Nanocomposite Ni/ZrO2-AN catalyst consisting of comparably sized Ni metal and ZrO2 nanoparticles is studied in comparison with zirconia-and alumina-supported Ni catalysts (Ni/ZrO2-CP and commercial Ni/Al2O3-C) for steam reforming of methane (SRM) and for combined steam and CO2 reforming of methane (CSCRM). The reactions are performed under atmospheric pressure with stoichiometric amounts of H2O and CH4 or (H2O + CO2) and CH4 at 1073 K. Under a wide range of methane space velocity (gas hourly space velocity of methane GHSV(CH4) = 12,000-96,000 ml/(h g(cat.)), the nanocomposite Ni/ZrO2-AN catalyst always shows higher activity and stability for both SRM and CSCRM reactions. The two supported Ni catalysts (Ni/ZrO2-CP and Ni/Al2O3-C) exhibit fairly stable catalysis under low GHSV(CH4) but they are easily deactivated under high GHSV(CH4) and become completely inactive when they are reacted for ca. 100 h at GHSV(CH4) = 48,000 ml/(h g(cat.)). The CSCRM reaction is carried out with different H2O/CO2 ratios in the reaction feed while keeping the molar ratio (H2O + CO2)/CH4 = 1.0, the results prove that the nanocomposite Ni/ZrO2-AN catalyst can be highly promising in enabling a catalytic technology for the production of syngas with flexible H-2/CO ratios (ca. H-2/CO = 1.0-3.0) to meet the requirements of various downstream chemical syntheses. (C) 2004 Elsevier B.V. All rights reserved.