Microwave-irradiated acetylation of glycerol catalyzed by acid activated clays.

In this study, the investigation of the effects related to glycerol and acetic acid esterification over solid acid catalysts under microwave radiation by full factorial design 2³ is described. Using clay minerals activated with H₃PO₄ as catalysts it was possible to produce 26.4 wt% of acetins with molar ratio of 1:3 (glycerol:acetic acid), at 90 °C and using 10 wt% catalysts (in relation to glycerol mass) in 1 h of reaction. On the other hand, under the same conditions and conventional heating, 22.5 wt% of acetins were obtained, without selectivity, while under microwave radiation 67% of produced acetins were monoacetin, which is an important intermediate in organic synthesis. The influence of independent variables at 95% confidence level for reactions under microwave was evaluated and the molar ratio (acetic acid:glycerol) had a negative effect on acetin production. Finally, the catalysts were characterized after its exposure to conventional and microwave heating and no structural modifications were observed, which indicates the possibility of catalysts reuse. [ABSTRACT FROM AUTHOR]