CN110857222A - Preparation method of vanadium trioxide powder - Google Patents
Preparation method of vanadium trioxide powder Download PDFInfo
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- CN110857222A CN110857222A CN201810966949.5A CN201810966949A CN110857222A CN 110857222 A CN110857222 A CN 110857222A CN 201810966949 A CN201810966949 A CN 201810966949A CN 110857222 A CN110857222 A CN 110857222A
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Abstract
The invention discloses a preparation method of vanadium trioxide powder, which comprises the following steps: will V2O5Mixing the solution with oxalic acid in proportion, adding the mixture into a reaction solvent, fully dissolving and reacting the mixture at a low temperature by magnetic stirring, reducing the mixture in a liquid phase to obtain a blue-green solution, heating and concentrating the solution, drying the solution in vacuum to obtain a blue solid, grinding the blue solid, and calcining the blue solid in an argon atmosphere to obtain grey-black vanadium trioxide solid powder. The method has simple process and does not need H2And NH3And the like has dangerous reducing atmosphere, the production cost is low, no waste gas is generated, the loss rate of vanadium is low, the purity of the obtained powder is high, and the large-scale production is favorably realized.
Description
Technical Field
The invention relates to a preparation method of vanadium trioxide, belonging to the field of chemical material synthesis.
Background
Vanadium trioxide, chemical formula: v2O3As a typical phase-change material, the phase-change process is accompanied by the sudden change of the properties of the electromagnetic property and the like, and the phase-change material is widely applied to the thermosensitive materialNon-linear resistance material, electrothermal allochroic display material, etc. The method for preparing the + 3.5-valent vanadium electrolyte by reducing vanadium pentoxide by using vanadium trioxide as a reducing agent has the advantages of simple production process, good reduction effect, no addition of other impurities, chemical reduction method and electrolysis method, and reduction of the production cost of the vanadium electrolyte.
At present, because the reduction force required by the valence of vanadium from +5 to +3 is large, the reduction method comprises the reduction of an external reinforcement reducing agent (such as sulfur, carbon powder, graphite and the like) and the reduction of a reducing gas (such as H)2CO, etc.). The method for reducing by adding reducing agents such as graphite, carbon and the like has simple production process, but the required reduction temperature is high, and carbon is easy to remain in the product or bring other impurities into the product; h2Or reducing gases such as CO and the like have good reducing effect and high product purity, but have the dangers of combustion, explosion or toxic gas leakage and the like. And by decomposition of vanadate, wherein ammonia gas generated by ammonium vanadate is cracked into H2And N2The method for preparing vanadium trioxide by reduction is clean and environment-friendly, does not need to add any reducing agent, but has incomplete ammonia gas cracking, insufficient reduction and higher requirement on equipment. In addition to the above main preparation methods, vanadium-containing hydrazine salt can be calcined under the condition of protective gas, and vanadium trioxide with uniform and fine particle size can be synthesized by adding an organic reducing agent and then adopting hydrothermal synthesis or solvothermal and other methods, and a good application effect can be obtained in related fields.
Disclosure of Invention
The invention aims to provide a method for preparing vanadium trioxide by sol-gel, which overcomes the defects of high cost, complex operation and low safety performance of the existing production process.
The invention provides a preparation method of vanadium trioxide, which comprises the following steps:
(1) will V2O5Mixing the powder and oxalic acid according to a certain molar ratio, adding the mixture into a reaction solvent, heating and dissolving the mixture under stirringFully reacting to obtain a precursor solution;
(2) concentrating, drying and grinding the precursor solution into powder;
(3) and calcining the obtained powder to obtain vanadium trioxide solid powder.
Further, the V2O5The powder has a purity of 96%.
Further, the V2O5The molar ratio of oxalic acid to oxalic acid is 1: (3-5).
Further, the reaction solvent is a mixed solution of absolute ethyl alcohol and water, wherein the volume content of the water is 0-66.7%.
