Method for simultaneously recovering noble metal and carrier in supported waste catalyst

Abstract

The invention relates to the technical field of catalyst recovery, and discloses a method for simultaneously recovering noble metal and a carrier in a supported waste catalyst. The roasted waste catalyst is added into dilute acid and chloride to be dissolved, and solid-liquid separation is carried out; adding alkali, a ligand and water into the solid, carrying out complex reaction, and carrying out solid-liquid separation; and washing the solid for multiple times to obtain a carrier, mixing washing water with liquid obtained by two times of solid-liquid separation, and extracting noble metal. According to the method provided by the invention, use of high-concentration strong acid is avoided, the structure of the carrier is perfectly maintained, and efficient recovery of noble metal components and the carrier in the waste noble metal catalyst is realized; meanwhile, the method is simple and easy to implement, mild in operation condition and suitable for industrial production.

Description

Technical Field

[0001] The invention relates to the technical field of catalyst recovery, and in particular to a method for simultaneously recovering precious metals and carriers in supported waste catalysts. Background Art

[0002] Catalysts are the "chips" of the petrochemical industry, and the role of carriers is extremely critical. Alumina carriers are the most widely used in the petrochemical industry, accounting for more than 55%. At present, the cost of using catalysts is high and it is difficult to recycle and reuse them. If the deactivated waste catalysts are not properly disposed of, it will cause the loss of precious metal resources and pollute the environment, endangering human health. Therefore, recycling precious metals from waste catalysts has obvious environmental and economic benefits. At present, the recycling of waste catalysts mainly focuses on the recovery of precious metal components. During the recycling process, the carrier is usually destroyed and cannot be reused. Therefore, it is urgent to break through key technologies to achieve the simultaneous recycling of precious metal components and carriers of waste catalysts.

[0003] At present, the main methods for recovering precious metals from waste catalysts include roasting and leaching, ion exchange, acid hydrolysis and oxidation, high-temperature roasting and acid leaching. The roasting and leaching method requires grinding the waste catalyst into powder and then roasting it at high temperature, then dissolving it with aqua regia, and reducing it with hydrazine hydrate to obtain a crude product for further purification. The ion exchange method is to completely or selectively dissolve the waste catalyst, pass the leaching solution through an anion exchange resin column, wash the resin with dilute acid, and then desorb it with ammonia water to separate various precious metals. The acid hydrolysis and oxidation method requires adding formaldehyde or hydrogen to reduce the waste catalyst under alkaline conditions, and then extracting it with concentrated hydrochloric acid and chlorine to dissolve the precious metals, and replacing the filtrate with aluminum sheets to obtain a crude product. In the high-temperature roasting method, the waste catalyst is heated to 2100°C in an electric furnace, and the carrier is poured out from the top after melting, and the precious metals sink to the bottom of the electric furnace, so that the precious metals can be separated. The acid leaching method is to use concentrated sulfuric acid to sulfatize and roast the catalyst to convert the alumina carrier into aluminum sulfate, which can then be dissolved in water to separate the aluminum sulfate from the precious metals.

[0004] CN115537571A discloses a method for leaching palladium from waste alumina-supported palladium catalyst. The waste catalyst is first ground, added to a reducing agent solution after grinding, and reduced at room temperature; then added to a concentrated hydrochloric acid solution, ozone is introduced, ultrasonic enhanced oxidation leaching is performed, and solid-liquid separation is performed to obtain leached residue and leaching liquid; then palladium is recovered from the leaching liquid. This method requires the waste catalyst to be crushed and dissolved, the carrier is destroyed, and this method uses ozone, the reaction conditions are difficult to control, the amount of waste acid is large, the pollution is serious, and it is not conducive to industrial application.

[0005] CN117165775A discloses a method for recovering palladium from waste palladium catalysts. In this method, the waste catalyst is roasted at high temperature, a mixed system of ammonium chloride, concentrated hydrochloric acid and chlorine dioxide solution is used as an extractant, and reaction leaching is carried out under the assistance of ultrasound and microwave, and the pH value of the leaching solution is adjusted to 1-7 with alkali, and a palladium-containing filtrate is obtained after filtration. This method uses a large amount of hydrochloric acid, and the carrier is severely damaged during the palladium leaching process; at the same time, a large amount of highly polluting strong oxidants are required, and the amount of sewage discharged is large, which is not conducive to environmental protection.

[0006] CN104232900A discloses a method for recovering palladium from waste palladium-alumina catalyst. The waste catalyst is first calcined at high temperature, and then ground; the waste catalyst powder is mixed with metal powder (iron powder, aluminum powder, zinc powder), added to sulfuric acid solution and heated to dissolve; an oxidant is slowly added, and the palladium is stirred and dissolved at a higher temperature to obtain a low-concentration palladium-containing solution, and then a sulfiding agent is added and heated and stirred to completely precipitate the palladium, and the solid-liquid separation is performed to obtain a palladium sulfide concentrate. This method requires the use of a large amount of strong oxidants and sulfiding agents, which is highly polluting and costly.

