Abstract

The effect of Al₂O₃-ZrO₂, Al₂O₃-TiO₂ and Al₂O₃-La₂O₃ mixed oxides on the deactivation of bifunctional Pt-Sn/ Al₂O₃ reforming catalysts has been investigated. The n-heptane reforming at 500°C was used as a test reaction. Changes in the catalytic behavior due to differences of the acidity and the support-metal interaction were observed. Levenspiel´s and Beltramini´s deactivation models were developed assuming a series fouling for the carbonaceous deposits. Through the Beltramini’s model it was possible to distinguish the amount of acidity that participates in the deactivation processes. Both models successfully correlated with the experimental profiles of n-heptane activity decay. The following deactivation decreasing order, Al₂O₃-TiO₂-1>Al₂O₃-ZrO₂-25>Al₂O₃-TiO₂-2> Al₂O₃>Al₂O₃-La₂O₃-10 was found with both deactivation models. A quasi-linear correlation between the deactivation order and the coke formation kinetic constant (Levenspiel’s parameters) was observed. The catalyst acidity and the n-heptane conversion were correlated with Beltramini’s model. It was found that a high acidity (12 X 10-17 acid sites/g cat.) or metal dispersion (83%) increases the catalyst deactivation and it is necessary to have a balance of active sites in order to have a catalyst working as a bifunctional catalyst. On the other hand, the auto-regeneration Beltramini’s parameter suggests that the lowest deactivation of the Pt-Sn/ Al₂O₃-La₂O₃-10 catalyst is attributed to the cleaning capacity of the active sites. It was observed that the highest deactivation (80-92%) of the platinum-tin catalysts supported in alumina-titania mixed oxides were a result of the strong metal-support interaction (SMSI) effect. The Pt-Sn/Al₂O₃-La₂O₃-10 showed the best catalytic behavior with high initial and residual conversions (70 and 48%, respectively) and low deactivation (17 %) at a 50-minute reaction time. Furthermore, in the Pt-Sn/Al₂O₃ catalyst, the benzene yield was 1%, while the Pt-Sn/Al₂O₃-La₂O₃-10 showed a total inhibition of benzene production yield at residual conversions.

Recommended Citation

Contreras, Ignacio; Pérez, Gustavo; and Viveros, Tomás (2005) "The Influence Of The Support On The Deactivation Behaviour of Pt-Sn Reforming Catalysts," International Journal of Chemical Reactor Engineering: Vol. 3: A32.
Available at: http://www.bepress.com/ijcre/vol3/A32

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