Characterization of Pt,Sn/Mg(Al)O Catalysts for Light Alkane Dehydrogenation by FT-IR Spectroscopy and Catalytic Measurements

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• 作者：Anastasia Virnovskaia ; Sara Morandi ; Erling Rytter ; Giovanna Ghiotti ; Unni Olsbye
• 刊名：Journal of Physical Chemistry C
• 出版年：2007
• 出版时间：October 11, 2007
• 年：2007
• 卷：111
• 期：40
• 页码：14732 - 14742
• 全文大小：183K
• 年卷期：v.111,no.40(October 11, 2007)
• ISSN：1932-7455

文摘

The Pt function in Pt,Sn/Mg(Al)O and in Pt/Mg(Al)O catalysts has been studied by a combination of catalytictesting for ethane dehydrogenation at 450-650 C under a C₂H₆/H₂/CO₂/N₂/Ar = 10:1.6:6.8:5.9:75.7 flowand Fourier transform infrared spectroscopy (FT-IR), using CO as a probe molecule. The acid-base propertiesof the support were also investigated by FT-IR, using CH₃CN as a probe molecule. CO adsorption experimentsrevealed the presence of Pt terraces, as well as Pt sites with low coordination number (steps, edges, corners,or defects) on Pt/Mg(Al)O. The same experiments on Pt,Sn/Mg(Al)O revealed that Sn covers the steps, corners,edges, and defects of the Pt particles, thus developing simultaneously a geometric and a chemical effect onthe surface properties of the exposed Pt atoms. Accordingly, the ethane dehydrogenation reaction proceedswith a lower activation energy over Pt,Sn/Mg(Al)O compared to Pt/Mg(Al)O. Further, Sn addition leads tomore selective and more stable ethane dehydrogenation catalysts. The higher dehydrogenation selectivity ofPt,Sn catalysts was correlated to the masking of low-coordinated Pt sites. The Pt/Mg(Al)O and Pt,Sn/Mg(Al)O catalysts were subjected to an activation procedure consisting of several test-regeneration cycles.Good correlation was found between the number of accessible Pt sites and the catalytic activity after eachcycle.