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a relaxation delay time of 1.5 s, 24 scans, and 1024 data points.
The spectra were processed using squared cosine bell in both di-
mensions. Volume integration of cross-peaks in the HSQC spectra
was carried out using MestReNova software. Semi-quantification of
the ratios of lignin linkages and aromatic units was calculated fol-
lowing the reported method,[19] in which the integrals of S2,6 signals
from syringyl units and G2 signals from guaiacyl units were used as
Catalytic depolymerization of real lignin: Typically, raw Beech
sawdust (100 mesh, 1.0 g), solvent (20 mL), and Ni/C catalyst were
placed in a 50 mL autoclave. The reactor was sealed, purged with
H2 to expel air and filled with 20 bar H2 at room temperature. The
reaction was conducted at the desired temperature at a stirring
speed of 1000 rpm. After reaction, the autoclave was cooled in an
ice-water bath. To analyze the phenolic monomers, a weighed
amount of external standard (n-decane) was added into the mix-
ture and a sample was filtrated and collected for gas chromato-
graph (GC)–flame ionization detector (FID) and GC–MS analysis.
Phenolic monomers were identified by matching of their retention
times to authentic standard samples and through the use of exact
mass from GC–MS spectra in the context of expected products.
The monomer yield was calculated using the following equation:
the internal reference (100 C9 units): C9 units (100)=0.5(S2,6 +S‘2,6
Scondensed)+G2.
+
All calculations presented were accomplished using the DFT
method with hybrid meta-GGA M062X[13] functional and 6-
31g(2d,2p) basis set by Gaussian 09 program.[21] These structures
were optimized without constraints. At the optimized structures,
vibrational frequencies were analyzed to confirm that the struc-
tures were at the minima corresponding to the local minima (with-
out imaginary frequency). The zero-point energies and the thermal-
ly corrected enthalpies at 298 K were obtained during the frequen-
cy analysis. The BDE was calculated as the difference of the sum of
the zero-point corrected enthalpies of the parent molecule and the
thermally corrected enthalpies of the unimolecular dissociation
products.[15]
ꢀ
ꢁ
mass of x monomer
mass of Klason lignin in sawdust
Yieldx ðwt %Þ ¼
ꢂ 100 %
Acknowledgements
This work was financially supported by the National Natural Sci-
ence Foundation of China (91545102, 21473188, 21233008).
Catalyst preparation: Metal-based catalysts were prepared using
an incipient-wetness impregnation method and activated by re-
ducing in hydrogen. Typically, supports were added into the aque-
ous metal salt solution. After ultrasonic dispersion, the slurry was
kept at room temperature for 24 h and then dried at 1108C over-
night. Prior to each reaction, the catalysts were activated in a flow
of H2 at 4508C for Ni-based catalyst, 3508C for Ru-based catalyst,
and 2508C for Pd-based catalyst, respectively. In particular, activat-
ed charcoal support was treated in the nitric acid solution
(38 wt%) at 808C for 3 h before use.
Keywords: carbon–oxygen bond cleavage · etherification ·
heterogeneous catalysis · hydrogen bond · lignin
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Catalytic depolymerization of b-O-4 model compounds: In a typi-
cal catalytic hydrogenolysis experiment of b-O-4 model com-
pounds, 0.1 g of substrate, 10 mL of solvent, and 0.025 g of cata-
lyst were loaded into a 50 mL autoclave (T316 Stainless Steel,
ASME SA-479, Parr Instrument). The autoclave was sealed, purged
with H2 to expel air (repeated 5 times), and pressurized with 20 bar
H2 at room temperature. Then the mixture was heated to the de-
sired temperature within 20 min under stirring at a speed of
1000 rpm. After reaction, the autoclave was cooled in an ice-water
bath and depressurized at room temperature. The mixture was fil-
trated to remove the catalyst and filtrate was collected for analysis.
Liquid products were identified by GC–MS and HPLC-MS/MS, and
the quantification was performed on a Waters e2695 HPLC system
equipped with 2489 UV/Vis detector at 272 nm. The products were
[2] a) A. J. Ragauskas, G. T. Beckham, M. J. Biddy, R. Chandra, F. Chen, M. F.
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separated using
a C18 column (Agilent ZORBAX extend-C18
column, 4.6 mmꢂ150 mm, 5 mm) and acetonitrile/water as the
mobile phase. A non-linear gradient elution with a flow rate of
1.0 mLminꢀ1 was used as follows: 25!22% CH3CN over 10 min,
22% CH3CN for 5 min, 22!60% CH3CN over 5 min, 60% CH3CN
for 2 min, 60!100% CH3CN over 1 min, 100% CH3CN for 5 min,
return to initial conditions over 2 min and re-equilibrate for 5 min.
The column was maintained at 308C. Products were quantified by
using a standard calibration curve in HPLC/UV. Conversion and
yield were calculated using the following equations:
[8] a) N. Yan, C. Zhao, P. J. Dyson, C. Wang, L. T. Liu, Y. Kou, ChemSusChem
2008, 1, 626–629; b) T. Parsell, S. Yohe, J. Degenstein, T. Jarrell, I. Klein,
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Meilan, N. Mosier, F. Ribeiro, W. N. Delgass, C. Chapple, H. I. Kenttꢄmaa,
Van den Bosch, W. Schutyser, R. Vanholme, T. Driessen, S. F. Koelewijn, T.
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ꢀ
ꢁ
moles of substrate
moles of substrate loaded
Conversion ¼ 1ꢀ
ꢂ 100 %
ꢀ
ꢁ
moles of product ꢂ number of C6 rings
moles of substrate loaded ꢂ 2
Yield ¼
ꢂ 100 %
ChemSusChem 2016, 9, 1 – 9
7
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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