Method for recovering ruthenium on metal fluoride carrier

Abstract

The invention provides a method for recovering ruthenium on a metal fluoride carrier, and belongs to the technical field of noble metal catalyst recovery. The method comprises the following steps: carrying out microwave treatment on an inactivated RuO2-based catalyst, and carrying out a reaction on a solid subjected to microwave treatment and a low-melting-point hydrofluoride salt under protective gas to obtain a molten salt system; the method comprises the following steps: adding potassium-containing fluoride into a molten salt system in a molten state, and reacting to obtain a K2 [RuF6] solid; the K2 [RuF6] solid is subjected to a reduction reaction in the hydrogen atmosphere, and metal Ru is obtained; or carrying out oxidation reaction in an oxygen atmosphere to obtain a RuO2 solid. According to the method, oxidation volatilization and loss of Ru are avoided, the crystal phase and the stable specific surface area of the carrier are kept, the Ru recovery rate can reach 99.2-99.9%, the Ru purity ranges from 99.91% to 99.98%, and the fluoride carrier can be recycled after being simply washed.

Description

Technical Field

[0001] This invention relates to the field of precious metal catalyst recovery technology, and in particular to a method for recovering ruthenium from a metal fluoride support. Background Technology

[0002] The oxidation of HCl to Cl2 is a crucial process in the chlor-alkali and fluorine-containing chemical industries. In recent years, to meet the demand for the recovery and utilization of fluorine-containing HCl resources, the industry has adopted RuO2-based catalyst systems, with RuO2 as the active component and metal fluorides such as MgF2, CaF2, and AlF3 as supports, for the catalytic oxidation of fluorine-containing HCl. These catalysts exhibit high activity and fluorine resistance, with Ru loading typically ranging from 1% to 5%. However, as the catalyst's operating time increases, its performance gradually declines, leading to activity degradation, shortened operating cycles, and increased economic costs. Since Ru is an expensive precious metal element, the efficient recovery of Ru from deactivated catalysts is of great significance for reducing production costs and improving resource utilization.

[0003] Studies have found that the main reason for the deactivation of metal fluoride catalysts such as RuO2 / MgF2 is that the feed gas often contains trace amounts of C1-C3 organic fluorides (such as CH2F2, CHF3, C2HF5, etc.). These substances are prone to thermal decomposition and free radical coupling reactions at high temperatures, generating heterogeneous polycarbonate residual layers. RuO2 deposits and covers the catalyst surface, blocking pores and shielding Ru active sites; on the other hand, some RuO2 active sites react with HF or fluorination intermediates in the reaction system to form partially fluorinated RuO2 species, which hinders the redox cycle of ruthenium and leads to fluorine poisoning and deactivation of the catalyst.

[0004] In existing technologies, Ru recovery typically employs two methods: one is the alkaline fusion oxidation method (CN101663242A, CN109055738B, CN115874060B), which involves treating a Ru-containing solid catalyst with alkaline fusion, then adding a strong oxidant (such as NaClO3, NaClO, etc.) to oxidize Ru to volatile RuO4, which is then absorbed in hydrochloric acid to generate a RuCl3 solution; the other is the reduction-oxidation combined method (such as CN101583729B, CN101654740A, CN101316656A, CN101331240B), which involves first reducing RuO2 to metallic Ru under a reducing atmosphere such as H2 or CO, and then reacting it with a strong oxidant under alkaline conditions to dissolve Ru from the solid catalyst into the solution, or oxidizing it under acidic conditions and being absorbed by hydrochloric acid to form a RuCl3 solution.

[0005] However, the aforementioned traditional methods have significant limitations when dealing with deactivated RuO2 / MgF2 catalysts containing carbon and fluorine residues and ruthenium fluoride species. This is due to the dense... The polymer residue covering the active surface of Ru hinders the contact between the oxidant and Ru, making it difficult for Ru to be completely oxidized to RuO4 gas. Simultaneously, the partially fluorinated RuO2 species exhibits high chemical stability, making it difficult to decompose and transform under alkaline fusion and oxidation conditions, resulting in a significant reduction in Ru leaching rate and overall recovery rate. Furthermore, the traditional alkaline fusion process requires a high-temperature, highly corrosive environment, which not only places high demands on equipment materials but also easily causes secondary pollution.

[0006] Therefore, there is an urgent need for a novel Ru recovery method that targets the characteristics of carbon-fluorine residual layers and partially fluorinated RuO2 species, which can effectively break the fluoropolymer coating layer on the catalyst surface, activate inert Ru species, and achieve efficient, low-energy, and controllable recovery of Ru element, so as to solve the problems of low recovery rate and poor process applicability in existing technologies. Summary of the Invention

[0007] The purpose of this invention is to provide a method for recovering ruthenium from a metal fluoride carrier, so as to solve the problems of low Ru recovery rate and low purity in the prior art.

