Catalytic hydrogenation of carbon dioxide over LaNi5 activated during the reaction

The hydrogenation of carbon dioxide to methane can be catalyzed over an int ermetallic compound of LaNi5 at 250-350 degrees C. The catalytic activity a t 250 degrees C increases during the reaction while X-ray diffraction (XRD) analyses show that the structure of the compound decomposes to La(OH)(3), LaCO3OH, and metallic nickel. Formation of metallic nickel species during t he reaction also takes place in a nickel-lanthanum oxides catalyst prepared by a coprecipitation method, however, the activity is not so high as the f ormer catalyst. Surface analyses by X-ray photoelectron spectroscopy (XPS) suggest that new nickel species interacting with lanthanum cation, possibly Ni-O-La, are formed in LaNi5 during the reaction, and the species are supp osed to be rather active than metallic nickel. (C) 1999 Elsevier Science B. V. All rights reserved.