Preparation Of Diacid Ionic Liquid Catalysis System And Their Application For Degradation Of PET

The amount of plastic that humans produce and use every year is far more than nature can handle.Polyethylene terephthalate(PET)is widely used in packaging,clothing,machinery,electronics,automotive and other industries because of its excellent comprehensive performance.However,due to the huge amount of waste after the use of PET polyester,and the strong resistance to atmospheric and microbial reagents,its natural decomposition cycle in more than 48 years,so the effective degradation of PET waste has become one of the problems that need to be solved in today's society.Ionic liquids are widely used in catalysis,extraction,material preparation and synthesis because of their unique properties.This topic by changing the length and the stability of the ionic compound molecular design and preparation of a series of Br(?)nsted-Lewis dual acidic ionic liquid catalyst,and applied to the alcoholysis reaction of polyethylene terephthalate,by alcoholysis rate and product bis(2-hydroxyethyl)terephthalate(BHET)yield as the evaluation index,at double acid ionic liquid catalyst performance of the degradation of PET.It is expected that this kind of diacid ionic liquid catalyst will make a technological breakthrough in future industrial catalytic polyester degradation projects.The first type is 1,3 propane sulfonate lactone and pyridine as raw materials to prepare the N-3-sulfonic acid group-propy pyridine chloride salt system.The experimental data show that the Lewis acid salt selected is the optimal Fe Cl₃,the optimal process is the reaction temperature 210?,the reaction time 8h,and the optimal catalyst amount is 2.7%.Under the optimal reaction conditions,the PET alcoholysis rate reached 97.6%and the yield of BHET reached 94.2%.Under the condition of reaction,the catalyst could still maintain high catalytic activity after 6 times of recycling.The second type is 1,4 butane sulfonate lactone and N-methyl imidazole as raw materials to prepare 1-butyl sulfonate-3-methyl imidazole chloride salt system.Experimental data show that the Lewis acid salt with the best effect is Fe Cl₃.The best process is the reaction temperature of 220?,the reaction time of 10h,and the best catalyst dosage of 2.7%.Under the optimal reaction conditions,the PET alcoholysis rate and BHET yield reached95.3%and 93.1%respectively.Under the condition of the second reaction,the catalyst could still maintain high catalytic activity after being reused for 6 times.The third type of system is the 1-propylsulfonate-3-methylimidazole chloride system,which degrades polyethylene terephthalate with ethylene glycol.This system has the best catalytic effect,and the Lewis acid salt is selected as Fe Cl₃.The best process is the reaction temperature of 190?,the reaction time of 6h,and the best catalyst dosage of 2.7%.Under the optimal reaction conditions,the PET alcoholysis rate reached 98.7%and the yield of BHET reached 95.5%.Under the condition of the second reaction,the catalyst could be reused for 6 times and still maintain high catalytic activity.By changing the structure and length of the molecular chain,the Br(?)nsted-Lewis biacid site distance could be adjusted to demonstrate better synergistic effect during the catalytic process.Orthogonal tests were conducted to explore the effects of interaction of reaction time,reaction temperature and catalyst dosage on the PET alcoholysis rate and the yield of BHET.The results showed that the effect of three factors on the PET alcoholysis rate was as follows:reaction time>catalyst dosage>action temperature,and the effect on the yield of BHET was as follows:the amount of catalyst>reaction time>action temperature,that is,the best reaction process conditions for PET alcoholysis rate is A₂B₃C_2,that is,the reaction temperature is 190?,the reaction time is 7h,the amount of catalyst is 2.7%dosage,for BHET yield is A₂B₃C₃,that is,the reaction temperature is 190?,the reaction time is 7h,the amount of catalyst is 3.3%dosage is the best catalytic process.At the same time,the mechanism of alcoholysis reaction was revealed by further product characterization.By comparing the catalytic performance of the traditional catalyst with that of the diacid ionic liquid catalyst,it is proved that the catalytic performance of the diacid ionic liquid catalyst is significantly improved compared with that of the traditional catalyst and the single acid catalyst.The ethylene glycol degradation experiment of bottle grade polyester was carried out.Under the condition of 190o C temperature,6h reaction time and 2.7%of the catalyst,the PET alcoholysis rate of the bottle grade polyester ethylene glycol degradation reaction catalyzed by the[HO₃S-(CH₂)₃-mim]Cl-Fe Cl₃catalyst reached 93.40%,and the yield of BHET reached 91.52%.