A method for efficiently preparing trimanganese tetraoxide

Abstract

The application discloses a method for efficiently preparing trimanganese tetraoxide, and comprises the following steps: adding manganese sulfate solution, composite lye and hydrogen peroxide into a bottom liquid containing an ammonium salt buffer system in parallel flow, and synchronously introducing oxidizing gas; continuously stirring the reaction at 40-60 DEG C for 4-6 hours, filtering, washing and drying the precipitate generated in the reaction to obtain trimanganese tetraoxide product; wherein the reaction maintains the pH value of the reaction system in the range of 8.5-10.5 through the ammonium salt buffer system. Through the process of adding manganese sulfate solution, composite lye and hydrogen peroxide into the bottom liquid containing the ammonium salt buffer system in parallel flow, the preparation efficiency of trimanganese tetraoxide is effectively improved, the generation of intermediate manganese hydroxide can be effectively inhibited, the probability of adsorbing SO4 2‑ , NH4 + of the manganese hydroxide is reduced, the manganese content of the trimanganese tetraoxide product is improved, and the sulfur content in the product is reduced.

Description

Technical Field

[0001] This invention relates to the field of manganese tetroxide preparation technology, and in particular to a method for efficiently preparing manganese tetroxide. Background Technology

[0002] Manganese tetroxide (MTO) is an important functional material widely used in lithium manganese oxide materials, soft magnetic materials, catalysts, and other fields. Especially in the preparation of lithium manganese oxide cathode materials, MTO, as one of the key raw materials, plays a crucial role in influencing the performance of lithium manganese oxide materials due to its purity and particle morphology.

[0003] Chinese patent document CN103172117A discloses a method for preparing manganese tetroxide by liquid-phase oxidation. The method involves first preparing manganese hydroxide precipitate by adding manganese sulfate and ammonia to a reaction vessel, followed by filtration and washing. Then, the manganese hydroxide is slurried with dilute alkaline solution and oxidized by air to obtain manganese tetroxide. This disclosed technology employs a two-step process of "precipitation separation followed by dissolution oxidation," where manganese sulfate reacts with alkaline solution to generate manganese hydroxide precipitate, which is then filtered, washed, and dissolved and oxidized. This method suffers from long reaction cycles and high energy consumption, making it difficult to improve production efficiency and reduce production costs. Furthermore, the manganese hydroxide precipitate easily adsorbs SO4 impurities during the separation process. 2- NH4 + This makes it difficult for manganese hydroxide to be further oxidized to manganese tetroxide, and the purity of manganese tetroxide is difficult to be further improved. Summary of the Invention

[0004] The purpose of this invention is to provide an efficient method for preparing manganese tetroxide, which shortens the reaction cycle of manganese tetroxide, improves the preparation efficiency of manganese tetroxide, and increases the manganese content in the manganese tetroxide product.

[0005] To solve the above-mentioned technical problems, the embodiments of the present invention provide a technical solution as follows: A method for efficiently preparing manganese tetroxide, comprising the following steps: Manganese sulfate solution, compound alkali solution, and hydrogen peroxide are added concurrently to a base solution containing an ammonium salt buffer system, while oxidizing gas is simultaneously introduced. The reaction is continuously stirred at 40-60°C for 4-6 hours. The precipitate generated is filtered, washed, and dried to obtain manganese tetroxide product. The pH value of the reaction system is maintained within the range of 8.5-10.5 by the ammonium salt buffer system.

[0006] Furthermore, the composite alkaline solution is a mixture of ammonia and sodium hydroxide solution, wherein the volume ratio of ammonia to sodium hydroxide solution is (2.5-3.5):1.

[0007] Furthermore, the ammonia solution has a mass concentration of 5%-10%, the sodium hydroxide solution has a concentration of 1-3 mol / L, and the initial pH of the composite alkaline solution is 10-10.5.

[0008] Furthermore, the ammonium salt buffer system is composed of ammonium sulfate and ammonia water, and the initial concentration of ammonium sulfate in the reaction substrate is 10-30 g / L.

[0009] Furthermore, the oxidizing gas is air, and the air introduction rate is 1-2 VVM.

[0010] Furthermore, the concentration of the manganese sulfate solution is 2-4 mol / L, the mass concentration of the hydrogen peroxide is 10%-30%, and the molar ratio of the hydrogen peroxide to the manganese sulfate is 1:(1.2-1.4).

