Seven kinds of ionic liquids

N-methyl-imidazolium bisulfate（［Hmim］HSO4)

1-butyl-3-methyl imidazole phosphate（［Bmim］H2PO4)

1-butyl-3-methyl imidazole bisulfate(［Bmim］HSO4)

1-butyl-3-methyl imidazole tetrafluoroborate（［Bmim］BF4)

N-butyl-pyridine bisulfate（［Bpy］HSO4)

N-butyl-pyridine phosphate（［Bpy］H2PO4)

N-ethyl-pyridine bisulfate（［Epy］HSO4)

were designed and synthesized.The synthesis of dimethyl succinate catalyzed by ionic liquids was studied for the first time.It was shown that［Epy］HSO4 had the best catalytic performance

and optimal conditions for the synthesis of dimethyl succinate were obtained

succinic acid and methanol molar ratio 1∶3.0

amount of catalyst 5%（g/g)of succinic acid

reaction temperature 70℃ and reaction time 2 h.Under the optimal conditions

the yield of dimethyl succinate was up to 91.83%

esterification rate was 96.32%.The catalyst was recycled 7 times without substantial decrease in activity.Moreover

compared to conventional industrial catalysts

ionic liquid catalyst had the superiority of smaller catalyst dosage

less by-product

mild reaction conditions

high yield

and recycled catalyst usage.Finally

the mechanism of esterification catalyzed by ionic liquids was discussed.