Introduction Of Fe3 Research Articles

Iron-functionalized Al-SBA-15 for benzene hydroxylation

For the first time an ordered mesoporous silica (Fe-Al-SBA-15) with catalytically active isolated Fe surface species for the hydroxylation of benzene with nitrous oxide is prepared by introduction of Fe3+ in the synthesis gel of Al-SBA-15.

Coexisting chromian omphacite and diopside in tremolite schist from the Chugoku Mountains, SW Japan: The effect of Cr on the omphacite-diopside immiscibility gap

Chromian clinopyroxenes with exsolution textures were found in high-pressure (HP) tremolite schist from the Osayama serpentinite melange in the Chugoku Mountains, Southwestern Japan. Chromian omphacite [jadeite (Jd)23.3-41.4 diopside (Di)46.7-60.7 kosmochlor (Ko)4.5-19.6 aegirine (Ae)<7.0] with up to 6.6 wt% Cr2O3 occurs as neoblastic crystals in a foliated tremolite-rich matrix, or as pseudomorphs after relict chromian spinel, and contains irregular-shaped thin lamellae of chromian diopside (Jd3.8-18.2Di72.5- 93.6Ko1.1-13.9Ae<3.4). Chromian omphacite contains roughly constant jadeite plus kosmochlor components at 38.2-51.6 mol%; this is equivalent to the jadeite component of ordered P2/n omphacite. Systematic analyses of coexisting chromian pyroxenes yield a clear immiscibility gap between “omphacite” and “diopside.” The compositional gap becomes much narrower with increasing Ko component; addition of only 10 mol% Ko component narrows the omphacite-diopside gap by an order of magnitude. Such an effect is similar to, but more effective than, the introduction of Fe3+ on the omphacite-diopside immiscibility gap.

A Magnetically Ordered Non-Stoichiometric Zinc Ferrite for the Oxidative Dehydrogenation Reactions.

ABSTRACTZnFe2O4nanoparticles were prepared by hydrothermal reduction approach. A considerable amount of α-Fe2O3was segregated in the as-synthesized sample, which diffused into the tetrahedral and octahedral sites of the ZnFe2O4spinel structure with increasing the annealing temperature. The introduction of Fe3+into the tetrahedral positions was observed by Mössbauer spectra. Magnetization measurements showed an unusual ferrimagnetic behavior of the ZnFe2O4phase, even at room temperature, confirming the introduction of Fe3+into the tetrahedral sites of the spinel structure. Catalytic activity measured in the oxidative dehydrogenation of 1-butene reaction increased with increasing annealing temperature, indicating that those interactions of Fe3+in tetrahedral and octahedral positions also promotes the activity and selectivity to butadiene formation.

Structural study of X-ray amorphous Fe-Zr-O materials

Radial-distribution-function analysis was used to study the structure of x-ray amorphous Fe-Zr-O materials prepared by heat treatment between 383 and 673 K. The chemical and structural formulas of the materials were established. The results demonstrate that the introduction of Fe3+ into ZrO2 favors the formation of vacancies and reduces interatomic distances in comparison with cubic ZrO2. The materials contain OH- groups, whose concentration decreases with increasing heat-treatment temperature.

Isomerization ofn-butane on the SO4/ZrO2 catalyst promoted by IV Period metals

The catalytic activity of superacidic systems based on SO4/ZrO2 and modified by IV Period metals in isomerization ofn-butane was studied. At low temperatures of the reaction, the introduction of Fe3+, Sc3+, Co2+, or Zn2+ ions (1%) increases the yield of isobutane by 1.5 times due to the activation ofn-butane on the sites created by the promoting ions. The addition of Cr3+, V4+, or Mn2+ (1%) decreases the catalytic activity because of a decrease in the catalyst acidity, most likely, due to the reduction of surface sulfur species. The influence of the nature of the support and surface additives of SiO2, TiO2, and ZrO2 on the activity and selectivity of the catalytic system inn-butane isomerization was studied.

Colossal magnetoresistance of spin-glass perovskite La0.67Ca0.33Mn0.9Fe0.1O3

The magnetic and magnetotransport properties of the perovskite La0.67Ca0.33Mn0.9Fe0.1O3 have been investigated, and the spin-glass behavior with a spin freezing temperature of 42 K has been well confirmed for this compound. A metal-to-insulator transition and colossal magnetoresistance have been observed near its spin freezing temperature; besides, the insulator behavior has been found to reappear at lower temperature. The formation of ferromagnetic and antiferromagnetic clusters and the competition between them with the introduction of Fe3+ ions, which do not participate in the double-exchange process, have been suggested to explain the experimental results.

Catalytic properties of Fe3+ and Cu2+ silicates with the structure of zeolites

1. Silicates with the crystal structure of type ZSM zeolite were obtained by hydrothermal synthesis in the presence of Al(III), Fe(III), and Cu(II) salts. 2. The selectivity of the aluminosilicates for the aromatic products of the transformation of methanol decreased with an increase in the concentration of Fe(III) and Cu(II); synthesis of aromatic hydrocarbons was not observed on ferrosilicates. 3. It was hypothesized that the introduction of Fe3+ and Cu3+ ions decreases the value of n in the active site of Si(OAl)n(SiO)4−n aluminosilicate, which results in a decrease in the rate of hydrogen redistribution in the unsaturated intermediate compounds formed in the transformation of methanol.

Effect of iron admixtures on the physical properties of TGS crystals

Abstract The influence of Fe3+ admixture on the dielectric properties of TGS crystals was studied. As shown by EPR, the Fe3+ ion in the TGS lattice was found to lie in an actohedral environment as well as Cr3+. The introduction of Fe3+ gives rise to an intense charge transfer band with a maximum at λ = 280nm in the optical spectrum.