Method for leaching waste catalyst containing tungsten and molybdenum through pressurized oxygen enrichment

Abstract

The invention relates to a pressurized oxygen-enriched leaching method for a waste catalyst containing tungsten and molybdenum, and relates to the technical field of solid waste resource utilization, in particular to a pressurized oxygen-enriched leaching method for efficiently recovering tungsten and molybdenum from the waste catalyst containing tungsten and molybdenum, which comprises the following steps: firstly, removing organic matters and sulfides in the waste catalyst through anaerobic pyrolysis and oxidizing roasting steps; tungsten and molybdenum are oxidized into tungsten oxide and molybdenum oxide. Then, the treated catalyst is smashed and subjected to oxygen-enriched alkaline leaching in a high-pressure reaction kettle, a mixed solution of sodium carbonate and sodium hydroxide is selected as a leaching agent, and tungsten and molybdenum are converted into water-soluble sodium tungstate and sodium molybdate respectively under the conditions that the temperature is 150-200 DEG C and the oxygen pressure is 0.1-1.5 MPa, so that efficient leaching is achieved. By means of the method, the leaching rates of molybdenum and tungsten can reach 99% or above and 95% or above respectively, the recovery efficiency of valuable metal is remarkably improved, and the process is simple, environmentally friendly and suitable for large-scale industrial production.

Description

Technical Field

[0001] The present invention relates to the technical field of solid waste resource utilization, and in particular to a method for pressurized oxygen-enriched leaching of tungsten- and molybdenum-containing waste catalysts. Background Art

[0002] In the petrochemical industry, hydrodesulfurization catalysts are widely used to remove sulfides from fuels. However, due to the deposition of carbon, sulfur and heavy metals during use, the catalyst gradually becomes ineffective. When the hydrodesulfurization catalyst loses its catalytic activity, it is called "waste HDS catalyst" and usually needs to be replaced after 1 to 3 years. These waste catalysts contain a large amount of valuable metals, such as aluminum (Al), molybdenum (Mo) and tungsten (W), so the waste catalysts have extremely high recovery value as secondary resources. At present, many research and technical solutions have been proposed to recover these valuable metals. However, the existing technology still has problems such as low leaching rate, complex process, high cost, and difficulty in large-scale industrialization.

[0003] For example, the patent application with publication number CN113981207A reports a method for leaching tungsten and molybdenum, which roasts tungsten- and molybdenum-containing waste by adding roasting additives, and then uses an alkaline leaching agent to leach the roasted product, and finally obtains a liquid phase enriched in tungsten and molybdenum. Although this method has low equipment requirements and is easy to operate, the roasting process requires additional additives, which increases the process cost. In addition, this method has poor leaching effect on difficult-to-treat metal compounds.

[0004] Another example is a patent application with publication number CN108425011A, which discloses a method for extracting tungsten and molybdenum from high-molybdenum scheelite, which extracts tungsten and molybdenum from high-molybdenum scheelite by leaching with sulfuric acid solution and extracting with hydrogen peroxide. However, hydrogen peroxide, as an extractant, is expensive and not suitable for large-scale industrial production. In addition, the use of hydrogen peroxide increases safety risks, which limits the promotion of this method.

[0005] The patent application with publication number CN116043038A reports a method for synergistic oxidation leaching of low-grade tungsten-molybdenum ore, which uses a mixed alkali to wet-leach the molybdenum-tungsten ore. The leaching rate of molybdenum exceeds 85%, but the leaching rate of tungsten is only 45%. There is still a problem of low tungsten recovery rate, which limits the feasibility of its industrial application.

[0006] Alkali leaching under high pressure conditions has been proven to be an effective method for metal recovery. For example, patent CN107641724A discloses a method for improving the leaching rate of WO3 in scheelite, which achieves the enrichment and separation of molybdenum and tungsten through high-pressure alkaline leaching. However, this method still requires relatively high reaction temperature and pressure, and the process is complex and the equipment cost is high.