Further, the heating and dissolving reaction temperature is 90-120 ℃.
Further, the heating dissolution reaction was carried out under magnetic stirring at a speed of 500 r/min.
Further, in order to prevent the precursor solution from caking after drying, the precursor solution is magnetically stirred in the concentration and drying process.
Further, the calcination was performed in the presence of a protective atmosphere Ar gas.
Further, the calcination temperature is 400-600 ℃.
Further, the calcination time was 2 hours.
Further, the calcined powder was subjected to ultrasonic washing.
Compared with the prior art, the invention has the advantages that:
(1) the preparation method of vanadium trioxide provided by the invention overcomes the defects of high cost and complex operation of the existing production process, and can obtain nano powder with uniform appearance and fine particles. (2) According to the method, vanadium pentoxide is used as a raw material, and is reduced by oxalic acid and calcined to obtain high-purity vanadium trioxide.
(3) The production process has the advantages of simple operation, low energy consumption, safety and low equipment requirement, is suitable for industrial large-scale production, and can obviously reduce the production cost of vanadium trioxide.
Drawings
FIG. 1 is a schematic view of a process for producing vanadium trioxide according to the present invention.
FIG. 2 shows that the molar ratio of vanadium pentoxide to oxalic acid in Experimental example 1 is 1: 4 in 100ml of absolute ethyl alcohol, and the XRD diffraction pattern of the obtained product.
FIG. 3 shows that the molar ratio of vanadium pentoxide to oxalic acid in Experimental example 2 is 1: 3 in 80ml of absolute ethyl alcohol, and the XRD diffraction pattern of the obtained product.
FIG. 4 shows that the molar ratio of vanadium pentoxide to oxalic acid in Experimental example 3 is 1: 4 in 60ml of 95% ethanol, and the XRD diffraction pattern of the obtained product.
FIG. 5 shows the molar ratio of vanadium pentoxide to oxalic acid in comparative example 1 being 1: 4 in the solvent of 100ml deionized water and 50ml absolute ethyl alcohol mixed solution, 50ml deionized water and 50ml absolute ethyl alcohol mixed solution, 100ml absolute ethyl alcohol and 100ml deionized water, respectively, and obtaining the XRD diffraction pattern of the product.
FIG. 6 shows the molar ratio of vanadium pentoxide to oxalic acid in comparative example 2 being 1: 3 and 1: 4 and 1: 5 in 100ml of absolute ethyl alcohol respectively, and the XRD diffraction pattern of the obtained product.
FIG. 7 shows that the molar ratio of 3 parts of vanadium pentoxide to oxalic acid in comparative example 3 is 1: 4, respectively adding the mixture into a precursor containing 100ml of absolute ethyl alcohol, respectively calcining for 2 hours at 400 ℃, 500 ℃ and 600 ℃ in an Ar gas protective atmosphere, and obtaining an XRD diffraction pattern of the product.
Detailed Description
The raw materials and equipment used in the embodiment of the present invention are known products and obtained by purchasing commercially available products.
The invention provides a preparation method of vanadium trioxide, which comprises the following steps (a production process schematic diagram is shown in figure 1):
(1) will V2O5Mixing the powder with oxalic acid according to a certain molar ratio (1: 3/1: 4/1: 5), adding the mixture into a reaction solvent (the molar weight of vanadium in a vanadium source: the volume of the reaction solvent is 50 mmol/L-200 mmol/L), and magnetically stirring the mixture at the temperature of 90-120 ℃ at 500 r/min-1000 r/min to fully dissolve and react the powder to obtain a dark green solution.
(2) And heating and concentrating the dark green solution, drying in vacuum to obtain a blue solid, and grinding into powder as a precursor.
(3) Annealing the obtained powder for 2h under the atmosphere of Ar at the temperature of 500 ℃, and cooling to room temperature under the protection of argon to obtain grey-black vanadium trioxide solid powder.
