(280b) Catalytic Regeneration of Aqueous Potassium Sarcosinate Solvent to Improve Energy Efficiency of CO2 Direct Air Capture

Absorption of CO₂ in a chemical solvent is technologically a matured carbon capture method. However, cost-effective commercialization is yet to be realized due to the high energy requirement of solvent regeneration. The total regeneration energy (ΔH_total) is a combination of sensible heat (ΔH_sen) required to raise the solvent temperature, heat of vaporization (ΔH_vap) needed to vaporize a part of the solvent, and heat of CO₂-desorption (ΔH_des). Potassium sarcosinate (K-SAR) is an attractive direct air capture solvent but needs heating at temperatures in excess of 100°C for an extended period to release the absorbed CO₂. The current work aims to develop catalyst-aided solvent regeneration that can operate at a lower temperature (<100°C) to reduce the sensible and vaporization heats of K-SAR, as well as provide faster CO₂ desorption kinetics, thereby decreasing the overall energy requirement.

The experimental procedure involved heating 100-mL CO₂-loaded 3M K-SAR solvent on a heater-stirrer with or without catalysts. Various catalytic materials were used in these tests to evaluate their effectiveness: Fe₂O₃, TiO₂, SiO₂, and Fe-ZSM-5 (0.5g catalyst for 100 mL of solvent). The extent of solvent regeneration and its kinetics were determined by analyzing the CO₂ content in the evolved gas with a CO₂ sensor, as well as solvent samples via an acid-base titration. Combined thermogravimetric analysis (TGA-DSG) and FTIR experiments were also performed to quantify the overall regeneration energy and isolate the contributions of ΔH_sen, ΔH_vap, and ΔH_des.

Results obtained with Fe-ZSM5 catalysts showed that 30% better solvent regeneration, in terms of energy requirements, can be achieved in the presence of the catalyst than without it. These preliminary results clearly demonstrate that the regeneration energetics and kinetics of K-SAR solvent can be improved significantly by a catalyst. Such a concept of catalyst-assisted regeneration can also be extended to other common CO₂-capture solvents investigated for point-source capture, such as MEA.