Partner und Internationale Organisationen
(Englisch)
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Dr. Cesar Pulgarin et Dr. Giovanna Rincon, EPFL Dr. Adil Barakat, Granit Recherche Développement SA AT, HR, DK, FI, FR, DE, HU, IT, LV, NL, NO, PT, RO, SI, ES, CH, UK
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Abstract
(Englisch)
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Development on the multiple aspects of an standardised cluster of analytical characteristics of lignin has been carried out. Main analytical features and corresponding methods have been identified: elemental analysis (C, H, O, S, N), Methoxyl, phenolic OH, aliphatic OH, Carboxyl, acid insoluble lignin, acid soluble lignin, sugars, ash, extractives, NMR, FTIR, molecular weight (Mn, Mw), melting temperature, organoleptic properties (odour, taste, colour). During the project, lignin samples from different plant origin and prepared with different preparation methods including derivatisation methods ('modified lignins') were analysed. Plant origin included different hard wood species (Aspen, Poplar, Eucalyptus) as well as soft wood (Norway Spruce and various of non specified origin) and non wood plants (flax, wheat straw, sarkanda). Preparation methods covered technical processes ( Kraft pulping, sulfite pulping, soda pulping, steam explosion followed by extraction) as well as laboratory processes (MWL, enzymatically prepared samples). Carboxylation, methylsulphonation, methylolation, oxidation and polymerisation were among the derivatisations of lignins, used for challenging the methods in the here developed analytical cluster. As expected, the main difficulties were encountered in molecular weight determination and NMR. For the first, a complete experimental verification of the main methods recommended in literature has been carried out (DMF, THF with bromoacetylated lignin, THF with acetylated lignins, ion pairing in THF and in DMF). Calibration could be improved by the use of a standard lignin that has been analysed by MALDI-TOF. A putative standard method, that appears to give the most reliable results among the methods here verified, was developed as a result of this work (based on DMF with different additives as solvent and underivatised lignins). However for making size exclusion useful for routine analysis, new approaches must be further worked out about how to reduce the influence of variations in the functional groups between lignins (decrease of interaction with columns, improved calibration standards). For NMR, improved more appropriate formulations of solvents, with increased solubility for lignins that are difficult to dissolve, must be developed. A Swiss pole of expertise on lignin, updated with the newest findings of European research could be created thanks to this project. Further aspects will be developed in a second step of this project (solubility improvement, fractionations). An international coordination action was also developed in this project which has the objective to improve the standardisation of the methods used for lignin analysis. The data and methods developed in this project will serve as a base for this activity.
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