[0011] Furthermore, the feed rate of the manganese sulfate solution is 0.0008-0.0016 VVM; the feed rate of the composite alkali solution is 0.0006-0.001 VVM; and the feed rate of the hydrogen peroxide is 0.0002-0.0004 VVM.

[0012] Furthermore, a composite additive is added to the reaction system, which includes sodium dodecylbenzenesulfonate at a relative mass ratio of 0.1% to 0.2% of the alkali solution and ethylene glycol at a relative mass ratio of 5% to 8% of the alkali solution.

[0013] Furthermore, the drying process is carried out using microwave drying.

[0014] To address the aforementioned technical problems, this invention also provides an efficient method for preparing manganese tetroxide, comprising the following steps: preparing a 2-4 mol / L manganese sulfate solution, a 2-5 mol / L composite alkali solution, and hydrogen peroxide with a mass concentration of 10%-30%, and adding an acidic additive to the manganese sulfate solution; adding ammonium sulfate to the bottom solution of the reaction system, wherein the initial concentration of ammonium sulfate is 10-30 g / L, and bubbling ammonia water to form NH3 / NH4+. 4+ A buffer system is used to control the pH value within the range of 8.5-10.5. The manganese sulfate solution is added to the reactor at 0.0008-0.0016 VVM, the composite alkali solution at 0.0006-0.001 VVM, and hydrogen peroxide at 0.0002-0.0004 VVM, while air is introduced at 1-2 VVM. The reaction is continuously stirred at 40-60℃ for 4-6 hours. When the reaction precipitate turns uniformly reddish-black, the precipitate is filtered, washed, and dried to obtain manganese tetroxide. The manganese tetroxide product has a manganese content of 71.8%-72.0%, a sulfur content ≤0.02%, and a near-spherical morphology.

[0015] The present invention provides an efficient method for preparing manganese tetroxide, which, compared with the existing liquid-phase method for preparing manganese tetroxide, involves the concurrent addition of manganese sulfate solution, composite alkali solution, and hydrogen peroxide to a base solution containing an ammonium salt buffer system, while simultaneously introducing oxygen-containing gas. This process reduces the amount of Mn in the reaction system. 2+ Direct oxidation to manganese tetroxide effectively shortens the overall reaction time and improves production efficiency. The ammonium salt buffer system maintains pH stability, preventing localized over-alkalinity and effectively inhibiting the formation of intermediate manganese hydroxide, thus reducing SO4 adsorption. 2- NH4 + This increases the probability of manganese content in manganese tetroxide products and reduces sulfur content, thereby improving the chemical properties of manganese tetroxide products. Furthermore, the morphology is spherical, exhibiting high uniformity and performance consistency, making it suitable for the preparation of high-end lithium manganese oxide cathode materials and soft magnetic material applications. Attached Figure Description

[0016] One or more embodiments are illustrated by way of example with reference to the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Elements with the same reference numerals in the drawings represent similar elements. Unless otherwise stated, the figures in the drawings do not constitute a limitation on scale.

[0017] Figure 1 This is a flowchart of a method for efficiently preparing manganese tetroxide in an embodiment of the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the various embodiments of this invention will be described in detail below with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been provided in the various embodiments of this invention to facilitate a better understanding of this application. However, the technical solutions claimed in the claims of this application can be implemented even without these technical details and various variations and modifications based on the following embodiments. The terms "comprising," "including," and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that comprises a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or apparatuses.

[0019] It should be noted that VVM, as described in the following embodiments, stands for Volume per Volume per Minute, a unit of volumetric flow rate. Its definition and calculation formula are as follows: VVM = Gas or liquid volumetric flow rate (L / min) / Effective volume of reaction vessel (L).

[0020] like Figure 1 As shown, one embodiment of the present invention relates to a method for efficiently preparing manganese tetroxide, comprising the following steps: Manganese sulfate solution, compound alkali solution, and hydrogen peroxide are added concurrently to a base solution containing an ammonium salt buffer system, while oxidizing gas is simultaneously introduced. The reaction is carried out with continuous stirring at 40-60°C for 4-6 hours. The precipitate generated is filtered, washed, and dried to obtain manganese tetroxide. The pH value of the reaction system is maintained within the range of 8.5-10.5 by the ammonium salt buffer system. Preferably, the washed reaction precipitate is treated by microwave drying. Microwave heating avoids the "hard outside, wet inside" problem of traditional oven drying, reduces particle surface cracking and agglomeration, preserves the spherical morphology, and shortens the drying time by more than 50% compared to traditional oven drying.

