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Identification of phenyldibenzothiophenes in coals and the effects of thermal maturity on their distributions based on geochemical data and theoretical calculations
Organic Geochemistry ( IF 3 ) Pub Date : 2019-12-01 , DOI: 10.1016/j.orggeochem.2019.103910
Zhili Zhu , Meijun Li , Youjun Tang , Ling Qi , Junying Leng , Xiaoqiang Liu , Hong Xiao

Abstract All four phenyldibenzothiophene (PhDBT) isomers were unequivocally identified in coals for the first time by the co-injection of authentic standards and comparison of the retention indices with those reported in previous studies. Based on density functional theory (DFT) calculations, the relative thermodynamic stability order of the phenyldibenzothiophene isomers (PhDBTs) was determined to be 3-PhDBT > 2-PhDBT > 4-PhDBT > 1-PhDBT. All PhDBT isomers were observed in a suite of coals from the Junggar and Ordos basins, and the effects of thermal maturity on their distributions were systematically investigated. Based on geochemical data and theoretical calculations, two phenyldibenzothiophene maturity indicators, i.e., PhDR1 (2-PhDBT/4-PhDBT) and PhDR2 ((2-PhDBT + 3-PhDBT)/4-PhDBT), are proposed. For high maturity coals (≥0.96 %Ro), PhDR1 and PhDR2 increase gradually with increasing thermal maturity. Two preliminary calibrations of these parameters against measured %Ro were made: %Rc = 0.60 × PhDR1 + 1.00 (≥1.00 %Ro) and %Rc = 0.30 × PhDR2 + 1.00 (≥1.00 %Ro). Compared to their corresponding methylated counterparts, phenyldibenzothiophenes are particularly useful as molecular markers of maturity at higher levels of thermal stress and provide a molecular assessment for sedimentary rocks containing types II and III kerogens where few biomarker parameters are available. PhDBTs in coals are likely to be generated during diagenesis/catagenesis as intermediate products in the formation of more condensed heterocyclic polycyclic aromatic compounds, such as triphenyleno[1,12-bcd]thiophene and benzobisbenzothiophenes, which were detected in the highly mature samples. This study broadens the current understanding of the occurrence, distribution, geochemical significance, and origin of phenyldibenzothiophenes in sedimentary organic matter.

中文翻译:

基于地球化学数据和理论计算的煤中苯基二苯并噻吩的鉴定及热成熟度对其分布的影响

摘要 通过共注入可靠标准品并将保留指数与先前研究报告的保留指数进行比较,首次在煤中明确鉴定了所有四种苯基二苯并噻吩 (PhDBT) 异构体。基于密度泛函理论 (DFT) 计算,确定苯基二苯并噻吩异构体 (PhDBT) 的相对热力学稳定性顺序为 3-PhDBT > 2-PhDBT > 4-PhDBT > 1-PhDBT。在准噶尔和鄂尔多斯盆地的一组煤中观察到了所有的PhDBT异构体,并系统地研究了热成熟度对其分布的影响。根据地球化学数据和理论计算,提出了两种苯基二苯并噻吩成熟度指标,即PhDDR1(2-PhDBT/4-PhDBT)和PhDDR2((2-PhDBT+3-PhDBT)/4-PhDBT)。对于高成熟度煤 (≥0.96 %Ro),随着热成熟度的增加,PhDDR1 和PhDDR2 逐渐增加。针对测量的 %Ro 对这些参数进行了两次初步校准:%Rc = 0.60 × PhDR1 + 1.00 (≥1.00 %Ro) 和 %Rc = 0.30 × PhDR2 + 1.00 (≥1.00 %Ro)。与其相应的甲基化对应物相比,苯基二苯并噻吩作为在较高热应力水平下成熟度的分子标志物特别有用,并为含有 II 型和 III 型干酪根的沉积岩提供分子评估,其中几乎没有可用的生物标志物参数。煤中的PhDBTs很可能在成岩/催化作用过程中产生,作为形成更多稠合杂环多环芳族化合物的中间产物,如三苯并[1,12-bcd]噻吩和苯并双苯并噻吩,这些化合物在高度成熟的样品中被检测到。
更新日期:2019-12-01
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