In the production process, main components obtained in the early-stage preparation of the precursor are vanadyl oxalate, residual ethanol and acetaldehyde produced by reaction, and the main components play a certain reduction role in the later-stage annealing so as to obtain vanadium trioxide, and the production process has the remarkable advantages that: the equipment is simple, the preparation of the high-purity vanadium trioxide powder is realized at a lower temperature in a shorter time, the process stability is strong, and the quality of the obtained product is high.
In addition, the invention further inspects the parameter conditions in the preparation process, and the result shows that the dosage of oxalic acid and the concentration and dosage of the reaction solvent have obvious influence on the product. When the molar weight ratio of vanadium pentoxide to oxalic acid is low, the reaction and dissolution time is longer, the reaction is insufficient, the time for obtaining a precursor is longer, and the granularity of the prepared powder is larger; when deionized water is added into a solvent, the time for obtaining the precursor is shortened, but the particle size of the obtained powder is relatively not uniform enough, and other high-valence vanadium oxide is mixed in the obtained vanadium trioxide. The calcination temperature has important significance for preparing vanadium trioxide powder, and the vanadium trioxide in the obtained powder has low purity and more impurity phases at the calcination temperature of 400 ℃. Particularly, the requirement on the annealing temperature is higher under the condition that the solvent is absolute ethyl alcohol, the reduction and decomposition are insufficient at low temperature, and the purity of vanadium trioxide is difficult to meet the requirement. The selection of proper oxalic acid dosage, reaction solvent and annealing temperature has important significance for preparing high-purity vanadium trioxide powder.
At present, no report exists for preparing vanadium trioxide by reducing vanadium pentoxide with oxalic acid. Compared with the prior art, the method has the advantages that the reducing agent (such as sulfur, carbon powder, graphite and the like) or reducing gas (such as H) is added into the external reinforcement body2CO, and the like), the utilization rate of reducing gas is lower, certain potential safety hazards exist in the production process, and the production energy consumption is higher; the method for hydrolyzing the vanadium salt has simple process and production efficiencyThe method has the advantages of high rate, good repeatability, large influence of the calcining atmosphere, high cost and high requirement on experimental conditions. Relatively speaking, the invention has the obvious advantages of low production cost, simple and convenient operation, safety and the like.
The following further describes embodiments of the present invention with reference to examples.
In the examples, V2O5Is high-purity vanadium pentoxide.
Example 1 preparation of vanadium trioxide by the Process of the invention
(1) Fetch 1g V2O5Adding 2.76g H2C2O4·2H2O (the molar ratio of vanadium pentoxide to oxalic acid is 4) is uniformly mixed, added into a conical flask filled with 100ml of absolute ethyl alcohol (the molar weight of vanadium: the volume of the solvent =110 mmol/L), stirred at the magnetic stirring speed of 500r/min, and reacted in a water bath kettle at the temperature of 90 ℃ for 7 hours until the vanadium is completely dissolved;
(2) heating, concentrating, drying and grinding the obtained reaction solution to obtain a precursor;
(3) and calcining the precursor for 2h under the protection of Ar gas at the temperature of 500 ℃, and cooling to room temperature under the protective atmosphere to obtain vanadium trioxide powder. Fig. 2 is an XRD diffractogram of the resulting product.
