Vanadyl phosphate ammonium, process for its preparation and process for preparing vanadium phosphorus oxide compounds using it

Abstract

This invention provides ammonium vanadium oxyphosphate, its preparation method, and a method for preparing vanadium phosphate oxides using it. The preparation method of ammonium vanadium oxyphosphate includes the following steps: adding a reducing agent to a vanadium-containing leachate to reduce the vanadium in the solution to an average valence state of 4.5; then adding a phosphorus source and an ammonium source; reacting to form a precipitate; filtering; and washing to obtain ammonium vanadium oxyphosphate NH4(VOPO4)2. The reaction steps of this invention are simple, the reaction conditions are mild, and the reaction process is easily controlled. This invention also discloses a method for preparing vanadium phosphate oxides using ammonium vanadium oxyphosphate, comprising the following steps: reducing and calcining ammonium vanadium oxyphosphate to prepare vanadium pyrophosphate and / or vanadium phosphate; and then oxidizing and calcining to prepare vanadium oxyphosphate. The vanadium oxyphosphate (VOPO4) prepared by this invention has high crystallinity and a large specific surface area (8-20 μm²). 2 / g), which is beneficial to improving the activity of the catalyst.

Description

Technical Field

[0001] This invention relates to materials technology, and more particularly to a vanadium oxyphosphate, its preparation method, and a method for preparing vanadium oxyphosphate compounds using the same. Background Technology

[0002] Vanadium oxyphosphate (VPO) is an important composite oxide that exhibits excellent catalytic performance in reactions such as selective oxidation of low-chain alkanes and ammonia oxidation. Among them, the vanadium oxyphosphate catalyst is currently the only catalyst that has achieved industrial-scale selective oxidation of butane to maleic anhydride.

[0003] Currently, the main methods for preparing vanadium oxyphosphate (VPO) are hydrothermal method and reflux method, which generally have disadvantages such as low purity, long preparation time, and poor material uniformity.

[0004] Furthermore, traditional methods for preparing vanadium oxyphosphate, such as patent CN201410854493.5, which describes a method for preparing vanadium oxyphosphate crystals, include the following steps: (1) dissolving a vanadium source, a phosphorus source, and a carbon-containing organic compound in water to obtain a solution; (2) stirring the solution in a constant temperature water bath at 20–100°C; (3) adjusting the pH to 3–14; (4) heating the solution for 1–72 hours to obtain a gel; (5) vacuum drying to form an amorphous vanadium oxyphosphate precursor; and (6) sintering the solution at 300–750°C for 2–20 hours under an oxidizing atmosphere, followed by cooling to room temperature. These methods suffer from problems such as complex reaction steps, the need for prolonged material drying, high energy consumption, poor gel uniformity, and inconsistent material preparation.

[0005] Therefore, there is an urgent need for a simple and easy-to-implement method for preparing vanadium oxyphosphate. Summary of the Invention

[0006] The purpose of this invention is to address the problems of complex preparation methods, high energy consumption, and poor product uniformity in current methods for preparing vanadium oxyphosphate. This invention proposes a method for preparing vanadium oxyphosphate that is simple and easy to implement, and yields vanadium oxyphosphate with good uniformity, excellent dispersibility, and high activity.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is: a method for preparing vanadium oxyphosphate, comprising the following steps:

[0008] A reducing agent is added to the vanadium-containing leachate to reduce the vanadium in the solution to an average valence state of 4.2-4.7. Then, a phosphorus source and an ammonium source are added, and a precipitate is formed by reaction. The precipitate is filtered and washed to obtain ammonium vanadium phosphate NH4(VOPO4)2.

[0009] Furthermore, the vanadium in the solution was reduced to an average valence state of 4.5.

[0010] Furthermore, the vanadium concentration in the vanadium-containing leachate is 0.1-2 mol / L. The sulfate content in the vanadium-containing leachate is 0.5-3 mol / L.

[0011] Furthermore, the vanadium-containing leachate also includes sodium ions, potassium ions, etc. The sodium ion content is 0.3-1.0 mol / L, and the potassium ion content is 0.01-0.05 mol / L.

[0012] Furthermore, the vanadium-containing leachate is purified before the reaction to reduce the total content of impurity elements to below 0.01 g / L. These impurities include, but are not limited to, Fe, Mn, Cr, Mg, Ca, Al, and Ni.

[0013] Furthermore, the reducing agent is one or more of SO2, sodium metabisulfite, and sodium sulfite.

[0014] Furthermore, the phosphorus source is one or more of phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and phosphorus pentoxide.

[0015] Furthermore, the ammonium source is one or more of ammonia, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, ammonium sulfate, ammonium chloride, and ammonium carbonate.

