| Coal-based crude oil refers to liquid products obtained from thermal process of coal,which includes coal tar,coal direct liquefaction oil,and Fischer-Tropsch oil.Accurately analyzing the chemical composition characteristics of coal-based crude oil is beneficial to the fine application of coal-based crude oil,and the targeted conversion with a product-demand-oriented production mode.At the same time,an intensive study of the composition of coal-based crude oil also contributes to coal processing improvement.Due to the complexity,no exact composition and content of coal-based crude oil is reported.Particularly the problem of material balance in the analysis has not been solved yet.Therefore,a more accurate and real qualitative and quantitative analysis of coal-based crude oil with material balance as a constraint,and the establishment of a comprehensive and systematic analysis method in this process is still an urgent problem to be solved.Coal tar and coal direct liquefaction oil are selected as the research objects.Firstly,the basic properties of coal-based crude oil are determined by moisture analyzer,elemental analyzer,gel permeation chromatography and thermogravimetric distillation.Then,GC-MS/FID（Gas Chromatography-Mass Spectrometer/Flame Ionization Detector）is used to analyze the light weight fractions（<350o C）of coal-based crude oil with material balance as a constraint,and a FID quantitative method system is established during this process.Finally,the coal-based crude oil heavy components（coal tar pitch,>350oC）was separated intoα,β,andγcomponents,and then they were characterized by using modern analytical instruments separately.Obtained the following main results and conclusions.（1）Establishment of FID quantitative method system.According to the mechanism of FID,a new method for calculating the effective carbon number（ECN）based on the type and quantity of the elements in the molecule was proposed.The formula(4)=（141-1.12-8.962-6.863+0.564）×4,（8）/4))for predicting the FID response factor of the substance mainly by using the molecular formula of the organic substance was deduced,and the scope of applicability of the formula（k>0.78）was given,too.Then a FID quantification method system is established by combining the FID response factor predicting formula with the area normalization method.The recovery experiment with a recovery of 99.07 wt%shows that the method system is accurate and effective,and it could be applied to the quantitative analysis of the other complex organic mixtures.（2）Analysis of basic properties of coal-based crude oil.Elemental and moisture analysis found that due to different treatment processes,the content of moisture,oxygen,nitrogen,and sulfur in coal tar is higher than that of coal direct liquefaction oil,however,the ratio of hydrogen to carbon in coal direct liquefaction oil is higher than that of coal tar.Gel permeation chromatography analysis found that the average molecular weight of coal tar（158.00 u）is higher than coal direct liquefaction oil（139.42 u）,but the molecular weight distribution of coal direct liquefaction oil is more concentrated than that of coal tar,the components with molecular weight less than 300 u accounted for 73.11 wt%in the coal tar,and accounting for 81.99 wt%in the coal direct liquefaction oil.Thermogravimetric distillation reveals that the distribution of the boiling points of the components in the coal direct liquefaction oil is more concentrated than that of the coal tar,the boiling point of the components in the coal direct liquefaction oil is mainly concentrated in the range of（240±40）oC,and the coal tar oil shows two boiling ranges,one is（195±20）oC,and the other is（343±40）oC.（3）Analysis of light weight fractions（<350oC）of coal-based crude oil.GC-MS/FID is used to analyze the light weight fractions,in which MS is used for qualitative analysis and FID is used for quantification.The results show that the content of the light weight fractions of coal-based crude oil can be balanced between 70 wt%and 80 wt%.The content of hydrocarbons（61.57 wt%）in the light weight fractions of coal direct liquefaction oil is much greater than that of non-hydrocarbons（17.36 wt%）,and the hydrocarbons are mainly tetralins,alkyl naphthalenes,alkyl pyrenes,etc.Non-hydrocarbons are mainly oxygen containing compounds.The content of non-hydrocarbons（43.68 wt%）in coal tar light weight fractions is greater than that of hydrocarbons（29.59 wt%）,and the hydrocarbons are mainly alkyl benzenes,alkyl naphthalenes,alkyl pyrenes,long chain alkanes,etc.Hydrocarbons are mainly oxygen containing compounds.In addition,the carbon number in coal direct liquefaction oil is mainly concentrated on 11-15（54.46 wt%）,and the carbon number in coal tar is mainly concentrated on≤10（29.24 wt%）and 11-15（28.82 wt%）.（4）Coal-based crude oil fractions analysis.When the coal-based crude oil is divided into different fractions according to the boiling points,the amount of the most of coal direct liquefaction oil fractions which can be balanced is 85 wt%or more,but the amount of coal tar fractions can be balanced varying from 49 wt%to 102 wt%.Coal direct liquefaction oil fractions are mainly hydrocarbons.Most of the coal tars fractions before 260oC are mainly non-hydrocarbons,and other fractions are mainly hydrocarbons.The molecular weight distribution analysis by gel permeation chromatography show that the fundamental reason for the insufficient material balance is:the obtained samples still contain a large amount of large molecular weight substances that are difficult to vaporize.（5）Analysis of acidic,basic,and neutral components.Coal-based crude oil light components is separated into acidic,basic,and neutral components by acid-base extraction,and then analyzed by GC-MS/FID.In coal direct liquefaction oil,the hydrocarbons in the neutral component accounted for 81.17 wt%,the oxygen containing compound in the acidic component accounted for 75.48 wt%,the nitrogenous compound in the basic component accounted for 60.64 wt%.The total amount of the acidic,basic,and neutral components which can balanced is 70.96wt%.In coal tar,the hydrocarbons in the neutral component accounted for 74.45wt%,the oxygen containing compound in the acidic component accounted for84.17 wt%,the nitrogenous compound in the basic component accounted for81.63 wt%.The amount of the acidic,basic,and neutral components which can be balanced is 68.67 wt%.（6）Determination of the structural parameters of coal tar pitch（>350oC）.The heavy components of coal tar are extracted and separated into three parts ofγ,β,andα,and then they are determined by element analyzer,infrared spectroscopy（IR）,nuclear magnetic resonance spectroscopy（NMR）and gel permeation chromatography（GPC）.Some structural parameters’information is obtained.According the above information,it can be deduced that:the molecular formula of coal tar pitch is C21.74H20.00O1.20N0.26,and the molecular formula of theγ-components is C21.64H22.30O1.13N0.18.The coal tar pitch andγ-components have the similar aromatic ring peripheral carbon number（10）and cycloalkane rings number（1）.The number of aromatic carbon（16）,bridge carbon（6）,aromatic rings（4）in the asphalt molecule is higher than the number of aromatic carbon（14）,bridge carbon（4）,aromatic rings（3）in theγ-components.Andγ-components has more saturated carbon atoms（7）and cycloalkane carbon number（4）than the saturated carbon atoms（6）and cycloalkane carbons number（1）in the coal tar pitch.The aromatic ring of the coal tar pitch molecule has less alkyl substituent sites（2）with longer aliphatic carbon chain（carbon atoms 5）. |
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