New Mechanistic Insights into the Lignin beta-O-4 Linkage Acidolysis with Ethylene Glycol Stabilization Aided by Multilevel Computational Chemistry

Alessandra De Santi, Susanna Monti*, Giovanni Barcaro, Zhenlei Zhang, Katalin Barta*, Peter J. Deuss*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

Acidolysis in conjunction with stabilization of reactive intermediates has emerged as one of the most powerful methods of lignin depolymerization that leads to high aromatic monomer yields. In particular, stabilization of reactive aldehydes using ethylene glycol results in the selective formation of the corresponding cyclic acetals (1,3-dioxolane derivatives) from model compounds, lignin, and even from softwood lignocellulose. Given the high practical utility of this method for future biorefineries, a deeper understanding of the method is desired. Here, we aim to elucidate key mechanistic questions utilizing a combination of experimental and multilevel computational approaches. The multiscale computational protocol used, based on ReaxFF molecular dynamics, represents a realistic scenario, where a typical experimental setup can be reproduced confidently given the explicit molecules of the solute, catalyst, and reagent. The nudged elastic band (NEB) approach allowed us to characterize the key intermolecular interactions involved in the reaction paths leading to crucial intermediates and products. The high level of detail obtained clearly revealed for the first time the unique role of sulfuric acid as a proton donor and acceptor in lignin beta-O-4 acidolysis as well as the reaction pathways for ethylene glycol stabilization, and the difference in reactivity between compounds with different methoxy substituents.

Original languageEnglish
Pages (from-to)2388-2399
Number of pages12
JournalACS Sustainable Chemistry & Engineering
Volume9
Issue number5
DOIs
Publication statusPublished - 8-Feb-2021

Keywords

  • Lignin
  • acidolysis
  • model compounds
  • ReaxFF Molecular Dynamics
  • reaction mechanism
  • NEB profiles

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