Transesterification of sunflower oil using catalysts obtained from the dispersion of potassium and calcium salts in mesoporous silica matrices

Abstract

A set of catalysts was synthesized by impregnating mesoporous silicas (SBA-15 and MCF) with calcium and potassium salts. The solids obtained were characterized by Fourier transform infrared, scanning electron microscopy, N2 adsorption/desorption porosimetry, energy dispersive X-ray analysis and X-ray diffraction. These catalysts were assessed for the transesterification of sunflower oil into fatty acid methyl esters. The catalyst support and the solids containing calcium exhibited low activity under the mild conditions chosen for this study (65°C and self-generated pressure). In contrast, the presence of potassium significantly enhanced transesterification at very short reaction times, irrespective of the support nature. The methyl ester content was found to be strongly influenced by the basicity of the catalysts, attributed to different potassium compounds, achieving conversions exceeding 98%. However, catalytic activity declined upon reuse, with only a 5% methyl ester content achieved in the second cycle. This confirmed the hypothesis that metal species leach into the reaction mixture with a mechanism similar to that of homogeneous ones.