DOCSLIB.ORG

Surface Models in Heterogeneous Catalysis the Synthesis of Ammonia and the Conversion of Carbon Monoxide

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Surface Models in Heterogeneous Catalysis the Synthesis of Ammonia and the Conversion of Carbon Monoxide JOURNAL OF CATALYSIS 8, 29-35 (1967) Surface Models in Heterogeneous Catalysis The Synthesis of Ammonia and the Conversion of Carbon Monoxide G. PARRAVANO From the Deparzment qf Chemical and Metallurgical Engineering, University qf Michigan Ann Arbor, Machigan Received November 16, 1966, revised January 16, 1967 The establishment of chemical equilibria between gas and solid catalysts during the synthesis of NH3 and the conversion of CO is considered. Suitable solid-gas equilibrium reactions are discussed. With the correct choice of the rate-controlling step, the equilib- rium surface models are able to reproduce the experimental expressions for the rates of reaction. These models represent a drastic departure from the concept of a fixed, hetero- geneous surface that has been extensively used in the past for the interpretation of the experimental results on the above reactions. The two approaches, however, complement each other and the validity of each one may well be justified under different experimental conditions. Thus, a model may be considered the extension of the other by modification of some of the parameters of the system. Over the past several years many investi- view and it is certainly invalid for relatively gations have been carried out on the catalytic long periods of catalyst operation. It is, synthesis of NH3 and on the conversion of therefore, of interest to consider other CO. The studies have generally been directed possibilities more physically justifiable. toward the understanding of the nature, In this direction it seems particularly properties, and operation of the catalytic important to consider the possibility that surface through the analysis of experimental equilibration reactions between surface and results of reaction rates. gas phase modify the chemical composition While the nature of the preponderant of the surface and, as a result, its chemical surface intermediates is still uncertain, the reactivity and catalytic activity (1). The. physical model of the surface is similar for model of an equilibrium surface must also all the reaction schemes advanced so far. be based upon several assumptions and, in Essentially, the surface is considered as a some instances, may not turn out to be more fixed array of atomic centers with catalytic compelling than its “frozen” counterpart, properties controlled by the physicochemical but it offers a more plausible surface picture, manipulation of the catalyst prior to use. in accord with the increased knowledge of These reaction schemes assume that at surface transport processes and consistent synthesis conditions no modification of with the realization of the ready occur- surface properties occurs. rence of the latter even at moderately low At the temperatures in which both re- temperatures (2). actions have been studied, there is likelihood The basic ideas on the role of surface of ready surface mobility bringing redistri- equilibration reactions in catalytic kinetics bution of matter between various parts of were formulated several years ago (S), but the surface and between the surface and the no attempt has been made to apply these gas phase. The model of aLLfrozen” surface, concepts to the reactions of NH, synthesis although mathematically successful, is prob- and of CO conversion. For the latter reaction, ably unrealistic from a physical point of a recent, study (4) employing a kinetic 29 30 G. PARRAVANO relaxation method has shown the correctness brings us to consider the following reaction of treating the overall reaction as a sequence sequence : of two steps, one of which represents the equilibrium between surface and gas phase. N&g) + Hdg) -+ &K44 (4 In this paper we wish to show that, by N2H2(a) + 2Hz(g) + 2NH3(g) (b) employing a surface model in which equili- bration reactions with the gas phase take To bring out explicitly the possible influences place concurrently with the catalytic reac- of reaction steps (a) and (b) upon the tion, and thereby modify the properties of activity of the surface, the rates of steps (a) the surface, it is possible to obtain a satis- and (b), V~ and 2)b,are expressed in terms of factory agreement with the experimental first order dependence upon the gas partial rate results. pressures. Surface effects upon the rate of reaction are considered by means of a AMMONIA SYNTHESIS function of the concentration of surface A large number of studies on the reaction intermediates, f([N2H2]), or Nz + 3Hz + 2NH3 0) va/A = kf,([N&l)p~,p~, - ~‘J’aWzHzl) (3) have shown that the experimental observa- tions can be satisfactorily represented by a vt,/A = k&([&&])&~ - ~‘bf’b([Ndbl) rate expression x PRHl (4) where I&, k’,, kb, k’b are the rate of reaction dpNHa/dt = ~~N,@&~HI)‘-~ (2) steps (a) and (b) per unit surface area, A, where /3 = 0.5 