[0007] In addition, the patent application with publication number CN113684378A proposes a method for improving the leaching rate of tungsten and molybdenum in molybdenum sulfide-containing scheelite. The method first leaches scheelite by acid to obtain tungstic acid containing molybdenum sulfide, and then uses ammonia water to further treat tungsten trioxide (WO3) and molybdenum trioxide (MoO3) in the leached product. The molybdenum sulfide in the ammonia leaching residue after roasting is converted into molybdenum trioxide, and then the roasted residue is leached with sodium hydroxide to leach tungsten and molybdenum. Although this method improves the leaching rate of tungsten and molybdenum in molybdenum sulfide-containing scheelite, it has the following disadvantages: multi-step processing is complex: the process needs to go through multiple steps such as acid leaching, ammonia leaching, roasting and sodium hydroxide leaching, and the process flow is complicated, which makes industrial application difficult; high cost: ammonia water and roasting treatment add additional costs, especially in large-scale production, it is difficult to reduce the overall recovery cost; high equipment requirements: the roasting process has high requirements for equipment, and the safety during operation also needs special attention.

[0008] In general, the existing technology has the problems of low leaching rate, high cost and complicated process when recovering tungsten and molybdenum from spent hydrodesulfurization catalysts. Therefore, it is an urgent technical problem to develop a new method that can effectively improve the leaching rate of molybdenum and tungsten, simplify the process and reduce the production cost. Summary of the invention

[0009] The technical problem to be solved by the present invention is to provide a method for pressurized oxygen-enriched leaching of waste catalysts containing tungsten and molybdenum, so as to solve the problems of low leaching rate of tungsten and molybdenum, complex process and high cost existing in conventional methods in the prior art.

[0010] The present invention provides a method for leaching waste catalyst containing tungsten and molybdenum under pressure and oxygen-enriched conditions, comprising the following steps:

[0011] S1: performing anaerobic pyrolysis on the spent hydrodesulfurization catalyst to remove oil; performing oxidative roasting on the spent hydrodesulfurization catalyst after anaerobic pyrolysis to oxidize sulfur into sulfate ions, and simultaneously oxidize molybdenum ions and tungsten ions into molybdenum oxide and tungsten oxide;

[0012] S2: crushing the waste hydrodesulfurization catalyst after the reaction in step S1, and then placing it in a high-pressure reactor for alkali leaching, wherein the alkali leaching agent used in the alkali leaching is a mixture of sodium hydroxide solution and sodium carbonate solution, and sodium tungstate and sodium molybdate are leached out;

[0013] S3: introducing oxygen into the autoclave after the treatment in step S2 to carry out high-pressure oxidation reaction, reacting with the alkaline leaching agent to form a water-soluble substance, and separating the solid and the liquid after the reaction is completed to obtain a filtrate enriched in Mo and W.

[0014] The present application discloses a method for pressurized oxygen-enriched leaching of waste catalysts containing tungsten and molybdenum. In the step S1, the waste catalyst is first subjected to oxygen-free pyrolysis at 500-650°C to remove oil and remove impurities such as carbon and sulfur on the surface of the catalyst. This process helps to reduce impurity interference in subsequent reactions and improves leaching efficiency. Since organic impurities are removed during the pyrolysis process, the impact on subsequent metal oxidation reactions is reduced, especially the content of sulfides is reduced, making the metal leaching process smoother and effectively improving the oxidation conversion rate of molybdenum and tungsten. Secondly, oxidative roasting is carried out at 600-800°C to oxidize sulfur into sulfate ions, reducing the impact on subsequent leaching, and at the same time oxidizing molybdenum and tungsten ions into molybdenum oxide and tungsten oxide, providing a good premise for alkaline leaching. Through high-temperature oxidative roasting, metal sulfides are converted into oxides, which are subsequently more soluble in alkaline leaching agents. The oxides obtained after roasting are more easily treated by alkaline leaching agents, thereby improving the recovery efficiency of tungsten and molybdenum.

[0015] In step S2, the calcined catalyst is placed in a high-pressure reactor and alkali-leached with a mixed solution of sodium hydroxide and sodium carbonate to convert molybdenum and tungsten into sodium molybdate and sodium tungstate. The synergistic effect of NaOH and Na2CO3 provides sufficient OH for the metal oxides. - ions, making it easier for molybdenum oxide and tungsten oxide to be converted into water-soluble compounds, thereby improving the leaching efficiency of molybdenum and tungsten.

[0016] In step S3, pressurized oxygen promotes the continued oxidation of unreacted sulfides, further improving the leaching efficiency. Through the high-pressure oxidation reaction under oxygen-rich conditions, the metal sulfides are converted into oxides that are more easily leached, thereby improving the leaching rate and ultimately achieving efficient recovery of molybdenum and tungsten.

