Dehydrogenation of Ethylbenzene with Nitrous Oxide in the Presence of Mesoporous Silica Materials Modified with Transition Metal Oxides

2005 ◽  
Vol 109 (2) ◽  
pp. 330-336 ◽  
Author(s):  
Piotr Kuśtrowski ◽  
Lucjan Chmielarz ◽  
Roman Dziembaj ◽  
Pegie Cool ◽  
Etienne F. Vansant
Keyword(s):  
Nitrous Oxide ◽  
Transition Metal ◽  
Mesoporous Silica ◽  
Metal Oxides ◽  
Transition Metal Oxides ◽  
Silica Materials ◽  
Mesoporous Silica Materials ◽  
Dehydrogenation Of Ethylbenzene

The carbon monoxide/nitrous oxide reaction. Kinetics of catalysis on TiO2 (anatase) and ZnO and activity correlations for the first-row transition metal oxides

1979 ◽  
Vol 57 (3) ◽  
pp. 320-325 ◽  
Author(s):  
Bordan Walter Krupay ◽  
Robert Anderson Ross
Keyword(s):  
Carbon Monoxide ◽  
Nitrous Oxide ◽  
Transition Metal ◽  
Metal Oxides ◽  
Transition Metal Oxides ◽  
Flow Reactor ◽  
Activation Energies ◽  
Tio2 Anatase ◽  
Carbonate Formation ◽  
Experimental Activation Energy

The catalytic reaction between carbon monoxide and nitrous oxide on titanium dioxide (anatase) and zinc oxide has been examined in a continuous flow reactor at atmospheric pressure. The experimental activation energy was 144 ± 4 kJ mol−1 from 723 to 793 K on TiO2 and 121 ± 4 kJ mol−1 from 543 to 653 K on ZnO. Analyses of kinetic results indicated that a transient carbonate-like species may be involved in catalysis on both oxides. Relationships between the experimental activation energies for the CO/N2O reaction on first-row transition metal oxides and (i) activation energies for isotopic oxygen exchange, (ii) heats of carbonate formation, and (iii) the charge/radius ratio of the cation are interpreted in terms of the influence on catalysis of the cohesive properties of the metal/oxygen bonds in the oxide surfaces.

Oxidation of 1-butene by nitrous oxide over manganese(III) and related transition metal oxides

1984 ◽  
Vol 62 (8) ◽  
pp. 1483-1486 ◽  
Author(s):  
Robert A. Ross ◽  
Craig Fairbridge
Keyword(s):  
Nitrous Oxide ◽  
Transition Metal ◽  
Metal Oxides ◽  
Transition Metal Oxides ◽  
Continuous Flow ◽  
Flow System ◽  
Reaction Rates ◽  
Radical Reactions ◽  
Exponential Relationship ◽  
Activity Series

The oxidation of 1-butene by nitrous oxide over manganese(III) oxide was studied in a continuous flow system from 573 to 673 K. Kinetic parameters were derived from the exponential relationship:[Formula: see text] over reactant partial pressure ranges, [Formula: see text] and [Formula: see text]. The reaction mechanism proposed involves a complex sequence of steps which include surface radical reactions. On the basis of a comparison of specific reaction rates, the catalytic activity series for the reaction over a number of transition metal oxides was: CuO > Fe2O3 > NiO > Mn2O3 > Cr2O3 > TiO2 > Sc2O3 > SnO > ZnO > V2O5 > AlO3.

HREM Study of electron-induced surface radiation damage in ReO3

1991 ◽  
Vol 49 ◽  
pp. 636-637
Author(s):  
R. Ai ◽  
H.-J. Fan ◽  
L. D. Marks
Keyword(s):  
Transition Metal ◽  
Metal Ions ◽  
Metal Oxides ◽  
Electron Irradiation ◽  
Transition Metal Oxides ◽  
Carbon Film ◽  
Transition Metal Ions ◽  
Surface Radiation ◽  
Valence Transition ◽  
Electron Microscopes

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.

Problems with oxygen analysis in the system MgO-Al2O3-SiO2 with the electron microprobe

1992 ◽  
Vol 50 (2) ◽  
pp. 1624-1625
Author(s):  
Michel Fialin ◽  
Guy Rémond
Keyword(s):  
Transition Metal ◽  
Metal Oxides ◽  
Transition Metal Oxides ◽  
Electrostatic Charge ◽  
Carbon Layer ◽  
Sample Holder ◽  
Rock Matrix ◽  
Electrical Discharges ◽  
Thin Carbon ◽  
Beam Instabilities

Oxygen-bearing minerals are generally strong insulators (e.g. silicates), or if not (e.g. transition metal oxides), they are included within a rock matrix which electrically isolates them from the sample holder contacts. In this respect, a thin carbon layer (150 Å in our laboratory) is evaporated on the sections in order to restore the conductivity. For silicates, overestimated oxygen concentrations are usually noted when transition metal oxides are used as standards. These trends corroborate the results of Bastin and Heijligers on MgO, Al2O3 and SiO2. According to our experiments, these errors are independent of the accelerating voltage used (fig.l).Owing to the low density of preexisting defects within the Al2O3 single-crystal, no significant charge buildup occurs under irradiation at low accelerating voltage (< 10keV). As a consequence, neither beam instabilities, due to electrical discharges within the excited volume, nor losses of energy for beam electrons before striking the sample, due to the presence of the electrostatic charge-induced potential, are noted : measurements from both coated and uncoated samples give comparable results which demonstrates that the carbon coating is not the cause of the observed errors.

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