The conversion of cyclohexane in the dehydrogenation reaction over Mo03/-Al203 catalysts, measured in a pulse reactor, increases with the metal oxide content. Up to 15 wt% Mo03 only dehydrogenation products are observed (cyclohexene and/or benzene) with cyclohexene being present in limited amounts only and completely absent on catalysts with more than 10% Mo03• Above 15 wt% Mo03 combustion products are formed at the expense of benzene. On oxidized catalysts the reaction proceeds through oxodehydrogenation:carbon oxides mainly stem from octahedral oxomolybdenum configurations, while formation of benzene is favored by a tetrahedral molybdenum stereogeometry. For reduced catalysts an alternative simple dehydrogenation scheme is required in which the catalytic activity is directly related to the d-electron configuration of the metal in its various valence states. The proposed mechanisms are sustained by observations on the influence of reductants (H2, CO), oxidants (02, CO2) and water and by a study of the catalyst deactivation
The mechanism of dehydrogenation of cyclohexane on MoO3/Al2O3 Catalysts
CASTELLI, Francesco;
1979-01-01
Abstract
The conversion of cyclohexane in the dehydrogenation reaction over Mo03/-Al203 catalysts, measured in a pulse reactor, increases with the metal oxide content. Up to 15 wt% Mo03 only dehydrogenation products are observed (cyclohexene and/or benzene) with cyclohexene being present in limited amounts only and completely absent on catalysts with more than 10% Mo03• Above 15 wt% Mo03 combustion products are formed at the expense of benzene. On oxidized catalysts the reaction proceeds through oxodehydrogenation:carbon oxides mainly stem from octahedral oxomolybdenum configurations, while formation of benzene is favored by a tetrahedral molybdenum stereogeometry. For reduced catalysts an alternative simple dehydrogenation scheme is required in which the catalytic activity is directly related to the d-electron configuration of the metal in its various valence states. The proposed mechanisms are sustained by observations on the influence of reductants (H2, CO), oxidants (02, CO2) and water and by a study of the catalyst deactivationI documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