[0008] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for recovering ruthenium from a metal fluoride support, comprising the following steps: 1) The deactivated RuO2-based catalyst is microwave-treated, and the microwave-treated solid reacts with a low-melting-point hydrofluoric acid salt under a protective gas to obtain a molten salt system. 2) Potassium-containing fluorides are added to a molten salt system to react and obtain solid K2[RuF6]. 3) K2[RuF6] solid undergoes a reduction reaction under a hydrogen atmosphere to obtain metallic Ru; or K2[RuF6] solid undergoes an oxidation reaction under an oxygen atmosphere to obtain RuO2 solid.

[0009] Preferably, in the deactivated RuO2-based catalyst, the active component is RuO2, and the support is a metal fluoride, which includes one or more of magnesium fluoride, calcium fluoride, and aluminum fluoride.

[0010] Preferably, the microwave processing in step 1) has a frequency of 2.25~2.65GHz, a power of 200~600W, and a time of 10~30min.

[0011] Preferably, the low-melting-point hydrofluoric acid salt in step 1) is ammonium hydrogen fluoride and lithium hydrogen fluoride, and the molar ratio of ammonium hydrogen fluoride and lithium hydrogen fluoride is 1~3:1; the mass ratio of the low-melting-point hydrofluoric acid salt to the deactivated RuO2-based catalyst is 0.5~1.5:1.

[0012] Preferably, the protective gas in step 1) is one or more of nitrogen, argon and helium; the reaction temperature is 120~180℃ and the reaction time is 2~6h.

[0013] Preferably, the potassium-containing fluoride in step 2) is KF and / or KHF2; the molar ratio of K in the potassium-containing fluoride to Ru in the deactivated RuO2-based catalyst is 2.2~5:1.

[0014] Preferably, the temperature of the molten salt system in the molten state is 120~200℃, and the reaction time is 25~35min.

[0015] Preferably, the reduction and oxidation reactions in step 3) are carried out at temperatures of 300-400°C and for times of 2-6 hours.

[0016] Preferably, after the reduction and oxidation reactions are completed, the reaction products are washed with water, and the washed KF is added to the molten salt system as a potassium fluoride for recycling.

[0017] The beneficial effects of this invention are: 1) This invention employs microwave selective decoupling technology, fully utilizing the high dielectric loss and strong local Joule heating effect of RuO2 in a microwave field. In contrast, the metal fluoride support and the fluoropolymer layer on its surface are almost transparent to microwaves and do not produce a significant heating effect. Through the selective absorption of microwaves by RuO2, a local high-temperature region can be formed on the catalyst surface, achieving a dense fluoropolymer layer ( The method involves localized thermal decomposition and removal of Ru, effectively exposing the coated Ru active species. Without damaging the structure of the metal fluoride support, this method thoroughly removes the fluorocarbon residue that hinders the participation of Ru active sites in the reaction, providing a sufficient reaction interface for subsequent fluorine complexation reactions. Compared with traditional high-temperature incineration or alkaline fusion pretreatment, the method of this invention not only avoids the oxidation, volatilization, and loss of Ru, but also maintains the crystal phase and stable specific surface area of ​​the support, increasing the overall Ru recovery rate from less than 50% to over 99%. Furthermore, the fluoride support can be recycled after simple washing.

[0018] 2) This invention uses a low-melting-point hydrofluoric acid salt system as an anhydrous complexing medium. Without the need for strong oxidants, inert RuO2 and its partial fluorides RuO2 can be complexed at 120-180°C. x F yIt is converted into a soluble fluorine complex [RuF6]. 2- Throughout the reaction, Ru exists in a solid or molten salt dissolved state, without generating volatile RuO4, thus avoiding the problems of Ru volatilization loss and incomplete recovery in traditional alkaline fusion oxidation methods. The process of this invention is carried out entirely in an anhydrous hydrofluoric acid salt system, without using strong acids, strong bases, or strong oxidizing media; no alkaline fusion, acid washing, or multi-stage solution extraction operations are required during the reaction. The process system is closed, has low corrosivity, and produces no waste acid or wastewater discharge. The by-product fluoride salt can be recycled, making the overall process green, controllable, and environmentally friendly.

