Cycling Performance and Hydriding Kinetics of LaNi5 and LaNi4.73Sn0.27 Alloys in the Presence of CO

MEYER G. O.; BORZONE E. M.; BLANCO M. V.; BARUJ A.

Rio de Janeiro

Congreso; Hy-SEA; 2014

Two AB5 alloys, LaNi5 and LaNi4.73Sn0.27, were cycled in H2 gas containing 10 and100 ppm of CO to evaluate their potential for hydrogen purification applications. Nosignificant loss of capacity was observed when samples were given enough time tocomplete the reaction, in contrast with previous reports that mention a strong poisoningeffect. Instead, the reaction kinetics was progressively retarded during the first few cyclesand then it reached a stationary, repeteable condition. No further degradation wasobserved after this point. The results also suggest that a fraction of the adsorbed CO isreleased during the desorption process. Differences between present and previous resultsare discussed in terms of the experimental conditions.The effect of temperature was studied for the Sn-containing alloy. The main resultsindicate that at 90ºC the reaction is only slightly retarded by the presence of 10 ppm ofCO, showing a half-time of less than a minute. At 40ºC, on the other hand, the retardingfactor in the presence of 100 ppm of CO with respect to the kinetics in pure hydrogen isof about 600. The reaction is more retarded with increasing CO concentration anddecreasing temperature. Results of these alloys? cycling performance in pure H2 areincluded for comparison.