A method for preparing a manganese nitrate solution

Abstract

The application belongs to the field of manganese nitrate solution preparation and discloses a preparation method of manganese nitrate solution, which is combined with a tower column reaction kettle. The tower column reaction kettle comprises a reaction kettle body and a jacket arranged on the outer surface of the reaction kettle body. The outer surface of the tower column reaction kettle is provided with a feeding port, a discharging port, a water inlet and a water outlet. The feeding port and the discharging port are respectively communicated with the reaction kettle body and not communicated with the jacket. The water inlet and the water outlet are respectively communicated with the jacket and not communicated with the reaction kettle body. In the preparation method, manganese metal pieces are first put into the reaction kettle body, and then nitric acid solution is introduced into the reaction kettle body containing the manganese metal pieces at a flow rate of 4.5-7.5 ml / min. During the introduction of the nitric acid, the external cooling water circulating device is communicated with the jacket through the water inlet and the water outlet, and the temperature of the jacket is controlled to be 80-100 DEG C. The above method inhibits the generation of by-products in the preparation process of manganese nitrate, improves the purity of the manganese nitrate solution and improves the utilization rate of the nitric acid.

Description

Technical Field

[0001] This application relates to the field of manganese nitrate solution preparation technology, and in particular to a method for preparing manganese nitrate solution. Background Technology

[0002] Manganese nitrate is an inorganic compound, appearing as a pink or pale rose-red solution. It undergoes thermal decomposition between 160 and 200°C to form manganese dioxide, and precipitates as pink crystals below 15°C. It is readily soluble in water and ethanol, supports combustion, and is hygroscopic. Manganese nitrate is mainly used as an intermediate, catalyst, and in the manufacture of manganese dioxide. It is also used as a ceramic colorant, metal phosphating agent, and analytical reagent. Common industrial methods for producing manganese nitrate include the manganese sulfide-nitric acid process and the metallic manganese-nitric acid process.

[0003] Chinese patent application 201310355830.1 discloses a high-purity manganese nitrate and its preparation method. The method includes: (1) sulfidation, where a mixed gas containing ammonia and hydrogen sulfide is added to a manganese sulfate solution of 150–300 g / L to carry out a sulfidation reaction until the concentration of Mn in the solution reaches a certain level. 2+ The reaction was stopped when the concentration was less than 500 ppm, the solid and liquid were separated, and the resulting manganese sulfide filter cake was washed and set aside for later use.

[0004] (2) Acidification: Under a nitrogen atmosphere, nitric acid is added to the manganese sulfide filter cake obtained in (1) sulfidation step. The temperature of the reaction system is maintained below 50°C. During the reaction, nitrogen is used to replace the hydrogen sulfide gas generated in the reaction. The acid is stopped when the pH value reaches 3.5 to 4.0. Then, solid-liquid separation is performed, and the obtained filtrate is manganese nitrate product.

[0005] Meanwhile, observing the instructions for this scheme reveals its advantage: the manganese nitrate prepared using this scheme has an Fe content of <0.34ppm and is free of impurities such as Cu, Co, Ni, Pb, As, Cr, and Cd. However, observing the sulfidation process of this scheme shows that a mixed gas containing ammonia and hydrogen sulfide needs to be passed into the manganese sulfate solution to prepare a manganese sulfide filter cake. That is, this scheme prepares high-purity manganese nitrate through a manganese sulfide-nitric acid process. However, this process route inevitably requires the use of sulfur-containing gases, and the use of sulfur-containing gases also increases the difficulty of subsequent waste gas treatment to some extent.

[0006] Chinese patent application 201310736407.6 discloses a method for preparing manganese nitrate solution using pyrolusite. The method involves adding pyrolusite powder (≤180 mesh) and distiller's grains (≤1.5 mm) to a pressure-resistant and nitric acid-corrosion-resistant reactor. A mixed solution of nitric acid and manganese nitrate is added, and the mixture is stirred and leached under sealed conditions. After leaching for a period of time, the slurry in the reactor is discharged for solid-liquid separation to obtain the desired manganese nitrate solution. Part of the obtained manganese nitrate solution is used for subsequent manganese nitrate processing, and the other part is mixed with nitric acid and leaching residue washing water to prepare a mixed solution for pyrolusite leaching. The initial concentration of nitric acid in the mixed solution for leaching is 30 g / L to 50 g / L, and the initial concentration of manganese nitrate is 150 g / L to 400 g / L. The amount of nitric acid added is 101% to 105% of the theoretical amount of manganese to be leached from the pyrolusite.

