SUMMARY
Deep eutectic solvent is an alternative green solvent for ionic liquids to extract phenolic compounds from pyrolysis oil. The study is carried out to screen 15 DESs through COSMO – RS model to predict the activity coefficient at infinite dilution and to identify the factors affecting separation performance of DESs in phenol extraction process. Based on the COSMO – RS screening, Choline Chloride – based DES have the highest selectivity because Cl- has larger electronegativity and a stronger interaction with the phenol hydroxyl group than that of Br-. For the experimental work, 3 DESs of Choline Chloride (ChCl), Methyltriphenylphosphonium bromide (MTPPBr) and Tetrabutylphosphonium bromide (TBPBr) with ethylene glycol (EG) at a mole ratio of 1:2, 1:4 and 1:2 was used respectively. Model oil containing liquefied phenol and hexane were used to replace pyrolysis oil as feed. Mixing speed, extraction time and solvent to feed (S: F) ratio were varied to obtain the optimum operating conditions for the DESs. Mixing speed of 150 rpm were optimum for ChCl:EG (1:2) and MTPPBr: EG (1:4) and 200 rpm for TBPBr:EG (1:2). Optimum extraction time for ChCl:EG (1:2) and MTPPBr: EG (1:4) were 45 minutes whereas for TBPBr:EG (1:2) was 30 minutes. ChCl:EG (1:2) have an optimum S: F ratio of 1:3 whereas MTPPBr: EG (1:4) and TBPBr:EG (1:2) is 1:2.5. This is preferable as more feed can be extracted with less amount of DES. DES reusability is tested by carrying out another 2 extraction cycles. Extraction efficiency for all DES increases for the second cycle and the highest efficiency is obtained for ChCl:EG (1:2) at 81.10 %. Efficiency remained constant for the third cycle which signifies that DES has reached its saturation stage. ChCl: EG (1:2) is recommended to be the alternative solvent to Ionic Liquid (IL) for extraction of phenolic compounds from pyrolysis oil.