PROCESS FOR THE PURIFICATION OF A MIXTURE COMPRISING N-ALKYL-HYDROXYLAMMONIUM SALTS

Abstract

The present invention relates to a process for purification of a mixture comprising water, N-alkyl-hydroxylammonium salts and some byproducts wherein from the mixture water and byproducts are distilled off until the purity of N-alkyl-hydroxylammonium salts in the residue is 95% or higher and additionally keeping the water content during and after the distillation ≥40 wt.-% according to the residue.

Claims

1.-13. (canceled)

14. Process for the purification of a mixture comprising three compounds: a) water, b) 1 to 60 wt.-% of N-alkyl hydroxylammonium salt of formula I and ##STR00003## wherein: R1, R2, R3 each independently are selected from the group of H, methyl, ethyl, n-propyl, isopropyl, n-butyl, 2-butyl and tert-butyl, X is selected from Cl, SO.sub.4, PO.sub.4, CH.sub.3COO, (COO).sub.2, n dependent of the valence of X in water is a natural number selected from the group of 1, 2 and 3 and c) byproducts wherein the process comprises the following steps: I) putting the mixture into a purification apparatus, II) bringing the mixture in contact with steam III) removing a composition comprising water vapor and compound c) by distillation until the purity of compound b) in the residue is 95% or greater wherein the amount of water in the residue remains during and after the distillation ≥40 wt.-%.

15. The process according to claim 14, wherein the purification apparatus is a packed column as it is used for a continuous reverse flow stripping process.

16. The process according to claim 14, wherein the purification apparatus is a distillation apparatus.

17. The process according to claim 16, wherein the purification apparatus is a steam distillation apparatus

18. The process according to claim 14, wherein water is added either before step II) and/or during and/or after distillation of step III).

19. The process according to a claim 14, wherein the water that is added during the distillation of step III) in a steam distillation apparatus or in the packed column as it is used for continuous reverse flow stripping process is added as steam.

20. The process according to claim 14, wherein the water that is added during the distillation of step III) in a distillation apparatus is added according to the following steps: i) stopping the distillation, ii) adding the water in liquid form to the residue and iii) starting the distillation again.

21. The process according to claim 14, wherein the distillation temperature during step III) is in the range of 10 to 100° C. and the pressure is in the range of 1 to 1000 mbar.

22. The process according to claim 14, wherein the composition distilled off in step III) comprises more than 50 wt. % of water.

23. The process according to claim 14, wherein X is Cl and n is 1.

24. The process according to a claim 14, wherein R.sup.1 is ≠R.sup.2 and R.sup.3 is H.

25. The process according to claim 14, wherein R.sup.1 is methyl, R.sup.2 and R.sup.3 are H, X is Cl and n is 1.

26. The process according to claim 14, wherein none of R.sup.1, R.sup.2 and R.sup.3 is H.

Description

EXAMPLE 1

[0048] 99 g (1.35 mol) of diethyl amine are dissolved in 95 ml water. While stirring this mixture 14.3 g of gaseous CO.sub.2 are bubbled in over a period of 30 min. During the addition of CO.sub.2 the temperature is kept below 40° C. via external cooling. 301 g of a 40 wt.-% H.sub.2O.sub.2 solution (3.54 mol H.sub.2O.sub.2) are then slowly added over a period of 6 hours. During the addition of H.sub.2O.sub.2 the temperature must be kept below 60° C. via external cooling and optionally by lowering the rate of H.sub.2O.sub.2 addition. The pH value of the solution is continuously controlled during the addition using a calibrated glass electrode. When the pH value drops below 10 aqueous NaOH solution (50 wt.-%) is added as required in order to keep the pH value slightly above 10. After addition of all reactants the mixture is stirred at 50° C. and samples are taken for peroxide titration (pH value still has to be kept above 10 by addition of NaOH). As soon as the peroxide value drops below 0.5 wt.-% H.sub.2O.sub.2 the reaction is completed, and the temperature reduced to 20° C.

[0049] To this mixture 171.7 g HCl solution (37 wt.-% in water) are carefully added (dissolved CO.sub.2 gases out during this procedure). The temperature is increased to 50° C. and the pressure reduced to allow a slight refluxing of the solution (˜50-150 mbar). The condenser temperature has to be kept above 10° C. to allow for the removal of the acetaldehyde formed. After 4 hours of refluxing another portion of HCl solution (17 g) is added and refluxing continued for another 1.5 hours.

