Catalyst dynamics

In the case of selective oxidation catalysis, the use of spectroscopy has provided critical Information about surface and solid state mechanisms. As Is well known( ), some of the most effective catalysts for selective oxidation of olefins are those based on bismuth molybdates. The Industrial significance of these catalysts stems from their unique ability to oxidize propylene and ammonia to acrylonitrile at high selectivity. Several key features of the surface mechanism of this catalytic process have recently been descrlbed(3-A). However, an understanding of the solid state transformations which occur on the catalyst surface or within the catalyst bulk under reaction conditions can only be deduced Indirectly by traditional probe molecule approaches. Direct Insights Into catalyst dynamics require the use of techniques which can probe the solid directly, preferably under reaction conditions. We have, therefore, examined several catalytlcally Important surface and solid state processes of bismuth molybdate based catalysts using multiple spectroscopic techniques Including Raman and Infrared spectroscopies, x-ray and neutron diffraction, and photoelectron spectroscopy. 

The papers in this book were selected so that both the chemical and the engineering aspects of catalyst dynamics are represented in addition, an attempt was made to draw a balance between theory and experiment. 

The recent accomplishments of near-edge X-ray absorption spectroscopy in catalysis studies are already quite impressive, in particular if one considers the limited availability of suitable X-ray spectrometers. Developments of catalytic interest have concerned the Shell Higher Olefin process, size effects, metal-support interaction, mono- and bimetallic catalysts (in particular the PtRe/Al203 system), the reactivity of supported metal catalysts, dynamical and in situ catalyst studies, and a variety of oxide and sulfide catalysts. Other catalytic problems are now coming within easy experimental reach, such as the study of sulfur poisoning and the nature of coking. 

Enzymes are, however, much more than just a combination of substrate binding site and the catalytically active site. Important contributions to enzymatic catalysis arise from substrate preorganization, restriction of substrate motion, catalyst dynamics, transition state binding, and desolvation of the substrates, and natural evolution has used these... 

Hofmann S, Sharma R, Ducati C, Du G, Mattevi C, Cepek C, et al. In-situ observations of catalyst dynamics during surface-bound carbon nanotube nucleation. Nano Lett 2007 7 602-8. 

Fredriksson, H.O.A., Lancee, R.J., Thiine, PC. et al. (2013) Olivine as tar removal catalyst in biomass gasification catalyst dynamics under model conditions. Applied Catalysis B Environmental, 130-131, 168-177. 

Comparing the leading coefficient of the two accumulation terms shows that the ratio of the fluid dynamics to the catalyst dynamics is... 

Tuttlies U, Schmeisser V, Eigenberger G A mechanistic simulation model for NO storage catalyst dynamics, Chem Eng Sci 59 4731—4738, 2004. 

Tuttlies, U., Schmeisser, V., and Eigenberger, G. (2004) A mechanistic simulation model for NOx storage catalyst dynamics. Chem. Eng. Sci., 59,4731-4738. 

The type, density and energy distribution of active center of catalyst, dynamic behavior and reaction mechanism of reaction molecules. 

The actuated fit model of Koshland (Koshland Jr, 1958) illuminated the idea of substrate specificity in light of the requirement for a transition state adjustment by the catalyst dynamic site. According to him, catalysts are adaptable structures the dynamic site is ceaselessly reshaped by interactions with the substrate as the substrate connects with the compound... 

Eustache F, Dalko PI, Cossy J. Enantioselective monoreduction of 2-alkyl-1,3-diketones mediated by chiral ruthenium catalysts, dynamic kinetic resolution. Org. Lett. 2002 4 1263-1265. 

Two heterogeneous models were reported. One of them takes into account the external and internal resistance for mass and heat transfer in the catalyst particle (Dynamic model I) and the other one considers only the external resistance to the catalyst (Dynamic model II). 

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