Size- and support-dependency in the catalysis of gold

Bulk gold is chemically inert and is generally regarded as a poor catalyst. However, when gold is in very small particles with diameters below 10 nm and is deposited on metal oxides or activated carbon, it becomes surprisingly active, especially at low temperatures, for many reactions such as CO oxidation and propylene epoxidation. The catalytic performance of Au is defined by three major factors: contact structure, support selection, and particle size. The role of the perimeter interfaces of Au particles as the sites for reactions is discussed as well as the change in chemical reactivity of Au clusters composed of fewer than 300 atoms.

When Gold Is Not Noble: Catalysis by Nanoparticles

Despite occasional references in the older literature to the ability of gold to catalyze certain reactions, the metal has until recently had the reputation of being one of the least catalytically useful. The recent discovery that some supported gold catalysts can affect the oxidation of carbon monoxide at or below ambient temperature has, however, focused attention on the metal's ability in this respect. For oxidation of carbon monoxide at low temperature, catalysts comprising small (<5 nm) gold particles supported preferably on an oxide of the first transition series (e.g., TiO2, α-Fe2O3) are needed. Deposition–precipitation and coprecipitation are better methods than impregnation for this purpose and provide the desired intimacy of contact between metal and support. High activity may well originate at sites at the gold–support interface, with the support making a vital contribution. Stable activity can result by optimizing aging in solution during the preparation, and low calcination temperatures are ge...

Catalysis By Gold

Gold can be deposited as nanoparticles on a variety of support materials by coprecipitation or deposition-precipitation of Au(OH)3, grafting of organo-gold complexes such as dimethyl-Au(III)-acetylacetonate, mixing of colloidal Au particles, and vacuum deposition. Owing to the moderate adsorption of at least one of reactants (for example, CO) on the edges and corners of Au nanoparticles and to the activation of the counter reactant (for example, O2) at the perimeter interface with the supports, supported Au nanoparticle catalysts exhibit unique and practically useful catalytic properties at relatively low temperature below 473K. They have already been commercially used for deodorizers in rest rooms in Japan and will find growing applications in indoor air quality control, pollutant emission control, production of hydrogen energy carrier, and innovations in chemical processes. Cluster science of Au may also open an exciting area of research showing some magic numbers for dramatic changes in reactivity.

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Gold as a novel catalyst in the 21st century: Preparation, working mechanism and applications

Application of ZrO2 as a catalyst and a catalyst support

Methanol synthesis reaction over copper-group IV metal amorphous alloys as catalyst precursor

An amorphous Au25Zr75 alloy showed a high catalytic activity for hydrogenation of carbon monoxide. Thus, the rate of methanation was 2.3 μmol s−1 g−1 under 6.0 MPa at 523 K, being much higher than that over Au/ZrO2 or ZrO2. It was found that the alloy was oxidized into metallic gold and ZrO2 under the reaction conditions.

Co hydrogenation over an amorphous gold-zirconium alloy

Production of higher alcohols from synthesis gas over nickel containing catalysts

Reaction path study of styrene-α-olefin codimerization catalyzed by σ-Arylnickel(II) halide-boron trifluoride etherate

The codimerization of styrene with ethylene was studied using the catalyst system composed of bis(triphenylphosphine)σ-aryl(bromo)nickel(II) and trifluoroboron etherate in methylene dichloride. The codimerization takes place readily at 0 °C under atmospheric pressure to give 3-phenyl-1-butene selectively. The reaction scheme was discussed on the basis of the product distribution during the course of reaction and its kinetics.

Noboru Kawata

Papers

Methanol synthesis reaction over copper-group IV metal amorphous alloys as catalyst precursor

Co hydrogenation over an amorphous gold-zirconium alloy

Production of higher alcohols from synthesis gas over nickel containing catalysts

Reaction path study of styrene-α-olefin codimerization catalyzed by σ-Arylnickel(II) halide-boron trifluoride etherate

Codimerization of Ethylene and Styrene Catalyzed by Bis(triphenylphosphine)σ-aryl Nickel(II) Halide- Trifluoroboron Etherate