Synthesis and CO2 Adsorption Behavior of Amine-functionalized Porous Polyacrylonitrile Resin

The objective of this study was to develop a novel solid amine adsorbent using porous polyacrylonitrile resin instead of mesoporous silica as support for CO2 adsorption from flue gas. This solid amine adsorbent was prepared by a suspension polymerization of divinylbenzene (DVB) with acrylonitrile (AN), followed by aminating with tetraethylenepentamine (TEPA). Scanning electronic microscope, nitrogen adsorption-desorption isotherms at 77 K, and thermogravimetry (TG) were employed to characterize the surface structure, porosity, and thermal stability of the solid amine adsorbent. Factors that could determine the CO2 adsorption performance of the solid amine adsorbent, such as amine species, adsorption temperature and moisture, were investigated. The experimental results showed that the maximum adsorption capacity of CO2 (1.87 mmol/g) was achieved at 25 degrees C with CO2 concentration of 10 vol%, the flow rate of 30 mL/min and TEPA as the organic amine. The solid amine adsorbent modified with TEPA (PAN-TEPA), a longer chain amine among all amines used, showed superior amine efficiency and CO2 adsorption capacity to the other two amine species with shorter chains CO2 adsorption capacity decreased obviously as the adsorption temperature increased, because the reaction between CO2 and amine groups was an exothermic reaction. The presence of water could significantly improve CO2 amount adsorbed on the adsorbent by promoting the chemical adsorption of CO2 on PAN-TEPA. A higher equilibrium adsorption capacity (2.97 mmol/g) was achieved in the presence of moisture. Meanwhile, the kinetics study found that Avrami kinetic model was more fitted to accurately describe CO2 adsorption than the Pseudo-first and Pseudo-second order models, indicating that both physical adsorption and chemical adsorption were involved in CO2 adsorption. Moreover, this solid amine adsorbent could be regenerated with nitrogen stream at 75 degrees C, and it kept stable CO2 adsorption capacity after ten cycles of adsorption-desorption. All these features indicated that the amine-functionalized porous polyacrylonitrile resin has a high potential for CO2 capture and separation from flue gas.