Contribution à l'étude de l'activation des catalyseurs métalliques supportés préparés sous irradiation microonde PDF Download

Author: Stéphanie Hilaire
Publisher:
ISBN:
Category :
Languages : fr
Pages : 113

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Ce travail est consacré à l'étude de la préparation et de la réactivité, sous irradiation microonde, de catalyseurs métalliques supportés (Pt, Pd, Ir, Pt-Re, Pt-Sn, Pt-Co et Pt-W). La réaction-test d'isomérisation des hexanes sur ces catalyseurs permet d'évaluer l'influence du traitement microonde sur leur préparation et leur activation. Les catalyseurs au platine dispersé sur différents supports - alumine y, alumine acide-chlorée et silice - présentent un accroissement significatif et permanent de leur sélectivité en isomères lorsqu'ils sont activés sous chauffage microonde par comparaison à la sélectivité en isomères qu'ils présentent lorsqu'ils sont préparés classiquement. L'effet du traitement microonde est en relation directe avec l'étape de réduction. Il dépend de l'état de viellissement de la solution d'acide hexachloroplatinique, de la proportion en eau du mélange d'imprégnation et de la présence de rhénium (EuroPt-4) ou d'étain. Il ne dépend pas de la présence d'ions chlorures sur le support (EuroPt-3). [...]

Author: DJAHIDA.. ROUABAH
Publisher:
ISBN:
Category :
Languages : fr
Pages :

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LES CATALYSEURS PT-AU ONT ETE PREPARES PAR IMPREGNATION D'UNE ALUMINE NON POREUSE PAR UNE SOLUTION HEXACHLOROPLATINIQUE ET TETRACHLOROAURIQUE. APRES DECOMPOSITION SOUS OXYGENE, ILS ONT ETE REDUITS SOUS HYDROGENE A LA TEMPERATURE DE 220 A 400C. LES METHODES UTILISEES POUR ETUDIER CES CATALYSEURS SONT: - CHIMISORPTION D'HYDROGENE PAR VOLUMETRIE; - MICROSCOPIE ELECTRONIQUE; - R.M.N.-#1H; - R.M.N.-#1#2#9XE; - ACTIVITE CATALYTIQUE; - THERMODESORPTION PROGRAMMEE. LA CONCENTRATION MAXIMALE DE METAL EST DE 10% PONDERALE. LA DISPERSION DETERMINEE PAR MICROSCOPIE ELECTRONIQUE AUGMENTE AVEC LA CONCENTRATION EN OR. L'ETUDE PAR R.M.N.-#1H NOUS A PERMIS DE PRECISER L'INFLUENCE DE LA CONCENTRATION EN ADSORBAT H#2, DE LA TEMPERATURE DE CHIMISORPTION ET DE LA TAILLE DES PARTICULES DE PLATINE SUPPORTE SUR LE DEPLACEMENT CHIMIQUE DE L'HYDROGENE CHIMISORBE SUR CES DERNIERES. CE PREMIER STADE DE LA CHIMISORPTION CORRESPOND A UN RECOUVREMENT BIEN DETERMINE, D'AUTANT PLUS GRAND QUE LA TEMPERATURE EST BASSE. LE DEPLACEMENT CHIMIQUE CORRESPONDANT EST NEGATIF ET AUGMENTE EN VALEUR ABSOLUE AVEC LA TAILLE DES PARTICULES. AINSI, LE SPECTRE COMPREND AUTANT DE COMPOSANTS QU'IL EXISTE DE DISTRIBUTIONS DE TAILLE DE PARTICULES PRESENTANT DES MAXIMA BIEN DIFFERENCIES. LA CONNAISSANCE DU RECOUVREMENT A HAUTE TEMPERATURE PERMET DE DETERMINER LE NOMBRE DE PARTICULES DANS L'ECHANTILLON DONC LE NOMBRE MOYEN D'ATOMES PAR PARTICULES (CONNAISSANT LA CONCENTRATION EN METAL DU CATALYSEUR), LA DISPERSION AINSI MESUREE EST EN BON ACCORD AVEC LES RESULTATS DE MICROSCOPIE ELECTRONIQUE ET DE CHIMISORPTION D'HYDROGENE. LA THERMODESORPTION PROGRAMMEE NOUS A PERMIS DE METTRE EN EVIDENCE DIVERSES ESPECES D'HYDROGENE ADSORBE SUR LES CATALYSEURS, DONT LA NATURE ET LA QUANTITE DEPENDENT DES CONCENTRATIONS RELATIVES PT-AU ET DES CONDITIONS DE REDUCTION DES METAUX. LA REACTION DE DESHYDROGENATION DU METHYLCYCLOHEXANE EST DETECTABLE A LA TEMPERATURE DE 230C. L'ACTIVITE PAR SITE DE PLATINE POUR LA FORMATION DU TOLUENE AUGMENTE D'UN RAPPORT 4 QUAND ON PASSE DU 100% PT AU 20% PT. CES ETUDES MONTRENT QUE NOUS POUVONS PRODUIRE DES PARTICULES METALLIQUES PT-AU TRES PETITES. L'ACTIVITE DESHYDROGENATION DE CES CATALYSEURS AUGMENTE AVEC L'ADDITION D'OR

