Enhanced Production of High-Value BTEX Aromatic Hydrocarbons from the Pyrolysis/Nonthermal Plasma/Catalysis of Waste Plastics

The escalating accumulation of waste polypropylene poses a severe environmental challenge, necessitating advanced upcycling technologies to convert this carbon-rich resource into high-value chemical feedstocks. In this study, a two-stage pyrolysis/nonthermal plasma/catalysis reactor was investigated to maximize the production of single-ring aromatic hydrocarbons (benzene, toluene, ethylbenzene, xylene (BTEX)). The synergistic effects of plasma input power, catalyst temperature, and zeolite topology (Y-zeolite vs β-zeolite) on product distribution were systematically evaluated. Furthermore, to enhance aromatization efficiency, β-zeolite was modified with four distinct metal promoters (Ni, Ga, Mo, Zn). The results indicated that optimal conditions of 40 W plasma power and 500 °C catalyst temperature achieved high BTEX yields for both Y-zeolite (∼32.5%) and β-zeolite (∼40.0%), with the latter exhibiting superior shape-selectivity. Among the metal-modified catalysts, the Ga-β-zeolite achieved the highest BTEX yield of 45.6%. This enhanced performance is attributed to a triple synergy: the generation of reactive intermediates by nonthermal plasma, the shape-selective confinement of the β-zeolite pores, and the specific promotion of dehydrogenation-cyclization pathways by gallium species. This work demonstrates that integrating plasma with Ga-modified zeolites offers a highly efficient, sustainable route for upcycling waste plastics into essential petrochemical precursors.