Alkali metal-promoted MgO catalysts such as Li/MgO, Na/MgO, K/MgO, and Cs/MgO were studied for the acrylonitrile synthesis from methanol and acetonitrile in the range 300-500 degreesC. The doping of alkali metal with larger cationic radius than that of Mg2+ increased the basic strength of MgO and facilitated the formation of acetonitrile carbanion, a reaction intermediate for acrylonitrile synthesis. Thermodynamic analysis showed that oxidative conditions were necessary to suppress the production of propionitrile. the main product under non-oxidative conditions. The doping of alkali metal also decreased the Lewis acid strength of MgO and consequently inhibited complete oxidation of anionic intermediates to CO and CO2. The catalytic activity for acrylonitrile production under oxidative conditions was in the order of K/MgO > Na/MgO > Cs/MgO > Li/MgO. (C) 2000 Elsevier Science B.V. All rights reserved.