[0019] 3) This invention further utilizes [RuF6] formed in the hydrofluoric acid salt system. 2- The ion exchange properties between complexed anions and potassium ions allow for the directional formation of K2[RuF6] crystals by introducing KF or KHF2 in the molten state. K2[RuF6] crystals possess a stable chemical structure and high purity, and can be used as intermediates to produce high-purity Ru metal or RuO2 oxide via hydrogen reduction or oxygen calcination. This crystallization-regeneration process achieves closed-loop recovery of the precious metal Ru and recycling of the carrier, with a product purity exceeding 99.9%. The process is simple, highly controllable, and environmentally friendly, showing promising prospects for industrial application. Detailed Implementation

[0020] This invention provides a method for recovering ruthenium (Ru) from a metal fluoride support, comprising the following steps: 1) The deactivated RuO2-based catalyst is microwave-treated, and the microwave-treated solid reacts with a low-melting-point hydrofluoric acid salt under a protective gas to obtain a molten salt system. 2) Potassium-containing fluorides are added to a molten salt system to react and obtain solid K2[RuF6]. 3) K2[RuF6] solid undergoes a reduction reaction under a hydrogen atmosphere to obtain metallic Ru; or K2[RuF6] solid undergoes an oxidation reaction under an oxygen atmosphere to obtain RuO2 solid.

[0021] In the deactivated RuO2-based catalyst of the present invention, the active component is RuO2, and the support is a metal fluoride, which preferably includes one or more of magnesium fluoride, calcium fluoride and aluminum fluoride.

[0022] In this invention, the mass content of Ru in the deactivated RuO2-based catalyst is preferably 1-5%, and more preferably 2-4%.

[0023] In this invention, the frequency of the microwave processing in step 1) is preferably 2.25~2.65GHz, more preferably 2.35~2.55GHz, and even more preferably 2.45GHz; the power is preferably 200~600W, more preferably 300~500W, and even more preferably 400W; and the time is preferably 10~30min, more preferably 15~25min, and even more preferably 20min.

[0024] In this invention, microwave treatment enables the localized thermal pyrolysis removal of the fluoropolymer layer on the surface of the deactivated RuO2-based catalyst; the selective microwave absorption effect of RuO2 is used to achieve localized thermal pyrolysis and decoating of the surface fluoropolymer layer.

[0025] In this invention, the low-melting-point hydrofluoric acid salt in step 1) is preferably ammonium hydrogen fluoride (NH4HF2) and lithium hydrogen fluoride (LiHF2), and the molar ratio of ammonium hydrogen fluoride to lithium hydrogen fluoride is preferably 1~3:1, more preferably 1.5~2.5:1, and more preferably 2:1; the mass ratio of the low-melting-point hydrofluoric acid salt to the deactivated RuO2-based catalyst is preferably 0.5~1.5:1, more preferably 0.8~1.2:1, and more preferably 1:1.

[0026] In this invention, the protective gas in step 1) is preferably one or more of nitrogen, argon and helium; the reaction temperature is preferably 120~180℃, more preferably 130~160℃, more preferably 140~150℃, and the reaction time is preferably 2~6h, more preferably 3~5h, and more preferably 4h.

[0027] In this invention, the microwave-treated solid reacts with a low-melting-point hydrofluoric acid salt under a protective gas atmosphere, causing RuO2 and RuO to react. x F y The species transformed into [RuF6]. 2- Complex.

[0028] In this invention, the potassium-containing fluoride in step 2) is preferably KF and / or KHF2; the molar ratio of K in the potassium-containing fluoride to Ru in the deactivated RuO2-based catalyst is preferably 2.2~5:1, more preferably 2.8~4.5:1, and even more preferably 3.5~4:1.

[0029] In this invention, the temperature of the molten salt system in the molten state is preferably 120~200℃, more preferably 130~180℃, and even more preferably 140~170℃, and the reaction time is preferably 25~35min, and even more preferably 30min.

[0030] In this invention, potassium-containing fluoride is added to a molten salt system in a molten state, and K2[RuF6] is generated by directional crystallization.

[0031] In this invention, the temperatures of the reduction and oxidation reactions in step 3) are preferably 300-400°C, more preferably 320-380°C, and even more preferably 350-360°C, and the times are preferably 2-6 hours, more preferably 3-5 hours, and even more preferably 4 hours.

[0032] In this invention, after the reduction and oxidation reactions are completed, the reaction products are washed with water, and the washed KF is added to the molten salt system as a potassium fluoride for recycling.

