中低温煤焦油沥青质的分析表征

采用XPS、XRD、FT IR、13C NMR、元素分析等手段分析表征了中低温煤焦油正庚烷沥青质(CT C7沥青质),系统研究了CT C7沥青质表面元素的赋存状态、相对含量以及其晶体结构。结果表明,该沥青质的主要结构为多环稠合芳香烃并富含杂原子,其芳香度(fa)明显大于一般原油沥青质;烷基链间距和芳香片层直径值较小,其芳环上烷基侧链短而少且难以形成堆积结构;表面C主要以sp2和sp3碳的形式存在,二者摩尔分数之和达699%,以C=O和COO-基团存在的C较少。该沥青质表面的杂原子以O原子为主,N和S原子较少,其中含氧官能团主要是酚羟基和醚氧基,摩尔分数达619%。含氮官能团主要以吡啶氮(N 6)和吡咯氮(N 5)为主,二者摩尔分数之和为805%;含硫官能团中,噻吩硫、烷基硫比较多,摩尔分数之和达517%。该C7沥青质表面加氢难度较大的N 6、N 5和噻吩硫的摩尔分数低于石油沥青质,这可能是煤焦油加氢工艺中N、S脱除效率较高的原因之一。

Analysis and Characterization of Medium/Low Temperature Coal Tar Asphaltene

The n heptane asphaltene from medium/low temperature coal tar was analyzed and characterized by XPS,XRD,FT IR, 13C NMR and elemental analysis. The occurrence state and content of element, crystal structure of the CT C7 asphaltene were systematically discussed. The results showed that the main component of CT C7 asphaltene was polycyclic aromatic hydrocarbon combined with heteroatoms. Its aromaticity (fa) was obviously larger than that of crude asphaltene. The diameter of aromatic sheet plus alkyl chains and the distance between interchain or internaphthene layers were small, which resulted in the short aromatic ring alkyl side chain and made it difficult to form a stacked structure. The sp2 carbon and sp3 carbon were the main forms of carbon element with the total molar fraction of 699%. The heteroatoms on the surface of the asphaltene were mainly oxygen atoms, while the nitrogen atoms and sulfur atoms were fewer. In oxygen containing groups, 619% molar fraction were phenolic hydroxyl and ether oxygen groups. In nitrogen containing groups, 805% molar fraction were pyridine(N 6) and pyrrolic(N 5). In sulfur containing groups, 517% molar fraction were alkyl sulphides and thiophene sulfur. Less molar fractions of N 6, N 5 and thiophene sulfur of being difficultly hydrogenated on the surface of the C7 asphaltene might be the main reason that the nitrides and sulfide in coal tar could be easily removed in catalytic hydrogenation.