for a typical iron catalyst gas partial pressure, and [N2H2]. For step (a) under conditions sufficiently removed from at complete equilibration let us set equilibrium (5). The generally accepted interpretation of Eq. (2) considers the [N2H2lequil(a) = &&'N (5) overall reaction occurring as a sequence of elementary steps taking place on a non- where K, is the equilibrium constant for re- uniform catalytic surface. The surface is action step (a). Substituting the equilibrium pictured as an array of sites with reactivity condition (5) into the rate equation (3) and varying according to an ad hoc distribution using the expression of the rate at equi- function, which controls the chemisorption librium va = 0, Eq. (3) becomes of Nz. The result is a Freundlich isotherm, whose pressure dependence is assumed to be valA = k.fd[NzHzl)~PN~PH, the correct value to fit the experimentally - [NJ3lequil(a)lKaj (6) determined dependence of the rate upon the Similarly for reaction step (b), the equi- partial pressure of Nz. This scheme results librium condition gives in a large degree of consistency among various experimental measurements of reac- [NdLIequil(b) = @/Kb) (Pm/P& (7) tion rates, adsorption heats, and isotope where Kb is the equilibrium constant of effects. However, it is not possible to provide an independent physical justification for reaction step (b). Substituting the equi- librium condition (7) into the rate expression the assumed distribution function of the Freundlich isotherm. (4) and using the expression for the rate at equilibrium vb = 0, it is found In the present discussion, we shall retain two of the features common to the majority h/A = h?b([Ndhl) ( &, of the analytical treatments suggested so - (PaHsIKb[N2H2Iequil(b)) ] (3) far, namely that the kinetically determining step is the chemisorption of Nz and that the In a catalytic flow reactor steady state preponderant surface intermediates are imine conditions prevail, and, as a result, the radicals, NH, or closely analogous species concentration of adsorbed species at steady containing nitrogen and hydrogen (6). This state [NzH&, must lie between [N2H2]equii(a) SYNTHESIS OF NH3 AND CONVERSION OF CO 31 and [NzH2]equii(b).Since the majority of the “TB-” H-N=yN-H experimental results indicate that k, < kb, Fe Fe Fe we shall assume the limiting case W&.lss E PLEJrqoiuw (9) (I) (II) The steady state rate of reaction (1) is us8% va. In the rate equation (6) an explicit Alternatively, direct r-bond complexing form of the function f([N2H2]) should be with surface Fe atoms may be considered introduced. Since the rate of formation of (II). There is increasing evidence for the role NzHz [reaction step (a)] is adversely influ- of this type of surface bond in several enced by [NZHS],it is possible to set heterogeneous catalytic reactions (hydro- fd[N&l) = [NdWm~ (10) genation, isomerization, polymerization) (7) , but it is less likely for bonding Nz, since the where m, is a constant. If reaction step (a) corresponding ?r orbitals are energetically is the slowest of the sequence, its reverse more stable. The atomic structure of the reaction may be neglected, and from Eq. (6), catalytic surface is unknown, but in the (7), (9), and (lo), one gets presence of impurities of various kinds (catalyst, gas phase) at the temperatures employed for the synthesis, it is likely that = k,Kb”aPN,(p~,/paHs)m’ (11) a relatively thick surface layer compound (or alloy) may be formed with structure and For m, = 0.5, the rate expressions (11) and (2) are similar. properties closer to those of a metallic salt To carry further the analysis of the (nitride, hydride, nitrohydride) than to reactive surface, let us focus the discussion those of metallic Fe. Strong support for this upon step (a) and suggest some possibilities view was obtained by measuring the adsorp- for its occurrence. Equation (11) is rewritten tion of Nz during the decomposition of NH,. as follows : On W it was found that the amount adsorbed was several times as much as that required to completely saturate the surface (8). The thickness of the nitride layer is controlled by the relative rates of nitride where koxpti = k~b0.6(pNH~/pN2)-’ is the rate formation and decomposition, and the coefficient obtained directly from the experi- temperatures prevailing during synthesis mental results and k, is the true rate con- conditions would favor relatively thick stant, independent of the partial pressure of surface nitride layers. It is also pertinent to the gaseouscomponents. recall the well-known work on the effect of The molecular structure of the dimer promoters, showing that nonreducible oxides radical is unknown, but likely it involves tend to concentrate on the surface of the Q and ?r bonds, by sp hybridization of the crystallites (9). corresponding atomic orbitals of Nz, giving If this picture of the surface is accepted, a flat, linear species. The -N=N- bond the equilibrium of formation of the surface distance is = 1.20 A” [1.24 A0 in Nz(CH,)z, compound by means of reaction step (a) 1.13 A” in diazomethane].