[0033] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0034] Example 1

[0035] 100.0 g of deactivated RuO2 / MgF2 catalyst (Ru content 2.58 wt%) was uniformly spread in a quartz boat and placed in a 2.45 GHz microwave reaction chamber. The mixture was treated at 300 W for 25 min to induce localized thermal decomposition and removal of the fluoropolymer layer on the catalyst surface. After cooling to room temperature, the microwave-treated solid was mixed with 57.0 g of NH4HF2 and 23.0 g of LiHF2 (molar ratio 2:1), and melted at 150 °C in a nickel crucible. The mixture was then reacted for 3 h under a N2 atmosphere to allow RuO2 and RuO2 to react. x F y Convert to [RuF6] 2- Complex. After the reaction was complete, 5.57 g of KHF2 (KH) was slowly added to the molten system at 130 °C. The molar ratio of K to Ru in the deactivated catalyst was 2.8:1. The reaction was continued for 30 min to generate K2[RuF6] precipitate. The obtained K2[RuF6] precipitate was placed in a quartz tube furnace and reduced at 320℃ under H2 atmosphere for 3 h to generate metallic Ru powder.

[0036] Example 2

[0037] 100.0 g of deactivated RuO2 / CaF2 catalyst (Ru content 3.54 wt%) was uniformly spread in a quartz boat and placed in a 2.45 GHz microwave reaction chamber. The mixture was treated at 400 W for 10 min to remove the fluoropolymer layer on the catalyst surface through localized thermal decomposition. After cooling the microwave-treated solid to room temperature, it was mixed with 38.7 g NH4HF2 and 31.3 g LiHF2 (molar ratio 1:1) and melted in a nickel crucible at 170 °C. The mixture was then reacted for 4 h under an Ar atmosphere to allow RuO2 and RuO2 to react. x F y Convert to [RuF6] 2-Complex. After the reaction was complete, 12.29 g of KHF2 (the molar ratio of K in KHF2 to Ru in the deactivated catalyst was 4.5:1) was slowly added to the molten system at 170 °C, and the reaction was continued for 30 min to generate K2[RuF6] precipitate. The obtained K2[RuF6] precipitate was placed in a quartz tube furnace and reduced at 340 °C under H2 atmosphere for 4 h to generate metallic Ru powder.

[0038] Example 3

[0039] 100.0 g of deactivated RuO2 / AlF3 catalyst (Ru content 4.27 wt%) was uniformly spread in a quartz boat and placed in a 2.45 GHz microwave reaction chamber. The mixture was treated at 500 W for 15 min to remove the fluoropolymer layer on the catalyst surface through localized thermal decomposition. After cooling the microwave-treated solid to room temperature, it was mixed with 70.9 g of NH4HF2 and 19.1 g of LiHF2 (molar ratio 3:1), and melted at 160 °C in a nickel crucible. The mixture was reacted for 2 h under a He atmosphere to allow RuO2 and RuO2 to react. x F y Convert to [RuF6] 2- Complex. After the reaction was complete, 5.39 g of KF (the molar ratio of K in KF to Ru in the deactivated catalyst was 2.2:1) was slowly added to the molten system at 160 °C, and the reaction was continued for 30 min to generate K2[RuF6] precipitate. The obtained K2[RuF6] precipitate was placed in a quartz tube furnace and reduced at 380 °C under H2 atmosphere for 6 h to generate metallic Ru powder.

[0040] Example 4

[0041] 100.0 g of deactivated RuO2 / CaF2 catalyst (Ru content 1.03 wt%) was uniformly spread in a quartz boat and placed in a 2.45 GHz microwave reaction chamber. The mixture was treated at 250 W for 30 min to remove the fluoropolymer layer on the catalyst surface through localized thermal decomposition. After cooling the microwave-treated solid to room temperature, it was mixed with 83.2 g NH4HF2 and 26.8 g LiHF2 (molar ratio 2.5:1) and melted in a nickel crucible at 120 °C. The mixture was then reacted under an Ar atmosphere for 5 h to allow RuO2 and RuO2 to react. x F y Convert to [RuF6] 2- Complex. After the reaction was complete, 2.36 g of KF (the molar ratio of K in KF to Ru in the deactivated catalyst was 4:1) was slowly added to the molten system at 120 °C, and the reaction was continued for 30 min to generate K2[RuF6] precipitate. The obtained K2[RuF6] precipitate was placed in a quartz tube furnace and oxidized at 300 °C under an O2 atmosphere for 5 h to generate RuO2 powder.

