Valorizing disposable face masks into non-condensable hydrocarbon gases via optimal reactor configurations in thermal pyrolysis

Abstract

Pyrolysis studies often overlook the potential of pyrolytic gas as a valuable hydrocarbon resource, thereby hindering the production of advanced carbonaceous nanomaterials (CNM). This study aims to explore various configurations of a multi-zone tubular reactor to upcycle disposable face masks into non-condensable hydrocarbons as potential CNM precursors. The highest gas yield (56.2 wt%) was achieved using a 3-zone configuration (Z-1,3,4), attributed to the end chain scission mechanism. The increased abundance of light hydrocarbons (≤C10) in the resulting liquid confirms a greater extent of end chain scission in the optimum reactor configuration with cold zone retainment. Employing this configuration, different face mask types, including 3ply (polypropylene-based), KF94 (polypropylene-based) and N95 (polyester-based), were utilized as individual feedstocks or in various ratios as mixtures to investigate the resultant composition of hydrocarbon gases. This composition was compared with existing literature studies to identify suitable hydrocarbon gas compositions for CNM production. Mixing 3ply and KF94 face masks produced a consistent gas composition predominantly comprising propylene (62.3 – 66.9%) and ethane (15.4 – 16.8%) via thermal pyrolysis at 500 ℃ with a constant heating rate of 20 ℃/min. However, the inclusion of N95 face masks increased CO2 level fivefold, diminishing the gas quality as a CNM precursor. These findings underscore the necessity of segregating polyester face mask material from polypropylene face mask material prior to pyrolysis to ensure a consistent quality and yield of CNM precursors.