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Title:
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New insights into the structure and composition of technical lignins: a comparative characterisation study
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Author(s):
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Constant, S.; Wienk, H.L.J.; Frissen, G.A.E.; Peinder, P. de; Boelens, R.; Es, D.S. van; Grisel, R.J.H.; Weckhuysen, B.M.; Huijgen, W.J.J.; Gosselink, R.J.A.; Bruijnincx, P.C.A.
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Published by:
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Publication date:
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ECN
Biomass & Energy Efficiency
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10-5-2016
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ECN report number:
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Document type:
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ECN-W--15-025
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Article (scientific)
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Number of pages:
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18
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Published in: Green Chemistry (The Royal Society of Chemistry), , 2016, Vol.Volume 18 - Number 9, p.2563-2910.
Abstract:
Detailed insight into the structure and composition of industrial (technical) lignins is needed to devise e?cient thermal, bio- or chemocatalytic valorisation strategies. Six such technical lignins covering three main industrial pulping methods (Indulin AT Kraft, Protobind 1000 soda lignin and Alcell, poplar, spruce and wheat straw organosolv lignins) were comprehensively characterised by lignin composition analysis, FT-IR, pyrolysis-GC-MS, quantitative 31 P and 2D HSQC NMR analysis and molar mass distribution by Size Exclusion Chromatography (SEC). A comparison of nine SEC methods, including the ?rst analysis of lignins with commercial alkaline SEC columns, showed molar masses to vary considerably, allowing some recommendations to be made. The lignin molar mass decreased in the order: Indulin Kraft > soda P1000 > Alcell > OS-W ~ OS-P ~ OS-S, regardless of the SEC method chosen. Structural identi?cation and quanti?cation of aromatic units and inter-unit linkages indicated that all technical lignins, including the organosolv ones, have considerably been degraded and condensed by the pulping process. Importantly, low amounts of ß- ether linkages were found compared to literature values for protolignin and lignins obtained by other, milder isolation processes. Stilbenes and ether furfural units could also be identi?ed in some of the lignins. Taken together, the insights gained in the structure of the technical lignins, in particular, the low ß-O-4 contents, carry implications for the design of lignin valorisation strategies including (catalytic) depolymerisation and material applications.
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