[0017] Compared with the prior art, the pressurized oxygen-enriched leaching method of tungsten-containing molybdenum waste catalyst of the present application has the following advantages: through a series of optimized operations such as anaerobic pyrolysis, oxidative roasting, high-pressure alkaline leaching, and oxygen-enriched oxidation, the technical problems existing in the background technology are solved: high leaching rate: the leaching rate of tungsten is increased to 95%, and the leaching rate of molybdenum reaches 99%, which is much higher than the low leaching rate of tungsten in the prior art; reduced cost: the alkaline leaching agent (sodium hydroxide and sodium carbonate) used in the present invention is relatively cheap, and no expensive oxidant is required, thereby reducing the production cost; environmentally friendly: through oxygen pressure leaching, the use of a large amount of acid, alkali and harmful oxidants is avoided, the emission of waste liquid and waste gas is reduced, the environmental protection requirements are met, and it is suitable for large-scale industrial production. The pressurized oxygen-enriched leaching method of tungsten-containing molybdenum waste catalyst of the present invention optimizes the leaching process, which is different from the alkaline leaching method, water leaching method, and ammonia leaching method of the prior art. By oxidizing valuable metals into oxides, the recovery rate is improved, and the problems of low leaching rate of molybdenum and tungsten, complex process, high cost and environmental pollution in the prior art are solved, and an efficient, economical and environmentally friendly metal recovery method is realized.

[0018] In a possible implementation, in the step S1, the temperature of the anaerobic pyrolysis is 500-650° C., the temperature of the oxidative roasting is 600-800° C., and the time of the oxidative roasting is 2-3 hours.

[0019] Compared with the prior art, the above technical scheme can realize effective anaerobic pyrolysis and oxidative roasting of waste hydrodesulfurization catalyst. By controlling the pyrolysis temperature, impurities such as oil, carbon, and sulfur in the catalyst can be effectively removed under anaerobic conditions. At the same time, during the oxidative roasting process, sulfur is oxidized into sulfate ions, and molybdenum ions and tungsten ions are oxidized into their corresponding oxides, thereby improving the oxidation conversion rate of molybdenum and tungsten, and providing good raw materials for subsequent alkaline leaching treatment.

[0020] In a possible implementation, in the step S1, the temperature of the anaerobic pyrolysis is 600° C., the temperature of the oxidative roasting is 700° C., and the time of the oxidative roasting is 2.5 h.

[0021] Compared with the prior art, the above technical solution can more accurately control the reaction conditions. By setting the temperature of anaerobic pyrolysis to 600°C and the oxidative roasting temperature to 750°C, the heat energy transfer of the reaction can be effectively optimized to ensure the uniformity and thoroughness of the reaction. Increasing the roasting temperature can accelerate the oxidation of sulfur and the conversion of metals, thereby effectively improving the formation of the final oxide, further improving the quality and leaching rate of molybdenum oxide and tungsten oxide, and the overall leaching effect is significantly better than the prior art, meeting the needs of industrial large-scale production.

[0022] In a possible implementation, in step S2, in the alkaline leaching agent, the amount of sodium carbonate added is 15-30wt% of the spent hydrodesulfurization catalyst, and the amount of sodium hydroxide added is 15-30wt% of the spent hydrodesulfurization catalyst.

[0023] Compared with the prior art, the above technical solution can improve the leaching efficiency of molybdenum and tungsten by optimizing the ratio of the alkaline leaching agent during the leaching process. By adjusting the amount of the alkaline leaching agent added, the pH value of the reaction and the alkalinity of the reaction medium can be better controlled to ensure that the reaction environment is suitable for the dissolution of metal oxides, ensure the effective generation of sodium tungstate and sodium molybdate, significantly improve the leaching rate, and ultimately achieve a higher metal recovery efficiency.

[0024] In a possible implementation, in step S2, the amount of sodium carbonate added is 30 wt% of the spent hydrodesulfurization catalyst, and the amount of sodium hydroxide added is 15 wt% of the spent hydrodesulfurization catalyst.

