Carbon sequestration in carbon nanotube synthesis from polyvinyl chloride-containing plastic: Catalyst deactivation mechanism and anti-chlorine strategies

• Chloride ions have little impact on the carbon products. • Volatiles from PVC pyrolysis deplete the active site of catalyst. • Fe2O3 converts to a stable FeAlO4 spinel upon reduction, protecting the active site. • The catalyst demonstrates increased resistance to volatiles at a lower temperature. Understanding the influence of polyvinyl chloride (PVC) on carbon nanotubes (CNT) production from waste plastics is essential for enhancing the high-value utilization of real plastic waste. Hence, the influence of chlorine (Cl) on plastic catalytic pyrolysis for CNT formation was investigated from the perspective of Cl in the volatile phase and the catalyst phase, aiming to find the potential strategy to mitigate the impact of Cl. The results showed that catalyst reduction effectively converts Fe 2 O 3 into a more stable Fe 2 AlO 4 spinel structure, thereby safeguarding the active Fe site from deactivation. The carbon yield increased from 17 wt% to 25 wt%, in the instance of real plastic with roughly 10 wt% PVC content. And, at a lower catalytic temperature (600 °C), the catalyst also displays increased resistance to hydrogen chloride (HCl) volatiles. Optimal adjustment of pyrolysis and catalytic temperatures can significantly mitigate catalyst deactivation by Cl and produce CNT with a maximum carbon yield of 28 wt%. This work proposes a pioneering anti-chlorine process designed to recover high-value products from plastic waste, advancing carbon sequestration strategies.