The stoichiometry of thiophene adsorption, desorption, and conversion on H-ZSM5 and H-Y zeolites, were analyzed using chromatographic methods and mass spectrometry. It was observed that adsorption uptakes were 1.7 and 2.8 thiophene/Al at 363 K on H-ZSM5 and H-Y zeolites, respectively after removal of physisorbed thiophene. The thiophene oligomers decomposed at ∼534 K during thermal treatment to form molecular thiophene with all carriers, leaving behind unsaturated thiophene-derived species with a 0.9-1.1 thiophene/Al stoichiometry. The results show that hydrogen atoms formed during propane dehydrogenation reactions on H-ZSM5 are more effective at removing the unsaturated hydrocarbons formed during thiophene desorption-reaction steps.