Method for preparing anhydrous acetaldoxime

Abstract

The invention relates to a method for preparing anhydrous acetaldoxime, which comprises the following steps: adding a hydroxylamine solution, aldehyde and alkali into an oximation reactor with a stirring or external circulating system to perform reactions so as to prepare aldehyde oximation solution; passing the aldehyde oximation solution through a cooler and then sending the same into a liquid-liquid separator; sending the upper layer oil phase into a rectifying tower A to perform rectification so as to obtain an acetaldoxime aqueous solution of which the mass percent is about 50 percent and anhydrous acetaldoxime; and sending the solution on the lower layer and containing an inorganic salt into a rectifying tower B to perform rectification so as to obtain the acetaldoxime aqueous solution of which the mass percent is about 50 percent from the tower top, wherein the product at the bottom of the tower is acetaldoxime-free inorganic salt aqueous solution. The method makes full use of the functions that the solubility of the acetaldoxime is reduced at a low temperature and the inorganic salt is salted out, avoids the defects that the conventional extraction method and the vapor phase extraction method consume a large amount of organic solvent, are not environment-friendly and have complex and difficultly-controlled devices in the preparation of the anhydrous acetaldoxime, effectively improves the production condition, is an environment-friendly novel process, and has excellent economic and social benefits.

Description

technical field [0001] The invention relates to a method for preparing anhydrous acetaldehyde oxime, in particular to a method for preparing anhydrous acetaldehyde oxime from an acetaldehyde oximation solution without using an organic solvent. Background technique [0002] Acetaldoxime is an organic synthesis intermediate, well-known as an intermediate used in the synthesis of the pesticide methomyl, and acetaldoxime is also an important organic synthesis reagent and analytical reagent. Sometimes the acetaldehyde oxime used in organic synthesis requires anhydrous, such as the reaction of acetaldehyde oxime with acid chloride and isocyanate, etc. The commercial acetaldehyde oxime provided by the current acetaldehyde oxime manufacturer is basically an aqueous solution with a content of about 50%, mainly used Due to the intermediate of the pesticide methomyl, it cannot meet the requirements of organic synthesis that needs to use anhydrous acetaldoxime, and this demand has incre...

AI Technical Summary

Problems solved by technology

Among the above-mentioned methods, no matter it is the conventional extraction method or the vapor-phase extraction method, they all belong to the method of solvent extraction. Although the amount of solvent used in the vapor-phase extraction method is slightly smaller than that of the conventional extraction method, the device is complicated, the control is difficult, and there are problems The extraction tower requires a high number of separation stages, consumes a large amount of solvent, the extraction is incomplete, and the yield is low, especially the solvent volatilization and mixing into the inorganic salt solution, which is not conducive to the recycling of inorganic salts such as ammonium sulfate, which brings environmental problems. greater damage

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