Collect. Czech. Chem. Commun. 1995, 60, 428-442

Effect of Li, Na, K and Cs on Vacuum Decomposition of Tetraammineplatinum(II) in Zeolites. Catalytic Activity in CO + NO Reaction

Jana Nováková, Libor Brabec and Ludmila Kubelková

J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, 182 23 Prague 8, Czech Republic


[Pt(NH3)4]2+ ions were exchanged for alkali (Li, Na, K and Cs) in -X and -Y zeolites and decomposed in vacuum. TPR after this decomposition showed that autoreduction accompanying this process reduced roughly 2/3 of all Pt2+ to Pt0. The extent of the autoreduction rose with the ammonia pressure over the zeolite. The decomposition rate increased with increasing electropositivity of the alkali ion and this effect completely overlapped that of the zeolite structure. The CO + NO reaction rate also increased from Li to Cs, but -X zeolites were substantially more active than the -Y ones. Oxygen layer on the resulting Pt catalyst affected positively the reaction rate. The dispersion of Pt particles was relatively low, when compared to that obtained by decomposition of the Pt tetraammine complex in oxygen followed by hydrogen reduction. However, the reaction rate was higher.