Synthesis of acetonitrile from syngas and ammonia over silica-supported molybdenum catalysts modified by silver.

Abstract

Direct synthesis of acetonitrile from syngas and ammonia over silica-supported molybdenum catalysts was studied. The catalysts were prepared by impregnation of silica followed by calcination and reduction. The reduction treatment in the preparation, however, had little influence on the activity of Mo/SiO2, because the reduction of Mo species on silica proceeds under the reaction atmosphere. Ag had an excellent effect on the catalyst to improve its activity and selectivity to acetonitrile. The optimum reaction temperature was between 450°C and 500°C. The weight change of Mo/SiO2 and Mo-Ag/SiO2 during reduction treatment suggested that MoO2 is the supported Mo species, regardless of whether Ag is added as a promoter or not. From the X-ray diffraction measurements, it was speculated that MoO2 is the active species for the formation of acetonitrile and that Ag has an effect of making MoO2 amorphous or more dispersed. The deactivation of the catalysts may be caused by both crystal growth of MoO2 and surface fouling.