The aromatization of methane was investigated over Mo2C supported on several HZSM-5 zeolites with different morphologies and Si/Al ratios. X-ray diffraction, elemental analyses, X-ray photoelectron spectroscopy, Al-27 NMR spectroscopy, nitrogen adsorption, and scanning electron microscopy were used to characterize the supports. Support morphology was observed to play a crucial role in this reaction, which was studied under conditions in which actual rates could be compared. Although rates did not vary linearly either with the total number of the acid sites or with the external surface area, turnover frequencies of the surface acid sites, calculated using the Si/Al ratios determined from XPS measurements, were observed to vary linearly with the external surface area. (c) 2006 Published by Elsevier Inc.