The decomposition of thiophene on a series of partially exchanged MOR and LTL zeolites in the presence and absence of Pt was studied by temperature-programmed 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 hydrogen sulfide formation. Hydrogen desorption increased with increasing acid site concentration and available Pt surface area. Hydrogen is formed presumably via a bimolecular decomposition of thiophene at Bronsted acid sites and 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 significant amounts of hydrogen. This suggests that the thiophene decomposition occurs 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.