Download or read book Synthesis of Titanium Catalyst Containing Polystyrene and Its Catalytic Activity in Epoxidation of 1 octene with Using Hydrogen Peroxide written by Mohd. Hayrie Mohd. Hatta and published by . This book was released on 2011 with total page 47 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Silica Coated Titanium Oxide as Catalyst in the Epoxidation of 1 octene with Aqueous Hydrogen Peroxide written by Yew Hean Chua and published by . This book was released on 2006 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Enhancing the Catalytic Activity of Site Isolated Heterogeneous Transition Metal Expoxidation Catalysts Prepared Via the Thermolytic Molecular Precursor Method written by Paul Joseph Cordeiro and published by . This book was released on 2010 with total page 242 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation describes the application of the thermolytic molecular precursor (TMP) method for the synthesis of new heterogeneous catalysts and the performance of these catalysts in the epoxidation of olefins with simple peroxides. The precursors used in this method include complexes of the form LnM[OE(X)3]m, where Ln = OiPr, E = Si or Ge, X = iPr or OtBu, and M = Ti(IV) or Ta(V). These precursors were employed to introduce site-isolated metal centers onto the surface of mesoporous silica (SBA-15), and represent excellent models for the supported metal sites generated. The precursors and materials were characterized using a variety of analytical techniques, and structural comparisons are presented. Surface modification has been used to introduce new functionalities designed to enhance the catalytic activity of two types of supported catalysts, and the effect of the new functionalities was explored. Additionally, a new precursor containing some of these new functionalities has been synthesized and employed to generate new catalytic materials. Site-isolated Ta(V) centers were introduced onto the surface of a mesoporous SBA-15 support via the thermolytic molecular precursor method. After treatment in oxygen, the resulting Si-OH and Ta-OH sites of TaSBA15-O2 were modified with a series of trimethyl group 14 species, Me3E-, by treatment with Me3E-NMe2 (E = Si, Ge, Sn) reagents. The surface modified catalysts, (Me3E)capTaSBA15, exhibit a significantly increased rate of cyclohexene epoxidation with H2O2 as an oxidant, and a decreased amount of allylic oxidation products with respect to the unmodified material, TaSBA15-O2. The rate of non-productive H2O2 decomposition, as monitored via 1H NMR spectroscopy, significantly decreased after the surface modification. The structure of the TaSBA15 catalysts and potential Ta(V) epoxidation intermediates (formed upon treatment of Ta(V) materials with H2O2) were probed using UV-visible absorbance and diffuse-reflectance UV-visible spectroscopy. A Ta(V)([eta]2-O2) intermediate species is proposed for the TaSBA15-O2, (Me3Si)capTaSBA15, and (Me3Ge)capTaSBA15 catalysts, while intermediate species for the (Me3Sn)capTaSBA15 catalysts could not be characterized. The thermolytic molecular precursor method was used to introduce site-isolated Ti(IV) centers onto the surface of a mesoporous SBA-15 support. Prior to thermal treatment to generate Ti-OH sites, residual silanol groups were capped via reaction with Me2N-SiMe3 to give TiMecapSBA15. After low-temperature treatment in oxygen, the resulting Ti-OH sites of TiMecapSBA15-O2 were modified by reaction with a series of protic reagents: phenol, pentafluorophenol, acetic acid, and trifluoroacetic acid. The structure of the resulting TiSBA15 catalysts and the Ti(IV) epoxidation intermediates (formed upon treatment of Ti(IV) materials with tert-butyl hydroperoxide or H2O2) were probed using diffuse-reflectance UV-visible spectroscopy and infrared spectroscopy. A titanium-hydroperoxo species similar to that found in TS-1 is proposed for all catalysts. Samples modified with phenol and pentafluorophenol exhibited conversions of 1-octene that are 20 to 50% higher than those for TiMecapSBA15-O2, without a significant drop in selectivity for the epoxide product, 1,2-epoxyoctane, when TBHP was used as the oxidant. With aqueous H2O2 as the oxidant, the phenol-treated materials exhibited 1-octene conversions that are 