[0042] Example 5

[0043] 100.0 g of deactivated RuO2 / AlF3 catalyst (Ru content 4.25 wt%) was uniformly spread in a quartz boat and placed in a 2.45 GHz microwave reaction chamber. The mixture was treated at 350 W for 15 min to remove the fluoropolymer layer on the catalyst surface through localized thermal decomposition. After cooling the microwave-treated solid to room temperature, it was mixed with 85.5 g of NH4HF2 and 34.5 g of LiHF2 (molar ratio 2:1), and melted in a nickel crucible at 140 °C. The mixture was then reacted for 3 h under a He atmosphere to allow RuO2 and RuO2 to react. x F y Convert to [RuF6] 2- Complex. After the reaction was complete, 8.78 g of KF (the molar ratio of K in KF to Ru in the deactivated catalyst was 3.6:1) was slowly added to the molten system at 140 °C, and the reaction was continued for 30 min to generate K2[RuF6] precipitate. The obtained K2[RuF6] precipitate was placed in a quartz tube furnace and oxidized at 360 °C under an O2 atmosphere for 3 h to generate RuO2 powder.

[0044] Example 6

[0045] 100.0 g of deactivated RuO2 / MgF2 catalyst (Ru content 1.94 wt%) was uniformly spread in a quartz boat and placed in a 2.45 GHz microwave reaction chamber. The mixture was treated at 400 W for 20 min to remove the fluoropolymer layer on the catalyst surface through localized thermal decomposition. After cooling the microwave-treated solid to room temperature, it was mixed with 78.8 g of NH4HF2 and 21.2 g of LiHF2 (molar ratio 3:1), and melted at 130 °C in a nickel crucible. The mixture was then reacted for 4 h under a N2 atmosphere to allow RuO2 and RuO2 to react. x F y Convert to [RuF6] 2- Complex. After the reaction was complete, 3.74 g of KH was slowly added to the molten system at 130 °C. (KH) The molar ratio of K to Ru in the deactivated catalyst was 2.5:1. The reaction was continued for 30 min to generate K2[RuF6] precipitate. The obtained K2[RuF6] precipitate was placed in a quartz tube furnace and oxidized at 350℃ under an O2 atmosphere for 6 h to generate RuO2 powder.

[0046] Example 7

[0047] 100.0 g of deactivated RuO2 / AlF3 catalyst (Ru content 4.67 wt%) was uniformly spread in a quartz boat and placed in a 2.45 GHz microwave reaction chamber. The mixture was treated at 200 W for 30 min to remove the fluoropolymer layer on the catalyst surface through localized thermal decomposition. After cooling the microwave-treated solid to room temperature, it was mixed with 84.5 g NH4HF2 and 45.5 g LiHF2 (molar ratio 1.5:1) and melted in a nickel crucible at 180 °C. The mixture was then reacted under a He atmosphere for 5 h to allow RuO2 and RuO2 to react. x F y Convert to [RuF6] 2- Complex. After the reaction was complete, 8.04 g of KF (the molar ratio of K in KF to Ru in the deactivated catalyst was 3:1) was slowly added to the molten system at 180 °C, and the reaction was continued for 30 min to generate K2[RuF6] precipitate. The obtained K2[RuF6] precipitate was placed in a quartz tube furnace and reduced at 400 °C under H2 atmosphere for 3 h to generate metallic Ru powder.

[0048] Example 8

[0049] 100.0g of RuO2 / Mg was deactivated after use. The catalyst (Ru content 3.89 wt%) was uniformly spread in a quartz boat and placed in a 2.45 GHz microwave reaction chamber. It was treated at 550 W for 15 min to induce localized thermal decomposition and removal of the fluoropolymer layer on the catalyst surface. After cooling to room temperature, the microwave-treated solid was mixed with 118.2 g NH4HF2 and 31.8 g LiHF2 (molar ratio 3:1), and melted at 150 °C in a nickel crucible. The mixture was then reacted for 2 h under a N2 atmosphere to allow RuO2 and RuO2 to react. x F y Convert to [RuF6] 2- Complex. After the reaction was complete, 9.37 g of KF (the molar ratio of K in KF to Ru in the deactivated catalyst was 4.2:1) was slowly added to the molten system at 150 °C, and the reaction was continued for 30 min to generate K2[RuF6] precipitate. The obtained K2[RuF6] precipitate was placed in a quartz tube furnace and reduced at 320 °C under H2 atmosphere for 4 h to generate metallic Ru powder.

