Catalytic Oxidative Dehydrogenation of N-Butane under Oxygen-Free Reaction Conditions in a Fluidized CREC Riser Simulator: Reactivity, Kinetic Modelling
Abstract
This study investigates the performance of fluidizable VOx/MgO-γAl2O3 catalysts for producing C4-olefins through n-butane oxidative dehydrogenation (BODH). Catalysts were prepared using vacuum incipient wetness impregnation and characterized through a variety of analytical methods, including BET (Brunauer–Emmett–Teller) for surface area, XRD (X-ray diffraction), LRS (laser Raman spectroscopy), and XPS (X-ray photoelectron spectroscopy) to confirm the presence of amorphous VOx phases. Additional analyses—TPR/TPO (temperature-programmed reduction/oxidation), NH3-TPD (temperature-programmed desorption), NH3-desorption kinetics, and pyridine-FTIR—assessed catalyst stability, acidity levels, and metal-support interactions. The fluidizable catalysts were evaluated in a fluidized CREC Riser Simulator under anaerobic conditions, with reaction times ranging from 10 to 20 seconds and temperatures between 475°C and 550°C. Among the catalysts studied, the 5 wt% V-doped MgO-γAl2O3 demonstrated the highest selectivity for C4-olefins (82%-86%) and a butane conversion rate of 24%-27% at 500°C with a 10 second reaction time. After six BODH cycles, catalyst regeneration and coke formation were analyzed using Total Organic Carbon (TOC). The study also developed a kinetic model for the BODH reaction using a VOx/MgO−γAl2O3 catalyst containing 5 wt% V. This model, which applies Langmuir-Hinshelwood kinetics incorporating reactions such as cracking, oxydehydrogenation, and complete oxidation, achieved optimal C4-olefin selectivity of 86% at 500°C and 10 seconds. The kinetic parameters were precisely defined, showing narrow confidence intervals and minimal cross-correlation, highlighting the catalyst’s compelling performance and stability under the tested conditions.