Abstract Pure acrylic acid is isolated from an aqueous crude acid containing acrylic acid together with minor proportions of acetic acid, formaldehyde and high boilers boiling at a temperature higher than 220* C by liquid-liquid extraction with the use of 3,3,5-trimethylcyclohexanone and/or isophorone as the extractant(s). To this end, the aqueous acrylic acid-containing crude acid is subjected in an extraction zone to counterflow extraction with the use of the extractant(s) and with the resultant formation of an organic extract containing acrylic acid, acetic acid, high boilers and minor proportions of water, which are dissolved in the extractant; the extract is introduced approximately into the midsection of a first distilling column; acetic acid and water are removed overhead under reduced pressure; the base product of the first distilling column, containing extractant(s), acrylic acid and high boilers, is delivered approximately to the midsection of a second distilling column; pure acrylic acid is distilled off overhead under reduced pressure; and the base product of the second distilling column, consisting of high boilers and extractant(s), is recycled to the extraction zone.
Inventors
👤 Kurt Sennewald
👤 Heinz Erpenbach
👤 Heinz Handte
👤 Winfried Lork
Bibliographic Details
Application Number—
JurisdictionUS
Data Sourcegoogle_patents
Last Synchronized2026-10-31 09:58
CPC Classifications
C; C07; C07C; C07C51/00; C07C51/42; C07C51/48
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
49 words
The process as claimed in claim 1, wherein a portion of the base product of the second distilling zone, consisting of high boilers and extractant, is removed from the said second distilling zone, distilled and the extractant distillatively freed from the high boilers is recycled to the extraction zone.
Claim 2
Dependent Claim
64 words
The process as claimed in claim 1, wherein aqueous raffinate, which is obtained in the extraction zone and contains dissolved extractant, is delivered approximately to the midsection of a stripping zone, the extractant is recovered by removing an azeotrope of extractant and water overhead, the azeotrope is recycled to the extraction zone, and waste water is discharged through the base of the stripping zone.
Claim 3
Dependent Claim
26 words
The process as claimed in claim 1, wherein the first and second distilling zones are operated under a pressure of between 5 and 200 mm Hg.
Claim 4
Dependent Claim
45 words
The process as claimed in claim 1, wherein the aqueous crude acid contains between 5 and 40 weight percent acrylic acid, between 0.5 and 8 weight percent acetic acid, between 0.5 and 5 weight percent formaldehyde and between 0.2 and 5 weight percent high boilers.
Claim 5
Dependent Claim
37 words
The process as claimed in claim 1, wherein the aqueous crude acid is extracted with the use of between one and 10 parts by weight extractant, per part by weight acrylic acid in the aqueous crude acid.