Aplikasi dan Peranan Pelarut Ramah Lingkungan (Room Temperature Ionic Liquid, RTIL) dalam Proses Konversi Lignoselulosa: Review

Bio refinery process has an important role in the ethanol production made of the renewable resources especially agricultural waste (lignocelluloses). Lignocelluloses (woods, grass, leaves) usually consist of (i) lignin, (ii) cellulose, (iii) hemicelluloses and, (iv) other small molecules such as tannins, turpentine, waxes and fats. Lignin is a part of the non biodegradable lignocelluloses, non sugar compound, and must be separated before the cellulose and hemicelluloses could be use as starting materials in the ethanol production. Delignification process using conventional method as well as explosive steam process fibres (SEF) is the heating process of lignocelluloses in the alkaline solution at high temperature and pressure (2120C and 20 atm). The result is a fibre (cellulose and hemicelluloses) and lignin-containing solution that has been fragmented. SEF process leaves chemical waste and is not economic. In addition, the residual lignin that is deposited on the surface of the fibre (5% lignin) requires further process by bleaching. Ionic liquid (RTIL) is one of many solution for delignification. RTIL is a liquid salt at room temperature and has the ability to dissolve various type of organic and inorganic components so that are very wide spread used such as: in the electrochemistry, bio-refinery and heavy metal waste treatment. RTIL solvent that is suitable for lignocelluloses are the type of imidazolium. RTIL role in the lignocelluloses dissolution is acetylation by cation interaction (aromatic group that is positively charged) of the RTIL with the lignin in the lignocelluloses. The result is celluloses that are hydrolyzed enzymatically prepared and fermentation to produces bio-ethanol. Delignification process using RTIL solvent can be performed at low temperature and pressure (below 1000C and atmospheric pressure) and almost all the lignin can be separated from the fibre. Solvent separation by adding anti-solvent. The boiling temperature of the RTIL is above 3000C that is why the vapour pressure would be very low and almost all the solvent can be reused. Weaknesses are the solvent still relatively expensive, therefore the attempt to industrial scale production of solvent is a challenge in an effort to decrease the dependency from fossil energy usage