Esterification of oleic acid and high acid content palm oil over an acid-activated bentonite catalyst

• Acid activated bentonite showed superior catalytic activity than Amberlyst-15.
• Bentonite, which was treated with 0.5 M H2SO4, gave highest methyl oleate yield.
• Acidic bentonite showed higher efficiency in esterification than acidic kaolin.

The esterification of oleic acid with methanol and that of a high acid content palm or Jatropha oil with methanol or ethanol were evaluated with different acid-activated bentonite catalysts. Na-bentonite was acid-activated by either H2SO4 at varying concentrations from 0.25 to 2.0 M or with 0.5 M HNO3. The characterization of the raw and acid-activated bentonite was then conducted by nitrogen adsorption, XRD, XRF, SEM and acid–base titration analysis. The 0.5 M H2SO4 acid-activated bentonite exhibited the best catalytic activity with 100% methyl oleate yield and 99% free fatty acid conversion in the esterification of pure oleic acid and oleic acid in palm oil with methanol, respectively. Both conversions were higher than that obtained from esterification via commercial Amberlyst-15 catalyst.

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