USOO6531.108B1 (12) United States Patent (10) Patent No.: US 6,531,108 B1 Bansho et al. (45) Date of Patent: Mar. 11, 2003 (54) PROCESS FOR PRODUCING FREE 5,837,107 A * 11/1998 Watzenberger et al. ..... 423/387 HYDROXYLAMINEAQUEOUS SOLUTION 6,299,734 B1 * 10/2001 Watzenberger et al. ..... 423/387 (75) Inventors: Kumiko Bansho, Shiga (JP); Yoshio * cited by examiner Noguchi, Shiga (JP) Primary Examiner Wayne A. Langel (74) Attorney, Agent, or Firm-Schnader Harrison Segal & (73) Assignee: Toray Fine Chemicals Co., Ltd. (JP) Lewis LLP (*) Notice: Subject to any disclaimer, the term of this (57) ABSTRACT patent is extended or adjusted under 35 U.S.C. 154(b) by 0 days. This invention provides a highly pure and highly concen trated free hydroxylamine aqueous Solution Substantially not (21) Appl. No.: 09/619,156 containing any Salt or organic Substance. (22) Filed: Jul. 19, 2000 This invention is a process for obtaining a free hydroxy lamine aqueous Solution, comprising the Steps of letting an (30) Foreign Application Priority Data aqueous Solution or Slurry containing hydroxylammonium Mar. 13, 2000 (JP) ......................................... 2000-68354 Sulfate and an alkali react with each other, to obtain an aqueous Solution or Slurry containing free hydroxylamine (51) Int. Cl." ................................................ C01B 21/20 and dissolved or partially precipitated Sulfates, mixing the (52) U.S. Cl. ........................... 423/387; 203/63; 203/66; obtained reaction Solution and a lower alcohol, to precipitate 423/545; 423/551 Solid Sulfates; Separating a Solution containing the lower (58) Field of Search ................................. 423/387, 388, alcohol and Some of water by distillation from the aqueous 423/545, 551; 203/63, 66 Solution remaining after Separating and removing the Solid Sulfates, and obtaining a free hydroxylamine aqueous Solu (56) References Cited tion from the remaining Solution by distillation. U.S. PATENT DOCUMENTS 4,778,669 A * 10/1988 Fuchs et al. ................ 423/387 30 Claims, 1 Drawing Sheet U.S. Patent Mar. 11, 2003 US 6,531,108 B1 Iº6p.) US 6,531,108 B1 1 2 PROCESS FOR PRODUCING FREE nium Sulfate or an oxime, etc. German Patent Publication HYDROXYLAMINEAQUEOUS SOLUTION No. 1247282 discloses a method in which an alcohol Solu tion of free hydroxylamine is obtained by removing the ammonium Sulfate precipitated in the reaction between BACKGROUND OF THE INVENTION hydroxylammonium Sulfate and ammonia in an alcohol. However, these reactions in an alcohol are low in produc The present invention relates to a process for producing a tivity and yield since the solubility of hydroxylammonium free hydroxylamine aqueous Solution, in more detail, a Sulfate is low, and to improve the disadvantage, complicated process for producing a free hydroxylamine aqueous equipment Such as a powerful Stirrer is required for the Solution, in which hydroxylammonium Sulfate and an alkali reaction System. Furthermore, in these methods, Since the are caused to react with each other for obtaining free Salt dissolved in the alcohol Solution remains in the product, hydroxylamine, comprising the Steps of adding a lower the purity of the product comes into question. alcohol for precipitating the Sulfates produced in the In German Patent Publication No. 3601803 (Japanese reaction, to Separate and remove them, Separating the lower Patent Laid-Open (Kokai) No. Sho62-171905 and U.S. Pat. alcohol by distillation, and obtaining a free hydroxylamine No. 4,778,669), as described above, an alcohol solution of aqueous Solution by distillation from the remaining Solution. 15 free hydroxylamine is obtained by removing the ammonium Sulfate precipitated in the reaction between hydroxylammo PRIOR ART nium Sulfate and ammonia in a lower alcohol. Furthermore, a hydroxylamine Stabilizer and water are added to the Hydroxylamine is industrially widely used as a medical alcohol Solution, and the alcohol is separated by distillation, and agricultural intermediate raw material or as a metal to obtain a free hydroxylamine aqueous Solution. However, Surface treating agent, etc. Since this method is also a reaction in an alcohol, the However, Since free hydroxylamine is very unstable and productivity and yield are low because of the low solubility is easily decomposed, it is generally converted into a rela of hydroxylammonium Sulfate, and to improve the tively stable hydroxylamine salt (hydroxylammonium salt) disadvantage, complicated equipment Such as a powerful for use. The decomposition of free hydroxylamine is espe 25 Stirrer is required for the reaction System. Moreover, Since cially likely to occur, for example, in the presence of heavy the aqueous Solution as a product is the residue of metal ions, at a high