Characterization And Hydrogenation Performance Of Heavy Componenys Of Medium And Low Temperature Coal Tar

Heavy components refer to those components with boiling point more than350 ^oC separated by distillation of medium and low temperature coal tar.It has the characteristics of high boiling point,high relative molecular weight and high content of heteroatoms.There are many kinds of heteroatom groups in the molecule.So far,the structure and composition of heavy components are still not clear.With the increasing demand for light weight oil products and the increasing trend of heavy crude oil resources worldwide,the utilization of heavy oil has been paid more attention.How to convert heavy oil into light oil and other chemical raw materials is the primary problem to be solved in heavy oil processing.The structural characteristics of heavy components play an important role in guiding the subsequent rational processing and utilization.At the same time,the hydrocracking reactivity of heavy components can provide basic data for the lightening of oil products.In this study,the heavy components of medium and low temperature coal tar were selected as the research object.According to the difference of solubility and boiling point,four group components of saturates,aromatics,resins and asphaltenes,and five fractions of 276-410 ^oC,410-441 ^oC,441-471 ^oC,471-501^oC and>501 ^oC were obtained.Elemental analysis,gel permeation chromatography,FTIR,UV and Fluorescence spectra were used to characterize the group components and fractions.Based on the analysis of heavy components of coal tar,the hydrocracking characteristics of heavy components,toluene soluble substances of heavy components,410-441 ^oC and>501 ^oC fractions were investigated by batch reactor,and the role of biomass in hydrogenation of heavy components was preliminarily explored.The main results are as follows:1.Content determination of heavy components.Different fractions of heavy components were obtained by Soxhlet extraction and column chromatography.The amounts of saturates,aromatics,resins and asphaltenes are 16.90 wt%,21.30wt%,20.10 wt%and 29.90 wt%,respectively.Molecular weight of four group components is asphaltenes>resins>aromatics>saturates.2.Structural analysis of heavy components.The saturates of heavy components are mainly aliphatic hydrocarbons.Aromatics,resins and asphaltenes have distinct condensation aromatic ring structures.The aromatic components are mainly tricyclic and tetracyclic aromatics.The resin is mainly composed of tricyclic aromatic hydrocarbons,with a small amount of heavy components of tetracyclic and pentacyclic aromatic hydrocarbons,and asphaltene is mainly composed of pentacyclic aromatic hydrocarbons.The main forms of oxygen in asphaltene and resins are phenolic hydroxyl groups,while the oxygen in aromatic compounds mainly exists in the form of ether bonds.3.Determination of the content of distilled fractions and their group components.Five fractions of 270-410 ^oC,410-441 ^oC,441-471 ^oC,471-501 ^oC and>501 ^oC were obtained by vacuum distillation of heavy components.Their amounts are 10.40 wt%,31.80 wt%,9.50 wt%,16.10 wt%and 30.50 wt%,respectively.With the increase of distilling temperature,the amounts of saturates and aromatics of fractions decreased gradually,while the amounts of resins and asphaltenes increased gradually.Toluene insolubles mainly exist in the fraction of>501 ^oC.4.Structural analysis of vacuum distillates of heavy components.The main functional groups and chemical structures of the fractions are similar to those of the group components.The fractions<501 ^oC are mainly composed of tricyclic and tetracyclic aromatic hydrocarbons.With the increase of ditilling temperature,the side chains of components in fractions also increased.5.Hydrogenation experiments of heavy components,toluene soluble substances and vacuum fractions.Compared with the results of heavy components hydrogenation reaction,the total hydrogenation efficiency of toluene soluble substances is higher,and the oil yield increased from 40.37 wt%to 60.06 wt%.The hydrogenation performance is more obvious of 410-441 ^oC fraction than that of>501 ^oC fraction,and the oil yield is 81.38%and 6.06%,respectively.6.The role of biomass in the hydrogenation of heavy components.The co-hydrogenation of biomass and heavy components in the presence of tetrahydro-naphthalene as hydrogen donor at H₂ pressure of 6 MPa showed that the addition of biomass promoted the lightening of heavy components of medium and low temperature coal tar.Compared with the alone heavy components hydrogenation,the oil yield of co-hydrogenation of biomass and heavy components increased from 66.63 wt%to 75.43 wt%in the absence of catalysts.