Issue 1, 2016

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

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

Supplementary files

Article information

Article type
Paper
Submitted
22 Sep 2015
Accepted
15 Oct 2015
First published
15 Oct 2015

Green Chem., 2016,18, 271-281

Author version available

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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