Taguchi method for optimization of reaction conditions in microwave glycolysis of waste PET

With ever increase in the consumption of bottled beverages; waste polyethylene terephthalate (wPET) bottles are rapidly emerging as a major constituent of urban waste. Amongst the various chemical techniques in vogue for recycling of wPET, glycolysis shows distinct advantage due to its ability to synthesize value added products. The current work was carried with the aim of optimizing the reaction conditions for microwave-induced catalytic glycolysis of wPET. As a first step, the effect of various cations like Zn, Ti, Fe and Co ions is reported which showed that zinc ions exhibit higher efficiency. In the second step the effect of variation in the loading of ethylene glycol (EG) glycolyzing agent showed that above a certain limit, the yield of bis-hydroxyethyl terephthalate monomer (BHET) reduced. In order to find the optimum ratio of reactants (wPET: EG) and weight of catalyst, a Taguchi design of experiments was formulated and experiments were carried. Our results show that at an optimal condition of 1:3 wPET: EG with a 1 wt% of zinc acetate gives a 65% molar yield of BHET product within 30 min.