Evaluation of CO₂ Adsorption Dynamics of Polymer/Silica Supported Poly(ethylenimine) Hollow Fiber Sorbents in Rapid Temperature Swing Adsorption

Rapid temperature swing adsorption (RTSA) using polymer/silica supported amine hollow fiber sorbents is a new post combustion CO₂ capture methodology that facilitates CO₂ adsorption under nearly isothermal conditions with improved energy efficiency via heat integration. In this work, the dynamic CO₂ adsorption characteristics of polymer/silica supported poly(ethylenimine) hollow fiber sorbents (CA-S-PEI-PI) are evaluated in a bench scale RTSA system. Non-isothermal fibers have breakthrough and pseudo-equilibrium CO₂ capacities of 0.67 mmol/g and 1.03 mmol/g at 35°C, respectively, under humid simulated flue gas conditions (100% R.H.). Prolonged exposure of the fiber sorbents to water vapor enabled the breakthrough and pseudo-equilibrium CO₂ capacities to increase by 60% and 43%, respectively. Upon the removal of the heat of adsorption by flowing cooling water in the bores of the fiber sorbents, there is a substantial increase in the CO₂ breakthrough capacity, reaching 1.16 mmol/g using simulated humid flue gases. The breakthrough capacity is found to increase 5% upon increasing the adsorption temperature from 35°C to at 45°C, suggesting improved mass transfer in the fiber sorbent at the higher temperature. The CO₂ adsorption and desorption rates are shown to be very rapid, with CO₂ breakthrough occurring in less than 72s and the majority of the adsorbed CO₂ desorbing in 5 min. Extensive cycling studies demonstrate that the CA-S-PEI-PI sorbents have good dynamic swing capacities, stabilizing over 60 cycles. A newly developed rechargeable post-spinning amine infusion technique provides the feasibility of recovering the CO₂ adsorption performance of deactivated CA-S-PEI-PI fiber modules, by allowing for straightforward re-infusion of PEI into the deactivated sorbents. Amine-incorporated hollow fiber sorbents have good potential for practical use as scalable, adsorbing heat-exchangers.