Semiconductive and Redox Properties of Ti and Zr Pyrophosphate Catalysts (TiP2O7 and ZrP2O7). Consequences for the Oxidative Dehydrogenation of n-Butane |
| |
Authors: | Ioan-Cezar Marcu Jean-Marc M. Millet Jean-Marie Herrmann |
| |
Affiliation: | (1) Institut de Recherches sur la Catalyse, CNRS, associé à l'Université Claude Bernard Lyon I, 2 avenue A. Einstein, F-69626 Villeurbanne Cedex, France;(2) Laboratoire de Photocatalyse, Catalyse et Environnement, (LPCE), UMR CNRS 5621, Ecole Centrale de Lyon, BP 163, 69131 Ecully Cedex, France |
| |
Abstract: | The electrical conductivity of titanium and zirconium pyrophosphates used as catalysts in n-butane oxidative dehydrogenation has been measured under oxygen and n-butane at 400 and 500 °C and under subsequent exposures to both gases at the catalytic reaction temperature. The two compounds appeared to be p-type semiconductors under air with positive holes as the main charge carriers but became n-type when contacted with n-butane. If their conductivities are comparable as p-type semiconductors (within one order of magnitude), by contrast, they differ by 3 orders of magnitude when being n-type semiconductors. These results explain the difference in catalytic reaction mechanism encountered on the two solids. The alkane activation was proposed to be related in both cases to the p-type semiconducting properties of the solids, likely through hydrogen abstraction by a surface O- species, forming a C4H9 radical which will similarly undergo a second hydrogen abstraction to form butenes. The changes in activation energy and in selectivity on TiP2O7 at higher temperatures (>450 C) are indicative of a change in mechanism, possibly with the transient formation of an alkoxide species. |
| |
Keywords: | TiP2O7 and ZrP2O7 catalysts dehydrogenation of n-butane |
本文献已被 SpringerLink 等数据库收录! |
|