Effect of the Feedstock Type on the Volumetric Low-Pressure CO₂ Capture Performance of Activated Carbons

Abstract

Activated carbons (ACs) display attractive gravimetric performance for CO2 capture, but it is unclear which carbon precursor suits preparation of ACs with high adsorption performance on a volumetric basis. Thus, we prepared ACs from five feedstocks (bamboo, rice husk, peanut shell, coconut shell, and anthracite) to study impacts of the feedstock type on the densities, volumetric pore parameters, and volumetric CO2 adsorption performance of ACs. The feedstock type was found to affect tap density of ACs, mainly because ACs possessed different macropore volumes. Because of the influence of tap density, the decreasing order of ACs for volumetric pore parameters was different from that for the corresponding gravimetric parameters. When AC was expected to display a high volumetric fine micropore volume (V <0.7 nm,v and V <1 nm,v), its tap density and gravimetric fine micropore volume should be both high. The feedstock type affected the volumetric CO2 uptakes of ACs at 0.15 and 1 bar, mainly because it changed volumetric fine micropore volume (V <0.7 nm,v and V <1 nm,v). The CO2/N2 selectivity of ACs was impacted by feedstock type, because ACs had different ultramicropore/micropore volume ratios (V <0.7 nm/V micro) and nitrogen contents. The feedstock type also affected the volumetric CO2 adsorption rate of ACs, because ACs had different volumetric micropore volumes (V <1 nm,v and V 1–2 nm,v). Coconut shell was the most suitable feedstock for the preparation of the carbonaceous CO2 adsorbent used in the adsorption bed, because of the high volumetric CO2 adsorption capacity, superior volumetric adsorption rate, and acceptable CO2/N2 selectivity of the yielded AC. This study showed the necessity to evaluate ACs by their volumetric CO2 capture performance and provided an effective way to tune this performance via a rational choice of carbon precursor.

Highly Selective CO2 Uptake in Novel Fishnet-like Polybenzoxazine-Based Porous Carbon

“…However, this conventional method has serious drawbacks such as toxicity, volatility, corrosion of the equipment, and energy-intensive regeneration . To circumvent these issues, a number of porous CO 2 adsorbents, such as metal oxides, zeolites, metal–organic frameworks (MOFs), − covalent organic frameworks (COFs), and porous carbons, − have been reported. Among these adsorbents, porous carbons are considered to be promising candidates for CO 2 capture because of their high surface area, tunable porosity, high stability, abundant resources, and tailorable surface properties. , The major drawbacks of commercial porous carbons are their moderate CO 2 capture capacity and low CO 2 /N 2 selectivity, which have limited their practical application.…”

Selectable Microporous Carbons Derived from Poplar Wood by Three Preparation Routes for CO2 Capture

“…HKC-800-1 was also comparable with c-CBAP-1N (223.5 mg/g), H150-800 (228.1 mg/g), NPC500 (235.8 mg/g), Bamboo-1-973 (233.2 mg/g), and AC-KOH-W-2-700 (237.6 mg/g) . Of course, the CO 2 uptake of HKC-800-1 was inferior to those of some advanced carbon materials including ACDS-800-2 (264 mg/g), CMS-K3 (286.4 mg/g), and CSC-650 (295.7 mg/g) . To deeply understand the CO 2 adsorption behavior, two adsorption models (Langmuir and Freundlich) were used to simulate the CO 2 adsorption isotherms (Figure S7), and Table S4 summarizes these parameters such as Q m , K L , K F , and the correlation coefficient ( R 2 ).…”

“…The initial Q st of the above activated carbons (21.1–43.2 kJ/mol) exceeded the heat of liquefaction of CO 2 (17 kJ/mol), 67 and Q st of these carbons at low CO 2 loading were comparable, even higher than many other carbon-based adsorbents, such as OM-CNS (28.4 kJ/mol), 50 PMMC-800 (∼24.5 kJ/mol), 53 NET2-2-700-2 (23.2 kJ/mol), 54 AcA5 (∼29.7 kJ/mol), 55 FC4 (24.9 kJ/mol), 57 and CSC-650 (25.8 kJ/mol). 72 Fortunately, HKC-800-1 with the highest CO 2 uptake had a moderate Q st of 24.9 kJ/mol, which was beneficial to easy regeneration and good cycling of adsorbents. The reclaimed HKC-800-1 was degassed at 30 °C for 30 min before the next cycle, and the reusability was measured ( Figure 10 c).…”

“… 68 Of course, the CO 2 uptake of HKC-800-1 was inferior to those of some advanced carbon materials including ACDS-800-2 (264 mg/g), 70 CMS-K3 (286.4 mg/g), 71 and CSC-650 (295.7 mg/g). 72 To deeply understand the CO 2 adsorption behavior, two adsorption models (Langmuir and Freundlich) were used to simulate the CO 2 adsorption isotherms ( Figure S7 ), and Table S4 summarizes these parameters such as Q m , K L , K F , and the correlation coefficient ( R 2 ). At 273 K, the Langmuir and Freundlich models both could well fit CO 2 adsorption isotherms with R 2 > 0.99, and the Freundlich model exhibited better fitting with a higher R 2 .…”

“…The Henry’s law selectivity of HKC-800-1 (27.93) surpassed those of many porous carbons, such as commercial activated carbon (17), 48 NPC-4-600 (16.6), 64 c-CBAP-1N (25.7), 66 Bamboo-1-973 (11.0), 33 NHPCT-4-7 (22), 23 HCP2a-K700 (8.7), 69 and CSC-650 (26.7). 72 …”