METHOD FOR CONTINUOUS PRODUCTION OF UNSATURATED CARBOXYLIC ACID ANHYDRIDES Russian patent published in 2012 - IPC C07C51/56 C07C51/573 C07C57/04 C07C51/54 

FIELD: chemistry.

SUBSTANCE: invention relates to an improved method for continuous production of unsaturated carboxylic acid anhydrides of general formula R-C(O)-O-C(O)-R (I), in which R denotes an unsaturated organic residue having 2-12 carbon atoms, through reaction of a ketene of general formula R'-CR"=C=O (III), in which R' and R" are identical or different and represent hydrogen or an alkyl residue having 1-4 carbon atom, with an unsaturated carboxylic acid of general formula R-COOH (II), which the value of R is as given above, in which in an apparatus comprising a reaction zone (1) for reaction of ketene with the unsaturated carboxylic acid of general formula II, a reaction zone (2) for further reaction of the formed mixture of crude anhydride and a fractionation column with a top, a middle and a bottom region, into the still of which inert boiling oil is fed, a) the unsaturated carboxylic acid of general formula II is fed into the reaction zone (1), b) the formed mixture of crude anhydride from step a) is fed into the next reaction zone (2) lying outside or inside the column or contained in the reaction zone (1), c) the mixture of crude anhydride from step b) is purified in the fractionation column, d) the formed carboxylic acid distilled in the top part of the column and returned once more for production of ketene, e) unconverted reagents and intermediate products formed are returned to reaction zone (1) and/or (2) and f) a product of formula I is obtained between the middle and the bottom region of the fractionation column, where the process is carried out in the presence of a polymerisation inhibitor, and a heterogeneous catalyst is used in reaction zone (2).

EFFECT: method enables complete conversion of the unsaturated carboxylic acid used and obtain high-purity unsaturated anhydride and carboxylic acid.

9 cl, 1 dwg, 2 ex