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Abstract  

The surface properties of supported gallium oxide catalysts prepared by impregnation of various supports (γ-Al2O3, SiO2, TiO2, ZrO2) were investigated by adsorption microcalorimetry, using ammonia and water as probe molecules. In the case of acidic supports (γ-Al2O3, ZrO2, TiO2), the acidic character of supported gallium catalysts always decreased in comparison with gallium-free supports; on very weakly acidic SiO2, new acidic centers were created when depositing Ga2O3. The addition of gallium oxide decreased the hydrophilic properties of alumina, titania and zirconia, but increased the amount of water adsorbed on silica. The catalytic performances in the selective catalytic reduction of NO by C2H4 in excess oxygenwere in the order Ga/Al2O3>Ga/TiO2>Ga/ZrO2>>Ga/SiO2. This order is more related to the quality of the dispersion of Ga2O3 on the support than to the global acidity of the solids.

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-cleaning applications using semiconducting powders or thin films have become a subject of increasing interest especially in the last 20 years. Among semiconductor oxides, TiO 2 is one of the most widely used materials for self-cleaning application [ 4 – 9

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Kinetic studies on the effect of metal oxide catalysts, (25% w/w) such as Cr2O3, CuO, MnO2, Al2O3 and TiO2, on the thermal decomposition of KBrO3 have been carried out. The kinetic parameters of the catalysed and uncatalysed decompositions were calculated by the Freeman-Carroll, Coats-Redfern and Horowitz-Metzger methods. It has been found that Al2O3 is almost as good a catalyst as any other oxide used unlike in the thermal decomposition of KClO3. In the case of TiO2 there was an increase in the activation energy of decomposition. Of the other oxides Cr2O3 underwent reaction and was converted to dichromate and so the parameters of the reaction were not calculated. The effect of varying amounts of Al2O3 on the thermal decomposition was also studied.

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Abstract  

Standard entropies of adsorption (Δs 0) of CO on different materials (Cu catalysts, Au catalysts, ZnO and to TiO2) are obtained from static adsorption microcalorimetry, adsorption isobars and temperature-programmed desorption, based on the thermodynamics of adsorption on energetically heterogeneous surfaces. Vibrational entropies of the surfaces s vib α are normally between the rotational and the standard translational entropy of CO in gas phase, and decrease with increasing adsorption energy, which agrees with the explanation of statistical thermodynamics. Δs 0 reflects both the mobility of adsorbates and the specific adsorbate-adsorbent interaction. Limits for reasonable values of the entropy of adsorption are proposed.

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Abstract  

Samples with various amounts of tin oxide were prepared by impregnating γ-Al2O3, TiO2(anatase), SiO2, ZrO2 and MgO with tin tetrachloride or tributyltin acetate solutions. After drying and calcination, the samples were characterized by chemical analysis, XRD and BET measurements. Ammonia adsorption microcalorimetry was used in order to determine the number, strength and strength distribution of surface acid sites. The influence of the adsorption temperature, evacuation temperature, amount of SnO2 deposited and of the nature of the support on the adsorption properties were studied.

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Journal of Thermal Analysis and Calorimetry
Authors:
L. Chmielarz
,
M. Zbroja
,
P. Kuśtrowski
,
B. Dudek
,
A. Rafalska-Łasocha
, and
R. Dziembaj

Abstract  

Alumina, zirconia and titania pillared montmorillonites additionally modified with silver were tested as catalysts of NO reduction with NH3 or C2H4. Ammonia was much more effective reducer of NO than ethylene. The silver containing TiO2-pillared clay has been found to be the most active catalyst for NO reduction both with NH3 or C2H4. Oxidation of the reducing agents by oxygen limited the NO conversion in the high temperature region. The ammonia and nitric oxide adsorption sites were studied by the temperature programmed desorption methods (TPD).

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Abstract  

DTA, TG, XRD and IR methods were used to study the formation of solid solutions in the selected subsolidus range of the PbZrO3-K0.5Bi0.5TiO3 system by heating mixtures prepared using oxide substrates, i.e. PbO, Bi2O3, ZrO2, TiO2 and K2CO3. It was found that solid solutions are formed in the reaction of PbO and ZrO2 with intermediate compound, i.e. K0.5Bi0.5TiO3. PbZrO3 was not found to be formed as an intermediate phase.

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Abstract  

The potential uses of hydrous oxides in the treatment of radioactive wastes may be affected by the physical-chemical properties of these materials. The sorption behavior of trace level (less than 10-14 g/ml) 235U fission products in aqueous solutions was studied under static conditions on TiO2, MnO2 and SnO sorbents. A variety of anions, cations and neutral species of 132Te,95Zr, 99Mo and 103Ru in aqueous solutions at 1, 3, 5, 7 and 10 pH values were identified and their retention values were calculated. High voltage electrophoresis was used to establish the chemical species of these radioisotopes formed in the solution.

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Abstract  

A multistage process combining photocatalytic degradation of organic complexes and complexants followed by separation of the radionuclides by ion exchange was developed and tested for the treatment of aqueous waste from chemical or electrochemical decontamination of NPP primary circuit internals. In these solutions, both the oxalic and citric acids could be quantitatively degraded within 10-12 hours of irradiation by 254 nm UV radiation in the presence of TiO2 photocatalyst. For the group radionuclides separation, a standard cation exchanger was found to be preferable to any of the set of the tested inorganic-organic composite absorbers.

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Abstract  

Neutron capture γ-ray spectrometry has been applied for the simultaneous determination of Co, Mo, Ni, W and moisture in hydrodesulfurization catalysts. The Co, Mo and water content are determined in a 10 min irradiation using a 500–2500 keV calibration. Ni and W, if present, require, and additional 30 min irradiation, using a 5000–9000 keV calibration. In both cases TiO2 is used as internal standard. Results are in good agreement with those obtained by NAA for metals and by TGA for moisture.

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