| The influences of the different temperatures, solvents and steam pretreatment onthermal dissolution (TD) of Shengli lignite (SL) were investigated, and the TDbehavior of SL in the various solvents at high temperatures was also studied in thisthesis. Then the effects of hydro-liquefaction of the TD soluble fraction (TDSF) wereprobed. The TDSFs, TD insoluble fractions (TDIFs) and the products of hydro-liquefaction were characterized by FTIR, GPC, thermogravimetric analysis, elementalanalysis and synchronous fluorescence spectrometry.The results show that the TD process has an obvious de-ashing effect, almost allof the ash in the lignite was transferred into the TDIFs. The TD soluble yield (TDSY)of SL increased with the rising of TD temperatures from280to400℃with1-methylnaphthalene(1-MN) as solvent, and the TDSY of30.4%was obtained at360℃.Further rising temperature to400℃, the TDSY increased rapidly，but condensationpolymerization tendcy became obvious at400℃. When the polar solvent ethanol (ET)was added into1-MN or CMNO, the TDSY of SL at360℃was higher than that at320℃. These prove that pyrolysis reaction in TD process of SL at highertemperatures is more obvious.When N-methyl-2-pyrrolidinone (NMP) or methanol (MT) or ET was added into1-MN, and MT or ET was added into CMNO, the TDSY greatly increased. Polarfunctional group containing oxygen and bridge bonds in lignite were partially brokenbecause of the addition of polar solvents, thus promoting dissociation the strongcross-links in the lignite, resulting in the increase of the TDSY. CMNO, the polarsolvent containing nitrogen (N) was more effective than1-MN, and the TDSYachieved42.2%at360℃in it. Adding5%MT to CMNO, the TDSY increased to77.1%. With the increase of the amount of MT addition, the TDSY remained almostunchanged. However the TDSY increased along with adding more than5%MT to1-MN. The result indicated that methanol may interact with some active fractions ofCMNO, thus decreasing the effect of TD.Alcoholysis reaction occurred in the TD process with addition of MT or ET to1-MN or CMNO, resulting in the better effects of TD than by adding NMP to1-MN. Adding15%ET to1-MN and CMNO, the TDSY achieved81.8%and88.1%at360℃respectively, about11%increase than that in the solvent of addition of15%MT tothe corresponding solvent at the same temperature. The results indicated ET was moreeffective in promoting deplymerization of SL and increasing its TD effect. ThereforeET is the better polar additive to TD solvent than ME.The influences of steam pretreatment of SL on the TDSY varied with the solventused. It is almost no obvious effect on the TDSY in1-MN, but the TDSY decreasingin1-MN or CMNO with the addition of15%ET, and great increasing in CMNO,especially steam treatment at200℃, the TDSY of SL increased by about16%. Thehigher the steam temperature is, the better the SL TD effects are.The effcts of hydro-liquefaction of TDSFs indicated that the activities of hydro-liquefaction of TDSFs were better than that of the raw lignite and that the conversionand oil yield of hydro-liquefaction deeply depended on the molecular structure ofTDSF. The catalyst Ni-Mo-S/Al2O3has a good catalytic hydro-liquefaction activityon both SL and TDSFs. The conversion of hydro-liquefaction of the most TDSFsavhieved above97%and the highest of oil yield among them achieved about72%. Inaddition, the conversion and oil yield of hydro-liquefaction of TDSF from1-MN withaddition of15%ET at360℃increased by2.1%and5.9%respectively than those ofTDSF from the same solvent at320℃, indicating the effcts of hydro-liquefaction ofTDSFs obtained at lower TD temperatures are better. |
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