ADSORPTION AND SEPARATION OF CO2 AND CH4 ON ACTIVATED CARBON MODIFIED BY ACETIC ACID

Compared with the modification of activated carbons by alkalis for gas adsorption, fewer studies of that by acids have been reported, especially by organic acids. The acid modified activated carbons are usually utilized to treat wastewater, whereas the application in the separation of CO2/CH4 has less been studied. In this study, acetic acid was used to modify activated carbon. N-2 adsorption/desorption isotherms, FT-IR and SEM were adopted to describe the properties of the samples. The adsorption of CO2 and CH4, selectivity for binary gas mixtures and thermodynamics were analyzed. The adsorption capacity of CO2 and CH4 calculated by the Sips model is 12.87 mmol/g and 7.02 mmol/g on 15H-AC, increasing about 29.48% and 15.84%, respectively. The selectivity of CO2/CH4 gas mixtures at 298 K and 1 MPa is reached up to 4.70 for a binary mixture of 50/50 vol.% and 4.60 for that of 40/60 vol.%. The adsorbent obtained in this study exhibits higher adsorption capacity, greater CO2/CH4 gas selectivity, and is hoped to be promising in industrial separation of CO2/CH4 gas mixtures.