Supported metals support effect

Volume 11 Metal-Support and Metal-Additive Effects in Catalysis. Proceedingsof an International Symposium, Ecully (Lyon), September 14-16,1982 edited by B. Imelik,C. Naccache, G. Coudurier, H. Praliaud, P. Meriaudeau,... 

In all these cases the support has a dramatic effect on the activity and selectivity of the active phase. In classical terminology all these are Schwab effects of the second kind where an oxide affects the properties of a metal. Schwab effects of the first kind , where a metal affects the catalytic properties of a catalytic oxide, are less common although in the case of the Au/Sn02 oxidation catalysts9,10 it appears that most of the catalytic action takes place at the metal-oxide-gas three phase boundaries. 

Volume 11 Metal-Support and Metal-Additive Effects in Catalysis. Proceedings of an... 

Imellk, B. et al., eds. "Metal-Support and Metal Additive Effects In Catalysis" Elsevier Amsterdam, 1982, and references cited therein. 

Chemisorption on nonmetallic catedysts should provide the number of catal3rtic sites and for comparative purposes a single Mg can be taken as a catalytic site on metals. This permits the calculation of turnover frequencies which was a new concept in post ICC 1 and which permitted intercomparison of catalyst activities. For the first time then, one has been able, for example, quantitatively to discuss support effects in Rh/support catalysts. 

From the previous results, it has been proven that the nature of the support, although it has no significant influence on the Pd electronic properties, modifies the catalytic properties of the solids To permit a better understanding of these supports effects, the surface properties of the supports (in the presence of the metal) have been studied, in particular the acidic properties and the oxygen mobilities. The A1203 and Z1O2 supports have been mainly onsidered. 

Except Ru (not usable in TWC because of the volatility of its oxide [68]), the most active metal is the rhodium. This has been largely confirmed by further studies so that Rh may be considered as a key-component of TWC for NO reduction [69,70], As far as Pd is concerned, it seems that the active site is composed of Pd"+ —Pd° pairs, which may explain the higher activity of Pd in N0+C0+02 mixture (T5( 200°C) [71]. A detailed kinetic study by Pande and Bell on Rh catalysts has evidenced a significant support effect [72], The kinetic data were represented by a conventional power law expression ... 

Dhainaut, F., Pietrzyk, S. and Granger, P. (2007) Kinetics of the NO + H2 reaction over supported noble metal based catalysts Support effect on their adsorption properties, Appl. Catal. B 70, 100. 

Raney Type and Supported Group VIII Metal Catalysts. Effect of Metal on Selectivity... 

Because the size regime of n=l-6 atoms is of great practical significance to the spectroscopic, chemical and catalytic properties of supported metal clusters in both weakly and strongly interacting environments (28), it is important to study very small metal clusters in various types of substrate as well as in the gas phase. In this way, one can hope to develop a scale of metal cluster-support effects (guest-host interactions) and evaluate the role that they play in diverse technological phenomena. 

Iglesia, E., Soled, S.L., and Fiato, R.A. 1992. Fischer-Tropsch synthesis on cobalt and ruthenium. Metal dispersion and support effects on reaction rate and selectivity. J. Catal. 137 212-24. 

Duprez and coworkers—support effect on WGS rate/180-160 switching method to quantify surface O diffusion and role of metal as porthole for exchange/ relationship of formate and carbonate surface mobility to O mobility during WGS. 

Imamura, Kaito, and coworkers—metal-support effects observed after calcination. Imamura et al 9X reported a strong metal-support interaction between Rh and Ce02, whereby high surface area ceria calcined at low temperature (550 °C) was able to transport Rh particles to the bulk, as measured by XPS. They suggested that despite the low degree of exposure of the Rh particle at the surface, the exposed Rh was highly active for the methanol decomposition reaction. 

Fischer-Tropsch synthesis rates, metal crystallite size and support effects, 39 242-246... 

Co catalysts, metal crystallite size and support effects, 39 242-246 Ru catalysts, metal crystallite size and support effects, 39 237-242 Thiele modulus effect, 39 275 reaction-transport models, 39 222-223 readsorption probability, 39 264-265 secondary chain growth, hydrogenation, and depolymerization reactions, 39 224—225... 

The organoactinide surface complexes exhibited catalytic activities comparable to Pt supported on sihca [at 100% propylene conversion at —63°C, >0.47s (U) and >0.40 s (Th)], despite there being only a few active sites (circa 4% for Th, as determined by CO poisoning experiments and NMR spectroscopy) [92]. Cationic organoactinide surface complexes [Cp An(CH3 ) ] were proposed as catalytic sites. This hypothesis could be corroborated by the use of alkoxo/hydrido instead of alkyl/hydrido surface ligands, which led to a marked decrease of the catalytic activity, owing to the oxophilic nature of the early actinides [203, 204]. Thermal activation of the immobihzed complexes, support effects, different metal/ligand environments and different olefins were also studied. The initial rate of propylene conversion was increased two-fold when the activation temperature of the surface complexes under H2 was raised from 0 to 150°C (for Th 0.58 0.92 s" ). 

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