Indexed on: 31 Oct '17Published on: 11 Sep '17Published in: Energy & Fuels
China is one of the largest coal producers in the world and abundant coal tar is produced from coal gasification and carbonization every year. Thus, catalytic hydrotreating coal tar for the production of clean fuel has received substantial attention. In this work, clean liquid fuel was obtained from the catalytic hydrogenation of a low temperature coal tar (LTCT) distillate in a four-stage fixed bed reactor with various catalyst combinations on the pilot scale. Effects of dominant hydrotreating parameters, reaction temperature (290–390 °C), H2 pressure (8–15 MPa), and liquid hourly space velocity (0.2–0.6 h–1), on hydrotreating activity, the intermediate and final products, and chemical components of the hydrogenated oils were evaluated. Meanwhile, a possible reaction scheme for the conversion of alkyl-naphthalenes (AN) and phenols in feedstock was probed. The results showed that the four-stage reacting system was capable of removing sulfur and nitrogen to less than 10 μg/g. Furthermore, after hydrotreating, AN were transformed into decalins, tetralin, and indenes, and alkyl-cycloalkanes (CA) were the main and final products of phenolic compound hydrodeoxygenation (HDO). In addition, coke formation of the spent catalysts was also studied by thermogravimetric techniques, which suggested that the coke deposits are mainly concentrated in the second and third stages of the reactor. The results of this work show that high-quality clean fuels can be obtained through the multistage hydrotreating process with a catalyst gradation technology, which may bridge the gap between fundamental research and industrial production and offer a route for deep processing of LTCT.