Concepts of Modern Catalysis and Kinetics

Chorkendorff, Ib; Niemantsverdriet, J.W.

doi:10.1002/3527602658

Cited by 899 publications

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“…[23][24][25][26] While the competition of phononic and + ¡ F (eV/Å) Figure 1: (color online). Schematic illustration of the QM/Me embedding scheme defined by Equation (1). A tractable embedding cell for the periodic QM calculations is indicated in blue (3-layer slab formed out of a 3 × 8 multiple of the primitive surface unit cell).…”

Section: Dedicated To My Parents Brigitte and Siegfried Meyermentioning

confidence: 99%

“…The resulting Markovian state-to-state hopping underlies, for example, all presentday microkinetic formulations in heterogeneous catalysis. [1,2] The validation of this picture would require detailed insight into the energy-conversion process at the interface. To date this is limited at best, and if at all centered on reactions at well-defined single-crystal surfaces in ultrahigh vacuum.…”

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confidence: 99%

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Modeling Heat Dissipation at the Nanoscale: An Embedding Approach for Chemical Reaction Dynamics on Metal Surfaces

Meyer

Reuter

2014

Angew Chem Int Ed

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Hot or not:An embedding technique for metallic systems makes it possible to model energy dissipation into substrate phonons during surface chemical reactions from first principles. Application to O2 dissociation at Pd(100) predicts translationally "hot" oxygen adsorbates as a consequence of the released adsorption energy (ca. 2.6 eV). This questions the instant thermalization of reaction enthalpies generally assumed in heterogeneous catalysis modeling.Modeling Heat Dissipation at the Nanoscale:An Abstract: We present an embedding technique for metallic systems that makes it possible to model energy dissipation into substrate phonons during surface chemical reactions from first principles. The separation of chemical and elastic contributions to the interaction potential provides a quantitative description of both electronic and phononic band structure. Application to the dissociation of O 2 at Pd(100) predicts translationally "hot" oxygen adsorbates as a consequence of the released adsorption energy (ca. 2.6 eV). This finding questions the instant thermalization of reaction enthalpies generally assumed in models of heterogeneous catalysis.Exothermic surface chemical reactions may easily release several electron volts of energy. Though sizable in view of potential microscopic dissipation channels, the prevalent picture in chemical kinetics is that this energy is quasi-instantaneously thermalized, ultimately into * joerg.meyer@ch.tum.de present address: Leiden Institute of Chemistry, Gorlaeus Laboratories, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands phononic degrees of freedom. This motivates theoretical treatments on the level of a local temperature and separates the continuous chemical motion into rare-event sequences of thermal reactions. The resulting Markovian state-to-state hopping underlies, for example, all presentday microkinetic formulations in heterogeneous catalysis. [1,2] The validation of this picture would require detailed insight into the energy-conversion process at the interface. To date this is limited at best, and if at all centered on reactions at well-defined single-crystal surfaces in ultrahigh vacuum. For a prototypical model reaction like the dissociative adsorption of O 2 molecules scanningtunneling microscopy experiments have suggested the formation of so-called "hot adatoms" on several metal surfaces. [3][4][5][6] As a consequence of the released chemical energy, this transient mobility thus intricately couples the elementary reaction steps of dissociation and diffusion.As the experimental quest to generate molecular movies of such reactions is still ongoing, theory has been challenged to elucidate the equilibration dynamics of this process. [7][8][9] Here, the bond breaking and making in highly corrugated surface potentials dictates computationally demanding quantum mechanical (QM) treatments, in par- ticular periodic boundary condition (PBC) supercell approaches to adequately describe the delocalized (surface) metallic band structure. [2] Complementing this with a...

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Section: Dedicated To My Parents Brigitte and Siegfried Meyermentioning

confidence: 99%

mentioning

confidence: 99%

Modeling Heat Dissipation at the Nanoscale: An Embedding Approach for Chemical Reaction Dynamics on Metal Surfaces

Meyer

Reuter

2014

Angew Chem Int Ed

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“…Thus, it would also be a fair assumption that the surface of the catalyst has a low coverage of the reactant while predominantly being saturated by other compounds in the feed. Considering the different species as inhibitors competing for the active sites on the catalyst, the 1 st order rate constants can be expressed by the availability of free sites, in a Langmuir-Hinshelwood kinetic model [63,64]:…”

Section: Inhibition Strength Of H2s H2o and Chlorinementioning

confidence: 99%

Deactivation of Ni-MoS2 by bio-oil impurities during hydrodeoxygenation of phenol and octanol

Mortensen

Gardini

Damsgaard

et al. 2016

Applied Catalysis A: General

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Deactivation of Ni-MoS2 by bio-oil impurities during hydrodeoxygenation of phenol and octanol, Applied Catalysis A, General http://dx.doi.org/10. 1016/j.apcata.2016.06.002 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Graphical abstractHighlights  Impurities as Cl, S, and K found in bio-oil will deactivate or inhibit MoS2-type catalyst by competing for the active sites  MoS2-based catalysts will produce sulfur containing hydrocarbons during HDO, but these can be removed again if a sufficiently high residence time is used enabling desulfurization of the product  Chlorine binds more strongly to the active sites of MoS2 based catalysts compared to H2O and H2S, while K irreversibly deactivates the catalyst 3 AbstractThe stability of Ni-MoS2/ZrO2 toward water, potassium, and chlorine containing compounds during hydrodeoxygenation (HDO) of a mixture of phenol and 1-octanol was investigated in a high pressure gas and liquid continuous flow fixed bed setup at 280°C and 100 bar. To maintain the stability of the catalyst, sufficient co-feeding of a sulfur source was necessary to avoid oxidation of the sulfide phase by oxygen replacement of the edge sulfur atoms in the MoS2 structure. However, the addition of sulfur to the feed gas resulted in the formation of sulfur containing compounds, mainly thiols, in the oil product if the residence time was too low. At a weight hourly space velocity (WHSV) of 4.9 h -1 the sulfur content in the liquid product was 980 ppm by weight, but this could be decreased to 5 ppm at a WHSV of 1.4 h -1 . A high co-feed of sulfur was needed when water was present in the feed and the H2O/H2S molar ratio should be below ca. 10 to maintain a decent stability of the catalyst. Chlorine containing compounds caused a reversible deactivation of the catalyst when co-fed to the reactor, where the catalytic activity could be completely regained when removing it from the feed. Commonly, chlorine, H2O, and H2S all inhibited the activity of the catalyst by competing for the active sites, with chlorine being by far the strongest inhibitor and H2S and H2O of roughly the same strength. Dissimilar, potassium was a severe poison and irreversibly deactivated the catalyst to <5% degree of deoxygenation when impregnated on the catalyst in a stoichiometric ratio relative to the active metal. This deactivation was a result of adsorption of potassium on the edge vacancy sites of the MoS2 slabs.

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“…Note that heterogeneous catalysis makes up the largest part of industrial processing (85-90%) and is therefore a very relevant class of reactions [30]. However, heterogeneous catalytic reactions are chosen merely for convenience and energy efficiency as the core idea of pulsed activation does not critically depend on it.…”

Section: Why Heterogeneous Catalysis?mentioning

confidence: 99%

“…Note that strictly speaking ν is also temperature dependent, but this dependence is so much weaker than that of the exponential that it is usually neglected. [30] 24…”

Section: Catalyst Is Optimized For Multiple Tasks Simultaneouslymentioning

confidence: 99%