Four novel Brønsted acidic ionic liquids were synthesized and characterized by FT-IR, 1H NMR and 13C
NMR for the first time. Their catalytic activities for the synthesis of biodiesel via the transesterification
of coconut oil and methanol were investigated. Among all the tested ionic liquids, [CyN1,1PrSO3H][Tos]
performed best, and its catalytic performance was systematically explored by orthogonal experiment
based on the single factor experiment. The results show that the order of factors on the yield of biodiesel
is reaction temperature, molar ratio of methanol/oil, catalyst dosage and reaction time. The maximum
biodiesel yield of 98.7% was obtained under the optimal reaction conditions. There was no significant
decrease of its catalytic activity after being reused for five successive cycles. The refined biodiesel meets
the European biodiesel standard (EN 14214).