Pyrolytic depolymerization mechanisms for post-consumer plastic wastes

Authors: KOHLI, KIRTIKA - Council Of Scientific And Industrial Research (CSIR); CHANDRASEKARAN, SRIRAAM - University Of Illinois; PRAJAPATI, RAVINDRA - University Of Illinois; KUNWAR, BIDHYA - University Of Illinois; AL-SALEM, SULTAN - Kuwait Institute For Science; Moser, Bryan; Sharma, Brajendra - Bk

Submitted to: Energies
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/15/2022
Publication Date: 11/23/2022
Citation: Kohli, K., Chandrasekaran, S.R., Prajapati, R., Kunwar, B., Al-Salem, S., Moser, B.R., Sharma, B.K. 2022. Pyrolytic depolymerization mechanisms for post-consumer plastic wastes. Energies. 15(23). Article 8821. https://doi.org/10.3390/en15238821.
DOI: https://doi.org/10.3390/en15238821

Interpretive Summary: A large amount of post-consumer plastic along with agricultural plastic ends up in the environment and stays in there for a very long time. This research discussed the use of an analytical technique to study the thermal and catalytic degradation mechanisms of five post-consumer plastic wastes (landfill liners, prescription medicine bottles, packaging materials, and two different industrial plastic wastes). The outcome of this study is to detect the presence of different polymers present in plastic wastes, the impact of catalysts and impurities on the process, and the information can also be used to aid in designing the pyrolysis process on a large scale to convert these plastic wastes into fuels. As a good amount of plastic is used on farms, this information will add value to the thermochemical conversion of biomass and agricultural plastic by increasing utilization of waste plastic in the process and will also provide a way for the farmers to deal with the plastic waste generated on farms.

Technical Abstract: Pyrolysis coupled with gas chromatography-mass spectrometry (py-GC/MS) was used to study the thermal and catalytic degradation mechanisms of five post-consumer plastic wastes. These included landfill liners, prescription medicine bottles, packaging materials, and two different industrial plastic wastes (IPW1 and IPW2). The pyrolysis experiments were conducted at a temperature of 600°C and a residence time of 5 min to study the effect of temperature on catalytic pyrolysis. The degradation product helped to identify the chemical compounds present in the plastic wastes and, with this information, the reaction mechanisms were proposed for each plastic waste studied. The results suggested that prescription medicine bottles, packaging materials, and IPW2 plastic wastes resembled polypropylene, polystyrene, and polyurethane plastic polymers, respectively. The degradation product from both landfill liners and IPW1 plastic waste showed a resemblance to polyethylene; however, different products detected showed that the impurities present in industrial wastes influence the pyrolytic degradation mechanism to a large extent. Results from the catalytic runs showed that the addition of catalysts greatly influences product compositions and has a significant effect on the selectivity of a specific compound.