the yield of formic acid significantly increased as the O2 partial pressure increased from 0% to 100%.With increasing O2 partial pressure from 0% to 20%, the yield of furfural decreased rapidly. When the O2 partial pressure was larger
than 20%, furfural was almost completely decomposed. In contrast,there were negligible changes in lactic acid yields in the operation range of the O2 partial pressures from 0% to 10%. The catalyst loading effect on xylose conversion was shown in Without adding the ZrO2 catalyst, the main product was furfural through the dehydration of xylose in high-temperature water. The lactic acid yield rapidly increased to 30% when adding 0.5 g ZrO2, i.e., at
the catalyst to xylose ratio of 0.5. The highest lactic acid yield of 42.5% was achieved when the ratio of ZrO2 to xylose was 2:1. However, the lactic acid yield varied little as the catalyst loading was
above 1 g. Other carboxylic acids such as glycolic acid and formic acid followed the same trend as lactic acid. Contrarily, the furfural yield consistently decreased with increasing the ZrO2 loading