Adsorption of CO₂, CH₄, and N₂ in Micro-Mesoporous Nanographene: A Comparative Study

Abstract

In this work, we have measured the adsorption isotherms and calculated the equilibrium selectivity for CO 2 , CH 4 , and N 2 on micro-mesoporous nanographene at three temperatures of 298 K, 278 K, and 263 K and pressures up to 760 Torr. The nanographene sample possesses a particle size range of 50 nm to 250 nm along with a Brunauer−Emmett−Teller (BET) specific surface area of 514 m 2 /g and total pore volume of 3 cm 3 /g. The pore widths varied from 3.5 Å to 8 Å in the microporous region and very large distributed widths within 45 Å to 250 Å in the region of mesoporosity. The calculated equilibrium selectivity of gas separation at 298 K by pressure swing adsorption for CO 2 /N 2 , CO 2 /CH 4 , and CH 4 /N 2 are 55, 8.2, and 6.5, respectively, whereas the adsorption selection parameters for same pair of gases are 540, 101, and 117, respectively. To compare the equilibrium selectivity values with other adsorbents, we have measured the gas adsorption isotherms for CO 2 , CH 4 , and N 2 on Maxsorb (a commercial activated carbon with BET surface area 3200 m 2 /g) and calculated the selectivity values for several adsorbents based on their adsorption isotherms reported in the literature. We have found that equilibrium selectivity for all the gas pairs are higher for graphene compared to Maxsorb. We also found that the equilibrium selectivity for CO 2 /N 2 for graphene is higher than all the carbon-based materials reported so far. The equilibrium selectivity for CO 2 /CH 4 and CH 4 /N 2 in graphene is also higher than the majority of the adsorbents reported in the literature. Our findings suggest that graphene can serve as a potential adsorbent for gas separation purposes.

Miscible Fluid Displacement in Rock Cores Evaluated with NMRT2Relaxation Time Measurements

“…CO2 ≈ N2O > CH4 > N2 > He. 42,[58][59][60][61][62][63] The adsorption capacities of CO2 and N2O are normally much higher than that of CH4, which usually has a slightly higher adsorption capacity than that of N2. 58,59,61 The adsorption capacity of He is very low and is commonly assumed to be negligible.…”

“…42,[58][59][60][61][62][63] The adsorption capacities of CO2 and N2O are normally much higher than that of CH4, which usually has a slightly higher adsorption capacity than that of N2. 58,59,61 The adsorption capacity of He is very low and is commonly assumed to be negligible. 58,60,64 The same order of adsorption capacities for the respective fluids was observed for the carbonate rock cores, this data can however only be treated as qualitative as the measured qabs was of the order of 0.001 mmol/g which is comparable to the measurement uncertainty.…”

CO2 and CH4 Adsorption Behavior of Biomass Based Activated Carbons

“…On this type of separation technology, the components of a gas mixture are separated based on their molecular characteristics and affinity to an adsorbent material. For this purpose, a variety of materials have been studied including zeolites [7][8][9], carbon molecular sieves (CMS) [10][11][12], metal organic frameworks (MOFs) [13][14][15] and activated carbons (AC) [16][17][18].Among this materials, activated carbons present advantages in terms of (i) hydrophobicity, no need of water removal step before upgrading, (ii) low heat of adsorption, low energy of regeneration, (iii) possibility of heteroatoms functionalization to modify their adsorption behavior and (iv) high CO 2 adsorption capacity at ambient pressure [19]. Furthermore, activated carbons can be produced with a lower cost than other adsorbents, with a wide range of available precursor material.…”

CO2 and CH4 Adsorption Behavior of Biomass-Based Activated Carbons

“…In this type of separation technology, the components of a gas mixture are separated by their molecular characteristics and affinity to an adsorbent material. For this purpose, a variety of materials have been studied including zeolites [7][8][9], carbon molecular sieves (CMS) [10][11][12], metal organic frameworks (MOFs) [13][14][15] and activated carbons (ACs) [16][17][18]. Among these materials, activated carbons present advantages in terms of: (i) hydrophobicity; thus, there is no need for a drying step before upgrading; (ii) low heat of adsorption, therefore a low energy of regeneration; (iii) the possibility of heteroatoms' functionalization to modify their adsorption behavior; and (iv) high CO 2 adsorption capacity at ambient pressure [19].…”