[0007] At present, the main method for recycling waste precious metal catalysts usually requires destroying the carrier and using high-concentration strong acids and strong oxidants, and mainly focuses on the recovery of precious metals such as palladium, platinum, and gold. Since high-concentration strong acids are extremely destructive to the carrier, they will cause the carrier to disintegrate, destroy the mechanical strength of the carrier, and even completely dissolve the carrier. The use of a large amount of strong acid and strong oxidants will inevitably produce a large amount of strong acid wastewater and discharge a large amount of hazardous waste, which is extremely harmful to the environment.

[0008] Therefore, there is an urgent need to develop a green recovery method for waste precious metal catalysts, which can maintain the pore structure and mechanical strength of the carrier while recovering the precious metal components of the loaded waste catalyst, thereby simultaneously realizing the recovery and reuse of the carrier and greatly reducing the amount of high-concentration strong acid used, thereby significantly reducing wastewater discharge and achieving sustainable development of waste precious metal catalyst recovery technology and industry. Summary of the invention

[0009] The purpose of the present invention is to overcome the problems existing in the prior art and to provide a method for simultaneously recovering precious metals and carriers in supported waste catalysts, so as to solve the problems of large amount of strong acid used, serious damage to the carrier, large amount of wastewater discharge, etc. in the current waste catalyst recovery process.

[0010] In order to achieve the above object, the present invention provides a method for simultaneously recovering precious metals and carriers from supported waste catalysts, wherein the method comprises the following steps:

[0011] (1) adding the calcined spent catalyst into dilute acid for a first dissolution, and then adding chloride for a second dissolution;

[0012] (2) performing a first solid-liquid separation on the system obtained in step (1) to obtain a first liquid and a first solid; adding a base, a ligand and water to the first solid to carry out a complex reaction; performing a first evaporation on the first liquid to obtain a first concentrated liquid and a first vapor, and condensing the first vapor for use in the complex reaction;

[0013] (3) performing a second solid-liquid separation on the reaction product obtained in step (2) to obtain a second liquid and a second solid; washing the second solid to obtain a carrier and washing water; performing a second evaporation on the second liquid to obtain a second concentrated liquid and a second steam, and condensing the second steam for the washing;

[0014] The washing is performed multiple times; the washing water obtained from the previous washing is evaporated, and the obtained steam is condensed and used for the next washing; the concentrated liquids obtained from the multiple evaporations are combined into a third concentrated liquid;

[0015] (4) The first concentrated solution, the second concentrated solution and the third concentrated solution are combined and subjected to reduction reaction to obtain precious metals.

[0016] Through the above technical solution, the beneficial technical effects achieved by the present invention are as follows:

[0017] (1) The method provided by the present invention avoids the use of high-concentration strong acid, the carrier structure is perfectly maintained, and the efficient recovery of precious metal components and carriers in waste precious metal catalysts is achieved; at the same time, the method of the present invention is simple and easy to operate, the operating conditions are mild, and it is suitable for industrial production.

[0018] (2) The washing process provided by the present invention realizes the efficient concentration of precious metal extraction mother liquor and washing liquid and the recovery and reuse of condensed water, which significantly improves the efficiency of resource and energy utilization, avoids the generation of a large amount of waste acid solution, greatly reduces the discharge of wastewater, and has significant environmental benefits.

[0019] (3) The method of the present invention not only improves the utilization value of waste catalysts, but also realizes the recycling of resources and environmental protection; therefore, the implementation of the present invention will have a positive impact on promoting the comprehensive utilization of waste catalyst resources and environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a digital photo of the spent catalyst and recovered alumina carrier in Example 1 of the present invention.

[0021] Figure 2 This is the XRD spectrum of the waste catalyst and the recovered alumina carrier in Example 1 of the present invention.

[0022] Figure 3 These are the nitrogen adsorption-desorption curves of the waste catalyst and the recovered alumina carrier in Example 1 of the present invention.

[0023] Figure 4 This is the pore size distribution curve of the waste catalyst and the recovered alumina carrier in Example 1 of the present invention.

[0024] Figure 5 These are the crushing strength data of the spent catalyst and the recovered alumina carrier in Example 1 of the present invention.

