Microwave heating and synthesis method influence in SiO2–ZrO2 mixed oxides preparation and its use as heterogeneous catalyst for biodiesel obtainment

ZrO2–SiO2 mixed oxides were obtained by two different methods. The influence of microwave-assisted hydrothermal treatment and the differences of two different synthesis methods were investigated. The obtained materials were characterized by DSC, XRD, SEM and FTIR spectrometry. The N2 adsorption analysis data (BET and BJH) was used for the determination of textural properties of the mixed oxides. The two synthesis methods point out differences in the way Zr is incorporated in the silica matrix. The microwave heating was responsible to change the textural properties but not the crystallinity. Finally, the catalytic activity was tested in the transesterification of soybean oil and esterification of oleic acid, both with methanol. The reaction conversions were measured by H-NMR. None of the samples presented catalytic activity in the transesterification of soy oil with methanol. However, the oleic acid was esterified with methanol at subcritical conditions.