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Issue 1, 2016
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Low temperature hydrogenation of pyrolytic lignin over Ru/TiO2: 2D HSQC and 13C NMR study of reactants and products

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Abstract

Pyrolytic lignin and hydrogenated pyrolytic lignin were characterized by 2D 1H–13C HSQC and quantitative 13C NMR techniques. The pyrolytic lignin was produced from a mixed maple wood feedstock and separated from the bio-oil by water extraction. p-Hydroxyphenyl (H), guaiacyl (G), and syringyl (S) aromatics were the basic units of pyrolytic lignin. The native lignin β-aryl ether, phenylcoumaran and resinol structures were not present in the pyrolytic lignin. The hydrogenation was conducted with a Ru/TiO2 catalyst at temperatures ranging from 25–150 °C with higher temperatures exhibiting higher levels of hydrogenation. Solid coke formed on the catalyst surface (1% coke yield) even for hydrogenation at 25 °C. The carbon yield of pyrolytic lignin to coke increased from 1% to 5% as the hydrogenation temperature increased from 25 to 150 °C. A single-step hydrogenation at 150 °C resulted in a reduction from 65% to 39% aromatic carbons. A three-step hydrogenation scheme at this same temperature resulted in a reduction of aromatic carbons from 65% to 17%. The decrease in the aromatic carbon corresponded with an increase in the aliphatic carbon. Coke formation reduced from a 5% carbon yield of pyrolytic lignin in the first hydrogenation step to a 1% carbon yield in each of the second and third hydrogenation steps. The pyrolytic lignin could be separated into a high and low molecular weight fraction. The coke yield from the high molecular weight fraction was twice as much as that from the low molecular weight fraction.

Graphical abstract: Low temperature hydrogenation of pyrolytic lignin over Ru/TiO2: 2D HSQC and 13C NMR study of reactants and products

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Publication details

The article was received on 22 sep. 2015, accepted on 15 okt. 2015 and first published on 15 okt. 2015


Article type: Paper
DOI: 10.1039/C5GC02286J
Citation: Green Chem., 2016,18, 271-281
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    Low temperature hydrogenation of pyrolytic lignin over Ru/TiO2: 2D HSQC and 13C NMR study of reactants and products

    W. Chen, D. J. McClelland, A. Azarpira, J. Ralph, Z. Luo and G. W. Huber, Green Chem., 2016, 18, 271
    DOI: 10.1039/C5GC02286J

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