[0050] Example 9

[0051] 100.0g of RuO2 / Mg was deactivated after use. The catalyst (Ru content 2.11 wt%) was uniformly spread in a quartz boat and placed in a 2.45 GHz microwave reaction chamber. It was treated with 600 W power for 10 min to induce localized thermal decomposition and removal of the fluoropolymer layer on the catalyst surface. After cooling to room temperature, the microwave-treated solid was mixed with 35.6 g NH4HF2 and 14.4 g LiHF2 (molar ratio 2:1), and melted at 160 °C in a nickel crucible. The mixture was reacted for 3 h under a He atmosphere to allow RuO2 and RuO2 to react. x F y Convert to [RuF6] 2- Complex. After the reaction was completed, 8.14 g of KHF2 (the molar ratio of K in KHF2 to Ru in the deactivated catalyst was 5:1) was slowly added to the molten system at 160 °C, and the reaction was continued for 30 min to generate K2[RuF6] precipitate. The obtained K2[RuF6] precipitate was placed in a quartz tube furnace and reduced at 360 °C under H2 atmosphere for 2 h to generate metallic Ru powder.

[0052] Example 10

[0053] 100.0g of inactivated RuO2 / Ca was used. The catalyst (Ru content 1.54 wt%) was uniformly spread in a quartz boat and placed in a 2.45 GHz microwave reaction chamber. It was treated with 150 W power for 20 min to induce localized thermal decomposition and removal of the fluoropolymer layer on the catalyst surface. After cooling to room temperature, the microwave-treated solid was mixed with 75.6 g NH4HF2 and 24.4 g LiHF2 (molar ratio 2.5:1), and melted at 170 °C in a nickel crucible. The mixture was then reacted for 3 h under an Ar atmosphere to allow RuO2 and RuO2 to react. x F y Convert to [RuF6] 2- Complex. After the reaction was complete, 3.80 g of KH was slowly added to the molten system at 170 °C. (KH) The molar ratio of K to Ru in the deactivated catalyst was 3.2:1. The reaction was continued for 30 min to generate K2[RuF6] precipitate. The obtained K2[RuF6] precipitate was placed in a quartz tube furnace and oxidized at 350℃ under an O2 atmosphere for 5 h to generate RuO2 powder.

[0054] Example 11

[0055] 100.0 g of deactivated RuO2 / AlF3 catalyst (Ru content 2.91 wt%) was uniformly spread in a quartz boat and placed in a 2.45 GHz microwave reaction chamber. The mixture was treated at 400 W for 25 min to remove the fluoropolymer layer on the catalyst surface through localized thermal decomposition. After cooling the microwave-treated solid to room temperature, it was mixed with 33.2 g NH4HF2 and 26.8 g LiHF2 (molar ratio 1:1) and melted in a nickel crucible at 140 °C. The mixture was then reacted under a N2 atmosphere for 6 h to allow RuO2 and RuO2 to react. x F y Convert to [RuF6] 2- Complex. After the reaction was complete, 8.01 g of KF (the molar ratio of K in KF to Ru in the deactivated catalyst was 4.8:1) was slowly added to the molten system at 140 °C, and the reaction was continued for 30 min to generate K2[RuF6] precipitate. The obtained K2[RuF6] precipitate was placed in a quartz tube furnace and oxidized at 380 °C under an O2 atmosphere for 3 h to generate RuO2 powder.

[0056] Example 12

[0057] 100.0g of RuO2 / Mg was deactivated after use. The catalyst (Ru content 3.09 wt%) was uniformly spread in a quartz boat and placed in a 2.45 GHz microwave reaction chamber. It was treated with 500 W power for 30 min to induce localized thermal decomposition and removal of the fluoropolymer layer on the catalyst surface. After cooling to room temperature, the microwave-treated solid was mixed with 77.5 g NH4HF2 and 62.5 g LiHF2 (molar ratio 1:1), and melted at 130 °C in a nickel crucible. The mixture was then reacted for 4 h under an Ar atmosphere to allow RuO2 and RuO2 to react. x F y Convert to [RuF6] 2- Complex. After the reaction was completed, 8.86 g of KHF2 (the molar ratio of K in KHF2 to Ru in the deactivated catalyst was 5:1) was slowly added to the molten system at 130 °C, and the reaction was continued for 30 min to generate K2[RuF6] precipitate. The obtained K2[RuF6] precipitate was placed in a quartz tube furnace and oxidized at 310 °C under an O2 atmosphere for 4 h to generate RuO2 powder.

[0058] Comparative Example 1

[0059] The deactivated RuO2 / Mg in Example 6 is omitted. The microwave treatment steps for the catalyst, and other process conditions, are the same as in Example 6.

