干酪根的X射线衍射研究

本文讨论了干酪根X射线衍射（XRD）数据的处理方法,XRD的002峰参数t₀₀₂与化学结构参数芳碳率f_芳的关系及其计算;根据XRD谱图,研究了抚顺、茂名油页岩未成熟干酪根的化学结构。在干酪根的人工热模拟过程中,发现XRD参数t₀₀₂与芳核C轴高度L_c均随干酪根的类型和成熟度不同而变化,据此提出了不同类型干酪根的XRD(f₀₀₂-L_c)演化途经图。该图可以帮助我们判别干酪根的类型与成熟度。

X-RAY DIFFRACTION STUDIES OF KEROGEN

Kerogen structures of oil shales (Type Ⅰ, Ⅱ) sampling from Fushun, Maoming, Huangxian and lignite (Type Ⅲ) from Huanxian, and their artificial-thermal-degradation samples (the final thermal temperature is 375-510℃) have been investigated by using the X-ray diffaction technique (XRD). The XRD experimental curves were adjusted for polarization;normalized to electron units by fitting the adjusted curve to the independent scattering curve of carbon at the angle sin θ/A = 0.50;expressed in "reduced intensity" by substracting the incoherent scattering intensity of carbon and dividing by the independent coherent scattering intensity of carbon. The information extracted from the XRD structural parameters, such as intensity fractions (f), stacking height (L_c), peak position (sin9/A) of 002 and gamma band, indicates that the immature oil shale kerogen is constructed mainly by aliphatics, taking shape of a three dimentional netted and cage structure crosslinked by ring clusters and alkyl chains randomly, with bitumen trapped in the pores. The carbon aromaticity of an immature kerogen assessed by the XRD parameter f₀₀₂ often gives a negative deviation with that measured by n. m. r. spectroscopy, it implies that part of aromatic rings may not be presented in the stacking structure of the aromatic clusters. The deviation is eliminated gradually as the maturity of the kerogen increases due to the progress of graphitization. Two XRD parameters, f001 and L_c, have shown their close relations both to the kerogen type and to maturity. Owing to the higher content of aromatic carbon and heteroatoms, the type Ⅲ kerogen gives higher f₀₀₂ and lower L_c values than those of the type Ⅰ and Ⅱ with analogous maturity. A XRD diagram with f₀₀₂ versus L_c of kerogens of different types and maturities can indicate the different evolution paths for different types of kerogen (Fig. 7), so it may be available to characterize kerogen as well as the H/C-O/C diagram which is commonly used.