Method for recovering platinum group metal and separating tin from automobile waste three-way catalyst

Abstract

The invention provides a method for recovering platinum group metal and separating tin from an automobile waste three-way catalyst, which comprises the following steps: weighing 100 parts by weight of waste catalyst, 60-70 parts by weight of fluxing agent, 8-9 parts by weight of borax, 8-12 parts by weight of carbon powder, 8-12 parts by weight of Fe and 10-15 parts by weight of Sn, and uniformly mixing to obtain a mixture; smelting the mixture for 2.5-3.5 hours at the temperature of 1300-1400 DEG C, and cooling to room temperature to obtain a smelted material; separating an alloy phase from smelting slag in the smelted material; weighing 100 parts by weight of the alloy phase, 44-60 parts by weight of nitrate of alkali metal and 50-60 parts by weight of hydroxide of alkali metal, and roasting at 600-700 DEG C for 3-5 hours to obtain a roasted product; and the roasted product is added into water, solid-liquid separation is conducted, and platinum group metal and a stannate solution are obtained respectively.

Description

Technical Field

[0001] The invention relates to the technical field of catalyst recovery, and in particular to a method for recovering platinum group metals and separating tin from automobile waste three-way catalyst. Background Art

[0002] With the development of the automobile industry, the number of cars in use has increased rapidly. At the same time, the car scrapping period has gradually arrived. A large number of scrapped car three-way catalysts urgently need to be processed and developed and utilized.

[0003] Automobile three-way catalysts generally use platinum group metals such as platinum, palladium, and rhodium as active components. The content of platinum group metals in spent catalysts is still very high, and has extremely high recycling value. At present, the recycling of platinum group metals usually adopts high-temperature iron capture smelting method. However, SiO2 in the carrier is reduced to Si element under the action of high temperature and reducing agent and enters the metal phase, forming a silicon-iron alloy with dense structure, extremely high hardness, and extremely corrosion resistance, which seriously hinders the subsequent separation and purification of platinum group metals. Summary of the invention

[0004] The object of the present invention is to provide a method for recovering platinum group metals and separating tin from automobile waste three-way catalysts, so as to solve the problems in the prior art.

[0005] In order to solve the above technical problems, the present invention provides a method for recovering platinum group metals and separating tin from automobile waste three-way catalysts, comprising the following steps:

[0006] According to weight parts, 100 parts of waste catalyst, 60-70 parts of flux, 8-9 parts of borax, 8-12 parts of carbon powder, 8-12 parts of Fe and 10-15 parts of Sn are weighed and mixed uniformly to obtain a mixture;

[0007] The mixture is melted at a temperature of 1300° C. to 1400° C. for 2.5 to 3.5 hours, and cooled to room temperature to obtain a melt;

[0008] separating the alloy phase and the smelting slag in the smelt;

[0009] According to weight parts, 100 parts of the alloy phase, 44-60 parts of alkali metal nitrate, and 50-60 parts of alkali metal hydroxide are weighed, and roasted at 600° C. to 700° C. for 3 h to 5 h to obtain a roasted product;

[0010] The calcined product is added into water and solid-liquid separation is performed to obtain platinum group metal and stannate solutions respectively.

[0011] In one embodiment, the mass ratio of the calcined product to water is 1:10 to 1:12.

[0012] In one embodiment, the particle size of the spent catalyst is less than 100 μm.

[0013] In one embodiment, the flux comprises, by mass percentage, 36-42% anhydrous sodium carbonate, 38-43% calcium oxide and 15-21% calcium fluoride.

[0014] In one embodiment, the alkali metal nitrate may be sodium nitrate or potassium nitrate;

[0015] The alkali metal hydroxide may be sodium hydroxide or potassium hydroxide, and the obtained dilute acid salt solutions are sodium stannate solution and dilute potassium stannate solution respectively.

[0016] In one embodiment, in the step of separating the alloy phase and the smelting slag in the smelt:

[0017] The alloy phase is separated along the boundary line between the alloy phase and the smelting slag.

