Process for the ammonia-free preparation of high-purity molybdic acid

Abstract

The application relates to an ammonia-free preparation process of high-purity molybdic acid and high-purity molybdenum trioxide, which comprises the following operation steps: (1) preliminary chemical impurity removal; (2) precision filtration; (3) ion exchange method deep impurity removal; (4) molybdenum adsorption; (5) washing; (6) elution; (7) deacidification; (8) high-purity molybdic acid is prepared; (8) after the solution is deacidified, the solution is heated to 60-70 DEG C to start turbidity, and is kept at 60-70 DEG C for 3-6 h to make the crystal grow, and then the temperature is continuously increased to 90-95 DEG C to make the molybdenum precipitate completely; (9) high-purity molybdic acid is obtained after filtration; and (10) high-purity molybdenum trioxide is obtained after dehydration of the high-purity molybdic acid. The high-purity molybdic acid prepared by the process has extremely low impurity content, and high-purity molybdenum trioxide can be directly obtained after drying and dehydration, and compared with the current ammonium molybdate decomposition method for preparing high-purity molybdenum trioxide, the process is simple and has no pollutants.

Description

Technical Field

[0001] This invention belongs to the field of preparation of high-purity molybdic acid and high-purity molybdenum trioxide, specifically involving an ammonia-free preparation process of high-purity molybdic acid and an ammonia-free preparation process of high-purity molybdenum trioxide. Background Technology

[0002] Residue oil, the most difficult heavy component of petroleum to utilize, has an extremely high sulfur content and contains certain amounts of metals (mainly nickel and vanadium). It is typically only used as asphalt or in the production of petroleum coke, resulting in low economic value. Furthermore, the use of high-sulfur petroleum coke, as a highly polluting product, is significantly limited, while the rigid demand in the fuel industry will shift towards low-sulfur petroleum coke or alternative fuels. To reduce pollution in the petroleum refining process and increase refining profits, hydrogenating residue oil into economical oil products such as gasoline and diesel is the optimal production route, and residue oil hydrogenation catalysts play a crucial role in this process. Molybdic acid is the main effective component in the preparation of residue oil hydrogenation catalysts. It is a white or slightly yellow monoclinic columnar crystal or powder. The main components of molybdic acid can be understood as molybdenum trioxide and water. The molybdenum-based catalyst prepared from it catalyzes the hydrogenation reaction of residue oil to produce hydrogenated heavy oil. This hydrogenated heavy oil can then be used as feedstock in catalytic converters, further processed into high-value-added light components such as gasoline, kerosene, and diesel. The residue hydrotreating catalyst has extremely high purity requirements for the molybdic acid used, and the number of impurity elements controlled is as high as 26, including 19 metallic impurities such as sodium, potassium and aluminum, and 7 non-metallic impurities such as sulfur, phosphorus and chlorine.

[0003] The preparation of ordinary molybdic acid mainly involves acidifying a molybdate solution. This produces molybdic acid with high impurity content and fine particle size, making filtration difficult and unsuitable for the raw material requirements of residue oil hydrogenation catalyst production. While the process of preparing molybdenum trioxide through molybdic acid dehydration is simple and produces no pollutants, the excessive impurities in the molybdic acid result in molybdenum trioxide that does not meet the quality standards for high-purity molybdenum trioxide.

[0004] Patent CN104445411 uses molybdenum calcined sand washing wastewater as raw material, adding sodium carbonate solution to precipitate impurity ions such as copper, iron, calcium, and magnesium in the wastewater. Simultaneously, the sodium carbonate solution dissolves fine molybdate ions in the wastewater, resulting in a clear filtrate. Then, nitric acid is used to precipitate molybdate ions in the filtrate, followed by crystallization at high temperature to form large-particle molybdate. The scanning electron microscope (SEM) image of the prepared molybdate in this example shows hexagonal prisms and octahedrons of uniform size with clear interfaces and uniform dispersion. However, using molybdenum calcined sand washing wastewater as raw material limits its applicability and makes it unsuitable for large-scale production. Furthermore, the Na and K content is 0.X%, and the Ca, Mg, and Fe content is 0.0X%, not fully meeting the high-purity requirements. Other impurities are not described. In the comparative example, the SEM image of molybdate prepared by direct acid precipitation with ammonium molybdate solution shows small crystals, agglomeration, and blurred interfaces. Scanning electron microscopy (SEM) images of molybdic acid prepared by heating molybdenum trioxide hydrochloric acid solution show small, elongated crystals with relatively clear interfaces. SEM images of molybdic acid prepared by adding ammonium nitrate and molybdic acid seed crystals to ammonium molybdate solution and then precipitating them show relatively clear interfaces and the presence of hexagonal prisms and octahedral crystals, but the crystals are small, under 3000x magnification.

