Oct. 23, 1951 F. A. JENKNS 2,572,156 PROCESS OF PRODUCING HEXACHLORIDE Filed July 13, 1943

12

2/ To Vacuum Line

//

Original Charge | Residue UCls

INVENTOR. Francis A. Jenkins

-á4-2-4-2-2-121ATTORNEY. Patented Oct. 23, 1951 2,572,156

UNITED STATES PATENT of FICE PROCESSES OF PRODUCING URANUM HEXACHORDE Francis A. Jenkins, Berkeley, Calif., assignor to the United States of America as represented by the United States Atomic Energy Commission Application July 13, 1943, Serial No. 494,447 Claims. (CI.23-14.5) 1 The present invention relates to UCls and suitable charge of uranium pentachloride is processes of producing the Same. placed in a substantially conventional molecular Heretofore the compound UCls has not been Still which comprises a hot Surface heated in any known. Moreover, it has been predicted that the Suitable manner, such, for example, as by a hot possibility of its production is virtually negligible Sandbath, and a cold Surface. cooled in any Suit in view of its expected great instability. This able manner, Such, for example, as by liquid air. view is entirely plausible since the tetrahalides In the still the hot surface and the cold surface of uranium form a series decreasing in stability are disposed in Spaced apart relation, and the in a regular-manner-from the fluoride through space therebetween is evacuated to -an-extremely the -and-the-bromide to the iodide, and O low pressure by Suitable vacuum pumping ap since UF6 is... extremely unstable. Thus it has paratus. More particularly, the charge is placed always been assumed that the hexahalide Series on the hot surface of the still and the tempera of uranium terminates abruptly at the COm ture of the sand bath is suitably controlled, in pound UEs, ...... order that the charge is maintained at a tem . . The present invention is predicated upon the s perature within the range 80° to 180° C. Also, discoveries that uranium pentachloride is a bi the amount of liquid air which is applied to the nary compound of the form. UCl4. UCl6 rather cold surface of the still is such that the tempera than a monomeric compound of the form UCls ture of the cold surface is maintained at 10°C. and that in this compound the molecular bond or below. Finally, the vacuum pumping appara may be broken under certain conditions, pro tus is adjusted, so that the pressure within the ducing as two independent compounds UCl4 still between the hot surface and the cold Sur and UCls. face is maintained at a value between 106 and Accordingly, it is an object of the invention to 10-3 mm. Hg. Preferably in carrying out the provide UCls as a stable, compound. process, the space between the normal hot-sur Another object of the invention is to provide a 25 face and the normal cold surface of the still is process of producing UCls as a stable compound. evacuated to obtain the Subatmospheric preSSure Another object of the invention is to provide. a within the range mentioned, before the normal process of producing UCls which utilizes uranium hot surface is heated by the Sand bath and the pentachloride. normal cold surface is cooled by the liquid air. Another object of the invention is to provide a 30 When the charge of uranium pentachloride is process utilizing uranium pentachloride, whereby thus heated under stoatmospheric preSSure, it UCl4 and UCls are produced, and separated. is converted into UCl4 and UCl6, the UCl6 being A further object of the invention is to provide sublimed as it is produced. The UCl4 remains as a process in which the molecular bond in the bi a residue upon the hot surface. and the Sublimed nary compound UCl4. UCls is broken, whereby 35 UCls traverses the space between the hot and cold UCl4. and UCls are produced as independent surfaces to condense. upon-the cold-Surface.in the compounds. form of iridescent, darkgreen, fine-grained crys A further object of the invention is to provide tals as the temperature of the charge is above a process utilizing UCl4. UCls, whereby UCl4 and the sublimation point of UCls and below the Sub UCls are produced and UCls is sublimed away 40 lination point of UCl4. from UCl4. The process is continued until the charge of A still further object of the invention is to uranium pentachloride is substantially come provide a combination.heating and vacuum proc pletely converted, at which time the residue re ess of producing UCl4 and UClg from uranium maining - on the hot surface is Substantially pentachloride and of separating these products 45 chemically pure UCl4 and the Sublimate collected from each other. on the cold surface is substantially pure UCls. The invention, both -as to its organization and At this time, when further production and sub method of operation, together with further ob innation of UCls ceases, aid the process is Con jects and advantages thereof, will best be under plete, the UCl4, residue is removed from the hot stood by reference to the following Specification 50 surface and the UCls sublimate:is removed from taken in connection with the accompanying the cold surface. Ordinarily in carrying out the drawing, in which the single figure is a schematic process a charge of 100 grams of uranium penta illustration of apparatus-Suitable for carrying Out chloride may be substantially completely con the processes of the present invention, Verted into a residue of UCl4 and a Sublimate of Inaecordance with the present invention, a 55 UCl6 in approximately three hours. 