Heterogeneous Catalysis in Fluoride Melts: Reduction of Uranium(V) and Niobium(Iv) by Hydrogen

摘要

The reduction of uranium(V) or niobium(IV) dissolved in fluoride melts at 550 exp 0 C by hydrogen gas in the absence of catalysts exhibits zero-order kinetics, i.e., the quantity reduced per unit time is independent of the concentration of dissolved species or the hydrogen gas partial pressure. Platinum catalysts accelerate the reaction rate 10- to 100-fold and, with uranium(V), the catalyzed reaction exhibits first-order kinetics, suggesting that the catalyzed reaction may be diffusion limited. Platinum was catalytically active when present as platinum black powder, sponge, sheet or powder that has sintered to or alloyed with the gold reaction crucible. (ERA citation 01:020277)