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Effect of Pressure on the Thermal Cracking and Polymerization of Pentacosane (n-C25), an n-Alkane
| Title: | Effect of Pressure on the Thermal Cracking and Polymerization of Pentacosane (n-C25), an n-Alkane |
| Authors: | Shinozaki, Ayako Browse this author |
| Keywords: | hydrocarbon | | amorphous carbon | | high pressure | | pyrolysis | | subduction zone | | carbon cycle |
| Issue Date: | 19-Jan-2023 |
| Publisher: | American Chemical Society |
| Journal Title: | ACS Earth and Space Chemistry |
| Volume: | 7 |
| Issue: | 1 |
| Start Page: | 69 |
| End Page: | 76 |
| Publisher DOI: | 10.1021/acsearthspacechem.2c00235 |
| Abstract: | Hydrocarbons are important carbon components in the subducting slab and play a crucial role in the Earth's deep carbon cycle. In this study, the thermal reaction of pentacosane (n- C25), a long n-alkane, was experimentally investigated under high-pressure and high-temperature conditions at 0.5-1.5 GPa and 360-400 degrees C. The gas chromatography-mass spectrometry (GC/ MS) analyses of the reaction products revealed that the radical reaction of n-C25 proceeded above 360 degrees C at 0.5 GPa and above 380 degrees C at 1.5 GPa, while the rate constant decreased with increasing pressure. Lighter n-alkanes and heavier straight/branched alkanes were detected in the reaction products. The formation of lighter n-alkanes indicates thermal cracking progression, even at high-pressure conditions. During thermal cracking, lighter 1-alkenes were likely to form but were instead rapidly added to the initial n-C25 to form heavier alkanes when enhanced by pressure. Thus, lighter 1-alkenes were not detected in the reaction products. As the secondary reaction, the heavier alkanes were polymerized with dehydrogenation to form amorphous carbon when the remaining percentage of the initial material became <10% and <20% at 0.5 and 1.5 GPa, respectively, while the lighter n-alkanes were detected simultaneously. Both lighter alkanes with high H/C ratios and amorphous carbon with a low H/C ratio eventually formed through the reaction of n-alkanes at high-pressure and high-temperature conditions of the deep Earth. |
| Rights: | This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Earth and Space Chemistry, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://pubs.acs.org/articlesonrequest/AOR-NZ5HVH76WQGX62UJAVKJ. |
| Type: | article (author version) |
| URI: | http://hdl.handle.net/2115/91067 |
| Appears in Collections: | 理学院・理学研究院 (Graduate School of Science / Faculty of Science) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)
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Submitter: 篠崎 彩子
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