Metal Oxide-supported Cluster Catalysts Derived from Organometallic Precursors PDF Download
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Author: Felix ShangChung Lai
Publisher:
ISBN:
Category :
Languages : en
Pages : 1092
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Author: Felix ShangChung Lai
Publisher:
ISBN:
Category :
Languages : en
Pages : 1092
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Author: Bruce C. Gates
Publisher: Elsevier Publishing Company
ISBN:
Category : Science
Languages : en
Pages : 686
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Book Description
Research on metal clusters (compounds with metal-metal bonds) has undergone explosive growth and the subject is now perhaps one of the hottest'' topics in organometallic chemistry. The prospect of catalytic applications has motivated a large part of the research mentioned in this book - the long term goal being to exploit the unique properties of metal clusters to prepare catalysts with new activities and selectivities. This is the first book to address the role of metal clusters in catalysis. The coverage is up-to-date and is particularly comprehensive, ranging from molecular chemistry of clusters (synthesis, structure, thermochemistry, reactivity, and homogeneous catalysis) to supported clusters (molecular analogues on polymers, and metal oxides and metals in zeolite cages). Preparation by methods of organometallic surface chemistry and metal atom chemistry and characterization of surface structures by physical methods are highlighted. Concepts unifying metal cluster chemistry and the chemistry of metal surfaces are elucidated. Of particular value to the user will be the cluster and subject indexes. The cluster index is organized in alphabetical order according to the metal.
Author: Jean-Marie Basset
Publisher: Springer Science & Business Media
ISBN: 9400929714
Category : Science
Languages : en
Pages : 340
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Book Description
Surface organometallic chemistry is a new field bringing together researchers from organometallic, inorganic, and surface chemistry and catalysis. Topics ranging from reaction mechanisms to catalyst preparation are considered from a molecular basis, according to which the "active site" on a catalyst surface has a supra-molecular character. This. the first book on the subject, is the outcome of a NATO Workshop held in Le Rouret. France, in May. 1986. It is our hope that the following chapters and the concluding summary of recommendations for research may help to provide a definition of surface organometallic chemistry. Besides catalysis. the central theme of the Workshop, four main topics are considered: 1) Reactions of organometallics with surfaces of metal oxides, metals. and zeolites; 2) Molecular models of surfaces, metal oxides, and metals; 3) Molecular approaches to the mechanisms of surface reactions; 4) Synthesis and modification of zeolites and related microporous solids. Most surface organometallic chemistry has been carried out on amorphous high-surf ace-area metal oxides such as silica. alumina. magnesia, and titania. The first chapter. contributed by KNOZINGER. gives a short summary of the structure and reactivity of metal oxide surfaces. Most of our understanding of these surfaces is based on acid base and redox chemistry; this chemistry has developed from X-ray and spectroscopic data, and much has been inferred from the structures and reactivities of adsorbed organic probe molecules. There are major opportunities for extending this understanding by use of well-defined (single crystal) oxide surfaces and organometallic probe molecules.
Author: Y. Iwasawa
Publisher: Springer Science & Business Media
ISBN: 9789027718662
Category : Science
Languages : en
Pages : 358
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Book Description
Well tailored metal catalysts are catalysts of the new generation resulting from scientific development at the boundary between homogeneous and hetero geneous chemistry. The main factors involved in making tailored metal catalysts are not those of traditional impregnation in which the chemistry is in general unknown and ill-defined, or of simple ion exchange which involves long-range forces with little control on the local structure through definite and special bond direction. Tailored Metal Catalysts thus has a rather different emphasis from normal review publications in the field of catalysis. Here we concentrate more on the distinct surface chemistry and catalytic properties of important established materials with well-characterized active structures or precursors, although at the same time providing a systematic presentation of relevant data. Many pioneering works have been undertaken in the field of tailored metal catalysts since the early research on polymer-attached homogeneous metal complexes by the British Petroleum Company Ltd. and the Mobil Oil Corpora tion around 1969; transition metal complexes attached on polymers by Grubbs (1971), Heinemann (1971), Manassen (1971), Pittman (1971), Bursian et al. (1972), Kagan (1973), Bailar (1974); transition metal complexes attached on inorganic oxides by Allum et al. (1972), Ballard (1973), Candlin and Thomas (1974), Murrell (1974), Yermakov (1974); metal carbonyls/polymers by Moffat (1970); metal carbonyls/inorganic oxides by Parkyns (1965), Davie et al. (1969), Banks et al. (1969), Howe (1973), Burwell (1975); metal carbonyl clusters/ polymers by Colhnan (1972); metal carbonyl clusters/inorganic oxides by Robertson and Webb (1974), Anderson (1974), Smith et al. (1975).
