Synthesis of dioctyl phthalate using acid functionalized ionic liquid as catalyst

Dioctyl phthalate were synthesized by using acid functionalized ionic liquid as catalyst. The results indicated that HSO3-functionalized Brønsted acidic ionic liquids show better catalytic and reusable performance than non-functionalized ionic liquids or the combination of neutral ionic liquids and Brønsted acid. Under the optimum conditions, using 1-methyl-3-(3-sulfopropyl)-imidazolium hydrogen sulfate as catalyst, the conversion of phthalic anhydride was 98%. After easily separated from the products the ionic liquid could be reused 8 times without any disposal, and the conversion of phthalic anhydride was not less than 95%. Therefore, an environmental friendly approach for the synthesis of dioctyl phthalate is provided.