Continuous preparation of unsaturated carboxylic acid anhydride comprises anhydrating aliphatic carboxylic acid anhydride with carboxylic acid in rectification column, recycling the non-reacted educt in reaction medium and collecting

摘要

Continuous preparation of unsaturated carboxylic acid anhydride (A) comprises anhydrating an aliphatic carboxylic acid anhydride with a carboxylic acid (B) in a rectification column (2) with an upper, middle and lower region, where the sump of the column contains an inert boiled oil. The educt is provided into the column in a stoichiometric ratio, where the carboxylic acid is emerging out from top of the column, as a by product, the non-reacted educt is led back into the reaction medium, and (A) is collected over the side outlet, preferably in between the middle- and lower part of the column. Continuous preparation of unsaturated carboxylic acid anhydride (A) of formula R-C(O)-O-C(O)-R comprises anhydrating an aliphatic carboxylic acid anhydride with a carboxylic acid (B) of formula R-COOH in a rectification column with an upper- (2a), middle- (2b) and lower- (2c) region, where the sump of the column contains an inert boiled oil. The educt is provided into the column in a stoichiometric ratio, where the carboxylic acid is emerging out from top of the column, as a by product, the non-reacted educt is led back into the reaction medium, and (A) is collected over the side outlet, preferably in between the middle- and lower part of the column. R : 2-12C-unsaturated organic remainder.