15 to 50% greater than those observed for TiMecapSBA15-O2, and an increased selectivity for 1,2-epoxyoctane of 10 to 30%. Additionally, the efficiency of H2O2 usage, as monitored via 1H NMR spectroscopy, increased by a factor of two to three for catalysts modified with phenol and pentafluorophenol, with respect to the efficiency observed over TiMecapSBA15-O2. Catalysts modified with acetic acid and trifluoroacetic acid displayed decreased catalytic turnover numbers and epoxide selectivities when TBHP was used as the oxidant, but exhibited catalytic turnover numbers and epoxide selectivities similar to TiMecapSBA15-O2 when H2O2 was used as the oxidant. After treatment of TiMecapSBA15-O2 with acetic acid, the H2O2 efficiency decreased by a factor of two for the epoxidation of 1-octene with H2O2. The complex Ti[OGe(iPr)3]4 (1) was prepared via the reaction of Ti(OiPr)4 with (iPr)3GeOH, and is a useful structural and spectroscopic model for titanium-germanium species dispersed on silica. This precursor was used to introduce site-isolated Ti(IV) centers onto the surface of a mesoporous SBA-15 support via the thermolytic molecular precursor method. The supported materials, TiGe4SBA15, are active catalysts for the epoxidation of cyclic and terminal olefins with alkyl hydroperoxides under anhydrous conditions. Compared to catalysts synthesized from siloxide-only precursors (TiSi4SBA15), the new catalysts (TiGe4SBA15) displayed two to three times higher catalytic turnover numbers during identical cyclohexene and 1-octene epoxidation reactions, while simultaneously maintaining higher selectivity. The new materials did not significantly leach under these conditions, demonstrating the robustness of this new complex as a molecular precursor to supported titanium(IV) epoxidation catalysts.
Download or read book Catalytic Reaction Engineering of Propene Epoxidation with Hydrogen Peroxide Over Titanium Silicalite TS 1 written by Sang Baek Shin and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Ruthenium written by Hitoshi Ishida and published by BoD – Books on Demand. This book was released on 2022-01-26 with total page 228 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ruthenium is a precious metal not widely known to non-scientists. It is a target of much research, however. It is used in computer hard drives, the tips of fountain pens, and as a catalyst to purify car exhaust, among other uses. This book presents information and research on the properties and applications of ruthenium, including potential uses in phytochemical functions and anticancer activity.
Download or read book Applications of Polymers written by Raymond Seymour and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 154 pages. Available in PDF, EPUB and Kindle. Book excerpt: Natural polymers, such as proteins, starch, cellulose, hevea rubber, and gum which have been available for centuries, have been applied as materials for food, leather, sizings, fibers, structures, waterproofing, and coatings. During the past century, the use of both natural and syn thetic polymers has been expanded to include more intricate applications, such as membranes, foams, medicinals, conductors, insulators, fibers, films, packaging and applications requiring high modulus at elevated temperatures. The topics in this symposium which are summarized in this book are illustrative of some of the myriad applications of these ubiquitous mater ials. As stated in forecast in the last chapter in this book, it is cer tain that revolutionary applications of polymers will occur during the next decades. Hopefully, information presented in other chapters in this book will catalyze some of these anticipated applications. It is appropriate that these reports were presented at an American Chemical Society Polymer Science and Engineering Division Award Symposium honoring Dr. O.A. Battista who has gratifying to note that Phillips Pet roleum Company, which has paved the way in applications of many new poly mers, is the sponsor of this important award. We are all cheerfully expressing our thanks to this corporate spon sor and to Distinguished Professor Raymond B. Seymour of the University of Southern Mississippi who served as the organizer of this symposium and editor of this important book.
