Towards understanding kraft lignin depolymerisation under hydrothermal conditions
Journal article, 2021

Kraft lignin depolymerisation using hydrothermal liquefaction suffers from the formation of char, resulting in a decreased product yield as well as causing operational problems. While this may be mitigated by the addition of capping agents such as phenol and isopropanol, other reaction parameters, for example reaction time and temperature, are also important for the product yields. In this work, the effect of short reaction times on the hydrothermal liquefaction of kraft lignin in an alkaline water and isopropanol mixture was investigated at 1-12 min and 290 °C. The results show that there were swift initial reactions: the major ether bonds in the lignin were broken within the first minute of reaction, and the molecular weight of all product fractions was halved at the very least. Longer reaction times, however, do not cause as pronounced structural changes as the initial reaction, indicating that a recalcitrant carbon-carbon skeleton remained in the products. Nevertheless, the yields of both char and monomers increased slowly with increasing reaction time. The swift initial depolymerising reactions were therefore followed by slower repolymerisation as well as a slow formation of monomers and dimers, which calls for careful tuning of the reaction time.

isopropanol

hydrothermal liquefaction

HTL

kraft lignin

Author

Anders Ahlbom

Chalmers, Chemistry and Chemical Engineering, Chemical Technology

Marco Maschietti

Chalmers, Chemistry and Chemical Engineering, Chemical Technology

Aalborg University

Rudi Nielsen

Aalborg University

Merima Hasani

Chalmers, Chemistry and Chemical Engineering, Chemical Technology

Hans Theliander

Chalmers, Chemistry and Chemical Engineering, Chemical Technology

Holzforschung

0018-3830 (ISSN) 1437-434X (eISSN)

Vol. 76 1 37-48

Subject Categories

Polymer Technologies

Other Chemical Engineering

Organic Chemistry

DOI

10.1515/hf-2021-0121

More information

Latest update

4/5/2022 5