Rutger A. van Santen

University of Oxford, Oxford, England, United Kingdom

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Publications (687)1638.18 Total impact

  • Rutger A. van Santen
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    ABSTRACT: Review: aspects of computational chemistry as well as kinetics and physical state of the reactive catalyst, 22 refs.
    ChemInform 11/2014; 45(46).
  • John M. Brown, Andreas Pfaltz, Rutger A. van Santen
    ChemInform 11/2014; 45(44).
  • Ivo A. W. Filot, Rutger A. van Santen, Emiel J. M. Hensen
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    ABSTRACT: Microkinetics simulations are presented based on DFT-determined elementary reaction steps of the Fischer–Tropsch (FT) reaction. The formation of long-chain hydrocarbons occurs on stepped Ru surfaces with CH as the inserting monomer, whereas planar Ru only produces methane because of slow CO activation. By varying the metal–carbon and metal–oxygen interaction energy, three reactivity regimes are identified with rates being controlled by CO dissociation, chain-growth termination, or water removal. Predicted surface coverages are dominated by CO, C, or O, respectively. Optimum FT performance occurs at the interphase of the regimes of limited CO dissociation and chain-growth termination. Current FT catalysts are suboptimal, as they are limited by CO activation and/or O removal.
    Angewandte Chemie International Edition 08/2014; · 11.34 Impact Factor
  • John M. Brown, Andreas Pfaltz, Rutger A. van Santen
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    ABSTRACT: A graphical abstract is available for this content
    Catal. Sci. Technol. 08/2014;
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    ABSTRACT: Low-temperature Fischer–Tropsch reaction data are reported for Ru nanoparticles suspended in the water phase. Their activity and selectivity strongly depends on particle size, when varied between 1 to 5 nm. Small particles display high oxygenates selectivity. The Anderson–Schulz–Flory (ASF) chain-growth probability for oxygenates is significantly lower than that observed for hydrocarbons. The chain growth parameter for hydrocarbon formation is independent of particle size. For oxygenates it is constant only for particles larger than 3 nm. Oxygenate and hydrocarbon formation occur on different sites. The ASF chain-growth probability for oxygenate formation increases with temperature. For very small 1.2 nm particles it shows a maximum as a function of temperature. This unusual temperature dependence is due to relatively slow CO dissociation compared to the rate of C–C bond formation.
    Catal. Sci. Technol. 07/2014;
  • I. A. W. Filot, R. A. van Santen, E. J. M. Hensen
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    ABSTRACT: A comprehensive density functional theory study of the Fischer–Tropsch mechanism on the corrugated Ru(111) surface has been carried out. Elementary reaction steps relevant to the carbide mechanism and the CO insertion mechanism are considered. Activation barriers and reaction energies were determined for CO dissociation, C hydrogenation, CHx + CHy and CHx + CO coupling, CHxCHy–O bond scission and hydrogenation reactions, which lead to formation of methane and higher hydrocarbons. Water formation that removes O from the surface was studied as well. The overall barrier for chain growth in the carbide mechanism (preferred path CH + CH coupling) is lower than that for chain growth in the CO insertion mechanism (preferred path C + CO coupling). Kinetic analysis predicts that the chain-growth probability for the carbide mechanism is close to unity, whereas within the CO insertion mechanism methane will be the main hydrocarbon product. The main chain propagating surface intermediate is CH via CH + CH and CH + CR coupling (R = alkyl). A more detailed electronic analysis shows that CH + CH coupling is more difficult than coupling reactions of the type CH + CR because of the σ-donating effect of the alkyl substituent. These chain growth reaction steps are more facile on step-edge sites than on terrace sites. The carbide mechanism explains the formation of long hydrocarbon chains for stepped Ru surfaces in the Fischer–Tropsch reaction.
    Catal. Sci. Technol. 06/2014;
  • Rutger A. van Santen
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    ABSTRACT: Der perfekte Katalysator: Es wird untersucht, welche Vorzüge der gezielte Entwurf von Katalysatoren aus theoretischen Grundprinzipien bietet. Aspekte der Computerchemie sowie der Kinetik und des physikalischen Zustands des reaktiven Katalysators werden diskutiert.
    Angewandte Chemie 06/2014;
  • Rutger A van Santen
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    ABSTRACT: The perfect catalyst: The advances towards the ability to design a catalyst from first principles are explored. Aspects of computational chemistry as well as the kinetics and physical state of the reactive catalyst are discussed.
    Angewandte Chemie International Edition in English 06/2014; · 13.45 Impact Factor
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    ABSTRACT: Synchrotron X-ray diffraction coupled to atomic pair distribution function analysis and Reverse Monte Carlo simulations is used to determine the atomic-scale structure of Ru nanoparticle catalysts for the Fischer-Tropsch reaction. The rate of CO hydrogenation strongly correlates with the abundance of surface atoms with coordination numbers of 10 and 11. DFT calculations confirm that CO dissociation proceeds with a low barrier on these Ru surface atom ensembles.
