JP2014218390A - Method for producing trimanganese tetraoxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method which can produce trimanganese tetraoxide in higher efficiency than conventional production methods.SOLUTION: A method for producing trimanganese tetraoxide comprises a crystallization process where manganese tetraoxide is crystallized from a manganese salt aqueous solution containing manganese ions without passing through manganese hydroxide. By a production process of trimanganese tetraoxide which, in the crystallization process, includes crystallization of trimanganese tetraoxide with an overall volumetric oxygen transfer coefficient set at 2.2 minor more, trimanganese tetraoxide can be produced in higher efficiency.

Description

  The present invention relates to a method for producing trimanganese tetraoxide used as a raw material for a lithium manganese composite oxide. In detail, it is related with the manufacturing method of trimanganese tetraoxide which can crystallize trimanganese tetraoxide more efficiently.

  Since manganese tetraoxide has a high theoretical density among manganese oxides, it has been attracting attention as a manganese raw material from which a lithium-manganese composite oxide having a high filling property can be obtained.

  For example, manganese trioxide obtained by obtaining manganese hydroxide from a manganese complex salt obtained by reacting manganese ions with a complexing agent in an aqueous solution and oxidizing the manganese hydroxide is reported. (Patent Document 1).

  Further, trimanganese tetraoxide having a tap density of 1.6 g / mL or more obtained by direct crystallization from manganese ions has been reported (Patent Document 2).

JP 2001-114521 A International Publication 2012 / 046735A1

  In the production method described in Patent Document 1, a complexing agent and manganese ions are aged to obtain manganese hydroxide, which is then oxidized to obtain trimanganese tetraoxide. In the manufacturing method of trimanganese tetraoxide that oxidizes manganese hydroxide, when manganese hydroxide is not sufficiently oxidized, manganese oxide having a layer structure is by-produced, and the tap density of the resulting manganese oxide is lowered. In addition to this, cations and anions in the reaction slurry are taken in between the layers, increasing the amount of impurities.

  The production method described in Patent Document 2 can produce manganese trioxide from manganese ions without going through manganese hydroxide, aging time of manganese hydroxide, and switching of atmosphere from the aging process to the oxidation process Do not need. Therefore, compared with the manufacturing method which oxidizes manganese hydroxide, trimanganese tetraoxide can be obtained efficiently.

  However, in order to respond to the recent increase in demand for lithium manganese composite oxides, it is required to produce manganese trioxide with higher efficiency. Therefore, an object of this invention is to provide the manufacturing method which can manufacture trimanganese tetroxide with higher efficiency than the conventional manufacturing method.

  The inventors of the present invention have made extensive studies on a method for producing manganese trioxide from manganese ions without producing manganese hydroxide through a manganese hydroxide, and a method capable of producing this with higher efficiency.

  The crystallization of manganese ions is promoted by strengthening a reducing or oxidizing atmosphere, or by using a reducing agent having a strong reducing power or an oxidizing agent having a strong oxidizing power. Therefore, when crystallization of manganese oxide from manganese ions, this is promoted by using an oxidizing agent having a strong oxidizing atmosphere or a strong oxidizing power. However, the present inventors, in the case of crystallizing manganese trioxide from manganese ions without going through manganese hydroxide, do not require strong atmosphere control or use of a special oxidizing agent. It has been found that crystallization of manganese oxide can be promoted. Furthermore, the present inventors pay attention to the overall oxygen transfer capacity coefficient, and crystallize manganese trioxide while controlling this, thereby promoting crystallization of manganese trioxide per unit volume and unit time. As a result, the present invention has been completed.

That is, the present invention is a method for producing trimanganese tetraoxide having a crystallization step of crystallizing trimanganese tetraoxide from an aqueous manganese salt solution containing manganese ions without going through manganese hydroxide, In the crystallization step, the manganese tetroxide is crystallized with a total oxygen transfer capacity coefficient of 2.2 min ⁻¹ or more, and is a method for producing trimanganese tetroxide.

  Hereinafter, the method for producing trimanganese tetraoxide of the present invention will be described.

  In the method for producing trimanganese tetraoxide of the present invention, in the crystallization step, a manganese salt aqueous solution containing manganese ions (hereinafter, simply referred to as “manganese salt aqueous solution”) can be used without passing through manganese hydroxide. Crystallize manganese trioxide.

In the crystallization process, “without going through manganese hydroxide” means not only the form in which manganese hydroxide does not occur at all, but also quaternary oxidation before the growth of hexagonal plate-like crystal particles of manganese hydroxide. Includes forms that convert to manganese. Therefore, the crystallization step in the production method of the present invention is a step in which manganese ions (Mn ²⁺ ) crystallize trimanganese tetroxide without going through manganese hydroxide, or sufficient crystal growth of manganese hydroxide. Any process may be used as long as it crystallizes trimanganese tetraoxide under the conditions suppressed.