[0016] Furthermore, the V:P:NH4 content in the vanadium-containing leachate, phosphorus source, and ammonium source... + The molar ratio is 1:1.0-1.5:0.5-2.0, and the preferred molar ratio is 1:1.0-1.3:0.5-1.5.

[0017] Furthermore, the reaction temperature is 50-100℃ and the reaction time is 1-6h; preferably, the reaction temperature is 70-90℃ and the reaction time is 2-4h.

[0018] Taking SO2 as the reducing agent as an example, the reaction principle for preparing ammonium vanadium oxyphosphate in this invention is as follows:

[0019] (VO2)2SO4 + SO2 = 2VOSO4

[0020] (VO2)2SO4+2VOSO4+8NH4OH+4H3PO4=2NH4(VOPO4)2+3(NH4)2SO4+10H2O

[0021] Another object of the present invention discloses a vanadium oxyphosphate prepared by the above preparation method.

[0022] Another object of the present invention discloses a method for preparing vanadium phosphate oxides using the above-mentioned vanadium oxyphosphate ammonium, comprising the following steps:

[0023] Vanadium oxyphosphate and / or vanadium phosphate are prepared by reduction and calcination of ammonium vanadium oxyphosphate.

[0024] Furthermore, the reduction calcination temperature is 400-1000℃, and the reduction calcination time is 1-20h; preferably, the reduction calcination temperature is 500-900℃, and preferably, the reduction calcination time is 1-10h.

[0025] Furthermore, when the reduction calcination temperature is 400-600℃, vanadium oxyphosphate is reduced and calcined to prepare vanadium pyrophosphate. In a reducing atmosphere, vanadium oxyphosphate is calcined at 400-600℃ to reduce vanadium to its tetravalent state, thus preparing vanadium pyrophosphate.

[0026] Furthermore, vanadium phosphate is prepared by reducing and calcining ammonium vanadium oxyphosphate at a reduction calcination temperature of 800-1000℃. In a reducing atmosphere, ammonium vanadium oxyphosphate is calcined at 800-1000℃ to reduce vanadium to its trivalent state, thus preparing vanadium phosphate.

[0027] Furthermore, when the reduction and calcination temperature is greater than 600°C and less than 800°C, the reduction and calcination of ammonium vanadium oxyphosphate yields a mixture of vanadium pyrophosphate and vanadium phosphate.

[0028] Furthermore, the reducing calcination atmosphere is one or more of ammonia, hydrogen, methane, and carbon monoxide.

[0029] Further, the above-mentioned vanadium pyrophosphate and / or vanadium phosphate are oxidized and calcined to prepare vanadium oxyphosphate (VOPO4).

[0030] Furthermore, the oxidation and calcination temperature is 300-700℃, and the oxidation and calcination time is 1-10h; preferably, the oxidation and calcination temperature is 400-500℃, and preferably, the oxidation and calcination time is 3-6h, to prepare vanadium oxyphosphate (VOPO4).

[0031] Furthermore, the oxidizing and calcining atmosphere is oxygen and / or air.

[0032] The vanadium oxyphosphate (VOPO4) can be used in the field of vanadium-based sodium / lithium-ion battery cathode materials.

[0033] The present invention, comprising ammonium vanadium oxyphosphate, its preparation method, and a method for preparing vanadium phosphate oxides therefrom, has the following advantages compared with the prior art:

[0034] 1) This invention produces vanadium oxyphosphate NH4(VOPO4)2 by reduction precipitation using a vanadium-containing source solution (such as a vanadium-containing leachate). The material has good uniformity and uniform particle size distribution.

[0035] 2) The reaction steps of this invention are simple, the reaction conditions are mild, and it is beneficial to control the reaction process;

[0036] 3) The raw materials involved in this invention (such as vanadium and phosphorus sources) are widely available, offer many choices, and are inexpensive;

[0037] 4) This invention first prepares ammonium vanadyl phosphate, then reduces and roasts it to obtain vanadyl pyrophosphate and / or vanadium phosphate, and finally oxidizes and roasts it to obtain vanadyl phosphate (VOPO4). That is, this invention can prepare various vanadium phosphate compounds using ammonium vanadyl phosphate as a raw material. The vanadyl phosphate (VOPO4) prepared by this invention has high crystallinity and a large specific surface area (8-20 μm²). 2 / g), which is beneficial to improving the activity of the catalyst. Attached Figure Description

[0038] Figure 1 The XRD diffraction pattern of the vanadium oxyphosphate prepared in Example 1 is shown below.

