Liquid phase oxidation via heterogeneous catalysis organic synthesis and industrial applications

CERN Document Server

Clerici, Mario G

2013-01-01

Sets the stage for environmentally friendly industrial organic syntheses From basic principles to new and emerging industrial applications, this book offers comprehensive coverage of heterogeneous liquid-phase selective oxidation catalysis. It fully examines the synthesis, characterization, and application of catalytic materials for environmentally friendly organic syntheses. Readers will find coverage of all the important classes of catalysts, with an emphasis on their stability and reusability. Liquid Phase Oxidation via Heterogeneous Catalysis features contributions from an internation

Fundamental concepts in heterogeneous catalysis

CERN Document Server

Norskov, Jens K; Abild-Pedersen, Frank; Bligaard, Thomas

2014-01-01

This book is based on a graduate course and suitable as a primer for any newcomer to the field, this book is a detailed introduction to the experimental and computational methods that are used to study how solid surfaces act as catalysts.   Features include:First comprehensive description of modern theory of heterogeneous catalysisBasis for understanding and designing experiments in the field   Allows reader to understand catalyst design principlesIntroduction to important elements of energy transformation technologyTest driven at Stanford University over several semesters

Concepts in catalysis

International Nuclear Information System (INIS)

Boudart, M.

1992-01-01

This paper reports on concept in catalysis which are very important in heterogeneous catalysis, even today, when in spite of surface science, the complexity of events at a real catalytic surface is still evading the understanding necessary for design. In this paper the authors will attempt to give an update on evolving concepts in heterogeneous catalysis. The topics include: counting active centers on metal surfaces; the notion of turnover frequency for a catalytic cycle; the concept of structure (in) sensitive reactions; the ensemble (geometric) vs. The ligand (electronic) effect following Sachtler's school; the idea of a rate determining step and of a most abundant reactive intermediate; the effect of surface non-uniformity on catalytic kinetics; what makes catalytic cycles turnover

Bridging heterogeneous and homogeneous catalysis concepts, strategies, and applications

CERN Document Server

Li, Can

2014-01-01

This unique handbook fills the gap in the market for an up-to-date work that links both homogeneous catalysis applied to organic reactions and catalytic reactions on surfaces of heterogeneous catalysts.

International symposium on 'applications of zeolites in heterogeneous catalysis'

Energy Technology Data Exchange (ETDEWEB)

1978-11-01

The International Symposium on applications of zeolites in heterogeneous catalysis, organized by the Hungarian Chemical Society (Szeged, Hung. 9/11-14/78), included 48 papers, which were published in the Vertical Bar3Vertical BarActa Phys. Chem. (Szeged) 24.

Molecular catalysis science: Perspective on unifying the fields of catalysis.

Science.gov (United States)

Ye, Rong; Hurlburt, Tyler J; Sabyrov, Kairat; Alayoglu, Selim; Somorjai, Gabor A

2016-05-10

Colloidal chemistry is used to control the size, shape, morphology, and composition of metal nanoparticles. Model catalysts as such are applied to catalytic transformations in the three types of catalysts: heterogeneous, homogeneous, and enzymatic. Real-time dynamics of oxidation state, coordination, and bonding of nanoparticle catalysts are put under the microscope using surface techniques such as sum-frequency generation vibrational spectroscopy and ambient pressure X-ray photoelectron spectroscopy under catalytically relevant conditions. It was demonstrated that catalytic behavior and trends are strongly tied to oxidation state, the coordination number and crystallographic orientation of metal sites, and bonding and orientation of surface adsorbates. It was also found that catalytic performance can be tuned by carefully designing and fabricating catalysts from the bottom up. Homogeneous and heterogeneous catalysts, and likely enzymes, behave similarly at the molecular level. Unifying the fields of catalysis is the key to achieving the goal of 100% selectivity in catalysis.

Catalysis by Design: Well-Defined Single-Site Heterogeneous Catalysts

KAUST Repository

Pelletier, Jeremie

2016-03-09

ConspectusHeterogeneous catalysis, a field important industrially and scientifically, is increasingly seeking and refining strategies to render itself more predictable. The main issue is due to the nature and the population of catalytically active sites. Their number is generally low to very low, their "acid strengths" or " redox properties" are not homogeneous, and the material may display related yet inactive sites on the same material. In many heterogeneous catalysts, the discovery of a structure-activity reationship is at best challenging. One possible solution is to generate single-site catalysts in which most, if not all, of the sites are structurally identical. Within this context and using the right tools, the catalyst structure can be designed and well-defined, to reach a molecular understanding. It is then feasible to understand the structure-activity relationship and to develop predictable heterogeneous catalysis. Single-site well-defined heterogeneous catalysts can be prepared using concepts and tools of surface organometallic chemistry (SOMC). This approach operates by reacting organometallic compounds with surfaces of highly divided oxides (or of metal nanoparticles). This strategy has a solid track record to reveal structure-activity relationship to the extent that it is becoming now quite predictable. Almost all elements of the periodical table have been grafted on surfaces of oxides (from simple oxides such as silica or alumina to more sophisticated materials regarding composition or porosity).Considering catalytic hydrocarbon transformations, heterogeneous catalysis outcome may now be predicted based on existing mechanistic proposals and the rules of molecular chemistry (organometallic, organic) associated with some concepts of surface sciences. A thorough characterization of the grafted metal centers must be carried out using tools spanning from molecular organometallic or surface chemistry. By selection of the metal, its ligand set, and the

Surface science and model catalysis with ionic liquid-modified materials.

Science.gov (United States)

Steinrück, H-P; Libuda, J; Wasserscheid, P; Cremer, T; Kolbeck, C; Laurin, M; Maier, F; Sobota, M; Schulz, P S; Stark, M

2011-06-17

Materials making use of thin ionic liquid (IL) films as support-modifying functional layer open up a variety of new possibilities in heterogeneous catalysis, which range from the tailoring of gas-surface interactions to the immobilization of molecularly defined reactive sites. The present report reviews recent progress towards an understanding of "supported ionic liquid phase (SILP)" and "solid catalysts with ionic liquid layer (SCILL)" materials at the microscopic level, using a surface science and model catalysis type of approach. Thin film IL systems can be prepared not only ex-situ, but also in-situ under ultrahigh vacuum (UHV) conditions using atomically well-defined surfaces as substrates, for example by physical vapor deposition (PVD). Due to their low vapor pressure, these systems can be studied in UHV using the full spectrum of surface science techniques. We discuss general strategies and considerations of this approach and exemplify the information available from complementary methods, specifically photoelectron spectroscopy and surface vibrational spectroscopy. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Combination of sunlight irradiated oxidative processes for landfill leachate: heterogeneous catalysis (TiO2 versus homogeneous catalysis (H2O2

Directory of Open Access Journals (Sweden)

Oswaldo Luiz Cobra Guimarães

2013-04-01

Full Text Available The objective of this work was to study the treatment of landfill leachate liquid in nature, after the use of a combination of advanced oxidation processes. More specifically, it compared heterogeneous catalysis with TiO2 to homogeneous catalysis with H2O2, both under photo-irradiated sunlight. The liquid used for the study was the leachate from the landfill of the city of Cachoeira Paulista, São Paulo State, Brazil. The experiments were conducted in a semi-batch reactor open to the absorption of solar UV radiation, with 120 min reaction time. The factors and their respective levels (-1, 0 and 1 were distributed in a experimental design 24-1 with duplicate and triplicate in the central point, resulting in an array with 19 treatment trials. The studied factors in comparing the two catalytic processes were: liquid leachate dilution, TiO2 concentration on the reactor plate, the H2O2 amount and pH level. The leachate had low photo-catalytic degradability, with NOPC reductions ranging from 1% to a maximum of 24.9%. When considering each factor alone, neither homogeneous catalysis with H2O2, nor heterogeneous catalysis with TiO2, could degrade the percolated liquid without significant reductions (5% level in total NOPC. On the other hand, the combined use of homogenous catalysis with H2O2 and heterogeneous catalysis H2O2 resulted in the greatest reductions in NOPC. The optimum condition for the NOPC reduction was obtained at pH 7, dilution of percolated:water at 1:1 (v v-1 rate; excess of 12.5% H2O2 and coating plate reactor with 0.025 g cm-2 TiO2.

ISHHC XIII International Symposium on the Relations betweenHomogeneous and Heterogeneous Catalysis

Energy Technology Data Exchange (ETDEWEB)

Somorjai (Ed.), G.A.

2007-06-11

The International Symposium on Relations between Homogeneous and Heterogeneous Catalysis (ISHHC) has a long and distinguished history. Since 1974, in Brussels, this event has been held in Lyon, France (1977), Groeningen, The Netherlands (1981); Asilomar, California (1983); Novosibirsk, Russia (1986); Pisa, Italy (1989); Tokyo, Japan (1992); Balatonfuered, Hungary (1995); Southampton, United Kingdom (1999); Lyon, France (2001); Evanston, Illinois (2001) and Florence, Italy (2005). The aim of this international conference in Berkeley is to bring together practitioners in the three fields of catalysis, heterogeneous, homogeneous and enzyme, which utilize mostly nanosize particles. Recent advances in instrumentation, synthesis and reaction studies permit the nanoscale characterization of the catalyst systems, often for the same reaction, under similar experimental conditions. It is hoped that this circumstance will permit the development of correlations of these three different fields of catalysis on the molecular level. To further this goal we aim to uncover and focus on common concepts that emerge from nanoscale studies of structures and dynamics of the three types of catalysts. Another area of focus that will be addressed is the impact on and correlation of nanosciences with catalysis. There is information on the electronic and atomic structures of nanoparticles and their dynamics that should have importance in catalyst design and catalytic activity and selectivity.

Seventh BES [Basic Energy Sciences] catalysis and surface chemistry research conference

International Nuclear Information System (INIS)

1990-03-01

Research programs on catalysis and surface chemistry are presented. A total of fifty-seven topics are included. Areas of research include heterogeneous catalysis; catalysis in hydrogenation, desulfurization, gasification, and redox reactions; studies of surface properties and surface active sites; catalyst supports; chemical activation, deactivation; selectivity, chemical preparation; molecular structure studies; sorption and dissociation. Individual projects are processed separately for the data bases

Seventh BES (Basic Energy Sciences) catalysis and surface chemistry research conference

Energy Technology Data Exchange (ETDEWEB)

1990-03-01

Research programs on catalysis and surface chemistry are presented. A total of fifty-seven topics are included. Areas of research include heterogeneous catalysis; catalysis in hydrogenation, desulfurization, gasification, and redox reactions; studies of surface properties and surface active sites; catalyst supports; chemical activation, deactivation; selectivity, chemical preparation; molecular structure studies; sorption and dissociation. Individual projects are processed separately for the data bases. (CBS)

Heterogeneous Catalysis: Understanding for Designing, and Designing for Applications

OpenAIRE

Corma Canós, Avelino

2016-01-01

Despite the introduction of high-throughput and combinatorial methods that certainly can be useful in the process of catalysts optimization, it is recognized that the generation of fundamental knowledge at the molecular level is key for the development of new concepts and for reaching the final objective of solid catalysts by design … Corma Canós, A. (2016). Heterogeneous Catalysis: Understanding for Designing, and Designing for Applications. Angewandte Chemie International Edition. 55(21)...

Interrelation of chemistry and process design in biodiesel manufacturing by heterogeneous catalysis

NARCIS (Netherlands)

Dimian, A.C.; Srokol, Z.W.; Mittelmeijer-Hazeleger, M.C.; Rothenberg, G.

2010-01-01

The pros and cons of using heterogeneous catalysis for biodiesel manufacturing are introduced, and explained from a chemistry and engineering viewpoint. Transesterification reactions of various feed types are then compared in batch and continuous process operation modes. The results show that the

Chemistry, spectroscopy and the role of supported vanadium oxides in heterogeneous catalysis

NARCIS (Netherlands)

Weckhuysen, B.M.; Keller, D.E.

2003-01-01

Supported vanadium oxide catalysts are active in a wide range of applications. In this review, an overview is given of the current knowledge available about vanadium oxide-based catalysts. The review starts with the importance of vanadium in heterogeneous catalysis, a discussion of the molecular

Regulating the surface of nanoceria and its applications in heterogeneous catalysis

Science.gov (United States)

Ma, Yuanyuan; Gao, Wei; Zhang, Zhiyun; Zhang, Sai; Tian, Zhimin; Liu, Yuxuan; Ho, Johnny C.; Qu, Yongquan

2018-03-01

Ceria (CeO2) as a support, additive, and active component for heterogeneous catalysis has been demonstrated to have great catalytic performance, which includes excellent thermal structural stability, catalytic efficiency, and chemoselectivity. Understanding the surface properties of CeO2 and the chemical reactions occurred on the corresponding interfaces is of great importance in the rational design of heterogeneous catalysts for various reactions. In general, the reversible Ce3+/Ce4+ redox pair and the surface acid-base properties contribute to the superior intrinsic catalytic capability of CeO2, and hence yield enhanced catalytic phenomenon in many reactions. Particularly, nanostructured CeO2 is characterized by a large number of surface-bound defects, which are primarily oxygen vacancies, as the surface active catalytic sites. Many efforts have therefore been made to control the surface defects and properties of CeO2 by various synthetic strategies and post-treatments. The present review provides a comprehensive overview of recent progress in regulating the surface structure and composition of CeO2 and its applications in catalysis.

Solar fuels generation and molecular systems: is it homogeneous or heterogeneous catalysis?

Science.gov (United States)

Artero, Vincent; Fontecave, Marc

2013-03-21

Catalysis is a key enabling technology for solar fuel generation. A number of catalytic systems, either molecular/homogeneous or solid/heterogeneous, have been developed during the last few decades for both the reductive and oxidative multi-electron reactions required for fuel production from water or CO(2) as renewable raw materials. While allowing for a fine tuning of the catalytic properties through ligand design, molecular approaches are frequently criticized because of the inherent fragility of the resulting catalysts, when exposed to extreme redox potentials. In a number of cases, it has been clearly established that the true catalytic species is heterogeneous in nature, arising from the transformation of the initial molecular species, which should rather be considered as a pre-catalyst. Whether such a situation is general or not is a matter of debate in the community. In this review, covering water oxidation and reduction catalysts, involving noble and non-noble metal ions, we limit our discussion to the cases in which this issue has been directly and properly addressed as well as those requiring more confirmation. The methodologies proposed for discriminating homogeneous and heterogeneous catalysis are inspired in part by those previously discussed by Finke in the case of homogeneous hydrogenation reaction in organometallic chemistry [J. A. Widegren and R. G. Finke, J. Mol. Catal. A, 2003, 198, 317-341].

Contrast and Synergy between Electrocatalysis and Heterogeneous Catalysis

Directory of Open Access Journals (Sweden)

Andrzej Wieckowski

2011-01-01

Full Text Available The advances in spectroscopy and theory that have occurred over the past two decades begin to provide detailed in situ resolution of the molecular transformations that occur at both gas/metal as well as aqueous/metal interfaces. These advances begin to allow for a more direct comparison of heterogeneous catalysis and electrocatalysis. Such comparisons become important, as many of the current energy conversion strategies involve catalytic and electrocatalytic processes that occur at fluid/solid interfaces and display very similar characteristics. Herein, we compare and contrast a few different catalytic and electrocatalytic systems to elucidate the principles that cross-cut both areas and establish characteristic differences between the two with the hope of advancing both areas.

Biodiesel forming reactions using heterogeneous catalysis

Science.gov (United States)

Liu, Yijun

Biodiesel synthesis from biomass provides a means for utilizing effectively renewable resources, a way to convert waste vegetable oils and animal fats to a useful product, a way to recycle carbon dioxide for a combustion fuel, and production of a fuel that is biodegradable, non-toxic, and has a lower emission profile than petroleum-diesel. Free fatty acid (FFA) esterification and triglyceride (TG) transesterification with low molecular weight alcohols constitute the synthetic routes to prepare biodiesel from lipid feedstocks. This project was aimed at developing a better understanding of important fundamental issues involved in heterogeneous catalyzed biodiesel forming reactions using mainly model compounds, representing part of on-going efforts to build up a rational base for assay, design, and performance optimization of solid acids/bases in biodiesel synthesis. As FFA esterification proceeds, water is continuously formed as a byproduct and affects reaction rates in a negative manner. Using sulfuric acid (as a catalyst) and acetic acid (as a model compound for FFA), the impact of increasing concentrations of water on acid catalysis was investigated. The order of the water effect on reaction rate was determined to be -0.83. Sulfuric acid lost up to 90% activity as the amount of water present increased. The nature of the negative effect of water on esterification was found to go beyond the scope of reverse hydrolysis and was associated with the diminished acid strength of sulfuric acid as a result of the preferential solvation by water molecules of its catalytic protons. The results indicate that as esterification progresses and byproduct water is produced, deactivation of a Bronsted acid catalyst like H2SO4 occurs. Using a solid composite acid (SAC-13) as an example of heterogeneous catalysts and sulfuric acid as a homogeneous reference, similar reaction inhibition by water was demonstrated for homogeneous and heterogeneous catalysis. This similarity together with

A spectral study of the elementary step of proton transfer in heterogeneous acid catalysis

Energy Technology Data Exchange (ETDEWEB)

Kazanskii, V B

1977-09-01

A spectral study of the elementary step of proton transfer in heterogeneous acid catalysis involved a determination of the potential curves of the OH bond in surface hydroxyl groups (e.g., those on silica, NaHY zeolite, or glass) of differing acidity from IR stretching frequency data in the overtone region; a calculation of the activation energies for proton transfer during acid catalysis from the changes in the curve forms after adsorption of various molecules (e.g., water, ammonia, benzene, toluene, xylenes, acetone, and cyclohexane); and a comparison of the IR predictions with quantum-chemical calculations of the potential curves. The results appear to furnish a new criterion for the coordinate of reactions involving Broensted sites: if the activation energy measured during actual catalysis is close to that calculated from the IR stretching data, the reaction proceeds by the stepwise mechanism of acid catalysis; but if these values differ greatly, the reaction involves a concerted mechanism (i.e., activation of the adsorbed molecule without involvement of OH groups). Tables, graphs, and 15 references.

Surface Science Foundations of Catalysis and Nanoscience

CERN Document Server

Kolasinski, Kurt K

2012-01-01

Surface science has evolved from being a sub-field of chemistry or physics, and has now established itself as an interdisciplinary topic. Knowledge has developed sufficiently that we can now understand catalysis from a surface science perspective. No-where is the underpinning nature of surface science better illustrated than with nanoscience. Now in its third edition, this successful textbook aims to provide students with an understanding of chemical transformations and the formation of structures at surfaces. The chapters build from simple to more advanced principles with each featuring exerc

Catalysis seen in action

NARCIS (Netherlands)

Tromp, M.

2015-01-01

Synchrotron radiation techniques are widely applied in materials research and heterogeneous catalysis. In homogeneous catalysis, its use so far is rather limited despite its high potential. Here, insights in the strengths and limitations of X-ray spectroscopy technique in the field of homogeneous

Practical Engineering Aspects of Catalysis in Microreactors

Czech Academy of Sciences Publication Activity Database

Křišťál, Jiří; Stavárek, Petr; Vajglová, Zuzana; Vondráčková, Magdalena; Pavlorková, Jana; Jiřičný, Vladimír

2015-01-01

Roč. 41, č. 12 (2015), s. 9357-9371 ISSN 0922-6168. [Pannonian Symposium on Catalysis /12./. Castle Trest, 16.09.2014-20.09.2014] Institutional support: RVO:67985858 Keywords : heterogeneous catalysis * homogeneous catalysis * photo catalysis Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 1.833, year: 2015

First Principles Molecular Dynamics Study of Catalysis for Polyolefins: the Ziegler-Natta Heterogeneous System.

Directory of Open Access Journals (Sweden)

Michele Parrinello

2002-04-01

Full Text Available Abstract: We review part of our recent ab initio molecular dynamics study on the Ti-based Ziegler-Natta supported heterogeneous catalysis of α-olefins. The results for the insertion of ethylene in the metal-carbon bond are discussed as a fundamental textbook example of polymerization processes. Comparison with the few experimental data available has shown that simulation can reproduce activation barriers and the overall energetics of the reaction with sufficient accuracy. This puts these quantum dynamical simulations in a new perspective as a virtual laboratory where the microscopic picture of the catalysis, which represents an important issue that still escapes experimental probes, can be observed and understood. These results are then discussed in comparison with a V-based catalyst in order to figure out analogies and differences with respect to the industrially more successful Tibased systems.

At the frontier between heterogeneous and homogeneous catalysis : hydrogenation of olefins and alkynes with soluble iron nanoparticles

NARCIS (Netherlands)

Rangheard, Claudine; Julián Fernández, César de; Phua, Pim-Huat; Hoorn, Johan; Lefort, Laurent; Vries, Johannes G. de

2010-01-01

The use of non-supported Fe nanoparticles in the hydrogenation of unsaturated C–C bonds is a green catalytic concept at the frontier between homogeneous and heterogeneous catalysis. Iron nanoparticles can be obtained by reducing Fe salts with strong reductants in various solvents. FeCl3 reduced by 3

Long-lived CO/sub 2/ lasers with distributed heterogeneous catalysis

Energy Technology Data Exchange (ETDEWEB)

Browne, P G; Smith, A L.S.

1974-12-11

In a sealed CO/sub 2/-N/sub 2/-He system with a clean discharge tube the degree of dissociation of the CO/sub 2/ is greater than 80 percent (with no hydrogen present), and laser action cannot be obtained. If Pt is distributed along the discharge tube walls as a discontinuous film it catalyses back-reactions reforming CO/sub 2/. The degree of dissociation is then less than 40 percent, and efficient laser action at 10.6 ..mu.. is obtained. Using such distributed heterogeneous catalysis, a CO/sub 2/-N/sub 2/-He-Xe laser has operated for more than 3000 h. In this system, both H/sub 2/ and D/sub 2/ are undesirable additives because they decrease the excitation rate of the upper laser level. (auth)

Hydrogen Production by Homogeneous Catalysis: Alcohol Acceptorless Dehydrogenation

DEFF Research Database (Denmark)

Nielsen, Martin

2015-01-01

in hydrogen production from biomass using homogeneous catalysis. Homogeneous catalysis has the advance of generally performing transformations at much milder conditions than traditional heterogeneous catalysis, and hence it constitutes a promising tool for future applications for a sustainable energy sector...

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

Energy Technology Data Exchange (ETDEWEB)

Somorjai, Gabor A.; Li, Yimin

2009-11-21

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 surface-sensitive 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.

Biodiesel production through in situ transesterification of sunflower seeds by homogeneous and heterogeneous catalysis; Producao de biodiesel atraves de transesterificacao in situ de sementes de girassol via catalise homogenea e heterogenea

Energy Technology Data Exchange (ETDEWEB)

Fama, Paola Ervatti; San Gil, Rosane Aguiar da Silva; Lachter, Elizabeth Roditi, E-mail: lachter@iq.ufrj.b [Universidade Federal do Rio de Janeiro (IQ/UFRJ), RJ (Brazil). Inst. de Quimica

2010-07-01

The objective of this work is to show the results of the in situ transesterification of sunflower seed oil with methanol on basic homogeneous and heterogeneous catalysis for the production of biodiesel. In homogeneous catalysis, the activity of K{sub O}H and K{sub 2}CO{sub 3} were evaluated using the same oil:methanol ratio of 1:90. KOH showed to be more active than K2CO{sub 3}, leading to total conversion in biodiesel after 1h reaction time. In the heterogeneous catalysis the activity of K{sub 2}CO{sub 3}/Al{sub 2}O{sub 3} was comparable to the activity of K{sub 2}CO{sub 3} bulk: 53.0 and 66.6% resp. The properties of samples of biodiesel produced by homogeneous and heterogeneous catalysis were evaluated and are in accordance with the recommended fuel properties. (author)

Editorial: Nanoscience makes catalysis greener

KAUST Repository

Polshettiwar, Vivek; Basset, Jean-Marie; Astruc, Didier

2012-01-01

Green chemistry by nanocatalysis: Catalysis is a strategic field of science because it involves new ways of meeting energy and sustainability challenges. The concept of green chemistry, which makes the science of catalysis even more creative, has

Heterogeneous catalysis in highly sensitive microreactors

DEFF Research Database (Denmark)

Olsen, Jakob Lind

This thesis present a highly sensitive silicon microreactor and examples of its use in studying catalysis. The experimental setup built for gas handling and temperature control for the microreactor is described. The implementation of LabVIEW interfacing for all the experimental parts makes...

Francois Garin: Pioneer work in catalysis through synchrotron radiation

International Nuclear Information System (INIS)

Bazin, Dominique

2014-01-01

Starting from the late seventies, the progressively increased availability of beamlines dedicated to X-ray absorption spectroscopy allowed the execution of experiments in chemistry. In this manuscript, I describe the contribution of Francois Garin at the frontier of heterogeneous catalysis and synchrotron radiation. Working at LURE as a scientific in charge of a beamline dedicated to X-ray absorption spectroscopy during almost twenty years and thus, having the opportunity to discuss with research groups working in heterogeneous catalysis in Europe as well as in the United States, it was quite easy to show that his work is clearly at the origin of current research in heterogeneous catalysis, not only in France, but in different synchrotron radiation centres. (authors)

Accurate Experimental and Theoretical Enthalpies of Association of TiCl4 with Typical Lewis Bases Used in Heterogeneous Ziegler-Natta Catalysis

KAUST Repository

Credendino, Raffaele; Minenkov, Yury; Liguori, Dario; Piemontesi, Fabrizio; Melchior, Andrea; Morini, Giampiero; Tolazzi, Marilena; Cavallo, Luigi

2017-01-01

Adducts of TiCl4 with Lewis bases used as internal or external donors in heterogeneous Ziegler-Natta (ZN) catalysis represents a fundamental interaction contributing to the final composition of MgCl2 supported ZN-catalysts. This study presents

Metal nanoparticles in liquid phase catalysis; from recent advances to future goals.

Science.gov (United States)

Zahmakıran, Mehmet; Ozkar, Saim

2011-09-01

Metal nanoparticles have attracted much attention over the last decade owing to their unique properties, different to their bulk counterparts, which pave the way for their application in different fields from materials science and engineering to biomedical applications. Of particular interest, the use of metal nanoparticles in catalysis has brought superior efficiency in terms of activity, selectivity and lifetime to heterogeneous catalysis. This article reviews the recent developments in the synthesis routes and the catalytic performance of metal nanoparticles depending on the solvent used for various organic and inorganic transformations. Additionally, we also discuss the prevalent complications and their possible solutions plus future prospects in the field of nanocatalysis.

DOE Laboratory Catalysis Research Symposium - Abstracts

Energy Technology Data Exchange (ETDEWEB)

Dunham, T.

1999-02-01

The conference consisted of two sessions with the following subtopics: (1) Heterogeneous Session: Novel Catalytic Materials; Photocatalysis; Novel Processing Conditions; Metals and Sulfides; Nuclear Magnetic Resonance; Metal Oxides and Partial Oxidation; Electrocatalysis; and Automotive Catalysis. (2) Homogeneous Catalysis: H-Transfer and Alkane Functionalization; Biocatalysis; Oxidation and Photocatalysis; and Novel Medical, Methods, and Catalyzed Reactions.

Plasma-assisted heterogeneous catalysis for NOx reduction in lean-burn engine exhaust

Energy Technology Data Exchange (ETDEWEB)

Penetrante, B.M.; Hsaio, M.C.; Merritt, B.T.; Vogtlin, G.E. [Lawrence Livermore National Lab., CA (United States); Wan, C.Z.; Rice, G.W.; Voss, K.E. [Engelhard Corp., Iselin, NJ (United States)

1997-12-31

This paper discusses the combination of a plasma with a catalyst to improve the reduction of NO{sub x} under lean-burn conditions. The authors have been investigating the effects of a plasma on the NO{sub x} reduction activity and temperature operating window of various catalytic materials. One of the goals is to develop a fundamental understanding of the interaction between the gas-phase plasma chemistry and the heterogeneous chemistry on the catalyst surface. The authors have observed that plasma assisted heterogeneous catalysis can facilitate NO{sub x} reduction under conditions that normally make it difficult for either the plasma or the catalyst to function by itself. By systematically varying the plasma electrode and catalyst configuration, they have been able to elucidate the process by which the plasma chemistry affects the chemical reduction of NO{sub x} on the catalyst surface. They have discovered that the main effect of the plasma is to induce the gas-phase oxidation of NO to NO{sub 21}. The reduction of NO{sub x} to N{sub 2} is then accomplished by heterogeneous reaction of O with activated hydrocarbons on the catalyst surface. The use of a plasma opens the opportunity for a new class of catalysts that are potentially more durable, more active, more selective and more sulfur-tolerant compared to conventional lean-NO{sub x} catalysts.

Density functional theory studies of transition metal nanoparticles in catalysis

DEFF Research Database (Denmark)

Greeley, Jeffrey Philip; Rankin, Rees; Zeng, Zhenhua

2013-01-01

Periodic Density Functional Theory calculations are capable of providing powerful insights into the structural, energetics, and electronic phenomena that underlie heterogeneous catalysis on transition metal nanoparticles. Such calculations are now routinely applied to single crystal metal surfaces...... and to subnanometer metal clusters. Descriptions of catalysis on truly nanosized structures, however, are generally not as well developed. In this talk, I will illustrate different approaches to analyzing nanocatalytic phenomena with DFT calculations. I will describe case studies from heterogeneous catalysis...... and electrocatalysis, in which single crystal models are combined with Wulff construction-based ideas to produce descriptions of average nanocatalyst behavior. Then, I will proceed to describe explicitly DFT-based descriptions of catalysis on truly nanosized particles (

Quantum catalysis : the modelling of catalytic transition states

NARCIS (Netherlands)

Hall, M.B.; Margl, P.; Naray-Szabo, G.; Schramm, Vern; Truhlar, D.G.; Santen, van R.A.; Warshel, A.; Whitten, J.L.; Truhlar, D.G.; Morokuma, K.

1999-01-01

A review with 101 refs.; we present an introduction to the computational modeling of transition states for catalytic reactions. We consider both homogeneous catalysis and heterogeneous catalysis, including organometallic catalysts, enzymes, zeolites and metal oxides, and metal surfaces. We summarize

Sustainable green catalysis by supported metal nanoparticles.

Science.gov (United States)

Fukuoka, Atsushi; Dhepe, Paresh L

2009-01-01

The recent progress of sustainable green catalysis by supported metal nanoparticles is described. The template synthesis of metal nanoparticles in ordered porous materials is studied for the rational design of heterogeneous catalysts capable of high activity and selectivity. The application of these materials in green catalytic processes results in a unique activity and selectivity arising from the concerted effect of metal nanoparticles and supports. The high catalytic performances of Pt nanoparticles in mesoporous silica is reported. Supported metal catalysts have also been applied to biomass conversion by heterogeneous catalysis. Additionally, the degradation of cellulose by supported metal catalysts, in which bifunctional catalysis of acid and metal plays the key role for the hydrolysis and reduction of cellulose, is also reported. Copyright 2009 The Japan Chemical Journal Forum and Wiley Periodicals, Inc.

Kinetics of heterogeneous catalytic reactions

CERN Document Server

Boudart, Michel

2014-01-01

This book is a critical account of the principles of the kinetics of heterogeneous catalytic reactions in the light of recent developments in surface science and catalysis science. Originally published in 1984. The Princeton Legacy Library uses the latest print-on-demand technology to again make available previously out-of-print books from the distinguished backlist of Princeton University Press. These paperback editions preserve the original texts of these important books while presenting them in durable paperback editions. The goal of the Princeton Legacy Library is to vastly increase acc

Catalysis seen in action.

Science.gov (United States)

Tromp, Moniek

2015-03-06

Synchrotron radiation techniques are widely applied in materials research and heterogeneous catalysis. In homogeneous catalysis, its use so far is rather limited despite its high potential. Here, insights in the strengths and limitations of X-ray spectroscopy technique in the field of homogeneous catalysis are given, including new technique developments. A relevant homogeneous catalyst, used in the industrially important selective oligomerization of ethene, is taken as a worked-out example. Emphasis is placed on time-resolved operando X-ray absorption spectroscopy with outlooks to novel high energy resolution and emission techniques. All experiments described have been or can be done at the Diamond Light Source Ltd (Didcot, UK). © 2015 The Author(s) Published by the Royal Society. All rights reserved.

Advancing Sustainable Catalysis with Magnetite Surface ...

Science.gov (United States)

This article surveys the recent developments in the synthesis, surface modification, and synthetic applications of magnetitenanoparticles. The emergence of iron(II,III) oxide (triiron tetraoxide or magnetite; Fe3O4, or FeO•Fe2O3) nanoparticles as a sustainable support in heterogeneous catalysis is highlighted. Use of an oxide of earth-abundant iron for various applications in catalysis and environmental remediation.

Catalysis Science Initiative: Catalyst Design by Discovery Informatics

Energy Technology Data Exchange (ETDEWEB)

Delgass, William Nicholas [Purdue Univ., West Lafayette, IN (United States). Chemical Engineering; Abu-Omar, Mahdi [Purdue Univ., West Lafayette, IN (United States) Department of Chemistry; Caruthers, James [Purdue Univ., West Lafayette, IN (United States). Chemical Engineering; Ribeiro, Fabio [Purdue Univ., West Lafayette, IN (United States). Chemical Engineering; Thomson, Kendall [Purdue Univ., West Lafayette, IN (United States). Chemical Engineering; Schneider, William [Univ. of Notre Dame, IN (United States)

2016-07-08

Catalysts selectively enhance the rates of chemical reactions toward desired products. Such reactions provide great benefit to society in major commercial sectors such as energy production, protecting the environment, and polymer products and thereby contribute heavily to the country’s gross national product. Our premise is that the level of fundamental understanding of catalytic events at the atomic and molecular scale has reached the point that more predictive methods can be developed to shorten the cycle time to new processes. The field of catalysis can be divided into two regimes: heterogeneous and homogeneous. For the heterogeneous catalysis regime, we have used the water-gas shift (WGS) reaction (CO + H2O + CO2 + H2O) over supported metals as a test bed. Detailed analysis and strong coupling of theory with experiment have led to the following conclusions: • The sequence of elementary steps goes through a COOH intermediate • The CO binding energy is a strong function of coverage of CO adsorbed on the surface in many systems • In the case of Au catalysts, the CO adsorption is generally too weak on surface with close atomic packing, but the enhanced binding at corner atoms (which are missing bonding partners) of cubo-octahedral nanoparticles increases the energy to a near optimal value and produces very active catalysts. • Reaction on the metal alone cannot account for the experimental results. The reaction is dual functional with water activation occurring at the metal-support interface. It is clear from our work that the theory component is essential, not only for prediction of new systems, but also for reconciling data and testing hypotheses regarding potential descriptors. Particularly important is the finding that the interface between nano-sized metal particles and the oxides that are used to support them represent a new state of matter in the sense that the interfacial bonding perturbs the chemical state of both metals atoms and the support

Study of gas-liquid flow in model porous media for heterogeneous catalysis

Science.gov (United States)

Francois, Marie; Bodiguel, Hugues; Guillot, Pierre; Laboratory of the Future Team

2015-11-01

Heterogeneous catalysis of chemical reactions involving a gas and a liquid phase is usually achieved in fixed bed reactors. Four hydrodynamic regimes have been observed. They depend on the total flow rate and the ratio between liquid and gas flow rate. Flow properties in these regimes influence transfer rates. Rather few attempts to access local characterization have been proposed yet, though these seem to be necessary to better describe the physical mechanisms involved. In this work, we propose to mimic slices of reactor by using two-dimensional porous media. We have developed a two-dimensional system that is transparent to allow the direct observation of the flow and the phase distribution. While varying the total flow rate and the gas/liquid flow rate ratio, we observe two hydrodynamic regimes: at low flow rate, the gaseous phase is continuous (trickle flow), while it is discontinuous at higher flow rate (pulsed flow). Thanks to some image analysis techniques, we are able to quantify the local apparent liquid saturation in the system. Its fluctuations in time are characteristic of the transition between the two regimes: at low liquid flow rates, they are negligible since the liquid/gas interface is fixed, whereas at higher flow rates we observe an alternation between liquid and gas. This transition between trickle to pulsed flow is in relative good agreement with the existing state of art. However, we report in the pulsed regime important flow heterogeneities at the scale of a few pores. These heterogeneities are likely to have a strong influence on mass transfers. We acknowledge the support of Solvay.

Editorial: Nanoscience makes catalysis greener

KAUST Repository

Polshettiwar, Vivek

2012-01-09

Green chemistry by nanocatalysis: Catalysis is a strategic field of science because it involves new ways of meeting energy and sustainability challenges. The concept of green chemistry, which makes the science of catalysis even more creative, has become an integral part of sustainability. This special issue is at the interface of green chemistry and nanocatalysis, and features excellent background articles as well as the latest research results. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Recent progress in surface science v.2

CERN Document Server

Danielli, J F; Riddiford, A C

1964-01-01

Recent Progress in Surface Science, Volume 2 is a 10-chapter text that covers the significant advances in some aspects of surface science, including in catalysis, genetic control of cell surface, and cell membrane. The opening chapter deals with the major factors affecting adsorption at the gas-solid interface. The subsequent chapters explore the advances in understanding of heterogeneous catalysis in terms of fundamental surface processes, as well as the concept of dynamic contact angles. These topics are followed by discussions on emulsions, flotation, and the extraordinary complexity of cel

High-density biosynthetic fuels: the intersection of heterogeneous catalysis and metabolic engineering.

Science.gov (United States)

Harvey, Benjamin G; Meylemans, Heather A; Gough, Raina V; Quintana, Roxanne L; Garrison, Michael D; Bruno, Thomas J

2014-05-28

Biosynthetic valencene, premnaspirodiene, and natural caryophyllene were hydrogenated and evaluated as high performance fuels. The parent sesquiterpenes were then isomerized to complex mixtures of hydrocarbons with the heterogeneous acid catalyst Nafion SAC-13. High density fuels with net heats of combustion ranging from 133-141 000 Btu gal(-1), or up to 13% higher than commercial jet fuel could be generated by this approach. The products of caryophyllene isomerization were primarily tricyclic hydrocarbons which after hydrogenation increased the fuel density by 6%. The isomerization of valencene and premnaspirodiene also generated a variety of sesquiterpenes, but in both cases the dominant product was δ-selinene. Ab initio calculations were conducted to determine the total electronic energies for the reactants and products. In all cases the results were in excellent agreement with the experimental distribution of isomers. The cetane numbers for the sesquiterpane fuels ranged from 20-32 and were highly dependent on the isomer distribution. Specific distillation cuts may have the potential to act as high density diesel fuels, while use of these hydrocarbons as additives to jet fuel will increase the range and/or time of flight of aircraft. In addition to the ability to generate high performance renewable fuels, the powerful combination of metabolic engineering and heterogeneous catalysis will allow for the preparation of a variety of sesquiterpenes with potential for pharmaceutical, flavor, and fragrance applications.

Catalysis looks to the future. Panel on new directions in catalytic science and technology

Energy Technology Data Exchange (ETDEWEB)

1992-12-31

Catalysts play a vital role in providing society with fuels, commodity and fine chemicals, pharmaceuticals, and means for protecting the environment. To be useful, a good catalyst must have a high turnover frequency (activity), produce the right kind of product (selectivity), and have a long life (durability), all at an acceptable cost. Research in the field of catalysis provides the tools and understanding required to facilitate and accelerate the development of improved catalysts and to open opportunities for the discovery of new catalytic processes. The aim of this report is to identify the research opportunities and challenges for catalysis in the coming decades and to detail the resources necessary to ensure steady progress. Chapter 2 discusses opportunities for developing new catalysts to meet the demands of the chemical and fuel industries, and the increasing role of catalysis in environmental protection. The intellectual challenges for advancing the frontiers of catalytic science are outlined in Chapter 3. The human and institutional resources available in the US for carrying out research on catalysis are summarized in Chapter 4. The findings and recommendations of the panel for industry, academe, the national laboratories, and the federal government are presented in Chapter 5.

The effect of hot electrons and surface plasmons on heterogeneous catalysis

International Nuclear Information System (INIS)

Kim, Sun Mi; Lee, Si Woo; Moon, Song Yi; Park, Jeong Young

2016-01-01

Hot electrons and surface-plasmon-driven chemistry are amongst the most actively studied research subjects because they are deeply associated with energy dissipation and the conversion processes at the surface and interfaces, which are still open questions and key issues in the surface science community. In this topical review, we give an overview of the concept of hot electrons or surface-plasmon-mediated hot electrons generated under various structural schemes (i.e. metals, metal–semiconductor, and metal–insulator–metal) and their role affecting catalytic activity in chemical reactions. We highlight recent studies on the relation between hot electrons and catalytic activity on metallic surfaces. We discuss possible mechanisms for how hot electrons participate in chemical reactions. We also introduce controlled chemistry to describe specific pathways for selectivity control in catalysis on metal nanoparticles. (topical review)

Coupling chemical and biological catalysis: a flexible paradigm for producing biobased chemicals.

Science.gov (United States)

Schwartz, Thomas J; Shanks, Brent H; Dumesic, James A

2016-04-01

Advances in metabolic engineering have allowed for the development of new biological catalysts capable of selectively de-functionalizing biomass to yield platform molecules that can be upgraded to biobased chemicals using high efficiency continuous processing allowed by heterogeneous chemical catalysis. Coupling these disciplines overcomes the difficulties of selectively activating COH bonds by heterogeneous chemical catalysis and producing petroleum analogues by biological catalysis. We show that carboxylic acids, pyrones, and alcohols are highly flexible platforms that can be used to produce biobased chemicals by this approach. More generally, we suggest that molecules with three distinct functionalities may represent a practical upper limit on the extent of functionality present in the platform molecules that serve as the bridge between biological and chemical catalysis. Copyright © 2016 Elsevier Ltd. All rights reserved.

Competing role of catalysis-coagulation and catalysis-fragmentation in kinetic aggregation behaviours

International Nuclear Information System (INIS)

Li Xiao-Dong; Lin Zhen-Quan; Song Mei-Xia; Ke Jian-Hong

2010-01-01

We propose a kinetic aggregation model where species A aggregates evolve by the catalysis-coagulation and the catalysis-fragmentation, while the catalyst aggregates of the same species B or C perform self-coagulation processes. By means of the generalized Smoluchowski rate equation based on the mean-field assumption, we study the kinetic behaviours of the system with the catalysis-coagulation rate kernel K(i,j;l) ∝ l ν and the catalysis-fragmentation rate kernel F(i,j;l) ∝ l μ , where l is the size of the catalyst aggregate, and ν and μ are two parameters reflecting the dependence of the catalysis reaction on the size of the catalyst aggregate. The relation between the values of parameters ν and μ reflects the competing roles between the two catalysis processes in the kinetic evolution of species A. It is found that the competing roles of the catalysis-coagulation and catalysis-fragmentation in the kinetic aggregation behaviours are not determined simply by the relation between the two parameters ν and μ, but also depend on the values of these two parameters. When ν > μ and ν ≥ 0, the kinetic evolution of species A is dominated by the catalysis-coagulation and its aggregate size distribution a k (t) obeys the conventional or generalized scaling law; when ν k (t) approaches the scale-free form; and in other cases, a balance is established between the two competing processes at large times and a k (t) obeys a modified scaling law. (cross-disciplinary physics and related areas of science and technology)

EMSL and Institute for Integrated Catalysis (IIC) Catalysis Workshop

Energy Technology Data Exchange (ETDEWEB)

Campbell, Charles T.; Datye, Abhaya K.; Henkelman, Graeme A.; Lobo, Raul F.; Schneider, William F.; Spicer, Leonard D.; Tysoe, Wilfred T.; Vohs, John M.; Baer, Donald R.; Hoyt, David W.; Thevuthasan, Suntharampillai; Mueller, Karl T.; Wang, Chong M.; Washton, Nancy M.; Lyubinetsky, Igor; Teller, Raymond G.; Andersen, Amity; Govind, Niranjan; Kowalski, Karol; Kabius, Bernd C.; Wang, Hongfei; Campbell, Allison A.; Shelton, William A.; Bylaska, Eric J.; Peden, Charles HF; Wang, Yong; King, David L.; Henderson, Michael A.; Rousseau, Roger J.; Szanyi, Janos; Dohnalek, Zdenek; Mei, Donghai; Garrett, Bruce C.; Ray, Douglas; Futrell, Jean H.; Laskin, Julia; DuBois, Daniel L.; Kuprat, Laura R.; Plata, Charity

2011-05-24

Within the context of significantly accelerating scientific progress in research areas that address important societal problems, a workshop was held in November 2010 at EMSL to identify specific and topically important areas of research and capability needs in catalysis-related science.

Green chemistry by nano-catalysis

KAUST Repository

Polshettiwar, Vivek

2010-01-01

Nano-materials are important in many diverse areas, from basic research to various applications in electronics, biochemical sensors, catalysis and energy. They have emerged as sustainable alternatives to conventional materials, as robust high surface area heterogeneous catalysts and catalyst supports. The nano-sized particles increase the exposed surface area of the active component of the catalyst, thereby enhancing the contact between reactants and catalyst dramatically and mimicking the homogeneous catalysts. This review focuses on the use of nano-catalysis for green chemistry development including the strategy of using microwave heating with nano-catalysis in benign aqueous reaction media which offers an extraordinary synergistic effect with greater potential than these three components in isolation. To illustrate the proof-of-concept of this "green and sustainable" approach, representative examples are discussed in this article. © 2010 The Royal Society of Chemistry.

Transformation of Sorbitol to Biofuels by Heterogeneous Catalysis: Chemical and Industrial Considerations

International Nuclear Information System (INIS)

Vilcocq, L.; Cabiac, A.; Guillon, E.; Especel, C.; Duprez, D.

2013-01-01

Decreasing oil supplies and increasing energy demand provide incentives to find alternative fuels. First, the valorisation of edible crops for ethanol and bio-diesel production led to first generation biofuels. Nowadays, research is focused on lignocellulosic biomass as a source of renewable carbon (second generation biofuels). Whereas the cellulosic ethanol production is in progress, a new way consisting of the transformation of ex-lignocellulose sugars and polyols towards light hydrocarbons by heterogeneous catalysis in aqueous phase has been recently described. This process is performed under mild conditions (T < 300 deg. C and P < 50 bar). It requires on one hand hydrogen formation by catalytic reforming of carbohydrates in aqueous phase and on the other hand, the dehydration/hydrogenation of polyols leading to alkanes by selective C-O bond cleavages. The challenge here is to conceive multifunctional catalytic systems that are stable, active and selective under the reaction conditions. The aim of this article is to present the involved reactions, the catalytic systems described in literature for that kind of transformation and examples of industrial applications. (authors)

New and future developments in catalysis catalysis by nanoparticles

CERN Document Server

Suib, Steven L

2013-01-01

New and Future Developments in Catalysis is a package of seven books that compile the latest ideas concerning alternate and renewable energy sources and the role that catalysis plays in converting new renewable feedstock into biofuels and biochemicals. Both homogeneous and heterogeneous catalysts and catalytic processes will be discussed in a unified and comprehensive approach. There will be extensive cross-referencing within all volumes. The use of catalysts in the nanoscale offers various advantages (increased efficiency and less byproducts), and these are discussed in this volume along with the various catalytic processes using nanoparticles. However, this is not without any risks and the safety aspects and effects on humans and the environment are still unknown. The present data as well as future needs are all part of this volume along with the economics involved. Offers in-depth coverage of all catalytic topics of current interest and outlines future challenges and research areas A clear and visual descr...

Neutrons for Catalysis: A Workshop on Neutron Scattering Techniques for Studies in Catalysis

International Nuclear Information System (INIS)

Overbury, Steven H.; Coates, Leighton; Herwig, Kenneth W.; Kidder, Michelle

2011-01-01

This report summarizes the Workshop on Neutron Scattering Techniques for Studies in Catalysis, held at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL) on September 16 and 17, 2010. The goal of the Workshop was to bring experts in heterogeneous catalysis and biocatalysis together with neutron scattering experimenters to identify ways to attack new problems, especially Grand Challenge problems in catalysis, using neutron scattering. The Workshop locale was motivated by the neutron capabilities at ORNL, including the High Flux Isotope Reactor (HFIR) and the new and developing instrumentation at the SNS. Approximately 90 researchers met for 1 1/2 days with oral presentations and breakout sessions. Oral presentations were divided into five topical sessions aimed at a discussion of Grand Challenge problems in catalysis, dynamics studies, structure characterization, biocatalysis, and computational methods. Eleven internationally known invited experts spoke in these sessions. The Workshop was intended both to educate catalyst experts about the methods and possibilities of neutron methods and to educate the neutron community about the methods and scientific challenges in catalysis. Above all, it was intended to inspire new research ideas among the attendees. All attendees were asked to participate in one or more of three breakout sessions to share ideas and propose new experiments that could be performed using the ORNL neutron facilities. The Workshop was expected to lead to proposals for beam time at either the HFIR or the SNS; therefore, it was expected that each breakout session would identify a few experiments or proof-of-principle experiments and a leader who would pursue a proposal after the Workshop. Also, a refereed review article will be submitted to a prominent journal to present research and ideas illustrating the benefits and possibilities of neutron methods for catalysis research.

Neutrons for Catalysis: A Workshop on Neutron Scattering Techniques for Studies in Catalysis

Energy Technology Data Exchange (ETDEWEB)

Overbury, Steven {Steve} H [ORNL; Coates, Leighton [ORNL; Herwig, Kenneth W [ORNL; Kidder, Michelle [ORNL

2011-10-01

This report summarizes the Workshop on Neutron Scattering Techniques for Studies in Catalysis, held at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL) on September 16 and 17, 2010. The goal of the Workshop was to bring experts in heterogeneous catalysis and biocatalysis together with neutron scattering experimenters to identify ways to attack new problems, especially Grand Challenge problems in catalysis, using neutron scattering. The Workshop locale was motivated by the neutron capabilities at ORNL, including the High Flux Isotope Reactor (HFIR) and the new and developing instrumentation at the SNS. Approximately 90 researchers met for 1 1/2 days with oral presentations and breakout sessions. Oral presentations were divided into five topical sessions aimed at a discussion of Grand Challenge problems in catalysis, dynamics studies, structure characterization, biocatalysis, and computational methods. Eleven internationally known invited experts spoke in these sessions. The Workshop was intended both to educate catalyst experts about the methods and possibilities of neutron methods and to educate the neutron community about the methods and scientific challenges in catalysis. Above all, it was intended to inspire new research ideas among the attendees. All attendees were asked to participate in one or more of three breakout sessions to share ideas and propose new experiments that could be performed using the ORNL neutron facilities. The Workshop was expected to lead to proposals for beam time at either the HFIR or the SNS; therefore, it was expected that each breakout session would identify a few experiments or proof-of-principle experiments and a leader who would pursue a proposal after the Workshop. Also, a refereed review article will be submitted to a prominent journal to present research and ideas illustrating the benefits and possibilities of neutron methods for catalysis research.

Catalysis studies

International Nuclear Information System (INIS)

Taylor, T.N.; Ellis, W.P.

1977-11-01

The New Research Initiatives Program (NRIP) project on catalysis in Los Alamos Scientific Laboratory (LASL) Group CMB-8 has made significant progress towards performing the first basic in situ experimental studies of heterogeneous catalysis on solid compound surfaces in a LEED-Auger system. To further understand the surface crystallography of a possible catalyst compound, LEED-Auger measurements were made on UO 2 (approximately 100) vicinal surfaces. These (approximately 100) vicinal surfaces were shown to decompose irreversibly into lower index facets, including prominent (100) facets, at temperatures below those needed for creation of lowest index faceting on (approximately 111) vicinal surfaces. LEED examination of fully faceted surfaces from both types of UO 2 vicinal cuts did not show evidence of cyclopropane or propene chemisorption. The existing LEED-Auger system was modified to allow catalytic reactions at approximately less than 10 -3 torr. A sample holder, specifically designed for catalysis measurements in the modified system, was tested while examining single crystals of CoO and Cr 2 O 3 . Extensive LEED-Auger measurements were made on CoO in vacuo and in the presence of light hydrocarbons and alcohols plus H 2 O, NO, and NH 3 . No chemisorptive behavior was observed except with H 2 O in the presence of the electron beam. Although only examined briefly, the Cr 2 O 3 was remarkable for the sharp LEED features obtained prior to any surface treatment in the vacuum system

Preface: Catalysis Today

DEFF Research Database (Denmark)

Li, Yongdan

2016-01-01

This special issue of Catalysis Today with the theme “Sustain-able Energy” results from a great success of the session “Catalytic Technologies Accelerating the Establishment of Sustainable and Clean Energy”, one of the two sessions of the 1st International Symposium on Catalytic Science and Techn...

New and future developments in catalysis catalysis for remediation and environmental concerns

CERN Document Server

Suib, Steven L

2013-01-01

New and Future Developments in Catalysis is a package of seven books that compile the latest ideas concerning alternate and renewable energy sources and the role that catalysis plays in converting new renewable feedstock into biofuels and biochemicals. Both homogeneous and heterogeneous catalysts and catalytic processes will be discussed in a unified and comprehensive approach. There will be extensive cross-referencing within all volumes. The various sources of environmental pollution are the theme of this volume. The volume lists all current environmentally friendly catalytic chemical processes used for environmental remediation and critically compares their economic viability. Offers in-depth coverage of all catalytic topics of current interest and outlines future challenges and research areas A clear and visual description of all parameters and conditions, enabling the reader to draw conclusions for a particular case Outlines the catalytic processes applicable to energy generation and design of green proce...

Insights into reaction mechanisms in heterogeneous catalysis revealed by in situ NMR spectroscopy.

Science.gov (United States)

Blasco, Teresa

2010-12-01

This tutorial review intends to show the possibilities of in situ solid state NMR spectroscopy in the elucidation of reaction mechanisms and the nature of the active sites in heterogeneous catalysis. After a brief overview of the more usual experimental devices used for in situ solid state NMR spectroscopy measurements, some examples of applications taken from the recent literature will be presented. It will be shown that in situ NMR spectroscopy allows: (i) the identification of stable intermediates and transient species using indirect methods, (ii) to prove shape selectivity in zeolites, (iii) the study of reaction kinetics, and (iv) the determination of the nature and the role played by the active sites in a catalytic reaction. The approaches and methodology used to get this information will be illustrated here summarizing the most relevant contributions on the investigation of the mechanisms of a series of reactions of industrial interest: aromatization of alkanes on bifunctional catalysts, carbonylation reaction of methanol with carbon monoxide, ethylbenzene disproportionation, and the Beckmann rearrangement reaction. Special attention is paid to the research carried out on the role played by carbenium ions and alkoxy as intermediate species in the transformation of hydrocarbon molecules on solid acid catalysts.

Molecular catalysis and high-volume organic synthesis

Energy Technology Data Exchange (ETDEWEB)

Khidekel, M L; Vasserberg, V E

1977-01-01

The field of catalysis is very wide. The properties of catalysts are briefly reviewed and compared with the properties of enzymes. Various uses of enxymes in industry (sugar from corn, cellulose breakdown, etc.) are pointed out. The types of homogeneous and heterogeneous catalysts for use in organic synthesis are discussed. 48 refs. (SJR)

Assessment of research needs for advanced heterogeneous catalysts for energy applications. Final report: Volume 2, Topic reports

Energy Technology Data Exchange (ETDEWEB)

Mills, G.A.

1994-04-01

This report assesses the direction, technical content, and priority of research needs judged to provide the best chance of yielding new and improved heterogeneous catalysts for energy-related applications over the period of 5-20 years. It addresses issues of energy conservation, alternate fuels and feedstocks, and the economics and applications that could alleviate pollution from energy processes. Recommended goals are defined in 3 research thrusts: catalytic science, environmental protection by catalysis, and industrial catalytic applications. This study was conducted by an 11-member panel of experts from industry and academia, including one each from Japan and Europe. This volume first presents an in-depth overview of the role of catalysis in future energy technology in chapter 1; then current catalytic research is critically reviewed and research recommended in 8 topic chapters: catalyst preparation (design and synthesis), catalyst characterization (structure/function), catalyst performance testing, reaction kinetics/reactor design, catalysis for industrial chemicals, catalysis for electrical applications (clean fuels, pollution remediation), catalysis for control of exhaust emissions, and catalysts for liquid transportation fuels from petroleum, coal, residual oil, and biomass.

Crown ethers and phase transfer catalysis in polymer science

CERN Document Server

Carraher, Charles

1984-01-01

Phase transfer catalysis or interfacial catalysis is a syn­ thetic technique involving transport of an organic or inorganic salt from a solid or aqueous phase into an organic liquid where reaction with an organic-soluble substrate takes place. Over the past 15 years there has been an enormous amount of effort invested in the development of this technique in organic synthe­ sis. Several books and numerous review articles have appeared summarizing applications in which low molecular weight catalysts are employed. These generally include either crown ethers or onium salts of various kinds. While the term phase transfer catalysis is relatively new, the concept of using a phasetrans­ fer agent (PTA) is much older~ Both Schnell and Morgan employed such catalysts in synthesis of polymeric species in the early 1950's. Present developments are really extensions of these early applications. It has only been within the last several years that the use of phase transfer processes have been employed in polymer synthesis...

Approaches to single-nanoparticle catalysis.

Science.gov (United States)

Sambur, Justin B; Chen, Peng

2014-01-01

Nanoparticles are among the most important industrial catalysts, with applications ranging from chemical manufacturing to energy conversion and storage. Heterogeneity is a general feature among these nanoparticles, with their individual differences in size, shape, and surface sites leading to variable, particle-specific catalytic activity. Assessing the activity of individual nanoparticles, preferably with subparticle resolution, is thus desired and vital to the development of efficient catalysts. It is challenging to measure the activity of single-nanoparticle catalysts, however. Several experimental approaches have been developed to monitor catalysis on single nanoparticles, including electrochemical methods, single-molecule fluorescence microscopy, surface plasmon resonance spectroscopy, X-ray microscopy, and surface-enhanced Raman spectroscopy. This review focuses on these experimental approaches, the associated methods and strategies, and selected applications in studying single-nanoparticle catalysis with chemical selectivity, sensitivity, or subparticle spatial resolution.

Tandem catalysis: a new approach to polymers.

