A model Co/SiO2 catalyst was prepared by depositing cobalt on silica films in ultrahigh vacuum conditions. Fischer-Tropsch synthesis was carried out at a total pressure of carbon monoxide and hydrogen between 0.33 and 1.0 bar. The effects of reaction temperature and pressure on kinetics and chain growth probability were investigated. The turnover frequency. activation energy, and product distributions were found in good agreement with those obtained on real catalysts. The formation of cobalt oxide or cobalt carbide was not detected after Fischer-Tropsch reaction at the low conversions and low water partial pressures of this work. (c) 2009 Elsevier Inc. All rights reserved.