[0025] Compared with the prior art, the above technical solution can enhance the leaching capacity of the waste catalyst by reasonably configuring the alkaline leaching agent. The increased proportion of sodium carbonate can more effectively promote the conversion of tungsten and molybdenum into soluble salts, further optimize the mass ratio of the alkaline leaching agent, make the reaction more complete, promote the leaching of metals, and achieve the best leaching rate of molybdenum and tungsten through precise alkaline leaching agent ratio, thereby improving the overall economic benefits of metal recovery.

[0026] In a possible implementation, in step S2, the reaction formula of the alkali leaching reaction process includes:

[0027] WO3+2Na2CO3+H2O→Na2WO4+2NaHCO3;

[0028] MoO3+2Na2CO3+H2O→Na2MoO4+2NaHCO3;

[0029] WO3+2NaOH→Na2WO4+H2O;

[0030] MoO3+2NaOH→Na2MoO4+H2O;

[0031] Al2O3+2NaOH→2NaAlO2+H2O

[0032] Compared with the existing technology, the reaction process using the above technical solution can more clearly define and analyze the chemical changes in each reaction step, and demonstrate the conversion reaction of molybdenum and tungsten through reaction equations, providing theoretical support for the chemical mechanism of alkaline leaching, making the reaction process clearer, and helping to optimize subsequent processes, improve the recovery rate of molybdenum and tungsten, and ensure the controllability and stability of the production process.

[0033] In a possible implementation, in step S2, the temperature of the alkali leaching treatment is 170-175° C., and the time is 2-3 hours; the mass ratio of the alkali leaching agent to the spent hydrodesulfurization catalyst is (3-7):1.

[0034] Compared with the prior art, the above technical solution can accelerate the dissolution reaction of molybdenum and tungsten oxides in the waste catalyst by alkaline leaching treatment within a higher temperature range, and significantly improve the leaching efficiency of molybdenum and tungsten. Under high temperature conditions of 170-175°C, the reaction rate between molybdenum and tungsten oxides and alkaline solution (a mixture of sodium hydroxide and sodium carbonate) is significantly accelerated. Higher temperatures can enhance the solubility of alkaline solutions for oxides and promote the formation of sodium molybdate and sodium tungstate. A longer reaction time (2-3 hours) can ensure the completeness of the leaching process, allowing the reactants to fully contact the alkali, further improving the leaching efficiency of the metal. By optimizing the temperature and time of alkaline leaching treatment, the dissolution reaction of tungsten and molybdenum can be accelerated, the leaching time can be reduced, and the leaching can be ensured to be complete, so that more sodium tungstate and sodium molybdate are dissolved into the filtrate, the recovery rate is improved, and the metal recovery process is more stable and efficient.

[0035] In a possible embodiment, in step S3, in the high-pressure oxidation reaction, the oxygen pressure is 0.1-1.5 MPa, the reaction time is 1-4 h, the reaction temperature is 150-200° C., and the liquid-to-solid ratio of the alkali leachate to the waste hydrodesulfurization catalyst is (3-7) mL / g.

[0036] Compared with the existing technology, the above technical solution can significantly improve the reaction rate and effect under high pressure conditions. The direct technical principle is that high-pressure oxygen can promote the rapid oxidation of metal sulfides and increase the reaction rate; by optimizing the reaction conditions, the reaction time is reduced and the reaction efficiency is improved; through pressurized oxidation treatment, the leaching efficiency of molybdenum and tungsten is further improved, so that the final filtrate is rich in molybdenum and tungsten, meeting the needs of industrial applications.

[0037] In a possible implementation, in step S3, the gas pressure of oxygen is 0.5 MPa, the reaction temperature is 175° C., the reaction time is 2 h, and the liquid-to-solid ratio is 5:1.

[0038] Compared with the existing technology, the above technical scheme can carry out the reaction at a lower temperature and a reasonable liquid-to-solid ratio, which can effectively save energy. By setting appropriate reaction conditions, effective metal oxidation and leaching can be achieved in a milder environment, thereby maintaining efficient leaching while reducing production costs and energy consumption, achieving the dual goals of economy and environmental friendliness. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a flow chart of the method for pressurized oxygen-enriched leaching of waste catalyst containing tungsten and molybdenum in the present invention;

[0040] Figure 2 It is a schematic diagram showing the effect of different conditions on the final Mo and W leaching rates in the method of pressurized oxygen-enriched leaching of tungsten-containing molybdenum waste catalyst in the present invention. DETAILED DESCRIPTION

[0041] First, those skilled in the art should understand that these implementations are only used to explain the technical principles of the embodiments of the present application, and are not intended to limit the protection scope of the embodiments of the present application. Those skilled in the art can make adjustments to them as needed to adapt to specific application scenarios.

