Utilization of biodiesel byproduct glycerol: Production of methyl lactate over Au/CuO and Sn-Beta binary catalyst under mild reaction conditions

Utilization of glycerol is important for the sustainable development of biodiesel industry. In this study, green conversion of glycerol to methyl lactate was realized over Au/CuO and Sn-Beta binary catalyst at low temperature in base-free methanol, 86% glycerol conversion and 60% methyl lactate yield can be obtained at 90 degrees C. Precursors for preparation of CuO have significant influence on the catalytic oxidative activity of Au/CuO. Oxygen mobility of CuO prepared from copper acetate (CuO-CA) is the highest compared to CuO materials prepared from copper nitrate (CuO-CN) and commercial CuO (CuO-Commercial). Meanwhile, dispersion of Au particles is significantly affected by the precursor for synthesis of CuO. Au particles on CuO-CA are small (2-4 nm) and uniform. Accordingly, Au/CuO-CA shows the best catalytic activity for the oxidation of glycerol. Synergism of oxidative active sites on Au/CuO-CA and Lewis acid sites on Sn-Beta facilitates the production of methyl lactate from glycerol. Meanwhile, the catalysts are recyclable and can be reused easily without any treatment.