Quantification and classification of carbonyls in industrial humins and lignins by 19F NMR

Sandra Constant, Christopher S. Lancefield, Bert M. Weckhuysen, Pieter C.A. Bruijnincx*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

34 Citations (Scopus)

Abstract

Lignin and humins are both (by-)products of biorefining processes aimed at the valorization of lignocellulosic biomass. In order to improve the efficiency of such biorefineries and to develop new valorization pathways for these polymeric materials, detailed insight into their complex chemical structure and functional group distribution is required. Here, we report on the quantification and classification of the ketone and aldehyde carbonyl functional groups contained in these two polymers by 19F NMR. The known method of carbonyl derivatization with 4-(trifluoromethyl)phenylhydrazine to the corresponding hydrazone has been improved and simplified, allowing derivatization directly in an NMR tube, requiring no additional workup before quantification by 19F NMR. Furthermore, the scope of the method was assessed and expanded, with model compound studies, which included monomeric and dimeric compounds as well as synthetic polymers, showing that the carbonyl functions can indeed be reproducibly quantified. Using this model compound library, the carbonyl functional groups in two technical lignins (Indulin Kraft and Alcell) and, for the first time, an industrial humin could be quantified and classified. The industrial humin was found to contain 6.6 wt % of carbonyl functions, with aliphatic and conjugated carbonyls being detected. The relatively high abundance of such functional groups, which are amenable to further chemical modification, provides opportunities for the use of these humin byproducts in various applications, e.g., as materials after derivatization.

Original languageEnglish
Pages (from-to)965-972
Number of pages8
JournalACS Sustainable Chemistry and Engineering
Volume5
Issue number1
Early online date1 Dec 2016
DOIs
Publication statusPublished - 3 Jan 2017

Keywords

  • Biomass
  • Carbonyl quantification
  • Functional group analysis
  • Humin
  • Lignin

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