Enhanced generation of light olefins and aromatic-enriched oil via catalytic pyrolysis of instant waste plastic rice containers over activated biochar

The large amount of plastic waste has significantly affected human life and the environment, necessitating the development of appropriate alternatives. In this study, we explore the generation of light olefins and aromatic-enriched oil via catalytic pyrolysis of waste rice containers using activated biochar catalysts. Chemical activation significantly alters the physicochemical properties of biochar and enhances its catalytic performance. In particular, compared to other catalysts, KOH-treated biochar (AC-K) showed superior activity, maximizing the light olefins and C₆–C₈ aromatics (35.7 wt% and 73.0 %) while suppressing the waxy material. However, using AC-Z exhibited a greater oil yield compared to AC-K (42.2 and 35.5 wt%, respectively). This phenomenon can be correlated with the balanced coexistence of weak-moderate and strong acidic sites, as well as the enhanced surface area, total pore volume, and porosity of the employed catalyst. Meanwhile, the abundant surface functional groups (e.g., C[dbnd]O) of AC-K enhanced the hydrogen transfer reactions of alkenes. The promoted hydrogen release and reception on the surface of AC-K played a crucial role in facilitating the transformation of n-alkanes and n-alkenes into aromatics. Furthermore, the increase in temperature from 450 to 550 °C positively affected the simultaneous generation of light olefins (from 19.5 to 32.4 wt%) and C₆–C₈ aromatics (from 7.3 % to 39.0 %). This correlates with the cleavage of long-chain olefins into smaller molecules at elevated temperatures. This study addresses concerns regarding the immense production of waste rice containers by converting them into value-added substances using low-cost and environmentally friendly waste-derived activated biochar.