Conversion Of Glycerol Catalyzed By Poly(ionic Liquid)s Catalysts

As a kind of renewable energy,Biodiesel has a good application prospect,but a large amount of glycerol is accumulated during the production process.If this part of glycerol can be used,the production cost of biodiesel can be reduced to a great extent.In this paper,a new kind of“Green”catalyst named Poly?ionic liquid?s?PILs?was synthesized and was used in the high value-added conversion of glycerol produced from the Biodiesel.The PILs-A solid acidic catalyst and and PILs-B solid basic catalyst were synthesized by a two-steps method:functionalization after free radical polymerization.The synthesis method is simple and easy operated.The catalysts were characterized by FT-IR,XPS,EA,SEM,TEM,TGA,potentiometric titration and Hammett indicator.Finally,they were used to catalyze the synthesis of glycerol acetate and glycerol carbonate respectively.The PILs solid acid catalyst has good catalyst effect in the acetylation of glycerol and acetic acid.The precursor was synthesised by polymerization of sulfonic imidazole and[1,1-?Butane-1,4-diyl?-bis?3-vinylimidazolium?]Br₂,then it was functionalized by H₂SO₄ to obtain the PILs-A.PILs-A has good chemical stability and high decomposition temperature.Sponge like structure stacked by nanosized polymer particles was observed by electron microscope.PILs-A has a proton acid concentration of 3.13 mmol/g and exhibits good catalytic selectivity in the acetylation of glycerol.The glycerol conversion rate reached to 98.2%and the total selectivity of diacetate and triacetate was up to 88.4%under the optimal conditions?acetic acid and glycerol as the molar ratio of 6,temperature 120°C,catalyst dosage 4 wt%,reaction time 4 h?,which was better than that of commercial resin under the same reaction conditions.The PILs-A solid acid catalyst has good hydrothermal stability.It was easily to be separated and can be reused for 4 times without deactivation.The PILs solid base catalyst has good catalyst effect in the transesterificiton of glycerol and dimethyl-carbonate.The precursor was synthesised by polymerization of amino imidazole and divinylbenzene,then it was functionalized by NaOH to obtain PILs-B?1?,PILs?2?and PILs?3?.The PILs-B?3?has good chemical stability,thermal stability and multi-layer structure.PILs-B?3?has a pKa value of 11.2¹5 and has an appropriate base strength.It exhibits good catalytic activity in the transesterification of glycerol.The yield of glycerol carbonate was 90.2%and no by-product was produced under the optimal conditions?dimethyl carbonate and glycerol as the molar ratio of 3.5,temperature 75°C,catalyst dosage 8 wt%,reaction time 3 h?.The PILs-B?3?solid basic catalyst was easily to be separated and can be reused for 4 times without deactivation.