基于可分离-选择性破坏分析方法的煤沥青有机结构研究

Investigation of organic structures in coal pitch based on separable-selective destruction analysis method

我国煤焦油沥青(CTP)产量丰富,但利用水平低下。从分子水平上研究CTP的有机结构特征是实现其高效利用的前提。然而CTP结构复杂,通过单一的直接表征手段得到的仅是CTP中各种混合组分重叠交叉的平均结果。以山西某焦油加工厂生产的CTP为样品,采取可分离-选择性破坏的研究思路,从分子水平探究CTP的有机结构特征。基于溶剂溶解度参数的差异及其对CTP萃取效果,使用甲醇、环己烷和甲苯对CTP进行逐级萃取将CTP分为3个萃取物和萃余渣,并采用现代仪器分析结合钌离子催化氧化手段,对各组分进行系统表征。研究发现,逐级萃取可有效地将CTP分为可溶组分和难溶组分,并能将可溶组分进一步分离为3个族组分。从甲醇萃取物到萃余渣,芳香度逐渐增大,热稳定性依次增强。其中甲醇萃取物中含有较多的含氮化合物,环己烷和甲苯萃取物中芳香族组分含量逐渐提高,在环己烷萃取物中5环化合物的相对含量最高,而甲苯萃取物中6环化合物的相对含量最高,萃余渣则以致密的迫位缩合芳环结构为骨架,结构单元中芳环平均尺寸接近7个。各组分通过分子间作用力构成CTP整体,可溶组分以游离或嵌入形式存在于难溶组分的大分子芳环骨架中。通过萃取作用,溶剂逐级破坏这些作用力,将可溶组分带走,而留下表面有较多凹陷和孔的萃余渣。

Coal tar pitch(CTP)is abundant in China,but its utilization level is low.Investigating the organic structure and composition of CTP at the molecular level is essential for its efficient utilization.However,the structure of CTP is complex,and it is difficult to accurately understand its structural characteristics through a single direct characterization method.Herein,CTP produced by a tar processing plant in Shanxi was used as a sample.Based on the method of separable-selective destruction,the organic structural characteristics of CTP were explored at the molecular level.Considering the different solubility parameters and extraction effects on CTP of solvents,methanol,cyclohexane and toluene were adopted for sequentially extracting CTP,which was divided into three extracts and residue.These components were systematically analyzed using modern instrument analysis methods combined with ruthenium ion catalytic oxidation methods.It was found that the sequential extraction could effectively realize the separation of soluble and insoluble components in CTP,and further separate the soluble components into three groups of components.From the methanol extract to the residue,the aromaticity increased gradually and the thermal stability increased successively.Furthermore,the methanol extract contained more nitrogen-containing compounds,whereas,the content of aromatic components in cyclohexane and toluene extracts gradually increased,and the residue had a condensed peri-condensed aromatic structure as its skeleton with the average number of aromatic rings was close to 7 in its structural unit.All components constituted the whole CTP through intermolecular force,and the soluble component existed in the macromolecular aromatic ring skeleton of the insoluble component in free or embedded form.Through extraction,the solvent destroyed these forces step by step,taking away the soluble components,and leaving the residue with more depressions and holes on the surface.