[0005] Patent CN106698517 describes a pretreatment process involving adding flake sodium hydroxide to a molybdate solution, followed by evaporation. Once crystals appear, they are dissolved in pure water, then acidified with nitric acid, followed by solid-liquid separation and drying to obtain high-purity molybdate. The pretreatment with flake sodium hydroxide aims to completely displace ammonium ions and ammonia gas, while also removing some metallic impurities such as calcium ions. However, ammonia gas has a strong odor, requiring proper disposal and increasing waste gas treatment costs. Furthermore, adding alkali for calcium removal is ineffective. Using fuming nitric acid to precipitate molybdate results in significant exothermic activity; as the exothermic reaction increases, the precipitated molybdate becomes viscous, clumping severely after drying and failing to form a powder. In this example, the product has a high sodium salt content of 2.0%. Other anionic impurities such as chloride and phosphorus are not described, but the product's crystal structure shows some improvement.

[0006] Patent CN107915256 uses waste oil hydrogenation catalyst as raw material. After degreasing, sodium roasting and leaching, calcium, aluminum, silicon and phosphorus are removed by pure sodium hydroxide or pure calcium hydroxide. After vanadium is precipitated in the purified liquid, the molybdenum liquid after vanadium adsorption by ion exchange is then extracted and back-extracted to obtain sodium molybdate solution. Concentrated sulfuric acid is added to obtain molybdate precipitate. The method does not clearly describe the composition and crystal form of the obtained molybdate product, but based on the description of other patents and actual production conditions, the Na and S content in the product should be high, making it difficult to guarantee the requirement of high purity.

[0007] Patent CN112875753 uses high-purity molybdenum trioxide as raw material. After slurry formation, sodium hydroxide is dissolved to obtain a sodium molybdate solution. Nitric acid solution is slowly added until the solution becomes acidic, and the temperature is increased until molybdenum acid crystals precipitate. The sodium salt content in the molybdenum acid obtained by this method is 0.2%. The eight impurities measured meet the requirements for high-purity molybdenum acid, while other impurities are not described. However, the high-purity molybdenum trioxide used is expensive, exceeding the selling price of molybdenum acid, making it uneconomical.

[0008] Patent CN118026261 and its accompanying paper, "Research on a New Process for Preparing High-Purity Molybdate from Crude Sodium Molybdate Solution," use crude sodium molybdate as raw material. Impurities in the molybdate are deeply removed through precipitation and ion exchange methods. The resulting pure sodium molybdate solution is then converted into a molybdate solution via a bipolar membrane electrolysis system. High-purity molybdate is then produced by adding crystallization aids or heating for crystallization. Removing P, As, Si, W, and V solely through calcium precipitation has limited effectiveness and results in significant molybdenum loss. A cation exchange resin is used to remove calcium and magnesium ions, followed by desalination via a bipolar membrane electrodialysis system. The sodium molybdate solution is heated to a pH of 0-1.5 before precipitation. However, the desalination efficiency of electrodialysis gradually decreases with prolonged operation and lower pH. To ensure desalination, the voltage and operating time must be increased, leading to increased costs. Adding high-purity molybdenum trioxide as a seed crystal results in relatively perfect crystals, but XRD analysis reveals its composition to be H₂MoO. 10 It is not the common molybdate expression MoO3▪H2O or H2MoO4.

[0009] Patent CN116397100 uses an oil hydrogenation catalyst as raw material. After crushing, deoiling, sodium roasting, and leaching, calcium oxide is added to the leachate to precipitate calcium vanadate and calcium molybdate respectively. Calcium molybdate is added to an ammonium solution, thoroughly mixed, and filtered. The filtered solution is crystallized to obtain solid ammonium molybdate. The ammonium molybdate is then ground into a fine powder, neutralized with nitric acid, and washed and dried to obtain molybdic acid. The prepared molybdic acid is consistent with that prepared by direct acid precipitation with ammonium molybdate solution, with fine crystals, agglomeration, blurred interfaces, and excessive NH4+.

[0010] Patent CN113981251 describes a process where waste heavy oil hydrogenation catalyst is pulverized, roasted, and mixed with ammonium bicarbonate solution, followed by hydrothermal treatment to obtain a molybdenum-containing solution. Concentrated nitric acid is then added to precipitate molybdic acid. However, simple precipitation and washing alone cannot effectively remove impurity ions and ensure purity.

[0011] Patent CN115710018 describes a process where the catalyst is calcined and pulverized, then dissolved in ammonia and hydrogen peroxide. The resulting solid-liquid separation should yield an ammonium molybdate solution, not the molybdate solution described. Adding sodium hydroxide, filtering, and evaporating at atmospheric pressure are actually methods to expel ammonia gas. Adding nitric acid for precipitation yields molybdate. The resulting product is identical to that obtained with sodium molybdate solution precipitated with nitric acid. While the process is simple, the impurity content cannot be guaranteed.

