Study On Synthesis Of Dioctyl Terephthalate By Waste Polyethylene Terephthalate

The weight of waster PET is increasing quickly with the rapid development of polyester industry. The polyester waste recycling and reuse have great significance for easing world oil crisis and reduce waste pollution to the environment. Chemical method was one of advantaged ways to recycling the waste polyester. In this paper, the waster PET as material to synthesize dioctyl terephthalate((DOTP).The influences of synthesis conditions such as amount of catalyst, temperature, reaction time and the ratio of raw materials on waste polyester degradation and DOTP yield rate were studied. By IR and 1H-NMR spectroscopy to identify the right products, and high performance liquid chromatography(HPLC) under different reaction conditions on the composition of the products.The reaction process is transesterification process. With the catalyzer presence, long-chain molecules of PET was fracture, ethylene glycol was replaced by 2-ethylhexanol to preparative DOTP;Tetrabutyl titanate as a homogeneous catalyst has the ideal activity such as the amount is less, polyester conversion rate is high and the high-yield of DOTP, easily removed from the reaction system after the reaction was finished; Under the condition of n(2-EH)/n(PET)=4, m(TBT)/m(PET)=0.5%, reaction time was 6-8h, the yield of DOTP was above 83%. The acid value under 0.02mgKOH/g and the color within 100; Founded that the dye was the main factors to restrict polyester-cloth effective use, because the oil-soluble dye difficult to remove, how effective use of waste polyester with colors need to further studied; The reaction was two phases: non-homogeneous and homogeneous. In the initial phase, solid-liquid mass transfer coefficient is the main factor on the reaction rate, N-methyl-2-pyrrolidone can accelerate the dissolution of polyester film and prompted the reaction into homogeneous process. In the homogeneous phase, proportion and catalyzer become the main factor on the reaction rate.