Microstructure and morphology of mechanically sulfated acid catalysts of α-Al₂O₃

Abstract

This work reports the evaluation of the microstructure, morphology, and catalytic behavior of α-Al₂O₃ synthesized via combustion method for esterification reaction of oleic acid in soybean oil with ethanol to produce biodiesel. The reaction was evaluated with 2 wt% of catalyst at 160 °C for 3 h when the molar ratio of fatty acid:ethanol was 1:12. To enhance the catalytic performance of α-Al₂O₃, its sulfation was done by a different method using mechanical milling. The microcatalysts were characterized by X-ray diffraction, Fourie transform infrared spectroscopy, granulometric analysis, and scanning electron microscopy. Results showed α-Al₂O₃ as the major phase, presence of SO₄ ^2- groups, the contribution of the sulfation process to morphology with reduction of agglomerates, and particle size from 18.98 to 15.30 mm. The yield of ester was enhanced from 80% (α-Al₂O₃ as a catalyst) to 93% (SO₄ ^2-/α-Al₂O₃ as a catalyst), which showed the milling as a fast method for synthesis of a highly efficient acid catalyst to produce biodiesel.

Keywords:
catalyst; sulfation; esterification; biodiesel