Polyethylenimine-Modified Zeolite 13X for CO₂ Capture: Adsorption and Kinetic Studies

A class of high molecular weight polyethylenimine (PEI)-modified zeolite 13X adsorbents were synthesized by varying the concentration of imines and screened for preliminary investigation of CO₂ capture studies. The impregnated molecular amine zeolite composite was characterized and CO₂ adsorption performance was investigated through TGA in the presence of atmospheric pure CO₂ gas at 25, 50, 75, and 100 °C, respectively, using 20-80 wt % of PEI-loaded zeolite 13X adsorbents. This paper reports on the effects of temperature and amine (PEI) loading on CO₂ adsorption capacity and estimated kinetic parameters through modeling of selected models which represent the reaction rate and diffusion rate models. The studied adsorbents showed the highest adsorption capacity at 75 °C with 60 wt % PEI loading. Thus, the optimum temperature of 75 °C and optimal loading of 60 wt % was observed from the current studies for CO₂ capture. From modeling study, it was found that Avrami's fractional order and dual kinetic models (DKM) described well the adsorption behavior of CO₂ on PEI-impregnated zeolite 13X at all temperatures accurately and up to 75 °C, respectively. Besides, intraparticle diffusion was found to be the rate-limiting step when compared with the film diffusion model.