Insights of Ethanol Organosolv Pretreatment on Lignin Properties of Broussonetia papyrifera

Abstract

Delignification of Broussonetia papyrifera during ethanol organosolv pretreatment was studied. Milled wood lignin (MWL), the ethanol organosolv lignin recovered at 5 min (PL5), 10 min (PL10), and 60 min (PL60) during the pretreatment, and the residual lignin (RL60) after the pretreatment were characterized and compared. GPC results demonstrated that the weight-average molecular weights (M w ) of the ethanol organosolv lignin fractions increased as the pretreatment time extended from 5 to 60 min. 31 P NMR analysis revealed that the content of aliphatic OH decreased in the following order: RL60 < PL60 < PL5 < PL10 < MWL. HSQC NMR results suggested that the contents of syringyl, guaiacyl, p-hydroxybenzoate unit, phenylcoumaran, and resinol in the solubilized lignin fractions were significantly changed during the pretreatment. In addition, a significant portion of β-O-4 interunit linkages of lignin was cleaved during the pretreatment, leading to the formation of stilbene structures in lignin samples such as PL60.

Influence of Ethanol Organosolv Pulping Conditions on Physicochemical Lignin Properties of European Larch

“…As can be seen in Table 4, the total amount of free hydroxyl groups does indeed not change signi cantly between all the acid-catalyzed fractionation experiments, just a slight increase from OS-C to OS-G can be observed. Both the MWL and the autocatalyzed organosolv lignin contain a signi cantly higher amount of total hydroxyl groups, 9.12 mmol/g and 8.65 mmol/g, respectively, which is in good accordance with the literature [43]. Furthermore, the content of free carboxylic acid groups was low in all larch organosolv fractions, ranging from 0.07 to 0.2 mmol•g −1 .…”

Characterization of Organosolv Birch Lignins: Toward Application-Specific Lignin Production

“…The development of the methoxy group content is thus better explained by taking into consideration the nature of the biomass used in the process. G-lignin is extracted at earlier stages during organosolv treatment, whereas S-lignin gradually builds up and can be extracted only upon prolonged treatment 39 or acid addition to enhance delignification during treatment, 11 whereby in the latter case, regions naturally rich in G-lignin such as the middle lamella were readily delignified due to simultaneous fiber separation. 40 As indicated above and in Table 1 , the increased acid concentration seems to gradually decrease the contents of intact β- O -4′ structures (C α ) via cleavage, from 1.30 to 1.49 and 0.92 mmol/g in B4 , B5 , and B6 , respectively, and this drop can eventually also be associated with an increased content S-type aromatics in the extracted lignin molecules: the loss in β- O -4′ originates mostly from S-based structures such as C β in syringyl β- O -4′, which went from 0.97 ( B4 ) to 0.91 ( B5 ) and 0.43 mmol/g ( B6 ), when comparing guaiacyl β- O -4′, which augmented from 0.21 ( B4 ) to 0.30 ( B5 ) and 0.29 mmol/g ( B6 ) according to the 13 C NMR-based quantification of HSQC data.…”

Effect of Fenton pretreatment on enzymatic hydrolysis of poplar

“…The acetyl in hemicellulose was one of the main obstacles in the destruction process of lignocellulose structure, and the deacetylation reaction in hemicellulose could improve the efficiency of enzymatic hydrolysis. The absorption peak at 1236 cm -1 belongs to the vibration of the C-O bond in hemicellulose or lignin, and the absorption peak at 1375 cm -1 belongs to the C-H vibration of cellulose and hemicellulose (Yao et al 2018). The reduction of the absorption peak strength of the samples pretreated with Fenton at these two sites was partly due to the degradation of hemicellulose.…”