Science.gov (United States)

Robert, Carine; Thomas, Christophe M

2013-12-21

The creation of polymers by tandem catalysis represents an exciting frontier in materials science. Tandem catalysis is one of the strategies used by Nature for building macromolecules. Living organisms generally synthesize macromolecules by in vivo enzyme-catalyzed chain growth polymerization reactions using activated monomers that have been formed within cells during complex metabolic processes. However, these biological processes rely on highly complex biocatalysts, thus limiting their industrial applications. In order to obtain polymers by tandem catalysis, homogeneous and enzyme catalysts have played a leading role in the last two decades. In the following feature article, we will describe selected published efforts to achieve these research goals.

New and future developments in catalysis activation of carbon dioxide

CERN Document Server

Suib, Steven L

2013-01-01

New and Future Developments in Catalysis is a package of books that compile the latest ideas concerning alternate and renewable energy sources and the role that catalysis plays in converting new renewable feedstock into biofuels and biochemicals. Both homogeneous and heterogeneous catalysts and catalytic processes will be discussed in a unified and comprehensive approach. There will be extensive cross-referencing within all volumes. This volume presents a complete picture of all carbon dioxide (CO2) sources, outlines the environmental concerns regarding CO2, and critica

Nanoscale heterogeneity at the aqueous electrolyte-electrode interface

Science.gov (United States)

Limmer, David T.; Willard, Adam P.

2015-01-01

Using molecular dynamics simulations, we reveal emergent properties of hydrated electrode interfaces that while molecular in origin are integral to the behavior of the system across long times scales and large length scales. Specifically, we describe the impact of a disordered and slowly evolving adsorbed layer of water on the molecular structure and dynamics of the electrolyte solution adjacent to it. Generically, we find that densities and mobilities of both water and dissolved ions are spatially heterogeneous in the plane parallel to the electrode over nanosecond timescales. These and other recent results are analyzed in the context of available experimental literature from surface science and electrochemistry. We speculate on the implications of this emerging microscopic picture on the catalytic proficiency of hydrated electrodes, offering a new direction for study in heterogeneous catalysis at the nanoscale.

Complexes with charge transfer and ion-radical salts in catalysis

Energy Technology Data Exchange (ETDEWEB)

Krylov, O V [AN SSSR, Moscow. Inst. Khimicheskoj Fiziki

1978-01-01

Considered are the data experimentally proving formation of complexes with charge transfer as intermediate complexes in homogeneous and heterogeneous catalysis. Catalytic activity correlations with charge transfer energy (and in heterogeneous catalysis with width of semiconductor forbidden band can be useful while selection of catalysts (MoO/sub 3//MgO; V/sub 2/O/sub 5//MgO; MoO/sub 3//Al/sub 2/O/sub 3/; V/sub 2/O/sub 5//Al/sub 2/O/sub 3/). A review of papers on catalytic activity of the previously prepared complexes with charge transfer and ion-radical salts is given. The use of alkali metal complexes with aromatic compounds showed their high activity in hydrogenation reactions and proved principle possibility of activation of hydrogen and hydrocarbons by the systems which do not contain transfer metals.

Chemical kinetics: on the heterogeneous catalysis processes leading to an exchange between two phases. Example: isotopic exchange reactions; Cinetique chimique: sur les processus de catalyse 'heterogene' conduisant a un echange entre deux phases. Exemple: reactions d'echange isotopique

Energy Technology Data Exchange (ETDEWEB)

Dirian, G; Grandcollot, P [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1961-07-01

For an exchange reaction between a gaseous and a liquid phase proceeding by 'heterogeneous' catalysis in the liquid phase, diffusion in the liquid and the chemical reaction are two simultaneous and indivisible processes. We have nevertheless been able to establish criteria making it possible to distinguish between a really homogeneous kinetic process and a pseudo-homogeneous one. (author) [French] Pour une reaction d'echange entre une phase gazeuse et une phase liquide procedant par catalyse 'heterogene' en phase liquide, la diffusion dans le liquide et la reaction chimique sont deux etapes simultanees et indissociables. Nous avons pu neanmoins etablir des criteres permettant de distinguer entre une cinetique homogene vraie et une cinetique pseudo-homogene. (auteur)

Heterogeneously Catalysed Chemical Reactions in Carbon Dioxide Medium

DEFF Research Database (Denmark)

Musko, Nikolai E.

In this PhD-study the different areas of chemical engineering, heterogeneous catalysis, supercritical fluids, and phase equilibrium thermodynamics have been brought together for selected reactions. To exploit the beneficial properties of supercritical fluids in heterogeneous catalysis, experimental...... studies of catalytic chemical reactions in dense and supercritical carbon dioxide have been complemented by the theoretical calculations of phase equilibria using advanced thermodynamic models. In the recent years, the use of compressed carbon dioxide as innovative, non-toxic and non-flammable, cheap......, and widely available reaction medium for many practical and industrial applications has drastically increased. Particularly attractive are heterogeneously catalysed chemical reactions. The beneficial use of CO2 is attributed to its unique properties at dense and supercritical states (at temperatures...

Bridging the Gap: From Model Surfaces to Nanoparticle Analogs for Selective Oxidation and Steam Reforming of Methanol and Selective Hydrogenation Catalysis

Science.gov (United States)

Boucher, Matthew B.

Most industrial catalysts are very complex, comprising of non-uniform materials with varying structures, impurities, and interaction between the active metal and supporting substrate. A large portion of the ongoing research in heterogeneous catalysis focuses on understanding structure-function relationships in catalytic materials. In parallel, there is a large area of surface science research focused on studying model catalytic systems for which structural parameters can be tuned and measured with high precision. It is commonly argued, however, that these systems are oversimplified, and that observations made in model systems do not translate to robust catalysts operating in practical environments; this discontinuity is often referred to as a "gap." The focus of this thesis is to explore the mutual benefits of surface science and catalysis, or "bridge the gap," by studying two catalytic systems in both ultra-high vacuum (UHV) and near ambient-environments. The first reaction is the catalytic steam reforming of methanol (SRM) to hydrogen and carbon dioxide. The SRM reaction is a promising route for on-demand hydrogen production. For this catalytic system, the central hypothesis in this thesis is that a balance between redox capability and weak binding of reaction intermediates is necessary for high SRM activity and selectivity to carbon dioxide. As such, a new catalyst for the SRM reaction is developed which incorporates very small amounts of gold (liquid-phase, stirred-tank batch reactor under a hydrogen head pressure of approximately 7 bar. Palladium alloyed into the surface of otherwise inactive copper nanoparticles shows a marked improvement in selectivity when compared to monometallic palladium catalysts with the same metal loading. This effect is attributed hydrogen spillover onto the copper surface. In summary, the development of new, highly active and selective catalysts for the methanol steam reforming reaction and for the partial hydrogenation of alkynes

At the frontier between heterogeneous and homogeneous catalysis: hydrogenation of olefins and alkynes with soluble iron nanoparticles.

Science.gov (United States)

Rangheard, Claudine; de Julián Fernández, César; Phua, Pim-Huat; Hoorn, Johan; Lefort, Laurent; de Vries, Johannes G

2010-09-28

The use of non-supported Fe nanoparticles in the hydrogenation of unsaturated C-C bonds is a green catalytic concept at the frontier between homogeneous and heterogeneous catalysis. Iron nanoparticles can be obtained by reducing Fe salts with strong reductants in various solvents. FeCl(3) reduced by 3 equivalents of EtMgCl forms an active catalyst for the hydrogenation of a range of olefins and alkynes. Olefin hydrogenation is relatively fast at 5 bar using 5 mol% of catalyst. The catalyst is also active for terminal olefins and 1,1' and 1,2-cis disubstituted olefins while trans-olefins react much slower. 1-Octyne is hydrogenated to mixtures of 1-octene and octane. Kinetic studies led us to propose a mechanism for this latter transformation where octane is obtained by two different pathways. Characterization of the nanoparticles via TEM, magnetic measurements and poisoning experiments were undertaken to understand the true nature of our catalyst.

Towards an atomic level understanding of niobia based catalysts and catalysis by combining the science of catalysis with surface science

Directory of Open Access Journals (Sweden)

Martin Schmal

2009-06-01

Full Text Available The science of catalysis and surface science have developed, independently, key information for understanding catalytic processes. One might argue: is there anything fundamental to be discovered through the interplay between catalysis and surface science? Real catalysts of monometallic and bimetallic Co/Nb2O5 and Pd-Co/Nb2O5 catalysts showed interesting selectivity results on the Fischer-Tropsch synthesis (Noronha et al. 1996, Rosenir et al. 1993. The presence of a noble metal increased the C+5 selectivity and decreased the methane formation depending of the reduction temperature. Model catalyst of Co-Pd supported on niobia and alumina were prepared and characterized at the atomic level, thus forming the basis for a comparison with "real" support materials. Growth, morphology and structure of both pure metal and alloy particles were studied. It is possible to support the strong metal support interaction suggested by studies on real catalysts via the investigation of model systems for niobia in comparison to alumina support in which this effect does not occur. Formation of Co2+ penetration into the niobia lattice was suggested on the basis of powder studies and can be fully supported on the basis of model studies. It is shown for both real catalysts and model systems that oxidation state of Co plays a key role in controlling the reactivity in Fischer-Tropsch reactions systems and that the addition of Pd is a determining factor for the stability of the catalyst. It is demonstrated that the interaction with unsaturated hydrocarbons depends strongly on the state of oxidation.As ciências da catálise e da superfície têm desenvolvido independentemente temas básicos para o entendimento de processos catalíticos. Pode-se até questionar se há ainda algo fundamental para ser descoberto através da interface entre catálise eciência da superfície? Catalisadores mono e bimetálicos de Co/Nb2O5 e Pd-Co/ Nb2O5 apresentaram resultados interessantes de

Advances in catalysis

International Nuclear Information System (INIS)

Eley, D.D.; Pine, H.; Weisz, P.B.

1989-01-01

This book reports on the current state of knowledge concerning structure and catalysis of metals and metal oxide particles, old and new. It addresses the basic and broad problems of what the catalytically relevant surface structures of metals are, where we stand in techniques capable of attacking this problem, and what the current state of knowledge is. The focus is on long-standing, important, and central problem of general investigative methodology and strategy: the pressure gap is created by the fact that the best techniques of surface analysis require high-vacuum conditions, while useful catalysis is confined to conditions of near ambient or higher pressures. The authors review the basic question of the influence of particle size on catalytic behavior of metal particles which involves questions of the basic sciences as much as practical considerations of catalyst design and use. They discuss preparatory techniques, analytical technology, and methods of characterization of these materials

Kinetic evolutionary behavior of catalysis-select migration

International Nuclear Information System (INIS)

Wu Yuan-Gang; Lin Zhen-Quan; Ke Jian-Hong

2012-01-01

We propose a catalysis-select migration driven evolution model of two-species (A- and B-species) aggregates, where one unit of species A migrates to species B under the catalysts of species C, while under the catalysts of species D the reaction will become one unit of species B migrating to species A. Meanwhile the catalyst aggregates of species C perform self-coagulation, as do the species D aggregates. We study this catalysis-select migration driven kinetic aggregation phenomena using the generalized Smoluchowski rate equation approach with C species catalysis-select migration rate kernel K(k;i,j) = Kkij and D species catalysis-select migration rate kernel J(k;i,j)= Jkij. The kinetic evolution behaviour is found to be dominated by the competition between the catalysis-select immigration and emigration, in which the competition is between JD 0 and KC 0 (D 0 and C 0 are the initial numbers of the monomers of species D and C, respectively). When JD 0 −KC 0 > 0, the aggregate size distribution of species A satisfies the conventional scaling form and that of species B satisfies a modified scaling form. And in the case of JD 0 −KC 0 0 −KC 0 > 0 case. (interdisciplinary physics and related areas of science and technology)

Cooperative catalysis by silica-supported organic functional groups

OpenAIRE

Margelefsky, Eric L.; Zeidan, Ryan K.; Davis, Mark E.

2008-01-01

Hybrid inorganic–organic materials comprising organic functional groups tethered from silica surfaces are versatile, heterogeneous catalysts. Recent advances have led to the preparation of silica materials containing multiple, different functional groups that can show cooperative catalysis; that is, these functional groups can act together to provide catalytic activity and selectivity superior to what can be obtained from either monofunctional materials or homogeneous catalysts. This tutorial...

Reactor for in situ measurements of spatially resolved kinetic data in heterogeneous catalysis

Science.gov (United States)

Horn, R.; Korup, O.; Geske, M.; Zavyalova, U.; Oprea, I.; Schlögl, R.

2010-06-01

The present work describes a reactor that allows in situ measurements of spatially resolved kinetic data in heterogeneous catalysis. The reactor design allows measurements up to temperatures of 1300 °C and 45 bar pressure, i.e., conditions of industrial relevance. The reactor involves reactants flowing through a solid catalyst bed containing a sampling capillary with a side sampling orifice through which a small fraction of the reacting fluid (gas or liquid) is transferred into an analytical device (e.g., mass spectrometer, gas chromatograph, high pressure liquid chromatograph) for quantitative analysis. The sampling capillary can be moved with μm resolution in or against flow direction to measure species profiles through the catalyst bed. Rotation of the sampling capillary allows averaging over several scan lines. The position of the sampling orifice is such that the capillary channel through the catalyst bed remains always occupied by the capillary preventing flow disturbance and fluid bypassing. The second function of the sampling capillary is to provide a well which can accommodate temperature probes such as a thermocouple or a pyrometer fiber. If a thermocouple is inserted in the sampling capillary and aligned with the sampling orifice fluid temperature profiles can be measured. A pyrometer fiber can be used to measure the temperature profile of the solid catalyst bed. Spatial profile measurements are demonstrated for methane oxidation on Pt and methane oxidative coupling on Li/MgO, both catalysts supported on reticulated α -Al2O3 foam supports.

Advances in catalysis

CERN Document Server

Gates, Bruce C

2012-01-01

Advances in Catalysis fills the gap between the journal papers and the textbooks across the diverse areas of catalysis research. For more than 60 years Advances in Catalysis has been dedicated to recording progress in the field of catalysis and providing the scientific community with comprehensive and authoritative reviews. This series in invaluable to chemical engineers, physical chemists, biochemists, researchers and industrial chemists working in the fields of catalysis and materials chemistry. * In-depth, critical, state-of-the-art reviews * Comprehensive, covers of all as

Dedicated Beamline Facilities for Catalytic Research. Synchrotron Catalysis Consortium (SCC)

Energy Technology Data Exchange (ETDEWEB)

Chen, Jingguang [Columbia Univ., New York, NY; Frenkel, Anatoly [Yeshiva Univ., New York, NY (United States); Rodriguez, Jose [Brookhaven National Lab. (BNL), Upton, NY (United States); Adzic, Radoslav [Brookhaven National Lab. (BNL), Upton, NY (United States); Bare, Simon R. [UOP LLC, Des Plaines, IL (United States); Hulbert, Steve L. [Brookhaven National Lab. (BNL), Upton, NY (United States); Karim, Ayman [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Mullins, David R. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Overbury, Steve [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

2015-03-04

Synchrotron spectroscopies offer unique advantages over conventional techniques, including higher detection sensitivity and molecular specificity, faster detection rate, and more in-depth information regarding the structural, electronic and catalytic properties under in-situ reaction conditions. Despite these advantages, synchrotron techniques are often underutilized or unexplored by the catalysis community due to various perceived and real barriers, which will be addressed in the current proposal. Since its establishment in 2005, the Synchrotron Catalysis Consortium (SCC) has coordinated significant efforts to promote the utilization of cutting-edge catalytic research under in-situ conditions. The purpose of the current renewal proposal is aimed to provide assistance, and to develop new sciences/techniques, for the catalysis community through the following concerted efforts: Coordinating the implementation of a suite of beamlines for catalysis studies at the new NSLS-II synchrotron source; Providing assistance and coordination for catalysis users at an SSRL catalysis beamline during the initial period of NSLS to NSLS II transition; Designing in-situ reactors for a variety of catalytic and electrocatalytic studies; Assisting experimental set-up and data analysis by a dedicated research scientist; Offering training courses and help sessions by the PIs and co-PIs.

Design of sintering-stable heterogeneous catalysts

DEFF Research Database (Denmark)

Gallas-Hulin, Agata

One of the major issues in the use of metal nanoparticles in heterogeneous catalysis is sintering. Sintering occurs at elevated temperatures because of increased mobility of nanoparticles, leading to their agglomeration and, as a consequence, to the deactivation of the catalyst. It is an emerging...... problem especially for the noble metals-based catalysis. These metals being expensive and scarce, it is worth developing catalyst systems which preserve their activity over time. Encapsulation of nanoparticles inside zeolites is one of the ways to prevent sintering. Entrapment of nanoparticles inside...

2010 CATALYSIS GORDON RESEARCH CONFERENCE, JUNE 27 - JULY 2, 2010, NEW LONDON, NEW HAMPSHIRE

Energy Technology Data Exchange (ETDEWEB)

Abhaya Datye

2010-07-02

Catalysis is a key technology for improving the quality of life while simultaneously reducing the adverse impact of human activities on the environment. The discovery of new catalytic processes and the improvement of existing ones are also critically important for securing the nation's energy supply. The GRC on Catalysis is considered one the most prestigious conference for catalysis research, bringing together leading researchers from both academia, industry and national labs to discuss the latest, most exciting research in catalysis and the future directions for the field. The 2010 GRC on Catalysis will follow time-honored traditions and feature invited talks from the world's leading experts in the fundamentals and applications of catalytic science and technology. We plan to have increased participation from industry. The extended discussions in the company of outstanding thinkers will stimulate and foster new science. The conference will include talks in the following areas: Alternative feedstocks for chemicals and fuels, Imaging and spectroscopy, Design of novel catalysts, Catalyst preparation fundamentals, Molecular insights through theory, Surface Science, Catalyst stability and dynamics. In 2010, the Catalysis conference will move to a larger conference room with a new poster session area that will allow 40 posters per session. The dorm rooms provide single and double accommodations, free WiFi and the registration fee includes all meals and the famous lobster dinner on Thursday night. Afternoons are open to enjoy the New England ambiance with opportunities for hiking, sailing, golf and tennis to create an outstanding conference that will help you network with colleagues, and make long lasting connections.

Surface science of single-site heterogeneous olefin polymerization catalysts

OpenAIRE

Kim, Seong H.; Somorjai, Gabor A.

2006-01-01

This article reviews the surface science of the heterogeneous olefin polymerization catalysts. The specific focus is on how to prepare and characterize stereochemically specific heterogeneous model catalysts for the Ziegler–Natta polymerization. Under clean, ultra-high vacuum conditions, low-energy electron irradiation during the chemical vapor deposition of model Ziegler–Natta catalysts can be used to create a “single-site” catalyst film with a surface structure that produces only isotactic ...

Theoretical mo delling of nanoparticles with applications to catalysis and sustainable energy

DEFF Research Database (Denmark)

Brodersen, Simon Hedegaard

The aim of this thesis is to gain a better understanding of the shape and structure of nanoparticles. Nanoparticles are important in heterogeneous catalysis, where the chemical reaction happens at the surface, since they maximise the available surface area for a given amount of catalyst. Studies...

Magnetic catalysis and inverse magnetic catalysis in QCD

International Nuclear Information System (INIS)

Mueller, N.

2015-01-01

We investigate the effects of strong magnetic fields on the QCD phase structure at vanishing density by solving the gluon and quark gap equations. The chiral crossover temperature as well as the chiral condensate is computed. For asymptotically large magnetic fields we find magnetic catalysis, while we find inverse magnetic catalysis for intermediate magnetic fields. Moreover, for large magnetic fields the chiral phase transition for massless quarks turns into a crossover. The underlying mechanisms are then investigated analytically within a few simplifications of the full numerical analysis. We find that a combination of gluon screening effects and the weakening of the strong coupling is responsible for the phenomenon of inverse catalysis seen in lattice studies. In turn, the magnetic catalysis at large magnetic field is already indicated by simple arguments based on dimensionality. (author)

Real-Time Monitoring of Heterogeneous Catalysis with Mass Spectrometry

Science.gov (United States)

Young, Mark A.

2009-01-01

Heterogeneous, gas-solid processes constitute an important class of catalytic reactions that play a key role in a variety of applications, such as industrial processing and environmental controls. Heterogeneous catalytic chemistry can be demonstrated in a simple heated flow reactor containing a fragment of the catalytic converter from a vehicular…

On the compensation effect in heterogeneous catalysis

DEFF Research Database (Denmark)

Pedersen, Thomas Bligaard; Honkala, Johanna Karoliina; Logadottir, Ashildur

2003-01-01

For a class of heterogeneously catalyzed reactions, we explain the compensation effect in terms of a switching of kinetic regimes leading to a concomitant change in the apparent activation energy and in the prefactor for the overall rate of the reaction. We first use the ammonia synthesis...

Titanium Dioxide as a Catalyst Support in Heterogeneous Catalysis

Science.gov (United States)

Bagheri, Samira; Muhd Julkapli, Nurhidayatullaili; Bee Abd Hamid, Sharifah

2014-01-01

The lack of stability is a challenge for most heterogeneous catalysts. During operations, the agglomeration of particles may block the active sites of the catalyst, which is believed to contribute to its instability. Recently, titanium oxide (TiO2) was introduced as an alternative support material for heterogeneous catalyst due to the effect of its high surface area stabilizing the catalysts in its mesoporous structure. TiO2 supported metal catalysts have attracted interest due to TiO2 nanoparticles high activity for various reduction and oxidation reactions at low pressures and temperatures. Furthermore, TiO2 was found to be a good metal oxide catalyst support due to the strong metal support interaction, chemical stability, and acid-base property. The aforementioned properties make heterogeneous TiO2 supported catalysts show a high potential in photocatalyst-related applications, electrodes for wet solar cells, synthesis of fine chemicals, and others. This review focuses on TiO2 as a support material for heterogeneous catalysts and its potential applications. PMID:25383380

Development of Molecular Catalysts to Bridge the Gap between Heterogeneous and Homogeneous Catalysts

Science.gov (United States)

Ye, Rong

Catalysts, heterogeneous, homogeneous, and enzymatic, are comprised of nanometer-sized inorganic and/or organic components. They share molecular factors including charge, coordination, interatomic distance, bonding, and orientation of catalytically active atoms. By controlling the governing catalytic components and molecular factors, catalytic processes of a multichannel and multiproduct nature could be run in all three catalytic platforms to create unique end-products. Unifying the fields of catalysis is the key to achieving the goal of 100% selectivity in catalysis. Recyclable catalysts, especially those that display selective reactivity, are vital for the development of sustainable chemical processes. Among available catalyst platforms, heterogeneous catalysts are particularly well-disposed toward separation from the reaction mixture via filtration methods, which renders them readily recyclable. Furthermore, heterogeneous catalysts offer numerous handles - some without homogeneous analogues - for performance and selectivity optimization. These handles include nanoparticle size, pore profile of porous supports, surface ligands and interface with oxide supports, and flow rate through a solid catalyst bed. Despite these available handles, however, conventional heterogeneous catalysts are themselves often structurally heterogeneous compared to homogeneous catalysts, which complicates efforts to optimize and expand the scope of their reactivity and selectivity. Ongoing efforts are aimed to address the above challenge by heterogenizing homogeneous catalysts, which can be defined as the modification of homogeneous catalysts to render them in a separable (solid) phase from the starting materials and products. Specifically, we grow the small nanoclusters in dendrimers, a class of uniform polymers with the connectivity of fractal trees and generally radial symmetry. Thanks to their dense multivalency, shape persistence and structural uniformity, dendrimers have proven to

Multicatalyst system in asymmetric catalysis

CERN Document Server

Zhou, Jian

2014-01-01

This book introduces multi-catalyst systems by describing their mechanism and advantages in asymmetric catalysis.  Helps organic chemists perform more efficient catalysis with step-by-step methods  Overviews new concepts and progress for greener and economic catalytic reactions  Covers topics of interest in asymmetric catalysis including bifunctional catalysis, cooperative catalysis, multimetallic catalysis, and novel tandem reactions   Has applications for pharmaceuticals, agrochemicals, materials, and flavour and fragrance

Spatial coupling in heterogeneous catalysis

Science.gov (United States)

Yamamoto, S. Y.; Surko, C. M.; Maple, M. B.

1995-11-01

Spatial coupling mechanisms are studied in the heterogeneous catalytic oxidation of carbon monoxide over platinum at atmospheric pressure under oscillatory conditions. Experiments are conducted in a continuous flow reactor, and the reaction rate is monitored using both infrared imaging and thermocouples. The catalysts are in the form of platinum annular thin films on washer-shaped quartz substrates, and they provide highly repeatable oscillatory behavior. Oscillations are typically spatially synchronized with the entire catalyst ``flashing'' on and off uniformly. Spatial coupling is investigated by introducing various barriers which split the annular ring in half. Infrared images show that coupling through the gas phase dominates coupling via the diffusion of CO on the surface or heat diffusion through the substrate. The introduction of a localized heat perturbation to the catalyst surface does not induce a transition in the reaction rate. Thus, it is likely that the primary mode of communication is through the gas-phase diffusion of reactants.

Green catalysis by nanoparticulate catalysts developed for flow processing? case study of glucose hydrogenation

NARCIS (Netherlands)

Gericke, D.; Ott-Reinhardt, D.; Matveeva, V.; Sulman, E.M.; Aho, A.; Murzin, D.Y.; Roggan, S.; Danilova, L.; Hessel, V.; Löb, P.; Kralisch, D.

2015-01-01

Heterogeneous catalysis, flow chemistry, continuous processing, green solvents, catalyst immobilization and recycling are some of the most relevant, emerging key technologies to achieve green synthesis. However, a quantification of potential effects on a case to case level is required to provide a

Nano-catalysts: Bridging the gap between homogeneous and heterogeneous catalysis

Science.gov (United States)

Functionalized nanoparticles have emerged as sustainable alternatives to conventional materials, as robust, high-surface-area heterogeneous catalyst supports. We envisioned a catalyst system, which can bridge the homogenous and heterogeneous system. Postsynthetic surface modifica...

Graphene: a promising two-dimensional support for heterogeneous catalysts

Directory of Open Access Journals (Sweden)

Xiaobin eFan

2015-01-01

Full Text Available Graphene has many advantages that make it an attractive two-dimensional (2D support for heterogeneous catalysts. It not only allows the high loading of targeted catalytic species, but also facilitates the mass transfer during the reaction processes. These advantages, along with its unique physical and chemical properties, endow graphene great potential as catalyst support in heterogeneous catalysis.

Theoretical Studies in Heterogenous Catalysis: Towards a Rational Design of Novel Catalysts for Hydrodesulfurization and Hydrogen Production

Energy Technology Data Exchange (ETDEWEB)

Rodriguez,J.A.; Liu, P.

2008-10-01

Traditionally, knowledge in heterogeneous catalysis has come through empirical research. Nowadays, there is a clear interest to change this since millions of dollars in products are generated every year in the chemical and petrochemical industries through catalytic processes. To obtain a fundamental knowledge of the factors that determine the activity of heterogeneous catalysts is a challenge for modern science since many of these systems are very complex in nature. In principle, when a molecule adsorbs on the surface of a heterogeneous catalyst, it can interact with a large number of bonding sites. It is known that the chemical properties of these bonding sites depend strongly on the chemical environment around them. Thus, there can be big variations in chemical reactivity when going from one region to another in the surface of a heterogeneous catalyst. A main objective is to understand how the structural and electronic properties of a surface affect the energetics for adsorption processes and the paths for dissociation and chemical reactions. In recent years, advances in instrumentation and experimental procedures have allowed a large series of detailed works on the surface chemistry of heterogeneous catalysts. In many cases, these experimental studies have shown interesting and unique phenomena. Theory is needed to unravel the basic interactions behind these phenomena and to provide a general framework for the interpretation of experimental results. Ideally, theoretical calculations based on density-functional theory have evolved to the point that one should be able to predict patterns in the activity of catalytic surfaces. As in the case of experimental techniques, no single theoretical approach is able to address the large diversity of phenomena occurring on a catalyst. Catalytic surfaces are usually modeled using either a finite cluster or a two-dimensionally periodic slab. Many articles have been published comparing the results of these two approaches. An

Catalysis in flow microreactors with wall coatings of acidic polymer brushes and dendrimer-encapsulated nanoparticles

NARCIS (Netherlands)

Ricciardi, R.

2015-01-01

Continuous-flow microreactors are an invaluable tool to carry out organic reactions owing to their numerous advantages with respect to batch scale synthesis. In particular, supported catalysts enable heterogeneous catalysis to be conducted in an efficient way. In this thesis, the development and

Assessment of research needs for advanced heterogeneous catalysts for energy applications. Final report: Volume 1, Executive summary

Energy Technology Data Exchange (ETDEWEB)

Mills, G.A.

1994-04-01

This report assesses the direction, technical content, and priority of research needs judged to provide the best chance of yielding new and improved heterogeneous catalysts for energy-related applications over a period of 5--20 years. It addresses issues of energy conservation, alternate fuels and feedstocks, and the economics and applications that could alleviate pollution from energy processes. Recommended goals are defined in 3 major, closely linked research thrusts: catalytic science, environmental protection by catalysis, and industrial catalytic applications. This volume provides a comprehensive executive summary, including research recommendations.

Data and Network Science for Noisy Heterogeneous Systems

Science.gov (United States)

Rider, Andrew Kent

2013-01-01

Data in many growing fields has an underlying network structure that can be taken advantage of. In this dissertation we apply data and network science to problems in the domains of systems biology and healthcare. Data challenges in these fields include noisy, heterogeneous data, and a lack of ground truth. The primary thesis of this work is that…

Active sites engineering of metal-organic frameworks for heterogeneous catalysis

Energy Technology Data Exchange (ETDEWEB)

Li, Xinle [Iowa State Univ., Ames, IA (United States)

2016-12-17

In conclusion, we have for the first time developed a novel solid base catalyst, Ndoped MOF-253 derived porous carbons (Cz-MOF-253). Cz-MOF-253 is highly porous and exhibit high efficiency in Knoevenagel condensation reaction. Furthermore, Cz-MOF-253 is robust and can be reused up to five times. In comparison, the analogous nitrogen-free catalyst-Cz-DUT-5, and other nitrogen- MOFs derived carbon showed an inferior performance. Moreover, the high basicity and porous nature enable the design of bifunctional catalyst and facilitate tandem condensation-hydrogenation reactions. This work delineates the first attempt that demonstrates MOF-derived carbons as solid base catalyst and its potential application in tandem catalysis. Future work on exploring new catalytic reactions based on such porous Lewis basic MOF-derived carbons is currently underway.

Surface-Enhanced Raman Spectroscopy for Heterogeneous Catalysis Research

NARCIS (Netherlands)

Harvey, C.E.

2013-01-01

Raman spectroscopy is valuable characterization technique for the chemical analysis of heterogeneous catalysts, both under ex-situ and in-situ conditions. The potential for Raman to shine light on the chemical bonds present in a sample makes the method highly desirable for detailed catalyst

Heterogeneous catalysis: on bathroom mirrors and boiling stones

NARCIS (Netherlands)

Philipse, A.P.

2011-01-01

A catalyst is defined as a substance that accelerates a process without undergoing a net change due to that process. Most chemistry students learn about catalysts in the context of chemical reactions, such as the enzymes in biochemistry or the heterogeneous metal catalysts in inorganic chemistry (1,

Coal-related research, organic chemistry, and catalysis

International Nuclear Information System (INIS)

Anon.

1980-01-01

Coal chemistry research topics included: H exchange at 400 0 C, breaking C-C bonds in coal, molecular weight estimation using small-angle neutron scattering, 13 C NMR spectra of coals, and tunneling during H/D isotope effects. Studies of coal conversion chemistry included thermolysis of bibenzyl and 1-naphthol, heating of coals in phenol, advanced indirect liquefaction based on Koelbel slurry Fischer-Tropsch reactor, and plasma oxidation of coal minerals. Reactions of PAHs in molten SbCl 3 , a hydrocracking catalyst, were studied. Finally, heterogeneous catalysis (desulfurization etc.) was studied using Cu, Au, and Ni surfaces. 7 figures, 6 tables

Structural basis for catalysis at the membrane-water interface.

Science.gov (United States)

Dufrisne, Meagan Belcher; Petrou, Vasileios I; Clarke, Oliver B; Mancia, Filippo

2017-11-01

The membrane-water interface forms a uniquely heterogeneous and geometrically constrained environment for enzymatic catalysis. Integral membrane enzymes sample three environments - the uniformly hydrophobic interior of the membrane, the aqueous extramembrane region, and the fuzzy, amphipathic interfacial region formed by the tightly packed headgroups of the components of the lipid bilayer. Depending on the nature of the substrates and the location of the site of chemical modification, catalysis may occur in each of these environments. The availability of structural information for alpha-helical enzyme families from each of these classes, as well as several beta-barrel enzymes from the bacterial outer membrane, has allowed us to review here the different ways in which each enzyme fold has adapted to the nature of the substrates, products, and the unique environment of the membrane. Our focus here is on enzymes that process lipidic substrates. This article is part of a Special Issue entitled: Bacterial Lipids edited by Russell E. Bishop. Copyright © 2016 Elsevier B.V. All rights reserved.

Horizons in catalysis

Energy Technology Data Exchange (ETDEWEB)

Idol, J D

1979-04-21

A discussion covers a brief historical review of industrial catalysis; a survey of major present-day catalytic processes in the petroleum and petrochemical industries; the outlook for the industrial catalyst applications in coal liquefaction, conversion of coal liquids, shale oil, and other synthetic crude sources for transportation fuels, and synthesis gas-based processes; some important directions for future developments, including phase transfer catalysis, photocatalysis, and advanced techniques for catalyst studies; and the need for closer industry-university and industry-government cooperation in the field of catalysis.

Gender-heterogeneous working groups produce higher quality science.

Directory of Open Access Journals (Sweden)

Lesley G Campbell

Full Text Available Here we present the first empirical evidence to support the hypothesis that a gender-heterogeneous problem-solving team generally produced journal articles perceived to be higher quality by peers than a team comprised of highly-performing individuals of the same gender. Although women were historically underrepresented as principal investigators of working groups, their frequency as PIs at the National Center for Ecological Analysis and Synthesis is now comparable to the national frequencies in biology and they are now equally qualified, in terms of their impact on the accumulation of ecological knowledge (as measured by the h-index. While women continue to be underrepresented as working group participants, peer-reviewed publications with gender-heterogeneous authorship teams received 34% more citations than publications produced by gender-uniform authorship teams. This suggests that peers citing these publications perceive publications that also happen to have gender-heterogeneous authorship teams as higher quality than publications with gender uniform authorship teams. Promoting diversity not only promotes representation and fairness but may lead to higher quality science.

Gender-heterogeneous working groups produce higher quality science.

Science.gov (United States)

Campbell, Lesley G; Mehtani, Siya; Dozier, Mary E; Rinehart, Janice

2013-01-01

Here we present the first empirical evidence to support the hypothesis that a gender-heterogeneous problem-solving team generally produced journal articles perceived to be higher quality by peers than a team comprised of highly-performing individuals of the same gender. Although women were historically underrepresented as principal investigators of working groups, their frequency as PIs at the National Center for Ecological Analysis and Synthesis is now comparable to the national frequencies in biology and they are now equally qualified, in terms of their impact on the accumulation of ecological knowledge (as measured by the h-index). While women continue to be underrepresented as working group participants, peer-reviewed publications with gender-heterogeneous authorship teams received 34% more citations than publications produced by gender-uniform authorship teams. This suggests that peers citing these publications perceive publications that also happen to have gender-heterogeneous authorship teams as higher quality than publications with gender uniform authorship teams. Promoting diversity not only promotes representation and fairness but may lead to higher quality science.

Treatment of decontamination liquid waste of nuclear power plant components by heterogeneous photo catalysis with a continuous recirculation equipment

International Nuclear Information System (INIS)

Litter, Marta I.; La Gamma, Ana M.; Chocron, Mauricio; Blesa, Miguel A.; Repetto, Pablo

1999-01-01

It has been designed a bench scale, recirculation device, for testing the degradation of solutions of ethylendiamine tetraacetic acid (EDTA) by heterogeneous photo catalysis under irradiation with UV and titanium dioxide (TiO 2 ). Solutions of EDTA have been employed at concentrations and pH values similar to those used when a decontamination of nuclear power plant equipment is carried out. The circuit is composed of a photo reactor, a heat exchanger, a reservoir tank and a peristaltic pump. In the present paper, the results of the experiments of photo catalytic degradation of aqueous suspensions of TiO 2 (Degussa P-25) 1 g/L with EDTA (10 g/L) at pH 3.7 and 25 degree C and two irradiation wavelengths (366 and 254 nm) have been presented. At 366 nm the full degradation of EDTA has occurred in 10 hours. The 95% degradation of total organic carbon (TOC) has been achieved after 39 hours of irradiation. The irradiation at 254 nm in the same conditions has been much less effective (EDTA and TOC reduction of approximately 1%), due to a screening effect produced by the semiconductor. (author)

Recent Progress in Asymmetric Catalysis and Chromatographic Separation by Chiral Metal–Organic Frameworks

Directory of Open Access Journals (Sweden)

Suchandra Bhattacharjee

2018-03-01

Full Text Available Metal–organic frameworks (MOFs, as a new class of porous solid materials, have emerged and their study has established itself very quickly into a productive research field. This short review recaps the recent advancement of chiral MOFs. Here, we present simple, well-ordered instances to classify the mode of synthesis of chiral MOFs, and later demonstrate the potential applications of chiral MOFs in heterogeneous asymmetric catalysis and enantioselective separation. The asymmetric catalysis sections are subdivided based on the types of reactions that have been successfully carried out recently by chiral MOFs. In the part on enantioselective separation, we present the potentiality of chiral MOFs as a stationary phase for high-performance liquid chromatography (HPLC and high-resolution gas chromatography (GC by considering fruitful examples from current research work. We anticipate that this review will provide interest to researchers to design new homochiral MOFs with even greater complexity and effort to execute their potential functions in several fields, such as asymmetric catalysis, enantiomer separation, and chiral recognition.

Selective Oxidations using Nanostructured Heterogeneous Catalysts

DEFF Research Database (Denmark)

Mielby, Jerrik Jørgen

and because they produce H2O as the only by-product. Chapter 1 gives a short introduction to basic concepts in heterogeneous catalysis and green chemistry. Furthermore, the chapter gives an overview of the most important strategies to synthesise functional nanostructured materials and highlights how detailed......The aim of this thesis is to investigate and develop new efficient methods to oxidise alcohols and amines using heterogeneous catalysts and either O2 or H2O2 as oxidants. From an economic and environmental point of view, these oxidants are ideal, because they are cheap and readily available...... understanding of size, shape and structure can help in the development of new and more efficient heterogeneous catalysts. The chapter is not intended to give a complete survey, but rather to introduce some of the recent developments in the synthesis of nanostructured heterogeneous catalysts. Finally...

Applications of neutron scattering to heterogeneous catalysis

International Nuclear Information System (INIS)

Parker, Stewart F; Lennon, David

2016-01-01

Historically, most studies of heterogeneous catalysts that have used neutron vibrational spectroscopy have employed indirect geometry instruments with a low (<40 cm -1 ) final energy. In this paper we examine the reasons why this has been the case and highlight the advantages and disadvantages of this approach. We then show how some of these may be overcome by the use of direct geometry spectrometers. We illustrate the use of direct geometry spectrometers with examples from reforming of methane to synthesis gas (CO + H 2 ) over Ni/Al 2 O 3 catalysts and an operando study of CO oxidation. We conclude with a proposal for a unique instrument that combines both indirect and direct geometry spectrometers. (paper)

Environmental catalysis

International Nuclear Information System (INIS)

Montes Consuelo; Villa, Aida Luz

1996-01-01

The term environmental catalysis has been used lately to refer to a variety of applications of the catalysis, those which, they have grouped in the following categories: a) Control of emissions (chimney Gases and gases of the vehicles, Compound Organic Volatile (VOC), Scents, Chlorofluorocarbons) b) Conversion of having undone solids or liquids. C) Selective obtaining of alternating products that replace polluting compounds. d)replacement of catalysis environmentally dangerous And e)Development of catalysts for the obtaining of valuable chemical products without the formation of polluting by-products. In the group of Environmental Catalysis comes working in the first category, Particularly, in the exploration of active catalysts in the decrease of the emissions coming from combustion systems, carbon monoxide, hydrocarbons, nitrogen oxides (NOx), N20 and sulfur (SOx). Our fundamental premise is that the molecular meshes are catalytic potential for the development of a technology environmentally clean. These materials understand a class of inorganic compound with unique properties and intimately related with the structure. The net of the molecular meshes consists on tetrahedral configuration atoms (Al,Si, P, etc.) united to each other by oxygen atoms. As a result they are not formed three-dimensional structures alone with channels and cavities but also, with openings bounded by rings that consist of a certain number of tetrahedral atoms

Heterogeneous Organo-Catalysis: Sustainable Pathways to Furanics from Biomass

Science.gov (United States)

Glucose and fructose are among the most abundant plant-derived materials1 and have been converted into useful building units often used in the drug discovery and polymer architecture.2 Unfortunately, most of these conversions require mineral acids and complex heterogeneous cataly...

Features of the kinetics of heterogeneous reactions with phase transformations on catalyst surfaces

Energy Technology Data Exchange (ETDEWEB)

Berman, A D; Krylov, O V

1978-01-01

This paper presents a review of 41 bibliographic references to experiments on the adsorption of various gases (e.g., carbon monoxide, formic acid, ammonia, and oxygen) on metals (e.g., nickel, molybdenum, and platinum) and oxides covers observations of two-dimensional phases during adsorption; the kinetics of adsorption and catalysis associated with two-dimensional phase transitions; and several approximate models for describing the kinetics of heterogeneous catalysis which account for two-dimensional phase transformations on catalyst surfaces.

Contributions to a rational design of heterogeneous catalysts: from experimentation to numerical simulation; Contributions a une conception rationnelle des catalyseurs heterogenes: de l'experimentation a la simulation numerique

Energy Technology Data Exchange (ETDEWEB)

Toulhoat, H

2002-03-01

I present through this dissertation a synthesis of my contributions to the field of heterogeneous catalysis, along two decades of research undertaken as a scientist at Institut Francais du Petrole. I started my itinerary on the 'floor', with the task of developing industrial hydro-treating catalysts, then I had the nice opportunity to lead advanced research on various subjects. However, I have been devoting myself for the past ten years to the encounter between catalysis and theoretical chemistry. The presentation of my work follows therefore a guideline starting with preparation and ending at modelization of the catalytic solid, after having gone through its characterization and the assessment of its activity. Modelization is thus founded on a consistent set of experimental informations. This guideline is applied to the four main themes to which this work is confined: hydro-treating catalysts, hydro-de-metallation catalysts, thio-resistance of noble metals, and solid acids. In summary, I believe I have contributed significantly, on the one hand to strong conceptual and technical advances in the area of ab initio simulation of elementary phenomena in heterogeneous catalysis, with the elaboration of original knowledge on catalysis by sulfides, metals and acids, as well as the genesis of alumina carriers, and on the other hand to a new approach of periodic trends in catalysis: this can be considered as a re-visitation of the principle of Sabatier, leading to a predictive tool for catalytic activity of solids. In a near future it will be possible to say if practical results validate this conceptual tool, and justify or not the ambitious title I gave to my work. (author)

Surface and nanomolecular catalysis

CERN Document Server

Richards, Ryan

2006-01-01

Using new instrumentation and experimental techniques that allow scientists to observe chemical reactions and molecular properties at the nanoscale, the authors of Surface and Nanomolecular Catalysis reveal new insights into the surface chemistry of catalysts and the reaction mechanisms that actually occur at a molecular level during catalysis. While each chapter contains the necessary background and explanations to stand alone, the diverse collection of chapters shows how developments from various fields each contributed to our current understanding of nanomolecular catalysis as a whole. The

UV Catalysis, Cyanotype Photography, and Sunscreens

Science.gov (United States)

Lawrence, Glen D.; Fishelson, Stuart

1999-09-01

This laboratory experiment is intended for a chemistry course for non-science majors. The experiment utilizes one of the earliest photographic processes, the cyanotype process, to demonstrate UV catalysis of chemical reactions. In addition to making photographic prints from negatives, the process can be used to test the effectiveness of sunscreens and the relative efficacy of the SPF (sun protection factor) rating of sunscreens. This is an inexpensive process, requiring solutions of ammonium ferric citrate and potassium ferricyanide, with options to use hydrogen peroxide and ammonium hydroxide solutions. Students can prepare their own UV-sensitized paper with the indicated chemicals and watch the photographic image appear as it is exposed to sunlight or fluorescent UV lamps in a light box designed for use in this experiment. The laboratory experiment should stimulate discussion of UV catalysis, photographic processes and photochemistry, sunscreens, and UV damage to biological organisms. The chemicals used are relatively nontoxic, and the procedure is simple enough to be used by groups of diverse ages and abilities.

Molecular water oxidation catalysis

CERN Document Server

Llobet, Antoni

2014-01-01

Photocatalytic water splitting is a promising strategy for capturing energy from the sun by coupling light harvesting and the oxidation of water, in order to create clean hydrogen fuel. Thus a deep knowledge of the water oxidation catalysis field is essential to be able to come up with useful energy conversion devices based on sunlight and water splitting. Molecular Water Oxidation Catalysis: A Key Topic for New Sustainable Energy Conversion Schemes presents a comprehensive and state-of-the-art overview of water oxidation catalysis in homogeneous phase, describing in detail the most importan

Contributions to a rational design of heterogeneous catalysts: from experimentation to numerical simulation; Contributions a une conception rationnelle des catalyseurs heterogenes: de l'experimentation a la simulation numerique

Energy Technology Data Exchange (ETDEWEB)

Toulhoat, H.

2002-03-01

I present through this dissertation a synthesis of my contributions to the field of heterogeneous catalysis, along two decades of research undertaken as a scientist at Institut Francais du Petrole. I started my itinerary on the 'floor', with the task of developing industrial hydro-treating catalysts, then I had the nice opportunity to lead advanced research on various subjects. However, I have been devoting myself for the past ten years to the encounter between catalysis and theoretical chemistry. The presentation of my work follows therefore a guideline starting with preparation and ending at modelization of the catalytic solid, after having gone through its characterization and the assessment of its activity. Modelization is thus founded on a consistent set of experimental informations. This guideline is applied to the four main themes to which this work is confined: hydro-treating catalysts, hydro-de-metallation catalysts, thio-resistance of noble metals, and solid acids. In summary, I believe I have contributed significantly, on the one hand to strong conceptual and technical advances in the area of ab initio simulation of elementary phenomena in heterogeneous catalysis, with the elaboration of original knowledge on catalysis by sulfides, metals and acids, as well as the genesis of alumina carriers, and on the other hand to a new approach of periodic trends in catalysis: this can be considered as a re-visitation of the principle of Sabatier, leading to a predictive tool for catalytic activity of solids. In a near future it will be possible to say if practical results validate this conceptual tool, and justify or not the ambitious title I gave to my work. (author)

Heterogenization of Homogeneous Catalysts: the Effect of the Support

Energy Technology Data Exchange (ETDEWEB)

Earl, W.L.; Ott, K.C.; Hall, K.A.; de Rege, F.M.; Morita, D.K.; Tumas, W.; Brown, G.H.; Broene, R.D.

1999-06-29

We have studied the influence of placing a soluble, homogeneous catalyst onto a solid support. We determined that such a 'heterogenized' homogeneous catalyst can have improved activity and selectivity for the asymmetric hydrogenation of enamides to amino acid derivatives. The route of heterogenization of RhDuPhos(COD){sup +} cations occurs via electrostatic interactions with anions that are capable of strong hydrogen bonding to silica surfaces. This is a novel approach to supported catalysis. Supported RhDuPhos(COD){sup +} is a recyclable, non-leaching catalyst in non-polar media. This is one of the few heterogenized catalysts that exhibits improved catalytic performance as compared to its homogeneous analog.

Constructing Bridges between Computational Tools in Heterogeneous and Homogeneous Catalysis

KAUST Repository

Falivene, Laura; Kozlov, Sergey M.; Cavallo, Luigi

2018-01-01

Better catalysts are needed to address numerous challenges faced by humanity. In this perspective, we review concepts and tools in theoretical and computational chemistry that can help to accelerate the rational design of homogeneous and heterogeneous catalysts. In particular, we focus on the following three topics: 1) identification of key intermediates and transition states in a reaction using the energetic span model, 2) disentanglement of factors influencing the relative stability of the key species using energy decomposition analysis and the activation strain model, and 3) discovery of new catalysts using volcano relationships. To facilitate wider use of these techniques across different areas, we illustrate their potentials and pitfalls when applied to the study of homogeneous and heterogeneous catalysts.

Constructing Bridges between Computational Tools in Heterogeneous and Homogeneous Catalysis

KAUST Repository

Falivene, Laura

2018-05-08

Better catalysts are needed to address numerous challenges faced by humanity. In this perspective, we review concepts and tools in theoretical and computational chemistry that can help to accelerate the rational design of homogeneous and heterogeneous catalysts. In particular, we focus on the following three topics: 1) identification of key intermediates and transition states in a reaction using the energetic span model, 2) disentanglement of factors influencing the relative stability of the key species using energy decomposition analysis and the activation strain model, and 3) discovery of new catalysts using volcano relationships. To facilitate wider use of these techniques across different areas, we illustrate their potentials and pitfalls when applied to the study of homogeneous and heterogeneous catalysts.

Catalytic Ionic-Liquid Membranes: The Convergence of Ionic-Liquid Catalysis and Ionic-Liquid Membrane Separation Technologies.

Czech Academy of Sciences Publication Activity Database

Izák, Pavel; Bobbink, F.D.; Hulla, M.; Klepic, M.; Friess, K.; Hovorka, Š.; Dyson, P.J.

2018-01-01

Roč. 83, č. 1 (2018), s. 7-18 ISSN 2192-6506 R&D Projects: GA ČR(CZ) GA17-00089S; GA ČR GA17-05421S Institutional support: RVO:67985858 Keywords : heterogeneous catalysis * ionic liquids * membranes Subject RIV: CI - Industrial Chemistry, Chemical Engineering OBOR OECD: Chemical process engineering Impact factor: 2.797, year: 2016

Lignin Valorization using Heterogenous Catalytic Oxidation

DEFF Research Database (Denmark)

Melián Rodríguez, Mayra; Shunmugavel, Saravanamurugan; Kegnæs, Søren

The research interests in biomass conversion to fuels and chemicals has increased significantly in the last decade in view of current problems such as global warming, high oil prices, food crisis and other geopolitical scenarios. Many different reactions and processes to convert biomass into high...... of the reaction conditions 4. Here, we therefore present an overview of the recent research about conversion of some lignin model compounds using heterogeneous catalysis in oxidation reactions....

Monopole catalysis: an overview

International Nuclear Information System (INIS)

Dawson, S.

1983-11-01

A summary of the talks presented in the topological workshop on monopole catalysis at this conference is given. We place special emphasis on the conservation laws which determine the allowed monopole-fermion interactions and on catalysis as a probe of the structure of a grand unified theory. 11 references

Molecular dynamics for reactions of heterogeneous catalysis

NARCIS (Netherlands)

Jansen, A.P.J.; Brongersma, H.H.; Santen, van R.A.

1991-01-01

An overview is given of Molecular Dynamics, and numerical integration techniques, system initialization, boundary conditions, force representation, statistics, system size, and simulations duration are discussed. Examples from surface science are used to illustrate the pros and cons of the method.

Surface science principles and current applications

CERN Document Server

Taglauer, E; Wandelt, K

1996-01-01

Modern technologies increasingly rely on low-dimensional physics at interfaces and in thin-films and nano-structures. Surface science holds a key position in providing the experimental methods and theoretical models for a basic understanding of these effects. This book includes case studies and status reports about research topics such as: surface structure determination by tensor-LEED and surface X-ray diffraction; the preparation and detection of low-dimensional electronic surface states; quantitative surface compositional analysis; the dynamics of adsorption and reaction of adsorbates, e.g. kinetic oscillations; the characterization and control of thin-film and multilayer growth including the influence of surfactants; a critical assessment of the surface physics approach to heterogeneous catalysis.

Hydrogen and methane synthesis through radiation catalysis. Final report

International Nuclear Information System (INIS)

DuBow, J.

1980-09-01

The goal of this research was to evaluate the potential for using reactor wastes to synthesize useful products in quasi-photochemical configuration. It was found that semiconductor oxides act as heterogenous catalysts for the formation of H 2 in aqueous media under 60 Co irradiation. The principle of a gamma-ray solar cell was demonstrated experimentally. Experiments with ultraviolet irradiated TiO 2 and ZnO grains demonstrated that both H 2 and H 2 O 2 were formed, in contrast to the results of work by previous authors. These results were rationalized by energy band diagram representations and by applying principles of semiconductor photoelectrochemistry. The concept of gamma-ray assisted desulfurization of coal through radiological degradation and heterogenous catalysis was experimentally demonstrated. The proof-of-concept experiments in the present study provide the basis for further fundamental and applied investigations, particularly in a potentially efficient system with a fresh source and 1.5 m path length

Catalysis of Supramolecular Hydrogelation

NARCIS (Netherlands)

Trausel, F.; Versluis, F.; Maity, C.; Poolman, J.M.; Lovrak, M.; van Esch, J.H.; Eelkema, R.

2016-01-01

ConspectusOne often thinks of catalysts as chemical tools to accelerate a reaction or to have a reaction run under more benign conditions. As such, catalysis has a role to play in the chemical industry and in lab scale synthesis that is not to be underestimated. Still, the role of catalysis in

New and future developments in catalysis batteries, hydrogen storage and fuel cells

CERN Document Server

Suib, Steven L

2013-01-01

New and Future Developments in Catalysis is a package of seven books that compile the latest ideas concerning alternate and renewable energy sources and the role that catalysis plays in converting new renewable feedstock into biofuels and biochemicals. Both homogeneous and heterogeneous catalysts and catalytic processes will be discussed in a unified and comprehensive approach. There will be extensive cross-referencing within all volumes. Batteries and fuel cells are considered to be environmentally friendly devices for storage and production of electricity, and they are gaining considerable attention. The preparation of the feed for fuel cells (fuel) as well as the catalysts and the various conversion processes taking place in these devices are covered in this volume, together with the catalytic processes for hydrogen generation and storage. An economic analysis of the various processes is also part of this volume and enables an informed choice of the most suitable process. Offers in-depth coverage of all ca...

Charge Transfer and Catalysis at the Metal Support Interface

Energy Technology Data Exchange (ETDEWEB)

Baker, Lawrence Robert [Univ. of California, Berkeley, CA (United States)

2012-07-31

Kinetic, electronic, and spectroscopic characterization of model Pt–support systems are used to demonstrate the relationship between charge transfer and catalytic activity and selectivity. The results show that charge flow controls the activity and selectivity of supported metal catalysts. This dissertation builds on extensive existing knowledge of metal–support interactions in heterogeneous catalysis. The results show the prominent role of charge transfer at catalytic interfaces to determine catalytic activity and selectivity. Further, this research demonstrates the possibility of selectively driving catalytic chemistry by controlling charge flow and presents solid-state devices and doped supports as novel methods for obtaining electronic control over catalytic reaction kinetics.

Catalysis for alternative energy generation

CERN Document Server

2012-01-01

Summarizes recent problems in using catalysts in alternative energy generation and proposes novel solutions  Reconsiders the role of catalysis in alternative energy generation  Contributors include catalysis and alternative energy experts from across the globe

Green chemistry by nano-catalysis

KAUST Repository

Polshettiwar, Vivek; Varma, Rajender S.

2010-01-01

the homogeneous catalysts. This review focuses on the use of nano-catalysis for green chemistry development including the strategy of using microwave heating with nano-catalysis in benign aqueous reaction media which offers an extraordinary synergistic effect

Solid acid catalysis from fundamentals to applications

CERN Document Server

Hattori, Hideshi

2014-01-01

IntroductionTypes of solid acid catalystsAdvantages of solid acid catalysts Historical overviews of solid acid catalystsFuture outlookSolid Acids CatalysisDefinition of acid and base -Brnsted acid and Lewis acid-Acid sites on surfacesAcid strengthRole of acid sites in catalysisBifunctional catalysisPore size effect on catalysis -shape selectivity-Characterization of Solid Acid Catalysts Indicator methodTemperature programmed desorption (TPD) of ammoniaCalorimetry of adsorption of basic moleculesInfrare

Heterogeneous Metal Catalysts for Oxidation Reactions

Directory of Open Access Journals (Sweden)

Md. Eaqub Ali

2014-01-01

Full Text Available Oxidation reactions may be considered as the heart of chemical synthesis. However, the indiscriminate uses of harsh and corrosive chemicals in this endeavor are threating to the ecosystems, public health, and terrestrial, aquatic, and aerial flora and fauna. Heterogeneous catalysts with various supports are brought to the spotlight because of their excellent capabilities to accelerate the rate of chemical reactions with low cost. They also minimize the use of chemicals in industries and thus are friendly and green to the environment. However, heterogeneous oxidation catalysis are not comprehensively presented in literature. In this short review, we clearly depicted the current state of catalytic oxidation reactions in chemical industries with specific emphasis on heterogeneous catalysts. We outlined here both the synthesis and applications of important oxidation catalysts. We believe it would serve as a reference guide for the selection of oxidation catalysts for both industries and academics.

Computational Design of Clusters for Catalysis

Science.gov (United States)

Jimenez-Izal, Elisa; Alexandrova, Anastassia N.

2018-04-01

When small clusters are studied in chemical physics or physical chemistry, one perhaps thinks of the fundamental aspects of cluster electronic structure, or precision spectroscopy in ultracold molecular beams. However, small clusters are also of interest in catalysis, where the cold ground state or an isolated cluster may not even be the right starting point. Instead, the big question is: What happens to cluster-based catalysts under real conditions of catalysis, such as high temperature and coverage with reagents? Myriads of metastable cluster states become accessible, the entire system is dynamic, and catalysis may be driven by rare sites present only under those conditions. Activity, selectivity, and stability are highly dependent on size, composition, shape, support, and environment. To probe and master cluster catalysis, sophisticated tools are being developed for precision synthesis, operando measurements, and multiscale modeling. This review intends to tell the messy story of clusters in catalysis.

The physical chemistry and materials science behind sinter-resistant catalysts.