[0021] One embodiment relates to a method for efficiently preparing manganese tetroxide. Before adding manganese sulfate solution, a compound alkali solution, and hydrogen peroxide concurrently to a base solution containing an ammonium salt buffer system, it is necessary to first prepare manganese sulfate solution and a compound alkali solution of a certain concentration. The concentration of the manganese sulfate solution is 2–4 mol / L, and the compound alkali solution is a mixture of ammonia and sodium hydroxide solution, with a volume ratio of ammonia to sodium hydroxide solution in the range of (2.5–3.5):1. The mass concentration of ammonia is 5%–10%, the concentration of sodium hydroxide solution is 1–3 mol / L, the concentration of the compound alkali solution is controlled at 2–5 mol / L, and the initial pH value of the compound alkali solution is 10–10.5.

[0022] The ammonium salt buffer system consists of ammonium sulfate and ammonia water. The initial concentration of ammonium sulfate in the reaction solution is 10-30 g / L. Ammonium sulfate (NH4)2SO4 and ammonia water (NH3·H2O) form an NH3 / NH4+ buffer system. 4+ The buffer system can effectively reduce pH fluctuations in the reaction system caused by oxidation, prevent local over-alkaliness, and inhibit the formation of manganese hydroxide Mn(OH)2.

[0023] The ammonia in the compound alkaline solution is weakly alkaline, and it can further react with ammonium sulfate in the reaction system to form NH3 / NH4. + The buffer pair effectively stabilizes the pH value and inhibits the formation of manganese hydroxide (Mn(OH)2); in existing technologies, the OH- provided by ammonia alone is not sufficient. - The capacity is limited, and the ability to control the pH of the reaction system is weak. During the oxidation reaction, a large amount of ammonia water needs to be introduced to maintain or raise the pH of the reaction system to the target range, which leads to the expansion of the reactant volume and reduces production efficiency. The strong alkalinity of sodium hydroxide in the composite alkaline solution can efficiently provide OH-. -The presence of ions helps to efficiently raise the pH of the reaction system to the target range, reducing the amount of alkali input; in the NH3 / NH4+ mixture of ammonium sulfate and ammonia, 4+ The buffer system ensures that the addition of sodium hydroxide does not cause an uncontrolled spike in the pH of the reaction system, keeping the pH precisely stable within the ideal range of 8.5-10.5. Within this range, Mn... 2+ It can be directly oxidized to Mn3O4, inhibiting the formation of manganese hydroxide Mn(OH)2 precipitate and reducing the adsorption of SO4 by manganese hydroxide. 2- NH4 + The probability of increasing sulfur content and decreasing manganese content in manganese tetroxide is reduced; the formation rate of manganese tetroxide is related to OH... - The concentration of ions is relevant; the addition of sodium hydroxide effectively increases the OH- concentration. - Concentration can significantly accelerate Mn 2+ This reduces the oxidation reaction rate, thereby shortening the reaction time and improving equipment utilization and production efficiency.

[0024] Preferably, an acidic additive, such as dilute sulfuric acid, is added to the manganese sulfate solution to adjust and stabilize the pH value of the manganese sulfate solution within a low range, thereby preventing the formation of basic manganese sulfate precipitate and preventing hydrolysis of the manganese sulfate solution during storage and feeding, thus ensuring the stability of the parallel feeding process and the consistency of the product.

[0025] One embodiment relates to a method for efficiently preparing manganese tetroxide, wherein manganese sulfate solution, a composite alkali solution, and hydrogen peroxide are added concurrently to a base solution containing an ammonium salt buffer system, and air is simultaneously introduced as an oxidizing gas. The concentration of the manganese sulfate solution is 2-4 mol / L, the mass concentration of the hydrogen peroxide is 10%-30%, and the molar ratio of hydrogen peroxide to manganese sulfate is 1:(1.2-1.4). Preferably, the mass concentration of hydrogen peroxide is 20%-25%, and the concentration of Mn is adjusted to achieve the desired Mn content. 2+ The oxidation rate is matched with the particle growth rate to avoid excessive local reactions, which is conducive to the formation of a spherical manganese tetroxide product structure with high morphological consistency.

[0026] One embodiment relates to a method for efficiently preparing manganese tetroxide, comprising the following steps: Prepare a 2-4 mol / L manganese sulfate solution, a 2-5 mol / L composite alkali solution, and hydrogen peroxide with a mass concentration of 10%-30%. Add an acidic additive to the manganese sulfate solution. The composite alkali solution is a mixture of ammonia and sodium hydroxide solution, with a volume ratio of ammonia to sodium hydroxide solution in the range of (2.5-3.5):1. The mass concentration of ammonia is 5%-10%, the concentration of sodium hydroxide solution is 1-3 mol / L, and the initial pH value of the composite alkali solution is 10-10.2.

