Microtextural and surface chemical heterogeneities of activated carbons (AC) have been studied to see their distinctive role for the adsorption of CO2, CO and N2 at 25 °C and up to 850 Torr. Not only the microtextural properties influence the adsorption of the gases, particularly CO2, but the chemical surface heterogeneity also plays a significant role for CO2 adsorption. The volume of ultramicropores < 7 Å is of predominantly importance in high CO2 adsorption at pressures above 30 Torr. However, the average size of micropores and their size distribution, and the chemical surface heterogeneity are much more critical at the Henry’s law region (< 30 Torr). The latter could be well characterized by the amount and Henry constant of CO2 adsorption at the low pressures, the Toth model parameters, the change in CO2/ CO and CO2/ N2 selectivities with respect to pressure, the amount of CO from the thermal decomposition, and the direct probing of very strong basicity sites using a technique that is the temperature-programmed desorption of CO2 adsorbed. All of them are consistent with the difference in the energetic nonuniformity between ACs studied, except for the last measure whose results could be reasonably explained when combining with the microtextural heterogeneity.

A role of the microtextural and surface chemical heterogeneities of porous carbons for the adsorption of CO2, CO and N2
    Abstract
    1 Introduction
    2 Experimental
        2.1 AC adsorbents
        2.2 Gas adsorption
        2.3 Determination of textural properties
        2.4 CO2 mass-TPD measurements
        2.5 High-temperature thermal decomposition
    3 Results and discussion
        3.1 Adsorption of CO2, CO, and N2
        3.2 Influence of microtextural heterogeneity
        3.3 Influence of surface chemical heterogeneity
            3.3.1 Toth isotherm model parameter and Henry constant
            3.3.2 Changes in selectivity factor with equilibrated pressure
            3.3.3 Basicity of surface functionalities
                3.3.3.1 Direct probing of strong basic sites and their distribution 
                3.3.3.2 Thermochemical properties 
    4 Conclusions
    References

• Moon Hyeon Kim(Department of Environmental Engineering, Daegu University)
• Sang Ok Choi(Experiment and Research Team, Lotte-BP Chemicals Co. Ltd.)
• Soo Tae Choo(Optimization Team, Lotte-BP Chemicals Co. Ltd.)