Activation of Au

Because of the fact that the NO conversion on AljO, increases faster than linearly with sample weight, the contribution of AI2O3 to the observed activity of AU/AI2O3 increases when a larger amount of catalyst is used, and at higher temperatures. When 0.1 g of catalyst is used, the data in Tables 2 and 3 show that A1,0, does not contribute much to the observed NO reduction... 

Figure2.2 Products arisingfromC-H bond activation of Au(N)Cl3 adducts (N = mono-ligated 6-substituted 2,2 -bipyridine).

The curves representing the relationship between temperature and OAg/oAu (ttAg, activity of Ag component in native gold or electrum oau, activity of Au component in native gold or electrum) are shown in Fig. 1.190. It is assumed that aK+/ H+ is controlled... 

The Au/Ti02 catalyst shows activity for photocatalytic dehydrogenation of 2-propanol at 298 K. The activity of Au/Ti02 is attributed to its unique capability for producing photogenerated electrons evidenced by the featureless IR adsorption during UV-irradiation. 

Catalytic activities of Au core/Pd shell bimetallic nanoparticles have also been investigated [43,44], Okitsu et al. reported that catalytic activities are closely related to the nanostructure of bimetallic nanoparticles [44], where Au core/Pd shell bimetallic nanoparticles on and inside Si02 are prepared by consecutive sonochemical and sol-gel processes. 

T., and Haruta, M. (1995) Photoassisted hydrogen production from a water-efhanol solution a comparison of activities of Au-TiOj and Pt-Ti02. Journal of Photochemistry and Photobiology A Chemistry, 89 (2), 177-189. 

Tabakova, T., Idakiev, V., Andreeva, D., and Mitov, I. 2000. Influence of the microscopic properties of the support on the catalytic activity of Au/ZnO, Au/Zr02, Au/ Fe203, Au/Fe203-Zn0, Au/Fe203-Zr02 catalysts for the WGS reaction. Appl. Catal. A Gen. 202 91-97. 

The authors ascribed the high activity of Au/thoria to a Schottky junction effect between the metal and oxide leading to an enhancement of active OH groups associated with oxygen deficiencies. The authors did observe formation of formate, carbonate, and bicarbonate species, but are still elucidating which, if any, of the species are important for the mechanism. 

The presence of HzO provokes a significant decrease in the activity of Au/a-Fe203 and CuxCc, x02 y catalysts. In fact, for both of these samples, a given CO conversion (obtained in the absence of HzO) is achieved at about 40 to 45°C higher reaction temperature in the presence of H20 in the feed. A slightly lower inhibition of the activity is observed for the Oz conversion in both... 

S. Carrettin, P. Concepcion, A. Corma, J. Lopez-Nieto, and V. F. Puntes, Gold catalysts Nanocrystalline Ce02 increases the activity of Au for CO oxidation by two orders of magnitude, Angew. Chem. Int. Ed. 43(19), 2538-2540 (2004). 

YD. Kim, M. Fischer, and G. Gantefor, Origin of unusual catalytic activities of Au-based catalysts, Chem. Phys. Lett, ill, 170-176 (2003). 

Figure 10. Photocatalytic activity of Au/titania nanocomposites containing 0 to 5 % Au in phenol-oxidation and chromium-reduction reactions [57].

In 2005, Rossi and coworkers investigated the effect of the carbon support on the activity of Au/C catalysts in the oxidation of glucose under atmospheric pressure of oxygen at 323 K and a pH of 9.5 [121]. Au nanoparticles (in a range of 1-6 nm) dispersed on carbon XC72R (specific area 254 m g pore volume 0.19 mL g ) were more active than Au nanoparticles dispersed on carbon X40S (specific area 1,100 m g pore volume 0.37 mL g ). However, if the nature of the carbon support played a role on the catalyst activity, authors pointed out that the major role was played by the size of the Au nanoparticles, the smaller particles being the most active. 

Table 2 shows the activity of Au/Ti0x-Si02 and Au/Ti02-Si02 for propylene partial oxidation at 200 °C under transient condition. 

In situ infrared study of catalytic CO oxidation over Au/Ti02 shows that the catalyst prepared from AuCls exhibits higher activity than those prepared from HAuC. The high activity of Au appears to be related to the presence of reduced and oxidized Au sites as well as carbonate/carboxylate intermediates during CO oxidation. Addition of H2O2 further promotes the oxidation reaction on Au/Ti02 catalysts. 

The reaction pathway, reactivity of the active sites, and the nature of adsorbed intermediates constitute the catalytic reaction mechanism. Our study has been focused on the investigation of the nature of adsorbed intermediates under reaction conditions. We report the results of in situ infrared study of CO and ethanol oxidation on Au/Ti02 catalysts. This study revealed the high activity of Au/Ti02 is related to the presence of reduced Au and oxidized Au sites which may promote the formation of carbonate/carboxylate intermediates during CO oxidation. 

However, selectivity continued to be a problem in the process due to the hard conditions required by the method. Thus, in parallel research, Haruta et al. [253] and Ishihara and coworkers [254] achieved the reaction at only 10 °C. These studies compared the activity of Au/Si02 and Au-Pd/Si02 catalysts and the authors concluded that the enhancement observed when Pd was added to Au was directly related to the activation of hydrogen. However, excess Pd also induced rapid decomposition of H202. 

Subsequent studies focused on Au/Ce02 catalysts [267]. One study showed that the addition of C ions increased the catalytic activity of Au/Ce02 by removing most of the gold from the catalyst, and it was proposed that the resulting cationic gold was the... 

Reproducibility of elution activity of Au-195m. A 2.5 x 1.3 cm heavily shielded Nal (Tl) detector with a 1 cm opening in the collimator was placed 20 cm from the outlet of the generator. This outlet was connected to the intravenous tubing inserted into an antecubital vein of the patient. The detector was connected to a spectrometer set at 260 keV with a 10% window. Three-second measurements were performed immediately after elution in groups of 6 elutions repeated every 3 min in each patient. 

Reproducibility of elution activity of Au-195m. The reproducibility of the eluted Au-195m activity was evaluated from 81 sequential measurements obtained on-line from the intravenous tubing utilized for patient injections. The... 

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