Process for recovering iminodiacetic acid from sodium chloride solutions

Claim 2

A PROCESS FOR RECOVERING IMINODIACETIC ACID FROM AN AQUEOUS SOLUTION CONSISTING ESSENTIALLY OF WATER, IMINODIACETIC ACID, AND SODIUM CHLORIDE, THE MOLE RATIO OF IMIODIACETIC ACID TO SODIUM CHLORIDE BEING 1:1.0-15.0, SAID SOLUTION HAVING A TEMPERATURE OF ABOUT 0*-50*C AND CONTAINING AT LEAST AOUT 5 PERCENT IMINODIACETIC, SAID PROCESS COMPRISING ADJUSTING THE PH OF SAID AQUEOUS SOLUTION OF 1.4-3.0 TO PRECIPITATE IMINODIACETATIC ACID THEREFROM; SEPARATING THE PRECIPITATED IMINODIACETIC ACID; AND RECOVERING THE SEPARATED IMINODIACETIC ACID.

Claim 3

The process of claim 1 in which the pH is adjusted tc 1.5-2.2.

Claim 4

The process of claim 1 in which the pH is adjusted to 1.8-2.0.

Claim 5

The process of claim 1 in which the mole ratio of iminodiacetic acid to sodium chloride in the aqueous solution is 1:2.0-5.0.

Claim 6

A process for recovering iminodiacetic acid from a starting solution consisting essentially of water, iminodiacetic acid and sodium chloride, said starting solution having a temperature of about 10*-30*C and analyzing at least about 5 percent iminodiacetic acid, said process comprising; a. forming a first slurry consisting essentially of a first crop of precipitated iminodiacetic acid and a first mother liquor by adjusting the pH of the starting solution to 1.8-2.0; b. separating the first crop of precipitated iminodiacetic acid from the first mother liquor and recovering the separated iminodiacetic acid; c. forming a second slurry having a temperature effective for preventing the precipitation of iminodiacetic acid therefrom and consisting essentially of precipitated sodium chloride and a second mother liquor analyzing at least 5 percent dissolved iminodiacetic acid by evaporating water from the first mother liquor; d. separating the precipitated sodium chloride from the second mother liquor while maintaining the second slurry and the second mother liquor at a temperature effective for preventing iminodiacetic acid from precipitating therefrom; e. forming a third slurry consisting essentially of a second crop of precipitated iminodiacetic acid and a third mother liquor by cooling the second mother liquor to 10*-30*C; and f. separating the second crop of precipitated iminodiacetic acid from the third mother liquor and recovering the separated iminodiacetic acid.

Claim 7

A process for recovering iminodiacetic acid from a starting solution consisting essentially of water, iminodiacetic acid and sodium chloride, said starting solution having a temperature of about 10*-30*C and analyzing at least about 5 percent iminodiacetic acid, said process comprising; a. forming a first slurry consisting essentially of a first crop of precipitated iminodiacetic acid and a first mother liquor by adjusting the pH of the starting solution to 1.8-2.0; b. separating the first crop of precipitated iminodiacetic acid from the first mother liquor and recovering the separated iminodiacetic acid; c. forming a second slurry having a temperature effective for preventing the precipitation of iminodiacetic acid therefrom and consisting essentially of precipitated sodium chloride and a second mother liquor analyzing at least 5 percent dissolved iminodiacetic acid by evaporating water from the first mother liquor; d. separating the precipitated sodium chloride from the second mother liquor while maintaining the second slurry and the second mother liquor at a temperature effective for preventing iminodiacetic acid from precipitating therefrom; e. forming a third slurry consisting essentially of a second crop of precipitated iminodiacetic acid and a third mother liquor by cooling the second mother liquor to 10*-30*C; and f. separating the second crop of precipitated iminodiacetic acid from the third mother liquor and recovering the separated iminodiacetic acid.

Claim 8

The process of claim 5 in which the iminodiacetic acid concentration of the starting solution consisting essentially of water, iminodiacetic acid, and sodium chloride is 7-26 percent.

