Solvent-free esterification of stearic acid and ethylene glycol with heterogeneous catalysis in a stirred batch microwave reactor

Ethylene glycol distearate (EGDS) is extensively used in the pharmaceutical and cosmetics industries. Even in textile industries as a softener, EGDS is in demand. In this paper, synthesis of EGDS by esterification of ethylene glycol and stearic acid has been described using a solid acid catalyst under microwave (MW) irradiation in a solvent-free system. Conventional heating takes more than 4–6 h to give a mixture of EGDS and ethylene glycol monostearate (EGMS). Under MW irradiation, the highest conversion of 97% of the acid was obtained in 10 min. The reaction mixture was analyzed by acid value, FT-IR, 1 H-NMR and mass spectroscopy. The EGDS synthesis was optimized concerning various parameters such as reaction time, different catalysts, catalyst loading (wt/wt%), temperature, and MW power. Heterogeneous catalysis, intensified with MW irradiation, makes the esterification process more promising route for possible application at industrial scale. Graphic abstract