It has been investigated that (CH4)-C-13 reacts with ethylene over metal cations such as indium cations-loaded H-ZSM-5 to form singly C-13-labeled propylene ((CC2H6)-C-13-C-12) and hydrogen at 673 K. The heterolytic dissociation of C-H bond in methane presumably proceeds by the reaction of methane with metal cations for the formation of CH3delta+ and metal hydride species, thus allowing the reaction of CH3delta+ with ethylene to form propylene and acidic protons. Metal cations are regenerated by the reaction of silver-hydride species with acidic protons, and hydrogen is simultaneously formed. Thus, bifunctionality of metal cations and acidic protons is essential for the activation of methane. (C) 2003 Elsevier B.V. All rights reserved.