A kinetic approach to the temperature-programmed pyrolysis of low- and high-density polyethylene in a fixed bed reactor: determination of kinetic parameters for the evolution of n-paraffins and 1-olefins

The thermal degradation of both low-density polyethylene (LDPE) and high-density polyethylene (HDPE) have been investigated under non-isothermal conditions. The weight loss data have been analyzed by Flynn and Wall methods. The activation energies for overall degradation of LDPE and HDPE were determined. In addition, the recovery of carbon as 1-olefins and n-paraffins was determined by temperature-programmed pyrolysis of polyethylene. A fixed bed reactor under argon flow was used to pyrolyze small samples of LDPE and HDPE. A special gas-phase sampling technique was used to determine the composition of products eluted from the reactor as a function of temperature and time. Hydrocarbon evolution data have been analyzed by Coats–Redfern and Chen–Nuttall combinations. It must be emphasized that the evaluation of temperature-programmed pyrolysis data by combined use of Coats–Redfern and Chen–Nuttall methods provide satisfactory mathematical approaches to obtain kinetic parameters for 1-olefin and n-paraffins formation from degradation of polyethylene. Using this method, it is possible to identify every stage of pyrolysis and derive values for kinetic parameters.