Catalytic consequences

Experimental evidence illustrating the effect that hydrides of nickel or its alloys with copper have on the catalytic activity of the respective metals is to be found in papers which discuss catalytic consequences of the special pretreatment of these metal catalysts with hydrogen during their preparation. One must also look very carefully into cases where self-poisoning has been reported as appearing in reactions of hydrogen with other reactants. 

The temperature of hydrogen reduction of impregnated catalysts may influence the amount of halogen retained by the catalyst. This residual chlorine may have catalytic consequences. For instance, Dorling, Eastlake,... 

From images of these particles, it was found that the particles in Figures 11a, lib, 11c and peak A of lid were of nearly the same morphology as those analyzed in Figures 8 and 9. Peak B of Figure lid was comprised entirely of the well-formed ZSM-5 crystals shown in Figures 7b and 10. The differences in particle morphology and A1 distribution for particles in peak A and peak B are likely to have considerable catalytic consequence. Diffusion paths are shorter for the particles of peak A while the A1 distribution is quite different between the two types of particles. 

J. Am. Chem. Soc., 126. 4494. (i) Takacs, J.M., Chaiseeda, K. and Moteki, S.A. (2006) Rhodium-catalyzed asymmetric hydrogenation using self-assembled chiral bidentate ligands. Pure Appl. Chem., 78, 501. (j) Duckmanton, P.A., Blake, A.J. and Love, f.B. (2005) Palladium and rhodium ureaphosphine complexes Exploring structural and catalytic consequences of anion binding. Inorg. Chem., 44, 7708-7710. 

Measurements of Crystal Structures. - (a) Zeolites. Improved understanding of the catalytic behaviour of zeolites has tended to proceed in parallel with improvements in their structural characterization. The recent advent of magic-angle spinning n.m.r. (m.a.s.n.m.r.)for instance, has reawakened interest in the ordering of the Si and A1 atoms in zeolites and its catalytic consequences. This renewed interest has in turn lead to a re-examination of the neutron diffraction patterns of certain zeolites in order to obtain confirmatory evidence for the the predictions of the n.m.r. experiments. A useful introduction to the benefits of using neutrons rather than X-rays for powder diffraction can be found in ref. 55. 

Of course, such a chemical probing would be possible only if we can prove, by means of other (mainly physical) techniques, that the existence of electron-deficient palladium in supported palladium is possible. Therefore, the organization of this section is as follows First, we discuss the results of XPS studies of electronic properties of small Pd particles deposited on various supports. Then we examine other evidence for the existence of positively charged Pd species using other techniques, such as electron spin resonance (ESR) and infrared (IR) spectroscopy of adsorbed CO. Finally, catalytic consequences of the appearance of positively charged species in the Pd/support catalysts will be demonstrated. 

We hope objectively to access what is known and what is not known about spillover. Our specific focus is on the phenomena and the catalytic consequences. 

More recent work has concentrated on the study of model systems in which the characteristic metal-support interaction effects were reproduced by depositing controlled amounts of titania species on metal surfaces (116-124). To ascertain the chemisorption and catalytic consequences of the TiOx overlayer, the evaporation has usually been carried out under 10-7-10-6 torr of oxygen. In this section we analyze the more relevant metaI/Ti02 and TiOx/metal model studies and their impact on our understanding of the metal-support interactions taking place on real supported catalysts. 

By monitoring the surface phase with LEED, one can also keep track of other potentially important catalytic variables as order-disorder transitions at critical temperatures, segregation of new phases, and island growth. Catalytic consequences of such changes are at present unknown. Our knowledge of the behavior of individual adsorbates is small. Little wonder, then, that LEED has been slow in its approach to catalysis. Yet much of interest has already been learned, though it is too early to extract useful generalizations from the results. All of the work is of an exploratory kind. 

We must first differentiate metal-support interactions that undoubtedly occur when a metal particle is placed on a support that has distinctly either acidic or basic character from true bifunctional catalysis. Such interactions have been shown to introduce delicate but significant alteration to the organisation of the metal s valence electrons, and these have important catalytic consequences but reactions that are affected are still metal-catalysed, and should not be regarded as instances of... 

C. R. F. Lund, J. A. Dumesic, Strong oxide-oxide interactions in silica-supported magnetite catalysts IV. Catalytic consequences of the interaction in water-gas shift, J. Catal. 76 (1982) 93-100. 

Mesecar, A. D., Stoddard, B. L., Koshland Jr., D. E. (1997). Orbital steering in the catalytic power of enzymes small structural changes with large catalytic consequences, Science, 277, 202-206. Recent example Meyer, D., Neumann, R, Parthier, C., Friedemann, R., Nemeria, N., Jordan, F., Tittmann, K. (2010). Double Duty for a Conserved Glutamate in Pyruvate Decarboxylase Evidence of the Participation in Stereoelectronically Controlled Decarboxylation and in Protonation of the Nascent Carbanion/Enamine Intermediate. Biochemistry, 49, 8197-8212. 

Mesecar, A. D., Stoddard, B. L., and Koshland, D. E., Jr. "Orbital Steering in the Catalytic Power of Enzymes Small Structural Changes with Large Catalytic Consequences." Science, 277,202-206 (1997). 

Chiang, H., Bhan, A., 2010. Catalytic consequences of hydroxyl group location on the rate and mechanism of parallel dehydration reactions of ethanol over acidic zeolites. Journal of Catalysis 271,251-261. 

The dealumination of zeolite Y has been studied intensively during the past two decades, mainly for the purpose of developing new FCC catalysts. The changes in acidity upon dealumination of zeolite Y samples has received much attention from the theoretical point of view (refs.1-11). The catalytic consequences of the depletion of the framework with aluminium and, in particular, the changes in product selectivity with the framework aluminium (Al ) and extra-framework aluminium (Al F) content of the zeolite are extremely important in FCC. Reviews on this subject are available (refs.12-14). 

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