The adsorption and reactions of butyl iodide on Mo2C/ZSM-5 and Mo2C/SiO2 have been investigated by means of FTIR spectroscopy and mass spectrometry. Adsorption bands were observed following the adsorption of butyl iodide at 200-230 K that corresponds well to the vibrations of molecularly adsorbed C4H9I. At higher adsorption temperatures, bands due to the adsorbed butene and butylidyne also appeared. From the comparison of the adsorption and desorption characteristics determined on pure and Mo2C-containing ZSM-5, it was concluded that the majority of butyl iodide is attached to ZSM-5. The presence of Mo2C on ZSM-5 and SiO2, however, enhanced the rate of the decomposition, promoted the coupling of butyl species and catalyzed the formation of xylene and benzene. It was assumed that Mo2C interacting with the acidic sites of the support is the active center for the latter processes. (C) 2004 Elsevier B.V. All rights reserved.