Evaluation of Structural Characteristics of Huadian Oil Shale Kerogen Using Direct Techniques (Solid-State 13C NMR, XPS, FT-IR, and XRD)

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• 作者：Jianhui Tong ; Xiangxin Han ; Sha Wang ; Xiumin Jiang
• 刊名：Energy & Fuels
• 出版年：2011
• 出版时间：September 15, 2011
• 年：2011
• 卷：25
• 期：9
• 页码：4006-4013
• 全文大小：853K
• 年卷期：v.25,no.9(September 15, 2011)
• ISSN：1520-5029

文摘

A sample of kerogen isolated from Huadian oil shale was studied using a combination of solid-state ¹³C NMR, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR), and X-ray diffraction (XRD) techniques to evaluate its structural characteristics. ¹³C NMR results indicate that the carbon skeletal structure of this kerogen is mainly composed of a fairly high fraction of aliphatic carbon (86.1%), with a very low aromaticity (f_a) of 9.7%; methylene (CH₂) carbons dominate in all types of aliphatic carbons and the majority of them exist as many long straight chains but not saturated alicyclics. The average methylene carbon chain length (C_n) is between 12 and 24. There are only one fused aromatic ring (e.g., naphthalene) or two single aromatic rings (one benzene ring and one penta-heterocycle) per 100 carbon atoms. However, aromatic rings in this kerogen have a very high value of substitutive degree (未 = 0.42鈥?.75). Furthermore, XRD analysis suggests that most methylene straight chains and aromatic carbons can not form crystalline but amorphous structure and are linked to each other by various bridge bonds and methylene (CH₂) chains. FT-IR, XPS, and ¹³C NMR results show that organic oxygen in the kerogen exists as mainly three types of oxygen functional groups. Both XPS and ¹³C NMR results agree on the same ordering of their respective contents: C鈥揙 and C鈥揙H groups are dominant, followed by O鈺怌鈥揙, and C鈺怬 or O鈥揅鈥揙 groups. The ¹³C NMR results further suggest that more oxygen of C鈥揙 and C鈥揙H groups is bound to aromatic carbons. XPS shows that over half the total amount of organic nitrogen in Huadian kerogen exists as aromatic heterocycles, which concludes pyrrolic nitrogen richest in total organic nitrogen, pyridinic, and protonated-pyridinic forms. A relatively high content of amino nitrogen over 30 mol % also is present in this kerogen, which is much higher than that of other same type kerogens. Organic sulfur is distributed in this kerogen as aromatic and aliphatic sulfur, sulfone, and sulfoxide in the order of the relative mole fraction.