Strong metal-support interaction platinum

Salama, T. M., Hattori,H., Kita,H., Ebitani, K., and Tanaka, T., X-ray adsorption spectroscopic and electron paramagnetic resonance studies on the strong metal-support interaction of platinum supported on titania dispersed on silica, J. Chem. Soc. Faraday Trans. 89(12), 2067 (1993). 

Baker R.T.K., Kim K.S., Emerson A.B., Dumesic J.A. (1986) A Study of the Platinum-Titanium Dioxide System for the Hydrogenation of Graphite Ramifications of Strong Metal-Support Interactions, J. Phys. Chem. 90(5), 860-866. 

Titania-supported Metals. - After reduction at 473 K, platinum-group metals supported on Ti02 chemisorbed both hydrogen and carbon monoxide in quantities indicative of moderate-to-high dispersion, but following reduction at 773 K chemisorption was drastically lowered e.g., H/Mt <0.01 for Pt, Ir, and Rh, 0.05-0.06 for Pd and Ru, and 0.11 for Os). Agglomeration, encapsulation, and impurities were eliminated as possible causes and a strong metal-support interaction (SMSI) was proposed. Titania is not unique in its SMSI properties and 11 oxides used to support iridium were classified as follows ... 

Equilibrium and kinetic calculations, based on bulk properties, support the view that strong metal-support interactions in Pt/Ti02 catalysts arise from the decoration of platinum crystallites with TiOx species. 

The reducibility of platinum should be affected both by SOOI effect (see above) and strong metal-support interaction (SMSI) between platinum and transition metal oxide monolayer. Both mentioned effects were observed by means of temperature-programmed techniques. TPR investigations put in evidence that the reducibility of platinum strongly depended on the type of primary carrier as well as on the type of transition metal monolayer. The results of TPR investigations are presented in Fig. 1 and Table 2. 

D.N. Belton, Y.M. Sun, and J.M. White. Thin-Film Models of Strong Metal-Support Interaction Catalysts. Platinum on Oxidized Titanium. J. Phys. Chem. 88 1690 (1984). 

J.A. Horsley. A Molecular Orbital Study of Strong Metal-Support Interaction between Platinum and Titanium Dioxide. J. Am. Chem. Soc. 101 2870 (1979). 

Before proceeding to consider kinetic equations and implied reaction mechanisms, we may note some other pertinent features of these reactions. (A) Benzene hydrogenation was subject to the influence of the Strong Metal-Support Interaction (Section 3.35) when titania and vanadium sesquioxide were used as supports for rhodium, platinum and iridium - even Pt/Si02 and Ni/Si02 when heated... 

Many authors have shown that the support could play a role, not only in changing particle size but also in modifying adsorption properties of the metals. Ceria could stabilize ionic species of platinum leading to a strong metal-support interaction. Bera et al. have compared the behavior of Pt/Ce02 and Pt/Al203 in TW catalysis." The enhanced activity observed in several reachons (CO-I-O2, CO - - NO and HC -f O2, Table 1.10) has been attributed to the formation of new sites (-0 Ce" +-0 Pt"+-0 with = 2 or 4). Ceria-supported catalysts are more active than alumina ones for all the reactions. NO as an oxidant is more sensitive in nature to support than O2. Moreover, ceria is a better promoter for oxidation of CO and propane than that of methane. Whatever the oxidant (NO or O2), methane oxidation remains difficult with a modest promotion by ceria. 

However, the Pt/Ti02 catalyst exhibits reduction at room temperature and at 112 °C, 372 °C, and above 500 °C, besides peak shift to lower temperatures due to the reduction of PtO. Partial reduction of Ti02 to Ti02 x occurs at higher temperatures which are attributed to the strong metal support interaction (SMSI). The presence of Pt atoms promoted the reduction of titanium which in turn facilitates the reduction of platinum at the surface. 

Horsley JA. A molecular orbital study of strong metal-support interaction between platinum and titanium dioxide. J Am Chem Soc. 1979 101(11) 2870. 

The rhenium interacts strongly with the oxygen atoms of the support and also with platinum platinum interacts less strongly with the support than rhenium. One is tempted to generalize that when one of the metals in a supported bimetallic cluster is noble and the other oxophihc, the oxophUic metal interacts more strongly with the support than the noble metal if the bimetalhc frame of the precursor is maintained nearly intact, then this metal-support interaction helps keep the noble metal highly dispersed. 

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