Method for recycling metal elements from waste residue oil hydrogenation catalyst

Abstract

The invention relates to the technical field of metal recovery, and particularly discloses a method for recycling metal elements from a waste residue oil hydrogenation catalyst, which comprises the following steps: (1) crushing and roasting a waste cobalt-molybdenum-based hydrogenation catalyst to obtain a sintered material; (2) mixing the sintered material with a leaching agent, and leaching and filtering to obtain leaching residues and leaching liquid; the leaching agent is prepared from the following components: nitric acid, 1-butyl-3-methylimidazolium tetrafluoroborate and modified nano titanium dioxide; (3) adding a precipitator into the leachate to obtain cobalt hydroxide, and reducing the cobalt hydroxide to obtain a cobalt elementary substance; and (4) adding a reducing agent into the filtrate containing the molybdenum ions, and reducing to obtain the elemental molybdenum. According to the recovery method, by controlling the proper volume ratio of nitrous oxide to nitrogen, the mass ratio of the sintered material to the leaching agent and the components of the leaching agent, the recovery rate of cobalt and molybdenum metal in the waste catalyst is effectively increased.

Description

Technical Field

[0001] This application relates to the technical field of metal recycling, and more specifically, it relates to a method for recycling metal elements from spent residue hydrotreating catalysts. Background Art

[0002] Residue hydrotreating catalysts play a crucial role in the petroleum refining process. Their main function is to promote the reaction of residue under a hydrogenation environment to achieve processes such as desulfurization, denitrification, demetallization, and hydrocracking, thereby improving the quality of oil products and meeting environmental protection requirements and product standards. Cobalt-molybdenum-based catalysts have good hydrodesulfurization and hydrodenitrification performance and can effectively convert sulfur-containing and nitrogen-containing compounds in petroleum fractions into corresponding hydrocarbons, hydrogen sulfide, ammonia, etc. After long-term use, due to reasons such as carbon deposition, metal deposition, and loss of active components, the residue hydrotreating catalysts will gradually lose their activity, and a large amount of waste catalysts will be generated. The cobalt and molybdenum metals in the waste catalysts have high economic value. Recycling them as secondary resources can not only directly obtain certain economic benefits, but also improve the resource utilization rate, avoid environmental problems caused by catalysts, and achieve sustainable development.

[0003] In related technologies, a patent document with the publication number CN109652649B discloses a method for improving the recovery rates of cobalt and molybdenum from waste catalysts, including the following steps: (1) obtaining an acid solution, where the acid solution contains hydrofluoric acid; (2) impregnating the waste cobalt-molybdenum-based hydrotreating catalyst with the acid solution to recover cobalt and molybdenum; the acid solution includes nitric acid, phosphoric acid, and hydrofluoric acid; the cobalt in the waste catalyst exists in the form of CoO; the total acid concentration of the acid solution in terms of H+ is 2 mol / L to 4 mol / L; the concentration of hydrofluoric acid in the acid solution is 0.1 to 1 mol / L; the molar concentration ratio of nitric acid to phosphoric acid is 5 to 20. By using a composite of multiple acidic leaching solutions, the leaching efficiency of cobalt and molybdenum can be improved.

[0004] Using the above method, in the actual production process, due to the complex composition of the waste cobalt-molybdenum-based hydrotreating catalyst, the carbon deposition and carrier materials present will interfere with the leaching process of the acid solution. The carbon deposition will wrap some cobalt and molybdenum metals, preventing the full contact between the acid solution and the metals and making the reaction difficult to proceed completely; the dissolution behavior of the carrier material in the acid solution will compete with cobalt and molybdenum ions for the active components in the acid solution, further affecting the leaching efficiency. Under the combined action of these factors, the actual recovery rate of cobalt is lower than 85% and the actual recovery rate of molybdenum is also lower than 90%. Therefore, the method in related technologies needs to further improve the recovery rates of cobalt and molybdenum metals. Summary of the Invention

[0005] In order to improve the recovery rate of cobalt and molybdenum metals in waste catalysts, the present application provides a method for recycling metal elements from waste residue oil hydrogenation catalysts.

