Catalytic upgrading of levulinic acid to ethyl levulinate using reusable silica-included Wells-Dawson heteropolyacid as catalyst

Abstract

In this paper we report, for the first time, the direct incorporation of a heteropolyacid (HPA) with Wells-Dawson structure during the synthesis of silica by the sol?gel technique, in acidic media, using tetraethyl orthosilicate. Thecatalyst characterization was carried out by 31P MAS-NMR, FT-IR, XRD, N2 adsorption?desorption measurements, and the acidic properties were determined through potentiometric titration with n-butylamine. The synthesizedcatalysts were used in the esterification of levulinic acid with ethanol, at 78 °C, to obtain ethyl levulinate. The synthesis of silica-included HPAs was satisfactory, and the samples kept their HPA structure intact after synthesis.The catalytic tests for the esterification reaction between levulinic acid and ethanol to produce ethyl levulinate have shown that the silica-included Wells-Dawson HPA is an active and selective catalyst for this reaction. Itmust be noted that silica-included HPAs also kept their structure and catalytic activity after three consecutive reaction cycles. These results indicated that these solid acids are promissory catalysts for the esterification reactionof levulinic acid and ethanol to ethyl levulinate.