Background technology
As an industrially important precursor, vanadyl oxalate is used in a wide range of applications. For example, Functional Materials 2007 Supplement (38) uses ammonium hydrolysis of vanadyl oxalate. The cubic phase VN powder with an average particle size of about 50 mm was prepared using the precursor method.
In view of the need for new utilization pathways of vanadium oxalate and the expansion of the field of vanadium resource utilization, it is inevitable to develop a new vanadium oxalate preparation process. The current preparation method of vanadium oxalate involves raw material conversion. The efficiency is low and the product purity is not high.
For example, CN1693212A discloses a carbon dioxide The preparation method of vanadium nanopowder materials mentions using vanadium pentoxide and oxalic acid as raw materials to directly heat and reduce in an aqueous solution to prepare the precursor vanadyl oxalate. This method uses vanadium oxalate as a precursor, and the preparation process is relatively simple. Simple, but the conversion rate of vanadium pentoxide in the raw material is low, and the impurity content in the vanadium oxalate product is high.
Content of the invention
The purpose of the invention is to overcome the low conversion rate of vanadium pentoxide in the raw materials in the method of preparing vanadyl oxalate using the existing technology, and the prepared oxalic acid The defect of high impurity content in vanadium oxalate products provides a preparation method of vanadium oxalate. The method of the present invention can improve the raw material conversion rate and product purity.
In order to achieve the above object, the present invention provides a preparation method of vanadium oxalate, which method includes the following steps: (1) In the presence of sulfuric acid aqueous solution, the raw material containing vanadium pentoxide is mixed with Contact the reducing agent to obtain a tetravalent vanadium solution; (2) Contact the tetravalent vanadium solution obtained in step (1) with the hydroxide of an alkali metal to perform a precipitation reaction, and perform solid-liquid separation to obtain a solid phase product; (3) Contact the solid phase product obtained in step (2) with oxalic acid to obtain vanadyl oxalate.
The method of the present invention has the following beneficial effects: the conversion rate of vanadium pentoxide in the raw material is high, and the purity of the prepared vanadium oxalate product is high.
Detailed Embodiments
The specific embodiments of the present invention will be described in detail below. It should be understood that the specific embodiments described here are only used to illustrate and explain the present invention, and are not intended to limit the present invention.
According to the method of the present invention, in the step (1), the sulfuric acid aqueous solution is a commonly used raw material in this field and functions to activate the vanadium pentoxide in the raw material. In order to make the activation effect better, Preferably, based on vanadium pentoxide, the mass ratio of the raw material containing vanadium pentoxide to the sulfuric acid aqueous solution is 1:2.5-5, and the mass percentage concentration of the sulfuric acid aqueous solution can be 20%-85%.
In the step (1), the reducing agent can be a reducing agent commonly used in this field. The reducing agent functions to reduce the pentavalent vanadium in the raw material to a tetravalent state. In order to prevent the vanadium from being reduced to a higher valence, Low valence, preferably, the reducing agent is selected from one or more of sodium thiosulfate, oxalic acid and formic acid. More preferably, when sodium thiosulfate and/or formic acid is used, it can be more fully reduced to obtain tetrafluoroethylene. valent vanadium solution to help improve the conversion rate of raw materials.
In the step (1), the optional range of the amount of the reducing agent is relatively wide. In order to make the reaction proceed better, it is preferred that, based on vanadium pentoxide, the amount of the reducing agent contains vanadium pentoxide. The molar ratio of the raw material of vanadium oxide to the reducing agent is 1: 1.4-3.2.
In the step (1), in the presence of a sulfuric acid aqueous solution, the raw material containing vanadium pentoxide is contacted with the reducing agent to react in a wide range of conditions, in order to make the reduction reaction To better carry out the conversion rate of vanadium pentoxide, the conditions for contacting the raw material containing vanadium pentoxide with the reducing agent include a temperature of 95-100°C and a time of 0.5-5 hours, and further Preferably, the time is 0.5-2 hours.
In the step (2), the tetravalent vanadium solution is contacted with the hydroxide of an alkali metal to perform a precipitation reaction, and solid-liquid separation is performed to obtain a solid phase product. The purpose of this step is to remove impurities in the raw materials and separate and obtain a solid phase product containing tetravalent vanadium. The reaction system is acidic, and the addition of alkali metal hydroxide causes a precipitation reaction of tetravalent vanadium in the solution. In order to make the reaction effect better and the precipitation reaction more complete, the pH is preferably 2-5.