Download or read book Development of Homogeneous and Heterogeneous Epoxidation Catalysts Using Simple Mn II superscript Complexes and Peracetic Acid written by Andrew J. Murphy and published by . This book was released on 2005 with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Oligomerization and Polymerization of Ethylene by Phenoxy imine Titanium Catalysts written by Astrid Cordier and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: 1-hexene is one of the most important olefin used as comonomer for the production of value-added polyethylenes (HDPE, LLDPE). In the field of selective ethylene trimerization employing titanium-based catalysts, specific single tridentate phenoxy-imine complexes (SFI) display the highest activity and 1-hexene selectivity upon activation with methylaluminoxane (MAO). However, ethylene polymerization is an unavoidable side reaction affecting both 1-hexene selectivity and process operations. Although being a major drawback, the causes of polymerization remain a grey area since few studies were dedicated to its deciphering. To handle this challenge , an original “polymer-to-catalyst” strategy was implemented. An extensive temperature study (26-80°C) revealed that the highest 1-hexene activity is reached between 30 °C and 40 °C while polymer production is prominent above 50 °C. Polyethylenes obtained were analyzed by SEC, NMR DSC, and advanced segregation techniques (CEF, SIST, rheology). Molar masses above 10^5 g mol-1 were identified along with a 1-hexene content below 1 mol %. An increase of dispersity (Ɖ > 2) with temperature was ascribed to an evolution from single to multi-site polymerization catalysis. Kinetic studies proved that polymer is continuously produced even at short reaction time, for any reaction temperature. Other parameters (addition of 1-hexene, hydrogen and use of trimethylaluminum) were found to impair the trimerization selectivity and/or activity of the system. Nevertheless, it was possible to lower the selectivity in polyethylene by premixing the complex with MAO. After analyzing the possible routes for the polymerization catalyst formation, the hypotheses of temperature and MAO-induced complex alterations were considered. Regarding the latter, a molecular ligand-free Ziegler-Natta catalyst, modeled using TiCl4/MAO, and the synthesized (FI)Ti(III)Cl2 activated by MAO could not explain polymer production in the SFI system. Formation of a polymerization species upon thermal alteration of the SFI complex was evidenced. This [O-,N,O-]-type species displays common features regarding catalytic response to 1-hexene compared to the polymerization catalyst in the SFI system although it could not reach the same catalytic performances. The formation of a bis(phenoxy-imine) complex (FI)2TiCl2 was evidenced in this thesis and is a promising avenue worth exploring. Eventually, although the exact species has not yet been identified, this work enabled to guide the focus of further investigations on activation process and complex rearrangement by ligand mobility.
Download or read book New Systems for Catalytic Asymmetric Epoxidation written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis describes the catalytic asymmetric epoxidation of olefins mediated by chiral iminum salts. The first chapter introduces some of the most novel and effective catalytic asymmetric methods for preparing chiral oxiranes. The second chapter is divided into three sections. The first section of chapter two is dedicated to our efforts to develop new aqueous oxidative conditions using both hydrogen peroxide and sodium hypochlorite as efficient, green oxidants that remove the temperature boundaries observed with the use of Oxone® as the stoichiometric oxidant. A wider range of available temperatures was examined allowing optimization of both oxidative systems. Ethereal hydrogen peroxide was observed to mediate asymmetric epoxidation within an acetonitrile monophasic co-solvent system giving enantioselectivities of up to 56%. When sodium hypochlorite was used in a biphasic solvent system in conjunction with dichloromethane; it was observed to mediate oxidation of the substrate alkenes in up to 71% ee. The second and third sections of chapter two are dedicated to our efforts to synthesize chiral iminium salts as catalysts for asymmetric epoxidation based on a biphenyl azepinium salt catalyst structure. From previous work within the Page group, the asymmetric synthesis and subsequent defined stereochemistry of a chiral carbon atom α to the iminium nitrogen atom was shown to have significant effect on the enantiocontrol of epoxidation using the iminium salt catalyst. Work was completed on biphenyl azepinium salt catalysts, inserting an alkyl or aryl Grignard reagent into the iminium bond using a pre-defined dioxane unit as a chiral auxiliary. Oxidation of the subsequent azepine gave a single diastereoisomerically pure azepinium salt. The methyl analogue of this sub-family of azepinium catalysts has been shown to give up to 81% ee for epoxidation of 1-phenylcyclohexene, furthermore, the binaphthalene azepinium salt with an additional methyl group was also synthesized a.
