Hydroquinone clathrate based gas separation (HCBGS): Application to the CO2/CH4 gas mixture

Hydroquinone (HQ) clathrates have recently been identified as promising candidates for selective gas capture and storage processes. This study evaluates the effectiveness of HQ clathrates in the separation of CO2 from CO2/CH4 gas mixtures, through direct gas/solid reactions in a fixed-bed reactor. The influence of the process operating parameters (i.e. reaction time, pressure, temperature and feed gas composition) on the CO2 capture kinetics, selectivity towards CO2, and transient storage capacity were investigated. The experiments were performed using either pure HQ or HQ-based composite materials, with temperatures ranging from about 283 to 343 K, pressures from 3.0 to 9.0 MPa, and CO2 mole fraction in the gas mixture ranging from 0.2 to 1. The experimental results show that over the range of gas composition investigated, the enclathration reaction is selective to CO2. This preferential CO2 capture is enhanced at high CO2 mole fractions, low temperatures and high pressures. Regarding gas capture kinetics, it was confirmed that the composite material is much more efficient than pure HQ crystals. The CO2 enclathration rate increases with temperature, pressure and CO2 fraction in the feed gas. For the first time, the feasibility of such gas separation techniques using HQ clathrates was demonstrated at bench scale.