This paper focuses on the preparation and characterization of CaO, MgO and ZnO, both bulk and supported on -Al 2 O 3 and their catalytic activity in the transesterification of soybean oil and castor oil with methanol and butanol in order to produce biodiesel. XRD, SEM, CO 2-adsorption followed by TGA and N 2 adsorption have been employed to characterize the prepared catalysts. In supported catalysts, the presence of -Al 2 O 3 improves alcohol dissociation on the superficial basic sites. The first step of the reaction mechanism is then favored (hydrogen abstraction). In the transesterification of castor oil with butanol, MgO/-Al 2 O 3 and ZnO/-Al 2 O 3 catalysts showed high yields to FABE (Fatty Acid Butyl Ester) (97% and 85%, respectively). These last catalysts constitute an efficient alternative for obtaining second-generation biodiesel, taking into account that castor oil is a nonedible source and butanol is an alcohol that can be obtained from biomass.
This paper describes the preparation and characterization of MgO and ZnO-based catalysts, pure and mixed in different proportions, supported on γ-Al 2 O 3. Their catalytic performance was studied in the transesterification of soybean oil and castor oil with methanol and butanol, attempting to produce biodiesel. XRD (X-ray diffraction), SEM-EDS (scanning electron microscopy-energy dispersive X-ray spectroscopy), CO 2-adsorption and N 2-adsorption allowed characterizing the prepared catalysts. The characterization results were in all cases consistent with mesoporous solids with high specific surface area. All the catalysts exhibited good results, especially in the transesterification of castor oil using butanol. For this reaction, the reuse was tested, maintaining high FABE (fatty acid butyl esters) yields after four cycles. This good performance can be attributed to the basic properties of the Mg species, and simultaneously, to the amphoteric properties of ZnO, which allow both triglycerides and free fatty acids to be converted into esters. Using these catalysts, it is possible to obtain second-generation biodiesel, employing castor oil, a raw material that does not compete with the food industry. In addition, butanol can be produced from renewable biomass.
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