Facile synthesis of ultramicroporous carbon adsorbents with ultra‐high CH₄ uptake by in situ ionic activation

Abstract

We introduce a straightforward method for the preparation of novel starch‐based ultramicroporous carbons (SCs) that demonstrate high CH4 uptake and excellent CH4/N2 selectivity. These SCs are derived from a combination of starch and 1–6 wt.% of acrylic acid, and the resulting materials are amenable to surface cation exchangeability as demonstrated by the formation of highly dispersed K+ in carbon precursors. Following activation, these SCs contain ultramicropores with narrow pore‐size distributions of <0.7 nm, leading to porous carbon‐rich materials that exhibit CH4 uptake values as high as 1.86 mmol/g at 100 kPa and 298 K, the highest uptake value for CH4 to date, with the IAST‐predicted CH4/N2 selectivity up to 5.7. Both the potential mechanism for the formation of the narrow pores and the origin of the favorable CH4 adsorption properties are discussed and examined. This work may potentially guide future designs for carbon‐rich materials with excellent gas adsorption properties.

Influence of ultra-micropore volume of activated carbons prepared from noble mung bean on the adsorption properties of CO2, CH4, and N2

“…6(g), the AED peak maxima calculated can be well correlated with the polarizability, generating the stronger van der Waals interaction closely related to the instantaneous dipole within adsorbate. 54,59,60 Thus the greater the polarizability, the higher adsorption energy, indicating a stronger dominance of van der Waals interaction between target gases and MACs.…”

“…High adsorption selectivity and high adsorption capacity are essential factors to evaluate the adsorption performances of an adsorbent, in general. Thus, the IAST selectivity values at 25 1C for flue gas (CO 2 /N 2 = 20/80), [61][62][63][64][65] landfill (or biogas) gas (CO 2 / CH 4 = 50/50), [66][67][68] and coal bed gas (CH 4 /N 2 = 50/50) 59,60,69,70 were calculated using the Sips isotherm parameters and compared, as shown in Fig. 6(h).…”

Enrichment of low concentration methane: an overview of ventilation air methane

“…As shown in Table 3, a lot of carbon materials with high CH 4 adsorption capacity and high CH 4 /N 2 selectivity have been reported recently. So far the highest CH 4 adsorption capacity of 1.86 mmol g À1 with a CH 4 /N 2 selectivity of 5.7 (for a 50 : 50 gas mixture) has been reported by Du et al 137 and the highest CH 4 / N 2 selectivity of 13.7 (for a 5 : 95 mixture) with a CH 4 adsorption capacity of 0.5 mmol g À1 has been reported by Li et al 63 It is noteworthy that some of these ACs show CH 4 /N 2 selectivity higher than the CO 2 /CH 4 selectivity. 31,63,64,132,139 Given that ventilation air usually contains CO 2 , it is highly desirable to study the VAM enrichment with SPA processes using these adsorbents.…”

Superhydrophobic zeolitic imidazolate framework with suitable SOD cage for effective CH4/N2 adsorptive separation in humid environments

“…Li et al 15 The reported works reveal that microporous MOFs are conducive to achieve a desirable CH 4 /N 2 selectivity by distinguishing gas molecules with similar sizes (3.8 Å for CH 4 and 3.6 Å for N 2 ) and inspire the development of highly selective adsorbents for low-concentration CMM enrichment. 17,18 Apart from the high requirement of selectivity, the issue of the hydrophobicity of adsorbents should also be taken into account during practical application, owing to that the extracted CMM usually carries a large amount of water absorbed in coal seams, 19 whereas most MOFs with a high CH 4 /N 2 separation performance are hydrophilic. 20,21 The zeolitic imidazolate frameworks (ZIFs), which is a subfamily of the MOFs with a zeolite topology, tends to be constructed from a transition metal, which is linked by imidazolate organic groups, and the imidazole links that contain hydrophobic groups enable the creation of hydrophobic ZIFs.…”