Method for purifying light acrylates

Abstract

The present invention relates to the production of light (meth)acrylic acid esters, such as methyl or ethyl (meth)acrylate, by direct esterification of (meth)acrylic acid with a corresponding light alcohol. More specifically, the subject of the present invention is a method for recovering / purifying C1-C2 alkyl acrylates, comprising steps of evaporation and partial condensation, which allows for the removal of fractions rich in alkylalkoxypropionate byproducts, which are extremely difficult to remove when pure because their boiling point is close to that of acrylic acid, or when in the form of an azeotropic mixture with water because their boiling point is close to that of the acrylic acid ester.

Claims

1. From the reaction mixture resulting from the esterification of an alcohol selected from methanol and ethanol with acrylic acid, carried out in the presence of a polymerization inhibitor, C １ -C ２ A method for recovering / purifying alkyl acrylate, the method comprising at least the following steps: - The reaction mixture is subjected to azeotropic distillation using a first distillation column to achieve the following separation: - Separation of the stream containing alkyl acrylate, unreacted alcohol, and water at the top; - Separation of the fraction containing unreacted acrylic acid and heavy products at the bottom. - A step of processing the top flow from the first distillation column by liquid / liquid extraction to produce an aqueous phase containing alcohol and an organic phase rich in alkyl acrylates; - A step of processing the alkyl acrylate-rich organic phase in at least one column for the purification of alkyl acrylates to separate the following: • At the top, purified alkyl acrylate, and • At the bottom, heavy products and polymerization inhibitors, - A step that allows for continuous processing of the bottom flow from at least one column for the purification of alkyl acrylates by evaporation and at least two consecutive condensations of the gas phase resulting from said evaporation, thereby obtaining the following: • Alkyl acrylate flow; • Alkylalkoxypropionate flow, and • Residue containing polymerization inhibitors, Methods that include...

2. The method according to claim 1, wherein the first distillation column is equipped with side-stream extraction of a fraction rich in alkylalkoxypropionate.

3. The method according to claim 1, wherein azeotropic distillation is performed by two distillation columns in series.

4. The method according to claim 1, wherein the evaporation of the bottom product from at least one column for the purification of the alkyl acrylate is carried out in a temperature range of 80°C to 110°C.

5. The method according to claim 1, wherein the azeotropic distillation is carried out under mild reduced pressure, which may be in the range of 200 to 600 mmHg.

6. The method according to claim 1, wherein the at least one column for the purification of alkyl acrylates comprises a tailing column and a topping column.

7. The method according to claim 1, wherein the at least one column for the purification of alkyl acrylates includes a split-wall distillation column.

8. The method according to claim 5, wherein the at least one column for the purification of alkyl acrylates includes a column having a sidestream extraction.

9. The method according to claim 1, wherein the treatment of the alkyl acrylate-rich organic phase is carried out by distillation using a purification column comprising at least one distillation column.

10. The method according to claim 1, wherein the alcohol is methanol, the alkyl acrylate is methyl acrylate, and the alkyl alkoxypropionate is methyl methoxypropionate.

11. The method according to claim 10, wherein methyl acrylate having a purity of more than 99.5% by weight is obtained in a distillation column called a tailing column or a split-wall distillation column operating in a pressure range of 10,000 Pa to 50,000 Pa and a temperature range of 80°C to 110°C.

12. The method according to claim 1, wherein the alcohol is ethanol, the alkyl acrylate is ethyl acrylate, and the alkyl alkoxypropionate is ethyl ethoxypropionate.

13. - In a second distillation column, the aqueous phase containing the alcohol produced by the liquid / liquid extraction is treated by distillation to separate the following: • At the top, the alcohol that is reused in the esterification reaction, - At the bottom, the flow shows a decrease in alcohol content; The method according to claim 1, further comprising:

14. - A step of processing the bottom flow from the first distillation column using a third distillation column and / or evaporator to separate the following: - At the top, a flow containing residual acrylic acid and lighter products, and • At the bottom, a flow consisting of heavy products; The method according to claim 1, further comprising:

15. The method according to claim 14, wherein the maintained pressure of the evaporator is 10,000 Pa to 80,000 Pa.

16. The top flow from the evaporator is in the following two consecutive steps: - A process of partial condensation at a temperature range of 70°C to 110°C at the same pressure as the evaporator, in order to obtain a liquid flow of Michael adducts to be purged on the one hand, and a vapor flow on the other hand; - A step of condensing the vapor stream in a temperature range of 20°C to 50°C before the liquid stream is taken in by a pump and supplied to the at least one column for the purification of alkyl acrylates; The method according to claim 14, wherein cooling is performed in the present.

17. The method according to claim 1, wherein the alkyl acrylate stream produced by continuously processing the bottom flow from the at least one column for the purification of alkyl acrylates by evaporation and at least two consecutive condensations of the gas phase resulting from the evaporation is reused in the at least one column for the purification of alkyl acrylates.

18. The method according to any one of claims 1 to 17, wherein the evaporation step is performed by a thin-film evaporator.

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