Abstract
In this work, we have measured the adsorption isotherms and calculated the equilibrium selectivity for CO2, CH4 and N2 on micro-mesoporous nanographene at three temperatures of 298 K, 278 K and 263 K and pressures upto 760 torr. The nanographene sample possesses the size range of 50 -250 nm along with Brunauer–Emmett–Teller (BET) specific surface area 514 m2/g and total pore volume 3 cm3/g. The pore widths varied from 3.5 Å to 8 Å in microporous region and a very large distributed widths within 45 Å to 150 Å in the region of mesoporosity. The calculated equilibrium selectivity of gas separation at 298 K by pressure swing adsorption for CO2/N2, CO2/CH4 and CH4/N2 are 55, 8.2 and 6.5, respectively, whereas the adsorption selection parameters for same pair gases are 540, 101 and 117, respectively. In the order to compare the equilibrium selectivity values with other adsorbents, we have measured the gas adsorption isotherms for CO2, CH4 and N2 on Maxsorb (a commercial activated carbon with BET surface area 3200 m2/g) and calculated the selectivity values on several adsorbents based on their adsorption isotherms reported in 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 CO2/N2 for graphene is higher than all the carbon-based materials reported so far. The equilibrium selectivity for CO2/CH4 and CH4/N2 in graphene is also higher than majority of the adsorbents reported in literature. Our findings suggest that graphene can serve as a potential adsorbent for gas separation purposes.