  In the conventional production method, it was necessary to produce manganese hydroxide under a reducing atmosphere, and then oxidize the manganese hydroxide under an oxidizing atmosphere to produce trimanganese tetraoxide. On the other hand, in the crystallization step in the production method of the present invention, trimanganese tetraoxide can be crystallized from manganese ions without changing the atmosphere. Therefore, in the crystallization step in the production method of the present invention, trimanganese tetraoxide can be continuously produced.

In the crystallization process, trimanganese tetraoxide is crystallized with an overall oxygen transfer capacity coefficient of 2.2 min ⁻¹ or more. The larger the overall oxygen transfer capacity coefficient, the faster the crystallization rate of trimanganese tetraoxide, and the more efficient production of trimanganese tetraoxide. Therefore, it is preferred that the overall volumetric oxygen transfer coefficient is 2.5 min ^-1 or more, more preferably 3min ^-1 or more, more preferably 3.3Min ^-1 or more.

  The overall oxygen transfer capacity coefficient in the present invention is a value that represents the state of the aqueous manganese salt solution when trimanganese tetroxide is crystallized. The manganese salt aqueous solution here includes a manganese salt aqueous solution containing crystallized manganese trioxide (hereinafter also referred to as “trimanganese tetraoxide slurry” or “reaction slurry”).

The overall oxygen transfer capacity coefficient can be determined by the following method. That is, water or an aqueous solution having a dissolved oxygen concentration of 0.01 volume ppm or less is stirred, and air is blown until the dissolved oxygen concentration of the aqueous solution or the like is substantially saturated. At this time, the elapsed time (t) from the start of air blowing and the dissolved oxygen concentration of the aqueous solution at the time t are measured. The measurement is performed at 30 points or more until the dissolved oxygen concentration is substantially saturated. From the relationship between the dissolved oxygen concentration (C _St ) and the saturated oxygen concentration (C _L ) at t, the coefficient (X _t ) at the _t was obtained from the following equation.

_{X t = -ln (C L -C} St)

To obtain a straight line by linear approximation by a least square method the value of X _t at each elapsed time t over 30 points, with the slope of the resulting straight line can be summarized oxygen transfer capacity coefficient. The saturated oxygen concentration C _L depends on the temperature of the aqueous solution and the oxygen partial pressure. For example, when the temperature of the aqueous solution is 80 ° C. and air is blown at atmospheric pressure, C _L becomes 2.86 ppm by volume.

  In the crystallization step, the overall oxygen transfer capacity coefficient tends to increase by stirring the aqueous manganese salt solution. Therefore, in the crystallization step, it is preferable to crystallize trimanganese tetraoxide while stirring an aqueous manganese salt solution or the like.

As the power required for stirring increases, the overall oxygen transfer capacity coefficient tends to increase. The power required for stirring is power for stirring the aqueous manganese salt solution. In the crystallization step, the stirring power requirement of 1.4 kW / ^{m 3} or more, further 1.5 kW / ^{m 3} or more, and more preferably be crystallized trimanganese tetraoxide as 1.8 kW / ^{m 3} or more . On the other hand, since the particle size of trimanganese tetraoxide is appropriately increased, the power required for stirring is 6 kW / m ³ or less, further 4.8 kW / m ³ or less, further 4 kW / m ³ or less, or even 3 kW / It is preferable to crystallize trimanganese tetraoxide as m ³ or less.

  In the crystallization step, the manganese salt aqueous solution preferably contains an appropriate concentration of oxygen. In the crystallization step, the dissolved oxygen concentration is preferably 0.2 volume ppm or more, more preferably 0.3 volume ppm or more, still more preferably 0.6 volume ppm or more, and even more preferably 1.0 volume ppm or more. .

  In the crystallization step, it is preferable to crystallize manganese trioxide from an aqueous manganese salt solution while blowing an oxygen-containing gas. By blowing the oxygen-containing gas, the overall oxygen transfer capacity coefficient is easily within the range of the present invention. Examples of the oxygen-containing gas include oxygen gas and air. For simplicity, the oxygen-containing gas is preferably air.

  In order to obtain the overall oxygen transfer capacity coefficient of the present invention, the amount of oxygen-containing gas blown into the manganese salt aqueous solution in the crystallization step is 10 L / min or more, more preferably 20 L / min or more, or even 30 L / min or more. Is mentioned.

In the crystallization step, as a method of crystallizing manganese trioxide from an aqueous manganese salt solution without passing through a manganese hydroxide, manganese ions (Mn ²⁺ ) in the aqueous manganese salt solution and hydroxide ions in the aqueous alkaline solution ( A method of mixing an aqueous manganese salt solution and an aqueous alkaline solution while controlling the ratio to OH ⁻ ) (OH ⁻ / Mn ²⁺ ; hereinafter referred to as “manganese molar ratio”) can be mentioned.