2,572,156 w 3 It is virtually essential that the still be trans is considerably below that of UCl4 and that UCIs ferred to a dry cabinet containing CO2 or other has a much higher vapor pressure at a given tem inert before it is opened, in view of the fact perature than UCl4. Further, it is thought that that the Sublimate UCls is extremely hygroscopic the following specific reaction takes place: and readily decomposes in the presence of ordi nary atmosphere into UO2Cl2. The product UCl4. UCls--heat->UCl4--UCls UCls is then bottled in an atmosphere of CO2 Or Theoretically, one mole of the binary compound in a vacuum and Sealed for future use. The prod UCl4. UCl6 (831 grams) should yield one mole of uct UCls so produced is particularly well suited for the monomeric compound UCl4 (380 grams) and use in vacuum apparatus, in that it has a very. 10 One mole of the monomeric compound UCl6 (451 much greater vapor pressure at a considerably grams); the weight percent of in the lower temperature than other volatile residue UCl4 should be 37.34; and the weight per of uranium, such, for example, as UCl4. cent of chlorine in the sublimate UCls should be While the process may be carried out at a tem 47.19. The analyses of the residue and the sub perature below the lower end of the preferred 15 limate produced incident to carrying out the range, it is noted that in the event the temper present process checked very closely with the ature is much lower than 80 C. the yield of theoretical values indicated. For instance, in a UCls from the charge is extremely poor and typical run utilizing a charge of 100 grams of very slow. Similarly, while the process may be uranium pentachloride, when the process is. Sub carried out at a temperature above the upper 20 stantially complete analyses have indicated a end of the preferred range, it is noted that in the weight of UCl4 residue of 47 grams, a weight of event the temperature is much higher than 180 UCls Sublimate collected of 52 grams, and a C. the UCl4 produced as a residue in the charge Weight of UCl6 Sublimate lost of one gram. Also, itself begins to sublime, and the UCls is decom analyses for total uranium and total chlorine, posed to UCl4 and C2 before it can be sublimed made gravimetrically by tested procedure, indi from the hot surface. In other words, it is es cated the following for the Sublimed material: sential that the process be carried out under conditions such that the newly formed UCls is Per cent removed from the hot Zone, or region of maxi Total U------53.30 mum temperature, before any substantial decon 30 Quadrivalent U------(2.3). position of the product UCl6 can take place. Also, Chlorine------46.41: when the temperature is much higher than 180 C., the sublimate is of very low chemical purity 99.71 in that large amounts of UCl4 are mixed with Atomic ratio Cl/U------5.85 - the UCl6, and furthermore the yield is low. 35 When allowance is made for the inevitable Of course the vapor pressure-temperature decomposition which accompanies any transfer curves of UCls and UCl4 are of usual form, the of material, except under vacuum in thoroughly vapor pressure increasing disproportionately baked-out apparatus, the analyses are so close to with temperature, whereby there is a negligible that required for UCls that there can be no serious Sublimation of UCl4. Within the normal Sublima 40 doubt that the Sublimate is Substantially chemi tion temperature range of UCl6. However, for cally pure UCls; the atomic ratio Cl/U of 5.85 practical purposes of obtaining correspondingly. obtained from the analyses is well within experi reasonable yields, it may be said that the Subli mental error of the theoretical atomic ratio mation temperature of UCls is well below that Cl/U of 6. Also, analyses of the residue yield of UCl4 as indicated below: 45 an atomic ratio of Cl/U of 3.94, clearly indicat ing that the residue is Substantially chemically Wapor Pressure pure UCl4. - W mn. Hg In further evidence of the fact that the binary Temperature, c compound uranium pentachloride is converted UCl3 UCl 50 into the two monomeric compounds mentioned,

