Method for recovering vanadium and molybdenum from waste catalyst

Abstract

The invention relates to the technical field of waste catalyst treatment, and discloses a method for recovering vanadium and molybdenum from a waste catalyst, which comprises the following steps: (1) contacting the waste catalyst with an organic acid solution for leaching to obtain a leaching solution containing Mo and V, and then controlling the valence state of V in the leaching solution to be + 4; (2) Mo in the feed liquid obtained in the step (1) is extracted with a first extraction agent, first extraction liquid containing Mo and first raffinate containing V are obtained, the first extraction liquid is washed and reversely extracted, and a Mo-rich solution is obtained; (3) adjusting the valence state of V in the first raffinate to be + 5; and (4) extracting V in the feed liquid obtained in the step (3) by adopting a second extraction agent to obtain a second extraction liquid containing V, and then carrying out washing and reverse extraction to obtain a V-rich solution. According to the method, Mo and V in the catalyst can be recovered at the same time, and high purity and yield are achieved.

Description

Technical Field

[0001] This invention relates to the field of spent catalyst treatment technology, and specifically to a method for recovering vanadium and molybdenum from spent catalysts. Background Technology

[0002] Vanadium is a rare metal characterized by its high melting point and low density. In steelmaking, trace amounts of vanadium can significantly improve the strength of steel; in the chemical industry, vanadium is widely used as a catalyst; and in the new energy field, vanadium redox flow batteries, as aqueous batteries, offer high safety and can be used in large-scale energy storage systems.

[0003] Solvent extraction is a commonly used method for separating metal ions. It is stable, operates under mild conditions, and can yield high-purity metal components. Furthermore, the extractant can be recycled, resulting in low emissions of waste. Currently, vanadium extraction primarily relies on coal shale. However, coal shale has a low vanadium content and contains a variety of impurity ions, leading to a complex leachate composition and complicated purification processes.

[0004] Waste catalysts used in petroleum processing, especially hydrodemetallization catalysts from waste residue oil, often have high levels of vanadium (V) deposits. Effective recovery and reuse of these metals from waste catalysts would facilitate the resource utilization of waste hydrotreating catalysts. From a petroleum processing perspective, while refining petroleum fully utilizes hydrocarbons, the deposition of vanadium on catalysts and its initial enrichment, followed by purification and recovery through solvent extraction, also improves the efficiency of petroleum resource utilization.

[0005] CN105274344A discloses a method for recovering molybdenum and vanadium from waste petroleum catalysts. The method includes: sequentially deoiling the waste catalyst by air burning, crushing, roasting after mixing with sodium carbonate, then leaching the resulting roasted material with water and adjusting the pH of the leaching solution to alkaline, adding ammonium chloride to the leaching solution to precipitate vanadium, and finally enriching the vanadium-precipitated solution by ion exchange to obtain an ammonium molybdate solution.

[0006] CN112342389A discloses a method for recovering valuable metals from waste chemical catalysts. The waste chemical catalysts are wet-milled and acid-leached to obtain a leachate containing nickel, molybdenum and vanadium. Then, vanadium is extracted to obtain a back-extraction solution and a vanadium raffinate. Molybdenum is then extracted from the vanadium raffinate to obtain a molybdenum raffinate and a back-extraction solution.

[0007] Although these processes can improve the efficiency of molybdenum recovery, their operation is complex, they generate a lot of waste and have high treatment costs, the purity of the recovered metal is low, and additional evaporation and crystallization steps are required. Summary of the Invention

[0008] The purpose of this invention is to overcome the problems of low recovery efficiency and low product purity of molybdenum and vanadium from waste catalysts in the prior art, and to provide a method for recovering vanadium and molybdenum from waste catalysts. This method can achieve efficient recovery of vanadium and molybdenum from waste catalysts and produce vanadium and molybdenum products with high purity.

[0009] To achieve the above objectives, the present invention provides a method for recovering vanadium and molybdenum from spent catalysts, the method comprising:

[0010] (1) The waste catalyst is leached by contacting an organic acid solution to obtain a leachate containing Mo and V, and then the valence state of V in the leachate is adjusted to +4.

