Pyrolysis kinetics and reaction mechanism of representative non-charring polymer waste with micron particle size

Abstract

Pyrolysis is considered as a promising method to dispose polymer waste. To provide guidance for pyrolysis recycling of representative non-charring polymer namely poly(methyl methacrylate) (PMMA) waste with micron particle size, the pyrolysis kinetics and reaction mechanism of micron PMMA waste in nitrogen are studied in the present study. Thermogravimetric analyses at 5, 10, 20, 30 and 40 K/min coupled with two model-free methods including Senum-Yang and advanced Vyazovkin method as well as one model-fitting method namely Coats-Redfern method are employed. Results indicate that the micron PMMA waste pyrolysis may be nominally considered as one-step reaction. The reaction model and mechanism in charge of the micron PMMA waste pyrolysis may be g(α)=1-α-1/2-1 and chemical reaction, respectively. The average values of the activation energy and pre-exponential factor are 243.69 kJ/mol and 1.19 × 1019 min−1, respectively, which are both larger than those of traditional PMMA with particle size in millimeter or larger level. Based upon the one-step reaction model and the obtained kinetic parameters, the predicted thermogravimetric data agree well with the experimental results not only at heating rates of 5, 10 and 20 K/min which are employed to calculate the kinetic parameters, but also at heating rates of 30 and 40 K/min beyond those used to calculate the kinetic parameters.