Science.gov (United States)

Dai, Yunqian; Lu, Ping; Cao, Zhenming; Campbell, Charles T; Xia, Younan

2018-06-18

Catalyst sintering, a main cause of the loss of catalytic activity and/or selectivity at high reaction temperatures, is a major concern and grand challenge in the general area of heterogeneous catalysis. Although all heterogeneous catalysts are inevitably subjected to sintering during their operation, the immediate and drastic consequences can be mitigated by carefully engineering the catalytic particles and their interactions with the supports. In this tutorial review, we highlight recent progress in understanding the physical chemistry and materials science involved in sintering, including the discussion of advanced techniques, such as in situ microscopy and spectroscopy, for investigating the sintering process and its rate. We also discuss strategies for the design and rational fabrication of sinter-resistant catalysts. Finally, we showcase recent success in improving the thermal stability and thus sinter resistance of supported catalytic systems.

Specific acid catalysis and Lewis acid catalysis of Diels–Alder reactions in aqueous media

NARCIS (Netherlands)

Mubofu, Egid B.; Engberts, Jan B.F.N.

2004-01-01

A comparative study of specific acid catalysis and Lewis acid catalysis of Diels–Alder reactions between dienophiles (1, 4 and 6) and cyclopentadiene (2) in water and mixed aqueous media is reported. The reactions were performed in water with copper(II) nitrate as the Lewis acid catalyst whereas

Specific acid catalysis and Lewis acid catalysis of Diels-Alder reactions in aqueous media

NARCIS (Netherlands)

Mubofu, E.B.; Engberts, J.B.F.N.

A comparative study of specific acid catalysis and Lewis acid catalysis of Diells-Alder reactions between dienophiles (1, 4 and 6) and cyclopentadiene (2) in water and mixed aqueous media is reported. The reactions were performed in water with copper(II) nitrate as the Lewis acid catalyst whereas

Modeling and simulation of heterogeneous catalytic processes

CERN Document Server

Dixon, Anthony

2014-01-01

Heterogeneous catalysis and mathematical modeling are essential components of the continuing search for better utilization of raw materials and energy, with reduced impact on the environment. Numerical modeling of chemical systems has progressed rapidly due to increases in computer power, and is used extensively for analysis, design and development of catalytic reactors and processes. This book presents reviews of the state-of-the-art in modeling of heterogeneous catalytic reactors and processes. Reviews by leading authorities in the respective areas Up-to-date reviews of latest techniques in modeling of catalytic processes Mix of US and European authors, as well as academic/industrial/research institute perspectives Connections between computation and experimental methods in some of the chapters.

Heterogeneous catalytic materials solid state chemistry, surface chemistry and catalytic behaviour

CERN Document Server

Busca, Guido

2014-01-01

Heterogeneous Catalytic Materials discusses experimental methods and the latest developments in three areas of research: heterogeneous catalysis; surface chemistry; and the chemistry of catalysts. Catalytic materials are those solids that allow the chemical reaction to occur efficiently and cost-effectively. This book provides you with all necessary information to synthesize, characterize, and relate the properties of a catalyst to its behavior, enabling you to select the appropriate catalyst for the process and reactor system. Oxides (used both as catalysts and as supports for cata

Chemical catalysis in biodiesel production (I): enzymatic catalysis processes

International Nuclear Information System (INIS)

Jachmarian, I.; Dobroyan, M.; Veira, J.; Vieitez, I.; Mottini, M.; Segura, N.; Grompone, M.

2009-01-01

There are some well known advantages related with the substitution of chemical catalysis by enzymatic catalysis processes.Some commercial immobilized lipases are useful for the catalysis of bio diesel reaction, which permits the achievement of high conversions and the recovery of high purity products, like a high quality glycerine. The main disadvantage of this alternative method is related with the last inactivation of the enzyme (by both the effect of the alcohol and the absorption of glycerol on catalyst surface), which added to the high cost of the catalyst, produces an unfavourable economical balance of the entire process. In the work the efficiency of two commercial immobilized lipases (Lipozyme TL IM y Novozyme 435 NNovozymes-Dinamarca) in the catalysis of the continuous transesterification of sunflower oil with different alcohols was studied. The intersolubility of the different mixturesinvolving reactans (S oil/alkyl esters/alcohol) and products (P mixtures with a higher content of 1% of glycerol,while for ethanol homogeneous mixtures were obtained at 12% of glycerol (44.44 12).Using and ethanolic substrate at the proportion S=19:75:6 and Lipozyme TL IM, it was possible to achieve a 98% of convertion to the corresponding biodiesel.When Novozymes 435 catalyzed the process it was possible to increase the oil concentration in the substrateaccording to proportion S=35:30:35, and a 78% conversion was obtained. The productivity shown by the firt enzyme was 70mg biodiesel g enzime-1, hora-1 while with the second one the productivity increased to 230. Results suggested that the convenient adjustement of substrate composition with the addition of biodiesel to reactants offers an efficient method for maximizing the enzyme productivity, hence improving the profitability of the enzymatic catalyzed process. (author)

Journal of Chemical Sciences | Indian Academy of Sciences

Indian Academy of Sciences (India)

Home; Journals; Journal of Chemical Sciences. CHANDRASEKAR PRAVEEN. Articles written in Journal of Chemical Sciences. Volume 128 Issue 1 January 2016 pp 73-83 Regular Articles. Cycloisomerization of acetylenic oximes and hydrazones under gold catalysis: Synthesis and cytotoxic evaluation of isoxazoles and ...

Parallel array of nanochannels grafted with polymer-brushes-stabilized Au nanoparticles for flow-through catalysis.

Science.gov (United States)

Liu, Jianxi; Ma, Shuanhong; Wei, Qiangbing; Jia, Lei; Yu, Bo; Wang, Daoai; Zhou, Feng

2013-12-07

Smart systems on the nanometer scale for continuous flow-through reaction present fascinating advantages in heterogeneous catalysis, in which a parallel array of straight nanochannels offers a platform with high surface area for assembling and stabilizing metallic nanoparticles working as catalysts. Herein we demonstrate a method for finely modifying the nanoporous anodic aluminum oxide (AAO), and further integration of nanoreactors. By using atomic transfer radical polymerization (ATRP), polymer brushes were successfully grafted on the inner wall of the nanochannels of the AAO membrane, followed by exchanging counter ions with a precursor for nanoparticles (NPs), and used as the template for deposition of well-defined Au NPs. The membrane was used as a functional nanochannel for novel flow-through catalysis. High catalytic performance and instantaneous separation of products from the reaction system was achieved in reduction of 4-nitrophenol.

Parallel array of nanochannels grafted with polymer-brushes-stabilized Au nanoparticles for flow-through catalysis

Science.gov (United States)

Liu, Jianxi; Ma, Shuanhong; Wei, Qiangbing; Jia, Lei; Yu, Bo; Wang, Daoai; Zhou, Feng

2013-11-01

Smart systems on the nanometer scale for continuous flow-through reaction present fascinating advantages in heterogeneous catalysis, in which a parallel array of straight nanochannels offers a platform with high surface area for assembling and stabilizing metallic nanoparticles working as catalysts. Herein we demonstrate a method for finely modifying the nanoporous anodic aluminum oxide (AAO), and further integration of nanoreactors. By using atomic transfer radical polymerization (ATRP), polymer brushes were successfully grafted on the inner wall of the nanochannels of the AAO membrane, followed by exchanging counter ions with a precursor for nanoparticles (NPs), and used as the template for deposition of well-defined Au NPs. The membrane was used as a functional nanochannel for novel flow-through catalysis. High catalytic performance and instantaneous separation of products from the reaction system was achieved in reduction of 4-nitrophenol.

Cosmic strings and baryon decay catalysis

Energy Technology Data Exchange (ETDEWEB)

Gregory, R.; Perkins, W.B.; Davis, A.C.; Brandenberger, R.H. (Fermi National Accelerator Lab., Batavia, IL (USA); Cambridge Univ. (UK); Brown Univ., Providence, RI (USA). Dept. of Physics)

1989-09-01

Cosmic strings, like monopoles, can catalyze proton decay. For integer charged fermions, the cross section for catalysis is not amplified, unlike in the case of monopoles. We review the catalysis processes both in the free quark and skyrmion pictures and discuss the implications for baryogenesis. We present a computation of the cross section for monopole catalyzed skyrmion decay using classical physics. We also discuss some effects which can screen catalysis processes. 32 refs., 1 fig.

Cosmic strings and baryon decay catalysis

International Nuclear Information System (INIS)

Gregory, R.; Perkins, W.B.; Davis, A.C.; Brandenberger, R.H.; Cambridge Univ.; Brown Univ., Providence, RI

1989-09-01

Cosmic strings, like monopoles, can catalyze proton decay. For integer charged fermions, the cross section for catalysis is not amplified, unlike in the case of monopoles. We review the catalysis processes both in the free quark and skyrmion pictures and discuss the implications for baryogenesis. We present a computation of the cross section for monopole catalyzed skyrmion decay using classical physics. We also discuss some effects which can screen catalysis processes. 32 refs., 1 fig

Catalysis as a foundational pillar of green chemistry

Energy Technology Data Exchange (ETDEWEB)

Anastas, Paul T. [White House Office of Science and Technology Policy, Department of Chemistry, University of Nottingham Nottingham, (United Kingdom); Kirchhoff, Mary M. [U.S. Environmental Protection Agency and Trinity College, Washington, DC (United States); Williamson, Tracy C. [U.S. Environmental Protection Agency, Washington, DC (United States)

2001-11-30

are serving as a strong incentive to industry to adopt greener technologies. Developing green chemistry methodologies is a challenge that may be viewed through the framework of the Twelve Principles of Green Chemistry . These principles identify catalysis as one of the most important tools for implementing green chemistry. Catalysis offers numerous green chemistry benefits including lower energy requirements, catalytic versus stoichiometric amounts of materials, increased selectivity, and decreased use of processing and separation agents, and allows for the use of less toxic materials. Heterogeneous catalysis, in particular, addresses the goals of green chemistry by providing the ease of separation of product and catalyst, thereby eliminating the need for separation through distillation or extraction. In addition, environmentally benign catalysts such as clays and zeolites, may replace more hazardous catalysts currently in use. This paper highlights a variety of ways in which catalysis may be used as a pollution prevention tool in green chemistry reactions. The benefits to human health, environment, and the economic goals realized through the use of catalysis in manufacturing and processing are illustrated by focusing on the catalyst design and catalyst applications.

CATALYSIS OF CHEMICAL PROCESSES: PARTICULAR ...

African Journals Online (AJOL)

IICBA01

secondary/high schools and universities, the inhibition of the chemical reactions is frequently ... As a result, the lesson catalysis is frequently included in chemistry education curricula at ... Misinterpretations in teaching and perception of catalysis ... profile is shown as a dependence of energy on reaction progress, without ...

Spectroscopy in catalysis : an introduction

NARCIS (Netherlands)

Niemantsverdriet, J.W.

2007-01-01

Spectroscopy in Catalysis is an introduction to the most important analytical techniques that are nowadays used in catalysis and in catalytic surface chemistry. The aim of the book is to give the reader a feeling for the type of information that characterization techniques provide about questions

Cooperative catalysis designing efficient catalysts for synthesis

CERN Document Server

Peters, René

2015-01-01

Written by experts in the field, this is a much-needed overview of the rapidly emerging field of cooperative catalysis. The authors focus on the design and development of novel high-performance catalysts for applications in organic synthesis (particularly asymmetric synthesis), covering a broad range of topics, from the latest progress in Lewis acid / Br?nsted base catalysis to e.g. metal-assisted organocatalysis, cooperative metal/enzyme catalysis, and cooperative catalysis in polymerization reactions and on solid surfaces. The chapters are classified according to the type of cooperating acti

Current advances and trends in electro-Fenton process using heterogeneous catalysts - A review.

Science.gov (United States)

Poza-Nogueiras, Verónica; Rosales, Emilio; Pazos, Marta; Sanromán, M Ángeles

2018-06-01

Over the last decades, advanced oxidation processes have often been used alone, or combined with other techniques, for remediation of ground and surface water pollutants. The application of heterogeneous catalysis to electrochemical advanced oxidation processes is especially useful due to its efficiency and environmental safety. Among those processes, electro-Fenton stands out as the one in which heterogeneous catalysis has been broadly applied. Thus, this review has introduced an up-to-date collation of the current knowledge of the heterogeneous electro-Fenton process, highlighting recent advances in the use of different catalysts such as iron minerals (pyrite, magnetite or goethite), prepared catalysts by the load of metals in inorganic and organic materials, nanoparticles, and the inclusion of catalysts on the cathode. The effects of physical-chemical parameters as well as the mechanisms involved are critically assessed. Finally, although the utilization of this process to remediation of wastewater overwhelmingly outnumber other utilities, several applications have been described in the context of regeneration of adsorbent or the remediation of soils as clear examples of the feasibility of the electro-Fenton process to solve different environmental problems. Copyright © 2018 Elsevier Ltd. All rights reserved.

New developments in oxidation catalysis

Energy Technology Data Exchange (ETDEWEB)

Rosowski, F. [BASF SE, Ludwigshafen (Germany)

2011-07-01

The impact of heterogeneous catalysis on the economy can be depicted by the global revenue of the chemical industry in 2006, which accounted for 2200 billion Euros with a share of all chemical products produced applying heterogeneous catalysis of about two thirds. [1] The range of products is enormous and they contribute greatly to the quality of our lifes. The advancement in the development of basic and intermediate chemical products is crucially dependent on either the further development of existing catalyst systems or the development of new catalysts and key to success for the chemical industry. Within the context of oxidation catalysis, the following driving forces are guiding research activities: There is a continuous desire to increase the selectivity of a given process in response to both economic as well as ecological needs and taking advantage of higher efficiencies in terms of cost savings and a better utilization of raw materials. A second motivation focuses on raw material change to all abundant and competitive feedstocks requiring both new developments in catalyst design as well as process technology. A more recent motivation refers to the use of metal oxide redox systems which are key to success for the development of novel technologies allowing for the separation of carbon dioxide and the use of carbon dioxide as a feedstock molecule as well as storing renewable energy in a chemical. To date, general ab initio approaches are known for the design of novel catalytic materials only for a few chemical reactions, whereas most industrial catalytic processes have been developed by empirical methods. [2] The development of catalytic materials are either based on the targeted synthesis of catalytic lead structures as well as high throughput methods that allow for the screening of a large range of parameters. [3 - 5] The successful development of catalysts together with reactor technology has led to both significant savings in raw materials and emissions. The

Magnetic monopole catalysis of proton decay

International Nuclear Information System (INIS)

Marciano, W.J.; Salvino, D.

1986-09-01

Catalysis of proton decay by GUT magnetic monopoles (the Rubakov-Callan effect) is discussed. Combining a short-distance cross section calculation by Bernreuther and Craigie with the long-distance velocity dependent distortion factors of Arafune and Fukugita, catalysis rate predictions which can be compared with experiment are obtained. At present, hydrogen rich detectors such as water (H 2 O) and methane (CH 4 ) appear to be particularly well suited for observing catalysis by very slow monopoles. 17 refs., 1 fig

Catalysis as an Enabling Science for Sustainable Polymers.

Science.gov (United States)

Zhang, Xiangyi; Fevre, Mareva; Jones, Gavin O; Waymouth, Robert M

2018-01-24

The replacement of current petroleum-based plastics with sustainable alternatives is a crucial but formidable challenge for the modern society. Catalysis presents an enabling tool to facilitate the development of sustainable polymers. This review provides a system-level analysis of sustainable polymers and outlines key criteria with respect to the feedstocks the polymers are derived from, the manner in which the polymers are generated, and the end-of-use options. Specifically, we define sustainable polymers as a class of materials that are derived from renewable feedstocks and exhibit closed-loop life cycles. Among potential candidates, aliphatic polyesters and polycarbonates are promising materials due to their renewable resources and excellent biodegradability. The development of renewable monomers, the versatile synthetic routes to convert these monomers to polyesters and polycarbonate, and the different end-of-use options for these polymers are critically reviewed, with a focus on recent advances in catalytic transformations that lower the technological barriers for developing more sustainable replacements for petroleum-based plastics.

Heterogeneous self-assembled media for biopolymerization

DEFF Research Database (Denmark)

Monnard, Pierre-Alain

2011-01-01

Heterogeneous media, such as micro-structured aqueous environments, could offer an alternative approach to the synthesis of biopolymers with novel functions. Structured media are here defined as specialized, self-assembled structures that are formed, e.g, by amphiphiles, such as liposomes, emulsion...... polymerization, the initial elongation rates clearly depended on the complementarity of the monomers with the templating nucleobases3. However, metal-ion catalyzed reactions deliver RNA analogs with heterogeneous linkages. Moreover, the usefulness of this medium in the form of quasi-compartmentalization extends...... beyond metal-ion catalysis reactions, as we have recently demonstrated the catalytic power of a dipeptide, SerHis, for the regioselective formation of phosphodiester bonds. These results in conjonction with the synthesis of nucleobases at -78˚C, the demonstration of ribozyme activity (RNA ligase ribozyme...

Charge Transfer and Support Effects in Heterogeneous Catalysis

Energy Technology Data Exchange (ETDEWEB)

Hervier, Antoine [Univ. of California, Berkeley, CA (United States)

2011-12-21

The kinetic, electronic and spectroscopic properties of two-dimensional oxide-supported catalysts were investigated in order to understand the role of charge transfer in catalysis. Pt/TiO₂ nanodiodes were fabricated and used as catalysts for hydrogen oxidation. During the reaction, the current through the diode, as well as its I-V curve, were monitored, while gas chromatography was used to measure the reaction rate. The current and the turnover rate were found to have the same temperature dependence, indicating that hydrogen oxidation leads to the non-adiabatic excitation of electrons in Pt. A fraction of these electrons have enough energy to ballistically transport through Pt and overcome the Schottky barrier at the interface with TiO₂. The yield for this phenomenon is on the order of 10^-4 electrons per product molecule formed, similar to what has been observed for CO oxidation and for the adsorption of many different molecules. The same Pt/TiO₂ system was used to compare currents in hydrogen oxidation and deuterium oxidation. The current through the diode under deuterium oxidation was found to be greater than under hydrogen oxidation by a factor of three. Weighted by the difference in turnover frequencies for the two isotopes, this would imply a chemicurrent yield 5 times greater for D₂ compared to H₂, contrary to what is expected given the higher mass of D₂. Reversible changes in the rectification factor of the diode are observed when switching between D₂ and H₂. These changes are a likely cause for the differences in current between the two isotopes. In the nanodiode experiments, surface chemistry leads to charge flow, suggesting the possibility of creating charge flow to tune surface chemistry. This was done first by exposing a Pt/Si diode to visible light while using it as a catalyst for H₂ oxidation. Absorption of the light in the Si, combined with

Supported Ionic Liquid Phase (SILP) catalysis

DEFF Research Database (Denmark)

Riisager, Anders; Fehrmann, Rasmus; Haumann, Marco

2006-01-01

Applications of ionic liquids to replace conventional solvents in homogeneous transition-metal catalysis have increased significantly during the last decade. Biphasic ionic liquid/organic liquid systems offer advantages with regard to product separation, catalyst stability, and recycling...... but utilise in the case of fast chemical reactions only a small amount of expensive ionic liquid and catalyst. The novel Supported Ionic Liquid Phase (SILP) catalysis concept overcomes these drawbacks and allows the use of fixed-bed reactors for continuous reactions. In this Microreview the SILP catalysis...

Activities of Heterogeneous Acid-Base Catalysts for Fragrances Synthesis: A Review

Directory of Open Access Journals (Sweden)

Hartati Hartati

2013-06-01

Full Text Available This paper reviews various types of heterogeneous acid-base catalysts for fragrances preparation. Catalytic activities of various types of heterogeneous acid and base catalysts in fragrances preparation, i.e. non-zeolitic, zeolitic, and mesoporous molecular sieves have been reported. Generally, heterogeneous acid catalysts are commonly used in fragrance synthesis as compared to heterogeneous base catalysts. Heteropoly acids and hydrotalcites type catalysts are widely used as heterogeneous acid and base catalysts, respectively. © 2013 BCREC UNDIP. All rights reservedReceived: 20th January 2013; Revised: 31st March 2013; Accepted: 1st April 2013[How to Cite: Hartati, H., Santoso, M., Triwahyono, S., Prasetyoko, D. (2013. Activities of Heterogeneous Acid-Base Catalysts for Fragrances Synthesis: A Review. Bulletin of Chemical Reaction Engineering & Catalysis, 8 (1: 14-33. (doi:10.9767/bcrec.8.1.4394.14-33][Permalink/DOI: http://dx.doi.org/10.9767/bcrec.8.1.4394.14-33] | View in  |

Surface science and catalysis

International Nuclear Information System (INIS)

Somorjai, G.A.

1985-02-01

Modern surface science studies have explored a large number of metal catalyst systems. Three classes of catalytic reactions can be identified: (1) those that occur over the metal surface; (2) reactions that take place on top of a strongly adsorbed overlayer and (3) reactions that occur on co-adsorbate modified surfaces. Case histories for each class are presented. 44 refs., 13 figs., 3 tabs

Bricolage, métissage, hybridity, heterogeneity, diaspora: concepts for thinking science education in the 21st century

Science.gov (United States)

Roth, Wolff-Michael

2008-12-01

The ongoing globalization leads to an increasing scattering of cultural groups into other cultural groups where they the latter continue to be affiliated with one another thereby forming diasporic identities. Diasporic identities emerge from a process of cultural bricolage that leads to cultural métissage and therefore hybridity and heterogeneity. To escape the hegemonies that arise from the ontology of the same—which, as I show, undergirds much of educational thought—I ground the notion of diaspora in the ontology of difference. Difference and heterogeneity are the norm, not something less than sameness and purity. This ontology allows framing bricolage, métissage, hybridity, and heterogeneity as positive concepts for theorizing the experiences of learning science and identity not only as a consequence of cross-national migrations—Mexicans in the US, Asians and Europeans in Canada, Africans in Europe—but also the experience of native speakers who, in science classrooms, find themselves (temporarily) at home away from home. My exemplary analyses show how the very fact of cultural and linguistic differences within themselves gives rise to the possibility of symbolic violence in science classrooms even to those whose ethos is or is closest to the one at the heart of science.

Argonne Chemical Sciences & Engineering - Awards Home

Science.gov (United States)

Argonne National Laboratory Chemical Sciences & Engineering DOE Logo CSE Home About CSE Argonne Home > Chemical Sciences & Engineering > Fundamental Interactions Catalysis & Energy Computational Postdoctoral Fellowships Contact Us CSE Intranet Awards Argonne's Chemical Sciences and

Faraday Discussions meeting Catalysis for Fuels.

Science.gov (United States)

Fischer, Nico; Kondrat, Simon A; Shozi, Mzamo

2017-05-02

Welcome to Africa was the motto when after more than 100 years the flag ship conference series of the Royal Society of Chemistry, the Faraday Discussions was hosted for the first time on the African Continent. Under the fitting topic 'Catalysis for Fuels' over 120 delegates followed the invitation by the conference chair Prof. Graham Hutchings FRS (Cardiff Catalysis Institute), his organizing committee and the co-organizing DST-NRF Centre of Excellence in Catalysis c*change (). In the presentations of 21 invited speakers and 59 posters, cutting edge research in the field of catalysis for fuels, designing new catalysts for synthetic fuels, hydrocarbon conversion in the production of synthetic fuels and novel photocatalysis was presented over the two-day meeting. The scene was set by the opening lecture of Prof. Enrique Iglesias (UC Berkeley) and wrapped-up with the concluding remarks by Philip Gibson (SASOL).

Catalysis induced by radiations

International Nuclear Information System (INIS)

Jimenez B, J.; Gonzalez J, J. C.

2010-01-01

In Mexico is generated a great quantity of residuals considered as dangerous, for its capacity of corrosion, reactivity, toxicity to the environment, inflammability and biological-infectious potential. It is important to mention that the toxic compounds cannot be discharged to the sewerage systems and much less to the receiving bodies of water. The usual treatment that receives the dangerous residuals is the incineration and the bordering. The incineration is an efficient form of treating the residuals, but it can be dioxins source and benzofurans, being the phenol and chloro phenol the precursors of these compounds. At the present time the radiolytic degradation of organic compounds has been broadly studied, especially the 4-chloro phenol and of same form the photo catalysis of organic compounds. However the combination of both processes, called radio catalysis is barely reported. In this work the results of the experiments realized for to degrade the 4-chloro phenol by means of radio catalysis are reported. (Author)

High-throughput heterogeneous catalyst research

Science.gov (United States)

Turner, Howard W.; Volpe, Anthony F., Jr.; Weinberg, W. H.

2009-06-01

With the discovery of abundant and low cost crude oil in the early 1900's came the need to create efficient conversion processes to produce low cost fuels and basic chemicals. Enormous investment over the last century has led to the development of a set of highly efficient catalytic processes which define the modern oil refinery and which produce most of the raw materials and fuels used in modern society. Process evolution and development has led to a refining infrastructure that is both dominated and enabled by modern heterogeneous catalyst technologies. Refineries and chemical manufacturers are currently under intense pressure to improve efficiency, adapt to increasingly disadvantaged feedstocks including biomass, lower their environmental footprint, and continue to deliver their products at low cost. This pressure creates a demand for new and more robust catalyst systems and processes that can accommodate them. Traditional methods of catalyst synthesis and testing are slow and inefficient, particularly in heterogeneous systems where the structure of the active sites is typically complex and the reaction mechanism is at best ill-defined. While theoretical modeling and a growing understanding of fundamental surface science help guide the chemist in designing and synthesizing targets, even in the most well understood areas of catalysis, the parameter space that one needs to explore experimentally is vast. The result is that the chemist using traditional methods must navigate a complex and unpredictable diversity space with a limited data set to make discoveries or to optimize known systems. We describe here a mature set of synthesis and screening technologies that together form a workflow that breaks this traditional paradigm and allows for rapid and efficient heterogeneous catalyst discovery and optimization. We exemplify the power of these new technologies by describing their use in the development and commercialization of a novel catalyst for the

Surface Science Foundations of Catalysis and Nanoscience

CERN Document Server

Kolasinski, Kurt K

2012-01-01

Surface science has evolved beyond being a sub-field of chemistry or physics and has now become an underpinning science. The Third Edition of this book incorporates extensive worked solutions, as well as details on how problem solving relevant to surface science should be performed. It contextualizes the exercises and their solutions to further explicate the methods of problem solving, application of scientific principles and to deliver a deeper understanding of the field of surface science. Solutions will be accompanied by figures and/or graphs of data, as appropriate.

Biopolymer-stabilized Pt nanoparticles colloid: a highly active and recyclable catalyst for biphasic catalysis

Energy Technology Data Exchange (ETDEWEB)

Wang, Yujia; Shen, Yueyue; Qiu, Yunfei; Zhang, Ting; Liao, Yang; Zhao, Shilin; Ma, Jun, E-mail: 1044208419@qq.com; Mao, Hui, E-mail: rejoice222@163.com [Sichuan Normal University, College of Chemistry and Materials Science (China)

2016-10-15

Noble metal nanoparticles are promising candidates to replace conventional bulk counterparts owing to their high activity and selectivity. To enable catalyst recovery, noble metal nanoparticles are often supported onto solid matrices to prepare heterogeneous catalyst. Although recycle of noble metal nanoparticles is realized by heterogenization, a loss of activity is usually encountered. In the present investigation, Pt nanoparticles with tunable particle size (1.85–2.80 nm) were facilely prepared by using polyphenols as amphiphilic stabilizers. The as-prepared Pt nanoparticles colloid solution could be used as highly active catalyst in aqueous–organic biphasic catalysis. The phenolic hydroxyls of polyphenols could constrain Pt nanoparticles in aqueous phase, and simultaneously, the aromatic scaffold of polyphenols ensured effective interactions between substrates and Pt nanoparticles. As a consequence, the obtained polyphenols-stabilized Pt nanoparticles exhibited high activity and cycling stability in biphasic hydrogenation of a series of unsaturated compounds. Compared with conventional heterogeneous Pt-C and Pt-Al{sub 2}O{sub 3} catalysts, polyphenols-stabilized Pt nanoparticles showed obvious advantage both in activity and cycling stability.

Biopolymer-stabilized Pt nanoparticles colloid: a highly active and recyclable catalyst for biphasic catalysis

International Nuclear Information System (INIS)

Wang, Yujia; Shen, Yueyue; Qiu, Yunfei; Zhang, Ting; Liao, Yang; Zhao, Shilin; Ma, Jun; Mao, Hui

2016-01-01

Noble metal nanoparticles are promising candidates to replace conventional bulk counterparts owing to their high activity and selectivity. To enable catalyst recovery, noble metal nanoparticles are often supported onto solid matrices to prepare heterogeneous catalyst. Although recycle of noble metal nanoparticles is realized by heterogenization, a loss of activity is usually encountered. In the present investigation, Pt nanoparticles with tunable particle size (1.85–2.80 nm) were facilely prepared by using polyphenols as amphiphilic stabilizers. The as-prepared Pt nanoparticles colloid solution could be used as highly active catalyst in aqueous–organic biphasic catalysis. The phenolic hydroxyls of polyphenols could constrain Pt nanoparticles in aqueous phase, and simultaneously, the aromatic scaffold of polyphenols ensured effective interactions between substrates and Pt nanoparticles. As a consequence, the obtained polyphenols-stabilized Pt nanoparticles exhibited high activity and cycling stability in biphasic hydrogenation of a series of unsaturated compounds. Compared with conventional heterogeneous Pt-C and Pt-Al 2 O 3 catalysts, polyphenols-stabilized Pt nanoparticles showed obvious advantage both in activity and cycling stability.

Degradation of organic dyes by a new heterogeneous Fenton reagent - Fe2GeS4 nanoparticle.

Science.gov (United States)

Shi, Xiaoguo; Tian, Ang; You, Junhua; Yang, He; Wang, Yuzheng; Xue, Xiangxin

2018-07-05

The heterogeneous Fenton system has become the hotspot in the decontamination field due to its effective degradation performance with a wide pH range. Based on the unstable chemical properties of pyrite, in this article, Fe 2 GeS 4 nanoparticles with better thermodynamic stability were prepared by vacuum sintering and high energy ball milling and its potential as Fenton reagent was investigated for the first time. Three determinants of the heterogeneous Fenton system including the iron source, hydrogen peroxide, pH and the degradation mechanism were investigated. The catalyst dosage of 0.3 g/L, initial H 2 O 2 concentration in the Fenton system of 50 m mol/L and pH of 7 were chosen as the best operational conditions. An almost complete degradation was achieved within 5 min for methylene blue and rhodamine b while 10 min for methyl orange. The total organic carbon removal efficiencies of Fe 2 GeS 4 heterogeneous Fenton system for methylene blue, methyl orange and rhodamine b in 10 min were 56.3%, 66.2% and 74.2%, respectively. It's found that the degradation ability could be attributed to a heterogeneous catalysis occurring at the Fe 2 GeS 4 surface together with a homogeneous catalysis in the aqueous phase by the dissolved iron ions. Copyright © 2018 Elsevier B.V. All rights reserved.

Homogeneous and heterogeneous photoredox-catalyzed hydroxymethylation of ketones and keto esters: catalyst screening, chemoselectivity and dilution effects

Directory of Open Access Journals (Sweden)

Axel G. Griesbeck

2014-05-01

Full Text Available The homogeneous titanium- and dye-catalyzed as well as the heterogeneous semiconductor particle-catalyzed photohydroxymethylation of ketones by methanol were investigated in order to evaluate the most active photocatalyst system. Dialkoxytitanium dichlorides are the most efficient species for chemoselective hydroxymethylation of acetophenone as well as other aromatic and aliphatic ketones. Pinacol coupling is the dominant process for semiconductor catalysis and ketone reduction dominates the Ti(OiPr4/methanol or isopropanol systems. Application of dilution effects on the TiO2 catalysis leads to an increase in hydroxymethylation at the expense of the pinacol coupling.

Understanding of catalysis on early transition metal oxide-based catalysts through exploration of surface structure and chemistry during catalysis using in-situ approaches

Energy Technology Data Exchange (ETDEWEB)

Tao, Franklin [Univ. of Kansas, Lawrence, KS (United States). Dept. of Chemical and Petroleum Engineering. Dept. of Chemistry

2015-09-14

Two main categories of heterogeneous catalysts are metal and metal oxide which catalyze 80% chemical reactions at solid-gas and solid-liquid interfaces. Metal oxide catalysts are much more complicated than metal catalysts. The reason is that the cations of the metal atoms could exhibit a few different oxidation states on surface of the same catalyst particle such as Co₃O₄ or change of their oxidation states under different reactive environments. For a metal catalyst, there is only one oxidation state typically. In addition, surface of a metal oxide can be terminated with multiple surface functionalities including O atoms with different binding configurations and OH group. For metal, only metal atoms are exposed typically. Obviously, the complication of surface chemistry and structure of a metal oxide makes studies of surface of an oxide catalyst very challenging. Due to the complication of surface of a meal oxide, the electronic and geometric structures of surface of a metal oxide and the exposed species have received enormous attention since oxide catalysts catalyze at least 1/3 chemical reactions in chemical and energy industries. Understanding of catalytic reactions on early transition metal oxide-based catalysts is fundamentally intriguing and of great practical interest in energy- and environment-related catalysis. Exploration of surface chemistry of oxide-based catalysts at molecular level during catalysis has remained challenging though it is critical in deeply understanding catalysis on oxide-based catalysts and developing oxide-based catalysts with high activity and selectivity. Thus, the overall objective of this project is to explore surface chemistry and structure of early transition metal oxide-based catalysts through in-situ characterization of surface of catalysts, measurements of catalytic performances, and then build an intrinsic correlation of surface chemistry and structure with their catalytic performances in a few

Catalysis by metal-organic frameworks: fundamentals and opportunities.

Science.gov (United States)

Ranocchiari, Marco; van Bokhoven, Jeroen Anton

2011-04-14

Crystalline porous materials are extremely important for developing catalytic systems with high scientific and industrial impact. Metal-organic frameworks (MOFs) show unique potential that still has to be fully exploited. This perspective summarizes the properties of MOFs with the aim to understand what are possible approaches to catalysis with these materials. We categorize three classes of MOF catalysts: (1) those with active site on the framework, (2) those with encapsulated active species, and (3) those with active sites attached through post-synthetic modification. We identify the tunable porosity, the ability to fine tune the structure of the active site and its environment, the presence of multiple active sites, and the opportunity to synthesize structures in which key-lock bonding of substrates occurs as the characteristics that distinguish MOFs from other materials. We experience a unique opportunity to imagine and design heterogeneous catalysts, which might catalyze reactions previously thought impossible.

Nano catalysis: Academic Discipline and Industrial Realities

International Nuclear Information System (INIS)

Olveira, S.; Forster, S.P.; Seeger, S.

2014-01-01

Nano technology plays a central role in both academic research and industrial applications. Nano enabled products are not only found in consumer markets, but also importantly in business to business markets (B2B). One of the oldest application areas of nano technology is nano catalysis—an excellent example for such a B2 B market. Several existing reviews illustrate the scientific developments in the field of nano catalysis. The goal of the present review is to provide an up-to-date picture of academic research and to extend this picture by an industrial and economic perspective. We therefore conducted an extensive search on several scientific databases and we further analyzed more than 1,500 nano catalysis-related patents and numerous market studies. We found that scientists today are able to prepare nano catalysts with superior characteristics regarding activity, selectivity, durability, and recoverability, which will contribute to solve current environmental, social, and industrial problems. In industry, the potential of nano catalysis is recognized, clearly reflected by the increasing number of nano catalysis-related patents and products on the market. The current nano catalysis research in academic and industrial laboratories will therefore enable a wealth of future applications in the industry

Catalysis Research of Relevance to Carbon Management: Progress, Challenges, and Opportunities

Energy Technology Data Exchange (ETDEWEB)

Arakawa, Hironori; Aresta, Michele; Armor, John; Barteau, Mark; Beckman, Eric J.; Bell, Alexis T.; Bercaw, John E.; Creutz, Carol; Dinjus, Eckhard; Dixon, David A.; Domen, Kazunari; Dubois, Daniel L.; Eckert, Juergen; Fujita, Etsuko; Gibson, Dorothy H.; Goddard, William A.; Goodman, Wayne D.; Keller, Jay; Kubas, Gregory J.; Kung, Harold H.; Lyons, James E.; Manzer, Leo; Marks, Tobin J.; Morokuma, Keiji; Nicholas, Kenneth M.; Periana, Roy; Que, Lawrence; Rostrup-Nielson, Jens; Sachtler, Woflgang M H.; Schmidt, Lanny D.; Sen, Ayusman; Somorjai, Gabor A.; Stair, Peter C.; Stults, Bailey R.; Tumas, William

2001-04-11

The goal of the 'Opportunities for Catalysis Research in Carbon Management' workshop was to review within the context of greenhouse gas/carbon issues the current state of knowledge, barriers to further scientific and technological progress, and basic scientific research needs in the areas of H{sub 2} generation and utilization, light hydrocarbon activation and utilization, carbon dioxide activation, utilization, and sequestration, emerging techniques and research directions in relevant catalysis research, and in catalysis for more efficient transportation engines. Several overarching themes emerge from this review. First and foremost, there is a pressing need to better understand in detail the catalytic mechanisms involved in almost every process area mentioned above. This includes the structures, energetics, lifetimes, and reactivities of the species thought to be important in the key catalytic cycles. As much of this type of information as is possible to acquire would also greatly aid in better understanding perplexing, incomplete/inefficient catalytic cycles and in inventing new, efficient ones. The most productive way to attack such problems must include long-term, in-depth fundamental studies of both commercial and model processes, by conventional research techniques and, importantly, by applying various promising new physicochemical and computational approaches which would allow incisive, in situ elucidation of reaction pathways. There is also a consensus that more exploratory experiments, especially high-risk, unconventional catalytic and model studies, should be undertaken. Such an effort will likely require specialized equipment, instrumentation, and computational facilities. The most expeditious and cost-effective means to carry out this research would be by close coupling of academic, industrial, and national laboratory catalysis efforts worldwide. Completely new research approaches should be vigorously explored, ranging from novel compositions

Keynotes in energy-related catalysis

CERN Document Server

Kaliaguine, S

2011-01-01

Catalysis by solid acids, which includes (modified) zeolites, is of special relevance to energy applications. Acid catalysis is highly important in modern petroleum refining operations - large-scale processes such as fluid catalytic cracking, catalytic reforming, alkylation and olefin oligomerization rely on the transformation of hydrocarbons by acid catalysts. (Modified) zeolites are therefore essential for the improvement of existing processes and for technical innovations in the conversion of crude. There can be little doubt that zeolite-based catalysts will play a major role in the futu

Organocatalysis: Fundamentals and Comparisons to Metal and Enzyme Catalysis

Directory of Open Access Journals (Sweden)

Pierre Vogel

2016-08-01

Full Text Available Catalysis fulfills the promise that high-yielding chemical transformations will require little energy and produce no toxic waste. This message is carried by the study of the evolution of molecular catalysis of some of the most important reactions in organic chemistry. After reviewing the conceptual underpinnings of catalysis, we discuss the applications of different catalysts according to the mechanism of the reactions that they catalyze, including acyl group transfers, nucleophilic additions and substitutions, and C–C bond forming reactions that employ umpolung by nucleophilic additions to C=O and C=C double bonds. We highlight the utility of a broad range of organocatalysts other than compounds based on proline, the cinchona alkaloids and binaphthyls, which have been abundantly reviewed elsewhere. The focus is on organocatalysts, although a few examples employing metal complexes and enzymes are also included due to their significance. Classical Brønsted acids have evolved into electrophilic hands, the fingers of which are hydrogen donors (like enzymes or other electrophilic moieties. Classical Lewis base catalysts have evolved into tridimensional, chiral nucleophiles that are N- (e.g., tertiary amines, P- (e.g., tertiary phosphines and C-nucleophiles (e.g., N-heterocyclic carbenes. Many efficient organocatalysts bear electrophilic and nucleophilic moieties that interact simultaneously or not with both the electrophilic and nucleophilic reactants. A detailed understanding of the reaction mechanisms permits the design of better catalysts. Their construction represents a molecular science in itself, suggesting that sooner or later chemists will not only imitate Nature but be able to catalyze a much wider range of reactions with high chemo-, regio-, stereo- and enantioselectivity. Man-made organocatalysts are much smaller, cheaper and more stable than enzymes.

Spatially resolved observation of crystal-face-dependent catalysis by single turnover counting

Science.gov (United States)

Roeffaers, Maarten B. J.; Sels, Bert F.; Uji-I, Hiroshi; de Schryver, Frans C.; Jacobs, Pierre A.; de Vos, Dirk E.; Hofkens, Johan

2006-02-01

Catalytic processes on surfaces have long been studied by probing model reactions on single-crystal metal surfaces under high vacuum conditions. Yet the vast majority of industrial heterogeneous catalysis occurs at ambient or elevated pressures using complex materials with crystal faces, edges and defects differing in their catalytic activity. Clearly, if new or improved catalysts are to be rationally designed, we require quantitative correlations between surface features and catalytic activity-ideally obtained under realistic reaction conditions. Transmission electron microscopy and scanning tunnelling microscopy have allowed in situ characterization of catalyst surfaces with atomic resolution, but are limited by the need for low-pressure conditions and conductive surfaces, respectively. Sum frequency generation spectroscopy can identify vibrations of adsorbed reactants and products in both gaseous and condensed phases, but so far lacks sensitivity down to the single molecule level. Here we adapt real-time monitoring of the chemical transformation of individual organic molecules by fluorescence microscopy to monitor reactions catalysed by crystals of a layered double hydroxide immersed in reagent solution. By using a wide field microscope, we are able to map the spatial distribution of catalytic activity over the entire crystal by counting single turnover events. We find that ester hydrolysis proceeds on the lateral {1010} crystal faces, while transesterification occurs on the entire outer crystal surface. Because the method operates at ambient temperature and pressure and in a condensed phase, it can be applied to the growing number of liquid-phase industrial organic transformations to localize catalytic activity on and in inorganic solids. An exciting opportunity is the use of probe molecules with different size and functionality, which should provide insight into shape-selective or structure-sensitive catalysis and thus help with the rational design of new or

[Prediction of common buffer catalysis in hydrolysis of fenchlorazole-ethyl].

Science.gov (United States)

Lin, Jing; Chen, Jing-wen; Zhang, Si-yu; Cai, Xi-yun; Qiao, Xian-liang

2008-09-01

The purpose of this study was to elucidate the effects of temperatures, pH levels and buffer catalysis on the hydrolysis of FCE. The hydrolysis of FCE follows first-order kinetics at different pH levels and temperatures. FCE hydrolysis rates are greatly increased at elevated pH levels and temperatures. The maximum contribution of buffer catalysis to the hydrolysis of FCE was assessed based on application of the Bronsted equations for general acid-base catalysis. The results suggest that the buffer solutions play an obvious catalysis role in hydrolysis of FCE and the hydrolysis rates of FCE are quickened by the buffer solutions. Besides, the buffer catalysis capacity of different buffer solutions is diverse, and the buffer catalysis capacity at different pH levels with the same buffer solutions is different, too. The phosphate buffer at pH = 7 shows the maximal buffer catalysis capacity. The hydrolysis rate constants of FCE as a function of temperature and pH, which were remedied by the buffer catalysis factor, were mathematically combined to predict the hydrolytic dissipation of FCE. The equation suggests that the hydrolysis half-lives of FCE ranged from 7 d to 790 d. Hydrolysis metabolites of FCE were identified by liquid chromatography-mass spectrometry. In basic conditions (pH 8-10), fenchlorazole was formed via breakdown of the ester bond of the safener.

Controllable Catalysis with Nanoparticles: Bimetallic Alloy Systems and Surface Adsorbates

KAUST Repository

Chen, Tianyou

2016-05-16

Transition metal nanoparticles are privileged materials in catalysis due to their high specific surface areas and abundance of active catalytic sites. While many of these catalysts are quite useful, we are only beginning to understand the underlying catalytic mechanisms. Opening the “black box” of nanoparticle catalysis is essential to achieve the ultimate goal of catalysis by design. In this Perspective we highlight recent work addressing the topic of controlled catalysis with bimetallic alloy and “designer” adsorbate-stabilized metal nanoparticles.

Controllable Catalysis with Nanoparticles: Bimetallic Alloy Systems and Surface Adsorbates

KAUST Repository

Chen, Tianyou; Rodionov, Valentin

2016-01-01

Transition metal nanoparticles are privileged materials in catalysis due to their high specific surface areas and abundance of active catalytic sites. While many of these catalysts are quite useful, we are only beginning to understand the underlying catalytic mechanisms. Opening the “black box” of nanoparticle catalysis is essential to achieve the ultimate goal of catalysis by design. In this Perspective we highlight recent work addressing the topic of controlled catalysis with bimetallic alloy and “designer” adsorbate-stabilized metal nanoparticles.

Catalysis and sustainable (green) chemistry

Energy Technology Data Exchange (ETDEWEB)

Centi, Gabriele; Perathoner, Siglinda [Dipartimento di Chimica Industriale ed Ingegneria dei Materiali, University of Messina, Salita Sperone 31, 98166 Messina (Italy)

2003-01-15

Catalysis is a key technology to achieve the objectives of sustainable (green) chemistry. After introducing the concepts of sustainable (green) chemistry and a brief assessment of new sustainable chemical technologies, the relationship between catalysis and sustainable (green) chemistry is discussed and illustrated via an analysis of some selected and relevant examples. Emphasis is also given to the concept of catalytic technologies for scaling-down chemical processes, in order to develop sustainable production processes which reduce the impact on the environment to an acceptable level that allows self-depuration processes of the living environment.

Understanding the Relationship Between Kinetics and Thermodynamics in CO ₂ Hydrogenation Catalysis

Energy Technology Data Exchange (ETDEWEB)

Jeletic, Matthew S. [Catalysis Science Group, Pacific Northwest National Laboratory, Richland, Washington 99352, United States; Hulley, Elliott B. [Catalysis Science Group, Pacific Northwest National Laboratory, Richland, Washington 99352, United States; Helm, Monte L. [Catalysis Science Group, Pacific Northwest National Laboratory, Richland, Washington 99352, United States; Mock, Michael T. [Catalysis Science Group, Pacific Northwest National Laboratory, Richland, Washington 99352, United States; Appel, Aaron M. [Catalysis Science Group, Pacific Northwest National Laboratory, Richland, Washington 99352, United States; Wiedner, Eric S. [Catalysis Science Group, Pacific Northwest National Laboratory, Richland, Washington 99352, United States; Linehan, John C. [Catalysis Science Group, Pacific Northwest National Laboratory, Richland, Washington 99352, United States

2017-08-14

Linear free-energy relationships have been identified that link the kinetic activity for catalytic hydrogenation of CO2 to formate with the thermodynamic driving force for the rate-limiting steps of catalysis. Cobalt and rhodium bis(diphosphine) complexes with different hydricities (G°H-), acidities (pKa), and free energies for H2 addition (G°H2) were examined. Catalytic CO2 hydrogenation was studied under 1.8 and 20 atm of pressure (1:1 CO2:H2) at room temperature in tetrahydrofuran with a spread of turnover frequencies (TOF) ranging from 0 to 74,000 h-1. The catalysis was followed by 1H and 31P NMR in real time under all conditions to yield information about the rate determining step. Catalysts exhibiting the highest activities were found to have hydride transfer and hydrogen addition steps that were each downhill by approximately 6 to 7 kcal/mol, and the deprotonation step was thermoneutral. The research by M.S.J., A.M.A., E.S.W., and J.C.L. was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences. The research by E.B.H., M.L.H., and M.T.M. (X-ray crystallography, synthesis) was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. The authors thank Dr. Samantha A. Burgess for assistance in collecting cyclic voltammetry data. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.

Heterogeneous continuous-time random walks

Science.gov (United States)

Grebenkov, Denis S.; Tupikina, Liubov

2018-01-01

We introduce a heterogeneous continuous-time random walk (HCTRW) model as a versatile analytical formalism for studying and modeling diffusion processes in heterogeneous structures, such as porous or disordered media, multiscale or crowded environments, weighted graphs or networks. We derive the exact form of the propagator and investigate the effects of spatiotemporal heterogeneities onto the diffusive dynamics via the spectral properties of the generalized transition matrix. In particular, we show how the distribution of first-passage times changes due to local and global heterogeneities of the medium. The HCTRW formalism offers a unified mathematical language to address various diffusion-reaction problems, with numerous applications in material sciences, physics, chemistry, biology, and social sciences.

Understanding the mechanism of catalytic fast pyrolysis by unveiling reactive intermediates in heterogeneous catalysis

Science.gov (United States)

Hemberger, Patrick; Custodis, Victoria B. F.; Bodi, Andras; Gerber, Thomas; van Bokhoven, Jeroen A.

2017-06-01

Catalytic fast pyrolysis is a promising way to convert lignin into fine chemicals and fuels, but current approaches lack selectivity and yield unsatisfactory conversion. Understanding the pyrolysis reaction mechanism at the molecular level may help to make this sustainable process more economic. Reactive intermediates are responsible for product branching and hold the key to unveiling these mechanisms, but are notoriously difficult to detect isomer-selectively. Here, we investigate the catalytic pyrolysis of guaiacol, a lignin model compound, using photoelectron photoion coincidence spectroscopy with synchrotron radiation, which allows for isomer-selective detection of reactive intermediates. In combination with ambient pressure pyrolysis, we identify fulvenone as the central reactive intermediate, generated by catalytic demethylation to catechol and subsequent dehydration. The fulvenone ketene is responsible for the phenol formation. This technique may open unique opportunities for isomer-resolved probing in catalysis, and holds the potential for achieving a mechanistic understanding of complex, real-life catalytic processes.

Accurate Experimental and Theoretical Enthalpies of Association of TiCl4 with Typical Lewis Bases Used in Heterogeneous Ziegler-Natta Catalysis

KAUST Repository

Credendino, Raffaele

2017-09-18

Adducts of TiCl4 with Lewis bases used as internal or external donors in heterogeneous Ziegler-Natta (ZN) catalysis represents a fundamental interaction contributing to the final composition of MgCl2 supported ZN-catalysts. This study presents the accurate experimental evaluation, from titration calorimetry, of the formation enthalpy of TiCl4 adducts with 15 Lewis bases of industrial interests. In addition, we report accurate energies of association of TiCl4 with the same Lewis bases from calculations at the DLPNO-CCSD(T) level of theory. These accurate experimental and theoretical association values are compared with selected methods based on density functional theory (DFT) in combination with popular continuum solvation models. Calculations suggest that the PBE-D3, and M06 functionals in combination with a triple-ζ plus polarization quality basis set provide the best performance when the basis set superposition error (BSSE) is not removed from the association energies. Cleaning the association energies by the BSSE with the counterpoise protocol suggests the B3LYP-D3, TPSS-D3 and M06L as the best performing functionals. Introducing solvent effects with the PCM and SMD continuum solvation models allows comparing the DFT based association enthalpies with the experimental values obtained from titration calorimetry. Both solvation models in combination with the PBE-D3, PBE0-D3, B3LYP-D3, TPSS-D3, M06L, and M06 functionals provide association enthalpies close to the experimental values with MUEs in range 10 – 15 kJ/mol.

C-C Coupling on Single-Atom-Based Heterogeneous Catalyst.

Science.gov (United States)

Zhang, Xiaoyan; Sun, Zaicheng; Wang, Bin; Tang, Yu; Nguyen, Luan; Li, Yuting; Tao, Franklin Feng

2018-01-24

Compared to homogeneous catalysis, heterogeneous catalysis allows for ready separation of products from the catalyst and thus reuse of the catalyst. C-C coupling is typically performed on a molecular catalyst which is mixed with reactants in liquid phase during catalysis. This homogeneous mixing at a molecular level in the same phase makes separation of the molecular catalyst extremely challenging and costly. Here we demonstrated that a TiO 2 -based nanoparticle catalyst anchoring singly dispersed Pd atoms (Pd 1 /TiO 2 ) is selective and highly active for more than 10 Sonogashira C-C coupling reactions (R≡CH + R'X → R≡R'; X = Br, I; R' = aryl or vinyl). The coupling between iodobenzene and phenylacetylene on Pd 1 /TiO 2 exhibits a turnover rate of 51.0 diphenylacetylene molecules per anchored Pd atom per minute at 60 °C, with a low apparent activation barrier of 28.9 kJ/mol and no cost of catalyst separation. DFT calculations suggest that the single Pd atom bonded to surface lattice oxygen atoms of TiO 2 acts as a site to dissociatively chemisorb iodobenzene to generate an intermediate phenyl, which then couples with phenylacetylenyl bound to a surface oxygen atom. This coupling of phenyl adsorbed on Pd 1 and phenylacetylenyl bound to O ad of TiO 2 forms the product molecule, diphenylacetylene.

Asymmetric cation-binding catalysis

DEFF Research Database (Denmark)

Oliveira, Maria Teresa; Lee, Jiwoong

2017-01-01

The employment of metal salts is quite limited in asymmetric catalysis, although it would provide an additional arsenal of safe and inexpensive reagents to create molecular functions with high optical purity. Cation chelation by polyethers increases the salts' solubility in conventional organic...... solvents, thus increasing their applicability in synthesis. The expansion of this concept to chiral polyethers led to the emergence of asymmetric cation-binding catalysis, where chiral counter anions are generated from metal salts, particularly using BINOL-based polyethers. Alkali metal salts, namely KF...... highly enantioselective silylation reactions in polyether-generated chiral environments, and leading to a record-high turnover in asymmetric organocatalysis. This can lead to further applications by the asymmetric use of other inorganic salts in various organic transformations....

ESR study into mechanism of heterogeneous-catalytic oxidation on oxides

Energy Technology Data Exchange (ETDEWEB)

Topchieva, K V; Loginov, A Yu; Kostikov, S V [Moskovskij Gosudarstvennyj Univ. (USSR)

1977-12-11

The role of radical particles in heterogeneous-catalytic oxidation of H/sub 2/; CO; SO/sub 2/; NH/sub 3/; C/sub 3/H/sub 6/ on the rare earth oxides (yttrium, lanthanum, magnesium and scandium oxides) and alkaline earth metal oxides was studied by the ESR method. The conclusion was made about the great reactivity of the peroxide structures O/sub 2//sup -/ in the oxidation catalysis in comparison to other formulas of chemisorption oxigen on oxides. The kinetic investigations are chemisorption oxigen on oxides. The kinetic investigations are carried out on the change of the concentration of paramagnetic particles O/sub 2/ during the catalysis. On the basis of the received data the conclusion is made about the reaction process of catalytic oxidation on rare and alkaline-earth oxides according to radical-chain mechanism with the formation of radical particles O/sub 2//sup -/, CO/sub 3//sup -/, SO/sub 4//sup -/, CO/sub 2//sup -/ as interediate products.

Argonne Chemical Sciences & Engineering - Center for Electrical Energy

Science.gov (United States)

Laboratory Chemical Sciences & Engineering DOE Logo CSE Home About CSE Research Facilities People Publications Awards News & Highlights Events Search Argonne ... Search Argonne Home > Chemical Sciences & Engineering > Fundamental Interactions Catalysis & Energy Conversion Electrochemical

Solid Base Catalysis

CERN Document Server

Ono, Yoshio

2011-01-01

The importance of solid base catalysts has come to be recognized for their environmentally benign qualities, and much significant progress has been made over the past two decades in catalytic materials and solid base-catalyzed reactions. The book is focused on the solid base. Because of the advantages over liquid bases, the use of solid base catalysts in organic synthesis is expanding. Solid bases are easier to dispose than liquid bases, separation and recovery of products, catalysts and solvents are less difficult, and they are non-corrosive. Furthermore, base-catalyzed reactions can be performed without using solvents and even in the gas phase, opening up more possibilities for discovering novel reaction systems. Using numerous examples, the present volume describes the remarkable role solid base catalysis can play, given the ever increasing worldwide importance of "green" chemistry. The reader will obtain an overall view of solid base catalysis and gain insight into the versatility of the reactions to whic...

Materials Sciences Division 1990 annual report

International Nuclear Information System (INIS)

1990-01-01

This report is the Materials Sciences Division's annual report. It contains abstracts describing materials research at the National Center for Electron Microscopy, and for research groups in metallurgy, solid-state physics, materials chemistry, electrochemical energy storage, electronic materials, surface science and catalysis, ceramic science, high tc superconductivity, polymers, composites, and high performance metals

Heterogeneous catalysis afford biodiesel of babassu, castor oil and blends

International Nuclear Information System (INIS)

Carvalho, Lee M.G. de; Abreu, Wiury C. de; Silva, Maria das Gracas de O. e; Matos, Jose Milton E. de; Moura, Carla V.R. de; Moura, Edmilson M. de; Lima, Jose Renato de O.; Oliveira, Jose Eduardo de

2013-01-01

This work describes the preparation of babassu, castor oil biodiesel and mixtures in various proportions of these oils, using alkaline compounds of strontium (SrCO 3 + SrO + Sr (OH) 2 ) as heterogeneous catalysts. The mixture of oils of these oleaginous sources was used in the production of biodiesel with quality parameters that meet current legislation. The catalyst was characterized by X-ray diffractometry (XDR), physisorption of gas (BET method), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDX) and Fourier transform infrared spectroscopy (FTIR). The viscometric technique was used to monitor the optimization.The transesterification reactions performed using strontium compounds reached conversion rates of 97.2% babassu biodiesel (BB), 96.4% castor oil biodiesel (COB) and 95.3% Babassu/Castor Oil Biodiesel 4:1 (BBCO41). (author)

Residual waters treatment by heterogeneous photocatalysis: a study of experimental parameters applied to the photoelectrocatalysis

Directory of Open Access Journals (Sweden)

Henrique de Santana

2006-02-01

Full Text Available In this paper, the use of electrochemically-assisted heterogeneous photo-catalysis will be discussed. Several operational parameters will also be discussed, in order to achieve optimum efficiency of this photo-degradation system, such as: the influence of variables as support electrolyte, applied potential, dye initial concentration, pH and choice of a UV source on dye degradation.

Materials Sciences Division 1990 annual report

Energy Technology Data Exchange (ETDEWEB)

1990-12-31

This report is the Materials Sciences Division`s annual report. It contains abstracts describing materials research at the National Center for Electron Microscopy, and for research groups in metallurgy, solid-state physics, materials chemistry, electrochemical energy storage, electronic materials, surface science and catalysis, ceramic science, high tc superconductivity, polymers, composites, and high performance metals.

