Preparation method of low-valence vanadium oxide

Abstract

The invention discloses a preparation method of a low-valence vanadium oxide, which comprises the following steps: adding V2O5 and H2C2O4. 2H2O into distilled water, and heating until boiling; dropwise adding hydrochloric acid into the obtained reaction system, heating and boiling, then dropwise adding N2H4.H2O, and stirring at the same time until the reaction system becomes a dark blue VOCl2 solution; introducing CO2 protective gas into the saturated NH4HCO3 solution, simultaneously dropwise adding the VOCl2 solution obtained in the step 3 in the atmosphere of the protective gas, fully mixing, transferring into a closed container, standing, crystallizing, and filtering to obtain a purple intermediate (NH4) 3 [(VO) 6 (CO) 4 (OH) 9]. 10H2O; flatly laying the obtained intermediate in a quartz boat, then putting the quartz boat into a tubular furnace, sequentially introducing high-purity nitrogen and high-purity hydrogen, and roasting to obtain a low-valence vanadium oxide; and the low-valence vanadium oxide comprises VO2 and V2O3.

Description

Technical Field

[0001] The present invention relates to the technical field of vanadium metallurgy, and more specifically, to a method for preparing low-valence vanadium oxides. Background Art

[0002] The comprehensive utilization process of vanadium resources in Pangang mainly uses vanadium-titanium magnetite as raw material. After beneficiation, the obtained vanadium-titanium magnetite concentrate will be sintered and then enter the blast furnace process. In this process, most vanadium oxides will be reduced into vanadium-containing hot metal. Subsequently, through the converter blowing process, the vanadium in it is selectively oxidized to obtain high-grade vanadium slag, realizing the separation of vanadium slag and hot metal. Finally, through a series of operations such as roasting, leaching, vanadium precipitation, and calcination of the vanadium slag, a V2O5 product is obtained. At present, the main vanadium extraction processes applied industrially are calcium calcification-acid leaching vanadium extraction and sodium calcification-water leaching vanadium extraction, and the vanadium recovery rates are 87% and 90% respectively. However, the recovery rate of vanadium elements still needs to be further improved. To achieve this goal, it is first necessary to clarify the main mineral phase factors affecting the recovery of vanadium elements in vanadium slag.

[0003] By deeply studying the relevant literatures of domestic and foreign scientific workers and combining with the previous research on the phase transformation behavior in the vanadium extraction process of Pangang vanadium-titanium, the applicant found that the main mineralogical factor affecting the recovery of vanadium elements is the Fe2TiO5 phase containing vanadium. However, at present, the solid solution mode of vanadium elements and other elements in this phase, and whether this solid solution mode is related to the valence state of vanadium are still unclear. It should be noted that in the vanadium spinel in Pangang vanadium slag itself, vanadium elements exist in the form of coexistence of +3 valence and +4 valence.

[0004] In order to be used to study the solid solution behavior of vanadium with different valence states in vanadium slag and provide a theoretical basis for the subsequent optimization of the vanadium extraction process system and phase design, therefore, the preparation of low-valence vanadium oxides has become a research hotspot for domestic and foreign scientific research institutions. Summary of the Invention

[0005] The purpose of the present invention is to overcome the above-mentioned defects existing in the prior art and provide a method for preparing low-valence vanadium oxides, aiming to provide a key raw material for studying the solid solution behavior of vanadium with different valence states in vanadium slag. This method not only helps to deeply understand the solid solution characteristics of vanadium in the Fe2TiO5 phase, but also can provide a solid theoretical basis for the subsequent optimization of the vanadium extraction process and phase design, thereby maximizing the comprehensive recovery rate of vanadium elements. Through this method, it can provide strong technical support for the green vanadium extraction technology of vanadium-titanium magnetite in China, and at the same time promote the sustainable development of the vanadium metallurgy industry in China. In addition, this preparation process has broad popularization and application value, and is applicable to scientific research institutions and universities producing VO2 and V2O3, providing a new idea and reference for the research in related fields.

