Ammonium metavanadate crystal and crystallization method thereof

Abstract

The invention relates to a crystallization method of ammonium metavanadate crystals. The crystallization method comprises the following steps: cooling an ammonium metavanadate concentrated solution to obtain an ammonium metavanadate supersaturated solution; the cooling treatment process comprises the step of adding a crystallization regulating agent into the ammonium metavanadate concentrated solution; sequentially carrying out aging treatment and solid-liquid separation on the ammonium metavanadate supersaturated solution to obtain an ammonium metavanadate solid phase; by adding a crystallization regulating agent in the cooling treatment process, regulating the growth rate and growth direction of ammonium metavanadate crystals, matching with the steps of aging treatment and the like, the crystallization rate of the crystallization method is improved, preferably, the crystallization rate is up to 89.5% or above, and the high-purity ammonium metavanadate product with large grain size and regular morphology is obtained. Wherein the median particle size preferably reaches up to 86.5 microns or above, the purity reaches up to 99.97% or above, and the requirement for high-quality vanadium products at present is met.

Description

Technical Field

[0001] The invention relates to the technical field of chemical synthesis, and in particular to an ammonium metavanadate crystal and a crystallization method thereof. Background Art

[0002] Ammonium metavanadate (NH4VO3) is an important vanadium compound, which is widely used in the preparation of catalyst precursors, optoelectronic materials and basic raw materials for high-purity vanadium pentoxide (V2O5). The crystal morphology and particle size of ammonium metavanadate have an important influence on its performance and application. For example, in the field of catalysis, large-particle crystals help improve the mechanical stability of catalysts, while in optoelectronic materials, the purity and particle size of the crystals directly affect the optical properties and electrochemical behavior of the materials.

[0003] At present, the preparation of ammonium metavanadate in industry mainly adopts the reaction crystallization method, that is, the ammonium metavanadate is precipitated by adjusting the pH value and temperature of the vanadate solution. However, the existing production process faces the following technical difficulties: (1) The purity of the ammonium metavanadate product is insufficient. This is because the conventional cooling crystallization process is difficult to control the content of impurities such as molybdenum, silicon and iron, resulting in the purity of ammonium metavanadate being below 98.5%, which cannot meet the demand for ultra-high purity ammonium metavanadate for high-end applications; (2) The particle size control ability of the ammonium metavanadate product is poor. Chemical precipitation is difficult to control the particle size of the ammonium metavanadate crystal. The obtained crystals are often uneven in particle size and the median particle size is small, resulting in easy crystal agglomeration and poor product fluidity; (3) The ammonium metavanadate crystal morphology is uneven, and it is easy to produce a large number of needle-shaped or flat plate-shaped crystals, resulting in poor dispersibility; Therefore, achieving controllable regulation of ammonium metavanadate crystals is of great significance for the preparation of high-purity vanadium products.

[0004] For example, CN106241872A discloses a method for preparing large-particle ammonium metavanadate, in which a small amount of ammonium metavanadate powder is added as a seed crystal into an aqueous solution to form a suspension, and then an ammonium metavanadate solution with a vanadium concentration of 35 to 140 g / L and an ammonium salt solution with a concentration of 2 to 10 mol / L are added dropwise to the suspension after constant temperature stirring, and the large-particle ammonium metavanadate is obtained by vacuum filtration after standing and aging. This method introduces ammonium salts, which may lead to the deposition of impurity ions, and fails to regulate the crystallization process, which may lead to a low crystallization rate. The filtrate is not recycled, and the vanadium yield is low.

[0005] CN104098137A discloses a method for preparing and purifying ammonium metavanadate, wherein NaOH solution, EDTA, ammonia water and HF solution are used in sequence to adjust the pH value and remove impurities such as iron and titanium. The method introduces additional chemical reagents and has a long process. During the complex precipitation to remove iron, a portion of vanadium will co-precipitate, resulting in vanadium loss. At the same time, chemical precipitation crystallization is difficult to regulate the crystallization process, and the particle size and morphology of the ammonium metavanadate product cannot be controlled.

[0006] Based on this, there is an urgent need to develop an ammonium metavanadate crystallization method that can control the crystallization process, so as to achieve the preparation of high-purity ammonium metavanadate crystals with large grain size and regular morphology, and provide high-quality raw materials for catalytic materials, optoelectronic materials and other fields. Summary of the invention

[0007] In order to solve the above technical problems, the present invention provides an ammonium metavanadate crystal and a preparation method thereof. By adding a crystallization regulator during the cooling process and controlling the process parameters of the cooling process, the crystallization process of ammonium metavanadate can be controlled and regulated, so as to successfully prepare ammonium metavanadate crystals with large grain size, regular morphology and high purity, and have a high yield, thereby meeting the high requirements of high-end applications such as optoelectronic materials for ammonium metavanadate products.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a method for crystallizing ammonium metavanadate crystals, the crystallization method comprising the following steps:

[0010] (1) cooling the ammonium metavanadate concentrated solution to obtain an ammonium metavanadate supersaturated solution; the cooling process includes adding a crystallization regulator to the ammonium metavanadate concentrated solution;

[0011] (2) The supersaturated ammonium metavanadate solution in step (1) is subjected to aging treatment and solid-liquid separation to obtain an ammonium metavanadate solid phase.

[0012] The crystallization method of the present invention adds a crystallization regulator to the ammonium metavanadate concentrated solution during the cooling process to regulate the isotropic growth rate of the crystal, thereby avoiding the formation of excessive needle-shaped, sheet-shaped or other irregular crystals; and the addition of the crystallization regulator can also inhibit excessively fast nucleation, which is conducive to the full growth of existing crystals, so that the particle size of the ammonium metavanadate crystals is larger and the particle size distribution is more uniform; in addition, the crystallization regulator can selectively adsorb or complex the co-precipitation of impurity elements such as aluminum and molybdenum in the ammonium metavanadate concentrated solution, thereby improving the purity of the ammonium metavanadate crystals.

[0013] Preferably, the vanadium concentration in the ammonium metavanadate concentrate in step (1) is 30-60 g / L, for example, 30 g / L, 35 g / L, 40 g / L, 45 g / L, 50 g / L, 55 g / L or 60 g / L.

