{"title":"On-line hydropyrolysis gas chromatography-mass spectrometry (HyPy-GC–MS) for kerogen-bound biomarkers","authors":"Fu Wang , Yuhong Liao , Chang Samuel Hsu","doi":"10.1016/j.orggeochem.2024.104927","DOIUrl":null,"url":null,"abstract":"<div><div>Flash pyrolysis gas chromatography-mass spectrometry (Py-GC–MS) is seldom used to release bound biomarkers, because its hydrogen-poor pyrolysis conditions usually result in a low yield of bound biomarkers and high concentrations of olefins. In this study, by using a Py-GC–MS system and immature kerogen/coal samples, we investigated the effects of heating rate (flash versus 30 °C/min), carrier/reaction gas (He versus H<sub>2</sub>), hydrogen pressure, and catalyst [(NH<sub>4</sub>)<sub>2</sub>MoO<sub>2</sub>S<sub>2</sub>] on the yields and distributions of bound biomarkers. Also, the bound biomarkers obtained by different pyrolysis conditions were compared with those from catalytic offline hydropyrolysis (HyPy) and free biomarkers from extracted organic matter (EOM). We propose a new technology of hydropyrolysis-gas chromatography-mass spectrometry (HyPy-GC–MS) to be used to release bound biomarkers. HyPy-GC–MS using low-pressure H<sub>2</sub> at slow heating rate can increase the yield of bound biomarkers by 3–9 times, minimize the cracking of the hopanes side chain, better preserve the original sterane and terpane distributions, and have characteristics<!--> <!-->of lower maturity, compared with conventional flash Py-GC–MS without H<sub>2</sub>. Additionally, the steroidal and terpenoid yields by HyPy-GC–MS using low-pressure H<sub>2</sub> at slow heating rate from immature kerogens were 3–6 times that by HyPy. Compared with EOM, biomarker maturity parameter derived from HyPy-GC–MS may not fully represent the actual maturity of samples. Higher hydrogen pressure can significantly facilitate the hydrogenation of unsaturated hydrocarbons into saturated hydrocarbons, but it can also decrease the yields of pyrolysates with higher carbon numbers (i.e., >C<sub>25</sub>), leading to a change in the biomarker ratios related to carbon numbers (e.g., the proportion of C<sub>27</sub>-C<sub>28</sub>-C<sub>29</sub> ααα20R steranes and TT<sub>23</sub>/H<sub>30</sub> ratio).</div></div>","PeriodicalId":400,"journal":{"name":"Organic Geochemistry","volume":"200 ","pages":"Article 104927"},"PeriodicalIF":2.6000,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Organic Geochemistry","FirstCategoryId":"89","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S014663802400192X","RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"GEOCHEMISTRY & GEOPHYSICS","Score":null,"Total":0}
引用次数: 0
Abstract
Flash pyrolysis gas chromatography-mass spectrometry (Py-GC–MS) is seldom used to release bound biomarkers, because its hydrogen-poor pyrolysis conditions usually result in a low yield of bound biomarkers and high concentrations of olefins. In this study, by using a Py-GC–MS system and immature kerogen/coal samples, we investigated the effects of heating rate (flash versus 30 °C/min), carrier/reaction gas (He versus H2), hydrogen pressure, and catalyst [(NH4)2MoO2S2] on the yields and distributions of bound biomarkers. Also, the bound biomarkers obtained by different pyrolysis conditions were compared with those from catalytic offline hydropyrolysis (HyPy) and free biomarkers from extracted organic matter (EOM). We propose a new technology of hydropyrolysis-gas chromatography-mass spectrometry (HyPy-GC–MS) to be used to release bound biomarkers. HyPy-GC–MS using low-pressure H2 at slow heating rate can increase the yield of bound biomarkers by 3–9 times, minimize the cracking of the hopanes side chain, better preserve the original sterane and terpane distributions, and have characteristics of lower maturity, compared with conventional flash Py-GC–MS without H2. Additionally, the steroidal and terpenoid yields by HyPy-GC–MS using low-pressure H2 at slow heating rate from immature kerogens were 3–6 times that by HyPy. Compared with EOM, biomarker maturity parameter derived from HyPy-GC–MS may not fully represent the actual maturity of samples. Higher hydrogen pressure can significantly facilitate the hydrogenation of unsaturated hydrocarbons into saturated hydrocarbons, but it can also decrease the yields of pyrolysates with higher carbon numbers (i.e., >C25), leading to a change in the biomarker ratios related to carbon numbers (e.g., the proportion of C27-C28-C29 ααα20R steranes and TT23/H30 ratio).
期刊介绍:
Organic Geochemistry serves as the only dedicated medium for the publication of peer-reviewed research on all phases of geochemistry in which organic compounds play a major role. The Editors welcome contributions covering a wide spectrum of subjects in the geosciences broadly based on organic chemistry (including molecular and isotopic geochemistry), and involving geology, biogeochemistry, environmental geochemistry, chemical oceanography and hydrology.
The scope of the journal includes research involving petroleum (including natural gas), coal, organic matter in the aqueous environment and recent sediments, organic-rich rocks and soils and the role of organics in the geochemical cycling of the elements.
Sedimentological, paleontological and organic petrographic studies will also be considered for publication, provided that they are geochemically oriented. Papers cover the full range of research activities in organic geochemistry, and include comprehensive review articles, technical communications, discussion/reply correspondence and short technical notes. Peer-reviews organised through three Chief Editors and a staff of Associate Editors, are conducted by well known, respected scientists from academia, government and industry. The journal also publishes reviews of books, announcements of important conferences and meetings and other matters of direct interest to the organic geochemical community.