Patent GB-880515-A (GB)
Title: Method of separating isotopes
IPC: C01B35/00
Filed: 1945-06-20
Abstract: <PICT:0880515/III/1> The isotopes of an element are separated by forming a liquid compound of the element which when vapourized dissociates by a reversible dissociation, but which has the same chemical composition in the liquid and vapour phases, heating the compound to convert a portion thereof into the vapour phase, and establishing a countercurrent flow of the liquid and vapour phases while maintaining the liquid and vapour in intimate contact, whereby the different isotopes of the element are concentrated in the different phases by isotope exchange between the phases.  B isotopes of mass 10 and 11 and O isotopes of mass 16 and 18 are separated by effecting the countercurrent contact of liquid and vapour of a complex of BF3 and an aliphatic, e.g. di-methyl, or di-ethyl, ether or trimethyl borate.  B10 and O18 concentrate at the bottom of the contact column and B11 and O16 at the top.  (CH3)2 from 18, 20 and BF3 from 22, 24 are reacted in chamber 30, and the complex (CH3)2O.BF3 is passed to column 10, which is heated by partially dissociated vapour (BF3+(CH3)2O) of the complex from reboiler 34, which receives liquid complex from column 10 and is heated by steam coil 38.  Vapours are condensed in 44 and part of the condensate is withdrawn through 46 to tanks 48, 50 to prevent build-up of decomposition products in the column, and the remainder is returned at 52 as reflux.  Complex enriched in B11 is passed at 54 through cooler 56 to tanks 58, 60. Reduced pressure sufficiently low to boil the complex at not more than 105 DEG C. is established through vacuum line 62.  Liquid complex from the base of column 10 is passed through 64 to the top of column 12 provided with reboiler 70 and whence part of the condensate from 72 is returned as reflux to column 12 and part is returned to reboiler 34.  Liquid complex from 12 is passed to column 14 and successively through the remaining columns of the system, all similar to columns 10, 12, for further B10 enrichment. Complex enriched in B10 is withdrawn from the last column at 82 to storage 88, 90 through cooler 84.  BF3 enriched in a B isotope is recovered from the complex by heating with CaF2, while the O isotopes are present in the ether residue of the isolated complex.ALSO:B isotopes of mass 10 and 11 and O isotopes of mass 16 and 18 are separated by forming a liquid complex of BF3 and an aliphatic, e.g. di-methyl or di-ethyl, ether, or tri-methyl borate which reversibly dissociates on vapourisation into its constituents, but which has the same chemical composition in the liquid and vapour phases, heating the complex to vapourise a portion thereof, and establishing countercurrent intimate contact between liquid and vapour, whereby the different isotopes are concentrated in the different phases by isotope exchange between the phases.  B10 and O18 concentrate at the bottom of the contact column and B10 and O16 at the top.  A multi-column exchange system is described for preparing B10 enriched complex of BF3 and (CH3)2O.  BF3 enriched in a B isotope and ether enriched in an O isotope are recovered by heating the complex with CaF2.