凝胶色谱和紫外光谱法对煤四氢呋喃抽提物的分析

本实验选取大同、铁法大兴、义马和神府4种煤样,用乙腈、四氢呋喃、吡啶作溶剂连续抽提后,对其中的四氢呋喃抽提物进行了凝胶色谱及二极管阵列检测分析,以确定煤抽提物中中等极性化合物的分子量分布和结构特征。通过对样品的凝胶色谱及紫外光谱分析发现,煤四氢呋喃抽提物的分子量小于840 amu,分子量分布在840~340 amu(组分1)、340~175 amu(组分2)及175~110 amu(组分3)间的组分均为芳香族化合物。但由于芳环上有不同分子量的取代基存在,使分子量分布相差极大;分子量在110 amu以下(位于标定曲线以外)的(组分4)为小分子量的链烃或脂环烃类化合物;1、2、4组分是煤四氢呋喃抽提物主要组分;而组分3在抽提物样品中含量极少。分子量在110 amu以下的小分子化合物(组分4)除大同样品中含量(8.68%)较少外,在其余3个样品中占的比例很大(神府72.96%,义马54.05%,铁法大兴51.74%)。组分1随煤变质程度增加,相对含量增加,其它组分相对含量与煤变质程度没有直接关系。

Analysis of Coal Tetrahydrofuran Extracts by Gel Permeation Chromatography Coupled with Photodiode Array Detection

The chemical structural analysis of coal extracts in terms of the different polarity range is a critical step in coal liquefaction,these results can be used in the selection of extraction liquids,product separation and enrichment of selective products.Nevertheless,the higher polar compositions in the sample need some special column to fit these properties and pre-preparation steps become very complicated.Usually,only about 12~20 percent of lower polar compositions in the coal extraction were analyzed,it could not provide enough fundamental information to support the coal liquefaction.In this case,four Chinese coal samples(shenfu,(datong),Yima,Tiefa) were extracted by acetonitrile,tetrahydrofuran(THF),pyridine sequentially under room temperature according to the solvent polarity order to find the molecular weight(MW) distribution and chemical structure information that could represent more parts of the extracts.The middle polar components,THF(extraction) ratios of these four samples were 2.7%,2.89%,9.19% and 9.42% respectively.Gel(permeation) chromatography(GPC) was adopted to separate these THF extracts and photodiode array(PDA) detector was used to detect separated compounds under 200 to 400 nm wavelength.GPC results showed that the MW of THF extracts alas less than 840 amu,the composition of MW lower than the 110 amu was in the(order) of SF,YM,TFDX and DT with extraction ratio of 72.89%,54.05%,51.74% and,8.68%,(respectively).It could be found,from the GPC and PDA spectra,that the components of which MW from 340 amu to 840 amu(fraction 1),175 amu to 340 amu(fraction 2) and 110 to 175 amu mainly consist of(aromatic) species,with the different kind of substituted function groups,which have different molecular weight distributions.The(compounds) with MW lower than 110 amu(fraction 4) were mainly belonged to unsaturated cycloalkane(species).Moreover,the relative amount of the first part of THF extracts increased with the higher coal rank,no relation ship was found between coal ranks with other parts of the THF extracts amount.