Ultrafast Glycerol Conversion to Lactic Acid over Magnetically Recoverable Ni–NiO<i>_x</i>@C Catalysts

Abstract

Lactic acid (LA), a key platform chemical from biomass, is an ideal feedstock for biodegradable plastic synthesis. The conversion of glycerol to LA was investigated over graphitic-carbon-layer-encapsulated Ni–NiOx core/shell (Ni–NiOx@C) catalysts, which were prepared by controlled oxidation from pristine Ni@C. The oxidation temperature greatly influenced the percentage of NiOx and thus the amount of Lewis acid. In the conversion of glycerol, the catalyst oxidized at 200 °C provided hitherto the highest LA formation rate (5.67 mol/(m3·gcat·s)), which is at least 15 times faster than those obtained over the reported Cu and noble metal catalysts under comparable reaction conditions. The excellent performance of Ni–NiOx@C was attributed to the synergistic effect of the homogenous base, metallic Ni, and acidic NiOx sites, which accelerates the bond cleavage of α-C–H and C–O and promotes ultrafast formation of LA within 30 min.