[0011] The waste catalyst contains not less than 25 wt% V (calculated as V2O5) and not less than 4 wt% Mo (calculated as MoO3).

[0012] (2) Mo is extracted from the feed liquid obtained in step (1) using the first extractant to obtain a first extract containing Mo and a first raffinate containing V. The first extract is washed and back-extracted to obtain a Mo-rich solution.

[0013] (3) Adjust the valence state of V in the first raffinate to +5;

[0014] (4) Use the second extractant to extract V from the feed liquid obtained in step (3) to obtain a second extract containing V, and then wash and back-extract to obtain a V-rich solution.

[0015] The method for recovering vanadium and molybdenum from spent catalysts provided by this invention firstly involves selectively leaching the metals in the spent catalysts with organic acids. The leachate is then modulated by adjusting the valence state of the variable-valence metal V to control its direction. A two-stage extraction process is employed, in which Mo is extracted in the first stage and V is extracted in the second stage. After extraction, washing, and back-extraction, the resulting product has a vanadium purity of 99.9% and a Mo purity of over 97%. Detailed Implementation

[0016] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0017] This invention provides a method for recovering vanadium and molybdenum from spent catalysts, the method comprising:

[0018] (1) The waste catalyst is leached by contacting an organic acid solution to obtain a leachate containing Mo and V, and then the valence state of V in the leachate is adjusted to +4.

[0019] The waste catalyst contains not less than 25 wt% V (calculated as V2O5) and not less than 4 wt% Mo (calculated as MoO3).

[0020] (2) Mo is extracted from the feed liquid obtained in step (1) using the first extractant to obtain a first extract containing Mo and a first raffinate containing V. The first extract is washed and back-extracted to obtain a Mo-rich solution.

[0021] (3) Adjust the valence state of V in the first raffinate to +5;

[0022] (4) Use the second extractant to extract V from the feed liquid obtained in step (3) to obtain a second extract containing V, and then wash and back-extract to obtain a V-rich solution.

[0023] Existing technologies for recovering V and Mo from spent catalysts typically involve extracting vanadium first, followed by molybdenum. However, vanadium extraction is difficult when organic acid complexing agents are present in the leachate. The inventors of this invention discovered that by utilizing the variable valence of V, adjusting its valence state to control its trajectory, and employing a two-stage extraction process—first extracting Mo, then extracting V—followed by extraction, washing, and back-extraction, efficient recovery of vanadium and molybdenum can be achieved. The resulting product exhibits a vanadium purity of 99.9% and a Mo purity exceeding 97%. Compared to existing recovery methods, this process is simpler, operates under milder conditions, and is easily implemented industrially.

[0024] This invention does not have special requirements regarding the source of the spent catalyst. Any spent catalyst containing a certain amount of V and Mo can be used in the method provided by this invention, wherein the V content (calculated as V₂O₅) is not less than 25 wt%, and the Mo content (calculated as MoO₃) is not less than 4 wt%. In particular, spent residue oil hydrotreating catalysts obtained during petroleum processing, especially spent residue oil hydrotreating demetallization catalysts, typically use Mo as the active metal component and exhibit high V deposition after long-term use. These catalysts are particularly suitable for simultaneously recovering Mo and V using the method provided by this invention, resulting in high recovery and purification efficiency.

[0025] According to the present invention, preferably, the waste catalyst contains 25-50 wt% V (calculated as V2O5) and 4-25 wt% Mo (calculated as MoO3).

[0026] According to the present invention, the spent catalyst can be leached by directly contacting an organic acid solution, or the spent catalyst can be calcined first to remove carbon deposits before acid leaching. Those skilled in the art can choose the appropriate method based on the specific circumstances. The calcination can be carried out using conventional methods in the art, and the present invention does not impose any particular limitation on this method.

[0027] In this invention, in step (1), an organic acid solution is used to leach the spent catalyst. The organic acid can act as a complexing agent, which is beneficial for the selective leaching of V and Mo in the catalyst, thus facilitating subsequent extraction.

