Mg改性对Co/γ-Al2O3-TiO2催化燃烧丙烷性能影响

采用分步浸渍法制备了系列Mg改性的Co/γ-Al_2O_3-TiO_2催化剂,通过X射线衍射(XRD)、紫外可见漫反射光谱(DR-UV-vis)、N_2吸附-脱附(BET)、X射线光电子能谱(XPS)和H_2程序升温还原(H_2-TPR)等技术对催化剂进行表征,并考察了其对丙烷燃烧的催化性能。结果表明,Co在原始γ-Al_2O_3-TiO_2载体和Mg改性MgO/γ-Al_2O_3-TiO_2载体上均以Co_3O_4的形式存在;Mg掺入后与Al_2O_3作用形成MgAl_2O_4尖晶石,改善了载体的织构性质,提升了Co_3O_4在催化剂载体表面的暴露数量和分散程度。此外,MgAl_2O_4与Co_3O_4相互作用提升了Co_3O_4颗粒表面Co~(3+)/Co~(2+)和O_(ads)/O_(latt)的比例,并削弱了Co-O键键能,从而提升了其对丙烷的催化燃烧活性。当Mg负载量为15%(质量分数)时,在Co/MgO(15%)/γ-Al_2O_3-TiO_2催化剂上进行丙烷燃烧,丙烷90%转化率的温度比无Mg掺杂的Co/γ-Al_2O_3-TiO_2催化剂的降低了45℃,并且连续反应40 h其活性保持稳定。

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.