Honeycomb Palladium Catalyst for the Oxidation of Tritiated Hydrocarbons Produced in Tritium Facilities

Abstract

We have developed a honeycomb palladium catalyst to be used for the oxidation of tritiated hydrocarbons. Since the suitable loading rate of palladium deposited on the base material is a technical point, honeycomb-shaped palladium catalysts of three different loading rates—2, 5, and 10 g/L—were prepared to investigate the effect of loading rate of palladium on reaction rate in this study. Tritiated methane was selected as the typical hydrocarbon. A 12 m3 tank was prepared to prevent tritiated methane at tracer concentration fed to the catalytic reactor from fluctuating. The overall reaction rate constant for tritiated methane oxidation on the honeycomb palladium catalyst was determined with a flow-through system as a function of space velocity from 1000 to 6300 h−1, methane concentration in carrier from 0.004 to 100 ppm, and temperature of catalyst from 322 to 673 K. The honeycomb palladium catalyst without pretreatment for activation initially lowers the overall reaction rate constant at lower temperatures. However, the constant recovers steeply to the original value during the continuous combustion of tritiated methane. The loading rate of palladium deposited on the base material has little effect on reaction rate for tritiated methane combustion. The overall reaction rate constant is proportional to the space velocity. The overall reaction rate constant is independent on the methane concentration when it is less than 10 ppm.