Regensburg 2004 – wissenschaftliches Programm

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O: Oberflächenphysik

O 31: Oberflächenreaktionen II

O 31.4: Vortrag

Donnerstag, 11. März 2004, 12:00–12:15, H36

First-principles Investigation of Structural and Chemical Properties of Nanoporous Carbon — •Suljo Linic, Johan M. Carlsson, and Matthias Scheffler — Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin

Production of styrene by dehydrogenation of ethylbenzene(ET) is one of the most important processes in chemical industry. Iron oxide is used as catalyst, but it has been observed that ET decomposes during an induction period leaving nanoporous carbon (NPC) on the oxide support. NPC are curved, defective, graphitic sheets and experiments have shown that such materials are active catalysts for oxidative dehydrogenation of ET.[1] Recently, it was therefore suggested that the actual catalyst under reaction conditions is NPC.[2] This motivates a theoretical study of NPC. Our results indicate on the one hand that flat and curved basal planes of graphitic sheets are chemically inert. Vacancies on the other hand leave dangling bonds and increase the density of state close to the Fermi level. This gives the vacancies a much higher reactivity, which is examplified by a large exothermal energy for dissociative adsorption of O2. We have then studied oxidation of the defects as function of pressure and temperature. The resulting oxygenated vacancies show interesting properties as active sites in the dehydrogenation process. [1] M. S. Kane et al., Ind. Eng. Chem. Res. 35, 3319 (1996). [2] G. Mestl et al., Angew. Chem. Int. Ed. 40, 2066 (2001).

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