US 6,599,398 B1Granted

Recovery of adiponitrile from a mixture of adiponitrile, aminocapronitrile and hexamethylenediamine

AssigneeE. I. Du Pont de Nemours and Company

InventorsJohn Ostermaier, Leon Scott, James Hastings

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Abstract

Process for the recovery of a purified adiponitrile (ADN) from a mixture of adiponitrile, aminocapronitrile and hexamethylenediamine, utilizing two sequential distillations: (1) a first distillation in which the mixture is distilled in a distillation column at a head pressure that causes at least 7% of the ADN to go into the distillate, along with bishexamethylenetriamine (BHMT) and 2-cyanocyclopentylideneimine (CPI), and (2) a second distillation in which the distillate from the first distillation is distilled in a second distillation column at a head pressure sufficient to cause minimum-temperature azeotropy between ADN and BHMT, thereby allowing the majority of the BHMT and CPI to be removed from the second distillation as distillate, and ADN, substantially free of both BHMT and CPI, to be removed as bottoms.

Claims4

Dependent claims

A process for recovering a purified adiponitrile (ADN) from a feed mixture comprising bishexamethylenetriamine (BHMT), ADN, 2-cyanocyclopentylideneimine (CPI), and high boiling tars, said process comprising the following sequential steps:

(1) distilling the mixture in an ADN Recovery Distillation Column having a head pressure in the range of 2 to 150 mm Hg to produce a substantially tar-free distillate comprising at least 70% of the ADN in the feed mixture, BHMT and CPI, and a bottoms product comprising substantially all of the tars and the remainder of the ADN in the feed mixture;
and then
(2) distilling the distillate from step (1) in an ADN Refining Distillation Column having a head pressure in the range of 20 to 150 mm Hg, which causes minimum-temperature azeotropy between ADN and BHMT, thereby allowing the removal from the ADN Refining Distillation Column of (i) a distillate containing the majority of the BHMT and CPI present in the distillate from step (1), and (ii) a bottoms product that comprises ADN that is substantially free of both BHMT and CPI.

Dependencies are inferred from the claim text.