[0012] CN114275816 describes a process where a molybdenum source is treated with an alkaline solution to obtain a sodium molybdate leachate. This leachate is then subjected to adsorption purification to obtain an adsorption-exchange solution. This solution is heated, hydrochloric acid is added, and after stirring, it is filtered, washed, and dried to obtain molybdate particles. Anion exchange resin alone is effective for removing cationic impurities but ineffective for anionic impurities, resulting in a high sodium salt content in the precipitate.

[0013] CN114349050 describes a process using calcium molybdate as raw material. A leaching solvent is added to obtain a sodium molybdate leachate, which is then subjected to air stripping to remove ammonia, yielding a deaminated molybdenum-containing solution. Hydrogen peroxide is added for oxidation, nitric acid is added to adjust the pH, and the reaction is heated to precipitate molybdic acid crystals. No impurity removal process is used, and the resulting molybdic acid crystals have poor morphology, exhibiting octahedral shapes rather than hexagonal prisms.

[0014] In summary, in view of the shortcomings of the existing processing technology, the present invention provides an ammonia-free preparation process for high-purity molybdic acid and an ammonia-free preparation process for high-purity molybdenum trioxide. Summary of the Invention

[0015] The present invention aims to solve at least one of the technical problems existing in the prior art.

[0016] Therefore, this invention proposes an ammonia-free preparation process for high-purity molybdic acid and ammonia-free preparation process for high-purity molybdenum trioxide. The high-purity molybdic acid prepared by this process has extremely low impurity content, and can be directly obtained as high-purity molybdenum trioxide after drying and dehydration. Compared with the current method of preparing high-purity molybdenum oxide by decomposition of ammonium molybdate, the process is simple and free of pollutants.

[0017] A process for preparing high-purity molybdic acid without ammoniaation involves treating a molybdenum salt solution, including the following steps: (1) Preliminary chemical purification Adjust the pH of the solution to 8-10, add magnesium salt, and heat to boiling for 0.5-2 hours.

[0018] In this step, silicon is removed by precipitation in the form of H2SiO3 and MgSiO3, phosphorus is removed by precipitation in the form of MgHPO4, and arsenic is removed by precipitation in the form of MgHAsO4. In the ammonium salt solution, the phosphorus and arsenic precipitates are further converted into MgNH4PO4 and MgNH4AsO4 precipitates. At the same time, the amphoteric metals aluminum and tin are hydrolyzed to generate Al(OH)3 and Sn(OH)4 and removed. After filtration to remove the precipitate, the levels of silicon, phosphorus, and arsenic in the filtrate can be reduced to 30-50 mg / L. The pH of the filtrate was further adjusted to 10-14, calcium chloride was added to form calcium sulfate precipitate, and silicon, phosphorus and arsenic were further removed to <30 mg / L; (2) Precision filtration After filtering the above solution, the pH of the filtrate is readjusted to 6-10, and then it is filtered through a filter membrane with a pore size of 0.1-1μm to remove tiny colloidal precipitates such as silica gel and aluminum hydroxide. (3) Deep purification by ion exchange (4) Adsorption of molybdenum (5) Washing After washing the ion exchange resin with pure water until the sodium ion concentration is <10mg / L, it is washed with dilute acid at a concentration of 1%~10% to further remove cations precipitated in the resin due to impurities and pH changes. The washing solution is then washed until the cation concentration is <1mg / L. (6) Analysis (7) Deacidification The acidity of the high-acid solution is too high to directly precipitate molybdic acid; Recover excess acid.

[0019] The acidity in the eluent was reduced by using diffusion dialysis, cathode membrane electrolysis, and bipolar membrane electrodialysis. After treatment, the acidity of the solution decreased to 0.5~1 mol / L. Further reduction by diffusion dialysis was ineffective, and the voltage of membrane electrolysis and electrodialysis had increased significantly, increasing power consumption costs. The recovered acid can be reused to adjust the pH of the solution.

[0020] (8) High-purity molybdic acid was prepared. After deacidification, the solution begins to become turbid when heated to 60-70℃. Keep it at this temperature for 3-6 hours to allow crystal growth, and then continue to raise the temperature to 90-95℃ to ensure complete molybdenum precipitation. High-purity molybdic acid was obtained after filtration.

[0021] As a further improvement to this scheme, the specific operation steps of the (3) ion exchange method for deep impurity removal are as follows: The filtrate is passed through a macroporous resin with active rare earth element groups, and the pH is controlled at 3-7 for column adsorption, which can reduce the concentration of silicon, phosphorus, and arsenic to <1 mg / L.

