chosen as the best AT conditions. It is noteworthy that cellulose
was almost no loss under all these conditions. The AT mainly
hydrolyzed the hemicellulose and partly removed lignin, which
led to the weight loss of RS. Under the best AT conditions, 86.7%
hemicellulose and 11.7% lignin in the origin RS were removed,
which caused 33.6% weight loss of RS. The main composition of
the obtained acid treated RS was moisture 9.8 ± 0.3%, cellulose
57.1 ± 0.8%, lignin 21.5 ± 0.5%, and hemicellulose 4.4 ± 0.3%.
The sulfuric acid is used as catalyst during AT, so in principle it
does not consume and the AT hydrolyzate can be reused for further
AT. Reuse of the AT hydrolyzate can not only reduce the sulfuric
acid consumption but also benefit for the xylose recovery by raising the xylodextrin concentration in the AT hydrolyzate. However,
the AT hydrolyzate becomes a more viscous and dark brown solution with its recycle times increasing, which decreases the AT efficiency and the xylose recovery yield. Therefore, the recycle times
of the AT hydrolyzate is an important parameter for the AT process.