Load more

Recommended publications
  • Surface Reactions and Chemical Bonding in Heterogeneous Catalysis
    Surface reactions and chemical bonding in heterogeneous catalysis Henrik Öberg Doctoral Thesis in Chemical Physics at Stockholm University 2014 Thesis for the Degree of Doctor of Philosophy in Chemical Physics Department of Physics Stockholm University Stockholm 2014 c Henrik Oberg¨ ISBN 978-91-7447-893-8 Abstract This thesis summarizes studies which focus on addressing, using both theoretical and experimental methods, fundamental questions about surface phenomena, such as chemical reactions and bonding, related to processes in heterogeneous catalysis. The main focus is on the theoretical approach and this aspect of the results. The included articles are collected into three categories of which the first contains detailed studies of model systems in heterogeneous catalysis. For example, the trimerization of acetylene adsorbed on Cu(110) is measured using vibrational spectroscopy and modeled within the framework of Density Functional Theory (DFT) and quantitative agreement of the reaction barriers is obtained. In the second category, aspects of fuel cell catalysis are discussed. O2 dissociation is rate-limiting for the reduction of oxygen (ORR) under certain conditions and we find that adsorbate-adsorbate interactions are decisive when modeling this reaction step. Oxidation of Pt(111) (Pt is the electrocatalyst), which may alter the overall activity of the catalyst, is found to start via a PtO-like surface oxide while formation of a-PtO2 trilayers precedes bulk oxidation. When considering alternative catalyst materials for the ORR, their stability needs to be investigated in detail under realistic conditions. The Pt/Cu(111) skin alloy offers a promising candidate but segregation of Cu atoms to the surface is induced by O adsorption.
    [Show full text]
  • Water Splitting by Heterogeneous Catalysis
    !"#$ #"%"" &' () * ( +# ,% - . ( (.( ( . %/ .0! 1 ( % 2 3 . 4 . 5 % . . % . . . . . . 3 % !# 3 ( 3 ( 3 ( 3 %/. . - % . (. 6 7 % ( 2!0! . (/ (3 . 7 % ( ( 3 % . 3 ( %/ . 8 9 3 8 % ( :;0 9 . <= 3 9 . % ( . ( 3 > % !"#$ ?@@ %% @ A B ?? ? ? #;C#C# ,8D$CD#$$D$":D! ,8D$CD#$$D$";"C ! " # $ (#" D# WATER SPLITTING BY HETEROGENEOUS CATALYSIS Henrik Svengren Water splitting by heterogeneous catalysis Henrik Svengren ©Henrik Svengren, Stockholm University 2017 ISBN print 978-91-7797-039-2 ISBN PDF 978-91-7797-040-8 Printed in Sweden by Universitetsservice US-AB, Stockholm 2017 Distributed by the Department of Materials and Environmental Chemistry To my beloved family Cover image + Heterogeneous catalysis of water oxidation according to 2H2O ĺ O2 + 4H on CoSbO4/CoSb2O6, investigated in Paper II. The figure is composed of SEM- and TEM images, structural drawings, reactant- and product molecules. i Examination Faculty opponent Docent Tomas Edvinsson Solid State Physics Department of Engineering Sciences Uppsala University,
    [Show full text]
  • Catalytic Oxidation of NO to NO2 for Nitric Acid Production Over a Pt
    1 Catalytic oxidation of NO to NO2 for nitric acid production over a Pt/Al2O3 catalyst Ata ul Rauf Salmana, Bjørn Christian Engerb, Xavier Auvraya c, Rune Lødengb, Mohan Menond, David Wallerd, Magnus Rønninga* a Department of Chemical Engineering, Norwegian University of Science and Technology (NTNU), Sem Sælands vei 4, NO-7491 Trondheim, Norway. b SINTEF Industry, Kinetic and Catalysis group, P.O. Box 4760 Torgarden, NO-7465 Trondheim, Norway. c Current address: Competence Centre for Catalysis, Chemical Engineering, Chalmers University of Technology, S-412 96 Gothenburg, Sweden d YARA Technology Center, Herøya Forskningspark, Bygg 92, Hydrovegen 67, NO-3936 Porsgrunn, Norway. * Corresponding author. Tel.: +47 73594121. E-mail address: [email protected] (M. Rønning). 2 Abstract The oxidation of nitric oxide (NO) to nitrogen dioxide (NO2) is a key step both in NOx abatement technologies as well as in the Ostwald process for nitric acid production. A 1 wt.