[0022] In this step, the macroporous resin with active rare earth element groups has a high specific surface area and porosity. Using advanced active component introduction technology, zirconium inorganic polymer is introduced into the porous resin with high specific surface area and porosity, which has a high selectivity for silicate, phosphate and arsenate in solution. If the column liquid contains tungsten and vanadium impurities, first remove the vanadium by passing it through a macroporous strong basic anion exchange resin.

[0023] In this step, vanadium is mainly in the form of V3O9. 3- Molybdenum exists primarily in the form of MoO4. 2- It exists in the form of V3O9 3- Because it carries a large amount of charge, it can be preferentially adsorbed by strong base macroporous chloride anion exchange resin.

[0024] The column chromatography solution is then passed through a weakly basic anion exchange resin to remove tungsten, which is mainly in the form of W7O. 24 6- It exists in a form with a radius greater than MoO4. 2- In solutions with high molybdenum and low tungsten, polytungstate ions have a greater nucleophilic potential and are preferentially adsorbed.

[0025] As a further improvement to this plan, The specific steps for the adsorption of molybdenum in (4) are as follows: After impurity removal, the pH of the solution is adjusted to 1.5-4. The solution is then passed through a macroporous weakly basic anion exchange resin to adsorb molybdenum, and most of the cationic impurities are removed along with the column chromatography solution.

[0026] In this step, molybdenum mainly exists as Mo8O. 26 4- and Mo7O 21 (OH) 3- In sodium molybdate solution obtained by alkaline leaching, only amphoteric metals may leach out; other metals such as copper and nickel are not leached out. However, in ammonium molybdate solution obtained by ammonia leaching, impurities such as copper, nickel, and zinc are present, along with ammonium complex ions [Me(NH3)4]. 2- By adjusting the pH, it is made to use Me 2+ It exists in the form of.

[0027] As a further improvement to this plan, In the preliminary chemical purification process (1), the magnesium salt is any one or more of magnesium chloride, magnesium sulfate, and basic nickel carbonate.

[0028] As a further improvement to this plan, The dilute acid used in the washing process (5) is any one or more of hydrochloric acid, sulfuric acid, and nitric acid.

[0029] As a further improvement to this plan, The specific steps for the analysis (6) are as follows: analysis is performed using high-concentration acid; The high-concentration acid is any one or more of hydrochloric acid, sulfuric acid, and nitric acid, and the acidity is 4~9 mol / L.

[0030] As a further improvement to this scheme, the molybdenum salt solution is a sodium molybdate or ammonium molybdate solution.

[0031] As a further improvement to this scheme, the molybdenum salt solution is molybdenum calcined sand or an alkaline leaching solution or an ammonia leaching solution obtained by sodium calcination of molybdenum-containing catalyst.

[0032] A process for the ammonia-free preparation of high-purity molybdenum trioxide includes the following preparation steps: direct calcination and dehydration of high-purity molybdic acid to obtain high-purity molybdenum trioxide; The high-purity molybdenum acid is prepared using the ammonia-free preparation process of the high-purity molybdenum acid.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) Anionic impurity removal method: First, chemical impurity removal methods that are currently industrially applied are used to initially remove silicon, phosphorus, and arsenic. However, the removal capacity of this method is limited, generally only reducing the concentration to 15~50 mg / L. The introduction of excessive magnesium and calcium salts can also cause molybdenum precipitation loss. After detecting the impurity content in the original solution, a precise amount of chemical reagents (MgCl2, CaCl2) are added to remove most of the impurities such as silicon, phosphorus, arsenic, and sulfur. Filtration is then performed, and the filtrate does not directly enter the ion exchange stage. Precision filtration is added, and fine colloidal impurities that are not visible to the naked eye in the solution are further removed by selecting the pore size of the filter membrane. The filtrate then enters the ion exchange stage for deep impurity removal. It passes through a selected special functional group resin, and the pH is precisely controlled. The resin further adsorbs impurities, reducing the concentration to <1 mg / L.

