Direct synthesis of mesoporous silica containing cobalt: A new strategy using a cobalt soap as a co-template

A novel approach to incorporate transition metals into porous structures is presented, which makes use of a cobalt soap in combination with the templating agent C16TMABr. An ordered mesoporous silica MCM-41 type material doped with Co is obtained after removal of the organic part by calcination. The a unit cell parameter of the cobalt containing mesoporous matrices is larger than that of pure MCM-41 and increases with the amount of cobalt present in the sample as well as the diameter of the pores. This is not observed when e.g. cobalt acetate is employed instead of the metal soap. The procedure presented establishes a new route for the incorporation of a transition metal into MCM-41 together with a tuning of the porous structure

Monitoring by in situ neutron diffraction of simultaneous dehydration and Ni2+ mobility in partially exchanged NaY zeolites

International audiencePowder neutron diffraction is used to follow structural changes occurring during heat and vacuum assisted dehydration of 3 wt% nickel exchanged NaY. The structures determined from Rietveld refinement confirm the nickel ion displacement from the supercages and sodalite cages towards hexagonal prisms upon water removal. Not only this mobility but also its relationship with the dehydration level is demonstrated, owing to real time quantification of dehydration through changes in the intensity of the incoherent neutron scattering signal. Comparison with TGA data proves that this signal is fully attributable to water molecules adsorbed in the zeolite. STEM/EDX and in situ heating TEM studies provide complementary information on homogeneous Ni distribution (initial state) and on reductive sintering in vacuum at a high temperature

The determination of new stable zeolite frameworks using a parallel hybrid genetic algorithm

International audienc

On the nature of metallic nanoparticles obtained from molecular Co3Ru–carbonyl clusters in mesoporous silica matrices

We report on the impregnation of THF solutions of the low-valent heterometallic cluster NEt4[Co3Ru(CO)12] into two mesoporous silica matrices, amorphous xerogels and ordered MCM-41, and a study of its thermal decomposition into metallic nanoparticles by X-ray diffraction, transmission electron microscopy and in situ magnetic measurements under controlled atmospheres. The decomposition of the cluster was monitored as a function of temperature by examining the chemical composition of the particles, their size distributions and their structures as well as their magnetic properties. Treatment under inert atmosphere (i.e. argon) at temperatures below 200 °C resulted in the formation of segregated spherical particles of hcp-ruthenium (2.3 ± 1.0 nm) and hcp-cobalt (3.1 ± 0.9 nm). The latter is transformed to fcc-cobalt (3.2 ± 1.0 nm) above 270 °C. At higher temperatures, Co–Ru alloying takes place and the Ru content of the particles increases with increasing temperature to reach the nominal composition of the molecular precursor, Co3Ru. The particles are more evenly distributed in the MCM-41 framework compared to the disordered xerogel and also show a narrower size distribution. Owing to the different magnetic anisotropy of hcp- and fcc-cobalt, which results in different blocking temperatures, we were able to clearly identify the products formed at the early stages of the thermal decomposition procedure

Ferromagnetisme dans des composes organiques ou inorganiques de basse dimensionalite: etude des correlations magneto-structurales

SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : T 79475 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Direct synthesis of metal containing mesoporous matrices from a cobalt soap. Research opportunities at interface aspects between nanoporous, polymeric and magnetic materials

Congrès du 10 au 11 mars 200

Traitement d'effluents aqueux pollués par des ions nitrate ou phosphate ou des hydrocarbures de type BTEX (utilisation d'une zéolithe naturelle modifiée (SMZ) ou de zéolithes synthétiques)

Ce travail s'inscrit dans le cadre de la protection de l'environnement et s'intéresse spécifiquement à la dépollution d'effluents aqueux en vue de piéger d'une part les anions nitrate et/ou phosphate, responsables du phénomène d'eutrophisation, mais également le toluène, hydrocarbure couramment rencontré dans les effluents aqueux urbains et industriels ou les eaux naturelles. Le piégeage de ces polluants a été effectué sur des matériaux zéolithiques. Une grande partie des expérimentations utilise un matériau potentiellement efficace pour le piégeage des trois polluants cités plus haut, à savoir la SMZ ("Surfactant-Modified Zeolite"), classiquement préparée à partir d'une zéolithe naturelle, la clinoptilolite, et d'un tensioactif, le bromure d'hexadecyltriméthylammonium (HDTMA+). En piégeage d'ions nitrate, d'autres SMZ, réalisées à partir de zéolithes synthétiques (LTA, FAU) et diverses espèces organiques tensioactives ou non se montrent moins performantes que la SMZ classique, à l'exception d'un nouveau matériau préparé à partir de nanofeuillets de zéolithe MFI et modifié avec l'ion HDTMA+ (SMZN). Pour le piégeage des ions phosphate, les performances de la SMZ classique ont été comparées à celles de plusieurs zéolithes calciques. Enfin, le piégeage de toluène a été expérimenté sur quatre matériaux, la SMZ classique, un charbon actif et deux zéolithes hydrophobes, la silicalite-1 et la zéolithe bêta. Les expérimentations de piégeage ont été réalisées en système fermé ou en système ouvert. L'influence de la concentration initiale en polluants, du rapport liquide/solide, du débit de filtration, de la présence de compétiteurs et du temps de contact a été examinée.This work concerns the environmental protection, specifically the treatment of aqueous effluents. Effluents containing nitrate and/or phosphate anions, responsible for the eutrophication phenomenon, and also toluene, which is commonly found in urban and industrial flows and natural waters, were specifically studied. The removal of these pollutants was performed on zeolitic materials. A large part of the experiments use a material potentially efficient to remove the three pollutants mentioned above, namely the SMZ ("Surfactant-Modified Zeolite"), conventionally prepared from a natural zeolite, clinoptilolite, and a surfactant, hexadecyltrimethylammonium bromide (HDTMA+). For nitrate removal, other SMZ, prepared from synthetic zeolites (LTA, FAU) and various organic species (surfactant or not) were less efficient than conventional SMZ except a new material prepared from zeolite MFI nanosheets and modified with HDTMA+ ion. The efficiency of the conventional SMZ for the phosphate ions uptake was compared with those of several calcic zeolites. Finally, removal of toluene was performed on four materials, conventional SMZ, an activated carbon and two hydrophobic zeolites, namely silicalite-1 and beta zeolite. Uptake experiments were conducted in batch-wise and fixed-bed column systems, the second representing a more realistic simulation of dynamic field condition The influence of the initial pollutant concentration, the liquid/solid ratio, the filtration rate, the presence of competitive species and the contact time was examined.MULHOUSE-SCD Sciences (682242102) / SudocSudocFranceF

Editorial

International audienc