Materials Sciences Division 1990 annual report

Energy Technology Data Exchange (ETDEWEB)

1990-01-01

This report is the Materials Sciences Division's annual report. It contains abstracts describing materials research at the National Center for Electron Microscopy, and for research groups in metallurgy, solid-state physics, materials chemistry, electrochemical energy storage, electronic materials, surface science and catalysis, ceramic science, high tc superconductivity, polymers, composites, and high performance metals.

Positron studies in catalysis research

International Nuclear Information System (INIS)

1994-01-01

During the past eight months, the authors have made progress in several areas relevant to the eventual use of positron techniques in catalysis research. They have come closer to the completion of their positron microscope, and at the same time have performed several studies in their non-microscopic positron spectrometer which should ultimately be applicable to catalysis. The current status of the efforts in each of these areas is summarized in the following sections: Construction of the positron microscope (optical element construction, data collection software, and electronic sub-assemblies); Doppler broadening spectroscopy of metal silicide; Positron lifetime spectroscopy of glassy polymers; and Positron lifetime measurements of pore-sizes in zeolites

Heterogeneous catalysis afford biodiesel of babassu, castor oil and blends

Energy Technology Data Exchange (ETDEWEB)

Carvalho, Lee M.G. de; Abreu, Wiury C. de; Silva, Maria das Gracas de O. e; Matos, Jose Milton E. de; Moura, Carla V.R. de; Moura, Edmilson M. de, E-mail: mmoura@ufpi.edu.br [Universidade Federal do Piaui (UFPI), Teresina, PI (Brazil). Departamento de Quimica; Lima, Jose Renato de O.; Oliveira, Jose Eduardo de [Universidade Estadual Paulista Julio de Mesquita Filho (UNESP/IQ/CEMPEQC), Araraquara, SP (Brazil). Instituto de Quimica. Centro de Monitoramento e Pesquisa da Qualidade de Combustiveis, Biocombustiveis, Petroleo e Derivados

2013-04-15

This work describes the preparation of babassu, castor oil biodiesel and mixtures in various proportions of these oils, using alkaline compounds of strontium (SrCO{sub 3} + SrO + Sr (OH){sub 2}) as heterogeneous catalysts. The mixture of oils of these oleaginous sources was used in the production of biodiesel with quality parameters that meet current legislation. The catalyst was characterized by X-ray diffractometry (XDR), physisorption of gas (BET method), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDX) and Fourier transform infrared spectroscopy (FTIR). The viscometric technique was used to monitor the optimization.The transesterification reactions performed using strontium compounds reached conversion rates of 97.2% babassu biodiesel (BB), 96.4% castor oil biodiesel (COB) and 95.3% Babassu/Castor Oil Biodiesel 4:1 (BBCO41). (author)

Camphor as Chiral Motif in Ligand Design - Applications in Catalysis and Complexation Gas-Chromatography

OpenAIRE

Spallek, Markus Jürgen

2012-01-01

This thesis is intended to further extend the scope of camphor and camphor-derived building blocks in the synthesis of chiral ligands, catalysts and selectors, their successful application in catalysis and in enantioseparation sciences. The thesis is divided into four independent chapters each focusing on the development of novel camphor-based compounds and their application as catalysts or metal-selectors. A short introduction is given for each chapter dealing with recent progress in the fie...

MRI of Heterogeneous Hydrogenation Reactions Using Parahydrogen Polarization

Energy Technology Data Exchange (ETDEWEB)

Burt, Scott Russell [Univ. of California, Berkeley, CA (United States)

2008-01-01

The power of magnetic resonance imaging (MRI) is its ability to image the internal structure of optically opaque samples and provide detailed maps of a variety of important parameters, such as density, diffusion, velocity and temperature. However, one of the fundamental limitations of this technique is its inherent low sensitivity. For example, the low signal to noise ratio (SNR) is particularly problematic for imaging gases in porous materials due to the low density of the gas and the large volume occluded by the porous material. This is unfortunate, as many industrially relevant chemical reactions take place at gas-surface interfaces in porous media, such as packed catalyst beds. Because of this severe SNR problem, many techniques have been developed to directly increase the signal strength. These techniques work by manipulating the nuclear spin populations to produce polarized} (i.e., non-equilibrium) states with resulting signal strengths that are orders of magnitude larger than those available at thermal equilibrium. This dissertation is concerned with an extension of a polarization technique based on the properties of parahydrogen. Specifically, I report on the novel use of heterogeneous catalysis to produce parahydrogen induced polarization and applications of this new technique to gas phase MRI and the characterization of micro-reactors. First, I provide an overview of nuclear magnetic resonance (NMR) and how parahydrogen is used to improve the SNR of the NMR signal. I then present experimental results demonstrating that it is possible to use heterogeneous catalysis to produce parahydrogen-induced polarization. These results are extended to imaging void spaces using a parahydrogen polarized gas. In the second half of this dissertation, I demonstrate the use of parahydrogen-polarized gas-phase MRI for characterizing catalytic microreactors. Specifically, I show how the improved SNR allows one to map parameters important for characterizing the heat and mass

Large epidemic thresholds emerge in heterogeneous networks of heterogeneous nodes

Science.gov (United States)

Yang, Hui; Tang, Ming; Gross, Thilo

2015-08-01

One of the famous results of network science states that networks with heterogeneous connectivity are more susceptible to epidemic spreading than their more homogeneous counterparts. In particular, in networks of identical nodes it has been shown that network heterogeneity, i.e. a broad degree distribution, can lower the epidemic threshold at which epidemics can invade the system. Network heterogeneity can thus allow diseases with lower transmission probabilities to persist and spread. However, it has been pointed out that networks in which the properties of nodes are intrinsically heterogeneous can be very resilient to disease spreading. Heterogeneity in structure can enhance or diminish the resilience of networks with heterogeneous nodes, depending on the correlations between the topological and intrinsic properties. Here, we consider a plausible scenario where people have intrinsic differences in susceptibility and adapt their social network structure to the presence of the disease. We show that the resilience of networks with heterogeneous connectivity can surpass those of networks with homogeneous connectivity. For epidemiology, this implies that network heterogeneity should not be studied in isolation, it is instead the heterogeneity of infection risk that determines the likelihood of outbreaks.

Large epidemic thresholds emerge in heterogeneous networks of heterogeneous nodes.

Science.gov (United States)

Yang, Hui; Tang, Ming; Gross, Thilo

2015-08-21

One of the famous results of network science states that networks with heterogeneous connectivity are more susceptible to epidemic spreading than their more homogeneous counterparts. In particular, in networks of identical nodes it has been shown that network heterogeneity, i.e. a broad degree distribution, can lower the epidemic threshold at which epidemics can invade the system. Network heterogeneity can thus allow diseases with lower transmission probabilities to persist and spread. However, it has been pointed out that networks in which the properties of nodes are intrinsically heterogeneous can be very resilient to disease spreading. Heterogeneity in structure can enhance or diminish the resilience of networks with heterogeneous nodes, depending on the correlations between the topological and intrinsic properties. Here, we consider a plausible scenario where people have intrinsic differences in susceptibility and adapt their social network structure to the presence of the disease. We show that the resilience of networks with heterogeneous connectivity can surpass those of networks with homogeneous connectivity. For epidemiology, this implies that network heterogeneity should not be studied in isolation, it is instead the heterogeneity of infection risk that determines the likelihood of outbreaks.

Heterogeneous catalysis : introduction

NARCIS (Netherlands)

Niemantsverdriet, J.W.; Schlögl, R.; Reedijk, J.; Poeppelmeier, K.

2013-01-01

Comprehensive Inorganic Chemistry II reviews and examines topics of relevance to today’s inorganic chemists. Covering more interdisciplinary and high impact areas, Comprehensive Inorganic Chemistry II includes biological inorganic chemistry, solid state chemistry, materials chemistry, and

Chemistry Division: Annual progress report for period ending March 31, 1987

International Nuclear Information System (INIS)

1987-08-01

This report is divided into the following sections: coal chemistry; aqueous chemistry at high temperatures and pressures; geochemistry of crustal processes to high temperatures and pressures; chemistry of advanced inorganic materials; structure and dynamics of advanced polymeric materials; chemistry of transuranium elements and compounds; separations chemistry; reactions and catalysis in molten salts; surface science related to heterogeneous catalysis; electron spectroscopy; chemistry related to nuclear waste disposal; computational modeling of security document printing; and special topics

Planar, Polysilazane-Derived Porous Ceramic Supports for Membrane and Catalysis Applications.

Science.gov (United States)

Konegger, Thomas; Williams, Lee F; Bordia, Rajendra K

2015-10-01

Porous, silicon carbonitride-based ceramic support structures for potential membrane and catalysis applications were generated from a preceramic polysilazane precursor in combination with spherical, ultrahigh-molecular weight polyethylene microparticles through a sacrificial filler approach. A screening evaluation was used for the determination of the impact of both porogen content and porogen size on pore structure, strength, and permeability characteristics of planar specimens. By optimizing both the composition as well as cross-linking parameters, maximum characteristic biaxial flexural strengths of 65 MPa and porosities of 42% were achieved. The evolution of an interconnected, open-pore network during thermal porogen removal and conversion of the preceramic polymer led to air permeabilities in the order of 10 -14 m 2 . The materials were further exposed to long-term heat treatments to demonstrate the stability of properties after 100 h at 800°C in oxidizing, inert, and reducing environments. The determined performance, in combination with the versatile preparation method, illustrates the feasibility of this processing approach for the generation of porous ceramic support structures for applications at elevated temperatures in a variety of fields, including membrane and catalysis science.

Opportunities for Catalysis in The 21st Century. A report from the Basic Energy Sciences Advisory Committee

Energy Technology Data Exchange (ETDEWEB)

White, J. M.; Bercaw, J.

2002-05-16

Chemical catalysis affects our lives in myriad ways. Catalysis provides a means of changing the rates at which chemical bonds are formed and broken and of controlling the yields of chemical reactions to increase the amounts of desirable products from these reactions and reduce the amounts of undesirable ones. Thus, it lies at the heart of our quality of life: The reduced emissions of modern cars, the abundance of fresh food at our stores, and the new pharmaceuticals that improve our health are made possible by chemical reactions controlled by catalysts. Catalysis is also essential to a healthy economy: The petroleum, chemical, and pharmaceutical industries, contributors of $500 billion to the gross national product of the United States, rely on catalysts to produce everything from fuels to ''wonder drugs'' to paints to cosmetics. Today, our Nation faces a variety of challenges in creating alternative fuels, reducing harmful by-products in manufacturing, cleaning up the environment and preventing future pollution, dealing with the causes of global warming, protecting citizens from the release of toxic substances and infectious agents, and creating safe pharmaceuticals. Catalysts are needed to meet these challenges, but their complexity and diversity demand a revolution in the way catalysts are designed and used. This revolution can become reality through the application of new methods for synthesizing and characterizing molecular and material systems. Opportunities to understand and predict how catalysts work at the atomic scale and the nanoscale are now appearing, made possible by breakthroughs in the last decade in computation, measurement techniques, and imaging and by new developments in catalyst design, synthesis, and evaluation.

Performance of the undulator based ultraviolet and soft x-ray beamline for catalysis and surface science at National Synchrotron Radiation Laboratory

Energy Technology Data Exchange (ETDEWEB)

Du, Liangliang [University of Science and Technology of China, Department of Precision Machinery and Precision Instrumentation, Hefei, Anhui 230029 (China); University of Science and Technology of China, National Synchrotron Radiation Laboratory, Hefei, Anhui 230029 (China); Du, Xuewei, E-mail: xwdu@ustc.edu.cn [University of Science and Technology of China, National Synchrotron Radiation Laboratory, Hefei, Anhui 230029 (China); Wei, Shen [University of Science and Technology of China, National Synchrotron Radiation Laboratory, Hefei, Anhui 230029 (China); Li, Chaoyang [China Academy of Engineering Physics, Mianyang, Sichuan 621900 (China); Pan, Congyuan; Ju, Huanxin [University of Science and Technology of China, National Synchrotron Radiation Laboratory, Hefei, Anhui 230029 (China); Wang, Qiuping, E-mail: qiuping@ustc.edu.cn [University of Science and Technology of China, National Synchrotron Radiation Laboratory, Hefei, Anhui 230029 (China); Zhu, Junfa [University of Science and Technology of China, National Synchrotron Radiation Laboratory, Hefei, Anhui 230029 (China)

2016-12-01

The undulator based ultraviolet and soft x-ray beamline BL11U for catalysis and surface science at National Synchrotron Radiation Laboratory (NSRL) has been under opteration for months and the present performance is described. This beamline utilizes radiation from an in-vacuum undulator, which has 30 magnetic periods with the period length of 40 mm. A varied-line-spacing plane grating monochromator is employed tto cover the photon energy region of 20–600 eV by two gratings with nominal groove densities of 400 llmm and 1200 l/mm respectively. The energy resolution power E/ΔE is measured with a gas ionization chamber and the photon flux is measured by a photodiode. Results show that the resolution power is better than 10,000 at a photon energy of 29.2 eV. And the flux is higher than 1×10{sup 10} phs/s under 300 mA ring beam current for most of the covered photon energy.

Synthesis of a molecularly defined single-active site heterogeneous catalyst for selective oxidation of N-heterocycles.

Science.gov (United States)

Zhang, Yujing; Pang, Shaofeng; Wei, Zhihong; Jiao, Haijun; Dai, Xingchao; Wang, Hongli; Shi, Feng

2018-04-13

Generally, a homogeneous catalyst exhibits good activity and defined active sites but it is difficult to recycle. Meanwhile, a heterogeneous catalyst can easily be reused but its active site is difficult to reveal. It is interesting to bridge the gap between homogeneous and heterogeneous catalysis via controllable construction of a heterogeneous catalyst containing defined active sites. Here, we report that a molecularly defined, single-active site heterogeneous catalyst has been designed and prepared via the oxidative polymerization of maleimide derivatives. These polymaleimide derivatives can be active catalysts for the selective oxidation of heterocyclic compounds to quinoline and indole via the recycling of -C=O and -C-OH groups, which was confirmed by tracing the reaction with GC-MS using maleimide as the catalyst and by FT-IR analysis with polymaleimide as the catalyst. These results might promote the development of heterogeneous catalysts with molecularly defined single active sites exhibiting a comparable activity to homogeneous catalysts.

Interfacial mechanisms of heterogeneous Fenton reactions catalyzed by iron-based materials: A review.

Science.gov (United States)

He, Jie; Yang, Xiaofang; Men, Bin; Wang, Dongsheng

2016-01-01

The heterogeneous Fenton reaction can generate highly reactive hydroxyl radicals (OH) from reactions between recyclable solid catalysts and H2O2 at acidic or even circumneutral pH. Hence, it can effectively oxidize refractory organics in water or soils and has become a promising environmentally friendly treatment technology. Due to the complex reaction system, the mechanism behind heterogeneous Fenton reactions remains unresolved but fascinating, and is crucial for understanding Fenton chemistry and the development and application of efficient heterogeneous Fenton technologies. Iron-based materials usually possess high catalytic activity, low cost, negligible toxicity and easy recovery, and are a superior type of heterogeneous Fenton catalysts. Therefore, this article reviews the fundamental but important interfacial mechanisms of heterogeneous Fenton reactions catalyzed by iron-based materials. OH, hydroperoxyl radicals/superoxide anions (HO2/O2(-)) and high-valent iron are the three main types of reactive oxygen species (ROS), with different oxidation reactivity and selectivity. Based on the mechanisms of ROS generation, the interfacial mechanisms of heterogeneous Fenton systems can be classified as the homogeneous Fenton mechanism induced by surface-leached iron, the heterogeneous catalysis mechanism, and the heterogeneous reaction-induced homogeneous mechanism. Different heterogeneous Fenton systems catalyzed by characteristic iron-based materials are comprehensively reviewed. Finally, related future research directions are also suggested. Copyright © 2015. Published by Elsevier B.V.

Graphene-Based Nanomaterials as Heterogeneous Acid Catalysts: A Comprehensive Perspective

Directory of Open Access Journals (Sweden)

Bhaskar Garg

2014-09-01

Full Text Available Acid catalysis is quite prevalent and probably one of the most routine operations in both industrial processes and research laboratories worldwide. Recently, “graphene”, a two dimensional single-layer carbon sheet with hexagonal packed lattice structure, imitative of nanomaterials, has shown great potential as alternative and eco-friendly solid carbocatalyst for a variety of acid-catalyzed reactions. Owing to their exceptional physical, chemical, and mechanical properties, graphene-based nanomaterials (G-NMs offer highly stable Brønsted acidic sites, high mass transfer, relatively large surface areas, water tolerant character, and convenient recoverability as well as recyclability, whilst retaining high activity in acid-catalyzed chemical reactions. This comprehensive review focuses on the chemistry of G-NMs, including their synthesis, characterization, properties, functionalization, and up-to-date applications in heterogeneous acid catalysis. In line with this, in certain instances readers may find herein some criticisms that should be taken as constructive and would be of value in understanding the scope and limitations of current approaches utilizing graphene and its derivatives for the same.

Chemistry Division: Annual progress report for period ending March 31, 1987

Energy Technology Data Exchange (ETDEWEB)

1987-08-01

This report is divided into the following sections: coal chemistry; aqueous chemistry at high temperatures and pressures; geochemistry of crustal processes to high temperatures and pressures; chemistry of advanced inorganic materials; structure and dynamics of advanced polymeric materials; chemistry of transuranium elements and compounds; separations chemistry; reactions and catalysis in molten salts; surface science related to heterogeneous catalysis; electron spectroscopy; chemistry related to nuclear waste disposal; computational modeling of security document printing; and special topics. (DLC)

Catalysis in electrochemistry: from fundamentals to strategies for fuel cell development

National Research Council Canada - National Science Library

Santos, Elizabeth; Schmickler, Wolfgang

2011-01-01

"Catalysis in Electrochemistry: From Fundamentals to Strategies for Fuel Cell Development is a modern, comprehensive reference work on catalysis in electrochemistry, including principles, methods, strategies, and applications...

Catalysis in the Primordial World

Directory of Open Access Journals (Sweden)

Nenad Raos

2017-11-01

Full Text Available Catalysis provides orderly prebiotic synthesis and eventually its evolution into autocatalytic (self-reproduction systems. Research on homogeneous catalysis is concerned mostly with random peptide synthesis and the chances to produce catalytic peptide oligomers. Synthesis of ribose via formose reaction was found to be catalysed by B(OH4−, presumably released by weathering of borate minerals. Oxide and clay mineral surfaces provide catalytic sites for the synthesis of oligopeptides and oligonucleotides. Chemoautotrophic or iron-sulphur-world theory assumes that the first (pioneer organisms developed by catalytic processes on (Fe/NiS particles formed near/close hydrothermal vents. The review provides an overlay of possible catalytic reactions in prebiotic environment, discussing their selectivity (regioselectivity, stereoselectivity as well as geological availability of catalytic minerals and geochemical conditions enabling catalytic reactions on early Earth.

Pollution Control by Catalysis

DEFF Research Database (Denmark)

Eriksen, Kim Michael; Fehrmann, Rasmus

1998-01-01

The report summarises the results of two years of collaboration supported by INTAS between Department of Chemistry,DTU,DK , IUSTI,Universite de Provence,FR, ICE/HT University 6of Patras,GR, and Boreskov Institute of Catalysis,RU.The project has been concerned with mechanistic studies of deNOx and...

Resonance – Journal of Science Education | Indian Academy of ...

Indian Academy of Sciences (India)

Keywords. Fermentation; enzymes; catalysis; proteins; biochemistry. Author Affiliations. T Ramasarma1. INSA Honorary Scientist Solid State and Structural Chemistry Unit and Department of Biochemistry Indian Institute of Science Bangalore 560 012, India. Resonance – Journal of Science Education. Current Issue : Vol.

Special section on Nano-Catalysis

CSIR Research Space (South Africa)

Makgwane, PR

2013-01-01

Full Text Available to achieve sustainable and green catalytic processes. The special issue contains 40 peer reviewed scientific papers that include four comprehensive review articles contributions from the invited experts in the respective catalysis fields....

Spectroscopy in catalysis : an introduction

NARCIS (Netherlands)

Niemantsverdriet, J.W.

2000-01-01

Spectroscopy in Catalysis describes the most important modern analytical techniques used to investigate catalytic surfaces. These include electron spectroscopy (XPS, UPS, AES, EELS), ion spectroscopy (SIMS, SNMS, RBS, LEIS), vibrational spectroscopy (infrared, Raman, EELS), temperature-programmed

Catalysis by nonmetals rules for catalyst selection

CERN Document Server

Krylov, Oleg V

1970-01-01

Catalysis by Non-metals: Rules of Catalyst Selection presents the development of scientific principles for the collection of catalysts. It discusses the investigation of the mechanism of chemosorption and catalysis. It addresses a series of properties of solid with catalytic activity. Some of the topics covered in the book are the properties of a solid and catalytic activity in oxidation-reduction reactions; the difference of electronegativities and the effective charges of atoms; the role of d-electrons in the catalytic properties of a solid; the color of solids; and proton-acid and proton-ba

Advanced electron microscopy characterization of nanomaterials for catalysis

Directory of Open Access Journals (Sweden)

Dong Su

2017-04-01

Full Text Available Transmission electron microscopy (TEM has become one of the most powerful techniques in the fields of material science, inorganic chemistry and nanotechnology. In terms of resolutions, advanced TEM may reach a high spatial resolution of 0.05 nm, a high energy-resolution of 7 meV. In addition, in situ TEM can help researchers to image the process happened within 1 ms. This paper reviews the recent technical progresses of applying advanced TEM characterization on nanomaterials for catalysis. The text is organized based on the perspective of application: for example, size, composition, phase, strain, and morphology. The electron beam induced effect and in situ TEM are also introduced. I hope this review can help the scientists in related fields to take advantage of advanced TEM to their own researches. Keywords: Advanced TEM, Nanomaterials, Catalysts, In situ

Cu and Cu-Based Nanoparticles: Synthesis and Applications in Catalysis.

Science.gov (United States)

Gawande, Manoj B; Goswami, Anandarup; Felpin, François-Xavier; Asefa, Tewodros; Huang, Xiaoxi; Silva, Rafael; Zou, Xiaoxin; Zboril, Radek; Varma, Rajender S

2016-03-23

The applications of copper (Cu) and Cu-based nanoparticles, which are based on the earth-abundant and inexpensive copper metal, have generated a great deal of interest in recent years, especially in the field of catalysis. The possible modification of the chemical and physical properties of these nanoparticles using different synthetic strategies and conditions and/or via postsynthetic chemical treatments has been largely responsible for the rapid growth of interest in these nanomaterials and their applications in catalysis. In addition, the design and development of novel support and/or multimetallic systems (e.g., alloys, etc.) has also made significant contributions to the field. In this comprehensive review, we report different synthetic approaches to Cu and Cu-based nanoparticles (metallic copper, copper oxides, and hybrid copper nanostructures) and copper nanoparticles immobilized into or supported on various support materials (SiO2, magnetic support materials, etc.), along with their applications in catalysis. The synthesis part discusses numerous preparative protocols for Cu and Cu-based nanoparticles, whereas the application sections describe their utility as catalysts, including electrocatalysis, photocatalysis, and gas-phase catalysis. We believe this critical appraisal will provide necessary background information to further advance the applications of Cu-based nanostructured materials in catalysis.

Asymmetric Aldol Additions: A Guided-Inquiry Laboratory Activity on Catalysis

Science.gov (United States)

King, Jorge H. Torres; Wang, Hong; Yezierski, Ellen J.

2018-01-01

Despite the importance of asymmetric catalysis in both the pharmaceutical and commodity chemicals industries, asymmetric catalysis is under-represented in undergraduate chemistry laboratory curricula. A novel guided-inquiry experiment based on the asymmetric aldol addition was developed. Students conduct lab work to compare the effectiveness of…

Statistical Analysis of Past Catalytic Data on Oxidative Methane Coupling for New Insights into the Composition of High-Performance Catalysts

Czech Academy of Sciences Publication Activity Database

Zavyalova, U.; Holeňa, Martin; Schlögl, R.; Baerns, M.

2011-01-01

Roč. 3, č. 12 (2011), s. 1935-1947 ISSN 1867-3880 Institutional research plan: CEZ:AV0Z10300504 Keywords : catalyst development * heterogeneous catalysis * methane * oxidative coupling * catalyst composition * statistical analysis Subject RIV: IN - Informatics, Computer Science Impact factor: 5.207, year: 2011

Cyclopalladated complexes in enantioselective catalysis

Energy Technology Data Exchange (ETDEWEB)

Dunina, Valeria V; Gorunova, Olga N; Zykov, P A; Kochetkov, Konstantin A

2011-01-31

The results of the use of optically active palladacycles in enantioselective catalysis of [3,3]-sigmatropic rearrangements, aldol condensation, the Michael reaction and cross-coupling are analyzed. Reactions with allylic substrates or reagents and some other transformations are considered.

Time-resolved chromatographic analysis and mechanisms in adsorption and catalysis.

Science.gov (United States)

Roubani-Kalantzopoulou, Fani

2009-03-06

The main object of this review is the study of fundamentals of adsorption and heterogeneous catalysis, a benefit for the understanding of adsorptive and catalytic properties. This work aims to define and record, with the utmost accuracy, the phenomena and the possible reactions. A new methodology for the study of the adsorption is presented, which is a version of the well-known inverse gas chromatography. This reversed-flow inverse gas chromatography (RF-IGC) is technically very simple, and it is combined with a mathematical analysis that gives the possibility for the estimation of various physicochemical parameters related to adsorbent or catalyst characterization, under conditions compatible with the operation of real adsorbents and catalysts. On this base, this methodology has been successfully applied to the study of the impact of air pollutants, volatile organic and/or inorganic, on many solids such as marbles, ceramics, oxide-pigments of works of art, building materials, authentic statues of the Greek Archaeological Museums. Moreover, this methodology proved to be a powerful tool for studying the topography of active sites of heterogeneous surfaces in the nano-scale domain. Thus, some very important local quantities for the surface chemistry have been determined experimentally for many solids including thin films. These physicochemical local quantities (among which adsorption energy and entropy, surface diffusion coefficient, probability density function) have been determined from the experimental pairs of height of extra chromatographic peaks and time by a nonlinear least-squares method, through personal computer programs written in GW BASIC and lately in FORTRAN. Through the time-resolved analysis the surface characterization of the examined materials took place. In addition, the kinetic constants responsible for adsorption/desorption and surface chemical reactions have also been calculated. Thus, important answers have been provided to the following

Gold nanoparticles on OMS-2 for heterogeneously catalyzed aerobic oxidative α,β-dehydrogenation of β-heteroatom-substituted ketones.

Science.gov (United States)

Yoshii, Daichi; Jin, Xiongjie; Yatabe, Takafumi; Hasegawa, Jun-Ya; Yamaguchi, Kazuya; Mizuno, Noritaka

2016-12-06

In the presence of Au nanoparticles supported on manganese oxide OMS-2 (Au/OMS-2), various kinds of β-heteroatom-substituted α,β-unsaturated ketones (heteroatom = N, O, S) can be synthesized through α,β-dehydrogenation of the corresponding saturated ketones using O 2 (in air) as the oxidant. The catalysis of Au/OMS-2 is truly heterogeneous, and the catalyst can be reused.

Resonance – Journal of Science Education | Indian Academy of ...

Indian Academy of Sciences (India)

Home; Journals; Resonance – Journal of Science Education; Volume 4; Issue 9. Transition Metal Complexes and Catalysis. Balaji R Jagirdar. General Article Volume 4 Issue 9 ... Author Affiliations. Balaji R Jagirdar1. Department of Inorganic & Physical Chemistry, Indian Institute of Science, Bangalore 560 012, India.

Yolk-shell gold nanoparticles as model materials for support-effect studies in heterogeneous catalysis: Au, @C and Au, @ZrO2 for CO oxidation as an example.

Science.gov (United States)

Galeano, Carolina; Güttel, Robert; Paul, Michael; Arnal, Pablo; Lu, An-Hui; Schüth, Ferdi

2011-07-18

The use of nanostructured yolk-shell materials offers a way to discriminate support and particle-size effects for mechanistic studies in heterogeneous catalysis. Herein, gold yolk-shell materials have been synthesized and used as model catalysts for the investigation of support effects in CO oxidation. Carbon has been selected as catalytically inert support to study the intrinsic activity of the gold nanoparticles, and for comparison, zirconia has been used as oxidic support. Au, @C materials have been synthesized through nanocasting using two different nonporous-core@mesoporous-shell exotemplates: Au@SiO(2)@ZrO(2) and Au@SiO(2)@m-SiO(2). The catalytic activity of Au, @C with a gold core of about 14 nm has been evaluated and compared with Au, @ZrO(2) of the same gold core size. The strong positive effect of metal oxide as support material on the activity of gold has been proved. Additionally, size effects were investigated using carbon as support to determine only the contribution of the nanoparticle size on the catalytic activity of gold. Therefore, Au, @C with a gold core of about 7 nm was studied showing a less pronounced positive effect on the activity than the metal oxide support effect. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

First principles study of propene polymerization in Ziegler-Natta heterogeneous catalysis

Energy Technology Data Exchange (ETDEWEB)

Boero, M.; Parrinello, M.; Hueffer, S.; Weiss, H.

2000-01-26

In this work the authors address the problem of isotacticity in a realistic heterogeneous Ziegler-Natta system by means of ab initio molecular dynamics. A previously identified 5-fold catalytic center was selected and examined for its ability to select the appropriate olefin enantioface in the chain growth process. The first steps in the propene polymerization process were studied to determine the energetics of the initial complexation phase for the different stereochemical orientations of the incoming propene. Then the authors analyze the subsequent insertions which represent the crucial issue for the formation of a stereospecific polymer chain, and find that the 5-fold catalytic center possesses a huge degree of stereoselectivity. The role of the agostic interaction was examined which can switch from {alpha} to {beta} and allow, even in the presence of a substrate, process that can lead to chain termination.

3. International conference on catalysis in membrane reactors

Energy Technology Data Exchange (ETDEWEB)

NONE

1998-09-01

The 3. International Conference on Catalysis in Membrane Reactors, Copenhagen, Denmark, is a continuation of the previous conferences held in Villeurbanne 1994 and Moscow 1996 and will deal with the rapid developments taking place within membranes with emphasis on membrane catalysis. The approx. 80 contributions in form of plenary lectures and posters discuss hydrogen production, methane reforming into syngas, selectivity and specificity of various membranes etc. The conference is organised by the Danish Catalytic Society under the Danish Society for Chemical Engineering. (EG)

Biodiesel production from castor oil using heterogeneous Ni doped ZnO nanocatalyst.

Science.gov (United States)

Baskar, G; Aberna Ebenezer Selvakumari, I; Aiswarya, R

2018-02-01

In the present study, castor oil with high free fatty acid was used for biodiesel production using heterogeneous Ni doped ZnO nanocatalyst. Ni doped ZnO nanocomposite calcinated at 800 °C has shown better catalytic activity. Process parameters on heterogeneous catalysis of castor oil into biodiesel were optimized using conventional and Response Surface Methodology (RSM). RSM was found more accurate in estimating the optimum conditions with higher biodiesel yield (95.20%). The optimum conditions for transesterification was found to be oil to methanol molar ratio of 1:8, catalyst loading 11% (w/w), reaction temperature of 55 °C for 60 min of reaction time by response surface method. The reusability studies showed that the nanocatalyst can be reused efficiently for 3 cycles. Copyright © 2017 Elsevier Ltd. All rights reserved.

Particle-based modeling of heterogeneous chemical kinetics including mass transfer.

Science.gov (United States)

Sengar, A; Kuipers, J A M; van Santen, Rutger A; Padding, J T

2017-08-01

Connecting the macroscopic world of continuous fields to the microscopic world of discrete molecular events is important for understanding several phenomena occurring at physical boundaries of systems. An important example is heterogeneous catalysis, where reactions take place at active surfaces, but the effective reaction rates are determined by transport limitations in the bulk fluid and reaction limitations on the catalyst surface. In this work we study the macro-micro connection in a model heterogeneous catalytic reactor by means of stochastic rotation dynamics. The model is able to resolve the convective and diffusive interplay between participating species, while including adsorption, desorption, and reaction processes on the catalytic surface. Here we apply the simulation methodology to a simple straight microchannel with a catalytic strip. Dimensionless Damkohler numbers are used to comment on the spatial concentration profiles of reactants and products near the catalyst strip and in the bulk. We end the discussion with an outlook on more complicated geometries and increasingly complex reactions.

Particle-based modeling of heterogeneous chemical kinetics including mass transfer

Science.gov (United States)

Sengar, A.; Kuipers, J. A. M.; van Santen, Rutger A.; Padding, J. T.

2017-08-01

Connecting the macroscopic world of continuous fields to the microscopic world of discrete molecular events is important for understanding several phenomena occurring at physical boundaries of systems. An important example is heterogeneous catalysis, where reactions take place at active surfaces, but the effective reaction rates are determined by transport limitations in the bulk fluid and reaction limitations on the catalyst surface. In this work we study the macro-micro connection in a model heterogeneous catalytic reactor by means of stochastic rotation dynamics. The model is able to resolve the convective and diffusive interplay between participating species, while including adsorption, desorption, and reaction processes on the catalytic surface. Here we apply the simulation methodology to a simple straight microchannel with a catalytic strip. Dimensionless Damkohler numbers are used to comment on the spatial concentration profiles of reactants and products near the catalyst strip and in the bulk. We end the discussion with an outlook on more complicated geometries and increasingly complex reactions.

Curvature bound from gravitational catalysis

Science.gov (United States)

Gies, Holger; Martini, Riccardo

2018-04-01

We determine bounds on the curvature of local patches of spacetime from the requirement of intact long-range chiral symmetry. The bounds arise from a scale-dependent analysis of gravitational catalysis and its influence on the effective potential for the chiral order parameter, as induced by fermionic fluctuations on a curved spacetime with local hyperbolic properties. The bound is expressed in terms of the local curvature scalar measured in units of a gauge-invariant coarse-graining scale. We argue that any effective field theory of quantum gravity obeying this curvature bound is safe from chiral symmetry breaking through gravitational catalysis and thus compatible with the simultaneous existence of chiral fermions in the low-energy spectrum. With increasing number of dimensions, the curvature bound in terms of the hyperbolic scale parameter becomes stronger. Applying the curvature bound to the asymptotic safety scenario for quantum gravity in four spacetime dimensions translates into bounds on the matter content of particle physics models.

ELECTROCHEMICAL PROMOTED CATALYSIS: TOWARDS PRACTICAL UTILIZATION

Directory of Open Access Journals (Sweden)

DIMITRIOS TSIPLAKIDES

2008-07-01

Full Text Available Electrochemical promotion (EP of catalysis has already been recognized as “a valuable development in catalytic research” (J. Pritchard, 1990 and as “one of the most remarkable advances in electrochemistry since 1950” (J. O’M. Bockris, 1996. Laboratory studies have clearly elucidated the phenomenology of electrochemical promotion and have proven that EP is a general phenomenon at the interface of catalysis and electrochemistry. The major progress toward practical utilization of EP is surveyed in this paper. The focus is given on the electropromotion of industrial ammonia synthesis catalyst, the bipolar EP and the development of a novel monolithic electropromoted reactor (MEPR in conjunction with the electropromotion of thin sputtered metal films. Future perspectives of electrochemical promotion applications in the field of hydrogen technologies are discussed.

Final Technical Report

Energy Technology Data Exchange (ETDEWEB)

Spivey, James J. [Louisiana State Univ., Baton Rouge, LA (United States)

2016-02-02

The research summarized here has the goal of developing a fundamental understanding of how catalysts work. These materials are demonstrably essential to our daily life, from the cars we drive to the clothes we wear. Our Center advances the science behind how we prepare, analyze, and describe catalysts. This has been identified by one of the documents guiding Federal research objectives (Directing Matter and Energy: Five Challenges for Science and the Imagination): “Major challenges in heterogeneous catalysis are to more clearly define the nature of the active sites, to engineer at the molecular level catalysis with designed properties in three dimensions, and to create new catalysts for new transformations.” This directly addresses this objective.

Resonance – Journal of Science Education | Indian Academy of ...

Indian Academy of Sciences (India)

Home; Journals; Resonance – Journal of Science Education. K Vipin Raj. Articles written in Resonance – Journal of Science Education. Volume 22 Issue 11 November 2017 pp 1025-1037 General Article. Understanding Ziegler-Natta Catalysis Through Your Laptop · K Vipin Raj Kumar Vanka · More Details Abstract Fulltext ...

Catalysis in Molten Ionic Media

DEFF Research Database (Denmark)

Boghosian, Soghomon; Fehrmann, Rasmus

2013-01-01

This chapter deals with catalysis in molten salts and ionic liquids, which are introduced and reviewed briefly, while an in-depth review of the oxidation catalyst used for the manufacturing of sulfuric acid and cleaning of flue gas from electrical power plants is the main topic of the chapter...

Stereodirection of an α-ketoester at sub-molecular sites on chirally modified Pt(111): Heterogeneous asymmetric catalysis

DEFF Research Database (Denmark)

Demers-Carpentier, V.; Rasmussen, A.M.H.; Goubert, G.

2013-01-01

Chirally modified Pt catalysts are used in the heterogeneous asymmetric hydrogenation of α-ketoesters. Stereoinduction is believed to occur through the formation of chemisorbed modifier–substrate complexes. In this study, the formation of diastereomeric complexes by coadsorbed methyl 3,3,3-triflu......Chirally modified Pt catalysts are used in the heterogeneous asymmetric hydrogenation of α-ketoesters. Stereoinduction is believed to occur through the formation of chemisorbed modifier–substrate complexes. In this study, the formation of diastereomeric complexes by coadsorbed methyl 3...

Metal-organic frameworks and their applications in catalysis; Redes metalorganicas e suas aplicacoes em catalise

Energy Technology Data Exchange (ETDEWEB)

Ramos, Andre Luis Dantas, E-mail: aldramos@ufs.br [Universidade Federal de Sergipe (UFSE), Sao Cristovao, SE (Brazil). Departamento de Engenharia Quimica; Tanase, Stefania; Rothenberg, Gadi [Van' t Hoff Institute for Molecular Sciences, University of Amsterdam, Amsterdam (Netherlands)

2014-07-01

Metal-organic frameworks (MOFs) form a new class of materials with well-defined yet tunable properties. These are crystalline, highly porous and exhibit strong metal-ligand interactions. Importantly, their physical and chemical properties, including pore size, pore structure, acidity, and magnetic and optical characteristics, can be tailored by choosing the appropriate ligands and metal precursors. Here we review the key aspects of synthesis and characterization of MOFs, focusing on lanthanide-based and vanadium-based materials. We also outline some of their applications in catalysis and materials science. (author)

2008 Gordon Research Conference on Catalysis [Conference summary report

Energy Technology Data Exchange (ETDEWEB)

Soled, Stuart L.; Gray, Nancy Ryan

2009-01-01

The GRC on Catalysis is one of the most prestigious catalysis conferences as it brings together leading researchers from around the world to discuss their latest, most exciting work in catalysis. The 2008 conference will continue this tradition. The conference will cover a variety of themes including new catalytic materials, theoretical and experimental approaches to improve understanding of kinetics and transport phenomena, and state of the art nanoscale characterization probes to monitor active sites. The conference promotes interactions among established researchers and young scientists. It provides a venue for students to meet, talk to and learn from some of the world leading researchers in the area. It also gives them a platform for displaying their own work during the poster sessions. The informal nature of the meeting, excellent quality of the presentations and posters, and ability to meet many outstanding colleagues makes this an excellent conference.

Catalytic Science and Technology in Sustainable Energy II

DEFF Research Database (Denmark)

Wang, Yuxin; Xiao, Feng-Shou; Seshan, Kulathu K.

2017-01-01

This special issue of Catalysis Today results from four sessions, under the collective theme "Catalysis in Sustainable Energy", of the 2ndInternational Symposium on Catalytic Science and Technology in Sustainable Energy and Environment, held in Tianjin, China during October 12-14, 2016. This bien...... whom the special issue would not have been possible. As the organizer of the EECAT 2016, Y Li expresses his special gratitude to the sponsors, especially Haldor Topsoe and Synfuels China, the participants and the co-organizers for their great contribution to the success of EECAT 2016....

Mo-II Cluster Complex-Based Coordination Polymer as an Efficient Heterogeneous Catalyst in the Suzuki–Miyaura Coupling Reaction

Czech Academy of Sciences Publication Activity Database

Bůžek, Daniel; Hynek, Jan; Kučeráková, Monika; Kirakci, Kaplan; Demel, Jan; Lang, Kamil

2016-01-01

Roč. 2016, č. 28 (2016), s. 4668-4673 ISSN 1434-1948 R&D Projects: GA ČR GA13-05114S; GA ČR GA15-12653S EU Projects: European Commission(XE) CZ.2.16/3.1.00/24510 Institutional support: RVO:61388980 ; RVO:68378271 Keywords : C–C coupling * Heterogeneous catalysis * Molybdenum * Palladium * Polymers Subject RIV: CA - Inorganic Chemistry ; CF - Physical ; Theoretical Chemistry (FZU-D) Impact factor: 2.444, year: 2016

Titanium oxide modification with oxides of mixed cobalt valence for photo catalysis

International Nuclear Information System (INIS)

Alanis O, R.; Jimenez B, J.

2010-01-01

In the present work, heterogenous photo catalysis, a technique often used for organic compound degradation toxic in water, was used. The photo catalyst most often used in this technique is TiO 2 , which due to its physical and chemical properties, can degrade a great number of organic compounds. In addition, in recent years it has been verified that the doping of semiconductors with metals or metallic oxides increases the photo catalytic activity of these semiconductors, which is why it was proposed for doping by the impregnating method using commercial TiO 2 synthesized by the Degussa company (TiO 2 Degussa P25) with and oxide of mixed cobalt valence (Co 3 O 4 ) synthesized using the sol-gel method. The synthesized photo catalyst TiO 2 /Co 3 O 4 was characterized by the techniques of X-ray diffraction, scanning electronic microscopy, Raman spectroscopy and finally, photo catalytic tests by means of the degradation of methylene blue. (Author)

Progress in surface and membrane science

CERN Document Server

Cadenhead, D A; Rosenberg, M D

1975-01-01

Progress in Surface and Membrane Science, Volume 9 covers the developments in surface and membrane science. The book discusses the physical adsorption of gases and vapors in micropores; the chemisorption theory; and the role of radioisotopes in the studies of chemisorption and catalysis. The text also describes the interaction of ions with monolayers; and the isolation and characterization of mycoplasma membranes. Chemists, physical chemists, and microbiologists will find the book useful.

Asymmetric C-C Bond-Formation Reaction with Pd: How to Favor Heterogeneous or Homogeneous Catalysis?

DEFF Research Database (Denmark)

Reimann, S.; Grunwaldt, Jan-Dierk; Mallat, T.

2010-01-01

The enantioselective allylic alkylation of (E)-1,3-diphenylallyl acetate was studied to clarify the heterogeneous or homogeneous character of the Pd/Al2O3-(R)-BINAP catalyst system. A combined approach was applied: the catalytic tests were completed with in situ XANES measurements to follow...

Asymmetric Aminalization via Cation-Binding Catalysis

DEFF Research Database (Denmark)

Park, Sang Yeon; Liu, Yidong; Oh, Joong Suk

2018-01-01

Asymmetric cation-binding catalysis, in principle, can generate "chiral" anionic nucleophiles, where the counter cations are coordinated within chiral environments. Nitrogen-nucleophiles are intrinsically basic, therefore, its use as nucleophiles is often challenging and limiting the scope of the...

Universality in heterogeneous catalysis

DEFF Research Database (Denmark)

Nørskov, Jens Kehlet; Pedersen, Thomas Bligaard; Logadottir, Ashildur

2002-01-01

Based on an extensive set of density functional theory calculations it is shown that for a class of catalytic reactions there is a universal, reactant independent relation between the reaction activation energy and the stability of reaction intermediates. This leads directly to a universal relati...

Micromechanics of heterogeneous materials

CERN Document Server

Buryachenko, Valeriy

2007-01-01

Here is an accurate and timely account of micromechanics, which spans materials science, mechanical engineering, applied mathematics, technical physics, geophysics, and biology. The book features rigorous and unified theoretical methods of applied mathematics and statistical physics in the material science of microheterogeneous media. Uniquely, it offers a useful demonstration of the systematic and fundamental research of the microstructure of the wide class of heterogeneous materials of natural and synthetic nature.

Effect of catalysts on heterogeneous oxidation of coal

Energy Technology Data Exchange (ETDEWEB)

Glazkova, A P; Kazarova, Yu A; Suslov, A V

1978-01-01

Analyzes the effects of catalysts on the heterogeneous oxidation of coal in deflagration processes of stoichiometric mixtures. The following substances are studied as catalysts: alkali and alkaline-earth metals, and compounds of copper, lead, chromium, iron, and sulfur. In the first case the catalysts are used in the form of nitrates and the nitrate simultaneously plays the role of an oxidizer. In the second case the catalysts are added to stoichiometric mixtures of ammonium nitrate with carbon. It is shown that during carbon oxidation by nitrates the catalytic efficiency of the metals studied forms the following order: sodium > lead > potassium > barium > aluminium > calcium > magnesium > copper. The calculated and experimental parameters of combustion are given. The problem of dependence of combustion rate on combustion heat, the mechanism of the combustion reaction and the catalytic effects of the additives are discussed. Features of heterogeneous catalysis in the oxidation process of carbon by various oxidizers are analyzed. The investigations on the combustion process are important as the process takes place during explosion of coal dust in underground coal mines and during burning of coal in industrial furnaces. (34 refs.) (In Russian)

Tandem rhodium catalysis: exploiting sulfoxides for asymmetric transition-metal catalysis.

Science.gov (United States)

Kou, K G M; Dong, V M

2015-06-07

Sulfoxides are uncommon substrates for transition-metal catalysis due to their propensity to inhibit catalyst turnover. In a collaborative effort with Ken Houk, we developed the first dynamic kinetic resolution (DKR) of allylic sulfoxides using asymmetric rhodium-catalyzed hydrogenation. A detailed mechanistic analysis of this transformation using both experimental and theoretical methods revealed rhodium to be a tandem catalyst that promoted both hydrogenation of the alkene and racemization of the allylic sulfoxide. Using a combination of deuterium labelling and DFT studies, a novel mode of allylic sulfoxide racemization via a Rh(III)-π-allyl intermediate was identified.

"Nanocrystal bilayer for tandem catalysis"

Energy Technology Data Exchange (ETDEWEB)

Yamada, Yusuke; Tsung, Chia Kuang; Huang, Wenyu; Huo, Ziyang; E.Habas, Susan E; Soejima, Tetsuro; Aliaga, Cesar E; Samorjai, Gabor A; Yang, Peidong

2011-01-24

Supported catalysts are widely used in industry and can be optimized by tuning the composition and interface of the metal nanoparticles and oxide supports. Rational design of metal-metal oxide interfaces in nanostructured catalysts is critical to achieve better reaction activities and selectivities. We introduce here a new class of nanocrystal tandem catalysts that have multiple metal-metal oxide interfaces for the catalysis of sequential reactions. We utilized a nanocrystal bilayer structure formed by assembling platinum and cerium oxide nanocube monolayers of less than 10 nm on a silica substrate. The two distinct metal-metal oxide interfaces, CeO2-Pt and Pt-SiO2, can be used to catalyse two distinct sequential reactions. The CeO2-Pt interface catalysed methanol decomposition to produce CO and H2, which were subsequently used for ethylene hydroformylation catalysed by the nearby Pt-SiO2 interface. Consequently, propanal was produced selectively from methanol and ethylene on the nanocrystal bilayer tandem catalyst. This new concept of nanocrystal tandem catalysis represents a powerful approach towards designing high-performance, multifunctional nanostructured catalysts

Transition metal catalysis in confined spaces

NARCIS (Netherlands)

Leenders, S.H.A.M.

2016-01-01

Chemical reactions are required for the conversion of feedstocks to valuable materials, such as different types of plastics, pharmaceutical ingredients and advanced materials. In order to facilitate the conversion of these feedstocks to a wide array of products, catalysis plays a prominent role.

Enzyme-Like Catalysis of the Nazarov Cyclization by Supramolecular Encapsulation

Energy Technology Data Exchange (ETDEWEB)

Hastings, Courtney; Pluth, Michael; Bergman, Robert; Raymond, Kenneth

2010-03-29

A primary goal in the design and synthesis of molecular hosts has been the selective recognition and binding of a variety of guests using non-covalent interactions. Supramolecular catalysis, which is the application of such hosts towards catalysis, has much in common with many enzymatic reactions, chiefly the use of both spatially appropriate binding pockets and precisely oriented functional groups to recognize and activate specific substrate molecules. Although there are now many examples which demonstrate how selective encapsulation in a host cavity can enhance the reactivity of a bound guest, all have failed to reach the degree of increased reactivity typical of enzymes. We now report the catalysis of the Nazarov cyclization by a self-assembled coordination cage, a carbon-carbon bond-forming reaction which proceeds under mild, aqueous conditions. The acceleration in this system is over a million-fold, and represents the first example of supramolecular catalysis that achieves the level of rate enhancement comparable to that observed in several enzymes. We explain the unprecedented degree of rate increase as due to the combination of (a) preorganization of the encapsulated substrate molecule, (b) stabilization of the transition state of the cyclization by constrictive binding, and (c) increase in the basicity of the complexed alcohol functionality.

Cluster size matters: Size-driven performance of subnanometer clusters in catalysis, electrocatalysis and Li-air batteries

Science.gov (United States)

Vajda, Stefan

2015-03-01

This paper discusses the strongly size-dependent performance of subnanometer cluster based catalysts in 1) heterogeneous catalysis, 2) electrocatalysis and 3) Li-air batteries. The experimental studies are based on I. fabrication of ultrasmall clusters with atomic precision control of particle size and their deposition on oxide and carbon based supports; II. test of performance, III. in situand ex situ X-ray characterization of cluster size, shape and oxidation state; and IV.electron microscopies. Heterogeneous catalysis. The pronounced effect of cluster size and support on the performance of the catalyst (catalyst activity and the yield of Cn products) will be illustrated on the example of nickel and cobalt clusters in Fischer-Tropsch reaction. Electrocatalysis. The study of the oxygen evolution reaction (OER) on size-selected palladium clusters supported on ultrananocrystalline diamond show pronounced size effects. While Pd4 clusters show no reaction, Pd6 and Pd17 clusters are among the most active catalysts known (in in terms of turnover rate per Pd atom). The system (soft-landed Pd4, Pd6, or Pd17 clusters on an UNCD Si coated electrode) shows stable electrochemical potentials over several cycles, and the characterization of the electrodes show no evidence for evolution or dissolution of either the support Theoretical calculations suggest that this striking difference may be a demonstration that bridging Pd-Pd sites, which are only present in three-dimensional clusters, are active for the oxygen evolution reaction in Pd6O6. Li-air batteries. The studies show that sub-nm silver clusters have dramatic size-dependent effect on the lowering of the overpotential, charge capacity, morphology of the discharge products, as well as on the morphology of the nm size building blocks of the discharge products. The results suggest that by precise control of the active surface sites on the cathode, the performance of Li-air cells can be significantly improved

Catalysis by metallic nanoparticles in solution: Thermosensitive microgels as nanoreactors

OpenAIRE

Roa, Rafael; Angioletti-Uberti, Stefano; Lu, Yan; Dzubiella, Joachim; Piazza, Francesco; Ballauff, Matthias

2018-01-01

Metallic nanoparticles have been used as catalysts for various reactions, and the huge literature on the subject is hard to overlook. In many applications, the nanoparticles must be affixed to a colloidal carrier for easy handling during catalysis. These "passive carriers" (e.g., dendrimers) serve for a controlled synthesis of the nanoparticles and prevent coagulation during catalysis. Recently, hybrids from nanoparticles and polymers have been developed that allow us to change the catalytic ...

Dynamic heterogeneity: a framework to promote ecological integration and hypothesis generation in urban systems

Science.gov (United States)

S. T. A. Pickett; M. L. Cadenasso; E. J. Rosi-Marshall; Ken Belt; P. M. Groffman; Morgan Grove; E. G. Irwin; S. S. Kaushal; S. L. LaDeau; C. H. Nilon; C. M. Swan; P. S. Warren

2016-01-01

Urban areas are understood to be extraordinarily spatially heterogeneous. Spatial heterogeneity, and its causes, consequences, and changes, are central to ecological science. The social sciences and urban design and planning professions also include spatial heterogeneity as a key concern. However, urban ecology, as a pursuit that integrates across these disciplines,...

Supported ionic liquid-phase (SILP) catalysis

DEFF Research Database (Denmark)

Riisager, Anders; Fehrmann, Rasmus; Wasserscheid, P.

2005-01-01

The concept of supported ionic liquid-phase (SILP) catalysis has been demonstrated for gas- and liquid-phase continuous fixed-bed reactions using rhodium phosphine catalyzed hydroformylation of propene and 1-octene as examples. The nature of the support had important influence on both the catalytic...

Final Technical Report for DOE Grant DE-FG02-03ER15473 ''Molecular Level Design of Heterogeneous Chiral Catalysis''

International Nuclear Information System (INIS)

David Sholl; Andrew Gellman

2007-01-01

The production of enantiomerically pure chiral compounds is of great importance in the pharmaceutical industry. Although processes involving chiral catalysis and separations involving solid surfaces are known, the molecular-scale details of these processes are not well understood. This lack of understanding strongly limits the development of new chiral processes. Our collaborative research effort examines several intertwined aspects of chirality and enantioselectivity at catalytically active metal surfaces. At Carnegie Mellon, our efforts focus on the development of chirally imprinted metal powders as materials for chiral columns and the experimental and theoretical study of small chiral molecules adsorbed on well-characterized metal surfaces, both achiral and chiral. These efforts are being performed in close collaboration with our team members at the University of California Riverside and the University of Wisconsin Milwaukee

Micro-reactor for heterogeneous catalysis. Application: hydrogen production from methyl-cyclohexane; Microreacteur pour la catalyse heterogene. Application: production d'hydrogene a partir du methylcyclohexane

Energy Technology Data Exchange (ETDEWEB)

Roumanie, M.; Pijolat, C. [Ecole des Mines de Saint Etienne, Centre SPIN (DMICC/LPMG/URA/CNRS-D2021), 42 - Saint Etienne (France); Meille, V.; Bellefon, C. de [Centre National de la Recherche Scientifique (CNRS/CPE), Lab. de Genie des Procedes Catalytiques, 69 - Villeurbanne (France); Pouteau, P.; Delattre, C. [CEA Grenoble, Lab. d' Electronique et de Technologie de l' Informatique (LETI), 38 (France)

2004-07-01

First developed by the pharmaceutical industry to find new drugs (combinatorial analysis), the lab on chip is also extremely interesting for the catalysis field. This major interest comes from the miniaturize size and the high surface on volume ratio which lead to improve mass and heat transfer but also the safety in regards of industrial application. The use of micro-technology and the miniaturization of various systems such as micro-fuel cell is also a current field of activity. So for the future research the production of hydrogen is a point to develop in order to supply a micro-fuel cell. The aim of this work is to study and to realize an autonomous catalytic micro-reactor for hydrogen production from methyl-cyclohexane. For this reaction of dehydrogenation, the common catalyst is platinum supported on alumina. Consequently, the general objectives of this work are: 1)to develop a micro-reactor with its heaters, sensors...2)to deposit catalysts in the micro-reactor 3)to study the catalytic conversion of this system.

The ultrasound-assisted oxidative scission of monoenic fatty acids by ruthenium tetroxide catalysis: influence of the mixture of solvents.

Science.gov (United States)

Rup, Sandrine; Zimmermann, François; Meux, Eric; Schneider, Michel; Sindt, Michele; Oget, Nicolas

2009-02-01

Carboxylic acids and diacids were synthesized from monoenic fatty acids by using RuO4 catalysis, under ultrasonic irradiation, in various mixtures of solvents. Ultrasound associated with Aliquat 336 have promoted in water, the quantitative oxidative cleavage of the CH=CH bond of oleic acid. A design of experiment (DOE) shows that the optimal mixture of solvents (H2O/MeCN, ratio 1/1, 2.2% RuCl3/4.1 eq. NaIO4) gives 81% azelaic acid and 97% pelargonic acid. With the binary heterogeneous mixture H2O/AcOEt, the oxidation of the oleic acid leads to a third product, the alpha-dione 9,10-dioxostearic acid.

Heterogeneous photo-Fenton oxidation with natural clays for phenol and tyrosol remediation

Directory of Open Access Journals (Sweden)

Djeffal L.

2013-09-01

Full Text Available Due to their excellent properties, clays have been widely used in several applications, particularly in catalysis. In this paper, three clays were used as heterogeneous photo-Fenton catalysts for phenol and tyrosol oxidations. Particular attention was given to the effect of the main operating conditions on the process performance. A total conversion was obtained for both organic pollutants with studied catalysts in 20 minutes reaction. For phenol, a total organic carbon (TOC conversion of 93% was obtained using sieved and calcined smectite clay. The TOC conversion was 60% for tyrosol with the same catalyst. Clays were characterized by chemical analysis, BET, XRD, TPR and SEM.

Understanding plasma catalysis through modelling and simulation—a review

International Nuclear Information System (INIS)

Neyts, E C; Bogaerts, A

2014-01-01

Plasma catalysis holds great promise for environmental applications, provided that the process viability can be maximized in terms of energy efficiency and product selectivity. This requires a fundamental understanding of the various processes taking place and especially the mutual interactions between plasma and catalyst. In this review, we therefore first examine the various effects of the plasma on the catalyst and of the catalyst on the plasma that have been described in the literature. Most of these studies are purely experimental. The urgently needed fundamental understanding of the mechanisms underpinning plasma catalysis, however, may also be obtained through modelling and simulation. Therefore, we also provide here an overview of the modelling efforts that have been developed already, on both the atomistic and the macroscale, and we identify the data that can be obtained with these models to illustrate how modelling and simulation may contribute to this field. Last but not least, we also identify future modelling opportunities to obtain a more complete understanding of the various underlying plasma catalytic effects, which is needed to provide a comprehensive picture of plasma catalysis. (paper)

Stitching together the heterogeneous party: A complementary social data science experiment

Directory of Open Access Journals (Sweden)

Anders Blok

2017-11-01

Full Text Available The era of ‘big data’ studies and computational social science has recently given rise to a number of realignments within and beyond the social sciences, where otherwise distinct data formats – digital, numerical, ethnographic, visual, etc. – rub off and emerge from one another in new ways. This article chronicles the collaboration between a team of anthropologists and sociologists, who worked together for one week in an experimental attempt to combine ‘big’ transactional and ‘small’ ethnographic data formats. Our collaboration is part of a larger cross-disciplinary project carried out at the Danish Technical University (DTU, where high-resolution transactional data from smartphones allows for recordings of social networks amongst a freshman class (N = 800. With a parallel deployment of ethnographic fieldwork among the DTU students, this research set-up raises a number of questions concerning how to assemble disparate ‘data-worlds’ and to what epistemological and political effects? To address these questions, a specific social event – a lively student party – was singled out from the broader DTU dataset. Our experimental collaboration used recordings of Bluetooth signals between students’ phones to visualize the ebb and flow of social intensities at the DTU party, juxtaposing these with ethnographic field-notes on shifting party atmospheres. Tracing and reflecting on the process of combining heterogeneous data, the article offers a concrete case of how a ‘stitching together’ of digital and ethnographic data-worlds might take place.

