Coal-derived synthetic oil

Direct coal liquefaction refers to the direct conversion of the complex organic polymer structures in coal into lower-molecular-weight liquid fuels through hydrogenation. This conversion process takes place in a slurry system containing coal powder, solvent, and catalyst, involving hydrogenation and depolymerization, and requires high temperatures and pressures. The advantage of direct liquefaction is higher thermal efficiency and a higher yield of liquid product ； The main drawback is that the overall operating conditions of the coal slurry hydrogenation process are relatively stringent. Coal indirect liquefaction involves first gasifying coal to produce syngas (CO+H2); the syngas is then purified and the H2/CO ratio is adjusted, after which it is catalytically converted into liquid fuel. Its advantages include a wide range of coal types that can be used, relatively mild operating conditions, and the resolution of waste issues such as coal ash during the gasification process. Its disadvantage is that its efficiency is lower compared to the other method.

The cost is relatively high, and it requires support from high international oil prices