Catalysis/catalysts surface chemistry

The application of IR spectroscopy to catalysis and surface chemistry was later developed in the fifties by Eischens and coworkers at Texaco laboratories (Beacon, New York) in the USA [7] and, almost simultaneously, by Sheppard and Yates at Cambridge University in the UK [8]. Mapes and Eischens published the spectra of ammonia chemisorbed on a silica-alumina cracking catalyst in 1954 [6], showing the presence of Lewis acid sites and also the likely presence of Br0nsted acid sites. Eischens, Francis and Pliskin published the IR spectra of carbon monoxide adsorbed on nickel and its oxide in 1956 [9]. Later they presented the results of an IR study of the catalyzed oxidation of CO on nickel at the First International Congress on Catalysis, held in Philadelphia in 1956 [10]. Eischens and Pliskin also published a quite extensive review on the subject of Infrared spectra of adsorbed molecules in Advances in Catalysis in 1958, where data on hydrocarbons, CO, ammonia and water adsorbed on metals, oxides and minerals were reviewed [11]. These papers evidence clearly the two tendencies observed in subsequent spectroscopic research in the field of catalysis. They are the use of probes to test the surface chemistry of solids and the use of spectroscopy to reveal the mechanism of the surface reactions. They used an in situ cell where the catalyst sample was... 

C.G. Vayenas, and S. Neophytides, Electrochemical Activation of Catalysis In situ controlled promotion of catalyst surfaces, in Catalysis-Special periodical Report, Royal Society of Chemistry, Cambridge (1996), pp. 199-253. 

Surface Chemistry and Catalysis on Some Platinum-Bimetallic Catalysts... 

Department of Surface Chemistry and Catalysis, Institute of Isotope, HAS, Budapest Laboratory for Nanostructured Metal Catalysts, Institute of Surface Chemistry and Catalysis, Chemical Research Center,... 

Spectroscopy in Catalysis is an introduction to the most important analytical techniques that are nowadays used in catalysis and in catalytic surface chemistry. The aim of the book is to give the reader a feeling for the type of information that characterization techniques provide about questions concerning catalysts or catalytic phenomena, in routine or more advanced applications. 

In this chapter, we have discussed the application of metal oxides as catalysts. Metal oxides display a wide range of properties, from metallic to semiconductor to insulator. Because of the compositional variability and more localized electronic structures than metals, the presence of defects (such as comers, kinks, steps, and coordinatively unsaturated sites) play a very important role in oxide surface chemistry and hence in catalysis. As described, the catalytic reactions also depend on the surface crystallographic structure. The catalytic properties of the oxide surfaces can be explained in terms of Lewis acidity and basicity. The electronegative oxygen atoms accumulate electrons and act as Lewis bases while the metal cations act as Lewis acids. The important applications of metal oxides as catalysts are in processes such as selective oxidation, hydrogenation, oxidative dehydrogenation, and dehydrochlorination and destructive adsorption of chlorocarbons. 

Reetz, M.T., Quaiser, S.A., Breinbauer, R., and Tesche, B., A New Strategy in Heterogeneous catalysis the design of cortex catalysts/catalysis/clusters/ immobilization/ surface chemistry, Angew. Chem. Int. Ed. Engl., 34, 2728,1995. 

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. 

It must thus be possible to transpose the concepts of modern molecular chemistry to design heterogeneous catalysts and especially the single sites that are necessary to obtain higher activities, better selectivihes, higher life times and, eventually, discover new catalytic reactions. This will be developed in the next chapter, based on catalysis by surface organometallic chemistry. 

Somorjai, G.A. Salmeron, M. (1986) Surface properties of catalysts. Iron and its oxides. Surface chemistry, photochemistry and catalysis. In Pelizzetti, E. Serpone, N. (eds.) Homogeneous and heterogeneous photocatalysis. D. Reidel Publ. Co., Doordrecht, The Netherlands, NATO ASI Series C, 174 445-478... 

It has to be noted that the adsorption of reactants is generally not uniform across the catalyst surface. Adsorption, and therefore catalysis, takes place mainly at certain favorable locations on a surface called active sites. In environmental chemistry, catalysts are essential for breaking down pollutants such as automobile and industrial exhausts. 

The zeolites are also known as molecular sieves because of their capacity to discriminate between molecules they find numerous uses in separation and catalytic processes. Although they appear to be solid particles to the naked eye, they are highly porous, with a typical specific surface area of about 1000 m2/g. Catalysis is discussed in Chapter 9, but the scope of that chapter does not permit detailed discussions of the various types of catalysts and the role of physisorption and chemisorption in catalysis this vignette provides a glimpse of the rationale used in the molecular design of new materials of interest in surface chemistry and how the concepts introduced in Chapter 1 and Chapter 9 fit into the larger scheme. 

It should be emphasized here that there is a vast difference between the microenvironment of the catalyst surface as examined by the type of analytical techniques mentioned in Section 9.1 and the overall surface that influences commercial processes. Until the modern techniques became available, however, catalyst preparation was mostly a matter of trial and error we have now entered an era in which science has a chance to catch up with technology. It seems fairly safe to predict that a greatly increased understanding of heterogeneous catalysis will emerge as modern surface chemistry matures. 

Somorjai, G. A., Introduction to Surf ace Chemistry and Catalysis, Wiley, New York, 1994. (Undergraduate level. This in-depth treatment of surface chemistry and catalysis brings the experience and perspectives of a pioneer in the field to the general audience. The book is meant to be an introductory-level description of modern developments in the area for students at the junior level. However, it is also an excellent source of the current literature and contains numerous, extensive tables of data on kinetic parameters, surface structure of catalysts, and so on. Chapter 3, Thermodynamics of Surfaces, and Chapter 7, Catalysis by Surfaces, cover information relevant to the present chapter. Chapter 8 discusses applications in tribology and lubrication (not discussed in this chapter).)... 

For more than five decades, the methods of surface physics and chemistry have provided some of the most incisive results advancing our understanding of the catalytic action of solids at the molecular scale. Characterizations by physical methods have demonstrated the dynamic nature of catalyst surfaces, showing that their structures, compositions, and reactivities may all be sensitive to temperature and the composition of the reactive environment. Thus, the most insightful catalyst characterizations are those of catalysts as they function. This volume of Advances in Catalysis is dedicated to the topic of physical characterization of solid catalysts in the functioning state. Because the literature of this topic has become so extensive, the representation will extend beyond the present volume to the subsequent two volumes of the Advances. 

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