Efficient production of biodiesel from both esterification and transesterification over supported SO42−–MoO3–ZrO2–Nd2O3/SiO2 catalysts

Abstract

SO42−–MoO3–ZrO2–Nd2O3/SiO2 (SMZN/SiO2) catalysts for the production of biodiesel via both esterification and transesterification were prepared and characterized by N2 adsorption-desorption isotherms, X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetry analysis (TGA), ammonia adsorption Fourier transform infrared spectra (NH3-FTIR), and ammonia adsorption temperature programmed desorption (NH3-TPD) to reveal the dependence of the stable catalytic activity on calcination time. The reason for catalyst deactivation was also studied. The calcination time remarkably affected the types of active centers on SMZN/SiO2, and 4 h was found to be the optimal calcination time. SO42− species bonded with small size ZrO2 were found to be the stable active centers, where the leaching of SO42− and the deposition of coke were inhibited. The deposition of coke was easier on large size ZrO2 than on small size ones. Calcination in air flow could eliminate the deposited coke to recover the deactivated catalysts.