[PDF] Investigations Into The Direct Synthesis Of Hydrogen Peroxide And Co Oxidation Using Precious Metal Catalysts eBook

Author : Simon James Freakley
Publisher :
Page : pages
File Size : 26,6 MB
Release : 2012
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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.

Author : G. Strukul
Publisher : Springer Science & Business Media
Page : 287 pages
File Size : 30,59 MB
Release : 2013-03-14
Category : Science
ISBN : 940170984X

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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.

Author : C W Jones
Publisher : Royal Society of Chemistry
Page : 276 pages
File Size : 15,90 MB
Release : 2007-10-31
Category : Science
ISBN : 1847550134

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Simple, but beautifully versatile. Perhaps not a description many would choose for hydrogen peroxide, but an accurate one none the less, and this unique book explains the reasons behind the description. Beginning with an historical overview, and guidelines for the safe handling of peroxygens, Applications of Hydrogen Peroxide and Derivatives goes on to cover key activation mechanisms, organic functional group oxidations and the use of hydrogen peroxide with heterogeneous catalysts. The clean-up of environmental pollutants; chemical purification; and extraction of metals from their ores are also discussed in detail, using actual examples from industry. The versatility of this reagent may well prove to be a key to integrated pollution control in the future. This book should therefore be read by academics and industrialists at all levels, to encourage wider applications of the use of hydrogen peroxide in laboratories.

Author : Anthony David Plauck
Publisher :
Page : 0 pages
File Size : 36,52 MB
Release : 2016
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The widespread use of hydrogen peroxide (H2O2) for catalytic oxidations is limited by the wasteful process by which it is currently produced: the anthraquinone process. The direct synthesis of H2O2 (DSHP) is a promising alternative process. One primary technical obstacle to its commercialization is the identification of sufficiently active and selective heterogeneous catalysts. Although Pd is a promising active component that is used in most catalyst formulations, two factors have restricted the search directions for improved DSHP catalysts to experimental trial and error: (i) the reaction mechanisms are not resolved, and (ii) the active site requirements are poorly understood. Addressing these factors is complicated by the existence of multiple side reactions and the inherent complexities of heterogeneous catalysts and the DSHP reaction environment. In this dissertation, we employ density functional theory calculations to develop an atomic-scale understanding of the DSHP on Pd-based catalysts. We propose reaction mechanisms and analyze Pd's intrinsic reactivity toward forming H2O2 versus H2O from H2 and O2. We also develop an experimentally-consistent microkinetic model that describes H2O2 decomposition on Pd; one of the major drawbacks of Pd catalysts is high activity toward this undesirable reaction. Through these studies we highlight specific mechanistic challenges, including the identification of likely rate-limiting steps. We then consider how catalyst structure and composition can be modified to mitigate these challenges. We analyze the impact of the coordinative saturation of the Pd surface, the role of halides and Au as catalytic promoters, and the effect of phase transformations induced by the reaction environment. Our work demonstrates the utility of computational chemistry in deconvoluting complex catalytic systems - especially when coupled with experimental and microkinetic analyses. The results can potentially be used to build a framework that guides the search for new DSHP catalysts.

Author : Michel Boudart
Publisher : Princeton University Press
Page : 241 pages
File Size : 30,66 MB
Release : 2014-07-14
Category : Science
ISBN : 1400853338

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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 editions preserve the original texts of these important books while presenting them in durable paperback and hardcover editions. The goal of the Princeton Legacy Library is to vastly increase access to the rich scholarly heritage found in the thousands of books published by Princeton University Press since its founding in 1905.

Author : H.U. Blaser
Publisher : Elsevier
Page : 693 pages
File Size : 22,69 MB
Release : 1997-06-19
Category : Technology & Engineering
ISBN : 0080533930

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After three meetings in Poitiers, France, the 4th International Symposium on Heterogeneous Catalysis and Fine Chemicals was held under the auspices of the New Swiss Chemical Society in Basel, Switzerland. Fundamental as well as applied contributions on the use of heterogeneous catalysis for the preparation of fine chemicals were presented and discussed. The program consisted of 4 plenary lectures, 28 oral contributions and around 90 posters covering a broad range of reactions and catalytic aspects. 82 of these contributions are collected in the present proceedings, grouped into the following 8 topical areas: - Industrial and engineering problems (7 contributions) - Alkylation and acylation reactions (11 contributions) - Enantio- and diastereoselective hydrogenation reactions (9 contributions) - Chemoselective hydrogenation reactions (12 contributions) - Oxidation reactions (14 contributions) - Immobilized and encapsulated complex catalysts (12 contributions) - Zeolite and clay catalysts (12 contributions) - Miscellaneous topics (5 contributions)

Author : Greg Shaw
Publisher :
Page : pages
File Size : 20,48 MB
Release : 2013
Category :
ISBN :

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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.