During the last decade, considerable attention has been devoted to the development of biofuels, above all biodiesel, as a promising alternative to fossil fuels. The transesterification reaction to produce biodiesel yields as by-product an amount of glycerol that represents approximately 10 wt % of the total biodiesel manufacture. With the increase of biodiesel production, glycerol is now considered as a waste and solutions for its efficient utilization are needed. A promising route is represented by the condensation of glycerol with acetone to produce solketal, an added-value product with several applications such as surfactant, flavoring agent, plastifying agent, safe solvent or in blend with biodiesel to improve its properties. A sustainable way to perform this reaction envisages the use of heterogeneous catalysts displaying Brønsted and Lewis acidities. Porous silicates presenting a metal inserted as single site in the framework can be active and selective catalysts for this reaction. In particular, it has been already reported that Ga-MCM-41 nanoparticles are one of the most efficient catalysts in the conversion of glycerol into solketal. Here, the aerosol assisted sol-gel process was used as a powerful tool to synthesize silica-based solids with Ga inserted as single-site in the structure. The influence of different parameters on both morphological properties and catalytic activity, as the Si/Ga ratio or the nature of the templating agent, were studied. Furthermore, to optimize the design of the catalysts, the role played by the hydrophobic/hydrophilic balance of the catalyst surface was investigated. The aerosol process was successfully used to synthesize a series of Ga-silicates with different degrees of methyl-functionalization using a co-synthetic one-pot approach. All the synthesized materials were fully characterized and tested for the conversion of glycerol into solketal with promising results.
|Date of Award||Jun 2019|
|Supervisor||Carmela APRILE (Supervisor)|