Gold alloy catalysts

Anderson that at this level the mechanistic details are a matter of opinion (7). There is, however, a difference as far as the number of surface atoms participating in the reaction is concerned. Mechanism A requires more than one Mechanism C, however, requires only one metal atom. Van Schaik et al. 89) reported skeletal isomerization according to Mechanism A over platinum-rich platinum-gold alloys, whereas over gold-rich catalysts, isolated platinum atoms could promote Mechanism C only. Garin and Gault (82) assumed the formation of a C4 cyclic intermediate with the insertion of a platinum atom as the fourth member of the ring. This concept of Mechanism B would also involve one metal atom. 

Mkaline Fuel Cell The electrolyte for NASA s space shnttle orbiter fuel cell is 35 percent potassinm hydroxide. The cell operates between 353 and 363 K (176 and I94°F) at 0.4 MPa (59 psia) on hydrogen and oxygen. The electrodes contain platinnm-palladinm and platinum-gold alloy powder catalysts bonded with polytetraflnoro-ethylene (PTFE) latex and snpported on gold-plated nickel screens for cnrrent collection and gas distribution. A variety of materials, inclnding asbestos and potassinm titanate, are used to form a micro-porous separator that retains the electrolyte between the electrodes. The cell structural materials, bipolar plates, and external housing are nsnally nickel-plated to resist corrosion. The complete orbiter fuel cell power plant is shown in Fig. 24-48. 

P. V. Geenen, H. J. Boss, G. T. Pott, A study of the vapor phase epoxidation of propylene and ethylene on silver and silver-gold alloy catalysts, J. Catal. T7 (1982) 499. 

N. Tories, X. E. Verikios, The oxidation of ethylene over silver-based alloy catalysts Silver-gold alloys, J. Catal. 123 (1987) 161. 

The aim of this contribution is to present data on the preparation of catalysts containing as embedding species a large family of eolloids such as colloids of ruthenium, platinum, or palladium-gold alloys and triflate derivatives such as lanthanum and silver triflate or tert-butyldimethylsilyltrifluoromethanesulfonate (BMSTM). Silica, zirconia and tantalum oxides were used as carrier. All these preparations considered the polymeric sol-gel route using as starting materials silicon, zirconium or tantalum alcoxides. 

The commercial route to vinyl acetate is a gas-phase process, utilizing palladium or a palladium-gold alloy supported on alumina or a spinel. The catalyst also carries potassium acetate, and sometimes other metal acetates, to provide a supported liquid phase (KOAc-HOAc) in which the reaction takes place. The role of palladium may be described by the reaction scheme... 

Gold and gold alloys (with Ag, Ir, Pt) and cationic gold (I) phosphines act as selective catalysts in hydrogenation, oxidation, and reduction reactions [ 1.264— 266]. Nanometer-sized Au particles ( 5 nm) in the presence of ceria or a transition-metal oxide have superior catalytic activities [1.267-269,269]. 

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