[0018] It can be seen from the above technical solution that the advantages and positive effects of the present invention are:

[0019] The method of the present invention adds Sn during the process of iron capturing Pt, Pd, and Rh, and uses the relatively low melting point of tin to reduce the overall melting point, thereby greatly reducing the capture temperature. At the same time, due to the addition of Sn, the fluidity of the melt is enhanced and the viscosity is reduced, which reduces the energy loss during the melt flow and thus achieves the effect of reducing energy consumption. In addition, adding Sn during the process of iron capturing Pt, Pd, and Rh can enhance the affinity of the capture agent for platinum group metals and the melt fluidity, so that the platinum group metals can be more effectively separated from the catalyst into the alloy phase during the capture process, reducing the capture of other non-target metals, thereby enhancing its capture effect and improving the metal recovery rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The present invention is a schematic flow diagram of a method for recovering platinum group metals and separating tin from automobile waste three-way catalysts. DETAILED DESCRIPTION

[0021] Typical embodiments that embody the features and advantages of the present invention will be described in detail in the following description. It should be understood that the present invention can have various changes in different embodiments without departing from the scope of the present invention, and the descriptions and illustrations therein are essentially used for illustration purposes rather than for limiting the present invention.

[0022] In order to further illustrate the principle and structure of the present invention, preferred embodiments of the present invention are now described in detail with reference to the accompanying drawings.

[0023] Figure 1 A schematic diagram showing a method for recovering platinum group metals and separating tin from automobile waste three-way catalysts is shown in FIG. Figure 1The method for recovering platinum group metals and separating tin from automobile waste three-way catalyst (hereinafter referred to as the method) comprises the following steps:

[0024] S1. According to weight parts, 100 parts of waste catalyst, 60-70 parts of flux, 8-9 parts of borax, 8-12 parts of carbon powder, 8-12 parts of Fe and 10-15 parts of Sn are weighed and mixed uniformly to obtain a mixture.

[0025] The particle size of the waste catalyst is less than 100 μm.

[0026] In terms of mass percentage, the flux includes 36-42% of anhydrous sodium carbonate, 38-43% of calcium oxide and 10-15% of calcium fluoride.

[0027] The above substances are mixed uniformly by grinding to obtain a mixture.

[0028] S2. Smelting the mixture at a temperature of 1300° C. to 1400° C. for 2.5 to 3.5 hours, cooling to room temperature, and obtaining a molten material.

[0029] The mixture includes carbon powder, which can react with oxygen at high temperature to create a reducing atmosphere. Calcium oxide, calcium fluoride, borax, tin and sodium carbonate act as fluxes to generate compounds such as sodium silicate, calcium borate, aluminum borate and calcium boroaluminate to lower the melting temperature. The addition of iron and tin allows the metals of the platinum group to interact with each other during the eutectic process to form alloys or compounds, thereby improving the separation efficiency.

[0030] Specifically, the mixture is placed in a smelting furnace for smelting. During the process of cooling from 1300°C to 1400°C to room temperature, the smelted mixture is left to stand in the smelting furnace, at which time the heavier alloy phase sinks, while the lighter smelting slag floats, so that the alloy phase and the smelting slag are separated into layers, forming a clear dividing line.

[0031] S3. Separating the alloy phase and smelting slag in the smelt.

[0032] Since the boundary between the alloy phase and the smelting slag is obvious, they can be separated by gently breaking or tapping.

[0033] The alloy phase includes not only platinum group metals but also tin.

[0034] S4. Weigh 100 parts of alloy phase, 44-60 parts of alkali metal nitrate, and 50-60 parts of alkali metal hydroxide according to weight parts, and calcine at 600° C. to 700° C. for 3 h to 5 h to obtain a calcined product.

[0035] The nitrate of the alkali metal may be sodium nitrate or potassium nitrate.

[0036] The alkali metal hydroxide may be sodium hydroxide or potassium hydroxide.

[0037] By roasting the alloy phase with alkali, the tin in the alloy phase is converted into water-soluble stannate and subsequently recovered.

[0038] Exemplarily, the reaction formula of tin and sodium hydroxide during roasting is:

[0039] 2Sn+3NaOH+NaNO 3 =2Na 2 SnO 3 +NH 3 ↑.

[0040] In this step, the platinum group metals are substantially unreacted.

[0041] S5. Add the calcined product into water and perform solid-liquid separation to obtain platinum group metal and stannate solutions respectively.

[0042] The calcined products are mainly platinum group metals and stannates. After adding water, the stannates dissolve in water to form stannate solutions, while the platinum group metals remain solid.

[0043] The solid and the liquid can be separated by filtering to obtain platinum group metal and stannate solutions respectively.

[0044] Preferably, the mass ratio of the calcined product to water is 1:10 to 1:12, so that the concentration of the sodium stannate solution is relatively high and can be stored and transported in fewer containers.

[0045] When the alkali metal nitrate and the alkali metal hydroxide are both sodium salts, the stannate is sodium stannate. When the alkali metal nitrate and the alkali metal hydroxide are both potassium salts, the stannate is potassium stannate.

