Efficient CO₂ Capture by Porous Carbons Derived from Coconut Shell

Abstract

A series of porous carbons for CO2 capture were developed by simple carbonization and KOH activation of coconut shells under very mild conditions. Different techniques such as nitrogen sorption, X-ray diffraction, scanning emission microscopy, and transmission electron microscopy were used to characterize these sorbents. Owing to the high amount of narrow micropores within the carbon framework, the porous carbon prepared at a KOH/precursor ratio of 3 and 600 °C exhibits an enhanced CO2 adsorption capacity of 4.23 and 6.04 mmol/g at 25 and 0 °C under 1 bar, respectively. In addition to the high CO2 uptake, these samples also show fast adsorption kinetics, moderate heat of adsorption, high CO2 over N2 selectivity, excellent recyclability and stability, and superior dynamic CO2 capture capacity. The application of coconut shell as precursors for porous carbons provides a cost-effective way for the development of better adsorbents for CO2 capture.

Ultra-microporous adsorbents prepared from vine shoots-derived biochar with high CO2 uptake and CO2/N2 selectivity

“…In some previous studies, similar or slightly lower ultra-micropore volumes (also estimated using DFT or NLDFT methods) were reported by Hao et al [8] (0.072-0.128 cm 3 g -1 , for several biowaste-derived hydrochars physically activated with CO2 at 800 °C), Li et al [14] (0.08-0.15 cm 3 g -1 , for rice husk-derived chars chemically activated with KOH at 640-780 °C), and Li et al [32] (0.079-0.115 cm 3 g -1 , for chitosan-derived chars chemically activated with KOH at 600 °C). It should be pointed out that other previously reported ultramicropore volumes, which were estimated using alternative methods, such as the Horvath-Kawazoe approach (used by Ren et al [33]) or the procedure based on the Dubinin−Radushkevich equation (used by Yang et al [9], and Chen et al [17]), are not directly comparable, since the appropriateness of these estimation techniques was questioned [34]. Fig.…”

“…The highest CO2 adsorption capacity reported here is similar or higher than that reported in some earlier studies [8,10,17,31,35,36,38], including some adsorbents produced via surface modification pretreatments (such as urea modification for ACs prepared by Chen et al [17] and preoxidation with H2O2 followed by an ammoxidation step used by Guo et al [35]). Table 2, however, also reports slightly or appreciably higher CO2 uptakes for some adsorbents produced from N-doped non-lignocellulosic precursors [33,39] as well as from certain biomass sources (such as rice husks [14], coconut shells [9], pine nut shells [40], and Jujun grass [41]) through pyrolysis or hydrothermal carbonization and subsequent chemical activation with KOH. This fact also suggests that the nature of the precursor plays a key role in determining the performance of the derived AC in terms of CO2 adsorption capacity, regardless of the presence of absence of nitrogen functionalities on surface.…”

“…For postcombustion CO2 capture, suitable adsorbents must meet the following requirements [8,9]: (i) high CO2 adsorption capacity at low CO2 partial pressures (5-15 kPa), (ii) high selectivity towards CO2 over N2, (iii) low or moderate heat of adsorption, and (iv) fast adsorption kinetics.…”

“…Numerous studies were focused on producing activated carbons (ACs) from different biomass precursors; for instance: olive stones [10], almond shells [10], coconut shell [9], eucalyptus wood [11] and sawdust [12], pinewood sawdust [13], wheat straw [13], grass cuttings [8], poultry litter [13], and horse manure [8]. The preparation of ACs usually involves two steps [2]: (1) converting biomass into biochar or hydrochar (through pyrolysis and hydrothermal carbonization, respectively) and (2) activating the produced char at high temperature conditions (600-900 °C) either physically (by steam, CO2, or O2) or chemically (with KOH or H3PO4) to develop a porous structure [13].…”

Adsorption selectivity of CO2 over CH4, N2 and H2 in melamine–resorcinol–formaldehyde xerogels

“…It has been suggested that any sorbent used for postcombustive CO 2 removal must demonstrate high adsorption capacity at low relative concentrations of CO 2 , while exhibiting selective adsorption in industrially relevant timescales and a low heat of regeneration (Hao et al 2013;Yang et al 2017). This last factor has been previously reported for MRF xerogels , and this work seeks to addressed in the present study.…”