Ionic liquid supported acid-catalysed esterification of lauric acid

Abstract

Ionic Liquid (IL) based on 1-n-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMI.NTf2) under acidic condition was used as catalyst for the esterification reaction of fatty acid. Various acids namely sulphuric acid, perchloric acid, p-toulene sulphonic acid and various chloride salts such as zinc chloride (ZnCl2) and iron(III) chloride (FeCl3) immobilized in ionic liquid BMI.NTf2 gave acidic ILs. These acidic ILs were tested as catalysts for esterification reactions. Esterification of alcohol (methanol) with fatty acid (lauric acid) using ionic liquid BMI.NTf2 combined with H2SO4 (BMI.NTf2(H2SO4)) gave high activity (>85%) and selectivity (100%) observed over a period of 2 hours reaction with reaction temperature 70oC. The ester became easily separated due to IL forming biphasic with product after the reaction where ester accumulated as the upper phase and IL with water produced after reaction at lower phase. Catalytic activities comparison also be studied between acidic ionic liquid BMI.NTf2 with acidic ionic liquid ChCl.2ZnCl2 and conventional acid catalyst. These ILs were characterised by using FTIR, NMR and TGA. Results from FTIR were showed no significant difference between ILs with ILs in acidic condition. The TGA curve show BMI.NTf2 thermal's decomposition is =400°C but when BMI.NTf2 combination with H2SO4, TGA curve show weight loss increase and becomes unstable. The advantages of ILs as catalyst are "clean process" and "green chemistry" due to its behaviour such as non-volatile, no loss of solvent through evaporation and reduced environmentally impact. This ILs-catalyst system can be recycle for futher reaction.