The preparation method of high-purity N,N-dimethylformamide is characterized in that, the extraction step comprises:
a. Take the waste liquid N,N-dimethylformamide, add sulfuric acid solution with a volume concentration of 30% to it, and control the pH value within the range of 6 to 8; and mix it with the waste liquid N,N-dimethylformamide Impurities such as organic bases in the amide react to precipitate the reactants from the solution.
b. Preheat the N,N-dimethylformamide obtained by the above quenching and tempering to 120°C, the vacuum of the flash tank is 30mmhg, and flash evaporation to remove low-boiling impurities and water.
c. The N,N-dimethylformamide obtained by the above distillation is preheated to 70°C, and the air heated to 90°C is introduced to remove residual methylene chloride, methyl tert-butyl ether, water, free amine.
d. The N,N-dimethylformamide decompressed rectification after the removal of metal ions is processed, the rectified distillate is tested qualified and then canned, and stored with nitrogen to obtain a medicinal product with a purity of ≥99.9% (wt) Grade N,N-dimethylformamide.
A preparation method of chromatographic grade N,N-dimethylformamide, the steps are as follows:
(1) with raw material N, N-dimethylformamide (content is about 99.5%) through the calcium hydride adsorption column that particle diameter is 5mm～10mm, the amount of column packing is 4/5 of the column length, and the flow rate is about 50mL/ min, N,N-dimethylformamide raw material is fully contacted with calcium hydride to adsorb impurities such as moisture in it, and the effluent to be adsorbed is qualified for inspection (that is, each index of the effluent is close to the technical index requirements of the chromatographic grade, and the specific technical index requirements are See Table 1.) and enter the next step;
(2) The adsorption effluent in the step (1) is pumped into a still, and 5% of alumina (weight ratio) is added to the still, and pre-burned at 500-600° C. for about 1 hour. Under the pressure of 5～10mmHg, vacuum distillation is carried out to further dehydrate and dry N,N-dimethylformamide, remove a small amount of amine impurities, and discard the front distillate;
(3) Collect the finished product after passing the test of the distillate in step (2), filter it with a 0.45 μm NYL microporous membrane, and store it in a nitrogen-filled reagent bottle to obtain chromatographic grade N,N-dimethylformamide.
After the methanol is gasified, the reaction temperature is 220 °C on a composite catalyst with copper as the main body (the amount of methanol is 1 wt%), and the pressure is normal pressure, and the catalytic dehydrogenation generates methyl formate, which is then mixed with dimethyl formate. The amine undergoes amination reaction to obtain crude N,N-dimethylformamide and methanol, and the crude product is purified to obtain high-purity N,N-dimethylformamide.
20 g of hydroxyapatite was weighed and immersed in a solution of 48.6 mmol·L-1 of hydrated ruthenium trichloride, stirred at room temperature for 20 h, dried at 130 °C, and reduced under a hydrogen atmosphere at 350 °C for 3 h to obtain 2wt% Ru-HAP; The 2wt% Ru-HAP was immersed in a certain volume of 0.1M cerium nitrate aqueous solution, left standing overnight, and vacuum dried at 200°C to obtain a 1wt% CeO2-2wt% Ru-HAP composite catalyst. The 14-25 mesh catalyst was taken from the forming screen and filled into the reaction tube, and the 15 mm bed was filled. Under the pressure of 4.0 MPa, the space velocity of dimethylamine was 200 h-1, and the flow rate of raw material CO was 5 mL·min-1. The reaction was carried out at 200° C., the reaction was sampled for 2 h and the chromatographic analysis showed that the yield of DMF (N,N-dimethylformamide) was 75%.