沥青质包裹饱和烃的分散固相萃取分离与分子组成特征分析

Dispersive Solid-Phase Extraction Separation and Molecular Composition Characterization of Asphaltene-Occluded Saturated Hydrocarbons

  • 摘要: 在烃源岩或原油体系中,沥青质结构包裹的烃组分被认为是追溯有机质原始组成的重要载体,其无损(非化学破坏性)分离与表征对于揭示沉积有机质来源和演化具有重要意义。本文以烃源岩、煤、原油和固体沥青等不同成因类型的沉积有机质为样品,采用分散固相萃取法(DSPE)结合柱层析技术,分离样品中的沥青质包裹饱和烃,并分析其中正构链烃的组成特征及含义。结果表明:DSPE法可有效分离多种地质成因样品中的沥青质包裹饱和烃;烃源岩、原油和固体沥青样品中均检测到标志性的偶碳数正构1-烯烃(C16~C28),而煤样品中未检出;不同成因类型的样品中沥青质包裹正构烷烃的分布特征差异显著,其中陆相沉积有机质中的高碳数正构烷烃相对更丰富,这与其母质来源密切相关;偶碳数正构1-烯烃(C16~C28)普遍被包裹于还原性沉积环境形成的沥青质中,其成因可追溯至成岩作用阶段。本研究证实了DSPE法适用于分离多种成因的地质样品中的沥青质包裹饱和烃,为分析沉积有机质的原始地球化学信息提供了可靠方法,同时揭示了沥青质包裹饱和烃的分子组成特征对沉积有机质来源的潜在指示意义。

     

    Abstract: In source rocks or crude oil systems, asphaltene-occluded hydrocarbons serve as important carriers for tracing the original composition of organic matter. The non-destructive (non-chemically disruptive) separation and characterization of these hydrocarbons are critical for understanding the source and evolution of sedimentary organic matter. This study employed dispersive solid-phase extraction (DSPE) combined with column chromatography to isolate asphaltene-occluded saturated hydrocarbons from various genetic types of sedimentary organic matter, including source rocks, coal, crude oil, and solid bitumen, and analyzed the compositional characteristics and implications of their normal chain hydrocarbons. The results indicate that: The DSPE method effectively separates asphaltene-occluded saturated hydrocarbons from samples of diverse geological origins; Signature even-carbon-numbered n-1-alkenes (C16~C28) were detected in source rocks, crude oil, and solid bitumen samples but not in coal samples; The distribution of n-alkanes in asphaltene-occluded hydrocarbons varies significantly among genetic types, with terrestrial sedimentary organic matter exhibiting relative enrichment of higher-molecular-weight n-alkanes, closely linked to source input; Even-carbon-numbered n-1-alkenes (C16-C28) are commonly occluded in asphaltenes formed in reducing depositional environments, with origins traceable to the diagenetic stage. This study confirms the applicability of DSPE for separating asphaltene-occluded saturated hydrocarbons across diverse geological samples, offering a reliable method for analyzing the original geochemical information of sedimentary organic matter. Furthermore, it highlights the potential of molecular composition characteristics in asphaltene-occluded hydrocarbons as indicators of sedimentary organic matter sources.

     

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