Heptane dehydrocyclization over Pt/KL catalysts doped with barium or lanthanum

Several 1 wt% Pt/KL catalysts doped with different concentrations of either BaO or La2O3 were prepared by successive impregnation of a zeolite KL and then characterized by H-2-O-2 titration, TPR, CO-FTIR, TEM-XEDS and XPS. Catalytic activity measurements in the hydroconversion of n-heptane showed that barium highly enhances the aromatization activity of Pt/KL, the more so the higher the barium concentration. The yield to aromatics increases to a lesser degree by adding 1 wt% La, but it is little modified at higher La concentrations. The CO-FTIR results suggest that the promoter effect of barium is related to an electron enrichment of Pt produced by the BaO --> Pt-0 interaction which, according to the TEM-XEDS and XPS results, is more favored than the La2O3 --> Pt interaction.