Hydrolysis Of PET Using Quaternary Heteropoly Acid Ionic Liquid As Catalyst And Kinetic Studies

Waste PET (polyethylene terephthalate), one of the excellent polymer materials, is widely used in packaging materials, beverage bottles, tape, home medical equipment, and other fields. With increasing demand for PET, a large amount of PET waste was poured into the environment. The traditional way of PET degradation would generate a lot of inorganic salts, and consume large amounts of concentrated acid concentrated alkali, corrosion of equipment, causing environmental pollution and difficulties in catalyst’s recycle. As a kind of green solvents, Ionic liquids are environmentally friendly solvent with favorable prospects whose structure is adjustable, and have excellent solubility and catalytic properties in the polymer materials, and recyclable catalyst.This paper synthesized three heteropolyacid quaternary ammonium ionic liquids: [(CH3)3NC12H25]3PW12040、[(CH3)3NC16H33]3PW12040、[(CH3)3NC18H37]3PW12O40and then we investigated its effects on PET hydrolysis, then factors such as the reaction time, reaction temperature, amount of catalyst, the solvent amount of water, material ratio, PET size and the kind of quaternary ammonium cations, were optimized to give optimum hydrolysis process. The results showed that:cetyl trimethyl ammonium heteropolyacid were more effective than dodecane and octadecane in hydrolysis of PET, the reaction temperature was 190℃, reaction time 12h, polyester size 3 mm×3mm, m (PET):m (H2O)= 1:15, the weight of catalyst 0.3g, which could achieve 100 percent conversion of PET and more than 90% terephthalic acid yield; the effect of hydrolysis catalyst was much better than water hydrolysis through blank control test; the catalyst reused four times and the yield of terephthalic acid, conversion of PET remained unchanged and the structure of the catalyst was stable.We also investigated four temperature 160℃,170℃,180℃,190℃, under different reaction time in depolymerization process. Hydrolysis kinetics PET model was optimized, then established the reaction rate equation to calculate the apparent rate constant and hydrolysis reaction activation energy and clear mechanism of the hydrolysis reaction-Results indicated that:in the presence of a catalyst, energy for the hydrolysis reaction PET was 25.67 KJ/mol, significantly lower than energy of other degradation methods. In one word, the catalyst promote the progress of the reaction.