Thermodynamic analysis of competitive adsorption of CO_2 and CH_4 on coal matrix
Abstract：Based on the calculation of surface free energy change and isosteric heat of adsorption,affinity of coal with CO2 and adsorption capacity differences of coal for CO2 and CH4 were theoretically investigated by using the isothermal adsorption test data at 25,30 and 40 ℃ conditions.Compared to adsorption of CH4 and CO2 on coal matrix generally gave rise to more surface free energy change of coal,implying the thermodynamics of coal matrix have more adsorption capacity of CO2 than that of CH4 per unit surface area.The initial isosteric heat of adsorption（Qst0） that was able to quantify adsorption force of coal and gas was calculated by transforming adsorption isosterics curve of coal for CO2 and CH4.The initial isosteric heat of CO2 and CH4 adsorption on coal matrix was 48.2 and 33.4 kJ/mol respectively,so more adsorption force existing between CO2 and coal was concluded.Due to the inter-gas molecules force,isosteric heat of adsorption of CO2 increases with the increasing of adsorption volume,which indicates that multi-molecule layer adsorption happens during the adsorption of CO2 on coal matrix.
Keywords：carbon dioxidemethanecompetitive adsorptionsurface free energyisosteric heat of adsorption
Publication Date：2011-01-01
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)