To determine the appropriate operating conditions for separating carbon dioxide from flue gas via the hydrate formation, the effects of the concentrations of dodecyl trimethyl ammonium chloride (DTAC) in 0.29 mol% Tetra-n-butyl ammonium bromide (TBAB) aqueous solution and the initial pressures on the induction time of the hydrate formation and CO2 separation efficiency are investigated. The experiments are conducted at the DTAC concentration range of 0-0.056 mol%, initial pressures range of 0.66 MPa-2.66 MPa and temperature range of 274.95 K-277.15 K. The results indicate that the initial pressure of 1.66 MPa in conjunction with the concentration of 0.028 mol% DTAC is most favorable for CO2 separation. At the condition, the induction time of forming the hydrate can be shortened considerably and CO2 can be purified from 17.0 mol% to 99.4% with the two-stage hydrate separation process. CO2 split fractions for Stage 1 and Stage 2 are 0.54 and 0.39, respectively, and the separation factors are 9.60 and 62.25, respectively. Crown Copyright (C) 2010 Published by Elsevier Ltd. All rights reserved.