[0034] (2) Molybdenum analysis: The adsorption of molybdenum using anion exchange resins has been widely used in industrial production. After passing through the resin, most cationic impurities can be removed, and the cations entrained in the resin can be further removed by water washing. However, a very small amount of amphoteric metal ions such as aluminum and tin cannot be removed by simple water washing. Therefore, an acid washing process is added, and the pH of the acid washing solution is controlled to further remove cationic impurities. Currently, conventional analysis methods all use sodium hydroxide or ammonia water analysis, which reintroduces sodium and ammonium ions. These ions are easy to enter the molybdenum acid precipitate during acid precipitation and are difficult to remove by washing (the washing effect is poor and cannot be washed multiple times. After multiple washings, the molybdenum acid will lose its original crystal form, become viscous, and be difficult to filter). The innovative method of acid analysis requires a high acid concentration. Low-concentration acid analysis is ineffective or has no effect. In high-acid analysis solutions, molybdenum exists in the form of cations. If the acidity is reduced by neutralization to precipitate molybdenum acid, impurity ions such as sodium or ammonium ions brought in by the alkali will be reintroduced. This is not essentially different from direct alkaline or ammonia analysis and increases costs. Diffusion dialysis and electrodialysis technologies have been widely used in waste acid recovery in recent years. These technologies recover acid from high-acid eluents, containing tens of mg / L of molybdenum, which can then be used in the upstream pH adjustment process. The acid can be reused without loss of the small amount of molybdenum. Once the acidity of the eluent decreases to 0.5-1 mol / L, diffusion dialysis becomes largely ineffective. Electrodialysis can further reduce the acidity, but this leads to a sharp increase in cell voltage and power consumption costs. Therefore, molybdate precipitation is performed under these conditions.

[0035] (3) Molybdic acid crystallization process: After the acidity of the solution is reduced, it is heated to 60-70 degrees Celsius. The solution becomes turbid. In order to ensure that the precipitated molybdic acid has a regular hexagonal shape, the temperature is controlled and kept at that temperature for 3-6 hours to allow crystal growth. Then, the temperature is further increased to 90-95 degrees Celsius to ensure complete molybdenum precipitation. After filtration, high-purity molybdic acid is obtained. If the temperature is too high directly during the process, a large number of crystal nuclei will be generated, resulting in agglomeration. The precipitated molybdic acid will have a poor crystal form, making it difficult to filter and resulting in a viscous texture.

[0036] (4) Molybdenum trioxide process: The high-purity molybdic acid prepared by this process has extremely low impurity content. After drying and dehydration, high-purity molybdenum trioxide can be obtained directly. Compared with the current method of preparing high-purity molybdenum oxide by decomposition of ammonium molybdate, the process is simple and has no pollutants. Attached Figure Description

[0037] Figure 1 This is a flow chart of the ammonia-free preparation process of high-purity molybdenum trioxide according to the present invention; Figure 2 This is a scanning electron microscope image of the high-purity molybdic acid product in Example 1 of the present invention; Figure 3 This is the XRD analysis diagram of high-purity molybdic acid in Example 1 of the present invention; Figure 4 This is a screenshot of the XRD analysis of high-purity molybdate in Example 1 of the present invention; Figure 5 This is a scanning electron microscope image of the sodium molybdate product in Comparative Example 2 of the present invention; Figure 6 This is the XRD analysis diagram of sodium molybdate in Comparative Example 2 of the present invention; Figure 7 This is a screenshot of the XRD analysis of sodium molybdate in Comparative Example 2 of this invention; Figure 8 This is a scanning electron microscope image of the high-acid precipitated molybdic acid product in Comparative Example 3 of the present invention. Detailed Implementation

[0038] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0039] The ammonia-free preparation process of high-purity molybdenum trioxide of the present invention is as follows: The molybdenum salt solution is a sodium molybdate or ammonium molybdate solution, generally an alkaline leaching solution or ammonia leaching solution after sodium roasting of molybdenum calcined sand or molybdenum-containing catalyst, containing anions such as silicon, phosphorus, and arsenic, as well as a certain amount of sulfate and cationic impurities.

[0040] (1) Preliminary chemical purification Adjust the solution pH to 8-10, add magnesium salt (such as magnesium chloride, magnesium sulfate, or basic nickel carbonate), and heat to boiling for 0.5-2 hours. Silicon is removed as precipitates in the form of H₂SiO₃ and MgSiO₃, phosphorus is removed as MgHPO₄, and arsenic is removed as MgHAsO₄. In the ammonium salt solution, the phosphorus and arsenic precipitates are further converted into MgNH₄PO₄ and MgNH₄AsO₄ precipitates. At the same time, the amphoteric metals aluminum and tin undergo hydrolysis to form Al(OH)₃ and Sn(OH)₄, which are removed. Filter to remove the precipitates. The concentrations of silicon, phosphorus, and arsenic in the filtrate can be reduced to 15-50 mg / L. Further adjust the pH of the filtrate to 10-14, add calcium chloride to form calcium sulfate precipitate, and further remove silicon, phosphorus, and arsenic to <30 mg / L.

[0041] (2) Precision filtration After filtering the above solution, the pH of the filtrate is readjusted to 6-10, and then it is subjected to precision filtration through a filter membrane with a pore size of 0.1-1μm to remove tiny colloidal precipitates such as silica gel and aluminum hydroxide.

