ACTIVATION BEHAVIOR OF NI HYDROUS TITANIUM-OXIDE (HTO) CATALYSTS

The activation of Ni-TiO2 catalysts prepared via both impregnation on commercial TiO2 and by ion exchange on hydrous titanium oxide (HTO) supports was investigated. The reactivity of these catalysts for a structure-sensitive reaction (n-butane hydrogenolysis) was investigated as a function of different activation treatments (temperature, time) in a H-2 atmosphere. Complete activation of the ion exchanged Ni/HTO catalyst in H-2 required temperatures > 623 K and times > 18 h. Low temperature (573 K) activation of the ion exchanged Ni/HTO catalyst in H-2 was not possible without performing a mild (573 K) reduction/oxidation/reduction cycle. Observations of the ion exchanged Ni/HTO catalyst microstructures by transmission electron microscopy revealed that inactive samples contained a distinct film which covered Ni particle surfaces. The exact nature of this film has not yet been determined; experimental evidence is consistent with the film being composed of either carbonaceous residue or TiO(x) which has migrated to the Ni particle surfaces from the bulk support phase.