Dr. Liyuan Deng
Associate Professor, Gas Membrane Separation Group, NTNU, Norway.

Speech title: CO₂/H₂ separation by ionic liquid membrane absorption

Abstract: In the past few decades CO₂ capture and storage (CCS) has become the most important part of the portfolio in clean energy production by mitigating greenhouse gas emissions. Among the three CO₂ capture strategies, namely pre-combustion, post-combustion and oxy-combustion, CO₂ separation is much easier and cheaper in the pre-combustion process (CO₂ captured and H2 purification for combustion) owing to the high operating pressure and CO₂ concentration. However, the high operation temperature of the pre-combustion process limits most of the commonly used CO₂ separation technologies. In recent years, ionic liquids (ILs) have attracted great attentions as promising CO₂ absorbents, especially for applications at elevated temperatures. ILs have very low volatility, high CO₂/H₂ selectivity, sorption capacity and thermal stability. In addition, ILs are tailorable in physical and chemical properties.
This work focuses on H₂ purification at pre-combustion conditions by CO₂ absorption in gas–liquid membrane contactors using ILs as absorbents. Membrane contactor can be an effective alternative for the CO₂ absorption/stripping with larger interfacial area, better device-modularity, and more operational flexibility compared with conventional absorption columns [1]. Moreover, membrane contactor overcomes the disadvantages of traditional packed columns such as emulsions, foaming, unloading and flooding.
In this work, thermally robust glass tubular membranes and polymeric composite membranes are applied in the membrane contactor. ILs with high CO₂ absorption capacity and good long-term thermal stability at elevated temperature and pressure were chosen as the absorbents. The effects of the operating parameters on the CO₂ capture performance were systematically investigated, including the operating temperature, pressure, and gas flow rate.
Recently ILs have been reported as good catalysts for CO₂ conversion. For example, Rosen et al. reported an electro-catalytic system that reduces CO₂ to carbon monoxide (CO) at overpotentials below 0.2 volts (V) [2]. The system relies on an ionic liquid electrolyte to lower the energy of the (CO₂) – intermediate, most likely by complexation, and thereby lower the initial reduction barrier. Instead of using the conventional absorption/desorption loop, the potential of developing an integrated CO₂ membrane absorption/conversion system will be discussed.