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Green Chemistry
Page 6 of 8
DOI: 10.1039/C5GC01325A
ARTICLE
Journal Name
hours, then cooled to room temperature. Upon cooling, the (Table 1, entries 1-4) and lignin model compounds (Table 2, entry 1)
reaction mixture was filtered to remove Pd/C, and rinsed with with Pd/C and ZnII which cleaves both the benzylic OH at Cα, and
additional methanol. In reactions containing intact biomass, a solid the primary OH at Cγ yielding mainly propylguaicol, as well as
carbohydrate residue was removed by filtration with extensive propylsyringol in the case of lignocellulosic biomass. It has been
characterisation of the carbohydrate residue appearing in previous demonstrated herein that the key difference in reactivity lies in the
work.4 The filtrate was collected and diluted in a volumetric flask for ability of ZnII to activate and facilitate removal of the OH group at
analysis by GC-FID and/or HPLC/MS.
the Cγ position of the β-O-4 ether linkage.
Biomass Preparation
Acknowledgements
Biomass was milled to pass through a 40 mesh screen using a Mini
Wiley Mill (Thomas Scientific, Swedesboro, NJ). Biomass was
washed with water, followed by ethanol using a soxholet apparatus
using the NREL LAP Determination of Extractives in Biomass
procedure.24 Following soxholet extraction, biomass samples were
dried at 45 oC and water content evaluated with a moisture
analyzer (Halogen model HB43-S, Mettler-Toledo LLC, Columbus,
OH).
This work was supported by the Center for direct Catalytic
Conversion of Biomass to Biofuels (C3Bio), an Energy Frontier
Research Center (EFRC) funded by the U.S. Department of
Energy, Office of Science, Office of Basic Energy Sciences under
award no. DE-SC000097.
Notes and References
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GC-FID Analysis
2
3
Gas chromatography was performed using an Agilent
Technologies 6890N Network GC System equipped with a FID
detector, auto-sampler, and DB-5 capillary column of
dimension 0.25 mm ID × 0.25 µm × 30 m. injection volume
1.0 µL, inlet temperature 275 °C, detector temperature 275
°C and a split ratio 1:10. Initial column temperature was 50
°C (1 min) with a temperature rise at 10 °C/min up to 250 °C
and then at 25 °C/min to the final temperature of 300 °C. GC
peaks for all lignin derived products (PG, PS, PG-OH, PS-OH,
G) were identified by retention time in comparison with
authentic samples. Each peak of GC chromatogram was
properly integrated and the actual concentration of each
product was obtained from the pre-calibrated plot of peak
area against concentrations of authentic samples.
4
5
6
7
8
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NMR Spectroscopy
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NMR spectra were recorded on
a
Bruker DRX-500 NMR
BB coil.
spectrometer equipped with TBI probe using
a
a
BrukerTopSpin software (version 1.3) was used for data acquisition
and MestReNova (version 8) was used in processing spectra. All
spectra obtained were referenced to residual solvent peaks.
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Conclusions
We have shown that the β-O-4 ether linkage can be selectively
cleaved in both lignocellulosic biomass (Table 1, entry 6) and lignin
model compounds (Table 2, entry 2) with Pd/C alone in methanol,
at elevated temperatures, under H2 pressure. In both cases the
primary OH at the Cγ position of the β-O-4 ether linkage remains
intact, yielding PG-OH (as well as PS-OH in the case of lignocellulosic
biomass). This contrasts the reaction of lignocellulosic biomass
20 T. Parsell, B. C. Owen, I. Klein, T. M. Jarell, C. L. Marcum, L. J.
Haupert, L. M. Amundson, H. I. Kenttämaa, F. Ribeiro, J. T.
Miller and M. M. Abu-Omar, Chem. Sci.,2013, 4, 806-813.
6 | J. Name., 2012, 00, 1-3
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