[0025] Figure 6 The Pd and Ag contents in the waste catalyst and the recovered alumina carrier in Example 1 of the present invention. DETAILED DESCRIPTION

[0026] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0027] The present invention provides a method for simultaneously recovering precious metals and carriers from a supported waste catalyst, wherein the method comprises the following steps:

[0028] (1) adding the calcined spent catalyst into dilute acid for a first dissolution, and then adding chloride for a second dissolution;

[0029] (2) performing a first solid-liquid separation on the system obtained in step (1) to obtain a first liquid and a first solid; adding a base, a ligand and water to the first solid to carry out a complex reaction; performing a first evaporation on the first liquid to obtain a first concentrated liquid and a first vapor, and condensing the first vapor for use in the complex reaction;

[0030] (3) performing a second solid-liquid separation on the reaction product obtained in step (2) to obtain a second liquid and a second solid; washing the second solid to obtain a carrier and washing water; performing a second evaporation on the second liquid to obtain a second concentrated liquid and a second steam, and condensing the second steam for the washing;

[0031] The washing is performed multiple times; the washing water obtained from the previous washing is evaporated, and the obtained steam is condensed and used for the next washing; the concentrated liquids obtained from the multiple evaporations are combined into a third concentrated liquid;

[0032] (4) The first concentrated solution, the second concentrated solution and the third concentrated solution are combined and subjected to reduction reaction to obtain precious metals.

[0033] The present invention uses a dilute acid and chloride system to dissolve most of the precious metals (such as silver and palladium), and the undissolved part is dissolved by converting the precious metal into a coordination complex by means of coordination complexation, thereby avoiding the use of high-concentration strong acid that has a strong destructive effect on the carrier, so that the carrier structure is perfectly maintained, and the extraction of precious metal components in the supported waste catalyst and the non-destructive recovery of the carrier are realized.

[0034] The present invention also realizes efficient concentration of precious metal extraction mother liquor and washing water and recycling of condensed water through a washing process, significantly improving resource and energy utilization efficiency and avoiding the generation of a large amount of waste liquid. The method provided by the present invention is simple and easy to operate, has mild operating conditions, and is suitable for industrial production.

[0035] The washing process of the present invention can be carried out in a washing device. When the water covers the solid by 10-80 cm, the carrier is separated from the washing water. In addition, the complex reaction can also be carried out in the same washing device, in which case the second concentrated solution is first combined with the third concentrated solution and then combined with the first concentrated solution.

[0036] In some embodiments of the present invention, the precious metal in the spent catalyst is selected from at least one of gold, silver, ruthenium, rhodium, palladium, osmium, iridium and platinum.

[0037] In some embodiments of the present invention, the carrier in the spent catalyst is alumina.

[0038] In some embodiments of the present invention, the calcination conditions include: heating to 400-800° C. at a heating rate of 5-20° C. / min, and calcining for 1-4 h.

[0039] In some embodiments of the present invention, the heating rate is 5-15°C / min, preferably 10°C / min.

[0040] In some embodiments of the present invention, the temperature at the end point of heating is 500-700°C, preferably 600-650°C.

[0041] In some embodiments of the present invention, the calcination time is 2-3 hours.

[0042] In some embodiments of the present invention, in step (1), the dilute acid is dilute nitric acid and / or dilute hydrochloric acid.

[0043] In some embodiments of the present invention, the concentration of the dilute acid is 0.1-2 mol / L, preferably 0.2-1 mol / L, more preferably 0.6-0.9 mol / L, and more preferably 0.8 mol / L.

[0044] In some embodiments of the present invention, the mass ratio of the dilute acid to the waste catalyst is 1-3:1.

[0045] In some embodiments of the present invention, the first dissolution conditions include: temperature of 20-100°C, preferably 40-60°C, more preferably 50°C; time of 0.5-4h, preferably 1-3h, more preferably 2h.

[0046] In some embodiments of the present invention, in step (1), the chloride is ammonium chloride and / or sodium chloride.

[0047] In some embodiments of the present invention, the amount of the chloride is 10-80% of the mass of the spent catalyst.

[0048] In some embodiments of the present invention, the second dissolution conditions include: temperature of 90-200°C, preferably 120-160°C, more preferably 140-150°C; time of 1-8h, preferably 2-6h, more preferably 3h.

[0049] In some embodiments of the present invention, in step (2), the base is selected from at least one of sodium hydroxide, potassium hydroxide, ammonia water and sodium carbonate. The role of the base is to provide neutral or weak alkaline conditions for the complex reaction.

[0050] In some embodiments of the present invention, the amount of the base used is 0.2-10% of the mass of the waste catalyst.

[0051] In some embodiments of the present invention, the ligand is selected from at least one of ammonium thiosulfate, sodium thiosulfate, ammonium citrate, sodium ethylenediaminetetraacetate, sodium diethylenetriaminepentacarboxylate, sodium ethylenediaminetetramethylenephosphonate, sodium diethylenetriaminepentamethylenephosphonate and sodium tartrate.

[0052] In some embodiments of the present invention, the amount of the ligand used is 0.4-8% of the mass of the waste catalyst.

[0053] In some embodiments of the present invention, in step (2), the conditions of the complexation reaction include: temperature of 60-90° C.; time of 0.2-2 h.

