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Polymers 2018, 10(7), 729; https://doi.org/10.3390/polym10070729

Thermal Decomposition of Kraft Lignin under Gas Atmospheres of Argon, Hydrogen, and Carbon Dioxide

1,†
,
2,†
,
1,* and 2,*
1
Department of Sustainable Bioproducts, Mississippi State University, Mississippi State, MS 39762, USA
2
U.S. Department of Agriculture, Forest Service, Forest Products Laboratory, Madison, WI 53726, USA
These authors contributed equally to this work.
*
Authors to whom correspondence should be addressed.
Received: 6 June 2018 / Revised: 27 June 2018 / Accepted: 28 June 2018 / Published: 3 July 2018
(This article belongs to the Special Issue Lignin Polymers: Structures, Reactions and Applications)
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Abstract

The behaviors of thermal decomposition of kraft lignin under three different gases (Ar, CO2, or H2) were analyzed and compared using a temperature-programmed decomposition-mass spectrometry (TPD-MS) system. Experimental results indicated that Ar atmosphere produced the highest yield of solid chars, while H2 atmosphere generated the highest yield of liquids and CO2 atmosphere had the highest yield of gases. TPD-MS results showed that H2 atmosphere was consumed at the temperature range from 205 to 810 °C and CO2 atmosphere was consumed at the temperature range from 185 to 1000 °C. The H2 promoted the cleavage of lignin side chains and significantly enhanced the formation of CH4, C6H6, HCHO, C6H5OH, CH3OH, and tars. The percentages of water in produced liquids were 90.1%, 85.3%, and 95.5% for Ar, H2, and CO2 as atmosphere, respectively. The H2 yielded more organic chemicals in produced liquids compared to the other two gases. The observed organic chemicals were mainly acetic acid, phenols, ketones, alcohols, aldehydes, and esters. BET surface areas of solid products were 11.3, 98.5, and 183.9 m2/g for Ar., H2, and CO2 as the atmosphere, respectively. C–H–O–N–S elemental and morphology analyses on solid products indicated that the lowest carbon content and the highest oxygen content were obtained if Ar atmosphere was used, while H2 and CO2 yielded more carbon in final solid products. Solid products obtained under CO2 or H2 atmosphere contained sphere-shaped nanoparticles. View Full-Text
Keywords: kraft lignin; thermal decomposition; H2 atmosphere; CO2 atmosphere kraft lignin; thermal decomposition; H2 atmosphere; CO2 atmosphere
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
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Yan, Q.; Li, J.; Zhang, J.; Cai, Z. Thermal Decomposition of Kraft Lignin under Gas Atmospheres of Argon, Hydrogen, and Carbon Dioxide. Polymers 2018, 10, 729.

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