The hydrate-based CO2 (carbon dioxide) separation and capture from CO2/H-2 (hydrogen) gas mixtures with the different CO2 concentrations is investigated in 0.29 mol% TBAB (tetra-n-butyl ammonium bromide) solution. Raman spectroscopic analysis is employed to determine the compositions of the mixed hydrates containing CO2, H-2, TBAB and H2O (water). The phase equilibrium conditions shift to extreme conditions as decreasing CO2 from 40.0% to 10.0% in the gas mixtures. At the temperature of 274.15 K and under driving force of 3.0 MPa, the hydrate formation induction time increases while the CO2 recovery (or separation fraction) decreases with the decrease of CO2. Raman peaks for CO2 gas shift to higher frequency side of 6-10 cm(-1) as the CO2 concentration turns from 40.0% to the range of 10.0 -18.0%. Meanwhile, no Raman spectral signal is detected for H H stretching vibration in the mixed hydrates. (C) 2013 Elsevier Ltd. All rights reserved,