In-situ Moessbauer and EXAFS investigations of the structural and magnetic properties of bimetallic iron-nickel/silica and iron-copper/silica catalysts

Role of iron contaminants in the pathway of ultra-stable Y zeolite degradation

“…Quadrupole splitting (QS) is determined by the nuclear quadrupole moment ( Q ), the principal component of the electric field gradient (EFG) and the lattice contribution (Vzz). 37–45 Due to the few d-electrons at the nucleus, the ferrous Fe 2+ exhibits larger positive isomer shifts than its ferric counterpart.…”

“…the lattice contribution (Vzz). [37][38][39][40][41][42][43][44][45] Due to the few d-electrons at the nucleus, the ferrous Fe 2+ exhibits larger positive isomer shifts than its ferric counterpart. The Mössbauer spectra of USY 2.5 treated at different calcination temperatures are shown in Fig.…”

Promotional effect of Fe on performance of Ni/SiO2for deoxygenation of methyl laurate as a model compound to hydrocarbons

“…S2 †), we also found the existence of Fe-O-Fe species with ferri-, ferro-, and/or antiferromagnetic behavior on FeNi(0.25)/SiO 2 , 56 in agreement with the other observations. 16,[57][58][59] The oxygen vacancies on the iron oxide can bind oxygen atom in the C]O group via the donation of the lone pair of electrons and subsequently the C]O bond is activated. 21,[32][33][34]60,61 The strong oxygen affinity of Fe and the role of oxygen vacancies in Fe oxide can account for the dominating HDO pathway on Fe/SiO 2 because the activated C]O group via O adsorption on Fe site can be readily hydrogenated to dodecanol and subsequently dehydrated/hydrogenated to produce C12 hydrocarbon.…”

Decomposition of CO−H2 over Graphite Nanofiber-Supported Iron and Iron−Copper Catalysts

“…[11][12][13][14] It has been suggested that the observed enhancement in the performance exhibited by bimetallics can be attributed to the components being in a state that is more easily reduced due to a weakening of the strength of the metal-support interaction that ensues from alloy formation. 15 The electrical conductivity properties of graphite offer some interesting possibilities when the material is used as a support medium for small metal particles. 16,17 Unfortunately, in its conventional form, graphite has limitations for this type of application due to the low surface area (1 m 2 /g) and restricted number of reactive sites (edge regions).…”

“…The performance of a supported catalyst system is governed to a large degree by a combination of the chemical nature of the reactant gas and the strength of the metal−support interaction. − These factors together with the reaction conditions can induce perturbations in the metal crystallites that modify both the reactivity and the selectivity of the catalyst and ultimately the pathway of the reaction. , Further modifications can result from the incorporation of a second metal to the formation of a bimetallic catalyst system. This procedure can alter the adsorptive and chemical properties of the catalyst, making its overall performance quite different from that of either of the respective monometallic entities. − It has been suggested that the observed enhancement in the performance exhibited by bimetallics can be attributed to the components being in a state that is more easily reduced due to a weakening of the strength of the metal−support interaction that ensues from alloy formation …”