Thanh Khoa Phung, A. Lagazzo, M. A. Crespo
Mar 1, 2014
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Influential Citations
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Journal
Journal of Catalysis
Abstract
Abstract Conversion of ethanol was investigated over four commercial aluminas prepared by different industrial procedures and one commercial silica-alumina. Characterization was performed by TEM, XRD, S BET and porosity measurements, and IR spectroscopy of the surface OH groups and of adsorbed CO and pyridine. Different features are attributed to different phases (γ-, δ-, θ-Al 2 O 3 ) and different impurities (Na + , Cl − ). Total conversion of ethanol with >99% selectivity to ethylene is achieved at 623 K over the purer Al 2 O 3 catalyst (Na 3+ sites in a tetrahedral environment located on edges and corners of the nanocrystals. Ethanol adsorbs dissociatively on Lewis acid-base pair sites but may also displace water and/or hydroxyl groups from Lewis acidic Al 3+ sites forming the active intermediate ethoxy species. Surface ethoxy groups are supposed to be intermediate species for both diethyl ether and ethylene production. Silica-alumina also works as a Lewis acid catalyst. The slightly lower activity on surface area basis of silica-alumina than aluminas attributed to the lower density of Lewis acid sites and the absence of significant basicity.