Esterification of Oleic Acid in Biodiesel Synthesis with SO42-/ZrO2/MCM-41 as Catalyst

Abstract

SO₄^2-/ZrO₂/MCM-41 was prepared by impregnation method with self-synthesized MCM-41. The investigation of effects on ZrO₂ load ratio and sulphur acid concentration sifted that the catalyst with 40 % ZrO₂ load ratio, 1.5 mol/L sulphur acid performed best. Oleic acid was chosen as a simulation of high-acid-value oil to esterify with methanol. The experimental results showed that SO₄^2-/ZrO₂/MCM-41 was a high active catalyst in esterification. The optimal condition was as following: the reaction temperature was 80 ºC, the oleic acid/methanol molar ratio was 4:1, the catalyst amount was 5 % (wt. /wt.) of the oleic acid and reaction time was 4 h. Under this condition, the oleic acid conversion could reach 82.6 %. Characterization results of XRD, TEM and SEM showed that SO₄^2-/ZrO₂/MCM-41 had the typical structure of MCM-41 and SO₄^2-/ZrO₂. Reusability tests indicated that the load progress largely improved the water tolerance of SO₄^2-/ZrO₂ and reduced the sulphur leaching rate of it.