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Reaction mechanisms in catalysis

Tinnemans, S.J., Mesu, J.G., Kervinen, K. el al. (2006) Combining operando techniques in one spectroscopic-reaction cell New opportunities for elucidating the active site and related reaction mechanism in catalysis, Catal. Today, 113, 3. [Pg.142]

The technique of TPD has proved particularly useful for the elucidation of reaction mechanisms in catalysis and in surface reactions more generally. It has been of especial utility for the discovery of the nature of adsorbed intermediates on surfaces, and in the following, two examples of the application of this technique will be given, with further examples described in sect. 6. [Pg.316]

A deeper understanding of reaction mechanisms in catalysis is highly recommended to practitioners in this field, despite the difficulty of identifying a unique rate expression for many, if not all, bimolecular catalytic reactions, as illustrated in the rather simple reaction considered here. In particular, the difficulty of mechanism identification is overwhelming if just one feed composition has been studied. Even when one has available the wealth of data from a TS-PFR experiment, the best fit is hard to find on the basis of one experiment. Regardless of this complication, the rewards of understanding the details of the reaction mechanism and its kinetics are substantial. [Pg.235]

J. F. Haw, Zeolite acid strength and reaction mechanisms in catalysis, Phys. Chem. Chem. Phys., 2002, 4, 5431-5441. [Pg.139]

Happel, J., Sellers, P.H. Multiple reaction mechanisms in catalysis. Ind. Eng. Chem. Fimdam. 21,... [Pg.59]

Combined Use of Both Experimental and Theoretical Methods in the Exploration of Reaction Mechanisms in Catalysis by Transition Metals... [Pg.187]

Theoretical calculations using modern quantum chemical methods provided an outstanding opportunity to make a valuable insight into the problem and allowed reliable description of reaction mechanisms in catalysis from the first principles. Application of informative and flexible computational procedures on numerous examples has demonstrated accurate computational modeling - often within the accuracy achieved in experimental measurements. [Pg.401]

The Holy Grail of catalysis has been to identify what Taylor described as the active site that is, that ensemble of atoms which is responsible for the surface reactions involved in catalytic turnover. With the advent of atomically resolving techniques such as scanning tunnelling microscopy it is now possible to identify reaction centres on planar surfaces. This gives a greater insight also into reaction kinetics and mechanisms in catalysis. In this paper two examples of such work are described, namely CO oxidation on a Rh(llO) crystal and methanol selective oxidation to formaldehyde on Cu(llO). [Pg.287]

Metal oxides possess multiple functional properties, such as acid-base, redox, electron transfer and transport, chemisorption by a and 71-bonding of hydrocarbons, O-insertion and H-abstract, etc. which make them very suitable in heterogeneous catalysis, particularly in allowing multistep transformations of hydrocarbons1-8 and other catalytic applications (NO, conversion, for example9,10). They are also widely used as supports for other active components (metal particles or other metal oxides), but it is known that they do not act often as a simple supports. Rather, they participate as co-catalysts in the reaction mechanism (in bifunctional catalysts, for example).11,12... [Pg.365]

Increased understanding of reaction mechanisms in the 1940s and 1950s pinpointed general acid or base catalysis as likely to be of importance in many hydrolytic reactions. The imidazole nucleus in histidine was the obvious center in proteins to donate or accept protons at physiological pH. The involvement of histidine was shown by photochemical oxidation in the presence of methylene blue (Weil and Buchert, 1951) which destroyed histidine and tryptophan and inactivated chymotrypsin and trypsin. [Pg.186]

Fig. 9.2. Simplified reaction mechanisms in the hydrolytic decomposition of organic nitrites. Pathway a Base-catalyzed hydrolysis with liberation of nitrite. Pathway b Reversible nitro-syl exchange between organic nitrites and alcohols. Pathway c General acid catalysis with concerted mechanism in the acid hydrolysis of organic nitrites. Fig. 9.2. Simplified reaction mechanisms in the hydrolytic decomposition of organic nitrites. Pathway a Base-catalyzed hydrolysis with liberation of nitrite. Pathway b Reversible nitro-syl exchange between organic nitrites and alcohols. Pathway c General acid catalysis with concerted mechanism in the acid hydrolysis of organic nitrites.
The structure of a reacting molecule can be used as the chemical probe for the reaction mechanism in several ways. Ample experience is available with these methods from the research of noncatalytic homogeneous reactions, and their possibilities and limitations are well known. However, the solid catalyst restricts the scope to some extent on the one hand, but opens new applications on the other. For this reason, the methods of physical organic and inorganic chemistry developed for noncatalytic reactions cannot simply be transferred into the field of heterogeneous catalysis. The following remarks should identify some of the problems. [Pg.153]

The proteolytic enzymes are classified into endopeptidases and exopeptidases, according to their site of attack in the substrate molecule. The endopeptidases or proteinases cleave peptide bonds inside peptide chains. They recognize and bind to short sections of the substrate s sequence, and then hydrolyze bonds between particular amino acid residues in a relatively specific way (see p. 94). The proteinases are classified according to their reaction mechanism. In serine proteinases, for example (see C), a serine residue in the enzyme is important for catalysis, while in cysteine proteinases, it is a cysteine residue, and so on. [Pg.176]

The study of detailed chemical reaction mechanisms in homogeneous catalysis requires the identification and characterization of reaction intermediates. However, limitations arise due to both the short life time (transient type) and the low concentration of such species [203]. [Pg.51]

Erom the preceding discussion, the distinction between misfit defects shear domains formed by pure shear and CS planes formed by the elimination of anion vacancies in a specific crystallographic plane by shear and the collapse of the oxide lattice on that plane can be understood. This distinction between defects is central to catalytic reaction mechanisms in oxides. However, it is often not made in the literature on oxide catalysis and solid state oxide chemistry. This can result in an incorrect interpretation of observed data and of the role played by lattice oxygen atoms in catalytic reactions. The former are regions containing... [Pg.90]

The key role of electron microscopy in the discovery of novel reaction mechanisms in selective oxidation catalysis... [Pg.131]

Finally, the application of computational methods to the study of catalysis continues to increase dramatically. C.G.M. Hermse and A.P.J. Jensen (Eindhoven University of Technology, the Netherlands) present a review of the kinetics of surface reactions with lateral interactions. These methods can be used in predicting catalytic reaction mechanisms. In particular, the authors discuss the role of lateral interactions in adsorbed layers at equilibrium and the determination of lateral interactions from experiments—using the simulations to interpret experimental results. This chapter illustrates the increasing use of computational methods to understand and to design catalysts. [Pg.6]

For the past decade, the major thrust of one of the authors has been the elucidation of reaction mechanisms in heterogeneous catalysis on zeolites, metal oxides and other materials. The primary experimental tool has been in situ NMR spectroscopy, and this is increasingly coupled with theoretical calculations carried out by the other author. [Pg.63]


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See also in sourсe #XX -- [ Pg.316 ]




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