Preparation of Acidic Ionic Liquids and Their Catalytic Performance in Synthesis of Biobased Poly(ethylene 2,5-furandicarboxylate)
Five acidic ionic liquid catalysts,[DA-2PS][X]2,were prepared,characterized and tested for their chemical structures,Brønsted acidity and thermal properties using a Fourier transform infrared(FTIR)spectrometer,a nuclear magnetic resonance instrument(1H NMR),an ultraviolet(UV-Vis)spectrosmeter,and a thermal gravimetric analyser(TGA).The acidic ionic liquid catalysts were then used to replace conventional metal catalysts to catalyze the direct esterification of 2,5-furanodicarboxylic acid(FDCA)with ethylene glycol(EG)to poly(ethylene 2,5-furandicarboxylate)(PEF),and the effect of the strength of Brønsted acidity on the catalytic performance was discussed,in which the[DA-2PS][HSO4]2 with the strongest Brønsted acidity had the best catalytic performance.The optimal parameters obtained from orthogonal tests are as follows:the catalyst dosage was 0.10%of the molar number of FDCA,the feeding ratio was n(EG)∶n(FDCA)=2∶1,the esterification temperature was 210℃,the poly-condensation temperature was 240℃,and the polycondensation time was 6 h.Experiments were carried out under the optimal conditions process parameters,and the conversion rate of FDCA was 98.1%,the intrinsic viscosity of PEF was 0.63 dL/g,the number average molecular weight of PEF reached 25592.The structural characterization and thermal properties of PEF were tested by FTIR,1H NMR,TGA and differential scanning calorimetry(DSC)analyzer,and the results showed that the synthesized substance is the target product,and it had the comparable thermal properties to those of PEF synthesized by the traditional metal catalysts.
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