Green synthesis of polypyrrole for CO2 capture from humid flue gases

Abstract

Post-combustion carbon capture from fossil fuels for concentrated sources such as power plants is considered as one of the efficient ways to mitigate CO₂ emissions. However, conventional adsorbents in physical adsorption processes have faced challenges in the presence of moisture in flue gases. Here, we successfully synthesized polypyrrole (PPy) adsorbent using Fenton's reagent and demonstrated that the filtrate could be recycled for the synthesis of PPy. The single-component gas-adsorption capacities of PPy were measured to obtain CO₂, CH₄, and N₂ adsorption amounts of 16.73, 5.19, and 1.06 cm³ g⁻¹ at 303 K and 101 kPa, respectively. Calculations by the IAST method demonstrated that PPy had excellent gas selectivities for CO₂/N₂ and CO₂/CH₄ of 46 and 4.0, which could be utilized for CO₂ separation in flue gases and biogas. To simulate flue gas carbon capture, we investigated the dynamic adsorption capacity of PPy on CO₂ in the presence of water vapor using a breakthrough device in the laboratory. The CO₂ adsorption capacity was twice higher in moisture than in dry conditions, which was attributed to the presence of water vapor-formed hydrogen bonds that enhance its adsorption capacity through electrostatic and acid–base interactions of CO₂ with PPy. This green and facilely synthesized polypyrrole adsorbent has great potential for carbon capture in high humidity flue gases.