New imidazole-type acidic ionic liquid polymer for biodiesel synthesis from vegetable oil

• New imidazole-type acidic ionic liquid polymer was synthesized as acidic catalyst.
• The PIL showed high activities, high hydrophobic surface and high stability.
• The PIL showed high capacity of preparation of biodiesel.
• The PIL showed high activities and stability after recycling of preparation of biodiesel.

The new imidazole-type solid acidic ionic liquid polymer (PIL) has been synthesized through the copolymerization of acidic ionic liquid oligomers and divinylbenzene (DVB). Its catalytic activities are investigated through the biodiesel synthesis from vegetable oil. This catalyst showed good catalytic and reusable performance under mild conditions and without any additional organic solvent. The PIL is very efficient with the conversion reaching 94.2% at 343 K for 4 h with the solvent–oil ratio of 1:1. The PIL could be reused for four times maintaining the stability. Therefore, an efficient and environmentally friendly catalyst is provided for the synthesis of biodiesel from vegetable oils. The catalyst also has the advantages of high activities and high stability.