[0014] The present invention further preferably has a vanadium concentration of 30 to 60 g / L in the ammonium metavanadate concentrate in step (1), which is beneficial for controlling the balance between crystal nucleation and growth, thereby obtaining crystals with uniform particle size and larger median particle size. This is because the concentration of the concentrate is a key factor in determining supersaturation, and supersaturation is one of the most important thermodynamic driving forces in the crystallization process of ammonium metavanadate. When the vanadium concentration in the ammonium metavanadate concentrate is low, it leads to insufficient supersaturation, low nucleation rate, and slow crystal growth, resulting in larger crystal particles but longer growth time and low crystallization efficiency. When the vanadium concentration in the ammonium metavanadate concentrate is high, it leads to rapid nucleation due to excessive supersaturation, an increase in the number of crystals but a decrease in particle size, and the formation of aggregates or irregular morphology crystals.

[0015] Preferably, the initial temperature of the ammonium metavanadate concentrate in step (1) is 80-120°C, for example, 80°C, 90°C, 100°C, 110°C or 120°C.

[0016] Preferably, the ammonium metavanadate concentrate in step (1) is obtained by evaporating and concentrating an ammonium metavanadate solution.

[0017] Preferably, the vanadium concentration in the ammonium metavanadate solution is 6.0-15.0 g / L, for example, it can be 6.5 g / L, 7.0 g / L, 7.5 g / L, 8.0 g / L, 8.5 g / L, 9.0 g / L, 9.5 g / L, 10.0 g / L, 10.5 g / L, 11.0 g / L, 11.5 g / L, 12.0 g / L, 12.5 g / L, 13.0 g / L, 13.5 g / L, 14.0 g / L, 14.5 g / L or 15.0 g / L, etc.

[0018] Preferably, the evaporation concentration method includes any one of atmospheric pressure evaporation concentration, reduced pressure evaporation concentration, thin film evaporation concentration or multiple effect evaporation concentration, wherein typical but non-limiting combinations include a combination of atmospheric pressure evaporation concentration and reduced pressure evaporation concentration, a combination of atmospheric pressure evaporation concentration and multiple effect evaporation concentration, etc.

[0019] The present invention does not impose any special restrictions on the evaporation concentration method, and the specific evaporation concentration method is selected according to the volume of the ammonium metavanadate solution and the demand for evaporation concentration efficiency.

[0020] Preferably, the temperature of the evaporation concentration is 100-250°C, for example, it can be 100°C, 120°C, 140°C, 160°C, 180°C, 200°C, 220°C, 240°C or 250°C.

[0021] Preferably, the absolute pressure of the evaporation concentration is 0.001 MPa to 0.1 MPa, for example, it may be 0.001 MPa, 0.02 MPa, 0.04 MPa, 0.06 MPa, 0.08 MPa or 0.1 MPa.

[0022] Preferably, the endpoint of the evaporation concentration is that the vanadium concentration in the ammonium metavanadate concentrated solution is 30-60 g / L, for example, it can be 30 g / L, 35 g / L, 40 g / L, 45 g / L, 50 g / L, 55 g / L or 60 g / L.

[0023] Preferably, the cooling rate of the cooling treatment in step (1) is 1 to 10°C / min, for example, it can be 1°C / min, 2°C / min, 3°C / min, 4°C / min, 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min or 10°C / min, etc., preferably 3 to 8°C / min.

[0024] Preferably, the terminal temperature of the cooling treatment in step (1) is 0 to 20°C, for example, 0°C, 5°C, 10°C, 15°C or 20°C, etc., preferably 8 to 18°C.

[0025] The present invention further regulates the cooling process of step (1), that is, the cooling rate of the cooling process is preferably 3 to 8°C / min, and the terminal temperature of the cooling process is 8 to 18°C. The combined effect provides better solubility and kinetic conditions for the crystallization process of ammonium metavanadate, so that supersaturation is slowly formed, the crystals are fully grown, and crystals with larger particle size and regular appearance are obtained.

[0026] Preferably, the cooling process in step (1) is accompanied by a first stirring.

[0027] Preferably, the first stirring rate is 10-200 r / min, for example, 10 r / min, 50 r / min, 100 r / min, 150 r / min or 200 r / min.

[0028] The present invention further preferably carries out a first stirring during the cooling treatment in step (1), and further preferably the first stirring rate is 10 to 200 r / min, thereby increasing the ion diffusion rate in the ammonium metavanadate concentrate, so that the nucleation rate of the ammonium metavanadate increases slowly, with crystal growth being dominant, and obtaining crystals with larger particle size and regular morphology; at the same time, reducing the occurrence of ammonium metavanadate crystal agglomeration, avoiding the entrainment of impurity elements, and improving the product purity.

[0029] Preferably, the crystallization regulator in step (1) comprises any one of sodium dodecyl sulfate, sodium dodecyl sulfonate, sodium dodecylbenzene sulfonate, hexadecyltrimethylammonium bromide, polyvinyl alcohol or polyvinyl pyrrolidone, or a combination of at least two thereof, wherein typical but non-limiting combinations include a combination of sodium dodecyl sulfate and sodium dodecyl sulfonate, a combination of polyvinyl alcohol solution and sodium dodecyl sulfate, or a combination of polyvinyl alcohol and polyvinyl pyrrolidone, etc.

[0030] Preferably, the ratio of the molar amount of the crystallization regulator to the volume of the ammonium metavanadate concentrate is 0.5 to 5 mmol / L, for example, it can be 0.5 mmol / L, 1.0 mmol / L, 1.5 mmol / L, 2.0 mmol / L, 2.5 mmol / L, 3.0 mmol / L, 3.5 mmol / L, 4.0 mmol / L, 4.5 mmol / L or 5.0 mmol / L, etc., preferably 1.0 to 2.5 mmol / L.

