Insight into esterification of eugenol to eugenol benzoate using a solid super acidic modified zirconia catalyst UDCaT-5

Eugenol benzoate is a potent lipoxygenase inhibitor prepared by esterification of eugenol with benzoic acid. The current paper depicts synthesis of eugenol benzoate using several solid acids among which super acid catalyst UDCaT-5 was found to be the best. UDCaT-5, a zirconia-based catalyst, with high sulfur content (9% w/w) but preservation of the tetragonal phase of zirconia was synthesized and is much better than the conventional sulfated zirconia (S-ZrO2). As compared to other solid acid catalysts it gives excellent conversion under moderate conditions of 110 °C. The effects of various parameters were studied in a batch reactor to establish kinetics and mechanism of reaction under optimized conditions. The reaction is intrinsic kinetically controlled. The detailed kinetics of eugenol esterification by solid super acid catalyst is studied using various parameters. The reaction follows Langmuir–Hinshelwood–Hougen–Watson mechanism involving weak adsorption of the reactants and products. The apparent energy of activation was found to be 9.36 kcal/mol. The catalyst is highly active and reusable.

Graphical abstractEsterification of eugenol to eugenol benzoate using a solid super acidic modified sulfated catalyst UDCaT-5.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► UDCaT-5 is a very active catalyst for esterification of eugenol. ► Various parameters affecting the rate of reaction were investigated. ► Kinetic study revealed that reaction follows LHHW model. ► A pseudo first order rate equation was successfully developed. ► A highly efficient and green protocol for preparation of eugenol benzoate.