Preparation of tert-butyl esters of aliphatic carboxylic acids

Patent metadata

Field	Value
Publication number	US-10023520-B2
Application number	US-201615086715-A
Country	US
Kind code	B2
Filing date	Mar 31, 2016
Priority date	Mar 31, 2015
Publication date	Jul 17, 2018
Grant date	Jul 17, 2018

Abstract

A process for continuously preparing the tert-butyl ester of an aliphatic C1-C4 carboxylic acid comprises: a) the reaction of an aliphatic C1-C4 carboxylic acid with isobutene in the presence of an acidic catalyst to give an esterification mixture (G1); b) the partial evaporation of the esterification mixture (G1), giving a liquid first high boiler phase (SPh1) comprising the acidic catalyst, and a first vapor (B1) comprising tert-butyl ester; c) the fractional condensation of the first vapor (B1) by partially condensing the first vapor (B1) at a first pressure and a first temperature and obtaining a first condensate (K1), partially condensing the uncondensed second vapor (B2) at a second pressure and a second temperature and obtaining a second condensate (K2), the first temperature being 0 to 45° C. below the condensation temperature of the tert-butyl ester at the first pressure and the second temperature being 45 to 80° C. below the condensation temperature of the tert-butyl ester at the second pressure, with the proviso that the second temperature is at least 5° C. below the first temperature; and d) the combination of the first condensate (K1) and the second condensate (K2) and the feeding to a combined workup, and recycling of the third vapor (B3) not condensed at the second temperature into step a). The process allows the preparation of the tert-butyl ester of an aliphatic C1-C4 carboxylic acid by reaction of the carboxylic acid with isobutene, with isolation of unconverted isobutene from the esterification mixture in an energetically favorable manner and with an improved degree of removal.

First claim

The invention claimed is:

1. A process for continuously preparing the tert-butyl ester of an aliphatic C 1 -C 4 carboxylic acid, the process comprising:
a) reacting the aliphatic C 1 -C 4 carboxylic acid with isobutene in the presence of an acidic catalyst to give an esterification mixture (G 1 );
b) partially evaporating the esterification mixture (G 1 ) in a first distillation unit, giving a liquid first high boiler phase (SPh 1 ) comprising the acidic catalyst, and a first vapor (B 1 ) comprising the tert-butyl ester and unreacted isobutene;
c) fractionally condensing the first vapor (B 1 ) by partially condensing the first vapor (B 1 ) at a first pressure and a first temperature and obtaining a first condensate (K 1 ), partially condensing an uncondensed second vapor (B 2 ) at a second pressure and a second temperature and obtaining a second condensate (K 2 ) and an uncondensed third vapor (B 3 ), comprising isobutene, the first temperature being 0 to 45° C. below the condensation temperature of the tert-butyl ester at the first pressure which is from 10 to 200 mbar abs and the second temperature being 45 to 80° C. below the condensation temperature of the tert-butyl ester at the second pressure which is from 10 to 200 mbar abs, with the proviso that the second temperature is at least 5° C. below the first temperature: and
d) feeding a combination of the first condensate (K 1 ) and the second condensate (K 2 ) to a combined workup, and
recycling the third vapor (B 3 ) comprising isobutene into reaction a).

2. The process according to claim 1 , in which the combined condensate is fed to a first distillation column (D 1 ) wherein a first liquid bottom product (S 1 ) and a fourth vapor (B 4 ) comprising isobutene are obtained; the first liquid bottom product (S 1 ) is fed to a further workup; the fourth vapor (B 4 ) is fractionally condensed by partially condensing the fourth vapor (B 4 ) at a third pressure and a third temperature and obtaining a first low boiler condensate (K 3 ), an uncondensed fifth vapor (B 5 ) comprising isobutene is partially condensed at a fourth pressure and a fourth temperature and a second low boiler condensate (K 4 ) is obtained, the fourth temperature being lower than the third temperature; a sixth vapor (B 6 ) comprising isobutene uncondensed at the fourth temperature is recycled into a); and the first and/or second low boiler condensate (K 3 ) and (K 4 ) is recycled partly as reflux to the top of the first distillation column (D 1 ).

3. The process according to claim 2 , wherein the third temperature is 5 to 40° C. below the condensation temperature of diisobutene at the third pressure and the fourth temperature is 30 to 55° C. below the condensation temperature of diisobutene at the fourth pressure, with the proviso that the fourth temperature is at least 5° C. below the third temperature.

