*Corresponding author: zalita_y@yahoo.com
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 ≥400oC
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.
Keywords: 1-n-butyl-3-methylimidazolium
bis(trifluoromethylsulfonyl)imide; Choline chloride; Ionic liquids; Acidic
condition; Esterification; Fatty acid
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