The reaction of phosgene with thorium oxide has been shown to be a good method for preparing thorium tetrachloride. The equilibria of the reaction showed that nearly complete utilization of phosgene could be attained in a properly designed reactor. The kinetics of the reaction could not be represented by a simple rate law but the effects of bed depth, particle size, mode of oxide preparation and temperature on the rate of reaction were established. The depth of the bed of thorium oxide and the particle size of the oxide did not affect the initial rate of reaction. At high conversions the rate of the reaction was probably controlled by the slow solid state diffusion of oxygen to the surface of the thorium tetrachloride crystals and the highest conversion of thorium oxide to thorium tetrachloride obtained was approximately 91 o/o. The size of the crystallites in the thorium oxide particles increased as the temperature at which thorium oxalate was calcined to thorium oxide was increased. The resulting decrease in surface area decreased the initial rate of reaction. The temperature coefficient of the reaction rate was small and a temperature increase of approximately 200° C was required to double the rate of reaction.
Peterson, D. T. and Sundquist, D. J., "Equilibria and kinetics of the reaction of phosgene with thorium oxide" (1964). Ames Laboratory Technical Reports. 76.