Application of KF/waste glass catalyst in the synthesis of fatty acid esters under pressurized conditions without glycerol generation

In this study, the efficiency of applying the KF/waste glass catalyst was tested in the transesterification of crambe oil under pressurized conditions for the synthesis of esters and glycerol carbonate (GLC). For this, a miscella pressurized extraction was used. The influence of temperature on different residence times was evaluated, and to verify the effect of the catalyst on the process, non-catalytic reactions were conducted. In reactions without the use of catalyst, a temperature of 250 °C was required to obtain >90 % esters yield. In the catalytic reactions, the operating conditions were reduced to 225 °C, to obtain ∼96 % esters yield, also providing the synthesis of a greater quantity of GLC, and a glycerol-free sample. The wet modification of powdered glass waste with KF results in the K2SiF6, NaF, CaF2, and KCaF3 phases. The laser-induced breakdown spectroscopy analyses showed the presence of fluorinated compounds in the catalyst. Furthermore, calcium and sodium ions from the glass waste matrix support were the source for the crystalization of K2SiF6/CaF2/KCaF3 and NaF phases, respectively. The catalyst showed a good catalytic activity, promoting high ester and GLC formation at 225 °C, 10 min and 10 MPa, remaining with good performance even after 8h of reaction, but it is important to mention that the stability of the catalyst needs to be improved due to the leaching of K to Ca.