Autothermal reforming (ATR) of n-dodecane was systematically investigated with O/C = 0.6 and H2O/C = 2.0 over nickel-based catalysts supported on cordierite monoliths. Both nickel supported on monolith (Ni/monolith) and nickel supported on cerium-zirconium oxide (CZO) loaded on monolith (Ni/CZO/monolith) were tested for ATR activity. The influence of nickel weight loading (0-16 wt%) on ATR product yields was examined. Experimental results showed that 2 wt% Ni/CZO/monolith was an optimal composition for ATR. The roles of Ni and CZO were determined by comparing n-dodecane conversion, oxygen conversion, the extent of reforming, and product yields (i.e., CO, CO2, and H-2). The reaction studies indicated that nickel catalyzed the conversion of n-dodecane by POX and SR, yielding a hydrogen rich effluent, whereas CZO alone catalyzed the conversion of n-dodecane though catalytic oxidation and cracking, yielding an effluent rich in smaller hydrocarbon species. Nickel supported on CZO showed the greatest hydrogen, carbon monoxide, and carbon dioxide yields of the catalysts studied. ATR, partial oxidation (POX), steam reforming (SR), and the influence of reaction temperature on ATR were studied separately and compared at similar conditions over 2 wt% Ni/monolith and 2 wt% Ni/CZO/monolith to elucidate the primary reforming reactions. An n-dodecane ATR reaction schematic is postulated, and the influences of homogeneous activity and oxygen conversion are discussed. It is proposed that POX, homogeneous cracking, and oxidative cracking are the major routes for n-dodecane conversion during ATR, whereas POX of n-dodecane and SR of smaller hydrocarbons are the primary routes to reforming products (i.e., H-2, CO2 and CO2). (c) 2007 Elsevier Inc. All rights reserved.