Organic compounds -- part of the class 532-570 series – Organic compounds – Amino nitrogen containing
Patent
1999-12-08
2000-11-28
Richter, Johann
Organic compounds -- part of the class 532-570 series
Organic compounds
Amino nitrogen containing
203 87, C01B 2114
Patent
active
061537993
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for the preparation of very pure, aqueous solutions of free hydroxylamine.
2. Description of the Related Art
Very pure, concentrated, aqueous hydroxylamine solutions are used, inter alia, in the electronics industry, for example in combination with other substances for preliminary cleaning of the circuit boards. For use in the electronics industry, concentrations of the impurities, in particular metal ions, well below 1 ppm, ie. electronic grade products, are usually required. However, the aqueous hydroxylamine solutions commercially available at present contain impurities in the ppm range from the preparation, for example sodium sulfate or other metal compounds.
Hydroxylamine is produced on a large industrial scale as hydroxylammonium salt, usually as hydroxylammonium sulfate. Frequently, however, it is necessary to use a highly concentrated salt-free aqueous solution of free hydroxylamine. In order to avoid the abovementioned problems and in particular the instability of the hydroxylamine, those skilled in the art have avoided the use of traditional methods of large-scale chemistry for concentrating distillable substances, for example distillation, in the recovery of salt-free hydroxylamine solutions. The distillation of hydroxylamine, even on the laboratory scale, is even said to be a particularly dangerous operation; cf. Roth-Weller: Gefahrliche Chemische Reaktionen, Stoffinformationen Hydroxylamin, page 3, 1984, 2, Ecomed-Verlag. The distillation of hydroxylamine on an industrial scale has therefore also never been considered in technical publications. Instead, special methods have been used, although all of them have serious disadvantages.
Attempts were thus made to isolate free hydroxylamine from aqueous salt solutions with the aid of ion exchangers; cf., for example, U.S. Pst. No. 4,147,623, EP-A-1787, EP-A-237 052 and Z. Anorg. Ch. 288, 28-35 (1956). However, such a process leads only to dilute solutions with low space-time yields. Moreover, hydroxylamine reacts with many ion exchangers or is decomposed by them.
A further method comprises the electrodialysis of an aqueous hydroxylammonium salt solution in electrolysis cells with semipermeable membranes, as described, for example, in DE-A-33 47 259, JP-A-123 771 and JP-A-123 772. However, such a process is technically complicated and expensive and has to date not become established in industry.
DE-A-35 28 463 discloses the preparation of free hydroxylamine from hydroxylammonium sulfate by treatment with calcium oxide, strontium oxide or barium oxide and removal of the insoluble alkaline earth metal sulfates. In this method, the removal of the sulfates obtained in finely divided form presents considerable difficulties. In addition, only dilute solutions are obtained and, when calcium oxide or calcium hydroxide is used, free hydroxylamine still contains undesirably large amounts of ions owing to the relatively good solubility of the calcium sulfate. When strontium compounds and barium compounds are used, the relatively high price and especially the toxicity are moreover disadvantageous with regard to an industrial production process.
DE-A-12 47 282 describes a process in which alcoholic solutions of free hydroxylamine are obtained by reacting hydroxylammonium sulfate with ammonia in alcohol as a solvent and removing the ammonium sulfate. A similar process is described in EP-A-108 294. However, alcoholic solutions are unsuitable and undesirable for a number of applications. For example, particular precautions must be taken during the handling of such solutions, owing to their flammability. Furthermore, the alcohol used must as a rule be recovered by an expensive procedure, since the discharge of relatively large amounts of alcohol into waste water treatment plants or into outfalls is prohibited.
Finally, DE-A-36 01 803 describes a process for obtaining aqueous solutions of free hydroxylamine, in which hydroxylammonium sulfate is reacted with ammonia in lo
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Z. Anorg. Chem., 288, 1956, 28-35.
Roth-Weller: Gef. Chem. Reak., Stoffinformmation Hydroxylamin, p. 3, 1984.
Pfab Peter
Schelling Heiner
Strofer Eckhard
Watzenberger Otto
BASF - Aktiengesellschaft
Davis Brian J.
Richter Johann
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