[0006] The method for recycling metal elements from waste residue oil hydrogenation catalysts provided by the present application adopts the following technical solutions: A method for recycling metal elements from waste residue oil hydrogenation catalysts includes the following steps: (1) Crushing the waste cobalt-molybdenum-based hydrogenation catalyst to obtain a crushed material, and roasting the crushed material in a mixed gas atmosphere of dinitrogen monoxide and nitrogen to obtain a sintered material; (2) Mixing the sintered material with a leaching agent, stirring and leaching at 85-95 °C for 30-60 min, and then filtering to obtain a leaching residue and a leaching solution; the components of the leaching agent include nitric acid, 1-butyl-3-methylimidazolium tetrafluoroborate, and modified nano-titanium dioxide; (3) Adding a precipitating agent to the leaching solution, adjusting the pH value of the leaching solution to 8-10, and then filtering to obtain cobalt hydroxide and a filtrate containing molybdenum ions. After washing and drying the cobalt hydroxide, a reduction reaction is carried out at 400-600 °C for 2-4 h in a hydrogen atmosphere to obtain cobalt metal; (4) Adding a reducing agent to the filtrate containing molybdenum ions, reacting at 50-70 °C for 1-3 h, and then filtering to obtain molybdenum metal.

[0007] The effect is as follows: During the roasting process of step (1), dinitrogen monoxide decomposes at high temperature to produce oxygen and nitrogen. The oxygen reacts with the carbon deposition through an oxidation reaction and converts it into carbon dioxide and discharges it, thereby effectively removing the carbon deposition on the surface and in the pores of the catalyst, enabling the acid solution to more smoothly contact the metal. The nitrogen-oxygen bond in the dinitrogen monoxide molecule has a certain polarity and a special electronic structure. During the roasting process, it interacts with the metal atoms on the surface of the metal oxide, resulting in a change in the electron cloud distribution around the metal atoms. This change causes the redistribution of the electron cloud density of the metal atoms, changes the strength and properties of the chemical bonds, reduces the binding energy between the metal and the carrier, makes the metal more easily dissolved by the leaching agent, and thus is conducive to improving the recovery rates of cobalt and molybdenum.

[0008] The ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate has good solubility and low volatility. 1-butyl-3-methylimidazolium tetrafluoroborate acts synergistically with nitric acid to change the microstructure and ionic environment of the solution, enhancing the ability to dissolve metals. In addition, the ionic liquid can also form specific complexes with metal ions, improving the stability of metal ions in the solution and preventing their re-precipitation, thereby increasing the leaching efficiency. It can reduce the surface tension of the leaching agent, improve the wettability of the leaching agent to the catalyst particles, enable the leaching agent to better penetrate into the catalyst interior, increase the contact area between the metal and the leaching agent, improve the leaching efficiency, and further facilitate the improvement of the recovery rates of cobalt and molybdenum.

[0009] Optionally, the particle size of the crushed material described in step (1) is 20 - 60 mesh.

[0010] By adopting the above technical solution, the above particle size can ensure that the catalyst particles have a large specific surface area, increase the contact area with the mixed gas and the leaching agent, and improve the roasting and leaching efficiency. If the particle size is too large, the specific surface area is small and the reaction is incomplete; if the particle size is too small, it may cause dust flying, difficult operation, and is prone to blockage in subsequent operations such as filtration.

[0011] Optionally, the volume ratio of nitrous oxide to nitrogen described in step (1) is 1:(4 - 9).

[0012] By adopting the above technical solution, this volume ratio can ensure that an appropriate amount of oxygen is provided during the roasting process for carbon deposition removal and changing the electron cloud distribution of metal oxides. If the proportion of nitrous oxide is too high, the roasting reaction may be too intense, damaging the catalyst structure; if the proportion is too low, the carbon deposition removal is incomplete and the change in the electron cloud distribution of metal oxides is not obvious, affecting the subsequent leaching effect.

[0013] Optionally, the mass ratio of the sintered material to the leaching agent described in step (2) is 1:(10 - 20).

[0014] Optionally, the modified nano-titanium dioxide described in step (2) is prepared by the following method: A. Add nano-titanium dioxide powder to a γ-aminopropyltriethoxysilane ethanol solution, ultrasonically disperse for 30 - 60 min, and then under the condition of a constant temperature water bath at 40 - 60 °C, stir and react for 3 - 5 h; after the reaction, filter, wash, and dry to obtain surface-modified nano-titanium dioxide; B. Place the surface-modified nano-titanium dioxide in an ultraviolet light reactor and irradiate and activate it under ultraviolet light for 2 - 4 hours to obtain the modified nano-titanium dioxide.