it is pointed out that check runs in the still under the conditions specified, utilizing the residue UCl4 and the Sublimate UCls, yield very interest ing results. More particularly, in a check run utilizing the residue UCl4, there is virtually no Sublimate, indicating that the residue is already substantially chemically pure UCl4. On the other hand, in a check run utilizing the sublimate UCls, there is virtually no residue, indicating that the sublimate is already substantially chemically purePreferably, UCl6. the uranium M pentachloride em. ployed as a charge in the still in carrying out the present process is produced by the improved 65 process disclosed in the copending application of Decomposition of UCls begins. Horace R. McCombie, Serial No. 506,336, filed 2 Pressure of UCl4 below 300° C. is negligible. October 15, 1943. More particularly, it has been Eacamples found that when the charge of uranium penta When the process is carried out employing a chloride is produced in accordance with the proc charge of uranium pentachloride, UCl4. UCls, it 70 ess disclosed in the above mentioned McCombie is believed that the molecular bond is broken, application as contrasted with other known proc whereby UCl4 and UCls are produced as inde esses, the yield of UCls from the charge in the pendent monomeric compounds, and that the still is considerably higher, and of the order of UCls is sublimed away from the UCl4, as it is 50% greater. . . . * ...... noted that the Sublimation temperature of UC6 75 Referring now.more particularly. to the single 2,572, i56 5 6 figure of the drawing, there is illustrated a Sub thereof, thus insuring maximum production and stantially conventional molecular still which is recovery of UCl6 as Such suitable for carrying out the present process, the Reconsidering the properties of the mono still comprising lower and upper casing members meric compound UCl6, it is again noted that this and 2, respectively, formed of Pyrex glass. 5 product is of fine crystalline structure, having an The lower casing member is provided with an iridescent dark green color. The vapor pressure outwardly directed Sealing flange 3 adjacent the of the product UCl6 is of the order of 1 to 3 mm. upper end thereof, and the upper Casing member Hg at 100° C.; and the product is extremely hy 2 is provided with an outwardly directed seal groscopic and unstable in ordinary atmosphere. ing flange 4 adjacent the lower end thereof, the g) When the product UCl6 is subjected to normal sealing flanges 3 and f4 being adapted to mate atmosphere containing moisture, it rapidly de to provide a hernetic Sea between the lower and composes to UO2Cl2. However, the product, UCl6 upper casing members and 2, respectively, of exists instable form in dry air, , , the still. The upper casing member 2 is pro and other inert . vided with a re-entrant portion 5 projecting The vapor of UCG readily attacks most of the into and Spaced in Wardly from the Side Wall of ordinary metals considerably more actively than the lower casing member if, in order to define does the vapor of UCl4, decomposing to UCl4. a vacuum space between the lower and upper :For example, UCl6 vapor at 100 C. readily at casing members and 2, respectively. The tacks copper, copper alloys, silver, iron, graphite, lower casing member is provided with a bottom 20 etc., and exhibits no Substantial attack upon end Wall 6, constituting a normally hot Sur stainless steel, monel metal, nickel, and gold. face adapted to receive a charge of uranium The product UCl6 is Soluble in Water, decompos pentachloride; and the re-entrant portion 5 of ing immediately to UO2Cl2, and cannot be dis the upper casing member 2 is provided with a Solved in ionic oxygenated Solvents Without de bottom end Wall 8 constituting a normally cold 25 composition to UO2Cl2. Finally, the product surface. The bottom end wall 6 of the lower UCls is readily soluble in CCl4, producing a dark Casing member is arranged Within a hot sand brown Solution. bath 9, whereby the charge 7 is heated; and While there has been described what is at the re-entrant portion 5 of the upper casing present considered to be the preferred embodi member 2 is adapted to contain a body 20 of liq 30 ment of the invention, it will be understood that uid air, whereby the surface f8 is cooled. Finally, various modifications may be made therein and the lower casing member has a conduit 2 it is intended to cover in the appended claims formed integrally therewith and communicating all such modifications as fall Within the true With the vacuum space disposed between the spirit and Scope of the invention. lower and upper casing members and 2. The 35 What is claimed is: conduit 2 is suitably connected to vacuum pump 1. The process comprising heating uranium ing apparatus, not shown, and includes a Stop