KOH activation effect on CMK-3 carbons mesoporous structure, and its CO2:CH4 selective adsorption

The recent demand for biogas requires exploring new materials with tunable porosity to improve the selective adsorption capacity of CO2:CH4. Experimental results of N-2 adsorption at 77 K were reported to evaluate the textural changes of three CMK-3 KOH-activated samples in mass ratios 1, 3, and 5. Also, the CO2 and CH4 adsorption isotherms at 243-303 K were obtained. The individual isotherms were used to calculate the ideal selectivity, assuming an ideal mixture of 30: 70%, respectively. The results showed the increased microporosity for the activated samples associated with the gradual destruction of the mesoporous structure shown in the SEM micrographs and the pore size distribution (PSD) graphics. These changes improved the preferential adsorption of CO2 over CH4 from S-CO2/CH4 = 5.9 for CMK-3 to S-CO2/CH4 = = 7.6 for NAC-1 at 0.2 P/P-0 and specific surface areas of 1350 and 1500 m(2)/g respectively.