Valorization of 3D printing filament waste into syngas via CO2-assisted pyrolysis

Abstract

Three-dimensional (3D) printing is adopted in manufacturing field due to its ability to rapidly fabricate complex objects. However, a substantial amount of polymeric waste derived from 3D printing process and its limited recyclability have raised environmental concerns. This study proposes a strategic approach for the valorization of 3D printing waste into pyrolytic gas by employing CO2 as a reaction medium. A commercial 3D printing filament (3DPF) was used as a model compound of 3D printing waste and identified as acrylonitrile-butadiene-styrene (ABS) by FT-IR analysis. Thermo-gravimetric analysis (TGA) suggested that∼98 wt% of 3DPF are volatilized and reallocated into pyrolytic oil and gas. In single-stage pyrolysis, the volatiles from 3DPF predominantly converted into pyrolytic oil, while the gas yield suppressed (<0.5 %) due to insufficient thermal cracking. For enhancement in the yield of pyrolytic gas, experimental configuration was modified into double-stage pyrolysis. Under the CO2 condition, CO enhancement was observed though 3DPF contains no intrinsic oxygen content. This CO evolution was attributed to the homogeneous reactions between CO2 and volatiles released from the 3DPF. To accelerate homogeneous gas phase reaction and enhance the yield of pyrolytic gas, a Ni/Al2O3 catalyst was adopted in this study. Catalytic pyrolysis enhanced H2 and CO formations by the catalytically expedited homogeneous reactions, while suppressing the formations of aromatic, nitrogen-containing compounds, and PAHs in pyrolytic oil. These experimental observations suggests that CO2 can be used as an effective reactant for converting polymeric waste into pyrolytic gas, providing an environmentally benign platform for 3D printing waste management.