Flue gas and coal bed methane are two important sources of greenhouse gases. Pressure swing adsorption process has a wide range of application in the field of gas separation

and the selection of adsorbent is crucial. In this regard

in order to assess the better adsorbent for separating CO

2

from flue gas and CH

4

from coal bed methane

adsorption isotherms of CO

2

CH

4

and N

2

on activated carbon and carbon molecular sieve are measured at 303.15

318.15 and 333.15 K

and up to 250 kPa. The experimental data fit better with Langmuir 2 compared to Langmuir 3 and Langmuir-Freundlich models

and Clausius-Clapeyron equation was used to calculate the isosteric heat. Both the order of the adsorbed amount and the adsorption heat on the two adsorbents are CO

2

CH

4

N

2

. The adsorption kinetics are calculated by the pseudo-first kinetic model

and the order of adsorption rates on activated carbon is N

2

≥ CH

4

CO

2

while on carbon molecular sieve

it is CO

2

≥ N

2

CH

4

. It is shown that relative molecular mass and adsorption heat are the primary effect on kinetics for activated carbon

while kinetic diameter is the main resistance factor for carbon molecular sieve. Moreover

the adsorption selectivity of CH

4

/N

2

and CO

2

/N

2

were estimated with the ideal a

dsorption solution theory

and carbon molecular sieve performed best at 318.15 K for both CO

2

and CH

4

separation. The study suggested that activated carbon is a better choice for separating flue gas and carbon molecular sieve can be a strong candidate for separating coal bed methane.