[0050] The solution still contains some intermediate and byproducts and has a purity of about 70% (NMR analysis: 400 MHz in D.sub.2O: The mixture contains residual nitrone (typical peak: δ=3.92 ppm, 1H) N-ethyl-hydroxylammonium chloride (typical peak: δ=3.17 ppm, 2H), acetaldehyde oxime (typical peaks: δ=7.44 ppm, 7.19 ppm, 2 isomers, 1H each) and acetaldehyde (typical peak: δ=8.31 ppm, 1H), other peaks contribute less than 3% of the total integral, excluding water). For purification, the solution is transferred to a distillation apparatus. The temperature is increased to 50° C. and the pressure adjusted to allow a distillation of water (p<50 mbar). After about 50% of the water initially present in the mixture is distilled off, at which point the concentration of the hydroxylammonium salt is approximately 30-35 wt.-%, the same amount of water is added to the residue before distillation is continued. This procedure is repeated for a total of three times. In the last distillation step, the amount of water removed is adjusted in such a way that solution of the hydroxylammonium salt remaining in the sump has a concentration of approximately 30-35 wt.-%. The purity of this solution of N-ethyl-hydroxylammonium chloride is ˜95% (via NMR analysis).

[0051] DSC analysis (T.sub.initial=30° C.−T.sub.final=410° C., T.sub.ramp=2.5° C./min, glass crucible) of the purified aqueous solutions of N-ethyl-hydroxylammonium chloride and of the pure salt showed the following energy releases and onset temperatures (concentration determined by elemental analysis of the corresponding solutions) in Table 1:

TABLE-US-00001 TABLE 1 Concentration Energy released Onset (wt.- %) (J/g) (° C.) 27.8 583 75 43.3 872 67 61.1 1242 71 100 1989 78

EXAMPLE 2

[0052] 91.5 g (0.91 mol) of diisopropyl amine are dissolved in 88.7 ml water and the mixture is homogenized by addition of 4.9 g methanol. To this mixture CO.sub.2 is added and subsequently hydrogen peroxide solution is added as described in example 1. After acidification with HCl solution and refluxing for 4 h the solution still contains some intermediate and byproducts and has a purity of about 90% ((NMR analysis: 400 MHz in D.sub.2O: The mixture contains N-isopropyl-hydroxylammonium chloride (typical peak: δ=3.60 ppm, 1H) and acetone (typical peak: δ=2.29 ppm, 6H); apart from the solvent peaks (methanol and water) other peaks contribute less than 3% of the total integral). For purification, the solution is transferred to a distillation apparatus. The temperature is increased to 50° C. and the pressure adjusted to allow a distillation of water (p<50 mbar). After about 50% of the solvent contained in the initial mixture is distilled off, at which point the concentration of the hydroxylammonium salt is approximately 30-35 wt. %, the same amount of water is added to the residue. This procedure is repeated in total three times. In the last distillation step, the amount of water removed is adjusted in such a way that solution of the hydroxylammonium salt remaining in the sump has a concentration of approximately 30-35 wt.-%. The purity of this solution of N-isopropyl-hydroxylammonium chloride is ˜98% (via NMR analysis).

EXAMPLE 3

[0053] 89.1 g (0.88 mol) N-tert-butyl-N-ethyl amine are dissolved in 91 ml of water. The mixture is treated with CO.sub.2 and homogenized afterwards by the addition of 35 mL MeOH. Then, hydrogen peroxide is added as is described in example 1. After acidification with HCl solution and refluxing for 4 h the solution still contains some intermediate and byproducts and has a purity of about 90% based (NMR analysis: 400 MHz in D.sub.2O: The mixture contains the desired product (δ=0.95 ppm, 9H), unconverted nitrone (typical peak: δ=7.33 ppm, 1H) and acetaldehyde (typical peak: δ=8.30 ppm, 1H); apart from solvents (methanol and water) other peaks contribute less than 3% of the total integral). For purification and liberation of N-tert-butyl hydroxylamine, the solution is transferred to a distillation apparatus. The temperature is increased to 50° C. and the pressure adjusted to allow a distillation of water (p<50 mbar). After about 50% of the solvent contained in the initial mixture are distilled off, at which point the concentration of the hydroxylammonium salt is approximately 35-40 wt.-%, the same amount of water is added to the residue. This procedure is repeated in total three times. In the last distillation step, the amount of water removed is adjusted in such a way that solution of the hydroxylammonium salt remaining in the sump has a concentration of approximately 35-40 wt.-%. The purity of this solution of N-tert-butyl-hydroxylammonium chloride is ˜99% (via NMR analysis).