CTL is a technology that uses coal as raw material to produce petroleum products and petrochemical products through chemical processing, including direct coal liquefaction and indirect coal liquefaction.

Direct coal liquefaction is to grind suitable coal into fine powder, and then directly convert coal liquefaction into liquid fuel through catalytic hydrogenation reaction at high temperature and high pressure. The conversion process is hydrogenation and depolymerization in slurry system containing pulverized coal, solvent and catalyst. After refining, it can be made into high-quality gasoline, diesel oil and aviation fuel. The process includes coal liquefaction, hydrogen production from coal, solvent hydrogenation, hydrogenation modification and so on.