Mini review of coal liquefaction using solvent extraction

Coal, which reserve is still abundant, can be a vital primary energy source in Indonesia in the coming decade to substitute oil and gas. The oil and gas reserves has nearly depleted but they have not been compensated by other new and renewable energy sources. However, coal as a solid fuel cannot be used as versatile as liquid fuel, especially for transportation fuel. Therefore, it is important to study the coal liquefaction technology in order to substitute the petroleum based liquid fuel. Among other technologies, solvent coal liquefaction has an interesting potential since it usually employs moderate operating conditions and does not require as much hydrogen supply as other technologies. From this review, we found that the choice of solvent is important factor in coal liquefaction. Solvent polarity will affect the yield and the product composition. Another important factor is operating temperature. The solvent liquefaction rate will increase if the operating temperature is closer to the coal softening temperature. In the coal liquefaction process, coal particle size can be an essential element. Depending on the initial size, the particle may remain intact or may completely dissolved during the process, therefore it will significantly affect the extraction rate.