Abstract :
[en] In this work, materials have been produced by sol-gel route. This synthesis way has been used for immobilization on a support of a function focused on green chemistry. The different
functions are related with different applications that allow to illustrate the versatility and the
flexibility of this sol-gel process.
The two applications are:
- Photocatalysis: Synthesis of material with photocatalytic property or with an additional
property
- Cyclocarbonation: Synthesis of an immobilized catalyst for polyurethane production
through a green process
The first application concerns the use of a photocatalyst that allows to degrade volatile organic
compounds (VOC). The main photocatalyst is TiO2. It has been studied as a powder or as a film
deposited on a support. A comparison of these two shapes has shown that an identical
photocatalyst can have different performances depending on the final shape. A catalyst must be
considered in its totality and with its environment rather than as a chemical composition only.
To increase the photocatalyst performances, modifications have been added as the Zn doping
to increase the photocatalytic activity and the superhydrophilicity. These new photocatalysts
have been compared with pure ZnO and bilayer films composed of TiO2 and of ZnO. Different
photocatalytic tests have been performed and depending on the test the best photocatalyst was
different.
Then, to increase the economic interest, some dopant have been used. In addition of the
improvement of the photocatalytic activity and superhydrophilicity, theses dopants add a new
property such as electrical conductivity and anticorrosion. First, metallic silver has been
incorporated to add antistatic property and to increase the photocatalytic activity. The
photocatalytic property has been improved, superhydrophilicity has been kept but no antistatic
property was observed. Multiwall carbon nanotubes (MWCNTs) have been tested with TiO2 to
increase the electrical conductivity. This doping is efficient because MWCNTs increase the
conductivity, the photocatalytic activity and maintain the superhydrophilicity. In addition,
anticorrosive property has been observed on stainless steel in a preliminary study with the
MWCNTs incorporation.
The second study is focused on the heterogeneous cyclocarbonation catalyst synthesis to
produce, in fine, polyurethane. The catalyst was immobilized on different matrices that are inert
from catalytic point of view but that have a potential activator effect.
First, with the preselected catalyst, different supports have been investigated. The comparison
between the supports has highlighted the activator effect and the texture influence (accessibility
of the active sites) on cyclocarbonation yields.
Then, with the optimal matrix, different catalysts from a same family have been grafted to
choose the best catalyst. Therefore, it has been possible to define the best catalyst and the best
support. With this combination, a kinetic study has been performed to determine the best
experimental conditions to produce cyclocarbonates.
