Effect Of Pretreatment On Coal Swelling And Coal-oil Coprocessing

In this paper, the influence of coal swelling was investigated after NaBH₄ reduction, H₂O₂ oxidation and alkali treatment with Shenhua bitumite and Neimeng lignite as feed. Then, the changes structure of pretreated coal were analyzed. And the effects of coal pretreatment on the liquefaction of coal-oil coprocessing were investigated.Firstly, the swelling performance of two different coals was investigated. It was found that reduction treatment with NaBH₄ could reduce the swelling ratio of the two coals. The reduction of swelling ratio was more apparent in strong polar solvents such as DMF, while the change in weak solvents methanol or H₂O was less obvious. Higher swelling temperature was helpful to improve the swelling ratio of the two raw coals, however the sensitivity of higher temperature in improving the swelling ratio became weak after reduction treatment; Secondly, the change of the swelling ratio of the two raw coals after H₂O₂ oxidation pretreatment was on the comtrast to after NaBH4 reduction treatment and displayed increase of coal swelling. The increase degree of swelling in the polar solvent DMF after oxidation treatment was bigger than in the solvent methanol or H₂O for the two coals.It is found that NaBH4 reduction pretreatment decreased reaction activity of coal in the coal-oil coprocessing, and reduced the cooperativity of coal-oil. Thus that makes coal liquefaction effects becomes poor. The two coals after oxidation treatment, the number of hydroxyl groups of coals were increased. On the other hand, there are certain relations between O/C ratio in coal and coal reactivity. O/C ratio increased after oxidation treatment, enhancing the coal - oil hydrogenation reaction activity of processing. Three surfactants in DMF could improve swelling ratio of the bitumite while the three surfactants in methanol showed some inhibitory effects on the swelling. The presence of surfactants could improve the coprocessing of oil and swellon coal with DMF and the effect of non-ionic surfactant was better than that of the two ionic surfactants.