Kinetic analysis of thermal and catalytic degradation of polymers found in waste electric and electronic equipment

Thermo-chemical recycling of plastics originating in waste electric and electronic equipment (WEEE) is always a challenge due to the production of secondary value-added compounds or energy from obsolete materials. The dominant step for a suitable design of any pyrolysis reactor is to understand the kinetics of thermal degradation of the input materials. Therefore, in this investigation thermal and catalytic degradation of several polymers found in WEEE, such as High-Impact Polystyrene (HIPS), polypropylene (PP), and polycarbonate (PC) as well as PC/MgO and PP/MCM-41 was investigated. The random scission model developed by Sanchez-Jimenez et al., with L = 2 was used for the simulation of the degradation of all systems at several heating rates. The activation energy was estimated using an isoconversional approach. A system of differential equations were set and solved using as an adjustable parameter only the pre-exponential factor. It was found that using the same set of parameters, thermogravimetric data at different heating rates can be simulated very well in the range 0.3 < alpha < 0.9. This observation verified the hypothesis that at this region of degradation the dominant mechanism is that of random scission. Better simulation was obtained at higher heating rates. Using catalysts of variable acidity, it was verified that the activation energy of the catalytic was decreased compared to the conventional thermal degradation.