Design of Gas Separation Processes Using Type II Porous Liquids As Physical Solvents

The separation of gas mixtures is necessary to capture CO₂ and lower anthropogenic greenhouse gas emissions. Solvent-based absorption systems are frequently used for industrial-scale CO₂ capture from point sources. Physical and chemical solvents are well understood; however, there are drawbacks like low gas capacity, high regeneration energy, and large operating units. Porous liquids (liquids with intrinsic microporosity) present an opportunity to improve the effectiveness of solvent-based separation processes. Type II porous liquids are developed by dissolving a discrete, microporous material in a sterically hindered solvent that cannot penetrate the pores of the porous material. These liquids exhibit dual-mode sorption and show excellent potential for gas separations. In this work, a CO₂/CH₄ separation process is modeled using a porous liquid comprised of a discrete porous material dissolved in a sterically hindered solvent. A McCabe-Thiele approach was employed to estimate the amount of solvent and size of the absorption tower needed compared to an industrial solvent. The energy requirements for a variety of regeneration scenarios were calculated. The porous liquid shows potential to significantly reduce the amount of solvent and size of operating units for gas separations which would lower the overall cost and energy required to capture CO₂.