Preparation of biodiesel oil from cottonseed oil catalyzed by ionic liquids

Preparation of biodiesel oil from cottonseed oil catalyzed by B-acidic ionic liquids was studied. Several water-stable B-acidic ionic liquids with an alkane sulfonic acid group were synthesized and showed good catalytic activity in transesterification of cottonseed oil to biodiesel oil. Catalytic activity of each ionic liquid depended upon the type of nitrogen containing group and length of carbon chain. The ionic liquid 1-(4-sulfonic acid) butyl-pyridinium hydrosulfate exhibited the best catalytic activity to transesterification. Effects of ionic liquids dosage, mole ratio of methanol/cottonseed oil and reaction temperature on transesterification and stability of ionic liquids were examined. Under optimal transesterification conditions: n(methanol)/n(cottonseed oil)/n(ionic liquids) 12:1:0.057, 170°C, and 5 hr, mass fraction of fatty acid methyl ester could reach 92%. The ionic liquids were stable and could be reused.