Relation between Hydrogen Evolution and Hydrodesulfurization Catalysis

DEFF Research Database (Denmark)

Šaric, Manuel; Moses, Poul Georg; Rossmeisl, Jan

2016-01-01

A relation between hydrogen evolution and hydrodesulfurization catalysis was found by density functional theory calculations. The hydrogen evolution reaction and the hydrogenation reaction in hydrodesulfurization share hydrogen as a surface intermediate and, thus, have a common elementary step...

Supported phosphate and carbonate salts for heterogeneous catalysis of triglycerides to fatty acid methyl esters

Science.gov (United States)

Britton, Stephanie Lynne

Fatty acid methyl esters made from vegetable oil, or biodiesel, have been identified as a substitute for diesel derived from crude oil. Biodiesel is currently made using a homogeneous base catalyst to perform the transesterification of triglycerides with methanol to generate fatty acid methyl esters (FAME). The use of a homogeneous catalyst necessitates additional purification of the product and byproducts before sale, and the catalyst is consumed and discarded. The development of a heterogeneous basic catalyst for the production of FAME is desirable. Tribasic phosphate salts and dibasic carbonate salts are active for the production of FAME but generally operate as homogeneous catalysts. Supporting these phosphate and carbonate salts on mesoporous MCM-41, microporous silica gel, and nonporous a-alumina proved successful to greater or lesser degrees depending on the identity of the support and pretreatment of the support. Although these salts were supported and were active for the production of FAME from canola oil, they proved to be operating as homogeneous catalysts due to leaching of the active species off the surface of the support. Further investigation of the active species present in the tribasic phosphate catalysts identified the active support as orthophosphate, and NMR studies revealed the phosphorus to be present as orthophosphate and diphosphate in varying proportions in each catalyst. Evaluation of the acid-washing support pretreatment process revealed that the exposure of the support to acid plays a large role in the development of activity on the surface of the catalyst, but manipulation of these parameters did not prevent leaching of the active site off the surface of the catalyst. Alternate methods of support pretreatment were no more effective in preventing leaching. Tribasic phosphate supported on silica gel is not effective as a heterogeneous catalyst for FAME production from triglycerides because of the lack of stability of the phosphate on the

Sustainable Catalysis_Energy efficient reactions and Applications

Science.gov (United States)

This book chapter discusses various catalysts for environmental remediation. Detailed information on catalysis using ferrate and ferrite oxidation, TiO2 photocatalysis, and new catalysts (i.e., graphene, perovskites and graphitic carbon nitride) is provided for the degradation of...

Utilisation of CO2, fixation of nitrogen and exhaust gas cleaning in electric discharge with electrode catalysis

International Nuclear Information System (INIS)

Marcela, M.; Imrich, M.; Mario, J.

2001-01-01

The method reported here provides a contribution to CO 2 utilisation, nitrogen fixation and combustion exhaust cleaning using synergetic effect of electric discharge with heterogeneous catalysis on electrodes. The efficiency of CO 2 removal is about 40-65%. The process of CO 2 removal is always accompanied by NO x , VOC, SX and other component removal and is connected with O 2 formation. The final product of process is powder with fractal microstructure, low specific weight, water insoluble suitable for use as nitrogen containing fertilizer. The main component (95%) of solid product is amorphous condensate of amino acids with about 5% of metal organic compound with catalytic properties. The condensate has character of statistical proteinoid. Its creation seems to play important role during formation of life in pre-biotic Earth

On the origin of the cobalt particle size effects in Fischer−Tropsch catalysis

NARCIS (Netherlands)

den Breejen, J.P.|info:eu-repo/dai/nl/304837318; Radstake, P.B.|info:eu-repo/dai/nl/304829587; Bezemer, G.L.; Bitter, J.H.|info:eu-repo/dai/nl/160581435; Froseth, V.; Holmen, A.; de Jong, K.P.|info:eu-repo/dai/nl/06885580X

2009-01-01

The effects of metal particle size in catalysis are of prime scientific and industrial importance and call for a better understanding. In this paper the origin of the cobalt particle size effects in Fischer−Tropsch (FT) catalysis was studied. Steady-State Isotopic Transient Kinetic Analysis (SSITKA)

Titanium oxide modification with oxides of mixed cobalt valence for photo catalysis

Energy Technology Data Exchange (ETDEWEB)

Alanis O, R.; Jimenez B, J., E-mail: jaime.jimenez@inin.gob.m [ININ, Departamento de Quimica, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico)

2010-07-01

In the present work, heterogenous photo catalysis, a technique often used for organic compound degradation toxic in water, was used. The photo catalyst most often used in this technique is TiO{sub 2}, which due to its physical and chemical properties, can degrade a great number of organic compounds. In addition, in recent years it has been verified that the doping of semiconductors with metals or metallic oxides increases the photo catalytic activity of these semiconductors, which is why it was proposed for doping by the impregnating method using commercial TiO{sub 2} synthesized by the Degussa company (TiO{sub 2} Degussa P25) with and oxide of mixed cobalt valence (Co{sub 3}O{sub 4}) synthesized using the sol-gel method. The synthesized photo catalyst TiO{sub 2}/Co{sub 3}O{sub 4} was characterized by the techniques of X-ray diffraction, scanning electronic microscopy, Raman spectroscopy and finally, photo catalytic tests by means of the degradation of methylene blue. (Author)

Kokes Awards for the 25th North American Catalysis Society Meeting

Energy Technology Data Exchange (ETDEWEB)

Pylypenko, Svitlana [Colorado School of Mines, Golden, CO (United States). Chemistry Dept. and Materials Science Program

2018-03-13

The biennial North American Catalysis Society (NACS) meeting is the premiere conferences in the area of catalysis, surface science, and reaction engineering. The 25th installment of this meeting will be held the week of June 4-9, 2017 in Denver, CO at the Hyatt Regency Hotel. Meeting objectives include bringing together leading researchers for intensive scientific exchange, providing students with an opportunity to present their work and interact with leaders in the field, and participate in service to scientific/technical community. Financial support to offset a portion of the associated costs – and specifically, registration fees, airline tickets, and hotel accommodations – encourages greater participation by graduate and undergraduate students, and often provides them the only opportunity to attend and meaningfully contribute to the conference. The funds sought in this proposal will be in support of the Richard J. Kokes Travel Award program. The eligibility criteria for undergraduates and graduate students applying for a merit-based Awards are that they must study at a university within the United States and present either a poster or presentation at the meeting. In the previous meeting in Pittsburgh, NACS received 200 applications and funded 110 students. Similarly, during the meeting in Louisville, NACS received 225 applications and funded nearly half of them. The NACS has an on-going tradition of encouraging graduate students (and more recently, undergraduates as well) to participate in and serve at the national meetings Providing financial support is one of the most effective means of accomplishing this goal. Their attendance significantly broadens their scientific training beyond what can be accomplished in the classroom, and offers them an opportunity to improve their communication and presentation skills. As an attendee to the 25th NAM, students will participate by listening to presentations from leading researchers from the U.S. and abroad, and they

Metallic nanosystems in catalysis

International Nuclear Information System (INIS)

Bukhtiyarov, Valerii I; Slin'ko, Mikhail G

2001-01-01

The reactivities of metallic nanosystems in catalytic processes are considered. The activities of nanoparticles in catalysis are due to their unique microstructures, electronic properties and high specific surfaces of the active centres. The problems of increasing the selectivities of catalytic processes are discussed using several nanosystems as examples. The mutual effects of components of bimetallic nanoparticles are discussed. The prospects for theoretical and experimental investigations into catalytic nanosystems and the construction of industrial catalysts based on them are evaluated. The bibliography includes 207 references.

DNA-based asymmetric organometallic catalysis in water

NARCIS (Netherlands)

Oelerich, Jens; Roelfes, Gerard

2013-01-01

Here, the first examples of DNA-based organometallic catalysis in water that give rise to high enantioselectivities are described. Copper complexes of strongly intercalating ligands were found to enable the asymmetric intramolecular cyclopropanation of alpha-diazo-beta-keto sulfones in water. Up to

The Development of Visible-Light Photoredox Catalysis in Flow.

Science.gov (United States)

Garlets, Zachary J; Nguyen, John D; Stephenson, Corey R J

2014-04-01

Visible-light photoredox catalysis has recently emerged as a viable alternative for radical reactions otherwise carried out with tin and boron reagents. It has been recognized that by merging photoredox catalysis with flow chemistry, slow reaction times, lower yields, and safety concerns may be obviated. While flow reactors have been successfully applied to reactions carried out with UV light, only recent developments have demonstrated the same potential of flow reactors for the improvement of visible-light-mediated reactions. This review examines the initial and continuing development of visible-light-mediated photoredox flow chemistry by exemplifying the benefits of flow chemistry compared with conventional batch techniques.

KCC1: First Nanoparticle developed by KAUST Catalysis Center

KAUST Repository

Basset, Jean-Marie

2010-08-01

KCC1 is the first Nanoparticle developed by KAUST Catalysis Center. Director of KAUST Catalysis Center, Dr. Jean-Marie Basset, Senior Research Scientist at KCC, Dr. Vivek Polshettiwar, and Dr. Dongkyu Cha of the Advanced Nanofabrication Imaging & Characterization Core Laboratory discuss the details of this recent discovery. This video was produced by KAUST Visualization Laboratory and KAUST Technology Transfer and Innovation - Terence McElwee, Director, Technology Transfer and Innovation - IP@kaust.edu.sa This technology is part of KAUST\\'s technology commercialization program that seeks to stimulate development and commercial use of KAUST-developed technologies. For more information email us at ip@kaust.edu.sa.

Symmetry and asymmetry in mandelate racemase catalysis

International Nuclear Information System (INIS)

Whitman, C.P.; Hegeman, G.D.; Cleland, W.W.; Kenyon, G.L.

1985-01-01

Kinetic properties of mandelate racemase catalysis (Vmax, Km, deuterium isotope effects, and pH profiles) were all measured in both directions by the circular dichroic assay of Sharp. These results, along with those of studying interactions of mandelate racemase with resolved, enantiomeric competitive inhibitors [(R)- and (S)-alpha-phenylglycerates], indicate a high degree of symmetry in both binding and catalysis. Racemization of either enantiomer of mandelate in D 2 O did not show an overshoot region of molecular ellipticity in circular dichroic measurements upon approach to equilibrium. Both the absence of such an overshoot region and the high degree of kinetic symmetry are consistent with a one-base acceptor mechanism for mandelate racemase. On the other hand, results of irreversible inhibition with partially resolved, enantiomeric affinity labels [(R)- and (S)-alpha-phenylglycidates] reveal a ''functional asymmetry'' at the active site. Mechanistic proposals, consistent with these results, are presented

Metal Catalysts for Heterogeneous Catalysis: From Single Atoms to Nanoclusters and Nanoparticles.

Science.gov (United States)

Liu, Lichen; Corma, Avelino

2018-05-23

Metal species with different size (single atoms, nanoclusters, and nanoparticles) show different catalytic behavior for various heterogeneous catalytic reactions. It has been shown in the literature that many factors including the particle size, shape, chemical composition, metal-support interaction, and metal-reactant/solvent interaction can have significant influences on the catalytic properties of metal catalysts. The recent developments of well-controlled synthesis methodologies and advanced characterization tools allow one to correlate the relationships at the molecular level. In this Review, the electronic and geometric structures of single atoms, nanoclusters, and nanoparticles will be discussed. Furthermore, we will summarize the catalytic applications of single atoms, nanoclusters, and nanoparticles for different types of reactions, including CO oxidation, selective oxidation, selective hydrogenation, organic reactions, electrocatalytic, and photocatalytic reactions. We will compare the results obtained from different systems and try to give a picture on how different types of metal species work in different reactions and give perspectives on the future directions toward better understanding of the catalytic behavior of different metal entities (single atoms, nanoclusters, and nanoparticles) in a unifying manner.

Shock wave science and technology reference library. Vol. 4. Heterogeneous detonation

Energy Technology Data Exchange (ETDEWEB)

Zhang, Fan (ed.) [Defence Research and Development Canada, Suffield, AB (Canada)

2009-07-01

This book, as a volume of the Shock Wave Science and Technology Reference Library, is primarily concerned with detonation waves or compression shock waves in reactive heterogeneous media, including mixtures of solid, liquid and gas phases. The topics involve a variety of energy release and control processes in such media - a contemporary research field that has found wide applications in propulsion and power, hazard prevention as well as military engineering. The six extensive chapters contained in this volume are: - Spray Detonation (SB Murray and PA Thibault) - Detonation of Gas-Particle Flow (F Zhang) - Slurry Detonation (DL Frost and F Zhang) - Detonation of Metalized Composite Explosives (MF Gogulya and MA Brazhnikov) - Shock-Induced Solid-Solid Reactions and Detonations (YA Gordopolov, SS Batsanov, and VS Trofimov) - Shock Ignition of Particles (SM Frolov and AV Fedorov). Each chapter is self-contained and can be read independently of the others, though, they are thematically interrelated. They offer a timely reference, for graduate students as well as professional scientists and engineers, by laying out the foundations and discussing the latest developments including yet unresolved challenging problems. (orig.)

Individual heterogeneity generating explosive system network dynamics.

Science.gov (United States)

Manrique, Pedro D; Johnson, Neil F

2018-03-01

Individual heterogeneity is a key characteristic of many real-world systems, from organisms to humans. However, its role in determining the system's collective dynamics is not well understood. Here we study how individual heterogeneity impacts the system network dynamics by comparing linking mechanisms that favor similar or dissimilar individuals. We find that this heterogeneity-based evolution drives an unconventional form of explosive network behavior, and it dictates how a polarized population moves toward consensus. Our model shows good agreement with data from both biological and social science domains. We conclude that individual heterogeneity likely plays a key role in the collective development of real-world networks and communities, and it cannot be ignored.

Individual heterogeneity generating explosive system network dynamics

Science.gov (United States)

Manrique, Pedro D.; Johnson, Neil F.

2018-03-01

Individual heterogeneity is a key characteristic of many real-world systems, from organisms to humans. However, its role in determining the system's collective dynamics is not well understood. Here we study how individual heterogeneity impacts the system network dynamics by comparing linking mechanisms that favor similar or dissimilar individuals. We find that this heterogeneity-based evolution drives an unconventional form of explosive network behavior, and it dictates how a polarized population moves toward consensus. Our model shows good agreement with data from both biological and social science domains. We conclude that individual heterogeneity likely plays a key role in the collective development of real-world networks and communities, and it cannot be ignored.

CAT-ACT—A new highly versatile x-ray spectroscopy beamline for catalysis and radionuclide science at the KIT synchrotron light facility ANKA

Science.gov (United States)

Zimina, A.; Dardenne, K.; Denecke, M. A.; Doronkin, D. E.; Huttel, E.; Lichtenberg, H.; Mangold, S.; Pruessmann, T.; Rothe, J.; Spangenberg, Th.; Steininger, R.; Vitova, T.; Geckeis, H.; Grunwaldt, J.-D.

2017-11-01

CAT-ACT—the hard X-ray beamline for CATalysis and ACTinide/radionuclide research at the KIT synchrotron radiation facility ANKA—is dedicated to X-ray spectroscopy, including "flux hungry" photon-in/photon-out and correlative techniques and combines state-of-the-art optics with a unique infrastructure for radionuclide and catalysis research. Measurements can be performed at photon energies varying between 3.4 keV and 55 keV, thus encompassing the actinide M- and L-edge or potassium K-edge up to the K-edges of the lanthanide series such as cerium. Well-established X-ray absorption fine structure spectroscopy in transmission and fluorescence detection modes is available in combination with high energy-resolution X-ray emission spectroscopy or X-ray diffraction techniques. The modular beamline design with two alternately operated in-line experimental stations enables sufficient flexibility to adapt sample environments and detection systems to many scientific challenges. The ACT experimental station focuses on various aspects of nuclear waste disposal within the mission of the Helmholtz association to contribute to the solution of one of the greatest scientific and social challenges of our time—the safe disposal of heat producing, highly radioactive waste forms from nuclear energy production. It augments present capabilities at the INE-Beamline by increasing the flux and extending the energy range into the hard X-ray regime. The CAT experimental station focuses on catalytic materials, e.g., for energy-related and exhaust gas catalysis. Characterization of catalytically active materials under realistic reaction conditions and the development of in situ and operando cells for sample environments close to industrial reactors are essential aspects at CAT.

Molecular Active Sites in Heterogeneous Ir-La/C-Catalyzed Carbonylation of Methanol to Acetates.

Science.gov (United States)

Kwak, Ja Hun; Dagle, Robert; Tustin, Gerald C; Zoeller, Joseph R; Allard, Lawrence F; Wang, Yong

2014-02-06

We report that when Ir and La halides are deposited on carbon, exposure to CO spontaneously generates a discrete molecular heterobimetallic structure, containing an Ir-La covalent bond that acts as a highly active, selective, and stable heterogeneous catalyst for the carbonylation of methanol to produce acetic acid. This catalyst exhibits a very high productivity of ∼1.5 mol acetyl/mol Ir·s with >99% selectivity to acetyl (acetic acid and methyl acetate) without detectable loss in activity or selectivity for more than 1 month of continuous operation. The enhanced activity can be mechanistically rationalized by the presence of La within the ligand sphere of the discrete molecular Ir-La heterobimetallic structure, which acts as a Lewis acid to accelerate the normally rate-limiting CO insertion in Ir-catalyzed carbonylation. Similar approaches may provide opportunities for attaining molecular (single site) behavior similar to homogeneous catalysis on heterogeneous surfaces for other industrial applications.

Genetic Manipulation of Outer Membrane Permeability: Generating Porous Heterogeneous Catalyst Analogs in Escherichia coli

Energy Technology Data Exchange (ETDEWEB)

Patel, TN; Park, AHA; Bantat, S

2014-12-01

The limited permeability of the E. coli outer membrane can significantly hinder whole-cell biocatalyst performance. In this study, the SARS coronavirus small envelope protein (SCVE) was expressed in E. coli cells previously engineered for periplasmic expression of carbonic anhydrase (CA) activity. This maneuver increased small molecule uptake by the cells, resulting in increased apparent CA activity of the biocatalysts. The enhancements in activity were quantified using methods developed for traditional heterogeneous catalysis. The expression of the SCVE protein was found to significantly reduce the Thiele moduli (phi), as well as increase the effectiveness factors (eta), effective diffusivities (D-e), and permeabilities (P) of the biocatalysts. These catalytic improvements translated into superior performance of the biocatalysts for the precipitation of calcium carbonate from solution which is an attractive strategy for long-term sequestration of captured carbon dioxide. Overall, these results demonstrate that synthetic biology approaches can be used to enhance heterogeneous catalysts incorporated into microbial whole-cell scaffolds.

Environmental catalysis

Energy Technology Data Exchange (ETDEWEB)

Janssen, F.J.J.G.; Santen, R.A. van (eds.)

1999-04-01

Catalysts play key roles in the production of clean fuels, the conversion of waste and green raw materials into energy, clean combustion engines including control of NOx and soot production and reduction of greenhouse gases, production of clean water and polymers, as well as reduction from polymers to monometers. This book contains 15 chapters by experts in the field, on the theme of catalysts used to create a sustainable society. Chapters include: catalysts for renewable energy and chemicals, fuel cells, catalytic processes for high-quality transportation fuels; oxidative coupling of methane, methane utilisation via synthesis gas generation, catalytic combustion, catalytical removal of nitrate from water, contribution of catalysis towards the reduction of atmospheric air pollution (CO{sub 2}, CFCs, N{sub 2}O), ozone), emission control from mobile sources and from stationary sources, and deactivation, regeneration and recycling of hydroprocessing catalysts.

A Catálise no Brasil nos últimos 25 anos: uma história de sucesso

Directory of Open Access Journals (Sweden)

Dupont Jairton

2002-01-01

Full Text Available In the last 25 years the research in catalysis has passed from heterogeneous processes mainly applied to petrochemical industries to homogeneous processes applied to fine chemicals and green chemistry. In this context the Brazilian Chemical Society (SBQ is playing an important role in the organization of this interdisciplinary area involving researches from different fields of physical sciences.

Simple preparation of tungsten supported carbon nanoreactors for specific applications: Adsorption, catalysis and electrochemical activity

Energy Technology Data Exchange (ETDEWEB)

Mayani, Vishal J.; Mayani, Suranjana V.; Kim, Sang Wook, E-mail: swkim@dongguk.ac.kr

2015-08-01

Graphical abstract: - Highlights: • Tungsten carbon composites have shown great recognition in catalysis and electrochemistry. • W-carbon composites are prepared by template replication and W-doping on carbon cage. • Nanocomposites offer enormous assurance as adsorbent, electrode and heterogeneous catalyst. - Abstract: Porous carbon supported tungsten carbide nanoreactors, two sizes (∼25 and 170 nm), were designed using economical petroleum pitch residue followed by tungsten (W) doping. X-ray diffractions showed both carbon tungsten composites (CTC-25 and CTC-170) contained tungsten subcarbide (W{sub 2}C) and monocarbide (WC) as the major and minor crystalline phases, respectively. The present study provides a multiple perspective of carbon tungsten composites (CTCs) for methanol oxidation (as an electrode), adsorption (as an adsorbent) and degradation (as a solid catalyst) of methylene blue (MB). The operational electrodes were designed from both CTCs and used as a catalyst in an electrocatalysis process. The electrocatalysts exhibited high and stable catalytic performance (CTCE-25 > CTCE-170) in methanol electro-oxidation. The newly synthesized W-doped carbon nanoreactors were used successfully as an adsorbent for MB and a heterogeneous catalyst for MB oxidation. Ordered CTC-25 and CTC-170 exhibited dynamic MB adsorption within 15 min and complete oxidation of MB in 25–40 min. A synergetic effect between tungsten carbide and the carbon cage framework was noted.

Highly Dispersed Pseudo-Homogeneous and Heterogeneous Catalysts Synthesized via Inverse Micelle Solutions for the Liquefaction of Coal

Energy Technology Data Exchange (ETDEWEB)

Hampden-Smith, M.; Kawola, J.S.; Martino, A.; Sault, A.G.; Yamanaka, S.A.

1999-01-05

The mission of this project was to use inverse micelle solutions to synthesize nanometer sized metal particles and test the particles as catalysts in the liquefaction of coal and other related reactions. The initial focus of the project was the synthesis of iron based materials in pseudo-homogeneous form. The frost three chapters discuss the synthesis, characterization, and catalyst testing in coal liquefaction and model coal liquefaction reactions of iron based pseudo-homogeneous materials. Later, we became interested in highly dispersed catalysts for coprocessing of coal and plastic waste. Bifunctional catalysts . to hydrogenate the coal and depolymerize the plastic waste are ideal. We began studying, based on our previously devised synthesis strategies, the synthesis of heterogeneous catalysts with a bifunctional nature. In chapter 4, we discuss the fundamental principles in heterogeneous catalysis synthesis with inverse micelle solutions. In chapter 5, we extend the synthesis of chapter 4 to practical systems and use the materials in catalyst testing. Finally in chapter 6, we return to iron and coal liquefaction now studied with the heterogeneous catalysts.

Morphology-controlled synthesis of silver nanostructures via a seed catalysis process

Science.gov (United States)

Chen, Chang; Wang, Li; Yu, Haojie; Wang, Jianjun; Zhou, Junfeng; Tan, Qiaohua; Deng, Libo

2007-03-01

A novel, effective strategy named 'seed catalysis' has been described here to synthesize silver nanostructures with controllable morphology. Typically, we added Na2S into the reaction system and the Ag2S semiconductor colloids formed at the initial stage would act as both seeds and catalyst in the silver reduction. The morphology of products is controlled by the concentration of Na2S added to the system. Low concentration of Na2S gives nanocubes of 40-50 nm in size, while a high concentration of Na2S is of benefit to obtain nanowires. The growth of the silver crystal is also accelerated by the catalysis of Ag2S. Electron microscopy and UV-vis absorption spectra have been used to investigate the evolution of silver nanowires, and a reasonable mechanism to explain the role of Ag2S seeds has also been suggested. This semiconductor seed catalysis strategy will provide wide applications in the fabrication of metal nanomaterials.

Morphology-controlled synthesis of silver nanostructures via a seed catalysis process

International Nuclear Information System (INIS)

Chen Chang; Wang Li; Yu Haojie; Wang Jianjun; Zhou Junfeng; Tan Qiaohua; Deng Libo

2007-01-01

A novel, effective strategy named 'seed catalysis' has been described here to synthesize silver nanostructures with controllable morphology. Typically, we added Na 2 S into the reaction system and the Ag 2 S semiconductor colloids formed at the initial stage would act as both seeds and catalyst in the silver reduction. The morphology of products is controlled by the concentration of Na 2 S added to the system. Low concentration of Na 2 S gives nanocubes of 40-50 nm in size, while a high concentration of Na 2 S is of benefit to obtain nanowires. The growth of the silver crystal is also accelerated by the catalysis of Ag 2 S. Electron microscopy and UV-vis absorption spectra have been used to investigate the evolution of silver nanowires, and a reasonable mechanism to explain the role of Ag 2 S seeds has also been suggested. This semiconductor seed catalysis strategy will provide wide applications in the fabrication of metal nanomaterials

Sequential rhodium/palladium catalysis: enantioselective formation of dihydroquinolinones in the presence of achiral and chiral ligands.

Science.gov (United States)

Zhang, Lei; Qureshi, Zafar; Sonaglia, Lorenzo; Lautens, Mark

2014-12-08

Compatible combinations of achiral and chiral ligands can be used in rhodium/palladium catalysis to achieve highly enantioselective domino reactions. The difference in rates of catalysis and minimal effects of ligand interference confer control in the domino sequence. The "all-in-one" 1,4-conjugate arylation and C-N cross-coupling through sequential Rh/Pd catalysis provides access to enantioenriched dihydroquinolinone building blocks. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Homogeneous Catalysis with Metal Complexes Fundamentals and Applications

CERN Document Server

Duca, Gheorghe

2012-01-01

The book about homogeneous catalysis with metal complexes deals with the description of the reductive-oxidative, metal complexes  in a liquid phase (in polar solvents, mainly in water, and less in nonpolar solvents). The exceptional importance of the redox processes in chemical systems, in the reactions occuring in living organisms, the environmental processes, atmosphere, water, soil, and in industrial technologies (especially in food-processing industries) is discussed. The detailed practical aspects of the established regularities are explained for solving the specific practical tasks in various fields of industrial chemistry, biochemistry, medicine, analytical chemistry and ecological chemistry. The main scope of the book is the survey and systematization of the latest advances in homogeneous catalysis with metal complexes. It gives an overview of the research results and practical experience accumulated by the author during the last decade.

Chemical Sciences Division annual report 1994

Energy Technology Data Exchange (ETDEWEB)

NONE

1995-06-01

The division is one of ten LBL research divisions. It is composed of individual research groups organized into 5 scientific areas: chemical physics, inorganic/organometallic chemistry, actinide chemistry, atomic physics, and chemical engineering. Studies include structure and reactivity of critical reaction intermediates, transients and dynamics of elementary chemical reactions, and heterogeneous and homogeneous catalysis. Work for others included studies of superconducting properties of high-{Tc} oxides. In FY 1994, the division neared completion of two end-stations and a beamline for the Advanced Light Source, which will be used for combustion and other studies. This document presents summaries of the studies.

Porous metallosilicates for heterogeneous, liquid-phase catalysis: perspectives and pertaining challenges

Science.gov (United States)

Hammond, Ceri; Padovan, Daniele; Tarantino, Giulia

2018-02-01

Porous silicates containing dilute amounts of tri-, tetra- and penta-valent metal sites, such as TS-1, Sn-β and Fe-ZSM-5, have recently emerged as state of the art catalysts for a variety of sustainable chemical transformations. In contrast with their aluminosilicate cousins, which are widely employed throughout the refinery industry for gas-phase catalytic transformations, such metallosilicates have exhibited unprecedented levels of performance for a variety of liquid-phase catalytic processes, including the conversion of biomass to chemicals, and sustainable oxidation technologies with H2O2. However, despite their unique levels of performance for these new types of chemical transformations, increased utilization of these promising materials is complicated by several factors. For example, their utilization in a liquid, and often polar, medium hinders process intensification (scale-up, catalyst deactivation). Moreover, such materials do not generally exhibit the active-site homogeneity of conventional aluminosilicates, and they typically possess a wide variety of active-site ensembles, only some of which may be directly involved in the catalytic chemistry of interest. Consequently, mechanistic understanding of these catalysts remains relatively low, and competitive reactions are commonly observed. Accordingly, unified approaches towards developing more active, selective and stable porous metallosilicates have not yet been achieved. Drawing on some of the most recent literature in the field, the purpose of this mini review is both to highlight the breakthroughs made with regard to the use of porous metallosilicates as heterogeneous catalysts for liquid-phase processing, and to highlight the pertaining challenges that we, and others, aim to overcome during the forthcoming years.

Nitrogen doped carbon nanotubes : synthesis, characterization and catalysis

NARCIS (Netherlands)

van Dommele, S.

2008-01-01

Nitrogen containing Carbon Nanotubes (NCNT) have altered physical- and chemical properties with respect to polarity, conductivity and reactivity as compared to conventional carbon nanotubes (CNT) and have potential for use in electronic applications or catalysis. In this thesis the incorporation of

Generating single-photon catalyzed coherent states with quantum-optical catalysis

Energy Technology Data Exchange (ETDEWEB)

Xu, Xue-xiang, E-mail: xuxuexiang@jxnu.edu.cn [Center for Quantum Science and Technology, Jiangxi Normal University, Nanchang 330022 (China); Yuan, Hong-chun [College of Electrical and Optoelectronic Engineering, Changzhou Institute of Technology, Changzhou 213002 (China)

2016-07-15

We theoretically generate single-photon catalyzed coherent states (SPCCSs) by means of quantum-optical catalysis based on the beam splitter (BS) or the parametric amplifier (PA). These states are obtained in one of the BS (or PA) output channels if a coherent state and a single-photon Fock state are present in two input ports and a single photon is registered in the other output port. The success probabilities of the detection (also the normalization factors) are discussed, which is different for BS and PA catalysis. In addition, we prove that the generated states catalyzed by BS and PA devices are actually the same quantum states after analyzing photon number distribution of the SPCCSs. The quantum properties of the SPCCSs, such as sub-Poissonian distribution, anti-bunching effect, quadrature squeezing effect, and the negativity of the Wigner function are investigated in detail. The results show that the SPCCSs are non-Gaussian states with an abundance of nonclassicality. - Highlights: • We generate single-photon catalyzed coherent states with quantum-optical catalysis. • We prove the equivalent effects of the lossless beam splitter and the non-degenerate parametric amplifier. • Some nonclassical properties of the generated states are investigated in detail.

Rapid trifluoromethylation and perfluoroalkylation of five-membered heterocycles by photoredox catalysis in continuous flow.

Science.gov (United States)

Straathof, Natan J W; Gemoets, Hannes P L; Wang, Xiao; Schouten, Jaap C; Hessel, Volker; Noël, Timothy

2014-06-01

Trifluoromethylated and perfluoroalkylated heterocycles are important building blocks for the synthesis of numerous pharmaceutical products, agrochemicals and are widely applied in material sciences. To date, trifluoromethylated and perfluoroalkylated hetero-aromatic systems can be prepared utilizing visible light photoredox catalysis methodologies in batch. While several limitations are associated with these batch protocols, the application of microflow technology could greatly enhance and intensify these reactions. A simple and straightforward photocatalytic trifluoromethylation and perfluoroalkylation method has been developed in continuous microflow, using commercially available photocatalysts and microflow components. A selection of five-membered hetero-aromatics were successfully trifluoromethylated (12 examples) and perfluoroalkylated (5 examples) within several minutes (8-20 min). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Heterogeneous catalysis in a micro channel using a layer of carbon nano fibers on the channel wall

NARCIS (Netherlands)

Loos, de S.R.A.; Schaaf, van der J.; Croon, de M.H.J.M.; Nijhuis, T.A.; Schouten, J.C.

2012-01-01

This paper presents the increase of the overall reaction rate of a heterogeneously catalyzed multi-phase reaction using a carbon nanofiber (CNF) based catalyst with a factor of 3.5–4 compared with an unsupported flat plate catalyst in a microreactor. This was done by quantifying the hydrogen

Does Everyone's Motivational Beliefs about Physical Science Decline in Secondary School?: Heterogeneity of Adolescents' Achievement Motivation Trajectories in Physics and Chemistry.

Science.gov (United States)

Wang, Ming-Te; Chow, Angela; Degol, Jessica Lauren; Eccles, Jacquelynne Sue

2017-08-01

Students' motivational beliefs about learning physical science are critical for achieving positive educational outcomes. In this study, we incorporated expectancy-value theory to capture the heterogeneity of adolescents' motivational trajectories in physics and chemistry from seventh to twelfth grade and linked these trajectories to science-related outcomes. We used a cross-sequential design based on three different cohorts of adolescents (N = 699; 51.5 % female; 95 % European American; M ages for youngest, middle, and oldest cohorts at the first wave = 13.2, 14.1, and 15.3 years) coming from ten public secondary schools. Although many studies claim that physical science motivation declines on average over time, we identified seven differential motivational trajectories of ability self-concept and task values, and found associations of these trajectories with science achievement, advanced science course taking, and science career aspirations. Adolescents' ability self-concept and task values in physics and chemistry were also positively related and interlinked over time. Examining how students' motivational beliefs about physical science develop in secondary school offers insight into the capacity of different groups of students to successfully adapt to their changing educational environments.

Modern heterogeneous catalysis: an introduction

NARCIS (Netherlands)

van Santen, R.A.

2017-01-01

Written by one of the world's leading experts on the topic, this advanced textbook is the perfect introduction for newcomers to this exciting field. Concise and clear, the text focuses on such key aspects as kinetics, reaction mechanism and surface reactivity, concentrating on the essentials. The

Vibrational excitation from heterogeneous catalysis

International Nuclear Information System (INIS)

Purvis, G.D. III; Redmon, M.J.; Woken, G. Jr.

1979-01-01

Classical trajectories have been used by numerous researchers to investigate the dynamics of exothermic chemical reactions (atom + diatom) with a view toward understanding what leads to vibrational excitation of the product molecule. Unlike these studies, the case where the reaction is catalyzed by a solid surface is considered. The trajectory studies indicate that there should be conditions under which considerable vibrational energy appears in the product molecules without being lost to the solid during the course of the reaction. 2 figures, 3 tables

USD Catalysis Group for Alternative Energy - Final report

Energy Technology Data Exchange (ETDEWEB)

Hoefelmeyer, James

2014-10-03

I. Project Summary Catalytic processes are a major technological underpinning of modern society, and are essential to the energy sector in the processing of chemical fuels from natural resources, fine chemicals synthesis, and energy conversion. Advances in catalyst technology are enormously valuable since these lead to reduced chemical waste, reduced energy loss, and reduced costs. New energy technologies, which are critical to future economic growth, are also heavily reliant on catalysts, including fuel cells and photo-electrochemical cells. Currently, the state of South Dakota is underdeveloped in terms of research infrastructure related to catalysis. If South Dakota intends to participate in significant economic growth opportunities that result from advances in catalyst technology, then this area of research needs to be made a high priority for investment. To this end, a focused research effort is proposed in which investigators from The University of South Dakota (USD) and The South Dakota School of Mines and Technology (SDSMT) will contribute to form the South Dakota Catalysis Group (SDCG). The multidisciplinary team of the (SDCG) include: (USD) Dan Engebretson, James Hoefelmeyer, Ranjit Koodali, and Grigoriy Sereda; (SDSMT) Phil Scott Ahrenkiel, Hao Fong, Jan Puszynski, Rajesh Shende, and Jacek Swiatkiewicz. The group is well suited to engage in a collaborative project due to the resources available within the existing programs. Activities within the SDCG will be monitored through an external committee consisting of three distinguished professors in chemistry. The committee will provide expert advice and recommendations to the SDCG. Advisory meetings in which committee members interact with South Dakota investigators will be accompanied by individual oral and poster presentations in a materials and catalysis symposium. The symposium will attract prominent scientists, and will enhance the visibility of research in the state of South Dakota. The SDCG requests

A new class of PN3-pincer ligands for metal–ligand cooperative catalysis

KAUST Repository

Li, Huaifeng

2014-12-01

Work on a new class of PN3-pincer ligands for metal-ligand cooperative catalysis is reviewed. While the field of the pyridine-based PN3-transition metal pincer complexes is still relatively young, many important applications of these complexes have already emerged. In several cases, the PN3-pincer complexes for metal-ligand cooperative catalysis result in significantly improved or unprecedented activities. The synthesis and coordination chemistry of PN3-pincer ligands are briefly summarized first to cover the synthetic routes for their preparation, followed by a focus review on their applications in catalysis. A specific emphasis is placed on the later section about the role of PN3-pincer ligands\\' dearomatization-rearomatization steps during the catalytic cycles. The mechanistic insights from density functional theory (DFT) calculations are also discussed.

A new class of PN3-pincer ligands for metal–ligand cooperative catalysis

KAUST Repository

Li, Huaifeng; Zheng, Bin; Huang, Kuo-Wei

2014-01-01

Work on a new class of PN3-pincer ligands for metal-ligand cooperative catalysis is reviewed. While the field of the pyridine-based PN3-transition metal pincer complexes is still relatively young, many important applications of these complexes have already emerged. In several cases, the PN3-pincer complexes for metal-ligand cooperative catalysis result in significantly improved or unprecedented activities. The synthesis and coordination chemistry of PN3-pincer ligands are briefly summarized first to cover the synthetic routes for their preparation, followed by a focus review on their applications in catalysis. A specific emphasis is placed on the later section about the role of PN3-pincer ligands' dearomatization-rearomatization steps during the catalytic cycles. The mechanistic insights from density functional theory (DFT) calculations are also discussed.

Catalysts for Environmental Remediation

DEFF Research Database (Denmark)

Abrams, B. L.; Vesborg, Peter Christian Kjærgaard

2013-01-01

The properties of catalysts used in environmental remediation are described here through specific examples in heterogeneous catalysis and photocatalysis. In the area of heterogeneous catalysis, selective catalytic reduction (SCR) of NOx was used as an example reaction with vanadia and tungsta...

Hydrogen Tunneling Links Protein Dynamics to Enzyme Catalysis

Science.gov (United States)

Klinman, Judith P.; Kohen, Amnon

2014-01-01

The relationship between protein dynamics and function is a subject of considerable contemporary interest. Although protein motions are frequently observed during ligand binding and release steps, the contribution of protein motions to the catalysis of bond making/breaking processes is more difficult to probe and verify. Here, we show how the quantum mechanical hydrogen tunneling associated with enzymatic C–H bond cleavage provides a unique window into the necessity of protein dynamics for achieving optimal catalysis. Experimental findings support a hierarchy of thermodynamically equilibrated motions that control the H-donor and -acceptor distance and active-site electrostatics, creating an ensemble of conformations suitable for H-tunneling. A possible extension of this view to methyl transfer and other catalyzed reactions is also presented. The impact of understanding these dynamics on the conceptual framework for enzyme activity, inhibitor/drug design, and biomimetic catalyst design is likely to be substantial. PMID:23746260

Morphology-controlled synthesis of silver nanostructures via a seed catalysis process

Energy Technology Data Exchange (ETDEWEB)

Chen Chang; Wang Li; Yu Haojie; Wang Jianjun; Zhou Junfeng; Tan Qiaohua; Deng Libo [State Key Laboratory of Polymer Reaction Engineering, Zhejiang University, Hangzhou 310027 (China)

2007-03-21

A novel, effective strategy named 'seed catalysis' has been described here to synthesize silver nanostructures with controllable morphology. Typically, we added Na{sub 2}S into the reaction system and the Ag{sub 2}S semiconductor colloids formed at the initial stage would act as both seeds and catalyst in the silver reduction. The morphology of products is controlled by the concentration of Na{sub 2}S added to the system. Low concentration of Na{sub 2}S gives nanocubes of 40-50 nm in size, while a high concentration of Na{sub 2}S is of benefit to obtain nanowires. The growth of the silver crystal is also accelerated by the catalysis of Ag{sub 2}S. Electron microscopy and UV-vis absorption spectra have been used to investigate the evolution of silver nanowires, and a reasonable mechanism to explain the role of Ag{sub 2}S seeds has also been suggested. This semiconductor seed catalysis strategy will provide wide applications in the fabrication of metal nanomaterials.

Modified silica-based heterogeneous catalysts for etherification of glycerol

Energy Technology Data Exchange (ETDEWEB)

Gholami, Zahra, E-mail: zahra.gholami@petronas.com.my [Centralized Analytical Laboratory, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 31750 Tronoh, Perak (Malaysia); Abdullah, Ahmad Zuhairi, E-mail: chzuhairi@usm.my; Gholami, Fatemeh, E-mail: fgholami59@gmail.com [School of Chemical Engineering, Universiti Sains Malaysia, Engineering Campus,14300 Nibong Tebal, Penang (Malaysia); Vakili, Mohammadtaghi, E-mail: farshid3601@gmail.com [School of Industrial Technology, Universiti Sains Malaysia, 11800 Penang (Malaysia)

2015-07-22

The advent of mesoporous silicas such as MCM-41 has provided new opportunities for research into supported metal catalysis. The loading of metals into framework structures and particularly into the pores of porous molecular sieves, has long been of interest because of their potential catalytic activity. Stable heterogeneous mesoporous basic catalysts were synthesized by wet impregnation of MCM-41 with calcium nitrate and lanthanum nitrate. The surface and structural properties of the prepared catalysts were characterized using BET surface analysis, SEM and TEM. MCM-41 and modified MCM-41 were used in the solventless etherification of glycerol to produce diglycerol as the desired product. The reaction was performed at 250 °C for 8 h, and catalyst activity was evaluated. Catalytic etherification over the 20%Ca{sub 1.6}La{sub 0.6}/MCM-41 catalyst resulted in the highest glycerol conversion of 91% and diglycerol yield of 43%.

Modified silica-based heterogeneous catalysts for etherification of glycerol

International Nuclear Information System (INIS)

Gholami, Zahra; Abdullah, Ahmad Zuhairi; Gholami, Fatemeh; Vakili, Mohammadtaghi

2015-01-01

The advent of mesoporous silicas such as MCM-41 has provided new opportunities for research into supported metal catalysis. The loading of metals into framework structures and particularly into the pores of porous molecular sieves, has long been of interest because of their potential catalytic activity. Stable heterogeneous mesoporous basic catalysts were synthesized by wet impregnation of MCM-41 with calcium nitrate and lanthanum nitrate. The surface and structural properties of the prepared catalysts were characterized using BET surface analysis, SEM and TEM. MCM-41 and modified MCM-41 were used in the solventless etherification of glycerol to produce diglycerol as the desired product. The reaction was performed at 250 °C for 8 h, and catalyst activity was evaluated. Catalytic etherification over the 20%Ca 1.6 La 0.6 /MCM-41 catalyst resulted in the highest glycerol conversion of 91% and diglycerol yield of 43%

Electro-Catalysis System for Biodiesel Synthesis from Palm Oil over Dielectric-Barrier Discharge Plasma Reactor

Directory of Open Access Journals (Sweden)

Istadi Istadi

2014-07-01

Full Text Available Biodiesel synthesis reaction routes from palm oil using plasma electro-catalysis process over Dielectric-Barrier Discharge (DBD plasma reactor were studied. The study was focused on finding possible reaction mechanism route during plasma electro-catalysis process. The prediction was performed based on the changes of Gas Chromatography Mass Spectrometer (GC-MS and Fourier Transform Infra Red (FT-IR analyses to the biodiesel products with respect to time length of plasma treatment. It was found that main reaction mechanism occurred in the plasma electro-catalysis system was non-thermal pyrolysis rather than transesterification. The main reactions within the plasma treatment were due to collision between high energetic electrons (supplied from high voltage power supply through high voltage electrode and the reaction mixtures. The high energetic electrons affected the electrons pair of covalent bonding to be excited or dissociated even ionized at higher energy. Therefore, this plasma electro-catalysis system was promising for biodiesel synthesis from vegetable oils due to only very short time reaction was needed, even no need a catalyst, no soap formation, and no glycerol by-product. This system could produce fatty acid methyl ester yield of 75.65% at 120 seconds and other possible chemicals, such as alkynes, alkanes, esters, carboxylic acid, and aldehydes. However, during the plasma process, the reaction mechanisms were still difficult to be controlled due the action of available high energetic electrons. The advanced studies on how to control the reaction mechanism selectively in the plasma electro-catalysis will be published elsewhere. © 2014 BCREC UNDIP. All rights reservedReceived: 23rd January 2014; Revised: 20th March 2014; Accepted: 23rd March 2014[How to Cite: Istadi, I., Yudhistira, A.D., Anggoro, D.D., Buchori, L. (2014. Electro-Catalysis System for Biodiesel Synthesis from Palm Oil over Dielectric-Barrier Discharge Plasma Reactor

Heterogeneity of Opioid Binding Sites in Guinea Pig Spinal Cord

Science.gov (United States)

1984-11-30

MEDICAL CENTER WILFORD HALL AIR FORCE MEDICAL CENTER Title of Thesis: "Heterogeneity of Opioid Binding Sites in Guinea Pig Spinal Cord" Name of...that the use of any copyrighted material in the dissertation manuscript entitled: "Heterogeneity of Opioid Binding Sites in Guinea Pig Spinal Cord...University of the Health Sciences 11 Abstract Title of Thesis: Heterogenity of Opioid Binding Sites In Guinea Pig Spinal Cord Gary Dean Zarr MAJ/ANC

Development and comparison of the effectivity of oxidation processes initiated by radicals, created by heterogeneous catalysis and by high pressure process for the reduction of persistent organic sewage pollutants. Final report; Entwicklung und vergleichende Bewertung der Leistungsfaehigkeit von radikalisch initiierten oxidativen Verfahren auf Traegerkatalysator- und Hochdruckbasis zum Abbau persistenter organischer Wasserschadstoffe. Abschlussbericht

Energy Technology Data Exchange (ETDEWEB)

Bach, G.; Maeurer, H.

2002-07-01

Persistente and highly toxic sewages with an extremely high content of substances are still a problem in the waste water management. Wet oxidation offers a possibility to reduce the pollutant content in the water. Comparative experiments of the efficiency of oxidation initiated by radicals were carried out, using as heterogeneous catalysis on strap catalyst base as cavitation. By means of the wet oxidation on strap catalyst base with H{sub 2}O{sub 2} as oxidation reagent it was possible, to decontaminate effectively as single pollutants in model sewages as complex substance mixtures in real sewages. The tested catalytic systems worked especially effectively for high pollutant concentrations. At lower concentrations of sewage pollutants the amount of H{sub 2}O{sub 2} must be increased in regard to the actual CSB. In real sewages the pollutant decrease was, related on the TOC, in the cut, at 50%, a raise of the average concentration of the oxidation agent didn't produce any further decrease of the pollutant concentration. Aromatic hydrocarbons could be reduced more effectively than aliphatic ones. The conception for a technical plant was developed including cost estimate. The reduction of pollutants by cavitation was fundamentally lower than by using the heterogeneous catalysis way. Without addition of an oxidation agent (i.e. H{sub 2}O{sub 2}) only a TOC decrease of approx. 15% was registered in real sewages. The pollutant reduction increased at higher pollutant concentration. A complete elimination of all pollutants could not be obtained in none of the examined cases neither at model nor at real sewages. Especially the long reaction times (6 to 24 h) of the cavitation process in comparison with those, necessary for the catalytic reaction (2 to 6 h) are hindering a technical realization of the cavitation process, which seems to be doubtful for this and other reasons. So the use of cavitation in industrial scale sewage cleaning plants under the parameter

Metal-Organic-Framework mediated supported-cobalt catalysts in multiphase hydrogenation reactions

OpenAIRE

Sun, X.

2017-01-01

The production of most industrially important chemicals involves catalysis. Depending on the difference in phases between the catalysts and reactants, one distinguishes homogenous catalysis and heterogeneous catalysis, with the latter being more attractive in real applications, due to the easy separation of products from catalysts and reusing the latter. In spite of the research and development of heterogeneous catalysts for decades, the exploration for catalysts system with outstanding activ...

Bionic catalysis of porphyrin for electrochemical detection of nucleic acids

International Nuclear Information System (INIS)

Li Jie; Lei Jianping; Wang Quanbo; Wang Peng; Ju Huangxian

2012-01-01

Highlights: ► This is the first application of bionic catalysis of porphyrin as detection probe in bioanalysis. ► Porphyrin–DNA–gold nanoparticle probe is synthesized. ► Binding model between FeTMPyP and DNA is verified. ► The detection probe shows excellent electrocatalytic behaviors toward the reduction of O 2 . ► The biosensor exhibited good performance with wide linear range and high specificity. - Abstract: A novel electrochemical strategy was designed for the detection of DNA based on the bionic catalysis of porphyrin. The detection probe was prepared via the assembly of thiolated double strand DNA (dsDNA) with gold nanoparticles (AuNPs), and then interacted with cationic iron (III) meso-tetrakis (N-methylphyridinum-4-yl) porphyrin (FeTMPyP) via groove binding along the dsDNA surface. The resulting nanocomplex was characterized with transmission electron microscopy, UV–vis absorption and circular dichroism spectroscopy. The FeTMPyP–DNA–AuNPs probe on gold electrode demonstrated the excellent electrocatalytic behaviors toward the reduction of O 2 due to the largely loading of FeTMPyP and good conductivity. Based on bionic catalysis of porphyrin for the reduction of O 2 , the resulting biosensor exhibited a good performance for the detection of DNA with a wide linear range from 1 × 10 −12 to 1 × 10 −8 mol L −1 and detection limit of 2.5 × 10 −13 mol L −1 at the signal/noise of 3. More importantly, the biosensor presented excellent ability to discriminate the perfectly complementary target and the mismatched stand. This strategy could be conveniently extended for detection of other biomolecules. To the best of our knowledge, this is the first application of bionic catalysis of porphyrin as detection probe and opens new opportunities for sensitive detection of biorecognition events.

Cometary science. Time variability and heterogeneity in the coma of 67P/Churyumov-Gerasimenko.

Science.gov (United States)

Hässig, M; Altwegg, K; Balsiger, H; Bar-Nun, A; Berthelier, J J; Bieler, A; Bochsler, P; Briois, C; Calmonte, U; Combi, M; De Keyser, J; Eberhardt, P; Fiethe, B; Fuselier, S A; Galand, M; Gasc, S; Gombosi, T I; Hansen, K C; Jäckel, A; Keller, H U; Kopp, E; Korth, A; Kührt, E; Le Roy, L; Mall, U; Marty, B; Mousis, O; Neefs, E; Owen, T; Rème, H; Rubin, M; Sémon, T; Tornow, C; Tzou, C-Y; Waite, J H; Wurz, P

2015-01-23

Comets contain the best-preserved material from the beginning of our planetary system. Their nuclei and comae composition reveal clues about physical and chemical conditions during the early solar system when comets formed. ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) onboard the Rosetta spacecraft has measured the coma composition of comet 67P/Churyumov-Gerasimenko with well-sampled time resolution per rotation. Measurements were made over many comet rotation periods and a wide range of latitudes. These measurements show large fluctuations in composition in a heterogeneous coma that has diurnal and possibly seasonal variations in the major outgassing species: water, carbon monoxide, and carbon dioxide. These results indicate a complex coma-nucleus relationship where seasonal variations may be driven by temperature differences just below the comet surface. Copyright © 2015, American Association for the Advancement of Science.

The Changing Landscape of Hydrocarbon Feedstocks for Chemical Production: Implications for Catalysis: Proceedings of a Workshop

Energy Technology Data Exchange (ETDEWEB)

Bell, Alexis T. [Univ. of California, Berkeley, CA (United States); Alger, Monty M. [Pennsylvania State Univ., University Park, PA (United States); Flytzani-Stephanopoulos, Maria [Tufts Univ., Medford, MA (United States); Gunnoe, T. Brent [Univ. of Virginia, Charlottesville, VA (United States); Lercher, Johannes A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Stevens, James [Dow Chemical Company, Torrance, CA (United States); Alper, Joe; Tran, Camly [National Academies of Sciences, Engineering, and Medicine, Washington, DC (United States)

2016-11-14

A decade ago, the U.S. chemical industry was in decline. Of the more than 40 chemical manufacturing plants being built worldwide in the mid-2000s with more than $1 billion in capitalization, none were under construction in the United States. Today, as a result of abundant domestic supplies of affordable natural gas and natural gas liquids resulting from the dramatic rise in shale gas production, the U.S. chemical industry has gone from the world’s highest-cost producer in 2005 to among the lowest-cost producers today. The low cost and increased supply of natural gas and natural gas liquids provides an opportunity to discover and develop new catalysts and processes to enable the direct conversion of natural gas and natural gas liquids into value-added chemicals with a lower carbon footprint. The economic implications of developing advanced technologies to utilize and process natural gas and natural gas liquids for chemical production could be significant, as commodity, intermediate, and fine chemicals represent a higher-economic-value use of shale gas compared with its use as a fuel. To better understand the opportunities for catalysis research in an era of shifting feedstocks for chemical production and to identify the gaps in the current research portfolio, the National Academies of Sciences, Engineering, and Medicine conducted an interactive, multidisciplinary workshop in March 2016. The goal of this workshop was to identify advances in catalysis that can enable the United States to fully realize the potential of the shale gas revolution for the U.S. chemical industry and, as a result, to help target the efforts of U.S. researchers and funding agencies on those areas of science and technology development that are most critical to achieving these advances. This publication summarizes the presentations and discussions from the workshop.

From engineering hydrology to Earth system science: milestones in the transformation of hydrologic science

Directory of Open Access Journals (Sweden)

M. Sivapalan

2018-03-01

Full Text Available Hydrology has undergone almost transformative changes over the past 50 years. Huge strides have been made in the transition from early empirical approaches to rigorous approaches based on the fluid mechanics of water movement on and below the land surface. However, progress has been hampered by problems posed by the presence of heterogeneity, including subsurface heterogeneity present at all scales. The inability to measure or map the heterogeneity everywhere prevented the development of balance equations and associated closure relations at the scales of interest, and has led to the virtual impasse we are presently in, in terms of development of physically based models needed for hydrologic predictions. An alternative to the mapping of heterogeneity everywhere is a new Earth system science view, which sees the heterogeneity as the end result of co-evolutionary hydrological, geomorphological, ecological, and pedological processes, each operating at a different rate, which help to shape the landscapes that we find in nature, including the heterogeneity that we do not readily see. The expectation is that instead of specifying exact details of the heterogeneity in our models, we can replace it (without loss of information with the ecosystem function that they perform. Guided by this new Earth system science perspective, development of hydrologic science is now addressing new questions using novel holistic co-evolutionary approaches as opposed to the physical, fluid mechanics based reductionist approaches that we inherited from the recent past. In the emergent Anthropocene, the co-evolutionary view has expanded further to involve interactions and feedbacks with human-social processes as well. In this paper, I present my own perspective of key milestones in the transformation of hydrologic science from engineering hydrology to Earth system science, drawn from the work of several students and colleagues of mine, and discuss their implication for

From engineering hydrology to Earth system science: milestones in the transformation of hydrologic science

Science.gov (United States)

Sivapalan, Murugesu

2018-03-01

Hydrology has undergone almost transformative changes over the past 50 years. Huge strides have been made in the transition from early empirical approaches to rigorous approaches based on the fluid mechanics of water movement on and below the land surface. However, progress has been hampered by problems posed by the presence of heterogeneity, including subsurface heterogeneity present at all scales. The inability to measure or map the heterogeneity everywhere prevented the development of balance equations and associated closure relations at the scales of interest, and has led to the virtual impasse we are presently in, in terms of development of physically based models needed for hydrologic predictions. An alternative to the mapping of heterogeneity everywhere is a new Earth system science view, which sees the heterogeneity as the end result of co-evolutionary hydrological, geomorphological, ecological, and pedological processes, each operating at a different rate, which help to shape the landscapes that we find in nature, including the heterogeneity that we do not readily see. The expectation is that instead of specifying exact details of the heterogeneity in our models, we can replace it (without loss of information) with the ecosystem function that they perform. Guided by this new Earth system science perspective, development of hydrologic science is now addressing new questions using novel holistic co-evolutionary approaches as opposed to the physical, fluid mechanics based reductionist approaches that we inherited from the recent past. In the emergent Anthropocene, the co-evolutionary view has expanded further to involve interactions and feedbacks with human-social processes as well. In this paper, I present my own perspective of key milestones in the transformation of hydrologic science from engineering hydrology to Earth system science, drawn from the work of several students and colleagues of mine, and discuss their implication for hydrologic observations

High mass resolution time of flight mass spectrometer for measuring products in heterogeneous catalysis in highly sensitive microreactors

DEFF Research Database (Denmark)

Andersen, Thomas; Jensen, Robert; Christensen, M. K.

2012-01-01

We demonstrate a combined microreactor and time of flight system for testing and characterization of heterogeneous catalysts with high resolution mass spectrometry and high sensitivity. Catalyst testing is performed in silicon-based microreactors which have high sensitivity and fast thermal...

Pincer-porphyrin hybrids : Synthesis, self-assembly, and catalysis

NARCIS (Netherlands)

Suijkerbuijk, B.M.J.M.