Claim 9

The process of claim 5 in which the mole ratio of iminodiacetic acid to sodium chloride in the solution consisting essentially of water, iminodiacetic acid, and sodium chloride is 1:1.8-2.5.

Claim 10

The process of claim 5 in which the pH of the starting solution is adjusted to 1.5-2.2.

Claim 11

The process of claim 5 in which the pH of the starting solution is adjusted to 1.8-2.0.

Claim 12

The process of claim 5 in which the third mother liquor is combined with separated first mother liquor from another run.

Claim 13

The process of claim 5 in which 80-95 percent of the third mother liquor is combined with separated first mother liquor from another run.

Claim 14

The process of claim 5 in which the starting solution consisting essentially of water, iminodiacetic acid, and sodium chloride is prepared by reacting an aqueous disodium iminodiacetate solution with an amount of hydrochloric acid effective to convert the disodium iminodiacetate to iminodiacetic acid.

Claim 15

A process for recovering iminodiacetic acid from a starting solution consisting essentially of water, iminodiacetic acid and sodium chloride, said starting solution having a temperature of about 10*-30*C said starting solution analyzing at least 4.5-6 percent iminodiacetic acid, said process comprising; a. forming a first slurry consisting essentially of a first crop of precipitated iminodiacetic acid and a first mother liquor by cooling said starting solution to 10*-30*C and adjusting the pH thereof to 1.8-2.0; b. separating the first crop of precipitated iminodiacetic acid from the first mother liquor and recovering the separated iminodiacetic acid; c. forming a second slurry consisting essentially of precipitated sodium chloride and a second mother liquor consisting essentially of water with sodium chloride and iminodiacetic acid dissolved therein, the second mother liquor analyzing at least 4.5-6 percent dissolved iminodiacetic acid, by evaporating water from the first mother liquor; d. separating the precipitated sodium chloride from the second mother liquor while maintaining the second slurry and the second mother liquor at a temperature effective to prevent iminodiacetic acid from precipitating therefrom; e. forming a third slurry consisting essentially of a second crop of precipitated iminodiacetic acid and a third mother liquor by cooling the second mother liquor to 10*-30*C; and f. separating the second crop of precipitated iminodiacetic acid from the third mother liquor and recovering the separated iminodiacetic acid.

Claim 16

A process for recovering iminodiacetic acid from a starting solution consisting essentially of water, iminodiacetic acid and sodium chloride, said starting solution having a temperature of about 10*-30*C said starting solution analyzing at least 4.5-6 percent iminodiacetic acid, said process comprising; a. forming a first slurry consisting essentially of a first crop of precipitated iminodiacetic acid and a first mother liquor by cooling said starting solution to 10*-30*C and adjusting the pH thereof to 1.8-2.0; b. separating the first crop of precipitated iminodiacetic acid from the first mother liquor and recovering the separated iminodiacetic acid; c. forming a second slurry consisting essentially of precipitated sodium chloride and a second mother liquor consisting essentially of water with sodium chloride and iminodiacetic acid dissolved therein, the second mother liquor analyzing at least 4.5-6 percent dissolved iminodiacetic acid, by evaporating water from the first mother liquor; d. separating the precipitated sodium chloride from the second mother liquor while maintaining the second slurry and the second mother liquor at a temperature effective to prevent iminodiacetic acid from precipitating therefrom; e. forming a third slurry consisting essentially of a second crop of precipitated iminodiacetic acid and a third mother liquor by cooling the second mother liquor to 10*-30*C; and f. separating the second crop of precipitated iminodiacetic acid from the third mother liquor and recovering the separated iminodiacetic acid.

Claim 17

The process of claim 13 in which the mole ratio of iminodiacetic acid to sodium chloride in the starting solution consisting essentially of water, iminodiacetic acid, and sodium chloride is 1:2.0-2.4.

Claim 18

The process of claim 13 in which the pH is adjusted to 1.8-2.0.

