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Lignin Depolymerisation and Lignocellulose Fractionation by Solvated Electrons in Liquid Ammonia
Pepijn Prinsen1, Anand Narani1, Gadi Rothenberg1
1Van 't Hoff Institute for Molecular Sciences, University of Amsterdam, PO Box 94157, 1090GD, Amsterdam, The Netherlands.
Chemsuschem
|February 1, 2017
Summary
Researchers investigated lignin depolymerization using liquid ammonia. Adding sodium enabled reductive depolymerization at room temperature, yielding significant bio-oil from native elephant grass lignin.
Area of Science:
- Chemical Engineering
- Biomass Conversion
- Polymer Chemistry
Background:
- Lignin depolymerization is crucial for valorizing biomass.
- Existing methods often require harsh conditions or external hydrogen donors.
- Liquid ammonia presents a unique solvent for lignin processing.
Purpose of the Study:
- To explore lignin depolymerization in liquid ammonia under varying conditions.
- To investigate reductive depolymerization using solvated electrons generated by sodium.
- To assess the efficiency of this method for different lignin types and wood fractionation.
Main Methods:
- Depolymerization of five different lignins (kraft, soda, organosolv, milled wood) in liquid ammonia at 120°C and 88 bar.
- Reductive depolymerization at room temperature using sodium metal in liquid ammonia.
- Application of the room temperature method to poplar wood fiber for delignification.
Main Results:
- Lignin treatment in pure liquid ammonia led to nitrogen incorporation, increasing molecular weight.
- Reductive depolymerization yielded 10-23% bio-oil for technical lignins and 40% for native elephant grass lignin.
- Improved delignification of poplar wood fiber was observed with sodium addition at room temperature.
Conclusions:
- Liquid ammonia can facilitate lignin depolymerization, with nitrogen incorporation occurring under high temperature/pressure.
- Reductive depolymerization using sodium in liquid ammonia is an effective method for bio-oil production, especially from native lignin.
- The room temperature method shows promise for efficient wood fractionation and lignin valorization.
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