12A- 6 4-4El ATTORNEY 3,039,846 United States Patent Office Patented June 19, 1962 1
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June 19, 1962 P. R. OGLE, JR 3,039,846 METHOD FOR THE RECOVERY AND PURIFICATION OF GASEOUS UF FROM GASEOUSPRODUCTS MIXTURES PRODUCEDANDUFNO AND UF, NO THEREBY Filed Oct. 9, 196l. : 8 s O O O O O o O t CN A. "NOISSWSNW.L INVENTOR Pearl R. Ogle, Jr. BY 12a- 6 4-4el ATTORNEY 3,039,846 United States Patent Office Patented June 19, 1962 1. 2 3,039,846 of UF are superimposed. The absorption bands at METHOD FOR THE RECOVERY AND PURIFICA 2320 and 2318, and 549 to 510 cm. are attributed to TION OF GASEOUS UFFROM GASEOUSMX the NO+ and UF ions, respectively, this indicating that TURES AND UFNO AND UFNO PRODUCTS the compound UFNO is a 1:1 addition complex having PRODUCED THEREBY a composition NOF.UF6. This compound has a vapor Pearl R. Ogle, Jr., Chilicothe, Ohio, assignor to the pressure of less than 1 mm. Hg at 25°C. with the vapor 'United States of America as represented by the United over the solid comprising approximately equal molar States Atomic Energy Commission quantities of uranium hexafluoride and nitrosyl fluoride. Filed Oct. 9, 1961, Ser. No. 143,986 Example II 8 Claims. (C. 23-14.5) 10. The present invention relates to a new and useful class This example illustrates the preparation of UFNO2. of chemical reactions involving gaseous uranium hexa The procedure of Example I was used to react UFa fluoride and to a new and useful method of recovering and nitryl fluoride. A greenish-white solid having a and/or purifying gaseous uranium hexafluoride values vapor pressure of 11.6 mm. Hg at 25.7 C, was obtained. from a gaseous mixture containing said values by utiliz 5 The reaction was presumed to occur as follows: ing said reactions. There are many ways of synthesizing uranium hexa fluoride. A number of methods for the preparation of An infrared spectrum of this compound revealed an ab uranium hexafluoride are disclosed in chapter VIII of sorption based at 2374 cm.-1 which is indicative of the “The Chemistry of Uranium” by Katz and Rabinowitch, 20 NO+ ion. Characteristic absorption bands of NOF National Nuclear Energy Series, VIII-V, McGraw-Hill, and UEs were also observed. 1951. Regardless of its source, a synthesized UFs prod An elemental analysis of the compound was obtained uct is usually found as a component of a gaseous mixture and compared with elemental composition for UFNO. from which it must be separated to a high degree of Theory based on UFNO: U, 57.08; F, 31.89; N, 3.36. purity. The most common volatile impurities in a gas 25 Found: U, 57.23; F, 28.51; N, 3.64. eous stream containing UFs include, among others, gase Based on the infrared spectrum and chemical analysis, ous fluorine, chlorine, bromine, oxygen, hydrogen chlo it was concluded that the compound had the composition ride and inert gases such as nitrogen, argon, hydrogen of a 1:1 addition complex NOF.UF6. The vapor above fluoride, carbon dioxide, and carbon monoxide. this compound comprises approximately equal molar It is accordingly an object of this invention to provide 30 quantities of uranium hexafluoride and nitry fluoride a method of removing and purifying gaseous UFs from NOF. The reaction of UF with either nitrosyl fluoride a gaseous stream. or nitry fluoride effects no change in the uranium oxida Another object of this invention is to provide a method tion state of UF. Thus when either UFNO or UFNO of converting gaseous UFs into a form from which it can is dissolved in water, it results in a solution containing easily be regenerated. hexavalent uranium, as the uranyl ion, and nitric acid. A further object of the invention is to provide a useful This is to be compared with the reaction product of NO and novel class of chemical reactions and uranium com or NO with UF which yields a solid UFN (O), where pounds resulting therefrom whereby the preceding ob X is a number from 1 to 2. Compounds of the class jects can be achieved. UFN (O) (which are disclosed and claimed in applica With these and other objects in mind the present in 40 tion S.N. 19,132, of common assignee) when dissolved vention comprises in its method aspect, the steps which in water, give a mixture of tetravalent uranium and comprise reacting a gaseous stream containing UFs and hexavalent uranium while UF6, UFNO and UFNO2 extraneous gaseous impurities at a temperature in the dissolved in water yield the hexavalent uranyl ion only. range - 100 to 50° C. with a compound selected from In order to utilize the compounds of this invention for the class nitrosyl fluoride and nitryl fluoride and there 45 the purposes of recovering gaseous UF6 from a gas mix after separating a solid uranium fluoride product having ture, it is only necessary to react the mixture with nitrosy an empirical formula UFN (O), where x is a number or nitryl fluoride at a temperature not exceeding about from to 2. 