[0042] (3) Deep purification by ion exchange The filtrate is passed through a macroporous resin with active rare earth element groups. This resin has a high specific surface area and porosity. Using advanced active component introduction technology, zirconium inorganic polymers are introduced into the porous resin, which exhibits high selectivity for silicate, phosphate, and arsenate ions in the solution. By controlling the pH to 3-7 during column adsorption, the concentrations of silicate, phosphate, and arsenic can be reduced to <1 mg / L. If the effluent contains tungsten and vanadium impurities, vanadium is first removed using a macroporous, strongly basic anion exchange resin. In this case, vanadium is mainly present as V3O9. 3- Molybdenum exists primarily in the form of MoO4. 2- It exists in the form of V3O9 3- Because of its high charge, it is preferentially adsorbed by a strong-base macroporous chloride-type anion exchange resin (preferably D231yt or D231Ⅱ type resin). The column buffer is then passed through a weakly basic anion exchange resin to remove tungsten, which is mainly in the form of W7O. 24 6- It exists in a form with a radius greater than MoO4. 2- In solutions with high molybdenum and low tungsten, polytungstate ions have a greater nucleophilic potential and are preferentially adsorbed (the resin is preferably of type D630).

[0043] (4) Adsorption of molybdenum After impurity removal, the solution pH is adjusted to 1.5-4. Molybdenum is mainly present as Mo8O. 26 4- and Mo7O 21 (OH) 3-In sodium molybdate solution obtained by alkaline leaching, only amphoteric metals may leach out; other metals such as copper and nickel are not leached out. However, in ammonium molybdate solution obtained by ammonia leaching, impurities such as copper, nickel, and zinc are present, along with ammonium complex ions [Me(NH3)4]. 2- By adjusting the pH, it is made to use Me 2+ The solution exists in the form of [a specific substance], and after adjustment, molybdenum is adsorbed by macroporous weakly basic anion exchange resin, while most cationic impurities are removed with the column chromatography solution.

[0044] (5) Washing After washing the ion exchange resin with pure water until the sodium ion concentration is <10 mg / L, wash it with dilute acid (such as hydrochloric acid, sulfuric acid, or nitric acid) at a concentration of 1% to 10% to further remove cations that have precipitated in the resin due to impurities and pH changes. Wash until the cation concentration in the washing solution is <1 mg / L.

[0045] (6) Analysis The analysis is performed using a high-concentration acid (such as hydrochloric acid, sulfuric acid, or nitric acid), with an acidity of 4-9 mol / L.

[0046] (7) Deacidification The acidity of the high-acid eluent is too high to directly precipitate molybdic acid. To recover excess acid, diffusion dialysis, cathode membrane electrolysis, and bipolar membrane electrodialysis can be used to reduce the acidity in the eluent. After treatment, the acidity of the solution is reduced to 0.5~2 mol / L. Further reduction by diffusion dialysis is ineffective, and the voltage of membrane electrolysis and electrodialysis increases significantly, increasing power consumption costs. The recovered acid can be reused to adjust the pH of the solution.

[0047] (8) High-purity molybdic acid was prepared. After deacidification, the solution is heated to 60-70℃ and begins to become turbid. This temperature is maintained for 3-6 hours to allow crystal growth, followed by further heating to 90-95℃ to ensure complete molybdenum precipitation. High-purity molybdic acid is obtained after filtration.

[0048] (9) High-purity molybdenum trioxide is obtained by direct roasting and dehydration of high-purity molybdenum acid.

[0049] The embodiments and comparative examples of the present invention are detailed below: Example 1 The molybdenum-containing spent catalyst, after sodium roasting, was leached at a solid-liquid ratio of 1:3, with pH controlled at 9, at 60-80℃. Theoretical amounts of MgCl2 were added to remove silicon and phosphorus. After heating and stirring for 60 min, the mixture was filtered. The pH of the filtrate was adjusted to 10, and 1.1 times the theoretical amount of CaCl2 was added to further remove silicon and phosphorus. After filtration through a 0.22 μm filter membrane, a sodium molybdate solution containing 15.02 g / L molybdate, 23.45 mg / L silicon, 18.77 mg / L phosphorus, 3.07 mg / L tungsten, 5.44 mg / L vanadium, and 1.95 mg / L vanadium was obtained. The collected filtrate was designated #1, a portion of which was used in this example, and a portion was used in Comparative Example 1.

[0050] The filtrate was adjusted to pH 7 and passed through a macroporous resin with active rare earth element groups (adsorption rate of 0.5 VB). h-1). After adsorption and elution, a solution was obtained with silicon, phosphorus, and arsenic <0.5 mg / L, W 3.20 mg / L, and V 1.06 mg / L, with molybdenum adsorption loss <2%. The solution was then passed sequentially through a vanadium-absorbing resin (adsorption rate 0.2V B). h-1) and tungsten adsorption resin (adsorption rate of 0.5 VB) After h-1), tungsten and vanadium concentrations were <0.5 mg / L. The column chromatography solution was collected as #2, a portion of which was used in this example and a portion in Comparative Example 2.

