5. Sulfite Proses
• Very aggressive
• Removes more lignin
sulfite + lignin -> lignosulfonate
lignosulfonate is a high MW and soluble in water
• Dissolve primary wall
acidic condition
• Dissolve hemicellulose
change xylan -> xylose + fructose
change glucomannan -> glucose + mannose
• Acidic extractives remain in the fiber
6. Sulfate Process
• Less aggressive
• Removes less lignin
hydroluzed lignin, break down and cut to small piece (low MW)
• Does NOT destroys primary wall
• Does NOT destroy hemicellulose
glucomannan -> glucoisosaccharinic acid + mannoisosccahrinic acid
• Acidic extractives removed from the fiber
7.
8.
9.
10.
11.
12. Reactions of lignins during kraft pulping can be divided into two categories:
1) degradation reactions which lead to the liberation of lignin
fragments and ultimately to their dissolution, and
2) condensation reactions which increase the molecular size of
lignin fragments and may result in their precipitation.
