Title: Chemical Transformations of Poplar Lignin during Cosolvent Enhanced Lignocellulosic Fractionation Process

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 molecularmore » weight, and high amount of phenolic hydroxyl groups, suitable for its development into fuels, chemicals, and materials.« less

Authors:

Meng, Xianzhi  ^[1];

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• Search DOE PAGES for ORCID "0000-0003-4303-3403"

Parikh, Aakash ^[2]; Seemala, Bhogeswararao ^[2]; Kumar, Rajeev ^[3]; Pu, Yunqiao ^[4]; Christopher, Phillip ^[5]; Wyman, Charles E. ^[2]; Cai, Charles M. ^[2]; Ragauskas, Arthur J.  ^[6]

• Search DOE PAGES for author "Ragauskas, Arthur J."
• Search DOE PAGES for ORCID "0000-0002-3536-554X"

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+ Show Author Affiliations

1. Department of Chemical and Biomolecular Engineering, University of Tennessee Knoxville, Knoxville, Tennessee 37996, United States
2. Bourns College of Engineering—Center of Environmental and Research Technology (CE-CERT), University of California, Riverside, California 92507, United States; Department of Chemical and Environmental Engineering, Bourns College of Engineering, University of California, Riverside, California 92521, United States
3. Bourns College of Engineering—Center of Environmental and Research Technology (CE-CERT), University of California, Riverside, California 92507, United States
4. Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
5. Department of Chemical and Environmental Engineering, Bourns College of Engineering, University of California, Riverside, California 92521, United States; Department of Chemical Engineering, University of California, Santa Barbara, Santa Barbara, California 93106, United States
6. Department of Chemical and Biomolecular Engineering, University of Tennessee Knoxville, Knoxville, Tennessee 37996, United States; Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States; Department of Forestry, Wildlife, and Fisheries, Center for Renewable Carbon, The University of Tennessee Knoxville, Institute of Agriculture, Knoxville, Tennessee 37996, United States

Publication Date:

Thu May 24 00:00:00 EDT 2018

Research Org.:

Univ. of California, Riverside, CA (United States); Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)

Sponsoring Org.:

USDOE Office of Energy Efficiency and Renewable Energy (EERE)

OSTI Identifier:

1581903

Alternate Identifier(s):

OSTI ID: 1513423

Grant/Contract Number:  

EE0007006; AC05-00OR22725

Resource Type:

Accepted Manuscript

Journal Name:

ACS Sustainable Chemistry & Engineering

Additional Journal Information:

Journal Volume: 6; Journal Issue: 7; Journal ID: ISSN 2168-0485

Publisher:

American Chemical Society (ACS)

Country of Publication:

United States

Language:

English

Subject:

09 BIOMASS FUELS; Pretreatment; Organic polymers; Biomass; Aromatic compounds; Biopolymers; Antioxidant; Biomass recalcitrance; Cosolvent Enhanced Lignocellulosic Fractionation; Lignin valorization