2007-01-01

Metal complexes play an important role in established research areas such as catalysis and materials chemistry as well as in emerging fields of chemical exploration such as bioinorganic chemistry. Changes in the metal center's ligand environment, i.e., the nature and number of the Lewis basic atoms

bond activation and catalysis by Ru -pac complexes

Indian Academy of Sciences (India)

and their reactivity towards oxidation of a few organic compounds. Keywords. Kinetics; catalysis; -O–O- bond activation; Ru-pac complex; oxidation. 1. Introduction. Ru-pac complexes exhibit catalytic properties,1 in homogeneous conditions in the presence of oxygen atom donors, that mimic the biological enzymatic oxi-.

Oxidase catalysis via aerobically generated hypervalent iodine intermediates

Science.gov (United States)

Maity, Asim; Hyun, Sung-Min; Powers, David C.

2018-02-01

The development of sustainable oxidation chemistry demands strategies to harness O2 as a terminal oxidant. Oxidase catalysis, in which O2 serves as a chemical oxidant without necessitating incorporation of oxygen into reaction products, would allow diverse substrate functionalization chemistry to be coupled to O2 reduction. Direct O2 utilization suffers from intrinsic challenges imposed by the triplet ground state of O2 and the disparate electron inventories of four-electron O2 reduction and two-electron substrate oxidation. Here, we generate hypervalent iodine reagents—a broadly useful class of selective two-electron oxidants—from O2. This is achieved by intercepting reactive intermediates of aldehyde autoxidation to aerobically generate hypervalent iodine reagents for a broad array of substrate oxidation reactions. The use of aryl iodides as mediators of aerobic oxidation underpins an oxidase catalysis platform that couples substrate oxidation directly to O2 reduction. We anticipate that aerobically generated hypervalent iodine reagents will expand the scope of aerobic oxidation chemistry in chemical synthesis.

Stabilizing ultrasmall Au clusters for enhanced photoredox catalysis.

Science.gov (United States)

Weng, Bo; Lu, Kang-Qiang; Tang, Zichao; Chen, Hao Ming; Xu, Yi-Jun

2018-04-18

Recently, loading ligand-protected gold (Au) clusters as visible light photosensitizers onto various supports for photoredox catalysis has attracted considerable attention. However, the efficient control of long-term photostability of Au clusters on the metal-support interface remains challenging. Herein, we report a simple and efficient method for enhancing the photostability of glutathione-protected Au clusters (Au GSH clusters) loaded on the surface of SiO 2 sphere by utilizing multifunctional branched poly-ethylenimine (BPEI) as a surface charge modifying, reducing and stabilizing agent. The sequential coating of thickness controlled TiO 2 shells can further significantly improve the photocatalytic efficiency, while such structurally designed core-shell SiO 2 -Au GSH clusters-BPEI@TiO 2 composites maintain high photostability during longtime light illumination conditions. This joint strategy via interfacial modification and composition engineering provides a facile guideline for stabilizing ultrasmall Au clusters and rational design of Au clusters-based composites with improved activity toward targeting applications in photoredox catalysis.

Heterogeneous Single-Atom Catalyst for Visible-Light-Driven High-Turnover CO2 Reduction: The Role of Electron Transfer.

Science.gov (United States)

Gao, Chao; Chen, Shuangming; Wang, Ying; Wang, Jiawen; Zheng, Xusheng; Zhu, Junfa; Song, Li; Zhang, Wenkai; Xiong, Yujie

2018-03-01

Visible-light-driven conversion of CO 2 into chemical fuels is an intriguing approach to address the energy and environmental challenges. In principle, light harvesting and catalytic reactions can be both optimized by combining the merits of homogeneous and heterogeneous photocatalysts; however, the efficiency of charge transfer between light absorbers and catalytic sites is often too low to limit the overall photocatalytic performance. In this communication, it is reported that the single-atom Co sites coordinated on the partially oxidized graphene nanosheets can serve as a highly active and durable heterogeneous catalyst for CO 2 conversion, wherein the graphene bridges homogeneous light absorbers with single-atom catalytic sites for the efficient transfer of photoexcited electrons. As a result, the turnover number for CO production reaches a high value of 678 with an unprecedented turnover frequency of 3.77 min -1 , superior to those obtained with the state-of-the-art heterogeneous photocatalysts. This work provides fresh insights into the design of catalytic sites toward photocatalytic CO 2 conversion from the angle of single-atom catalysis and highlights the role of charge kinetics in bridging the gap between heterogeneous and homogeneous photocatalysts. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Confined catalysis under two-dimensional materials

OpenAIRE

Li, Haobo; Xiao, Jianping; Fu, Qiang; Bao, Xinhe

2017-01-01

Small spaces in nanoreactors may have big implications in chemistry, because the chemical nature of molecules and reactions within the nanospaces can be changed significantly due to the nanoconfinement effect. Two-dimensional (2D) nanoreactor formed under 2D materials can provide a well-defined model system to explore the confined catalysis. We demonstrate a general tendency for weakened surface adsorption under the confinement of graphene overlayer, illustrating the feasible modulation of su...

USD Catalysis Group for Alternative Energy

Energy Technology Data Exchange (ETDEWEB)

Hoefelmeyer, James D.; Koodali, Ranjit; Sereda, Grigoriy; Engebretson, Dan; Fong, Hao; Puszynski, Jan; Shende, Rajesh; Ahrenkiel, Phil

2012-03-13

The South Dakota Catalysis Group (SDCG) is a collaborative project with mission to develop advanced catalysts for energy conversion with two primary goals: (1) develop photocatalytic systems in which polyfunctionalized TiO2 are the basis for hydrogen/oxygen synthesis from water and sunlight (solar fuels group), (2) develop new materials for hydrogen utilization in fuel cells (fuel cell group). In tandem, these technologies complete a closed chemical cycle with zero emissions.

Journal of Chemical Sciences | Indian Academy of Sciences

Indian Academy of Sciences (India)

Home; Journals; Journal of Chemical Sciences. SHWETA DHILLON. Articles written in Journal of Chemical Sciences. Volume 129 Issue 8 August 2017 pp 1277-1292 REGULAR ARTICLE. Theory for electrochemical impedance spectroscopy of heterogeneous electrode with distributed capacitance and charge transfer ...

Ferroelectrics: A pathway to switchable surface chemistry and catalysis

Science.gov (United States)

Kakekhani, Arvin; Ismail-Beigi, Sohrab; Altman, Eric I.

2016-08-01

It has been known for more than six decades that ferroelectricity can affect a material's surface physics and chemistry thereby potentially enhancing its catalytic properties. Ferroelectrics are a class of materials with a switchable electrical polarization that can affect surface stoichiometry and electronic structure and thus adsorption energies and modes; e.g., molecular versus dissociative. Therefore, ferroelectrics may be utilized to achieve switchable surface chemistry whereby surface properties are not fixed but can be dynamically controlled by, for example, applying an external electric field or modulating the temperature. Several important examples of applications of ferroelectric and polar materials in photocatalysis and heterogeneous catalysis are discussed. In photocatalysis, the polarization direction can control band bending at water/ferroelectric and ferroelectric/semiconductor interfaces, thereby facilitating charge separation and transfer to the electrolyte and enhancing photocatalytic activity. For gas-surface interactions, available results suggest that using ferroelectrics to support catalytically active transition metals and oxides is another way to enhance catalytic activity. Finally, the possibility of incorporating ferroelectric switching into the catalytic cycle itself is described. In this scenario, a dynamic collaboration of two polarization states can be used to drive reactions that have been historically challenging to achieve on surfaces with fixed chemical properties (e.g., direct NOx decomposition and the selective partial oxidation of methane). These predictions show that dynamic modulation of the polarization can help overcome some of the fundamental limitations on catalytic activity imposed by the Sabatier principle.

Growth mechanism of graphene on platinum: Surface catalysis and carbon segregation

International Nuclear Information System (INIS)

Sun, Jie; Lindvall, Niclas; Yurgens, August; Nam, Youngwoo; Cole, Matthew T.; Teo, Kenneth B. K.; Woo Park, Yung

2014-01-01

A model of the graphene growth mechanism of chemical vapor deposition on platinum is proposed and verified by experiments. Surface catalysis and carbon segregation occur, respectively, at high and low temperatures in the process, representing the so-called balance and segregation regimes. Catalysis leads to self-limiting formation of large area monolayer graphene, whereas segregation results in multilayers, which evidently “grow from below.” By controlling kinetic factors, dominantly monolayer graphene whose high quality has been confirmed by quantum Hall measurement can be deposited on platinum with hydrogen-rich environment, quench cooling, tiny but continuous methane flow and about 1000 °C growth temperature

Hybrid nuclear reactors and muon catalysis

International Nuclear Information System (INIS)

Petrov, Yu.

1983-01-01

Three methods are described of the conversion of isotope 238 U to 239 Pu by neutron capture in fast breeder reactors, in the breeding blanket of hybrid thermonuclear reactors using neutrons generated by fusion and electronuclear breeding in which the target is bombarded with 1 GeV protons. Their possible use in power production is discussed. Another prospective energy source is the use of muon catalysis in the fusion of deuterium and tritium nuclei. (J.P.)

Catalysis in micellar and macromoleular systems

CERN Document Server

Fendler, Janos

1975-01-01

Catalysis in Micellar and Macromolecular Systems provides a comprehensive monograph on the catalyses elicited by aqueous and nonaqueous micelles, synthetic and naturally occurring polymers, and phase-transfer catalysts. It delineates the principles involved in designing appropriate catalytic systems throughout. Additionally, an attempt has been made to tabulate the available data exhaustively. The book discusses the preparation and purification of surfactants; the physical and chemical properties of surfactants and micelles; solubilization in aqueous micellar systems; and the principles of

Alkylation of hydrothiophosphoryl compounds in conditions of interphase catalysis

International Nuclear Information System (INIS)

Aladzheva, I.M.; Odinets, I.L.; Petrovskij, P.V.; Mastryukova, T.A.; Kabachkin, M.I.

1993-01-01

A method of interphase catalysis permitted to develop a common method for synthesis of compounds with thiophosphoryl group. The effect of nature of hydrothiophosphoryl compound, alkylating agent, two-phase system and reaction conditions on alkylation product yields was investigated in detail

Chemistry Division annual progress report for period ending April 30, 1993

Energy Technology Data Exchange (ETDEWEB)

Poutsma, M.L.; Ferris, L.M.; Mesmer, R.E.

1993-08-01

The Chemistry Division conducts basic and applied chemical research on projects important to DOE`s missions in sciences, energy technologies, advanced materials, and waste management/environmental restoration; it also conducts complementary research for other sponsors. The research are arranged according to: coal chemistry, aqueous chemistry at high temperatures and pressures, geochemistry, chemistry of advanced inorganic materials, structure and dynamics of advanced polymeric materials, chemistry of transuranium elements and compounds, chemical and structural principles in solvent extraction, surface science related to heterogeneous catalysis, photolytic transformations of hazardous organics, DNA sequencing and mapping, and special topics.

Chemical bonding of water to metal surfaces studied with core-level spectroscopies

DEFF Research Database (Denmark)

Schiros, T.; Andersson, Klas Jerker; Pettersson, L.G.M.

2010-01-01

The nature of the contact layer of water on surfaces is of relevance for many practical fields, including corrosion, electrochemistry, environmental science and heterogeneous catalysis. Here we focus on the geometric and electronic structure of the water contact layer on transition metal surfaces......-specific information on the partial local density of states, local atomic structure, geometrical parameters and molecular orientation, allowing general principles for water-metal interaction to be derived....

Solvay Conference on Surface Science

CERN Document Server

1988-01-01

The articles collected in this volume give a broad overview of the current state of surface science. Pioneers in the field and researchers met together at this Solvay Conference to discuss important new developments in surface science, with an emphasis on the common area between solid state physics and physical chemistry. The contributions deal with the following subjects: structure of surfaces, surface science and catalysis, two-dimensional physics and phase transitions, scanning tunneling microscopy, surface scattering and surface dynamics, chemical reactions at surfaces, solid-solid interfaces and superlattices, and surface studies with synchrotron radiation. On each of these subjects an introductory review talk and a number of short research contributions are followed by extensive discussions, which appear in full in the text. This nineteenth Solvay Conference commemorates the 75th anniversary of the Solvay Institutes.

Uma perspectiva computacional sobre catálise enzimática A computational perspective on enzymatic catalysis

Directory of Open Access Journals (Sweden)

Guilherme M. Arantes

2008-01-01

Full Text Available Enzymes are extremely efficient catalysts. Here, part of the mechanisms proposed to explain this catalytic power will be compared to quantitative experimental results and computer simulations. Influence of the enzymatic environment over species along the reaction coordinate will be analysed. Concepts of transition state stabilisation and reactant destabilisation will be confronted. Divided site model and near-attack conformation hypotheses will also be discussed. Molecular interactions such as covalent catalysis, general acid-base catalysis, electrostatics, entropic effects, steric hindrance, quantum and dynamical effects will also be analysed as sources of catalysis. Reaction mechanisms, in particular that catalysed by protein tyrosine phosphatases, illustrate the concepts.

Role of catalysis in sustainable production of synthetic elastomers

Indian Academy of Sciences (India)

productions, the impact of synthetic elastomer business cannot be overlooked. The need of ... Keywords. Elastomers; catalysis; tyres and automobiles; mechanism; manufacturing process. 1. ..... level fractional factorial design model was also developed to ..... Polybutadiene can be manufactured by a number of pro- cesses ...

Probing the structure of heterogeneous diluted materials by diffraction tomography.

Science.gov (United States)

Bleuet, Pierre; Welcomme, Eléonore; Dooryhée, Eric; Susini, Jean; Hodeau, Jean-Louis; Walter, Philippe

2008-06-01

The advent of nanosciences calls for the development of local structural probes, in particular to characterize ill-ordered or heterogeneous materials. Furthermore, because materials properties are often related to their heterogeneity and the hierarchical arrangement of their structure, different structural probes covering a wide range of scales are required. X-ray diffraction is one of the prime structural methods but suffers from a relatively poor detection limit, whereas transmission electron analysis involves destructive sample preparation. Here we show the potential of coupling pencil-beam tomography with X-ray diffraction to examine unidentified phases in nanomaterials and polycrystalline materials. The demonstration is carried out on a high-pressure pellet containing several carbon phases and on a heterogeneous powder containing chalcedony and iron pigments. The present method enables a non-invasive structural refinement with a weight sensitivity of one part per thousand. It enables the extraction of the scattering patterns of amorphous and crystalline compounds with similar atomic densities and compositions. Furthermore, such a diffraction-tomography experiment can be carried out simultaneously with X-ray fluorescence, Compton and absorption tomographies, enabling a multimodal analysis of prime importance in materials science, chemistry, geology, environmental science, medical science, palaeontology and cultural heritage.

Magnetic Catalysis of Chiral Symmetry Breaking: A Holographic Prospective

International Nuclear Information System (INIS)

Filev, V.; Rashkov, R.; Rashkov, R.

2010-01-01

We review a recent investigation of the effect of magnetic catalysis of mass generation in holographic Yang-Mills theories. We aim at a self-contained and pedagogical form of the review. We provide a brief field theory background and review the basics of holographic flavordynamics. The main part of the paper investigates the influence of external magnetic field to holographic gauge theories dual to the D3/D5- and D3/D7-brane intersections. Among the observed phenomena are the spontaneous breaking of a global internal symmetry, Zeeman splitting of the energy levels, and the existence of pseudo, Goldstone modes. An analytic derivation of the Gell-Mann-Oaks-Renner relation for the D3/D7 set up is reviewed. In the D3/D5 case, the pseudo-Goldstone modes satisfy nonrelativistic dispersion relation. The studies reviewed confirm the universal nature of the magnetic catalysis of mass generation.

Chemical Ligation and Isotope Labeling to Locate Dynamic Effects during Catalysis by Dihydrofolate Reductase.

Science.gov (United States)

Luk, Louis Y P; Ruiz-Pernía, J Javier; Adesina, Aduragbemi S; Loveridge, E Joel; Tuñón, Iñaki; Moliner, Vincent; Allemann, Rudolf K

2015-07-27

Chemical ligation has been used to alter motions in specific regions of dihydrofolate reductase from E. coli and to investigate the effects of localized motional changes on enzyme catalysis. Two isotopic hybrids were prepared; one with the mobile N-terminal segment containing heavy isotopes ((2) H, (13) C, (15) N) and the remainder of the protein with natural isotopic abundance, and the other one with only the C-terminal segment isotopically labeled. Kinetic investigations indicated that isotopic substitution of the N-terminal segment affected only a physical step of catalysis, whereas the enzyme chemistry was affected by protein motions from the C-terminal segment. QM/MM studies support the idea that dynamic effects on catalysis mostly originate from the C-terminal segment. The use of isotope hybrids provides insights into the microscopic mechanism of dynamic coupling, which is difficult to obtain with other studies, and helps define the dynamic networks of intramolecular interactions central to enzyme catalysis. © 2015 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Scale-up of heterogeneous catalytic reactions

Energy Technology Data Exchange (ETDEWEB)

Heggs, P; Sunderland, P

1979-12-01

This report on the Institution of Chemical Engineers ''Problems in Applied Catalysis'' Meeting (Bath, U.K. 1/4-5/78) covers papers on the nature of the catalyst surface, including the use of IR spectroscopy, electron energy loss spectroscopy, low-energy electron diffraction, electron spectroscopy, secondary ion mass spectroscopy, and modular-beam scattering for investigating solid surfaces and their relevance to catalysis; study of the reaction mechanisms by which catalysis takes place; use of mechanistic models to determine the true chemical kinetics illustrated for the oxidation of benzene to maleic anhydride over a vanadium pentoxide/molybdenum trioxide catalyst; the study with respect to the importance of transport effects in catalyst pellets on scale-up, falsification of true kinetics, and the design of laboratory reactors; full-scale reactor design of packed-bed reactors; and practical scale-up problems illustrated for methanol synthesis over a copper catalyst, ammonia oxidation over a cobalt oxide catalyst, and the steam reforming of naphtha.

Journal of Chemical Sciences | Indian Academy of Sciences

Indian Academy of Sciences (India)

Home; Journals; Journal of Chemical Sciences. Batool Akhlaghinia. Articles written in Journal of Chemical Sciences. Volume 126 Issue 6 November 2014 pp 1903-1912 Regular Articles. Fe(HSO4)3: An efficient, heterogeneous and reusable catalyst for -alkylation of -dicarbonyl compounds · Samaneh Khafajeh Batool ...

Sulfated tin oxide (STO – Structural properties and application in catalysis: A review

Directory of Open Access Journals (Sweden)

Ravi Varala

2016-07-01

Full Text Available Catalysis is an important area of chemistry, with an extensive amount of work going on in this area of sciences, toward synthesis and evaluation of newer catalysts. There are many reports for different conversion reactions such as oxidation, reduction, coupling, alkylation, and acylation for which various catalysts have been used such as mixed metal oxides, metal nanoparticles, metal organic complexes and many others. Among the many catalysts reported, the one catalyst that caught our attention due to its exploitation for a plethora of organic conversions is the sulfated tin oxide (STO, which is due to the low cost, greater stability and high efficiency of the catalyst. In this review, we have attempted to compile data about the structural properties of STO, and its applications as catalysts in various organic synthesis are presented. The literature data up to 2014 were collected and considered for the review.

Ir/Sn dual-reagent catalysis towards highly selective alkylation of ...

Indian Academy of Sciences (India)

Wintec

Organometallic; bimetallic; catalysis; alkylation; benzyl alcohol; iridium, tin. 1. Introduction ... cording to our proposal, the oxidative addition of tin(IV) halides across a ..... 33. 4. Conclusion. In summary, we have demonstrated here an Ir/Sn.

Nanostructured Membranes for Green Synthesis of Nanoparticles and Enzyme Catalysis

Science.gov (United States)

Macroporous membranes functionalized with ionizable macromolecules provide promising applications in toxic metal capture at high capacity, nanoparticle synthesis, and catalysis. Our low‐pressure membrane approach is marked by reaction and separation selectivity and their tunabili...

Nanostructured Membranes for Enzyme Catalysis and Green Synthesis of Nanoparticles

Science.gov (United States)

Macroporous membranes functionalized with ionizable macromolecules provide promising applications in toxic metal capture at high capacity, nanoparticle synthesis, and catalysis. Our low-pressure membrane approach is marked by reaction and separation selectivity and their tunabil...

Nanoscale Advances in Catalysis and Energy Applications

Energy Technology Data Exchange (ETDEWEB)

Li, Yimin; Somorjai, Gabor A.

2010-05-12

In this perspective, we present an overview of nanoscience applications in catalysis, energy conversion, and energy conservation technologies. We discuss how novel physical and chemical properties of nanomaterials can be applied and engineered to meet the advanced material requirements in the new generation of chemical and energy conversion devices. We highlight some of the latest advances in these nanotechnologies and provide an outlook at the major challenges for further developments.

Understanding as Integration of Heterogeneous Representations

Science.gov (United States)

Martínez, Sergio F.

2014-03-01

The search for understanding is a major aim of science. Traditionally, understanding has been undervalued in the philosophy of science because of its psychological underpinnings; nowadays, however, it is widely recognized that epistemology cannot be divorced from psychology as sharp as traditional epistemology required. This eliminates the main obstacle to give scientific understanding due attention in philosophy of science. My aim in this paper is to describe an account of scientific understanding as an emergent feature of our mastering of different (causal) explanatory frameworks that takes place through the mastering of scientific practices. Different practices lead to different kinds of representations. Such representations are often heterogeneous. The integration of such representations constitute understanding.

Supported ionic liquids: versatile reaction and separation media

DEFF Research Database (Denmark)

Riisager, Anders; Fehrmann, Rasmus; Haumann, Marco

2006-01-01

The latest developments in supported ionic liquid phase (SILP) systems for catalysis and separation technology are surveyed. The SILP concept combines the advantages of homogeneous catalysis with heterogeneous process technology, and a variety of reactions have been studied where supported ionic ...... liquid catalysts proved to be more active and selective than common systems. In separation applications the use of supported ionic liquids can facilitate selective transport of substrates across membranes.......The latest developments in supported ionic liquid phase (SILP) systems for catalysis and separation technology are surveyed. The SILP concept combines the advantages of homogeneous catalysis with heterogeneous process technology, and a variety of reactions have been studied where supported ionic...

Extremely efficient catalysis of carbon-carbon bond formation using "click" dendrimer-stabilized palladium nanoparticles.

Science.gov (United States)

Astruc, Didier; Ornelas, Cátia; Diallo, Abdou K; Ruiz, Jaime

2010-07-20

This article is an account of the work carried out in the authors' laboratory illustrating the usefulness of dendrimer design for nanoparticle palladium catalysis. The "click" synthesis of dendrimers constructed generation by generation by 1-->3 C connectivity, introduces 1,2,3-triazolyl ligands insides the dendrimers at each generation. Complexation of the ligands by Pd(II) followed by reduction to Pd(0) forms dendrimer-stabilized Pd nanoparticles (PdNPs) that are extremely reactive in the catalysis of olefin hydrogenation and C-C bond coupling reactions. The stabilization can be outer-dendritic for the small zeroth-generation dendrimer or intra-dendritic for the larger first- and second-generation dendrimers. The example of the Miyaura-Suzuki reaction that can be catalyzed by down to 1 ppm of PdNPs with a "homeopathic" mechanism (the less, the better) is illustrated here, including catalysis in aqueous solvents.

Center for Catalysis at Iowa State University

Energy Technology Data Exchange (ETDEWEB)

Kraus, George A.

2006-10-17

The overall objective of this proposal is to enable Iowa State University to establish a Center that enjoys world-class stature and eventually enhances the economy through the transfer of innovation from the laboratory to the marketplace. The funds have been used to support experimental proposals from interdisciplinary research teams in areas related to catalysis and green chemistry. Specific focus areas included: • Catalytic conversion of renewable natural resources to industrial materials • Development of new catalysts for the oxidation or reduction of commodity chemicals • Use of enzymes and microorganisms in biocatalysis • Development of new, environmentally friendly reactions of industrial importance These focus areas intersect with barriers from the MYTP draft document. Specifically, section 2.4.3.1 Processing and Conversion has a list of bulleted items under Improved Chemical Conversions that includes new hydrogenation catalysts, milder oxidation catalysts, new catalysts for dehydration and selective bond cleavage catalysts. Specifically, the four sections are: 1. Catalyst development (7.4.12.A) 2. Conversion of glycerol (7.4.12.B) 3. Conversion of biodiesel (7.4.12.C) 4. Glucose from starch (7.4.12.D) All funded projects are part of a soybean or corn biorefinery. Two funded projects that have made significant progress toward goals of the MYTP draft document are: Catalysts to convert feedstocks with high fatty acid content to biodiesel (Kraus, Lin, Verkade) and Conversion of Glycerol into 1,3-Propanediol (Lin, Kraus). Currently, biodiesel is prepared using homogeneous base catalysis. However, as producers look for feedstocks other than soybean oil, such as waste restaurant oils and rendered animal fats, they have observed a large amount of free fatty acids contained in the feedstocks. Free fatty acids cannot be converted into biodiesel using homogeneous base-mediated processes. The CCAT catalyst system offers an integrated and cooperative catalytic

Molecular-level Design of Heterogeneous Chiral Catalysts

Energy Technology Data Exchange (ETDEWEB)

Gellman, Andrew John [Carnegie Mellon University; Sholl, David S. [Georgia Institute of Technology; Tysoe, Wilfred T. [University of Wisconsin - Milwaukee; Zaera, Francisco [University of California at Riverside

2013-04-28

Understanding and controlling selectivity is one of the key challenges in heterogeneous catalysis. Among problems in catalytic selectivity enantioselectivity is perhaps the most the most challenging. The primary goal of the project on “Molecular-level Design of Heterogeneous Chiral Catalysts” is to understand the origins of enantioselectivity on chiral heterogeneous surfaces and catalysts. The efforts of the project team include preparation of chiral surfaces, characterization of chiral surfaces, experimental detection of enantioselectivity on such surfaces and computational modeling of the interactions of chiral probe molecules with chiral surfaces. Over the course of the project period the team of PI’s has made some of the most detailed and insightful studies of enantioselective chemistry on chiral surfaces. This includes the measurement of fundamental interactions and reaction mechanisms of chiral molecules on chiral surfaces and leads all the way to rationale design and synthesis of chiral surfaces and materials for enantioselective surface chemistry. The PI’s have designed and prepared new materials for enantioselective adsorption and catalysis. Naturally Chiral Surfaces • Completion of a systematic study of the enantiospecific desorption kinetics of R-3-methylcyclohexanone (R-3-MCHO) on 9 achiral and 7 enantiomeric pairs of chiral Cu surfaces with orientations that span the stereographic triangle. • Discovery of super-enantioselective tartaric acid (TA) and aspartic acid (Asp) decomposition as a result of a surface explosion mechanism on Cu(643)R&S. Systematic study of super-enantiospecific TA and Asp decomposition on five enantiomeric pairs of chiral Cu surfaces. • Initial observation of the enantiospecific desorption of R- and S-propylene oxide (PO) from Cu(100) imprinted with {3,1,17} facets by L-lysine adsorption. Templated Chiral Surfaces • Initial observation of the enantiospecific desorption of R- and S-PO from Pt(111) and Pd(111

Soleil a new powerful tool for materials science; Soleil, un nouvel outil puissant pour les sciences des materiaux

Energy Technology Data Exchange (ETDEWEB)

Baudelet, F.; Belkhou, R.; Briois, V.; Coati, A.; Dumas, P.; Flank, A.M.; Fontaine, P.; Garreau, Y.; Lyon, O.; Quinkal, I.; Roy, P.; Sauvage, M.; Sirotti, F.; Somogyi, A.; Thiaudiere, D. [Synchrotron SOLEIL, 91 - Gif-sur-Yvette (France); Coati, A.; Flank, A.M.; Fontaine, P.; Garreau, Y [LURE, Bat 209D Centre Universitaire, 91 - Orsay (France); Etgens, V.H. [Paris- 6-7 Univ., Campus Boucicaut, Institut des NanoSciences de Paris, 75 - Paris (France); Rochet, F. [Laboratoire de Chimie Physique - Matiere et Rayonnement, 75 - Paris (France)

2005-07-01

The first photons delivered by the third generation synchrotron source SOLEIL will be soon available for the scientific community. In this context, this paper presents an overview of the potentialities offered by this new machine for the study of materials. The outstanding brilliance of the SOLEIL source will enable to reduce by several orders of magnitude the data collection time for most of the synchrotron techniques (X-ray absorption spectroscopy - EXAFS, wide and small angle X-ray scattering - WAXS and SAXS, X-ray diffraction -XRD, photoelectron spectroscopy and microscopy-XPS and PEEM, etc.) thus allowing an operando approach of catalysis processes. The spatial resolution, from a few micrometers to sub micrometer scale, accessible by micro-diffraction and micro-spectroscopy in the wavelength range from the far IR to the hard X-rays, will provide spatial distributions of different elements (atomic and chemical state selectivity) in a material, from the working heterogeneous catalyst to the reservoir rocks. The reactivity of surfaces and nano-particles exposed to controlled gas fluxes will be studied by several in situ techniques. Finally the combination of different synchrotron techniques (diffraction, absorption and fluorescence X) and the access to complementary information obtained through the simultaneous combination of these techniques with those routinely applied in Materials Science, such as UV-Vis or Raman spectroscopy, will offer enlarged capabilities for the operando characterization of materials. (authors)

Preparative semiconductor photoredox catalysis: An emerging theme in organic synthesis

Directory of Open Access Journals (Sweden)

David W. Manley

2015-09-01

Full Text Available Heterogeneous semiconductor photoredox catalysis (SCPC, particularly with TiO2, is evolving to provide radically new synthetic applications. In this review we describe how photoactivated SCPCs can either (i interact with a precursor that donates an electron to the semiconductor thus generating a radical cation; or (ii interact with an acceptor precursor that picks up an electron with production of a radical anion. The radical cations of appropriate donors convert to neutral radicals usually by loss of a proton. The most efficient donors for synthetic purposes contain adjacent functional groups such that the neutral radicals are resonance stabilized. Thus, ET from allylic alkenes and enol ethers generated allyl type radicals that reacted with 1,2-diazine or imine co-reactants to yield functionalized hydrazones or benzylanilines. SCPC with tertiary amines enabled electron-deficient alkenes to be alkylated and furoquinolinones to be accessed. Primary amines on their own led to self-reactions involving C–N coupling and, with terminal diamines, cyclic amines were produced. Carboxylic acids were particularly fruitful affording C-centered radicals that alkylated alkenes and took part in tandem addition cyclizations producing chromenopyrroles; decarboxylative homo-dimerizations were also observed. Acceptors initially yielding radical anions included nitroaromatics and aromatic iodides. The latter led to hydrodehalogenations and cyclizations with suitable precursors. Reductive SCPC also enabled electron-deficient alkenes and aromatic aldehydes to be hydrogenated without the need for hydrogen gas.

Melting of heterogeneous vortex matter: The vortex 'nanoliquid'

Indian Academy of Sciences (India)

E ZELDOV2, A SOIBEL3, F de la CRUZ4,CJ van der BEEK5,. M KONCZYKOWSKI5, T ... 2Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot. 76100, Israel ..... heterogeneous nature of the vortex nanoliquid.

Impact of Secondary Interactions in Asymmetric Catalysis

OpenAIRE

Frölander, Anders

2007-01-01

This thesis deals with secondary interactions in asymmetric catalysis and their impact on the outcome of catalytic reactions. The first part revolves around the metal-catalyzed asymmetric allylic alkylation reaction and how interactions within the catalyst affect the stereochemistry. An OH–Pd hydrogen bond in Pd(0)–π-olefin complexes of hydroxy-containing oxazoline ligands was identified by density functional theory computations and helped to rationalize the contrasting results obtained emplo...

Core–shell nanoparticles: synthesis and applications in catalysis and electrocatalysis

Science.gov (United States)

Core–shell nanoparticles (CSNs) are a class of nanostructured materials that have recently received increased attention owing to their interesting properties and broad range of applications in catalysis, biology, materials chemistry and sensors. By rationally tuning the cores as ...

Monodisperse Platinum and Rhodium Nanoparticles as Model Heterogeneous Catalysts

Energy Technology Data Exchange (ETDEWEB)

Grass, Michael Edward [Univ. of California, Berkeley, CA (United States)

2008-09-01

Model heterogeneous catalysts have been synthesized and studied to better understand how the surface structure of noble metal nanoparticles affects catalytic performance. In this project, monodisperse rhodium and platinum nanoparticles of controlled size and shape have been synthesized by solution phase polyol reduction, stabilized by polyvinylpyrrolidone (PVP). Model catalysts have been developed using these nanoparticles by two methods: synthesis of mesoporous silica (SBA-15) in the presence of nanoparticles (nanoparticle encapsulation, NE) to form a composite of metal nanoparticles supported on SBA-15 and by deposition of the particles onto a silicon wafer using Langmuir-Blodgett (LB) monolayer deposition. The particle shapes were analyzed by transmission electron microscopy (TEM) and high resolution TEM (HRTEM) and the sizes were determined by TEM, X-ray diffraction (XRD), and in the case of NE samples, room temperature H₂ and CO adsorption isotherms. Catalytic studies were carried out in homebuilt gas-phase reactors. For the nanoparticles supported on SBA-15, the catalysts are in powder form and were studied using the homebuilt systems as plug-flow reactors. In the case of nanoparticles deposited on silicon wafers, the same systems were operated as batch reactors. This dissertation has focused on the synthesis, characterization, and reaction studies of model noble metal heterogeneous catalysts. Careful control of particle size and shape has been accomplished though solution phase synthesis of Pt and Rh nanoparticles in order to elucidate further structure-reactivity relationships in noble metal catalysis.

The role of eclogite in the mantle heterogeneity at Cape Verde

DEFF Research Database (Denmark)

Barker, Abigail Katrine; Holm, Paul Martin; Troll, Valentin R.

2014-01-01

The Cape Verde hotspot, like many other Ocean Island Basalt provinces, demonstrates isotopic heterogeneity on a 100–200 km scale. The heterogeneity is represented by the appearance of an EM1-like component at several of the southern islands and with a HIMU-like component present throughout...... have been limited. We apply the minor elements in olivine approach (Sobolev et al. in Nature 434:590–597, 2005; Science, doi:10.1126/science.1138113, 2007), to determine and quantify the contributions of peridotite, pyroxenite and eclogite melts to the mantle heterogeneity observed at Cape Verde. Cores...... of olivine phenocrysts of the Cape Verde volcanics have low Mn/FeO and low Ni*FeO/MgO that deviate from the negative trend of the global array. The global array is defined by mixing between peridotite and pyroxenite, whereas the Cape Verde volcanics indicate contribution of an additional eclogite source...

Electroreduction of CO2 Catalyzed by a Heterogenized Zn–Porphyrin Complex with a Redox-Innocent Metal Center

Science.gov (United States)

2017-01-01

Transition-metal-based molecular complexes are a class of catalyst materials for electrochemical CO2 reduction to CO that can be rationally designed to deliver high catalytic performance. One common mechanistic feature of these electrocatalysts developed thus far is an electrogenerated reduced metal center associated with catalytic CO2 reduction. Here we report a heterogenized zinc–porphyrin complex (zinc(II) 5,10,15,20-tetramesitylporphyrin) as an electrocatalyst that delivers a turnover frequency as high as 14.4 site–1 s–1 and a Faradaic efficiency as high as 95% for CO2 electroreduction to CO at −1.7 V vs the standard hydrogen electrode in an organic/water mixed electrolyte. While the Zn center is critical to the observed catalysis, in situ and operando X-ray absorption spectroscopic studies reveal that it is redox-innocent throughout the potential range. Cyclic voltammetry indicates that the porphyrin ligand may act as a redox mediator. Chemical reduction of the zinc–porphyrin complex further confirms that the reduction is ligand-based and the reduced species can react with CO2. This represents the first example of a transition-metal complex for CO2 electroreduction catalysis with its metal center being redox-innocent under working conditions. PMID:28852698

Cheese whey protein recovery by ultrafiltration through transglutaminase (TG) catalysis whey protein cross-linking.

Science.gov (United States)

Wen-Qiong, Wang; Lan-Wei, Zhang; Xue, Han; Yi, Lu

2017-01-15

In whey ultrafiltration (UF) production, two main problems are whey protein recovery and membrane fouling. In this study, membrane coupling protein transglutaminase (TG) catalysis protein cross-linking was investigated under different conditions to find out the best treatment. We found that the optimal conditions for protein recovery involved catalyzing whey protein cross-linking with TG (40U/g whey proteins) at 40°C for 60min at pH 5.0. Under these conditions, the recovery rate was increased 15-20%, lactose rejection rate was decreased by 10%, and relative permeate flux was increase 30-40% compared to the sample without enzyme treatment (control). It was noticeable that the total resistance and cake resistance were decreased after enzyme catalysis. This was mainly due to the increased particle size and decreased zeta potential. Therefore, membrane coupling enzyme catalysis protein cross-linking is a potential means for further use. Copyright © 2016. Published by Elsevier Ltd.

Enzyme catalysis: a new definition accounting for noncovalent substrate- and product-like states.

Science.gov (United States)

Purich, D L

2001-07-01

Biological catalysis frequently causes changes in noncovalent bonding. By building on Pauling's assertion that any long-lived, chemically distinct interaction is a chemical bond, this article redefines enzyme catalysis as the facilitated making and/or breaking of chemical bonds, not just of covalent bonds. It is also argued that nearly every ATPase or GTPase is misnamed as a hydrolase and actually belongs to a distinct class of enzymes, termed here 'energases'. By transducing covalent bond energy into mechanical work, energases mediate such fundamental processes as protein folding, self-assembly, G-protein interactions, DNA replication, chromatin remodeling and even active transport.

Cyclopropanes and hypervalent iodine reagents: high energy compounds for applications in synthesis and catalysis.

Science.gov (United States)

Fernández González, Davinia; De Simone, Filippo; Brand, Jonathan P; Nicolai, Stefano; Waser, Jérôme

2011-01-01

One of the major challenges faced by organic chemistry is the efficient synthesis of increasingly complex molecules. Since October 2007, the Laboratory of Catalysis and Organic Synthesis (LCSO) at EPFL has been working on the development of catalytic reactions based on the Umpolung of the innate reactivity of functional groups. Electrophilic acetylene synthons have been developed using the exceptional properties of ethynyl benziodoxolone (EBX) hypervalent iodine reagents for the alkynylation of heterocycles and olefins. The obtained acetylenes are important building blocks for organic chemistry, material sciences and chemical biology. The ring-strain energy of donor-acceptor cyclopropanes was then used in the first catalytic formal homo-Nazarov cyclization. In the case of aminocyclopropanes, the method could be applied in the synthesis of the alkaloids aspidospermidine and goniomitine. The developed methods are expected to have a broad potential for the synthesis and functionalization of complex organic molecules, including carbocycles and heterocycles.

A case study of Markdale High School's implementation of heterogeneously-grouped classes in English, mathematics, science, and social studies

Science.gov (United States)

Pierre-Louis, Fred

The purpose of this study was to describe Markdale High School's change from separate college preparatory and general level classes to heterogeneously-grouped classes in English, mathematics, science, and social studies, with particular emphasis on the principal's leadership style, change process, and teacher concerns (Hall & Hord, 2006) experienced during this effort. The researcher used Hall and Hord's (2006) Concern-Based Adoption Model (CBAM) as a conceptual framework. Specifically, the researcher applied three elements of the CBAM model: (a) the Twelve Principles of Change, (b) the Change Facilitator Styles, and (c) the Stages of Concerns. Hall and Hord's framework served as a lens through which the researcher analyzed all data. The researcher used a mixed-method (qualitative and quantitative) approach to answer the four research questions. The participants completed three instruments: (a) the Stages of Concern Questionnaire (SoCQ), (b) the Principles of Change Survey, and (c) the Facilitator Style Survey. All three instruments were self-report, paper-pencil surveys. The sample included 72 faculty members who experienced the change over the past three years. Findings from the three data sources and the school principal's comments during debriefing are indicated for each research question and reported by unit of analysis. Respective to the research questions, the researcher concluded that: (1) Markdale High School accomplished the change by implementing both structural and instructional changes supporting to the change to heterogeneous grouping; (2) even though teachers had divergent opinions on the school principal's facilitation style, the principal thought of himself as an incrementalist and a practitioner of differentiated facilitation styles; (3) while half of the faculty felt that they received formal training on heterogeneous grouping, (4) half felt that they did not have a choice in the decision-making process as it occurred with college preparatory and

Predictive Modeling in Actinide Chemistry and Catalysis

Energy Technology Data Exchange (ETDEWEB)

Yang, Ping [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2016-05-16

These are slides from a presentation on predictive modeling in actinide chemistry and catalysis. The following topics are covered in these slides: Structures, bonding, and reactivity (bonding can be quantified by optical probes and theory, and electronic structures and reaction mechanisms of actinide complexes); Magnetic resonance properties (transition metal catalysts with multi-nuclear centers, and NMR/EPR parameters); Moving to more complex systems (surface chemistry of nanomaterials, and interactions of ligands with nanoparticles); Path forward and conclusions.

Two-dimensional zeolites in catalysis: current status and perspectives

Czech Academy of Sciences Publication Activity Database

Opanasenko, Maksym; Roth, Wieslaw Jerzy; Čejka, Jiří

2016-01-01

Roč. 6, č. 8 (2016), s. 2467-2484 ISSN 2044-4753 R&D Projects: GA ČR GP13-17593P; GA ČR(CZ) GAP106/12/0189 Institutional support: RVO:61388955 Keywords : mesoporous molecular sieves * catalysis * acylation reactions Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 5.773, year: 2016

Kokes Awards for the 23rd North American Catalysis Society Meeting

Energy Technology Data Exchange (ETDEWEB)

Jacobs, Gary [University of Kentucky Research Foundation, Lexington, KY (United States)

2014-01-31

The Tri-State Catalysis Society awarded 107 Kokes Travel Awards. The program was very successful and to date this was the most Kokes Travel Awards ever awarded at a North American Catalysis Society Meeting. It provided students who merited an award the opportunity to attend the meeting, present a paper in the form of either an oral presentation or a poster presentation, and to serve the North American Catalysis Society by participating in the organization of the meeting. Students worked very hard during the week of the meeting to make it a success. Financial support for the Kokes awards was provided by DOE, NSF, NACS, as well as the Tri-State Catalysis Society, the latter through fund raising activities, and other donations. AT the meeting, each student received over $1050 in kind to offset the costs of registration fees ($260), hotel accommodations ($295.7), transportation ($400 travel allowance), as well as T-shirts ($20), and banquet tickets ($95 provided by donations from society members). In addition, for the first time, students received certificates that were signed by the President of NACS, Professor Enrique Iglesia, and by the Kokes Awards Chair, Gary Jacobs (see last page). A list of meeting co-chairs (i.e., Uschi M. Graham, Umit S. Ozkan, and Madan Bhassin) and the honorary chair (Burtron H. Davis) was also included on the certificate, along with the name of the recipient. The awardees were chosen on a merit-based guideline which also included the requirements of having a presentation accepted at the meeting and being a student at a North American University. The Richard J. Kokes Student Travel Award Committee (Gary Jacobs, Rodney Andrews, and Peter Smirniotis) with help from the Organizing Committee were able to secure money from four sources as detailed in Table 1. As detailed by our Treasurer, Dr. Helge Toufar of Clariant, the total amount spent was $105,000.

Synthesis of Pt-Ru PSB-Py catalysis by {gamma}-irradiation and their electrocatalytic efficiency for methanol oxidation

Energy Technology Data Exchange (ETDEWEB)

Yoon, Jung Ah; Sim, Kwang Sik; Choi, Seong Ho [Hannam University, Daejeon (Korea, Republic of); Jung, Sung Hee [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2009-09-15

We report here that deposition of Pt-Ru catalysis on the surface of core-shell conductive balls by radiation-chemical reduction of Pt and Ru ions, in order to use as catalysis in a fuel cell. The poly(styrene-co-4-vinylphenylboronic acid)-pyrrole (PSB-Py) with core-shell structure was obtained by in situ polymerization of pyrrole in the presence of the poly(styrene-co-4-vinylphenylboronic acid) (PSB). Subsequently, Pt-Ru catalysis were deposited onto PSB-Py ball by {gamma}-irradiation, in the presence/absence of poly(vinypyrolidone) (PVP) to prepare electrocatalysis for a fuel cell. The catalytic efficiency of Pt-Ru PSB-Py catalyst was examined for carbon monoxide (CO) stripping and methanol oxidation.

Synthesis of Pt-Ru PSB-Py catalysis by γ-irradiation and their electrocatalytic efficiency for methanol oxidation

International Nuclear Information System (INIS)

Yoon, Jung Ah; Sim, Kwang Sik; Choi, Seong Ho; Jung, Sung Hee

2009-01-01

We report here that deposition of Pt-Ru catalysis on the surface of core-shell conductive balls by radiation-chemical reduction of Pt and Ru ions, in order to use as catalysis in a fuel cell. The poly(styrene-co-4-vinylphenylboronic acid)-pyrrole (PSB-Py) with core-shell structure was obtained by in situ polymerization of pyrrole in the presence of the poly(styrene-co-4-vinylphenylboronic acid) (PSB). Subsequently, Pt-Ru catalysis were deposited onto PSB-Py ball by γ-irradiation, in the presence/absence of poly(vinypyrolidone) (PVP) to prepare electrocatalysis for a fuel cell. The catalytic efficiency of Pt-Ru PSB-Py catalyst was examined for carbon monoxide (CO) stripping and methanol oxidation

Heterogeneous Materials I and Heterogeneous Materials II

International Nuclear Information System (INIS)

Knowles, K M

2004-01-01

In these two volumes the author provides a comprehensive survey of the various mathematically-based models used in the research literature to predict the mechanical, thermal and electrical properties of hetereogeneous materials, i.e., materials containing two or more phases such as fibre-reinforced polymers, cast iron and porous ceramic kiln furniture. Volume I covers linear properties such as linear dielectric constant, effective electrical conductivity and elastic moduli, while Volume II covers nonlinear properties, fracture and atomistic and multiscale modelling. Where appropriate, particular attention is paid to the use of fractal geometry and percolation theory in describing the structure and properties of these materials. The books are advanced level texts reflecting the research interests of the author which will be of significant interest to research scientists working at the forefront of the areas covered by the books. Others working more generally in the field of materials science interested in comparing predictions of properties with experimental results may well find the mathematical level quite daunting initially, as it is apparent that the author assumes a level of mathematics consistent with that taught in final year undergraduate and graduate theoretical physics courses. However, for such readers it is well worth persevering because of the in-depth coverage to which the various models are subjected, and also because of the extensive reference lists at the back of both volumes which direct readers to the various source references in the scientific literature. Thus, for the wider materials science scientific community the two volumes will be a valuable library resource. While I would have liked to see more comparison with experimental data on both ideal and 'real' heterogeneous materials than is provided by the author and a discussion of how to model strong nonlinear current--voltage behaviour in systems such as zinc oxide varistors, my overall

Fenton-like oxidation of 2,4-DCP in aqueous solution using iron-based nanoparticles as the heterogeneous catalyst.

Science.gov (United States)

Li, Renchao; Gao, Ying; Jin, Xiaoying; Chen, Zuliang; Megharaj, Mallavarapu; Naidu, Ravendra

2015-01-15

In this report, various iron-based nanoparticles (nZVI, n-Ni/Fe, n-Pd/Fe) were used for both heterogeneous Fenton oxidation of 2,4-dichlorophenol (2,4-DCP) and reductive dechlorination of 2,4-DCP in order to understand their roles in the Fenton oxidation and the reductive degradation of 2,4-DCP. The dechlorination efficiency of 2,4-DCP using nZVI, n-Ni/Fe, n-Fe/Pd and Fe(2)(+) was 6.48%, 6.80%, 15.95%, 5.02%, while Fenton oxidation efficiency of 2,4-DCP was 57.87%, 34.23%, 27.94%, 19.61% after 180 min, respectively. The new findings included a higher dechlorination using n-Fe/Pd due to Pd effective catalysis and the effective heterogeneous Fenton oxidation using nZVI depending on reductive dechlorination and heterogeneous Fenton oxidation occurs simultaneously. However, nZVI as the potential catalyst for heterogeneous Fenton was observed, and SEM, EDS and XRD demonstrate that change on the nZVI surface occurred due to the Fe(2+) leaching, and Total Organic Carbon (TOC) (30.71%) shows that 2,4-DCP was degraded. Furthermore, the experiment indicates that the pH values and concentration of 2,4-DCP significantly impacted on the heterogeneous Fenton oxidation of 2,4-DCP and the data fits well with the pseudo first-order kinetic model, which was a diffusion-controlled reaction. Finally, a possible mechanism for degradation of 2,4-DCP was proposed. Copyright © 2014 Elsevier Inc. All rights reserved.

Methylene blue and 4-chloro phenol degradation by photo catalysis with ultraviolet light, using TiO2 as catalyst

International Nuclear Information System (INIS)

Martinez H, A.

2010-01-01

Within the decontamination and remediation processes of the contaminated waters, as the refining or tertiary processes are the Advanced Oxidation Technologies. Among this technology is the heterogeneous photo catalysis, which is the object of this work to de grate 4-chloro phenol and methylene blue, using as semiconductor commercial titanium dioxide (TiO 2 ). On the degradation the combination is exposed in the use of TiO 2 under gamma irradiation of 60 Co at different doses 400, 500, 800, 1000 and 1500 kGy. The organic compounds degradation was determined and the results show that to more radiation dose, the material is modified in such way that shows a major absorption of the organic compound, in the same way it is determined that to more dose which undergoes the TiO 2 generally a major degradation is observed, but also it is has to give a more time of previous stabilization, for that the degradation is observed of better way. (Author)

Treatment of the liquid waste of the laboratories of the engineering Department by means of photo catalysis

International Nuclear Information System (INIS)

Porras, Paula; Avalos, Yasmin; Mejia, Gloria; Penuela, Gustavo

2000-01-01

In this paper are showed the results of wastewater treatment of CIA and ISA laboratories of engineering Department. Photo catalysis was used in treatment of wastewater, with a removal between 52% and 68% as chemical oxygen demand (COD) during 6 hours of photo degradation. In photo catalysis, TiO 2 , hydrogen peroxide and ultraviolet light were used

Radio catalysis application in degradation of complex organic samples

International Nuclear Information System (INIS)

Moreno L, A.

2014-01-01

The generation of wastewater is a consequence of human activities, industries to be the generators of a large part of these discharges. These contaminated waters can be processed for their remediation; however the recalcitrant organic compounds are hardly removed through conventional treatments applied, so that new technologies have been developed for disposal such as the advanced oxidation technologies or processes. With the aim of the study is to apply ionizing radiation as a method of remediation in wastewater, in this work were carried out experiments of radiolysis and radio catalysis, which are techniques considered advanced oxidation technologies, that consist in irradiate with 60 Co gamma radiation solutions of 4- chloro phenol and methylene blue, applied at different concentrations and using as process control measurements of the compound not degraded by UV-vis spectrophotometry at 507 and 664 nm for 4-chloro phenol and methylene blue respectively. At doses greater than 2.5 kGy were near-zero degradation. Degradation experiments were also conducted by photo catalysis by irradiation with a UV lamp of 354 nm wavelength. For 4-chloro phenol results showed that degradation is efficient (39%). With those previous results, these techniques were applied to degrade complex mixtures of organic compounds from samples of wastewater from a sewage treatment plant, where was considered as process control measurement of the dissolved organic carbon obtained by a spectrophotometric analysis at 254 nm, and a maximum of 26% degradation was obtained by applying 80 kGy. On the other hand, a series of experiments fractionating the irradiations at intervals of 20 kGy to obtain a cumulative dose of 80 kGy, which was 2.8 times greater with respect to degradation by radio catalysis with continuous irradiation. (Author)

Towards a generic model of catalysis | Grayson | Bulletin of the ...

African Journals Online (AJOL)

We consider polarizabilities and hardness/softness parameters to see how local polarizations of the electron density may also be responsible for activation of a localised area of a large molecule. KEY WORDS: Electrostatic catalysis, Geometrical strain, Environment strain, Entasis, Polarizability, Hardness and softness. Bull.

Heterogeneous Catalysis for Thermochemical Conversion Publications |

Science.gov (United States)

, Angewandte Chemie International Edition Characterization of upgraded fast pyrolysis oak oil distillate thermometer, the middle a condenser, and the right a syringe with liquid. There are organisms in the flask Illustration showing an image of a tree on the far left with an arrow leading right labeled Enlarge image

Solar-Powered Plasmon-Enhanced Heterogeneous Catalysis

Directory of Open Access Journals (Sweden)

Naldoni Alberto

2016-06-01

Full Text Available Photocatalysis uses semiconductors to convert sunlight into chemical energy. Recent reports have shown that plasmonic nanostructures can be used to extend semiconductor light absorption or to drive direct photocatalysis with visible light at their surface. In this review, we discuss the fundamental decay pathway of localized surface plasmons in the context of driving solar-powered chemical reactions. We also review different nanophotonic approaches demonstrated for increasing solar-to-hydrogen conversion in photoelectrochemical water splitting, including experimental observations of enhanced reaction selectivity for reactions occurring at the metalsemiconductor interface. The enhanced reaction selectivity is highly dependent on the morphology, electronic properties, and spatial arrangement of composite nanostructures and their elements. In addition, we report on the particular features of photocatalytic reactions evolving at plasmonic metal surfaces and discuss the possibility of manipulating the reaction selectivity through the activation of targeted molecular bonds. Finally, using solar-to-hydrogen conversion techniques as an example, we quantify the efficacy metrics achievable in plasmon-driven photoelectrochemical systems and highlight some of the new directions that could lead to the practical implementation of solar-powered plasmon-based catalytic devices.

Catalysis of heat-to-work conversion in quantum machines

Science.gov (United States)

Ghosh, A.; Latune, C. L.; Davidovich, L.; Kurizki, G.

2017-11-01

We propose a hitherto-unexplored concept in quantum thermodynamics: catalysis of heat-to-work conversion by quantum nonlinear pumping of the piston mode which extracts work from the machine. This concept is analogous to chemical reaction catalysis: Small energy investment by the catalyst (pump) may yield a large increase in heat-to-work conversion. Since it is powered by thermal baths, the catalyzed machine adheres to the Carnot bound, but may strongly enhance its efficiency and power compared with its noncatalyzed counterparts. This enhancement stems from the increased ability of the squeezed piston to store work. Remarkably, the fraction of piston energy that is convertible into work may then approach unity. The present machine and its counterparts powered by squeezed baths share a common feature: Neither is a genuine heat engine. However, a squeezed pump that catalyzes heat-to-work conversion by small investment of work is much more advantageous than a squeezed bath that simply transduces part of the work invested in its squeezing into work performed by the machine.

Surface and catalysis science in the Materials and Molecular Research Division

International Nuclear Information System (INIS)

1980-01-01

Surface science studies at Lawrence Berkeley Laboratory are detailed. Subject areas include: structure of surfaces and adsorbed monolayers; reduction and oxidation of surfaces; catalytic chemistry; and structure of interfaces and thin films

NMR Computational Studies of Solid Acidity/Fundamental Studies of Catalysis by Solid Acids

Energy Technology Data Exchange (ETDEWEB)

James F. Haw

2008-06-28

This project focused on catalysis by zeolites and the synergy of spectroscopic characterization and theoretical modeling. In collaboration with the Waroquier group in Belgium we used state-of-the-art quantum chemical simulations on a supramolecular model of both the HZSM-5 zeolite and the co-catalytic hydrocarbon pool species and calculated a full catalytic cycle (including all rate constants) for methanol-to-olefin (MTO) catalysis involving a hydrocarbon pool species. This work not only represents the most robust computational analysis of a successful MTO route to date, but it also succeeds in tying together the many experimental clues. That work was featured on the cover of Angewandte Chemie. More recently we elucidated several unsuspected roles for formaldehyde in methanol to olefin catalysis. Formaldehyde proves to be a key species responsible for both the growth of the catalytically active hydrocarbon pool and its inevitable aging into deactivated polycyclic aromatic species. The apparent inevitability of formaldehyde formation at high temperatures, in particular in contact with active metal or metal oxide surfaces, may put some fundamental limitations on the economic potential of conversion of methanol to olefins.

Examining the role of glutamic acid 183 in chloroperoxidase catalysis

NARCIS (Netherlands)

Yi, X.; Conesa, A.; Punt, P.J.; Hager, L.P.

2003-01-01

Site-directed mutagenesis has been used to investigate the role of glutamic acid 183 in chloroperoxidase catalysis. Based on the x-ray crystallographic structure of chloroperoxidase, Glu-183 is postulated to function on distal side of the heme prosthetic group as an acid-base catalyst in

Thermoswitchable catalysis controlled by reversible dispersion/aggregation change of nanoreactors in the presence of α-CD polymers

Science.gov (United States)

Li, Yinfeng; Hu, Jie; Niu, Chengrong; Leng, Jinghang; Li, Songjun

2018-06-01

The present work was aimed at preparing a thermosensitive nanoreactor system which could adjust its dispersion/aggregation status according to external temperature change to achieve the switchable catalysis. The mesoporous silica nanoparticle (MSNP) was selected as the framework material of the nanoreactor, and Ag nanoparticles were encapsulated in the mesoporous silica by an in situ reaction. Dodecyl groups were introduced onto MSNP surface, which could transform reversibly between complexation and disassociation with α-cyclodextrin (CD) cavity upon temperature change. It was found that the nanoreactors aggregated and the catalysis was effectively switched ‘off’ in the presence of CD polymers at low temperature (20 °C). However, when the temperature increased to 50 °C, the nanoreactors redispersed and catalysis successfully switched ‘on’.

Soleil a new powerful tool for materials science

International Nuclear Information System (INIS)

Baudelet, F.; Belkhou, R.; Briois, V.; Coati, A.; Dumas, P.; Flank, A.M.; Fontaine, P.; Garreau, Y.; Lyon, O.; Quinkal, I.; Roy, P.; Sauvage, M.; Sirotti, F.; Somogyi, A.; Thiaudiere, D.; Coati, A.; Flank, A.M.; Fontaine, P.; Garreau, Y; Etgens, V.H.; Rochet, F.

