Abstract
Vapor-phase ammoxidation of 2-picoline, 3-picoline, 4-picoline, methylpyrazine, 2-methylpyrimidine, and 5-methylpyrimidine was studied over 1% Cr2O3-10% V2O5-pumice stone catalyst. Experiments were carried out in a flow reactor system at atmospheric pressure. By these reactions, nitriles were formed selectively and by-product formation was negligible. From kinetic analysis, experimental rate data were found to be well interpreted by the Langmuir-Hinshelwood mechanism, where the rate-determining step was the surface reaction between adsorbed picoline or methyldiazine and dissociatively adsorbed oxygen. The rate constants and apparent activation energies of these compounds were compared with π-electron density on ring carbon atoms bonded to the methyl groups, and with carbon-13 chemical shifts of methyl carbons. From these results, it was found that the reactivity of these compounds under ammoxidation conditions decreased with increasing electron density on the methyl carbon atoms.
