Effect of Steam on the Performance of Pt-Sn-Ce Catalyst for Propane Dehydrogenation

0.3%Pt/γ-Al2O3,0.3%Pt-0.9%Sn/γ-Al2O3 and 0.3%Pt-0.9%Sn/2.2%Ce-γ-Al2O3 catalysts were prepared by impregnation method with γ-Al2O3 as support.The effects of the steam addition to the system of the catalytic dehydrogenation of propane to propylene on the performance of Pt catalysts were investigated.The results showed that the addition of steam accelerated the deactivation of 0.3%Pt/γ-Al2O3 and 0.3%Pt-0.9%Sn/γ-Al2O3 catalysts and decreased the selectivity of propylene.However,the steam had no obvious effect on the stability of 0.3%Pt-0.9%Sn/2.2%Ce-γ-Al2O3 catalyst.Moreover,the presence of steam in the reaction system of propane dehydrogenation could promote the conversion of propane and decrease the amount of coke over 0.3%Pt-0.9%Sn/2.2%Ce-γ-Al2O3 catalyst.H2-chemical adsorption of the Pt catalysts treated with steam showed that the ability of Pt particles to resist the sintering was increased by the strong interaction between Ce and Pt in steam atmosphere.The main reason for the increase of propane conversion is that the active oxygen species reacted with active hydrogen atom to produce OH groups,which may participate in the elimination of β hydrogen atom in propane,resulting in the increase of dehydrogenation rate.