[0060] Comparative Example 2

[0061] This comparative example uses a traditional alkaline fusion-oxidation method to recover Ru from the catalyst. The specific process is as follows: 100.0 g of deactivated RuO2 / MgF2 catalyst (Ru content 1.94 wt%) was thoroughly mixed with 250 g of NaOH and 50 g of NaNO3, placed in a nickel crucible, and alkali-fused at 650 °C for 3 h to convert RuO2 into soluble sodium salt. After cooling, the melt was leached with boiling water, filtered to remove residue, and 20 wt% hydrochloric acid was added to the resulting leachate to adjust the pH to 0. Then, 200 g of a 12.5 wt% NaClO aqueous solution was added, and the reaction was carried out at 90 °C for 2 h to further oxidize the Ru in the solution to Ru2. Gas. Nitrogen gas is continuously introduced during the reaction, carrying the generated RuO4 gas into an absorption flask containing 10 wt% hydrochloric acid. The absorption solution gradually turns brownish-red, yielding a RuCl3 solution. The resulting solution is evaporated to dryness under constant pressure to obtain brownish-black RuCl3·xH2O crystals.

[0062] Comparative Example 3

[0063] This comparative example employs a combined reduction-oxidation method to recover Ru from the catalyst. The specific process is as follows: 100.0 g of deactivated RuO2 / MgF2 catalyst (Ru content 1.94 wt%) was reduced at 400 °C for 4 h in an H2 atmosphere at a flow rate of 200 mL / min, reducing RuO2 to metallic Ru. This solid was then added to 300 mL of an alkaline solution containing NaClO (NaOH concentration 2.5 wt% and NaClO concentration 12.5 wt%), and reacted at 75 °C for 2 h. After the reaction, the solution was cooled to room temperature, filtered, and the resulting solution was evaporated to dryness under constant pressure to obtain the Ru-containing solid.

[0064] Comparative Example 4

[0065] The 78.8g NH4HF2 and 21.2g LiHF2 in Example 6 were replaced with 31.5g NH4HF2 and 8.5g LiHF2 (molar ratio of 3:1), and the other process conditions were the same as in Example 6.

[0066] Comparative Example 5

[0067] The 78.8g NH4HF2 and 21.2g LiHF2 in Example 6 were replaced with 31.5g NH4HF2 and 8.5g LiHF2 (molar ratio of 3:1). 2.69g KHF2 (molar ratio of K in KHF2 to Ru in the deactivated catalyst was 1.8:1) was slowly added to the molten system at 130°C. Other process conditions were the same as in Example 6.

[0068] The recovery rate and purity of Ru in each example and comparative example were tested using ICP-OES and ICP-MS.

[0069] First, the Ru standard solution was diluted to prepare five standard concentration solutions of 1 mg / L, 5 mg / L, 10 mg / L, 15 mg / L, and 20 mg / L. These solutions were then tested on an ICP-OES apparatus to establish a concentration-intensity standard curve. The Ru 240.272 nm line was selected as the main line, with an ICP plasma power of 1.25 kW, a nebulizer gas flow rate of 0.65 L / min, and a sample injection pump flow rate of 1.0 mL / min. Next, the Ru content of the recovered products from each example and comparative example was tested. This method is also applicable to testing catalysts or recovered Ru metal, RuO2, and other Ru-containing substances, after the same digestion process. 20.0 mg of the recovered product was weighed and placed in a microwave digestion vessel lined with PTFE. 15.0 mL of 37 wt% concentrated hydrochloric acid, 2.0 mL of 68 wt% concentrated nitric acid, 2.0 mL of 30 wt% hydrogen peroxide, and 1 mL of 40 wt% hydrofluoric acid were added sequentially, and the vessel was quickly sealed. Microwave digestion was performed at 180℃ for 30 min. After cooling to room temperature, the digester was opened, and the product was transferred to a 1000.0 mL volumetric flask and diluted to volume with ultrapure water. The intensity was then tested on ICP-OES, and the mass of Ru in the product was obtained using the aforementioned concentration-intensity standard curve. The total impurity element content (Na, K, Mg, Al, Si, Ca, etc.) was determined by ICP-MS. The recovery rate and purity of Ru were calculated using the following formula.

[0070] Ru recovery rate (100%) = mass of Ru in the product ÷ mass of Ru in the catalyst × 100%; Ru purity (100%) = 100% - total mass fraction of impurity elements.

[0071] The recovery rate and purity test results of Ru in Examples 1-12 and Comparative Examples 1-5 are shown in Table 1.

