Enhanced Ethanol and Biogas Production from Pinewood by NMMO Pretreatment and Detailed Biomass Analysis

Table 4

Characteristic frequencies and band intensities from the FTIR spectra of the treated and untreated pinewood powder.

Frequency (cm^−1)	Functional group/band assignment	Untreated powder	1 h treated	3 h treated	15 h treated	Reference
3352; (3447); (no band)	–OH stretching intramolecular hydrogen bonds; Cellulose I (3352), cellulose II (3447); Xylan	0.26; (0.18)	0.26; (0.22)	0.25; (0.22)	0.26; (0.24)	[12]; [12]; [13]
1732	C–O stretching of acetyl or carboxylic acid Hemicellulose and lignin (1730)	0.07	0.04	0.03	0.00	[6]
1600	C=C Lignin	0.07	0.07	0.06	0.05	[6, 14]
1508	C–C stretching of the aromatic ring, lignin (1510)	0.12	0.12	0.10	0.07	[6]
1452	–OH in plane bending; Cellulose I (1455), cellulose II (1470); Asymmetric bending in C–H3 (1465) lignin; –C–H deformation Xylan (1461)	0.11	0.11	0.11	0.11	[12]; [6]; [13]
1421	C–H2 symmetric bending; Cellulose II (1419), cellulose I (1431); Weak C–O stretching (1420), aromatic; C=C stretch (1433); Lignin (1423), Xylan (1420) [13]	0.14	0.14	0.13	0.13	[15]; [13]; [13]; [13]
1263	Vibration of guaiacyl rings (1270)	0.20	0.18	0.16	0.12	[14]
1230	C–O stretching in lignin and hemicel. (1235)	0.15	0.12	0.10	0.07	[16]
1101	Ring asymmetric stretching; Cellulose I (1111) Cellulose II (1007)	0.46	0.44	0.44	0.49	[12]
898	Asym., out of phase ring stretching; Cellulose I (893); Cellulose II, Amorphous Cellulose (895); Xylan (899)	0.13	0.12	0.12	0.12	[15]; [15]; [13]