Research On The Hydrogenation Conversion Law Of Medium And Low Temperature Coal Tar Asphaltenes

Asphaltene in medium-low temperature coal tar was the main cause of the problem of low hydrogenation of coal tar and short catalyst life cycle.However,there were few studies on the law of hydrogenation and conversion of medium-low temperature asphaltenes.Therefore,this dissertation focuses on the hydrogenation reaction temperature and reaction time of coal tar asphaltene hydrogenation conversion rate,structure and heteroatom form of the study,the results of the study can be a certain degree of hydrogenation of coal tar the guidance and reference.Firstly,the paper used high-pressure reactor and commercial Ni-Mo type hydrogenation catalyst to hydrogenate the whole fraction coal tar.The results showed that the H/C atomic ratio and the yield of toluene insoluble matter gradually increased after hydrogenation.Nitrogen,oxygen,and oxygen heteroatoms were gradually removed,and coal tar was significantly lighter.The asphaltene yield,sulfur and nitrogen atom content and chemical composition were studied for different hydrogenation process conditions.As the reaction temperature increased,the conversion rate of asphaltenes,the removal rate of sulfur,nitrogen,and oxygen atoms gradually increased.The relative molecular mass and the H/C atomic ratio both decreased,and the hydrogenolysis reaction of asphaltenes was obvious.As the reaction time increased,the conversion rate of asphaltene gradually increased,the atomic ratio of H/C decreased,and the molecular weight of asphaltene decreases first,after the increased,the removal rate of sulfur and oxygen atoms gradually increased,and the removal rate of nitrogen atoms gradually decreased.Second,in order to study the effects of different hydrogenation process conditions on the asphaltene structure,the asphaltenes after hydrogenation were characterized by GPC,FT-IR,1H-NMR and XRD.The results showed that with the increased of reaction temperature,the aromaticity,number of aromatic carbon atoms and number of aromatic rings were gradually increased,the aromatic ring substitution degree and the condensation degree parameter gradually decreased,the asphaltene condensation reaction was intensified,and the coking activity was enhanced.The alkyl side chain,the distance between the alkyl chain and the diameter of the aromatic sheet gradually decreased,the asphaltene alkyl side chain was removed obviously,and the hydrogenation and ring opening reaction in the periphery of the aromatic sheet was enhanced.As the reaction time increases,the aromaticity first decreased and then increased,the aromatic ring first increased and then decreased,the naphthenic ring number gradually decreases,and the dealkylation reaction and the cycloalkane ring opening reaction increased.The spacing of aromatic flakes and the height of aromatic flakes gradually decreased,the depth of hydrogenation of asphaltenes was enhanced,and the removal of alkyl chains was significant.Finally,the change rule of asphaltene heteroatoms in the hydrogenation process was investigated using XPS.The results show that with the increased of reaction temperature,the single bond oxygen content gradually decreased,the carbonyl oxygen content increased,the alkyl sulfur content decreased,the thiophene sulfur slightly increases,the pyridine nitrogen atom content decreases,and the protonated pyridine content increased.The effect of sulfur,nitrogen and nitrogen removal was obvious.With the prolongation of reaction time,the oxygen content of single bond was significantly reduced,the content of carboxyl oxygen was increased,the content of alkyl sulfur was decreased,but the content of thiophene sulfur and sulfone sulfur increased significantly,and pyrrole and pyridine nitrogen were significantly increased.Atomic content was basically the same,prolonging the reaction time was not conducive to the removal of nitrogen atoms.