Quantitative insights on de/repolymerization and deoxygenation of lignin in subcritical water

Audrey L LaVallie; Honza Bilek; Anastasia Andrianova; Kathryn Furey; Keith Voeller; Bin Yao; Evguenii Kozliak; Alena Kubátová

doi:10.1016/j.biortech.2021.125974

Quantitative insights on de/repolymerization and deoxygenation of lignin in subcritical water

Bioresour Technol. 2021 Dec:342:125974. doi: 10.1016/j.biortech.2021.125974. Epub 2021 Sep 20.

Authors

Audrey L LaVallie¹, Honza Bilek², Anastasia Andrianova³, Kathryn Furey⁴, Keith Voeller⁵, Bin Yao¹, Evguenii Kozliak¹, Alena Kubátová⁶

Affiliations

¹ Department of Chemistry, University of North Dakota, 151 Cornell St. Grand Forks, ND 58202, USA.
² Department of Chemistry, University of North Dakota, 151 Cornell St. Grand Forks, ND 58202, USA; PREOL, a.s. Terezínská 1214, 410 02 Lovosice, Czech Republic.
³ Department of Chemistry, University of North Dakota, 151 Cornell St. Grand Forks, ND 58202, USA; Agilent Technologies, Inc. 2850 Centerville Rd, Wilmington, DE 19808-1610, USA.
⁴ Department of Chemistry, University of North Dakota, 151 Cornell St. Grand Forks, ND 58202, USA; 3M Center, Building 260-3A-05, Saint Paul, MN 55119, USA.
⁵ Department of Chemistry, University of North Dakota, 151 Cornell St. Grand Forks, ND 58202, USA; Sciex, Minneapolis, MN 58203, USA.
⁶ Department of Chemistry, University of North Dakota, 151 Cornell St. Grand Forks, ND 58202, USA. Electronic address: alena.kubatova@und.edu.

PMID: 34600320
DOI: 10.1016/j.biortech.2021.125974

Abstract

The objective of the study was to investigate alkali lignin polymerization/depolymerization pathways in subcritical water (SW) without additives. Following a SW treatment at 200, 250, 275 and 300 °C, the products were subjected to a comprehensive suite of analyses addressing the product speciation and molecular weight (MW) distribution. The MW reduction (1.4 times) in the solid products following the SW treatment indicated a surprisingly reduced impact of cross-linking/repolymerization at 300 °C and lower temperatures. This was further confirmed by thermal carbon analysis (TCA) showing a reduction in pyrolytic charring after the SW treatment. The TD-Py gas chromatography analysis of the SW treated lignin indicated that the solid residue is less oxygenated than the initial lignin (23 vs. 29% as confirmed by elemental analysis). Thus, deoxygenation rather than re-polymerization appears to be the main process route in the absence of catalysts within the temperature range considered.

Keywords: Gel permeation chromatography; Lignin deoxygenation, lignin valorization; Pyrolysis–gas-chromatography-mass-spectrometry; Thermal carbon analysis.

MeSH terms

Lignin*
Polymerization
Pyrolysis
Temperature
Water*

Substances

Water
Lignin