Composition and structural changes of low temperature coal tar asphaltenes precipitated in different n-alkane solvents

doi:10.16085/j.issn.1000-6613.2017.06.019

Abstract

Abstract: Asphaltenes were precipitated with different n- alkanes from medium/low temperature coal tar,including n-pentane asphaltene(As-5),n-hexane asphaltene(As-6),n-heptane asphaltene(As-7),soluble in n-hexane but insoluble in n-pentane[As-(5-6)],soluble in n-heptane but insoluble in n-hexane[As-(6-7)] and soluble in n-heptane but insoluble in n-pentane[As-(5-7)]. They were characterized by XPS,elemental analysis and FTIR. The occurrence state and content of element,functional groups of elements in asphaltenes were obtained and systematically discussed. The results showed that the sp²carbon and sp³carbon were the main forms of carbon and the total content reached 85%,while the C=O and COO— were fewer. The aromaticity(f_a) of As-(5-7) was obviously smaller than that of As-7. The heteroatoms on the surface of the six kinds of asphaltenes were mainly oxygen atoms existed in the form of C—OH and C—O—C mostly. The pyridine and pyrrolic were the main forms of nitrogen with the sum of relative content up to more than 70%. Nitrogen were detected as amine and the protonation pyridine with the smaller content in the total nitrogen functional groups. The amine content of As-(5-6),As-(6-7) and As-(5-7) asphaltenes were higher than As-5,As-6 and As-7 asphaltenes due to the aromatic ring side chain length of the former were larger than the latter.

Key words: medium/low temperature coal tar, asphaltene, different solvents, XPS, surface structure

摘要： 利用X射线光电子能谱分析（XPS）、元素分析和FTIR对不同正构烷烃溶剂（正戊烷、正己烷、正庚烷）沉淀出的正戊烷沥青质（As-5）、正己烷沥青质（As-6）、正庚烷沥青质（As-7）、溶于正己烷不溶于正戊烷的沥青质[As-（5-6）]、溶于正庚烷不溶于正己烷的沥青质[As-（6-7）]、溶于正庚烷不溶于正戊烷的沥青质[As-（5-7）]共6种中低温煤焦油沥青质进行了表征，系统分析了元素的赋存形态、相对含量和官能团类型。结果表明，碳在沥青质表面主要以sp²碳和sp³碳的形式存在，二者相对含量之和均达85%以上，以C=O和COO—基团存在的C较少，且As-（5-7）的芳香度较小，As-7芳香度最大。6种沥青质表面的杂原子以O原子为主，主要以C—OH、C—O—C形式存在。N主要以吡啶、吡咯形态存在，两者含量之和均在70%以上，且含有少量的胺和质子化吡啶，As-（5-6）、As-（6-7）、As-（5-7）沥青质中胺类含量高于As-5、As-6、As-7，主要原因是前者芳香环侧链长度大于后者的。

关键词: 中低温煤焦油, 沥青质, 不同溶剂, X射线光电子能谱分析, 表面结构

CLC Number:

TE622.1

PEI Liangjun, LI Dong, YUAN Yang, XUE Fengfeng, LI Wenhong. Composition and structural changes of low temperature coal tar asphaltenes precipitated in different n-alkane solvents[J]. Chemical Industry and Engineering Progress, 2017, 36(06): 2101-2108.

裴亮军, 李冬, 袁扬, 薛凤凤, 李稳宏. 不同正构烷烃溶剂沉淀中低温煤焦油沥青质的结构组成变化规律[J]. 化工进展, 2017, 36(06): 2101-2108.

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