Iron (III) Silicotungstate: An Efficient and Recyclable Catalyst for Converting Glycerol to Solketal
Márcio José da Silva, Alana Alves Rodrigues, Milena Galdino Teixeira
Abstract
In this work, we describe the use of iron (III) silicotungstate as a catalyst for the synthesis of solketal, a fuel bioadditive, from glycerol and acetone. A high yield of solketal was achieved in glycerol acetalization with acetone at room temperature at short reaction time (ca. 1 h). Among the various metal silicotungstates (i.e., Fe4/3SiW12O40, Cu2SiW12O40, Al4/3SiW12O40, Co2SiW12O40, and Ni2SiW12O40), iron (III) silicotungstate was the most active catalyst (>99%, conversion) and highly selective (98%) toward the formation of solketal. Effects of main reaction parameters (e.g., the acetone to glycerol ratio and catalyst load) were investigated. In addition, the process was successfully extended to other cyclic and acyclic ketones. Insights into the reaction mechanism were obtained. The highest activity of the Fe4/3SiW12O40 catalyst was correlated to the greatest acidity. Although soluble, the iron (III) silicotungstate catalyst was easily reused without loss of activity and selectivity. The lower corrosiveness, facilitated handling, and potential for reuse without activity loss after simple recyclability are positive aspects of the Fe4/3SiW12O40 catalyst.