Hydrothermal acid etching of alumina beads and its effect on isobutane dehydrogenation performance over Pt/γ-Al2O3 catalyst

Millimeter-scale spherical alumina used as the support of Pt catalyst for isobutane dehydrogenation was prepared by alginate assisted sol-gel method, and then hydrothermal treated in 0.5 M HNO3 to improve its porous structure and surface properties. The effects of acid etching time on the composition, structure, surface acidity, redox property, catalytic dehydrogenation performance and carbon deposition of catalyst were investigated by ICP-OES, SEM, TEM, XRD, N2 adsorption-desorption, 27Al MAS NMR spectra, NH3-TPD, H2-TPR, isobutene transient response experiment and TGA. The results show that the acid treatment can effectively remove zinc species and partial aluminum from the surface of alumina beads, which can create defect sites and increase the specific surface area of alumina, thus improving the dispersion of Pt particles. In addition, acid etching significantly increases the acidity of alumina and enhances the interaction between Pt particles and alumina through the formation of defect sites. The Pt/Al2O3-NA-3 possesses the smallest size of Pt particles, the strongest Pt-alumina interaction, maximum number of acid sites and the highest isobutene yield of 33% even after 270 min reaction.