Background technology
Stannous pyrophosphate is mainly used in the electroplating industry and toothpaste manufacturing industry. It is also used in the coating industry, printing and dyeing industry, leather manufacturing industry and food industry. The current method for preparing stannous pyrophosphate is to use stannous chloride or stannous sulfate to undergo a metathesis reaction with an alkali metal pyrophosphate to form a precipitate of stannous pyrophosphate that is insoluble in water. After washing, filtering, and drying, the stannous pyrophosphate is obtained. Tin products, such as the patent application with the publication number CN101234757A and the name “Method for Preparing Stannous Pyrophosphate”, because the soluble stannous ions used in the preparation process are easily oxidized by air, resulting in the content of tetravalent tin in the stannous pyrophosphate products. It is too high, and tin ions are easily hydrolyzed, forming precipitated impurities that are difficult to remove by washing, resulting in high turbidity of stannous pyrophosphate products. Moreover, the crystal grains of stannous pyrophosphate generated during the preparation process are fine, carry many impurities, and are difficult to filter. It is difficult to wash, resulting in large washing water consumption and low product purity.
Content of the invention
The technical problem to be solved by the present invention is to provide a method for preparing high-purity stannous pyrophosphate. The stannous pyrophosphate prepared by this method for preparing pigment carbon black has large crystal grains, is easy to precipitate and washes, and uses little water. Product purity is high.
The technical solution to solve the above technical problems is: a method for preparing high-purity stannous pyrophosphate, which includes the following steps:
(1) Dissolve soluble stannous salt and soluble pyrophosphate in water to obtain a stannous salt solution and a pyrophosphate solution respectively, and vacuum to remove the stannous salt solution, pyrophosphate solution and the residue in the reactor Air, stir the two solutions to mix and react, filter, wash, centrifuge and dry the precipitate obtained from the reaction;
(2) Add an aqueous solution with PH=2~4 into the reactor, remove the air from the reactor, add the precipitate obtained in step (1), stir and wash, filter, centrifuge and dry to obtain The precipitate is high-purity white powdery stannous pyrophosphate.
A further technical solution of the present invention is: the water used to dissolve stannous salt and pyrophosphate in step (1) is degassed distilled water, deionized water, or newly prepared distilled water, and the precipitate obtained from the washing reaction The water used is a deaerated pyrophosphoric acid aqueous solution with pH=2~4.
The stannous salt described in step (1) is stannous chloride or stannous sulfate, the pyrophosphate is potassium pyrophosphate or sodium pyrophosphate, and the concentration of the stannous salt solution is 1 . 5mol . L-4mol.L-1 The concentration of pyrophosphate solution is 0. 3mol . L-1-1mol . L-1 During the reaction, Sn2+ and P in the two solutions The amount ratio of 2O74- is 1: 0. 5~1: 0. 53.
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The mixing reaction of the two solutions under stirring described in step (0) is to drop the stannous salt solution into the pyrophosphate solution under the condition of isolation of air and a temperature of 50°C~80°C, and stir After the two solutions were mixed and reacted, the reactor was closed and allowed to cool to room temperature.
The specific steps of step (2) are: add an aqueous solution with PH=2~4 into the reactor, remove the air in the reactor, add the precipitate obtained in step (1) under stirring, and heat to 50°C ~80°C, after constant temperature stirring and washing for 0.5~5 hours, let it cool to room temperature, filter, centrifuge and dry, and the precipitate obtained after vacuum drying is a high-purity white powdery stannous pyrophosphate product, wherein the The aqueous solution is pyrophosphate aqueous solution.
The vacuum drying described in step (2) is performed at a temperature of 60V~100°C.
Due to the adoption of the above technical solution, a method of preparing high-purity stannous pyrophosphate of the present invention has the following beneficial effects compared with the existing method of preparing stannous pyrophosphate:
1. High purity and large grain size:
Since the reaction operation and heating washing operation process in the present invention are completed in an isolated air environment, the water used is deaerated distilled water, deionized water, or newly prepared distilled water, which prevents soluble stannous ions from being Air oxidation generates tetravalent tin ions, and it is easy to obtain stannous pyrophosphate precipitates with less entrained impurities. The prepared stannous pyrophosphate product contains more than 99% of the stannous pyrophosphate content, which improves the purity of the stannous pyrophosphate precipitate. In addition, this invention In the further technical solution of the invention, the operation of reaction and washing precipitation at a higher temperature is adopted, which makes it easier to obtain stannous pyrophosphate precipitation with large crystal grains, easy washing, and high purity.
2. Easy to wash, low water consumption:
In the currently disclosed method of preparing stannous pyrophosphate, the reaction is carried out at a lower temperature. The generated stannous pyrophosphate precipitate has small crystal grains and contains many impurities. This method requires a large amount of water to wash the precipitate. Water not only causes a waste of water resources, but also makes it difficult to wash away impurities. However, in the washing process, the present invention uses a pyrophosphoric acid aqueous solution of PH=2~4 to wash the stannous pyrophosphate precipitation at a higher temperature, which can not only prevent Tin ions hydrolyze and easily wash away the impurities entrained in the precipitate, which greatly reduces the difficulty of washing, prevents the waste of water resources, and saves costs.
3. The method is simple and easy to promote and use:
The method described in the present invention only adopts simple basic steps such as dissolution, reaction, filtration, washing and drying, and does not need to adopt other complicated operating methods. The method uses conventional simple equipment, is easy to operate, and is easy to promote and use.
In the following, a preparation method of the present invention will be described with reference to specific examples.The technical characteristics of the method of purifying stannous pyrophosphate are further explained.
Detailed implementation:
A method for preparing high-purity stannous pyrophosphate, comprising the following steps:
(1) Dissolve soluble stannous chloride and soluble potassium pyrophosphate in degassed deionized water to obtain a stannous chloride solution with a concentration of 1.5 mol. L-1 and a stannous chloride solution with a concentration of 0. 5mol. L-1 potassium pyrophosphate solution, vacuum to remove the stannous chloride solution, potassium pyrophosphate solution and the air in the reactor, according to the amount of substances Sn2+😛2O74- =1:0.5, drop the stannous chloride solution in isolation from air and at a temperature of 50°C into the potassium pyrophosphate solution, mix the two solutions with stirring, then cool the sealed reactor to room temperature, filter, wash, and centrifuge to dry the precipitate obtained from the reaction;
(2) Add pyrophosphoric acid aqueous solution with pH=2 into the reactor, remove the air from the reactor, add the precipitate obtained in step (1) with stirring, stir to disperse the precipitate and heat to 50°C, constant temperature After stirring and washing for 0.5 hours, let it stand and cool to room temperature, filter, centrifuge and dry, and the precipitate obtained after vacuum drying at a temperature of 60°C is a high-purity white powdery stannous pyrophosphate product, pyrophosphoric acid The stannous content is 99.21%.
