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Mechanisms of formation of lamellar mixed phases during the synthesis of supported metal catalysts - hydrotalcites - mii/al2o3 - and phyllosilicates - mii/sio2 6

Objective



Research objectives and content
1 Deposition by classical syntheses . Nill/SiO2, CoIl/III / SiO2, Nill/Al203, and ColI/III /Al203 will be prepared by the classical 'wet impregnation' technique. The metal precursors will be aqua and ammine complexes; the amounts of metal deposited will be followed as a function of concentration in solution, reaction time, pH, and competing ion concentration. The formation of new phases will be monitored by XRD; both the solid phase and solution will be submitted to characterisation by UV-visible spectroscopy and 59Co, 27AI and 29Si NMR. 2 Study of thermal evolution The most individualised systems prepared in 2.3.1 will be dried, calcined and reduced and the evolution of the catalysts will be monitored by UV-vis and IR spectroscopies, NMR, EPR, XRD and TPR. Transmission Electron Microscopy, together with chemisorption techniques, will be used to check supported metals dispersion and exposed surface, and possibly their electronic state. 3 Non-classical deposition procedures The study will be extended to such preparation procedures as deposition-precipitation (by decomposition of urea), where the extent of mixed phase formation is expected to be maximal. 4 Studies of model systems It is hoped that precise hypotheses will be formulated on the mechanisms of mixed phases formation in the course of the above study. They may then be checked by careful modification of the chemical systems through techniques of inorganic chemistry (for instance, selective blocking of some positions in the coordination sphere of metal complexes); in opposition to '' 2.3.1 to 2.3.3, this part of the study is not meant to provide realistic catalysts preparation procedures, but rather to assure the validity and applicability of the molecular-level models which will be developed. Training content (objective, benefit and expected impact)
1)Learning of the new techniques employed in leading European laboratories in the control of dissolution/precipitation reactions at the interface between a support oxide and an aqueous solution of metal precursors. 2) to use this knowledge for the fine-tuning of supported metal catalysts properties.
Links with industry / industrial relevance (22)
The host laboratory is in permanent contact with major chemical companies (Rhone-Poulenc Elf-Atochem, Institut Franc,ais du Petrole...) interested in the development of new catalytic materials. This cooperation has taken several forms in the past, including several Ph.D. training grants with joint funding. Although no specific company is associated with the present grant request, there is a high level of interest, among industrials concerned with catalyst synthesis, for research aimed at rationalising the parameters of supported catalysts preparation. The quality of the links between the host institution and the industrial community will allow immediate valorisation of any significant advance reached.

Funding Scheme

RGI - Research grants (individual fellowships)

Coordinator

Université de Paris VI (Université Pierre et Marie Curie)
Address
4 Place Jussieu
75252 Paris
France