Production of propionic acid via hydrodeoxygenation of lactic acid over FexOy catalysts

Abstract

The gas-phase hydrodeoxygenation of LA to propionic acid over Fe and its oxides was firstly investigated under various conditions. The catalysts were characterized by nitrogen adsorption–desorption, XRD, FT-IR, H₂-TPR and SEM. Fe₃O₄ as active species was confirmed. Due to that reason, Fe₂O₃ can be efficiently transformed in situ to Fe₃O₄ under an atmosphere containing hydrogen derived from decarboxylation/or decarbonylation reaction of lactic acid, which offers the most excellent catalytic performance. The catalyst is sensitive to reaction temperature. LA conversion and its consumption rate increased with an increase of reaction temperature. Similarly, propionic acid selectivity also increased with reaction temperature in the range of 360–390 °C. But with further enhancement of reaction temperature from 390 to 400 °C, it drastically decreased since the formation rate of propionic acid reduced at 400 °C. The catalyst displayed an excellent adaptability in a wide range of LA LHSV except for 1.3 h⁻¹. More importantly, at high LA LHSV of 26.3 h⁻¹, the catalyst offered a satisfactory stability within 100 h on stream. Under the optimal reaction conditions, 96.7% of LA conversion and 46.7% of propionic acid selectivity were achieved.