(91b) High Capacity Regenerable Sorbent for Pre-Combustion CO2 Capture

TDA is developing a novel sorbent that removes CO₂ via physical adsorption from both synthesis gas, while the relatively strong affinity of the sorbent for CO₂ enables effective operation at temperatures up to 300^oC (well above the dew point of synthesis gas stream generated by most commercial gasifiers). However, because the sorbent and the CO₂ do not form a true covalent bond, the energy needed to regenerate our sorbent (5.4 kcal per mol of CO₂) is much lower than that observed for either chemical absorbents (e.g., 29.9 kcal/mol CO₂ for sodium carbonate) or amine-based solvents (e.g., 14.2 kcal/mol CO₂ for monoethanolamine). Our sorbent can be regenerated isothermally and CO₂ can be recovered at pressure (~150 psia). Thus, the energy needed to regenerate the sorbent and compress the CO₂ for sequestration is significantly lower than that for any technology reported to date. TDA's CO₂ sorbent could be used to capture CO₂ in a Integrated Gasification Combined Cycle (IGCC) power plant after the water-gas-shift (WGS) reaction when most of the carbon is in the form of CO₂. The high surface area and favorable porosity of the sorbent also provide a unique platform to introduce additional functionality, such as active groups to catalyze the or to remove trace metals (e.g., Hg, As).

We carried out bench-scale evaluations of TDA's CO₂ sorbent in both fixed-bed adsorber and a thermo gravimetric analyzer (TGA). The sorbent achieved high CO₂ capacity, high removal efficiency and excellent durability. The sorbent showed stable performance in both these systems under simulated synthesis gas (44 cycles in the bench-scale flow system and over 1,644 cycles in the TGA). We also studied the effect of operating parameters like temperature, pressure, and cycle time on the sorbent performance. The results from our on-going sorbent evaluations will be presented at the meeting.