Catalytic pyrolysis of linear low-density polyethylene using recycled coal ash: Kinetic study and environmental evaluation

Abstract

Catalytic pyrolysis offers a sustainable route to convert plastic wastes into fuel. We investigated the catalytic performance of coal ash (fly and bottom ash) at blending ratio of 5 wt%, and 15 wt% during pyrolysis of linear lowdensity polyethylene (LLDPE). The influence on activation energy and oil was characterized via thermogravimetric analyzer (TGA) and gas chromatography-mass spectrometry (GC-MS). Results have shown that 15 wt% bottom ash exhibited higher catalytic activity. The activation energy estimated by Coats-Redfern method decreased from 458.7 kJ•mol  1 to 437.8 kJ•mol  1 , while the alicyclic hydrocarbon yield increased from 5.97% to 32.09%. This implies that CaO, which is abundant in bottom ash, could promote the conversion of LLDPE. Furthermore, a cradle-to-factory gate life cycle assessment was performed to investigate three scenarios (non-catalytic pyrolysis, 15 wt% fly ash, and 15 wt% bottom ash) of LLDPE conversion strategies via a normalization and weighting approach. It was found that LLDPE pyrolysis with 15 wt% bottom ash also showed the lowest normalized score of 2.83, implying the lowest environmental impact. This work has demonstrated that the recycling of coal ash, particularly bottom ash, as catalysts for LLDPE pyrolysis is effective.

Kinetics Study of Polypropylene Pyrolysis by Non-Isothermal Thermogravimetric Analysis

“…Bu et al (2019) [ 29 ] presented the kinetic parameters for orders 1, 2, and 3. Lai et al (2021) [ 30 ] and Li et al (2022) [ 31 ] used only the first order of CR because it is considered as the main mechanism. Patidar et al (2022) [ 32 ] revealed that the diffusion model was best suited to reflect the degradation process using the CR method.…”

Catalytic Pyrolysis of PET Polymer Using Nonisothermal Thermogravimetric Analysis Data: Kinetics and Artificial Neural Networks Studies

“…They concluded that the low value of the activation energy would help to run experiments at lower temperatures. Lai et al (2021) [ 18 ] examined the performance of coal ash (fly and bottom ash) with different blending ratios for the catalytic pyrolysis of LLDPE. They showed that 15 wt% bottom ash had higher effect on catalytic activity compared to 15 wt% fly ash.…”

Research Progress of Basic Catalyst Used in Catalytic Cracking for Olefin Production and Heavy Oil Utilization

“…67 Subsequently, basic catalyst could promote the beta scission of unstable carbanions and get alkenes and smaller carbanions. 68 And smaller carbanions would proceed with the same cracking reaction as well. 69 Future study about the promotion of beta scission over basic catalyst is necessary, while it is suggested by Fu et al ( 2016) 70 that the presence of alkaline metals could change the electron density of the carbon atom and weaken the C−C bond.…”

“…While the difference is the hydrocarbon molecules after hydrogen abstraction would form carbanions . Subsequently, basic catalyst could promote the beta scission of unstable carbanions and get alkenes and smaller carbanions . And smaller carbanions would proceed with the same cracking reaction as well .…”