A method for recovering precious metals from waste catalysts using an ionic liquid composition

Abstract

The present invention discloses a method for recovering noble metals from waste catalysts by using an ionic liquid composition. The catalyst is a molecular sieve-supported catalyst, and the active component is a noble metal. The method includes: mixing an ionic liquid composition including 1-butylsulfonic acid-3-methylimidazole trifluoromethanesulfonate and 1-hydroxyethyl-3-methylimidazole bis(trifluoromethanesulfonyl)imide, trichloroisocyanuric acid and a solvent to obtain a noble metal leaching reagent; then mixing the noble metal leaching reagent with the waste catalyst, ultrasonically treating under light conditions, and then performing steps such as solid-liquid separation, Soxhlet extraction separation, and reacting with a reducing agent to obtain the noble metal. The two ionic liquids used in the present invention have a synergistic effect, significantly improving the recovery rate of noble metals. Moreover, the operation is simple, the conditions are mild, the recovery time is short, it is environmentally friendly, has a high resource utilization rate, is easy to industrialize, and has good application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of waste catalyst recovery, and particularly relates to a method for recovering precious metals from waste catalysts by using an ionic liquid composition. Background Art

[0002] Catalysts play an important role in industrial production, especially in the chemical industry, and are the core of production technology. However, with the extension of the service time, catalysts will be deactivated due to poisoning by toxic substances, thermal aging, blockage of pores by pollutants, etc., and cannot continue to be used normally. Therefore, a large amount of waste catalysts are generated globally every year.

[0003] Due to their special electrochemical properties and excellent catalytic properties, precious metals are widely used in fields such as petrochemical industry, energy, aerospace, experimental instruments, electronics, medicine, etc., and they play an important and irreplaceable role in each field. The precious metal content in waste catalysts is relatively high, especially platinum group precious metals such as platinum, palladium, and rhodium. According to statistics, more than 90% of the precious metals in industry exist in waste petrochemical catalysts, waste automotive exhaust catalysts, waste pharmaceutical and fine chemical homogeneous catalysts.

[0004] The existing waste catalyst treatment technologies mainly include biological methods, wet methods, and pyrometallurgical methods. In biological methods, the cultivation and reproduction conditions of microorganisms are relatively strict, and the leaching time of metals is long, which limits their large-scale application. Pyrometallurgy is to melt waste catalysts at high temperature to enrich precious metals in common metals and then recover them. This method has complex processes, high operating costs, and low precious metal yields. Currently, the wet method for recovery is widely used in industry. Generally, in the wet method for recovery, waste catalysts are crushed and then dissolved in an acidic solution to dissolve the waste catalyst powder, so that the metals enter the acidic solution and are thus separated from the carrier. The leaching agent is the key to determining the recovery rate. Commonly used leaching agents include aqua regia, sulfuric acid - sodium chloride, cyanides, hydrochloric acid - oxidants, supercritical fluids, etc. For example, Chinese Patent CN95104435.4 discloses a method for recovering palladium from waste palladium-carbon catalysts. This method requires prior oxidative roasting, then acid boiling with a sulfuric acid solution to remove impurities, then leaching palladium by the chlorination method, and finally recovering precious metal palladium through steps such as impurity removal, purification, and reduction. This method has the disadvantages of requiring high-temperature treatment, complicated operations, and low recovery rates. Therefore, there is an urgent need for a method for recovering precious metals from waste catalysts that is simple to operate and has a high precious metal recovery rate. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for recovering precious metals from waste catalysts by using an ionic liquid composition. This method is simple to operate, has a short recovery time, and a high precious metal recovery rate, realizes the recycling of waste resources, reduces environmental pollution, is environmentally friendly, and is easy to industrialize.

