(776i) Kinetic Modeling of CO2 Adsorption On Pore-Expanded MCM-41

Adsorption equilibrium and kinetics are critical parameters to assess the performance of an adsorbent. Equilibrium sorption studies are important in determining the efficiency of an adsorbent. The kinetic analysis allows the determination of the residence time required for completion of adsorption process. In a dynamic process such as adsorption in a fixed bed column, efficiency of an adsorbent and its capacity to withstand large adsorbate flows are associated with its rate of adsorption. Therefore, from a practical standpoint, it is important to characterize the rate-controlling steps for an adsorption process. More recently, our research group fabricated a pore-expanded MCM-41 (A) for CO₂ capture application. In the current work, we investigated the kinetics of CO₂ adsorption on A. Kinetic measurements of pure CO₂ in A sample at four different temperatures (30, 45, 60, and 75 ⁰C) were performed in the pressure range of 1-11 bar, using a Rubotherm magnetic suspension balance. To analyze the adsorption rate behavior of CO₂ on A under different pressure and temperature condition, we considered both pseudo first-order kinetic model and the pseudo second-order kinetic model to obtain the overall mass transfer coefficient. The pseudo-second order model failed to accurately fit the experimental data whereas pseudo-first order model provided a pretty good agreement between the measured and predicted data throughout the entire range of pressure and temperature analyzed. To further investigate the mechanism of CO₂ adsorption on A, intra particle diffusion and Boyd’s models were considered. A conclusion regarding mass transfer mechanism is derived from the information provided by both the models. It was found that external mass transport mainly governed the rate-limiting process of adsorption of CO₂ on A at low pressure conditions. Interestingly, it was also interpreted that pore diffusion becomes more important at higher pressure conditions.