Author: Joseph David Kistler
Publisher:
ISBN: 9781321211764
Category :
Languages : en
Pages :
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Site-isolated solid supported metal catalysts are important in industry and technology due to the cost efficiency to make and to recover and reuse them. These types of materials have catalytic properties similar to molecular complexes in solution while being easy to separate in heterogeneous catalytic reactions. The goal of this work was to synthesize supported metal complex catalysts while maintaining uniform catalytic sites. The syntheses were performed using precise glovebox and Schlenk techniques to achieve these highly uniform structures. These materials were then used to understand the relationship between structure of a catalytic site and the activity of the catalyst. This fundamental understanding of catalysts is important in advancing the field of catalysis. The structure of the catalysts were characterized using infrared (IR), extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge structure (XANES) spectroscopies along with high angle annular dark field- scanning transmission electron microscopy (HAADF-STEM), with the HAADF-STEM work carried out by colleagues in other research groups. The catalytic activity of the catalysts was examined with gas chromatography (GC) and mass spectrometry (MS). The samples characterized in this work include complexes and clusters of second and third row transition metals supported on highly crystalline metal oxides. Specifically, there is a large focus in this work on supported rhodium complexes prepared from the organometallic precursor, Rh(C2H4)2(C5H7O2) and a pre-calcined magnesium oxide (MgO). This specific catalyst is important as not only is it active for olefin hydrogenation at mild temperatures but also there are reports of a unique surface mediated synthesis of uniform rhodium dimers, which are ideal for catalytic comparison of structures with different nuclearities. Reactivities of the MgO-supported rhodium complexes and dimers for carbon monoxide oxidation were investigated with the results showing the dimers were significantly more active for the reaction at 353 K. The stability of the dimers was tested in different reactive conditions with the results showing that under conditions with excess oxygen, the dimers are less stable and less active than under conditions with excess carbon monoxide.A bimetallic catalyst was synthesized on MgO incorporating rhodium and osmium using Rh(C2H4)2 (acac) and Os3(CO)12 as precursors. A unique synthesis method was developed to create a site-isolated segregated bimetallic catalyst with the osmium and rhodium sites acting independently of each other for ethylene hydrogenation at 298 K. The metals remained structurally segregated and catalytically independent even following reduction in H2 at 393 K. Zeolites, another class of highly crystalline supports, were studied to gain information on the support effects in catalysts. The analogous rhodium complexes as were synthesized on the MgO were synthesized on zeolite HY. These catalysts were tested to determine structural and catalytic stability under hydrogen, a reducing gas, and CO, a catalyst poison, with the results showing that, as compared to the complexes on zeolite HY, MgO-supported rhodium complexes form more uniform stable clusters under H2 and develop unique catalytic properties, selectivity for partial hydrogenation of dienes, when exposed to CO. Another zeolite, KLTL, was studied with supported platinum complexes synthesized from the salt precursor, Pt(NH3)4(NO3)2. This catalyst was oxidized at 633K to form supported single-atom platinum complexes. Both the as-prepared Pt(NH3)4 and oxidized PtOx complexes were analyzed structurally and studied as catalysts for CO oxidation. The oxidized platinum complexes proved to have significantly higher activity for CO oxidation at 423 K. Furthermore, HAADF-STEM was used to directly identify the locations of the platinum atoms in the pores of the zeolite before and after oxidative treatment, providing a method of ex-situ tracking of supported metal atoms.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 12
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This research project, now in its third year, is an investigation of the synthesis, structure, and bonding of a family of metal complexes, clusters, and particles on the surfaces of high-area metal oxide supports. The focus is the structure of the metal-support interface. Surface species have been prepared by synthetic organometallic chemistry on the support surfaces. The organometallic precursors are complexes of W, Re, Os, Ir, and Pt, including W(CO)6, HRe(CO)5, Re2(CO)10, H3Re3(CO)12, H2Os(CO)4, Ir([eta]3-C3H5)3, and Pt([eta]3-C3H5)2. The supports are primarily MgO and [gamma]-Al2O3. The surface species have been characterized by infrared and EXAFS spectroscopies, among other techniques. 7 refs., 5 figs., 4 tabs.