[0051] The column chromatography solution was re-adjusted to pH 2.5 with hydrochloric acid, and molybdenum was adsorbed onto D314 resin at an adsorption rate of 0.5 VB. h -1 After adsorption saturation, the column was washed with pure water until the sodium content in the wash water was 8.6 mg / L. Then, it was washed with 0.1 mol / L HCl for two column volumes, followed by elution with 6 mol / L HCl (elution rate was 2 VB). h -1 The molybdenum concentration in the eluent was 85.62 g / L, and the acidity was 4.64 mol / L. After collection, it was labeled #3. Part of it was used in this example, and part of it was used in Comparative Example 3.

[0052] The high-acid eluent was passed through a diffusion dialysis device until the acidity decreased to 1.62 mol / L. The solution was heated to 60°C and became turbid. Hydrogen peroxide (1‰ by volume) was added, and the reaction was maintained at this temperature for 6 hours. The temperature was then raised to 95°C and the reaction continued for another hour. After cooling and filtration, high-purity molybdic acid was obtained. The molybdenum content in the filtrate was <5 g / L. The product analysis results are shown in Table 1. High-purity molybdic acid was dehydrated at 300°C to obtain high-purity molybdenum trioxide. The product analysis results are shown in Table 2. Electron microscopy analysis of the high-purity molybdic acid product is shown below. Figure 3 As shown, the XRD analysis of the high-purity molybdic acid product is as follows: Figure 2 and Figure 3 As shown.

[0053] Table 1. Analytical Results of High-Purity Molybdic Acid Table 2. Analytical Results of High-Purity Molybdenum Trioxide Figure 2 Scanning electron microscope image of the high-purity molybdic acid product in Example 1. Figure 3 XRD pattern of high-purity molybdate in Example 1 Figure 4 Screenshot of XRD analysis of high-purity molybdate in Example 1. Comparative Example 1: In the example, the pH of filtrate #1 was adjusted to 3 using a macroporous resin with active rare earth element groups (adsorption rate of 0.5 VB). h -1 After adsorption and elution, silicon, phosphorus, and arsenic were found to be <0.5 mg / L, but molybdenum was also adsorbed, and the molybdenum content in the column buffer was only 33.55 mg / L.

[0054] Comparative Example 2: In the example, column buffer #2 was adjusted to pH 2.5 with hydrochloric acid and then used to adsorb molybdenum using D314 resin (adsorption rate 0.5 VB). h -1 After adsorption saturation, the column was washed with pure water for two column volumes, and then eluted with 12% NaOH (elution rate 2VB). h -1 The molybdenum concentration in the eluent was 105.64 g / L. The solution was heated to 60℃, and hydrogen peroxide (1‰ by volume) was added, with the temperature further increased to 90℃. Hydrochloric acid was added to bring the pH to 0.5, and the reaction was maintained at this temperature for 2 hours. After cooling and filtration, molybdic acid was obtained. The molybdenum content in the filtrate was <5 g / L. The product analysis results are shown in Table 3, and the scanning electron microscopy analysis results are as follows: Figure 5 As shown: Table 3. Analytical results of sodium molybdate content Molybdic acid contains a large amount of sodium.

[0055] Figure 5 Scanning electron microscope image of sodium molybdate product in Comparative Example 2 Figure 6 XRD analysis chromatogram of sodium molybdate in Comparative Example 2 Figure 7 Screenshot of XRD analysis of sodium molybdate in Comparative Example 2. Comparative Example 3: In the example, the No. 3 high-acid desorption solution was heated to 60°C, and hydrogen peroxide at a volume ratio of 1‰ was added. The solution became clear. The temperature was further increased to 90°C, and a precipitate formed. The reaction was maintained at this temperature for 2 hours, then cooled and filtered to obtain molybdic acid product. The molybdenum content in the filtrate was >30 g / L, and the recovery rate was low. The scanning electron microscopy analysis results are as follows: Figure 8 As shown: Figure 8 Scanning electron microscope image of the high-acid precipitated molybdic acid product in Comparative Example 3. Molybdic acid products have non-hexagonal prism crystals, resulting in slow filtration.

