PANF supported polymeric ionic liquids: Amphiphilic microenvironment for efficient preparation of biodiesel

Efficient and green production is extremely essential to the development of society and environment, and sup-ported polymeric ionic liquids as heterogeneous catalysts are the current research hotspot for chemists. In this study, imidazolium ionic liquids were supported on modified polyacrylonitrile fiber (PANF) by reversible addition fragmentation chain transfer (RAFT) polymerization, and a series of fiber-supported basic catalysts (PANF@VIm-nX) were obtained by ion exchange with different anions. The modified fibers were characterized by FT-IR, XRD, TGA, SEM, 13C CP-MAS NMR and ICP-MS. The results show that the modified fibers are successful and the catalysts have sufficient active sites and mechanical strength to meet the application requirements. Several supported poly(ionic liquid)s catalysts were used to promote the transesterification of methanol and soybean oil to produce biodiesel. The effects of ionic liquids with different structures on the reaction yield were sufficiently investigated. The anions of ionic liquids and the length of hydrophobic alkyl chains have synergistic effects on the catalytic performance of the catalyst. The fiber catalyst (PANF@VIm-8OMe) with 8 carbon alkyl chains and OMe anion showed the optimal catalytic efficiency. The yield of biodiesel was as high as 95.4 % within 6 h with a catalyst dosage of 4 wt% and a methanol to oil ratio of 30:1 at 60 celcius. In addition, the fiber catalyst had excellent stability and durability, which could be recycled more than 6 times. Finally, the fiber could be twined on the stirring impeller of the reactor, indicating its potential industrial application prospect.