Title: Diol pretreatment to fractionate a reactive lignin in lignocellulosic biomass biorefineries

Abstract

Lignin-first fractionation has become a new biorefinery target to obtain valuable lignin monomers toward the complete utilization of lignocellulosic biomass, but increasing delignification through conventional pretreatment approaches often affects the structural integrity of the dissociated lignin. We discovered a new reactive lignin with a great solvent solubility and preserved β-O-4 linkages from eucalyptus after a modified organosolv pretreatment using 1,4-butanediol (1,4-BDO). Unlike conventional organosolv pretreatment using ethanol, lignin deposition was not observed in 1,4-BDO pretreatment. Similarly, 2D HSQC NMR analysis revealed that the residual lignin obtained from 1,4-BDO pretreated eucalypts contained a relatively higher amount of β-O-4 interunit linkages, indicating its higher integrity than ethanol pretreated lignin. This result agreed with the lower content of phenolic hydroxyl groups in dissolved lignin via³¹P NMR analysis. With increasing pretreatment severity, the amount of aliphatic hydroxyl groups decreased in ethanol pretreated lignin while it remained at a higher level in 1,4-BDO pretreated lignin. These results suggested that 1,4-BDO quenched the benzyl carbocation intermediate and formed ether linkages with a hydroxyl tail at the α position of the lignin. Solubility tests revealed that grafting aliphatic hydroxyl groups on 1,4-BDO lignin increased its dissolution. This phenomenon was further demonstrated for four different diols with similarmore » structures. Likewise, more than 90% cellulose conversion was obtained for all the diol pretreated eucalyptus after 48 h of enzymatic hydrolysis with cellulase at a loading of 7.5 FPU per gram of glucan. Diol pretreatment thus offers a promising reaction pathway to coincide with three pillars of biorefinery for lignin fractionation, lignin structural integrity, and cellulose hydrolysis.« less

Authors:

Dong, Chengyu  ^[1];

• Search DOE PAGES for author "Dong, Chengyu"
• Search DOE PAGES for ORCID "0000-0001-6594-1432"

Meng, Xianzhi ^[2]; Yeung, Chi Shun  ^[1];

• Search DOE PAGES for author "Yeung, Chi Shun"
• Search DOE PAGES for ORCID "0000-0002-3968-1718"

TSE, Ho-Yin  ^[1];

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• Search DOE PAGES for ORCID "0000-0003-0664-7692"

Ragauskas, Arthur J.  ^[3];

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

Leu, Shao-Yuan  ^[1]

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• Search DOE PAGES for ORCID "0000-0001-7262-1453"

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+ Show Author Affiliations

1. Hong Kong Polytechnic Univ., Kowloon (Hong Kong)
2. Univ. of Tennessee, Knoxville, TN (United States)
3. Univ. of Tennessee, Knoxville, TN (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Publication Date:

Wed Apr 24 00:00:00 EDT 2019

Research Org.:

Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)

Sponsoring Org.:

USDOE; Hong Kong General Research Fund; Environment and Conservation Fund; Innovation and Technology Fund; University Research Facility in Chemical and Environmental Analysis (UCEA)

OSTI Identifier:

1523726

Grant/Contract Number:  

AC05-00OR22725; 15212317; ECF85/2017; UIM/333

Resource Type:

Accepted Manuscript

Journal Name:

Green Chemistry

Additional Journal Information:

Journal Volume: 21; Journal Issue: 10; Journal ID: ISSN 1463-9262

Publisher:

Royal Society of Chemistry

Country of Publication:

United States

Language:

English

Subject:

09 BIOMASS FUELS