Highly Selective CO2 Capture on Waste Polyurethane Foam-Based Activated Carbon

Abstract

Low-cost activated carbons were prepared from waste polyurethane foam by physical activation with CO 2 for the first time and chemical activation with Ca(OH) 2 , NaOH, or KOH. The activation conditions were optimized to produce microporous carbons with high CO 2 adsorption capacity and CO 2 /N 2 selectivity. The sample prepared by physical activation showed CO 2 /N 2 selectivity of up to 24, much higher than that of chemical activation. This is mainly due to the narrower microporosity and the rich N content produced during the physical activation process. However, physical activation samples showed inferior textural properties compared to chemical activation samples and led to a lower CO 2 uptake of 3.37 mmol·g −1 at 273 K. Porous carbons obtained by chemical activation showed a high CO 2 uptake of 5.85 mmol·g −1 at 273 K, comparable to the optimum activated carbon materials prepared from other wastes. This is mainly attributed to large volumes of ultra-micropores (<1 nm) up to 0.212 cm 3 ·g −1 and a high surface area of 1360 m 2 ·g −1 . Furthermore, in consideration of the presence of fewer contaminants, lower weight losses of physical activation samples, and the excellent recyclability of both physical-and chemical-activated samples, the waste polyurethane foam-based carbon materials exhibited potential application prospects in CO 2 capture.Processes 2019, 7, 592 2 of 15 (Carbon Capture, Utilization and Storage) technologies are intended to reduce CO 2 emission, reaching the Paris Agreement targets is still a serious challenge. Nevertheless, in these techniques, adsorption is considered to be the approach with the most potential, since it involves simple operation and has low-cost and energy-saving benefits [8].Many adsorbents have been intensively studied for CO 2 capture, including zeolites [9], metal-organic frameworks [10], metallic oxide [11], graphene-based adsorbents [12], and porous carbon materials [13]. For future commercialization application, the selection of adsorbents is strongly dependent not only on CO 2 capture capacity but also the cost, including the availability of the raw materials, the preparation of the adsorbent, and the operating costs. Porous carbons (PCs) are considered to be the most competitive candidates due to their controlled pore structure, low cost, stable physicochemical properties, ease of chemical modification, and regeneration [14]. Micropore sizes smaller than 1 nm are beneficial to high-density CO 2 filling at ambient conditions [15,16]. In addition, a high surface area (>1000 m 2 ·g −1 ) and a rich nitrogen environment can improve the CO 2 adsorption capacity.The route of preparation, especially activation, will significantly affect the performance of CO 2 absorption. The porous carbons can be activated either by physical or chemical methods. Physical activation is usually achieved by carbonization in an inert atmosphere followed by oxidizing in CO 2 [17], steam [18], or air. In this way, activated carbons with a narrower pore size distribution can be obtained [19]. Gene...

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Modulating the porosity of carbons for improved adsorption of hydrogen, carbon dioxide, and methane: a review

“…KOH is the primary reagent used for synthesis of activated carbons intended for physisorption of small molecules as it yields superior carbons with high surface area and pore volume, a high degree of microporosity and tuneable PSD. 20,79,127,220,233,249,[287][288][289] Nonetheless, physical activating agents such as CO 2 and steam, 77,249,260,288,290 as well as other 'traditional' chemical agents such as ZnCl 2 , H 3 PO 4 and NaOH continue to be explored. 152,252,[287][288][289]291,292 A summary of textural properties of carbons derived using a variety of activating agents is presented in Table 2.…”

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