Coal liquefaction is the process of producing liquid fuels from coal. Coal liquefaction is a means of addressing the many energy applications that are suited for consuming liquids. The technology entails heating coal, often with various reagents such as hydrogen, which produces a liquid.
One of the main methods of direct conversion of coal to liquids by hydrogenation process is the Bergius process. In this process, dry coal is mixed with heavy oil recycled from the process. Catalyst is typically added to the mixture. The reaction occurs at between 400 °C (752 °F) to 500 °C (932 °F) and 20 to 70 MPa hydrogen pressure. The reaction is as follows:
nC + (n + 1) H2 → CnH2 n + 2
Coal liquefaction methods involve carbon dioxide (CO2) emissions in the conversion process. If coal liquefaction is done without employing either carbon capture and storage (CCS) technologies or biomass blending, the result is lifecycle greenhouse gas footprints that are generally greater than those released in the extraction and refinement of liquid fuel production from crude oil.