    Chemical Communications 04/2014; · 6.38 Impact Factor
  • Xin Zhou, Emiel J. M. Hensen, Rutger A. van Santen, Can Li
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    ABSTRACT: Density functional theory (DFT) calculations are used to explore water adsorption and activation on different α-Ga2O3 surfaces, namely (001), (100), (110), and (012). The geometries and binding energies of molecular and dissociative adsorption are studied as a function of coverage. The simulations reveal that dissociative water adsorption on all the studied low-index surfaces are thermodynamically favorable. Analysis of surface energies suggests that the most preferentially exposed surface is (012). The contribution of surface relaxation to the respective surface energies is significant. Calculations of electron local density of states indicate that the electron-energy band gaps for the four investigated surfaces appears to be less related to the difference in coordinative unsaturation of the surface atoms, but rather to changes in the ionicity of the surface chemical bonds. The electrochemical computation is used to investigate the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) on α-Ga2O3 surfaces. Our results indicate that the (100) and (110) surfaces, which have low stability, are the most favorable ones for HER and OER, respectively.
    Chemistry - A European Journal 04/2014; · 5.93 Impact Factor
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    ABSTRACT: doi: 10.1021/jp500053u
    The Journal of Physical Chemistry C 03/2014; · 4.84 Impact Factor
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    ABSTRACT: Liposomes composed of fatty acids and phospholipids are frequently used as model systems for biological cell membranes. In many applications, the encapsulation of proteins and other bio-macromolecules in these liposomes is essential. Intriguingly, the concentration of entrapped material often deviates from that in the solution where the liposomes were formed in. While some reports mention reduced concentrations inside the vesicles, concentrations are also reported to be enhanced in other cases. To elucidate possible drivers for efficient encapsulation, we here investigate the encapsulation of model proteins in spontaneously forming vesicles using molecular dynamics simulations with a coarse grained force field for fatty acids, phospholipids as well as water-soluble and transmembrane proteins. We show that, in this model system, the encapsulation efficiency is dominated by the interaction of the proteins with the membrane, while no significant dependence is observed on the size of the encapsulated proteins nor on the speed of the vesicle formation, whether reduced by incorporation of stiff transmembrane proteins or by the blocking of the bilayer bulging by the presence of another membrane.
    The Journal of Physical Chemistry B 03/2014; · 3.61 Impact Factor
  • Rutger A van Santen, Minhaj Ghouri, Emiel M J Hensen
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    ABSTRACT: Microkinetics simulations are presented on the intrinsic activity and selectivity of the Fischer-Tropsch reaction with respect to the formation of long chain oxygenated hydrocarbons. Two different chain growth mechanisms are compared: the carbide chain growth mechanism and the CO insertion chain growth mechanism. The microkinetics simulations are based on quantum-chemical data on reaction rate parameters of the elementary reaction steps of the Fischer-Tropsch reaction available in the literature. Because the overall rate constant of chain growth remains too low the CO insertion chain growth mechanism is not found to produce higher hydrocarbons, except for ethylene and acetaldehyde or the corresponding hydrogenated products. According to the carbide mechanism available quantum-chemical data are consistent with high selectivity to long chain oxygenated hydrocarbon production at low temperature. The anomalous initial increase with temperature of the chain growth parameter observed under such conditions is reproduced. It arises from the competition between the apparent rate of C-O bond activation to produce "CHx" monomers to be inserted into the growing hydrocarbon chain and the rate of chain growth termination. The microkinetics simulations data enable analysis of selectivity changes as a function of critical elementary reaction rates such as the rate of activation of the C-O bond of CO, the insertion rate of CO into the growing hydrocarbon chain or the rate constant of methane formation. Simulations show that changes in catalyst site reactivity affect elementary reaction steps differently. This has opposing consequences for oxygenate production selectivity, so an optimizing compromise has to be found. The simulation results are found to be consistent with most experimental data available today. It is concluded that Fischer-Tropsch type catalysis has limited scope to produce long chain oxygenates with high yield, but there is an opportunity to improve the yield of C2 oxygenates.
    Physical Chemistry Chemical Physics 02/2014; · 4.20 Impact Factor
