Table 2 Relative changes in poplar samples after dilute acid pretreatment by Fourier transform infrared spectroscopy
Band position | Pretreatment conditions | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|
PL23-t0 | PL23-t15 | PL23-t35 | PL19-t0 | PL19-t15 | PL19-t35 | PL14-t0 | PL14-t15 | PL14-t35 | ||
3340 | O-H stretching, related to cellulose-hydrogen bonds | 1.7 | 1.6 | 1.5 | 2.1 | 1.9 | 2.2 | 2.1 | 1.8 | 2.3 |
2900 | C-H stretching, related to biomass methyl/methylene group | 0.8 | 0.8 | 0.9 | 0.9 | 0.8 | 1.0 | 0.9 | 0.8 | 1.1 |
1740 | Carbonyl bonds ascribed to hemicelluloses | 1.3 | -- | -- | 1.6 | -- | -- | 1.5 | -- | -- |
1595 | Lignin aromatic ring stretch | 0.7 | 0.8 | 0.8 | 0.6 | 0.7 | 0.7 | 0.5 | 0.5 | 0.7 |
1510 | Lignin aromatic ring stretch | 0.6 | 0.9 | 1.0 | 0.5 | 0.8 | 0.8 | 0.4 | 0.7 | 0.7 |
1424 | CH2 scissor motion in cellulose | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 |
1367 | Aliphatic C-H stretch in CH3 | 1.1 | 0.9 | 0.8 | 1.3 | 1.1 | 1.1 | 1.4 | 1.2 | 1.1 |
1265 | Ester absorption associated with uronic acid | -- | 1.1 | 1.2 | -- | 1.2 | 1.1 | -- | 1.3 | 1.2 |
1240 | C-O absorption from acetyl group cleavage | 1.6 | 1.3 | 1.2 | 2.2 | 1.1 | 1.0 | 2.0 | 1.2 | 1.1 |
1059 | C-O stretch in secondary alcohol | 5.0 | 3.6 | 3.4 | -- | 4.0 | 4.3 | -- | 5.3 | 4.9 |
1100/900 | Crystalline to amorphous cellulose ration | 3.0 | 4.4 | 4.5 | 2.9 | 3.7 | 4.5 | 2.7 | 4.1 | 4.4 |
750/710 | Iα/Iβ | 0.9 | 0.6 | 0.4 | 0.3 | 0.3 | 0.2 | 0.3 | 0.3 | 0.2 |
900 | Amorphous cellulose | 1.1 | 0.6 | 0.6 | 1.2 | 0.8 | 0.8 | 1.2 | 0.9 | 0.7 |