Preparation And Properties Of Mesophase Pitch Produced From Coal And Oil Slurry Coliquefaction Residue

The coliquefaction of coal and FCCS can reduce circulating solventconsumption, the residue yield and increase the content of lightcomponents and oil than coal liquefaction alone. This technology couldalleviate the current situation of the shortage of petroleum resources inChina. Coliquefaction residue is a kind of by-product with high carboncontent which is mainly used for gasification, combustion, coking,pyrolysis and liquefaction, etc. In recent years, residue was used toprepare carbon materials because the coal industry tend to develop inintensive model. The raw materials used for preparing carbon materialsare mainly pure aromatics (naphthalene asphalt), coal tar, asphalt andtheir different proportion of mixture, but their price is almost high andaffected by the market, in addition to the uneven composition. The studyof coal liquefaction residue have important significance at efficientutilization of resources and environmental protection aspects. In this paper, mesophae pitch was prepared from coliquefactionresidue of Yanzhou coal and Shijiazhuang catalytic cracking slurry indifferent atmosphere by thermal polymerization reaction. The experimentexamined the effects of hydrogenation on the process and productdistribution. This work also looked into the possibility of preparingcarbon materials from asphaltene extracted from residue bythermogravimetric analysis (TG) and hot stage experiment. In addition,the factors (polymerization temperature, holding time, additives andheating rate) which affect the formation of mesophase pitch wereinvestigated by polarizing microscope and fourier infrared spectrumanalyzer (FT-IR). Finally, the structure and morphology of carbonizedmesophase were characterized by scanning electron microscope (SEM)and X-ray diffraction (XRD). The electrochemical performance of thecarbonized mesophase were tested. The main experimental results are asfollows:(1) The coliquefaction residue consists of asphaltene (30%-40%),heavy oil (50%) and tetrahydrofuran insoluble (THFIS,2%-10%).Compared liquefaction in nitrogen atmosphere with in hydrogenatmosphere, the results of latter are that the asphaltene content isincreased, the heavy oil and THFIS content are reduced, the molecularweight of heavy products are reduced at the same time. In addition, theasphaltene aggregation degree is higher than that produce in nitrogen atmosphere due to the introduction of hydrogen. The former containsmore alkyl side chain and naphthenic structures, while the latter containsmore aromatic hydrocarbon.(2) The appropriate temperature range for asphaltene to generatemesophase pitch is between350℃and500℃and the appropriatemolecular weight range of raw material to prepare anisotropic mesophaseis between500and600. With the increase of thermal polymerizationtemperature or holding time, toluene insolubles (TI) and quinolineinsolubles (QI) content are increased. The morphology of mesophase isvaried from microspheres to streamlined structure and even cokes. HI1sample could form anisotropy flow domain at440℃for6h, which wouldbe suitable to produce carbon fiber or needle coke. The asphaltene HI2(nitrogen liquefaction resultant) could generate body mesophase at440℃for12h. HI1and HI2would generate a large number of mesophasemicrospheres at380℃for10h.(3) PP increased the content of alkyl side chain of HI1polynucleararomatic, reduced the system viscosity and promoted the formation andgrowth of spherulite. Its promoting effect is enhanced with the increase ofPP content. PP promoted the crystallite nucleation of HI2. Carbon blackcan promote nucleation of system at the beginning of the mesophaseformation, while hinder the coalescence of microspheres at the later stage.(4) Mesophase would not form at lower heating rate and also would not form optical ordered structures at higher heating rate. These indicatethat ordered anisotropy mesophase could only be generated in theappropriate heating rate with moderate viscosity.(5) The morphology of carbonized mesophase microspheres indicatethat its nuclear mechanism follows “Building from Granular Basic Unit”theory and homogeneous nucleation. Its structure is Brooks-Taylor type.Needle coke has high crystallinity and preferred orientation aftercarbonization. The carbonized mesophase pitch has good characteristicsof cyclic voltammetry.