Examples of the manganese salt aqueous solution include an aqueous solution of a manganese compound containing manganese ions (Mn ²⁺ ), such as manganese sulfate, manganese chloride, manganese nitrate, and manganese acetate, or metal manganese, manganese oxide, and the like. And aqueous solutions dissolved in various acid aqueous solutions. On the other hand, examples of the alkaline solution include aqueous solutions of alkali metal hydroxides such as sodium hydroxide and potassium hydroxide. In addition, it is preferable not to use the alkaline solution containing the compound which has the complexing ability which forms complexes, such as ammonia.

  In the crystallization step, when the manganese salt aqueous solution and the alkaline aqueous solution are mixed, it is preferable to mix the two so that the manganese molar ratio is 0.55 or less, and further 0.5 or less. By setting the manganese molar ratio within this range, the relative standard deviation of the particle size of the resulting trimanganese tetroxide tends to be small. That is, it becomes easy to obtain trimanganese tetraoxide particles having a uniform particle diameter.

  The mixing method of the manganese salt aqueous solution and the alkaline aqueous solution is not particularly limited as long as both can be uniformly mixed. Examples of the mixing method include a method in which an alkaline aqueous solution is added to a manganese salt aqueous solution and mixed, a method in which a manganese salt aqueous solution and an alkaline aqueous solution are added to a solvent such as pure water, and the like. In order to sufficiently and uniformly mix the manganese salt aqueous solution and the alkaline aqueous solution, the mixing method is preferably a method in which the manganese salt aqueous solution and the alkaline aqueous solution are added to pure water and mixed. In addition, when adding and mixing a manganese salt aqueous solution and an alkaline aqueous solution in pure water, the pure water becomes an aqueous solution containing manganese ions, that is, a manganese salt aqueous solution by mixing the manganese salt aqueous solution with the pure water. Manganese ions contained therein crystallize as trimanganese tetraoxide.

  In the crystallization step, the oxidation-reduction potential (hereinafter simply referred to as “oxidation-reduction potential”) with respect to the standard hydrogen electrode when mixing the manganese salt aqueous solution and the alkaline aqueous solution is 0 mV or more, further 30 mV or more, or even 50 mV or more. It is preferable that When the oxidation-reduction potential of the manganese salt aqueous solution is within this range, manganese oxides other than trimanganese tetraoxide are less likely to be by-produced. On the other hand, when the oxidation-reduction potential is 300 mV or less, further 200 mV or less, and further 180 mV or less, the filling property of the obtained trimanganese tetraoxide tends to be high.

  The redox potential of the aqueous manganese salt solution is within these ranges, and it is preferable that it is constant. Here, in the present invention, the constant redox potential may be within the range of ± 50 mV, further ± 30 mV, or even ± 20 mV.

  The crystallization temperature in the crystallization step may be 40 ° C. or higher, further 60 ° C. or higher, and further 70 ° C. or higher. On the other hand, if the crystallization temperature is 95 ° C. or lower, and further 90 ° C. or lower, the fluctuation of manganese ion concentration in the manganese salt aqueous solution due to evaporation of the manganese salt aqueous solution becomes small.

  In the crystallization step, the manganese salt aqueous solution crystallized with trimanganese tetroxide, that is, the slurry containing crystallized trimanganese tetroxide may be stirred to allow the trimanganese tetroxide to stay in the slurry. . Examples of the average residence time of trimanganese tetraoxide in the slurry include 6 hours or more, and further 8 hours or more.

  In the crystallization step, crystallization of trimanganese tetraoxide from an aqueous manganese salt solution can be performed continuously. When crystallization is performed continuously, a part of the slurry having the same amount as the manganese salt aqueous solution to be mixed may be drained out of the system. Thereby, crystallization can be performed continuously while keeping the average residence time of trimanganese tetraoxide in the slurry within the above range. Therefore, the crystallization time in the crystallization step can be 50 hours or longer, and further 100 hours or longer.

  In the crystallization process, the complexing agent affects the crystallization behavior of trimanganese tetraoxide. Therefore, in the crystallization step, it is preferable to crystallize trimanganese tetraoxide in an atmosphere in which the complexing agent is not substantially present. Examples of complexing agents include ammonia, ammonium salts, hydrazine, and EDTA.

  The production method of the present invention may include a filtration and washing step, a drying step, or both after the crystallization step.

  In the filtration and washing steps, trimanganese tetraoxide is recovered from the reaction slurry. As a washing method, the crystallized manganese trioxide is filtered and solid-liquid separated, and this is washed with pure water or the like.

  In the drying step, the water content of trimanganese tetraoxide after crystallization or after filtration and washing is removed. As a drying method, it is possible to put trimanganese tetraoxide in air at about 100 ° C. to 120 ° C. for about 5 to 24 hours.

