Activity of metal oxides

Cargnello, M., et al., Multiwalled carbon nanotubes drive the activity of metal oxide core-shell catalysts in modular nanocomposites. Journal of the American Chemical Society, 2012. 134(28) p. 11760-11766. 

Haneda, M Kintaichi, Y Hamada, H. Enhanced activity of metal oxide-doped Ga203-AI2O3 for NO reduction by propene, Catal. Today, 1999, Volume 54, Issue 4, 391-400. 

Figure 3.13 Activity of metal oxide oxidants in the temperature range 300-450 °C.

The brief review emphasizes the useful catalytic activities of metal oxides, i.e., Ru02, towards 02-evolution but points to their limitations as a result of surface recombination with intermediate H-atoms. Possible routes to circumvent these difficulties could involve elimination of surface H-atom through the application of homogeneous H2-evolution catalysts (see Sect. 4.3), and compartmentalization of the oxidation catalyst from the H2-evolution catalyst, i.e., liposomes. Alternatively, reduction of other substrates rather than water i.e. C02, could lead to intermediate carbonous species being insensitive to oxidation by intermediate O-species. 

Catalytic Activity of Metal Oxides in the Extensive Oxidation of Hydrocarbons... 

Recent studies have indicated direct correlations between surface area and catalytic activity of metal oxide sensors (Li et al. 1999). Therefore, it is evident that incorporating catalytic particles by coating techniques may affect surface area and catalysis. Studies by Lee and Bhat (2003) have demonstrated that by incorporating small amounts of electrospun nanoflbers in spun-bond and melt-blown nonwovens, barrier properties such as flitration efficiency and air permeability can be improved. 

Molecular oxygen, if bonded to certain transition metal ions in solution or at oxide surfaces, can be more reactive than dissolved free oxygen. This property may contribute to the catalytic activity of metal oxide minerals in oxidation reactions. 

As FeOCl was not carbothermally reduced, it is suggested that FeOCl activates and transfers ojqrgen, just like CuCl. Interestingly, the application of FeOCl leads to the firrmation of surfiice oxygen complexes, whereas catalytic soot oxidation by Fe203 does not [19]. This is another indication that chlorine diemically affects the catalytic soot oxidation activity of metal oxides and that the previous scheme also holds for FeOCl. 

G. Parravano University of Notre Dame) In comparing catalytic activity of metal oxides for the hydrogen-deuterium exchange reaction (Lecture 9), a difficulty arises in trying to obtain a similar redox state for different oxide surfaces. Thus, it is well known that ZnO can be quite inactive in the range 200-300° or active down to —70° ) depending on pretreatment and the same pretreatment may not yield the same redox state with different oxides. 

Various attempts have been made to relate the activity of metal oxides for catalytic oxidation with various thermodynamic properties that would seem to be important, knowing that in a continuous system oxygen must adsorb from the gas... 

Therefore, the results considered above have shown that the catalytic activity of metal oxides nanoparticles is defined by their relative electronegativeness. The higher this parameter is the smaller metal solubility in methylbenzoate is. This results to the increase of the energetic barrier of methylbenzoate and heptanol-1 molecules repulsion, that decreases steric factor and results to raising the fractal dimension of heptylbenzoate molecule. The last factor decelerates sharply the transesterification reaction. 

Naphadzokova, L. Kh. Kozlov, G. V Shustov, G. B. Catalytic activity of metal oxides in transesterification reaction of methylbenzoate by heptanol-1. Catalysis in Industry, 2007, (5), 61-63. 

The catalytic activity of metal oxide composites depends both on the acidity and basicity of the surface that can be characterized by the level of ammonia sorption and The catalyst should adsorb 100-200 pmol/g NH3 and its pAT, should be in the range 15-17.5 [31]. Catalysts having low basicity and acidity of the snrface have too low activities, but a lot of undesired by-products (dioxane and PEGs) are formed when their acidities are too high. The activity of Al-Mg composite oxide catalyst increases with an increase in the calcination temperature and reaches a maximum of approximately 700°C [22]. Further increase in the calcination temperature results in reduced activities, attributed to the sintering of the catalyst surface. The catalyst activity increases with inaeasing aluminum content, but less narrow distributed products are formed. Filtration of the catalyst is not always possible. Therefore, addition of water (180 g of water/1063 g of oxyethylation product) and the use of activated clay or diatomaceous earth as a filter aid are proposed [33]. 

TABLE 11.1 List of oxides that are active photocatalysts for overall water splitting under UV irradiation (>3.0eV) and factors for activation of metal oxide photocatalysts"... 

Figure 5.12. The catalytic activity of metal oxides along the first row of the periodic table. Adapted from D.A. Dowden...

Pd-based catalysts containing Ce, Ni, Mn, or Co oxides. Results showed an excellent activity for the electro-oxidation of different alcohols whose oxidation started close to —0.6 V vs. Hg/HgO. The Pd-NiO/C catalyst gave the highest catalytic activity and the lowest rate of poisoning by intermediates. These same authors also compared the activity of metal oxides supported on Pt and Pd in alkaline medium, and the activity was higher in the case of oxides-Pd/C. 

Besides treatment with SbFs, treatment with NH4F, FSO3H, SbCls, and FSO3H —SbFs enhanced the activities of metal oxides for acid-catalyzed reactions. The FSO3H — SbFs-treated catalyst catalyzed the reaction of butane, although the ac-... 

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