[0015] By adopting the above technical solution, the surface of nano-titanium dioxide is modified with γ-aminopropyltriethoxysilane. One end of the silane coupling agent molecule undergoes chemical bonding with the hydroxyl groups on the surface of nano-titanium dioxide, and the other end extends into the solution. This can not only prevent the aggregation of nano-titanium dioxide particles and make them uniformly dispersed in the leaching agent, but also improve the hydrophilicity and chemical activity of the surface of nano-titanium dioxide. The uniformly dispersed nano-titanium dioxide can cover the surface of the catalyst particles more widely, increase the contact area with the metal, and make the photocatalytic oxidation and other effects promoting metal dissolution proceed more efficiently. After the modified nano-titanium dioxide is activated by ultraviolet light irradiation with a specific wavelength (250 - 300 nm), electron-hole pairs are generated. The holes have strong oxidizing properties and can react with water molecules in the solution to generate hydroxyl radicals (・OH), and the electrons react with dissolved oxygen in the solution to generate strongly oxidizing substances such as superoxide anion radicals (・O2⁻). These reactive oxygen species can attack metal compounds in the residue oil hydrogenation catalyst, such as oxides and sulfides of cobalt and molybdenum, and oxidize them into higher-valent metal ions that are more easily soluble, promoting the dissolution of the metal from the catalyst into the leaching agent. For example, originally insoluble cobalt sulfide, molybdenum sulfide, etc. can be oxidized into soluble cobalt ions and molybdenum ions, thereby increasing the leaching recovery rate of the metal.

[0016] Optionally, the wavelength of the ultraviolet light for irradiation activation is 250 - 300 nm.

[0017] Optionally, in step (2), the mass concentration of nitric acid in the leaching agent is 10 - 18%; the mass ratio of nitric acid, 1-butyl-3-methylimidazolium tetrafluoroborate, and modified nano-titanium dioxide in the leaching agent is (10 - 20) : (1 - 3) : (0.5 - 2).

[0018] By adopting the above technical solution, an appropriate mass concentration of nitric acid can provide a sufficient acidic environment to promote the dissolution of the metal. The mass ratio of each component is optimized, which can achieve the best synergistic effect among nitric acid, ionic liquid, and modified nano-titanium dioxide, improve the leaching efficiency, and thus be beneficial to increasing the recovery rate of the metal.

[0019] Optionally, in step (3), the precipitating agent is one of sodium hydroxide and potassium hydroxide.

[0020] Optionally, in step (4), the reducing agent is one of hydrazine hydrate and ascorbic acid.

[0021] Optionally, in step (4), the mass ratio of the filtrate containing molybdenum ions to the reducing agent is (10 - 20) : 1.

[0022] In summary, the present application has the following beneficial effects: 1. In this application, the crushed waste cobalt - molybdenum - based hydrogenation catalyst is calcined in an atmosphere of a mixed gas of nitrous oxide and nitrogen. The oxygen generated by the decomposition of nitrous oxide can remove carbon deposits, and its special electronic structure can change the electron cloud distribution around metal atoms and reduce the binding energy between the metal and the carrier. In the leaching agent, nitric acid, 1 - butyl - 3 - methylimidazolium tetrafluoroborate, and modified nano - titanium dioxide act synergistically. The ionic liquid enhances the dissolution ability of metals and improves the stability of metal ions, and the modified nano - titanium dioxide generates strongly oxidizing substances under ultraviolet light activation to promote metal dissolution, thus effectively improving the recovery rates of cobalt and molybdenum.

[0023] 2. In the method of this application, nitrous oxide reacts with carbon deposits during calcination to remove them through an oxidation reaction, avoiding carbon deposits from wrapping cobalt - molybdenum metals and preventing the acid solution from contacting them. At the same time, through the modification treatment of nano - titanium dioxide, the strongly oxidizing substances generated can attack metal compounds, reducing the interference of the carrier material on the leaching process and making the metal more easily leached. Therefore, the effects of reducing the interference of carbon deposits and carrier materials on the leaching process and improving the metal leaching efficiency are obtained. Detailed implementation mode

[0024] The following further elaborates on this application with reference to examples.