[0031] The present invention further preferably uses the crystallization regulator in an amount of 1.0 to 2.5 mmol / L, which is conducive to effectively exerting the crystallization regulation effect and effectively inhibiting the nucleation rate, thereby obtaining ammonium metavanadate crystals with larger particle size and uniform distribution, regular morphology, higher purity and yield; if the amount of the crystallization regulator is too low, the crystallization regulation effect will not be fully exerted, resulting in uneven particle size and irregular morphology of the ammonium metavanadate crystals; if the amount of the crystallization regulator is too high, the crystal growth will be excessively inhibited, the median particle size of the crystal may be significantly reduced, and a large number of small particles or fine crystals will be formed; and the excessive presence of the crystallization regulator will excessively change the growth interface energy of the crystal, resulting in uneven growth rates of each crystal face of the crystal, destroying the original symmetry and forming deformed crystals; at the same time, the excessive crystallization regulator may interact with the impurity ions in the solution to form stable complexes or micelles, and these complexes may be adsorbed or embedded in the crystal surface, resulting in a decrease in crystal purity.

[0032] Preferably, the crystallization regulator is added when the temperature of the ammonium metavanadate concentrate drops to 20-80°C, for example, it can be 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C or 80°C, etc., preferably 40-60°C.

[0033] The present invention further preferably adds the crystallization regulator when the temperature of the ammonium metavanadate concentrated solution drops to 40-60°C, which is beneficial to control the balance between nucleation and growth and ensure that the crystal particle size is moderate and the morphology is regular; if the crystallization regulator is added too early, that is, before the temperature of the ammonium metavanadate concentrated solution drops below 60°C, the crystallization regulator is added too early before the supersaturated ammonium metavanadate solution reaches the crystallization condition, which may reduce the supersaturation threshold required for crystal nucleation, induce nucleation too quickly, generate a large number of tiny crystal nuclei, thereby inhibiting the subsequent The crystal growth will not be continued; and the interaction with the solute (ammonium metavanadate molecules) in advance will change the movement mode and distribution of the solute molecules and reduce the driving force of crystal growth; if the crystallization regulator is added too late, that is, the temperature of the ammonium metavanadate concentrated solution has dropped to below 40°C before it is added, the supersaturated ammonium metavanadate solution gradually releases heat and some crystal nuclei have been generated, which may cause part of the growth surface of the crystal to be passivated, resulting in an uneven growth rate; it may not be possible to significantly change the initial nucleation behavior, but it will have an uneven effect on the directionality and rate of subsequent crystal growth.

[0034] Preferably, the process of adding the crystallization regulator comprises first dissolving the crystallization regulator to obtain a crystallization regulator solution, and then dropwise adding the crystallization regulator solution to the ammonium metavanadate concentrated solution.

[0035] Preferably, the dissolving solvent is water or hydrochloric acid.

[0036] It is worth noting that the present invention aims to dissolve the crystallization modifier, and does not impose any special restrictions on the concentration, volume, etc. of the solvent.

[0037] Preferably, the dripping method includes any one of one dripping, two dripping or continuous dripping, preferably continuous dripping.

[0038] The present invention further preferably adopts a continuous addition method, which controls the crystal growth process more uniformly compared to one or two additions, and the morphology and large particle size distribution of the finally obtained ammonium metavanadate crystals are more uniform.

[0039] Preferably, the ammonium metavanadate concentrated solution is first subjected to a first heat preservation treatment before the cooling treatment in step (1);

[0040] Preferably, the first heat preservation treatment lasts for 30 to 60 minutes, for example, 30 minutes, 40 minutes, 50 minutes or 60 minutes.

[0041] Preferably, the aging treatment time in step (2) is 30 to 180 min, for example, 30 min, 60 min, 90 min, 120 min, 150 min or 180 min.

[0042] Preferably, the temperature of the aging treatment in step (2) is 0-20°C, for example, 0°C, 5°C, 10°C, 15°C or 20°C.

[0043] Preferably, before the aging treatment in step (2), the supersaturated ammonium metavanadate solution is first subjected to a second heat preservation treatment.

[0044] Preferably, the second insulation treatment time is 30 to 120 min, for example, it can be 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, 100 min, 110 min or 120 min.

[0045] The present invention further preferably subjects the supersaturated ammonium metavanadate solution to a second heat preservation treatment before the aging treatment, and further preferably subjects the second heat preservation treatment to a time of 30 to 120 minutes, i.e., after the cooling treatment, subjects the supersaturated ammonium metavanadate solution to a second heat preservation treatment for 30 to 120 minutes. This is because during the cooling treatment, supersaturation drives nucleation and initial crystal growth, and the heat preservation process after the cooling stops can provide power for the continued growth of the crystal, and the release of the remaining supersaturation is gradually completed, which is beneficial to the increase in crystal size; and during the static aging treatment stage, the trace amount of supersaturated vanadium ions remaining in the solution will slowly deposit on the surface of the existing crystal, promoting the growth of the crystal and making it more stable. Due to the equilibrium adjustment of the solution, the structural defects on the surface of the crystal are gradually reduced, and the morphology is more regular.

[0046] Preferably, the solid-liquid separation method in step (2) includes plate and frame filter pressing.

[0047] Preferably, the supernatant after the solid-liquid separation in step (2) is circulated to the evaporation and concentration step.

[0048] The present invention further circulates the supernatant to the evaporation and concentration step, and then realizes recycling by adjusting the initial concentration of the ammonium metavanadate solution, thereby avoiding waste of resources and generation of liquid waste.

[0049] Preferably, after the solid-liquid separation in step (2), the ammonium metavanadate solid phase is washed and dried in sequence.

[0050] Preferably, the washing liquid used in the washing comprises water.

[0051] Preferably, the washing temperature is 5-20°C, for example, 5°C, 10°C, 15°C or 20°C.

[0052] Preferably, the solid-liquid ratio of the ammonium metavanadate solid phase to the washing liquid is 1:(5-20), for example, it can be 1:5, 1:7, 1:9, 1:10, 1:12, 1:15, 1:17 or 1:20, etc., preferably 1:(7-15).

[0053] Preferably, the washing time is 30 to 120 min, for example, 30 min, 60 min, 90 min or 120 min.

[0054] Preferably, the washing is performed 1 to 3 times, for example, 1 time, 2 times or 3 times.

[0055] Preferably, the washing process is accompanied by a second stirring.

[0056] Preferably, the stirring rate of the second stirring is 50-200 r / min, for example, 50 r / min, 100 r / min, 150 r / min or 200 r / min.

