The reducibility of highly stable Ni-containing species in catalysts derived from hydrotalcite-type precursors

Abstract

A study was conducted on the speciation and reducibility of Ni in catalysts derived from hydrotalcite-type\ud (HT) precursors intercalated by silicates. Silicate and nickel contents in Ni/Mg/Al HT precursors varied and\ud the products obtained by thermal decomposition in the 773–1373 K range were characterized. Sample\ud properties were related to the amount of silicates and nickel. The former altered the formation of the\ud spinel-type phase and decreased the ratio between MgO and MgAl2O4 phases in which the active\ud species were stabilized. On the other hand, the Ni distribution depended on the Ni-loading. Nicontaining\ud species in the spinel phase were more abundant for high Ni-loaded catalysts, and were\ud readily reduced by H2 treatment at 1023 K, whereas those in the Ni1xMgxO solid solution remained\ud partially unreduced

Comparative Study of Strategies for Enhancing the Performance of Co3O4/Al2O3 Catalysts for Lean Methane Combustion

“…The relatively low binding energy of the signal associated with the presence of Ni 2+ cations in a spinel lattice (855.3 eV) also denoted that these species were mainly a part of the NiCo2O4 spinel instead of the NiAl2O4, for which the binding energy of that signal would be expectedly higher (ca. 856.0 eV), as shown by other studies [36,37]. As for the Co/Al sample the two features with the lowest binding energies, located at 779.5 and 781.0 eV, were assigned to Co 3+ and Co 2+ ions, respectively, while the signal centered at 783.2 eV was attributed to the presence of CoO in the surface of the samples [32,33].…”

“…The relatively low binding energy of the signal associated with the presence of Ni 2+ cations in a spinel lattice (855.3 eV) also denoted that these species were mainly a part of the NiCo 2 O 4 spinel instead of the NiAl 2 O 4 , for which the binding energy of that signal would be expectedly higher (ca. 856.0 eV), as shown by other studies [36,37]. The deconvolution and integration of the XPS spectra allowed for a quantitative analysis of the composition of the surface, as shown in Table 2.…”

CO and CO2 methanation over Ni catalysts supported on CeO2, Al2O3 and Y2O3 oxides

“…The Ni 2p 3/2 XPS spectra of the as-prepared 15Ni/CeO 2 catalyst (Figure 7b) revealed two adjacent bands with maximum at BE ≈ 854 eV and BE ≈ 855.5 eV, labelled as Ni(II) and Ni(II)*, together with a broad satellite peak at BE ≈ 861 eV, consistent with the presence of Ni 2+ species [88][89][90]. This double peaked structure suggested the presence of surface Ni species with different environments [91]. In particular, the peak at highest binding energy (Ni(II)) was ascribed to presence of NiO highly dispersed on the support surface which created higher metal-support interaction.…”

Ultrasound-assisted sequentially precipitated nickel-silica catalysts and its application in the partial hydrogenation of edible oil

“…These results agreed well with those of several other investigations [53] , [54] . The SiO 2 support was amorphous, which did not contribute to any peaks on the diffractogram [55] , [56] . The NiO crystallite size was ascertained using the Scherrer equation, referencing the characteristic peak at 43°, with the results presented in Fig.…”