Design of Gas Separation Processes Using Type II Porous Liquids as Physical Solvents
Isaiah Borne, Natalie Simon, Christopher W. Jones, Ryan P. Lively
Abstract
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 such as 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, especially physisorption-based systems. 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 (i.e., Henry + Langmuir) and show excellent potential for gas separations. In this work, a first-order high-pressure CO2/CH4 separation process is modeled using a porous liquid comprised of a discrete porous material dissolved in a sterically hindered solvent. Gas–liquid phase equilibria of the porous liquids are modeled using gas-cage equilibrium data. A McCabe–Thiele approach is employed to estimate the amount of solvent and size of the absorption tower needed compared to an industrial solvent, revealing that porous liquids can decrease the capital needed to adequately separate a gaseous mixture. The energy requirements for a variety of regeneration scenarios are calculated, highlighting that porous liquids can lower the energy burden necessary for gas separation processes. The porous liquid shows the potential to significantly reduce the solvent consumption and size of operating units for this gas separation, with the potential to lower the overall cost and energy required to capture CO2.