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CO₂ (carbon dioxide) separation from CO₂–H₂ (hydrogen) gas mixtures by gas hydrates in TBAB (tetra-n-butyl ammonium bromide) solution and Raman spectroscopic analysis

Xu, Chun-Gang, Zhang, Shao-Hong, Cai, Jing, Chen, Zhao-Yang, Li, Xiao-Sen
Energy 2013 v.59 pp. 719-725
carbon dioxide, gas hydrate, hydrogen, spectroscopy, temperature, vibration
The hydrate-based CO₂ (carbon dioxide) separation and capture from CO₂/H₂ (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, H₂, 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.