Electrostatic Immobilization of Ionic Liquids onto SBA-15 as
Heterogenized Catalysts for Esterification of Oleic Acid with
Trimethylolpropane
Abstract
To overcome the drawbacks of homogeneous catalysts in the synthesis of
trimethylolpropane trioleate (TMPTO), ionic liquids with different
acidity were electrostatically immobilized onto SBA-15 to obtain
heterogenized catalysts. The catalytic performance of the as-prepared
two catalysts (IL1/SBA-15 and IL2/SBA-15) was investigated at different
temperature (100 -140oC) and molar ratio of oleic acid (OA) to
trimethylolpropane (TMP) (3:1 to 5:1) at fixed catalyst dosage of 3 wt.
% and reaction time of 20h; where the catalyst IL1/SBA-15 with higher
acidity exhibits higher activity. The optimum temperature (at OA: TMP =
3: 1) was obtained at 130oC, where the total conversion was 86.1% and
70% with selectivity towards TMPTO of 95.6% and 92.96% for IL1/SBA-15
and IL2/SBA-15, respectively. Above this temperature, the selectivity
began to decrease. The effect of OA: TMP molar ratio showed the increase
of conversion (92.7% and 79.1%) with the increase of OA: TMP molar
ratio up to 4.5. Further increase in OA concentration results in a
damping of the catalytic efficiency of the two catalysts. Through six
consecutive runs, the periodicity test refers to the relative stability
of the employed catalysts with slightly decrease in activity. All
results were interpreted and discussed in detail