Download or read book Catalyst Separation Recovery and Recycling written by David J. Cole-Hamilton and published by Springer Science & Business Media. This book was released on 2006-01-13 with total page 270 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book looks at new ways of tackling the problem of separating reaction products from homogeneous catalytic solutions. The new processes involve low leaching supported catalysts, soluble supports such as polymers and dendrimers and unusual solvents such as water, fluorinated organics, ionic liquids and supercritical fluids. The advantages of the different possibilities are discussed alongside suggestions for further research that will be required for commercialisation. Unlike other books, in addition to the chemistry involved, the book looks at the process design that would be required to bring the new approaches to fruition. Comparisons are given with existing processes that have already been successfully applied and examples are given where these approaches are not suitable. The book includes: - New processes for the separation of products from solutions containing homogeneous catalysts - Catalysts on insoluble or soluble supports – fixed bed catalysts - continuous flow or ultrafiltration - Biphasic systems: water - organic, fluorous - organic, ionic liquid – organic, supercritical fluids (monophasic or biphasic with water, organic or ionic liquid) - Comparisons with current processes involving atmospheric or low temperature distillation - Consideration of Chemistry and Process Design - Advantages and disadvantages of each process exposed - Consideration of what else is need for commercialisation
Download or read book Precision Synthesis of Heterogeneous Epoxidation Catalysts Based on Ti written by Philipp Mania and published by Sudwestdeutscher Verlag Fur Hochschulschriften AG. This book was released on 2014-05-13 with total page 240 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this work, different catalysts were synthesized by chemical vapor deposition of titanium tetrachloride onto Aerosil200 from Evonik(c) serving as an amorphous silica source, similar to the synthesis of the catalyst of Shell's SMPO process(c), and presumably also similar to the titanium site in TS-1(c). The catalysts were characterized by different spectroscopical methods (e.g. 35Cl NMR, 51V NMR, isotope exchange experiments) and molecuar models for the as obtained surface species were suggested. Finally, the prepared catalysts were used for kinetic experiments and compared to TS-1(c) in epoxidation of different olefi
Download or read book Precision Synthesis of Heterogeneous Epoxidation Catalysts Based on Titanium written by Philipp Mania and published by . This book was released on 2013 with total page 166 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Surface Organometallic Chemistry Molecular Approaches to Surface Catalysis written by Jean-Marie Basset and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 340 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book The Direct Synthesis of Hydrogen Peroxide Using Bimetallic Gold and Palladium Supported Catalysts written by Greg Shaw and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis the direct synthesis of hydrogen peroxide from hydrogen and oxygen using gold-palladium supported catalysts is described. The direct route presents a greener and sustainable alternative to the current industrial manufacture process. This work aims to meet industrial requirements set by Solvay® which would make the direct process industrially viable. The drawback preventing the requirements being met is the reaction of hydrogen and oxygen over a catalyst can yield water as well as hydrogen peroxide. Once H2O2 is formed, it can be consumed by either reduction or decomposition. Thus, the rates of the subsequent reactions must be minimized to increase the selectivity and therefore H2O2 concentration to a desirable level. Aspects of the catalyst design and reaction variables have been studied over three results chapters. Firstly, the thermal treatment conditions have been altered, ultimately producing a catalyst with no activity to the H2O2 consumption under standard conditions. Switching off H2O2 hydrogenation was concluded to be due to an increase in Pd2+, isolating active Pd0 species. Secondly, active catalysts to both the synthesis and hydrogenation of H2O2 have been produced with no halide; the addition of halide has been shown to decrease hydrogenation activity while maintaining synthesis activity. Finally, a biphasic solvent system and a constant flow of gases through the reaction medium have been examined in order to produce higher H2O2 concentrations. In the former case H2O2 is extracted in-situ from an immiscible organic phase. The production of a 3 wt% H2O2 solution highlights the potential of such a system. In the latter case a semi-continuous flow reactor is utilised increasing the H2O2 concentration up to ca. 1 wt% (from ca. 0.2 wt%). The reactor allowed H2 selectivity and H2O concentration to be measured as a function of time, thus providing greater insight into catalyst activity.
