Highly porous N-doped carbons impregnated with sodium for efficient CO₂ capture

Abstract

Highly porous sodium-impregnated and N-doped carbon sorbents (SNSs) were prepared by KOH activation of polyacrylonitrile (PAN), followed by NaOH impregnation of the activated N-doped carbons. These new types of materials were investigated as sorbents for CO 2 capture. Particularly, SNS2-20 prepared with the KOH/PAN ratio of 2 at 700 C and 20 wt% NaOH based on the weight of the activated carbon exhibited the adsorption capacity of 6.84 and 4.48 mmol g À1 at 0 and 25 C under ambient pressure. Among the carbon sorbents reported to date, it showed the highest CO 2 uptake of 3.03 and 1.90 mmol g À1 at 0 and 25 C under a typical pressure condition of post-combustion flue gas (0.15 bar CO 2 ). The enhanced CO 2 uptake is due to high porosity caused by KOH activation, enriched pyridonic/pyrrolic nitrogen contents, and strong basic sites generated by NaOH impregnation. Moreover, CO 2 /N 2 selectivities of 59.5, 68.9 and 79.4 at 0, 25 and 50 C were achieved for the gas mixture (CO 2 : N 2 ¼ 15 : 85) according to the ideal adsorbed solution theory (IAST). The consecutive adsorption-desorption cycle experiments using SNS2-20 showed almost unaltered CO 2 uptake capacities. Combined with its simple preparation, the high CO 2 adsorption capacity and selectivity of the synthesized SNS2-20 could provide potential for practical applications of CO 2 capture and storage.

Hierarchical N-Doped Carbon as CO2 Adsorbent with High CO2 Selectivity from Rationally Designed Polypyrrole Precursor

“…34,43 It is interesting to note that the ratio of N-5':N-6 decreased with increased activation temperature (Table S4). This is caused by a rearrangement in the C-N bond to a more thermodynamically stable state (N-6) under elevated temperature 41 45 To further elucidate the existence of such strong adsorption site within the carbon framework, we calculated a virial plot of CO 2 adsorption (Fig. S17).…”

Tunable Polyaniline‐Based Porous Carbon with Ultrahigh Surface Area for CO2 Capture at Elevated Pressure

“…This enhancement is ascribed to the dipole-quadrapole interactions between the nitrogen functionalities and the CO 2 molecules. [39,40] The relative magnitude of the enhancement is far less profound at high pressures. For example, for a pore width of 0.7 nm, NQ enhances the CO 2 density by 83% compared to perfect graphite at 0.15 bar (Figure 5d inset), while it only raises the density by 3% at 30 bar.…”

Polyacrylonitrile Nanoparticle‐Derived Hierarchical Structure for CO2 Capture

“…The possible chemical structure of the graphitic matrix containing nitrogen is depicted in Figure a) . Three main species are present in all three samples: quaternary‐N (QN) 401.4±0.3 eV, pyridine‐ N ‐oxide (PNO) 402.8±0.3 eV, and pyridine (P) 398.7±0.3 eV . The XPS results are shown in Figure b)–d) for S1, S2, and S3, respectively, and they confirm the presence of a trend at increasing oxidation temperature.…”

“…Moreover, the ternary‐coordinated nitrogen in the cyanide group permits some extent of chemisorption due to its partial basicity, without the necessity for high heat of regeneration, as it is required for amines . Several studies have shown that different nitrogen‐bearing species are formed depending on the temperature applied during the heat treatment and that their chemical nature influences the extent of CO 2 capture …”

“…[30] Severals tudies have shown that different nitrogen-bearing species are formed depending on the temperature applied during the heat treatment and that their chemical nature influences the extent of CO 2 capture. [31][32][33] In addition to the positive effect of nitrogen in CO 2 capture,t he importance of suitable pore size has also been reported. [34][35][36] Pore sizes below 0.7 nm have been shown to have at remendous effect on the final CO 2 uptake.…”