Pyrolytic conversion of polyimide into carbon-based CO2 adsorbent with in-situ suppression of toxic byproducts

Abstract

The polymer's physico-chemical property is reinforced by incorporating an aromatic molecule into the polymeric backbone. However, the persistence of aromatic plastics poses potential hazards against the liberation of toxic compounds. To address this issue, this work proposes a functional use of CO2 for the pyrolytic conversion of highly aromatised plastics, polyimide, into carbon-based materials while mitigating the toxic aromatic formations. Characterisations of polyimide clarified its exact type and pyrolysis mechanism. Polyimide pyrolysis yielded ≥ 60 wt.% of the char formation. Its surface functionalities revealed superior performance in CO2 adsorption than the reference materials. However, the production of polyimide-derived adsorbent inevitably generates toxic chemicals. To impede the toxic aromatic formations, CO2 was chosen as a detoxifying agent. The toxic chemicals liberated from polyimide can be converted into gaseous fuel, CO. This functional role of CO2 was improved in the presence of a nickel catalyst. CO2-mediated catalytic pyrolysis led to a 97.7% degradation in toxic chemicals, subsequently resulting in a 3.14-fold increase in CO formation. Therefore, the CO2-mediated pyrolysis provides insights into the sustainable valorization of aromatic plastic waste into CO2 adsorbent, simultaneously addressing the environmental issues related to the generation of toxic aromatic pollutants.