Table 2. Yield and Structural Quality of Collected Acetylated Lignin Fraction (D) from Wheat Straw.
| # | “cooking” liquors | T (°C) | time (h) | lignin rich yield (wt %) | β-O-4 signals (HSQC) | Mw | Mn | PDI (Mw/Mn) | carbohydrate signal (HSQC) |
|---|---|---|---|---|---|---|---|---|---|
| 1 | HCOOH | 101 | 0.5 | 13 | strong | 4270 | 1900 | 2.25 | weak |
| 2 | HWEa+ HCOOH | 101 | 0.5 | 8 | strong | 3640 | 1710 | 2.12 | weak |
| 3 | [TEAH][HSO4] | 120 | 4 | 12 | n.s. | 2530 | 1310 | 1.94 | n.s. |
| 4 | HWEa+ [TEAH][HSO4] | 120 | 4 | 8 | n.s. | 2270 | 1220 | 1.86 | n.s. |
| 5 | EtOH/Na2CO3 | 130 | 2 | 8 | strong | 3030 | 1300 | 2.33 | strong |
| 6 | HWEa+ EtOH/Na2CO3 | 130 | 2 | 13 | strong | 3120 | 1380 | 2.27 | weak |
| 7 | EtOH/NaOH | 130 | 2 | 14 | strong | 3180 | 1330 | 2.39 | strong |
| 8 | 0.1 M HCl + 0.1 M NaOH | 100 | 2 + 2 | 11 | strong | 3700 | 1390 | 2.66 | strong |
| 9 | 1 M NaOH | 130 | 2 | 24 | strong | 2980 | 1210 | 2.45 | strong |
a
HWE (5 min at 185 °C). No signal is specified as n.s. Mn = number-average molecular weight, MW = weight-average molecular weight, and polydispersity = PDI (Mw/Mn).