Continuous process for the preparation of pivaloyl chloride and of aroyl chloride

A continuous process for the preparation of pivaloyl chloride and of aroyl chloride (2) by reaction of pivalic-acid with a trichloromethylated aromatic compound (1) according to the reaction:

• in which R represents a halogen atom, a linear or branched alkyl radical having a carbon number of 1 to 4, a linear or branched perfluoroalkyl radical having a carbon number of 1 to 4 or a —COCl radical, m=0, 1 or 2 and n=1, 2 or 3 and in which the —CCl3 groups are situated on non-adjacent carbon atoms when n>1, in the presence of at least one Friedel-Crafts catalyst, said process comprising
• simultaneously and continuously introducing pivalic acid, at least one trichloromethylated aromatic compound (1) and at least one Friedel-Crafts catalyst into a reactor and reacting with stirring and under reduced pressure at a temperature of 60° C. to 180° C.,
• continuously separating unconverted reactants from products formed in gas flow exiting at the top of the reaction region,
• partially condensing the products formed into a liquid mixture comprising pivaloyl chloride and aroyl chloride (2),
• treating, in a washing region in which a trichloromethylated aromatic compound (1) moves countercurrentwise, remaining uncondensed gaseous mixture comprising hydrogen chloride, and
• continuously extracting, at the bottom of the said reaction region, a liquid mixture mainly comprising the aroyl chloride (2) formed and the catalyst used in the reaction region, said mixture being treated in a reactive distillation region, from which is extracted, at the top, the aroyl chloride (2).