title: Lignin Depolymerisation and Lignocellulose Fractionation by Solvated Electrons in Liquid Ammonia.
abstract: We explored the depolymerisation of several lignins in liquid ammonia at relatively high temperatures and pressures (120 °C and 88 bar). Five different lignins were tested: Indulin AT kraft, Protobind 1000 soda, wheat straw organosolv, poplar organosolv and elephant grass-milled wood lignin (EG MWL). In pure liquid ammonia, all lignins underwent slow incorporation of nitrogen into their structure, resulting in higher molecular weight and polydispersity index. Subsequently, we show a reductive depolymerisation by solvated electrons at room temperature by adding sodium metal to the liquid ammonia without any external hydrogen donor. The netto yields of bio-oil are low for technical lignins (10-23 %), but with higher yields of alkylphenols. In the case of native EG MWL, netto yields of 40 % bio-oil were achieved. Finally, when the room temperature method was applied to poplar wood fibre, we observe improved delignification upon the addition of sodium compared to poplar wood fractionation in pure liquid ammonia.
authors.affiliation: Van 't Hoff Institute for Molecular Sciences, University of Amsterdam, PO Box 94157, 1090GD, Amsterdam, The Netherlands.
authors.forename: Pepijn
authors.initials: P
authors.lastname: Prinsen
authors.affiliation: Van 't Hoff Institute for Molecular Sciences, University of Amsterdam, PO Box 94157, 1090GD, Amsterdam, The Netherlands.
authors.forename: Anand
authors.initials: A
authors.lastname: Narani
authors.affiliation: Van 't Hoff Institute for Molecular Sciences, University of Amsterdam, PO Box 94157, 1090GD, Amsterdam, The Netherlands.
authors.forename: Gadi
authors.identifier: 0000-0003-1286-4474
authors.initials: G
authors.lastname: Rothenberg
mesh_terms: D000641:Ammonia / Q000737:chemistry*; D004583:Electrons; D008031:Lignin / Q000737:chemistry*; D058105:Polymerization; D012997:Solvents / Q000737:chemistry*; D013696:Temperature
chemical_list: D012997:Solvents; C036909:lignocellulose; D000641:Ammonia; D008031:Lignin
keywords: bio-oils; biomass; depolymerization; lignin; liquid ammonia