Study on direct conversion of Naomaohu coal pyrolysis heavy oil to aromatics

Abstract

The pyrolysis tar from Naomaohu coal was separated by distillation apparatus. Four components of heavy oil above 320°C were analyzed. The result showed the colloid content was 28.84% and the asphaltene content was 35.12%, and both were difficult to convert in hydrogenation. 13C-NMR results showed that the relative molar ratio of aromatic carbon in heavy oil was 71.16%, which indicated that aromatic compounds in heavy fraction were dominant. The heavy fraction was treated by suspension bed and fixed bed cracking. The asphaltene and colloid were almost completely converted. The yield of naphtha with boiling point below 180°C was 66.95%, and the diesel with boiling point higher than 180°C was 17.84%. Oxygen, nitrogen and sulfur contained in heteroatoms were almost completely removed. Catalytic reforming of naphtha was carried out. The results showed that the number of cycloalkanes decreased by 60.23%, and the number of aromatics increased by 65.8%, which indicated that the dehydrogenation and aromatization of cycloalkanes occurred mainly. While the number of n-alkanes decreased by 13.42%, which indicated that the isomerization and cyclization of n-alkanes occurred simultaneously. The catalytic reforming oil contained more benzene, toluene, xylene and ethylbenzene, and the contents were 11.97%, 23.15%, 21.43% and 3.48% respectively. In the direct conversion process of heavy oil from coal pyrolysis, the transmissibility of basic structural units of coal was significantly reflected.