[0039] Figure 2 The XRD diffraction pattern of vanadium oxyphosphate prepared in Example 2 is shown. Detailed Implementation

[0040] The present invention will be further described below with reference to the embodiments:

[0041] Example 1

[0042] 1 L of vanadium-containing leaching solution (V concentration 0.8 mol / L) was heated and stirred in a 70 °C water bath. SO2 was introduced into the solution to reduce vanadium to an average valence state of 4.5. Ammonium dihydrogen phosphate was added at a V:P ratio of 1:1 to form ammonium vanadium oxyphosphate precipitate. After filtration and washing twice with pure water, the precipitate was dried at 70 °C for 3 h to obtain ammonium vanadium oxyphosphate.

[0043] The products were analyzed using XRD. The XRD standard card code is 01-070-4618. (See attached image) Figure 1 Vanadium oxyphosphate was prepared.

[0044] Example 2

[0045] Vanadium oxyphosphate was prepared using the ammonium vanadium oxyphosphate prepared in Example 1, and the following steps were included: ammonium vanadium oxyphosphate was placed in an ammonia atmosphere and calcined at 700°C for 2 hours to obtain vanadium phosphate, and then oxidized and calcined at 450°C in an air atmosphere for 4 hours to obtain vanadium oxyphosphate VOPO4.

[0046] The products were analyzed by XRD, see attached. Figure 2 Vanadium oxyphosphate was prepared. After oxidation and calcination, the material exhibited uniform particle distribution and significantly improved crystallinity compared to the precursor, with a specific surface area of ​​10 m². 2 / g.

[0047] Example 3

[0048] 1 L of vanadium-containing leaching solution (V concentration 1.0 mol / L) was heated and stirred in an 80 °C water bath. Sodium metabisulfite was added to reduce vanadium to an average valence state of 4.5. Ammonium dihydrogen phosphate was added at a V:P ratio of 1:1.2 to form ammonium vanadium oxyphosphate precipitate. After filtration and washing with pure water three times, the precipitate was dried at 80 °C for 3 h to obtain ammonium vanadium oxyphosphate.

[0049] Example 4

[0050] 1 L of vanadium-containing leaching solution (V concentration 1.2 mol / L) was heated and stirred in a 90℃ water bath. SO2 was introduced into the solution to reduce vanadium to an average valence state of 4.5. Ammonium dihydrogen phosphate was added at a V:P ratio of 1:1 to form ammonium vanadium oxyphosphate precipitate. After filtration and washing with pure water three times, the precipitate was dried at 90℃ for 2 hours to obtain ammonium vanadium oxyphosphate.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing vanadium phosphorus oxides, characterized in that, Includes the following steps: A reducing agent was added to the vanadium-containing leachate to reduce the vanadium in the solution to an average valence state of 4.

5. Then, a phosphorus source and an ammonium source were added, and the reaction formed a precipitate. The precipitate was filtered and washed to obtain vanadium oxyphosphate ammonium NH4(VOPO4)2. The reducing agent is one or more of SO2, sodium metabisulfite, and sodium sulfite; The reaction temperature is 70-90℃, and the reaction time is 2-4 hours. The vanadium-containing leachate, phosphorus source, and ammonium source contain V:P:NH4 + The molar ratio is 1:1.0-1.5:0.5-2.0; Vanadium oxyphosphate ammonium phosphate was reduced and calcined to prepare vanadium oxyphosphate pyrophosphate and / or vanadium phosphate. When the reduction and calcination temperature is 400-600℃, vanadium oxyphosphate is prepared by reduction and calcination of ammonium vanadium oxyphosphate. Vanadium phosphate is prepared by reducing and calcining ammonium vanadium oxyphosphate at a reduction and calcination temperature of 800-1000℃. When the reduction calcination temperature is greater than 600°C and less than 800°C, the reduction calcination of ammonium vanadium oxyphosphate yields a mixture of vanadium pyrophosphate and vanadium phosphate.

2. The method for preparing vanadium phosphorus oxides according to claim 1, characterized in that, The vanadium concentration in the vanadium-containing leachate is 0.1-2 mol / L.

3. The method for preparing vanadium phosphorus oxides according to claim 1, characterized in that, The phosphorus source is one or more of phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and phosphorus pentoxide; And / or, the ammonium source is one or more of ammonia, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, ammonium sulfate, ammonium chloride, and ammonium carbonate.

4. The method for preparing vanadium phosphorus oxides according to claim 1, characterized in that, Includes the following steps: Vanadium oxyphosphate is prepared by oxidative calcination of the vanadium pyrophosphate and / or vanadium phosphate.

5. The method for preparing vanadium phosphorus oxides according to claim 4, characterized in that, The oxidation and calcination temperature is 300-700℃, and the oxidation and calcination time is 1-10h.

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