[0042] The present invention provides a method for leaching waste catalyst containing tungsten and molybdenum under pressure and oxygen-enriched conditions, such as Figure 1 As shown, the following steps are included:

[0043] S1: performing anaerobic pyrolysis on the spent hydrodesulfurization catalyst to remove oil; performing oxidative roasting on the spent hydrodesulfurization catalyst after anaerobic pyrolysis to oxidize sulfur into sulfate ions, and simultaneously oxidize molybdenum ions and tungsten ions into molybdenum oxide and tungsten oxide;

[0044] S2: crushing the waste hydrodesulfurization catalyst after the reaction in step S1, and then placing it in a high-pressure reactor for alkali leaching, wherein the alkali leaching agent used in the alkali leaching is a mixture of sodium hydroxide solution and sodium carbonate solution, and sodium tungstate and sodium molybdate are leached out;

[0045] S3: introducing oxygen into the autoclave after the treatment in step S2 to carry out high-pressure oxidation reaction, oxidizing metal sulfides into oxides, and then reacting with alkaline leaching agent to form water-soluble substances. After the reaction is completed, solid-liquid separation is carried out to obtain a filtrate enriched in Mo and W.

[0046] As a preferred solution, in the step S1, the temperature of the anaerobic pyrolysis is 500-650°C, the temperature of the oxidative roasting is 600-800°C, and the time of the oxidative roasting is 2-3h.

[0047] As a preferred solution, in the step S1, the temperature of the anaerobic pyrolysis is 600°C, the temperature of the oxidative roasting is 700°C, and the time of the oxidative roasting is 2.5 hours.

[0048] As a preferred solution, in step S2, in the alkaline leaching agent, the amount of sodium carbonate added is 15-30wt% of the waste hydrodesulfurization catalyst, and the amount of sodium hydroxide added is 15-30wt% of the waste hydrodesulfurization catalyst.

[0049] As a preferred solution, in step S2, the amount of sodium carbonate added is 30 wt% of the waste hydrodesulfurization catalyst, and the amount of sodium hydroxide added is 15 wt% of the waste hydrodesulfurization catalyst.

[0050] As a preferred solution, in step S2, the reaction formula of the alkali leaching reaction process includes:

[0051] WO3+2Na2CO3+H2O→Na2WO4+2NaHCO3;

[0052] MoO3+2Na2CO3+H2O→Na2MoO4+2NaHCO3;

[0053] WO3+2NaOH→Na2WO4+H2O;

[0054] MoO3+2NaOH→Na2MoO4+H2O;

[0055] Al2O3+2NaOH→2NaAlO2+H2O.

[0056] As a preferred solution, in step S2, the temperature of the alkali leaching treatment is 170-175°C, and the time is 2-3h; the mass ratio of the alkali leaching agent to the waste hydrodesulfurization catalyst is (3-7):1.

[0057] As a preferred solution, in step S3, in the high-pressure oxidation reaction, the oxygen pressure is 0.1-1.5 MPa, the reaction time is 1-4 h, the reaction temperature is 150-200° C., and the liquid-to-solid ratio is (3-7) mL / g.

[0058] As a preferred solution, in step S3, the gas pressure of oxygen is 0.5 MPa, the reaction temperature is 175° C., the reaction time is 2 h, and the liquid-to-solid ratio is 5:1.

[0059] The following provides a specific embodiment combining the above data range to further illustrate the technical solution of the present invention:

[0060] Embodiment 1:

[0061] Example 1 provides a method for pressurized oxygen-enriched leaching of tungsten- and molybdenum-containing waste catalysts, comprising the following steps:

[0062] S1: performing anaerobic pyrolysis on the waste hydrodesulfurization catalyst to remove oil; performing oxidative roasting on the waste hydrodesulfurization catalyst after the anaerobic pyrolysis to oxidize sulfur into sulfate ions, and simultaneously oxidize molybdenum ions and tungsten ions into molybdenum oxide and tungsten oxide; the temperature of the anaerobic pyrolysis is 600°C, the temperature of the oxidative roasting is 700°C, and the time of the oxidative roasting is 2.5h.

