# US 5,710,325 A · Manufacture of adipic acid

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- Number: US 5,710,325 A
- Document ID: US5710325A
- Status: Granted
- Kind: A
- Application number: 08/740,812
- Filed: 1996-11-01
- Granted: 1998-01-20
- Earliest claimed: 1996-11-01
- Assignees: E. I. Du Pont de Nemours and Company; Dsm N.V.
- Inventors: Harold Stanley Bruner, Jr.; Samuel Livingston Lane; Bruce Edwin Murphree
- Web page: https://patentgrep.com/patent/US5710325A

## CPC

- C07C 51/10: by reaction with carbon monoxide
- C07C 67/38: by addition to an unsaturated carbon-to-carbon bond
- C07C: ACYCLIC OR CARBOCYCLIC COMPOUNDS

## Abstract

This invention provides a process for the preparation of adipic acid from pentenoic acids or esters of pentenoic acids by hydrocarboxylation of a reaction mixture in which gamma-valerolactone constitutes 30 to 70% by weight of the reaction mixture.

## Claims

### Claim 1

A process for the preparation of adipic acid from pentenoic acid or mixtures of pentenoic acid isomers which comprises:
(a) forming a reaction mixture containing the pentenoic acids or mixtures thereof, water, carbon monoxide, gamma-valerolactone, an iridium catalyst promoted with bromide or iodide and optionally a strong acid reaction promoter wherein the concentration of gamma-valerolactone is from 30 to 70% by weight of the reaction mixture; and
(b) reacting the mixture to convert pentenoic acid to adipic acid and branched six carbon dicarboxylic isomers of adipic acid.

### Claim 2 (depends on 1)

The process of claim 1 wherein the strong acid promoter is selected from the group consisting of triflic, p-toluenesulfonic and phosphoric acid.

### Claim 3 (depends on 1)

The process of claim 1 wherein the concentration of gamma-valerolactone is from 50 to 70% by weight of the reaction mixture.

### Claim 4 (depends on 1)

The process of claim 1 further comprising subsequent to step (b), the steps:
(c) removing a portion of the mixture as a product stream and recovering crude adipic acid and forming a by-product stream;
(d) subjecting the by-product stream to dehydrocarboxylation to convert a part of the by-product branched six carbon dicarboxylic isomers of adipic acid to pentenoic acid isomers forming a recycle stream; and
(e) combining the recycle stream and fresh feed to form the reaction mixture of step (a).

### Claim 5 (depends on 1, 4)

The process of claims 1 or 4 wherein all or a part of the pentenoic acid or pentenoic acid isomers feed is a pentenoic acid monoester and wherein the product adipic acid monoester formed therefrom is hydrolyzed to form adipic acid.