Thermal Liquefaction Performance Of Xilinguole Lignite And Its Products Characterization

In order to improve the liquefaction efficiency of low-rank coals,thermal liquefaction performance of Xilinguole lignite（XL）and the effects of main liquefaction conditions such as temperature,solvents,time,solvent-to-coal ratio,etc.were investigated in this thesis.Further,the hydrogen donoration in the process of thermal liquefaction at high temperature were studied by changing solvent,adding hydrogen transfer agents,and pre-extracting coal.Finally,the mechanism of thermal liquefaction was discussed by combination of structural characterization of products.The results show that the thermal liquefaction of XL display high reactivity in THN solvent,a hydrogen donor solvent,and are dominated by thermal cracking of coal matrix to produce oil and gas as major products.The yield of heavy product is low.The suitable liquefaction temperature of XL is in the range of 450-480°C.Increasing ratio of solvent to coal can promote the hydrogenation of coal,but it is not conducivetodeoxidation.Innon-hydrogendonorsolvents,suchas methylnaphthalene（MN）and washing oil（WO）,the thermal liquefaction conversion of XL is low,and the impurities in MN and WO solvents are obviously condensed with liquefied intermediates of XL to produce semicoke and coke at above 450°C so that the apparent conversion of XL obtained is negative.Meanwhile,the results also show that the thermal liquefaction of XL at high-temperature mainly depends on the hydrogen donor capacity of the solvent,and is also affected by the dissolving capacity of solvent.Adding THN to non-hydrogenating solvent can significantly improve the liquefaction conversion of XL and the yield of oil and gas.The effect of adding THN to MN is obviously better than that to toluene solvent.Under non-catalytic conditions,H₂ also display obvious hydrogenation ability in the process of thermal liquefaction of XL at high temperature,which is beneficial to the hydro-liquefaction of coal.The hydrogenation of H₂ in toluene solvent is more obvious than that in MN solvent.There is obvious hydrogenolysis in the process of thermal liquefaction of XL at high temperature.Adding hydrogen transfer agents.such as anthracene,naphthalene,etc.can increase the liquefaction conversion and the oil and gas yield.At the same time,there is obvious in-situ hydrogen donor from small-molecular compounds in coal in the process of thermal liquefaction of XL,and the liquefaction conversions of thermal dissolving residue and solvent extracted residue are lower than that of their parent coal.In addition,it is also found that the thermal liquefaction has different mechanism from the catalytic hydro-liquefaction,and it mainly dominates on the macromolecular structure of coal.Among them,the liquefaction performance of low rank coal depends on the pyrolysis reactivity of the coal matrix,and TYK bituminous coal with high metamorphism display the highest thermal liquefaction conversion at relative low liquefaction temperature.In summary,there is no any catalyst and a large amount of hydrogen used in the thermal liquefaction at high temperature,so it can carry out at low reaction pressure to obtain high liquefaction efficiency,which is expected to become a improtant liquefaction technology of low rank coal.