  According to the production method of the present invention, it is possible not only to produce manganese trioxide having a high filling property, but also to carry out additional sizing treatment such as classification and pulverization, and to have a uniform particle size distribution. Can be manufactured. Therefore, the production method of the present invention does not need to include a sizing step such as pulverization or classification for adjusting the particle diameter of manganese trioxide.

According to the present invention, it is possible to provide a method for producing trimanganese tetraoxide having a high crystallization rate of 7 kg / (m ³ · hr) or more, further 8 kg / (m ³ · hr) or more.

  In the production method of the present invention, trimanganese tetraoxide having a high filling property and a uniform particle size can be obtained.

  Manganese tetroxide obtained by the production method of the present invention has a spinel structure. The chemical formula is preferably MnOx (where 1.20 ≦ x ≦ 1.40, preferably 1.25 ≦ X ≦ 1.35).

  The spinel structure is the JCPDS pattern no. This is a structure showing an XRD pattern equivalent to the X-ray diffraction (hereinafter referred to as “XRD”) pattern of 24-734.

The tap density of trimanganese tetraoxide is preferably 1.8 g / cm ³ or more, more preferably 1.9 g / cm ³ or more, and still more preferably 1.95 g / cm ³ or more. If the tap density of trimanganese tetraoxide is 1.8 g / cm ³ or more, the density of the lithium manganese composite oxide obtained using this as a raw material tends to be high. On the other hand, the tap density of the trimanganese tetraoxide obtained by the process of the present invention is 2.3 g / cm ³ or less, more likely to be 2.1 g / cm ³ or less.

  The “tap density” in the present invention is the bulk density of the powder obtained after mechanically tapping the container filled with the powder multiple times. This is different from the density of the powder obtained after press molding the powder, that is, the so-called press density. The tap density can be measured, for example, by the method shown in the examples described later.

  The average particle size of trimanganese tetraoxide is preferably 1 μm or more, more preferably 3 μm or more, further preferably 5 μm or more, and further preferably 6 μm or more. On the other hand, the average particle diameter may be 50 μm or less, further 20 μm or less, and further 10 μm or less.

In the present invention, the average particle size is a particle size (so-called D ₅₀ ) that is 50% on a volume basis. When the particle size distribution is monomodal, the mode particle size and the average particle size match. In this case, the mode particle size is the average particle size.

  The particle diameter of trimanganese tetraoxide obtained by the production method of the present invention is uniform, and the relative standard deviation of the particle diameter is 40% or less, further 35% or less, and further 30% or less. The more uniform the particle size of trimanganese tetraoxide, the more easily the reaction with the lithium compound proceeds.

  The relative standard deviation of the particle diameter of trimanganese tetraoxide can be obtained from the following equation.

    Relative standard deviation of particle diameter (%) = (standard deviation of particle diameter / average particle diameter) x 100

  The standard deviation of the particle diameter can be obtained by measuring the particle size distribution and average particle of manganese trioxide.

  Trimanganese tetraoxide is preferably low in impurities, and particularly preferably low in sodium (Na). When there is little Na of trimanganese tetroxide, the battery characteristics when this is used as a lithium-based composite oxide obtained as a raw material tends to be high. As Na content of trimanganese tetraoxide, 200 weight ppm or less, Furthermore 150 weight ppm or less, Furthermore, 130 weight or less can be mentioned.

  The trimanganese tetraoxide obtained by the production method of the present invention can be used as a manganese raw material for a lithium manganese composite oxide. Furthermore, the trimanganese tetraoxide obtained by the production method of the present invention can be used as a manganese raw material that can be mixed with a lithium compound without requiring particle size adjustment after production such as classification, sizing or grinding.

  A lithium manganese based composite oxide using trimanganese tetraoxide obtained by the production method of the present invention comprises a mixing step of mixing at least one of the above-described trimanganese tetraoxide and a lithium compound, and a heating step of heat treatment. It can obtain by the manufacturing method of the lithium manganese type complex oxide which has.

  In the mixing step, when mixing trimanganese tetraoxide with a lithium compound, a different metal compound may be added in order to improve the characteristics of the lithium secondary battery positive electrode material of the lithium manganese composite oxide.

  The different metal compound is a metal element different from manganese and lithium as constituent elements, for example, aluminum (Al), magnesium (Mg), nickel (Ni), cobalt (Co), chromium (Cr), titanium (Ti) as constituent elements. And at least one selected from the group of zirconium (Zr).

  The lithium manganese composite oxide preferably has a spinel crystal structure, and is preferably represented by the following chemical formula.

_{Li 1 + x M y Mn 2} -x-y O 4

  However, 0 ≦ x ≦ 0.33, 0 ≦ y ≦ 1.0, and M is at least one metal element selected from elements other than Li, Mn and O.

