Synthesis and application of TiO2-supported phosphotungstic acid for ethyl levulinate production

The present study investigates synthesis, characterization, and application of TiO2 supported Keggin phosphotungstic acid in biorenewable transformations. In particular, 10 wt%, 20 wt%, 30 wt% and 40 wt% Keggin phosphotungstic acid was loaded over TiO2 support via wet impregnation method to prepare EPTN-1, EPTN-2, EPTN-3, and EPTN-4 catalysts, respectively. After this, synthesized catalysts were tested in a microwave reactor to measure reactivity trend in order HPW > EPTN-4 > EPTN-3 > EPTN-2 > EPTN-1. A maximum 95% levulinic acid (LA) conversion was measured in the presence of 72 mg EPTN-4 catalyst, two mmol LA in 1:42 LA: EtOH (ethanol) molar ratio at 393 K in 120 min at a stirring speed of 300 rpm. No significant loss in heterogenized EPTN-4 catalyst was measured after five application cycles. A detailed characterization of synthesized catalyst showed that the Keggin structure remained intact after heterogenization.