Catalysts, historical metal supported

Historically, it took many years to achieve the almost perfect stereocontrol of an enantioselechve hydrogenahon reaction using a heterogeneous catalyst, with a resultant 97-99% enanhomeric excess (ee) of the product One of the oldest such examples is that of tartaric acid-modified platinum black for the hydrogenahon of an oxime to give a chiral amine of <20% ee [2]. Nonetheless, many reviews in this field have provided a clear history of the enanhoselechve catalysis from silk-palladium-a palladium metal supported on a chiral silk fiber to hydrogenate a... 

Section 5.3 considered NMR spectroscopic approaches to the bulk characterization of oxides and oxidation catalysts. Gatalytic activity is, however, intrinsically linked with the nature of the catalyst surface and hence a number of techniques have been developed in order to probe this. As discussed in Section 5.1, two of the most significant parameters impacting on catalyst activity are the acid-base characteristics of a surface and the redox properties of the material, and NMR techniques exist to probe both of these characteristics. One of the most common techniques to probe surface structure is GP-MAS NMR, in particular CP from hydrogen to the nucleus of interest-either the metal or the oxygen of the metal oxide. Historically, the source of surface H species has often been those naturally present on the catalyst surface, as chemisorbed hydroxyls or physisorbed water. As such, much of the work in this area involves the study of supports such as Si02. Applications of CP-MAS and other spectroscopic approaches to the study of oxide surfaces are outlined in the following sections. 

The efficiency of the above catalysts for NO reduction depends definitely on the kind of metals and their loadings onto supports, the type of reductants and the feed gas composition employed as well as on the kinds of supports and structure of the parent zeolite and its historical nature during preparation. In particular, the effect of the presence of H2O and SO2 in the exhaust gas from mobile sources is well documented on the maintenance of time-on-stream deNOx activity of SCR catalysts, and their resistance to these co-existing gases is an essential parameter determining successful applications to engine sources. The durability of the documented catalysts under hydrothermal conditions should also be considered to verify if those were applicable to controlling vehicle NOx... 

The CLs of the early PEMFCs were prepared from the noble metal blacks and thns contained very high metal loadings per geometric MEA area. Later, it became apparent that precions metals in these CLs were not utilized efflciendy and the new generation of PEMFCs emerged, based on carbon-supported precious-metal catalysts (usually Pt or Pt-based alloy). The MEA preparation techniques have undergone continuous evolution since the early days of PEMFCs. For a historical overview, the reader is referred to refs. 1 and 5. In this chapter we focus on carbon materials as supports for PEMFCs and DMFCs. 

This book contains many publications which represent analyses of the steps of elaboration of effective heterogeneous enantioselective hydrogenation catalysts, of their significant role in the theory of catalysis, and of their role in the practice of asymmetric catalysis. In addition to reviewing the first works on catal Tic hydrogenation of C=C double bond in prochiral compounds on metal catalysts supported on chiral carriers, which admittedly have only historical interest, the Chapters 1-3 review data on asymmetric adsorption of enantiomers and separation of racemic mixtures on organic and inorganic adsorbents. 

The term bimetallic was introduced by Sinfelt to account for the fact that a catalyst may contain a muldtude of phases containing the acdve metallic components. Of these many phases, a characteristic is the binary alloy. The term alloy can describe a broad range of situations from well-defined phases or solid solutions to surface alloys in cases where bulk alloys are not thermodynamically favoured but a clearly defined surface local arrangement is obtained. Note that the novel core-shell bimetallic structures are included in this catchall term. An historical overview of the properties of alloys in connection with catalysis has been published by Ponec. At present, a broadly agreed view accepts that alloy components can be chemically recognised and, therefore, supports a somewhat localised interpretation of the alloy nature and properties. Obviously, a delocalised view loses most of its meaning in the case of clusters due to its finite dimensions. 

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