Dehydrochlorination of polyvinyl chloride and co-pyrolysis with maize cob: Insight into product composition and thermal behaviour

Abstract

Polyvinyl chloride (PVC) waste can be a good candidate as feedstock for co-pyrolysis with biomass. However, the high chlorine content in PVC pyrolysis products constitutes a barrier to their use. One way to eliminate chlorine from PVC is dehydrochlorination. This study explores the co-pyrolysis of maize cob with dehydrochlorinated PVC, focusing on product yields, chlorine distribution, and thermal interactions. Virgin PVC was dehydrochlorinated at 593 K, achieving 99 % chlorine removal, and its thermal behaviour was assessed using thermogravimetric analysis (TGA) coupled with Fourier transform infrared spectroscopy (FT-IR). For the three heating rates studied: 5, 10 and 30 K/min, HCl was the main compound released up to 593 K. Lab-scale co-pyrolysis experiments were conducted in a fixed-bed reactor at 873 K with varying biomass-to-PVC mass ratios. Increasing the PVC content enhanced oil yield and aromatic compound formation, slightly increased char carbon content, and redistributed chlorine predominantly into the oil phase. The gas phase was enriched with hydrocarbons such as methane, ethene, and ethane. The results indicate that dehydrochlorinated PVC alters biomass pyrolysis pathways, promoting deoxygenation reactions and reducing char formation. These findings provide insights into optimizing co-pyrolysis conditions for improved product quality, demonstrating the potential of dehydrochlorinated PVC as a carbon-rich additive for thermochemical biomass conversion.