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Wikipedia definition (similar term):

Coal liquefaction is a process of converting coal into liquid hydrocarbons: liquid fuels and petrochemicals. The conversion industry is commonly referred to as "coal conversion" or "Coal To X". "Coal to Liquid Fuels" is commonly called "CTL" or "coal liquefaction", although "liquefaction" is generally used for a non-chemical process of becoming liquid. Today, the share of converted coal used for CTL is less than 50%. It will decrease dramatically in the next years with the development of "coal to chemicals" and "coal to SNG" units, principally in China.

Source: Wikipedia - Coal liquefaction