% Pt/Al2O3 catalyst was used to study oxidation of nitric oxide at two different concentrations of NO; 400 ppm NO (representative of engine exhaust treatment) and 10% NO (nitric acid plant). The catalyst was characterised using N2 adsorption and CO chemisorption. The effect of temperature and feed concentration on catalytic activity was investigated. For a feed comprising of 10% NO and 6% O2, Pt/Al2O3 exhibits significant catalytic activity above o 300 C. Addition of 15% H2O in the feed had an insignificant effect on activity of the catalyst. We report for the first time the kinetics for oxidation of NO to NO2 under nitric acid plant conditions. An apparent activation energy of 33 kJ/mol was observed.
    [Show full text]
  • PDF (Chapter 5
    ~---=---5 __ Heterogeneous Catalysis 5.1 I Introduction Catalysis is a term coined by Baron J. J. Berzelius in 1835 to describe the property of substances that facilitate chemical reactions without being consumed in them. A broad definition of catalysis also allows for materials that slow the rate of a reac­ tion. Whereas catalysts can greatly affect the rate of a reaction, the equilibrium com­ position of reactants and products is still determined solely by thermodynamics. Heterogeneous catalysts are distinguished from homogeneous catalysts by the dif­ ferent phases present during reaction. Homogeneous catalysts are present in the same phase as reactants and products, usually liquid, while heterogeneous catalysts are present in a different phase, usually solid. The main advantage of using a hetero­ geneous catalyst is the relative ease of catalyst separation from the product stream that aids in the creation of continuous chemical processes. Additionally, heteroge­ neous catalysts are typically more tolerant ofextreme operating conditions than their homogeneous analogues. A heterogeneous catalytic reaction involves adsorption of reactants from a fluid phase onto a solid surface, surface reaction of adsorbed species, and desorption of products into the fluid phase. Clearly, the presence of a catalyst provides an alter­ native sequence of elementary steps to accomplish the desired chemical reaction from that in its absence. If the energy barriers of the catalytic path are much lower than the barrier(s) of the noncatalytic path, significant enhancements in the reaction rate can be realized by use of a catalyst. This concept has already been introduced in the previous chapter with regard to the CI catalyzed decomposition of ozone (Figure 4.1.2) and enzyme-catalyzed conversion of substrate (Figure 4.2.4).
    [Show full text]
  • Heterogeneous Catalysis on Metal Oxides
    catalysts Review Heterogeneous Catalysis on Metal Oxides Jacques C. Védrine ID Laboratoire de Réactivité de Surface, Université P. & M. Curie, Sorbonne Université, UMR-CNRS 7197, 4 Place Jussieu, F-75252 Paris, France; [email protected]; Tel.: +33-1-442-75560 Received: 8 October 2017; Accepted: 27 October 2017; Published: 10 November 2017 Abstract: This review article contains a reminder of the fundamentals of heterogeneous catalysis and a description of the main domains of heterogeneous catalysis and main families of metal oxide catalysts, which cover acid-base reactions, selective partial oxidation reactions, total oxidation reactions, depollution, biomass conversion, green chemistry and photocatalysis. Metal oxide catalysts are essential components in most refining and petrochemical processes. These catalysts are also critical to improving environmental quality. This paper attempts to review the major current industrial applications of supported and unsupported metal oxide catalysts. Viewpoints for understanding the catalysts’ action are given, while applications and several case studies from academia and industry are given. Emphases are on catalyst description from synthesis to reaction conditions, on main industrial applications in the different domains and on views for the future, mainly regulated by environmental issues. Following a review of the major types of metal oxide catalysts and the processes that use these catalysts, this paper considers current and prospective major applications, where recent advances in the science
