Low-temperature iron-modified cobalt oxide system

Journal of the American Chemical Society, 2015

Co3O4 with a spinel structure is a very active oxide catalyst for the oxidation of CO. In such catalysts, octahedrally coordinated Co(3+) is considered to be the active site, while tetrahedrally coordinated Co(2+) is assumed to be basically inactive. In this study, a highly ordered mesoporous CoO has been prepared by H2 reduction of nanocast Co3O4 at low temperature (250 °C). The as-prepared CoO material, which has a rock-salt structure with a single Co(2+) octahedrally coordinated by lattice oxygen in Fm3̅m symmetry, exhibited unexpectedly high activity for CO oxidation. Careful investigation of the catalytic behavior of mesoporous CoO catalyst led to the conclusion that the oxidation of surface Co(2+) to Co(3+) causes the high activity. Other mesoporous spinels (CuCo2O4, CoCr2O4, and CoFe2O4) with different Co species substituted with non/low-active metal ions were also synthesized to investigate the catalytically active site of cobalt-based catalysts. The results show that not on...

Applied Catalysis A: General, 2005

In the present work we studied the influence of the initial concentration of the impregnating solution used for mounting Co(II) species on the g-alumina surface by equilibrium deposition filtration method (edf) on the physicochemical properties and the catalytic activity of the ''cobalt oxide''/g-alumina catalysts. The complete oxidation of benzene has been used as a model reaction.

Materials Research Bulletin, 2013

Proceedings of The 17th International Electronic Conference on Synthetic Organic Chemistry, 2013

Organic ligands are widely applied in preparation of metallic complexes, and in high temperatures, can be burned and eliminated from the coordination sphere, remaining only oxide group. In a reaction between cobalt nitrate, ammonium oxalate and F-127 as a surfactant to control the particles size, a cobalt-oxalate complex was formed. After performing Thermal Gravimetric Analysis (TGA) to find the optimum decomposition temperature, the precipitate was calcined and the resulted nano cobalt oxide was characterized by Fourier Transform Infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD). The crystalline pure and nanosized particles had the average size<40 nm. Oxalic acid, Nano cobalt oxide, Surfactant

Nanoparticles (NPs) of cobalt oxide and Fe/Ni-doped cobalt oxide has been prepared by the co-precipitation method. XPS analysis established the chemical nature of these NPs in terms of atomic as well as molecular formulations and EDAX analysis complemented the XPS results displaying the presence of Fe and Ni atoms in the cobalt oxide NPs revealing successful doping of Fe and Ni in cobalt oxide NPs. The impact of Fe and Ni-doping on the structure and physico-chemical properties of cobalt oxide NPs was also established by XPS analysis. The presence of metal-oxide bonds was further established by FTIR (Fourier transform infrared spectroscopy) and HRTEM (High resolution transmission electron microscopy) analysis confirmed the formation of NPs. Among bare and Fe/Ni-doped cobalt oxide NPs, Fe-doped cobalt oxide NPs showed maximum photocatalytic activity against methylene blue as well as Fe-doped cobalt oxide NPs also acted as an excellent catalyst for the sulfoxidation of sulphides with 9...

Mesoporous cobalt oxides were synthesized using an inverse surfactant micelle method. The prepared materials are mono-dispersed nanoparticle aggregates with connected, well defined intra-particle voids. Powder X-ray diffraction, N 2 sorption, scanning electron microscopy and transmission electron microscopy revealed that both pore and nanoparticle sizes are enlarged with thermal treatment temperatures. Nitrogen sorption experiments revealed that the pore diameters increased from 12.1 to 31.9 nm with the final heat treatment increase from 150 to 550 • C. The reduction of 4-nitrophenol has been chosen as a well-controlled model reaction allowing us to determine the catalytic activity as a function of crystallite size and pore diameter. A comparison of the various cobalt oxide catalysts is made in terms of Langmuir-Hinshelwood kinetics.

New J. Chem.

A series of cobalt ferrite samples were synthesized from a metal nitrate solution at constant pH between 9 and 12 by the controlled co-precipitation method without any surfactant.

Advances in Colloid and Interface Science, 2004

In the present review article, we present the efforts done so far for elucidating the mechanism of adsorption of the Co(II) species, mainly Co(H 2 O) 6 2 + , on the interfacial region developed between metal oxide particles, used as catalytic supports, and aqueous electrolytic solutions. Specifically, we present: (i) the principal modes of deposition of the transition metal ionic species (TMIS) on the surface of oxidic supports related with the various methodologies used for the preparation of the supported catalysts; (ii) the state of the art concerning the general aspects of the adsorption mechanisms of the TMIS on the aforementioned interfacial region; and (iii) the works reported so far dealing with the adsorption of the Co(II) species on the surface of g-Al 2 O 3 (g-alumina), a-Al 2 O 3 (a-alumina), TiO 2 (rutile), and SiO 2 (silica).

Biosciences, Biotechnology Research Asia

In this work, cobalt oxide nanoparticles supported on γ γ γ γ γ-alumina were prepared and were well characterized by scanning electron micrograph (SEM) and X-ray diffraction patterns. These were employed as catalysts for the oxidation of alcohols to aldehydes or ketones with tert-butylhydroperoxide (TBHP) and hydrogen peroxide (H 2 O 2) as the oxidant in the liquid phase. For these cobalt oxide nanoparticles supported on γ γ γ γ γ-alumina, acetonitrile as the solvent was employed. The research results showed that oxidant and the catalyst type influenced the conversion percent of alcohols oxidation. TBHP was found to be better oxidant than H 2 O 2 since higher conversion percent of alcohols were observed when TBHP was employed. The catalytic activity of 10%Co 3 O 4 /nano-γ γ γ γ γ-alumina was superior to that of 5% and 15% Co 3 O 4 /nano-γ γ γ γ γ-alumina catalysts. Under the optimum reaction conditions, the catalytic system of 10%Co 3 O 4 nanoparticles supported on γ γ γ γ γalumina gave about 82.3% conversion percent of cyclohexanol.

Catalysts

Co4−iZniMnAlOx mixed oxides (i = 0, 0.5 and 1) were prepared by coprecipitation, subsequently modified with potassium (2 or 4 wt.% K), and investigated for direct catalytic NO decomposition, one of the most attractive and challenging NOx abatement processes. The catalysts were characterised by atomic absorption spectroscopy, powder X-ray diffraction, Raman and infrared spectroscopy, temperature-programmed reduction by hydrogen, the temperature-programmed desorption of CO2 and NO, X-ray photoelectron spectroscopy, scanning electron microscopy, the work function, and N2 physisorption. The partial substitution of cobalt increased the specific surface area, decreased the pore sizes, influenced the surface composition, and obtained acid-base properties as a result of the higher availability of medium and strong basic sites. No visible changes in the morphology, crystallite size, and work function were observed upon the cobalt substitution. The conversion of NO increased after the Co subs...