Polyethylenimine-Modified Zeolite 13X for CO 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 CO capture studies. The impregnated molecular amine zeolite composite was characterized and CO adsorption performance was investigated through TGA in the presence of atmospheric pure CO 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 CO 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 CO capture. From modeling study, it was found that Avrami's fractional order and dual kinetic models (DKM) described well the adsorption behavior of CO 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.