[0007] This scheme, through the aforementioned series of reactions, ultimately achieves near-complete leaching of Mn from pyrolusite, increasing the Mn leaching rate and reducing resource waste. The excess nitric acid in the process is relatively small, reducing the burden on subsequent solution purification. The entire leaching process is exothermic, with a low reaction temperature and low energy consumption. Because nitric acid readily reacts with distiller's grains, and the generated NO readily reacts with MnO2, the leaching process is rapid. The process is conducted under closed conditions, avoiding environmental pollution caused by NO escape. However, as can be seen from the scheme's specifications, nitric acid leaching of pyrolusite primarily...

[0008] The following chemical reaction will occur:

[0009] nC6H 10 O5 + 8nHNO3 = 8nNO + 6nCO2 + 9nH2O

[0010] 3MnO2+2NO+4HNO3=3Mn(NO3)2+2H2O

[0011] 3Fe2O3+2NO+10HNO3=6Fe(NO3)2+5H2O

[0012] The overall reaction is:

[0013] 12nMnO2+nC6H 10 O5+24nHNO3=12nMn(NO3)2+6nCO2+17nH2O

[0014] 12nFe2O3+nC6H 10 O5+48nHNO3=24nFe(NO3)2+6nCO2+29nH2O

[0015] Although the above-mentioned method explains in the instructions that "because the reaction rate of nitric acid with the distiller's grains is very fast, the reaction rate of the generated NO with MnO2 is also relatively fast, thereby accelerating the entire leaching process and achieving more complete leaching of MnO2. As long as the amount of nitric acid added is well controlled, the amount of Fe entering the leachate can be reduced," it can be seen from the above chemical reaction formula that, theoretically, although the amount of Fe entering the leachate can be suppressed, it is impossible to completely prevent it from entering the leachate. In other words, a certain amount of ferrous ions will inevitably exist in the leachate.

[0016] The problem this solution aims to solve is: how to provide a method for preparing manganese nitrate solution with a simple process route and high nitric acid utilization rate. Summary of the Invention

[0017] The purpose of this application is to provide a method for preparing manganese nitrate solution with a simple process route and high nitric acid utilization rate.

[0018] To achieve the above objectives, this application discloses a method for preparing a manganese nitrate solution, comprising the following steps:

[0019] Step 1: Add the manganese metal sheets into the column reactor;

[0020] Step 2: Pass the nitric acid solution into the column reactor containing manganese metal sheets at a flow rate of 4.5-7.5 ml / min;

[0021] The molar ratio of manganese in the metallic manganese sheet to nitrogen in the nitric acid solution is 1:2-2.2;

[0022] The column reactor includes a reactor body and a jacket fitted on the outer surface of the reactor body. The outer surface of the column reactor is provided with a feed inlet, a discharge outlet, a water inlet, and a water outlet. The feed inlet and discharge outlet are respectively connected to the reactor body but not to the jacket, and the water inlet and discharge outlet are respectively connected to the jacket but not to the reactor body.

[0023] Step 1 specifically involves: adding metallic manganese sheets into the reactor body;

[0024] Step 2 specifically involves: introducing nitric acid solution into the reactor body containing manganese metal sheets at a flow rate of 4.5-7.5 ml / min, and during the introduction of nitric acid, connecting the external cooling water circulation device and the jacket through the inlet and outlet, and keeping the temperature of the jacket at 80-100℃.

[0025] It should be noted that, in actual operation, the external cooling water circulation device is only used to reduce the temperature of the jacket and prevent the high-temperature decomposition of manganese nitrate inside the reactor body to generate manganese dioxide. Therefore, this application does not impose too many restrictions on the flow rate and temperature of the cooling water. In actual use, the operator can freely adjust the flow rate and temperature of the cooling water according to actual needs, and only needs to control the temperature of the jacket between 80 and 100°C.

[0026] Preferably, the mass fraction of nitric acid in the nitric acid solution is 45-70%.

