(680c) Kinetic Modelling and Measurement of Catalyst Deactivation for the Catalytic Co-Pyrolysis of PP and PET with HZSM-5

The pyrolysis of polypropylene (PP), as well as other polyolefins, is a method for the conversion of plastic waste to valuable fuels and chemicals. The temperature needed for PP pyrolysis can be decreased with the addition of HZSM-5 zeolite catalyst. Polyethylene terephthalate (PET) can be inherently mixed with PP and other polyolefins in multilayer packaging. PET is known to cause issues with catalyst deactivation, as it results in a high coke yields. Thermogravimetric analysis (TGA) is a tool which can be used to determine the degradation profiles of polymers during catalytic pyrolysis. In previous TGA work, it was observed that during the catalytic co-pyrolysis of LDPE and PET with HZSM-5, that PET was delaying the degradation of LDPE. These interactions between the two polymers were able to be modelled using an n^th-order lumped reaction scheme.

The reaction scheme used in our previous study was used to model experiments conducted with a TGA for the catalytic co-pyrolysis of PP and PET with HZSM-5. The number of experiments fitted to the kinetic model increased from 6 in our previous work to 26 in this work by varying more the catalyst:feedstock ratio, heating rate, and the PP:PET ratio, ultimately leading to a more robust set of kinetic parameters. Certain trends observed experimentally, such as an increased solid residual yield for higher catalyst:feedstock ratios, were also observed in the model. Used catalysts were characterized by pyridine temperature programmed desorption (Pyr-TPD), and a loss of acidity up to ca. 50% was observed, depending on the PP:PET ratio used. Subsequent pyrolysis experiments conducted with used catalysts showed significant changes in maximum degradation temperature, up to ca. 200K. Building a robust model which is also including catalyst deactivation phenomena, will allow us to better understand how PET can be included as a pyrolysis feedstock alongside polyolefins.