    [Show full text]
  • Heterogeneous Catalytic Hydrogenation
    •Platinum Metals Rev., 2012, 56, (4), 236–241• Heterogeneous Catalytic Hydrogenation Platinum group metals as hydrogenation catalysts in a two-day course http://dx.doi.org/10.1595/147106712X654187 http://www.platinummetalsreview.com/ Reviewed by Fabrizio Nerozzi Introduction Johnson Matthey, Catalysis and Chiral Technologies, Heterogeneous catalytic hydrogenations are important Orchard Road, Royston, Hertfordshire SG8 5HE, UK reactions that fi nd wide industrial application in Email: [email protected] the production of pharmaceuticals, agrochemicals, fi ne chemicals, fl avours, fragrances and dietary supplements. The reactions are generally highly selective and easy to work up, the catalyst can often be recovered and recycled, and the processes are atom effi cient. It is therefore no surprise that somewhere between 10–20% of the reactions used to produce chemicals today are catalytic hydrogenations. Despite the importance of the technique, and mainly because of its multidisciplinary nature, development chemists and engineers have a hard time fi nding training on this highly specialised subject. Scientifi c Update has fi lled this gap with a training course run for the fi rst time on the 16th and 17th of April 2012, in Brussels, Belgium (1). Attended by 35 scientists from 10 European countries and the USA, representing 27 chemical companies and research institutions, the course was an extensive scientifi c overview of heterogeneous catalytic hydrogenation, but also touched on engineering, safety and economic topics. The tutor was Felix Roessler, a catalysis expert who during his long career has worked at Roche and DSM, was honoured twice with the Sandmeyer Award granted by the Swiss Chemical Society (2), has authored 18 publications or monographs and holds 4 patents.
    [Show full text]
  • Design of Molecular Water Oxidation Catalysts Stabilized by Ultrathin Inorganic Overlayers—Is Active Site Protection Necessary?
    inorganics Article Design of Molecular Water Oxidation Catalysts Stabilized by Ultrathin Inorganic Overlayers—Is Active Site Protection Necessary? Laurent Sévery 1 , Sebastian Siol 2 and S. David Tilley 1,* 1 Department of Chemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland; [email protected] 2 EMPA, Uberlandstrasse 129, 8600 Dubendorf, Switzerland; [email protected] * Correspondence: [email protected]; Tel.: +41-44-635-46-75 Received: 4 September 2018; Accepted: 27 September 2018; Published: 29 September 2018 Abstract: Anchored molecular catalysts provide a good step towards bridging the gap between homogeneous and heterogeneous catalysis. However, applications in an aqueous environment pose a serious challenge to anchoring groups in terms of stability. Ultrathin overlayers embedding these catalysts on the surface using atomic layer deposition (ALD) are an elegant solution to tackle the anchoring group instability. The propensity of ALD precursors to react with water leads to the question whether molecules containing aqua ligands, such as most water oxidation complexes, can be protected without side reactions and deactivation during the deposition process. We synthesized two iridium and two ruthenium-based water oxidation catalysts, which contained an aqua ligand (Ir–OH2 and Ru–OH2) or a chloride (Ir–Cl and Ru–Cl) that served as a protecting group for the former. Using a ligand exchange reaction on the anchored and partially embedded Ru–Cl, the optimal overlayer thickness was determined to be 1.6 nm. An electrochemical test of the protected catalysts on meso-ITO showed different behaviors for the Ru and the Ir catalysts. The former showed no onset difference between protected and non-protected versions, but limited stability.
