Methane dehydroaromatization over the Mo/HZSM-5 catalyst under supersonic jet expansion condition was investigated via direct monitoring of the reactant and products using time-of-flight mass spectrometry. Our results showed that methane conversion was efficient, and differing from the result observed over the same catalyst at atmospheric pressure, naphthalene was the major product. The jet expansion approach for direct methane dehydroaromatization is expected to be more favorable for the production of hydrogen, which is important for fuel cell application. In addition, the effects of reaction temperature, time on stream, and pulsed laser (Nd:YAG at 266 nm) energy on the distribution of products were investigated. (c) 2006 Elsevier B.V. All rights reserved.