Author: Chao-Jun Li
Publisher: John Wiley & Sons
ISBN: 3527807691
Category : Science
Languages : en
Pages : 400

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Covers all the aspects of the recent achievements in silver catalyzed reactions Silver catalysis has emerged as a powerful tool in the field of organic synthesis. This comprehensive book systematically explores the unique performance of silver catalysis, introducing all the recent progress of silver catalysis in organic synthesis. It clearly emphasizes the unique features of silver catalysis and provides the reaction mechanism involved. This two-volume book also provides vivid schematics and tables throughout to enhance the accessibility to the relevant theory and mechanisms. Silver Catalysis in Organic Synthesis begins with an introduction to Silver Chemistry before moving on to chapters covering: Silver-Catalyzed Cycloaddition Reactions; Silver-Catalyzed Cyclizations; Silver-Mediated Radical Reactions; Silver-Mediated Fluorination, Perfluoroalkylation and Trifluoromethylthiolation Reactions; Coupling Reactions and C-H Functionalization; Silver-Catalyzed CO2 Incorporation; Silver-Catalyzed Carbene, Nitrene, and Silylene Transfer Reactions; Asymmetric Silver-Catalyzed Reactions; Silver-Catalyzed Reduction and Oxidation of Aldehydes and Their Derivatives; Silver Complexes in Organic Transformations; and Silver Nanoparticles in Organic Transformations. -Covers recently developed organic reactions catalyzed by silver, along with their reaction mechanism -Introduces many new reactions and mechanisms related to silver catalysis -Offers professionals and newcomers in the related fields a survey of new advances in silver catalysis in organic synthesis Silver Catalysis in Organic Synthesis will appeal to a wide readership including chemists, biochemists, pharmaceutical scientists, biomedical researchers, agriculture scientists, and graduate students in the related fields.

Author: Jean-Paul Kurtz
Publisher: Springer Science & Business Media
ISBN: 0306483173
Category : Technology & Engineering
Languages : en
Pages : 1520

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I am pleased to present a work which marks a milestone in the history of public works and, more precisely, in that of permanent structures—a comprehensive dictionary of Civil Engineering terms. Since the beginning of time, Man has always tried to find a means to clear the obstacles which nature erected to displace him. With the first tree trunk thrown across a river, man sought to improve the crossing structure. After the invention of the wheel, and to satisfy his thirst for conquest (Roman ways), and comfort (aqueducts), man built bridges that became a preremptory necessity to move quickly. Thus, Man started to build wooden and masonry works. With the passing centuries, the builders became masters in the art of building masonry works. Then came the Industrial Revolution and the advent of the steel (1864), which was closely followed by the invention of the reinforced concrete (1855). The need for railways and improving the road network inspired great works of crossing such as viaducts and tunnels. The boom of the railway network and the development of the car required the construction of an increasing number of new structures. This phenomenon continues today with hundreds of structures built each year throughout the world.

