Selective conversion of xylose to lactic acid over metal-based Lewis acid supported on γ-Al2O3 catalysts

Abstract Gamma-alumina (γ-Al2O3) is a low-cost amphoteric solid catalyst which can enhance the transformation of D-xylose into lactic acid. The deposition of metal oxides on γ-Al2O3 could further improve the yield of lactic acid from xylose. Therefore, in this work, the thermochemical catalytic conversion of D-xylose to lactic acid using the Cr, Cu, Co, Ni, and Sn oxides supported on γ-Al2O3 as heterogeneous catalysts was studied. The effects of metal oxides on the D-xylose conversion to lactic acid activity of the catalysts were investigated. It was found that, under identical testing conditions (170 °C, 4 h), Cr/Al2O3 is superior to the other catalysts with the 99 % conversion of D-xylose and the lactic acid yield of 74%. The outstanding activity could be attributed to its richness in Lewis-acid sites. Since the highly active Cr/Al2O3 catalyst is composed of the earth-abundant materials and can be prepared by a simple process, it has feasibility for industrial-scale application.