Abstract
The physicochemical and catalytic properties of platinum supported on beta zeolite both acid and exchanged with Cs and Li cations were characterized by X-ray diffraction, NH3-TPD, FTIR of adsorbed pyridine and CO, DSC, mass spectrometry and hydrogen chemisorption. The n-heptane conversion was performed to assess the selectivity variations in the exchanged solids. A high metal dispersion was verified in all of the catalysts, varying from 54 up to 81%. The FTIR of adsorbed CO revealed a shift towards lower frequencies for Pt on exchanged zeolite with respect to Pt on the acid zeolite, indicating that the basic character of Cs and Li enhance the electron donation from the support to the metal. The acid–base properties of the exchanged materials influence their selectivity for the catalytic conversion of n-heptane at 663 K and 1 atm, showing that Cs promotes the aromatization reactions while Li promotes isomerization and cracking. The cracking activity followed the acid/metal ratio for all of the catalysts studied.