[0006] To achieve the object of the present invention, the following technical solutions are adopted in the present invention:

[0007] The present invention provides a method for recovering precious metals from waste catalysts by using an ionic liquid composition. The catalyst is a molecular sieve supported catalyst, and the active component is a precious metal. The method comprises the following steps:

[0008] (1) Mix an ionic liquid composition, trichloroisocyanuric acid and a solvent to obtain a precious metal leaching reagent; wherein, by weight percentage, the ionic liquid composition comprises 60%-70% of 1-butylsulfonic acid-3-methylimidazolium trifluoromethanesulfonate and 30%-40% of 1-hydroxyethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide;

[0009] (2) Mix the precious metal leaching reagent obtained in step (1) with the waste catalyst, and ultrasonically treat the obtained mixture at 40°C - 120°C under light conditions for 1 - 8 h;

[0010] (3) Perform solid-liquid separation on the reaction system obtained in step (2) to obtain a solid phase and a liquid phase. The liquid phase is an ionic liquid containing a precious metal complex, and the solid phase is a solid catalyst;

[0011] (4) Use the Soxhlet extraction method to separate the ionic liquid adsorbed on the surface of the catalyst support from the solid catalyst obtained in step (3). After the extraction, a catalyst support and a liquid phase are obtained;

[0012] (5) Mix the liquid phase obtained in step (3) with the liquid phase obtained in step (4), add a reducing agent to react, perform solid-liquid separation after sufficient reaction, wash the obtained solid phase with deionized water first, and then wash away base metal impurities with nitric acid to obtain precious metals; the obtained liquid phase is rotary evaporated to remove the solvent to obtain a regenerated ionic liquid composition.

[0013] Preferably, the precious metals in the waste catalyst include one or more of gold, platinum, palladium, rhodium, and ruthenium.

[0014] Preferably, in step (1):

[0015] By weight percentage, the ionic liquid composition comprises 65%-70% of 1-butylsulfonic acid-3-methylimidazolium trifluoromethanesulfonate and 30%-35% of 1-hydroxyethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide.

[0016] The mass ratio of the ionic liquid composition to the trichloroisocyanuric acid is 20:1 - 4:1, preferably 15:1 - 6:1.

[0017] The volume ratio of the solvent to the ionic liquid composition is 12:1 - 1:1, preferably 10:1 - 2:1.

[0018] The solvent is selected from at least one of acetonitrile, ethanol, propanol, and isopropanol, and preferably acetonitrile or isopropanol.

[0019] Preferably, in step (2):

[0020] The mass ratio of the noble metal leaching reagent to the waste catalyst is 18:1 - 3:1, and preferably 12:1 - 5:1.

[0021] The light irradiation condition is to irradiate with light having a wavelength of 380 nm - 780 nm.

[0022] The temperature is 70°C - 90°C, the ultrasonic time is 1 - 3 h, and the ultrasonic power is 60 - 250 W.

[0023] Preferably, in steps (3) and (5), the solid-liquid separation is carried out using a water circulation filter.

[0024] Preferably, in step (4):

[0025] The solvent used for Soxhlet extraction is the same as the solvent in the noble metal leaching reagent, and the volume is 15 - 35 times, preferably 20 - 30 times, the volume of the noble metal leaching reagent used in step (2).

[0026] The extraction temperature is 40°C - 160°C, preferably 70°C - 110°C, and the extraction time is 10 - 60 h, preferably 20 - 50 h.

[0027] Preferably, in step (5):

[0028] The reducing agent is selected from at least one of NaBH4, LiAlH4, and hydrazine hydrate, and preferably NaBH4 or hydrazine hydrate.

[0029] The mass ratio of the reducing agent to the noble metal in the waste catalyst is 40:1 - 10:1, and preferably 30:1 - 20:1.

[0030] The reduction temperature is 15°C - 70°C, preferably 20°C - 40°C, and the reduction time is 0.5 - 6 h, preferably 1 - 2 h.

[0031] The present invention has no special requirements for the noble metal content in the waste catalyst. Generally, the noble metal loading of the molecular sieve-supported catalyst is between 0.1% and 10%.

[0032] In the present invention, the molecular sieve is selected from one of 10X molecular sieve, 13X molecular sieve, ZSM-5 molecular sieve, SAPO-34 molecular sieve, MCM-41 molecular sieve, etc., and can be processed into spherical or columnar shapes.

[0033] The present invention has the following beneficial effects compared with the prior art:

[0034] (1) The present invention provides a method for recovering precious metals from waste catalysts by using an ionic liquid composition. The components in the ionic liquid composition used in this method have a synergistic effect, and can produce a strong coordination complexation with the precious metals in the catalyst, thereby significantly weakening the interaction between the precious metals and the molecular sieve support, enabling the precious metals to enter the ionic liquid composition phase from the surface of the molecular sieve support, significantly improving the recovery rate of precious metals, and shortening the recovery time.

