# US 5,352,825 A · Recovery of organic acid salts from impure process streams by addition of bases

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- Number: US 5,352,825 A
- Document ID: US5352825A
- Status: Granted
- Kind: A
- Application number: 08/087,656
- Filed: 1993-07-06
- Granted: 1994-10-04
- Earliest claimed: 1993-07-06
- Assignees: Hoarmann & Reimer Corp.
- Inventors: Steven W. Felman; Chetna Patel; Bhalchandra H. Patwardhan; David J. Solow
- Web page: https://patentgrep.com/patent/US5352825A

## CPC

- C07C 51/43: by change of the physical state, e.g. crystallisation
- C07C: ACYCLIC OR CARBOCYCLIC COMPOUNDS

## Abstract

This invention provides an improved method for recovering an organic acid as a salt from various process streams by addition of a crystallizing base to a concentrated solution of neutralized organic acid. The addition of such a base causes crystallization of the salt. This process provides more efficient recovery of organic acid salt from a fermentation process stream than traditional recrystallization and it may be used essentially as a one step purification process. The improved method is particularly applicable to the recovery of trisodium or tripotassium citrate from process streams produced in the fermentation and recovery of citric acid, with the addition of a crystallizing base such as sodium hydroxide, potassium hydroxide or ammonia.

## Claims

### Claim 1

An improved process for recovering an organic acid salt from an impure process stream, comprising the steps of:
step a and step b in either order,
a. obtaining a solution of an organic acid salt of interest, concentrated to within about ten percent (by weight) of the saturation point;
b. adding a sufficient amount of a crystallizing base to the concentrated solution of the organic acid salt to produce crystals of the salt; and
c. separating the crystallized organic acid salt from mother liquor.

### Claim 2 (depends on 1)

The improved process of claim 1 in which the crystallizing base is chosen from the group consisting of sodium hydroxide, ammonia and potassium hydroxide.

### Claim 3 (depends on 2)

The improved process of claim 2 in which the crystallizing base is sodium hydroxide.

### Claim 4 (depends on 2)

The improved process of claim 2 in which the crystallizing base is ammonia.

### Claim 5 (depends on 1)

The improved process of claim 1 in which the separated mother liquor is treated to recover an additional yield of the organic acid salt.

### Claim 6 (depends on 1)

The improved process of claim 1 in which the separated mother liquor is treated to recover the crystallizing base.

### Claim 7

An improved process for the recovery of an organic acid salt from a fermentation broth containing such organic acid and/or salt thereof, comprising the steps of:
a. fermenting an appropriate carbon and hydrogen source as a substrate in the presence of an appropriate microorganism to produce a fermentation broth containing a desired organic acid and/or salt thereof together with impurities including the biomass residue of the microorganism;
b. treating the fermentation broth to substantially remove the biomass, thereby providing a partially purified fermentation broth containing the organic acid and/or salt thereof, unreacted substrate and other impurities;
and the steps c and d in either order,
c. neutralizing any residual organic acid in the partially purified fermentation broth to produce the desired organic acid salt with a neutralizing base in which the cation is the same as that in the desired salt;
d. treating the neutralized partially purified fermentation broth to provide a solution of the desired organic acid salt, concentrated to within about ten percent (by weight) of the saturation point;
e. adding a sufficient amount of a crystallizing base to the concentrated solution to produce the organic acid salt crystals; and
f. separating the organic acid salt crystals from mother liquor.

### Claim 8 (depends on 7)

The process of claim 7 in which the crystallizing base is chosen from the group consisting of sodium hydroxide, ammonia and potassium hydroxide.

### Claim 9 (depends on 8)

The process of claim 8 in which the crystallizing base is sodium hydroxide.

### Claim 10 (depends on 8)

The process of claim 8 in which the crystallizing base is ammonia.

### Claim 11 (depends on 7)

The process of claim 7 in which the mother liquor separated from the organic acid salt crystals is treated to recover an additional yield of organic acid salt.

### Claim 12 (depends on 7)

The process of claim 7 in which the mother liquor separated from the organic acid salt crystals is treated to recover the crystallizing base.