Author: Hans T. Clarke
Publisher: Princeton University Press
ISBN: 1400874912
Category : Medical
Languages : en
Pages : 1116

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This book makes available, for interested scientists to procure, absorb, and evaluate, the vast body of information on the research and results of the work on the chemistry of penicillin done in England and the United States during the war. The National Academy of Sciences arranged for the preparation of this summary, Dr. H. T. Clarke and Dr. J. R. Johnson representing the United States on the editorial board, and Sir Robert Robinson representing Britain. The body of the work was prepared by more than 60 outstanding biochemists and biophysicists, who describe the phases of research to which they contributed the most. The work of 23 academic, medical, industrial, and government laboratories is reported. Originally published in 1949. 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: Agnes Buka
Publisher: World Scientific
ISBN: 1848167997
Category : Science
Languages : en
Pages : 299

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The book intends to give a state-of-the-art overview of flexoelectricity, a linear physical coupling between mechanical (orientational) deformations and electric polarization, which is specific to systems with orientational order, such as liquid crystals. Chapters written by experts in the field shed light on theoretical as well as experimental aspects of research carried out since the discovery of flexoelectricity. Besides a common macroscopic (continuum) description the microscopic theory of flexoelectricity is also addressed. Electro-optic effects due to or modified by flexoelectricity as well as various (direct and indirect) measurement methods are discussed. Special emphasis is given to the role of flexoelectricity in pattern-forming instabilities. While the main focus of the book lies in flexoelectricity in nematic liquid crystals, peculiarities of other mesophases (bent-core systems, cholesterics, and smectics) are also reviewed. Flexoelectricity has relevance to biological (living) systems and can also offer possibilities for technical applications. The basics of these two interdisciplinary fields are also summarized.

Author: Goddard Space Flight Center. Office of Public Affairs
Publisher:
ISBN:
Category : Artificial satellites
Languages : en
Pages : 366

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Author: Paolo Mele
Publisher:
ISBN: 9781536160864
Category : Zinc oxide thin films
Languages : en
Pages : 0

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Zinc oxide (ZnO) is an n-type semiconductor with versatile applications such as optical devices in ultraviolet region, piezoelectric transducers, transparent electrode for solar cells and gas sensors. This book "ZnO Thin Films: Properties, Performance and Applications" gives a deep insight in the intriguing science of zinc oxide thin films. It is devoted to cover the most recent advances and reviews the state of the art of ZnO thin films applications involving energy harvesting, microelectronics, magnetic devices, photocatalysis, photovoltaics, optics, thermoelectricity, piezoelectricity, electrochemistry, temperature sensing. It serves as a fundamental information source on the techniques and methodologies involved in zinc oxide thin films growth, characterization, post-deposition plasma treatments and device processing. This book will be invaluable to the experts to consolidate their knowledge and provide insight and inspiration to beginners wishing to learn about zinc oxide thin films.

Author: Ulrich Schubert
Publisher: Springer Science & Business Media
ISBN: 3211751254
Category : Technology & Engineering
Languages : en
Pages : 220

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Materials syntheses are more complex than syntheses of inorganic or organic compounds. Materials synthesis protocols often suffer from unclarities, irreproducibility, lack in detail and lack in standards. The need to change this situation is the main motivation for this book. It collects a number of detailed protocols, ranging from organic polymers to carbonaceous and ceramic materials, from gels to porous and layered materials and from powders and nanoparticles to films.

Author: Reginald Biddle
Publisher:
ISBN:
Category : Marketing
Languages : en
Pages : 24

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