[0054] In some embodiments of the present invention, in step (2), the first liquid is concentrated to 5-10% of the original volume by a first evaporation.

[0055] In some embodiments of the present invention, in step (3), the number of washings is 2 or more times, preferably 8-20 times, and more preferably 10-15 times.

[0056] In some embodiments of the present invention, the washing water obtained after the last washing is used for the preparation of dilute acid.

[0057] In some embodiments of the present invention, in step (4), the reduction reaction conditions include: temperature of 20-100°C, preferably 30-80°C, more preferably 45-50°C; time of 1-8h, preferably 2-6h, more preferably 3h.

[0058] In some embodiments of the present invention, the reducing agent used in the reduction reaction is selected from at least one of sodium borohydride, ascorbic acid, formaldehyde and sodium hypophosphite.

[0059] According to a particularly preferred embodiment of the present invention, a method for simultaneously recovering precious metals and carriers from a supported waste catalyst comprises the following steps:

[0060] (1) placing the spent catalyst in a heating device, heating it to 400-800°C at a heating rate of 5-20°C / min, calcining it for 1-4h, and cooling it to room temperature after calcination;

[0061] (2) preparing a 0.1-2 mol / L dilute acid solution, with a mass ratio of the dilute acid solution to the waste catalyst of 1-3:1, adding the calcined waste catalyst to the dilute acid solution, and pre-treating at 20-100° C. for 0.5-4 h; then adding chloride at a ratio of 10-80% of the mass of the waste catalyst, mixing evenly, reacting at 90-200° C. for 1-8 h, and cooling to room temperature after the reaction is completed;

[0062] (3) The reaction system is subjected to solid-liquid separation, and the mother liquor obtained by separation is heated and evaporated to be concentrated to 5-10% of the volume of the mother liquor to obtain a concentrated mother liquor, and the steam is condensed and used as water for subsequent complexation reaction; the waste catalyst obtained by separation is placed in a washing device, and 0.2-10% of the mass of the waste catalyst, 0.4-8% of the ligand and water at a temperature of 60-90° C. are added, so that the liquid surface covers the waste catalyst carrier by 50-100 cm, and the waste catalyst carrier is allowed to stand for 0.2-2 hours;

[0063] (4) The reaction system is subjected to solid-liquid separation, and the obtained liquid is heated and evaporated to obtain a concentrated liquid. The steam is introduced into a washing device for condensation and directly used for washing the waste catalyst carrier. When the condensed water covers the waste catalyst carrier by 10-80 cm, solid-liquid separation is performed; the washing is repeated 8-20 times, and before the last solid-liquid separation operation, the concentrated liquid is discharged, and the liquid obtained from the last separation is returned to step (2) for preparing dilute acid, and the carrier can be reused again after drying;

[0064] (5) The concentrated mother liquor obtained in step (3) and all the concentrated liquor obtained in step (4) are mixed, a reducing agent is added, and the mixture is reacted at 20-100° C. for 1-8 hours. The obtained product is washed to obtain precious metal powder.

[0065] The present invention will be described in detail below through examples.

[0066] In the following examples and comparative examples, if no specific conditions are specified, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used, if no manufacturer is specified, are all conventional products that can be obtained through commercial channels.

[0067] Example 1

[0068] This example is used to illustrate the method for simultaneously recovering precious metals and carriers from supported waste catalysts.

[0069] (1) Weigh 30 g of spent Pd-Ag / Al2O3 catalyst and place it in a muffle furnace and heat it to 500°C at a rate of 10°C / min for 4 h. After the calcination, cool it to room temperature;

[0070] (2) preparing 40 mL of 0.6 mol / L nitric acid solution, placing the calcined spent catalyst into the nitric acid solution, and treating it in a water bath at 60° C. for 1 h; adding 8 g of ammonium chloride, and after the ammonium chloride is completely dissolved, placing the reactants into a reactor, reacting at 140° C. for 6 h, and cooling naturally to room temperature;

[0071] (3) placing the reaction system obtained in step (2) in a washing column for solid-liquid separation, introducing the obtained mother liquor into a heater for heating and evaporation to obtain a concentrated mother liquor and then conducting the concentrated mother liquor; introducing the obtained steam into a washing column for condensation for subsequent reaction; adding 0.5 g of sodium hydroxide and 0.6 g of ammonium thiosulfate to the washing column, adding 60° C. water until the spent catalyst carrier is submerged by 30 cm, and standing for 30 min;

[0072] (4) The reaction system obtained in step (3) is subjected to solid-liquid separation, and the liquid is introduced into a heater for heating and evaporation to obtain a concentrated liquid; the steam is introduced into a washing column for condensation and directly used for washing the alumina carrier, and solid-liquid separation is performed when the condensed water covers the waste catalyst carrier by 20 cm, and the above evaporation, washing, and solid-liquid separation are repeated 10 times, and the concentrated liquid is discharged before the last solid-liquid separation, and the liquid obtained from the last separation can be used to prepare the dilute acid in step (2);

[0073] (5) The concentrated mother liquor obtained in step (3) and all the concentrated liquor obtained in step (4) were mixed, 0.3 g of ascorbic acid was added, and the mixture was reacted at 80° C. for 6 h. The obtained product was washed to obtain 40.7 mg of palladium-silver alloy.

