In this study, we investigated the effect of tetra-n-butyl ammonium bromide (TBAB) on separation and/or collection of CO(2) from CO(2)/H(2) (40:60) gas mixture via hydrate crystallization. The phase equilibrium conditions shifted to milder conditions as increasing the amount of TBAB additive up to 3.0 mol%. The existence of the critical concentration of the additive effects on the phase equilibrium conditions was also observed. The hydrate formation rate in 1.0 mol% TBAB solution showed the highest value while the hydrate formation rate in 3.0 mol% TBAB solution showed the lowest value. Raman analyses revealed that only CO(2) gas molecules enclathrated under experimental conditions carried out in this study. The phase equilibrium temperature of CO(2)-H(2) (40:60) mixture gas hydrate systems with TBAB additive located in the range of between 283 and 290 K at the integrated gasification combined cycle (IGCC) process pressure range of 2.5-5.0 MPa. This study provides the potential of hydrate process to separate the CO(2) gas from CO(2)-H(2) (40:60) mixture gas in IGCC process without significantly lowering the processing temperature. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.