PROCESS FOR THE CONTINUOUS DISTILLATION OF ACRYLATES

Abstract

A process for continuously distiling acrylates by means of a rectification column, wherein the acrylate content in the feed to the rectification column is at least 80% by weight, the liquid in the bottom region of the rectification column is heated by means of an evaporator, and the parts of the evaporator that are in contact with product are made from stainless steel.

Claims

1.-12. (canceled)

13. A process for continuously distilling acrylates by means of a rectification column, wherein the acrylate content in the feed to the rectification column is at least 80% by weight, the liquid in the bottom region of the rectification column is heated by means of an evaporator, and the parts of the evaporator that are in contact with product are made from stainless steel.

14. The process according to claim 13, wherein methyl acrylate, ethyl acrylate, n-butyl acrylate or 2-ethylhexyl acrylate is used as acrylate.

15. The process according to claim 13, wherein the acrylate content in the feed to the rectification column is at least 85% by weight.

16. The process according to claim 13, wherein the acrylate content in the feed to the rectification column is at least 90% by weight.

17. The process according to claim 13, wherein the acrylate content in the feed to the rectification column is at least 95% by weight.

18. The process according to claim 13, wherein the evaporator is a shell and tube heat exchanger.

19. The process according to claim 13, wherein the parts of the evaporator that are in contact with product are made from stainless steel having 10.5% to 30.0% by weight of chromium.

20. The process according to claim 19, wherein the parts of the condensation column that are in contact with product are made from stainless steel additionally having 2.0% to 35.0% by weight of nickel.

21. The process according to claim 19, wherein the parts of the condensation column that are in contact with product are made from stainless steel additionally having 0.1% to 8.0% by weight of molybdenum.

22. The process according to claim 19, wherein the feed to the rectification column has an acid number of less than 100 mg of potassium hydroxide per g of feed.

23. The process according to claim 13, wherein the feed to the rectification column has an acid number of less than 10 mg of potassium hydroxide per g of feed.

24. The process according to claim 13, wherein the feed to the rectification column has an acid number of less than 1 mg of potassium hydroxide per g of feed.

Description

EXAMPLES

Example 1

[0038] Ethyl acrylate (99.88% by weight of ethyl acrylate, 0.05% by weight of isobutyl acrylate, 0.03% by weight of N,N-di-sec-butyl-para-phenylenediamine, 0.01% by weight of 4-hydroxy-2,2,6,6-tetramethylpiperidinyloxyl) was metered in continuously beneath the first tray of a rectification column (diameter 1000 mm, 15 dual-flow trays) with a shell and tube heat exchanger (62 m2) in the bottom region and an external cooler in the top region. The rectification column was operated at a pressure of 400 mbar. The reflux ratio was 0.2. The reflux was stabilized with 4-hydroxy-2,2,6,6-tetramethylpiperidinyloxyl. The feed to the rectification column was 6094 kg/h. At the top of the rectification column, 7386 kg/h of distillate was removed.

[0039] The parts of the evaporator that were in contact with the product were made from stainless steel (1.4571 material according to DIN EN 10088:16.5% to 18.5% by weight of chromium, 10.5% to 13.5% by weight of nickel, 2.0% to 2.5% by weight of molybdenum, up to 0.7% by weight of titanium). The corrosion rate was less than 0.01 mm/a.

[0040] In the evaporator, no polymer deposits were apparent after 100 days.

Example 2 (Comparative Example)

[0041] Ethyl acrylate (99.88% by weight of ethyl acrylate, 0.05% by weight of isobutyl acrylate, 0.03% by weight of N,N-di-sec-butyl-para-phenylenediamine, 0.01% by weight of 4-hydroxy-2,2,6,6-tetramethylpiperidinyloxyl) was metered in continuously to the 39th tray of a rectification column (diameter 1100 mm, 52 dual-flow trays) with a shell and tube heat exchanger (51 m2) in the bottom region and an external cooler in the top region. The rectification column was operated at a pressure of 1000 mbar. The reflux ratio was 0.93. The reflux was stabilized with 4-hydroxy2,2,6,6-tetramethylpiperidinyloxyl. The feed to the rectification column was 6399 kg/h. 6094 kg/h of product was discharged from the bottom of the rectification column.

[0042] The parts of the evaporator that were in contact with the product were made from nonalloyed steel (1.0425 material: up to 0.3% by weight of chromium, up to 0.3% by weight of nickel, up to 0.08% by weight of molybdenum, up to 0.03% by weight of titanium). The corrosion rate was less than 0.01 mm/a.

[0043] In the evaporator, distinct polymer deposits were apparent after 100 days.