Poly(ionic liquid)s as efficient and recyclable catalysts for methanolysis of PET

The methanolysis of polyethylene terephthalate (PET) was investigated using poly(ionic liquid)s (PILs) synthesized with 1-vinyl-3-ethylimidazole acetates ([VEIm]Ac) and acrylic acid metal salts, and the activities of the PILs were screened. The effects of reaction temperature, reaction time, methanol amount, catalyst amount and PET sources on the methanolysis of PET were investigated using the optimized catalyst PIL-Zn2+. Under the optimal conditions the conversion of PET was 100% and the yield of dimethyl terephthalate (DMT) was 89.1%. In addition, the catalyst has very good applicability for methanolysis of different PET raw materials. More importantly, the PIL-Zn2+ catalyst could be recycled by simple filtration after the reaction, and could be reused six times without significant decrease in PET conversion and DMT yield. The catalysts were analyzed by TGA, FT-IR, XRD and ICP before and after recycling, the results showed no change in the structure of the catalyst, reflecting the good stability of the catalyst. The reaction kinetics of PIL-Zn2+ was first-order with an activation energy of 107.6 kJ/mol. This work mainly provides a way to design efficient, stable and recyclable catalysts for PET methanolysis.