The catalytic properties of zeolite X containing transition metal ions Part 2?Methane oxidation

1972 ◽  
Vol 27 (2) ◽  
pp. 287-292 ◽  
Author(s):  
R RUDHAM
1982 ◽  
Vol 35 (7) ◽  
pp. 1335 ◽  
Author(s):  
M Chatterjee ◽  
D Ganguli

The exchange behaviour of some divalent transition metal ions M2+ (Zn2+, Cu2+, Ni2+, Co2+, Mn2+) in a zeolite NaX (SiO2/Al2O3 2.75) was studied at intermediate stages before equilibrium. The equivalent counter ion supply in the solution, given by the equivalent ratio of the two counter ions 2M2+/Na+, was found to be critical in determining the saturation level of exchange. The series of relative abilities of exchange was very similar to the well known selectivity series at equilibrium. It is suggested that water exchange of the metal ions in solution could be one of the factors controlling the relative ease of ion exchange.


2021 ◽  
Author(s):  
Anees AHMAD Ansari ◽  
Manawwer Alam

Abstract Chemically synthesized cobalt-doped cerium oxide nanoparticles(CeO2:Co;NPs) were successfully prepared by complexed based co-precipitation process. The structural, morphological, chemical composition, optical properties, and electro-catalytic properties were determined by X-ray diffraction pattern(XRD), transmission electron microscopy(TEM), energy dispersive x-ray analysis (EDX), UV/Visible absorption spectroscopy, and cyclic voltammetry techniques. Owing to the wide-spread applications of CeO2 NPs in various fields of applied material sciences, transition metal ions doped CeO2:Co NPs exhibited excellent electro-catalytic properties. Outstanding physiochemical properties of CeO2 such as reversible oxidation states, high ionic mobility, large oxygen storage ability, effective large specific surface area, and the excellent current response observed in the electrocatalytic oxidation of hydrazine. The presence of transition metal ions (cobalt) improves the oxidation potential of hydrazine. Cyclic voltammetry was analog with the electrochemical impedance spectroscopy results, which revealed the enhanced with rapid sensing response against hydrazine. The electro-catalytic results of the CeO2:Co NPs electrode exhibited excellent voltammetry and impedance spectroscopy performance towards the hydrazine oxidation. The fabricated chemical sensor shows a wide linear detection range from 7.18 to 1000 µM, a low detection limit 7.2 µM, and sensitivity of 2.42 µAmLµM-1cm-2. The fabricated sensing electrode demonstrated long-term steadiness resulting it shows high sensitivity, selectivity, repeatability/reproducibility, and rapid detection of hydrazine.


Author(s):  
R. Ai ◽  
H.-J. Fan ◽  
L. D. Marks

It has been known for a long time that electron irradiation induces damage in maximal valence transition metal oxides such as TiO2, V2O5, and WO3, of which transition metal ions have an empty d-shell. This type of damage is excited by electronic transition and can be explained by the Knoteck-Feibelman mechanism (K-F mechanism). Although the K-F mechanism predicts that no damage should occur in transition metal oxides of which the transition metal ions have a partially filled d-shell, namely submaximal valence transition metal oxides, our recent study on ReO3 shows that submaximal valence transition metal oxides undergo damage during electron irradiation.ReO3 has a nearly cubic structure and contains a single unit in its cell: a = 3.73 Å, and α = 89°34'. TEM specimens were prepared by depositing dry powders onto a holey carbon film supported on a copper grid. Specimens were examined in Hitachi H-9000 and UHV H-9000 electron microscopes both operated at 300 keV accelerating voltage. The electron beam flux was maintained at about 10 A/cm2 during the observation.


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