Strong metal/support interaction effects

Small metal particles are frequently expected (however, the evidence is sometimes questionable) to experience an electron transfer with the carrier, which modifies the adsorption and catalytic properties of the metal particles [sometimes called the Schwab effect (108-116)]. In other cases, by special conditions under preparations of the catalysts, a so-called strong metal support interaction effect (SMSI) (117-121) was evoked. In particular, with zeolites as carriers, there are pieces of experimental evidence reported (115, 116) in support of the existence of such transfer (for remarks on those conclusions, see 122, 123). 

Third Case Study Strong Metal/Support Interaction Effects... 

Recently, Pt/Nb20s catalysts have been investigated on dehydrogenation of alkanes. These systems have presented advantages on selectivity towards olefins when compared to Pt/ALOs or even Pt-Sn/A]20 , catalysts [4-6]. The promoting mechanism is related to both the SMSI (Strong Metal Support Interaction) effect and the low acidity of the support, which produce a sharp decrease in hydrogenolysis and aromatization, respectively [5]. 

In this section we will focus on the description of several aspects relevant to the preparation of both catalytically active metal particles and metal-supported catalysts via the microemulsion technique. Regarding the metal supported catalysts, in some cases both the metallic particles and the support were synthesized by microemulsions. However, in general metallic particles prepared from microemulsions were deposited on commercial supports. The catalytic behaviour of these microemulsion-derived materials will be commented and, when possible, compared to catalysts obtained from traditional techniques under similar reaction conditions. Selected results concerning the study of the strong metal-support interaction effect (SMSI) obtained with catalysts prepared by microemulsion will be detailed . Several papers dealing with the preparation of immobilized metal particles on supports have been described although the catalytic behaviour of the solids was not studied. However, their potential catalytic ability led us to include those papers within this chapter. 

Other Studies on the Reactivity of the Higher Rare Earth Oxides 2.3.7.1. Strong Metal/Support Interaction Effects in NM/Ce02 Systems... 

S CO adsorption as a tool for investigating strong metal/support interaction effects in Au/CZ catalysts... 

Other hand, the Pt/Ti02 catalyst presented two times more hydrogen consumptirai than the alumina-supported catalyst, indicating reduction of Ti02 and thus interaction with metallic Pt°. The H2 chemisorption is three times less (17 %) than the Pt/Al203 catalyst and confirms the strong metal support interaction effect after reduction at 500 °C [23]. 

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