[0074] Example 2

[0075] This example is used to illustrate the method for simultaneously recovering precious metals and carriers from supported waste catalysts.

[0076] (1) Weigh 50 g of spent Pd-Ag / Al2O3 catalyst and place it in a muffle furnace and heat it to 600°C at a rate of 10°C / min for 2 h. After the calcination, cool it to room temperature;

[0077] (2) preparing 50 mL of 0.8 mol / L nitric acid solution, placing the spent catalyst after calcination into the nitric acid solution, and treating it in a water bath at 50° C. for 1 h; adding 10 g of ammonium chloride, and after the ammonium chloride is completely dissolved, placing the reactants into a reactor, reacting at 160° C. for 2 h, and cooling naturally to room temperature;

[0078] (3) placing the reaction system obtained in step (2) in a washing column for solid-liquid separation, introducing the obtained mother liquor into a heater for heating and evaporation to obtain a concentrated mother liquor and then conducting the concentrated mother liquor; introducing the obtained steam into a washing column for condensation for subsequent reaction; adding 1 g of sodium hydroxide and 1.6 g of ammonium citrate to the washing column, adding 60° C. water until the waste catalyst carrier is covered by 50 cm, and standing for 1 hour;

[0079] (4) The reaction system obtained in step (3) is subjected to solid-liquid separation, and the liquid is introduced into a heater for heating and evaporation to obtain a concentrated liquid; the steam is introduced into a washing column for condensation and directly used for washing the alumina carrier, and the solid-liquid separation is performed when the condensed water covers the waste catalyst carrier by 40 cm, and the above evaporation, washing, and solid-liquid separation are repeated 10 times, and the concentrated liquid is discharged before the last solid-liquid separation, and the liquid obtained from the last separation can be used to prepare the dilute acid in step (2);

[0080] (5) The concentrated mother liquor obtained in step (3) and all the concentrated liquor obtained in step (4) were mixed, 0.5 g of sodium borohydride was added, and the mixture was reacted at 20° C. for 2 h. The obtained product was washed to obtain 116.4 mg of palladium-silver alloy.

[0081] Example 3

[0082] This example is used to illustrate the method for simultaneously recovering precious metals and carriers from supported waste catalysts.

[0083] (1) Weigh 40 g of spent Pt-Ag / Al2O3 catalyst and place it in a muffle furnace and heat it to 700°C at a rate of 10°C / min for 2 h. After calcination, cool it to room temperature;

[0084] (2) preparing 60 mL of a 1.0 mol / L hydrochloric acid solution, placing the calcined spent catalyst into the hydrochloric acid solution, and treating it in a water bath at 40° C. for 2 h; adding 12 g of ammonium chloride, and after the ammonium chloride is completely dissolved, placing the reactants into a reactor, reacting at 150° C. for 3 h, and then cooling naturally to room temperature;

[0085] (3) placing the reaction system obtained in step (2) in a washing column for solid-liquid separation, introducing the obtained mother liquor into a heater for heating and evaporation to obtain a concentrated mother liquor and then conducting the concentrated mother liquor; introducing the obtained steam into a washing column for condensation for subsequent reaction; adding 1.2 g of sodium carbonate and 1.8 g of sodium diethylenetriamine pentacarboxylate to the washing column, adding 80° C. water until the waste catalyst carrier is covered by 50 cm, and standing for 1 hour;

[0086] (4) The reaction system obtained in step (3) is subjected to solid-liquid separation, and the liquid is introduced into a heater for heating and evaporation to obtain a concentrated liquid; the steam is introduced into a washing column for condensation and directly used for washing the alumina carrier, and the solid-liquid separation is performed when the condensed water covers the waste catalyst carrier by 45 cm, and the above evaporation, washing, and solid-liquid separation are repeated 15 times, and the concentrated liquid is discharged before the last solid-liquid separation, and the liquid obtained from the last separation can be used to prepare the dilute acid in step (2);

[0087] (5) The concentrated mother liquor obtained in step (3) and all the concentrated liquor obtained in step (4) were mixed, 1.0 g of formaldehyde was added, and the mixture was reacted at 50° C. for 2 h. The obtained product was washed to obtain 77.4 mg of platinum-silver alloy.

[0088] Example 4

[0089] This example is used to illustrate the method for simultaneously recovering precious metals and carriers from supported waste catalysts.

