Abstract
Converting lignocellulosic biomass to biofuels and bioproducts is significantly hindered by the innate recalcitrance of biomass to chemical and biological breakdown, and it usually requires a pretreatment stage in order to improve conversion yields. A promising novel pretreatment named Cosolvent Enhanced Lignocellulosic Fractionation (CELF) involving dilute acid treatment of biomass in a THF-water mixture was recently developed to overcome biomass recalcitrance. Detailed elucidation of physicochemical structures of the fractionated lignin that is precipitated from CELF pretreatment of hardwood poplar, also called CELF lignin, reveals transformations in its molecular weights, monolignol composition, and hydroxyl group content. Isolated CELF lignin revealed dramatic reductions in its molecular weight by up to ∼90% compared with untreated native lignin. Furthermore, CELF lignin's β-O-4 interunit linkages were extensively cleaved after CELF pretreatment as indicated by a semiquantitative HSQC NMR analysis. This is further evidenced by a 31P NMR analysis showing a significant decrease in aliphatic OH groups due to the oxidation of lignin side chains, whereas the content of total phenolic OH groups in CELF lignin significantly increased due to cleavage of interunit linkages. In conclusion, the CELF process generated a uniquely tunable and highly pure lignin feedstock of low content aryl ether linkages, low molecular weight, and high amount of phenolic hydroxyl groups, suitable for its development into fuels, chemicals, and materials.
Original language | English |
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Pages (from-to) | 8711-8718 |
Number of pages | 8 |
Journal | ACS Sustainable Chemistry and Engineering |
Volume | 6 |
Issue number | 7 |
DOIs | |
State | Published - Jul 2 2018 |
Funding
The authors acknowledge primary funding support from Bioenergy Technologies Office (BETO) in the Office of Energy Efficiency and Renewable Energy (EERE) under Award No. DE-EE0007006 with U.S. Department of Energy (DOE). The poplar supplied in this study as well as the CELF lignin produced from poplar at milder conditions was supported by the Center for Bioenergy Innovation (CBI). CBI is a U.S. DOE Bioenergy Research Center supported by the Office of Biological and Environmental Research in the DOE Office of Science. The publisher, by accepting the article for publication, acknowledges that the United States Government retains a nonexclusive, paid-up, irrevocable, worldwide license to reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accord with the DOE Public Access Plan (https://www.energy.gov/downloads/doe-public-access-plan). The views and opinions of the authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights.
Keywords
- Antioxidant
- Biomass recalcitrance
- Cosolvent Enhanced Lignocellulosic Fractionation
- Lignin valorization