Thiophene decomposition on Pt-supported zeolites: a TPD study

The decomposition of thiophene on a series of partially exchanged MOR and L TL zeolites in the presence and absence of Pt was studied by temperature-pr ogrammed desorption (TPD). The increase of the alkali cation concentration increased the fraction of thiophene that desorbed from the samples without reacting. Increasing the concentration of acid sites increased coke and hyd rogen sulfide formation. Hydrogen desorption increased with increasing acid site concentration and available Pt surface area. Hydrogen is formed presu mably via a bimolecular decomposition of thiophene at Bronsted acid sites a nd is spilt over to Pt, where it recombines and desorbs. In contrast to Pt/ H-MOR, physical mixtures Of Pt/SiO2 and H-MOR were unable to produce signif icant amounts of hydrogen. This suggests that the thiophene decomposition o ccurs at metal-support interface sites or at sites with close distances to the Pt particle. Subtle differences between samples can be related to such minor variations in the distribution of acid sites and metal particles. (C) 2001 Elsevier Science B.V. All rights reserved.