Driving Hydrolysis and Acetolysis of Poly(ethylene terephthalate) (PET) by Microwave and Thermal Energy Inputs: A Comparative Study

This study compares microwave and conventional thermal energy inputs for the hydrolysis and acetolysis of both virgin and postconsumer poly(ethylene terephthalate) (PET). Reaction conditions in these experiments range from 200 to 300 °C and from 5 to 90 min. In no instances did the yields of terephthalic acid monomer or incompletely depolymerized PET demonstrate statistically significant or practically significant differences with these two different energy inputs. For fixed reaction conditions, yields of terephthalic acid were comparable from both methods, regardless of whether the reaction medium was water, acetic acid, or a mixture of the two. The visual appearance of the unreacted plastic was likewise the same for microwave and conventional thermal energy inputs when using identical solvents. These results suggest that the bulk fluid temperature is the controlling factor for PET depolymerization in a homogeneous fluid phase of water and/or acetic acid with no added catalyst. The reacting system responds similarly whether the heating is via microwave irradiation or via conduction across the reactor wall.