[0035] (2) The recovery method of the present invention does not require complex processes such as incineration and ion exchange, is simple to operate, has mild conditions, and is environmentally friendly. The main extraction component of the leaching reagent used is an ionic liquid, which has low volatility and stable properties, can be recycled during the entire recovery process, and has little impact on the environment; and it avoids the incineration process of traditional recovery methods, has no waste gas emissions, and also reduces the discharge of waste liquid.

[0036] (3) The molecular sieve support recovered by the recovery method of the present invention can be reused to prepare various catalysts. Compared with traditional recovery methods, it has high resource utilization rate, is easy to industrialize, and conforms to the development direction of green chemistry. Detailed Embodiments

[0037] The embodiments of the present invention are described in detail below. The embodiments are given to better illustrate the content of the present invention and are only used to explain the present invention, and should not be construed as a limitation to the present invention.

[0038] For those without specific technical or conditions noted in the embodiments, they are carried out according to the techniques or conditions described in the literature in this field or according to the product specifications. For reagents or instruments without the manufacturer noted, they are all conventional products that can be obtained through regular channels.

[0039] The experimental methods in the following embodiments are all conventional methods unless otherwise specified. The test materials used in the following embodiments are all commercially available products unless otherwise specified.

[0040] Example 1

[0041] A method for recovering precious metals from waste catalysts by using an ionic liquid composition. The catalyst is a molecular sieve-supported catalyst, and the active components are palladium and rhodium. The method includes the following steps:

[0042] (1) Mix 10 g of ionic liquid composition, 1 g of chlorobromo isocyanuric acid, and 20 mL of acetonitrile to obtain a precious metal leaching reagent; wherein, the ionic liquid composition includes 6.5 g of 1-butylsulfonic acid-3-methylimidazole trifluoromethanesulfonate and 3.5 g of 1-hydroxyethyl-3-methylimidazole bis(trifluoromethanesulfonyl)imide.

[0043] (2) Mix the precious metal leaching reagent obtained in step (1) with 3 g of waste catalyst, and ultrasonically treat the resulting mixture at 80 °C under visible light irradiation at a power of 200 W for 2 h;

[0044] (3) Perform solid-liquid separation on the reaction system obtained in step (2) using a water circulation filter press to obtain a solid phase and a liquid phase. The liquid phase is an ionic liquid containing palladium and rhodium complexes, and the solid phase is a solid catalyst;

[0045] (4) For the solid catalyst obtained in step (3), use the Soxhlet extraction method to separate the ionic liquid adsorbed on the surface of the catalyst support. The solvent is 700 mL of acetonitrile, the extraction temperature is 80 °C, and the extraction is carried out for 30 h to obtain the catalyst support and a liquid phase;

[0046] (5) Mix the liquid phase obtained in step (3) with the liquid phase obtained in step (4), add 7 g of NaBH4 at 30 °C for reaction. After reacting for 1 h, perform solid-liquid separation using a water circulation filter press. The obtained solid phase is first washed with deionized water, and then washed with 2 mL of 10% nitric acid to remove base metal impurities to obtain precious metals; analyze the obtained precious metals, and through calculation, the recovery rate of palladium is 94.89%, and the recovery rate of rhodium is 98.62%.

[0047] Example 2

[0048] A method for recovering precious metals from waste catalysts using an ionic liquid composition, wherein the catalyst is a molecular sieve-supported catalyst, and the active components are platinum and palladium. Steps (1)-(5) of the method are the same as those in Example 1; analyze the obtained precious metals, and through calculation, the recovery rate of platinum is 95.12%, and the recovery rate of palladium is 96.25%.

[0049] Example 3

[0050] A method for recovering precious metals from waste catalysts using an ionic liquid composition, wherein the catalyst is a molecular sieve-supported catalyst, and the active components are ruthenium and rhodium. Steps (1)-(5) of the method are the same as those in Example 1; analyze the obtained precious metals, and through calculation, the recovery rate of ruthenium is 94.76%, and the recovery rate of rhodium is 98.12%.

