Supported gold-containing bimetallic

Methods for preparing colloidal gold and also bimetallic colloids containing gold have been described in Section 3.2.3. The gold particles may be immobilised on supports by dipping the supports in the colloidal suspension,... 

Preparation of Supported Bimetallic Catalysts Containing Gold... 

Bimetallic molecular cluster compounds containing gold will adsorb intact on supports, and the ligands may then be removed by heating, but only a few such compounds are available. Simple carbonyl complexes do not exist,... 

Methods for preparing bimetallic colloids containing gold have been described in Section 3.2.3. Their composition may be easily tuned since solutions of the mixed chloride precursors are normally used, and are reduced in a variety of ways after addition of a stabiliser. As already mentioned in Section 4.3.6, for gas-phase catalytic reactions, after depositing the colloid on an oxide support the stabilisers must be removed, but for liquid-phase reactions they may be retained providing access to the metal is still possible. 

An infrared study of CO adsorption on Ru-Au supported on magnesia suggested that this bimetallic behaves differently from Ru-Cu, with no evidence of Au segregation at the cluster surface, (nor separate Au clusters although ruthenium and gold are practically immiscible in the bulk). At temperatures below 383 K where the reaction between cyclopropane and hydrogen adopted routes to propane or methane + ethane, no interaction between Au and Ru containing up to 36% Au was evident from the kinetic parameters.However, a more complete examination (unpublished) of these catalysts by XPS, EXAFS, SAXS, and other techniques has been made and it is believed that the surface contained Ru atoms only. 

Also, Marsh and co-workers [145] showed that gold on cobalt oxide particles, supported on a mechanical mixture of zirconia-stabilised ceria, zirconia and titania remains active in a gas stream containing 15 ppm SO2. Haruta and co-workers [207] found that although the low-temperature CO oxidation activity of Ti02-supported Au can be inhibited by exposure to SO2, the effect on the activity for the oxidation of H2 or propane is quite small. Venezia and co-workers [208] reported that bimetallic Pd-Au catalysts supported on silica/alumina are resistant to sulphur poisoning (up to 113 ppm S in the form of dibenzothiophene) in the simultaneous hydrogenation of toluene and naphthalene at 523 K. 

Such a reaction of Fe(CO)5 (at 293-363 K, PVP) without ultrasonic radiation proceeds very slowly and only after few days there, a material is formed with very low Fe content (2%, the isolated particles 2-5 nm in size). It is of interest that the sonochemical decomposition of Fe(CO)5 does not proceed in the presence of PVP if THF is used as the solvent, but the reaction is very effective when anisole is used as the solvent and PFO is used as the polymer matrix [93]. A black product formed contains up to 10% (in mass) of the spheric particles of nonoxidized Fe (mainly y-Fe, with little content of a-Fe) with 1-12 nm in size (the mean diameter is 3nm, as shown in Figure 3.7). It is likely that the big particles present the flocks of little ones ( 2-2.5nm). The sonochemical synthesis allows us to produce the functionalized amorphous nanoparticles of ferric oxide with 5-16 nm in diameter [94]. The ultrasonic irradiation in the PFO presence allows us to also produce the stabilized nanoparticles of copper, gold, and so on. In the literature the findings are not about the bimetallic particle formation in the ultrasonic fields by carbonyl metal reduction in the polymer matrices presence (as, for example, in the case of the carbon-supported Pt-Ru from PtRu5C(CO)i6 reduced clusters [95]). 

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