(628f) Thermal Modulation in High-Capacity Pressure-Swing Adsorption Via Incorporation of Microencapsulated Phase-Change Material

Post combustion separation of CO₂ from flue-gas will be a key component in the portfolio of technologies that enable reduction of global carbon emissions. Metal-organic-frameworks (MOFs) have shown promise as possible adsorbent materials for CO₂ capture due to their large capacity driven by both functionalized surfaces and high pore volume. This large capacity for CO₂ can be unlocked for high recovery separations using a small pressure swing at sub-ambient conditions. These high capacities are necessary to drive down post-combustion CO₂ capture costs; consequentially, large amounts of heat are released during the adsorption process, leading to significant thermal fronts propagating through the adsorption column. For sub-ambient adsorption processes, these fronts induce significant inefficiency in the sorbent utilization due to the elevation of local adsorption temperatures. Managing these thermal fronts can be achieved via incorporation of phase change materials, which adds both sensible thermal mass and latent heat storage into the system, dampening the thermal fronts created during rapid adsorption and desorption cycles. In this work, we demonstrate the ability to incorporate microencapsulated phase change materials (μPCM) into polymeric fiber contactors via solution spinning techniques at loadings up to 75 weight percent and in the presence of the MOF UiO-66. Moreover, we show that these composite monolithic contactors are effective in mitigating the thermal fronts created during the CO₂ adsorption process. Thermal gravimetric analysis and differential scanning calorimetry demonstrate that the μPCM remain intact through the spinning process and are operable for thermal modulation at the target temperature of -30 °C. Sub-ambient breakthrough experiments with simulated flue gas are performed to show the effect of thermal modulation on the breakthrough behavior and sorbent capacity for CO₂. In addition, temperature profiles in the bed under breakthrough of pure CO₂ are collected to better understand the effectiveness of μPCM for thermal front mitigation relative to fibers with no μPCM. Our findings suggest that further optimization of the relative loadings of sorbent to thermal modulator can result in more efficient pressure swing adsorption.