[0025] Preparation example of modified nano - titanium dioxide Preparation example 1 The modified nano - titanium dioxide is prepared by the following method: A. Add 1 kg of nano - titanium dioxide powder to 5 kg of a 3% γ - aminopropyltriethoxysilane ethanol solution, ultrasonically disperse for 30 min, and then stir and react for 3 h under the condition of a 40 °C constant - temperature water bath. After the reaction, filter, wash, and dry to obtain surface - modified nano - titanium dioxide. B. Place the surface - modified nano - titanium dioxide in an ultraviolet light reactor and irradiate and activate it for 2 hours under ultraviolet light with a wavelength of 250 nm to obtain the modified nano - titanium dioxide.

[0026] Preparation example 2 The modified nano - titanium dioxide is prepared by the following method: A. Add 1 kg of nano - titanium dioxide powder to 7 kg of a 5% γ - aminopropyltriethoxysilane ethanol solution, ultrasonically disperse for 50 min, and then stir and react for 4 h under the condition of a 50 °C constant - temperature water bath. After the reaction, filter, wash, and dry to obtain surface - modified nano - titanium dioxide. B. Place the surface - modified nano - titanium dioxide in an ultraviolet light reactor and irradiate and activate it for 3 hours under ultraviolet light with a wavelength of 280 nm to obtain the modified nano - titanium dioxide.

[0027] Preparation Example 3 The modified nano-titanium dioxide is prepared by the following method: A. Add 1 kg of nano-titanium dioxide powder to 8 kg of an ethanol solution of γ-aminopropyltriethoxysilane with a mass concentration of 8%, ultrasonically disperse for 60 min, and then stir and react for 5 h under the condition of a constant temperature water bath at 60 °C; after the reaction is completed, filter, wash, and dry to obtain surface-modified nano-titanium dioxide; B. Place the surface-modified nano-titanium dioxide in an ultraviolet light reactor and irradiate and activate it under ultraviolet light with a wavelength of 300 nm for 4 hours to obtain the modified nano-titanium dioxide.

[0028] Preparation Example 4 The modified nano-titanium dioxide, the difference from Preparation Example 3 is that in this preparation example, the surface-modified nano-titanium dioxide is irradiated and activated with ultraviolet light with a wavelength of 500 nm.

[0029] Example The XRF detection data of the waste cobalt-molybdenum-based hydrogenation catalyst used in this example are as follows Table 1 XRF Detection Data

[0030] According to the composition table of the above waste cobalt-molybdenum-based hydrogenation catalyst, the mass of Co2O3 in each kg of the waste cobalt-molybdenum-based hydrogenation catalyst is 177 g, and the mass of MoO3 is 189 g.

[0031] Furthermore, m （Co） = m （Co2O3） × w （Co） = 177 g × 71.08% = 125.81 g; m （Mo） = m （MoO3） × w （Mo） = 189 g × 66.67% = 126 g; Therefore, theoretically, there are 125.81 g of cobalt metal and 126 g of molybdenum metal in each kg of the waste cobalt-molybdenum-based hydrogenation catalyst.

[0032] Example 1 A method for recycling metal elements from a waste residue oil hydrogenation catalyst, comprising the following steps: (1) Crush the waste cobalt-molybdenum-based hydrogenation catalyst to obtain a crushed material with a particle size of 20 mesh, and calcine the crushed material in a mixed gas atmosphere of dinitrogen oxide and nitrogen at 450 °C for 5 h to obtain a sintered material, and the volume ratio of dinitrogen oxide to nitrogen is 1:4; (2) Mix 10 kg of sintered material with 100 kg of leaching agent, stir and leach at 85 °C for 30 min, and then filter to obtain leached residue and leachate; the components and dosages of the leaching agent are shown in Table 2, where the mass concentration of nitric acid is 10%, and the modified nano-titanium dioxide is the modified nano-titanium dioxide prepared in Preparation Example 1; (3) Add sodium hydroxide to the leachate to adjust the pH value of the leachate to 8, and then filter to obtain cobalt hydroxide and a filtrate containing molybdenum ions. After washing and drying the cobalt hydroxide, carry out a reduction reaction at 400 °C for 4 h in a hydrogen atmosphere to obtain cobalt metal; (4) Add 10 kg of hydrazine hydrate to 100 kg of the filtrate containing molybdenum ions, react at 50 °C for 1 h, and then filter to obtain molybdenum metal.

