US 10,889,539 B2
Aniline purification process
Michael Merkel, Düsseldorf (DE); Friedhelm Steffens, Leverkusen (DE); Murat Kalem, Neuss (DE); and Peter Lehner, Mülheim an der Ruhr (DE)
Assigned to Covestro Deutschland AG, Leverkusen (DE)
Filed by COVESTRO DEUTSCHLAND AG, Leverkusen (DE)
Filed on Oct. 16, 2019, as Appl. No. 16/654,303.
Claims priority of application No. 18200968 (EP), filed on Oct. 17, 2018.
Prior Publication US 2020/0123097 A1, Apr. 23, 2020
Int. Cl. C07C 209/84 (2006.01); B01D 3/14 (2006.01); B01D 3/36 (2006.01); B01D 5/00 (2006.01); C07C 211/46 (2006.01)
CPC C07C 209/84 (2013.01) [B01D 3/14 (2013.01); B01D 3/36 (2013.01); B01D 5/006 (2013.01); C07C 211/46 (2013.01)] 15 Claims
OG exemplary drawing
 
1. A process for preparing pure aniline, comprising:
a) providing a crude aniline fraction containing 80.000% by weight to 99.999% by weight of aniline and 0.001% by weight to 20.000% by weight of phenol, based on the total weight of aniline and phenol in the crude aniline fraction;
b) dividing the crude aniline fraction into a first partial stream and a second partial stream;
c) distilling the first partial stream in a first distillation column and distilling the second partial stream in a second distillation column, wherein the first distillation column is operated at a higher head pressure than the second distillation column, with the proviso that each of the first distillation column and the second distillation column is operated at a head pressure in the range from 1.0 mbar(abs.) to 500 mbar(abs.), and wherein from each of the first and the second distillation column,
a gaseous aniline distillate is removed as the overhead product and subsequently condensed, wherein a first partial stream of the condensed aniline distillate is returned to the first and/or the second distillation column as a reflux stream and a second partial stream of the condensed aniline distillate is removed as the product stream, and
a liquid bottom stream which is concentrated in phenol is removed, from which a first portion is partially or completely vaporised and is returned to the distillation column it originated from, and from which a second portion is discharged; and
d) using the heat released during the condensation of the aniline distillate from the first distillation column to provide the heat necessary for vaporising the first portion of the bottom stream from the second distillation column.