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The key parameters influencing the reactivity of magnesium silicate based catalysts : application to transesterification in liquid phase

Abstract : In the field of biomass derivatives valorisation, transesterification reactions have attracted numerous interest due to its importance to transform platform molecules. A study of the parameters governing the reactivity of magnesium silicate based catalyst in a model transesterification reaction was thoroughly undertaken. The set of experimental data (XRD, XPS, DRIFTS, NMR) demonstrated that a magnesium silicate hydrate (MSH) phase is formed at the surface of the most active silicates. It is thus concluded that this active phase, presented a clay-like structure with defects and specific acido-basic properties, is able to activate together the alcohol (over base sites) and the ester (over acid sites). This result fits with the kinetic study that implies the Langmuir-Hinshelwood mechanism. Moreover, the acid sites were revealed that are created from the water coordinated to magnesium located on the edge of the clay-like particles or in the defects present in the silicate layer.Besides, a series of phyllosilicates having the similar structure with MSH, were tested in the model transesterification reaction. The influence of the particles size was investigated and the best catalytic performances were obtained with talc and laponite with nanosheets. In addition, kinetic study indicates that the transesterification reaction on the laponite, with purely basic sites, undergoes Eley-Rideal mechanism. Finally, unlike the positive role of water on the formation of acid sites in MSH, on laponite, the dissociation of the water on basic sites poisons the reaction.
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  • HAL Id : tel-01719278, version 1

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Longfei Lin. The key parameters influencing the reactivity of magnesium silicate based catalysts : application to transesterification in liquid phase. Chemical Physics [physics.chem-ph]. Université Pierre et Marie Curie - Paris VI, 2017. English. ⟨NNT : 2017PA066313⟩. ⟨tel-01719278⟩

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