[0033] Example 2 A method for recycling metal elements from waste residue oil hydrogenation catalyst, comprising the following steps: (1) Crush the waste cobalt-molybdenum-based hydrogenation catalyst to obtain a crushed material with a particle size of 40 mesh. Roast the crushed material at 450 °C for 5 h in a mixed gas atmosphere of dinitrogen monoxide and nitrogen, and the volume ratio of dinitrogen monoxide to nitrogen is 1:7; (2) Mix 10 kg of sintered material with 150 kg of leaching agent, stir and leach at 90 °C for 45 min, and then filter to obtain leached residue and leachate; the components and dosages of the leaching agent are shown in Table 2, where the mass concentration of nitric acid is 14%, and the modified nano-titanium dioxide is the modified nano-titanium dioxide prepared in Preparation Example 2; (3) Add potassium hydroxide to the leachate to adjust the pH value of the leachate to 9, and then filter to obtain cobalt hydroxide and a filtrate containing molybdenum ions. After washing and drying the cobalt hydroxide, carry out a reduction reaction at 500 °C for 3 h in a hydrogen atmosphere to obtain cobalt metal; (4) Add 10 kg of ascorbic acid to 150 kg of the filtrate containing molybdenum ions, react at 60 °C for 2 h, and then filter to obtain molybdenum metal.

[0034] Example 3 A method for recycling metal elements from waste residue oil hydrogenation catalyst, comprising the following steps: (1) Crush the waste cobalt-molybdenum-based hydrogenation catalyst to obtain a crushed material with a particle size of 60 mesh. Roast the crushed material at 450 °C for 5 h in a mixed gas atmosphere of dinitrogen monoxide and nitrogen, and the volume ratio of dinitrogen monoxide to nitrogen is 1:9; (2) Mix 10 kg of sintered material with 200 kg of leaching agent, stir and leach at 95 °C for 60 min, and then filter to obtain leached residue and leachate; the components and dosages of the leaching agent are shown in Table 2, where the mass concentration of nitric acid is 18%, and the modified nano-titanium dioxide is the modified nano-titanium dioxide prepared in Preparation Example 3; (3) Add potassium hydroxide to the leachate to adjust the pH value of the leachate to 10, and then filter to obtain cobalt hydroxide and a filtrate containing molybdenum ions. After washing and drying the cobalt hydroxide, carry out a reduction reaction at 600 °C for 2 h in a hydrogen atmosphere to obtain cobalt metal; (4) Add 10 kg of ascorbic acid to 200 kg of the filtrate containing molybdenum ions, react at 70 °C for 3 h, and then filter to obtain molybdenum metal.

[0035] Table 2 Components and dosages (kg) of the leaching agent in Examples 1-3

[0036] Example 4 A method for recycling metal elements from waste residue oil hydrogenation catalyst, which is different from Example 1 in that in step (1) of this example, the volume ratio of nitrous oxide to nitrogen during the roasting process is 1:20.

[0037] Example 5 A method for recycling metal elements from waste residue oil hydrogenation catalyst, which is different from Example 1 in that in this example, the modified nano-titanium dioxide in the leaching agent in step (2) is the modified nano-titanium dioxide prepared in Preparation Example 4.

[0038] Comparative Example Comparative Example 1 A method for recycling metal elements from waste residue oil hydrogenation catalyst, which is different from Example 1 in that: in this comparative example, the leaching agent in step (2) is 100 kg of a mixed aqueous solution of nitric acid-phosphoric acid-hydrofluoric acid with a concentration of 3 mol / L (where the total concentration of nitric acid and phosphoric acid is 2.6 mol / L, the molar concentration ratio of nitric acid to phosphoric acid is 10, and hydrofluoric acid is 0.4 mol / L).

[0039] Comparative Example 2 A method for recycling metal elements from waste residue oil hydrogenation catalyst, which is different from Example 1 in that in this comparative example, step (1) is carried out under a roasting treatment in an oxygen atmosphere with a volume concentration of 25%.

[0040] Comparative Example 3 A method for recycling metal elements from waste residue oil hydrogenation catalyst, which is different from Example 1 in that in this comparative example, the leaching agent in step (2) is 100 kg of nitric acid with a mass concentration of 10%.

[0041] Comparative Example 4 A method for recycling metal elements from waste residue oil hydrogenation catalysts, which is different from Example 1 in that in this comparative example, modified nano-titanium dioxide is not added to the leaching agent in step (2), and the loss is made up with 1-butyl-3-methylimidazolium tetrafluoroborate.

