Pyrolysis kinetic modelling of abundant plastic waste (PET) and in-situ emission monitoring

Abstract

Background: Recycling the ever-increasing plastic waste has become an urgent global concern. One of the most convenient methods for plastic recycling is pyrolysis, owing to its environmentally friendly nature and its intrinsic properties. Understanding the pyrolysis process and the degradation mechanism is crucial for scale-up and reactor design. Therefore, we studied kinetic modelling of the pyrolysis process for one of the most common plastics, polyethylene terephthalate (PET). The focus was to better understand and predict PET pyrolysis when transitioning to a low carbon economy and adhering to environmental and governmental legislation. This work aims at presenting for the first time, the kinetic triplet (activation energy, pre-exponential constant, and reaction rate) for PET pyrolysis using the differential iso-conversional method. This is coupled with the in-situ online tracking of the gaseous emissions using mass spectrometry. Results: The differential iso-conversional method showed activation energy (E a) values of 165-195 kJ mol −1 , R 2 = 0.99659. While the ASTM-E698 method showed 165.6 kJ mol −1 and integral methods such as Flynn-Wall and Ozawa (FWO) (166-180 kJ mol −1). The in-situ Mass Spectrometry results showed the gaseous pyrolysis emissions, which are C 1 hydrocarbons and H-O-C=O along with C 2 hydrocarbons, C 5-C 6 hydrocarbons, acetaldehyde, the fragment of O-CH=CH 2 , hydrogen, and water. Conclusions: From the obtained results herein, thermal predictions (isothermal, non-isothermal and step-based heating) were determined based on the kinetic parameters. They can be used at numerous scale with a high level of accuracy compared with the literature.

Influence of the Feedstock on the Process Parameters, Product Composition and Pilot-Scale Cracking of Plastics

“…Although some product was collected, a yield of only about 52% was obtained. Osman et al have reported that, depending on process conditions (like heat rate), PET pyrolysis can already start below 350 °C [ 49 ]. PET pyrolysis can result in many different products, including terephthalic acid, which is suspected to be a reason for piping clogging [ 50 , 51 ].…”

Kinetics modeling, thermodynamics and thermal performance assessments of pyrolytic decomposition of Moringa oleifera husk and Delonix regia pod

“…The ICTAC recommendation on kinetic data gathering and processing were largely followed with at least an order of magnitude difference between the least and the highest heating rate. Furthermore, to ensure reproducibility and accuracy of the TGA data the heating rate at 20 °C/min was repeated 18 .…”

“…This obviates the need for the inclusion of a decomposition model in the rate equation and thus, relatively, simplifies the determination of the kinetic parameters. However, it requires multiple TGA measurements at a minimum of four different heating rates 18 . Vyazovkin et al 19 recommended that the difference between the lowest and highest heating rate should be at least an order of magnitude—starting with a very low heating rate (e.g., 2.5 °C/min).…”

Characterization and kinetic modeling for pyrolytic conversion of cotton stalks

“…7 The main model-free methods discussed in the literature include ASTM-E698, which is a model-free noniso-conversional approach, the Flynn-Wall and Ozawa (FWO), and Kissinger-Akahira-Sunrose (KAS), which are categorized as integral iso-conversional methods, and the Friedman method which is a differential iso-conversional method. [6][7][8][9][10][11][12][13] The main issue related to the ASTM-E698 method is that a single activation energy value is calculated, not considering reaction progress in such a complex thermochemical process. It is more suitable for a single-step reaction.…”