Download or read book Preparation of Cobalt Titanium Silicalite 1 Catalyst written by Nitiporn Sangngaen and published by . This book was released on 2005 with total page 188 pages. Available in PDF, EPUB and Kindle. Book excerpt: Titanium silicalite incorporated with various content of cobalt was synthesized by the hydrothermal method. The synthesized catalyst (Co-TS-1) were characterized by various techniques XRF, BET, XRD, FT-IR, SEM, XPS and NH[subscript 3]-TPD, to study the effects of cobalt on the formation of titanium silicalite crystal. The oxidation properties of Co-TS-1 catalysts were investigated by using the gas phase oxidation reaction of 2-propanol as the test reaction. The study reveals that the maximum amount of cobalt which can be incorporated into the TS-1 structure without any interference to the main TS-1 structure is about 0.38 mol%. The analysis by XPS reveals that the oxidation state of cobalt cation in the TS-1 framework is +2. In addition, the incorporation of cobalt increases the amount of the weak acid site while the amount of the strong acid site decreases. The Co-TS-1 catalysts exhibit higher catalytic activity for the dehydration reaction than theunmodified TS-1 was also found that the selectivity toward propylene of Co-TS-1 is also higher than that of the unmodified TS-1.
Download or read book Investigations Into the Direct Synthesis of Hydrogen Peroxide and CO Oxidation Using Precious Metal Catalysts written by Simon James Freakley and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The direct synthesis of hydrogen peroxide from molecular hydrogen and oxygen represents an attractive atom efficient alternative to the current industrial auto-oxidation process which relies on the sequential oxidation and reduction of an anthraquinone. The first and most widely studied catalysts for this reaction were palladium based however over-hydrogenation of the synthesised hydrogen peroxide is a problem. Recent advances demonstrate that the addition of gold to the catalyst has been shown to significantly improve the productivity of the catalysts by suppressing the hydrogenation and decomposition activity. The work in this thesis shows that tin can be used as a catalyst additive as a direct replacement for gold by a simple impregnation method. By tuning the heat treatments of these bimetallic tin-palladium catalysts it was possible to switch off the competing hydrogenation and decomposition reactions. The construction of a small scale flow system has allowed the independent study of reaction variables and the determination of global kinetics and rate constants for the synthesis and subsequent reactions. It was shown that in a flow system it was the decomposition reaction that had a greater limiting effect on the production of hydrogen peroxide than the hydrogenation reaction. A study was also carried out into CO oxidation using gold / iron oxide catalyst prepared in Cardiff and by Prof. Haruta's group in Tokyo. These catalysts underwent extensive tests to try and identify the active species of the catalyst. Detailed testing and STEM characterisation of the samples identified the possibility of different mechanisms operating at different temperatures and no correlation between the nanoparticle population and activity at sub ambient temperature could be made which challenges the hypothesis that nanoparticles are the most active species and that sub nanometer clusters may be the active species at low temperatures.
Download or read book Catalytic Oxidations with Hydrogen Peroxide as Oxidant written by G. Strukul and published by Springer Science & Business Media. This book was released on 2013-03-14 with total page 287 pages. Available in PDF, EPUB and Kindle. Book excerpt: Hydrogen peroxide is a chemical that is becoming increasingly fashionable as an oxidant, both in industry and in academia and whose production is expected to increase significantly in the next few years. This growth in interest is largely due to environmental considerations related to the clean nature of hydrogen peroxide as an oxidant, its by-product being only water. To date this chemical has largely been employed as a non-selective oxidant in operations like the bleaching of paper, cellulose and textiles, or in the formulation of detergents, and only to a minimal extent in the manufacture of organic chemicals. This book has been organized to cover the different aspects of the chemistry of hydrogen peroxide. The various chapters into which the book is divided have been written critically by the authors with the general aim of stimulating new ideas and emphasizing those aspects that are likely to lead to new developments in organic synthesis in the coming future.
