Direct Conversion of Sugars and Ethyl Levulinate into γ-Valerolactone with Superparamagnetic Acid-Base Bifunctional ZrFeOx Nanocatalysts

Acid-base bifunctional superparamagnetic FeZrOx nanoparticles were synthesized via a two-step process of solvothermal treatment and hydrolysis-condensation, and were further employed to catalyze the conversion of ethyl levulinate (EL) to gamma-valerolactone (GVL) using ethanol as both H-donor and solvent. ZrFeO(1:3)-300 nanoparticles (12.7 nm) with Fe3O4 core covered by ZrO2 layer (0.65 nm thickness) having well-distributed acid-base sites (0.39 vs 0.28 mmol/g), moderate surface area (181 m(2)/g), pore size (9.8 nm), and strong magnetism (35.4 Am-2 kg(-1)) exhibited superior catalytic performance, giving a high GVL yield of 87.2% at 230 degrees C in 3 h. The combination of the nanoparticles with solid acid HY2.6 promoted the direct transformation of sugars to produce GVL in moderate yield (around 45%). Moreover, the nanocatalyst was easily recovered by a magnet for six cycles with an average GVL yield of 83.9% from EL.