Author: R.M. Lambert
Publisher: Springer Science & Business Media
ISBN: 9401589119
Category : Science
Languages : en
Pages : 534
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Book Description
Heterogeneous catalysis provides the backbone of the world's chemical and oil industries. The innate complexity of practical catalytic systems suggests that useful progress should be achievable by investigating key aspects of catalysis by experimental studies on idealised model systems. Thin films and supported clusters are two promising types of model system that can be used for this purpose, since they mimic important aspects of the properties of practical dispersed catalysts. Similarly, appropriate theoretical studies of chemisorption and surface reaction clusters or extended slab systems can provide valuable information on the factors that underlie bonding and catalytic activity. This volume describes such experimental and theoretical approaches to the surface chemistry and catalytic behaviour of metals, metal oxides and metal/metal oxide systems. An introduction to the principles and main themes of heterogeneous catalysis is followed by detailed accounts of the application of modern experimental and theoretical techniques to fundamental problems. The application of advanced experimental methods is complemented by a full description of theoretical procedures, including Hartree-Fock, density functional and similar techniques. The relative merits of the various approaches are considered and directions for future progress are indicated.
Author: C. Copéret
Publisher: Springer Science & Business Media
ISBN: 9783540264965
Category : Science
Languages : en
Pages : 312
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Book Description
With contributions by numerous experts
Author: Robert Rioux
Publisher: Springer Science & Business Media
ISBN: 0387980490
Category : Science
Languages : en
Pages : 531
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Book Description
This book is an excellent compilation of cutting-edge research in heterogeneous catalysis and related disciplines – surface science, organometallic catalysis, and enzymatic catalysis. In 23 chapters by noted experts, the volume demonstrates varied approaches using model systems and their successes in understanding aspects of heterogeneous catalysis, both metal- and metal oxide-based catalysis in extended single crystal and nanostructured catalytic materials. To truly appreciate the astounding advances of modern heterogeneous catalysis, let us first consider the subject from a historical perspective. Heterogeneous catalysis had its beginnings in England and France with the work of scientists such as Humphrey Davy (1778–1829), Michael Faraday (1791–1867), and Paul Sabatier (1854–1941). Sabatier postulated that surface compounds, si- lar to those familiar in bulk to chemists, were the intermediate species leading to catalytic products. Sabatier proposed, for example, that NiH moieties on a Ni sur- 2 face were able to hydrogenate ethylene, whereas NiH was not. In the USA, Irving Langmuir concluded just the opposite, namely, that chemisorbed surface species are chemically bound to surfaces and are unlike known molecules. These chemisorbed species were the active participants in catalysis. The equilibrium between gas-phase molecules and adsorbed chemisorbed species (yielding an adsorption isotherm) produced a monolayer by simple site-filling kinetics.
Author: Irina Vladimirovna Gubkina Graf
Publisher:
ISBN:
Category :
Languages : en
Pages : 492
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