In the step (2), the alkali metal hydroxide can be a common raw material in this field, with the purpose of adjusting the pH value of the precipitation reaction, preferably NaOH and/or KOH, wherein, the The alkali metal hydroxides can be used in the form of pure substances or in the form of aqueous solutions.
In the step (2), the optional range of the precipitation reaction conditions is wider. In order to make the reaction effect better, the temperature is preferably 15-80°C, and further preferably, the temperature is 15-80°C. 40-70°C, time is 0.1-1 hour.
In the step (3), the solid phase product obtained in step (2) is contacted with oxalic acid. The mass ratio of the oxalic acid to be added to the solid phase product has a wide range of options, and comprehensive Considering cost and yield, preferably, in step (3), the mass ratio of the solid phase product obtained in step (2) to oxalic acid is 1:1-1.4.
In the step (3), the solid phase product obtained in step (2) is contacted with oxalic acid, and then crystallized by conventional methods to obtain vanadyl oxalate crystals, and the final product vanadyl oxalate is separated. Preferably, the conditions for contacting the solid phase product obtained in step (2) with oxalic acid include a temperature of15-40°C, time is 0. 1-0. 5 hours.
According to the method of the present invention, the raw material containing vanadium pentoxide can be a commonly used raw material in this field. In order to further improve the purity of the prepared vanadium oxalate, it is preferred to use a higher purity vanadium pentoxide-containing raw material. The raw material of vanadium oxide, the mass percentage content of V 205 in the raw material is > 99. 8%, the mass percentage content of Si is < 0. 01%, the mass percentage content of TFe is < 0. 02%, and the mass percentage content of P The mass percentage content is <0.005%, the mass percentage content of K is <0.01%, and the mass percentage content of Na is <0.01%.
The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above-mentioned embodiments. Within the scope of the technical concept of the present invention, the technical solutions of the present invention can be implemented in many ways. These simple modifications all belong to the protection scope of the present invention.
In addition, it should be noted that the specific technical features described in the above-mentioned specific embodiments can be combined in any suitable manner as long as they are not inconsistent. In order to avoid unnecessary repetition, Various possible combinations will not be further described in the present invention.
In addition, the various embodiments of the present invention can also be combined in any way. As long as they do not violate the idea of the present invention, they should also be regarded as the disclosed content of the present invention.
The method of the present invention will be further described below in conjunction with examples.
The purity determination method of the vanadium oxalate product prepared in the following examples and comparative examples is to first weigh 2.000g of vanadium oxalate, roast it for 1 hour at 300°C in a muffle furnace, and then use National Standard 8639. 1-1988 Chemical analysis method for vanadium. Potassium permanganate-ferrous sulfate is used to determine TV (total vanadium), and then the vanadium oxalate crystal content is obtained. The formula is vanadium oxalate crystal content % = 3. 3922 (conversion factor) X TV (Weigh the total vanadium content in vanadium oxalate in %).
Put 20g of raw material containing vanadium pentoxide (purchased from Panzhihua Iron and Steel Vanadium Products Factory, main components (by mass): V20 5> 99.8%, Si < 0.01%, TFe < 0. 02%, P < 0.005%, K < 0.01%, Na < 0.01%) is mixed with 75g of 45% sulfuric acid aqueous solution by mass percentage, and at a system temperature of 95°C, 40g of thiosulfate is added to the mixture. Sodium sulfate, the reaction time is 1 hour, obtain the tetravalent vanadium solution, then add NaOH to adjust the pH value to 2 at 70°C, the reaction time is 0.5 hours, generate a precipitate, filter it for solid-liquid separation, and incubate at 25°C Dry under vacuum to obtain 22.02g of solid material, then add 22g of oxalic acid at 25°C to dissolve the solid material, the reaction time is 0.1 hour, and heat to 85°C to crystallize to obtain vanadyl oxalate (the main component is Mass meter VOC2O4.H2099. l%, Si <0.01%, TFe<0.02%, K<0.01%, Na < 0.01%) crystal 37.48g.
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