[0042] Comparative Example 5 A method for recycling metal elements from waste residue oil hydrogenation catalysts, which is different from Example 1 in that in this comparative example, 1-butyl-3-methylimidazolium tetrafluoroborate is not added to the leaching agent in step (2), and the loss is made up with modified nano-titanium dioxide.

[0043] Performance detection test According to the composition table of the waste cobalt-molybdenum-based hydrogenation catalyst in Table 1, theoretically, there are 125.81 g of cobalt metal and 126 g of molybdenum metal in every kg of the waste cobalt-molybdenum-based hydrogenation catalyst. The recovered metal nickel powders in the above Examples 1-5 and Comparative Examples 1-5 were weighed respectively and the recovery rates were calculated. The results are shown in Table 3 Table 3 Metal recovery rates

[0044] As can be seen from Table 3, the recovery rates of cobalt and molybdenum in Examples 1-3 are relatively high, about 98%-99%. Since the method of the present application adopts optimized process conditions, such as appropriate particle size of the crushed material, volume ratio of nitrous oxide to nitrogen, mass ratio of the sintered material to the leaching agent, and the synergistic effect of nitric acid, 1-butyl-3-methylimidazolium tetrafluoroborate and modified nano-titanium dioxide in the leaching agent. These factors together improve the recovery rates of cobalt and molybdenum.

[0045] As can be seen from Table 3, compared with Example 1, in Example 4, the volume ratio of nitrous oxide to nitrogen becomes 1:20, and the recovery rates of cobalt and molybdenum decrease significantly, being 93.2% and 92.7% respectively. The reason is that the proportion of nitrous oxide is too low, resulting in incomplete removal of carbon deposition, and the change in the electron cloud distribution of metal oxides is not obvious, affecting the subsequent leaching effect and thus reducing the recovery rate.

[0046] As can be seen from Table 3, the difference between Example 5 and Example 1 is that the modified nano-titanium dioxide selected in Example 5 is the product activated by ultraviolet light with a wavelength of 500 nm in Preparation Example 4, and the recovery rate decreases. The recovery rate of cobalt is 95.6% and that of molybdenum is 90.8%. This is because the ultraviolet light with a wavelength of 500 nm is not the optimal activation wavelength of the modified nano-titanium dioxide, resulting in fewer strongly oxidizing substances generated, weaker oxidation effect on metal compounds, and the metal dissolution effect is not as good as that under the optimal wavelength treatment, so the recovery rate decreases.

[0047] As can be seen from Table 3, in Comparative Example 1, a mixed aqueous solution of nitric acid - phosphoric acid - hydrofluoric acid in the related art was used as the leaching agent, and the recovery rates of cobalt and molybdenum were 87.6% and 86.1% respectively, which were lower than those in Example 1. This is because the carbon deposition and carrier material in the waste catalyst interfere with the leaching process. The carbon deposition wraps the metal, hindering the contact of the acid solution, and the carrier material competes with metal ions for the active components in the acid solution, resulting in a decrease in leaching efficiency and a lower recovery rate than the method of the present application.

[0048] As can be seen from Table 3, in Comparative Example 2, roasting was carried out in an oxygen atmosphere with a volume concentration of 25%, and the recovery rates of cobalt and molybdenum were 81.3% and 83.3% respectively, which were lower than those in Example 1. This is because compared with the mixed gas atmosphere of dinitrogen monoxide and nitrogen, a pure oxygen atmosphere cannot change the electron cloud distribution around metal atoms, cannot reduce the binding energy between the metal and the carrier, and is not conducive to the leaching of the metal, so the recovery rate is relatively low.

[0049] As can be seen from Table 3, in Comparative Example 3, only nitric acid with a mass concentration of 10% was used as the leaching agent, and the recovery rates of cobalt and molybdenum were 75.7% and 75.1% respectively, which were much lower than those in Example 1. This is because in the absence of the synergistic effect of the ionic liquid and the modified nano - titanium dioxide, when nitric acid acts alone, its ability to dissolve metals is limited, and it cannot effectively prevent the re - precipitation of metal ions, nor can it promote the dissolution of metals from the catalyst, resulting in a relatively low recovery rate.

[0050] As can be seen from Table 3, in Comparative Example 4, the modified nano - titanium dioxide was not added to the leaching agent, and the recovery rates of cobalt and molybdenum were 65.8% and 72.8% respectively, which were significantly lower than those in Example 1. This indicates that the modified nano - titanium dioxide plays an important role in promoting the dissolution of metals. The lack of it will cause metal compounds not to be fully oxidized into easily soluble high - valence ions, thus affecting the leaching recovery rate.

