Supported bimetallic catalysts using carbon

Bahome, M. C., Jewell, K., Padayachy, L. L., Padayachy, K., Hildebrandt, D., Glasser, D., Datye, A. K., and Coville, N. J. 2007. Fe-Ru small particle bimetallic catalysts supported on carbon nano tubes for use in Fischer-Tropsch synthesis. Applied Catalysis A General 328 243-51. 

Another useful bimetallic for fuel cell electrodes is Pt/Ru. Ruthenium is readily oxidized to Ru02 by calcination after it is impregnated. The PZC of ruthenium oxide is unknown. Propose a comprehensive sequence of experiments with which the SEA method can be applied for the synthesis of a Pt/Ru bimetallic catalyst supported on carbon. The goal is to have intimate contact between the Pt and Ru phases in the final, reduced catalyst. 

Acetylene is a reactive molecnle with a low C H stoichiometry that can be used to evaluate the resistance of metal-based catalysts to the formation of carbonaceous residue (coking). Pt is very reactive, and the chemisorption of on Pt(lll) is irreversible under UHV conditions, with complete conversion of into surface carbon during heating in TPD. Alloying with Sn strongly reduces the amount of carbon formed during heating [49]. This is consistent with observations of increased lifetimes for commercial, supported Pt-Sn bimetallic catalysts compared to Pt catalysts used for hydrocarbon conversion reactions. 

Results from these studies are important for the ongoing debates on the existence and utility of Sn/Pt alloy phases in bimetallic Pt-Sn supported catalysts. For example, our observation of dramatically decreased carbon buildup on the alloy surfaces from acetylene (a coke-precursor), and the enhanced yield of aromatics and alkenes from alkane dehydrogenation mimics important aspects of the chemistry of commercial Pt-Sn supported catalysts used for reforming. On the contrary, it seems unlikely that Sn/Pt alloy phases are solely responsible for the high selectivity observed in crotonaldehyde hydrogenation using Pt-Sn bimetallic catalysts. 

Sinfelt has greatly contributed to the catalyses of bimetallic nanoparticles [18]. His group has thoroughly studied inorganic oxide-supported bimetallic nanoparticles for catalyses and analyzed their microstructures by an EXAFS technique [19-22]. Nuzzo and co-workers have also studied the structural characterization of carbon-supported Pt/Ru bimetallic nanoparticles by using physical techniques, such as EXAFS, XANES, STEM, and EDX [23-25]. These supported bimetallic nanoparticles have already been used as effective catalysts for the hydrogenation of olefins and carbon-skeleton rearrangement of hydrocarbons. The alloy structure can be carefully examined to understand their catalytic properties. Catalysis of supported nanoparticles has been studied for many years and is practically important but is not considered further here. 

Zhong and co-workers [530] described recent results of an investigation of the electrocatal3dic oxidation of methanol using carbon-supported An and Au-Pt nanoparticle catalysts. The exploration of the bimetallic composition on carbon black support was aimed at modifying the catalytic properties for the methanol oxidation reaction at the anode in direct methanol fuel cells (DMFCs). An and Au-Pt nanoparticles of 2-3 nm sizes encapsulated in an organic monolayer were prepared, assembled on carbon black materials and treated thermally. The results have revealed that these Au-Pt nanoparticles catalysts are potentially viable candidates for use in fuel cells under a number of conditions [530],... 

As mentioned above, the addition of promoters, and even the formation of bimetallic particles, can provide carbon-supported iron catalysts with better performances in CO hydrogenation. The method of preparation of these systems is going to determine the final effect, always taking advantage of the relative inertness of the carbon surface. The interaction between the different components of the active phase can be maximized by using mixed-metal carbonyl complexes. Furthermore, use of these precursors allows for the preparation of catalysts with... 

Pd-Ag bimetallic catalysts supported on carbon xerogels have been used in the hydrodechlorination reaction of 1,2-dichloroethane [103,104], Pd and Ag were deposited by co-impregnation using a solution of palladium and silver nitrates. Metal particle size ranged from 2 to 5 nm in Pd catalysts but had a wider distribution (4 to 20 mn) in Ag catalysts. Bimetallic Pd-Ag catalysts showed small particle alloys of 3 to 4 nm. The bulk Ag content in this alloy was limited to about 50 wt%, which fixed the minimum Pd surface content of the alloy at about 10 wt%. Pd catalysts produced mainly ethane, whereas bimetallic Pd-Ag catalysts were selective for the production of ethylene. The ethylene selectivity increased with silver fraction at the alloy surface. 

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