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    ABSTRACT: Fischer–Tropsch synthesis is an attractive process to convert alternative carbon sources, such as biomass, natural gas, or coal, to fuels and chemicals. Deactivation of the catalyst is obviously undesirable, and for a commercial plant it is of high importance to keep the catalyst active as long as possible during operating conditions. In this study, the reactivity of CO on carbon-covered cobalt surfaces has been investigated by means of density functional theory (DFT). An attempt is made to provide insight into the role of carbon deposition on the deactivation of two cobalt surfaces: the closed-packed Co(0001) surface and the corrugated Co(112̅1) surface. We also analyzed the adsorption and diffusion of carbon atoms on both surfaces and compared the mobility. Finally, the results for Co(0001) and Co(112̅1) are compared, and the influence of the surface topology is assessed.
    The Journal of Physical Chemistry C. 01/2014; 118(10):5317-5327.
  • Journal of Catalysis 12/2013; · 5.79 Impact Factor
  • Rutger van Santen
    ChemInform 10/2013; 44(42).
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    ABSTRACT: The influence of organic capping agents on the performance of Ru nanoparticles in aqueous-phase Fischer–Tropsch (FT) synthesis was investigated. Three organic capping agents were used: trimethyl(tetradecyl)ammonium bromide (TTAB), polyvinylpyrrolidone (PVP), and sodium 3-mercapto-1-propanesulfonate (SMPS). To exclude the effects of particle size, the capping agents were placed onto carbon-nanofiber-supported Ru nanoparticles of size 3.4 nm. The activity in the FT reaction increased in the order: Ru-SMPS≪Ru-PVP
    ChemCatChem 10/2013; 5(10). · 5.18 Impact Factor
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    ABSTRACT: The increasing availability of quantum-chemical data on surface reaction intermediates invites one to revisit unresolved mechanistic issues in heterogeneous catalysis. One such issue of particular current interest is the molecular basis of the Fischer-Tropsch reaction. Here we review current molecular understanding of this reaction that converts synthesis gas into longer hydrocarbons where we especially elucidate recent progress due to the contributions of computational catalysis. This perspective highlights the theoretical approach to heterogeneous catalysis that aims for kinetic prediction from quantum-chemical first principle data. Discussion of the Fischer-Tropsch reaction from this point of view is interesting because of the several mechanistic options available for this reaction. There are many proposals on the nature of the monomeric single C atom containing intermediate that is inserted into the growing hydrocarbon chain as well as on the nature of the growing hydrocarbon chain itself. Two dominant conflicting mechanistic proposals of the Fischer-Tropsch reaction that will be especially compared are the carbide mechanism and the CO insertion mechanism, which involve cleavage of the C-O bond of CO before incorporation of a CHx species into the growing hydrocarbon chain (the carbide mechanism) or after incorporation into the growing hydrocarbon chain (the CO insertion mechanism). The choice of a particular mechanism has important kinetic consequences. Since it is based on molecular information it also affects the structure sensitivity of this particular reaction and hence influences the choice of catalyst composition. We will show how quantum-chemical information on the relative stability of relevant reaction intermediates and estimates of the rate constants of corresponding elementary surface reactions provides a firm foundation to the kinetic analysis of such reactions and allows one to discriminate between the different mechanistic options. The paper will be concluded with a short perspective section dealing with the needs for future research. Many of the current key questions on the physical chemistry as well as computational study of heterogeneous catalysis relate to particular topics for further research on the fundamental aspects of Fischer-Tropsch catalysis.
    Physical Chemistry Chemical Physics 09/2013; · 4.20 Impact Factor
  • Rutger van Santen
    ChemInform 09/2013; 44(37).
  • Tianwei Zhu, Shi-Gang Sun, Rutger A. van Santen, Emiel J. M. Hensen
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    ABSTRACT: We studied clean and oxygen-covered surfaces of unreconstructed and reconstructed Pt(110) by density functional theory (DFT) calculations and used these data in thermodynamic considerations to establish the stabilities of these surfaces as a function of the oxygen surface coverage. The clean Pt(110) prefers to reconstruct into a (1 × n) missing-row structure with n = 2–4. The surface free energies of the three reconstructed surfaces are very similar within the accuracy of our calculations. Upon oxygen adsorption, the c(2 × 2) with 0.5 monolayer (ML) coverage on the unreconstructed surface is equally stable as the 0.5 ML coverage on the Pt(110)-(1 × 2) reconstructed surface. There is no clear transition between (1 × 1) and (1 × 2). With increasing oxygen pressure, the fully oxygen-covered (1 ML) Pt(110)-(1 × 2) becomes the most stable structure. We assume that this structure is relevant in the onset of the formation of bulk Pt-oxide. Compared to Au, we found that the Pt(110)-(1 × 2) surface is very stable even under very positive electro potential, and the (1 × 3) structure is not stabilized by impurities (e.g., oxygen).
    The Journal of Physical Chemistry C. 05/2013; 117(21):11251–11257.

