Synthesis of ethyl oleate catalyzed by solid superacid SO₄^2-/TiO₂/La³⁺

Rare-earth compound solid superacid SO₄^2-/TiO₂/La³⁺ was prepared. Its catalytic activity was examined under different synthetic conditions for the esterification of propanoic acid and n-butyl alcohol as probing reaction. The optimum conditions were also found, which were the pH=8, the depositing time was 24 h, the mass fraction of La(NO₃)₃ used in solid superacid was 5%, the concentration of H₂SO₄ was 1.25 mol/L, the soaking time in H₂SO₄ was 16 h and the calcining temperature was 500 ^oC. The ethyl oleate was synthesized from oleic acid and ethanol in the presence of SO₄^2-/TiO₂/La³⁺. The optimum reaction conditions were obtained which were the reaction time was 6 h, molar ratio of oleic acid to ethanol was 1:4 and the mass fraction of catalyst was 4%.