Structure And Performance Analysis Of Propane Dehydrogenation Oxide Catalysts

Supported vanadium oxide catalysts for direct and CO₂-assisted propane dehydrogenation were prepared by impregnation method.XRD,N₂-BET,Raman,UV-Vis,XPS,H₂-TPR,NH₃-TPD and other methods were used to characterize the supports and catalysts.The effects of support structure,vanadium surface density and the introduction of CO₂ on the structure,reducing performance,surface vanadium dispersion,acidity,coking and propane dehydrogenation performance of VO_x based catalysts were investigated.Supported vanadium oxide catalysts showed obvious support effects.The activity and coking of the catalysts can be regulated by the properties of support,surface acidity and the interaction between VO_x and the support.In the direct dehydrogenation of propane,the active site of V-O is affected by the Zr O₂ support,which makes the VO_x/Zr O₂ catalyst shows high activity,is a good propane dehydrogenation catalyst.The deactivation of VO_x/Zr O₂ catalyst due to coking can be inhibited by the introduction of hydrogen.More active sites of propane dehydrogenation could be obtained in the CO₂-assisted propane dehydrogenation reaction,which enhances the activity of VO_x/Si O₂ while ensuring its stability.However,the reduction of H₂ on the VO_x/Zr O₂ catalyst surface made the coke more easily generated,and covered the active site,which reduces the activity.The amount of coke increases with the increase of surface acidity of the catalyst.The ability of the coke precursors on the VO_x/Al₂O₃ catalyst to migrate to the acidic position of the alumina support makes it more stable in propane dehydrogenation reaction.Four kinds of transition aluminaγ-Al₂O₃,δ-Al₂O₃,θ-Al₂O₃andθ,α-Al₂O₃ with the same vanadium surface density were obta ined by calcinating boehmite at certain temperatures.The alumina calcination temperature was shown to affect the surface acid properties and VO_x-support interactions.The reduced interaction between VO_xand the support improves the intrinsic activity of t he catalyst.The lower VO_xdispersion and higher total acid sites causes the catalyst to deactivate more easily.Relative to other forms of alumina,-Al₂O₃ has high surface area,the weaker VO_x-support interactions and moderate surface acid,can also be used as a potential support of VO_x propane dehydrogenation catalysts.By investigating the performance of vanadium-based catalyst in direct and CO₂-assisted propane dehydrogenation reaction,the experimental and theoretical basis can be provided for adjusting the dehydrogenation performance of VO_x based catalyst.