[0051] As can be seen from Table 3, in Comparative Example 5, 1 - butyl - 3 - methylimidazolium tetrafluoroborate was not added to the leaching agent, and the recovery rates of cobalt and molybdenum were 79.6% and 83.4% respectively, which were lower than those in Example 1. This shows that the ionic liquid plays an important role in enhancing the metal dissolution ability, improving the stability of metal ions, and improving the wettability of the leaching agent to catalyst particles. The lack of it will cause the leaching efficiency to decline and the recovery rate to decrease.

[0052] This specific embodiment is only an explanation of the present application, and it does not limit the present application. After reading this specification, those skilled in the art can make modifications to this embodiment without creative contributions as needed, but as long as it is within the scope of the claims of the present application, it is protected by the patent law.

Claims

1. A method for recycling metal elements from a waste residue oil hydrogenation catalyst, characterized in that, The steps include: (1) crushing the waste cobalt-molybdenum-based hydrogenation catalyst to obtain a crushed material, and roasting the crushed material in a mixed gas atmosphere of nitrous oxide and nitrogen to obtain a sintered material; (2) mixing the sintered material with a leaching agent, stirring and leaching at 85-95° C. for 30-60 minutes, and then filtering to obtain a leaching residue and a leaching liquid; the leaching agent components include nitric acid, 1-butyl-3-methylimidazolium tetrafluoroborate and modified nano titanium dioxide; (3) adding a precipitant to the leaching solution, adjusting the pH value of the leaching solution to 8-10, and then filtering to obtain cobalt hydroxide and a filtrate containing molybdenum ions, washing and drying the cobalt hydroxide, and then performing a reduction reaction at 400-600° C. for 2-4 hours in a hydrogen atmosphere to obtain a single cobalt substance; (4) Add a reducing agent to the filtrate containing molybdenum ions, react at 50-70°C for 1-3 hours, and then filter to obtain molybdenum element.

2. A method for recycling metal elements from a waste residue oil hydrogenation catalyst according to claim 1, characterized in that: The particle size of the crushed material in step (1) is 20-60 mesh.

3. A method for recycling metal elements from a waste residue oil hydrogenation catalyst according to claim 1, characterized in that: The volume ratio of nitrous oxide to nitrogen in step (1) is 1:(4-9).

4. A method for recycling metal elements from a waste residue oil hydrogenation catalyst according to claim 1, characterized in that: The mass ratio of the sintering material to the leaching agent in step (2) is 1:(10-20).

5. A method for recycling metal elements from a waste residue oil hydrogenation catalyst according to claim 4, characterized in that, The modified nano titanium dioxide in step (2) is prepared by the following method: A. Add nano titanium dioxide powder to γ-aminopropyltriethoxysilane ethanol solution, ultrasonically disperse for 30-60 minutes, and then stir and react for 3-5 hours in a constant temperature water bath at 40-60°C; after the reaction, filter, wash and dry to obtain surface-modified nano titanium dioxide; B. Place the surface-modified nano-titanium dioxide in an ultraviolet light reactor and activate it under ultraviolet light for 2-4 hours to obtain modified nano-titanium dioxide.

6. A method for recycling metal elements from a waste residue oil hydrogenation catalyst according to claim 5, characterized in that, The wavelength of the ultraviolet light for irradiation activation is 250-300nm.

7. A method for recycling metal elements from a waste residue oil hydrogenation catalyst according to claim 1, characterized in that: The mass concentration of nitric acid in the leaching agent in step (2) is 10-18%; the mass ratio of nitric acid, 1-butyl-3-methylimidazolium tetrafluoroborate and modified nano-titanium dioxide in the leaching agent is (10-20): (1-3): (0.5-2).

8. A method for recycling metal elements from a waste residue oil hydrogenation catalyst according to claim 1, characterized in that: The precipitant in step (3) is one of sodium hydroxide and potassium hydroxide.

9. A method for recycling metal elements from a waste residue oil hydrogenation catalyst according to claim 1, characterized in that: The reducing agent in step (4) is one of hydrazine hydrate and ascorbic acid.

10. A method for recycling metal elements from a waste residue oil hydrogenation catalyst according to claim 1, characterized in that: The mass ratio of the filtrate containing molybdenum ions to the reducing agent in step (4) is (10-20):1.

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