(A) study on the deactivation and stability of hydrophobic catalyst for hydrogen isotope exchange

Abstract

The hydrophobic catalyst has been prepared by deposition of platinum on porous styrene divinylbenzene copolymers(Pt/SDBC) and at the same time a separated type catalytic reactor has been developed for the Wolsong tritium removal facility(WTRF). Several tests carried out to obtain the experimental performance data of the Pt/SDBC with a recycle reactor system. The long-term stability was also measured with the Pt/SDBC catalyst immersed in water for a long time. The long-term deactivations of the Pt/SDBC catalyst were evaluated quantitatively by mathematical models. The simple mathematical models were presented to evaluate the uniform poisoning and shell progressive poisoning to be occurred simultaneously during the hydrogen isotope exchange between hydrogen gas and liquid water in the Liquid Phase Catalytic Exchange(LPCE) column. The uniform poisoning was well characterized by a time on stream theory and then the deactivation parameters were determined from the experimental performance data. The impurity poisoning was derived by a shell progressive model with two-layer mass transfer. The water vapor condensation was a main cause of the reversible uniform poisoning for the Pt/SDBC catalyst. The values of the decay rate constant $(K_d)$ and order of the decay reaction(m) were of 2 and 4, respectively, based on the experimental data. It indicated that the decay might be attributable to pore mouth poisoning. From the long-term stability of the catalyst immersed in water, there was no intrinsic decay of catalyst activity due to waterlogging to the catalyst. The activity decreased by only 7% over 18 months, which was equivalent to a catalyst half-life longer than 15 years. On the basis of the above deactivation parameters, the values for $k_c/k_{c,o}$ with Thiele modulus=20 after 3 years and 10 years of operation were expected about 19% and 15% of the initial activity, respectively, while the values for $k_c/k_{c,o}$ with Thiele modulus=100 were of about 22% and ...