  Any lithium compound may be used. Examples of the lithium compound include lithium hydroxide, lithium oxide, lithium carbonate, lithium iodide, lithium nitrate, lithium oxalate, and alkyl lithium. Examples of preferable lithium compounds include lithium hydroxide, lithium oxide, and lithium carbonate.

  The lithium manganese composite oxide obtained using the trimanganese tetraoxide of the present invention as a raw material can be used as a positive electrode active material of a lithium ion secondary battery.

  By the production method of the present invention, trimanganese tetraoxide can be obtained from a manganese salt aqueous solution with high efficiency without going through manganese hydroxide. Further, in the production method of the present invention, trimanganese tetraoxide can be efficiently obtained without requiring additional components such as special atmosphere control and an oxidizing agent having strong oxidizing power.

In addition, according to the present invention, it is possible to provide a method for producing trimanganese tetraoxide having a crystallization rate of 7 kg / (m ³ · hr) or more and a high crystallization rate.

  Furthermore, with the production method of the present invention, it is possible to obtain trimanganese tetraoxide having a large particle size and high filling properties without slowing the rate of adding the manganese salt aqueous solution and the alkaline aqueous solution.

  By the production method of the present invention, trimanganese tetraoxide can be produced with higher efficiency. For example, even when the manganese salt aqueous solution is 100 L or more, and even 150 L or more, uniform manganese trioxide can be efficiently produced.

  By the production method of the present invention, it is possible to provide trimanganese tetraoxide that does not require particle size adjustment after production such as classification, sizing or pulverization.

  The trimanganese tetraoxide obtained by the production method of the present invention can be used for applications such as a raw material of lithium manganese composite oxide.

XRD pattern of Example 1 XRD pattern of Comparative Example 1

  Next, the present invention will be described with specific examples. However, the present invention is not limited to these examples.

(Overall oxygen transfer capacity coefficient)
The measurement of dissolved oxygen was performed using a commercially available optical oxygen concentration meter (VISIFERTM ^™ DO SENSORS, manufactured by HAMILTON). After the dissolved oxygen concentration of the sample solution was set to 0.01 volume ppm or less, air was blown into the sample solution while stirring while measuring the dissolved oxygen concentration. The air was blown in until the dissolved oxygen concentration reached a saturated oxygen concentration (C _L ; 2.86 vol ppm at 80 ° C.) with respect to air at atmospheric pressure. At this time, the dissolved oxygen concentration at each time was measured at an interval of 1 second from the start of air blowing. The measurement was performed at 30 points or more until the dissolved acid concentration was substantially saturated. From the relationship between the dissolved oxygen concentration (C _St ) and the saturated oxygen concentration (C _L ) at each time t, the coefficient (X _t ) at the _t was determined from the following equation.

_{X t = -ln (C L -C} St)

To obtain a straight line by linear approximation by a least square method the value of X _t at each elapsed time t over 30 points, with the slope of the resulting straight lines and the overall oxygen transfer capacity coefficient.

(Dissolved oxygen concentration)
The dissolved oxygen concentration of the manganese salt aqueous solution in the crystallization process was measured with a commercially available oxygen concentration measuring device (VISIFERTM ^™ DO SENSORS, manufactured by HAMILTON).

(Crystallization rate)
The crystallization rate was determined by the following equation from the amount of manganese used for crystallization, the amount of manganese crystallized, and the crystallization time. In addition, Mn1 and Mn2 measured the quantity of manganese salt aqueous solution, and also measured Mn density | concentration in manganese salt aqueous solution by the inductively coupled plasma emission-spectral-spectroscopy (ICP) measuring method.

α = [{(Mn1-Mn2) / Mn1} × Mn1] / (V · T)
here,
α: Crystallization rate (kg / (m ³ · hr))
Mn1: Manganese ion (Mn ²⁺ ) amount (kg) in the aqueous manganese sulfate solution used for crystallization
Mn2: Manganese ion (Mn ²⁺ ) amount (kg) in the filtrate recovered after crystallization
V: Amount of reaction slurry during crystallization (m ³ )
T: Crystallization time (hr)
It is.

(Tap density)
The density after 100 g of a sample was filled in a 100 mL graduated cylinder and tapped 200 times was defined as the tap density.

(Average particle size)
A sample was dispersed in pure water to obtain a measurement solution. Ammonia water was added to adjust the pH to 8.5, and then the measurement solution was subjected to ultrasonic dispersion for 3 minutes. The particle size distribution was calculated | required using the said measurement solution with the commercially available particle size measuring apparatus (brand name: MICROTRAC HRA 9320-X100, Nikkiso Co., Ltd. product). A particle diameter (so-called D ₅₀ ) that is 50% on a volume basis was determined, and this was defined as an average particle diameter.