2005-01-01

The first photons delivered by the third generation synchrotron source SOLEIL will be soon available for the scientific community. In this context, this paper presents an overview of the potentialities offered by this new machine for the study of materials. The outstanding brilliance of the SOLEIL source will enable to reduce by several orders of magnitude the data collection time for most of the synchrotron techniques (X-ray absorption spectroscopy - EXAFS, wide and small angle X-ray scattering - WAXS and SAXS, X-ray diffraction -XRD, photoelectron spectroscopy and microscopy-XPS and PEEM, etc.) thus allowing an operando approach of catalysis processes. The spatial resolution, from a few micrometers to sub micrometer scale, accessible by micro-diffraction and micro-spectroscopy in the wavelength range from the far IR to the hard X-rays, will provide spatial distributions of different elements (atomic and chemical state selectivity) in a material, from the working heterogeneous catalyst to the reservoir rocks. The reactivity of surfaces and nano-particles exposed to controlled gas fluxes will be studied by several in situ techniques. Finally the combination of different synchrotron techniques (diffraction, absorption and fluorescence X) and the access to complementary information obtained through the simultaneous combination of these techniques with those routinely applied in Materials Science, such as UV-Vis or Raman spectroscopy, will offer enlarged capabilities for the operando characterization of materials. (authors)

Amino-functionalized metal-organic frameworks as tunable heterogeneous basic catalysts

Energy Technology Data Exchange (ETDEWEB)

Fischer, M.; Hartmann, M. [Erlangen-Nuernberg Univ., Erlangen (Germany). Erlangen Catalysis Resource Center

2011-07-01

Metal-organic framework (MOF) materials have been explored for applications in heterogeneous catalysis in recent years. In addition to the use of MOFs as supports for the deposition of highly dispersed metal particles, the incorporation of active centers such as coordinatively unsaturated metal sites and the functionalization of the organic linkers with acidic or basic groups seems to be most promising. In our contribution, three different MOFs carrying amino groups at their organic linkers, namely Fe-MIL-101-NH{sub 2} (S{sub BET} = 3438 m{sup 2}g{sup -1}), Al-MIL-101-NH{sub 2} (S{sub BET} = 3099 m{sup 2}g{sup -1}) and CAU-1 (S{sub BET} = 1492 m{sup 2}g{sup -1}), were synthesized and tested in the Knoevenagel condensation of benzaldehyde with malononitrile and with ethyl cyanoacetate, respectively. It is shown that the expected products benzylidenemalononitrile (BzMN) and ethyl a-cyanocinnamate (EtCC) are formed with selectivities of more than 99 % and yields of 90 to 95 % after 3 h (for BzMN). Due to the very small pore windows of CAU-1 (0.3 to 0.4 nm) the reaction proceeds much slower over this catalyst in comparison to the amino-MIL-101 derivatives, which possess open pore windows of up to 1.6 nm. Finally, leaching tests confirm that the reaction is heterogeneously catalyzed. Moreover, the catalysts are recyclable without significant loss of activity. (orig.)

FATTY ACID ETHYL ESTERS FROM MICROALGAE OF Scenedesmus ecornis BY ENZYMATIC AND ACID CATALYSIS

Directory of Open Access Journals (Sweden)

Gabryelle F. de Almeida

Full Text Available Microalgae are an indispensable food source for the various growth stages of mollusks, crustaceans, and several fish species. Using a microalgae biomass present in the Amazonian ecosystem (Macapá-AP, we study extraction methods for fatty acid such as solvent extraction (magnetic stirring and/or Soxhlet and/or hydrolysis (acid and/or enzymatic catalysis followed by esterification and/or direct transesterification. Extraction of crude triacylglycerides by mechanical stirring at room temperature was more efficient than continuous reflux (Soxhlet. Subsequently, the lipid extract was subject to transesterification with ethanol and CAL-B as a biocatalyst, leading to production of fatty acid ethyl esters (FAEE. Additionally, FAEEs were prepared by hydrolysis of crude triacylglycerides followed by acid-mediated esterification or enzymatic catalysis (lipase. In this case, the type of catalyst did not significantly influence FAEE yields. In the lipid extract, we identified palmitic, linoleic, oleic, and stearic acids with palmitic acid being the most abundant. Our results suggest that enzymatic catalysis is a viable method for the extraction of lipids in the microalga, Scenedesmus ecornis.

Sustainable preparation of supported metal nanoparticles and their applications in catalysis.

Science.gov (United States)

Campelo, Juan M; Luna, Diego; Luque, Rafael; Marinas, José M; Romero, Antonio A

2009-01-01

Metal nanoparticles have attracted much attention over the last decade owing to their unique properties as compared to their bulk metal equivalents, including a large surface-to-volume ratio and tunable shapes. To control the properties of nanoparticles with particular respect to shape, size and dispersity is imperative, as these will determine the activity in the desired application. Supported metal nanoparticles are widely employed in catalysis. Recent advances in controlling the shape and size of nanoparticles have opened the possibility to optimise the particle geometry for enhanced catalytic activity, providing the optimum size and surface properties for specific applications. This Review describes the state of the art with respect to the preparation and use of supported metal nanoparticles in catalysis. The main groups of such nanoparticles (noble and transition metal nanoparticles) are highlighted and future prospects are discussed.

Molecular complexity from polyunsaturated substrates: the gold catalysis approach.

Science.gov (United States)

Fensterbank, Louis; Malacria, Max

2014-03-18

Over the last two decades, electrophilic catalysis relying on platinum(II), gold(I), and gold(III) salts has emerged as a remarkable synthetic methodology. Chemists have discovered a large variety of organic transformations that convert a great assortment of highly functionalized precursors into valuable final products. In many cases, these methodologies offer unique features, allowing access to unprecedented molecular architectures. Due to the mild reaction conditions and high function compatibility, scientists have successfully developed applications in total synthesis of natural products, as well as in asymmetric catalysis. In addition, all these developments have been accompanied by the invention of well-tailored catalysts, so that a palette of different electrophilic agents is now commercially available or readily synthesized at the bench. In some respects, researchers' interests in developing homogeneous gold catalysis can be compared with the Californian gold rush of the 19th century. It has attracted into its fervor thousands of scientists, providing a huge number of versatile and important reports. More notably, it is clear that the contribution to the art of organic synthesis is very valuable, though the quest is not over yet. Because they rely on the intervention of previously unknown types of intermediates, new retrosynthetic disconnections are now possible. In this Account, we discuss our efforts on the use of readily available polyunsaturated precursors, such as enynes, dienynes, allenynes, and allenenes to give access to highly original polycyclic structures in a single operation. These transformations transit via previously undescribed intermediates A, B, D, F, and H that will be encountered later on. All these intermediates have been determined by both ourselves and others by DFT calculations and in some cases have been confirmed on the basis of experimental data. In addition, dual gold activation can be at work in some of these transformations

Build/Couple/Pair and Multifunctional Catalysis Strategies for the Synthesis of Heterocycles from Simple Starting Materials

DEFF Research Database (Denmark)

Ascic, Erhad

. Multifunctional Catalysis: Synthesis of Heterocycles from Simple Starting Materials A multifunctional catalysis approach, involving a ruthenium-catalyzed tandem ringclosing metathesis/isomerization/N-acyliminium cyclization sequence, is described. Double bonds created during ring-closing metathesis isomerize......, a series of interesting indolizidinones are formed in good yields with excellent diastereoselectivities, including a formal total synthesis of the antiparasitic natural product harmicine and the first total synthesis of mescalotam. Furthermore, preliminary asymmetric variants of the tandem process have...

Summaries of FY 1978 research in the chemical sciences

International Nuclear Information System (INIS)

1979-04-01

This report provides on indexed compilation of individual research projects that make up the DOE Chemical Sciences basic energy research program. The DOE in-house projects and projects supported at university and other non-DOE laboratories are reported in separate sections. An analysis and summary of funding levels are given. The research covers areas such as coal chemistry, catalysis, H 2 , combustion, solar photoconversion, fusion, atmospheric chemistry, and MHD

Summaries of FY 1978 research in the chemical sciences

Energy Technology Data Exchange (ETDEWEB)

Pierce, Elliot S.

1979-04-01

This report provides on indexed compilation of individual research projects that make up the DOE Chemical Sciences basic energy research program. The DOE in-house projects and projects supported at university and other non-DOE laboratories are reported in separate sections. An analysis and summary of funding levels are given. The research covers areas such as coal chemistry, catalysis, H/sub 2/, combustion, solar photoconversion, fusion, atmospheric chemistry, and MHD. (DLC)

Homogeneous, heterogeneous and enzymatic catalysis for transesterification of high free fatty acid oil (waste cooking oil) to biodiesel: a review.

Science.gov (United States)

Lam, Man Kee; Lee, Keat Teong; Mohamed, Abdul Rahman

2010-01-01

In the last few years, biodiesel has emerged as one of the most potential renewable energy to replace current petrol-derived diesel. It is a renewable, biodegradable and non-toxic fuel which can be easily produced through transesterification reaction. However, current commercial usage of refined vegetable oils for biodiesel production is impractical and uneconomical due to high feedstock cost and priority as food resources. Low-grade oil, typically waste cooking oil can be a better alternative; however, the high free fatty acids (FFA) content in waste cooking oil has become the main drawback for this potential feedstock. Therefore, this review paper is aimed to give an overview on the current status of biodiesel production and the potential of waste cooking oil as an alternative feedstock. Advantages and limitations of using homogeneous, heterogeneous and enzymatic transesterification on oil with high FFA (mostly waste cooking oil) are discussed in detail. It was found that using heterogeneous acid catalyst and enzyme are the best option to produce biodiesel from oil with high FFA as compared to the current commercial homogeneous base-catalyzed process. However, these heterogeneous acid and enzyme catalyze system still suffers from serious mass transfer limitation problems and therefore are not favorable for industrial application. Nevertheless, towards the end of this review paper, a few latest technological developments that have the potential to overcome the mass transfer limitation problem such as oscillatory flow reactor (OFR), ultrasonication, microwave reactor and co-solvent are reviewed. With proper research focus and development, waste cooking oil can indeed become the next ideal feedstock for biodiesel.

The role of Fischer-Tropsch catalysis in solar nebula chemistry

NARCIS (Netherlands)

Kress, ME; Tielens, AGGM

Fischer-Tropsch catalysis, the iron/nickel catalyzed conversion of CO and H(2) to hydrocarbons, would have been the only thermally-driven pathway available in the solar nebula to convert CO into other forms of carbon. A major issue in meteoritics is to determine the origin of meteoritic organics:

Organometallic chemistry of bimetallic compounds. Progress report, January 1992--July 1995

International Nuclear Information System (INIS)

Casey, C.P.

1994-07-01

Four main projects at the interface between organometallic chemistry and homogeneous catalysis were pursued. All were designed to give increased understanding of the mechanisms of organometallic reactions related to homogeneous and heterogeneous catalysis. In addition, a minor study involving η 5 -to η 1 -cyclopentadienyl ring slippage in catalysis was completed

Characterization techniques for graphene-based materials in catalysis

Directory of Open Access Journals (Sweden)

Maocong Hu

2017-06-01

Full Text Available Graphene-based materials have been studied in a wide range of applications including catalysis due to the outstanding electronic, thermal, and mechanical properties. The unprecedented features of graphene-based catalysts, which are believed to be responsible for their superior performance, have been characterized by many techniques. In this article, we comprehensively summarized the characterization methods covering bulk and surface structure analysis, chemisorption ability determination, and reaction mechanism investigation. We reviewed the advantages/disadvantages of different techniques including Raman spectroscopy, X-ray photoelectron spectroscopy (XPS, Fourier transform infrared spectroscopy (FTIR and Diffuse Reflectance Fourier Transform Infrared Spectroscopy (DRIFTS, X-Ray diffraction (XRD, X-ray absorption near edge structure (XANES and X-ray absorption fine structure (XAFS, atomic force microscopy (AFM, scanning electron microscopy (SEM, transmission electron microscopy (TEM, high-resolution transmission electron microscopy (HRTEM, ultraviolet-visible spectroscopy (UV-vis, X-ray fluorescence (XRF, inductively coupled plasma mass spectrometry (ICP, thermogravimetric analysis (TGA, Brunauer–Emmett–Teller (BET, and scanning tunneling microscopy (STM. The application of temperature-programmed reduction (TPR, CO chemisorption, and NH3/CO2-temperature-programmed desorption (TPD was also briefly introduced. Finally, we discussed the challenges and provided possible suggestions on choosing characterization techniques. This review provides key information to catalysis community to adopt suitable characterization techniques for their research.

Electroreduction of CO ₂ Catalyzed by a Heterogenized Zn–Porphyrin Complex with a Redox-Innocent Metal Center

Energy Technology Data Exchange (ETDEWEB)

Wu, Yueshen [Department; Energy; Jiang, Jianbing [Department; Energy; Weng, Zhe [Department; Energy; Wang, Maoyu [School; Broere, Daniël L. J. [Department; Zhong, Yiren [Department; Energy; Brudvig, Gary W. [Department; Energy; Feng, Zhenxing [School; Wang, Hailiang [Department; Energy

2017-07-26

Transition-metal-based molecular complexes are a class of catalyst materials for electrochemical CO2 reduction to CO that can be rationally designed to deliver high catalytic performance. One common mechanistic feature of these electrocatalysts developed thus far is an electrogenerated reduced metal center associated with catalytic CO2 reduction. Here we report a heterogenized zinc–porphyrin complex (zinc(II) 5,10,15,20-tetramesitylporphyrin) as an electrocatalyst that delivers a turnover frequency as high as 14.4 site–1 s–1 and a Faradaic efficiency as high as 95% for CO2 electroreduction to CO at -1.7 V vs the standard hydrogen electrode in an organic/water mixed electrolyte. While the Zn center is critical to the observed catalysis, in situ and operando X-ray absorption spectroscopic studies reveal that it is redox-innocent throughout the potential range. Cyclic voltammetry indicates that the porphyrin ligand may act as a redox mediator. Chemical reduction of the zinc–porphyrin complex further confirms that the reduction is ligand-based and the reduced species can react with CO2. This represents the first example of a transition-metal complex for CO2 electroreduction catalysis with its metal center being redox-innocent under working conditions.

Microbial electro-catalysis in fuel cell

International Nuclear Information System (INIS)

Dumas, Claire

2007-01-01

Microbial fuel cells (MFC) are devices that ensure the direct conversion of organic matter into electricity using bacterial bio-films as the catalysts of the electrochemical reactions. This study aims at improving the comprehension of the mechanisms involved in electron transfer pathways between the adhered bacteria and the electrodes. This optimization of the MFC power output could be done, for example, in exploring and characterizing various electrode materials. The electrolysis experiments carried out on Geobacter sulfurreducens deal with the microbial catalysis of the acetate oxidation, on the one hand, and the catalysis of the fumarate reduction on the other hand. On the anodic side, differences in current densities appeared on graphite, DSA R and stainless steel (8 A/m 2 , 5 A/m 2 and 0.7 A/m 2 respectively). These variations were explained more by materials roughness differences rather than their nature. Impedance spectroscopy study shows that the electro-active bio-film developed on stainless steel does not seem to modify the evolution of the stainless steel oxide layer, only the imposed potential remains determining. On the cathodic side, stainless steel sustained current densities more than twenty times higher than those obtained with graphite electrodes. The adhesion study of G. sulfurreducens on various materials in a flow cell, suggests that the bio-films resist to the hydrodynamic constraints and are not detached under a shear stress threshold value. The installation of two MFC prototypes, one in a sea station and the other directly in Genoa harbour (Italy) confirms some results obtained in laboratory and were promising for a MFC scale-up. (author) [fr

Organometallic chemistry of bimetallic compounds. Progress report, January 1992--July 1995

Energy Technology Data Exchange (ETDEWEB)

Casey, C.P.

1994-07-01

Four main projects at the interface between organometallic chemistry and homogeneous catalysis were pursued. All were designed to give increased understanding of the mechanisms of organometallic reactions related to homogeneous and heterogeneous catalysis. In addition, a minor study involving {eta}{sup 5}-to {eta}{sup 1}-cyclopentadienyl ring slippage in catalysis was completed.

Heterogeneity in magnetic complex oxides

Science.gov (United States)

Arenholz, Elke

Heterogeneity of quantum materials on the nanoscale can result from the spontaneous formation of regions with distinct atomic, electronic and/or magnetic order, and indicates coexistence of competing quantum phases. In complex oxides, the subtle interplay of lattice, charge, orbital, and spin degrees of freedom gives rise to especially rich phase diagrams. For example, coexisting conducting and insulating phases can occur near metal-insulator transitions, colossal magnetoresistance can emerge where ferromagnetic and antiferromagnetic domains compete, and charge-ordered and superconducting regions are present simultaneously in materials exhibiting high-temperature superconductivity. Additionally, externally applied fields (electric, magnetic, or strain) or other external excitations (light or heat) can tip the energy balance towards one phase, or support heterogeneity and phase coexistence and provide the means to perturb and tailor quantum heterogeneity at the nanoscale. Engineering nanomaterials, with structural, electronic and magnetic characteristics beyond what is found in bulk materials, is possible today through the technique of thin film epitaxy, effectively a method of `spray painting' atoms on single crystalline substrates to create precisely customized layered structures with atomic arrangements defined by the underlying substrate. Charge transfer and spin polarization across interfaces as well as imprinting nanoscale heterogeneity between adjacent layers lead to intriguing and important new phenomena testing our understanding of basic physics and creating new functionalities. Moreover, the abrupt change of orientation of an order parameter between nanoscale domains can lead to unique phases that are localized at domain walls, including conducting domain walls in insulating ferroelectrics, and ferromagnetic domain walls in antiferromagnets. Here we present our recent results on tailoring the electronic anisotropy of multiferroic heterostructures by

Applications of secondary ion mass spectrometry in catalysis and surface chemistry

NARCIS (Netherlands)

Borg, H.J.; Niemantsverdriet, J.W.; Spivey, J.J.; Agarwal, S.K.

1994-01-01

A review with 182 refs. is given on phys. phenomena such as sputtering, ion emission, ionization and neutralization which are involved in SIMS. Applications of SIMS in catalysis and obtaining information about catalysts interactions with gases promoters and poisons are described. Also applications

Catalysis-enhanced strengthening of porous materials

International Nuclear Information System (INIS)

Sokolova, L.N.; Shchukin, E.D.; Burenkova, L.N.; Romanovskij, B.V.

2000-01-01

Change in the strength of compressed tablets of the catalyst on the basis of ZrO 2 (84 mass %) and Y 2 O 3 (16 mass %) after conducting the endothermal reaction of the methanol and ethanol dehydration at 700-800 deg C is studied. It is shown, that the key factor, determining the strengthening effect by 65-88% is not at all the reaction exothermal nature, which could lead to local heating of the catalyst surface. In reality significant increase in concentration of surface defects, as compared to the equilibrium at the given temperature is achieved on the account of conjugation of processes of catalysis and surface defects formation [ru

Evaluation of commercial and sulfated ZrO_2 aiming application catalysis

International Nuclear Information System (INIS)

Silva, F.N.; Dantas, J.; Costa, A.C.F.M.; Pallone, E.M.J.A.; Dutra, R.C.L.

2014-01-01

This study evaluates the performance of commercial and sulfated ZrO_2 for future application in catalysis. Commercial ZrO_2 was provided by the company Saint-Gobain Zirpro. The sulfation occurred with SO_4"-"2 ion content of 30% compared to the mass of ZrO_2. The samples were characterized by XRD, FTIR, EDX and GD. The results revealed the formation of a monoclinic phase for the commercial sample, and a monoclinic major phase with tetragonal traces for the sulfated sample. The commercial ZrO_2 showed a narrow, bimodal and asymmetric agglomerates distribution, while the sulfated sample showed a narrow, tetramodal and asymmetric agglomerates distribution. The presence of traces of the tetragonal phase in the SO_4"-"2/ZrO_2 XRD, and the presence of SO_3 in the EDX were good indicators for future use in catalysis to provide ester. (author)

A kinetic study on the catalysis of KCl, K2SO4, and K2CO3 during oxy-biomass combustion.

Science.gov (United States)

Deng, Shuanghui; Wang, Xuebin; Zhang, Jiaye; Liu, Zihan; Mikulčić, Hrvoje; Vujanović, Milan; Tan, Houzhang; Duić, Neven

2018-07-15

Biomass combustion under the oxy-fuel conditions (Oxy-biomass combustion) is one of the approaches achieving negative CO 2 emissions. KCl, K 2 CO 3 and K 2 SO 4 , as the major potassium species in biomass ash, can catalytically affect biomass combustion. In this paper, the catalysis of the representative potassium salts on oxy-biomass combustion was studied using a thermogravimetric analyzer (TGA). Effects of potassium salt types (KCl, K 2 CO 3 and K 2 SO 4 ), loading concentrations (0, 1, 3, 5, 8 wt%), replacing N 2 by CO 2 , and O 2 concentrations (5, 20, 30 vol%) on the catalysis degree were discussed. The comparison between TG-DTG curves of biomass combustion before and after water washing in both the 20%O 2 /80%N 2 and 20%O 2 /80%CO 2 atmospheres indicates that the water-soluble minerals in biomass play a role in promoting the devolatilization and accelerating the char-oxidation; and the replacement of N 2 by CO 2 inhibits the devolatilization and char-oxidation processes during oxy-biomass combustion. In the devolatilization stage, the catalysis degree of potassium monotonously increases with the increase of potassium salt loaded concentration. The catalysis degree order of the studied potassium salts is K 2 CO 3  > KCl > K 2 SO 4 . In the char-oxidation stage, with the increase of loading concentration the three kinds of potassium salts present inconsistent change tendencies of the catalysis degree. In the studied loading concentrations from 0 to 8 wt%, there is an optimal loading concentration for KCl and K 2 CO 3 , at 3 and 5 wt%, respectively; while for K 2 SO 4 , the catalysis degree on char-oxidation monotonically increases with the loading potassium concentration. For most studied conditions, regardless of the potassium salt types or the loading concentrations or the combustion stages, the catalysis degree in the O 2 /CO 2 atmosphere is stronger than that in the O 2 /N 2 atmosphere. The catalysis degree is also affected by the O 2

Recyclable enantioselective catalysts based on copper(II) complexes of 2-(pyridine-2-yl)imidazolidine-4-thione: their application in asymmetric Henry reactions

Czech Academy of Sciences Publication Activity Database

Nováková, G.; Drabina, P.; Frumarová, Božena; Sedlák, M.

2016-01-01

Roč. 358, č. 15 (2016), s. 2541-2552 ISSN 1615-4150 Institutional support: RVO:61389013 Keywords : asymmetric catalysis * enantioselectivity * heterogeneous catalysis Subject RIV: CC - Organic Chemistry Impact factor: 5.646, year: 2016

Comparison of the role that entropy has played in processes of non-enzymatic and enzymatic catalysis

International Nuclear Information System (INIS)

Dixon Pineda, Manuel Tomas

2012-01-01

The function that entropy has played is compared in processes of non-enzymatic and enzymatic catalysis. The processes followed are showed: the kinetics of the acid hydrolysis of 3-pentyl acetate and cyclopentyl acetate catalyzed by hydrochloric acid and enzymatic hydrolysis of ethyl acetate and γ-butyrolactone catalyzed by pig liver esterase. The activation parameters of Eyring were determined for each process and interpreted the contribution of the entropy of activation for catalysis in this type of model reactions. (author) [es

Heterogeneous Partial (ammOxidation and Oxidative Dehydrogenation Catalysis on Mixed Metal Oxides

Directory of Open Access Journals (Sweden)

Jacques C. Védrine

2016-01-01

Full Text Available This paper presents an overview of heterogeneous partial (ammoxidation and oxidative dehydrogenation (ODH of hydrocarbons. The review has been voluntarily restricted to metal oxide-type catalysts, as the partial oxidation field is very broad and the number of catalysts is quite high. The main factors of solid catalysts for such reactions, designated by Grasselli as the “seven pillars”, and playing a determining role in catalytic properties, are considered to be, namely: isolation of active sites (known to be composed of ensembles of atoms, Me–O bond strength, crystalline structure, redox features, phase cooperation, multi-functionality and the nature of the surface oxygen species. Other important features and physical and chemical properties of solid catalysts, more or less related to the seven pillars, are also emphasized, including reaction sensitivity to metal oxide structure, epitaxial contact between an active phase and a second phase or its support, synergy effect between several phases, acid-base aspects, electron transfer ability, catalyst preparation and activation and reaction atmospheres, etc. Some examples are presented to illustrate the importance of these key factors. They include light alkanes (C1–C4 oxidation, ethane oxidation to ethylene and acetic acid on MoVTe(SbNb-O and Nb doped NiO, propene oxidation to acrolein on BiMoCoFe-O systems, propane (ammoxidation to (acrylonitrile acrylic acid on MoVTe(SbNb-O mixed oxides, butane oxidation to maleic anhydride on VPO: (VO2P2O7-based catalyst, and isobutyric acid ODH to methacrylic acid on Fe hydroxyl phosphates. It is shown that active sites are composed of ensembles of atoms whose size and chemical composition depend on the reactants to be transformed (their chemical and size features and the reaction mechanism, often of Mars and van Krevelen type. An important aspect is the fact that surface composition and surface crystalline structure vary with reaction on stream until

Structure of adsorbed monolayers. The surface chemical bond

International Nuclear Information System (INIS)

Somorjai, G.A.; Bent, B.E.

1984-06-01

This paper attempts to provide a summary of what has been learned about the structure of adsorbed monolayers and about the surface chemical bond from molecular surface science. While the surface chemical bond is less well understood than bonding of molecules in the gas phase or in the solid state, our knowledge of its properties is rapidly accumulating. The information obtained also has great impact on many surface science based technologies, including heterogeneous catalysis and electronic devices. It is hoped that much of the information obtained from studies at solid-gas interfaces can be correlated with molecular behavior at solid-liquid interfaces. 31 references, 42 figures, 1 table

Acid-base catalysis of N-[(morpholine)methylene]daunorubicin.

Science.gov (United States)

Krause, Anna; Jelińska, Anna; Cielecka-Piontek, Judyta; Klawitter, Maria; Zalewski, Przemysław; Oszczapowicz, Irena; Wąsowska, Małgorzata

2012-08-01

The stability of N-[(morpholine)methylene]-daunorubicin hydrochloride (MMD) was investigated in the pH range 0.44-13.54, at 313, 308, 303 and 298 K. The degradation of MMD as a result of hydrolysis is a pseudo-first-order reaction described by the following equation: ln c = ln c(0) - k(obs)• t. In the solutions of hydrochloric acid, sodium hydroxide, borate, acetate and phosphate buffers, k(obs) = k(pH) because general acid-base catalysis was not observed. Specific acid-base catalysis of MMD comprises the following reactions: hydrolysis of the protonated molecules of MMD catalyzed by hydrogen ions (k(1)) and spontaneous hydrolysis of MMD molecules other than the protonated ones (k(2)) under the influence of water. The total rate of the reaction is equal to the sum of partial reactions: k(pH) = k(1) • a(H)+ • f(1) + k(2) • f(2) where: k(1) is the second-order rate constant (mol(-1) l s(-1)) of the specific hydrogen ion-catalyzed degradation of the protonated molecules of MMD; k(2) is the pseudo-first-order rate constant (s(-1)) of the water-catalyzed degradation of MMD molecules other than the protonated ones, f(1) - f(2) are fractions of the compound. MMD is the most stable at approx. pH 2.5.

Challenges and perspectives for catalysis in production of diesel from biomass

DEFF Research Database (Denmark)

Madsen, Anders Theilgaard; Søndergaard, Helle; Fehrmann, Rasmus

2011-01-01

oils or waste fats with methanol is the most prominent and has been applied industrially for a decade. Homogeneous acid and base catalysis is normally used, but solid acids, solid bases, ionic liquids and lipases are being developed as replacements. Hydrodeoxygenation of vegetable oils has likewise...

Prebiotic RNA Synthesis by Montmorillonite Catalysis

Directory of Open Access Journals (Sweden)

Sohan Jheeta

2014-08-01

Full Text Available This review summarizes our recent findings on the role of mineral salts in prebiotic RNA synthesis, which is catalyzed by montmorillonite clay minerals. The clay minerals not only catalyze the synthesis of RNA but also facilitate homochiral selection. Preliminary data of these findings have been presented at the “Horizontal Gene Transfer and the Last Universal Common Ancestor (LUCA” conference at the Open University, Milton Keynes, UK, 5–6 September 2013. The objective of this meeting was to recognize the significance of RNA in LUCA. We believe that the prebiotic RNA synthesis from its monomers must have been a simple process. As a first step, it may have required activation of the 5'-end of the mononucleotide with a leaving group, e.g., imidazole in our model reaction (Figure 1. Wide ranges of activating groups are produced from HCN under plausible prebiotic Earth conditions. The final step is clay mineral catalysis in the presence of mineral salts to facilitate selective production of functional RNA. Both the clay minerals and mineral salts would have been abundant on early Earth. We have demonstrated that while montmorillonite (pH 7 produced only dimers from its monomers in water, addition of sodium chloride (1 M enhanced the chain length multifold, as detected by HPLC. The effect of monovalent cations on RNA synthesis was of the following order: Li+ > Na+ > K+. A similar effect was observed with the anions, enhancing catalysis in the following order: Cl− > Br− > I−. The montmorillonite-catalyzed RNA synthesis was not affected by hydrophobic or hydrophilic interactions. We thus show that prebiotic synthesis of RNA from its monomers was a simple process requiring only clay minerals and a small amount of salt.

Cp2 TiX Complexes for Sustainable Catalysis in Single-Electron Steps.

Science.gov (United States)

Richrath, Ruben B; Olyschläger, Theresa; Hildebrandt, Sven; Enny, Daniel G; Fianu, Godfred D; Flowers, Robert A; Gansäuer, Andreas

2018-04-25

We present a combined electrochemical, kinetic, and synthetic study with a novel and easily accessible class of titanocene catalysts for catalysis in single-electron steps. The tailoring of the electronic properties of our Cp 2 TiX-catalysts that are prepared in situ from readily available Cp 2 TiX 2 is achieved by varying the anionic ligand X. Of the complexes investigated, Cp 2 TiOMs proved to be either equal or substantially superior to the best catalysts developed earlier. The kinetic and thermodynamic properties pertinent to catalysis have been determined. They allow a mechanistic understanding of the subtle interplay of properties required for an efficient oxidative addition and reduction. Therefore, our study highlights that efficient catalysts do not require the elaborate covalent modification of the cyclopentadienyl ligands. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Physical Heterogeneity and Aquatic Community Function in ...

Science.gov (United States)

The geomorphological character of a river network provides the template upon which evolution acts to create unique biological communities. Deciphering commonly observed patterns and processes within riverine landscapes resulting from the interplay between physical and biological components is a central tenet for the interdisciplinary field of river science. Relationships between the physical heterogeneity and food web character of functional process zones (FPZs) – large tracts of river with a similar geomorphic character - in the Kanawha River (West Virginia, USA) are examined in this study. Food web character was measured as food chain length (FCL), which reflects ecological community structure and ecosystem function. Our results show the same basal resources were present throughout the Kanawha River but their assimilation into the aquatic food web by primary consumers differed between FPZs. Differences in the trophic position of secondary consumers – fish - were also recorded between FPZs. Overall, both the morphological heterogeneity and heterogeneity of the river bed sediment of FPZs were significantly correlated with FCL. Specifically, FCL increases with greater FPZ physical heterogeneity, supporting tenet 8 of the river ecosystem synthesis. In previous research efforts, we delineated the functional process zones (FPZs) of the Kanawha River. In this study, we examined the relationship between the hydrogeomorphically-derived zones with food webs.

Computational Hydrodynamics: How Portable and Scalable Are Heterogeneous Programming Paradigms?

DEFF Research Database (Denmark)

Pawlak, Wojciech; Glimberg, Stefan Lemvig; Engsig-Karup, Allan Peter

New many-core era applications at the interface of mathematics and computer science adopt modern parallel programming paradigms and expose parallelism through proper algorithms. We present new performance results for a novel massively parallel free surface wave model suitable for advanced......-device system sizes from desktops to large HPC systems such as superclusters and in the cloud utilizing heterogeneous devices like multi-core CPUs, GPUs, and Xeon Phi coprocessors. The numerical efficiency is evaluated on heterogeneous devices like multi-core CPUs, GPUs and Xeon Phi coprocessors to test...

Preparation of Mn(III)-Porphyrin-Immobilized Fe{sub 3}O{sub 4}@SiO{sub 2} Mesoparticles and Their Use in Heterogeneous Catalysis of Styrene Epoxidation

Energy Technology Data Exchange (ETDEWEB)

Kim, Jun Yeol; Lee, Kyung Yeon; Kim, Sun Dol; Lee, Suk Joong [Dept. of Chemistry, Research Institute for Natural Sciences, Korea University, Seoul (Korea, Republic of)

2015-07-15

They show high stability over their homogeneous counterparts. However, traditional heterogeneous catalysts tend to be less selective for fine chemical synthesis because they usually require high operation temperature and have the nonuniformity of active sites. To overcome these problems, an emerging strategy for preparing heterogeneous catalytic systems with better selectivity and milder reaction condition comprises the immobilization of homogeneous catalysts on organic polymers and inorganic supports. We have designed and synthesized novel Mn(III)-porphyrin-immobilized core-shell magnetic mesoparticles that heterogeneously catalyze styrene to styrene oxide with remarkably high activity compared with its homogeneous counterpart. These magnetic heterogeneous catalysts can be readily separated from the reaction mixture by magnetic manipulation and used for subsequent reactions multiple times without dramatic loss of activity. This immobilization of catalysts on magnetic supports promises a great potential toward the development of new class of oxidation catalysts, and the modification of catalysts to extend their lifetime is in progress.

Combining X-ray Absorption and X-ray Diffraction Techniques for in Situ Studies of Chemical Transformations in Heterogeneous Catalysis: Advantages and Limitations

International Nuclear Information System (INIS)

Frenkel, A.I.; Hanson, J.; Wang, Q.; Marinkovic, N.; Chen, J.G.; Barrio, L.; Si, R.; Lopez Camara, A.; Estrella, A.M.; Rodriguez, J.A.

2011-01-01

Recent advances in catalysis instrumentations include synchrotron-based facilities where time-resolved X-ray scattering and absorption techniques are combined in the same in situ or operando experiment to study catalysts at work. To evaluate the advances and limitations of this method, we performed a series of experiments at the new XAFS/XRD instrument in the National Synchrotron Light Source. Nearly simultaneous X-ray diffraction (XRD) and X-ray absorption fine-structure (XAFS) measurements of structure and kinetics of several catalysts under reducing or oxidizing conditions have been performed and carefully analyzed. For CuFe 2 O 4 under reducing conditions, the combined use of the two techniques allowed us to obtain accurate data on kinetics of nucleation and growth of metallic Cu. For the inverse catalyst CuO/CeO 2 that underwent isothermal reduction (with CO) and oxidation (with O 2 ), the XAFS data measured in the same experiment with XRD revealed strongly disordered Cu species that went undetected by diffraction. These and other examples emphasize the unique sensitivity of these two complementary methods to follow catalytic processes in the broad ranges of length and time scales.

Plasma Chemistry and Catalysis in Gases and Liquids

CERN Document Server

Parvulescu, Vasile I; Lukes, Petr

2012-01-01

Filling the gap for a book that not only covers gases but also plasma methods in liquids, this is all set to become the standard reference on the topic. It considers the central aspects in plasma chemistry and plasma catalysis by focusing on the green and environmental applications, while also taking into account their practical and economic viability. With the topics addressed by an international group of major experts, this is a must-have for researchers, PhD students and postdocs specializing in the field.

Water-oxidation catalysis by synthetic manganese oxides--systematic variations of the calcium birnessite theme.

Science.gov (United States)

Frey, Carolin E; Wiechen, Mathias; Kurz, Philipp

2014-03-21

Layered manganese oxides from the birnessite mineral family have been identified as promising heterogeneous compounds for water-oxidation catalysis (WOC), a key reaction for the conversion of renewable energy into storable fuels. High catalytic rates were especially observed for birnessites which contain calcium as part of their structures. With the aim to systematically improve the catalytic performance of such oxide materials, we used a flexible synthetic route to prepare three series of calcium birnessites, where we varied the calcium concentrations, the ripening times of the original precipitates and the temperature of the heat treatment following the initial synthetic steps (tempering) during the preparation process. The products were carefully analysed by a number of analytical techniques and then probed for WOC activity using the Ce(4+)-system. We find that our set of twenty closely related manganese oxides shows large, but somewhat systematic alterations in catalytic rates, indicating the importance of synthesis parameters for maximum catalytic performance. The catalyst of the series for which the highest water-oxidation rate was found is a birnessite of medium calcium content (Ca : Mn ratio 0.2 : 1) that had been subjected to a tempering temperature of 400 °C. On the basis of the detailed analysis of the results, a WOC reaction scheme for birnessites is proposed to explain the observed trends in reactivity.

Oxidation of a Dimethoxyhydroquinone by Ferrihydrite and Goethite Nanoparticles: Iron Reduction versus Surface Catalysis.

Science.gov (United States)

Krumina, Lelde; Lyngsie, Gry; Tunlid, Anders; Persson, Per

2017-08-15

Hydroquinones are important mediators of electron transfer reactions in soils with a capability to reduce Fe(III) minerals and molecular oxygen, and thereby generating Fenton chemistry reagents. This study focused on 2,6-dimethoxy hydroquinone (2,6-DMHQ), an analogue to a common fungal metabolite, and its reaction with ferrihydrite and goethite under variable pH and oxygen concentrations. Combined wet-chemical and spectroscopic analyses showed that both minerals effectively oxidized 2,6-DMHQ in the presence of oxygen. Under anaerobic conditions the first-order oxidation rate constants decreased by one to several orders of magnitude depending on pH and mineral. Comparison between aerobic and anaerobic results showed that ferrihydrite promoted 2,6-DMHQ oxidation both via reductive dissolution and heterogeneous catalysis while goethite mainly caused catalytic oxidation. These results were in agreement with changes in the reduction potential (E H ) of the Fe(III) oxide/Fe(II) aq redox couple as a function of dissolved Fe(II) where E H of goethite was lower than ferrihydrite at any given Fe(II) concentration, which makes ferrihydrite more prone to reductive dissolution by the 2,6-DMBQ/2,6-DMHQ redox couple. This study showed that reactions between hydroquinones and iron oxides could produce favorable conditions for formation of reactive oxygen species, which are required for nonenzymatic Fenton-based decomposition of soil organic matter.

Structural and catalytic effects of an invariant purine substitution in the hammerhead ribozyme: implications for the mechanism of acid–base catalysis

Science.gov (United States)

Schultz, Eric P.; Vasquez, Ernesto E.; Scott, William G.

2014-01-01

The hammerhead ribozyme catalyzes RNA cleavage via acid–base catalysis. Whether it does so by general acid–base catalysis, in which the RNA itself donates and abstracts protons in the transition state, as is typically assumed, or by specific acid–base catalysis, in which the RNA plays a structural role and proton transfer is mediated by active-site water molecules, is unknown. Previous biochemical and crystallographic experiments implicate an invariant purine in the active site, G12, as the general base. However, G12 may play a structural role consistent with specific base catalysis. To better understand the role of G12 in the mechanism of hammerhead catalysis, a 2.2 Å resolution crystal structure of a hammerhead ribozyme from Schistosoma mansoni with a purine substituted for G12 in the active site of the ribozyme was obtained. Comparison of this structure (PDB entry 3zd4), in which A12 is substituted for G, with three previously determined structures that now serve as important experimental controls, allows the identification of structural perturbations that are owing to the purine substitution itself. Kinetic measurements for G12 purine-substituted schistosomal hammerheads confirm a previously observed dependence of rate on the pK a of the substituted purine; in both cases inosine, which is similar to G in pK a and hydrogen-bonding properties, is unexpectedly inactive. Structural comparisons indicate that this may primarily be owing to the lack of the exocyclic 2-amino group in the G12A and G12I substitutions and its structural effect upon both the nucleotide base and phosphate of A9. The latter involves the perturbation of a previously identified and well characterized metal ion-binding site known to be catalytically important in both minimal and full-length hammerhead ribozyme sequences. The results permit it to be suggested that G12 plays an important role in stabilizing the active-site structure. This result, although not inconsistent with the

Structural and catalytic effects of an invariant purine substitution in the hammerhead ribozyme: implications for the mechanism of acid-base catalysis.

Science.gov (United States)

Schultz, Eric P; Vasquez, Ernesto E; Scott, William G

2014-09-01

The hammerhead ribozyme catalyzes RNA cleavage via acid-base catalysis. Whether it does so by general acid-base catalysis, in which the RNA itself donates and abstracts protons in the transition state, as is typically assumed, or by specific acid-base catalysis, in which the RNA plays a structural role and proton transfer is mediated by active-site water molecules, is unknown. Previous biochemical and crystallographic experiments implicate an invariant purine in the active site, G12, as the general base. However, G12 may play a structural role consistent with specific base catalysis. To better understand the role of G12 in the mechanism of hammerhead catalysis, a 2.2 Å resolution crystal structure of a hammerhead ribozyme from Schistosoma mansoni with a purine substituted for G12 in the active site of the ribozyme was obtained. Comparison of this structure (PDB entry 3zd4), in which A12 is substituted for G, with three previously determined structures that now serve as important experimental controls, allows the identification of structural perturbations that are owing to the purine substitution itself. Kinetic measurements for G12 purine-substituted schistosomal hammerheads confirm a previously observed dependence of rate on the pK(a) of the substituted purine; in both cases inosine, which is similar to G in pK(a) and hydrogen-bonding properties, is unexpectedly inactive. Structural comparisons indicate that this may primarily be owing to the lack of the exocyclic 2-amino group in the G12A and G12I substitutions and its structural effect upon both the nucleotide base and phosphate of A9. The latter involves the perturbation of a previously identified and well characterized metal ion-binding site known to be catalytically important in both minimal and full-length hammerhead ribozyme sequences. The results permit it to be suggested that G12 plays an important role in stabilizing the active-site structure. This result, although not inconsistent with the potential

Heterogeneous propellant internal ballistics: criticism and regeneration

Science.gov (United States)

Glick, R. L.

2011-10-01

Although heterogeneous propellant and its innately nondeterministic, chemically discrete morphology dominates applications, ballisticcharacterization deterministic time-mean burning rate and acoustic admittance measures' absence of explicit, nondeterministic information requires homogeneous propellant with a smooth, uniformly regressing burning surface: inadequate boundary conditions for heterogeneous propellant grained applications. The past age overcame this dichotomy with one-dimensional (1D) models and empirical knowledge from numerous, adequately supported motor developments and supplementary experiments. However, current cost and risk constraints inhibit this approach. Moreover, its fundamental science approach is more sensitive to incomplete boundary condition information (garbage-in still equals garbage-out) and more is expected. This work critiques this situation and sketches a path forward based on enhanced ballistic and motor characterizations in the workplace and approximate model and apparatus developments mentored by CSAR DNS capabilities (or equivalent).

The Effect of Nitrogen Surface Ligands on Propane Metathesis: Design and Characterizations of N-modified SBA15-Supported Schrock-type Tungsten Alkylidyne

KAUST Repository

Eid, Ahmed A.

2014-04-01

Catalysis, which is primarily a molecular phenomenon, is an important field of chemistry because it requires the chemical conversion of molecules into other molecules. It also has an effect on many fields, including, but not limited to, industry, environment and life Science[1]. Surface Organometallic Chemistry is an effective methodology for Catalysis as it imports the concept and mechanism of organometallic chemistry, to surface science and heterogeneous catalysis. So, it bridges the gap between homogenous and heterogeneous catalysis[1]. The aim of the present research work is to study the effect of Nitrogen surface ligands on the activity of Alkane, Propane in particular, metathesis. Our approach is based on the preparation of selectively well-defined group (VI) transition metal complexes supported onto mesoporous materials, SBA15 and bearing amido and/or imido ligands. We choose nitrogen ligands because, according to the literature, they showed in some cases better catalytic properties in homogenous catalysis in comparison with their oxygen counterparts[2]. The first section covers the modification of a highly dehydroxylated SBA15 surface using a controlled ammonia treatment. These will result in the preparation of two kind of Nitrogen surface ligands: -\\tOne with vicinal silylamine/silanol, (≡SiNH2)(≡SiOH), noted [N,O]SBA15 and, -\\tAnother\\tone\\twith\\tvicinal\\tbis-silylamine moieties (≡SiNH2)2, noted [N,N]SBA15[3]. The second section covers the reaction of Schrock type Tungsten Carbyne [W(≡C- tBu)(CH2-tBu)3] with those N-surface ligands and their characterizations by FT-IR, multiple quantum solid state NMR (1H, 13C), elemental analysis and gas phase analysis. The third section covers the generation of the active site, tungsten hydride species. Their performance toward propane metathesis reaction using the dynamic reactor technique PID compared toward previous well-known catalysts supported on silica oxide or mesoporous materials[4]. A fairly good

Multi-Scale Computational Enzymology: Enhancing Our Understanding of Enzymatic Catalysis

Science.gov (United States)

Gherib, Rami; Dokainish, Hisham M.; Gauld, James W.

2014-01-01

Elucidating the origin of enzymatic catalysis stands as one the great challenges of contemporary biochemistry and biophysics. The recent emergence of computational enzymology has enhanced our atomistic-level description of biocatalysis as well the kinetic and thermodynamic properties of their mechanisms. There exists a diversity of computational methods allowing the investigation of specific enzymatic properties. Small or large density functional theory models allow the comparison of a plethora of mechanistic reactive species and divergent catalytic pathways. Molecular docking can model different substrate conformations embedded within enzyme active sites and determine those with optimal binding affinities. Molecular dynamics simulations provide insights into the dynamics and roles of active site components as well as the interactions between substrate and enzymes. Hybrid quantum mechanical/molecular mechanical (QM/MM) can model reactions in active sites while considering steric and electrostatic contributions provided by the surrounding environment. Using previous studies done within our group, on OvoA, EgtB, ThrRS, LuxS and MsrA enzymatic systems, we will review how these methods can be used either independently or cooperatively to get insights into enzymatic catalysis. PMID:24384841

Multi-Scale Computational Enzymology: Enhancing Our Understanding of Enzymatic Catalysis

Directory of Open Access Journals (Sweden)

Rami Gherib

2013-12-01

Full Text Available Elucidating the origin of enzymatic catalysis stands as one the great challenges of contemporary biochemistry and biophysics. The recent emergence of computational enzymology has enhanced our atomistic-level description of biocatalysis as well the kinetic and thermodynamic properties of their mechanisms. There exists a diversity of computational methods allowing the investigation of specific enzymatic properties. Small or large density functional theory models allow the comparison of a plethora of mechanistic reactive species and divergent catalytic pathways. Molecular docking can model different substrate conformations embedded within enzyme active sites and determine those with optimal binding affinities. Molecular dynamics simulations provide insights into the dynamics and roles of active site components as well as the interactions between substrate and enzymes. Hybrid quantum mechanical/molecular mechanical (QM/MM can model reactions in active sites while considering steric and electrostatic contributions provided by the surrounding environment. Using previous studies done within our group, on OvoA, EgtB, ThrRS, LuxS and MsrA enzymatic systems, we will review how these methods can be used either independently or cooperatively to get insights into enzymatic catalysis.

Molecular metal catalysts on supports: organometallic chemistry meets surface science.

Science.gov (United States)

Serna, Pedro; Gates, Bruce C

2014-08-19

-support bonding and structure, which identify the supports as ligands with electron-donor properties that influence reactivity and catalysis. Each of the catalyst design variables has been varied independently, illustrated by mononuclear and tetranuclear iridium on zeolite HY and on MgO and by isostructural rhodium and iridium (diethylene or dicarbonyl) complexes on these supports. The data provide examples resolving the roles of the catalyst design variables and place the catalysis science on a firm foundation of organometallic chemistry linked with surface science. Supported molecular catalysts offer the advantages of characterization in the absence of solvents and with surface-science methods that do not require ultrahigh vacuum. Families of supported metal complexes have been made by replacement of ligands with others from the gas phase. Spectroscopically identified catalytic reaction intermediates help to elucidate catalyst performance and guide design. The methods are illustrated for supported complexes and clusters of rhodium, iridium, osmium, and gold used to catalyze reactions of small molecules that facilitate identification of the ligands present during catalysis: alkene dimerization and hydrogenation, H-D exchange in the reaction of H2 with D2, and CO oxidation. The approach is illustrated with the discovery of a highly active and selective MgO-supported rhodium carbonyl dimer catalyst for hydrogenation of 1,3-butadiene to give butenes.

DOE Energy Frontiers Research Center for Heterogeneous Functional Materials; the “HeteroFoaM Center”

Energy Technology Data Exchange (ETDEWEB)

Reifsnider, Kenneth Leonard [Univ. of South Carolina, Columbia, SC (United States)

2016-11-03

Synopsis of five year accomplishments: Devices that convert and store energy are generally made from heterogeneous constituent materials that act and interact to selectively conduct, transport, and separate mass, heat, and charge. Controlling these actions and interactions enables the technical breakthroughs that have made fuel cells, batteries, and solid state membranes, for example, essential parts of our society. In the biological sense, these materials are ‘vascular’ rather than primitive ‘cellular’ materials, in which the arrangements and configurations of the constituents (including their void phases) play essential and definitive roles in their functional capabilities. In 2009 a group of investigators, with lifetime investments of effort in the understanding of heterogeneous materials, recognized that the design of such material systems is not an optimization problem as such. Local interactions of the constituents create “emergent” properties and responses that are not part of the formal set of constituent characteristics, in much the same sense that society and culture is created by the group interactions of the people involved. The design of emergent properties is an open question in all formal science, but for energy materials the lack of this foundation science relegates development tasks to Edisonian trial and error, with anecdotal success and frequent costly failures. That group defined, for the first time, multi-scale heterogeneous functional materials with functional disordered and void phase regions as “HeteroFoaM,” and formed the first multidisciplinary research team to define and codify the foundation science of that material class. The primary goal of the HeteroFoaM Center was, and is, to create and establish the multi-scale fundamental knowledge and related methodology required for the rational and systematic multiphysics design of heterogeneous functional materials and their interfaces and surfaces for applications in energy

Inorganic Chemistry in Hydrogen Storage and Biomass Catalysis

Energy Technology Data Exchange (ETDEWEB)

Thorn, David [Los Alamos National Laboratory

2012-06-13

Making or breaking C-H, B-H, C-C bonds has been at the core of catalysis for many years. Making or breaking these bonds to store or recover energy presents us with fresh challenges, including how to catalyze these transformations in molecular systems that are 'tuned' to minimize energy loss and in molecular and material systems present in biomass. This talk will discuss some challenging transformations in chemical hydrogen storage, and some aspects of the inorganic chemistry we are studying in the development of catalysts for biomass utilization.

The surface science of enzymes

DEFF Research Database (Denmark)

Rod, Thomas Holm; Nørskov, Jens Kehlet

2002-01-01

One of the largest challenges to science in the coming years is to find the relation between enzyme structure and function. Can we predict which reactions an enzyme catalyzes from knowledge of its structure-or from its amino acid sequence? Can we use that knowledge to modify enzyme function......? To solve these problems we must understand in some detail how enzymes interact with reactants from its surroundings. These interactions take place at the surface of the enzyme and the question of enzyme function can be viewed as the surface science of enzymes. In this article we discuss how to describe...... catalysis by enzymes, and in particular the analogies between enzyme catalyzed reactions and surface catalyzed reactions. We do this by discussing two concrete examples of reactions catalyzed both in nature (by enzymes) and in industrial reactors (by inorganic materials), and show that although analogies...

Design of a new reactor-like high temperature near ambient pressure scanning tunneling microscope for catalysis studies.

Science.gov (United States)

Tao, Franklin Feng; Nguyen, Luan; Zhang, Shiran

2013-03-01

Here, we present the design of a new reactor-like high-temperature near ambient pressure scanning tunneling microscope (HT-NAP-STM) for catalysis studies. This HT-NAP-STM was designed for exploration of structures of catalyst surfaces at atomic scale during catalysis or under reaction conditions. In this HT-NAP-STM, the minimized reactor with a volume of reactant gases of ∼10 ml is thermally isolated from the STM room through a shielding dome installed between the reactor and STM room. An aperture on the dome was made to allow tip to approach to or retract from a catalyst surface in the reactor. This dome minimizes thermal diffusion from hot gas of the reactor to the STM room and thus remains STM head at a constant temperature near to room temperature, allowing observation of surface structures at atomic scale under reaction conditions or during catalysis with minimized thermal drift. The integrated quadrupole mass spectrometer can simultaneously measure products during visualization of surface structure of a catalyst. This synergy allows building an intrinsic correlation between surface structure and its catalytic performance. This correlation offers important insights for understanding of catalysis. Tests were done on graphite in ambient environment, Pt(111) in CO, graphene on Ru(0001) in UHV at high temperature and gaseous environment at high temperature. Atom-resolved surface structure of graphene on Ru(0001) at 500 K in a gaseous environment of 25 Torr was identified.

Support for U.S. Participants at the 16th International Congress on Catalysis

Energy Technology Data Exchange (ETDEWEB)

Wachs, Israel E. [Lehigh Univ., Bethlehem, PA (United States)

2017-01-17

The enclosed report highlights the travel grant awarded to offset the cost of foreign travel of several faculty and students to attend the 16th International Congress on Catalysis (ICC) held in Beijing, China, July 3-8, 2016.

Effect of Electric Discharge on Properties of Nano-Particulate Catalyst for Plasma-Catalysis.

Science.gov (United States)

Lee, Chung Jun; Kim, Jip; Kim, Taegyu

2016-02-01

Heterogeneous catalytic processes have been used to produce hydrogen from hydrocarbons. However, high reforming temperature caused serious catalyst deteriorations and low energy efficiency. Recently, a plasma-catalyst hybrid process was used to reduce the reforming temperature and to improve the stability and durability of reforming catalysts. Effect of electric discharges on properties of nanoparticulate catalysts for plasma-catalysis was investigated in the present study. Catalyst-bed porosity was varied by packing catalyst beads with the different size in a reactor. Discharge power and onset voltage of the plasma were measured as the catalyst-bed porosity was varied. The effect of discharge voltage, frequency and voltage waveforms such as the sine, pulse and square was investigated. We found that the optimal porosity of the catalyst-bed exists to maximize the electric discharge. At a low porosity, the electric discharge was unstable to be sustained because the space between catalysts got narrow nearly close to the sheath region. On the other hand, at a high porosity, the electric discharge became weak because the plasma was not sufficient to interact with the surface of catalysts. The discharge power increased as the discharge voltage and frequency increased. The square waveform was more efficient than the sine and pulse one. At a high porosity, however, the effect of the voltage waveform was not considerable because the space between catalysts was too large for plasma to interact with the surface of catalysts.

Adaptação de forno de microondas doméstico para realização de reações de transesterificação sob refluxo e catálise por argilas Adapting a domestic microwave oven transesterification reactions for under reflux and clay catalysis

Directory of Open Access Journals (Sweden)

Fernando de C. da Silva

2006-04-01

Full Text Available The microwave oven became an important source of heating for many laboratory procedures including accelerating organic reactions. Reactions that require long reflux times can sometimes be carried out in a few hours or minutes in a conventional microwave oven. However, longer reflux times can be troublesome since domestic microwave ovens are not prepared for these harsh conditions. This technical note presents our finding on heterogeneous catalysis transesterification reactions between b-keto-esters and carbohydrate derivatives under heating or microwave irradiation using an adapted domestic microwave oven.

The Electronic Structure Effect in Heterogeneous Catalysis

DEFF Research Database (Denmark)

Nilsson, A.; Pettersson, L. G. M.; Hammer, Bjørk

2005-01-01

Using a combination of density functional theory calculations and X-ray emission and absorption spectroscopy for nitrogen on Cu and Ni surfaces, a detailed picture is given of the chemisorption bond. It is suggested that the adsorption bond strength and hence the activity of transition metal surf...

Heterogeneous catalysis: Catch me if you can!

NARCIS (Netherlands)

Weckhuysen, B.M.

2009-01-01

Chemists are like detectives: they like to know 'whodunit' during a catalytic reaction. Combining advanced electron microscopy with intelligent molecular design has now provided strong evidence for the presence of a highly active site within a complex catalytic solid.

Heterogeneous catalysis in complex, condensed reaction media

Energy Technology Data Exchange (ETDEWEB)

Cantu, David C.; Wang, Yang-Gang; Yoon, Yeohoon; Glezakou, Vassiliki-Alexandra; Rousseau, Roger; Weber, Robert S.

2017-07-01

Many reactions required for the upgrading of biomass into fuels and chemicals—hydrogenation, hydrodeoxygenation, hydrocracking—are ostensibly similar to those practiced in the upgrading of petroleum into fuels. But, repurposing hydroprocessing catalysts from refinery operations to treat bio-oil has proved to be unsatisfactory. New catalysts are needed because the composition of the biogenic reactants differs from that of petroleum-derived feedstocks (e.g. the low concentration of sulfur in cellulose-derived biomass precludes use of metal sulfide catalysts unless sulfur is added to the reaction stream). New processes are needed because bio-oils oligomerize rapidly, forming intractable coke and “gunk”, at temperatures so low that the desired upgrading reactions are impractically slow, and so low that the bio-oil upgrading must be handled as a condensed fluid. Ideally, the new catalysts and processes would exploit the properties of the multiple phases present in condensed bio-oil, notably the polarizability and structure of the fluid near a catalyst’s surface in the cybotactic region. The results of preliminary modeling of the cybotactic region of different catalyst surfaces in the hydrogenation of phenol suggest that Pd catalysts supported on hydrophilic surfaces are more active than catalysts based on lipophilic supports because the former serve to enhance the concentration of the phenol in the vicinity of the Pd. The effect stems from thermodynamics, not the rate of mass transport. This work was supported by the US Department of Energy, Office of Energy Efficiency and Renewable Energy, Bioenergy Technologies Office. Pacific Northwest National Laboratory (PNNL) is a multiprogram national laboratory operated for DOE by Battelle.

Noncontact Atomic Force Microscopy: An Emerging Tool for Fundamental Catalysis Research.