[0063] S2: The waste hydrodesulfurization catalyst after the reaction in step S1 is crushed and then placed in a high-pressure reactor for alkali leaching. The alkali leaching temperature is 170° C. and the time is 2 hours. The alkali leaching agent used in the alkali leaching is a mixture of sodium hydroxide solution and sodium carbonate solution to leach sodium tungstate and sodium molybdate. The amount of sodium carbonate added is 30wt% of the waste hydrodesulfurization catalyst, and the amount of sodium hydroxide added is 15wt% of the waste hydrodesulfurization catalyst.

[0064] The reaction formula of the alkali leaching reaction process includes:

[0065] WO3+2Na2CO3+H2O→Na2WO4+2NaHCO3;

[0066] MoO3+2Na2CO3+H2O→Na2MoO4+2NaHCO3;

[0067] WO3+2NaOH→Na2WO4+H2O;

[0068] MoO3+2NaOH→Na2MoO4+H2O;

[0069] Al2O3+2NaOH→2NaAlO2+H2O.

[0070] S3: introducing oxygen into the high-pressure reactor after the treatment in step S2 to carry out a high-pressure oxidation reaction, while oxidizing the metal sulfide to oxide, and then reacting with the alkali leaching agent to form a water-soluble substance. After the reaction is completed, the solid-liquid separation is carried out to obtain a filtrate enriched in Mo and W; in the high-pressure oxidation reaction, the oxygen pressure is 0.5MPa, the reaction time is 2h, the reaction temperature is 175°C, and the liquid-solid ratio after the reaction is completed is 5mL:1g, that is, the liquid-solid ratio of the alkali leaching agent to the spent hydrodesulfurization catalyst is 5:1.

[0071] Embodiment 2:

[0072] Example 2 A method for leaching waste catalyst containing tungsten and molybdenum by pressurized oxygen-enriched leaching is adopted, comprising the following steps:

[0073] S1: performing anaerobic pyrolysis on the waste hydrodesulfurization catalyst to remove oil; performing oxidative roasting on the waste hydrodesulfurization catalyst after the anaerobic pyrolysis to oxidize sulfur into sulfate ions, and at the same time oxidize molybdenum ions and tungsten ions into molybdenum oxide and tungsten oxide; the temperature of the anaerobic pyrolysis is 500°C, the temperature of the oxidative roasting is 600°C, and the time of the oxidative roasting is 2h.

[0074] S2: The waste hydrodesulfurization catalyst after the reaction in step S1 is crushed and then placed in a high-pressure reactor for alkali leaching. The temperature of the alkali leaching is 170° C. and the time is 2 hours. The alkali leaching agent used in the alkali leaching is a mixture of sodium hydroxide solution and sodium carbonate solution to leach sodium tungstate and sodium molybdate. The amount of sodium carbonate added is 15wt% of the waste hydrodesulfurization catalyst, and the amount of sodium hydroxide added is 15wt% of the waste hydrodesulfurization catalyst.

[0075] The reaction formula of the alkali leaching reaction process includes:

[0076] WO3+2Na2CO3+H2O→Na2WO4+2NaHCO3;

[0077] MoO3+2Na2CO3+H2O→Na2MoO4+2NaHCO3;

[0078] WO3+2NaOH→Na2WO4+H2O;

[0079] MoO3+2NaOH→Na2MoO4+H2O;

[0080] Al2O3+2NaOH→2NaAlO2+H2O.

[0081] S3: introducing oxygen into the high-pressure reactor after the treatment in step S2 to carry out a high-pressure oxidation reaction, while oxidizing the metal sulfide to oxide, and then reacting with the alkali leaching agent to form a water-soluble substance, and separating the solid and liquid after the reaction is completed to obtain a filtrate enriched in Mo and W; in the high-pressure oxidation reaction, the oxygen pressure is 0.1MPa, the reaction time is 1h, the reaction temperature is 150°C, and the liquid-solid ratio after the reaction is completed is 3mL:1g, that is, the liquid-solid ratio of the alkali leaching agent to the waste hydrodesulfurization catalyst is 3:1.

