Preparation of UF4 by Carbochlorination of U3O8 and Solid-State Halogen Exchange Reaction

Abstract

Uranium tetrafluoride was synthesized using a novel method, which consists of a combination of carbochlorination reaction between a mixture of U3O8 and sucrose carbon with chlorine, and a solid-state halogen exchange reaction between the products of the carbochlorination reaction and sodium fluoride. The thermodynamic feasibility to produce the halogen exchange reaction between UCl4 and NaF was analyzed. Reactions are favorable in standard conditions, even at low temperature. We have prepared a mixture of UCl4 and UCl2O2 by U3O8 treatment in Cl2 atmosphere with presence of sucrose carbon at 900 °C. UCl4 and UCl2O2 were obtained as a condensed product, which was collected in a quartz capsule containing NaF. The capsules were sealed after several repeated stages of argon purges and mechanic vacuum. Subsequently, they were treated at 300-350 °C for 2 h. We obtained that when NaF is the limiting reagent, the solid product of the thermal treatment of the capsules consists in a mixture of UF4 and NaCl. Solid products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), fluorescence spectroscopy, and energy dispersive X-ray spectroscopy. Gaseous products were identified by Fourier-transform infrared spectroscopy.