[0072] Table 1. Ru recovery and purity in Examples 1-12 and Comparative Examples 1-5

[0073] As shown in Table 1, the Ru recovery process in the deactivated catalyst of this invention exhibits significant advantages in both Ru recovery rate and product purity. In all embodiments, the Ru recovery rate exceeds 99%, reaching 99.2% to 99.9%, and the Ru purity remains stable between 99.91% and 99.98%, with minimal fluctuation, indicating that the recovery method of this invention has good repeatability and process controllability. The process conditions of this invention are mild, without the participation of strong acids, strong bases, or strong oxidants, and there is no RuO4 emission or waste liquid discharge, achieving efficient, clean, and closed-loop recovery of the precious metal Ru. In contrast, the Ru recovery rate of traditional or imperfect processes (Comparative Examples 1-5) is only 37.5% to 72.6%, and the product purity of some samples even drops to 82.9% to 89.4%, showing a significant difference.

[0074] The catalyst in Comparative Example 1, without microwave treatment, had a Ru recovery rate of only 37.5%, indicating that the dense fluoropolymer layer severely hindered the complexation and dissolution of Ru, highlighting the necessity of the microwave selective decoating step in this invention. The catalysts in Comparative Examples 2 and 3, using traditional alkali fusion-oxidation and reduction-oxidation methods, had Ru recovery rates of only 43.2% and 46.5%, respectively, with product purities of 86.7% and 82.9%, significantly lower than the embodiments of this invention. The main reason is that the dense fluoropolymer layer severely hinders Ru dissolution; the fluorinated RuO2 is extremely inert and difficult to dissolve effectively. Simultaneously, alkali metals, chlorides, and carrier leaching impurities are mixed into the product, resulting in low recovery and poor purity. Comparative Examples 4 and 5 were used to investigate the effect of insufficient amounts of low-melting-point hydrofluoric acid salts and potassium salts. The results showed that when the proportion of hydrofluoric acid salt was insufficient (Comparative Example 4), the Ru recovery rate decreased to 68.7%, indicating... When the amount of coordination is insufficient, Ru The complexation and dissolution of [RuF6] were incomplete; when the amount of potassium salt was too low (Comparative Example 5), the Ru recovery rate was only 72.6%, and the purity also dropped to 89.4%, indicating that insufficient K concentration would lead to incomplete [RuF6] recovery. 2- The complexed anions cannot be completely crystallized out, and some Ru remains in the melt.

[0075] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for the recovery of ruthenium from a metal fluoride support, characterized in that, The method comprises the following steps: 1) inactivating a RuO2-based catalyst and subjecting the inactivated RuO2-based catalyst to microwave treatment; subjecting the solid after the microwave treatment to reaction with a low-melting-point hydrofluoride salt under a protective gas to obtain a molten salt system; 2) adding a potassium-containing fluoride to the molten salt system in a molten state to perform reaction to obtain K2[RuF6] solid; 3) subjecting the K2[RuF6] solid to reduction reaction in a hydrogen atmosphere to obtain metal Ru, or subjecting the K2[RuF6] solid to oxidation reaction in an oxygen atmosphere to obtain RuO2 solid.

2. The recycling method according to claim 1, characterized in that, In the inactivated RuO2-based catalyst, the active component is RuO2, and the carrier is a metal fluoride, and the metal fluoride comprises one or more of magnesium fluoride, calcium fluoride and aluminum fluoride.

3. The recycling method according to claim 1 or 2, characterized in that, In step 1), the microwave treatment has a frequency of 2.25-2.65 GHz, a power of 200-600 W, and a time of 10-30 min.

4. The recycling method according to claim 3, characterized in that, In step 1), the low-melting-point hydrofluoride salt is ammonium bifluoride and lithium bifluoride, and the molar ratio of the ammonium bifluoride and the lithium bifluoride is 1-3:1; the mass ratio of the low-melting-point hydrofluoride salt to the inactivated RuO2-based catalyst is 0.5-1.5:

1.

5. The recycling method according to claim 4, characterized in that, In step 1), the protective gas is one or more of nitrogen, argon and helium; the reaction has a temperature of 120-180 ℃ and a time of 2-6 h.

6. The recycling method according to claim 4 or 5, characterized in that, In step 2), the potassium-containing fluoride is KF and / or KHF2; the molar ratio of K in the potassium-containing fluoride to Ru in the inactivated RuO2-based catalyst is 2.2-5:

1.

7. The recycling method according to claim 6, characterized in that, The molten salt system in the molten state has a temperature of 120-200 ℃, and the reaction has a time of 25-35 min.

8. The recycling method of claim 6, wherein, In step 3), the reduction reaction and the oxidation reaction independently have a temperature of 300-400 ℃ and a time of 2-6 h.

9. The recycling method of claim 8, wherein, After the reduction reaction and the oxidation reaction are completed, the reaction product is washed with water, and the washed KF is used as the potassium-containing fluoride to be added to the molten salt system in the molten state for recycling.

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