Ultramicroporous carbon granules with narrow pore size distribution for efficient CH₄ separation from coal‐bed gases

Abstract

The adsorptive separation of CH4 from low‐grade coal‐bed gas can be performed at decentralized and remote coal mines, and it uses more energy‐ and is cost‐efficient than the traditional cryogenic distillation process. Herein, we present a facile method to prepare ultramicroporous carbon granules with a narrow pore‐size distribution at 0.5–0.6 nm. To our knowledge, such centered and uniform pore‐size distribution in carbon granules has never been reported. The carbon granules can be directly utilized in adsorption columns without a granulation or pelletization process. The granular oil‐tea‐shell‐derived porous carbon (GOC‐2) exhibited a record‐high CH4 uptake of 1.82 mmol/g and CH4/N2 selectivity of 5.8 at 1.0 bar and 298 K among carbon granules. The excellent CH4/N2 separation performances were confirmed from the results of dynamic breakthrough experiments and pressure swing adsorption simulations. This work provides a novel strategy for developing ultramicroporous carbon granules and guides the future design of efficient CH4/N2 separation adsorbents.

Separation ofCH4/N2by an ultra‐stable metal–organic framework with the highest breakthrough selectivity

“…The corresponding BET surface area, pore volume, and pore size are respectively 626.1 m 2 /g, 0.3 cm 3 /g, and 5.7 Å (the calculation process is based on these literatures[65][66][67] and shown in the Supporting Information), revealing an ultramicroporous nature of this material. Additionally, the permanent pore structure of this MOF was also assessed based on CO 2 adsorption-desorption isotherms at 195 K,[68][69][70][71] as shown in FigureS4. The corresponding BET surface area, pore volume, and pore diameter are 642.1 m 2 /g, 0.3 cm 3 /g, and 5.8 Å, respectively, which are consistent with the results of N 2 adsorption measurement at 77 K, further indicating that the MOF belongs to ultramicroporous material.…”

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.…”

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.…”

“…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 …”