[0051] Comparative Example 1

[0052] A method for recovering precious metals from waste catalysts using an ionic liquid, wherein the catalyst is a molecular sieve-supported catalyst, and the active components are palladium and rhodium. The method includes the following steps:

[0053] (1) Mix 10 g of ionic liquid 1-butylsulfonic acid-3-methylimidazole trifluoromethanesulfonate, 1 g of chlorobromoisocyanuric acid, and 20 mL of acetonitrile to obtain a precious metal leaching reagent;

[0054] Steps (2)-(5) are the same as those in Example 1; the obtained precious metals were analyzed, and the recovery rate of palladium was calculated to be 78.23%, and the recovery rate of rhodium was 81.65%.

[0055] Comparative Example 2

[0056] A method for recovering precious metals from waste catalysts using ionic liquids, wherein the catalyst is a molecular sieve-supported catalyst, and the active components are palladium and rhodium. The method comprises the following steps:

[0057] (1) Mix 10 g of ionic liquid 1-hydroxyethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1 g of chlorobromoisocyanuric acid, and 20 mL of acetonitrile to obtain a precious metal leaching reagent;

[0058] Steps (2)-(5) are the same as those in Example 1; the obtained precious metals were analyzed, and the recovery rate of palladium was calculated to be 83.57%, and the recovery rate of rhodium was 82.16%.

[0059] Comparative Example 3

[0060] A method for recovering precious metals from waste catalysts using ionic liquids, wherein the catalyst is a molecular sieve-supported catalyst, and the active components are platinum and palladium. The method comprises the following steps:

[0061] (1) Mix 10 g of ionic liquid 1-butylsulfonic acid-3-methylimidazolium trifluoromethanesulfonate, 1 g of chlorobromoisocyanuric acid, and 20 mL of acetonitrile to obtain a precious metal leaching reagent;

[0062] Steps (2)-(5) are the same as those in Example 2; the obtained precious metals were analyzed, and the recovery rate of platinum was calculated to be 76.85%, and the recovery rate of palladium was 80.12%.

[0063] Comparative Example 4

[0064] A method for recovering precious metals from waste catalysts using ionic liquids, wherein the catalyst is a molecular sieve-supported catalyst, and the active components are platinum and palladium. The method comprises the following steps:

[0065] (1) Mix 10 g of ionic liquid 1-hydroxyethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1 g of chlorobromoisocyanuric acid, and 20 mL of acetonitrile to obtain a precious metal leaching reagent;

[0066] Steps (2)-(5) are the same as those in Example 2; the obtained precious metals were analyzed, and the recovery rate of platinum was calculated to be 83.75%, and the recovery rate of palladium was 79.08%.

[0067] Comparative Example 5

[0068] A method for recovering precious metals from waste catalysts using ionic liquids, wherein the catalyst is a molecular sieve supported catalyst, and the active components are ruthenium and rhodium. The method comprises the following steps:

[0069] (1) Mix 10 g of ionic liquid 1-butylsulfonic acid-3-methylimidazolium trifluoromethanesulfonate, 1 g of chlorobromo isocyanuric acid, and 20 mL of acetonitrile to obtain a precious metal leaching reagent;

[0070] Steps (2)-(5) are the same as those in Example 3; the obtained precious metals are analyzed, and the recovery rate of ruthenium is calculated to be 81.02%, and the recovery rate of rhodium is 78.35%.

[0071] Comparative Example 6

[0072] A method for recovering precious metals from waste catalysts using ionic liquids, wherein the catalyst is a molecular sieve supported catalyst, and the active components are ruthenium and rhodium. The method comprises the following steps:

[0073] (1) Mix 10 g of ionic liquid 1-hydroxyethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1 g of chlorobromo isocyanuric acid, and 20 mL of acetonitrile to obtain a precious metal leaching reagent;

[0074] Steps (2)-(5) are the same as those in Example 3; the obtained precious metals are analyzed, and the recovery rate of ruthenium is calculated to be 76.29%, and the recovery rate of rhodium is 80.67%.

