The Study Of PET Degradation Catalyzed By Metal Task Special Ionic Liquids

Polyethylene terephthalate（PET） is a kind of excellent linear polyester material, itis applied in many fields, such as beverage bottle, fibre, thin film and so on. However，due to the rapid growth of PET industry and the wide appliance of PET product，lots ofPET waste is produced. The conventional method of degradation of PET need salargequantity of concentrated acid or alkali, which can not be used and pollutionphenomenon are very serious. Ionic liquid is a kind of environment friendly solvent andcatalyst which has a good prospect of appliance, property of non-volatile, stability andrecyclable. It can dissolve or degrade many maeromoleular material.20different kinds of metal task specific ionic liquids were synthesized. Degradationof PET in metal task special ionic liquids was investigated. Glycolysis in glycol andaminolysis in ethanolamines of PET were investigated. The degradation product andcatalyst were characterized by FT-IR、¹H NMR、DSC、ESI.The degradation product of the glycolysis of PET were characterized by FT-IR,¹HNMR, DSC, the results indiciated that was bis（2-hydroxyethyl） terephthalate（BHET）. Indifferent kinds of metal task special ionic liquids, the effect of glycolysis of PETcatalyzed by l-butyl-3-methylimidazolium zinc chlorine ionic liquid （[Bmim]ZnCl₃）was excellent. The obtained optimum reaction conditions were m（[Bmim]ZnCl₃）:m（PET）=1:100, m（glycol）:m（PET）=10:1, reaction temperature at180℃, reaction timeat5h. Under above conditions, the conversion of PET and the yield of bis（2-hydroxyethyl） terephthalate（BHET） were97.86%and83.31%respectively. Despiteionic liquid reused for six times, the degradation of PET and yield of BHET weredecrease rarely slight．The effects of kinds of ionic liquids, reaction temperature,reaction time, dosages of catalyst on glycolysis results were examined. It was showedthat [Bmim]ZnCl₃was of better performance as a catalyst than ZnCl2. The effect oflewis acidic on glycolysis of PET was studied, found that the lewis acidic of ionic liquidcan enhanced performance in glycolysis of PET. The proposed mechanism indicates thatthe synergic effect of the cation and anion in metal task specific ionic liquidsaccomplished degradation of PET by froming tetrahedral intermediate. Moreover the glycolysis temperature and catalyst concentration are critical facts in the glycolysis ofPET.The aminolysis of PET，when was chosen a ethanolamine as solvent，wasinvestigated．It was shown that the excellent reaction conditions were specialized asfollows: l-pentyl-3-methylimidazolium zinc chlorine（[Pmim]ZnCl₃） as catalyst0.01mmol, m（PET）:m（ethanolamine）=1:6, reaction temperature at90℃, reaction timefor3hours. Under this condition, PET can be absolutely degraded. The recycle ratio ofbis（2-hydroxy ethylene）terephthalamide （BHETA） as the product characterized byFT-IR,¹H NMR, DSC can be over83.49％． Ionic liquid reused for three times, theconversion of PET and yield of BHETA were decrease distinctly. Zinc ionic liquid hasbetter performance in aminolysis of PET than other metal task special ionic liquids. Themechanism indicates that he amine group of ethanolamine attacks on the ester linkageof PET to accomplished degradation of PET. Because the nitrogen is more electronegative than oxygen. The amine group of ethanolamine attacks on the ester linkage ofPET much easier than hydroxyl group.