Co-conversion of methane and propane (CMP) over Zn-, Mo- and Ga-modified HZSM-5 catalysts has been studied under supersonic jet expansion condition at 400 degrees C and the products were detected using a time-of-flight mass-spectrometer. The major products obtained in the CMP are aromatic hydrocarbons: benzene, toluene, xylene, C9H8, naphthalene and methyl-naphthalene. A comparison of the CMP with methane dehydroaromatization reaction indicated that not only methane participated in the CMP reaction below 600 degrees C, but also methane activation and conversion on Lewis acid sites of the catalysts involved the methylation of aromatic hydrocarbons produced from propane dehydroaromatization. (C) 2013 Elsevier B.V. All rights reserved.