(X-ray diffraction measurement)
The crystal phase of the sample was measured by XRD. The measurement was performed with a general X-ray diffractometer. A CuKα ray (λ = 1.5405 mm) is used as the radiation source, the measurement mode is step scan, the scan condition is 0.04 ° per second, the measurement time is 3 seconds, and the measurement range is 2 ° to 5 ° to 80 °. Measured with

  JCPDS pattern No. The XRD pattern of 24-734 was used as a powder X-ray diffraction pattern of trimanganese tetraoxide, and the sample was identified by comparing this with the XRD pattern of the obtained sample.

(Chemical composition analysis)
After the sample was dissolved in a mixed aqueous solution of hydrochloric acid and hydrogen peroxide, the amount of Na was measured by an inductively coupled plasma emission spectroscopy (ICP) measurement method.

Example 1
The pure water was set to 80 ° C. while stirring 150 L of pure water by rotating the stirring blade with a required power of stirring of 1.9 kW / m ³ .

Next, nitrogen gas was blown to bring the dissolved oxygen concentration of the pure water to 0.01 mg / L or less, and then air was blown into the pure water at 36 L / min to measure the overall oxygen transfer capacity coefficient. The overall oxygen transfer capacity coefficient of this example was 2.3 min ⁻¹ .

Next, a 2 mol / L manganese sulfate aqueous solution and 6 mol / L were added so that the manganese molar ratio (OH ⁻ / Mn ²⁺ ) in pure water was 0.47 while maintaining the above air blowing amount and the required power for stirring. By adding L sodium hydroxide aqueous solution continuously to the pure water, manganese trioxide was crystallized from manganese ions in the pure water. The oxidation-reduction potential when crystallizing trimanganese tetraoxide was 160 mV. Thereby, a reaction slurry containing trimanganese tetraoxide was obtained. The crystallization is performed while draining the same amount of the reaction slurry as the addition amount of the manganese sulfate aqueous solution and the sodium hydroxide aqueous solution so that the reaction slurry amount is constant at 150 L, and the crystallization time is 100 hours. did. The average residence time of trimanganese tetroxide in the reaction slurry was set to 8 hours by extracting the reaction slurry. After crystallization, this was filtered, washed, and dried to obtain trimanganese tetraoxide of this example.

The crystallization rate was 8.0 kg / (m ³ · hr). Moreover, the amount of dissolved oxygen in the reaction slurry was 1.4 volume ppm.

  The production conditions of this example are shown in Table 1, and the physical properties of the obtained manganese trioxide are shown in Table 2. Moreover, the XRD pattern of the trimanganese tetraoxide of a present Example was shown in FIG.

Example 2
The overall oxygen transfer capacity coefficient was measured by the same method as in Example 1 except that the power required for stirring was 2.9 kW / m ³ and air was blown into pure water at 23 L / min. The overall oxygen transfer capacity coefficient of this example was 2.7 min ⁻¹ .

Thereafter, the same as in Example 1 except that an aqueous manganese sulfate solution and an aqueous sodium hydroxide solution were added so that the manganese molar ratio (OH ⁻ / Mn ²⁺ ) was 0.48, and that the oxidation-reduction potential was 110 mV. A reaction slurry was obtained by this method.

The crystallization rate was 8.1 kg / (m ³ · hr). Moreover, the amount of dissolved oxygen in the reaction slurry was 1.5 ppm by volume.

  The production conditions of this example are shown in Table 1, and the physical properties of the obtained manganese trioxide are shown in Table 2.

Example 3
The overall oxygen transfer capacity coefficient was measured by the same method as in Example 1 except that the power required for stirring was 4.6 kW / m ³ and air was blown into pure water at 23 L / min. The overall oxygen transfer capacity coefficient of this example was 3.8 min ⁻¹ .

Thereafter, the same as in Example 1 except that an aqueous manganese sulfate solution and an aqueous sodium hydroxide solution were added so that the manganese molar ratio (OH ⁻ / Mn ²⁺ ) was 0.48, and that the oxidation-reduction potential was 110 mV. A reaction slurry was obtained by this method.

The crystallization rate was 8.4 kg / (m ³ · hr). Moreover, the amount of dissolved oxygen in the reaction slurry was 1.6 volume ppm.

  The production conditions of this example are shown in Table 1, and the physical properties of the obtained manganese trioxide are shown in Table 2.

Example 4
The overall oxygen transfer capacity coefficient was measured by the same method as in Example 1 except that the power required for stirring was 2.6 kW / m ³ and air was blown into pure water at 53 L / min. The overall oxygen transfer capacity coefficient of this example was 3.3 min ⁻¹ .

Thereafter, the same as in Example 1 except that an aqueous manganese sulfate solution and an aqueous sodium hydroxide solution were added so that the manganese molar ratio (OH ⁻ / Mn ²⁺ ) was 0.48, and that the oxidation-reduction potential was 80 mV. The reaction slurry was obtained by various methods.