[0006] To achieve the above object, the technical solution of the present invention is as follows:

[0007] A preparation method of low-cost vanadium oxide, comprising the following steps:

[0008] Step 1, adding V2O5 and H2C2O4·2H2O into distilled water, and heating at 100°C to 110°C for 5 to 10 minutes;

[0009] Step 2, adding hydrochloric acid dropwise into the reaction system of Step 1, and heating at 100°C to 110°C for 20 to 30 minutes;

[0010] Step 3, adding N2H4·H2O dropwise into the reaction system of Step 2, while stirring, and the reaction system becomes a dark blue VOCl2 solution;

[0011] Step 4, introducing a CO2 protective gas into the saturated NH4HCO3 solution, and under the atmosphere of the protective gas, while adding dropwise the VOCl2 solution obtained in Step 3, fully mixing and then transferring to a closed container for static crystallization, and filtering to obtain a purple intermediate (NH4)3[(VO)6(CO)4(OH)9]·10H2O;

[0012] In Step 5, spreading the intermediate obtained in Step 4 on a quartz boat, then placing it in a tube furnace, successively introducing high-purity nitrogen and high-purity hydrogen and then performing roasting to obtain the low-cost vanadium oxide; the low-cost vanadium oxide includes VO2 and V2O3.

[0013] Optionally, in Step 1 and Step 5, roasting the tube furnace at 600°C for 30 minutes to obtain pure VO2 substance, or roasting the tube furnace at 650°C for 60 minutes to obtain pure V2O3 substance.

[0014] Optionally, in Step 1, the mass-volume ratio of V2O5, H2C2O4·2H2O and distilled water is 10:6.2:(5 - 10) (g / mL).

[0015] Optionally, in Step 2, the concentration of the hydrochloric acid is 1:1 (v / v); the addition amount of the hydrochloric acid is 50 mL, and the volume ratio of the concentrated hydrochloric acid to water is 1:1.

[0016] Optionally, in Step 3, the time for introducing the CO2 protective gas is ≥15 minutes.

[0017] Optionally, in Step 3, the addition amount of N2H4·H2O is 5 drops, and the volume fraction is 0.25 mL.

[0018] Optionally, in Step 4, the addition amount of the VOCl2 solution is 8 mL.

[0019] Optionally, in step 4, the standing crystallization time is 24 hours to 30 hours.

[0020] Optionally, in step 5, the tiling thickness is ≤5 mm.

[0021] Implementing the embodiments of the present invention will have the following beneficial effects:

[0022] The present invention proposes an innovative technology for preparing low-valent vanadium oxides (VO2 and V2O3). Through the effective coordination of carefully designed steps and processes, the characteristics of the intermediate decomposition products at different temperatures are fully utilized to achieve the goal of simultaneously preparing two vanadium oxide products in one method. Compared with the traditional method of adding a reducing agent (such as H2 or C) through V2O5, the present invention can obtain VO2 and V2O3 products with higher purity, effectively avoiding the problem of high impurity content caused by the introduction of reducing agents, and significantly improving the purity and quality of the products. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the XRD diagram of the product obtained in Example 1 of the present invention.

[0024] Figure 2 This is the XRD diagram of the product obtained in Example 2 of the present invention. DETAILED DESCRIPTION

[0025] The present invention is further described below in conjunction with specific embodiments, but the present invention is not limited in any way.

[0026] The present invention discloses a method for preparing low-valent vanadium oxide, comprising the following steps:

[0027] Step 1, adding V2O5 and H2C2O4·2H2O into distilled water, and heating at 100°C to 110°C for 5 to 10 minutes.

[0028] Step 2, adding hydrochloric acid dropwise into the reaction system of step 1, and heating at 100° C. to 110° C. for 20 min to 30 min.

[0029] Step 3, adding N2H4·H2O dropwise into the reaction system of step 2 while stirring, and the reaction system turns into a dark blue VOCl2 solution.

