Combustion of coke deposits of Pt-Sn/Al2O3 catalysts with ozone-rich air

C.L. PIECK; C.R. VERA; C.A. QUERINI; J.M. PARERA

Paris, Francia

Congreso; XIII International Congress on Catalysis; 2004

Centre National de la Recherche Scientifique

Two regeneration schemes of Pt-Sn naphtha reforming catalysts, coked by reacting cyclopentane at 500 °C, were compared:  with O2 at 450 °C and with O3 at 125 °C.  The coke was analyzed by temperature-programmed-oxidation (TPO), FT-IR and C-NMR.  The activity and its recovery after coke burning-off were assessed by cyclohexane dehydrogenation while temperature-programmed-reduction (TPR) was used to study the Pt-Sn interaction.             The O3-TPO trace shows that coke burning with O3 starts at a low temperature and has a maximum at 150 °C due to the simultaneous acceleration of the burning rate and of the O3 decomposition at higher temperatures.  O2 burns coke with a maximum at 500 °C.  Partial decoking with O3 at 125 °C yields a residual coke which is more oxygenated and easy to burn than that remaining after O2 decoking at 450 °C.  After regeneration with O3 the dehydrogenation activity is recovered to the original level of the fresh catalyst while after O2 regeneration the level is enhanced to a higher value. It must be concluded that O3 regeneration does not change the original Pt-Sn interaction while O2 regeneration dimminishes it, producing free Pt sites with higher dehydrogenation capacity.