[0057] The present invention further preferably has a solid-liquid ratio of the ammonium metavanadate solid phase to the washing liquid of 1: (7-15), which can effectively dilute impurities (such as sodium, molybdenum, iron, etc.), reduce residual impurities on the crystal surface, and improve the purity of the ammonium metavanadate crystal; the washing temperature is further preferably 5-20°C, which can not only significantly improve the efficiency of removing impurities on the crystal surface, but also effectively avoid crystal dissolution due to excessively high temperature; the stirring rate of the second stirring is further preferably 50-200r / min, which enhances the mixing of the solution and the diffusion removal efficiency of impurities, and ensures that the damage to the crystal morphology and particle size is minimized; the present invention significantly improves the purity and morphological stability of the ammonium metavanadate crystal by controlling various parameters of the washing process, and meets the requirements for high-quality products in industrial production.

[0058] Preferably, the drying temperature is 30-60°C, for example, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C or 60°C, etc., preferably 40-50°C.

[0059] Preferably, the drying time is 4 to 12 h, for example 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h or 12 h, etc., preferably 6 to 8 h.

[0060] Preferably, the drying method includes vacuum drying.

[0061] The present invention further preferably has a drying temperature of 40 to 50° C. and a drying time of 6 to 8 hours, which is conducive to forming ammonium metavanadate crystals with high purity, complete morphology and good dispersibility; preventing rapid evaporation within a too short time which may cause shrinkage or stress concentration on the crystal surface and affect the morphological integrity; and avoiding a too long drying time, which may cause the crystal surface to gradually lose activity and the particle size to increase due to agglomeration.

[0062] As a further preferred technical solution of the present invention, the crystallization method comprises the following steps:

[0063] (1) an ammonium metavanadate concentrated solution having an initial temperature of 80 to 120° C. is first subjected to a first heat preservation treatment for 30 to 60 minutes, and then subjected to a cooling treatment at a cooling rate of 1 to 10° C. / min to an end temperature of 0 to 20° C. to obtain an ammonium metavanadate supersaturated solution; the cooling treatment is accompanied by a first stirring at a rate of 10 to 200 r / min; a crystallization regulator is added when the temperature of the ammonium metavanadate concentrated solution drops to 20 to 80° C., and the ratio of the molar amount of the crystallization regulator to the volume of the ammonium metavanadate concentrated solution is 0.5 to 5 mmol / min. L; the vanadium concentration in the ammonium metavanadate concentrate is 30-60 g / L; the crystallization regulator comprises any one of sodium dodecyl sulfate, sodium dodecyl sulfonate, sodium dodecylbenzene sulfonate, hexadecyltrimethylammonium bromide, polyvinyl alcohol or polyvinyl pyrrolidone, or a combination of at least two thereof; the process of adding the crystallization regulator comprises first dissolving the crystallization regulator to obtain a crystallization regulator solution, and then dripping the crystallization regulator solution into the ammonium metavanadate concentrate; the dripping method comprises any one of dripping once, dripping twice or continuously dripping;

[0064] (2) The supersaturated ammonium metavanadate solution in step (1) is first subjected to a second heat preservation treatment for 30 to 120 minutes, then subjected to an aging treatment at 0 to 20° C. for 30 to 180 minutes, then subjected to solid-liquid separation, and then washed for 30 to 120 minutes at 5 to 20° C. and a solid-liquid ratio of 1:(5 to 20), and then vacuum dried at 30 to 60° C. for 4 to 12 hours to obtain an ammonium metavanadate solid phase.

[0065] In a second aspect, the present invention provides an ammonium metavanadate crystal, which is prepared by the crystallization method described in the first aspect.

[0066] The ammonium metavanadate crystals provided by the present invention have a large particle size, a uniform particle size distribution, a regular morphology and a high purity, and can meet the current demand for high-quality ammonium metavanadate crystals.

[0067] Preferably, the median particle size of the ammonium metavanadate crystals is greater than 80 μm, for example, 80.5 μm, 82.0 μm, 83.5 μm, 85.0 μm or 86.5 μm, etc., preferably ≥85.5 μm.

[0068] Preferably, the ammonium metavanadate crystal has a cuboid structure.

[0069] Preferably, the purity of the ammonium metavanadate crystals is ≥99.50%, for example, it may be 99.5%, 99.6%, 99.7%, 99.7%, 99.8% or 99.9%, etc.

[0070] Compared with the prior art, the present invention has at least the following beneficial effects:

[0071] (1) The crystallization method of ammonium metavanadate crystals provided by the present invention comprises adding a crystallization regulator during the cooling treatment of the ammonium metavanadate concentrated solution, and further optimizing the dosage and addition timing of the crystallization regulator, and optimizing the cooling procedure of the cooling treatment and the aging treatment time, such as the cooling rate and the terminal temperature of the cooling treatment; effectively controlling the nucleation rate and growth direction of the crystal growth, thereby avoiding the problems of crystal agglomeration and uneven particles; and combining the temperature and time parameters of subsequent washing and drying, thereby further reducing the residual impurities on the crystal surface and improving the purity of the ammonium metavanadate crystals; the combined effect of the various parameters makes the crystallization rate of the crystallization method preferably as high as 89.5% or more, and obtaining an ammonium metavanadate product with a median particle size preferably as high as 86.5% or more, a purity preferably as high as 99.97% or more, and a regular morphology.

