SULFONIC SILICA-BASED CATALYSTS FOR THE MICROWAVE- ASSISTED SOLKETAL SYNTHESIS

The glycerol (G) acetalization with acetone (A) is one of the most promising ways to revalorize the glycerol waste from biodiesel production. This reaction allows to obtain the cyclic compound, 2,2-dimethyl-1,3-dioxolane-4-methanol, called solketal, a molecule very useful as oxygenated additive for fuels, among many others applications such as solvent, plasticizer, etc. The most studied synthesis route involves the use of acid heterogeneous catalysts and conventional heating as thermal source [1]. However, the use of microwave (Mw) irradiation as heating source would lead to a considerable energy saving over conventional heating because of the reduction of time and temperature employed in the reaction, making greener the procedure. In this research, three types of silicas, one amorphous (Am) and two ordered (KIT-6 or SBA- 15), functionalized with sulfonic (-SO3H) or propylsulfonic groups (-PrSO3H), have been synthetized and tested as acid catalysts in the MW-assisted acetalization of glycerol to obtain solketal. Different synthetic approaches such as grafting, thermal grafting and hydrothermal grafting were employed, in order to evaluate with which of them the highest incorporation of sulfonic groups is achieved and, therefore, the highest acidity value.