Inertia and driving force of chemical reactions

Evans, M. G.; Polanyi, Michael

doi:10.1039/tf9383400011

Cited by 1,563 publications

(1,143 citation statements)

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“…Very similar values have been reported for other phases such as MnO 2 [24] and MnO [45], and the employed value is therefore expected to be reasonably representative for the manganese oxide system. The employed heats of desorption for the various metal oxides are in good agreement with the Brønsted-Evans-Polanyi [48,49] relationship for isotopic 16 O 2 / 18 O 2 exchange reported by Boreskov [46]. No direct measurement of the heat of oxygen desorption for CeO 2 could be found.…”

Section: Sources For the Heat Of Oxygen Chemisorptionsupporting

confidence: 69%

Importance of the oxygen bond strength for catalytic activity in soot oxidation

Christensen

Grunwaldt

Jensen

2016

Applied Catalysis B: Environmental

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The oxygen bond strength on a catalyst, as measured by the heat of oxygen chemisorption, is observed to be a very important parameter for the activity of the catalyst in soot oxidation. With both intimate contact between soot and catalyst (tight contact) and with the solids stirred loosely together (loose contact) the rate constants for a number of catalytic materials outline a volcano curve when plotted against their heats of oxygen chemisorption. However, the optima of the volcanoes correspond to different heats of chemisorption for the two contact situations. In both cases the activation energies for soot oxidation follow linear Brønsted-Evans-Polanyi relationships with the heat of oxygen chemisorption. Among the tested metal or metal oxide catalysts Co 3 O 4 and CeO 2 were nearest to the optimal bond strength in tight contact oxidation, while Cr 2 O 3 was nearest to the optimum in loose contact oxidation. The optimum of the volcano curve in loose contact is estimated to occur between the bond strengths of α-Fe 2 O 3 and α-Cr 2 O 3 . Guided by an interpolation principle Fe a Cr b O x binary oxides were tested, and the activity of these oxides was observed to pass through an optimum for an FeCr 2 O x binary oxide catalyst, which exhibited a rate constant at 550 °C that was 2.3 times higher than the one for pure α-Cr 2 O 3 and 29 times higher than the one for pure α-Fe 2 O 3 .

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Section: Sources For the Heat Of Oxygen Chemisorptionsupporting

confidence: 69%

Importance of the oxygen bond strength for catalytic activity in soot oxidation

Christensen

Grunwaldt

Jensen

2016

Applied Catalysis B: Environmental

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“…32,381,492,493,[516][517][518] Hence, if the zeolite increases the relative free energy of one of the reaction intermediates, the corresponding transition state increases similarly. The consequences of this relation are that the differences in the free energies of the transition states of competing reactions can be estimated from the differences in the free energies of formation of the corresponding reaction intermediates (see Figure 59).…”

Section: Transition State Selectivitymentioning

confidence: 99%

“…32 This linear relationship between the Gibbs free energy of formation of transition states and that of products is an example of the semiempirical Brønsted-Evans-Polanyi relationship. 32,492,493 According to this relationship, the prohibitively high Gibbs free energy of formation (and adsorption) of RR-dimethylalkane products inside TON-type zeolites 190,490,491,494 is an indication of a similarly high Gibbs free energy of formation of the transition state for RR-dimethylalkane formation, so that transition state shape selectivity will inhibit RRdimethylalkane product formation inside TON-type zeolite Figure 53. The hydrocracking precursors and products obtained by applying the mechanism shown in Figure 52 to C 10 .…”

Section: Transition State Shape Selectivitymentioning

confidence: 99%

Molecular Simulations of Zeolites: Adsorption, Diffusion, and Shape Selectivity

2008

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“…Fortunately, there are some empirical relations correlating the activation energy and reactivity with the chemisorption energy of reactants. One of them, the Brønsted-EvansPolanyi (BEP) relation [69][70][71][72], states that the activation energy for an elementary reaction step on surface depends linearly on the reaction energy, that is, the difference between the chemisorption energy of the products and the reactants. An example [72] for the activation energies for N 2 dissociation over various metal surfaces are shown in Fig.…”

Section: Reactivity and Selectivity In Heterogeneous Catalysismentioning

confidence: 99%

Major Successes of Theory-and-Experiment-Combined Studies in Surface Chemistry and Heterogeneous Catalysis

Somorjai

2010

Top Catal

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Experimental discoveries followed by theoretical interpretations that pave the way of further advances by experimentalists is a developing pattern in modern surface chemistry and catalysis. The revolution of modern surface science started with the development of surfacesensitive techniques such as LEED, XPS, AES, ISS and SIMS, in which the close collaboration between experimentalists and theorists led to the quantitative determination of surface structure and composition. The experimental discovery of the chemical activity of surface defects and the trends in the reactivity of transitional metals followed by the explanations from the theoretical studies led to the molecular level understanding of active sites in catalysis. The molecular level knowledge, in turn, provided a guide for experiments to search for new generation of catalysts. These and many other examples of successes in experiment-and-theory-combined studies demonstrate the importance of the collaboration between experimentalists and theorists in the development of modern surface science.

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Inertia and driving force of chemical reactions

Cited by 1,563 publications

References 0 publications

Importance of the oxygen bond strength for catalytic activity in soot oxidation

Importance of the oxygen bond strength for catalytic activity in soot oxidation

Molecular Simulations of Zeolites: Adsorption, Diffusion, and Shape Selectivity

Major Successes of Theory-and-Experiment-Combined Studies in Surface Chemistry and Heterogeneous Catalysis

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