Idris A. Bakare

Oxidative dehydrogenation of propane to propylene over VOx/CaO–γ-Al2O3 using lattice oxygen

Oxidative dehydrogenation (ODH) of propane to propylene is studied using a new vanadium catalyst supported on CaO–γ-Al2O3 under a gas phase oxygen free atmosphere. The catalysts are synthesized with different CaO/γ-Al2O3 ratios, keeping the vanadium loading at 10 percent. The prepared catalysts are characterized using various physicochemical techniques. Raman spectroscopy reveals that the catalysts have monovanadate and polyvanadate surface species (VOx) with minute crystal particles of V2O5. FTIR spectroscopy and XRD analysis confirm the presence of V2O5, CaO and γ-Al2O3 in the catalyst. The catalysts show stable reduction and re-oxidation behavior in repeated TPR and TPO cycles, respectively. NH3-TPD shows that catalyst acidity decreases with increasing CaO content. The NH3-TPD kinetics analysis reveals that the activation energy of desorption increases with higher CaO, indicating stronger active site–support interactions. The ODH of propane experiments are conducted in a fluidized CREC Riser Simulator under gas phase oxygen free conditions. Among the studied catalysts, VOx/CaO–γ-Al2O3 (1 : 1) displays the highest propane conversion (65%) and propylene selectivity (85%) and a low COx due to its excellent oxygen carrying capacity, balanced acidity and moderate active site–support interactions.

Conversion of methanol to olefins over Al-rich ZSM-5 modified with alkaline earth metal oxides

Aluminum-rich H-ZSM-5 zeolites modified with alkaline earth metal oxides of Mg, Ca and Ba were applied in the conversion of methanol to olefins (MTO). The pores of the parent H-ZSM-5 zeolite were blocked with a surfactant prior to metal oxide modification. The resulting Mg-ZSM-5, Ca-ZSM-5 and Ba-ZSM-5 exhibited similar structural and morphological patterns to the parent H-ZSM-5. The addition of these alkaline metal oxides affected the acidity of the ZSM-5-based catalysts. Mg-ZSM-5 was found to be the most stable in the MTO reaction, maintaining a conversion of 100% for over 8 h and having the highest selectivity of ca. 46% to propylene due to the presence of weak Bronsted acidity.