US 12,441,680 B2
Method for producing isocyanates
Joachim Zechlin, Neuss (DE); Tim Loddenkemper, Dormagen (DE); and Thomas Bludowsky, Ratingen (DE)
Assigned to Covestro Deutschland AG, Leverkusen (DE)
Appl. No. 17/640,419
Filed by Covestro Deutschland AG, Leverkusen (DE); and Covestro Intellectual Property GmbH & Co. KG, Leverkusen (DE)
PCT Filed Sep. 14, 2020, PCT No. PCT/EP2020/075591
§ 371(c)(1), (2) Date Mar. 4, 2022,
PCT Pub. No. WO2021/052894, PCT Pub. Date Mar. 25, 2021.
Claims priority of application No. 19197784 (EP), filed on Sep. 17, 2019; application No. 20155540 (EP), filed on Feb. 5, 2020; and application No. 20176532 (EP), filed on May 26, 2020.
Prior Publication US 2022/0332677 A1, Oct. 20, 2022
Int. Cl. C07C 263/10 (2006.01); C07C 263/20 (2006.01)
CPC C07C 263/10 (2013.01) [C07C 263/20 (2013.01)] 12 Claims
 
1. A process for preparing an isocyanate comprising:
(A) reacting an amine with a stoichiometric excess of phosgene using an aromatic solvent of formula C6H6-XClX, wherein X=1 or 2,
(a) as a diluent during the reaction and/or
(b) as a means for cooling the reaction mixture formed from the reaction of the amine with phosgene
to obtain a liquid product mixture comprising the isocyanate, the aromatic solvent, and a gaseous product mixture containing phosgene and hydrogen chloride; and
(B) isolating the isocyanate from the liquid product mixture obtained in step (A) by a process comprising a final distillation in which the isolated isocyanate is obtained as a product stream, wherein in the final distillation or in a distillation step upstream of the final distillation at least one stream comprising aromatic solvent of formula C6H6-YClY, wherein Y=X+1, is discharged such that the isolated isocyanate has a mass fraction, based on its total mass, of aromatic solvent of formula C6H6-YClY of 0.0 ppm to 9.9 ppm.