First Principles of Pretreatment and Cracking Biomass to Fundamental Building Blocks 193
Figure 6.8Cleavage of the ether
bond of lignin in alkaline solution
(Lin and Lin, 2002).
O−
CH 2 OH
CHO
CHS−
OCH 3
OCH 3
OH
CH 2 OH
CHO
CHOH
OCH 3
OCH 3
O
CH 2 OH
CHO
CH
OCH 3
OCH 3
O−
CH 2 OH
CH
S
CH −
+ O
OCH 3
OCH 3
NaOH
(−H 2 O)
HS−
(−H+)
Figure 6.9Hydrolysis of cellulose in
acidic media (Krassig and Schurz, 2002).
OH
OH
HO
R
+ +
O
O
R
CH 2 OH
OH
OH
OH
+ H+
O
O
R
CH 2 OH
+ H 2 O
+ H+
OH
OH
H
O+
R
O
O
R
CH 2 OH
OH
OH
O
R
O
O
R
CH 2 OH
OH
OH
O
O
O
R
R
CH 2 OH
OH
OH
OH
O
O
R
CH 2 OH
OH
O
O
O
R +HO
R
CH 2 OH
Figure 6.10Hydrolysis of cellulose in alkaline conditions (Krassig and Schurz, 2002).
and hydroxyl groups. This reaction is reversible and endothermic. The balance is
established by surplus water and high temperature. Acidic and alkaline catalysts are
used in this procedure. Under alkaline conditions, the reaction is named saponification
or esterification. The main difference between these two reactions is that alkaline
reaction results in irreversible hydrolysis of ester (Solomon, 1988).
