showed the presence of individual CaO and La2O3 phases
in the mixed metal oxide. The diffraction patterns observed in
CaOeLa2O3 catalysts with Ca/La atomic ratio from 0.5 to 10.0
showed intense La2O3 phases and low intensity of Ca crystallite
peaks. Although Ca loading was continuously increased for every
catalyst synthesis, the corresponded XRD peaks for CaO were small.
This suggested that La3þ ions in the host lattice were partially
substituted by Ca2þ ions, which corroborated with Liu's study