Effect of La<sub>2</sub>O<sub>3</sub> Derived from Thai Monazite Ore Chemical Processing on the Properties of SO<sub>4</sub><sup>-1</sup>/ZrO<sub>2</sub>

Abstract

La2O3 derived from Thai monazite ore chemical processing was used as a precursor to prepare SO4-1-1%La2O3/ZrO2 solid acid catalyst. The SO4-1-1%La/ZrO2 catalyst was synthesized by co-precipitation with subsequent impregnation method. Various characterization techniques such as X-ray diffraction (XRD), nitrogen adsorption-desorption (BET) and Fourier transform infrared spectroscopy (FTIR) were used to study crystalline structural, textural and acid properties of the prepared catalysts. XRD results revealed that the presence of stable La2O3/ZrO2 tetragonal phase for SO4-1-1%La2O3/ZrO2 was observed at calcined temperature up to 600 °C. No diffraction peaks of La2O3 appeared in the profile of SO4-1-1%La2O3/ZrO2, indicated that the La2O3 was finely dispersed on the ZrO2 support. The doping of SO4-1-ZrO2 with La2O3 led to a significant decrease in its BET surface area, total pore volume and pore diameter. A relatively uniform pore size distribution of SO4-1-1%La2O3/ZrO2 catalyst with average pore diameter of 6 nm was found at the calcined temperature of 600 °C. Lewis acid sites existed in the synthesized SO4-1-1%La2O3/ZrO2 were lower than that counterpart. A loss of sulfate species was noted at high calcined temperature. The prepared SO4-1-1%La2O3/ZrO2 will be further used as a solid catalyst for transesterification of waste cooking oil to biodiesel, and the addition of La2O3 on the support could lead to enhance the catalytic activity and thermal stability.