4. The process according to claim 2 , in which the first liquid bottom product (S 1 ) is fed to a second distillation column (D 2 ) to obtain a second liquid bottom product (S 2 ) and a seventh vapor (B 7 ); the second liquid bottom product (S 2 ) is at least partly recycled into a); the seventh vapor (B 7 ) is fractionally condensed by partially condensing the seventh vapor (B 7 ) at a fifth pressure and a fifth temperature and obtaining a first product condensate (P 1 ), an uncondensed eighth vapor (B 8 ) is partially condensed at a sixth pressure and a sixth temperature and a second product condensate (P 2 ) is obtained, the sixth temperature being lower than the fifth temperature; and the first and/or second product condensate (P 1 ) and (P 2 ) is recycled partly as reflux into the second distillation column (D 2 ).

5. The process according to claim 4 , wherein the fifth temperature is 0 to 45° C. below the condensation temperature of the tert-butyl ester at the fifth pressure and the sixth temperature is 45 to 80° C. below the condensation temperature of the tert-butyl ester at the sixth pressure, with the proviso that the sixth temperature is at least 5° C. below the fifth temperature.

6. The process according to claim 1 , wherein the aliphatic C 1 -C 4 carboxylic acid is acrylic acid, or methacrylic acid, or a mixture thereof.

7. The process according to claim 1 , wherein the esterification mixture (G 1 ) comprises 0.5% to 5.0% by weight of the acidic catalyst.

8. The process according to claim 1 , wherein the acidic catalyst is an inorganic acid.

9. The process according to claim 1 , wherein the acidic catalyst is an organic acid.

10. The process according to claim 1 , wherein the reacting a) is conducted in the presence of a stabilizer which is at least one phenothiazine.

11. The process according to claim 1 , wherein the fractional condensation c) is conducted in the presence of a stabilizer which is at least one N-oxyl compound.

12. The process according to claim 2 , wherein the fractional condensation of the fourth vapor (B 4 ) is conducted in the presence of a stabilizer which is at least one N-oxyl compound.

13. The process according to claim 12 , wherein the stabilizer is added to the first liquid bottom product (S 1 ).

14. The process according claim 4 , wherein a stabilizer, which is at least one phenol compound, is metered into a rectifying section of the second distillation column (D 2 ).

15. A process for continuously preparing the tert-butyl ester of an aliphatic C 1 -C 4 carboxylic acid, the process comprising:
aa) providing a plant comprising an esterification reactor, an evaporator, a first condenser and a second condenser;
bb) purging and filling the plant with an oxygenous gas having an oxygen content of 10% by volume or less;
a) reacting the aliphatic C 1 -C 4 carboxylic acid with isobutene in the presence of an acidic catalyst to give an esterification mixture (G 1 );
b) partially evaporating the esterification mixture (G 1 ), giving a liquid first high boiler phase (SPh 1 ) comprising the acidic catalyst, and a first vapor (B 1 ) comprising the tert-butyl ester and unreacted isobutene:
c) fractionally condensing the first vapor (B 1 ) by partially condensing the first vapor (B 1 ) at a first pressure and a first temperature and obtaining a first condensate (K 1 ), partially condensing an uncondensed second vapor (B 2 ) at a second pressure and a second temperature and obtaining a second condensate (K 2 ), the first temperature being 0 to 45° C. below the condensation temperature of the tert-butyl ester at the first pressure which is from 10 to 200 mbar abs and the second temperature being 45 to 80° C. below the condensation temperature of the tert-butyl ester at the second pressure which is from 10 to 200 mbar abs, with the proviso that the second temperature is at least 5° C. below the first temperature; and
d) feeding a combination of the first condensate (K 1 ) and the second condensate (K 2 ) to a combined workup, and a third vapor (B 3 ) comprising isobutene not condensed at the second temperature is recycled into a).

16. The process according to claim 15 , wherein the oxygenous gas having an oxygen content of 10% by volume or less is continuously fed into the plant ensure the presence of molecular oxygen in the plant.

17. The process according to claim 15 , wherein the oxygen concentration in the gas phase at any point in the plant is maintained in the range from 3% to 8% by volume.

Assignees

• Basf Se

Inventors

• Horstmann Catharina
• Hechler Claus
• Grackiewicz Gregor
• Schall Bernd

Classifications

• C07C67/04 Primary

  by reacting carboxylic acids or symmetrical anhydrides onto unsaturated carbon-to-carbon bonds · CPC title

• C07C67/54

  by distillation · CPC title

• C07C67/62

  Use of additives, e.g. for stabilisation · CPC title

• C07C69/54

  Acrylic acid esters; Methacrylic acid esters · CPC title