Example 2 vanadium trioxide prepared by the process of the invention
(1) Fetch 1g V2O5Adding 2.077g H2C2O4·2H2O (the molar ratio of vanadium pentoxide to oxalic acid is 3) is uniformly mixed, added into an erlenmeyer flask filled with 80ml of absolute ethyl alcohol (the molar weight of vanadium: the volume of the solvent =103.13 mmol/L), stirred at the magnetic stirring speed of 500r/min, and reacted in a water bath kettle at the temperature of 90 ℃ for 8 hours until the absolute ethyl alcohol is completely dissolved;
(2) heating, concentrating, drying and grinding the obtained reaction solution to obtain a precursor;
(3) and calcining the precursor for 2h under the protection of Ar gas at the temperature of 500 ℃, and cooling to room temperature under the protective atmosphere to obtain vanadium trioxide powder. FIG. 3 is an XRD diffraction pattern of the obtained product
Example 3
(1) Take 1gV2O5Adding 2.77gH2C2O4·2H2O (the molar ratio of vanadium pentoxide to oxalic acid is 4) is uniformly mixed, then the mixture is added into an erlenmeyer flask filled with 60ml of 95% ethanol (the molar weight of vanadium: the volume of the solvent =183.3 mmol/L), and magnetic stirring is carried out at the temperature of 120 ℃ at the stirring speed of 500r/min, and the reaction is carried out for 4 hours until the vanadium pentoxide and the oxalic acid are completely dissolved;
(2) heating, concentrating, drying and grinding the obtained reaction solution to obtain a precursor;
(3) and calcining the precursor for 2h under the protection of Ar gas at the temperature of 500 ℃, and cooling to room temperature under the protection atmosphere. And obtaining vanadium trioxide powder. FIG. 4 is an XRD diffraction pattern of the obtained product
Comparative example 1 Effect of the amount ratio of deionized Water in reaction solvent in production Process on product
Take 1.0g V2O5Adding 2.77g H2C2O4·2H2And O is uniformly mixed, then the mixture is respectively added into 100ml of deionized water and 50ml of absolute ethyl alcohol, 50ml of deionized water and 50ml of absolute ethyl alcohol, 100ml of absolute ethyl alcohol and 100ml of deionized water, magnetic stirring is carried out at the stirring speed of 1000r/min until the powder is completely dissolved and reacts to form a blue solution, heating, concentrating, drying and grinding are carried out, precursors marked as Q1, Q2, Q3 and Q4 are respectively obtained, and the precursors are respectively calcined for 2 hours at 500 ℃ under the atmosphere of Ar, so that the obtained products are respectively marked as a1, a2, a3 and a 4. The diffraction analysis of the obtained product was carried out, and the analysis results are shown in FIG. 5.
As can be seen from the spectrum analysis of FIG. 5, when the reaction solvent is absolute ethyl alcohol and no deionized water is added, the component of the obtained product is V2O3And deionized water is contained in the reaction solvent, and the product obtained in the experiment except the main product V2O3，All have V4O7The components are produced and reduced incompletely. Moreover, the comparison shows that the diffraction peak of the product obtained by high ethanol concentration is sharper, the particle size is finer, and the product purity is higher.
The above test resultsThe preparation process of the invention determines that although the deionized water is added into the solvent to accelerate the liquid phase reduction, the prepared powder has a relatively complicated phase, and anhydrous ethanol is selected as a reaction solvent to prepare the high-purity target product V2O3。
Comparative example 2 influence of oxalic acid amount on product in preparation Process
Take 1.0g V2O5And 2.07gH2C2O4·2H2O (molar ratio of vanadium pentoxide to oxalic acid = 3), 1.0g V2O5And 2.77g H2C2O4·2H2O (molar ratio of vanadium pentoxide to oxalic acid = 4) was mixed uniformly and then 1.0g V2O5And 3.46gH2C2O4·2H2And O (the molar ratio of vanadium pentoxide to oxalic acid = 5) is uniformly mixed, then the mixture is respectively added into 100ml of absolute ethyl alcohol, the mixture is magnetically stirred until the powder is reacted and dissolved to generate a blue-green solution, and the solution is heated, concentrated, dried, ground and calcined for 2 hours under the atmosphere of Ar and at the temperature of 500 ℃. The diffraction analysis of the obtained product was carried out, and the analysis results are shown in FIG. 6.
As can be seen from the graph analysis of FIG. 6, the comparison shows that V with higher purity is obtained in the absolute ethanol reaction solvent by comparing the molar ratio of vanadium pentoxide to oxalic acid of 4 or 5 with the molar ratio of vanadium pentoxide to oxalic acid of 32O3The oxalic acid is high in dosage, so that the +5 vanadium can be fully reduced into the +3 vanadium, but when the molar ratio of the vanadium pentoxide to the oxalic acid is 4, the diffraction peak of the obtained product is sharper, almost no diffraction impurity peak exists, the crystallinity is good, and the product purity is higher.
