Experimental study on two-stage catalytic hydroprocessing of middle-temperature coal tar to clean liquid fuels

Special Mo-Co/γ-Al₂O₃ and W-Ni/γ-Al₂O₃ catalysts with different metal loadings were prepared applying new synthesis technologies that combine ultrasonic-assisted impregnation and temperature-programming methods. Clean liquid oil was obtained from middle-temperature coal tar via hydrogenation in two-stage fixed beds filled with the laboratory made catalysts. The Mo-Co/γ-Al₂O₃ catalyst with 12.59 wt.% Mo and 3.37 wt.% Co loadings, and the W-Ni/γ-Al₂O₃ catalyst with 15.75 wt.% W and 2.47 wt.% Ni loadings were selected. The effects of pressure and liquid hourly space velocity on hydrogenation performance were investigated while other experimental conditions remained constant. Gasoline (≤180 °C) and diesel (180-360 °C) fractions were separated from the oil product and analyzed. The two-stage reacting system was capable of removing nitrogen and sulfur from 1.69 and 0.98 wt.% in the feed to less than 10 ppm and 100 ppm, respectively in the products. The results indicated that the raw coal tar could be considerably upgraded through catalytic hydroprocessing and high-quality fuels were obtained.