Kinetics, Product Evolution, and Mechanism for the Pyrolysis of Typical Plastic Waste

Abstract

This research investigates the kinetic, product evolution, mechanism of polyethylene (PE), polypropylene (PP), and a simulated mixture of plastic waste (SMP) via TGA/DSC−MS and Py-GC−MS. The pyrolysis reactions were predominantly endothermic, and the main degradation stage of PE, PP, and SMP ranged from 389.85 to 502.17 °C, from 374.91 to 495.15 °C, and from 368.30 to 496.29 °C, respectively. The kinetic results showed that polyolefin pyrolysis was identified to be the geometrical contraction models with apparent activation energies of 224.31−235.32 kJ mol −1 for PE and 199.00−207.66 kJ mol −1 for PP, respectively. The SMP pyrolysis follows the first-order reaction models, and its apparent activation energy was 185.29−199.54 kJ mol −1 . Polyolefin pyrolysis products only contain C 4 −C 35 paraffin with linear alkenes for PE and branch or cyclic alkenes for PP. The large amounts of benzene radicals in the pyrolysis of SMP tended to form aromatics. The pyrolysis behavior and product formation mechanism of the plastic waste could make available practical implications for the reactor design and parameter optimization.

Thermal Stability of Polycaprolactone Grafted Densely with Maleic Anhydride Analysed Using the Coats–Redfern Equation

“…These models and results indicate the pyrolysis of the PCL-g-MA structure so that the positions of MA grafted on a PCL main chain are more likely to undergo random scissions first due to the weak bonding from C-C structure to produce shorter monomers and generate free radicals of the polymer. After that, the PCL structure starts to degrade by random scissions via cis-elimination reactions and progresses with cyclic rupture via intramolecular transesterification at over 300 °C [ 74 , 81 ]. The pyrolysis results confirmed the same tendency as suggested by the TGA and DTA results in Figure 6 .…”

Non-thermal Plasma-Assisted Deconstruction of High-Density Polyethylene to Hydrogen and Light Hydrocarbons over Hollow ZSM-5 Microspheres

“…We therefore conclude that both plasma and the catalyst play an important role in the cracking of volatiles originating from the thermal decomposition zone. It is well accepted that thermal deconstruction of HDPE occurs by random chain scission involving initiation of radicals (carbocation formation), propagation with hydrogen transfer, and finally termination via recombination of free radicals to form various hydrocarbons. − The dissociation energy of the weakest C–C bond at the 4th and onward carbons is above 2.9 eV, which is lower than that of the terminal C–C bond, namely, above 3.4 eV . Therefore, the hydrocarbon chain is fragmented from an edge resulting in long hydrocarbons dominating in the thermal deconstruction, as also evidenced in Figure and Figure S9.…”

Pyrolysis of Polyolefins into Chemicals Using Low-Cost Natural Zeolites

“…The type of zeolites drives the product selectivity, such as H-ZSM-5, which has a 3-dimensional pore with shape selectivity favored 18% naphthene and 77% aromatic products such as benzene, toluene, xylene [39]. [7] was found 2,4-Dimethyl-1-heptene as the highest component in the thermal pyrolysis of PP. They proposed the mechanism for thermal pyrolysis of PE and PP.…”

“…Investigate the effect of catalysts on the oil impurities and pretreatment of the oil by adsorption technique using porous materials to eliminate the impurities also important to be performed. Gas product of PE and PP thermal pyrolysis components were reported mainly C 2 H 6 , C 3 H 8 , C 2 H 4, and C 3 H 6, with ole ns as the highest elements produced [7,10]. Ethylene and propylene could be utilized as raw materials for polyethylene and propylene.…”

“…Pyrolysis of polyole ns such as PE and PP could be carried out through the thermal and catalytic processes [6]. Thermal pyrolysis of PE produced mostly C 4 − C 35 para n with linear alkenes, while thermal pyrolysis of PP produced branch or cyclic alkenes [7].…”