Performances of Several Solvents on the Cleavage of Inter‐ and Intramolecular Linkages of Lignin in Corncob Residue

Abstract

The performances of solvents, including γ-butyrolactone (GBL), γ-valerolactone (GVL), tetrahydrofuran (THF), ethyl acetate (EAC), 2-methyltetrahydrofuran (2-MeTHF), and the corresponding mixtures with H O, on the cleavage of inter- and intramolecular linkages of lignin in corncob residue were investigated. At 200 °C, miscible cosolvents (H O-GBL, H O-GVL, and H O-THF) exhibited much better efficiency for lignin dissolution than that of both immiscible cosolvents (H O-EAC and H O-2-MeTHF) and pure solvents. The synergetic effect between H O and organic solvent significantly promoted the breakage of intermolecular linkages between C6-O-H of amorphous cellulose and lignin. GBL and THF solvents preferentially dissolved lignin with H and G units, whereas GVL, EAC, and 2-MeTHF solvents exhibited high selectivity for the dissolution of lignin with S and G units. In addition to dissolution, the intramolecular β-O-4 linkage in lignin could be selectively cleaved in H O-GBL cosolvent, whereas the β-O-4, α-O-4, and β-5 linkages were cleaved in H O-EAC, H O-THF, and H O-2-MeTHF cosolvents. At 300 °C, the breakage of the β-γ bond prior to β-O-4 in H O-GBL, H O-THF, H O-EAC, and H O-2-MeTHF produced 4-ethylphenol and 4-ethylguaiacol selectively (accounting for ≈70 % of the total identified monophenols), whereas the α-1 bond was preferably broken in H O-GVL to form guaiacol (accounting for ≈75 % of the total identified monophenols).

Recent Advances in the Catalytic Depolymerization of Lignin towards Phenolic Chemicals: A Review

“…In the late 20 th century, organosolv lignin appeared to be a promising strategy, which was generally obtained via the selective extraction of lignin in methanol, ethanol, isopropanol, n ‐butanol, THF, or H 2 O/organic co‐solvents, followed by precipitation, thus a lignin‐rich precipitate was obtained. In 1989, organosolv lignin, was produced in a semi‐commercial scale plant using ethanol‐water Alcell pulping technology .…”

Torrefaction at 200 °C of Pubescens Pretreated with AlCl3 Aqueous Solution at Room Temperature

“…The characteristic absorption bands of cellulose, hemicellulose, and lignin in raw pubescens and pretreated samples after torrefaction were assigned according to the literature. 15 − 18 The characteristic absorbance of lignin occurred at 1635, 1605, 1513, 1462, 1426, 1029, and 834 cm –1 , 16 , 19 where the weak band at 1635 cm –1 was assigned to the conjugated C=O stretching of the aromatic ring. 17 , 18 The absorbance bands at 1605 and 1513 cm –1 were assigned to C–C and C=C stretching of the aromatic ring of lignin, while the band at 1029 cm –1 was due to the C–O stretching of O-CH 3 and C-OH.…”

“… 17 , 21 The bands at 1378, 1165, 1117, and 896 cm –1 were assigned to the characteristic absorbance of cellulose, whereas those at 1165, 1117, and 896 cm –1 were assigned to C–O–C asymmetric stretching at the β-(1-4)-glycosidic linkage, stretching of the glucose ring in plane, and glucose ring stretching. 15 , 20 …”

“… 39 , 40 The yields of guaiacol, 4-methylguaiacol, 4-ethylguaiacol, 4-vinylguaiacol, 5-allylguaiacol, and vanillin were mainly from the degradation of G units (guaiacyl phenols) in lignin via cleavage of the saturated alkyl side-chain structure, cracking of C α –C β bonds in guaiacyl units, cleavage of C β –C γ on saturated and α-carbonyl, and cracking of C α –C β′ , as well as cleavage of C α -OH via dehydration and cleavage of saturated alkyl side chains. 15 , 41 The production of 2,6-dimethoxyphenol, 4-allyl-2,6-dimethoxyphenol, and syringaldehyde was due to the degradation of S units (syringyl phenols) in lignin via cracking of C 1 –C α bonds and C-O-H(R) in aliphatic side chains (C α -OH or C γ -OH/R position). 31 , 42 , 43 It could be easily observed that all of the paths for the formation of monoaromatic species via torrefaction involved the cleavage of β-O-4 linkage in lignin.…”

Effect of Ni(NO3)2 Pretreatment on the Pyrolysis of Organsolv Lignin Derived from Corncob Residue

“…Corncob residue was collected from Shandong Futaste Investment Co., Ltd. (Qingdao, Shandong Province, China). Corncob residue was an industrial waste left from the catalytic hydrolysis of hemicellulose to produce xylose, which meant cellulose and lignin were the major components of corncob residue [28]. The details of extraction of organsolv lignin (OL) from corncob residue and related characterizations can be found in our previous study [29].…”