Effect of the chemical composition of smectites used in KF/Clay catalysts on soybean oil transesterification into methyl esters

Three smectites with distinct chemical compositions were treated with potassium fluoride and the catalysts thus obtained were used in the transesterification of soybean oil with methanol. The smectites and catalysts were examined by X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDS), and the BET gas adsorption method to verify if their chemical composition influences the properties of the resulting catalysts. An experimental design was applied to evaluate the effect of the variables of the transesterification reaction: temperature, mass ratio of the catalyst, and the molar ratio of oil to methanol. The results indicate that increasing the SiO2/Al2O3 ratio of the smectites causes an increase in the basicity of the catalysts, and hence, in the conversion rate into methyl esters. •The modified clays with KF have a great potential for the production of methyl esters.•The highest SiO2/Al2O3 ratio causes a largest number of basic sites in KF/Clay.•Conversion to methyl esters varies with the ratio SiO2/Al2O3 of the clays.