Phenomenological-based kinetics of oxidative cracking of n-hexane to light olefins over tandem (V/Si)-ZSM-5 catalysts

The kinetics of n-hexane oxidative cracking to olefins using lattice oxygen on (V/Si)-ZSM-5 were examined. The catalyst shows a total acidity of 0.44 mmol g⁻¹, comprising 47 % weak sites that promote olefin selectivity and 53 % strong sites that enhance n-hexane conversion. TPR confirms that (V/Si)-ZSM-5 is readily reducible. In a CREC Riser simulator, oxidative cracking resulted in ∼72.2 % olefin selectivity at 74.8 % n-hexane conversion. A kinetic model was formulated, including (1) catalytic cracking and (2) oxidative dehydrogenation. The cracking pathway treats adsorption, C–H/C–C bond cleavage, and desorption as elementary steps under a pseudo–steady-state assumption, while the ODH reaction follows a Langmuir–Hinshelwood mechanism. The model reproduces the experiments with strong statistical agreement, and the estimated rate constantly aligns with the observed product selectivity.