This study takes place in the context of the use of a Synthesis Gas in Gas To Liquid process, liquid hydrocarbon production by conversion based on Fischer-Tropsch synthesis. Our aim is the process improvement by a selective recycling of the tail gas. So, we measure pure component isotherms for four gases (CO2, CH4, CO, N-2) of the tail gas until 2000 kPa and binary mixture (CO2-CH4; CO2-N-2; CH4-N-2) equilibria at 303.15 K and 400 and 950 kPa onto a ZSM-5 zeolite. We also predict the binary mixture equilibria by the Ideal Adsorbed Solution Theory (LAST) and the Vacancy Solution Model (VSM, Flory-Huggins and Wilson forms) and we obtain very good results. So not only binary mixture equilibria but also ternary and quaternary mixture adsorption can be predicted. With these data (experimental and simulated), we can conclude that the CO2 is the most adsorbed component while N-2 is the least one. These two components can be separated from CH4 and CO which are sent in the Synthesis Gas production step. (C) 2011 Elsevier Ltd. All rights reserved.