Fundamental research on pretreatment process for Kr-85 recovery system, (5)

In the cryogenic distillation process for Kr-85 recovery, oxygen and nitrogen oxides must be removed to prevent ozone formation and freeze in the pre-cleaning step. At the temperature below 600 deg C, the formation of NH3 is higher in the case of catalyst Pd than Ru. The Ru catalyst is low active to reduce O2 at low temperature. Pd catalyst is very active to reduce oxygen at low temperature. Ru catalyst inhibits NH3 formation. Two usages of Pd catalyst and Ru catalyst together were investigated; ''mono bed'' of Pd and Ru catalysts, and ''double bed'' of Pd catalyst and Ru catalyst packed in order. In the mono bed, NH3 formation is less, and the activity for the reduction of O2 is higher. Consequently, the mono bed is suitable for the reduction of O2 and nitrogen oxides with H2 as compared with the double bed. (J.P.N.)