Effect of Pore Size Distribution on Adsorption Capacities of Activated Carbons for CH4 and CO2

A series of activated carbons were prepared using coconut-shells as carbon precursor with different carbonization and activation temperatures. The activated carbons have almost the same structure properties and no adsorbed organic groups on the surface. The density functional theory (DFT) and BJH methods were used to estimate the pore size distribution of the activated carbons. The results reveal that the content of the micro-pores increase and then decrease with increase in temperature, and the content reaches to the maximum when the carbonization temperature is up to 700 degrees C and activation temperature elevates to 800 degrees C. The mesopores increase with the increase of the temperature. The adsorption capacities of CH4, CO2 were tested at room temperature. The results suggest that the activated carbons have high adsorption capacity, more than 1.0 mmol.g(-1), however, that of CH4 differs a lot. The activated carbons were applied to adsorption separation of CH4/CO2 mixed gas with molar ratio of 9 by pressure swing adsorption technology. The results show that the activated carbons have excellent property of adsorption separation of CH4/CO2 mixed gas at room temperature, especially for AC-2 carbonized at 700 degrees C activated at 800 degrees C.