The above test results show that the molar ratio of vanadium pentoxide to oxalic acid has a significant effect on the final product, and the reaction equation V is combined2O5+3H2C2O4=2VOC2O4+2CO2+3H2O, the oxalic acid is used in a proper excess amount for preparing the target product V with high purity2O3Has certain advantages, but the medicine is wasted due to excessive dosage and the effect is not goodThe effect is better when the molar ratio of vanadium oxide to oxalic acid is = 4.
Comparative example 3 Effect of annealing temperature on product in production Process
Taking three parts of 1.0g V2O5And 2.77g H2C2O4·2H2O, after being uniformly mixed, the mixture is respectively added into 100ml of absolute ethyl alcohol and reacts in a water bath kettle with the stirring speed of 500r/min and the temperature of 90 ℃ until the mixture is completely dissolved; heating, concentrating, drying and grinding the obtained reaction solution to obtain a precursor; the precursor was calcined under the protection of Ar gas at 400 deg.C, 500 deg.C and 600 deg.C for 2h, and the resulting product was analyzed by diffraction, the analysis results are shown in FIG. 7.
The test results show that the annealing temperature has great influence on the final product, the reduction is not complete enough when the temperature is low, more types of high-valence vanadium oxides are contained in the prepared product, the product prepared by the precursor at 500 ℃ and 600 ℃ needs to be further reduced, the product prepared by the precursor at the temperature is better than that prepared by the precursor at 400 ℃, and the high-purity target product V can be prepared at high temperature2O3There is an influence to facilitate a sufficient reduction reaction, but since the particle size increases with increasing temperature, 500 ℃ gives a product with finer particles than 600 ℃, preferably 500 ℃.
The test results show that the preparation process is simple and reliable, the product obtained at 500 ℃ has stable quality, and the effect is better when the solvent is absolute ethyl alcohol.
Claims (10)
1. The preparation method of vanadium trioxide is characterized by comprising the following steps:
(1) will V2O5Mixing the powder and oxalic acid according to a certain molar ratio, adding into a reaction solvent, heating for dissolving reaction under stirring, and obtaining a precursor solution after full reaction;
(2) concentrating, drying and grinding the precursor solution into powder;
(3) and calcining the obtained powder to obtain vanadium trioxide solid powder.
2. The method of claim 1, wherein the method further comprises the step of removing the solvent from the mixtureIn that said V2O5The powder has a purity of 96%.
3. The method of claim 1, wherein V is2O5The molar ratio of oxalic acid to oxalic acid is 1: (3-5).
4. The method according to claim 1, wherein the reaction solvent is a mixed solution of absolute ethanol and water having a water volume content of 0 to 66.7%.
5. The method of claim 1, wherein the heated dissolution reaction temperature is from 90 ℃ to 120 ℃.
6. The method of claim 1 or 5, wherein the heating dissolution reaction is performed under magnetic stirring at a speed of 500 r/min.
7. The method of claim 1, wherein the precursor solvent is magnetically stirred during the concentration and drying process to prevent agglomeration of the precursor solution after drying.
8. The method of claim 1, wherein the calcining is carried out in the presence of a protective atmosphere of Ar gas.
9. The method of claim 1, wherein the calcination temperature is 400 ℃ to 600 ℃.
10. The method of claim 1, wherein the calcination time is 2 hours.
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Cited By (2)
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| CN112811467A (en) * | 2021-01-18 | 2021-05-18 | 陕西科技大学 | V-shaped groove2O3Method for preparing nanoparticles |
| CN114684854A (en) * | 2022-03-30 | 2022-07-01 | 东风汽车集团股份有限公司 | Preparation method of nano vanadium trioxide |
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Application publication date: 20200303 |