# US 8,771,476 B2 · Methods for inhibiting polymerization of vinyl aromatic compounds during extractive distillation

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- Number: US 8,771,476 B2
- Document ID: US8771476B2
- Status: Granted
- Kind: B2
- Application number: 12/705,937
- Filed: 2010-02-15
- Published: 2011-01-20
- Granted: 2014-07-08
- Earliest claimed: 2009-07-17
- Assignees: GTC Technology Inc.
- Applicants: Amy Sealey; George A. Ball; B. Bryant Slimp, Jr.
- Inventors: Amy Sealey; George A. Ball; B. Bryant Slimp, Jr.
- Web page: https://patentgrep.com/patent/US8771476B2

## CPC

- C07C 7/08: by extractive distillation
- C07C 7/20: Use of additives, e.g. for stabilisation
- C07C: ACYCLIC OR CARBOCYCLIC COMPOUNDS

## Abstract

High temperatures and oxygen exposure during extractive distillation can result in polymerization of vinyl aromatic compounds. In various embodiments, the present disclosure relates to methods for inhibiting polymerization of vinyl aromatic compounds during extractive distillation. In various embodiments, the methods include a) providing a mixture containing at least one vinyl aromatic compound, b) adding at least one dinitrophenol inhibitor to the mixture, and c) after step b), performing an extractive distillation on the mixture to isolate the at least one vinyl aromatic compound. Purified styrene can be isolated by the methods described herein. In some embodiments, the dinitrophenol inhibitor is 2-sec-butyl-4,6-dinitrophenol (DNBP).

## Claims

### Claim 1

A method for inhibiting polymerization of vinyl aromatic compounds during extractive distillation, said method comprising the steps of:
a) providing a mixture;
wherein the mixture comprises at least one vinyl aromatic compound;
b) adding an inhibitor consisting of unmodified 2-sec-butyl-4,6-dinitrophenol to the mixture wherein a concentration of the inhibitor is at least about 1,000 wt ppm with respect to the at least one vinyl aromatic compound; and
c) after step b) occurs, performing an extractive distillation on the mixture to isolate the at least one vinyl aromatic compound; and
wherein less than 200 wt ppm of polymer is formed from the at least one vinyl aromatic compound.

### Claim 2 (depends on 1)

The method of claim 1, the extractive distillation is performed at a temperature of at least about 100° C.

### Claim 3 (depends on 1)

The method of claim 1, wherein the extractive distillation is performed at a temperature between about 80° C. and about 160° C.

### Claim 4 (depends on 1)

The method of claim 1, wherein a single vinyl aromatic compound is isolated from the extractive distillation.

### Claim 5 (depends on 4)

The method of claim 4, wherein the single vinyl aromatic compound is styrene.

### Claim 6 (depends on 1)

The method of claim 1, wherein a concentration of the dinitrophenol inhibitor is at least about 10,000 wt ppm with respect to the at least one vinyl aromatic compound.

### Claim 7 (depends on 1)

The method of claim 1, wherein the at least one vinyl aromatic compound comprises styrene.

### Claim 8 (depends on 1)

The method of claim 1, wherein the polymerization is thermal-induced.

### Claim 9 (depends on 1)

The method of claim 1, wherein the polymerization is free radical-induced.