[0028] According to some preferred embodiments of the present invention, in step (1), the organic acid is selected from at least one of acetic acid, oxalic acid, citric acid, and ethylenediaminetetraacetic acid. Using the above-mentioned preferred organic acids is beneficial for further improving the leaching rates of V and Mo.

[0029] According to the present invention, preferably, the concentration of the organic acid solution is 0.5-3 mol / L, for example, it can be a specific but not limiting concentration value such as 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, or any range between the two. Preferably, the concentration of the organic acid solution is 0.5-2 mol / L. Using the above preferred embodiments is beneficial for further improving the leaching rates of Mo and V.

[0030] Preferably, the solvent in the organic acid solution is water.

[0031] In this invention, the range of the amount of organic acid solution used is relatively wide, as long as it can fully leach V and Mo from the waste catalyst. Preferably, the ratio of the volume of the organic acid solution (mL) to the mass (g) of the waste catalyst is 10-50:1, and more preferably 15-40:1.

[0032] According to the present invention, preferably, the leachate contains 500-4000 mg / kg of Mo, more preferably 800-2000 mg / kg; and 6000-15000 mg / kg of V, more preferably 8000-12000 mg / kg. The leachate may also contain other metals besides Mo and V, such as Al, Fe, Ni, etc., and the present invention does not have any particular requirements in this regard.

[0033] In this invention, there are no special requirements for the method of controlling the valence state of V in the leachate in step (1), as long as the above-mentioned valence state adjustment can be achieved. The valence state of V in the leachate can be characterized by UV / Vis spectroscopy.

[0034] According to some preferred embodiments of the present invention, in step (1), the method of controlling the valence state of V in the leachate to +4 includes: mixing the leachate with a reducing agent under acidic conditions to carry out a reduction reaction. According to the present invention, preferably, sulfuric acid is added to the leachate to provide the acidic conditions, and then the valence state of V is adjusted by the reducing agent.

[0035] Preferably, the amount of sulfuric acid added is such that the sulfuric acid concentration in the feed solution obtained in step (1) is 0.1-1 mol / L. For example, it can be a specific but not limiting concentration value or any range between two such values, such as 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, or 1 mol / L. Preferably, the sulfuric acid concentration in the feed solution obtained in step (1) is 0.2-0.8 mol / L. Controlling the sulfuric acid concentration in the feed solution within the above-mentioned preferred range is beneficial for adjusting the valence state of V and improving the recovery efficiency of Mo and V.

[0036] The sulfuric acid can be provided by an aqueous solution of sulfuric acid, and the present invention does not have any particular requirement for this.

[0037] The present invention has a wide range of choices for the reducing agent. Conventional reducing agents that can achieve valence state adjustment can be used in the present invention. Preferably, the reducing agent is selected from at least one of iron powder, hydroxylamine sulfate and hydrazine.

[0038] Preferably, the reduction reaction is carried out at a temperature of 20-50°C, for example at room temperature, and the reduction reaction takes 0.1-3 hours.

[0039] According to some preferred embodiments of the present invention, step (2) further includes adjusting the pH of the solution obtained in step (1) to 1-3, preferably 1.5-2.5, and then performing the extraction. The present invention does not particularly limit the method of adjusting the pH. For example, an acid or alkali can be added to the solution obtained in step (1) to meet the above-mentioned pH range. The added acid can be, for example, sulfuric acid, and the alkali can be, for example, sodium hydroxide.

[0040] In this invention, the selection range of the first extractant is relatively wide, and conventional anionic extractants in the art can be used. Preferably, in step (2), the first extractant is at least one of P204, P507, TBP, N235 and A336.

[0041] Generally, the first extractant is diluted with an organic solvent before extraction. Preferably, the first extractant is provided by a first extractant solution, in which the mass concentration of the first extractant is 10-30%.

[0042] Preferably, the solvent in the first extractant solution is selected from at least one of hydrogenated kerosene, n-dodecane, and n-octanol.

