Background technology of synthesis method of chromium 2-picolinate
The synthesis process route of chromium 2-picolinate in the prior art:
1. Patent CN1408708A uses 2-vinylpyridine as raw material and uses potassium permanganate oxidation method to synthesize 2-pyridinecarboxylic acid and then complex it with chromium trichloride. The 2-picolinic acid obtained by this method has low purity and requires multiple crystallizations to obtain qualified 2-picolinic acid. Moreover, this process also produces a large amount of by-product manganese dioxide that needs to be treated. Potassium permanganate is also more expensive.
2. Patent CN1772737A uses 2-methylpyridine as raw material, oxidizes it with sulfuric acid to 2-picolinic acid, and then complexes it with chromium trichloride to obtain the product. Since this process uses sulfuric acid for oxidation, a large amount of waste acid is produced, which brings great difficulties to environmental protection treatment.
3. Use 2-methylpyridine as raw material, oxidize it with potassium permanganate to obtain 2-pyridinedimethoxypyridinecarboxylic acid, and then perform complexation to obtain the product. This process also produces a large amount of manganese dioxide as a by-product that needs to be disposed of. Potassium permanganate is also more expensive. The single-pass yield of the product is also low and there are many side reactions.
Synthesis method of chromium 2-picolinate Contents of the invention
The object of the present invention is to provide a synthesis method of chromium 2-picolinate with simple synthetic route, safe and reliable process, strong operability and high reaction yield.
The technical solution of the present invention is:
A synthesis method of chromium 2-picolinate, which is characterized by: first hydrolyzing 2-cyanopyridine to obtain a sodium salt solution of 2-picolinic acid, and then adding chromium trichloride solution for complexation to obtain 2-picolinic acid Chromium products.
The synthesis method of chromium 2-picolinate includes the following steps:
(1) Synthesis of aqueous solution of 2-pyridinecarboxylic acid: Add 2-cyanopyridine and deionized water into the flask in a ratio of 1:2, and start stirring.
Raise the temperature to 50~70°C, add 2-cyanopyridine:30% sodium hydroxide with a molar ratio of 1:1.0-1.5 to the flask. After the addition is completed, continue to heat up at 60 ~80°C insulation reaction for 6~10 hours, then, cool to 30~50°C, add 30% hydrochloric acid, adjust the pH value of the reaction solution at 3.5~5.5, and wait until the temperature of the reaction solution drops to 45~50°C. Use;
(2) Complexation reaction:
Add the prepared 20% chromium trichloride aqueous solution dropwise into the above flask. The dripping amount is 2-cyanopyridine: chromium trichloride molar ratio is 1: 1.02-1.22. After the addition is completed, Stir the complexation reaction for 1 hour, then cool to 20°C, discharge and drain, the filter cake is washed 4 times with 2-cyanopyridine: an ion-free water mass ratio of 5-10 of ion-free water, and then pumped Consider and dry to obtain chromium 2-picolinate. Reaction equation:
Compared with the traditional method of oxidatively synthesizing chromium 2-picolinate using 2-methylpyridine as raw material, the present invention has a simple synthesis route, safe and reliable process, strong operability, high reaction yield and good product quality. .
The present invention will be further described below in conjunction with examples.
Synthesis method of chromium 2-picolinate Synthesis method
(1) Synthesis of aqueous solution of 2-pyridinecarboxylic acid:
In a 200ml three-necked flask, add 40g of deionized water, then add 20g of 2-cyanopyridine, start stirring, raise the temperature to 70°C, and add 26g of 30°C sodium hydroxide into the flask. After the addition, continue to raise the temperature and keep the reaction at 70°C for 6 hours. Then, cool to 30°C, add 30% hydrochloric acid, adjust the pH value of the reaction solution to 5.5, and maintain the temperature of the reaction solution at 50°C for later use. ;
(2) Complexation reaction formylbenzeneboronic acid:
Add the prepared 20% chromium trichloride aqueous solution dropwise into the above 200ml three-necked flask. The dripping amount is 51.8g. After the addition, stir the complexation reaction for 1 hour, and then cool to 20 °C. , discharge and drain, the filter cake is washed 4 times with 100g of ion-free water, and then filtered and dried to obtain about 26.53g of chromium 2-picolinate, with a yield of 99.0%. The quality index exceeds the national standard, and the content is greater than 99. 5%.
