Synthesis of CaO/ZrO2 based catalyst by using UiO–66(Zr) and calcium acetate for biodiesel production

Ca2+ ion leaching and poor pore structure are obstacles of CaO for biodiesel production. To this end, a typical Zr–based metal organic framework, UiO–66(Zr) is adopted to support calcium acetate to prepare CaO/ZrO2 catalyst. For comparison, catalyst precursor is activated in nitrogen (UCN) and air (UCA) atmosphere, respectively. Preparation factors including calcium acetate addition and activation temperature are evaluated. Moreover, effects of transesterification parameters on oil conversion are investigated and the optimized parameters are further used to examine catalyst reusability. Meanwhile, catalysts are characterized with TG, XRD, XPS, FTIR, Hammett indicator titration, N2 adsorption and desorption. Results reveal UCN calcined at 650 °C (UCN650) and UCA calcined at 700 °C (UCA700) separately exhibits the best catalytic performance. The maximum conversion of 96.99% is achieved by UCN650 with catalyst amount of 6 wt% and molar ratio of methanol to oil of 9 at 65 °C for 60 min. Even after being used 3 cycles, conversion of 92.76% is still achieved by UCN650. By contrast, UCA700 shows lower conversion of 92.94% at the first cycle with catalyst amount of 8 wt% and molar ratio of methanol to oil of 9 at 65 °C for 60 min.