pentachloride to a temperature which is suffi cock 22. ciently high to convert it to UCl4 and UCl6 and In the operation of the molecular Still, the which is above the sublimation temperature of charge of uranium pentachloride is first posi 40 UCl6 and below the sublimation temperature of tioned on the normally heated Surface 6 of the UCl4, said heating being conducted under condi lower casing member , the upper casing men tions such that the UCls which is produced is ber 2 is brought into relation, and the flanges sublimed as it is formed, and recovering the 3 and 4 are appropriately Sealed. The pump UCls thus produced. ing apparatus is started, and the Stopcock 22 2. The process comprising heating uranium is opened, whereby the pressure in the vacuum pentachloride to a temperature which is suffi space between the lower casing member and ciently high to convert it to UCl4 and UCl6 and the upper casing member 2 is lowered to a which is above the Sublimation temperature of pressure of the order of 10-6 to 103 mm. Hg. UCl6 and below the Sublimation temperature of The temperature of the sand bath 9 is suitably UCl4 and simultaneously subjecting it to a pres adjusted, whereby the temperature of the charge Sure not appreciably greater than 103 mm. Hg, is maintained within the range 80 to 180° C., Said heating being conducted under conditions and the body 20 of liquid air is poured into the Such that the UCl6 which is produced is sublimed re-entrant portion 5 of the upper casing men as it is formed, and recovering the UCl6 thus ber 2, whereby the cold surface 8 is Suitably produced. cooled to a temperature of the order of 10° C. Or 3. The process comprising heating uranium below. When the charge T is thus heated, the penta chloride to a temperature Within the range conversion takes place, whereby the charge T 80° to 180° C. and simultaneously subjecting it of uranium pentachloride is progressively con to a pressure not appreciably greater than 10-8 verted into UCl4 and UCl6, the UCls Subliming as 60 mm. Hg, whereby UCls is produced and Sublimed it is produced and traversing the space between Substantially as it is formed, and recovering the the hot surface 6 and the cold surface 8. The UCls thus produced. UCl4 remains as a residue upon the hot surface 4. The process comprising heating UCl4. UCl6 6, and the sublimate UCls is condensed to its to an elevated temperature and simultaneously Solid state upon the cold surface 8. After the 65 Subjecting it to a Subatmospheric pressure, process has been completed, the stopcock 22 is whereby UCl4 and UCl6 are produced, subliming closed and the still is removed to the dry cabinet the UCl6 away from the UCl4 under conditions and opened, as previously explained. It will be Such that the UCl6 is removed from the heated noted from the foregoing that, since the UCl6 ZOne before any Substantial decomposition there is sublimed or vaporized substantially as it is 70 of takes place, and recovering the UCl6 thus pro produced apparently by the disruption of the duced. molecular bond of the uranium pentachloride 5. The process comprising heating UCl4. UCl6 (UCl4.UCl6) it is not permitted to remain in to an elevated temperature and simultaneously the hot zone for a time Suficient to cause any subjecting it to a subatmospheric pressure, substantial degree of thermal decomposition 5 whereby UCl4 and UCls are produced, Subliming 2,572,156 7 8 the UCls away from the UCl4, and condensing a temperature within the range 80° to 180° C. the sublimed UCls to its solid state; the UCls while subjecting it to a pressure not appreciably being removed from the heated Zone as it is greater than 103 mm. Hg, Subliming the UCls, formed and before any substantial decomposi conducting the sublimed UCl6 substantially as it tion thereof takes place, and recovering the UCl6 5 is formed away from the UCl4 to a remotely dis thus produced. posed cooled Zone, and condensing the Sublimed 6. The process comprising subjecting UCl6 to its solid state in the cooled zone. . . . F. A. J.ENKINS. . UCl4. UCl6 simultaneously to heat and a Subatmospheric O REFERENCEs CITED pressure in a heated Zone, whereby UCl4 and The following references are of record in the UCls are produced, subliming the UCl6 as it is file of this patent: produced, conducting the sublimed UCl6 away - Chemical Abstracts, vol. W, 1911, page 3772, from the heated zone to a remotely disposed Otto Ruff and Alfred Heinzelmann, Danzig Z. cooled zone, condensing the sublimed UCl6 to its 5 Anorg. Chem. 72, pages 63-84. - Solid state in the cooled Zone, and recovery the ... --Mellor, “Comprehensive Treatise on Inorganic UCls thus produced. and Theoretical Chemistry, vol. XII, 1932, pages 7. The process comprising converting uranium pentachloride to UCl4 and UCl6 by heating it to 35, 83, and 84. (Copy in Division 59.)