# US 9,517,999 B2 · Process for purifying (meth)acrylic acid

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- Number: US 9,517,999 B2
- Document ID: US9517999B2
- Status: Granted
- Kind: B2
- Application number: 14/766,541
- Filed: 2014-03-07
- Published: 2015-12-24
- Granted: 2016-12-13
- Earliest claimed: 2013-03-15
- Assignees: Rohm and Haas Company
- Applicants: Rohm and Haas Company
- Inventors: Alan E. Sopchik; Stephen T. Cohn
- Web page: https://patentgrep.com/patent/US9517999B2

## CPC

- C07C 51/487: by treatment giving rise to chemical modification (by chemisorption C07C51/47)
- C07C: ACYCLIC OR CARBOCYCLIC COMPOUNDS

## Abstract

A process for producing a grade of (meth)acrylic acid having residual formaldehyde levels of under 100 parts per million.

## Claims

### Claim 1

A process for producing a pure grade (meth)acrylic acid, comprising contacting an aqueous crude (meth)acrylic acid, which comprises formaldehyde as an impurity, with at least 0.5 molar equivalent of cysteine per mole of formaldehyde impurity, wherein the contacting is conducted under conditions sufficient to reduce the concentration of the formaldehyde impurity to less than 100 ppm per 100 weight parts (meth)acrylic acid, wherein the aqueous crude (meth)acrylic acid comprises at least 5 wt. % water, and wherein the contacting is conducted in an absorber, quench tower, or dehydration column.

### Claim 2 (depends on 1)

The process of claim 1 wherein the amount of cysteine is at least 1 molar equivalent.

### Claim 3 (depends on 1)

The process of claim 1 wherein the amount of cysteine is from 1 to 10 molar equivalents.

### Claim 4 (depends on 1)

The process of claim 1 wherein the amount of cysteine is from 1 to 5 molar equivalents.

### Claim 5 (depends on 1)

The process of claim 1 wherein the amount of cysteine is from 1 to 2 molar equivalents.

### Claim 6 (depends on 1)

The process of claim 1 wherein the aqueous crude (meth)acrylic acid comprises from 5 to 80 wt. % water.

### Claim 7 (depends on 1)

The process of claim 1 wherein the concentration of the formaldehyde impurity is reduced to less than 50 ppm per 100 weight parts (meth)acrylic acid.

### Claim 8 (depends on 1)

The process of claim 1 wherein the concentration of the formaldehyde impurity is reduced to less than 25 ppm per 100 weight parts (meth)acrylic acid.

### Claim 9 (depends on 1)

The process of claim 1 wherein the concentration of the formaldehyde impurity is reduced to less than 10 ppm per 100 weight parts (meth)acrylic acid.

### Claim 10 (depends on 1)

The process of claim 1 wherein the process is continuous.

### Claim 11 (depends on 1)

The process of claim 1 wherein the crude acid further comprises acrolein prior to the contacting with cysteine.