Science.gov (United States)

Altman, Eric I; Baykara, Mehmet Z; Schwarz, Udo D

2015-09-15

Although atomic force microscopy (AFM) was rapidly adopted as a routine surface imaging apparatus after its introduction in 1986, it has not been widely used in catalysis research. The reason is that common AFM operating modes do not provide the atomic resolution required to follow catalytic processes; rather the more complex noncontact (NC) mode is needed. Thus, scanning tunneling microscopy has been the principal tool for atomic scale catalysis research. In this Account, recent developments in NC-AFM will be presented that offer significant advantages for gaining a complete atomic level view of catalysis. The main advantage of NC-AFM is that the image contrast is due to the very short-range chemical forces that are of interest in catalysis. This motivated our development of 3D-AFM, a method that yields quantitative atomic resolution images of the potential energy surfaces that govern how molecules approach, stick, diffuse, and rebound from surfaces. A variation of 3D-AFM allows the determination of forces required to push atoms and molecules on surfaces, from which diffusion barriers and variations in adsorption strength may be obtained. Pushing molecules towards each other provides access to intermolecular interaction between reaction partners. Following reaction, NC-AFM with CO-terminated tips yields textbook images of intramolecular structure that can be used to identify reaction intermediates and products. Because NC-AFM and STM contrast mechanisms are distinct, combining the two methods can produce unique insight. It is demonstrated for surface-oxidized Cu(100) that simultaneous 3D-AFM/STM yields resolution of both the Cu and O atoms. Moreover, atomic defects in the Cu sublattice lead to variations in the reactivity of the neighboring O atoms. It is shown that NC-AFM also allows a straightforward imaging of work function variations which has been used to identify defect charge states on catalytic surfaces and to map charge transfer within an individual

Multi-Scale Computational Enzymology: Enhancing Our Understanding of Enzymatic Catalysis

OpenAIRE

Rami Gherib; Hisham M. Dokainish; James W. Gauld

2013-01-01

Elucidating the origin of enzymatic catalysis stands as one the great challenges of contemporary biochemistry and biophysics. The recent emergence of computational enzymology has enhanced our atomistic-level description of biocatalysis as well the kinetic and thermodynamic properties of their mechanisms. There exists a diversity of computational methods allowing the investigation of specific enzymatic properties. Small or large density functional theory models allow the comparison of a pleth...

Synergy between experimental and theoretical methods in the exploration of homogeneous transition metal catalysis

DEFF Research Database (Denmark)

Lupp, Daniel; Christensen, Niels Johan; Fristrup, Peter

2014-01-01

n this Perspective, we will focus on the use of both experimental and theoretical methods in the exploration of reaction mechanisms in homogeneous transition metal catalysis. We briefly introduce the use of Hammett studies and kinetic isotope effects (KIE). Both of these techniques can be complem......n this Perspective, we will focus on the use of both experimental and theoretical methods in the exploration of reaction mechanisms in homogeneous transition metal catalysis. We briefly introduce the use of Hammett studies and kinetic isotope effects (KIE). Both of these techniques can...... be complemented by computational chemistry – in particular in cases where interpretation of the experimental results is not straightforward. The good correspondence between experiment and theory is only possible due to recent advances within the applied theoretical framework. We therefore also highlight...

Asymmetric catalysis in the cyclopropanation of olefins; Catalise assimetrica na ciclopropanacao de olefinas

Energy Technology Data Exchange (ETDEWEB)

Leao, Raquel A.C.; Ferreira, Vitor F.; Pinheiro, Sergio [Universidade Federal Fluminense (UFF), Niteroi, RJ (Brazil). Dept. de Quimica Organica]. E-mail: cegvito@vm.uff.br

2007-07-01

The main methodologies in the asymmetric cyclopropanation of alkenes with emphasis on asymmetric catalysis are covered. Examples are the Simmons-Smith reaction, the use of diazoalkanes and reactions carried out by decomposition of alpha-diazoesters in the presence of transition metals. (author)

Reactivity of organic compounds in catalytic synthesis

Energy Technology Data Exchange (ETDEWEB)

Minachev, Kh M; Bragin, O V

1978-01-01

A comprehensive review of 1976 Soviet research on catalysis delivered to the 1977 annual session of the USSR Academy of Science Council on Catalysis (Baku 6/16-20/77) covers hydrocarbon reactions, including hydrogenation and hydrogenolysis, dehydrogenation, olefin dimerization and disproportionation, and cyclization and dehydrocyclization (e.g., piperylene cyclization and ethylene cyclotrimerization); catalytic and physicochemical properties of zeolites, including cracking, dehydrogenation, and hydroisomerization catalytic syntheses and conversion of heterocyclic and functional hydrocarbon derivatives, including partial and total oxidation (e.g., of o-xylene to phthalic anhydride); syntheses of thiophenes from alkanes and hydrogen sulfide over certain dehydrogenation catalysts; catalytic syntheses involving carbon oxides ( e.g., the development of a new heterogeneous catalyst for hydroformylation of olefins), and of Co-MgO zeolitic catalysts for synthesis of aliphatic hydrocarbons from carbon dioxide and hydrogen, and fabrication of high-viscosity lubricating oils over bifunctional aluminosilicate catalysts.

Accumulative charge separation for solar fuels production: coupling light-induced single electron transfer to multielectron catalysis.

Science.gov (United States)

Hammarström, Leif

2015-03-17

The conversion and storage of solar energy into a fuel holds promise to provide a significant part of the future renewable energy demand of our societies. Solar energy technologies today generate heat or electricity, while the large majority of our energy is used in the form of fuels. Direct conversion of solar energy to a fuel would satisfy our needs for storable energy on a large scale. Solar fuels can be generated by absorbing light and converting its energy to chemical energy by electron transfer leading to separation of electrons and holes. The electrons are used in the catalytic reduction of a cheap substrate with low energy content into a high-energy fuel. The holes are filled by oxidation of water, which is the only electron source available for large scale solar fuel production. Absorption of a single photon typically leads to separation of a single electron-hole pair. In contrast, fuel production and water oxidation are multielectron, multiproton reactions. Therefore, a system for direct solar fuel production must be able to accumulate the electrons and holes provided by the sequential absorption of several photons in order to complete the catalytic reactions. In this Account, the process is termed accumulative charge separation. This is considerably more complicated than charge separation on a single electron level and needs particular attention. Semiconductor materials and molecular dyes have for a long time been optimized for use in photovoltaic devices. Efforts are made to develop new systems for light harvesting and charge separation that are better optimized for solar fuel production than those used in the early devices presented so far. Significant progress has recently been made in the discovery and design of better homogeneous and heterogeneous catalysts for solar fuels and water oxidation. While the heterogeneous ones perform better today, molecular catalysts based on transition metal complexes offer much greater tunability of electronic and

Proton Mediated Chemistry and Catalysis in a Self-Assembled Supramolecular Host

Energy Technology Data Exchange (ETDEWEB)

Pluth, Michael; Bergman, Robert; Raymond, Kenneth

2009-04-10

Synthetic supramolecular host assemblies can impart unique reactivity to encapsulated guest molecules. Synthetic host molecules have been developed to carry out complex reactions within their cavities, despite the fact that they lack the type of specifically tailored functional groups normally located in the analogous active sites of enzymes. Over the past decade, the Raymond group has developed a series of self-assembled supramolecules and the Bergman group has developed and studied a number of catalytic transformations. In this Account, we detail recent collaborative work between these two groups, focusing on chemical catalysis stemming from the encapsulation of protonated guests and expanding to acid catalysis in basic solution. We initially investigated the ability of a water-soluble, self-assembled supramolecular host molecule to encapsulate protonated guests in its hydrophobic core. Our study of encapsulated protonated amines revealed rich host-guest chemistry. We established that self-exchange (that is, in-out guest movement) rates of protonated amines were dependent on the steric bulk of the amine rather than its basicity. The host molecule has purely rotational tetrahedral (T) symmetry, so guests with geminal N-methyl groups (and their attendant mirror plane) were effectively desymmetrized; this allowed for the observation and quantification of the barriers for nitrogen inversion followed by bond rotation. Furthermore, small nitrogen heterocycles, such as N-alkylaziridines, N-alkylazetidines, and N-alkylpyrrolidines, were found to be encapsulated as proton-bound homodimers or homotrimers. We further investigated the thermodynamic stabilization of protonated amines, showing that encapsulation makes the amines more basic in the cavity. Encapsulation raises the effective basicity of protonated amines by up to 4.5 pK{sub a} units, a difference almost as large as that between the moderate and strong bases carbonate and hydroxide. The thermodynamic stabilization

Proton-Mediated Chemistry and Catalysis in a Self-Assembled Supramolecular Host

International Nuclear Information System (INIS)

Pluth, Michael; Bergman, Robert; Raymond, Kenneth

2009-01-01

Synthetic supramolecular host assemblies can impart unique reactivity to encapsulated guest molecules. Synthetic host molecules have been developed to carry out complex reactions within their cavities, despite the fact that they lack the type of specifically tailored functional groups normally located in the analogous active sites of enzymes. Over the past decade, the Raymond group has developed a series of self-assembled supramolecules and the Bergman group has developed and studied a number of catalytic transformations. In this Account, we detail recent collaborative work between these two groups, focusing on chemical catalysis stemming from the encapsulation of protonated guests and expanding to acid catalysis in basic solution. We initially investigated the ability of a water-soluble, self-assembled supramolecular host molecule to encapsulate protonated guests in its hydrophobic core. Our study of encapsulated protonated amines revealed rich host-guest chemistry. We established that self-exchange (that is, in-out guest movement) rates of protonated amines were dependent on the steric bulk of the amine rather than its basicity. The host molecule has purely rotational tetrahedral (T) symmetry, so guests with geminal N-methyl groups (and their attendant mirror plane) were effectively desymmetrized; this allowed for the observation and quantification of the barriers for nitrogen inversion followed by bond rotation. Furthermore, small nitrogen heterocycles, such as N-alkylaziridines, N-alkylazetidines, and N-alkylpyrrolidines, were found to be encapsulated as proton-bound homodimers or homotrimers. We further investigated the thermodynamic stabilization of protonated amines, showing that encapsulation makes the amines more basic in the cavity. Encapsulation raises the effective basicity of protonated amines by up to 4.5 pK a units, a difference almost as large as that between the moderate and strong bases carbonate and hydroxide. The thermodynamic stabilization of

A Kumada Coupling Catalyst, [Ni{(Ph2P)2N(CH2)3Si(OCH3)3-P,P }Cl2], Bearing a Ligand for Direct Immobilization Onto Siliceous Mesoporous Molecular Sieves

Czech Academy of Sciences Publication Activity Database

Stamatopoulos, I.; Giannitsios, D.; Psycharis, V.; Raptopoulou, C. P.; Balcar, Hynek; Zukal, Arnošt; Svoboda, J.; Kyritsis, P.; Vohlídal, J.

2015-01-01

Roč. 2015, č. 18 (2015), s. 3038-3044 ISSN 1434-1948 R&D Projects: GA ČR GAP108/12/1143 Institutional support: RVO:61388955 Keywords : homogenous catalysis * heterogeneous catalysis * cross coupling Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.686, year: 2015

Enhanced Micellar Catalysis LDRD.

Energy Technology Data Exchange (ETDEWEB)

Betty, Rita G.; Tucker, Mark D; Taggart, Gretchen; Kinnan, Mark K.; Glen, Crystal Chanea; Rivera, Danielle; Sanchez, Andres; Alam, Todd Michael

2012-12-01

The primary goals of the Enhanced Micellar Catalysis project were to gain an understanding of the micellar environment of DF-200, or similar liquid CBW surfactant-based decontaminants, as well as characterize the aerosolized DF-200 droplet distribution and droplet chemistry under baseline ITW rotary atomization conditions. Micellar characterization of limited surfactant solutions was performed externally through the collection and measurement of Small Angle X-Ray Scattering (SAXS) images and Cryo-Transmission Electron Microscopy (cryo-TEM) images. Micellar characterization was performed externally at the University of Minnesotas Characterization Facility Center, and at the Argonne National Laboratory Advanced Photon Source facility. A micellar diffusion study was conducted internally at Sandia to measure diffusion constants of surfactants over a concentration range, to estimate the effective micelle diameter, to determine the impact of individual components to the micellar environment in solution, and the impact of combined components to surfactant phase behavior. Aerosolized DF-200 sprays were characterized for particle size and distribution and limited chemical composition. Evaporation rates of aerosolized DF-200 sprays were estimated under a set of baseline ITW nozzle test system parameters.

The CAT-ACT Beamline at ANKA: A new high energy X-ray spectroscopy facility for CATalysis and ACTinide research

Science.gov (United States)

Zimina, A.; Dardenne, K.; Denecke, M. A.; Grunwaldt, J. D.; Huttel, E.; Lichtenberg, H.; Mangold, S.; Pruessmann, T.; Rothe, J.; Steininger, R.; Vitova, T.

2016-05-01

A new hard X-ray beamline for CATalysis and ACTinide research has been built at the synchrotron radiation facility ANKA. The beamline design is dedicated to X-ray spectroscopy, including ‘flux hungry’ photon-in/photon-out and correlative techniques with a special infrastructure for radionuclide and catalysis research. The CAT-ACT beamline will help serve the growing need for high flux/hard X-ray spectroscopy in these communities. The design, the first spectra and the current status of this project are reported.

Responsive hydrogels--structurally and dimensionally optimized smart frameworks for applications in catalysis, micro-system technology and material science.

Science.gov (United States)

Döring, Artjom; Birnbaum, Wolfgang; Kuckling, Dirk

2013-09-07

Although the technological and scientific importance of functional polymers has been well established over the last few decades, the most recent focus that has attracted much attention has been on stimuli-responsive polymers. This group of materials is of particular interest due to its ability to respond to internal and/or external chemico-physical stimuli, which is often manifested as large macroscopic responses. Aside from scientific challenges of designing stimuli-responsive polymers, the main technological interest lies in their numerous applications ranging from catalysis through microsystem technology and chemomechanical actuators to sensors that have been extensively explored. Since the phase transition phenomenon of hydrogels is theoretically well understood advanced materials based on the predictions can be prepared. Since the volume phase transition of hydrogels is a diffusion-limited process the size of the synthesized hydrogels is an important factor. Consistent downscaling of the gel size will result in fast smart gels with sufficient response times. In order to apply smart gels in microsystems and sensors, new preparation techniques for hydrogels have to be developed. For the up-coming nanotechnology, nano-sized gels as actuating materials would be of great interest.

Planar, Polysilazane?Derived Porous Ceramic Supports for Membrane and Catalysis Applications

OpenAIRE

Konegger, Thomas; Williams, Lee F.; Bordia, Rajendra K.

2015-01-01

Porous, silicon carbonitride?based ceramic support structures for potential membrane and catalysis applications were generated from a preceramic polysilazane precursor in combination with spherical, ultrahigh?molecular weight polyethylene microparticles through a sacrificial filler approach. A screening evaluation was used for the determination of the impact of both porogen content and porogen size on pore structure, strength, and permeability characteristics of planar specimens. By optimizin...

Reactivating Catalytic Surface: Insights into the Role of Hot Holes in Plasmonic Catalysis.

Science.gov (United States)

Peng, Tianhuan; Miao, Junjian; Gao, Zhaoshuai; Zhang, Linjuan; Gao, Yi; Fan, Chunhai; Li, Di

2018-03-01

Surface plasmon resonance of coinage metal nanoparticles is extensively exploited to promote catalytic reactions via harvesting solar energy. Previous efforts on elucidating the mechanisms of enhanced catalysis are devoted to hot electron-induced photothermal conversion and direct charge transfer to the adsorbed reactants. However, little attention is paid to roles of hot holes that are generated concomitantly with hot electrons. In this work, 13 nm spherical Au nanoparticles with small absorption cross-section are employed to catalyze a well-studied glucose oxidation reaction. Density functional theory calculation and X-ray absorption spectrum analysis reveal that hot holes energetically favor transferring catalytic intermediates to product molecules and then desorbing from the surface of plasmonic catalysts, resulting in the recovery of their catalytic activities. The studies shed new light on the use of the synergy of hot holes and hot electrons for plasmon-promoted catalysis. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Silicon microreactors for measurements of catalytic activity

DEFF Research Database (Denmark)

Henriksen, Toke Riishøj

The topic of this project is the design and fabrication of chemical microreactors with short response time and high sensitivity to low catalyst areas. The microreactors are intended as analytical tools in experiments concerning heterogeneous catalysis, photocatalysis, and electrocatalysis...... bonding without collapse of 3μm deep, 1 cm diameter circular reaction chambers. During the project, a microreactor has been developed for photocatalysis and heterogeneous catalysis in gas phase reactions. To demonstrate the operation of the microreactor, CO oxidation on low-area platinum thin film circles...

Raney copper catalysts for the water-gas shift reaction: I. Preparation, activity and stability

CSIR Research Space (South Africa)

Mellor, JR

1997-12-23

Full Text Available , T Haltchev, V Kafedjiiski, B. Kunev, M. Kalchev, I. Orizarski, D. Shopov, Proceedings ofthe Sixth International Symposium, Heterogeneous Catalysis, Part 1, Sofia, 1987, p. 235. \\[18\\] W.L. Marsden, M.S. Wainwright, J.B. Friedrich, Ind. Eng. Chem, Prod... and Testing of Catalysts, Academic Press, New York, 1985. \\[33\\] J.M. Thomas, J.W. Thomas, Introduction to the Principles of Heterogeneous Catalysis, Academic Press, New York, 1975, p. 16. \\[34\\] A.D. Tomsett, H.E. Curry-Hyde, M.S. Wainwright. D.J. Young...

HKUST-1 as a Heterogeneous Catalyst for the Synthesis of Vanillin.

Science.gov (United States)

Yépez, Rebeca; Illescas, Juan F; Gijón, Paulina; Sánchez-Sánchez, Manuel; González-Zamora, Eduardo; Santillan, Rosa; Álvarez, J Raziel; Ibarra, Ilich A; Aguilar-Pliego, Julia

2016-07-23

Vanillin (4-hydoxy-3-methoxybenzaldehyde) is the main component of the extract of vanilla bean. The natural vanilla scent is a mixture of approximately 200 different odorant compounds in addition to vanillin. The natural extraction of vanillin (from the orchid Vanilla planifolia, Vanilla tahitiensis and Vanilla pompon) represents only 1% of the worldwide production and since this process is expensive and very long, the rest of the production of vanillin is synthesized. Many biotechnological approaches can be used for the synthesis of vanillin from lignin, phenolic stilbenes, isoeugenol, eugenol, guaicol, etc., with the disadvantage of harming the environment since these processes use strong oxidizing agents and toxic solvents. Thus, eco-friendly alternatives on the production of vanillin are very desirable and thus, under current investigation. Porous coordination polymers (PCPs) are a new class of highly crystalline materials that recently have been used for catalysis. HKUST-1 (Cu3(BTC)2(H2O)3, BTC = 1,3,5-benzene-tricarboxylate) is a very well known PCP which has been extensively studied as a heterogeneous catalyst. Here, we report a synthetic strategy for the production of vanillin by the oxidation of trans-ferulic acid using HKUST-1 as a catalyst.

Nonlinear Science

CERN Document Server

Yoshida, Zensho

2010-01-01

This book gives a general, basic understanding of the mathematical structure "nonlinearity" that lies in the depths of complex systems. Analyzing the heterogeneity that the prefix "non" represents with respect to notions such as the linear space, integrability and scale hierarchy, "nonlinear science" is explained as a challenge of deconstruction of the modern sciences. This book is not a technical guide to teach mathematical tools of nonlinear analysis, nor a zoology of so-called nonlinear phenomena. By critically analyzing the structure of linear theories, and cl

Oxide-supported metal clusters: models for heterogeneous catalysts

International Nuclear Information System (INIS)

Santra, A K; Goodman, D W

2003-01-01

Understanding the size-dependent electronic, structural and chemical properties of metal clusters on oxide supports is an important aspect of heterogeneous catalysis. Recently model oxide-supported metal catalysts have been prepared by vapour deposition of catalytically relevant metals onto ultra-thin oxide films grown on a refractory metal substrate. Reactivity and spectroscopic/microscopic studies have shown that these ultra-thin oxide films are excellent models for the corresponding bulk oxides, yet are sufficiently electrically conductive for use with various modern surface probes including scanning tunnelling microscopy (STM). Measurements on metal clusters have revealed a metal to nonmetal transition as well as changes in the crystal and electronic structures (including lattice parameters, band width, band splitting and core-level binding energy shifts) as a function of cluster size. Size-dependent catalytic reactivity studies have been carried out for several important reactions, and time-dependent catalytic deactivation has been shown to arise from sintering of metal particles under elevated gas pressures and/or reactor temperatures. In situ STM methodologies have been developed to follow the growth and sintering kinetics on a cluster-by-cluster basis. Although several critical issues have been addressed by several groups worldwide, much more remains to be done. This article highlights some of these accomplishments and summarizes the challenges that lie ahead. (topical review)

Consensus of heterogeneous multi-agent systems based on sampled data with a small sampling delay

International Nuclear Information System (INIS)

Wang Na; Wu Zhi-Hai; Peng Li

2014-01-01

In this paper, consensus problems of heterogeneous multi-agent systems based on sampled data with a small sampling delay are considered. First, a consensus protocol based on sampled data with a small sampling delay for heterogeneous multi-agent systems is proposed. Then, the algebra graph theory, the matrix method, the stability theory of linear systems, and some other techniques are employed to derive the necessary and sufficient conditions guaranteeing heterogeneous multi-agent systems to asymptotically achieve the stationary consensus. Finally, simulations are performed to demonstrate the correctness of the theoretical results. (interdisciplinary physics and related areas of science and technology)

Mapping soil heterogeneity using RapidEye satellite images

Science.gov (United States)

Piccard, Isabelle; Eerens, Herman; Dong, Qinghan; Gobin, Anne; Goffart, Jean-Pierre; Curnel, Yannick; Planchon, Viviane

2016-04-01

In the frame of BELCAM, a project funded by the Belgian Science Policy Office (BELSPO), researchers from UCL, ULg, CRA-W and VITO aim to set up a collaborative system to develop and deliver relevant information for agricultural monitoring in Belgium. The main objective is to develop remote sensing methods and processing chains able to ingest crowd sourcing data, provided by farmers or associated partners, and to deliver in return relevant and up-to-date information for crop monitoring at the field and district level based on Sentinel-1 and -2 satellite imagery. One of the developments within BELCAM concerns an automatic procedure to detect soil heterogeneity within a parcel using optical high resolution images. Such heterogeneity maps can be used to adjust farming practices according to the detected heterogeneity. This heterogeneity may for instance be caused by differences in mineral composition of the soil, organic matter content, soil moisture or soil texture. Local differences in plant growth may be indicative for differences in soil characteristics. As such remote sensing derived vegetation indices may be used to reveal soil heterogeneity. VITO started to delineate homogeneous zones within parcels by analyzing a series of RapidEye images acquired in 2015 (as a precursor for Sentinel-2). Both unsupervised classification (ISODATA, K-means) and segmentation techniques were tested. Heterogeneity maps were generated from images acquired at different moments during the season (13 May, 30 June, 17 July, 31 August, 11 September and 1 November 2015). Tests were performed using blue, green, red, red edge and NIR reflectances separately and using derived indices such as NDVI, fAPAR, CIrededge, NDRE2. The results for selected winter wheat, maize and potato fields were evaluated together with experts from the collaborating agricultural research centers. For a few fields UAV images and/or yield measurements were available for comparison.

Chemistry of Fluorinated Carbon Acids: Synthesis, Physicochemical Properties, and Catalysis.

Science.gov (United States)

Yanai, Hikaru

2015-01-01

The bis[(trifluoromethyl)sulfonyl]methyl (Tf2CH; Tf=SO2CF3) group is known to be one of the strongest carbon acid functionalities. The acidity of such carbon acids in the gas phase is stronger than that of sulfuric acid. Our recent investigations have demonstrated that this type of carbon acids work as novel acid catalysts. In this paper, recent achievements in carbon acid chemistry by our research group, including synthesis, physicochemical properties, and catalysis, are summarized.

Fabrication of magnetic carbon composites from peanut shells and its application as a heterogeneous Fenton catalyst in removal of methylene blue

Energy Technology Data Exchange (ETDEWEB)

Zhou, Lincheng, E-mail: zhoulc@lzu.edu.cn; Ma, Junjun; Zhang, He; Shao, Yanming; Li, Yanfeng

2015-01-01

Graphical abstract: Peanut shell magnetic carbon (PMC) were fabricated by carbonized the mixture of peanut shells and (NH{sub 4}){sub 3}Fe(C{sub 2}O{sub 4}){sub 3}. The obtained PMC exhibit high efficiency in catalysis oxidation methylene blue with the help of K{sub 2}S{sub 2}O{sub 8} and it can be easily separated from aqueous by external magnetic field. Meanwhile, the catalyst can be reused for seven times almost without decreased of activity. - Highlights: • Novel peanut shell magnetic carbon (PMC) catalysts were successfully synthesized. • PMC exhibited superior activity as a heterogeneous Fenton-like catalyst. • A high efficient Fenton-like system was set up for removal MB. • PMC posed excellent catalysis oxidation quality, stability and good reusability. - Abstract: Magnetic carbons were prepared from agricultural waste peanut shells and Ferric ammonium oxalate via a simple impregnation and carbonization process. The obtained composites were characterized by element analysis, MÖssbauer spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, X-ray diffraction, vibrating sample magnetometry and the Brunauer-Emmett-Teller surface area method, respectively. The magnetic carbon material was used as catalyst of heterogeneous Fenton reaction to remove methylene blue with the help of persulfate in waste water. The results indicated that both the removal rate and removal efficiency of this catalytic system are very excellent. The degradation efficiency was best (90% within 30 min) using initial concentrations of 0.5 g L{sup −1} persulfate and 40 mg L{sup −1} methylene blue. The removal mechanism was investigated by LC-MS. The catalyst retained its activity after seven reuses, indicating its good stability and reusability. It is inexpensive because it consists mainly of agricultural waste. Its porosity contributed to its high activity, which was achieved without any additional activation process. These indicating that the catalyst is

Synergistic dual activation catalysis by palladium nanoparticles for epoxide ring opening with phenols.

Science.gov (United States)

Seth, Kapileswar; Roy, Sudipta Raha; Pipaliya, Bhavin V; Chakraborti, Asit K

2013-07-04

Synergistic dual activation catalysis has been devised for epoxide phenolysis wherein palladium nanoparticles induce electrophilic activation via coordination with the epoxide oxygen followed by nucleophilic activation through anion-π interaction with the aromatic ring of the phenol, and water (reaction medium) also renders assistance through 'epoxide-phenol' dual activation.

Biogenic synthesis and characterization of gold nanoparticles by Escherichia coli K12 and its heterogeneous catalysis in degradation of 4-nitrophenol

Science.gov (United States)

Srivastava, Sarvesh Kumar; Yamada, Ryosuke; Ogino, Chiaki; Kondo, Akihiko

2013-02-01

Room-temperature extracellular biosynthesis of gold nanoparticles (Au NPs) was achieved using Escherichia coli K12 cells without the addition of growth media, pH adjustments or inclusion of electron donors/stabilizing agents. The resulting nanoparticles were analysed by ultraviolet-visible (UV-vis) spectrophotometry, atomic force microscopy, transmission electron microscopy and X-ray diffraction. Highly dispersed gold nanoplates were achieved in the order of around 50 nm. Further, the underlying mechanism was found to be controlled by certain extracellular membrane-bound proteins, which was confirmed by Fourier transformation-infrared spectroscopy and sodium dodecyl sulfate polyacrylamide gel electrophoresis. We observed that certain membrane-bound peptides are responsible for reduction and subsequent stabilization of Au NPs (confirmed by zeta potential analysis). Upon de-activation of these proteins, no nanoparticle formation was observed. Also, we prepared a novel biocatalyst with Au NPs attached to the membrane-bound fraction of E. coli K12 cells serving as an efficient heterogeneous catalyst in complete reduction of 4-nitrophenol in the presence of NaBH4 which was studied with UV-vis spectroscopy. This is the first report on bacterial membrane-Au NP nanobiocomposite serving as an efficient heterogeneous catalyst in complete reduction of nitroaromatic pollutant in water.

Hydrolyses of 2- and 4-fluoro N-heterocycles. 3. Nucleophilic catalysis by buffer bases in the general acid catalyzed hydrolysis of 4-fluoroquinaldine

International Nuclear Information System (INIS)

Muscio, O.J. Jr.; Theobald, P.G.; Rutherford, D.R.

1989-01-01

Pseudo-first-order rate constants and catalytic rate constants are reported for the buffer-catalyzed hydrolysis of 4-fluoroquinaldine (1) in carboxylic acid and phosphoric acid buffers. The buffer catalysis is consistent with specific acid, general base catalysis. Hydrolyses in 99% 18 O-labeled acetate, indicate that the predominant catalytic mode for the acetic acid/acetate buffer system is nucleophilic catalysis by the acetate anion coupled with specific acid catalysis. The other buffers presumably react in a similar manner. A Broensted-type plot of the catalytic rate constants for hydrolysis of protonated 1 has a slope of 0.57, with formate deviating positively from the line determined by acetate, chloroacetate, monohydrogen phosphate, and water. This Broensted slope is less than that found for hydrolysis of the 2-fluoro-1-methylpyridinium ion, 2, but is still within the range expected for aromatic nucleophilic substitution. Rate constants and 18 O-labeling results for hydrolysis in acetate buffer are also reported for 4-acetoxyquinaldine (3), the proposed intermediate in the acetate-catalyzed hydrolysis of 1. 15 references, 5 figures, 3 tables

Mechanism for Controlling the Dimer-Monomer Switch and Coupling Dimerization to Catalysis of the Severe Acute Respiratory Syndrome Coronavirus 3C-Like Protease

Energy Technology Data Exchange (ETDEWEB)

Shi,J.; Sivaraman, J.; Song, J.

2008-01-01

Unlike 3C protease, the severe acute respiratory syndrome coronavirus (SARS-CoV) 3C-like protease (3CLpro) is only enzymatically active as a homodimer and its catalysis is under extensive regulation by the unique extra domain. Despite intense studies, two puzzles still remain: (i) how the dimer-monomer switch is controlled and (ii) why dimerization is absolutely required for catalysis. Here we report the monomeric crystal structure of the SARS-CoV 3CLpro mutant R298A at a resolution of 1.75 Angstroms . Detailed analysis reveals that Arg298 serves as a key component for maintaining dimerization, and consequently, its mutation will trigger a cooperative switch from a dimer to a monomer. The monomeric enzyme is irreversibly inactivated because its catalytic machinery is frozen in the collapsed state, characteristic of the formation of a short 310-helix from an active-site loop. Remarkably, dimerization appears to be coupled to catalysis in 3CLpro through the use of overlapped residues for two networks, one for dimerization and another for the catalysis.

Heterogeneous Catalysis by Tetraethylammonium Tetrachloroferrate of the Photooxidation of Toluene by Visible and Near-UV Light

Directory of Open Access Journals (Sweden)

Kelsie R. Barnard

2018-02-01

Full Text Available Titanium dioxide is the most extensively used heterogeneous catalyst for the photooxidation of toluene and other hydrocarbons, but it has low utility for the synthesis of benzyl alcohol, of which little is produced, or benzaldehyde, due to further oxidation to benzoic acid and cresol, among other oxidation products, and eventually complete mineralization to CO2. Et4N[FeCl4] functions as a photocatalyst through the dissociation of chlorine atoms, which abstract hydrogen from toluene, and the photooxidation of toluene proceeds only as far as benzyl alcohol and benzaldehyde. Unlike TiO2, which requires ultraviolet (UV irradiation, Et4N[FeCl4] catalyzes the photooxidation of toluene with visible light alone. Even under predominantly UV irradiation, the yield of benzyl alcohol plus benzaldehyde is greater with Et4N[FeCl4] than with TiO2. Et4N[FeCl4] photocatalysis yields benzyl chloride as a side product, but it can be minimized by restricting irradiation to wavelengths above 360 nm and by the use of long irradiation times. The photonic efficiency of oxidation in one experiment was found to be 0.042 mol/einstein at 365 nm. The use of sunlight as the irradiation source was explored.

Communicating why land surface heterogeneity matters

Science.gov (United States)

Tague, C.; Burke, W.; Bart, R. R.; Turpin, E.; Wood, T.; Gordon, D.

2017-12-01

Critical Zone Observatory. We summarize current findings and present initial designs for translating these science based results into interactive visualization and conceptual art installations with the goal of better communicating the different components of landscape heterogeneity and why it matters

Numerical simulation of catalysis combustion inside micro free-piston engine

International Nuclear Information System (INIS)

Wang, Qian; Zhang, Di; Bai, Jin; He, Zhixia

2016-01-01

Highlights: • A modeling study is applied on methane HCCI process of micro power device. • Mathematical formulas are established to predict the combustion characteristics. • Impacts of catalysis on the combustion characteristics are analyzed respectively. • The catalyst can improve the work steadily and reliability of micro power device. - Abstract: In order to investigate the catalytic combustion characteristics concerning homogeneous charge compression ignition (HCCI) in micro power device, numerical simulations with a 3D computation model that coupled motion of free piston and fluid dynamics of methane–air mixture flow were carried out and detailed gas-phase and surface catalytic reaction mechanisms of methane–air mixture were applied to the catalytic reactions model, a series of mathematical formula are established to predict the characteristics of compression ignition condition, impacts of catalysis on temperature, pressure, work capacity and other factors were analyzed respectively. Simulation results reveal that catalytic combustion facilitates the improvement of energy conversion efficiency and extends the ignition limit of methane–air mixture obviously, the ignition timing is brought forward as well, while compression ratio decreases and ignition delay period shrinks significantly. Numerical results demonstrate that the existence of catalytic wall helped to restrain the peak combustion pressure and maximum rate of pressure rise contributing to the steadily and reliability of operation inside micro free-piston power device.

Conformational Dynamics of Thermus aquaticus DNA Polymerase I during Catalysis

Science.gov (United States)

Suo, Zucai

2014-01-01

Despite the fact that DNA polymerases have been investigated for many years and are commonly used as tools in a number of molecular biology assays, many details of the kinetic mechanism they use to catalyze DNA synthesis remain unclear. Structural and kinetic studies have characterized a rapid, pre-catalytic open-to-close conformational change of the Finger domain during nucleotide binding for many DNA polymerases including Thermus aquaticus DNA polymerase I (Taq Pol), a thermostable enzyme commonly used for DNA amplification in PCR. However, little has been done to characterize the motions of other structural domains of Taq Pol or any other DNA polymerase during catalysis. Here, we used stopped-flow Förster resonance energy transfer (FRET) to investigate the conformational dynamics of all five structural domains of the full-length Taq Pol relative to the DNA substrate during nucleotide binding and incorporation. Our study provides evidence for a rapid conformational change step induced by dNTP binding and a subsequent global conformational transition involving all domains of Taq Pol during catalysis. Additionally, our study shows that the rate of the global transition was greatly increased with the truncated form of Taq Pol lacking the N-terminal domain. Finally, we utilized a mutant of Taq Pol containing a de novo disulfide bond to demonstrate that limiting protein conformational flexibility greatly reduced the polymerization activity of Taq Pol. PMID:24931550

Pop-It Beads to Introduce Catalysis of Reaction Rate and Substrate Depletion Effects

Science.gov (United States)

Gehret, Austin U.

2017-01-01

A kinesthetic classroom activity was designed to help students understand enzyme activity and catalysis of reaction rate. Students served the role of enzymes by manipulating Pop-It Beads as the catalytic event. This activity illuminates the relationship between reaction rate and reaction progress by allowing students to experience first-hand the…

Process Parameters Optimization of Potential SO42-/ZnO Acid Catalyst for Heterogeneous Transesterification of Vegetable Oil to Biodiesel

Directory of Open Access Journals (Sweden)

Istadi Istadi

2012-12-01

Full Text Available Among the possible renewable energy resources, diesel fuels derived from triglycerides of vegetable oils and animal fats have shown potential as substitutes for petroleum-based diesel fuels. The biodiesel could be produced from vegetable oils over homogeneous catalyst, heterogeneous catalyst, or enzymatic catalyst. In this study, the synthesized SO42-/ZnO catalyst was explored to be used in the heterogeneous biodiesel production by using the vegetable oils and methanol. The study began with the preparation of SO42-/ZnO catalyst followed by the transesterification reaction between vegetable oil with methanol. The independent variables (reaction time and the weight ratio of catalyst/oil were optimized to obtain the optimum biodiesel (fatty acid methyl ester yield. The results of this study showed that the acid catalyst SO42-/ZnO was potential to be used as catalyst for biodiesel production through heterogeneous transesterification of vegetable oils. Optimum operating condition for this catalytic reaction was the weight ratio of catalyst/oil of 8:1 and reaction time of 2.6 h with respect to 75.5% yield of methyl ester products. The biodiesel product was also characterized to identify the respected fatty acid methyl ester components. Copyright © 2012 by BCREC UNDIP. All rights reserved. (Selected Paper from International Conference on Chemical and Material Engineering (ICCME 2012Received: 23rd October 2012, Revised: 25th November 2012, Accepted: 25th November 2012[How to Cite: I. Istadi, Didi D. Anggoro, Luqman Buchori, Inshani Utami, Roikhatus Solikhah, (2012. Process Parameters Optimization of Potential SO42-/ZnO Acid Catalyst for Heterogeneous Transesterification of Vegetable Oil to Biodiesel. Bulletin of Chemical Reaction Engineering & Catalysis, 7(2: 150-157. (doi:10.9767/bcrec.7.2.4064.150-157][How to Link / DOI: http://dx.doi.org/10.9767/bcrec.7.2.4064.150-157 ] | View in 

A conserved hydrogen-bond network in the catalytic centre of animal glutaminyl cyclases is critical for catalysis.

Science.gov (United States)

Huang, Kai-Fa; Wang, Yu-Ruei; Chang, En-Cheng; Chou, Tsung-Lin; Wang, Andrew H-J

2008-04-01

QCs (glutaminyl cyclases; glutaminyl-peptide cyclotransferases, EC 2.3.2.5) catalyse N-terminal pyroglutamate formation in numerous bioactive peptides and proteins. The enzymes were reported to be involved in several pathological conditions such as amyloidotic disease, osteoporosis, rheumatoid arthritis and melanoma. The crystal structure of human QC revealed an unusual H-bond (hydrogen-bond) network in the active site, formed by several highly conserved residues (Ser(160), Glu(201), Asp(248), Asp(305) and His(319)), within which Glu(201) and Asp(248) were found to bind to substrate. In the present study we combined steady-state enzyme kinetic and X-ray structural analyses of 11 single-mutation human QCs to investigate the roles of the H-bond network in catalysis. Our results showed that disrupting one or both of the central H-bonds, i.e., Glu(201)...Asp(305) and Asp(248)...Asp(305), reduced the steady-state catalysis dramatically. The roles of these two COOH...COOH bonds on catalysis could be partly replaced by COOH...water bonds, but not by COOH...CONH(2) bonds, reminiscent of the low-barrier Asp...Asp H-bond in the active site of pepsin-like aspartic peptidases. Mutations on Asp(305), a residue located at the centre of the H-bond network, raised the K(m) value of the enzyme by 4.4-19-fold, but decreased the k(cat) value by 79-2842-fold, indicating that Asp(305) primarily plays a catalytic role. In addition, results from mutational studies on Ser(160) and His(319) suggest that these two residues might help to stabilize the conformations of Asp(248) and Asp(305) respectively. These data allow us to propose an essential proton transfer between Glu(201), Asp(305) and Asp(248) during the catalysis by animal QCs.

Catalysis. Innovative applications in petrochemistry and refining. Preprints

Energy Technology Data Exchange (ETDEWEB)

Ernst, S.; Balfanz, U.; Jess, A.; Lercher, J.A.; Lichtscheidl, J.; Marchionna, M.; Nees, F.; Santacesaria, E. (eds.)

2011-07-01

Within the DGMK conference at 4th to 6th October, 2011 in Dresden (Federal Republic of Germany) the following lectures were held: (1) Developing linear-alpha-olefins technology - From laboratory to a commercial plant (A. Meiswinkel); (2) New developments in oxidation catalysis (F. Rosowski); (3) Study of the performance of vanadium based catalysts prepared by grafting in the oxidative dehydrogenation of propane (E. Santacesaria); (4) Hydrocracking for oriented conversion of heavy oils: recent trends for catalyst development (F. Bertoncini); (5) Acidic ionic liquids for n-alkane isomerization in a liquid-liquid or slurry-phase reaction mode (C. Meyer); (6) Dual catalyst system for the hydrocracking of heavy oils and residues (G. Bellussi); (7) Understanding hydrodenitrogenation on novel unsupported sulphide Mo-W-Ni catalysts (J. Hein); (8) Hydrocracking of ethyllaurate on bifunctional micro-/mesoporous composite materials (M. Adam); (9) Catalytic dehydration of ethanol to ethylene (Ying Zhu); (10) The Evonik-Uhde HPPO process for propylene oxide production (B. Jaeger); (11) A green two-step process for adipic acid production from cyclohexene: A study on parameters affecting selectivity (F. Cavani); (12) DISY: The direct synthesis of hydrogen peroxide, a bridge for innovative applications (R, Buzzoni); (13) Solid catalyst with ionic liquid layer (SCILL) - A concept to improve the selectivity of selective hydrogenations (A. Jess); (14) Co-Zn-Al based hydrotalcites as catalysts for Fischer-Tropsch process (C.L. Bianchi); (15) Honeycomb supports with high thermal conductivity for the Fischer-Tropsch synthesis (C.G. Visconti); (16) How to make Fischer-Tropsch catalyst scale-up fully reliable (L. Fischer); (17) New developments in FCC catalysis (C.P. Kelkar); (18) The potential of medium-pore zeolites for improved propene yields from catalytic cracking (F. Bager).

DNA-Accelerated Copper Catalysis of Friedel-Crafts Conjugate Addition/Enantioselective Protonation Reactions in Water

NARCIS (Netherlands)

García-Fernández, Almudena; Megens, Rik P.; Villarino, Lara; Roelfes, Gerard

2016-01-01

DNA-induced rate acceleration has been identified as one of the key elements for the success of the DNA-based catalysis concept. Here we report on a novel DNA-based catalytic Friedel-Crafts conjugate addition/enantioselective protonation reaction in water, which represents the first example of a

Asymmetric catalysis in Brazil: development and potential for advancement of Brazilian chemical industry

International Nuclear Information System (INIS)

Braga, Antonio Luiz; Luedtke, Diogo Seibert; Schneider, Paulo Henrique; Andrade, Leandro Helgueira; Paixao, Marcio Weber

2013-01-01

The preparation of enantiomerically pure or enriched substances is of fundamental importance to pharmaceutical, food, agrochemical, and cosmetics industries and involves a growing market of hundreds of billions of dollars. However, most chemical processes used for their production are not environmentally friendly because in most cases, stoichiometric amounts of chiral inductors are used and substantial waste is produced. In this context, asymmetric catalysis has emerged as an efficient tool for the synthesis of enantiomerically enriched compounds using chiral catalysts. More specifically, considering the current scenario in the Brazilian chemical industry, especially that of pharmaceuticals, the immediate prospect for the use of synthetic routes developed in Brazil in an enantioselective fashion or even the discovery of new drugs is practically null. Currently, the industrial production of drugs in Brazil is primarily focused on the production of generic drugs and is basically supported by imports of intermediates from China and India. In order to change this panorama and move forward toward the gradual incorporation of genuinely Brazilian synthetic routes, strong incentive policies, especially those related to continuous funding, will be needed. These incentives could be a breakthrough once we establish several research groups working in the area of organic synthesis and on the development and application of chiral organocatalysts and ligands in asymmetric catalysis, thus contributing to boost the development of the Brazilian chemical industry. Considering these circumstances, Brazil can benefit from this opportunity because we have a wide biodiversity and a large pool of natural resources that can be used as starting materials for the production of new chiral catalysts and are creating competence in asymmetric catalysis and related areas. This may decisively contribute to the growth of chemistry in our country. (author)

Marvels of enzyme catalysis at true atomic resolution: distortions, bond elongations, hidden flips, protonation states and atom identities.

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Neumann, Piotr; Tittmann, Kai

2014-12-01

Although general principles of enzyme catalysis are fairly well understood nowadays, many important details of how exactly the substrate is bound and processed in an enzyme remain often invisible and as such elusive. In fortunate cases, structural analysis of enzymes can be accomplished at true atomic resolution thus making possible to shed light on otherwise concealed fine-structural traits of bound substrates, intermediates, cofactors and protein groups. We highlight recent structural studies of enzymes using ultrahigh-resolution X-ray protein crystallography showcasing its enormous potential as a tool in the elucidation of enzymatic mechanisms and in unveiling fundamental principles of enzyme catalysis. We discuss the observation of seemingly hyper-reactive, physically distorted cofactors and intermediates with elongated scissile substrate bonds, the detection of 'hidden' conformational and chemical equilibria and the analysis of protonation states with surprising findings. In delicate cases, atomic resolution is required to unambiguously disclose the identity of atoms as demonstrated for the metal cluster in nitrogenase. In addition to the pivotal structural findings and the implications for our understanding of enzyme catalysis, we further provide a practical framework for resolution enhancement through optimized data acquisition and processing. Copyright © 2014 Elsevier Ltd. All rights reserved.

Pyrolysis-catalysis of waste plastic using a nickel-stainless-steel mesh catalyst for high-value carbon products.

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Zhang, Yeshui; Nahil, Mohamad A; Wu, Chunfei; Williams, Paul T

2017-11-01

A stainless-steel mesh loaded with nickel catalyst was produced and used for the pyrolysis-catalysis of waste high-density polyethylene with the aim of producing high-value carbon products, including carbon nanotubes (CNTs). The catalysis temperature and plastic-to-catalyst ratio were investigated to determine the influence on the formation of different types of carbon deposited on the nickel-stainless-steel mesh catalyst. Increasing temperature from 700 to 900°C resulted in an increase in the carbon deposited on the nickel-loaded stainless-steel mesh catalyst from 32.5 to 38.0 wt%. The increase in sample-to-catalyst ratio reduced the amount of carbon deposited on the mesh catalyst in terms of g carbon g -1 plastic. The carbons were found to be largely composed of filamentous carbons, with negligible disordered (amorphous) carbons. Transmission electron microscopy analysis of the filamentous carbons revealed them to be composed of a large proportion (estimated at ∼40%) multi-walled carbon nanotubes (MWCNTs). The optimum process conditions for CNT production, in terms of yield and graphitic nature, determined by Raman spectroscopy, was catalysis temperature of 800°C and plastic-to-catalyst ratio of 1:2, where a mass of 334 mg of filamentous/MWCNTs g -1 plastic was produced.

CO- and HCl-free synthesis of acid chlorides from unsaturated hydrocarbons via shuttle catalysis

Science.gov (United States)

Fang, Xianjie; Cacherat, Bastien; Morandi, Bill

2017-11-01

The synthesis of carboxylic acid derivatives from unsaturated hydrocarbons is an important process for the preparation of polymers, pharmaceuticals, cosmetics and agrochemicals. Despite its industrial relevance, the traditional Reppe-type carbonylation reaction using pressurized CO is of limited applicability to laboratory-scale synthesis because of: (1) the safety hazards associated with the use of CO, (2) the need for special equipment to handle pressurized gas, (3) the low reactivity of several relevant nucleophiles and (4) the necessity to employ different, often tailor-made, catalytic systems for each nucleophile. Herein we demonstrate that a shuttle-catalysis approach enables a CO- and HCl-free transfer process between an inexpensive reagent, butyryl chloride, and a wide range of unsaturated substrates to access the corresponding acid chlorides in good yields. This new transformation provides access to a broad range of carbonyl-containing products through the in situ transformation of the reactive acid chloride intermediate. In a broader context, this work demonstrates that isodesmic shuttle-catalysis reactions can unlock elusive catalytic reactions.

Synthesis, Characterization and Applications in Catalysis of Polyoxometalate/Zeolite Composites

Directory of Open Access Journals (Sweden)

Frédéric Lefebvre

2016-05-01

Full Text Available An overview of the synthesis, characterization and catalytic applications of polyoxometalates/zeolites composites is given. The solids obtained by direct synthesis of the polyoxometalate in the presence of the zeolite are first described with their applications in catalysis. Those obtained by a direct mixing of the two components are then reviewed. In all cases, special care is taken in the localization of the polyoxometalate, inside the zeolite crystal, in mesopores or at the external surface of the crystals, as deduced from the characterization methods.

A solvable two-species catalysis-driven aggregation model

CERN Document Server

Ke Jian Hong

2003-01-01

We study the kinetics of a two-species catalysis-driven aggregation system, in which an irreversible aggregation between any two clusters of one species occurs only with the catalytic action of another species. By means of a generalized mean-field rate equation, we obtain the asymptotic solutions of the cluster mass distributions in a simple process with a constant rate kernel. For the case without any consumption of the catalyst, the cluster mass distribution of either species always approaches a conventional scaling law. However, the evolution behaviour of the system in the case with catalyst consumption is complicated and depends crucially on the relative data of the initial concentrations of the two species.

Multi-catalysis cascade reactions based on the methoxycarbonylketene platform: diversity-oriented synthesis of functionalized non-symmetrical malonates for agrochemicals and pharmaceuticals.

Science.gov (United States)

Ramachary, Dhevalapally B; Venkaiah, Chintalapudi; Reddy, Y Vijayendar; Kishor, Mamillapalli

2009-05-21

In this paper we describe new multi-catalysis cascade (MCC) reactions for the one-pot synthesis of highly functionalized non-symmetrical malonates. These metal-free reactions are either five-step (olefination/hydrogenation/alkylation/ketenization/esterification) or six-step (olefination/hydrogenation/alkylation/ketenization/esterification/alkylation), and employ aldehydes/ketones, Meldrum's acid, 1,4-dihydropyridine/o-phenylenediamine, diazomethane, alcohols and active ethylene/acetylenes, and involve iminium-, self-, self-, self- and base-catalysis, respectively. Many of the products have direct application in agricultural and pharmaceutical chemistry.

A practical approach to the sensitivity analysis for kinetic Monte Carlo simulation of heterogeneous catalysis

Science.gov (United States)

Hoffmann, Max J.; Engelmann, Felix; Matera, Sebastian

2017-01-01

Lattice kinetic Monte Carlo simulations have become a vital tool for predictive quality atomistic understanding of complex surface chemical reaction kinetics over a wide range of reaction conditions. In order to expand their practical value in terms of giving guidelines for the atomic level design of catalytic systems, it is very desirable to readily evaluate a sensitivity analysis for a given model. The result of such a sensitivity analysis quantitatively expresses the dependency of the turnover frequency, being the main output variable, on the rate constants entering the model. In the past, the application of sensitivity analysis, such as degree of rate control, has been hampered by its exuberant computational effort required to accurately sample numerical derivatives of a property that is obtained from a stochastic simulation method. In this study, we present an efficient and robust three-stage approach that is capable of reliably evaluating the sensitivity measures for stiff microkinetic models as we demonstrate using the CO oxidation on RuO2(110) as a prototypical reaction. In the first step, we utilize the Fisher information matrix for filtering out elementary processes which only yield negligible sensitivity. Then we employ an estimator based on the linear response theory for calculating the sensitivity measure for non-critical conditions which covers the majority of cases. Finally, we adapt a method for sampling coupled finite differences for evaluating the sensitivity measure for lattice based models. This allows for an efficient evaluation even in critical regions near a second order phase transition that are hitherto difficult to control. The combined approach leads to significant computational savings over straightforward numerical derivatives and should aid in accelerating the nano-scale design of heterogeneous catalysts.

Investigating heterogeneous nucleation in peritectic materials via the phase-field method

International Nuclear Information System (INIS)

Emmerich, Heike; Siquieri, Ricardo

2006-01-01

Here we propose a phase-field approach to investigate the influence of convection on peritectic growth as well as the heterogeneous nucleation kinetics of peritectic systems. For this purpose we derive a phase-field model for peritectic growth taking into account fluid flow in the melt, which is convergent to the underlying sharp interface problem in the thin interface limit (Karma and Rappel 1996 Phys. Rev. E 53 R3017). Moreover, we employ our new phase-field model to study the heterogeneous nucleation kinetics of peritectic material systems. Our approach is based on a similar approach towards homogeneous nucleation in Granasy et al (2003 Interface and Transport Dynamics (Springer Lecture Notes in Computational Science and Engineering vol 32) ed Emmerich et al (Berlin: Springer) p 190). We applied our model successfully to extend the nucleation rate predicted by classical nucleation theory for an additional morphological term relevant for peritectic growth. Further applications to understand the mechanisms and consequences of heterogeneous nucleation kinetics in more detail are discussed

Controlled trifluoromethylation reactions of alkynes through visible-light photoredox catalysis.

Science.gov (United States)

Iqbal, Naeem; Jung, Jaehun; Park, Sehyun; Cho, Eun Jin

2014-01-07

The control of a reaction that can form multiple products is a highly attractive and challenging concept in synthetic chemistry. A set of valuable CF3 -containing molecules, namely trifluoromethylated alkenyl iodides, alkenes, and alkynes, were selectively generated from alkynes and CF3 I by environmentally benign and efficient visible-light photoredox catalysis. Subtle differences in the combination of catalyst, base, and solvent enabled the control of reactivity and selectivity for the reaction between an alkyne and CF3 I. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Large-scale compositional heterogeneity in the Earth's mantle

Science.gov (United States)

Ballmer, M.

2017-12-01

Seismic imaging of subducted Farallon and Tethys lithosphere in the lower mantle has been taken as evidence for whole-mantle convection, and efficient mantle mixing. However, cosmochemical constraints point to a lower-mantle composition that has a lower Mg/Si compared to upper-mantle pyrolite. Moreover, geochemical signatures of magmatic rocks indicate the long-term persistence of primordial reservoirs somewhere in the mantle. In this presentation, I establish geodynamic mechanisms for sustaining large-scale (primordial) heterogeneity in the Earth's mantle using numerical models. Mantle flow is controlled by rock density and viscosity. Variations in intrinsic rock density, such as due to heterogeneity in basalt or iron content, can induce layering or partial layering in the mantle. Layering can be sustained in the presence of persistent whole mantle convection due to active "unmixing" of heterogeneity in low-viscosity domains, e.g. in the transition zone or near the core-mantle boundary [1]. On the other hand, lateral variations in intrinsic rock viscosity, such as due to heterogeneity in Mg/Si, can strongly affect the mixing timescales of the mantle. In the extreme case, intrinsically strong rocks may remain unmixed through the age of the Earth, and persist as large-scale domains in the mid-mantle due to focusing of deformation along weak conveyor belts [2]. That large-scale lateral heterogeneity and/or layering can persist in the presence of whole-mantle convection can explain the stagnation of some slabs, as well as the deflection of some plumes, in the mid-mantle. These findings indeed motivate new seismic studies for rigorous testing of model predictions. [1] Ballmer, M. D., N. C. Schmerr, T. Nakagawa, and J. Ritsema (2015), Science Advances, doi:10.1126/sciadv.1500815. [2] Ballmer, M. D., C. Houser, J. W. Hernlund, R. Wentzcovitch, and K. Hirose (2017), Nature Geoscience, doi:10.1038/ngeo2898.

Bayesian inversion analysis of nonlinear dynamics in surface heterogeneous reactions.

Science.gov (United States)

Omori, Toshiaki; Kuwatani, Tatsu; Okamoto, Atsushi; Hukushima, Koji

2016-09-01

It is essential to extract nonlinear dynamics from time-series data as an inverse problem in natural sciences. We propose a Bayesian statistical framework for extracting nonlinear dynamics of surface heterogeneous reactions from sparse and noisy observable data. Surface heterogeneous reactions are chemical reactions with conjugation of multiple phases, and they have the intrinsic nonlinearity of their dynamics caused by the effect of surface-area between different phases. We adapt a belief propagation method and an expectation-maximization (EM) algorithm to partial observation problem, in order to simultaneously estimate the time course of hidden variables and the kinetic parameters underlying dynamics. The proposed belief propagation method is performed by using sequential Monte Carlo algorithm in order to estimate nonlinear dynamical system. Using our proposed method, we show that the rate constants of dissolution and precipitation reactions, which are typical examples of surface heterogeneous reactions, as well as the temporal changes of solid reactants and products, were successfully estimated only from the observable temporal changes in the concentration of the dissolved intermediate product.

Human Manganese Superoxide Dismutase Tyrosine 34 Contribution to Structure and Catalysis

Science.gov (United States)

Perry, J. Jefferson P.; Hearn, Amy S.; Cabelli, Diane E.; Nick, Harry S.; Tainer, John A.; Silverman, David N.

2009-01-01

Superoxide dismutase (SOD) enzymes are critical in controlling levels of reactive oxygen species (ROS) that are linked to aging, cancer and neurodegenerative disease. Superoxide (O2 •−) produced during respiration is removed by the product of the SOD2 gene, the homotetrameric manganese superoxide dismutase (MnSOD). Here, we examine the structural and catalytic roles of the highly conserved active-site residue Tyr34, based upon structure-function studies of MnSOD enzymes with mutations at this site. Substitution of Tyr34 with five different amino acids retained the active site protein structure and assembly, but causes a substantial decrease in the catalytic rate constant for the reduction of superoxide. The rate constant for formation of product inhibition complex also decreases but to a much lesser extent, resulting in a net increase in the product inhibition form of the mutant enzymes. Comparisons of crystal structures and catalytic rates also suggest that one mutation, Y34V, interrupts the hydrogen-bonded network, which is associated with a rapid dissociation of the product-inhibited complex. Notably, with three of the Tyr34 mutants we also observe an intermediate in catalysis, which has not been reported previously. Thus, these mutants establish a means to trap a catalytic intermediate that promises to help elucidate the mechanism of catalysis. PMID:19265433

ISOTOPE METHODS IN HOMOGENEOUS CATALYSIS.

Energy Technology Data Exchange (ETDEWEB)

BULLOCK,R.M.; BENDER,B.R.

2000-12-01

The use of isotope labels has had a fundamentally important role in the determination of mechanisms of homogeneously catalyzed reactions. Mechanistic data is valuable since it can assist in the design and rational improvement of homogeneous catalysts. There are several ways to use isotopes in mechanistic chemistry. Isotopes can be introduced into controlled experiments and followed where they go or don't go; in this way, Libby, Calvin, Taube and others used isotopes to elucidate mechanistic pathways for very different, yet important chemistries. Another important isotope method is the study of kinetic isotope effects (KIEs) and equilibrium isotope effect (EIEs). Here the mere observation of where a label winds up is no longer enough - what matters is how much slower (or faster) a labeled molecule reacts than the unlabeled material. The most careti studies essentially involve the measurement of isotope fractionation between a reference ground state and the transition state. Thus kinetic isotope effects provide unique data unavailable from other methods, since information about the transition state of a reaction is obtained. Because getting an experimental glimpse of transition states is really tantamount to understanding catalysis, kinetic isotope effects are very powerful.