PROCESS FOR MAKING MIXTURES OF CHELATING AGENTS

Abstract

Process for making a chelating agent according to the general formula (I),

R.sup.1CH(COOX.sup.1)N(CH.sub.2COOX.sup.1).sub.2(I)

wherein R.sup.1 is selected from hydrogen, C.sub.1-C.sub.4-alkyl, phenyl, benzyl, CH.sub.2OH, and CH.sub.2CH.sub.2COOX.sup.1, X.sup.1 is (M.sub.xH.sub.1-x), M being selected from alkali metal, x is in the range of from 0.6 to 1, said process comprising the following steps: (a) providing a solid, a slurry or a solution of a compound according to general formula (II a)

R.sup.1CH(COOX.sup.2)N(CH.sub.2CN).sub.2(II a) wherein X.sup.2 is (M.sub.yH.sub.1-y), M being selected from alkali metal, y is in the range of from zero to 1, (b) contacting said solid or slurry or solution with an aqueous solution of alkali metal hydroxide, wherein the molar ratio of alkali metal ions to nitrile groups is in the range of from 0.6:1 to 0.95:1, (c) reacting said compound according to general formula (II a) with said alkali metal hydroxide.

Claims

1: A process for making a chelating agent according to formula (I):
R.sup.1CH(COOX.sup.1)N(CH.sub.2COOX.sup.1).sub.2(I), wherein: R.sup.1 is selected from the group consisting of hydrogen, C.sub.1-C.sub.4-alkyl, phenyl, benzyl, CH.sub.2OH, and CH.sub.2CH.sub.2COOX.sup.1; X.sup.1 is (M.sub.xH.sub.1-x), M being an alkali metal; and x is in a range of from 0.6 to 1, the process comprising: (a) contacting a solid, a slurry, or a solution of a compound according to formula (II):
R.sup.1CH(COOX.sup.2)N(CH.sub.2CN).sub.2(II), wherein: X.sup.2 is (M.sub.yH.sub.1-y), M being an alkali metal; and y is in the range of from zero to 1, with an aqueous solution of alkali metal hydroxide, wherein a molar ratio of alkali metal ions to nitrile groups is in a range of from 0.6:1 to 0.95:1; and (b) reacting the compound according to formula (II) with the alkali metal hydroxide.

2: The process according to claim 1, wherein the reacting is performed at a temperature in a range of from 30 to 200 C.

3: The process according to claim 1, wherein M is at least one alkali metal selected from the group consisting of sodium and potassium.

4: The process according to claim 1, wherein, in formula (1), x is in a range of from 0.7 to 0.85.

5: The process according to claim 1, wherein in formula (II), R.sup.1 is methyl, and the compound of formula (II) is predominantly an L-enantiomer, wherein the ratio of L to D is in a range of from 95:1 to 100:1.

6: The process according to claim 1, wherein the reacting comprises at least two stages (c1) and (c2), wherein stage (c2) is performed at a temperature at least 20 C. higher than stage (c1).

7: The process according to claim 1, wherein the chelating agent according to formula (I) comprises at least one compound having a formula selected from the group consisting of formulae (III a) and (III b):
R.sup.1CH(COOX.sup.1)N(CH.sub.2COOX.sup.1)(CH.sub.2CONH.sub.2)(III a), and
R.sup.1CH(COOX.sup.1)N(CH.sub.2CONH.sub.2).sub.2(III b) wherein the variables are defined as for formula (I).

8-16. (canceled)

Description

EXAMPLE 1

[0288] Compound (I a): L-CH.sub.3CH(COOX.sup.2)N(CH.sub.2CN).sub.2 with X.sup.2 is (Na.sub.y y is 0.65. Compound (I a) was made according to WO 2015/036324.

[0289] Step (a.1): an amount of 293.3 g (31.6 wt.-%, 0.51 mol) of compound (I a) was used as aqueous solution.

[0290] Step (b.1): a 1-I-three-necked flask was charged with 100 g of 10% by weight aqueous solution of NaOH (corresponds to 0.25 mol NaOH). Under stirring, the solution from step (a.1) and 59.6 g of 50% by weight aqueous NaOH (0.745 mol) were added simultaneously over a period of 120 minutes under cooling. The temperature did not exceed 40 C. The reaction mixture was stirred additional 60 minutes at 40 C.

[0291] Step (c.1): the reaction mixture obtained from step (b.1) was stirred at 70 C. for 60 minutes, substep (c2.1).

[0292] Then, the reaction mixture was refluxed for 240 minutes at a reduced pressure of 900 to 950 mbar, the temperature rose up to 90 to 100 C., sub-step (c3.1). Since considerable amounts of ammonia evaporated together with water, the loss of water was partially compensated by adding deionized water. It was observed that the temperature dropped to lower temperatures.

[0293] After completion of sub-step (c3.1), an orange-brown reaction mixture of 362.2 g inventive mixture (IM.1) was obtained. (IM.1) displayed an iron-binding capacity of 1.513 mmol/g. This corresponds to a yield of 97% (calculated as MGDA-H.sub.3). The NTA content (calculated as NTA-H.sub.3) was <0.1 wt.-% according to HPLC analysis.

[0294] The ratio of components (A) to (B) was 1.4 to 1. The pH value was 10.2.

[0295] The content of NaCl was 16.6 mg/kg, and the content of Na.sub.2SO.sub.4 was about 4.4 mg/kg, both determined by ICP measurements.