Support Surface Chemistry

Similarly, for TiO whose spectrum consists of two band systems, the high-frequency one corresponds to basic, i.e. single-bonded, hydroxyl groups, while the other corresponds to more acidic bridged hydroxyls. Hie anionic character of the type I hydroxyls on alumina and titania is exemplified by the fact that they preferentially exchange with fluoride ions  

In their turn, the acidic hydroxyl groups on TiC 2 are preferentially methylated using such agents as methyl iodide and p-toluenesulphonic acid. The exchange of Cd2+ ions also involves primarily these groups, as one would expect  

The OH stretch region of the IR spectrum of Si02 typically consists of a strong sharp band at about 3740 cm-1 and a broader feature at lower wavenumbers (cf. Fig. 9.2b). The sharp band can be ascribed to isolated (A), and presumably also to geminal (B) hydroxyls, while the broader feature is due to vicinal (C) hydroxyl groups, which show internal hydrogen bonding  

When an oxide is brought into contact with an aqueous solution, the surface hydroxyl groups enter into the following equilibria  

A good example of outer-sphere complex formation is the adsorption of Co(CN -) ions on y Al203. As can be seen from Fig. 9.3, lowering the pH leads to a concomitant increase in the amount of anion adsorbed, while neutralizing the solution again induces the Co(CN) 3- ions to desorb again. The process is perfectly reversible, which is not usually the case for inner-sphere complex formation. 

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The influence of the support surface chemistry on the enantioselectivity of cellulose-carbamate-coated CSPs has also been investigated 1170). It was found that stable coated phases can be produced using underivati/ed. aminopropylated and octadecylated silica... 

In this case, attention is focussed on the effect of the support surface chemistry on the anchoring of the complex by ion-exchange. To favour the ion-exchange, the carbon surface has been oxidized to create surface oxygen complexes [16, 17], The expected ion-exchange process is presented in Scheme 1. 

Sipehia, R., G. Martucci, ). Lipscombe, Transplantation of human endothelial cell monolayer on artificial vascular prosthesis the effect of growth-support surface chemistry, cell seeding density, ECM protein coating, and growth factors. Artif. Cells Blood Substit. Immobil. Biotechnol., 1996, 24(1) 51-63. 

Roman-Martinez, M. et al. 1995. Metal-support interaction in Pt/C catalysts. Influence of the support surface chemistry and the metal precursor. Carbon 33 3-13. 

Puente G, Gil A, Pis JJ, Grange P. 1999. Effects of support surface chemistry in hydrodeoxygenation reactions over CoMo/activated carbon sulfided cattilysts. Langmuir 15 58(X)-5806. 

The development of new and improved catalysts requires advances in our understanding of how to make catalysts with specified properties the relationships between surface stracture, composition, and catalytic performance the dynamics of chemical reactions occurring at a catalyst surface the deployment of catalytic surface within supporting microstracture and the dynamics of transport to and from that surface. Research opportmuties for chemical engineers are evident in four areas catalyst synthesis, characterization of surface stracture, surface chemistry, and design. 

The National Science Formdation should expand its support to surface and interfacial engineering, focusing on surface chemistry, catalysis, electrochemistry, colloid and interfacial... 

The Division of Chemical Sciences in OER supports basic chemical research. The primary involvement of chemical engineers with this program has been in the areas of catalysis and separations. Given the broad range of energy apphcations in which the structure and chemistry of interfaces is important, the committee recommends that the Division undertake an initiative in the chemical control of surfaces, interfaces, and microstractures. This would include support of work by both chemists and chemical engineers in the areas of surface chemistry, plasma chemistry, and colloid and interfacial chemistry. 

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. 

Weckhuysen et al. [6,33] have recently published several UV-Vis DRS works devoted to investigate the surface chemistry of supported chromium catalysts as a function of the support composition. The same authors [34] have also tried... 

Metal particles Oxide supports Surface organometallic chemistry... 

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. 

It is unknown at this point why the gold particles on the decolorizing carbon had the largest average particle size. The decolorizing carbon had a surface area comparable to the X40S but the surface chemistry has not been studied. Previous studies have demonstrated the critical role carbon support properties have on the properties of... 

Carbon is inert in nature and has a high surface area, making it highly suitable as a support for catalysts. The surface characteristics and porosity of carbon may be easily tailored for different applications. Acid treatment is often applied to modify its surface chemistry for specific applications. Typically, active metal species are immobilized on carbon for catalytic applications. 

Research support from the United States Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences is gratefully acknowledged. Support from GTE Laboratories, Inc. and Dow Chemical Company, U.S.A. for aspects of this work is also acknowledged. Partial support from the Office of Naval Research for work on the surface chemistry of CdTe is appreciated. 

The symposium and this volume have benefited from financial support provided by the Division of Colloid and Surface Chemistry of the American Chemical Society, the Petroleum Research Fund, Shell... 

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. 

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