[0082] Embodiment 3:

[0083] Example 3 provides a method for pressurized oxygen-enriched leaching of tungsten- and molybdenum-containing waste catalysts, comprising the following steps:

[0084] S1: performing anaerobic pyrolysis on the spent hydrodesulfurization catalyst to remove oil; performing oxidative roasting on the spent hydrodesulfurization catalyst after the anaerobic pyrolysis to oxidize sulfur into sulfate ions, and simultaneously oxidize molybdenum ions and tungsten ions into molybdenum oxide and tungsten oxide; the temperature of the anaerobic pyrolysis is 650°C, the temperature of the oxidative roasting is 800°C, and the time of the oxidative roasting is 3h.

[0085] S2: The waste hydrodesulfurization catalyst after the reaction in step S1 is crushed and then placed in a high-pressure reactor for alkali leaching. The temperature of the alkali leaching is 175° C. and the time is 3 hours. The alkali leaching agent used in the alkali leaching is a mixture of sodium hydroxide solution and sodium carbonate solution to leach sodium tungstate and sodium molybdate. The amount of sodium carbonate added is 30wt% of the waste hydrodesulfurization catalyst, and the amount of sodium hydroxide added is 30wt% of the waste hydrodesulfurization catalyst.

[0086] The reaction formula of the alkali leaching reaction process includes:

[0087] WO3+2Na2CO3+H2O→Na2WO4+2NaHCO3;

[0088] MoO3+2Na2CO3+H2O→Na2MoO4+2NaHCO3;

[0089] WO3+2NaOH→Na2WO4+H2O;

[0090] MoO3+2NaOH→Na2MoO4+H2O;

[0091] Al2O3+2NaOH→2NaAlO2+H2O.

[0092] S3: introducing oxygen into the high-pressure reactor after the treatment in step S2 to carry out a high-pressure oxidation reaction, while oxidizing the metal sulfide to oxide, and then reacting with the alkali leaching agent to form a water-soluble substance. After the reaction is completed, the solid-liquid separation is carried out to obtain a filtrate enriched in Mo and W; in the high-pressure oxidation reaction, the oxygen pressure is 1.5MPa, the reaction time is 4h, the reaction temperature is 200°C, and the liquid-solid ratio after the reaction is completed is 7mL:1g, that is, the liquid-solid ratio of the alkali leaching agent to the waste hydrodesulfurization catalyst is 7:1.

[0093] like Figure 2 As shown, Figure 2 Schematic diagram of the effect of different conditions in each step of the method for pressurized oxygen-enriched leaching of tungsten-containing molybdenum waste catalyst in the present invention on the final Mo and W leaching rates.

[0094] from Figure 2 It can be seen from a that when the oxygen partial pressure is 0.5 MPa, the leaching rates of Mo and W are the highest;

[0095] from Figure 2 As can be seen in b, when the leaching time is 2.0 h, the comprehensive leaching rate of Mo and W is the highest;

[0096] from Figure 2 As can be seen from c, when the leaching temperature is 170 °C, the comprehensive leaching rate of Mo and W is the highest;

[0097] from Figure 2 d, it can be seen that when the addition amount of sodium carbonate is twice that of sodium hydroxide, the leaching rate of Mo and W is the highest;

[0098] from Figure 2 e, it can be seen that when the liquid-to-solid ratio is 5:1, the leaching rates of Mo and W are the highest;

[0099] from Figure 2 It can be seen from Figure f that when the calcination temperature is 700℃, the comprehensive leaching rate of Mo and W is the highest.

[0100] And from Figure 2 It is further proved that the tungsten and molybdenum in the waste HDS catalyst can be leached by using a method of pressurized oxygen-enriched leaching of waste catalyst containing tungsten and molybdenum in the present invention. Through the method of oxygen pressure alkaline leaching, the leaching rate of tungsten can reach 95%, and the leaching rate of molybdenum can reach 99%. After oxygen is introduced into the method of pressurized oxygen-enriched leaching of waste catalyst containing tungsten and molybdenum in the present invention, the substance in the catalyst further oxidizes the metal sulfide into oxide, and then reacts with the alkaline leaching agent to form a water-soluble substance. After the reaction is completed, the solid and liquid are separated to obtain a filtrate enriched in Mo and W. The alkaline leaching agent combines with molybdenum and tungsten to form a water-soluble compound, thereby improving the leaching rate. The above method does not require cumbersome steps and expensive materials. The use of an alkaline leaching agent can recover most of the valuable metals, is pollution-free, and is suitable for large-scale industrial production, which solves the problems existing in the background technology.

