Background technology
Manganese phosphate is a widely used chemical raw material. It is mainly used as a phosphating agent for steel products, especially for the phosphating treatment of large mechanical equipment, which can provide anti-rust effects. , can also be used as lubricants and protective agents in the defense industry. In recent years, manganese phosphate has important application value as a high-quality raw material for lithium manganese phosphate, the cathode material of lithium-ion batteries.
At present, there is relatively little research on the preparation methods of manganese phosphate at home and abroad. The existing preparation methods are mainly: (I) Oxidation-Precipitation method/hydrothermal synthesis method. For example, the invention patent with publication number CN101673819A discloses a method for preparing lithium manganese phosphate/carbon composite materials from manganese phosphate. In an acidic system, manganese source and phosphorus source are used as raw materials, and the manganese source is excessive. , add excess oxidant, stir for 0.5 to 24 hours, or perform a hydrothermal reaction at 80 to 200°C for 2 to 72 hours, and then finally prepare the manganese phosphate product through a series of washing, filtering, drying, crushing and other processes; ( 2) Solvothermal synthesis method, for example, the title of the paper is “Solvothermal synthesis and characterization of new titanium phosphate and manganese phosphate crystals of potassium dihydrogen phosphate” [D]. Jilin University, 2003, using various organic amines in n-butanol system As a structure directing agent, a layered manganese phosphate composed of manganese oxide octahedron and phosphorus oxide was prepared.
When the existing hydrothermal synthesis method is used to prepare manganese phosphate, excessive manganese sources are used, and the manganese precipitation rate is only about 50%, or even lower. Compared with phosphorus sources, manganese sources are more expensive, and manganese resources are The utilization rate is low and the production cost of PVC composite stabilizer is high; when manganese phosphate is prepared by oxidation-precipitation method, it is carried out in a single water phase system. The purity of the product is difficult to control, the amount of crystallization water is unknown, and the particle size distribution is uneven, thus affecting the quality of the product. Electrical properties; When preparing manganese phosphate by solvothermal synthesis, the reaction system has a complex composition, the composition and structure of the manganese phosphate product are complex, and it is not easy to produce on a large scale.
Content of the invention
In order to overcome the shortcomings of the prior art, the purpose of the present invention is to provide a preparation method of manganese phosphate, using an organic solvent-deionized water system instead of a single deionized water system. The ionized water system controls the production speed of the product and refines the product particle size. The resulting product has high purity, increases the manganese precipitation rate, makes full use of manganese resources, and has low production costs.
The present invention adopts an oxidation-precipitation process under an organic solvent-deionized water system, which includes the following steps:
1), the molar ratio P/Mn is (1~2): 1. Weigh the required soluble phosphorus source and manganese source compounds respectively, and dissolve them in deionized water to form a solution with a certain concentration;
2) Use a metering pump to feed manganese into the acid-resistant reaction kettle. source solution, then add a certain dose of phosphorus source solution and stir for 0.5 hours;
3), use a metering pump to feed excess oxidant into the acid-resistant reaction reactor, and adjust the pH value of the system to 0~6 ;
4), add a certain amount of organic solvent to the acid-resistant reactor, stir and react at a speed of 100~600r/min at 30~90°C for 0.5~5 hours;
5), naturally cool the obtained manganese phosphate slurry to room temperature, wash, filter, and dry to obtain the final manganese phosphate (MnPO4.H2O) product;
Among them, deionized water, manganese source The weight ratio of , phosphorus source and organic solvent is 100:1~20:1~30:1~200.
Further, the soluble phosphorus source is one of phosphoric acid, sodium phosphate, potassium phosphate, sodium dihydrogen phosphate, and ammonium phosphate.
Further, the soluble manganese source is one of manganous sulfate monohydrate, manganous nitrate, and manganous chloride.
Further, the oxidant is one of hydrogen peroxide, sodium peroxide, sodium hypochlorite, ozone, nitric acid, and sodium nitrate.
Further, the organic solvent is one of methanol, ethanol, ethylene glycol, propanol, butanol, and acetone, which can control the formation speed of the precipitate and refine the product particle size.
Further, the system pH adjuster is at least one of nitric acid and sodium hydroxide.
The manganese phosphate (MnPO4.H2O) obtained by the preparation method of the present invention is a dark green crystalline powder. The product has high purity, uniform particle size distribution, the average particle size is below 1 μm, and the morphology is flaky. .
Compared with the existing manganese phosphate preparation method, the preparation method of the present invention has the following characteristics: (1) the phosphorus source used is excessive, the molar ratio P/Mn is (1~2):1, manganese The precipitation rate reaches more than 99%, making full use of manganese resources; (2) This method uses an organic solvent-deionized water system instead of a single deionized water system, and controls the production speed and fineness of the product by controlling the amount and speed of the organic solvent. The product particle size is optimized, and the obtained product has high purity, with Mn content greater than 32%, P content between 18 and 19%, main impurity content S less than 0.5%, and Na less than 0.02%; the particle size distribution is uniform, and the average particle size is less than 1 μm; (3) The manganese phosphate product prepared has a positive trivalent valence state, with one crystal water, and a chemical composition of MnPO4.H2O; (4) The finished manganese phosphate product prepared by this method is a monoclinic crystal, and the primary particles are in the form of flakes.
Specific Embodiments
In an acid-resistant reaction kettle, configure a manganous sulfate monohydrate solution with a concentration of 0.5mol/L, and add phosphoric acid with a concentration of 1mol/L into the reaction kettle. solution, and then add hydrogen peroxide with a concentration of 0.5mol/L into the reaction kettle. The weight ratio of deionized water, manganese source, phosphorus source, and organic solvent is 100: 8.45: 9.80:100. Add nitric acid to adjust the pH value of the solution: 2.0, the reaction temperature is 600°C, the stirring speed is 200r/min, finally add an ethanol solution with a concentration of 0.5mol/L to the system, react for 5 hours, wash with water, filter and dry.�Obtain manganese phosphate (MnPO4.H2O) product.
