Kinetics of iodine poisoning of hydrophobic Pt/SDBC catalyst for hydrogen isotopic exchange reaction

Abstract

Changes with time in the isotopic exchange reaction rate between H, and HDO(v) over a hydrophobic PtiSDBC (styrene-divinylbenzene copolymer) catalyst induced by iodine have been studied experimentally. The addition of a trace amount of I2 to the reactor caused a remarkable decrease in the activity of the catalyst. The measurement results by means of the gas chromatographic pulse technique show that the H, adsorption onto the catalyst surface was strongly inhibited by iodine. A kinetic model for the poisoning was developed in terms of the competitive adsorption of I2 with H, onto the catalytic active site. The experimental results were explained reasonably by the proposed kinetic model based on the site balance by assuming that I2 adsorbs non-dissociatively on the active site. The poisoning could be prevented by the conversion of I . to Ior IO; through redox reactions.On a etudie experimentalement les changements dans le temps de la vitesse de reaction d'echange isotopique entre H2 et HDO(v) sur un catalyseur hydrophobe Pt/SDBC (copolymere styrene-divinylbenzene) induit par de I'iode. L'ajout de traces de I, au reacteur entraine une diminution notable de I'activite du catalyseur. Les mesures effectuees par la technique de chromatographie en phase gazeuse par impulsions. montrent que I'adsorption de H2 sur la surface du catalyseur est fortement inhibee par I'iode. Un modele cinetique d'empoisonnement a ete mis au point en utilisant I'adsorption competitive de 1: avec H, sur le site catalytique actif. Les resultats experimentaux ont ete expliques raisonnablement par le modele cinetique propose base sur le bilan des sites en supposant que I2 s'adsorbe de fagon non dissociative sur le site actif. L'empoisonnement peut etre evite par la conversion de I2 en Iou lo; par les reactions d'oxydo-reduction.

Recovery of Tritium from Wastewater Generated by Decommissioning of Gas Cooled Reactors (GCR)

“…Impurities, such as heavy metal ions, salts and suspended solid particles, may be contained in the wastewater. It seems to be important to consider the effect of these impurities on the recovery of tritium and to develop the pretreatment process to remove these impurities (Takeshita et al, 1995;Wei et al, 1997), however, the removal of impurities is not considered in this paper. The dimensions of a water distillation process and a hydrogen-isotope exchange process for the wastewater after the removal of impurities are evaluated.…”