[0030] Step 4, passing CO2 protective gas into the saturated NH4HCO3 solution, and under the protective gas atmosphere, adding the VOCl2 solution obtained in step 3 dropwise, after fully mixing, moving to a sealed container and standing for crystallization, and filtering to obtain the purple intermediate (NH4)3[(VO)6(CO)4(OH)9]·10H2O.

[0031] In Step 5, the intermediate obtained in Step 4 is laid flat in a quartz boat and then placed in a tube furnace. After sequentially introducing high-purity nitrogen and high-purity hydrogen, roasting is carried out to obtain low-valent vanadium oxides; the low-valent vanadium oxides include VO2 and V2O3.

[0032] In a specific embodiment, in Step 1, in Step 5, the tube furnace is roasted at 600 °C for 30 min to obtain pure VO2 substance, or the tube furnace is roasted at 650 °C for 60 min to obtain pure V2O3 substance.

[0033] In a specific embodiment, in Step 1, the mass-volume ratio of V2O5, H2C2O4·2H2O, and distilled water is 10:6.2:(5 - 10) (g / mL).

[0034] In a specific embodiment, in Step 2, the concentration of hydrochloric acid is 1:1 (v / v);

[0035] In a specific embodiment, the addition amount of hydrochloric acid is 50 mL, and the volume ratio is: concentrated hydrochloric acid: water = 1:1.

[0036] In a specific embodiment, in Step 3, the time for introducing CO2 protective gas is ≥15 min.

[0037] In a specific embodiment, in Step 3, the addition amount of N2H4·H2O is 5 drops, and the volume fraction is 0.25 mL.

[0038] In a specific embodiment, in Step 4, the addition amount of VOCl2 solution is 8 mL.

[0039] In a specific embodiment, in Step 4, the time for static crystallization is 24 h - 30 h.

[0040] In a specific embodiment, in Step 5, the laying thickness ≤5 mm.

[0041] The following are specific embodiments

[0042] Example 1

[0043] The preparation method of the intermediate in this embodiment comprises the following steps: Weigh 20 g of an analytical pure V2O5 sample (purity > 99%) and 12 g of an H2C2O4·2H2O sample, mix them evenly and place them in a sealed conical flask. Add 18 mL of distilled water to the conical flask, heat it to boiling, quickly add 100 mL of HCl (concentration 1:1 (v / v)) and 10 drops (10 drops cannot clearly express its specific addition amount. It should be modified to the specific total addition amount or the amount per drop should be defined) of N2H4·H2O. After cooling for 20 min, then take 25 mL of the coolant and transfer it to a sealed flask containing a saturated NH4HCO3 solution under a CO2 protective atmosphere. Shake it well and let it stand for 24 h. Finally, heat the crystals to 650 °C in a high-purity nitrogen atmosphere and keep them at this temperature for 60 min to obtain the calcined product A. Perform XRD analysis on the phase of the obtained calcined product A, and the results are as Figure 1 shown.

[0044] From Figure 1 the XRD phase results in it, it can be known that the product A is very pure V2O3

[0045] Example 2

[0046] The preparation method of the low-valent vanadium oxide in this embodiment comprises the following steps:

[0047] The preparation method of the intermediate in this embodiment comprises the following steps: Weigh 20 g of an analytical pure V2O5 sample (purity > 99%) and 12 g of an H2C2O4·2H2O sample, mix them evenly and place them in a sealed conical flask. Add 18 mL of distilled water to the conical flask, heat it to boiling, quickly add 100 mL of HCl (concentration 1:1 (v / v)) and 10 drops (10 drops cannot clearly express its specific addition amount. It should be modified to the specific total addition amount or the amount per drop should be defined) of N2H4·H2O. After cooling for 20 min, then take 25 mL of the coolant and transfer it to a sealed flask containing a saturated NH4HCO3 solution under a CO2 protective atmosphere. Shake it well and let it stand for 24 h. Finally, spread the crystals flat in a quartz boat, with the spreading thickness ≤ 5 mm, and then put it into a tubular furnace. First, introduce high-purity nitrogen for 15 min and then high-purity hydrogen for 15 min, and then carry out calcination. Set the calcination temperatures to 600 °C and 650 °C respectively, set the heating rate to 10 °C / min, and set the holding times to 30 min and 60 min respectively to obtain product B and product C. Perform XRD phase analysis on them, and the results are as Figure 2 shown.