[0043] According to some preferred embodiments of the present invention, in step (2), the volumetric flow rate ratio of the feed solution obtained in step (1) to the first extractant solution is 1-3:1, for example, it can be a specific but not limiting flow rate ratio such as 1:1, 1.5:1, 2:1, 2.5:1, 3:1, or any range between the two. Preferably, the volumetric flow rate ratio of the feed solution obtained in step (1) to the first extractant solution is 1.5-2.5:1. Using the above preferred embodiments is beneficial for further improving the purity and yield of Mo.

[0044] The present invention does not have any particular limitation on the specific operation method of the extraction. In order to further improve the recovery efficiency, preferably, the extraction in step (2) is a multi-stage countercurrent extraction, and the number of extraction stages is preferably 3-5 stages.

[0045] According to some preferred embodiments of the present invention, in step (2), the detergent used in the washing process is an acid solution, which can be at least one of hydrochloric acid, sulfuric acid, and nitric acid. Preferably, the acid used in the washing process is sulfuric acid. In the above preferred embodiments, the introduction of more heteroatoms can be avoided, thereby improving the purity of the product.

[0046] Preferably, the concentration of the acid solution is 0.1-2.5 mol / L.

[0047] Preferably, the volumetric flow rate ratio of the first extract to the detergent is 0.5-1.5:1, more preferably 0.7-1.2:1. Preferably, the washing process is multi-stage washing, and the number of washing stages is preferably 3-5 stages.

[0048] According to the present invention, the washed liquid is back-extracted to obtain a Mo-rich solution. Preferably, in step (2), the back-extraction includes mixing the washed liquid with a back-extracting agent.

[0049] This invention allows for a wide range of choices for the back-extraction agent, and conventional back-extraction agents in the art can be used to extract Mo from the organic phase to the aqueous phase. Preferably, the back-extraction agent is a sodium carbonate solution, and the concentration of the sodium carbonate solution is preferably 10-20 wt%.

[0050] Preferably, the back-extraction is carried out in a multi-stage back-extraction manner, with the number of stages preferably being 3-6 stages.

[0051] Preferably, the volumetric flow rate ratio of the washed feed liquid to the stripping agent is 1-3:1.

[0052] According to some preferred embodiments of the present invention, the method further includes: recovering the first extractant after back-extraction in step (2). The recovered first extractant can be reused in the extraction process of step (2).

[0053] According to the present invention, the first raffinate containing V obtained in step (2) is used as the raw material liquid for V extraction. V in the first raffinate exists in the +4 valence state. The valence state is first adjusted by step (3) and then V extraction is performed.

[0054] In this invention, there are no special requirements for the method of adjusting the valence state of V in the first raffinate in step (3), as long as the above-mentioned valence state adjustment can be achieved.

[0055] According to some preferred embodiments of the present invention, in step (3), the method of adjusting the valence state of V in the first raffinate to +5 includes: under acidic conditions, mixing the first raffinate with an oxidant to carry out an oxidation reaction.

[0056] In this invention, preferably, the pH of the acidic condition is 0.5-3.5, for example, it can be a specific pH value or any range between two such as 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 2, 2.5, 3, 3.5.

[0057] According to the present invention, preferably, an acid can be added to the first raffinate to provide the acidic conditions. The present invention does not particularly limit the type of acid; sulfuric acid can be used to avoid introducing other impurity atoms.

[0058] This invention allows for a wide range of oxidants; any conventional oxidant capable of adjusting valence state can be used. Preferably, the oxidant is selected from at least one of hydrogen peroxide, potassium permanganate, and ozone. This invention does not impose a particular limitation on the amount of oxidant used, as long as it achieves the aforementioned valence state change.

[0059] Preferably, the oxidation reaction is carried out at a temperature of 20-50°C, for example, at room temperature for a time of 0.1-3 hours.

[0060] In this invention, the selection range for the second extractant is relatively wide, and conventional anionic extractants in the art can be used. The extractant can be the same as or different from the first extractant. Preferably, in step (4), the second extractant is selected from at least one of P204, P507, TBP, N235, and A336.

