Supported Ionic Liquid Acid Catalysts For Biodiesel Production

For biodiesel production,traditional homogeneous acid catalysts are hard to reuse and can be harmful to the environment,and heterogeneous catalysts are low efficiency.In this paper,environmentally friendly acid ionic liquids that have catalytic performance for biodiesel production were selected to conduct the immobilization processes.And two types of immobilized ionic liquids for rapid esterification of palmitic acid were prepared through covalent bond method and polymerization method.The GC internal standard analysis approach for long-chain fatty acid esters and the detailed calculation formulas for esterification or transesterification yields were developed.To select ionic liquids for immobilization,thiol and double bond functionalized ionic liquids 1-(3-sulfonate)-propyl-3-allylimidazolium hydrogen sulfate,hydrogen trifluoromethanesulfonate and dihydrogen phosphotungstate.And the three ionic liquids were characterized by NMR and applied to transesterification of palm oil.Among the three ionic liquids,1-(3-sulfonate)-propyl-3-allylimidazolium hydrogen sulfate presented the highest catalytic activity and gave a 92.9% yield after 8 h,when the ambient temperature,methanol to oil molar ratio and catalyst dosage were 100 oC,9 and 10%wt respectively.Besides,the three ionic liquids also had the capacity to catalyze esterification of palmitic acid effectively with yields of 98%.Therefore,the three ionic liquids were supported on SBA-15 through thiol-ene reaction for esterification,and the supported processes were optimized.The supported ionic liquids were characterized by SEM,FTIR,NMR and BET.And then,the 1-(3-sulfonate)-propyl-3-allylimidazolium phosphotungstate supported ionic liquid was proved to have the highest catalytic performance which gave a 92.9% esterification yield after 8 h when the reaction temperature,methanol to acid molar ratio and catalyst dosage were 65 oC,9 and 15%wt respectively.And the supported ionic liquid could be reused for 5 times.Finally,three poly(ionic liquid)s were prepared by the reaction between poly(1-(4-sulfonate)-butyl-3-vinylimidazolium)and three acids which were sulphuric acid,trifluoromethanesulfonic acid and phosphotungstic acid.And the poly(ionic liquid)s were characterized by SEM,FTIR,NMR and BET.For esterification of palmitic acid,phosphotungstic acid based poly(ionic liquid)presented the highest catalytic performance under low catalyst dosage and the catalyst could be reused for more than 5 times.The esterification yield could reach 94.1% after 8 h while the reaction temperature,methanol to acid molar ratio and catalyst dosage were 65 oC,18 and 3%wt respectively.