The main target of this thesis is the design of a new aluminum-based surface ligand with low
coordination and expected high acidity. These new supports will serve for the immobilization of
different organometallic complexes with the surface organometallic chemistry (SOMC). The
resulting molecular like species will be used for various catalytic applications including alkane
metathesis, olefin metathesis and polymerization.
The first chapter is an introduction to the field of catalysis, more specifically, surface
organometallic with a summary of its concept and the main examples cited for the
immobilization of transition metal complexes on different oxide surfaces (silica, silica-alumina
and alumina). This chapter presents, as well, an overview of the use of the aluminum alkyls
compounds and their immobilization on a surface for the generation of various aluminum based
surfaces.
The Second chapter details the reaction involving the grafting of the monomeric
triisobutylaluminum on SBA-15700. The final structures and the mechanism involved were
determined by various characterization techniques including FT-IR, 1H and 13C solid-state
NMR, and DFT calculations. The reaction leads mainly to a bipodal [(≡Si-O-Si≡)(≡SiO)2AliBu]
species with 3 differents types of alumium coordinations (AlIV, AlV and AlVI) along with
37% [≡Si-H] and 63% [≡Si-ibu].
The Third chapter describes the reaction of a highly dehydroxylated SBA-15 with a trimeric
di-isobutyl aluminum hydride, [i-Bu2AlH]3 is investigated by both experiments and DFT
calculations. The mechanism involves very different pathway comparing to the TIBA case
where only AlIV-isobutyl were generated. Further β-H elimination leads to an well-defined AlIV
hydride analog [(≡Si-O-Si≡)(≡SiO)2Al-H]. The later shows good activity in ethylene
polymerization reaction with the formation of HDPE.
The Fourth Chapter deals with the immobilization of the 2nd generation Hoveyda-Grubbs
(HGII) catalyst onto well-ordered 2D hexagonal (SBA15), and 3D fibrous (KCC-1)
mesostructure silica containing tetra-coordinated [Al-H] sites. The resulting catalysts show high
activity in the non-functionalized olefin metathesis of propene. The results clarified that the
supported catalyst prepared using KCC-1 shows better performance than the one prepared using
SBA-15 due to the diffusion effect; and exhibits much higher activity than the HG-II itself, in
homogeneous phase.
The Fifth chapter of this thesis presents the formation of tetra-coordinated [(≡Si–O–Si≡)(≡Si–
O)2Al–OH], through [Al-H] oxidation using N2O. The synthesis was detailed and the grafted
species were fully characterized. This new site will serve as anchoring site for the
immobilization of the tungsten based complexes. Its activity was evaluated in the propane
metathesis reactions, where a TON of 800 was obtaine, which is the highest value obtained for a
SOMC monometallic catalyst.
Finally, the last chapter will present the thesis conclusion including most of the ongoing
applications related to the use of those new surfaces.
| Identifer | oai:union.ndltd.org:kaust.edu.sa/oai:repository.kaust.edu.sa:10754/630158 |
| Date | 11 1900 |
| Creators | Werghi, Baraa |
| Contributors | Basset, Jean-Marie, Physical Science and Engineering (PSE) Division, Cavallo, Luigi, Sarathy, Mani, Astruc, Didier |
| Source Sets | King Abdullah University of Science and Technology |
| Language | English |
| Detected Language | English |
| Type | Dissertation |
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