SEPARATION OF VOLATILE RARE EARTH COMPLEXES.

Work was directed towards investigating the feasibility of extractive fractional distillation as a method of separating mixtures of the tris-bi-dentate rare earth compounds when the chelating agent is 2,2,6,6-tetramethyl-3,5-heptanedione. Attempts to design and construct suitable packed columns for these fractionations did not lead to equipment that was satisfactory. A study of extractive distillation solvents indicated that candidates for this role include dihexyl phthalate, diamyl phthalate, phenylmethylsiloxane, eicosane, Drakeol-5 and Drakeol-7. Pure chelates of nine rare earths were synthesized. Several extractive distillations of binary chelate mixtures were conducted through a Nester-Faust platinum spinning band column. An economic evaluation of the separation of rare earth mixtures by fractional distillation and by extractive distillation was conducted by comparing these processes with the commercially operative ion exchange and liquid-liquid extraction systems. The feasibility of using azeotropic distillation or fractionation of chelate-solvent adduct mixtures was also investigated. Author