[0061] Preferably, the second extractant is provided by a second extractant solution, wherein the concentration of the second extractant in the second extractant solution is 10-30 wt%.

[0062] Preferably, the solvent in the second extractant solution is selected from at least one of hydrogenated kerosene, n-dodecane, and n-octanol.

[0063] According to some preferred embodiments of the present invention, in step (4), the volume flow ratio of the feed liquid obtained in step (3) to the second extractant solution is 1-3:1, preferably 1-2.5:1.

[0064] The present invention does not have any particular limitation on the specific operation method of the extraction. In order to further improve the recovery efficiency, preferably, the extraction in step (4) is a multi-stage countercurrent extraction, and the number of extraction stages is preferably 3-5 stages.

[0065] According to some preferred embodiments of the present invention, in step (4), the detergent used in the washing process is an acid solution, which may be at least one of hydrochloric acid, sulfuric acid, and nitric acid. Preferably, the acid used in the washing process is sulfuric acid. Preferably, the concentration of the acid solution is 0.1-2.5 mol / L.

[0066] Preferably, the volumetric flow rate ratio of the second extract to the detergent is 0.5-1.5:1, more preferably 0.6-1.3:1. Preferably, the washing process is multi-stage washing, with 3-5 stages.

[0067] According to the present invention, in step (4), the washed liquid is back-extracted to obtain a V-rich solution. Preferably, in step (4), the back-extraction includes mixing the washed liquid with a back-extracting agent.

[0068] This invention allows for a wide range of choices for the back-extraction agent, and conventional back-extraction agents in the art can be used to extract V from the organic phase to the aqueous phase. Preferably, the back-extraction agent is a sodium carbonate solution, and the concentration of the sodium carbonate solution is preferably 10-20 wt%.

[0069] Preferably, the back-extraction is carried out in a multi-stage back-extraction manner, with the number of stages preferably being 3-6 stages.

[0070] Preferably, the volumetric flow rate ratio of the washed feed liquid to the stripping agent is 1-3:1.

[0071] According to some preferred embodiments of the present invention, the method further includes: recovering the second extractant after back-extraction in step (4). The recovered second extractant can be reused in the extraction process of step (4). Adopting the above preferred embodiments is beneficial to further improve the economic efficiency of the overall recovery method.

[0072] The present invention will be described in detail below through embodiments.

[0073] The waste catalyst used in the following examples is a waste residue oil hydrogenation catalyst, whose composition includes: V content of 40.6 wt% (based on V2O5), Mo content of 5.6 wt% (based on MoO3), Ni content of 9.8 wt% (based on NiO), Al content of 22.9 wt% (based on Al2O3), Fe content of 4.8 wt% (based on Fe2O3), Ca content of 1.2 wt% (based on CaO), Na content of 0.8 wt% (based on Na2O), and other elements such as Si and P.

[0074] Example 1

[0075] (1) The waste catalyst was calcined at 600℃ for 3h, and then mixed with 3mol / L oxalic acid solution at a ratio of solution volume (mL) to waste catalyst mass (g) of 20:1 for leaching to obtain metal leachate. The composition of the leachate includes: 10034mg / kg V, 1710mg / kg Mo, 3149mg / kg Al, 184mg / kg Fe and 23mg / kg Ni.

[0076] The acidity of the leachate was adjusted using sulfuric acid, with the sulfuric acid concentration controlled at 0.2 mol / L. A slightly excess of a mixed solution of hydroxylamine sulfate and hydrazine was added, and the mixture was stirred at room temperature for 0.2 h. The valence state of V in the leachate was tested by UV / Vis spectroscopy, which proved that V exists primarily in the +4 valence state.

