Effect of Mg modification on the catalytic performance of Co/γ-Al₂O₃-TiO₂ in the combustion of propane

A series of Mg-modified Co/MgO/γ-Al₂O₃-TiO₂ catalysts were prepared by multi-step impregnation method and characterized by X-ray diffraction (XRD), diffuse reflectance visible ultra violet spectroscopy (DR-UV-vis), N₂ adsorption-desorption, X-ray photoelectron spectroscopy (XPS) and H₂ temperature-programmed reduction (H₂-TPR); the effect of Mg modification on the catalytic performance of Co/MgO/γ-Al₂O₃-TiO₂ in the combustion of propane was investigated. The results indicate that Co exists in the form of Co₃O₄ on both the pristine γ-Al₂O₃-TiO₂ and Mg-modified MgO/γ-Al₂O₃-TiO₂ supports; Mg added in the MgO/γ-Al₂O₃-TiO₂ support interacts with Al₂O₃, forming MgAl₂O₄ spinel, which can improve the textural properties and promote the dispersion of Co₃O₄. Moreover, the interaction between MgAl₂O₄ and Co₃O₄ can increase the proportions of Co³⁺/Co²⁺ and O_ads/O_latt on the catalyst surface, weaken the Co-O bond, and thereby enhance the activity of Co-based catalyst in propane combustion. For the propane combustion over the Co/MgO(15%)/γ-Al₂O₃-TiO₂ catalyst with an Mg loading of 15%, the temperature to achieve a propane conversion of 90% is decreased by 45℃ in comparison with that over the Mg-free Co/γ-Al₂O₃-TiO₂ catalyst; moreover, the Co/MgO(15%)/γ-Al₂O₃-TiO₂ catalyst exhibits excellent stability and no decrease in the activity is observed in a 40 h continuous reaction test for propane combustion.