catalyst layer. That is, it became clear that the catalyst layer could be exfoliated from the catalyst.

[0138] <4. Consideration regarding multiple exfoliation treatments> Similar to the <2. Exfoliation test of the catalyst layer> described above, as the catalyst, a large sample obtained by cutting out a catalyst having a honeycomb structure substrate and a catalyst layer provided on the substrate into a dice shape (30 mm × 20 mm × 40 mm) was used.

[0139] (First exfoliation treatment) A sample whose weight had been measured in advance was immersed in an aqueous sulfuric acid solution (a mixed solution of water (volume 5) and 98% concentrated sulfuric acid (volume 1), H 2 SO 4 with a concentration of 20 to 30 mass%) for 13 hours. Then, the sample was taken out from the aqueous sulfuric acid solution, and the sample was heated at 200 °C for 5 hours. During the heating, air was introduced into the system (electric furnace) for heating the sample at a flow rate of 8 L / min to discharge water vapor outside the system (electric furnace). The heated sample was immersed in water at room temperature.

[0140] After recovering the dice-shaped sample from the water, an aqueous NaOH solution was added to the water. As a result, the pH of the water was adjusted to about 7 and the water was neutralized. The water contained the exfoliated material of the catalyst layer and the precipitate (neutralization precipitate) generated by the neutralization. The recovered dice-shaped sample was subjected to the second exfoliation treatment described later.

[0141] The water containing the exfoliated material and the neutralization precipitate was subjected to centrifugation to separate it into water, the exfoliated material, and the neutralization precipitate. The separated water was filtered through a filter with a pore size of 0.2 μm, and the residue remaining on the filter that could not pass through the filter was collected.

[0142] The exfoliated material and the neutralization precipitate were rinsed out of the beaker with water. The beaker was heated to 200 °C to evaporate the water until the amount of water became approximately 20 mL. The exfoliated material, the neutralization precipitate, and the water in the beaker were transferred into a crucible made of alumina with a purity of 95%. The crucible was heated at 200 °C for 1 hour to completely evaporate the water, and the exfoliated material and the neutralization precipitate in the first exfoliation treatment were recovered.

[0143] (Second exfoliation treatment) The sample recovered in the first exfoliation treatment described above was immersed in an aqueous sulfuric acid solution (a mixed solution of water (volume 5) and 98% concentrated sulfuric acid (volume 1), H 2 SO 4 with a concentration of 20 - 30 mass%) for 15 hours. Then, the sample was taken out from the aqueous sulfuric acid solution and heated at 200 °C for 5 hours. During this heating, air was introduced into the system (electric furnace) for heating the sample at a flow rate of 8 L / min to discharge water vapor out of the system (electric furnace). The heated sample was immersed in water at room temperature.

[0144] After recovering the dice-shaped sample from the water, an aqueous NaOH solution was added to the water. As a result, the pH of the water was adjusted to approximately 7 and the water was neutralized. The water contained the exfoliated material of the catalyst layer and the precipitate (neutralization precipitate) generated by neutralization.

[0145] The water containing the exfoliated material and the neutralization precipitate was subjected to centrifugation to separate it into water, the exfoliated material, and the neutralization precipitate. The separated water was filtered through a filter with a pore size of 0.2 μm, and the residue remaining on the filter that could not pass through the filter was collected.

[0146] The separated matter and the neutralization precipitate were washed away in a beaker with water. The beaker was heated to 200 °C to evaporate the water until the amount of water became about 20 mL. The separated matter, the neutralization precipitate, and the water in the beaker were transferred into a crucible made of alumina with a purity of 95%. The crucible was heated at 200 °C for 1 hour to completely evaporate the water, and the separated matter and the neutralization precipitate in the second separation treatment were recovered.

[0147] The test results such as the amount of the catalyst before the separation treatment and the amount of the recovered separated matter and neutralization precipitate in the first separation treatment and the second separation treatment are as shown in Table 4 below.

[0148]

Table 4

[0149] FIG. 7 shows the EDS spectrum and the test results of the elemental composition of the mixture of the separated matter and the neutralization precipitate recovered by the first separation treatment. FIG. 8 shows the EDS spectrum and the test results of the elemental composition of the mixture of the separated matter and the neutralization precipitate recovered by the second separation treatment. As is clear from FIGS. 7 and 8, the separated matter and the neutralization precipitate contained the elements constituting the catalyst layer. That is, it became clear that the catalyst layer could be separated from the catalyst.

[0150] <5. Consideration Regarding the Size of the Catalyst> Similar to the <2. Catalyst Layer Separation Test> described above, as the catalyst, three samples of various sizes obtained by cutting out a catalyst including a substrate having a honeycomb structure and a catalyst layer provided on the substrate into a die shape were used. Specifically, a 10.111 g sample was used as Sample 1, a 19.722 g sample was used as Sample 2, and a 58.7435 g sample was used as Sample 3.

