Chemoselective synthesis of propionic acid from biomass and lactic acid over a cobalt catalyst in aqueous media

Abstract

A new non-fermentative process for the transformation of biomass carbohydrates and lactic acid (LA) into propionic acid (PA) was first reported over a cobalt catalyst in water. The Co catalyst exhibited high catalytic activity for the formation of PA with Zn as a reductant. Various parameters, such as catalyst loading, Zn weight, water volume, temperature and reaction time, were investigated to improve the yield of PA, and the maximum value of 58.8% was achieved in the presence of 4 mmol Co and 10 mmol Zn in 7.5 mL H₂O at 250 °C for 2 h. The recyclability of the Co catalyst showed that Co could be effectively repeated four times without the loss of activity. Moreover, the result showed that in situ-formed ZnO by oxidation of Zn in water could efficiently enhance the catalytic activity of the Co catalyst in the conversion of LA. Besides, direct conversion of carbohydrate biomass, such as glucose, cellulose and starch, or a similar compound such as glycolic acid also afforded the desired products. The present study provides great significance for practical application on the production of PA from LA and biomass carbohydrates.