| Abstrak/Abstract |
Recently, biodiesel production from palm oils has been thoroughly investigated to substitute
crude oil due to its scarcity. However, the biodiesel production process is time-consuming due to
its slow kinetics; thus, concentrated sulfuric acid has been used to fasten the reaction process in
some industries. Unfortunately, sulfuric acid is a toxic, corrosive, and non-environmentally
friendly catalyst. In this study, we prepared sulfated Calix[4]resorcinarene derived from
vanillin as an efficient organocatalyst to replace sulfuric acid. The catalytic activity of sulfated
Calix[4]resorcinarenes was evaluated through the methylation of palmitic acid and oleic acid as
model compounds due to their abundant amounts in palm oil. The Calix[4]resorcinarene and
sulfated Calix[4]resorcinarenes have been obtained through a one-pot reaction in 71.8–98.3%
yield. Their chemical structures were confirmed by using FTIR, NMR and HRMS spectrometry
analyses. The results showed that the sulfated Calix[4]resorcinarene exhibited high catalytic
activity for methyl palmitate and methyl oleate productions in 94.8 ± 1.8 and 97.3 ± 2.1% yield,
respectively, which was comparable to sulfuric acid (96.3 ± 1.8 and 95.9 ± 2.5%). The optimum
condition was achieved by using 0.020 wt equivalent of organocatalyst for 6 h reaction process at
338 K. The methylation of palmitic acid and oleic acid fits well with the first-order kinetic model
(R2 = 0.9940–0.9999) with a reaction rate constant of 0.6055 and 1.1403 h-1, respectively.
Further investigation reveals that the hydroxyl group of vanillin plays a pivotal role in the
organocatalytic activity of sulfated Calix[4]resorcinarene. |