[0072] (2) The ammonium metavanadate crystals provided by the present invention have a relatively high median particle size and purity, and have a non-uniform particle size, a regular morphology, and a rectangular parallelepiped structure, thus meeting the current requirements for high-quality ammonium metavanadate products. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] Figure 1 is a process flow chart of the crystallization method of the ammonium metavanadate crystals provided in Example 1 of the present invention;

[0074] Figure 2 is a SEM image of the ammonium metavanadate crystals obtained by the crystallization method of the ammonium metavanadate crystals provided in Example 1 of the present invention;

[0075] Figure 3 This is a SEM image of ammonium metavanadate crystals obtained by the crystallization method of ammonium metavanadate crystals provided in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0076] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and through specific implementation methods. However, the following examples are only simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0077] As a specific embodiment of the present invention, a crystallization method of ammonium metavanadate crystals is provided, and the crystallization method comprises the following steps:

[0078] (1) at 100 to 250° C., an ammonium metavanadate solution having a vanadium concentration of 6.0 to 15.0 g / L is concentrated by evaporation to obtain an ammonium metavanadate concentrate having a vanadium concentration of 30 to 60 g / L;

[0079] The ammonium metavanadate concentrated solution is first subjected to a first heat preservation treatment for 30 to 60 minutes at an initial temperature of 80 to 120° C., and then subjected to a cooling treatment at a cooling rate of 1 to 10° C. / min to an end temperature of 0 to 20° C. to obtain an ammonium metavanadate supersaturated solution; the cooling treatment is accompanied by a first stirring at a rate of 10 to 200 r / min; when the temperature of the ammonium metavanadate concentrated solution drops to 20 to 80° C., a crystallization regulator is added, and the ratio of the molar amount of the crystallization regulator to the volume of the ammonium metavanadate concentrated solution is 0.5 to 5 mmol / L;

[0080] The crystallization regulator comprises any one of sodium dodecyl sulfate, sodium dodecyl sulfonate, sodium dodecylbenzene sulfonate, hexadecyltrimethylammonium bromide, polyvinyl alcohol or polyvinyl pyrrolidone, or a combination of at least two thereof; the process of adding the crystallization regulator comprises first dissolving the crystallization regulator to obtain a crystallization regulator solution, and then dripping the crystallization regulator solution into the ammonium metavanadate concentrate; the dripping method comprises any one of dripping once, dripping twice or continuously dripping;

[0081] (2) The supersaturated ammonium metavanadate solution in step (1) is first subjected to a second heat preservation treatment for 30 to 120 minutes, then subjected to an aging treatment at 0 to 20° C. for 30 to 180 minutes, and then subjected to solid-liquid separation to obtain an ammonium metavanadate solid phase and a supernatant. The supernatant is then returned to step (1), and the ammonium metavanadate solid phase is then washed for 30 to 120 minutes at 5 to 20° C., a solid-liquid ratio of 1:(5 to 20), and a second stirring rate of 50 to 200 r / min. The washing is repeated 1 to 3 times, and the washed ammonium metavanadate solid phase is then vacuum dried at 30 to 60° C. for 4 to 12 hours to obtain an ammonium metavanadate solid phase product.

[0082] 1. Implementation

[0083] Example 1

[0084] This embodiment provides a method for crystallizing ammonium metavanadate crystals, referring to Figure 1 The process flow shown in FIG. 1 , the crystallization method comprises the following steps:

[0085] (1) at 150° C., an ammonium metavanadate solution having a vanadium concentration of 10 g / L is concentrated by evaporation at atmospheric pressure (0.1 MPa) to obtain an ammonium metavanadate concentrated solution having a vanadium concentration of 50 g / L;

[0086] The ammonium metavanadate concentrated solution is subjected to a first heat preservation treatment for 40 minutes at an initial temperature of 90°C, and then subjected to a cooling treatment at a cooling rate of 7°C / min to an end point temperature of 10°C to obtain an ammonium metavanadate supersaturated solution; the cooling treatment is accompanied by a first stirring at a rate of 50r / min; when the temperature of the ammonium metavanadate concentrated solution drops to 50°C, a crystallization regulator is added, i.e., sodium dodecyl sulfate solution is added dropwise, and the addition is continued until the temperature of the ammonium metavanadate concentrated solution drops to the end point temperature, i.e., 10°C; the ratio of the molar amount of sodium dodecyl sulfate in the sodium dodecyl sulfate solution to the volume of the ammonium metavanadate concentrated solution is 2.0mmol / L;

[0087] (2) The supersaturated ammonium metavanadate solution in step (1) is first subjected to a second heat preservation treatment for 60 minutes, then subjected to an aging treatment at 10° C., that is, allowed to stand for 60 minutes, and then subjected to plate and frame filter pressing to obtain an ammonium metavanadate solid phase and a supernatant, and then the supernatant is returned to step (1), and the ammonium metavanadate solid phase is then washed with water for 60 minutes at 15° C., a solid-liquid ratio of 1:10, and a second stirring rate of 100 r / min, filtered after washing once, and then the washed ammonium metavanadate solid phase is dried in a vacuum oven (vacuum degree of 10 -4 After vacuum drying for 6 h in 4% Pa, ammonium metavanadate crystals were obtained.

[0088] The SEM image of the ammonium metavanadate crystals obtained by the crystallization method described in this example is as follows: Figure 2 As shown, it can be seen that: its morphology is regular, with a rectangular structure, a large particle size, and a uniform particle size distribution; subsequently, the laser particle size analyzer tested its median particle size to be 86.9 μm.

[0089] Example 2

[0090] This embodiment provides a method for crystallizing ammonium metavanadate crystals, and the crystallization method comprises the following steps:

[0091] (1) at 100° C., an ammonium metavanadate solution having a vanadium concentration of 6.0 g / L is concentrated by evaporation under reduced pressure (0.06 MPa) to obtain an ammonium metavanadate concentrated solution having a vanadium concentration of 30 g / L;

[0092] The ammonium metavanadate concentrated solution is first subjected to a first heat preservation treatment for 30 minutes at an initial temperature of 120°C, and then subjected to a cooling treatment at a cooling rate of 3°C / min to an end point temperature of 18°C ​​to obtain an ammonium metavanadate supersaturated solution; the cooling treatment is accompanied by a first stirring at a rate of 150r / min; when the temperature of the ammonium metavanadate concentrated solution drops to 60°C, a crystallization regulator is added, i.e., a hexadecyltrimethylammonium bromide solution is added dropwise, and the addition is continued until the temperature of the ammonium metavanadate concentrated solution drops to the end point temperature, i.e., 18°C; the ratio of the molar amount of hexadecyltrimethylammonium bromide in the hexadecyltrimethylammonium bromide solution to the volume of the ammonium metavanadate concentrated solution is 1.0mmol / L;

[0093] (2) The supersaturated ammonium metavanadate solution in step (1) is first subjected to a second heat preservation treatment for 120 min, then subjected to an aging treatment at 18° C., that is, allowed to stand for 180 min, and then subjected to plate and frame filter pressing to obtain an ammonium metavanadate solid phase and a supernatant, and then the supernatant is returned to step (1), and the ammonium metavanadate solid phase is then washed with water for 120 min at 10° C., a solid-liquid ratio of 1:7, and a second stirring rate of 50 r / min, washed twice and then filtered, and then the washed ammonium metavanadate solid phase is placed in a vacuum drying oven (vacuum degree of 10 -3 After vacuum drying in 4% Pa for 8 h, ammonium metavanadate crystals were obtained.

