Investigation into the adsorption of CO2, N2 and CH4 on kaolinite clay

Abstract

Investigating the adsorption characteristics of CO 2 , N 2 and CH 4 on kaolinite clay is beneficial for enhanced shale gas recovery by gas injection. In this paper, the experiments of CO 2 , N 2 and CH 4 adsorption at 288 K, 308 K and 328 K on kaolinite clay were conducted, and the thermodynamics analysis of adsorption of three gases was performed. The findings reveal that the order of the uptakes of three gases on kaolinite clay is as follows: N 2 < CH 4 < CO 2 . Reducing temperature enlarges the separation coefficients of CO 2 over CH 4 ( α CO2/CH4 ), CO 2 over N 2 ( α CO2/N2 ), and CH 4 over N 2 ( α CH4/N2 ). The value of α CO2/CH4 greater than one validates that CO 2 is capable to directly replace the pre-adsorbed CH 4 . The spontaneity of CO 2 adsorption is the highest, while N 2 has the lowest adsorption spontaneity. Injecting N 2 into gas-bearing reservoir can cause CH 4 desorption by lowering the spontaneity of CH 4 adsorption. Adsorbed CO 2 molecules form a most ordered rearrangement on kaolinite surface. The decrease rate of entropy loss for N 2 adsorption is higher than those for CO 2 and CH 4 adsorption.