Esterification of itaconic acid using Ln∼SO42−/TiO2–SiO2 (Ln = La3+, Ce4+, Sm3+) as catalysts

A series of itaconate esters, e.g. dimethyl itaconate, dibutyl itaconate and diisooctyl itaconate, were synthesized using solid acid SO42−/MxOy (M = Ti4+, Fe3+, Zr4+, Al3+) and SO42−/TiO2–SiO2 modified with lanthanide ion (Ln = La3+, Ce4+, Sm3+) as catalysts. It was found that SO42−/TiO2–SiO2 modified with lanthanide ion were of the same excellent catalytic activity as sulfuric acid (H2SO4). Moreover, Ln∼SO42−/TiO2–SiO2 is of excellent stability. Take La3+∼SO42−/TiO2–SiO2 for example, the influence of the preparation conditions on catalytic performance was in detail examined by Py-FTIR, NH3-FTIR, XRD and NH3-TPD, and the optimum preparation conditions were obtained. Furthermore, the effective separation of product combined with the recyclable catalyst is expected to contribute to the development of clean and environmental friendly strategy for the synthesis of itaconate esters.

The results of three catalysts reused on the preparation of dimethyl itaconate. Conversion of itaconic acid using different solid acid as catalyst (a: La3+∼SO42−/TiO2–SiO2; c: La3+∼SO42−/TiO2; e: SO42−/TiO2); yield of dimethyl itaconate using different solid acid as catalyst (b: La3+∼SO42−/TiO2–SiO2; d: La3+∼SO42−/TiO2; f: SO42−/TiO2); molar ratio of Ti/Si = 25:1, concentration of La3+ = 0.07 mol/L, all solid catalysts were calcined at 500 °C. Reaction conditions: 4 wt.% of catalyst based on all reactants, itaconic acid 0.1 mol, molar ratio of methanol/itaconate acid = 10/1, and reaction for 6 h at 120 °C in 100 mL autoclave.Figure optionsDownload high-quality image (76 K)Download as PowerPoint slideHighlights
► La3+∼SO42−/TiO2–SiO2 was of excellent catalytic activity and stability.
► The co-promotion of Si and La led to high catalytic activity of La3+∼SO42−/TiO2–SiO2.
► La3+∼SO42−/TiO2–SiO2 is practical in the esterification of itaconic acid.