Thermal decomposition mechanism of Chang 7 sulfur-rich lacustrine kerogen: insights from combined thermogravimetric and pyrolysis mass spectrometric analysis

Studying the pyrolysis behavior of oil shale provides important guidance for its in-situ or external conversion. The pyrolysis characteristics of Chang 7 sulfur-rich lacustrine shale kerogen were investigated using coupled thermogravimetric analysis, Fourier-transform infrared spectroscopy and mass spectrometry (TG-FTIR-MS) and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) analyses. The TG results revealed four distinct stages: desorption, kerogen conversion, bitumen cracking, and aromatization, with major weight loss occurring between 400 and 600 °C. FTIR and MS analyses indicated that SO2 is generated within 200–700 °C, primarily originating from the decomposition of organic sulfur, while the formation of H2S dominates above 500 °C under a hydrogen radical environment accompanied by substantial hydrocarbon production. Py-GC/MS results showed a temperature-dependent evolution of products from long-chain alkanes to olefins and aromatics, with fatty acids indicating algal-derived kerogen. By integrating real-time gas evolution with temperature-resolved product composition, a multistage pyrolysis mechanism was proposed, demonstrating the coupled evolution of organic matter and sulfur species. This study provides mechanistic insight into the thermal decomposition pathways and differentiated sulfur gas release behavior of sulfur-rich kerogen, which is relevant for understanding sulfur behavior during oil shale thermal conversion.

Pyrolysis of sulfur-rich lacustrine kerogen by TG-IR-MS and Py-GC/MS was studied.
SO2 and H2S from organic sulfur and pyrite were identified at different temperatures.
Product shift from alkanes to olefins and aromatics with heating was observed.
Pyrolysis mechanism in distinct stages was summarized.

Pyrolysis of sulfur-rich lacustrine kerogen by TG-IR-MS and Py-GC/MS was studied.
SO2 and H2S from organic sulfur and pyrite were identified at different temperatures.
Product shift from alkanes to olefins and aromatics with heating was observed.
Pyrolysis mechanism in distinct stages was summarized.

研究油页岩的热解行为，可为其原位或异位转化提供重要指导。本研究采用热重-傅里叶变换红外-质谱（TG-FTIR-MS）联用技术与裂解气相色谱-质谱（Py-GC/MS）分析，探究了长7段富硫湖相页岩干酪根的热解特性。热重（TG）结果显示其热解过程分为四个显著阶段：解吸阶段、干酪根转化阶段、沥青裂解阶段与芳构化阶段，主要质量损失发生于400~600℃区间。傅里叶变换红外（FTIR）与质谱（MS）分析表明，二氧化硫（SO₂）在200~700℃范围内生成，主要源于有机硫的分解；而硫化氢（H₂S）的生成在500℃以上占据主导，此时处于氢自由基环境中，伴随大量烃类产生。Py-GC/MS结果显示，产物随温度变化呈现从长链烷烃向烯烃、芳烃演化的规律，且脂肪酸组分表明该干酪根为藻类来源。通过整合实时气体析出与温度分辨的产物组成数据，本研究提出了多段热解机理，阐明了有机质与硫物种的协同演化过程。本研究为富硫干酪根的热分解路径与差异化硫气体释放行为提供了机理性认识，可为理解油页岩热转化过程中的硫行为提供参考。
采用TG-FTIR-MS与Py-GC/MS技术对富硫湖相干酪根开展热解研究。
在不同温度下分别检测到有机硫与黄铁矿来源的SO₂和H₂S。
观察到产物随升温过程从烷烃向烯烃、芳烃转变的现象。
总结得到分阶段热解机理。
采用TG-FTIR-MS与Py-GC/MS技术对富硫湖相干酪根开展热解研究。
在不同温度下分别检测到有机硫与黄铁矿来源的SO₂和H₂S。
观察到产物随升温过程从烷烃向烯烃、芳烃转变的现象。
总结得到分阶段热解机理。