The Effect Of Oxygenated Model Compounds On Direct Coal Liquefaction

Oxygen is one of the important constituent elements in the coal. The oxygen content of low rank coal is about10-20%, the main existing forms are phenolic hydroxyl groups and carbonyl group, as well as furans and carbonyl, etc. Oxygen belongs to the active elements in the coal structure with a highly reactivity under direct coal liquefaction (DCL). In direct coal liquefaction, some scholars thought that undesired reverse reaction (polycondensation reaction) had relations with the quantity of the phenolic hydroxyl content in the coal, especially in low rank coals. Therefore, oxygen content and distribution in the different bituminous coals are studied in the paper; the influence and transferring disciplinarian of the oxygen functional groups on DCL are explored.Two low-rank bituminous coals were selected and studied the impact of the naphthol and anthraquinone to the liquefaction of coals and the model compounds to the liquefied products of coals.First, the coal samples were floated by ZnCl2and washed by HC1-HF; the ash contents of two coals were reduced to about2.00%in order to eliminate the impact of the ash content during DCL. And we find that the organic macromolecular structure of washed coal was essentially unchanged by infrared analysis, but the oxygen functional groups in coals were changed.Second, thermal gravimetric (TG) analysis shows that the400-450℃is the best liquefaction temperature of two kinds of coals. We processed the liquefaction experiments of two kinds of washed coals by WHF type Weihai self-control reaction kettle, and calculated the yield of liquefaction product.We find that as the hydrogen-donating solvent is tetralin, the anthraquinone and naphthol promote the liquefaction reaction of Yuanping coal, however, naphthol almost no effect to Yang fangkou coal, anthraquinone also promote the reaction of Yang fangkou coal, but the impact is small. While the non-hydrogen-donating solvent is1-methyl naphthalene, the naphthol played side effects to the liquefaction of Yuanping coal and polycondensation reaction occurred in liquefaction process.Finally, we draw the following conclusions through the analysis of the liquefaction product and liquefaction residue of Yuanping coal.(1) Gas product compositions primarily consist of CH4, C2H6, a small amount of CO, CO2, NH3, H2S, and trace amounts of hydrocarbon gas such as C2H4. The hydrogen donor solvent has greater impact to the gas component content but almost no effect to the gas composition. Further, the gas yield decreases and has a certain influence on the content of the gas composition when adding naphthol and anthraquinone to coal. Gases total yield and CH4dropped as the naphthol or anthraquinone were added, however, the C2H6and CO yields increased, the C2H4and CO2yields stayed the same.(2) The naphthol and anthraquinone have a certain influence on the components of oil, asphaltene and preasphaltene on coal liquefaction products. No matter adding naphthol or anthraquinone led to higher C%and lower H/C, O/C in oils. Clearly, in non-hydrogen-donating solvent1-methyl naphthalene, adding naphthol led to lower O/C and higher N%, S%in oils. It showed hydrogen donor solvent could effectively remove heteroatoms (O, N, and S) in coal. In good hydrogen-donating solvent tetralin, adding naphthol or anthraquinone led to lower C%, H/C and higher O/C in asphaltene and preasphaltene.(3) Adding the naphthol, phenols and fatty hydrocarbon in asphaltene fractions became higher, while only fatty hydrocarbon fractions increased was added the anthraquinone. No matter adding naphthol or anthraquinone made the hydroxyl groups of preasphaltene fractions and functional groups on the2928cm-1decreased.(4) The residue analysis can be seen heteroatom content higher in the residue, it showed that heteroatoms content remaining in the residue after coal liquefaction. Especially the oxygen content of good hydrogen-donating solvent was higher than non-hydrogen-donating solvent, which might be related to residue yields was higher in the poor hydrogen-donating solvent.(5) After coal liquefaction, a small part of hetero atoms in coal still remains in the liquefaction residues, and about40percent of the oxygen converted to water, about45percent nitrogen and80percent of the sulfur are transferred to the gases products, and oxygen of phenols and quinone is transferred to water.(6) The cracked functional group of Yuanping coal after liquefaction included the OH-π bond, the self-association of a hydroxyl group and aromatic hydrocarbon an ether oxygen bond.of fracture in the coal. And the pyrolysis capacity of liquefaction residue of Yuanping coal decreased, but it still has a certain ability to pyrolysis, a weight loss was approximately15%.