[0027] Ammonium sulfate is added to the bottom liquid of the reaction system. The initial concentration of ammonium sulfate is 10-30 g / L. Ammonia water is then introduced to form NH3 / NH4+. 4+ An ammonium salt buffer system is used to control the pH value within the range of 8.5-10.5; Manganese sulfate solution, alkali solution, and hydrogen peroxide are added concurrently to the base solution containing an ammonium salt buffer system, while air is introduced simultaneously. The feed rate of manganese sulfate solution is controlled at 0.0008-0.0016 VVM; the feed rate of compound alkali solution is 0.0006-0.001 VVM; the feed rate of hydrogen peroxide is 0.0002-0.0004 VVM; and the air introduction rate is 1-2 VVM.

[0028] The reaction system is continuously stirred at 40-60℃ for 4-6 hours. When the precipitate turns uniformly reddish-black, the reaction is stopped. The precipitate is then filtered, washed, and dried to obtain manganese tetroxide. Preferably, a composite additive is added simultaneously to the reaction system along with the manganese sulfate solution. The composite additive includes sodium dodecylbenzenesulfonate at a relative mass ratio of 0.1%-0.2% and ethylene glycol at a relative mass ratio of 5%-8% of the alkali solution. Sodium dodecylbenzenesulfonate acts as a dispersant to regulate the morphology of the precipitate, while ethylene glycol acts as a dispersant to effectively improve the low-temperature dispersion performance of the precipitate and prevent agglomeration. Preferably, the precipitate is filtered and washed multiple times with deionized water until no sulfate ions are detected in the washing liquid. The washed precipitate is then microwave-dried. Microwave heating avoids the "hard outside, wet inside" problem of traditional oven drying, reduces surface cracking and agglomeration of particles, preserves the spherical morphology, and shortens the drying time by more than 50% compared to traditional oven drying. The obtained manganese tetroxide product was tested and found to have a manganese content of 71.8% ≤ 72.0%, a sulfur impurity content of ≤ 0.02%, and a morphology of approximately spherical.

[0029] The efficient method for preparing manganese tetroxide according to the present invention is as follows: A 5L reactor is selected as the reaction vessel. Ammonium sulfate and ammonia are added to the bottom liquid of the reactor, wherein the concentration of ammonium sulfate is 10-30 g / L. Simultaneously, manganese sulfate solution, alkali solution, and hydrogen peroxide are added, wherein the concentration of manganese sulfate solution is 2-4 mol / L, and the feed flow rate is 4-8 mL / min. The composite alkali solution contains ammonia and sodium hydroxide, and the feed flow rate is 3-5 mL / min. The hydrogen peroxide concentration is 10-30 wt%, and the feed flow rate is 1-2 mL / min. Air is simultaneously introduced at a rate of 5-10 L / min. Multiple samples are prepared, and the process parameters are recorded in Table 1 (Manganese Tetroxide Process Parameter Record Table).

[0030] Table 1 Record of Manganese Tetraoxide Process Parameters

[0031] Samples were prepared according to the method and process parameters provided by this invention. The reaction was continuously stirred at 40-60°C until the reaction precipitate was observed to turn into a uniform blackish-red color. The reaction was then completed. The precipitate was filtered and washed multiple times with pure water. The washed precipitate was then dried using microwave to obtain manganese tetroxide product.

[0032] The reaction time and the obtained manganese tetroxide product were tested, and the results are shown in Table 2.

[0033] Table 2. Results of reaction time and physicochemical properties in the preparation of manganese tetroxide

[0034] The efficient method for preparing manganese tetroxide provided by this invention can complete the preparation reaction within 4-6 hours. The obtained manganese tetroxide has a manganese content between 71.8% and 72% and a sulfur content between 0.015% and 0.200%. It has outstanding chemical properties, with a manganese content close to the theoretical manganese content of 72.05%. The sulfur impurity content in the product is ≤0.02%, and the morphology is spherical with high uniformity.

