La2O3 contributed both
base and acid properties in the binary catalyst system. For metal
oxides (like La3þ
eO2), the surface lattice oxygen was attributed to
Lewis base sites (favor for transesterification) whereas the metal
ions are Lewis acid sites (favor for esterification). In this TPD-CO2
profile, the binary interaction between Ca and La species in binary
metal oxide induced the synergetic effect that further enhanced the
basicity and basic strength of CaOeLa2O3 compared to its single
oxides. The result indicated that mixed metal oxides rendered high