Surface chemistry oxide supports

Understanding the surface chemistry for supported vanadium oxide systems modified with phosphorus oxide at hydrocarbons oxidation... 

Filling the pores of the support with a solution of the catalytically active element, after which the solvent is removed by drying, is a straightforward way to load a support with active material. However, in this process various interactions are possible between the dissolved catalyst precursor and the surface of the support, which can be used to obtain a good dispersion of the active component over the support. To appreciate the importance of such interactions we need to take a closer look at the surface chemistry of hydroxylated oxides in solution. 

Vibrational spectroscopic studies of heterogeneously catalyzed reactions refer to experiments with low area metals in ultra high vacuum (UHV) as well as experiments with high area, supported metal oxides over wide ranges of pressure, temperature and composition [1]. There is clearly a need for this experimental diversity. UHV studies lead to a better understanding of the fundamental structure and chemistry of the surface-adsorbate system. Supported metals and metal oxides are utilized in a variety of reactions. Their study leads to a better understanding of the chemistry, kinetics and mechanisms in the reaction. Unfortunately, the most widely used technique for determining adsorbate molecular structure in UHV,... 

Metal particles Oxide supports Surface organometallic chemistry... 

In this review, we will specifically discuss the similarities and the differences between the chemistry on surfaces and molecular chemistry. In Sect. 2, we will first describe how to generate well-dispersed monoatomic transition metal systems on oxide supports and understand their reactivity. Then, the chemistry of metal surfaces, their modification and the impact on their reactivity will be discussed in Sect. 3. Finally, in Sect. 4, molecular chemistry and surface organometallic chemistry will be compared. 

Supported metal carbonyl clusters are alternatively formed from mononuclear metal complexes by surface-mediated synthesis [5,13] examples are [HIr4(CO)ii] formed from Ir(CO)2(acac) on MgO and Rh CCOlie formed from Rh(CO)2(acac) on y-Al203 [5,12,13]. These syntheses are carried out in the presence of gas-phase CO and in the absence of solvents. Synthesis of metal carbonyl clusters on oxide supports apparently often involves hydroxyl groups or water on the support surface analogous chemistry occurs in solution [ 14]. A synthesis from a mononuclear metal complex precursor is usually characterized by a yield less than that attained as a result of simple adsorption of a preformed metal cluster, and consequently the latter precursors are preferred when the goal is a high yield of the cluster on the support an exception is made when the clusters do not fit into the pores of the support (e.g., a zeolite), and a smaller precursor is needed. 

The decarbonylation of oxide-supported metal carbonyls yields gaseous products including not just CO, but also CO2, H2, and hydrocarbons [20]. The chemistry evidently involves the support surface and breaking of C - O bonds and has been thought to possibly leave C on the clusters [21]. The chemistry has been compared with that occurring in Fischer-Tropsch catalysis on metal surfaces [20] support hydroxyl groups are probably involved in the chemistry. 

D.C. Meier, X. Lai, and D.W. Goodman, Surface chemistry of model oxide-supported metal catalysts An overview of gold on Titania, in Surface Chemistry and Catalysis, eds. A.F. Carley et al. Kluwer, New York, 2002, pp. 147-189. 

In this chapter we report on the gas-phase preparation of metal-supported catalysts, that is on the deposition of dispersed metallic nanoparhcles onto a surface. Taking most of the examples from the thoroughly studied chemistry of the [Mo(CO)is]/oxide support system, we successively consider (i) surface organometallic chemistry issues, (ii) the methods used to avoid chemical contaminahon of the deposit and (iii) the competition between nucleation and growth. 

Coperet, C. Lefebvre, F. Basset, J.-M. Well-Defined Metallocarbenes and Metallocarbynes Supported on Oxide Supports Prepared via Surface Organometallic Chemistry. In Handbook of Metathesis, Grubbs, R. H., Ed. Wiley-VCH Weinheim, 2003 Vol. 1, pp 190-205. 

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