[0046] The method of the present application adds Sn during the process of iron capturing Pt, Pd, and Rh, and uses the relatively low melting point of tin (about 231.9°C) to reduce the overall melting point, thereby greatly reducing the capture temperature. At the same time, due to the addition of Sn, the fluidity of the melt is enhanced and the viscosity is reduced, which reduces the energy loss during the flow of the melt and achieves the effect of reducing energy consumption. In addition, the addition of Sn during the process of iron capturing Pt, Pd, and Rh can enhance the affinity of the capture agent for platinum group metals and the fluidity of the melt, so that the platinum group metals can be more effectively separated from the catalyst into the alloy phase during the capture process, reducing the capture of other non-target metals, thereby enhancing its capture effect and improving the metal recovery rate.

[0047] In addition, after the pyrometallurgical capture is completed, the tin in the collector is selectively recovered before the wet treatment by using the alkaline roasting-leaching process, by adding alkali metal nitrates and alkali metal roasting and leaching with pure water, rather than entering the wet treatment process and then adding hydrochloric acid, sulfuric acid, and hydrazine hydrate for treatment, thereby achieving the purpose of reducing wastewater discharge.

[0048] The method can achieve Pt, Pd and Rh capture rates of 98.83%, 98.30% and 93.94%, respectively, and the Sn leaching rate reaches 96.21% by utilizing an alkali roasting-leaching process.

[0049] That is, the method has the characteristics of high recovery rate, low energy consumption, and reuse of tin in the collector, and is suitable for industrial production.

[0050] The inventors of the present application have achieved a higher metal recovery rate by strictly designing the content of each component and the parameters in each step. The method is described below through various embodiments.

[0051] Example 1

[0052] The method for recovering platinum group metals and separating tin from automobile waste three-way catalyst in this embodiment comprises the following steps:

[0053] S11. Weigh 100 parts of waste catalyst, 60 parts of flux, 9 parts of borax, 12 parts of carbon powder, 12 parts of Fe and 15 parts of Sn in parts by weight, and mix them evenly to obtain a mixture.

[0054] The particle size of the spent catalyst was 80 μm.

[0055] The flux comprises, by mass percentage, 36% anhydrous sodium carbonate, 43% calcium oxide and 21% calcium fluoride.

[0056] S12, melting the mixture at a temperature of 1300° C. for 3.5 hours, and cooling to room temperature to obtain a molten material.

[0057] S13. Separating the alloy phase and the smelting slag in the smelt.

[0058] S14. Weigh 100 parts of alloy phase, 44 parts of alkali metal nitrate, and 60 parts of alkali metal hydroxide according to weight parts, and calcine at 600° C. for 5 hours to obtain a calcined product.

[0059] S15. Add the calcined product into water and perform solid-liquid separation to obtain platinum group metal and stannate solutions respectively.

[0060] Among them, the mass ratio of the roasted material to water is 1:10.

[0061] Example 2

[0062] The method for recovering platinum group metals and separating tin from automobile waste three-way catalyst in this embodiment comprises the following steps:

[0063] S21. Weigh 100 parts of waste catalyst, 70 parts of flux, 8 parts of borax, 8 parts of carbon powder, 8 parts of Fe and 10 parts of Sn in parts by weight, and mix them evenly to obtain a mixture.

[0064] The particle size of the spent catalyst was 50 μm.

[0065] The flux is calculated by mass percentage and includes 42% anhydrous sodium carbonate, 43% calcium oxide and 15% calcium fluoride.

[0066] S22, smelting the mixture at a temperature of 1400° C. for 2.5 hours, and cooling to room temperature to obtain a smelt.

[0067] S23. Separating the alloy phase and the smelting slag in the smelt.

[0068] S24. Weigh 100 parts of alloy phase, 60 parts of alkali metal nitrate, and 50 parts of alkali metal hydroxide according to weight parts, and calcine them at 700° C. for 3 hours to obtain a calcined product.

[0069] S25. Add the calcined product into water and perform solid-liquid separation to obtain platinum group metal and stannate solutions respectively.

[0070] Among them, the mass ratio of the roasted material to water is 1:12.

[0071] Example 3

[0072] The method for recovering platinum group metals and separating tin from automobile waste three-way catalyst in this embodiment comprises the following steps:

[0073] S31. According to weight parts, 100 parts of waste catalyst, 65 parts of flux, 8.5 parts of borax, 10 parts of carbon powder, 10 parts of Fe and 12 parts of Sn are weighed and mixed uniformly to obtain a mixture.

