At 190 ◦C, the highest lactic acid yield of 30% was obtained with
the ratio of 3 g ZrO2 to 1 g xylan and under 10% O2 partial presure among all experimental runs. By quickly identifying the most
sensitive reaction parameters on lactic acid yield, a detailed temperature and catalyst loading profiling study was performed. Fig. 6
shows that below 180 ◦C, lactic acid yield is negligible while a lactic acid yield of ∼17.3% was obtained at 220 ◦C. Fig. 7 illustrates
the considerable effect of the catalyst loading on the yield of lactic acid from xylan. Without a ZrO2 catalyst, almost no lactic acid
was formed while, under identical conditions, ∼26% lactic acid was
produced from xylan with adding the ZrO2 catalyst at to 4:1 ZrO2
to xylan ratio