Kinetic Study of Meta-Xylene Ammoxidation Reaction over a Commercial V–Cr Mixed Oxide Catalyst

The reaction behavior of meta-xylene ammoxidation on a commercial V–Cr mixed oxide catalyst (NC-IV) were studied in a fixed bed reactor, by kinetic modeling of experimental data of designed conditions. Specially, the oxidation of NH3 to N2 was also involved in the kinetic model, which is vital in the ammoxidation reaction. The catalyst showed monoclinic CrVO4 phase and spherical morphology with an average particle diameter of 45 μm. Nonlinear regression analysis of the evaluation data has been employed to determine the rate constant and the order of reaction. The results indicated that m-xylene, oxygen, and ammonia share similar kinetic reaction orders for the production of isophthalonitrile (IPN) and m-tolunitrile (MTN), while the NH3 oxidation reaction shows the highest reaction order, indicating that the partial pressure of ammonia and O2 requires a precise control. The calculation of activation energies implies that selective ammoxidation to IPN has the highest activation energy (170.6 kJ mol–1), which is higher than MTN formation (117.5 kJ mol–1). The oxidation of m-xylene to CO2 has slightly higher activation energy (122.9 kJ mol–1) than MTN production, implying the production of m-tolunitrile is the dominant reaction under high reaction WHSV. The NH3 oxidation shows the lowest activation energy (58.2 kJ mol–1) than the m-xylene participated reactions demonstrating a relatively easy NH3 oxidation. These kinetic analyses are useful for a better understanding of the catalytic ammoxidation reaction of alkyl substituted aromatics over V–Cr mixed oxide catalysts.