We studied the effect of the alkali metal type (Li, Na, and K) and the calcination temperature (500, 600 and 700 °C) in the activity for biodiesel production of catalysts prepared by impregnation method, with constant metal content of 10%w/w using ZrO2 as support. The results of the catalytic activity allowed to find an activity sequence regarding the alkali tested metals: Na > Li > K, with this sequence remaining constant independent of the calcination temperature. The high activity of the Na/ZrO2 system, and slightly lower activity of Li/ZrO2, can be explained by the fact that higher calcination temperatures promote the formation of alkali-based zirconate species, M2ZrO3 (M = Na or Li). The presence of these species is correlated with the higher activity of these catalysts, specifically with the Na and Li-based catalyst calcined at high temperatures (600-700 °C). These M2ZrO3 species show higher basicity respect to other alkali metal oxide species, as was demonstrated with CO2-TPD results. The higher activity corresponded to 10% Na supported on ZrO2 and calcined at 700 °C, which reached full conversion within just 30 minutes of reaction, which makes this system a promising heterogeneous replacement for the regular homogeneous systems.
- Alkali metal
- Heterogeneous catalysts