[0027] Preferably, the nitric acid solution contains 68% nitric acid by mass.

[0028] Preferably, the outer surface of the column reactor is provided with an exhaust port, which is connected to the reactor body but not to the jacket.

[0029] Preferably, the column reactor is equipped with a thermometer for measuring the temperature inside the jacket.

[0030] The beneficial effects of this application are as follows: This application uses a column dissolving vessel for dissolution, which is small in size and simplifies the process. The reaction temperature is controlled by introducing cooling water, reducing or avoiding the generation of manganese dioxide and the phenomenon of bubbles overflowing the vessel, achieving precise control. Nitric acid consumption is low, nitrogen-containing gases are easy to treat, and the amount of waste residue and wastewater generated is small, improving the utilization rate of raw materials and auxiliary materials. The simplified process omits the evaporation and concentration process, achieving high-efficiency production. The production line has a high degree of automation and is characterized by being "green, environmentally friendly, and efficient." Attached Figure Description

[0031] The present invention will be further described below with reference to the accompanying drawings and embodiments;

[0032] Figure 1 This is a schematic diagram of the reaction vessel of the present invention;

[0033] Figure 2 This is a schematic diagram of the reaction vessel body of the present invention. Detailed Implementation

[0034] The present application will be clearly and completely described below with reference to its embodiments. It should be noted that, unless specific conditions are specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0035] Before describing the embodiments, the column reactor used in the preparation of manganese nitrate solution will be explained and described as necessary.

[0036] The column reactor used in this preparation process includes a reactor body 1 and a jacket 2 fitted onto the outer surface of the reactor body 1. The outer surface of the column reactor has a feed inlet 3, a discharge outlet 4, a water inlet 5, and a water outlet 6. The water inlet 5 and water outlet 6 are connected to the reactor body 1 but not to the jacket 2, while the water inlet 5 and water outlet 6 are connected to the jacket 2 but not to the reactor body 1. In actual operation, the operator needs to connect the water inlet 5 and water outlet 6 to an external cooling water circulation device. The cooling water flow rate and temperature are adjusted to keep the temperature of the jacket 2 between 80 and 100°C. Since nitric acid is highly volatile and nitrogen-containing waste gas is inevitably generated during the reaction of manganese flakes and nitric acid, an exhaust port 7 is provided on the outer surface of the column reactor. The exhaust port 7 is connected to the reactor body 1 but not to the jacket 2, which can effectively and timely discharge the nitrogen-containing waste gas in the reactor body 1, thereby reducing the production safety risk caused by excessive internal pressure in the reactor body 1.

[0037] Meanwhile, in order to facilitate operators to observe the temperature inside the jacket, a thermometer is installed in the column reactor to measure the temperature inside the jacket 2.

[0038] Example 1

[0039] Step 1: Add the manganese metal sheets into the reactor body;

[0040] Step 2: A 68% nitric acid solution is introduced into the reactor body containing manganese metal sheets at a flow rate of 4.5 ml / min. During the introduction of nitric acid, the external cooling water circulation device is connected to the jacket through the inlet and outlet, and the temperature of the jacket is kept at 100±1℃. After all the manganese metal sheets have dissolved and there are no remaining manganese metal sheets inside the reactor, a manganese nitrate solution is obtained.

[0041] Example 2

[0042] Step 1: Add the manganese metal sheets into the reactor body;

[0043] Step 2: A 68% nitric acid solution is introduced into the reactor body containing manganese metal sheets at a flow rate of 7.5 ml / min. During the introduction of nitric acid, the external cooling water circulation device is connected to the jacket through the inlet and outlet, and the temperature of the jacket is kept at 81±1℃. After all the manganese metal sheets have dissolved and there are no remaining manganese metal sheets inside the reactor, a manganese nitrate solution is obtained.

[0044] Example 3

[0045] Step 1: Add the manganese metal sheets into the reactor body;

[0046] Step 2: A 68% nitric acid solution is introduced into the reactor body containing manganese metal sheets at a flow rate of 6 ml / min. During the introduction of nitric acid, the external cooling water circulation device is connected to the jacket through the inlet and outlet, and the temperature of the jacket is kept at 90±1℃. After all the manganese sheets have dissolved and there are no remaining manganese metal sheets inside the reactor, a manganese nitrate solution is obtained.

