Hydrogenation catalysts based on nickel and rare earth oxides

Reduction property and catalytic activity of Ce1−XNiXO2 mixed oxide catalysts for CH4 oxidation

“…In the case of the impregnated NiO-CeO 2 catalyst, since most NiO aggregated on the surface of CeO 2 and the H 2 consumption of step II reduction of NiO particle is small, only a few of the NiO molecules dispersed into CeO 2 . A small quantity of solid solution can be formed at the interface between NiO and CeO 2 , as proposed by Wrobel et al [18]. Therefore, the intensity of the ␣ peak becomes weak and the ␥ peak disappears.…”

“…This fact further confirms that only small amounts of Ni 2+ ions can incorporate into CeO 2 to form solid solution for low or for high Ni content, and CeO 2 is not changed so much by the incorporated Ni 2+ . But the Ni 2+ ions incorporated in solid solution are more difficult to reduce [18]. So, there is no hydrogen consumption peak corresponding to the reduction of Ni 2+ species incorporated into solid solution in the TPR profiles.…”

“…On comparing the symmetry of ␤ peak, one finds that there is a big shoulder peak along with the reduction peak at 400 • C. It can be ascribed to ␥ peak, similar to the case of Ce 0.7 Ni 0. there is still part of NiO dispersed in CeO 2 and this can only be reduced at higher temperatures (␥ peak). It is reported [18] that, when NiO has dispersed on the surface of solid solution, strong interaction between free NiO and solid solution is achieved. However, the present results show that it is not so easy to form a solid solution and that most NiO aggregates on the surface of CeO 2 , while only a little amount of NiO disperses on CeO 2 .…”

“…The strong interactions between cerium and nickel species occurred in the nickel-cerium solid solution and/or at the interface between NiO grains and ceria. Wrobel et al [18] pointed out that nickel either forms amorphous NiO with oxygen or inserts in CeO 2 lattice to form a solid solution for low Ni content. In the case of high Ni content, crystallized NiO and solid solution co-exist.…”

Ce - promoted catalyst from hydrotalcites for CO2 reforming of methane: calcination temperature effect

“…The binding energies of the electron Ni 2p3/2 reported by different authors for NiO are between 854.2 and 854.6 eV; the shifts towards greater binding energies may result in the strong interactions produced by the formation of the solid solution. [35][36][37] The spectrum of the oxide calcined at 1000 °C exhibited shifts of +0.4 eV for the electron Ni 2 p 3/2 and +0.3 eV for the level Ni 2p1/2 , related with the formation of the spinel-like phase in which Ni has greater interactions in the crystalline structure. The CeO 2 spectrum was composed of different signals denominated v, v", v"' and u, u", u"' that describe the intensities of the photoelectrons 3d 5/2 and 3d 3/2 .…”