[0074] The particle size of the spent catalyst was 90 μm.

[0075] The flux comprises, by mass percentage, 42% anhydrous sodium carbonate, 38% calcium oxide and 20% calcium fluoride.

[0076] S32, melting the mixture at a temperature of 1350° C. for 3 hours, and cooling to room temperature to obtain a molten material.

[0077] S33, separating the alloy phase and the smelting slag in the smelt.

[0078] S34. Weigh 100 parts of alloy phase, 50 parts of alkali metal nitrate, and 56 parts of alkali metal hydroxide according to weight parts, and calcine at 650° C. for 4 hours to obtain a calcined product.

[0079] S35, adding the calcined product into water, and performing solid-liquid separation to obtain platinum group metal and stannate solutions respectively.

[0080] Among them, the mass ratio of the roasted material to water is 1:11.

[0081] Example 4

[0082] The method for recovering platinum group metals and separating tin from automobile waste three-way catalyst in this embodiment comprises the following steps:

[0083] S41. According to weight parts, 100 parts of waste catalyst, 68 parts of flux, 8.8 parts of borax, 11 parts of carbon powder, 11 parts of Fe and 14 parts of Sn are weighed and mixed uniformly to obtain a mixture.

[0084] The particle size of the spent catalyst was 60 μm.

[0085] The flux is calculated by mass percentage, and the flux includes 40% anhydrous carbon, 42% calcium oxide and 18% calcium fluoride.

[0086] S42, smelting the mixture at a temperature of 1380° C. for 3 hours, cooling to room temperature, and obtaining a smelt.

[0087] S43, separating the alloy phase and the smelting slag in the smelt.

[0088] S44. Weigh 100 parts of alloy phase, 56 parts of alkali metal nitrate, and 54 parts of alkali metal hydroxide according to weight parts, and calcine them at 600° C. for 5 hours to obtain a calcined product.

[0089] S45, adding the calcined product into water and performing solid-liquid separation to obtain platinum group metal and stannate solutions respectively.

[0090] Among them, the mass ratio of the roasted product to water is 1:10.5.

[0091] Example 5

[0092] The method for recovering platinum group metals and separating tin from automobile waste three-way catalyst in this embodiment comprises the following steps:

[0093] S51. Weigh 100 parts of waste catalyst, 62 parts of flux, 8.2 parts of borax, 9 parts of carbon powder, 10 parts of Fe and 11 parts of Sn in parts by weight, and mix them evenly to obtain a mixture.

[0094] The particle size of the spent catalyst was 10 μm.

[0095] The flux comprises, by mass percentage, 42% anhydrous sodium carbonate, 38% calcium oxide and 19% calcium fluoride.

[0096] S52, smelting the mixture at a temperature of 1300° C. for 3.5 hours, cooling to room temperature, and obtaining a smelt.

[0097] S53, separating the alloy phase and the smelting slag in the smelt.

[0098] S54. Weigh 100 parts of alloy phase, 50 parts of alkali metal nitrate, and 54 parts of alkali metal hydroxide according to weight parts, and calcine at 650° C. for 5 hours to obtain a calcined product.

[0099] S55. Add the calcined product into water and perform solid-liquid separation to obtain platinum group metal and stannate solutions respectively.

[0100] Among them, the mass ratio of the roasted material to water is 1:10.

[0101] Example 6

[0102] The method for recovering platinum group metals and separating tin from automobile waste three-way catalyst in this embodiment comprises the following steps:

[0103] S61. Weigh 100 parts of waste catalyst, 66 parts of flux, 8.5 parts of borax, 10 parts of carbon powder, 12 parts of Fe and 12 parts of Sn in parts by weight, and mix them evenly to obtain a mixture.

[0104] The particle size of the spent catalyst was 30 μm.

[0105] The flux comprises, by mass percentage, 41% anhydrous sodium carbonate, 43% calcium oxide and 16% calcium fluoride.

[0106] S62, smelting the mixture at a temperature of 1400° C. for 2.5 hours, cooling to room temperature, and obtaining a smelt.

[0107] S63. Separating the alloy phase and the smelting slag in the smelt.

[0108] S64. Weigh 100 parts of alloy phase, 44 parts of alkali metal nitrate, and 60 parts of alkali metal hydroxide according to weight parts, and calcine them at 600° C. for 5 hours to obtain a calcined product.

[0109] S65. Add the calcined product into water and perform solid-liquid separation to obtain platinum group metal and stannate solutions respectively.

[0110] Among them, the mass ratio of the roasted material to water is 1:11.

