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An “ideal lignin” facilitates full biomass utilization

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Science Advances  28 Sep 2018:
Vol. 4, no. 9, eaau2968
DOI: 10.1126/sciadv.aau2968
  • Scheme 1 Mechanisms for lignin condensation, C-lignin structure, and monomer M3 formation.

    (A) Mechanism of lignin acidolysis and condensation routes. (B) The benzodioxane structure acts as a “shield” that can protect C-lignin from unwanted acidolysis and condensation reactions. (C) Proposed mechanism for the cyclization reaction of M1 to M3.

  • Fig. 1 NMR spectra.

    Partial 2D HSQC NMR spectra of (A) EL, (B) KL, and (C) LBL from vanilla (V. planifolia) seed coat. There are no obvious lignin structural changes after the acidic lignin extraction processes. Cellulose was labeled following the conventional monosaccharide nomenclature; NR is the nonreducing end of the cellulose. Protein residuals were labeled by the aromatic amino acid. Tyr, l-tyrosine; Phe, l-phenylalanine; ppm, parts per million.

  • Fig. 2 Molecular weight profiles.

    Molecular weight profiles of EL (cyan) and LBL (magenta) from V. planifolia seed coat measured by gel-permeation chromatography (GPC). The x axis indicates the apparent molecular weight of individual lignin polymers and is shown as a log scale. The y axis shows the response of a UV-light detector (at 280 nm) normalized to the most abundant signal in each chromatogram. The most abundant signal in the each of the two samples corresponds to a molecular weight of ~13,000 Da (determined via polystyrene standards); comparison shows that there was no obvious lignin polymer degradation during the acid pretreatment. PDI is the polydispersity index. a.u., arbitrary units. MW, molecular weight.

  • Fig. 3 GC-FID spectra of hydrogenolysis products from dimeric compound D1 and from CW.

    Hydrogenolysis condition: Pt/C, 200°C, 40-bar H2, 15 hours. Coloring of peaks matches that of the structures for monomers M1 to M8. Products from polysaccharide in the CW are colored light green, and unidentified products from other non-lignin compounds are left in black. TMS, trimethylsilyl. Note that the upper D1 product chromatogram is offset by ~0.3 min.

  • Fig. 4 Hydrogenolysis monomer yields from different catalyst and solvent combinations.

    Yields are on a C-lignin molar basis (see also table S3, from left to right: entries 1, 2, 3, 5, 7, 9, 10, 12, 14, 19, and 21).

  • Table 1 Mass balance and TOC on hydrogenolysis of C-LBL and its resulting product oil.
    FeedCWDissolved C-LBL
    Solid recovery*55–74%~100%
    Oil recovery23–35%50–60%
    TOC of C-LBL62.66 ± 0.23%
    TOC of product oil61.44 ± 0.34%

    *Solid includes recovered CW material and catalyst.

    †Oil yield on a CW and C-LBL mass basis.

    Supplementary Materials

    • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/4/9/eaau2968/DC1

      Synthetic model compounds and compound authentication.

      Calibration curves and NMR spectra.

      Fig. S1. 2D HSQC NMR.

      Fig. S2. Quantitative 13C NMR spectrum of C-LBL.

      Fig. S3. NBO and thioacidolysis products.

      Fig. S4. 2D HSQC NMR and molecular weight distributions.

      Fig. S5. GC-MS total-ion chromatograms of hydrogenolysis monomer products.

      Fig. S6. Yield and selectivity data.

      Fig. S7. GPC fractionation of hydrogenolysis products from LBL.

      Table S1. Compositional analysis of vanilla seed coat CWs.

      Table S2. Quantitative 13C NMR analysis of C-lignin content in the C-LBL and CW.

      Table S3. Monomer yields from hydrogenolysis.

    • Supplementary Materials

      This PDF file includes:

      • Synthetic model compounds and compound authentication.
      • Calibration curves and NMR spectra.
      • Fig. S1. 2D HSQC NMR.
      • Fig. S2. Quantitative 13C NMR spectrum of C-LBL.
      • Fig. S3. NBO and thioacidolysis products.
      • Fig. S4. 2D HSQC NMR and molecular weight distributions.
      • Fig. S5. GC-MS total-ion chromatograms of hydrogenolysis monomer products.
      • Fig. S6. Yield and selectivity data.
      • Fig. S7. GPC fractionation of hydrogenolysis products from LBL.
      • Table S1. Compositional analysis of vanilla seed coat CWs.
      • Table S2. Quantitative 13C NMR analysis of C-lignin content in the C-LBL and CW.
      • Table S3. Monomer yields from hydrogenolysis.

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