Issue 1, 2015

Lignin solubilisation and gentle fractionation in liquid ammonia


We present a simple method for solubilising lignin using liquid ammonia. Unlike water, which requires harsh conditions, ammonia can solubilise technical lignins, in particular kraft lignin. A commercial pine wood Kraft lignin (Indulin AT) was solubilized instantaneously at room temperature and 7–11 bars autogeneous pressure, while a commercial mixed wheat straw/Sarkanda grass soda lignin (Protobind™ 1000) was solubilized within 3 h at ambient temperature, and 30 min at. 85 °C. Hydroxide salts were not required. Wheat straw, poplar and spruce organosolv lignins, as well as elephant grass native lignin (MWL) were also solubilized, albeit at lower values. Different sequences of solubilisation and extraction were tested on the Protobind™ 1000 lignin. The remaining lignin residues were characterized by FTIR, size exclusion chromatography (SEC), elemental analysis (ICP), 2D-NMR and 31P NMR. Liquid ammonia is not an innocent solvent, as some nitrogen was incorporated in the residual lignin which then rearranged to higher molecular weight fractions. Nevertheless, the mild solubilisation conditions make liquid ammonia an attractive candidate as a solvent for lignin in future biorefinery processes.

Graphical abstract: Lignin solubilisation and gentle fractionation in liquid ammonia

Supplementary files

Article information

Article type
18 Jun 2014
09 Sep 2014
First published
18 Sep 2014
This article is Open Access
Creative Commons BY license

Green Chem., 2015,17, 325-334

Author version available

Lignin solubilisation and gentle fractionation in liquid ammonia

Z. Strassberger, P. Prinsen, F. V. D. Klis, D. S. V. Es, S. Tanase and G. Rothenberg, Green Chem., 2015, 17, 325 DOI: 10.1039/C4GC01143K

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

Read more about how to correctly acknowledge RSC content.

Social activity