Conversion of Glycerol to Lactic Acid Catalyzed by Different-Sized Cu₂O Nanoparticles in NaOH Aqueous Solution

Different-sized Cu₂O nanoparticles with the average particle sizes ranging from 115 to 423 nm were prepared starting from CuSO₄ using ascorbic acid as the reductant at room temperature. When Cu₂O nanoparticles were used as the catalysts for hydrothermal conversion of glycerol at 230 °C in a NaOH aqueous solution, Cu₂O nanoparticles effectively catalyzed the hydrothermal conversion of glycerol to lactic acid as compared to the conventional hydrothermal conversion of glycerol in a “pure” NaOH aqueous solution. Small-sized Cu₂O nanoparticles showed higher catalytic activity than the large-sized ones. In a wide glycerol concentration range of 1–2.5 mol/L and a low mole ratio of Cu₂O nanoparticle to glycerol of 2.5:100, the glycerol conversion and lactic acid selectivity were more than 86.2% and 87.2%, respectively, after reacting at 230 °C for 2 h.