4899-74-5Relevant articles and documents
Rapid flow-through fractionation of biomass to preserve labile aryl ether bonds in native lignin
Zhou, Hao,Xu, Jia Yun,Fu, Yingjuan,Zhang, Haiguang,Yuan, Zaiwu,Qin, Menghua,Wang, Zhaojiang
supporting information, p. 4625 - 4632 (2019/09/09)
Lignin is the second largest component of vascular plants and is the most abundant renewable aromatic polymer on our planet. The attractiveness of lignin valorization lies in its conversion into high value aromatic chemicals and biofuels through fractionation and upgrading. The literature has demonstrated that the presence of aryl ether bonds in native lignin was a key factor for the conversion, while the conventional technical lignins from carbohydrate-first processes, e.g. pulp and cellulose ethanol production, are intensively condensed and lack these linkages due to the intense delignification conditions. Here, by using the β-O-4 lignin model dimer GG, we reveal the dramatic degradation of GG and the synchronous formation of relatively stable intermediate β-O-4 dimers, C6C3 enol ether and the formylated enol ether, within the first 5 min under the conditions of 72 wt% aqueous formic acid and 130 °C, conditions suitable for biomass fractionation. Based on these findings, we propose a simple but effective strategy of rapid flow-through fractionation (RFF), which separates the dissolved lignin from the reactor in time and space, thereby preserving these labile aryl ether bonds in native lignin. The application of RFF of poplar wood with a short residence time of 2.6 min attained 75% delignification with an equivalent of the β-O-4 motif in native lignin. Structure-preserved lignins (β-O-4 retention, 75.0%-85.4%) were also harvested from wheat straw with good lignin yields (61.7%-78.5%). Contrarily, batch fractionation acted as a protracted war and resulted in extensive cleavage of aryl ether bonds as suggested by 92%-100% loss of the β-O-4 motif under the same conditions. Because of the well-preserved structure, RFF lignin can be used as a good feedstock to boost its downstream valorization, especially for hydrogenolysis into monophenolic chemicals and fuels. It is noteworthy that the carbohydrate fraction from RFF retained structural integrity and almost reached theoretical yields for glucan and xylan.
Imidazolium-Based Ionic Liquids as Efficient Reagents for the C?O Bond Cleavage of Lignin
Thierry, Marina,Majira, Amel,Pégot, Bruce,Cezard, Laurent,Bourdreux, Flavien,Clément, Gilles,Perreau, Fran?ois,Boutet-Mercey, Stéphanie,Diter, Patrick,Vo-Thanh, Giang,Lapierre, Catherine,Ducrot, Paul-Henri,Magnier, Emmanuel,Baumberger, Stéphanie,Cottyn, Betty
, p. 439 - 448 (2018/02/06)
The demethylation of lignin in ionic liquids (ILs) was investigated by using pure lignin model monomers and dimers together with dioxane-isolated lignins from poplar, miscanthus, and maize. Different methylimidazolium ILs were compared and the samples were treated with two different heating processes: microwave irradiation and conventional heating in a sealed tube. The conversion yield and influence of the treatment on the lignin structure were assessed by 31P NMR spectroscopy, size-exclusion chromatography, and thioacidolysis. The acidic methylimidazolium IL [HMIM]Br was shown to be an effective combination of solvent and reagent for the demethylation and depolymerization of lignin. The relatively mild reaction conditions, the clean work-up, and the ability to reuse the IL makes the described procedure an attractive and new green method for the conversion of lignin to produce phenol-rich lignin oligomers.
The synthesis and analysis of lignin-bound Hibbert ketone structures in technical lignins
Miles-Barrett, Daniel M.,Neal, Andrew R.,Hand, Calum,Montgomery, James R.D.,Panovic, Isabella,Ojo, O. Stephen,Lancefield, Christopher S.,Cordes, David B.,Slawin, Alexandra M.Z.,Lebl, Tomas,Westwood, Nicholas J.
supporting information, p. 10023 - 10030 (2016/11/06)
Understanding the structure of technical lignins resulting from acid-catalysed treatment of lignocellulosic biomass is important for their future applications. Here we report an investigation into the fate of lignin under acidic aqueous organosolv conditions. In particular we examine in detail the formation and reactivity of non-native Hibbert ketone structures found in isolated organosolv lignins from both Douglas fir and beech woods. Through the use of model compounds combined with HSQC, HMBC and HSQC-TOCSY NMR experiments we demonstrate that, depending on the lignin source, both S and G lignin-bound Hibbert ketone units can be present. We also show that these units can serve as a source of novel mono-aromatic compounds following an additional lignin depolymerisation reaction.
Metallo-deuteroporphyrin as a biomimetic catalyst for the catalytic oxidation of lignin to aromatics
Zhu, Chenjie,Ding, Weiwei,Shen, Tao,Tang, Chenglun,Sun, Chenguo,Xu, Shichao,Chen, Yong,Wu, Jinglan,Ying, Hanjie
, p. 1768 - 1778 (2015/06/08)
A series of metallo-deuteroporphyrins derived from hemin were prepared as models of the cytochrome P450 enzyme. With the aid of the highly active CoII deuteroporphyrin complex, the catalytic oxidation system was applied for the oxidation of several lignin model compounds, and high yields of monomeric products were obtained under mild reaction conditions. It was found that the modified cobalt deuteroporphyrin that has no substituents at the meso sites but does have the disulfide linkage in the propionate side chains at the β sites exhibited much higher activity and stability than the synthetic tetraphenylporphyrin. The changes in the propionate side chains can divert the reactivity of cobalt deuteroporphyrins from the typical C-C bond cleavage to C-O bond cleavage. Furthermore, this novel oxidative system can convert enzymolysis lignin into depolymerized products including a significant portion of well-defined aromatic monomers.