    [Show full text]
  • Heterogeneous Catalyst Deactivation and Regeneration: a Review
    Catalysts 2015, 5, 145-269; doi:10.3390/catal5010145 OPEN ACCESS catalysts ISSN 2073-4344 www.mdpi.com/journal/catalysts Review Heterogeneous Catalyst Deactivation and Regeneration: A Review Morris D. Argyle and Calvin H. Bartholomew * Chemical Engineering Department, Brigham Young University, Provo, UT 84602, USA; E-Mail: [email protected] * Author to whom correspondence should be addressed; E-Mail: [email protected]; Tel: +1-801-422-4162, Fax: +1-801-422-0151. Academic Editor: Keith Hohn Received: 30 December 2013 / Accepted: 12 September 2014 / Published: 26 February 2015 Abstract: Deactivation of heterogeneous catalysts is a ubiquitous problem that causes loss of catalytic rate with time. This review on deactivation and regeneration of heterogeneous catalysts classifies deactivation by type (chemical, thermal, and mechanical) and by mechanism (poisoning, fouling, thermal degradation, vapor formation, vapor-solid and solid-solid reactions, and attrition/crushing). The key features and considerations for each of these deactivation types is reviewed in detail with reference to the latest literature reports in these areas. Two case studies on the deactivation mechanisms of catalysts used for cobalt Fischer-Tropsch and selective catalytic reduction are considered to provide additional depth in the topics of sintering, coking, poisoning, and fouling. Regeneration considerations and options are also briefly discussed for each deactivation mechanism. Keywords: heterogeneous catalysis; deactivation; regeneration 1. Introduction Catalyst deactivation, the loss over time of catalytic activity and/or selectivity, is a problem of great and continuing concern in the practice of industrial catalytic processes. Costs to industry for catalyst replacement and process shutdown total billions of dollars per year. Time scales for catalyst deactivation vary considerably; for example, in the case of cracking catalysts, catalyst mortality may be on the order of seconds, while in ammonia synthesis the iron catalyst may last for 5–10 years.
    [Show full text]
  • Molecular Enhancement of Heterogeneous CO2 Reduction
    PERSPECTIVE https://doi.org/10.1038/s41563-020-0610-2 Molecular enhancement of heterogeneous CO2 reduction Dae-Hyun Nam 1,7, Phil De Luna 1,2,3,7, Alonso Rosas-Hernández 4,5, Arnaud Thevenon 4,5, Fengwang Li 1, Theodor Agapie4,5, Jonas C. Peters4,5, Osama Shekhah 6, Mohamed Eddaoudi 6 and Edward H. Sargent 1 ✉ The electrocatalytic carbon dioxide reduction reaction (CO2RR) addresses the need for storage of renewable energy in valuable carbon-based fuels and feedstocks, yet challenges remain in the improvement of electrosynthesis pathways for highly selective hydrocarbon production. To improve catalysis further, it is of increasing interest to lever synergies between heterogeneous and homogeneous approaches. Organic molecules or metal complexes adjacent to heterogeneous active sites provide additional bind- ing interactions that may tune the stability of intermediates, improving catalytic performance by increasing Faradaic efficiency (product selectivity), as well as decreasing overpotential. We offer a forward-looking perspective on molecularly enhanced het- erogeneous catalysis for CO2RR. We discuss four categories of molecularly enhanced strategies: molecular-additive-modified heterogeneous catalysts, immobilized organometallic complex catalysts, reticular catalysts and metal-free polymer catalysts. We introduce present-day challenges in molecular strategies and describe a vision for CO2RR electrocatalysis towards multi-carbon products. These strategies provide potential avenues to address the challenges of catalyst activity, selectivity and stability in the further development of CO2RR. he electrochemical carbon dioxide (CO2) reduction reac- loenzymes, which are able to mediate challenging multi-electron/ tion (CO2RR) to fuels and chemical feedstocks, powered by proton reductive transformations at remarkably fast rates with very renewable electricity, offers a pathway to long-term seasonal little applied bias8.
    [Show full text]
  • Theoretical Studies in Heterogeneous Catalysis: Towards a Rational Design of Novel Catalysts for Hydrodesulfurization and Hydrogen Production
    BNL-81930-2009-BC Theoretical Studies in Heterogenous Catalysis: Towards a Rational Design of Novel Catalysts for Hydrodesulfurization and Hydrogen Production José A. Rodriguez and Ping Liu To be published in “New Developments in QuantumChemistry” October 2008 Chemistry Department Brookhaven National Laboratory P.O. Box 5000 Upton, NY 11973-5000 www.bnl.gov Notice: This manuscript has been authored by employees of Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. The publisher by accepting the manuscript for publication acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. This preprint is intended for publication in a journal or proceedings. Since changes may be made before publication, it may not be cited or reproduced without the author’s permission. DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, nor any of their contractors, subcontractors, or their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or any third party’s use or the results of such use of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof or its contractors or subcontractors.
