A promising approach to transform levulinic acid into γ-valerolactone using niobic acid photocatalyst and the accumulated electron transfer technique

Abstract

The photocatalytic production of γ-valerolactone (GVL) from levulinic acid (LA) was performed using the UV-assisted accumulated electron transfer technique. For this purpose, a commercial niobic acid (HY-340) produced by Companhia Brasileira Metalurgia e Mineralurgia (CBMM) was used as photocatalyst. HY-340 showed higher efficiency in ethanol (a hole scavenger) and additional contact time with the substrate (48 h in the dark) after the reaction under UV light. Longer illumination time leads to the conversion of by-products to GVL with maximum selectivity of 44.7 %. Electron paramagnetic resonance (EPR) measurements allied with the spin trapping method indicated the reduction process occurs through the transfer of H•. Finally, O2 pulse titration was developed to quantify the electrons accumulated in the HY-340 conduction band. From this experiment, a significant TOF value was calculated to 3.3 × 10−6 s-1 considering that experiments were conducted at room temperature and ambient pressure.