concentration, in a strong alkali or at a distillation, coloration and the ingreSS of ammonium Sulfate relatively high temperature. and heavy metals come into question. When hydroxylamine is actually used in the above It can be seen that a consistent reaction using an alcohol applications, free hydroxylamine, not a hydroxylammonium solvent only is not preferable in view of productivity, yield, Salt, is preferably used, and an aqueous Solution containing equipment and quality. free hydroxylamine at a higher concentration is often In the method disclosed in German Patent Publication No. required. Such a free hydroxylamine aqueous Solution has 3528463, hydroxylammonium sulfate with a low ammo been obtained by several methods. nium ion content and the oxide and/or hydroxide of calcium, 35 Strontium or barium are caused to react with each other in For example, in U.S. Pat. Nos. 4,147,623, 4,202,765, water, and the alkaline earth metal Sulfate is separated, to 5,788,946 and 5,872,295, a free hydroxylamine aqueous obtain a free hydroxylamine aqueous Solution. Since the Solution is liberated from a hydroxylammonium Salt aqueous alkaline earth metal Sulfate is generally low in the Solubility Solution containing impurities by using an ion exchange in water, the grain size is extremely Small, and it is difficult resin. However, the hydroxylamine concentration in the 40 to industrially Separate the Solid. Furthermore, in this obtained aqueous Solution is low, and hydroxylamine expe method, no other operation than precipitation is attempted dites the degradation of the ion exchanger, to cause much for Separating Sulfates, and the obtained acqueous Solution temporal and economical waste. contains Sulfates by amounts corresponding to the Solubili Furthermore, as described in German Patent Publication ties. By the way, as for the hydroxylammonium Sulfate used No. 3347259, there is also a method of obtaining a free 45 for this reaction, the hydroxylammonium Sulfate aqueous hydroxylamine aqueous Solution by electrodialysis in an Solution as the raw material must be crystallized Several electrolyte from a hydroxylammonium Salt aqueous Solution times, to decrease the ammonium ion content beforehand. contained in an electrolytic cell having a Semipermeable Furthermore, the Strontium compounds and barium com membrane, but the method is technically complicated and pounds are relatively expensive and highly toxic. So, this low in yield. Furthermore, the equipment cost is high. So, 50 method is not appropriate for industrial production. the method is not yet established industrially. In U.S. Pat. Nos. 5,472,679 and 5,266,290, hydroxylam A recent method for obtaining free hydroxylamine uses monium Sulfate and the oxide and/or hydroxide of an alkali the reaction between a hydroxylammonium Salt and an metal or an alkaline earth metal are caused to react with each alkali. This reaction System contains a large amount of a Salt other in water not containing any alcohol, to obtain a formed by the anions derived from the hydroxylammonium 55 reaction Solution containing free hydroxylamine, and from Salt and the cations derived from the alkali. So, various the reaction Solution, a highly concentrated free hydroxy attempts are made to Separate the Salt and free lamine aqueous Solution not containing any alcohol is hydroxylamine, for obtaining more highly pure free obtained by simple distillation at 65 C. or lower. The hydroxylamine at a higher concentration. SulfateS precipitated in this reaction are removed before In the methods described in U.S. Pat. Nos. 4,707,294, 60 distillation, but Since the aqueous Solution contains much 4,551.323, 4,551.324 and 4,956,168, an alcohol Solution of Salts dissolved, much Salts are precipitated in the residue in free hydroxylamine is obtained by removing the Sulfates the Subsequent Simple distillation operation, making the precipitated in the reaction between hydroxylammonium Simple distillation operation difficult. Furthermore, Since Sulfate and an alkali or alkali alcoholate in an alcohol. This free hydroxylamine with a boiling point higher than that of alcohol Solution is then mixed with a reagent Such as an acid 65 water is deposited on the precipitated Salts, the yield of free other than Sulfuric acid or a ketone, to be used for Synthe hydroxylamine is extremely lowered. So, the method is not sizing a hydroxylammonium Salt other than hydroxylammo industrially advantageous. US 6,531,108 B1 3 4 In German Patent Publication No. 19547758 (U.S. Pat. or Slurry containing hydroxylammonium Sulfate and an No. 5,837,107), hydroxylammonium sulfate and an alkali alkali react with each other, to obtain an aqueous Solution or are caused to react with each other in water not containing Slurry (reaction Solution) containing free