Abstract
Keggin, Wells-Dawson and Preyssler structured polyoxometalates (POMs) were synthesized by different methodologies. The POMs were used as catalysts for ammoxidation of 2-methylpyrazine. The structural properties of POMs were determined by XRD, SEM, DRIFT, DRUV-vis, H 2 -TPR, NH3-TPD and N-2-physisorption. Preyssler POM sample showed highest 2-methylpyrazine conversion (69%) and 2-cyanopyrazine selectivity (98%) at 380 degrees C. Superior performance of Preyssler POM could be attributed to its redox behavior and relatively strong acid sites. Large number of ammonium ions in the secondary structure of Preyssler POM could also enhance the transformation of oxygenated 2-methylpyrazine species into 2-cyanopyrazine. A correlation between the amount of ammonium content of POMs and their catalytic ammoxidation activity was obtained.