Effect of Ba and rare earths cations on the properties and dehydrocyclization activity of Pt/K‐LTL catalysts

Abstract

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.