40° C. and preferably at a pressure below the vapor pres The following examples will serve to illustrate the sure of such compounds. The UF will react virtually preparation of the compounds of this invention. 50 immediately to form the solid addition compound. The solid compound is allowed to settle or is filtered off and Example I the volatile contaminants are removed by purging or This example illustrates the preparation of UFNO. under vacuum. This method is particularly valuable for Uranium hexafluoride (6.956 grams, 0.0198 M) was recovering uranium hexafluoride from gas streams con condensed into a vacuum-tight fluorothene reactor at 55 taining low concentrations or traces of uranium hexa -196° C. and, at the same temperature nitrosyl fluoride, fluoride. As between using nitrosyl, or nitry fluoride, NOF (1.635 grams, 0.0334 M), was condensed on top nitrosyl fluoride is the preferred reagent since it forms a of the UF. The mixture was warmed to 25 C. and compound of lower volatility. allowed to react at that temperature for about 16 hours. The unique advantage in using these compounds to All volatile components were evacuated from the reaction 60 recover UFs is that the uranium does not undergo a mixture after which 7.948 grams of a greenish-white solid valence change. Moreover, the resultant compounds can was recovered. The reaction was presumed to occur as easily be decomposed, preferably in vacuum, at slightly follows: elevated temperatures, over about 50° C. to regenerate the desired UFs. This is to be compared with other UFed)--NOF->UFNO 65 methods for stripping UFs where chemical traps are used An elemental analysis of the solid was conducted and the to strip the last traces of UF6 from gases. Essentially following results obtained. all the UFs can be removed by passing the UF containing Theory based on UFNO: U, 59.36; F, 33.16; N, 3.49. gas through a bed of calcium sulfate, calcium fluoride Found: U, 58.98; F, 29.66; N, 3.58. or activated alumina or by scrubbing the gas with water, An infrared spectrum of the solid was obtained and 70 but expensive wet processing methods are necessary to is shown in the accompanying FIGURE. For purposes of recover the uranium from the solids, comparison, the principal characteristic absorption peaks The reaction between UF and nitrogen oxyhalides 3,039,846 3 other than the nitrogen oxyfluorides can also be used to and extraneous gaseous impurities by the steps which recover UF6 gas from a gas stream. However, in a comprise reacting said mixture at a temperature in the sense, the rotation product is not analogous to UFNO range of -100 to 200° C. with oxyhalides of nitrogen to or UFNO. For example, the reaction product of UF6 form a solid addition compound of uranium hexafluoride, with gaseous or liquid nitrosyl chloride yields nitrosylium purging the atmosphere above with resultant compound hexafluorouranate UFNO, a compound in which the to remove said extraneous gases, and thereafter isolating apparent oxidation state of uranium has been changed as the said solid uranium compound. evidenced by the presence of U+4 in aqueous solutions of 5. In a method of recovering uranium hexafluoride UFNO. Other oxyhalides follow the reaction pattern of from a gaseous mixture containing said uranium hexa , nitrosyl chloride rather than nitrosyl fluoride to effect, 10 fluoride and extraneous gaseous impurities, the steps at least a partial reduction of the hexavalent uranium of which comprise reacting said mixture with a nitrogen UF. All of the nitrogen oxyhalides, however, may be oxyfluoride at a temperature in the range - 100 to 50° C. used to recover and purify UF6 from a UF6 containing to thereby form a solid compound having the empirical gas stream. The choice of oxyhalide will depend on formula UFN(O), where x is a number from 1 to 2. the uranium oxidation state desired in the final product. 15 6. The method according to claim 5, wherein the nitro If the hexavalent uranium is desired to be retained, then gen oxyfluoride is nitrosyl fluoride. the choice will be nitrosyl and/or nitryl fluoride. If 7. The method according to claim 5, wherein the solid uranium compound wherein the uranium is in a nitrogen oxyfluoride is nitryl fluoride. lower oxidation state is desired, the choice should be 8. A method of separating uranium hexafluoride from nitrosyl, or nitryl chloride, bromide or iodide. 20 a gaseous mixture containing said uranium hexafluoride Having thus described my invention, I claim: and extraneous gaseous impurities which comprises react 1.