Enhancing the selectivity of light olefins through synergistic VOx/ZSM-5 composite in the oxidative cracking of hexane

Oxidative-aided cracking of n-hexane is studied in a gas-phase oxygen-free environment over VOx/ZSM-5. The catalysts were prepared by impregnation of VOx on ZSM-5. Characterization of the prepared samples using XRD, SEM, and BET showed smooth, fine, highly crystalline, and highly dispersed VOx on ZSM-5. Raman spectroscopy revealed the presence of isolated moieties on the 1.5 and 2.5 % vanadia loading while a small number of polyvanadate species are detected on the 5 % VOx sample. TPR confirmed the ZSM-5 support contains highly reducible vanadia species. The amount of VOx loading also affected the activity and product distribution. The olefin and COx selectivities are affected by reaction time/temperature and amount/availability of lattice oxygen. VOx/ZSM-5(1.5) showed 99.9 % n-hexane conversion and 91.39 olefin selectivity at 575 degrees C and 25 s time-onstream. This superior performance is attributed to the intermittent release of oxygen, optimum acidity, microporosity, and mesoporosity.