Role of oxygen vacancy on activity of Fe-doped SrTiO3 perovskite bifunctional catalysts for biodiesel production

In this work, the catalytic performance of the mesoporous SrTi 1- x Fe x O 3 ( x  = 0.05, 0.10, 0.15 or 0.20) for biodiesel production from palm oil with a high acid value is investigated. The physicochemical properties of the catalysts are revealed by various characterization methods, including XRD , N 2 adsorption-desorption, XPS , Raman, EPR, SEM-EDS, and CO 2 /NH 3 -TPD. Fe doping results in many oxygen vacancies in the perovskite structure , which increases the electron density of the active sites on the surface and promotes the polarization of the perovskite structure, thus improving the catalytic activity of the catalyst. The most oxygen vacancies and the best catalytic performance are observed in the SrTi 0.85 Fe 0.15 O 3 catalyst, where the FAME yield of 97.52% is achieved with the catalyst concentration of 5  wt % and methanol to oil molar ratio of 18:1 at 150 °C for 3 h. Meanwhile, the catalyst maintains a FAME yield of 83.59% for the fourth reused cycle. Also, the catalyst exhibits strong resistance to FFAs, where the FAME yield is still 93.58% even with oleic acid addition of 12  wt % to show the capability in catalyzing the simultaneous esterification and transesterification .