Simple synthesis of Al₂O₃ sphere composite from hybrid process with improved thermal stability for catalytic applications

Aluminium oxide spheres were synthesized by the hybrid process applying the biopolymer chitosan. After the calcination process the porous spheres were characterized by Chemical elemental analysis (XRF), X-ray diffraction (XRD), Scanning electron microscopy and Energy Dispersive X-ray Spectroscopy (SEM-EDS), N₂ adsorption–desorption isotherms, infrared spectroscopy (IR), and CO₂ temperature programmed desorption (CO₂-TPD). The effect of thermal treatment on surface properties of the oxide spheres was also evaluated by the catalytic ethanol dehydration reaction. The hybrid method produced interesting results related to the thermal stability against sintering process and consequently low decreases of surface area. The hybrid spheres calcination at 900 and 1200 °C produced a metastable phases of alumina with a high surface area, and nanometric crystallites. Additionally, the spheres of mixed silica-alumina synthesized by this method reveal the formation of porous spheres with highly acidic OH groups, which was suggested by the catalytic performance. - Highlights: • Al and Si/Al oxide spheres with promising properties are synthesized by hybrid method. • Al₂O₃ spheres show high thermal stability and resistance the loss surface area. • The SiO₂ addition plays an important role in the structure and porosity of the spheres. • Al₂O₃ and SiO₂/Al₂O₃ spheres presented a good activity to conversion ethanol. • The activity is related to the surface area and density of OH groups on surface