中低温煤焦油化学组成及结构的分子水平表征

Composition and structure molecular characterizations of medium and low temperature coal tar

以内蒙褐煤提质装置生产的中低温煤焦油为原料,研究建立了中低温煤焦油自身结构-组成-性质的分子水平表征方法,从宏观水平描述了中低温煤焦油的物理化学性质,在分子层次上详细研究了中低温煤焦油及其不同馏程、不同性质亚组分的化学组成。首先将中低温煤焦油全馏分进行实沸点蒸馏分离为16个窄馏分并进行性质分析,其次对>180℃重质馏分通过酸碱萃取分离出酸性组分、碱性组分和中性组分,并且中性组分在萃取色谱装置上分离获取6个特征亚组分;利用GC/MS分析了其全馏分、窄馏分及各亚组分的分子结构特征。结果表明,该煤焦油全馏分的水含量为28%,20℃时密度1 003.7 kg/m^3,氧含量为7.4%,<180℃馏分含量为14.24%,<360℃馏分含量为63.4%,属一种典型的中低温煤焦油。中低温煤焦油的<180℃轻质馏分的分子组成以苯、甲苯和二甲苯为主,含有部分小分子烷烃和烯烃。在> 180℃重质馏分中,其酸性组分占27.6%,碱性组分占2.46%,中性组分占69.94%。中性组分中饱和分为33.60%,芳香分为38.70%,胶质占为25.10%,沥青质为2.60%。且中间馏分和重质馏分中含有大量酚类化合物,其分子结构类型以芳烃为主,同时存在长链正构烷烃。中低温煤焦油中含有大量含氧化合物,主要是酚类化合物,以烷基苯酚类为主,在160～280℃相对丰度较高,少部分以酮类化合物存在。

A molecular level characterization method for investigating composition and structure of medium and low temperature coal tar derived from Inner Mongolia lignite upgrading plant has been developed in this paper.The physical and chemical properties of medium and low temperature coal tar was described from macro level.The medium and low temperature coal tar and its chemical composition under different distillation ranges and subcomponent of different natures was investigated from molecular level.Firstly,the whole fraction of medium-low temperature coal tar was separated into 16 narrow fractions by real boiling distillation,and analyzed on their properties.Secondly,the acidic fraction,the alkaline component and the neutral component were separated by acid-base extraction for the >180 ℃ heavy fraction,and the neutral component was separated on the extraction chromatographic apparatus to obtain six characteristic subcomponents.The compositions and molecular structures of full-range fractions,narrow fractions and sub-fractions were analyzed by GC/MS.Results show that the water content of all coal tar fraction is 28%,at 20 ℃,the density is 1 003.7 kg/m 3,the oxygen content is 7.4%,and the fraction content (<180 ℃) is 14.24%,and the fraction content (<360 ℃) is 63.4%.This indicates that it is a typical medium and low temperature coal tar.The molecular compositions of light fractions (<180 ℃) mainly comprise benzene,toluene and xylene,with some small molecular alkanes and olefins.In heavy distillate (>180 ℃),acidic compound accounts for 27.6%,basic component 2.46%,neutral component 69.94%.In neutral components,Saturation is 33.60%,aromatic 38.70%,gelatine 25.10%,asphaltene 2.60%.The intermediate and heavy fractions also contain a large number of phenolic compounds,with aromatic hydrocarbons as main molecular structure,and long-chain n-alkanes as well.Medium and low temperature coal tar contains a large number of oxygenated compounds,mainly phenolic compounds,alkyl phenols,which are relatively abundant at 160-280 ℃,and also contains a few number of ketones.