Renewable Energy, Vol.81, 421-431, 2015
Preparation and application of Ce/ZrO2 - TiO2/SO42- as solid catalyst for the esterification of fatty acids
To develop heterogeneous and reusable catalyst for the esterification of fatty acids, in presence of tri-glycerides, sulfate species has been incorporated over Ce/ZrO2-TiO2 support. The catalyst activity was found to be a function of its Bronsted acidic sites which in turn depends on the cerium concentration in catalyst. The esterification of oleic acid with methanol or ethanol in presence of prepared catalyst has followed the first order kinetics and Koros-Nowak test has demonstrated that reaction rates are independent from diffusion limitations. An increase in acid or alcohol alkyl chain length (steric factor) was found to show negative effect on the esterification activity of catalyst. Although, the catalyst was able to catalyze the esterification even in presence of up to 12 wt% moisture (with respect to fatty acids), however, a decrease in turn over frequency (TOF) was observed. The catalyst has shown excellent stability as negligible sulfate leaching was observed and recovered catalyst was reused in five successive runs without significant loss in activity. Even in presence of triglyceride (vegetable oil) the catalyst was able to convert >98% free fatty acids into respective esters. The esterified oils were fruitfully employed, without any pre-neutralization and water washing, in homogeneous alkali catalyzed transesterification to achieve >98% fatty acid methyl ester (FAME) yield. (C) 2015 Elsevier Ltd. All rights reserved.
Keywords:Esterification;Heterogeneous catalyst;Transesterification;Biodiesel;Koras-Nowak test;Reusability