[0094] The ammonium metavanadate crystals obtained by the crystallization method described in this example have a regular morphology, a rectangular structure, and a large particle size, which is consistent with the morphology of the product obtained in Example 1.

[0095] Example 3

[0096] This embodiment provides a method for crystallizing ammonium metavanadate crystals, and the crystallization method comprises the following steps:

[0097] (1) at 250° C., an ammonium metavanadate solution having a vanadium concentration of 15.0 g / L was concentrated by evaporation at atmospheric pressure (0.1 MPa) to obtain an ammonium metavanadate concentrated solution having a vanadium concentration of 60 g / L;

[0098] The ammonium metavanadate concentrate is subjected to a first heat preservation treatment for 60 minutes at an initial temperature of 80°C, and then subjected to a cooling treatment at a cooling rate of 8°C / min to an end point temperature of 8°C to obtain an ammonium metavanadate supersaturated solution; the cooling treatment is accompanied by a first stirring at a rate of 50r / min; when the temperature of the ammonium metavanadate concentrate drops to 40°C, a crystallization regulator is added, i.e., sodium dodecyl sulfonate solution is added dropwise twice until the temperature of the ammonium metavanadate concentrate drops to the end point temperature, i.e., 8°C; the ratio of the molar amount of sodium dodecyl sulfonate in the sodium dodecyl sulfonate solution to the volume of the ammonium metavanadate concentrate is 2.5mmol / L;

[0099] (2) The supersaturated ammonium metavanadate solution in step (1) is first subjected to a second heat preservation treatment for 50 minutes, then subjected to an aging treatment at 5°C, that is, allowed to stand for 50 minutes, and then subjected to plate and frame filter pressing to obtain an ammonium metavanadate solid phase and a supernatant, and then the supernatant is returned to step (1), and the ammonium metavanadate solid phase is then washed with water for 40 minutes at 5°C, a solid-liquid ratio of 1:15, and a second stirring rate of 200 r / min, washed three times, and then filtered, and then the washed ammonium metavanadate solid phase is placed in a vacuum drying oven (vacuum degree of 10 -2 After vacuum drying for 7 h in 4% Pa, ammonium metavanadate crystals were obtained.

[0100] The ammonium metavanadate crystals obtained by the crystallization method described in this example have a regular morphology, a rectangular structure, and a large particle size, which is consistent with the morphology of the product obtained in Example 1.

[0101] Example 4

[0102] This embodiment provides a method for crystallizing ammonium metavanadate crystals. The crystallization method is the same as that of Embodiment 1 except that the cooling rate of the cooling treatment in step (1) is 1° C. / min.

[0103] Example 5

[0104] This embodiment provides a method for crystallizing ammonium metavanadate crystals. The crystallization method is the same as that of Embodiment 1 except that the cooling rate of the cooling treatment in step (1) is 10° C. / min.

[0105] Example 6

[0106] This embodiment provides a method for crystallizing ammonium metavanadate crystals. The crystallization method is the same as that of Embodiment 1 except that the terminal temperature of the cooling treatment in step (1) is 5°C.

[0107] Example 7

[0108] This embodiment provides a method for crystallizing ammonium metavanadate crystals. The crystallization method is the same as that of Embodiment 1 except that the terminal temperature of the cooling treatment in step (1) is 20°C.

[0109] Example 8

[0110] This embodiment provides a method for crystallizing ammonium metavanadate crystals. The crystallization method is the same as that of Example 1 except that the ratio of the molar amount of sodium dodecyl sulfate in the sodium dodecyl sulfate solution to the volume of the ammonium metavanadate concentrate in step (1) is 0.5 mmol / L.

[0111] Example 9

[0112] This embodiment provides a method for crystallizing ammonium metavanadate crystals. The crystallization method is the same as that of Example 1, except that the ratio of the molar amount of sodium dodecyl sulfate in the sodium dodecyl sulfate solution to the volume of the ammonium metavanadate concentrate in step (1) is 3 mmol / L.

[0113] Example 10

[0114] This embodiment provides a method for crystallizing ammonium metavanadate crystals. The crystallization method is the same as that of Embodiment 1 except that step (1) begins to dropwise add sodium dodecyl sulfate solution when the temperature of the ammonium metavanadate concentrate drops to 80°C.

[0115] Embodiment 11

[0116] This embodiment provides a method for crystallizing ammonium metavanadate crystals. The crystallization method is the same as that of Embodiment 1 except that the sodium dodecyl sulfate solution is added dropwise when the temperature of the ammonium metavanadate concentrate drops to 20°C.

[0117] Example 12

[0118] This embodiment provides a method for crystallizing ammonium metavanadate crystals. The crystallization method is the same as that of Embodiment 1 except that the aging treatment time in step (2) is 10 minutes.

[0119] Example 13

[0120] This embodiment provides a method for crystallizing ammonium metavanadate crystals. The crystallization method is the same as that of Embodiment 1 except that the aging treatment time in step (2) is 240 minutes.

[0121] Embodiment 14

[0122] This embodiment provides a method for crystallizing ammonium metavanadate crystals. The crystallization method is the same as that of Embodiment 1 except that the solid-liquid ratio of the washing in step (2) is 1:5.

[0123] Embodiment 15

[0124] This embodiment provides a method for crystallizing ammonium metavanadate crystals. The crystallization method is the same as that of Embodiment 1 except that the solid-to-liquid ratio of the washing in step (2) is 1:20.

[0125] Example 16

[0126] This embodiment provides a method for crystallizing ammonium metavanadate crystals. The crystallization method is the same as that of Embodiment 1 except that the drying temperature in step (2) is 30°C.

