Adsorption Thermodynamics Analysis of CO2 and CH4 on Anthracite Matrix Surface

Taking the anthracite sampled from Sichuan coalfield as the research object, the adsorption isotherms of CO2 and CH4 at the temperatures of 288 K, 308 K and 328 K are determined by the high precision intelligent weight adsorption instrument, and the adsorption thermodynamics properties of CO2 and CH4 on coal matrix surface are studied. Research results show that Henry’s constant of CH4 is lower than that of CO2, and CH4 has the weaker affinity on coal matrix surface. The increase of temperature can reduce Henry’s constant and thereby weaken the interaction of coal matrix surface and both of gases. The negative Gibbs free energy change and surface potential energy of CH4 are higher than those of CO2, which reveals that CO2 adsorption on anthracite is more spontaneous and favorable. With the increase of pressure, the negative Gibbs free energy change and surface potential energy decrease gradually, and the high pressure can facilitate gas adsorption. With the increase of adsorption amount, the isosteric heat of adsorption and entropy loss of CO2 rise, while the isosteric heat of adsorption and entropy loss of CH4 decrease. The isosteric heat of adsorption and entropy loss of CO2 are both bigger than those of CH4.