Catalysts for Coal Chemical Industry I. Coal tar hydroprocessing

1. Coal tar hydroprocessing

Coal tar is a black brown or pure black viscous liquid with irritating foul smell. Classified by carbonization temperature, coal tar can be named as low-temperature coal tar, medium-temperature coal tar, and high-temperature coal tar. Coal tar hydroprocessing technology is to remove impurities including sulfur, nitrogen, oxygen, metals, etc., and is to saturate olefins and aromaticis to produce naphtha, diesel, low-sulfur and low-nitrogen heavy fuels, etc. 

Raw coal tar is separated into light faction with FBP <350℃ and heavy faction with IBP>350℃ through atmospheric distillation and vacuum distillation. The light faction undergoes fixed-bed hydrotreating process intended for removing sulfur, nitrogen, and oxygen, and saturating olefins and some aromatics, generating naphtha and low-sulfur diesel. The hydrotreating process has the advantages of simplicity and low investment. However, this technology can only be used to process light distillates with FBP<350℃, and diesel product has relatively low cetane rating. When low-temperature coal tar is used as feedstock, product diesel has a cetane rating up to 40; when high-temperature coal tar is used a feedstock, product diesel has a cetane rating less than 38.

To enhance hydroprocessing efficiency and to extend the availability of feedstocks , Beijing Gaoxin Lihua Technology Co., Ltd. developed a new technology that can be used to process coal tar with high boiling point. In this new technology, coal tar is cut into two factions. The lighter one has an FBP<500℃, while the heavy one, which is asphalt, has an IBP>500℃. In our our new technology, the lighter faction sequentially undergoes hydrotreating process and then hydrocracking process. In the hydrotreating stage, impurities including sulfur, nitrogen, oxygen in the feedstock are removed, while olefins and some aromatics are saturated. In the hydrocracking stage, vacuum distillates between 350～500℃ are cracked into distillates with FBP<350℃, thus enhancing light distillates’ yield.