[0048] From Figure 2 the XRD phase results in it, it can be known that both product B and product C are relatively pure VO2 and V2O3.

[0049] In summary, the present invention proposes an innovative technology for preparing low-cost vanadium oxides (VO2 and V2O3). Through the effective cooperation of carefully designed steps of each process, making full use of the characteristics of the decomposition products of the intermediate at different temperatures, the goal of simultaneously preparing two vanadium oxide products by one method is achieved. Compared with the traditional method of adding a reducing agent (such as H2 or C) to V2O5, the present invention can obtain VO2 and V2O3 products with higher purity, effectively avoiding the problem of high impurity content caused by the introduction of the reducing agent, and significantly improving the purity and quality of the products.

[0050] The above-described embodiments merely represent several implementation manners of the present invention. The description thereof is relatively specific and detailed, but it should not be construed as a limitation on the scope of the patent application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A method for preparing low-valent vanadium oxide, characterized in that: The following steps are involved: Step 1, adding V2O5 and H2C2O4·2H2O into distilled water, and heating at 100°C to 110°C for 5 to 10 minutes; Step 2, adding hydrochloric acid dropwise into the reaction system of step 1, and heating at 100° C. to 110° C. for 20 min to 30 min; Step 3, adding N2H4·H2O dropwise into the reaction system of step 2 while stirring, and the reaction system turns into a dark blue VOCl2 solution; Step 4, introducing CO2 protective gas into the saturated NH4HCO3 solution, and under the protective gas atmosphere, adding the VOCl2 solution obtained in step 3 dropwise, mixing thoroughly, and then transferring to a sealed container to stand and crystallize, and filtering to obtain a purple intermediate (NH4)3[(VO)6(CO)4(OH)9]·10H2O; In step 5, the intermediate obtained in step 4 is spread flat in a quartz boat, and then placed in a tubular furnace, and high-purity nitrogen and high-purity hydrogen are introduced in sequence and then calcined to obtain the low-valent vanadium oxide; the low-valent vanadium oxide includes VO2 and V2O3.

2. The method for preparing low-valent vanadium oxide according to claim 1, characterized in that: In step 1 and step 5, the tube furnace is calcined at 600° C. for 30 minutes to obtain pure VO2, or the tube furnace is calcined at 650° C. for 60 minutes to obtain pure V2O3.

3. The method for preparing low-valent vanadium oxide according to claim 1, characterized in that: In step 1, the mass volume ratio of V2O5, H2C2O4·2H2O and distilled water is 10:6.2:(5-10) (g / mL).

4. The method for preparing low-valent vanadium oxide according to claim 1, characterized in that: In step 2, the concentration of the hydrochloric acid is 1:1 (v / v); The amount of hydrochloric acid added is 50 mL.

5. The method for preparing low-valent vanadium oxide according to claim 1, characterized in that: In step 3, the time for introducing CO2 protective gas is ≥15min.

6. The method for preparing low-valent vanadium oxide according to claim 1, characterized in that: In step 3, the amount of N2H4·H2O added is 5 drops, and the volume fraction is 0.25 mL.

7. The method for preparing low-valent vanadium oxide according to claim 1, characterized in that: In step 4, the amount of VOCl2 solution added is 8 mL.

8. The method for preparing low-valent vanadium oxide according to claim 1, characterized in that: In step 4, the crystallization time is 24 hours to 30 hours.

9. The method for preparing low-valent vanadium oxide according to claim 1, characterized in that: In step 5, the tiling thickness is ≤5mm.

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