[0127] Embodiment 17

[0128] This embodiment provides a method for crystallizing ammonium metavanadate crystals. The crystallization method is the same as that of Embodiment 1 except that the drying temperature in step (2) is 60°C.

[0129] Embodiment 18

[0130] This embodiment provides a method for crystallizing ammonium metavanadate crystals. The crystallization method is the same as that of Embodiment 1 except that the drying time in step (2) is 4 hours.

[0131] Embodiment 19

[0132] This embodiment provides a method for crystallizing ammonium metavanadate crystals. The crystallization method is the same as that of Embodiment 1 except that the drying time in step (2) is 12 hours.

[0133] 2. Comparison

[0134] Comparative Example 1

[0135] This comparative example provides a method for crystallizing ammonium metavanadate crystals. The crystallization method is the same as Example 1 except that no sodium dodecyl sulfate solution, that is, no crystallization regulator, is added during the cooling treatment in step (1).

[0136] The SEM image of the ammonium metavanadate crystals obtained in this comparative example is as follows Figure 3 As shown, it can be seen that its morphology is irregular, with a large number of needle-shaped and flat flake crystals, small and uneven particle size, and agglomeration.

[0137] 3. Test and its results

[0138] The median particle size and purity of the ammonium metavanadate crystals of the crystallization methods provided in the above embodiments and comparative examples were tested, and the crystallization rate of the crystallization method was calculated. The results are shown in Table 1;

[0139] Table 1

[0140]

[0141]

[0142] From the data in Table 1, we can see that:

[0143] (1) It can be seen from Examples 1 and 3 that the crystallization method of ammonium metavanadate crystals provided by the present invention successfully prepared high-purity ammonium metavanadate crystals with a large median particle size, and a high crystallization rate, wherein the median particle size is as high as 86.5 μm or more, the purity is as high as 99.97% or more, and the crystallization rate is as high as 89.5% or more, meeting the requirements of high-quality ammonium metavanadate products.

[0144] (2) It can be seen from Examples 1 and 4 to 7 that the cooling rate of the cooling treatment in step (1) of Example 4 is too low, resulting in a decrease in the crystallization rate to 80.1%; the cooling rate of the cooling treatment in step (1) of Example 5 is too high, resulting in a decrease in the crystallization rate to 80.5%, and the median particle size of the obtained ammonium metavanadate crystals is reduced to 80.2 μm; the terminal temperature of the cooling treatment in step (1) of Example 6 is too low, resulting in a decrease in the median particle size of the obtained ammonium metavanadate crystals to 84.5 μm; the terminal temperature of the cooling treatment in step (1) of Example 7 is too high, resulting in a decrease in the crystallization rate to 80.2%, and the median particle size of the obtained ammonium metavanadate crystals is reduced to 81.2 μm; It can be seen that the present invention further preferably has a cooling rate of 3 to 8°C / min and an end temperature of 8 to 18°C ​​for the cooling treatment, and further regulates the cooling process, thereby regulating the crystallization process, and further improving the crystallization rate of the crystallization method and the median particle size of the obtained product.

[0145] (3) It can be seen from Examples 1 and 8 to 11 that the molar amount of sodium dodecyl sulfate in the sodium dodecyl sulfate solution in step (1) of Example 8 is too low, which will cause the crystallization rate to decrease to 82.4%; the molar amount of sodium dodecyl sulfate in the sodium dodecyl sulfate solution added in step (1) of Example 9 is too high, which will cause the median particle size of the product to decrease to 70.28% and the purity to decrease to 99.08%; in Example 10, the temperature of the ammonium metavanadate concentrate was too high when the sodium dodecyl sulfate solution was added in step (1), that is, it was added too early, resulting in the crystallization rate to decrease to 81.0% and the median particle size of the product to decrease to 72. .54%; in Example 11, when the sodium dodecyl sulfate solution was added, the amount of the ammonium metavanadate concentrate was too low, that is, it was added too late, resulting in the crystallization rate dropping to 80.2%, and the median particle size of the product dropping to 75.68%; this shows that the present invention further preferably has a molar ratio of the crystallization regulator to the volume of the ammonium metavanadate concentrate of 1.0 to 2.5 mmol / L, and further preferably starts adding the crystallization regulator when the temperature of the ammonium metavanadate concentrate drops to 40 to 60°C, and further controllably regulates the crystallization process of the ammonium metavanadate, thereby further improving the crystallization rate and the median particle size and purity of the obtained product.

[0146] (4) It can be seen from Example 1 and Examples 12 to 13 that, due to the short aging time of step (2) of Example 12, the crystallization rate dropped to 81.8%, the purity of the obtained product dropped to 99.40%, and the median particle size dropped to 80.17 μm; the aging time of step (2) of Example 13 was long, resulting in the crystallization rate dropped to 81.2%, the purity of the obtained product dropped to 99.00%, and the median particle size dropped to 79.54 μm; this shows that the present invention further preferably sets the aging time of step (2) to 30 to 180 min, which further improves the crystallization rate of the crystallization method and the purity and median particle size of the obtained product.

[0147] (5) It can be seen from Example 1 and Examples 14 to 19 that the solid-liquid ratio of the washing in step (2) of Example 14 is too large, or the solid-liquid ratio of the washing in step (2) of Example 15 is too small, which will lead to a decrease in the crystallization rate and a decrease in the purity and median particle size of the product; the drying temperature in step (2) of Example 16 is too low, the drying temperature in step (2) of Example 17 is too high, the drying time in step (2) of Example 18 is too short, or the drying time in step (2) of Example 19 is too long, which will lead to a decrease in the crystallization rate and a decrease in the purity and median particle size of the product. This shows that the present invention further prefers that the solid-liquid ratio of the washing in step (2) is 1:(7 to 15), the drying temperature is 40 to 50°C, and the drying time is 6 to 8h, which further improves the purity and median diameter of the product.

