Investigation of the Metallic Phases in Reduced, Impregnated Nickel and Nickel—Copper Silica—Alumina Catalysts

In Situ Observation of Cu–Ni Alloy Nanoparticle Formation by X‐Ray Diffraction, X‐Ray Absorption Spectroscopy, and Transmission Electron Microscopy: Influence of Cu/Ni Ratio

“…The data support that at high Ni concentrations silica-supported Cu-Ni alloys form essentially a homogeneous solid solution of Cu and Ni, whereas at lower Ni contents Cu and Ni are partly segregated and form metallic Cu and Cu-Ni alloy phases. This is in agreement with previous XRD studies by Swift et al [51] on prereduced samples.…”

“…This is in agreement with earlier studies; that is, if the mixture is rich in Ni, homogeneous Cu and Ni alloys are formed. [28,51] Similar reduction behavior and alloy formation have been observed for the other three Cu-Ni samples, namely Cu 2 Ni 1 / SiO 2 , Cu 1 Ni 1 /SiO 2 , and Cu 1 Ni 9 /SiO 2 . The long scan (640 min) XRD patterns at room temperature after in situ reduction for all silica-supported Cu, Ni and Cu-Ni samples are shown in Figure 5.…”

“…For Cu-Ni samples supported on SiO 2 / Al 2 O 3 and prepared by an impregnation method (with a calcination step), ex situ XRD analysis on prereduced catalysts shows that Cu and Ni form homogeneous alloys if the alloy is rich in Ni. [51] Naghash et al [28] used a coprecipitation method and XRD and XPS characterizations on prereduced Cu-Ni/Al 2 O 3 samples and arrived at the same conclusion. They found that at high levels of Cu doping into Ni and at elevated reduction temperatures (700 8C), the binding energies tended to restore towards those of pure Ni owing to the formation of separated phases of metallic Cu and Cu-Ni alloys.…”

Support Induced Control of Surface Composition in Cu–Ni/TiO2 Catalysts Enables High Yield Co-Conversion of HMF and Furfural to Methylated Furans

“…The structural properties of Cu–Ni alloys have been extensively studied for their potential application to a range of reactions. − Bulk Cu–Ni alloys are miscible and equilibrated into alloy phases when heated above ∼400 °C . In bulk systems (polycrystalline films, single crystalline films, and other structures), Cu surface segregation has been reported to be due to the lower surface energy of Cu in a vacuum compared to Ni. ,− It has further been demonstrated that the surface segregation is a facet dependent phenomenon that occurs more predominantly on (100) surface facets compared to (111) surface facets. , Insights into the structure of bulk Cu–Ni alloys have not translated into a complete understanding of the structure of supported Cu–Ni alloy nanoparticles, where multiple surface facets are simultaneously exposed, and the distribution of Cu and Ni is also influenced by interfacial interactions with the support and environment.…”

Steam reforming of naphthalene on Ni–Cr/Al2O3 catalysts doped with MgO, TiO2, and La2O3

“…The carbon dioxide changes only slightly. The observation of lower activity but robustness for catalysts calcined above 1,023 K has at least two possible explanations: (1) increasing the temperature of calcined leads, by sintering, to relatively large particles of nickel oxide; subsequently, the dispersion of metal crystallites decreases (Bartholomew and Boudart, 1972) (Swift and Lutinski, 1965;Andrew, 1976; Bartholomew and Farrauto, 1976). The decrease of active sites was not apparent from experimental evidence.…”