[0035] The present invention provides an efficient method for preparing manganese tetroxide, which, compared with the existing liquid-phase method for preparing manganese tetroxide, involves the concurrent addition of manganese sulfate solution, composite alkali solution, and hydrogen peroxide to a base solution containing an ammonium salt buffer system, while simultaneously introducing oxygen-containing gas. This process reduces the amount of Mn in the reaction system. 2+ Direct oxidation to manganese tetroxide effectively shortens the overall reaction time and improves production efficiency. The ammonium salt buffer system maintains pH stability, preventing localized over-alkalinity and effectively inhibiting the formation of intermediate manganese hydroxide, thus reducing SO4 adsorption. 2- NH4 + This increases the probability of manganese content in manganese tetroxide products and reduces sulfur content, thereby improving the chemical properties of manganese tetroxide products. Furthermore, the morphology is spherical, exhibiting high uniformity and performance consistency, making it suitable for the preparation of high-end lithium manganese oxide cathode materials and soft magnetic material applications.

[0036] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications and improvements without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be defined by the claims.

Claims

1. A method for efficiently preparing manganese tetroxide, characterized in that, Includes the following steps: Manganese sulfate solution, compound alkali solution and hydrogen peroxide are added concurrently to the bottom liquid containing an ammonium salt buffer system, and oxidizing gas is introduced simultaneously. The reaction was continuously stirred at 40~60℃ for 4~6 hours. The precipitate generated by the reaction was filtered, washed and dried to obtain manganese tetroxide product. The reaction is carried out by using an ammonium salt buffer system to maintain the pH value of the reaction system within the range of 8.5-10.

5.

2. The method for efficiently preparing manganese tetroxide according to claim 1, characterized in that, The composite alkaline solution is a mixture of ammonia and sodium hydroxide solution, wherein the volume ratio of ammonia to sodium hydroxide solution is (2.5-3.5):

1.

3. The method for efficiently preparing manganese tetroxide according to claim 2, characterized in that, The ammonia solution has a mass concentration of 5%-10%, the sodium hydroxide solution has a concentration of 1-3 mol / L, and the initial pH of the composite alkaline solution is 10-10.

5.

4. The method for efficiently preparing manganese tetroxide according to claim 1, characterized in that, The ammonium salt buffer system consists of ammonium sulfate and ammonia water, and the initial concentration of ammonium sulfate in the reaction substrate is 10-30 g / L.

5. The method for efficiently preparing manganese tetroxide according to claim 1, characterized in that, The oxidizing gas is air, and the air introduction rate is 1-2 VVM.

6. The method for efficiently preparing manganese tetroxide according to claim 1, characterized in that, The concentration of the manganese sulfate solution is 2-4 mol / L, the mass concentration of the hydrogen peroxide is 10%-30%, and the molar ratio of the hydrogen peroxide to the manganese sulfate is 1:(1.2-1.4).

7. The method for efficiently preparing manganese tetroxide according to claim 1, characterized in that, The feed rate of the manganese sulfate solution is 0.0008-0.0016 VVM; the feed rate of the composite alkali solution is 0.0006-0.001 VVM; and the feed rate of the hydrogen peroxide is 0.0002-0.0004 VVM.

8. The method for efficiently preparing manganese tetroxide according to claim 1, characterized in that, A composite additive is also added to the reaction system, which includes sodium dodecylbenzenesulfonate at a relative mass ratio of 0.1% to 0.2% of the alkali solution and ethylene glycol at a relative mass ratio of 5% to 8% of the alkali solution.

9. The method for efficiently preparing manganese tetroxide according to claim 1, characterized in that, The drying process is carried out using microwave drying.

10. A highly efficient method for preparing manganese tetroxide, characterized in that, The process includes the following steps: preparing a 2-4 mol / L manganese sulfate solution, a 2-5 mol / L composite alkali solution, and hydrogen peroxide with a mass concentration of 10%-30%, and adding an acidic additive to the manganese sulfate solution; adding ammonium sulfate to the bottom solution of the reaction system, wherein the initial concentration of ammonium sulfate is 10-30 g / L, and bubbling ammonia water to form NH3 / NH4+. 4+ A buffer system is used to control the pH value within the range of 8.5-10.

5. The manganese sulfate solution is added to the reactor at 0.0008-0.0016 VVM, the composite alkali solution at 0.0006-0.001 VVM, and hydrogen peroxide at 0.0002-0.0004 VVM, while air is introduced at 1-2 VVM. The reaction is continuously stirred at 40-60℃ for 4-6 hours. When the reaction precipitate turns uniformly reddish-black, the precipitate is filtered, washed, and dried to obtain manganese tetroxide. The manganese tetroxide product has a manganese content of 71.8%-72.0%, a sulfur content ≤0.02%, and a near-spherical morphology.

Images