[0101] In the description of the present application, the description with reference to the terms "one embodiment", "some embodiments", "in the present embodiment", "specific example", or "some examples" etc. means that the specific features, mechanisms, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, mechanisms, materials or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0102] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A method for leaching waste catalyst containing tungsten and molybdenum by pressurized oxygen-enriched leaching, characterized in that: The following steps are involved: S1: performing anaerobic pyrolysis on the spent hydrodesulfurization catalyst to remove oil; performing oxidative roasting on the spent hydrodesulfurization catalyst after anaerobic pyrolysis to oxidize sulfur into sulfate ions, and simultaneously oxidize molybdenum ions and tungsten ions into molybdenum oxide and tungsten oxide; S2: crushing the waste hydrodesulfurization catalyst after the reaction in step S1, and then placing it in a high-pressure reactor for alkali leaching, wherein the alkali leaching agent used in the alkali leaching is a mixture of sodium hydroxide solution and sodium carbonate solution, and sodium tungstate and sodium molybdate are leached out; S3: introducing oxygen into the autoclave after the treatment in step S2 to carry out high-pressure oxidation reaction, reacting with the alkaline leaching agent to form a water-soluble substance, and separating the solid and the liquid after the reaction is completed to obtain a filtrate enriched in Mo and W.

2. The method for leaching waste catalyst containing tungsten and molybdenum by pressurized oxygen-enriched leaching according to claim 1, characterized in that: In the step S1, the temperature of the anaerobic pyrolysis is 500-650°C, the temperature of the oxidative roasting is 600-800°C, and the time of the oxidative roasting is 2-3h.

3. The method for leaching waste catalyst containing tungsten and molybdenum by pressurized oxygen-enriched leaching according to claim 2, characterized in that: In the step S1, the temperature of the anaerobic pyrolysis is 600° C., the temperature of the oxidative roasting is 700° C., and the time of the oxidative roasting is 2.5 hours.

4. The method for leaching waste catalyst containing tungsten and molybdenum by pressurized oxygen-enriched leaching according to claim 1, characterized in that: In the step S2, in the alkaline leaching agent, the amount of sodium carbonate added is 15-30wt% of the waste hydrodesulfurization catalyst, and the amount of sodium hydroxide added is 15-30wt% of the waste hydrodesulfurization catalyst.

5. The method for leaching waste catalyst containing tungsten and molybdenum by pressurized oxygen-enriched leaching according to claim 4, characterized in that: In the step S2, the amount of sodium carbonate added is 30 wt% of the waste hydrodesulfurization catalyst, and the amount of sodium hydroxide added is 15 wt% of the waste hydrodesulfurization catalyst.

6. The method for leaching waste catalyst containing tungsten and molybdenum by pressurized oxygen-enriched leaching according to claim 2, characterized in that: In step S2, the reaction formula of the alkali leaching reaction process includes: WO3+2Na2CO3+H2O→Na2WO4+2NaHCO3; MoO3+2Na2CO3+H2O→Na2MoO4+2NaHCO3; WO3+2NaOH→Na2WO4+H2O; MoO3+2NaOH→Na2MoO4+H2O; Al2O3+2NaOH→2NaAlO2+H2O.

7. The method for leaching waste catalyst containing tungsten and molybdenum by pressurized oxygen-enriched leaching according to claim 2, characterized in that: In the step S2, the temperature of the alkali leaching treatment is 170-175°C, and the time is 2-3 hours; the mass ratio of the alkali leaching agent to the spent hydrodesulfurization catalyst is (3-7):

1.

8. The method for leaching waste catalyst containing tungsten and molybdenum by pressurized oxygen-enriched leaching according to claim 2, characterized in that: In the step S3, in the high-pressure oxidation reaction, the oxygen pressure is 0.1-1.5 MPa, the reaction time is 1-4 hours, and the reaction temperature is 150-200°C.

9. The method for leaching waste catalyst containing tungsten and molybdenum by pressurized oxygen-enriched leaching according to claim 7, characterized in that: In the step S3, the gas pressure of oxygen is 0.5 MPa, the reaction temperature is 175° C., the reaction time is 2 h, and the liquid-to-solid ratio is 5:1.

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