Elf Atochem S.a.

Nathalie Hess

Michel Fauconet

Christian Lacroix

Jacqueline Bessalem

An acrylic acid ester is manufactured by reaction of the said acid and an alcohol chosen from C.sub.5 or above primary and secondary aliphatic monoalcohols, in the presence of an acid as esterification catalyst and of a polymerization inhibitor, the alcohol being capable of forming a heteroazeotrope with water, the water formed by the esterification reaction being entrained by distillation in a column in the form of a heteroazeotropic mixture with the alcohol, which mixture, containing an amount of unreacted acrylic acid, is then subjected, after condensation, to a separation in order to give an upper organic phase which is recycled to the head of the distillation column and a lower aqueous phase which is withdrawn; according to the invention, an extraction (for example in an extraction column EC) of the acrylic acid contained in the condensed heteroazeotropic mixture (M) intended for phase separation with an esterifying-alcohol-rich mixture, and the acrylic acid thus extracted is returned to the head of the distillation column (DC), as a constituent of the recycled organic phase, with an increase in the level of reflux into the distillation column (DC) relative to the natural reflux.

Process for the manufacture of alkyl acrylates by direct esterification

In this esterification, catalysed by H.sub.2 SO.sub.4, the crude reaction mixture comprising ester, butanol, acrylic acid, BuSO.sub.4 H and traces of H.sub.2 SO.sub.4 is obtained; BuSO.sub.4 H is hydrolysed (in R2) to H.sub.2 SO.sub.4 using pure water or water generated during the reaction; after hydrolysis, the medium is separated by settling (in D2) into an organic phase containing ester, butanol and part of the unconverted acid; and an aqueous phase containing H.sub.2 SO.sub.4 and the remainder of the unconverted acid; the organic phase is washed under alkaline conditions in order to neutralize the acrylic acid to alkaline acrylate which is soluble in the aqueous phase and then the neutralized organic phase is washed with water; the acid present in alkaline salt form in the aqueous phase from the 1st basic neutralization is regenerated by addition of the acidic aqueous phase (8) resulting from the separation by settling (in D2) of the hydrolysis stage; the acid (10) thus regenerated in this aqueous phase is extracted (in C5) by a solvent chosen from butanol, butyl acrylate or a mixture of butyl acrylate and butanol; the organic phase (13) obtained at the head of the extraction column (C5), containing mainly acid and butanol or ester, or a mixture of butanol and ester, is recycled to the esterification reactor (R1); the aqueous phase (15) recovered at the foot of the column (C5) is conveyed as feed to a distillation column (C6) for recovering butanol (16) at the head, for the purpose of recycling it upstream and of discarding the spent aqueous liquors, which are virtually free from organic pollution.

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Saint-Avold, France

Nathalie Hess