[0077] (2) Mo Extraction Section: Adjust the pH of the aqueous phase solution obtained in step (1) to 2.0. Dissolve A336 and TBP in hydrogenated kerosene, wherein the mass fraction of A336 is 10% and the mass fraction of TBP is 10%, to obtain the first extractant solution. The prepared aqueous phase flows from stage 5 to stage 1 of the Mo extraction section, the extractant solution flows in from stage 1, and the washing agent is 0.5 mol / L sulfuric acid, flowing in from stage 9. The extractant phase enters the back-extraction section and undergoes four stages of back-extraction with a 20 wt% sodium carbonate solution to obtain the Mo product. The flow ratio in the extraction process is A / O = 2, the flow ratio in the washing process is A / O = 1, and the flow ratio in the back-extraction stage is A / O = 0.8. ICP testing shows that the Mo / M ratio in the Mo product is... 总 =96wt%, based on the total amount of Mo in the leachate, the yield of Mo is 97wt%.

[0078] (3) Add acid to the aqueous phase of the Mo extraction section to adjust the pH to 3.2, and then introduce ozone to carry out the oxidation reaction. The valence state of V in the leachate was tested by UV / Vis spectroscopy, which proved that V basically exists in the +5 valence state.

[0079] (4) Extraction Stage V: N235 and TBP are dissolved in hydrogenated kerosene, with N235 having a mass fraction of 10% and TBP having a mass fraction of 15%, to obtain a second extractant solution. The aqueous phase flows from stage 5 to stage 1 of the extraction stage V, the extractant solution flows in from stage 1, and the washing agent is 0.1 mol / L sulfuric acid, flowing in from stage 8. The extract phase enters the back-extraction stage, where it undergoes six stages of back-extraction with a 20% sodium carbonate solution to obtain product V. The flow ratio during the extraction process is A / O = 2, the flow ratio during the washing process is A / O = 1, and the flow ratio during the back-extraction stage is A / O = 1. ICP testing shows that the V / M ratio in product V is... 总 >99.9 wt%, with a V yield of 95 wt% based on the total V in the leachate.

[0080] Example 2

[0081] (1) The waste catalyst was calcined at 550℃ for 4 hours, and then mixed with 2.5 mol / L acetic acid solution at a ratio of solution volume (mL) to waste catalyst mass (g) of 20:1 for leaching to obtain metal leachate. The composition of the leachate includes: 8046 mg / kg V, 1735 mg / kg Mo, 3854 mg / kg Al, 356 mg / kg Fe and 85 mg / kg Ni.

[0082] The acidity of the leachate was adjusted using sulfuric acid, with the sulfuric acid concentration controlled at 0.3 mol / L. A slightly excessive amount of iron powder was added and stirred for 0.5 h to control the oxidation state of V in the leachate to +4, and then the iron powder was filtered off.

[0083] (2) Mo Extraction Section: Adjust the pH of the aqueous solution obtained in step (1) to 2.2. Dissolve N235 and n-octanol in hydrogenated kerosene, wherein the mass fraction of N235 is 10% and the mass fraction of n-octanol is 10%, to obtain the first extractant solution. The prepared aqueous phase flows from stage 4 to stage 1 of the Mo extraction section, the extractant flows in from stage 1, and the washing agent is 0.8 mol / L sulfuric acid, flowing in from stage 9. The extractant phase enters the back-extraction section, where it undergoes four stages of back-extraction using a 20% sodium carbonate solution to obtain the Mo product. The flow ratio in the extraction process is A / O = 2, the flow ratio in the washing process is A / O = 1, and the flow ratio in the back-extraction stage is A / O = 1. ICP testing shows that the Mo / M ratio in the Mo product is... 总 =97wt%, based on the total amount of Mo in the leachate, the yield of Mo is 95wt%.

[0084] (3) The aqueous phase of the Mo extraction section was treated with hydrogen peroxide, the pH of the solution was adjusted to 1.8, and the valence state of V was adjusted to +5.