[0151] (First Separation Treatment) Samples 1 to 3 whose weights had been measured in advance were put into an aqueous sulfuric acid solution (a mixed solution of water (volume 5) and 98% concentrated sulfuric acid (volume 1), H 2 SO4 Samples 1 to 3 were immersed in a sulfuric acid aqueous solution with a concentration of 20 to 30% by mass for 13 to 141 hours. Thereafter, Samples 1 to 3 were taken out from the sulfuric acid aqueous solution. Sample 1 was heated at 200°C for 5 hours, Sample 2 was heated at 200°C for 1 hour, and Sample 3 was heated at 200°C for 5 hours. Samples 1 to 3 after heating were immersed in water at room temperature.

[0152] After recovering die-like Samples 1 to 3 from the water, an NaOH aqueous solution was added to the water. Thereby, the pH of the water was adjusted to about 7 and the water was neutralized. The water contained the exfoliated matter of the catalyst layer and the precipitate (neutralization precipitate) generated by the neutralization. The recovered die-like Samples 1 to 3 were subjected to the second exfoliation treatment described later.

[0153] The water containing the exfoliated matter and the neutralization precipitate was subjected to centrifugation to separate the water, the exfoliated matter, and the neutralization precipitate. The separated water was filtered through a filter with a pore size of 0.2 μm, and the residue remaining on the filter without passing through the filter was recovered.

[0154] The exfoliated matter and the neutralization precipitate were washed away into a beaker with water. The beaker was heated to 200°C to evaporate the water until the amount of water became about 20 mL. The exfoliated matter, the neutralization precipitate, and the water in the beaker were transferred into a crucible made of alumina with a purity of 95%. The crucible was heated at 200°C for 1 hour to completely evaporate the water, and the exfoliated matter and the neutralization precipitate in the first exfoliation treatment were recovered.

[0155] (Second exfoliation treatment) Samples 1 to 3 recovered in the first exfoliation treatment described above were immersed in a sulfuric acid aqueous solution (a mixed solution of water (volume 5) and 98% concentrated sulfuric acid (volume 1), H 2 SO 4 with a concentration of 20 to 30% by mass) for 13 to 141 hours. Thereafter, Samples 1 to 3 were taken out from the sulfuric acid aqueous solution, and Samples 1 to 3 were heated at 200°C for 5 hours. Samples 1 to 3 after heating were immersed in water at room temperature.

[0156] After collecting die cast - shaped samples 1 to 3 from water, an aqueous NaOH solution was added to the water. As a result, the pH of the water was adjusted to about 7 and the water was neutralized. The water contained the exfoliated matter of the catalyst layer and the precipitate (neutralization precipitate) generated by neutralization.

[0157] The water containing the exfoliated matter and the neutralization precipitate was subjected to centrifugation to separate it into water, and the exfoliated matter and the neutralization precipitate. The separated water was filtered through a filter with a pore size of 0.2 μm, and the residue remaining on the filter without passing through the filter was recovered.

[0158] The exfoliated matter and the neutralization precipitate were washed out into a beaker with water. The beaker was heated to 200 °C to evaporate the water until the amount of water became about 20 mL. The exfoliated matter, the neutralization precipitate, and the water in the beaker were transferred into a crucible made of alumina with a purity of 95%. The crucible was heated at 200 °C for 1 hour to completely evaporate the water, and the exfoliated matter and the neutralization precipitate in the second exfoliation treatment were recovered.

[0159] The amount A (g) of the catalyst before the first exfoliation treatment, the amount B (g) of the catalyst after the second exfoliation treatment, the weight loss rate calculated from the amount of the catalyst before the first exfoliation treatment and the amount of the catalyst after the second exfoliation treatment (=(1 - B / A)×100), the total amount C (g) of the exfoliated matter and the neutralization precipitate recovered in the first exfoliation treatment and the second exfoliation treatment, and the production rate of the exfoliated matter and the neutralization precipitate (=C / A×100) are as shown in Table 5 below.

[0160]

Table 5

[0161] From Table 5, although it shows a tendency that the larger the size of the catalyst, the lower the exfoliation efficiency of the catalyst layer, it has been clarified that in the present invention, the catalyst layer can be exfoliated even from a large catalyst.

[0162] <6. Examination on the heating method of the catalyst> Similar to the <2. Catalyst layer peeling test> described above, as the catalyst, a catalyst (10 mm × 20 mm × 90 mm, 7.8128 g) having a honeycomb structure substrate and a catalyst layer provided on the substrate was used as a sample.

[0163] The sample whose weight had been measured in advance was immersed in an aqueous sulfuric acid solution (a mixed solution of water (volume 5) and 98% concentrated sulfuric acid (volume 1), H 2 SO 4 with a concentration of 20 to 30% by mass) for 85 hours. Then, the sample was taken out from the aqueous sulfuric acid solution and heated using the electric tube furnace shown in Figure 2. Specifically, after placing the sample in the electric tube furnace, the temperature inside the electric tube furnace was raised to 270 °C over 14 minutes, and the sample was heated at 270 °C for 3 hours. The heated sample was immersed in normal temperature water.