[0148] (6) It can be seen from Example 1 and Comparative Example 1 that, since no sodium dodecyl sulfate solution, i.e., no crystallization modifier, was added in step (1) of Comparative Example 1, the crystallization rate dropped to 82.2%, the purity of the product dropped to 99.02%, and the median particle size dropped significantly to 68.5 μm. This indicates that the present invention significantly improves the median particle size and purity of the obtained product, as well as the crystallization rate of the crystallization method, by adding a crystallization modifier during the cooling process.

[0149] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention are within the protection scope and disclosure scope of the present invention.

Claims

1. A method for crystallizing ammonium metavanadate crystals, characterized in that: The crystallization method comprises the following steps: (1) cooling the ammonium metavanadate concentrated solution to obtain an ammonium metavanadate supersaturated solution; the cooling process includes adding a crystallization regulator to the ammonium metavanadate concentrated solution; (2) The supersaturated ammonium metavanadate solution in step (1) is subjected to aging treatment and solid-liquid separation to obtain an ammonium metavanadate solid phase.

2. The crystallization method according to claim 1, characterized in that The vanadium concentration in the ammonium metavanadate concentrated solution in step (1) is 30-60 g / L; Preferably, the initial temperature of the ammonium metavanadate concentrated solution in step (1) is 80-120°C.

3. The crystallization method according to claim 1 or 2, characterized in that The cooling rate of the cooling treatment in step (1) is 1 to 10°C / min, preferably 3 to 8°C / min; Preferably, the terminal temperature of the cooling treatment in step (1) is 0 to 20°C, preferably 8 to 18°C; Preferably, the cooling process in step (1) is accompanied by a first stirring; Preferably, the first stirring rate is 10-200 r / min.

4. The crystallization method according to any one of claims 1 to 3, characterized in that The crystallization regulator in step (1) comprises any one of sodium dodecyl sulfate, sodium dodecyl sulfonate, sodium dodecylbenzene sulfonate, hexadecyltrimethylammonium bromide, polyvinyl alcohol or polyvinyl pyrrolidone, or a combination of at least two thereof; Preferably, the ratio of the molar amount of the crystallization regulator to the volume of the ammonium metavanadate concentrate is 0.5 to 5 mmol / L, preferably 1.0 to 2.5 mmol / L; Preferably, the crystallization regulator is added when the temperature of the ammonium metavanadate concentrate drops to 20-80°C, preferably 40-60°C; Preferably, the process of adding the crystallization regulator comprises first dissolving the crystallization regulator to obtain a crystallization regulator solution, and then dropping the crystallization regulator solution into the ammonium metavanadate concentrated solution; Preferably, the dripping method includes any one of one dripping, two dripping or continuous dripping, preferably continuous dripping.

5. The crystallization method according to any one of claims 1 to 4, characterized in that Before the cooling treatment in step (1), the ammonium metavanadate concentrated solution is first subjected to a first heat preservation treatment; Preferably, the first heat preservation treatment lasts for 30 to 60 minutes.

6. The crystallization method according to any one of claims 1 to 5, characterized in that The aging time in step (2) is 30 to 180 minutes; Preferably, the temperature of the aging treatment in step (2) is 0 to 20°C; Preferably, the supersaturated ammonium metavanadate solution is first subjected to a second heat preservation treatment before the aging treatment in step (2); Preferably, the second heat preservation treatment is performed for 30 to 120 minutes.

7. The crystallization method according to any one of claims 1 to 6, characterized in that After the solid-liquid separation in step (2), the ammonium metavanadate solid phase is washed and dried in sequence; Preferably, the washing temperature is 5 to 20°C; Preferably, the solid-liquid ratio of the ammonium metavanadate solid phase to the washing liquid is 1:(5-20), preferably 1:(7-15); Preferably, the washing time is 30 to 120 minutes; Preferably, the drying temperature is 30 to 60°C, preferably 40 to 50°C; Preferably, the drying time is 4 to 12 hours, preferably 6 to 8 hours; Preferably, the drying method includes vacuum drying.

8. The crystallization method according to any one of claims 1 to 7, characterized in that The crystallization method comprises the following steps: (1) the ammonium metavanadate concentrate having an initial temperature of 80 to 120° C. is first subjected to a first heat preservation treatment for 30 to 60 minutes, and then subjected to a cooling treatment at a cooling rate of 1 to 10° C. / min to an end point temperature of 0 to 20° C. to obtain an ammonium metavanadate supersaturated solution; The cooling process is accompanied by a first stirring at a rate of 10 to 200 r / min; when the temperature of the ammonium metavanadate concentrated solution drops to 20 to 80° C., a crystallization regulator is added, and the ratio of the molar amount of the crystallization regulator to the volume of the ammonium metavanadate concentrated solution is 0.5 to 5 mmol / L; The vanadium concentration in the ammonium metavanadate concentrate is 30-60 g / L; the crystallization regulator comprises any one of sodium dodecyl sulfate, sodium dodecyl sulfonate, sodium dodecylbenzene sulfonate, hexadecyltrimethylammonium bromide, polyvinyl alcohol or polyvinyl pyrrolidone, or a combination of at least two thereof; the process of adding the crystallization regulator comprises first dissolving the crystallization regulator to obtain a crystallization regulator solution, and then dripping the crystallization regulator solution into the ammonium metavanadate concentrate; the dripping method comprises any one of dripping once, dripping twice or continuously dripping; (2) The supersaturated ammonium metavanadate solution in step (1) is first subjected to a second heat preservation treatment for 30 to 120 minutes, then subjected to an aging treatment at 0 to 20° C. for 30 to 180 minutes, then subjected to solid-liquid separation, and then washed for 30 to 120 minutes at 5 to 20° C. and a solid-liquid ratio of 1:(5 to 20), and then vacuum dried at 30 to 60° C. for 4 to 12 hours to obtain an ammonium metavanadate solid phase.

9. An ammonium metavanadate crystal, characterized in that: The ammonium metavanadate crystals are obtained by the crystallization method according to any one of claims 1 to 8.

10. The ammonium metavanadate crystal according to claim 9, characterized in that: The median particle size of the ammonium metavanadate crystals is greater than 80 μm, preferably greater than or equal to 85.5 μm; Preferably, the ammonium metavanadate crystal has a cuboid structure; Preferably, the purity of the ammonium metavanadate crystals is ≥99.50%.

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