Hydrolysis of poly(ethylene terephthalate) to recover terephthalic acid in ionic liquids

The hydrolysis of poly(ethylene terephthalate)(PET) to recover terephthalic acid(TPA) was studied by using ionic liquids 1-butyl-3-methylimidazolium chloride() as solvent and 1-methyl-3-(3-sulfopropyl)-imidazolium hydrogen sulfate([HSO3-pmim]) as catalyst.The effects of PET granule size,dosages of catalyst and solvent,temperature and time on the hydrolysis results were investigated.The results show that PET granule size and temperature are of significant effects on the hydrolysis results.Under the optimum conditions of 170 ℃,m(PET)∶m(H2O)∶m()∶m([HSO3-pmim])=3∶4∶6∶0.6 and 4.5 h,the PET conversion rate and TPA yield are more than 99% and more than 88% respectively.The reusability of ionic liquids was also investigated.It shows that there is no obvious decrease for PET conversion rate and TPA yield after the ionic liquid is reused for 8 times.