Acetone condensation was carried out over high surface area molybdenum nitride and carbide catalysts. Rates and selectivities for these materials were compared to those for MgO (a solid base catalyst), USY (a solid acid catalyst) and 1% Pt/SiO2 (a supported noble metal catalyst). The Mo2N catalyst as well as MgO and USY catalyzed the condensation of acetone to products including mesityl oxide (MO), mesitylene and isophorone. Areal rates for the Mo2C and Mo2N catalysts were higher than those for the MgO and USY catalysts. The Mo2N catalyst was most active for mesityl oxide production. The formation of mesitylene and isophorone over this catalyst indicated that Mo2N possessed strong acid and base sites, respectively. Results from the thermal desorption of CO2 and NH3 confirmed the presence of these sites. The hydrogenation of acetone to isopropanol (IPA) and its subsequent dehydration to propylene were predominant reactions for the Mo2C and 1% Pt/SiO2 catalysts. Differences between the Mo2N and Mo2C catalysts are explained based on their base, acid and metallic properties. (C) 2004 Elsevier B.V. All rights reserved.