2024 AIChE Annual Meeting

(569ai) Effect of Zeolite Desilication on the Catalytic Co-Pyrolysis of PP and PET with HZSM-5

Authors

Okonsky, S., Pennsylvania State University
McAlister, M., Pennsylvania State University
Toraman, H. E., Penn State University
Catalytic pyrolysis of heterogeneous plastic waste is an emerging technology for sustainable chemical production. Zeolite catalysts and their derivatives are used in catalytic pyrolysis due to their ability to lower the reaction temperature and improve the product yield. Polypropylene (PP) and polyethylene terephthalate (PET) can coexist as unsorted or inextricably mixed plastic waste streams. However, PET is a heteroatom-containing polymer and its contribution to catalyst deactivation in catalytic pyrolysis has rendered it an undesirable feedstock, consequently limiting its utilization. Though the effect of zeolite catalyst modification for catalytic pyrolysis of mixed polyolefins or actual plastic wastes has been studied, the effect of catalytic modification of zeolite for co-pyrolysis of PP and PET has not been investigated previously.

This study examined the effect of zeolite desilication on the catalytic co-pyrolysis of PP and PET with HZSM-5 catalyst. Mixtures of PP, PET, with parent or desilicated catalyst (1:1:4 wt ratio) were pyrolyzed with a thermogravimetric analyzer (TGA) and micropyrolyzer. Zeolite desilication increased the total pore volume by 82.5% due to the formation of mesopores. The desilicated catalyst led to a decrease in degradation temperatures for PP and PET observed in the TGA. Micro-pyrolysis experiments showed that the desilicated catalyst led to a 20% increase in the propylene yield compared to the parent catalyst. The propylene yield decreased to a lesser extent for the desilicated catalyst, when catalysts were re-used for a second experiment, indicating enhanced catalyst durability. This work demonstrated that the desilication of HZSM-5 enhances propylene production for the catalytic co-pyrolysis of PP and PET, contributing to the sustainable production of a valuable chemical from heterogeneous plastic wastes.