(71f) A Novel CO2 Absorption Process Enabled By Dedicated Biphasic Solvents: Solvent Screening and Process Development

Biphasic solvent-based absorption processes have recently been of growing research interest as an alternative technology to the conventional absorption processes for post-combustion CO₂ capture. Such processes employ biphasic solvents that can form dual liquid phases during CO₂ absorption, with the absorbed CO₂ concentrated in one phase and lean in the other. The CO₂-concentrated liquid phase is the only part of solvent to be regenerated, resulting in a reduced mass for CO₂ stripping, an elevated stripping pressure associated with high CO₂ loading, and thus reduced energy consumption.

We are presently developing a novel absorption process enabled by a dedicated new class of biphasic solvents to further improve the performance of biphasic absorption processes by maximizing absorption kinetics and minimizing the concern of high solvent viscosity associated with high CO₂ loading. Totally 34 solvent blends have been formulated and experimentally screened with respect to phase transition behavior, absorption kinetics, and vapor-liquid equilibrium performance. Preliminary results revealed that the phase transition, in terms of its dependence on CO₂ loading and volumetric distribution between two phases, could be tuned with selection of solvent components or composition. The solvents could be formulated to have faster absorption rates than that of the benchmark 5M monoethanolamine (MEA) aqueous solution. The loading capacities of the solvents for CO₂ stripping were 40 to 250% higher than 5M MEA and the stripping pressures generally ranged between 5 and 10 bar under the regenerated lean solution conditions at 120 °C. 

In this presentation, an overview of the novel biphasic absorption process will be provided, the preliminary results of the biphasic solvent screening study will be updated, and their indications to the process techno-economic performance will be discussed.