[0047] Example 4

[0048] It is basically the same as Example 1, except that the mass fraction of nitric acid in the nitric acid solution is 45%.

[0049] Example 5

[0050] It is basically the same as Example 1, except that the mass fraction of nitric acid in the nitric acid solution is 70%.

[0051] Comparative Example 1

[0052] It is basically the same as Example 1, except that the mass fraction of nitric acid in the nitric acid solution is 34%.

[0053] Comparative Example 2

[0054] The procedure is basically the same as in Example 1, except that in step 1, the flow rate of nitric acid is 3 ml / min.

[0055] Comparative Example 3

[0056] It is basically the same as Example 1, except that in step 1, the flow rate of nitric acid is 9 ml / min.

[0057] Comparative Example 4

[0058] It is basically the same as Example 1, except that in step 2, the temperature of the jacket is 70±1℃.

[0059] Comparative Example 5

[0060] It is basically the same as Example 1, except that in step 2, the temperature of the jacket is 110±1℃.

[0061] Results test:

[0062] In the preparation process of each embodiment and comparative example, the same mass of manganese sheets were added and the amount of nitric acid solution consumed to completely dissolve the manganese sheets in each embodiment and comparative example was recorded.

[0063] The method for calculating the theoretical consumption of nitric acid solution is as follows:

[0064] The theoretical consumption of nitric acid solution is calculated based on the fact that the molar ratio of nitrate ion to manganese in the chemical formula of Mn(NO3)2 is 1:2, that is, the molar ratio of manganese element in the manganese metal sheet to nitrogen element in the nitric acid solution is 1:2.

[0065] Nitric acid utilization rate = Theoretical consumption of nitric acid solution / Actual consumption of nitric acid solution

[0066] The results are shown in Table 1:

[0067] Table 1

[0068]

[0069] Results analysis:

[0070] 1. As can be seen from Examples 1-3, when the flow rate of nitric acid and the temperature of the column reactor are slightly changed, there is no significant difference in the nitric acid utilization rate among Examples 1-3;

[0071] 2. As can be seen from Examples 1, 4, and 5, when the mass fraction of nitric acid in the nitric acid solution is 68%, the utilization rate of the nitric acid solution is more advantageous. The reason for the decrease in mass fraction to 70% may be due to the excessively high concentration and the overly vigorous reaction.

[0072] 3. As can be seen from Example 1 and Comparative Example 1, when the mass fraction of nitric acid in the nitric acid solution is further reduced, the utilization rate of nitric acid is further reduced;

[0073] 4. As can be seen from Example 1 and Comparative Examples 2-5, when the flow rate of nitric acid and the temperature of the column reactor are significantly changed, the utilization rate of nitric acid solution shows a significant downward trend.

[0074] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a manganese nitrate solution, characterized in that, Includes the following steps: Step 1: Add the manganese metal sheets into the column reactor; Step 2: Pass the nitric acid solution into the column reactor containing manganese metal sheets at a flow rate of 4.5-7.5 ml / min; The molar ratio of manganese in the metal manganese sheet to nitrogen in the nitric acid solution is 1:2-2.2; The column reactor includes a reactor body and a jacket fitted on the outer surface of the reactor body. The outer surface of the column reactor is provided with a feed inlet, a discharge outlet, a water inlet, and a water outlet. The feed inlet and discharge outlet are respectively connected to the reactor body but not to the jacket. The water inlet and discharge outlet are respectively connected to the jacket but not to the reactor body. Step 1 specifically involves: adding metal manganese sheets into the reactor body; Step 2 specifically involves: introducing nitric acid solution into the reactor body containing manganese metal sheets at a flow rate of 4.5-7.5 ml / min; during the introduction of nitric acid, connecting the external cooling water circulation device and the jacket through the inlet and outlet, and maintaining the jacket temperature at 80-100℃; The nitric acid solution contains 68% nitric acid by mass.

2. The method for preparing manganese nitrate solution according to claim 1, characterized in that, The outer surface of the column reactor is provided with an exhaust port, which is connected to the reactor body but not to the jacket.

3. The method for preparing manganese nitrate solution according to claim 1, characterized in that, The column reactor is equipped with a thermometer, which is used to measure the temperature inside the jacket.

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