Successive two-stage hydrodenitrogenation using a commercial NiMo catalyst was applied to a heavy distillate of a coal liquid to achieve a high level of denitogenation. A successive hydrotreatment in 1-methylnaphthalene, at 390 °C for 2 h and at 440 °C for 2 h under hydrogen pressure of 12 MPa, removed 83% (overall) nitrogen from the distillate, while a single reaction at 420 °C for 3 h under 23 MPa removed only 34%. Addition of catalyst prior to the second stage reaction, or a four-ring aromatic such as pyrene or fluoranthrene as a component of the reaction solvent (20 wt%) increased markedly the removal of nitrogen in the two stage hydrotreatment. Based on preliminary analyses of the products, a combination of extensive hydrogenation in the first stage and effective CN bond cleavage in the second is suggested for the course of the effective denitrogenation. Suppression of catalyst deactivation, by proper choice of solvent may be another reason. The hydrogen pressure required for denitrogenation can be reduced in a two-stage process.
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