Surface Characterization of Sulfated Iron Oxide and Its Synthesis of Biodiesel Under Microwave Radiation

Abstract

AbstractThe solid acid catalysts SO42−/Fe2O3were prepared by impregnation technique, and the preparation conditions were different in calcination temperature, concentration of impregnation solution of H2SO4and impregnation time. The characterization was performed by using Fourier transform infrared spectrometer (FTIR), X-ray diffraction (XRD), Temperature programed desorption of NH3(NH3‒TPD), N2‒BET and microwave absorbing test. As shown by FTIR spectra, the S=O functional group existed in the sample, which was essential for the strong acidity of the SO42‒/MxOytype solid acids. The XRD results indicated that when the calcination temperature exceeded 400℃, iron in SO42‒/Fe2O3transformed from amorphous to crystalline phase. The results from NH3-TPD showed that the prepared sample possessed strong acid and superacid sites. As shown by N2-BET results, the BET surface area of the samples was up to 200m2/g, and their pore size distributions essentially belonged to mesoporous characteristic distribution. The SO42−/Fe2O3solid acid catalysts were used for the transesterification of castor oil under microwave radiation to produce biodiesel. The amounts of FAME in the product were analyzed by high-performance liquid chromatography. The highest yield of product was 65.3 wt.% when the reaction temperature was 65 ℃, alcohol/oil molar ratio was 30/1, catalyst loading was 20 wt.%, the reaction time was 3 h and the power of microwave was 300 w. Furthermore, the reaction results showed that SO42‒/Fe2O3had better catalytic activity under microwave radiation than under conventional heating condition.