Studies On The Preparation And Catalytic Properties Of Supported PtSn/γ-Al₂O₃ And PtSn/ZSM-5 Catalysts For The Dehydrogenation Of Propane

The preparation and catalytic properties of monolithic PtSnNa/γ-Al2O3 and PtSnNa/ZSM-5 catalysts for propane dehydrogenation have been studied by using X-ray diffraction(XRD),BET surface area/pore structure measurements,electron microscope(EM),hydrogen chemisorption and tempreture-programmed oxidation(TPO)combined with micro-reactor tests.Moreover,the different catalytic performance between the monolithic catalysts and the granular catalysts with same composition for propane dehydrogenation have been investigated by using computational fluid dynamics(CFD)theoretic method.The main research results are as follows.1.The catalytic properties of monolithic PtSnNa/γ-Al2O3 catalysts for propane dehydrogenation are closely related to the catalyst composition.When the Pt content in the catalysts is 0.5 wt%,the propane conversion and the propylene selectivity first increase and then decrease with increasing Sn content,and the optimum Sn/Pt molar ratio is ca.6;Also,the propane conversion and the propylene selectivity first increase and then decrease with increasing Na+ content,and the optimum Na+content is ca.0.9 wt%.2.The texture of catalyst exerts great influences on the catalytic properties for propane dehydrogenation.The monolithic PtSnNa/γ-Al2O3 catalysts have higher propane conversion,higher propylene selectivity and better reaction stability than those of granular catalysts with similar Pt dispersion.Moreover,under the same reaction conditions,the propane conversion over the monolithic PtSnNa/ZSM-5 catalysts are greatly higher than that of monolithic PtSnNa/γ-Al2O3 catalysts with the similar propylene selectivity3.The catalytic properties of monolithic catalysts for propane dehydronation can be optimized by adjusting Pt dispersion state in the catalyst layer of monolithic catalysts.When Pt is mainly dispersed in outer layers,the monolithic catalysts have higher propane conversion,higher propylene selectivity and better reaction stability than those of monolithic catalysts with Pt dispersed homogeneously in the catalyst layers.4.The reseach results obtained by computational fluid dynamics(CFD)have shown that for propane dehydrogenation reaction,there are the obvious differences of pressure field,feedstocks and products flow field between the monolithic catalysts and the granular catalysts,which are the main reasons for the obvious different catalytic properties for propane dehydrogenation.