The crystallization rate was 7.4 kg / (m ³ · hr). Moreover, the amount of dissolved oxygen in the reaction slurry was 0.6 ppm by volume.

  The production conditions of this example are shown in Table 1, and the physical properties of the obtained manganese trioxide are shown in Table 2.

Example 5
The overall oxygen transfer capacity coefficient was measured by the same method as in Example 1 except that the power required for stirring was 2.6 kW / m ³ and air was blown into pure water at 103 L / min. The overall oxygen transfer capacity coefficient of this example was 3.5 min ⁻¹ .

Thereafter, the same as in Example 1 except that an aqueous manganese sulfate solution and an aqueous sodium hydroxide solution were added so that the manganese molar ratio (OH ⁻ / Mn ²⁺ ) was 0.48, and the oxidation-reduction potential was 70 mV. A reaction slurry was obtained by this method.

The crystallization rate was 8.1 kg / (m ³ · hr). Moreover, the amount of dissolved oxygen in the reaction slurry was 0.8 ppm by volume.

  The production conditions of this example are shown in Table 1, and the physical properties of the obtained manganese trioxide are shown in Table 2.

Comparative Example 1
The pure water was brought to 80 ° C. while stirring 150 L of pure water by rotating the stirring blade with a required power of stirring of 1.3 kW / m ³ .

Next, nitrogen gas was blown to bring the dissolved oxygen concentration of the pure water to 0.01 mg / L or less, and then air was blown into the pure water at 76 L / min to measure the overall oxygen transfer capacity coefficient. The overall oxygen transfer capacity coefficient of this comparative example was 2.1 min ⁻¹ .

Next, a 2 mol / L manganese sulfate aqueous solution and 6 mol / L were added so that the molar ratio of manganese in pure water (OH ⁻ / Mn ²⁺ ) was 0.46 while maintaining the above air blowing amount and the required power for stirring. By adding L sodium hydroxide aqueous solution continuously to the pure water, manganese oxide was crystallized from manganese ions in the pure water. The oxidation-reduction potential for crystallization of manganese oxide was −90 mV. Thereby, a reaction slurry containing manganese oxide was obtained. The crystallization is performed while draining the same amount of the reaction slurry as the addition amount of the manganese sulfate aqueous solution and the sodium hydroxide aqueous solution so that the reaction slurry amount is constant at 150 L, and the crystallization time is 100 hours. did. By removing the reaction slurry, the average residence time of trimanganese tetraoxide in the reaction slurry was set to 11 hours. After crystallization, this was filtered, washed, and dried to obtain a manganese oxide of this comparative example.

The crystallization rate was 7.8 kg / (m ³ · hr), but the crystal phase of the obtained manganese oxide was JCPDS pattern No. 24-734 manganese trioxide and JCPDS pattern no. It was a manganese oxide in which the layer structure manganese oxide (Na-type banesite) of 23-1046 was mixed. Moreover, the amount of dissolved oxygen in the reaction slurry was 0.2 ppm by volume.

  The production conditions of this comparative example are shown in Table 1, and the physical properties of the obtained manganese oxide are shown in Table 2. Further, the comparative XRD pattern is shown in FIG.

Comparative Example 2
The pure water was brought to 80 ° C. while stirring 150 L of pure water by rotating the stirring blade with a required power of stirring of 1.3 kW / m ³ .

Next, nitrogen gas was blown to bring the dissolved oxygen concentration of the pure water to 0.01 mg / L or less, and then air was blown into the pure water at 76 L / min to measure the overall oxygen transfer capacity coefficient. The overall oxygen transfer capacity coefficient of this comparative example was 2.1 min ⁻¹ .

Next, a 2 mol / L manganese sulfate aqueous solution and 6 mol / L were added so that the molar ratio of manganese in pure water (OH ⁻ / Mn ²⁺ ) was 0.46 while maintaining the above air blowing amount and the required power for stirring. L sodium hydroxide aqueous solution was continuously added to the pure water to crystallize manganese trioxide from manganese ions in the pure water. The oxidation-reduction potential when crystallizing trimanganese tetraoxide was 30 mV. Thereby, a reaction slurry containing trimanganese tetraoxide was obtained. The crystallization is performed while draining the same amount of the reaction slurry as the addition amount of the manganese sulfate aqueous solution and the sodium hydroxide aqueous solution so that the reaction slurry amount is constant at 150 L, and the crystallization time is 100 hours. did. By draining the reaction slurry, the average residence time of trimanganese tetraoxide in the reaction slurry was set to 8 hours. After crystallization, this was filtered, washed, and dried to obtain trimanganese tetraoxide of this comparative example.

