Biodiesel preparation using Li/CaO catalysts: Activation process and homogeneous contribution

This work studies the influence of the lithium content and activation temperature of Li-doped CaO catalysts in the transesterification reaction of triglycerides with methanol and the homogeneous contribution. Several samples with different lithium content have been studied, and a lithium concentration >3.6 wt% of lithium was expected to exert a promoter effect. The influence of activation temperature has been investigated for 4.5LiCa catalyst, requiring a temperature of activation above the melting point of LiNO3 (492 K) to observe any catalytic activity. Moreover, it has been observed that the homogeneous contribution, and consequently the amount of lithium species leached, depends on activation temperature: the leaching of lithium and homogeneous contribution is significant for activation temperatures ≥973 K (87% in 3 h), when Li oxides was present in the sample, whereas the homogeneous contribution is little relevant at activation temperatures ≤773 K, where LiNO3 has not yet decomposed. Consequently at activation temperatures between 773 and 973 K, an intermediate situation, will be expected.