Synthesis and characterization of KF/waste glass catalyst for use in the transesterification process under pressurized conditions

The use of heterogeneous catalysts can make the transesterification process under pressurized conditions even more viable due to the possibility of minimizing the operation temperature. In this sense, the objective of this work was to determine an optimal synthesis condition of a catalyst based on KF and glass waste for use in transesterification under pressurized media in continuous reactor. A central composite rotational design was used with a mass ratio of potassium fluoride/waste glass particles (KF/WGP) and calcination temperature (CT) as factors and ethyl ester content and potassium leaching as the response variable. Transesterification reactions were performed at 275 °C, 20 MPa and mass ratio of soybean oil/ethanol of 1:1. The optimal synthesis condition of the catalyst was identified (KF/WGP = 50%, CT = 500 °C) wherein a content of 69% of ethyl esters and 8% potassium leaching were achieved. It was observed that the chemical treatment of waste glass with KF leads to the formation of compounds such KCaF3, K2O, and K2CO3 on its surface, which resulted in increased basicity and basic strength of the catalyst. These results indicated that the KF/WGP catalyst has the potential to produce esters in continuous flow under pressurized conditions.