Effect of Ba and Rare Earths Cations on the Properties and Reactivity of Pt/LTL Catalysts

J.M. GRAU; L. DAZA; X. L. SEOANE; A. ARCOYA

CATALYSIS LETTERS

SPRINGER

Lugar: Berlin; Año: 1998 vol. 53 p. 161 - 166

1011-372X

Several Pt/L-zeolite catalysts were prepared by the impregnation method from L-zeolite samples previously exchanged with Ba2+, La3+, Pr3+, Nd3+ and Sm3+. Lanthanides (Ln3+) increase the overall dispersion of platinum, measured by H2?O2 titration. TPR and CO/FTIR measurements indicate that these ions modify the distribution of Pt in the zeolite lattice, increasing the fraction of metal on the external surface. Additionally, both CO/FTIR and competitive hydrogenation of toluene?benzene mixtures indicate that, in the presence of Ln3+, the electron density of the platinum decreases in comparison with Pt/KL-zeolite. On the other hand, Ba2+ does not substantially modify neither the distribution nor the electronic state of Pt. The reactivity measurements in the hydroconversion of n-heptane show that Pt/BaKL and Pt/KL exhibit similar catalytic behaviour with a high dehydrocyclization activity. However, the exchange of K+ by Ln3+ increases the production of heptane isomers, while selectivities to aromatic and terminal hydrogenolysis products significantly decrease.