[0111] Comparative Example 1

[0112] The method for recovering platinum group metals and separating tin from automobile waste three-way catalyst in this embodiment comprises the following steps:

[0113] S71. Weigh 100 parts of waste catalyst, 65 parts of flux, 8.5 parts of borax, 10 parts of carbon powder and 10 parts of Fe according to weight, and mix them evenly to obtain a mixture.

[0114] The particle size of the spent catalyst is less than 100 μm.

[0115] The flux comprises, by mass percentage, 42% anhydrous sodium carbonate, 38% calcium oxide and 20% calcium fluoride.

[0116] S72, melting the mixture at a temperature of 1350° C. for 3 hours, and cooling to room temperature to obtain a molten material.

[0117] S73. Separating the alloy phase and the smelting slag in the smelt.

[0118] Examples 1 to 6 and Comparative Example 1 were evaluated respectively, and the evaluation method was as follows:

[0119] The raw materials, tin-iron alloy phase and smelting slag were analyzed by TTR III X-ray diffractometer. The microscopic composition and element distribution of the alloy phase and smelting slag were analyzed and detected by JSM-6360LV scanning electron microscope (SEM) and EDX-GENESIS 60S X-ray energy spectrometer (EDS). The content of platinum group metals in the smelting slag samples was determined by fire assay, and the recovery rate was calculated based on the content of platinum group metals in the raw materials and slag. The data are shown in Table 1.

[0120] Table 1 Platinum group metal capture rate and Sn leaching rate

[0121]

[0122]

[0123] It can be seen from Table 1 that the capture rates of the methods of Examples 1 to 6 are significantly better than that of Comparative Example 1, therefore, the addition of Sn is very important.

[0124] Through the above method detection and analysis, the leaching rate of Sn is greater than 96.21%, the capture rate of Pt reaches 98.83%, the capture rate of Pd reaches 98.30%, and the capture rate of Rh reaches 93.94%.

[0125] Although the present invention has been described with reference to several typical embodiments, it should be understood that the terms used are illustrative and exemplary, rather than restrictive. Since the present invention can be embodied in a variety of forms without departing from the spirit or essence of the invention, it should be understood that the above embodiments are not limited to any of the foregoing details, but should be interpreted broadly within the spirit and scope defined by the appended claims, so all changes and modifications falling within the scope of the claims or their equivalents should be covered by the appended claims.

Claims

1. A method for recovering platinum group metals and separating tin from automobile waste three-way catalysts, characterized in that: The following steps are involved: According to weight parts, 100 parts of waste catalyst, 60-70 parts of flux, 8-9 parts of borax, 8-12 parts of carbon powder, 8-12 parts of Fe and 10-15 parts of Sn are weighed and mixed uniformly to obtain a mixture; The mixture is melted at a temperature of 1300° C. to 1400° C. for 2.5 to 3.5 hours, and cooled to room temperature to obtain a melt; separating the alloy phase and the smelting slag in the smelt; According to weight parts, 100 parts of the alloy phase, 44-60 parts of alkali metal nitrate, and 50-60 parts of alkali metal hydroxide are weighed, and roasted at 600° C. to 700° C. for 3 h to 5 h to obtain a roasted product; The calcined product is added into water and solid-liquid separation is performed to obtain platinum group metal and stannate solutions respectively.

2. The method for recovering platinum group metals and separating tin from automobile waste three-way catalyst according to claim 1, characterized in that: The mass ratio of the calcined product to water is 1:10 to 1:

12.

3. The method for recovering platinum group metals and separating tin from automobile waste three-way catalyst according to claim 1, characterized in that: The particle size of the spent catalyst is less than 100 μm.

4. The method for recovering platinum group metals and separating tin from automobile waste three-way catalyst according to claim 1, characterized in that: In terms of mass percentage, the flux comprises 36-42% anhydrous sodium carbonate, 38-43% calcium oxide and 15-21% calcium fluoride.

5. The method for recovering platinum group metals and separating tin from automobile waste three-way catalyst according to claim 1, characterized in that: The alkali metal nitrate may be sodium nitrate or potassium nitrate; The alkali metal hydroxide may be sodium hydroxide or potassium hydroxide, and the obtained dilute acid salt solutions are sodium stannate solution and dilute potassium stannate solution respectively.

6. The method for recovering platinum group metals and separating tin from automobile waste three-way catalyst according to claim 1, characterized in that: In the step of separating the alloy phase and the smelting slag in the smelt: The alloy phase is separated along the boundary line between the alloy phase and the smelting slag.

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