碱土金属改性V/K-γ-Al_2O_3催化剂环己烷氧化脱氢性能的研究

Dehydrogenation of Cyclohexane with Alkaline-Earth Metal Modified V/K-γ-Al_2O_3 Catalyst

以γ-Al2O3为载体,采用浸渍法制备了以V和K为主活性组分、碱土元素为助剂的催化剂M-3%V-6%K/γ-Al2O3(M=Mg、Ca、Sr、Ba),考察了该催化剂在环己烷氧化脱氢制环己烯反应中的催化活性,并采用X射线衍射(XRD)、N2吸附(BET)、氢-程序升温还原(H2-TPR)、氨-程序升温脱附(NH3-TPD)和X射线光电子能谱(XPS)方法对催化剂进行了理化表征.H2-TPR和NH3-TPD的表征结果显示碱土助剂的添加会影响催化剂的氧化还原能力和酸性;XPS表征结果表明碱土金属的添加影响了催化剂上钒物种和氧物种的组成,其中添加助剂Ca和Ba后,催化剂上钒钾物种的相对浓度升高,且催化剂表面晶格氧物种的含量增加.活性评价结果表明经碱土助剂Ca和Ba修饰后的3%V-6%K/γ-Al2O3催化剂均具有较好的催化性能,在425℃反应时环己烯的选择性均达56%以上;催化剂也表现出较好的催化稳定性和再生性能.

M-3%V-6%K catalysts（M=Mg、 Ca、 Sr、 Ba） supported on γ-Al2O3 were prepared by impregnation,which were characterized using X-ray diffraction（XRD）,N2 adsorption（BET）,temperature-programmed reduction（H2-TPR）,NH3-TPD and X-ray photoelectron spectroscopy（XPS）.Their catalytic properties for the oxidative dehydrogenation of cyclohexane to cyclohexene were studied.Characterization data from H2-TPR and NH3-TPD demonstrated that addition of alkaline-earth affects the catalyst redox ability and acid character.The characterization results of XPS showed that the addition of the alkaline earth metal affects the composition of vanadium species and oxygen species in the catalyst.In addition,the relative concentration of K and V and the catalyst content of the surface lattice oxygen increased by the introduction of Ca and Ba.According to the results of activity evaluation,Ca-3%V-6%K/γ-Al2O3 and Ba-3%V-6%K/γ-Al2O3 showed better catalytic activity and high selectivity for cyclohexene（≥56%） under reaction temperature 425 ℃.Furthermore,these kinds of catalyst also showed the better catalytic stability and the regeneration of the catalyst.