[0085] (4) Extraction Stage V: A336 and TBP are dissolved in hydrogenated kerosene, with A336 having a mass fraction of 10% and TBP having a mass fraction of 15%, to obtain a second extractant solution. The aqueous phase flows from stage 6 to stage 1 of the extraction stage V, the extractant flows in from stage 1, and the washing agent is 0.2 mol / L sulfuric acid, flowing in from stage 10. The extractant phase enters the back-extraction stage, where it undergoes five stages of back-extraction with a 20% sodium carbonate solution to obtain product V. The flow ratios for the extraction, washing, and back-extraction stages are A / O = 1. ICP testing shows that the V / M ratio in product V is... 总 >99.9 wt%, with a V yield of 95 wt% based on the total V in the leachate.

[0086] Example 3

[0087] The method is the same as in Example 1, except that in step (2), the pH of the solution is adjusted to 3.0 and Mo is extracted.

[0088] According to ICP testing, the Mo / M content in the Mo product is... 总 =93wt%, based on the total amount of Mo in the spent catalyst, the Mo yield is 99wt%. V / M in the product 总 =99.9wt%, based on the total amount of V in the leachate, the yield of V is 96wt%.

[0089] Comparative Example 1

[0090] The method is the same as in Example 1, except that the valence state of V is not adjusted in step (1), and the valence state of V in the leachate is +5.

[0091] Mo and V were extracted sequentially according to the method in Example 1.

[0092] According to ICP testing, the Mo / M content in the Mo product is... 总 =90wt%, based on the total amount of Mo in the spent catalyst, the Mo yield is 96wt%. V / M in the product 总 = 98.2 wt%, based on the total amount of V in the leachate, the yield of V is 93 wt%.

[0093] Comparative Example 2

[0094] The method is the same as in Example 1, except that in step (1), an equimolar concentration of sulfuric acid solution is used for leaching.

[0095] Mo and V were extracted sequentially according to the method in Example 1.

[0096] According to ICP testing, the Mo / M content in the Mo product is... 总=94wt%, based on the total amount of Mo in the spent catalyst, the Mo yield is 95wt%. V / M in the product 总 =99.3wt%, with a V yield of 96wt% based on the total V in the leachate. Furthermore, ICP testing revealed that both the Mo and V product solutions contained a certain amount of Al impurity, Al / M... 总 Approximately 0.2 wt%.

[0097] The comparison of the above examples and comparative examples shows that the method for recovering vanadium and molybdenum from spent catalysts provided by the present invention can simultaneously and efficiently recover Mo and V, while maintaining high purity and yield of both Mo and V. A comparison of Example 1 and Comparative Example 1 shows that, under the complex composition of the spent catalyst leachate, without adjusting the valence state of V, the purity and yield of extracted Mo and V are both low. A comparison of Example 1 and Comparative Example 2 shows that using organic acids for spent catalyst leaching, followed by a subsequent extraction step, results in higher purity recovery of Mo and V.

[0098] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for recovering vanadium and molybdenum from spent catalysts, characterized in that, The method includes: (1) The waste catalyst is leached by contacting an organic acid solution to obtain a leachate containing Mo and V, and then the valence state of V in the leachate is controlled to be +4. The waste catalyst contains not less than 25 wt% V (calculated as V2O5) and not less than 4 wt% Mo (calculated as MoO3). (2) Mo is extracted from the feed liquid obtained in step (1) using the first extractant to obtain a first extract containing Mo and a first raffinate containing V. The first extract is washed and back-extracted to obtain a Mo-rich solution. (3) Adjust the valence state of V in the first raffinate to +5; (4) Use the second extractant to extract V from the feed liquid obtained in step (3) to obtain a second extract containing V, and then wash and back-extract to obtain a V-rich solution.

2. The method according to claim 1, wherein, The waste catalyst is a waste residue oil hydrogenation catalyst, preferably a waste residue oil hydrogenation demetallization catalyst; Preferably, the waste catalyst contains 25-50 wt% V (based on V₂O₅) and 4-25 wt% Mo (based on MoO₃).

3. The method according to claim 1 or 2, wherein, In step (1), the organic acid is selected from at least one of acetic acid, oxalic acid, citric acid and ethylenediaminetetraacetic acid; Preferably, the concentration of the organic acid solution is 0.5-3 mol / L; Preferably, the ratio of the volume (mL) of the organic acid solution to the mass (g) of the spent catalyst is 10-50:

1.

