The Research Of Coal Liquefaction Residue Solvent Extraction And The Characteristics Of The Extract

Coal liquefaction residue is a mixture with high carbon, high ash and high sullfur contents. The residue takes about 30% of all products. Taking account of the economy and environment, it is important to make effective use of residues. As a raw material for carbon materials, the residue has shown its potential value.As the improving on understanding of so-called coal liquefaction residues and progressing technology for it, more and more attention has been paid to the residue as a feedstock of carbon materials. Its unique property and utilization value will more be found.In this paper, firstly, some extract solvents for the residue is evaluated on its boiling point, viscosity, dipole moment, price, toxicity, extraction rates etc. N,N -Dimethyl acetamide is used as extract solvent. By changing extract temperature , ratio of solvent to residue, dissolving time, it is found that N,N-Dimethyl acetamide showed highest extract yield of 59.30% (daf) for the residue at 120℃,10min of dissolving time and 1 : 3 ratio of the solvent to residue. By elemental analysis, Fourier transform infrared spectra (FTIR), and solid nuclear magnetic resonance, it is found that the aromatic carbon rate of the coal liquefaction pitch reaches up to 76.50%. The coal liquefaction pitch were extracted from the residue by the N,N- Dimethyl acetamide.In this paper, thermal conversion of coal liquefaction residue to coal liquefaction pitch and coal liquefaction pitch to mesophase pitch are investigated. The tests were carried out in a multi-tube well-crucibe furnace controlled by programmed heating unit. Under the conditions of 410-440℃and 6~8h, mesophase pitch with the broad domain stream line structure was prepared from coal liquefaction residue. The mesophase was analyzed with elemental analyser, polarized light microscopy, FTIR and NMR. The results show that coal liquefaction pitch experienced three stages of the formation of mesophase ball, the growth and melting of the ball and formation of the mesophase pitch. The coal liquefaction pitch converts into mesophase pitch by thermal conversion. The aromatic carbon rate increases from 76.50% to 91.07%. It is illustrated that both thermal decomposition and condensation took place in the process of the formation of mesophase pitch. In the thermal process of coal liquefaction pitch, the side-chain of aliphatic hydrocarbons and alkanes fracture are broken to form aromatics.