[0090] (1) Weigh 50 g of waste Pt-Pd / Al2O3 catalyst and place it in a muffle furnace and heat it to 700°C at a rate of 15°C / min for 2 h. After calcination, cool it to room temperature;

[0091] (2) preparing 80 mL of 1.0 mol / L hydrochloric acid solution, placing the spent catalyst after calcination into the hydrochloric acid solution, and treating it in a water bath at 60° C. for 3 h; adding 15 g of ammonium chloride, and after the ammonium chloride is completely dissolved, placing the reactants into a reactor, reacting at 120° C. for 3 h, and cooling naturally to room temperature;

[0092] (3) placing the reaction system obtained in step (2) in a washing column for solid-liquid separation, introducing the obtained mother liquor into a heater for heating and evaporation to obtain a concentrated mother liquor and then conducting the concentrated mother liquor; introducing the obtained steam into a washing column for condensation for subsequent reaction; adding 1.3 g potassium hydroxide and 1.5 g sodium tartrate to the washing column, adding 80° C. water until the waste catalyst carrier is submerged by 60 cm, and standing for 1 hour;

[0093] (4) The reaction system obtained in step (3) is subjected to solid-liquid separation, and the liquid is introduced into a heater for heating and evaporation to obtain a concentrated liquid; the steam is introduced into a washing column for condensation and directly used for washing the alumina carrier, and the solid-liquid separation is performed when the condensed water covers the waste catalyst carrier by 35 cm, and the above evaporation, washing, and solid-liquid separation are repeated 12 times, and the concentrated liquid is discharged before the last solid-liquid separation, and the liquid obtained from the last separation can be used to prepare the dilute acid in step (2);

[0094] (5) The concentrated mother liquor obtained in step (3) and all the concentrated liquor obtained in step (4) were mixed, 1.0 g of sodium hypophosphite was added, and the mixture was reacted at 45° C. for 3 h. The obtained product was washed to obtain 146.4 mg of platinum-palladium alloy.

[0095] Example 5

[0096] This example is used to illustrate the method for simultaneously recovering precious metals and carriers from supported waste catalysts.

[0097] (1) Weigh 100 g of spent Pd-Pt-Ag / Al2O3 catalyst and place it in a muffle furnace and heat it to 650°C at a rate of 5°C / min for 3 h. After the calcination, cool it to room temperature;

[0098] (2) Prepare 120 mL of 0.9 mol / L hydrochloric acid solution, place the calcined spent catalyst into the hydrochloric acid solution, and treat it in a 50°C water bath at a constant temperature for 1 hour; add 20 g of sodium chloride, and after the sodium chloride is completely dissolved, load the reactants into a reactor, react at 160°C for 3 hours, and cool naturally to room temperature;

[0099] (3) placing the reaction system obtained in step (2) in a washing column for solid-liquid separation, introducing the obtained mother liquor into a heater for heating and evaporation to obtain a concentrated mother liquor and then conducting the concentrated mother liquor; introducing the obtained steam into a washing column for condensation for subsequent reaction; adding 4.0 g of potassium hydroxide and 3.0 g of sodium ethylenediaminetetraacetate to the washing column, adding 80° C. water until the waste catalyst carrier is covered by 50 cm, and standing for 1 hour;

[0100] (4) The reaction system obtained in step (3) is subjected to solid-liquid separation, and the liquid is introduced into a heater for heating and evaporation to obtain a concentrated liquid; the steam is introduced into a washing column for condensation and directly used for washing the alumina carrier, and the solid-liquid separation is performed when the condensed water covers the waste catalyst carrier by 45 cm, and the above evaporation, washing, and solid-liquid separation are repeated 15 times, and the concentrated liquid is discharged before the last solid-liquid separation, and the liquid obtained from the last separation can be used to prepare the dilute acid in step (2);

[0101] (5) The concentrated mother liquor obtained in step (3) and all the concentrated liquor obtained in step (4) were mixed, 2.0 g of sodium borohydride was added, and the mixture was reacted at 30° C. for 3 h. The obtained product was washed to obtain 315.7 mg of palladium-platinum-silver alloy.

[0102] Comparative Example 1

[0103] (1) Weigh 100 g of spent Pd-Ag / Al2O3 catalyst and place it in a muffle furnace and heat it to 600°C at a rate of 10°C / min for 4 h. After the calcination, cool it to room temperature;

[0104] (2) preparing 150 mL of a 0.5 mol / L hydrochloric acid solution, placing the calcined spent catalyst into the hydrochloric acid solution, and treating it in a 50°C water bath at a constant temperature for 2 h; adding 20 g of ammonium chloride, and after the ammonium chloride is completely dissolved, placing the reactants into a reactor, reacting at 160°C for 4 h, and cooling naturally to room temperature;

