Highly efficient oxidation of ethyl lactate to ethyl pyruvate with molecular oxygen over VxOy/SBA-15 catalysts

Abstract

The oxidation of biomass-derived alkyl lactate to alkyl pyruvate over a solid catalyst is a promising way to produce high-value chemicals. In the present work, a series of V_xO_y/SBA-15 catalysts of varying vanadium loading were prepared and employed for the oxidation of ethyl lactate (EL) to ethyl pyruvate (EP) in the presence of molecular oxygen. These catalysts were characterized in detail by ICP, XRD, N₂ physisorption, FTIR, SEM, TEM, XPS, O₂-TPD and H₂-TPR. The EL conversion increased with the increase of vanadium loading of the V_xO_y/SBA-15 catalyst, while the selectivity to EP was always higher than 95% regardless of the vanadium loading. 95.8% EL conversion and 98.7% EP selectivity were obtained under optimized reaction conditions (130 °C, 4 h in CH₃CN) over the 5.9V_xO_y/SBA-15 catalyst. The O₂-TPD and H₂-TPR results showed that there was strong interaction between V_xO_y and SBA-15, resulting in an increase of reducibility of the V_xO_y/SBA-15 catalysts. Correlations of turnover frequency (TOF) with vanadium loading and the percentage of V⁴⁺/(V⁴⁺ + V⁵⁺) were made to analyze the structure–activity relationships, and the probable catalytic mechanism was also proposed.