The crystallization rate was 4.6 kg / (m ³ · hr). Moreover, the amount of dissolved oxygen in the reaction slurry was 0.6 ppm by volume.

  The production conditions of this comparative example are shown in Table 1, and the physical properties of the obtained trimanganese tetraoxide are shown in Table 2.

Comparative Example 3
The pure water was brought to 80 ° C. while stirring 150 L of pure water by rotating the stirring blade with a required power of stirring of 0.9 kW / m ³ .

Subsequently, nitrogen gas was blown to make the dissolved oxygen concentration of the pure water 0.01 mg / L or less, and then air was blown into the pure water at 88 L / min to measure the overall oxygen transfer capacity coefficient. The overall oxygen transfer capacity coefficient of this comparative example was 1.8 min ⁻¹ .

Next, a 2 mol / L manganese sulfate aqueous solution and 6 mol / L were added so that the manganese molar ratio (OH ⁻ / Mn ²⁺ ) in pure water was 0.48 while maintaining the above air blowing amount and stirring required power. L sodium hydroxide aqueous solution was continuously added to the pure water to crystallize manganese trioxide from manganese ions in the pure water. The oxidation-reduction potential when crystallizing trimanganese tetraoxide was 60 mV. Thereby, a reaction slurry containing trimanganese tetraoxide was obtained. The crystallization is performed while draining the same amount of the reaction slurry as the addition amount of the manganese sulfate aqueous solution and the sodium hydroxide aqueous solution so that the reaction slurry amount is constant at 150 L, and the crystallization time is 100 hours. did. By removing the reaction slurry, the average residence time of trimanganese tetraoxide in the reaction slurry was set to 10 hours. After crystallization, this was filtered, washed, and dried to obtain a manganese oxide of this comparative example.

The crystallization rate was 5.8 kg / (m ³ · hr). Moreover, the amount of dissolved oxygen in the reaction slurry was 0.7 ppm by volume.

  The production conditions of this example are shown in Table 1, and the physical properties of the obtained manganese trioxide are shown in Table 2.

  From these results, it was found that in Examples and Comparative Examples 2 and 3, trimanganese tetraoxide having a single phase of trimanganese tetraoxide and a high tap density of 1.9 g / mL or more was obtained.

However, it can be seen that by setting the overall oxygen transfer capacity coefficient to 2.2 min ⁻¹ or more, the crystallization rate is increased to 7 kg / (m ³ · hr) or more, further 8 kg / (m ³ · hr) or more. . On the other hand, it was found that when the overall oxygen transfer capacity coefficient is less than 2.2 min ⁻¹ , the crystallization rate is less than 6 kg / (m ³ · hr), and the crystallization rate becomes slow.

Further, from the comparison between Example 4 and Comparative Example 2, even if the dissolved oxygen concentration is the same, if the overall oxygen transfer capacity coefficient is less than 2.2 min ⁻¹ , the crystallization rate is less than 0.6 times. I found out that

On the other hand, in Comparative Example 1, the overall oxygen transfer capacity coefficient was less than 2.2 min ⁻¹ and the crystallization rate was fast. However, the manganese oxide obtained in the comparative example was a manganese oxide mixed with a layered manganese oxide. From this, it was found that crystallization of trimanganese tetroxide was not promoted when the overall oxygen transfer capacity coefficient was within the range of the present application.

Claims (7)

A method for producing manganese trioxide having a crystallization step of crystallizing manganese trioxide from an aqueous manganese salt solution containing manganese ions without passing through manganese hydroxide, A method for producing trimanganese tetraoxide, characterized by crystallizing trimanganese tetraoxide with an oxygen transfer capacity coefficient of 2.2 min ⁻¹ or more.   The manufacturing method according to claim 1, wherein in the crystallization step, trimanganese tetraoxide is crystallized while stirring the manganese salt aqueous solution. The manufacturing method according to claim 2, wherein in the crystallization step, the manganese salt aqueous solution is stirred with a required power of stirring of 1.4 kW / m ³ or more.   The manufacturing method according to any one of claims 1 to 3, wherein in the crystallization step, manganese trioxide is crystallized from an aqueous manganese salt solution while blowing an oxygen-containing gas.   5. The production method according to claim 4, wherein in the crystallization step, an oxygen-containing gas is blown into the manganese salt aqueous solution at 10 L / min or more.   6. The production method according to claim 1, wherein in the crystallization step, manganese trioxide is crystallized at a dissolved oxygen concentration in the manganese salt aqueous solution of 0.2 vol ppm or more. . In the crystallization step, the ratio (OH ⁻ / Mn ²⁺ ) of manganese ions (Mn ²⁺ ) in the aqueous manganese salt solution to hydroxide ions (OH ⁻ ) in the aqueous alkaline solution was mixed at a rate of 0.55 or less. The production method according to any one of claims 1 to 6, wherein manganese trioxide is crystallized.

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