Effect of rare earth modification on structure and catalytic properties of SO₄^2-/ZrO₂ solid acid catalyst

The rare earth-promoted SO₄^2-/ZrO₂ solid super acid catalyst was prepared by the co-precipitation and impregnation method under different conditions. The catalytic properties of the samples were evaluated through transesterification of waste oil and methanol and characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and BET surface area measurement. The results showed that among all the prepared samples the one that was calcined at 600℃ with La doping 4% had the highest production rate of 64.68%. An analysis of XRD patterns revealed that the incorporation of rare earth into tetragonal zirconia stabilizes the compound, and the calcination at 600℃ increases the reactivity of the catalyst by producing a greater fraction of active tetragonal zirconia with a larger surface area. It could be seen from the FT-IR spectra that super acid structures were formed in the catalysts and the acidity was strengthened remarkably and the activated centre of the catalyst were increased.