Claim 19

A process for recovering iminodiacetic acid from a first solution consisting essentially of water, iminodiacetic acid, and sodium chloride said solution having a temperature of about 10*-30*C and analyzing at least 5 percent iminodiacetic acid, said process comprising; a. forming a first slurry consisting essentially of precipitated iminodiacetic acid and a first mother liquor by adjusting the pH of a first portion of the first solution to 1.8-2.0; b. separating the precipitated iminodiacetic acid from the first mother liquor and recovering the separated iminodiacetic acid; c. forming a second slurry consisting essentially of precipitated sodium chloride and a second mother liquor analyzing at least 5 percent dissolved iminodiacetic by evaporating water from the first mother liquor; d. separating the precipitated sodium chloride from the second mother liquor while maintaining the second slurry and the second mother liquor at a temperature effective for preventing iminodiacetic acid from precipitating therefrom; e. forming a second solution by admixing at least a portion of the second mother liquor with a second portion of the first solution; f. forming a third slurry consisting essentially oF precipitated iminodiacetic acid and a third mother liquor by adjusting the pH of the second solution to 1.8-2.0; g. separating the precipitated iminodiacetic acid from the third mother liquor and recovering the separated iminodiacetic acid; h. forming a fourth slurry consisting essentially of precipitated sodium chloride and a fourth mother liquor analyzing at least 5 percent of dissolved iminodiacetic by evaporating water from the first mother liquor; and i. separating the precipitated sodium chloride from the fourth mother liquor while maintaining the fourth slurry and the separated fourth mother liquor at a temperature effective for preventing iminodiacetic acid from precipitating therefrom.

Claim 20

A process for recovering iminodiacetic acid from a first solution consisting essentially of water, iminodiacetic acid, and sodium chloride said solution having a temperature of about 10*-30*C and analyzing at least 5 percent iminodiacetic acid, said process comprising; a. forming a first slurry consisting essentially of precipitated iminodiacetic acid and a first mother liquor by adjusting the pH of a first portion of the first solution to 1.8-2.0; b. separating the precipitated iminodiacetic acid from the first mother liquor and recovering the separated iminodiacetic acid; c. forming a second slurry consisting essentially of precipitated sodium chloride and a second mother liquor analyzing at least 5 percent dissolved iminodiacetic by evaporating water from the first mother liquor; d. separating the precipitated sodium chloride from the second mother liquor while maintaining the second slurry and the second mother liquor at a temperature effective for preventing iminodiacetic acid from precipitating therefrom; e. forming a second solution by admixing at least a portion of the second mother liquor with a second portion of the first solution; f. forming a third slurry consisting essentially oF precipitated iminodiacetic acid and a third mother liquor by adjusting the pH of the second solution to 1.8-2.0; g. separating the precipitated iminodiacetic acid from the third mother liquor and recovering the separated iminodiacetic acid; h. forming a fourth slurry consisting essentially of precipitated sodium chloride and a fourth mother liquor analyzing at least 5 percent of dissolved iminodiacetic by evaporating water from the first mother liquor; and i. separating the precipitated sodium chloride from the fourth mother liquor while maintaining the fourth slurry and the separated fourth mother liquor at a temperature effective for preventing iminodiacetic acid from precipitating therefrom.

Claim 21

The process of claim 16 in which the first solution consisting essentially of water, iminodiacetic acid, and sodium chloride is prepared by reacting an aqueous disodium iminodiacetate solution with an amount of hydrochloric acid effective to convert the disodium iminodiacetate to iminodiacetic acid.

Claim 22

The process of claim 16 in which the pH of the first solution is adjusted to 1.5-2.1.

Claim 23

The process of claim 16 in which the pH of the first solution is adjusted to 1.8-2.0.

Claim 24

The process of claim 16 in which the pH of the second solution is adjusted to 1.5-2.2.

Claim 25

The process of claim 16 in which the pH of the second solution is adjusted to 1.8-2.0.

Claim 26

The process of claim 16 in which the mole ratio of iminodiacetic acid to sodium chloride in the first solution is 1.0:2.0-2.4.

Claim 27

The process of claim 16 in which the iminodiacetic acid concentration of the first solution is 18-24 percent.

Claim 28

The process of claim 16 in which 80-95 percent of the second mother liquor is admixed with the second portion of the first solution to form the second solution.