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Title: Characterization of lignin derived from water-only and dilute acid flowthrough pretreatment of poplar wood at elevated temperatures

In this study, flowthrough pretreatment of biomass has high potential to valorize lignin derivatives to high-value products, which is vital to enhance the economy of biorefinery plants. Comprehensive understanding of lignin behaviors and solubilization chemistry in aqueous pretreatment such as water-only and dilute acid flowthrough pretreatment is of fundamental importance to achieve the goal of providing flexible platform for lignin utilization. In this study, the effects of flowthrough pretreatment conditions on lignin separation from poplar wood were reported as well as the characteristics of three sub-sets of lignin produced from the pretreatment, including residual lignin in pretreated solid residues (ReL), recovered insoluble lignin in pretreated liquid (RISL), and recovered soluble lignin in pretreatment liquid (RSL). Both the water-only and 0.05% (w/w) sulfuric acid pretreatments were performed at temperatures from 160 to 270°C on poplar wood in a flowthrough reactor system for 2-10 min. Results showed that water-only flowthrough pretreatment primarily removed syringyl (S units). Increased temperature and/or the addition of sulfuric acid enhanced the removal of guaiacyl (G units) compared to water-only pretreatments at lower temperatures, resulting in nearly complete removal of lignin from the biomass. Results also suggested that more RISL was recovered than ReL and RSL in bothmore » dilute acid and water-only flowthrough pretreatment at elevated temperatures. NMR spectra of the RISL revealed significant β-O-4 cleavage, α-β deoxygenation to form cinnamyl-like end groups, and slight β-5 repolymerization in both water-only and dilute acid flowthrough pretreatments. In conclusion, elevated temperature and/or dilute acid greatly enhanced lignin removal to almost 100% by improving G unit removal besides S unit removal in flowthrough system. A new lignin chemistry transformation pathway was proposed and revealed the complexity of lignin structural change during hot water and dilute acid flowthrough pretreatment.« less
Authors:
 [1] ;  [1] ;  [2] ;  [1] ;  [2] ;  [2] ;  [1]
  1. Washington State Univ., Pullman, WA (United States)
  2. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Publication Date:
OSTI Identifier:
1233779
Report Number(s):
PNNL-SA--113147
Journal ID: ISSN 1754-6834; 46208; 48664; KP1704020
Grant/Contract Number:
AC05-76RL01830
Type:
Accepted Manuscript
Journal Name:
Biotechnology for Biofuels
Additional Journal Information:
Journal Volume: 8; Journal ID: ISSN 1754-6834
Publisher:
BioMed Central
Research Org:
Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
09 BIOMASS FUELS lignin; biofuels; NMR; Environmental Molecular Sciences Laboratory; hot water; dilute acid; flowthrough pretreatment; poplar; characterization