    [Show full text]
  • Frontiers at the Interface of Homogeneous and Heterogeneous Catalysis
    FRONTIERS AT THE INTERFACE OF HOMOGENEOUS AND HETEROGENEOUS CATALYSIS Meeting of the Catalysis Science Program Chemical Sciences, Geosciences and Biosciences Division Office of Basic Energy Sciences U.S. Department of Energy Westin Annapolis Annapolis, Maryland June 30 – July 2, 2013 This document was produced under contract number DE-AC05-060R23100 between the U.S. Department of Energy and Oak Ridge Associated Universities. FOREWORD The 2013 Catalysis Science Program Meeting is sponsored by the Division of Chemical Sciences, Geosciences and Biosciences, Office of Basic Energy Sciences (BES), U.S. Department of Energy. It is being held on June 30 through July 2, 2013, at the Westin Annapolis Hotel, Annapolis, Maryland. The purposes of this meeting are to discuss the recent advances in the chemical, physical, and biological bases of catalysis science, to foster exchange of ideas and cooperation among participants, and to discuss the new challenges and opportunities recently emerging in energy technologies. Catalysis activities within BES emphasize fundamental research aimed at initially understanding and finally controlling the chemical conversion of natural and artificial feedstocks. The long-term goal of this research is to discover fundamental principles and produce ever more insightful approaches to predict structure-reactivity behavior. Such knowledge, integrated with advances in chemical and materials synthesis, in situ and operando analytical instrumentation, and chemical kinetics and quantum chemistry methods, will allow the control of chemical reactions along desired pathways. Ultimately, this new knowledge should impact the efficiency of conversion of natural resources into fuels, chemicals, materials, or other forms of energy, while minimizing the impact to the environment. This year’s meeting is focused on three topical areas: (i) the interface of homogeneous and heterogeneous catalysis, (ii) catalysis for biomass or solar energy conversion, and (iii) molecular catalysis, with an emphasis on organic synthesis.
    [Show full text]
  • Nitrogen-Containing Ligands for Asymmetric Homogeneous and Heterogeneous Catalysis
    Chem. Rev. 2000, 100, 2159−2231 2159 Nitrogen-Containing Ligands for Asymmetric Homogeneous and Heterogeneous Catalysis Fabienne Fache, Emmanuelle Schulz, M. Lorraine Tommasino, and Marc Lemaire* Laboratoire de Catalyse et Synthe`se Organique, UMR 5622, UCBL, CPE, 43 Bd du 11 Novembre 1918, 69622 Villeurbanne Cedex, France Received December 2, 1999 Contents VIII.4.1. Diels−Alder Reactions 2198 VIII.4.2. 1,3-Dipolar Cycloadditions 2203 I. Introduction 2159 VIII.5. Addition of Nucleophiles to CdC Bonds 2204 II. C−H Bond Formation 2161 VIII.5.1. Michael Additions 2204 II.1. Hydrogen as Reducing Agent 2161 VIII.5.2. Free Radical Conjugate Additions 2206 II.1.1. Homogeneous Systems 2162 VIII.6. Hydroformylation 2206 II.1.2. Heterogeneous Systems 2164 VIII.6.1. Regioselective Hydroformylation 2207 II.2. Borohydride and Other Inorganic Hydrides as 2165 Reducing Agents VIII.6.2. Enantioselective Hydroformylation 2207 II.2.1. Homogeneous Systems 2166 VIII.7. Carbonylation 2208 II.2.2. Heterogeneous Systems 2168 VIII.8. Grignard Cross-Coupling 2210 − II.3. Hydride Transfer Reduction 2169 VIII.9. Carbene Insertion into C H Bonds 2210 d II.3.1. Homogeneous Systems 2169 VIII.10. Addition to C O Bonds 2212 II.3.2. Heterogeneous Systems 2171 VIII.10.1. Aldol Reactions 2212 II.4. Hydrosilylation 2172 VIII.10.2. Nucleophilic Addition of Dialkylzinc 2215 III. C−O Bond Formation 2173 Reagents III.1. Epoxidation of Unfunctionalized Olefins 2173 VIII.10.3. Trimethylsilylcyanation 2218 III.1.1. Homogeneous Catalysis 2173 VIII.10.4. Ene Reaction 2220 d III.1.2. Heterogeneous System 2176 VIII.11.
    [Show full text]