Study of Ni catalysts on different supports to obtain synthesis gas

Abstract

Ni catalysts supported on α -Al 2O 3, ZrO 2 and α -Al 2O 3–ZrO 2 were studied in the synthesis gas reactions (partial oxidation, dry reforming and mixed reforming). The Ni/ α -Al 2O 3–ZrO 2 catalyst showed a very good performance in relation to the initial activity and selectivity, comparable to that of the Ni/ α -Al 2O 3 catalyst. Concerning the deactivation, the modification of the α -Al 2O 3 supported with ZrO 2 leads to a higher stability, due to the strong inhibition of the carbon formation during the reaction. These results suggest that ZrO 2 promotes the gasification of adsorbed intermediates, which are precursors of carbon formation. Temperature programmed oxidation, transmission electron microscopy and Raman spectroscopy experiments showed that on Ni/ α -Al 2O 3 catalyst high amounts of graphitic carbon (whisker-like) are deposited during CO 2 reforming reaction, while on Ni/ α -Al 2O 3–ZrO 2 lesser amounts of deposited carbon were observed (about one order lower); a fraction of this carbon is of the same nature as that observed on Ni/ α -Al 2O 3 catalyst, while the other fraction is composed of carbon nanotubes, both of single wall and multi wall.