[0105] (3) placing the reaction system obtained in step (2) in a washing column for solid-liquid separation, introducing the obtained mother liquor into a heater for heating and evaporation to obtain a concentrated mother liquor and then conducting the concentrated mother liquor; introducing the obtained steam into a washing column for condensation for subsequent reaction; adding 4.0 g of sodium thiosulfate to the washing column, adding 60° C. water until the waste catalyst carrier is covered by 50 cm, and standing for 30 min;

[0106] (4) The reaction system obtained in step (3) was subjected to solid-liquid separation. The liquid was heated and evaporated to obtain a concentrated solution. The steam was introduced into a washing column for condensation and directly used for washing the alumina carrier. When the condensed water covered the waste catalyst carrier by 40 cm, the solid-liquid separation was performed. The above evaporation, washing, and solid-liquid separation were repeated 10 times. The concentrated solution was drained out before the last solid-liquid separation. It was found that the drained concentrated solution contained black floccules because silver sulfide was formed without adding alkali. The surface of the small ball was also black. Therefore, no subsequent operation was performed.

[0107] Comparative Example 2

[0108] (1) Weigh 300 g of waste Pd-Ag / Al2O3 catalyst (the same as in Example 1) and place it in a muffle furnace and heat it to 700°C at a rate of 10°C / min, calcine it for 2 h, and cool it to room temperature after calcination;

[0109] (2) preparing 400 mL of 0.2 mol / L hydrochloric acid solution, placing the calcined spent catalyst into the hydrochloric acid solution, and treating it in a water bath at 45° C. for 3 h; adding 20 g of sodium chloride, and after the sodium chloride is completely dissolved, placing the reactants into a reactor, reacting at 140° C. for 6 h, and cooling naturally to room temperature;

[0110] (3) The reaction system obtained in step (2) is placed in a washing column for solid-liquid separation, and the obtained mother liquor is placed in a heater for heating and evaporation to obtain a concentrated mother liquor and then discharged; the obtained steam is introduced into a washing column for condensation for subsequent reaction; 3.0 g of potassium hydroxide is added to the washing column, and 60° C. water is added until the waste catalyst carrier is covered by 60 cm, and the column is allowed to stand for 1 hour;

[0111] (4) The reaction system obtained in step (3) is subjected to solid-liquid separation, and the liquid is heated and evaporated to obtain a concentrated liquid; the steam is introduced into a washing column for condensation and directly used for washing the alumina carrier; when the condensed water covers the waste catalyst carrier by 40 cm, the solid-liquid separation is performed; the above evaporation, washing, and solid-liquid separation are repeated 10 times; the concentrated liquid is discharged before the last solid-liquid separation; and the liquid obtained from the last separation can be used for preparing the dilute acid in step (2);

[0112] (5) The concentrated mother liquor obtained in step (3) and all the concentrated liquor obtained in step (4) were mixed, 2.0 g of hydrazine hydrate was added, and the mixture was reacted at 50° C. for 6 h. The obtained product was washed to obtain 144.8 mg of palladium-silver alloy.

[0113] Test Example 1

[0114] Figure 1 and Figure 2 The digital photos and XRD spectra of the waste catalyst and the recovered alumina carrier of Example 1 are respectively.

[0115] from Figure 1 It can be seen that the appearance of the recovered alumina support remains intact; Figure 2 It can be seen that the crystal form of the recovered alumina carrier is consistent with that of the waste catalyst, and the crystal structure is not destroyed.

[0116] Test Example 2

[0117] Figure 3 and Figure 4 They are the nitrogen adsorption-desorption curves and pore size distribution curves of the waste catalyst and the recovered alumina carrier of Example 1, respectively.

[0118] from Figure 3 It can be seen that the nitrogen adsorption and desorption curve of the recycled alumina carrier is consistent with that of the waste catalyst, indicating that the pore structure of the alumina carrier is well maintained; Figure 4 It can be seen that the pore size of the recovered alumina carrier remains consistent with that of the waste catalyst and has basically not changed.

[0119] The specific surface area of ​​the spent catalyst is 18.5876m 2 / g, the average pore size is 33.6934nm; the specific surface area of ​​the treated carrier is 22.0889m 2 / g, and the average pore size is 32.1790nm.

[0120] Test Example 3

[0121] The crushing strength test of the spent catalyst and the recovered alumina carrier of Example 1 was carried out:

[0122] Place the sample in the center of the particle strength tester, apply a uniform load of 1 N / s to 100 N and hold the load steady for 5 seconds, then unload and display the crushing strength. Repeat this method 12 times, remove the maximum and minimum values, and take the average value.

[0123] from Figure 5 It can be seen that the crush strength of the recovered alumina support is very close to that of the spent catalyst, indicating that the macro- and microstructures of the alumina support have hardly changed during the treatment process.

[0124] Test Example 4

[0125] from Figure 6 It can be seen that the Pd and Ag contents in the alumina carrier after treatment are 1.88% and 1.95% of the Pd and Ag contents in the waste catalyst, respectively, indicating that more than 98% of the Pd and Ag in the waste catalyst have been extracted.