### Claim 13

An improved process for the recovery of an alkali metal or alkaline earth metal salt of citric acid from a fermentation broth containing citric acid and/or a salt thereof, comprising the steps of:
a. fermenting an appropriate carbon and hydrogen source as a substrate in the presence of an appropriate microorganism to produce a fermentation broth containing citric acid and/or a salt thereof together with impurities including the biomass residue of the microorganism;
b. treating the fermentation broth to substantially remove the biomass, thereby providing a partially purified fermentation broth containing citric acid and/or salt thereof, unreacted substrate and other impurities;
and the steps c and d in any order,
c. neutralizing any residual citric acid present in the partially purified fermentation broth with a base in which the cation is the desired alkali metal or alkaline earth metal cation to produce the desired alkali metal or alkaline earth metal citrate salt;
d. treating the neutralized fermentation broth to provide a solution of the desired alkali metal or alkaline earth metal citrate salt, concentrated to within about ten percent (by weight) of the saturation point;
e. adding a sufficient amount of a crystallizing base to the concentrated solution to produce alkali metal or alkaline earth metal citrate salt crystals; and
f. separating the alkali metal or alkaline earth metal citrate salt crystals from mother liquor.

### Claim 14 (depends on 13)

The process of claim 13 in which the crystallizing base of step e is chosen from the group consisting of sodium hydroxide, ammonia and potassium hydroxide.

### Claim 15 (depends on 14)

The process of claim 14 in which the crystallizing base is sodium hydroxide.

### Claim 16 (depends on 14)

The process of claim 14 in which the crystallizing base is ammonia.

### Claim 17 (depends on 13)

The process of claim 13 in which the cation of the neutralizing base of step c is chosen from the group consisting of sodium and potassium.

### Claim 18 (depends on 17)

The process of claim 17 in which the cation of the neutralizing base is sodium and the desired citric acid salt is trisodium citrate.

### Claim 19 (depends on 17)

The process of claim 17 in which the cation of the neutralizing base is potassium and the desired citric acid salt is tripotassium citrate.

### Claim 20 (depends on 13)

The process of claim 13 in which the separated mother liquor is treated to recover an additional yield of the desired alkali metal or alkaline earth metal citrate salt.

### Claim 21 (depends on 13)

The process of claim 13 in which the separated mother liquor is treated to recover the crystallizing base.

### Claim 22

An improved process for recovering an alkali metal or alkaline earth metal salt of citric acid from an impure process stream, comprising the steps of:
the steps a and b in any order,
a. obtaining a solution of a desired alkali metal or alkaline earth metal citric acid salt, concentrated to within about ten percent (by weight) of the saturation point;
b. adding a sufficient amount of a crystallizing base to the concentrated solution of the alkali metal or alkaline earth metal citric acid salt to crystallize the salt; and
c. separating the salt crystals from mother liquor.

### Claim 23 (depends on 22)

The improved process of claim 22 in which the crystallizing base is chosen from the group consisting of sodium hydroxide, ammonia and potassium hydroxide.

### Claim 24 (depends on 23)

The improved process of claim 23 in which the crystallizing base is sodium hydroxide.

### Claim 25 (depends on 23)

The improved process of claim 23 in which the crystallizing base is ammonia.

### Claim 26 (depends on 22)

The improved process of claim 22 in which the separated mother liquor is treated to recover an additional yield of the desired citric acid salt.

### Claim 27 (depends on 22)

The improved process of claim 22 in which the separated mother liquor is treated to recover the crystallizing base.

### Claim 28

An improved process for the recovery of an alkali metal salt of citric acid in combination with the fermentation of citric acid and recovery by a solvent extraction or lime sulfuric process, comprising the steps of:
the steps a and b in any order,
a. treating an impure process stream resulting from a solvent extraction or lime-sulfuric recovery process to obtain a saturated solution of an alkali metal citric acid salt which solution also contains other impurities;
b. adding a crystallizing base chosen from the group consisting of sodium hydroxide, potassium hydroxide and ammonia to the concentrated solution to produce the alkali metal citric acid salt; and
c. separating the alkali metal salt crystals from the mother liquor.

### Claim 29 (depends on 28)

The process of claim 28 in which the desired alkali metal salt is chosen from the group consisting of trisodium and tripotassium citrate.

### Claim 30 (depends on 28)

The process of claim 28 in which the mother liquor is treated to recover an additional yield of the alkali metal salt crystals.

### Claim 31 (depends on 28)

The process of claim 28 in which the mother liquor is treated to recover the crystallizing base.