La nature des especes «vivantes» propagatrices en polymerisation anionique des dienes conjugues est etudiee par resonance magnetique nucleaire. Un choix judicieux des effects monomeres permet, en outre, de voir l'influence des effects... more
La nature des especes «vivantes» propagatrices en polymerisation anionique des dienes conjugues est etudiee par resonance magnetique nucleaire. Un choix judicieux des effects monomeres permet, en outre, de voir l'influence des effects electroniques et steriques sur les structures observees. Il est montre que les oligomeres «vivants» ne renferment que les motifs 4,1 et/ou 1,4 (cis et trans), et que l'espece active peut ětre decrite sous une forme π-allyle delocalisee. De plus, le point fondamental dans le mecanisme de l'action de l'amorceur sur le diene semble ětre l'association. En effet, l'association interne des organolithiens disparaǐt ou evolue vers l'association externe avec tout compose donneur d'electrons. Ce rǒle de nucleophile peut ětre joue par le diene lui-měme. Un mecanisme base sur le concept de l'association est propose. The nature of “living” propagating species in the anionic polymerization of conjugated dienes was studied by nucle...
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Resume Les oligobutadienes sont prepares en milieu hydrocarbone a l'aide des isomeres du butyllithium. La resonance magnetique nucleaire (RMN), la chromatographie en phase vapeur et la spectroscopie i.r. permettent l'etude de la... more
Resume Les oligobutadienes sont prepares en milieu hydrocarbone a l'aide des isomeres du butyllithium. La resonance magnetique nucleaire (RMN), la chromatographie en phase vapeur et la spectroscopie i.r. permettent l'etude de la microstructure de chaque unite monomerique dans les diverses additions. Differents parametres-tels que rapport monomere/amorceur; nature de l'agent de terminaison, du solvant et de l'organolithien amorceur-influencent largement cette microstructure. Ainsi, l'exces d'amorceur favorise la formation des motifs vinyliques; par contre, l'action d'un solvant aromatique peut etre subordonnee a la nature de l'agent destructeur. Les resultats trouvent leur justification dans la nature des especes actives propagatrices en polymerisation anionique des dienes conjuges. En effet, la repartition electronique d'une structure π-allyle delocalisee est etroitement conditionnee par la basicite des agents d'amorcage, de solvatation et de terminaison.
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Research Interests: Materials Science, Catalysis, Scanning Electron Microscopy, Transmission Electron Microscopy, Scanning Transmission Electron Microscopy, and 11 moreMagnetic Resonance Spectroscopy, Medicine, Heterogeneous Catalysis, Zeolites, Porosity, Methanol, Dehydration, Surface Area, X ray diffraction, Surface Properties, and Dimethyl Ether
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Research Interests: Environmental Engineering, Chemical Engineering, Carbon, Biomass, Transmission Electron Microscopy, and 13 moreHeterogeneous Catalysis, Catalyst, Activation Energy, Space Time, First-Order Logic, Nickel, Biomass gasification, X ray diffraction, TAR, Solid Solution, Magnesium Oxide, Steam Reforming, and Temperature programmed oxidation
Silica supported cobalt catalysts have been prepared by a new method combining the precipitation of the metal precursor (cobalt nitrate) by oxalic acid with the hydrolysis and condensation of the silicium precursor (tetraethoxysilane).... more
Silica supported cobalt catalysts have been prepared by a new method combining the precipitation of the metal precursor (cobalt nitrate) by oxalic acid with the hydrolysis and condensation of the silicium precursor (tetraethoxysilane). Depending on the pH during preparation, the ...
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Isomerization of light alkanes and alkenes was investigated on pure MoO3 powder which was gradually reduced under a rapid flow of hydrogen (1atm) at 350°C. Incompletely reduced MoO3 samples readily isomerize alkanes in the order... more
Isomerization of light alkanes and alkenes was investigated on pure MoO3 powder which was gradually reduced under a rapid flow of hydrogen (1atm) at 350°C. Incompletely reduced MoO3 samples readily isomerize alkanes in the order nC4⪡nC5<nC6=nC7=nC8. The rates are at least as high as those measured on platinum metal. Isomerization of olefins is always faster than those of the corresponding
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Mixed LaNi x Fe (1−x) O 3 perovskite oxides (0≤x≤1) have been prepared by a solgel related method, characterised by X-ray diffraction (XRD), specific surface area measurements, transmission electron microscopy (TEM) coupled to an energy... more
Mixed LaNi x Fe (1−x) O 3 perovskite oxides (0≤x≤1) have been prepared by a solgel related method, characterised by X-ray diffraction (XRD), specific surface area measurements, transmission electron microscopy (TEM) coupled to an energy dispersive X-ray spectrometer (EDS). ...
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La2NiO4/α-Al2O3 catalyst was prepared by a microwaves assisted self-combustion method using glycine or urea as fuel and metal nitrates as oxidizers. In order to understand the effect of the preparation method and the fuel type used on the... more
La2NiO4/α-Al2O3 catalyst was prepared by a microwaves assisted self-combustion method using glycine or urea as fuel and metal nitrates as oxidizers. In order to understand the effect of the preparation method and the fuel type used on the catalytic properties, a sample was prepared by an incipient wetness nitrate impregnation method (without fuel). All obtained samples were used as catalysts