Nitrogen-doped porous carbons with BET surface area of 1068.2–3314.5 m 2 /g and nitrogen contents of 3.2–6.5% were prepared with solid waste grape-seed as raw material, NaNH 2 as activator and nitrogen source at low activation temperature. Super The activation mechanism of NaNH 2 on hydrothermal carbon precursors was first explored by thermodynamic analysis and TG-IR, which provided theoretical support for pore forming of carbon materials. Maximum CO 2 and CH 4 adsorption capacity at 273 K and pressure of 101 kPa was 5.42 and 1.76 mmol g −1 respectively, which are higher than those of majority of carbon derived from most solid wastes reported in literature. IAST selectivities of GS-3-450 with the largest BET surface area for CO 2 /CH 4 (40v/60v), CO 2 /N 2 (15v/85v), CH 4 /N 2 (50v/50v) were found to be 20.3, 71.4, 6.0 under 101 kPa and 298 K respectively. The competitive adsorption of GS-3-450 for CO 2 /CH 4 (40v/60v), CO 2 /N 2 (15v/85v), CH 4 /N 2 (50v/50v) gases mixture were examined through breakthrough experiments, and the results showed that the breakthrough time of CO 2 was longer than that of CH 4 and N 2 , which was beneficial to the separation of CO 2 from gases mixture. Eight cycles of CH 4 adsorption–desorption studies revealed that the material exhibited excellent recycling stability. Low temperature preparation method, excellent BET specific surface area and total pore volume, as well as excellent adsorption ability of CO 2 and CH 4 make it have a very great potential for the capture of CO 2 and CH 4 .

Although carbon material are widely used for gas separation and adsorption due to its well-developed pore structure, their prevalent wide pore size distribution and scarcity of active adsorption sites limit its gas adsorption capacity. Therefore, in this paper, a series of N-doped microporous carbon adsorbent materials were prepared via utilizing cheap starch as the carbon source and the synthesized melamine resin as the N-doped modifier with the assistance of hydrothermal conversion and high temperature activation by KOH.BET test showed that MF@Cs was a typical microporous carbon material with a pore size distribution of 0.3–2 nm, and its most accessible pore size was about 0.6 nm,which benefits the adsorption of CO2 and CH4. MF@C–1–750 porous carbon material present prominent pore structure parameters, with a maximum specific surface area of 2415.9 cm2/g, a total pore volume of 1.36 cm2/g, and a maximum ultramicro pore volume of 0.42 cm2/g at 0.3 ~ 1.0 nm. MF@Cs porous carbon materials show high static adsorption capacity for CO2 and CH4, the adsorption capacity of CO2 of MF@C–1–750 is as high as 6.54 mmol/g at 273 K and 100 kPa, which is attributed to the excellent ultramicro pore volume of carbon materials. MF@Cs porous carbon material is expected to play a huge application potential in the separation and enrichment of CO2 in the future, due to its simple preparation and low cost, excellent specific surface area, outstanding ultrafine pore capacity and high adsorption capacity of CO2 gas.

Reasonable design of adsorbents for separating and purifying CH4 in coalbed methane is important to achieve sustainable development. However, KOH activation, the most widely used method for preparing activated-carbon adsorbents, requires the addition of a high proportion of KOH, which has disadvantages such as high cost and corrosion. In this study, a low proportion of KOH/KMnO4 is used as an activator and a mechanical ball-milling method is used to prepare cellulose-based microporous carbon for the selective adsorption of CH4 in low-concentration coalbed methane. The prepared microporous carbon has a large ultramicropore volume and narrow pore size distribution. The Vmic (<1 nm) of ACQ60 is 0.39 cm3/g, and the most probable pore size is 0.42 nm. At 273 K and 101.3 kPa, the CH4 adsorption capacity of this sample is up to 3.22 mmol/g. Ideal adsorption solution theory simulations show that CH4/N2 selectivity is 7.82. The ACQ60 regeneration adsorption performance was evaluated via a dynamic penetration experiment. After six cycles, the CH4 penetration time difference was found to be minor. This study serves as a reference for the excellent performance of carbon materials with rich narrow microporous structures applied to the effective separation of CH4 in low-concentration coalbed methane.