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The new alkaline sol-gel route presented here allows preparing meso-macrocellular self-standing aluminosilicate monoliths that are easy to cast and manipulate and that exhibit open and interconnected macroporosity, high surface area and strong acidic properties. Strong acidity is brought about by the formation of a true mixed oxide. Effectiveness of these catalysts is demonstrated here in the case of bioethanol dehydration, and good performance can be expected in other processes like cracking, isomerization, alkylation reactions, etc.

This work investigates the effect of Amberlyst 36, Purolite CT482 and Purolite CT275DR on the esterification of oleic acid with trimethylolpropane for production of the triester. The results assess that, while the three resins catalyze heterogeneously the formation of mono- and diesters, the final triester is generated thanks to the acidity of residual oleic acid. This cooperative scenario between heterogeneous and homogeneous catalysis is of first importance, as to complete the reaction over conventional heterogeneous catalyst was not feasible because of the strong steric hindrance of the intermediate product (diester) and the final product (triester).

Magnetic nanoparticles based on Fe3O4(MNP) were coated with a silica (with thin or thick layers) priorto grafting with (3-aminopropyl) triethoxysilane (APTES) and octyltriethoxysilane (OTES) to increasetheir hydrophobicity and their pH stability. The synthetic conditions for the APTES grafting were chosento achieve either mono- or polylayers of chemically attached silane on the surface. The synthesizedFe3O4@SiO2- APTES and Fe3O4@SiO2-OTES core-shell particles were characterized by different methodsincluding XRD, TEM, FTIR-ATR, N2physisorption, ICP AES and XPS. The stability tests showed that coatingwith silica shell and grafting with organosilanes considerably improve the stability of MNP at pH 3; thethicker the silica layer the less iron oxide dissolved. The MNP-based materials showed catalytic activity inthe esterifications of propionic acid (PA) with n-butanol and of oleic acid (OA) with trimethylolpropane.In the PA containing medium the particles partly leach into a liquid medium contrary to the OA containingmedium where they seemed to be resistant to leaching.

Four cation-exchange resins (Dowex 50wx2, Amberlyst 36, Purolite CT482 and Purolite CT275DR) were investigated as catalysts in the esterification of oleic acid (OA) with trimethylolpropane (TMP). All four resins accelerated the reaction kinetics. The results showed that in a solvent-free system, the gel-type resin Dowex 50wx2 must be pre-swollen prior the reaction to achieve high catalytic performance. Contrary, the macro-reticular Amberlyst 36, Purolite CT482 and Purolite CT275DR do not need any pre-treatment to be active. The latter is due to the high crosslinking degree of these resins. Recyclability tests showed that the resins slightly lose their activity after the first use but retain stable activity during the further uses. The activity decay of the recycled resins is referred to the partial blocking of the active sites by the co-produced water. Additional studies confirmed the high stability of the chosen resins toward leaching in polar medium. Overall, both high stability and possibility of reusing through still high catalytic activity make the resins attractive candidates as heterogeneous catalysts for such complex industrial process.

A new method of chemical immobilization of Keggin heteropolyacids (HPAs) was suggested. H3PW12O40, H4SiW12O40, and H3PMo12O40 were immobilized on the silica which was previously grafted with zirconium butoxide. The immobilization method promoted strong interaction HPA-support and yielded 25 wt.% of well-dispersed HPAs, so increasing the density of acid sites. The catalysts were active in the reaction of transesterification of methyl stearate with n-butanol and esterification of oleic acid with trimethylolpropane. We demonstrate that, contrary to the immobilized H3PMo12O40, the H3PW12O40 and H4SiW12O40-based catalysts are stable toward leaching in a non-polar oleic acid medium. A discussion on circumventing the leaching in non-polar versus polar media is proposed in terms of interaction strength HPA-support. The stronger interaction (i.e., better resistance for leaching) between the support and H3PW12O40 (or H4SiW12O40) is referred to the lower difference of electronegativity between Zr and W and the lower polarizability of the bonds Zr–O–W compared to Zr–O–Mo.

With the decline in reserves of certain raw materials, coupled with the ever growing needs of the population, there is increased pressure on industries to devise novel synthetic processes. The main way to improve the efficiency of those chemicals processes is the design of a new generation of inorganic chemistry based catalysts. The Sol-gel process is one of the most promising technologies permitting the development of an amazing new generation of mixed oxide materials featuring porous organizations at the nanometric scale, a controlled stoichiometry and an excellent homogeneity of the active sites. This class of materials could serve as catalysts for the fine chemistry as well as for petroleum cracking processes. However, the mixed oxide catalytical efficiency is strongly linked to the degree of the active sites dispersion into the silica framework. Usual synthetic methods systematically drive to a phase separation phenomenon, resulting from the different reactivity of the starting independent inorganic precursors used. Synthesized materials are inhomogeneous due to the formation of a poor loaded silica framework and independent metal oxide nanoparticles, characterized by a low catalytical activity. Currently, many efforts are devoted to the improvement of the incorporation of increasing amount of active metal centers into the framework without any phase separation processes. A very promising strategy consists in the use of single molecular source, instead of a mixture of independent inorganic precursors with different reactivities. The aqueous conversions of these single sources allow the construction of materials featuring unmatched homogeneity and totally controlled stoichiometry. This present work aims in the design of a new generation of homogeneous and porous mixed oxides, prepared from single molecular precursors, for some further catalytical applications. This lead first to the conception of porous and homogenenous zirconosilicate materials (Si/Zr ~ 4), fol, La raréfaction des matières premières et les besoins sans cesse croissants de l’humanité ont amenés à de nouveaux impératifs au niveau des procédés de synthèse dans l’industrie. Ceux-ci se doivent d’être plus sélectifs, plus spécifiques et plus efficaces tout en préservant l’environnement. De fait, une des grandes et très porteuses tendances actuelles dans le domaine de la chimie des matériaux est la conception de nouveaux oxydes mixtes, tels que des matériaux aluminosilicatés, présentant une ou plusieurs porosités structurées à l’échelle nanométrique, ainsi que des propriétés catalytiques acido-basiques et/ou rédox renforcées. Ce type de matériaux présente un intérêt essentiel dans les secteurs de la chimie fine ainsi que dans les procédés de raffinage du pétrole. L’efficacité catalytique de cette gamme d’oxydes mixtes est néanmoins tributaire de l’homogénéité avec laquelle les espèces actives sont dispersées au sein du réseau silicaté poreux. Les méthodes de synthèse conventionnelles mènent systématiquement à des phénomènes de séparation de phases. Ceci découle de la différence de réactivité des précurseurs employés. Ces solides obtenus sont inhomogènes d'un point de vue chimique car constitués d’un réseau silicaté appauvri en sites actifs, et de nanoparticules d’oxyde métallique d’activité catalytique limitée. Un grand nombre d’efforts tendent à contrôler, via le développement de stratégies scientifiques toujours plus efficaces, l’insertion de quantité importante de sites actifs au sein de la charpente silicatée, tout en prévenant ces processus de séparation de phases. Une stratégie prometteuse consiste en l’emploi de précurseurs moléculaires uniques. La conversion de ces sources moléculaires, se substituant à un mélange de précurseurs indépendants, ayant leur réactivité propre, permet l’obtention d’oxydes mixtes poreux arborant une homogénéité chimique supérieure. L’objectif ce travail est donc la mise au point d’une nouvelle génération de matériaux poreux homog, (DOCSC02) -- FUNDP, 2010