Epoxide-Functionalized, Poly(ethylenimine)-Confined Silica/Polymer Module Affording Sustainable CO₂ Capture in Rapid Thermal Swing Adsorption

Abstract

Creating a module that achieves sustainable CO2 capture while being compatible with the existing industry is paramount in overcoming the current CO2-driven environmental issues. This paper presents the fabrication of hollow fiber sorbents (HFSs) and their respective modules to capture CO2 by the rapid thermal swing adsorption process (RTSA). Poly­(amide-imide) (PAI)/microspheric SiO2 composites were fabricated with a so-called “sieve-in-a-cage” microarchitecture which promotes CO2 diffusion. More importantly, a selected amount of 1,2-epoxybutane (EB)-functionalized poly­(ethylenimine) (PEI), denoted as 0.37EB-PEI, was incorporated into our PAI/SiO2 composites forming PAI/SiO2/0.37EB-PEI HFSs which enhanced the thermal stability with a moderate CO2 sorption uptake of 0.88 mmol CO2 g–1. The resulting HFSs were assembled into a module using either stainless steel (SS) or poly­(tetrafluoroethylene) (PTFE), and their respective CO2-capturing performances in the RTSA process were compared. The two modules had a comparable breakthrough CO2 capacity of 0.42 mmol CO2 g–1 for a wet feed mixture of CO2/He/N2 (14 mol/14 mol/72 mol) (RH 100%) and a comparable CO2 desorption efficiency (i.e., 95% desorption within 2 min) under 100% CO2 at 120 °C due to the presence of the 0.37EB-PEI; however, different thermal properties inherent to the modular materials caused the PTFE-based module to outperform the SS-based counterpart in terms of cooling, enabling the execution of an entire RTSA cycle within 8 min. Additionally, the PAI/SiO2/0.37EB-PEI/PTFE module maintained its breakthrough capacity of 0.42 mmol CO2 g–1 over five consecutive RTSA cycles, confirming its good long-term stability as well.

Fabrication of Ultrathin Zeolitic Imidazolate Framework on Polymeric Hollow Fiber via Sequential Seed Layer Sputtering

“…The PAI hollow fiber was selected as the substrate for ultrathin ZIF-8 growth because it exhibits excellent chemical resistance and mechanical strength by interchain hydrogen bonding within the polymer backbone. 33 The as-prepared PAI fiber with the inner diameter of ∼500 μm was cut by 12 cm in length and used as the substrate for the ZnO sputtering. First, the ZnO seed layer was primarily RF-sputtered onto the fiber, which resulted in the partial coverage of the ZnO layer on the single lateral side of the fiber exposed to the ZnO target owing to the directionality of sputter deposition.…”

“…Porous PAI hollow fibers were fabricated by using a dry-jet/wet quench process. 33 The composition of polymer solutions and spinning conditions are summarized in Table 1. After the spinning procedure, the PAI fibers were preserved in deionized (DI) water for 3 days to remove any residual solvent.…”

Microporous Materials in Scalable Shapes: Fiber Sorbents

“…214,216 The long-term stability of 1,2-epoxybutane-functionalized poly(ethylenimine)−SiO 2 / poly(amide-imide) (PAI) fiber sorbents was improved as the alkylated primary amines can form isocyanates responsible for urea formation. 75 Because SO 2 with a higher acidic property than CO 2 strongly binds to amine, the cyclic SO 2 adsorption process rapidly blocked the active CO 2 sites of amine-based fiber sorbents. 76 Grafting tertiary amines onto the mesoporous silica/CA hollow fiber sorbents enabled easier regeneration for SO 2 owing to the noncovalent adduct between the tertiary amine and SO 2 than primary or secondary amines using acid/ base interaction.…”

“…The impermeable barriers and PCMs in fiber sorbents enabled the integration of the fibers to rapid temperature swing adsorption (RTSA) and rapid cycle pressure swing adsorption (RCPSA) processes. The RTSA process of the hollow fiber sorbents with the impermeable lumen layer includes cyclic adsorption, heating, sweeping, and cooling steps (Figure d) , with an average cycle time of less than 4 min . In the adsorption step of the RTSA cycle, the cooling water flowing on the lumen side effectively absorbed the heat generated during adsorption and was able to maintain the temperature condition of the entire fiber sorbent module at almost isothermal.…”

“…If the short desorption time at high temperature using the RTSA (Figure e) reduces the dehydration and formation of free radicals, amine-functionalized fiber sorbents could reduce the risk of amine loss via urea formation and oxidative degradation . The alkylation of primary amines to secondary or tertiary amines is another method to enhance the stability of amine-functionalized fiber sorbents. , The long-term stability of 1,2-epoxybutane-functionalized poly­(ethylenimine)–SiO 2 /poly­(amide-imide) (PAI) fiber sorbents was improved as the alkylated primary amines can form isocyanates responsible for urea formation . Because SO 2 with a higher acidic property than CO 2 strongly binds to amine, the cyclic SO 2 adsorption process rapidly blocked the active CO 2 sites of amine-based fiber sorbents .…”