A novel nanciparticle impregnation method was used to prepare an Fe-Ni nanciparticle (np) catalyst supported on Mg(Al)O for the production of CO- and CO2-free H-2 and carbon nanotubes (CNT) by nonoxidative dehydrogenation of methane. This novel catalyst and a catalyst of similar composition prepared by incipient wetness (IW) were evaluated for their catalytic performance and their structures were determined by several microscopic and spectroscopic techniques. Monosized Fe-0.65-Ni-0.35 oxide nanciparticles with an average particle size of 9 nm were prepared by thermal decomposition of an Fe-Ni oleate-surfactant complex in octadecene under reflux: these nanoparticles were dispersed onto a Mg(Al)O support to form a supported Fe-Ni np/Mg(Al)O catalyst. Compared with the Fe-Ni IW/Mg(Al)O catalyst, the nanoparticle catalyst was more easily reduced at a lower temperature (600 degrees C in H-2) and exhibited enhanced methane dehydrogenation and longer life-timese at both 600 and 650 degrees C. Each reduced Fe-Ni nanoparticle functioned as an active site for the growth of CNT. The CNT were in the form of multi-walled nanotubes (MWNT) of relatively uniform diameter. An invar-like Fe-Ni-C alloy phase is believed to be the active phase for methane dehydrogenation. The deactivation of the nanoparticle catalyst is principally due to encapsulation of catalyst particles by the CNT. (C) 2008 Elsevier B.V. All rights reserved.