[0056] Comparative Example 4: Sodium-calcined molybdenum-containing spent catalyst was leached at 60-80℃ with a solid-liquid ratio of 1:3 and pH controlled at 9. Theoretical amounts of MgCl2 were added to remove silicon and phosphorus. After heating and stirring for 60 min, the mixture was filtered. The pH of the filtrate was adjusted to 10, and 1.1 times the theoretical amount of CaCl2 was added to further remove silicon and phosphorus. After filtration using slow-speed quantitative filter paper, a sodium molybdate solution containing 14.33 g / L molybdate was obtained. The pH was adjusted to 2.5, and the solution changed from clear and transparent to slightly turbid and opaque. Molybdenum was then adsorbed using D314 resin (adsorption rate 0.5 VB). h -1 After adsorption saturation, the column was washed with pure water for two column volumes, and then eluted with 12% NaOH (elution rate was 2 VB). h -1 The molybdenum concentration in the eluent was 105.64 g / L. The solution was heated to 60℃, and hydrogen peroxide (1‰ by volume) was added. The temperature was further increased to 90℃, and hydrochloric acid was added to bring the pH to 0.5. The reaction was maintained at this temperature for 2 hours, cooled, and filtered to obtain molybdic acid. The molybdenum content in the filtrate was <5 g / L. The product analysis results are shown in Table 4. Table 4. Analytical Results of Sodium Molybdic Acid In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0057] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A process for the ammonia-free preparation of high-purity molybdic acid, characterized in that, The molybdenum salt solution is treated by the following steps: (1) Preliminary chemical purification Adjust the pH of the solution to 8-10, add magnesium salt, and heat to boiling for 0.5-2 hours; After filtration to remove the precipitate, the levels of silicon, phosphorus, and arsenic in the filtrate decreased to 15-50 mg / L. The pH of the filtrate was further adjusted to 10-14, calcium chloride was added to form calcium sulfate precipitate, and silicon, phosphorus and arsenic were further removed to <15mg / L; (2) Precision filtration After filtering the above solution, the pH of the filtrate is readjusted to 6-10, and then it is subjected to precision filtration through a filter membrane with a pore size of 0.1-1μm to remove tiny colloidal precipitates. (3) Deep purification by ion exchange (4) Adsorption of molybdenum (5) Washing After washing the ion exchange resin with pure water until the sodium ion concentration is <10mg / L, it is washed with dilute acid at a mass concentration of 1%~10% to further remove cations precipitated in the resin due to impurities and pH changes. The washing solution is then washed until the cation concentration is <1mg / L. (6) Analysis (7) Deacidification The acidity in the eluent was reduced by diffusion dialysis, cathode membrane electrolysis, and bipolar membrane electrodialysis. (8) High-purity molybdic acid was prepared. After deacidification, the solution begins to become turbid when heated to 60-70℃. Keep it at this temperature for 3-6 hours to allow crystal growth, and then continue to raise the temperature to 90-95℃ to ensure complete molybdenum precipitation. After filtration, high-purity molybdic acid was obtained; The specific operational steps for the deep impurity removal by ion exchange method (3) are as follows: The filtrate was passed through a macroporous resin with active rare earth element groups, and the pH was controlled at 3-7 for column adsorption to reduce the concentration of silicon, phosphorus and arsenic to <1 mg / L. If the column eluent contains tungsten and vanadium impurities, it should first be removed by passing it through a macroporous, strongly basic anion exchange resin. At this point, vanadium is mainly present as V3O9. 3- Molybdenum exists primarily in the form of MoO4. 2- It exists in the form of V3O9 3- Because it carries a large amount of charge, it is preferentially adsorbed by strong base macroporous chloride anion exchange resin. The column chromatography solution is then passed through a weakly basic anion exchange resin to remove tungsten. The specific steps for the adsorption of molybdenum in (4) are as follows: After impurity removal, the pH of the solution is adjusted to 1.5-4. The adjusted solution is then passed through a macroporous weakly basic anion exchange resin to adsorb molybdenum. Most of the cationic impurities are removed with the column chromatography solution. The specific steps for the analysis (6) are as follows: analysis is performed using high-concentration acid; The high-concentration acid is any one or more of hydrochloric acid, sulfuric acid, and nitric acid, and the acidity is 4~9 mol / L.

2. The ammonia-free preparation process of high-purity molybdic acid according to claim 1, characterized in that, In the preliminary chemical purification process (1), the magnesium salt is any one or more of magnesium chloride, magnesium sulfate, and basic nickel carbonate.

3. The ammonia-free preparation process of high-purity molybdic acid according to claim 1, characterized in that, The dilute acid used in the washing process (5) is any one or more of hydrochloric acid, sulfuric acid, and nitric acid.

4. The ammonia-free preparation process of high-purity molybdic acid according to claim 1, characterized in that, The molybdenum salt solution is a sodium molybdate or ammonium molybdate solution.

5. The ammonia-free preparation process of high-purity molybdic acid according to claim 4, characterized in that, The molybdenum salt solution is an alkaline leaching solution or an ammonia leaching solution obtained by sodium roasting of molybdenum calcined sand or a molybdenum-containing catalyst.

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