[0075] From the above results, it can be seen that the recovery method provided by the present invention uses a combination of two ionic liquids, 1-butylsulfonic acid-3-methylimidazolium trifluoromethanesulfonate and 1-hydroxyethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, to leach precious metals. Compared with using a single ionic liquid to leach precious metals, the recovery rate of precious metals is significantly improved. This shows that the used ionic liquid combination can produce a strong coordination complexation effect with the precious metals in the catalyst, significantly weaken the interaction between the precious metals and the molecular sieve support, and enable the precious metals to enter the ionic liquid combination phase from the surface of the molecular sieve support. Thus, it shows that there is a synergistic effect between the components in the ionic liquid combination of the present invention, significantly improving the recovery rate of precious metals.

[0076] Obviously, the above embodiments are only examples for clearly illustrating the present invention, and are not limitations on the embodiments of the present invention. Those skilled in the art can make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention also intends to include these modifications and variations.

Claims

1. A method for recovering precious metals from waste catalysts using an ionic liquid composition, characterized in that, The catalyst described is a molecular sieve supported catalyst, and the active component is a noble metal. The method includes the following steps: (1) Mix an ionic liquid composition, trichloroisocyanuric acid, and a solvent to obtain a noble metal leaching reagent; wherein, by weight percentage, the ionic liquid composition includes 60%-70% of 1-butylsulfonic acid-3-methylimidazole trifluoromethanesulfonate and 30%-40% of 1-hydroxyethyl-3-methylimidazole bis(trifluoromethanesulfonyl)imide salt; (2) Mix the noble metal leaching reagent obtained in step (1) with the waste catalyst, and ultrasonicate the resulting mixture at 40°C - 120°C under light conditions for 1 - 8 h; (3) Perform solid-liquid separation on the reaction system obtained in step (2) to obtain a solid phase and a liquid phase. The liquid phase is an ionic liquid containing a noble metal complex, and the solid phase is a solid catalyst; (4) For the solid catalyst obtained in step (3), use the Soxhlet extraction method to separate the ionic liquid adsorbed on the surface of the catalyst support. After the extraction, a catalyst support and a liquid phase are obtained; (5) Mix the liquid phase obtained in step (3) with the liquid phase obtained in step (4), add a reducing agent to carry out a reduction reaction. After sufficient reaction, perform solid-liquid separation. The resulting solid phase is first washed with deionized water and then washed with nitric acid to remove base metal impurities to obtain a noble metal; the resulting liquid phase is rotary evaporated to remove the solvent to obtain a regenerated ionic liquid composition; The noble metals in the waste catalyst include multiple ones among gold, platinum, palladium, rhodium, and ruthenium.

2. The method according to claim 1, wherein In step (1), by weight percentage, the ionic liquid composition includes 65%-70% of 1-butylsulfonic acid-3-methylimidazole trifluoromethanesulfonate and 30%-35% of 1-hydroxyethyl-3-methylimidazole bis(trifluoromethanesulfonyl)imide salt.

3. The method according to claim 1, wherein In step (1), the mass ratio of the ionic liquid composition to the trichloroisocyanuric acid is 20:1 - 4:1; the solvent is selected from at least one of acetonitrile, ethanol, propanol, and isopropanol, and the volume ratio of the solvent to the ionic liquid composition is 12:1 - 1:

1.

4. The method according to claim 1, characterized in that, In step (2), the mass ratio of the noble metal leaching reagent to the waste catalyst is 18:1 - 3:

1.

5. The method according to claim 1, wherein In step (2), the light condition is irradiation with light having a wavelength of 380 nm - 780 nm; the temperature is 70°C - 90°C, the ultrasonic time is 1 - 3 h, and the ultrasonic power is 60 - 250 W.

6. The method according to claim 1, wherein In step (4), the solvent used in the Soxhlet extraction method is the same as the solvent in the noble metal leaching reagent, and the volume is 15 - 35 times the volume of the noble metal leaching reagent used in step (2).

7. The method according to claim 1, wherein In step (4), the extraction temperature is 40°C - 160°C, and the extraction time is 10 - 60 h.

8. The method according to claim 1, characterized in that In step (5), the reducing agent is selected from at least one of NaBH4, LiAlH4, and hydrazine hydrate.

9. The method according to claim 1, characterized in that In step (5), the mass ratio of the reducing agent to the noble metal in the waste catalyst is 40:1 - 10:1; the reduction reaction temperature is 15°C - 70°C, and the reduction time is 0.5 - 6 h.