[0164] After removing the sample from the water, an aqueous NaOH solution was added to the water. As a result, the pH of the water was adjusted to about 7 and the water was neutralized. The water contained the peeled-off matter of the catalyst layer and the precipitate (neutralization precipitate) generated by neutralization.

[0165] The water containing the peeled-off matter and the neutralization precipitate was subjected to centrifugal separation to separate it into water, and the peeled-off matter and the neutralization precipitate. The separated water was filtered through a filter with a pore size of 0.2 μm, and the residue remaining on the filter without passing through the filter was recovered.

[0166] The peeled-off matter and the neutralization precipitate were washed away into a beaker with water. The beaker was heated to 200 °C to evaporate the water until the amount of water became about 20 mL. The peeled-off matter, the neutralization precipitate, and the water in the beaker were transferred into a crucible made of alumina with a purity of 95%. The crucible was heated at 200 °C for 1 hour to completely evaporate the water, and the peeled-off matter and the neutralization precipitate were recovered.

[0167] The test results such as the weight loss rate in this test are as shown in Table 6 below.

[0168]

Table 6

[0169] It was revealed from Table 6 that the catalyst layer could also be peeled off by the electric tube furnace shown in FIG. 2.

[0170] FIG. 9 shows the test results of the EDS spectrum and elemental composition of the mixture of the peeled-off material and the neutralization precipitate. As is clear from FIG. 9, the peeled-off material and the neutralization precipitate contained the elements constituting the catalyst layer. That is, it was revealed that the catalyst layer could be peeled off from the catalyst.

Industrial Applicability

[0171] The present invention can be used in the field of recovering a catalyst layer from a catalyst. More specifically, the present invention can be used in the recycling field of recovering and reusing useful resources from discarded catalysts (for example, catalysts for engine exhaust gas, honeycomb catalysts for engine exhaust gas).

Explanation of Signs

[0172] 1 Contact part 2 Heating part 3 Peeling part 5 Catalyst 6 Substrate 7 Catalyst layer 10 Aqueous sulfuric acid solution 11 Peeling solution 15 Heater 16 Heat 17 Removal part 20 Sulfuric acid supply path 21 Sulfuric acid recovery path 25 Return path 50 Pump 51 Flange 52 Tube furnace 53 Control part 60 Conveyor 61 Hot blast furnace 62 Sieving separator 63 Stirring tank 64 Filter separation tank 100 Peeling device S1 Contact step S2 Heating Process S3 Peeling Process S4 Recycling Process

Claims

1. A contacting step of bringing an aqueous sulfuric acid solution into contact with a catalyst comprising a base material and a catalyst layer provided on the base material; A heating step of heating the catalyst after the contacting step to 180°C to 260°C; A peeling step of peeling the catalyst layer from the base material into the peeling liquid by bringing the catalyst after the heating step into contact with the peeling liquid. A method for peeling a catalyst layer from a catalyst, comprising:

2. The method for peeling according to claim 1, wherein the aqueous sulfuric acid solution has a sulfuric acid concentration of 20% by mass to 30% by mass.

3. The method for peeling according to claim 1, wherein in the peeling step, the catalyst is brought into contact with the peeling liquid having a temperature lower than that of the catalyst.

4. The method for peeling according to claim 1, wherein the heating step includes removing water vapor from the system for heating the catalyst.

5. The method for peeling according to claim 1, further comprising a reuse step of reusing the catalyst after the peeling step as the catalyst in the contacting step.

6. The method for peeling according to claim 1, wherein the catalyst is unground.

7. A contacting part for bringing an aqueous sulfuric acid solution into contact with a catalyst comprising a base material and a catalyst layer provided on the base material; A heating part for heating the catalyst after bringing the aqueous sulfuric acid solution into contact to 180°C to 260°C; A peeling part for peeling the catalyst layer from the base material into the peeling liquid by bringing the heated catalyst into contact with the peeling liquid. A device for peeling a catalyst layer from a catalyst, comprising:

8. The peeling device according to claim 7, wherein the aqueous sulfuric acid solution has a sulfuric acid concentration of 20% by mass to 30% by mass.

9. The peeling device according to claim 7, wherein the peeling part brings the catalyst into contact with the peeling liquid having a temperature lower than that of the catalyst.

10. The peeling device according to claim 7, wherein the heating part includes a removing part for removing water vapor from the system for heating the catalyst.

11. The peeling device according to claim 7, further comprising a return path for returning the catalyst from which the catalyst layer has been peeled in the peeling part to the contacting part.

12. The peeling device according to claim 7, wherein the catalyst is unground.

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