Table 2.
Structural characteristics of various technical lignins as function of biomass feedstock and type of pretreatment.
|
Biomass |
Pretreatment |
Native linkages (per 100 Ar)[a] |
Process‐induced linkages (per 100 Ar) |
Molecular weight |
Functional groups |
Ref. |
|||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
feedstock |
process |
β‐O‐4 |
β‐β (β‐β′)[b] |
β‐5 |
atilbene |
aryl enol ether |
phenyl‐ glycerol |
M W [g mol−1] |
IP[c] |
COOH |
aliph‐OH |
Ph‐OH |
|
|
softwood |
Kraft |
3.2 |
2.4 (3.2) |
0.8 |
4.8 |
1.3 |
|
6000 |
6.2 |
0.5 |
2.6 |
2.1 |
[32] |
|
spruce |
Kraft |
n.d[d] |
6.2 |
3.1 |
|
6.2 |
1.5 |
|
|
|
|
|
[29] |
|
eucalyptus |
Kraft |
n.d |
12.9 |
n.d |
|
|
|
|
|
|
|
|
|
|
spruce |
Alkali |
6 |
6.3 |
5.2 |
|
13.2 |
8.4 |
|
|
|
|
|
|
|
eucalyptus |
Alkali |
n.d |
12.7 |
n.d. |
|
|
8.9 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
softwood |
Kraft (Indulin AT) |
6.1 |
1 |
0.3 |
2.3 |
|
|
4290 |
8.1 |
0.33 |
1.79 |
2.77 |
[24b] |
|
mixed straw |
Alkali (Protobind) |
3.4 |
0.7 |
0 |
0 |
|
|
3270 |
5.2 |
0.8 |
1.26 |
2.86 |
|
|
mixed straw |
Alcell |
5.3 |
2.8 |
0.8 |
0.4 |
|
|
2580 |
4.3 |
0.22 |
1.04 |
3.3 |
|
|
wheat straw |
organosolv |
4.3 |
0.1 |
4.5 |
0.4 |
|
|
1960 |
4.4 |
0.21 |
1.27 |
2.54 |
|
|
poplar |
organosolv |
0.1 |
1.1 |
1.8 |
0 |
|
|
2180 |
3.8 |
0.07 |
0.8 |
2.59 |
|
|
spruce |
organosolv |
0 |
0.2 |
3.3 |
0.7 |
|
|
2030 |
4.9 |
0.06 |
1.43 |
2.73 |
|
|
switchgrass |
ionic liquid |
48 |
3 |
10 |
|
|
|
1362 |
2.4 |
|
|
|
[35] |
|
eucalyptus |
ionic liquid |
57 |
9 |
2 |
|
|
|
844 |
1.9 |
||||
[a] Per 100 aromatic rings. [b] Hydrolyzed form of the resinol (β‐β) moiety. [c] Index of polydispersity. [d] not detected.