Publication Stats

3k Citations
1,638.18 Total Impact Points

Institutions

  • 2014
    • University of Oxford
      Oxford, England, United Kingdom
  • 1988–2014
    • Technische Universiteit Eindhoven
      • • Department of Chemical Engineering and Chemistry
      • • Department of Biomedical Engineering
      • • Schuit Institute of Catalysis
      • • Department of Applied Physics
      Eindhoven, North Brabant, Netherlands
  • 2010–2012
    • University of Amsterdam
      • Institute for Molecular Sciences Van 't Hoff
      Amsterdam, North Holland, Netherlands
    • Simon Fraser University
      • Department of Chemistry
      Burnaby, British Columbia, Canada
    • Carnegie Institution for Science
      • Geophysical Laboratory
      Washington, WV, United States
  • 2011
    • Middle East Technical University
      • Department of Chemical Engineering
      Ankara, Ankara, Turkey
  • 2007–2011
    • Northeast Institute of Geography and Agroecology
      • State Key Laboratory of Catalysis
      Beijing, Beijing Shi, China
    • Leibniz Universität Hannover
      Hanover, Lower Saxony, Germany
  • 2009
    • University of Cape Town
      • Department of Chemical Engineering
      Cape Town, Province of the Western Cape, South Africa
  • 2003–2007
    • University of Groningen
      • Centre for Ecological and Evolutionary Studies (CEES)
      Groningen, Province of Groningen, Netherlands
  • 2005
    • N. D. Zelinsky Institute of Organic Chemistry
      Moskva, Moscow, Russia
    • Boreskov Institute of Catalysis
      Novo-Nikolaevsk, Novosibirsk, Russia
  • 2004
    • Universiteit Twente
      Enschede, Overijssel, Netherlands
    • IMSA Amsterdam
      Amsterdamo, North Holland, Netherlands
  • 2000–2003
    • National Technical University of Ukraine Kiev Polytechnic Institute
      • Faculty of Chemical Technology
      Kievo, Kyiv City, Ukraine
  • 1998
    • Università degli Studi di Torino
      • Dipartimento di Fisica
      Torino, Piedmont, Italy
    • The University of Edinburgh
      • School of Chemistry
      Edinburgh, Scotland, United Kingdom
  • 1996
    • Delft University of Technology
      Delft, South Holland, Netherlands
  • 1994
    • University of Liverpool
      Liverpool, England, United Kingdom