4. The method according to any one of claims 1-3, wherein, The leachate contains 500-4000 mg / kg of Mo and 6000-15000 mg / kg of V.

5. The method according to any one of claims 1-4, wherein, In step (1), the method of adjusting the valence state of V in the leachate to +4 includes: mixing the leachate with a reducing agent under acidic conditions; Preferably, the reducing agent is selected from at least one of iron powder, hydroxylamine sulfate, and hydrazine; Preferably, the reduction reaction is carried out at a temperature of 20-50°C for a time of 0.1-3 hours.

6. The method according to any one of claims 1-5, wherein, Step (2) further includes first adjusting the pH of the feed solution obtained in step (1) to 1-3, preferably 1.5-2.5, and then performing the extraction; Preferably, in step (2), the first extractant is at least one of P204, P507, TBP, N235 and A336; Preferably, the first extractant is provided by a first extractant solution, wherein the mass concentration of the first extractant in the first extractant solution is 10-30%; Preferably, the solvent in the first extractant solution is selected from at least one of hydrogenated kerosene, n-dodecane, and n-octanol; Preferably, in step (2), the volume flow ratio of the feed solution obtained in step (1) to the first extractant solution is 1-3:1; Preferably, the extraction in step (2) is a multi-stage countercurrent extraction, and the number of extraction stages is preferably 3-5 stages.

7. The method according to any one of claims 1-6, wherein, In step (2), the detergent used in the washing process is an acid solution with a concentration of 0.1-2.5 mol / L; Preferably, the acid in the acid solution is selected from at least one of sulfuric acid, nitric acid, and hydrochloric acid, and is preferably sulfuric acid; Preferably, the volumetric flow rate ratio of the first extract to the detergent is 0.5-1.5:1; Preferably, the washing process has 3-5 stages; Preferably, in step (2), the back-extraction includes: mixing the washed feed solution with a back-extraction agent; Preferably, the stripping agent is a sodium carbonate solution, and the concentration of the sodium carbonate solution is preferably 10-20 wt%. Preferably, the number of back-extraction stages is 3-6.

8. The method according to any one of claims 1-7, wherein, In step (3), the method of adjusting the oxidation state of V in the first raffinate to +5 includes: mixing the first raffinate with an oxidant under acidic conditions to carry out an oxidation reaction; Preferably, the oxidant is selected from at least one of hydrogen peroxide, potassium permanganate, and ozone; Preferably, the oxidation reaction is carried out at a temperature of 20-50°C for a time of 0.1-3 hours.

9. The method according to any one of claims 1-8, wherein, In step (4), the second extractant is selected from at least one of P204, P507, TBP, N235, and A336; Preferably, the second extractant is provided by a second extractant solution, wherein the mass concentration of the second extractant in the second extractant solution is 10-30%; Preferably, the solvent in the second extractant solution is selected from at least one of hydrogenated kerosene, n-dodecane, and n-octanol; Preferably, in step (4), the volume flow ratio of the feed solution obtained in step (3) to the second extractant solution is 1-3:1; Preferably, the extraction in step (4) is a multi-stage countercurrent extraction, and the number of extraction stages is preferably 3-5 stages.

10. The method according to any one of claims 1-9, wherein, In step (4), the detergent used in the washing process is an acid solution with a concentration of 0.1-2.5 mol / L; Preferably, the acid in the acid solution is selected from at least one of hydrochloric acid, sulfuric acid, and nitric acid; Preferably, the volumetric flow rate ratio of the second extract to the detergent is 0.5-1.5:1; Preferably, the washing process has 3-5 stages; Preferably, in step (4), the back-extraction includes: mixing the washed feed solution with a back-extraction agent; Preferably, the stripping agent is a sodium carbonate solution, and the concentration of the sodium carbonate solution is preferably 10-20 wt%. Preferably, the number of back-extraction stages is 3-6.