[0126] The treatment object of comparative example 2 is the same as that of example 1. The obtained palladium-silver alloy is analyzed and it is found that the palladium is 136.4 mg, the silver is 8.4 mg, and the leaching rates are 91.32% and 9.5%, respectively. The reason is that no ligand is added in step 3, which affects the leaching of palladium and silver, especially the silver cannot be effectively recovered.

[0127] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for simultaneously recovering precious metals and carriers from supported waste catalysts, characterized in that: The method comprises the following steps: (1) adding the calcined spent catalyst into dilute acid for a first dissolution, and then adding chloride for a second dissolution; (2) performing a first solid-liquid separation on the system obtained in step (1) to obtain a first liquid and a first solid; adding a base, a ligand and water to the first solid to carry out a complex reaction; performing a first evaporation on the first liquid to obtain a first concentrated liquid and a first vapor, and condensing the first vapor for use in the complex reaction; (3) performing a second solid-liquid separation on the reaction product obtained in step (2) to obtain a second liquid and a second solid; washing the second solid to obtain a carrier and washing water; performing a second evaporation on the second liquid to obtain a second concentrated liquid and a second steam, and condensing the second steam for the washing; The washing is performed multiple times; the washing water obtained from the previous washing is evaporated, and the obtained steam is condensed and used for the next washing; the concentrated liquids obtained from the multiple evaporations are combined into a third concentrated liquid; (4) The first concentrated solution, the second concentrated solution and the third concentrated solution are combined and subjected to reduction reaction to obtain precious metals.

2. The method according to claim 1, wherein: The precious metal in the spent catalyst is selected from at least one of gold, silver, ruthenium, rhodium, palladium, osmium, iridium and platinum; Preferably, the carrier in the spent catalyst is alumina.

3. The method according to claim 1 or 2, wherein: The calcination conditions include: heating to 400-800°C at a heating rate of 5-20°C / min, and calcining for 1-4h; Preferably, the heating rate is 5-15°C / min, preferably 10°C / min; Preferably, the temperature at the end point of heating is 500-700°C, preferably 600-650°C; Preferably, the calcination time is 2-3 hours.

4. The method according to any one of claims 1 to 3, wherein: In step (1), the dilute acid is dilute nitric acid and / or dilute hydrochloric acid; Preferably, the concentration of the dilute acid is 0.1-2 mol / L, preferably 0.2-1 mol / L, further preferably 0.6-0.9 mol / L, and more preferably 0.8 mol / L; Preferably, the mass ratio of the dilute acid to the spent catalyst is 1-3:1; Preferably, the first dissolution conditions include: a temperature of 20-100°C, preferably 40-60°C, and more preferably 50°C; a time of 0.5-4h, preferably 1-3h, and more preferably 2h.

5. The method according to any one of claims 1 to 4, wherein: In step (1), the chloride is ammonium chloride and / or sodium chloride; Preferably, the amount of the chloride is 10-80% of the mass of the spent catalyst; Preferably, the second dissolution conditions include: temperature of 90-200°C, preferably 120-160°C, more preferably 140-150°C; time of 1-8h, preferably 2-6h, more preferably 3h.

6. The method according to any one of claims 1 to 5, wherein: In step (2), the base is selected from at least one of sodium hydroxide, potassium hydroxide, ammonia water and sodium carbonate; Preferably, the amount of the base is 0.2-10% of the mass of the spent catalyst; Preferably, the ligand is selected from at least one of ammonium thiosulfate, sodium thiosulfate, ammonium citrate, sodium ethylenediaminetetraacetate, sodium diethylenetriaminepentacarboxylate, sodium ethylenediaminetetramethylenephosphonate, sodium diethylenetriaminepentamethylenephosphonate and sodium tartrate; Preferably, the amount of the ligand used is 0.4-8% of the mass of the waste catalyst.

7. The method according to any one of claims 1 to 6, wherein: In step (2), the conditions of the complexation reaction include: temperature of 60-90° C.; time of 0.2-2 h.

8. The method according to any one of claims 1 to 7, wherein: In step (2), the first liquid is concentrated to 5-10% of the original volume by first evaporation.

9. The method according to any one of claims 1 to 8, wherein: In step (3), the number of washings is 2 or more times, preferably 8-20 times, and more preferably 10-15 times; Preferably, the washing water obtained after the last washing is used for the preparation of the dilute acid.

10. The method according to any one of claims 1 to 9, wherein: In step (4), the reduction reaction conditions include: temperature of 20-100°C, preferably 30-80°C, more preferably 45-50°C; time of 1-8h, preferably 2-6h, more preferably 3h; Preferably, the reducing agent used in the reduction reaction is selected from at least one of sodium borohydride, ascorbic acid, formaldehyde and sodium hypophosphite.

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