Development of Phase-Change-Based Thermally Modulated Fiber Sorbents

Microencapsulated phase change materials (μPCM) are combined with the metal–organic framework (MOF) UiO-66 and a cellulose acetate fiber support to introduce thermal modulation into CO₂ capture devices operating in subambient conditions. μPCM particles are incorporated into sorbent fibers during the fiber spin dope preparation step and are observed to withstand the spinning and subsequent solvent exchange steps with little to no loss of thermal modulating properties as determined by differential scanning calorimetry (DSC). The spinning of this novel sorbent-μPCM fiber sorbent is the first instance of single step spinning of sorbents with a thermal modulator. It was found that μPCM weight loading as high as 75 wt % was attainable while maintaining spinable fibers. Breakthrough adsorption experiments and subsequent temperature profile analysis were collected to compare CO₂ breakthrough capacity and heat release for sorbent systems with and without phase change materials incorporated. In adsorption modules with a diameter of 0.455 cm, where heat dissipation through the module wall dominates the global thermal response of the system, modulated fibers showed a 20–25% increase in breakthrough capacity at short times (CO₂ concentration C/C₀ = 0.05) as compared to their unmodulated counterparts. Higher breakthrough capacity indicates the phase change material would help manage the heat effects due to the local contact between the μPCM and the MOF. In larger diameter modules (0.7 cm) where wall heat dissipation effects are less dominant than the 0.455 cm diameter modules, fibers with “inactive” μPCM (i.e., 50 °C below their melting point) show larger sorption-induced thermal excursions and as much as 4× lower capacities at low adsorbate leakage as compared to fibers where the phase change material was active. Through the incorporation of phase change material, the sorbent in the system acts more efficiently, thus potentially driving down adsorption system cost.