(204b) Impact of Silane Agent Addition On the Stability of Amine Sorbents for Post-Combustion CO2 Capture

Sonia Hammache^{1, 2}, Adefemi Egbebi^{1, 2}, McMahan L. Gray¹, and Henry W. Pennline¹

¹ US DOE-National Energy Technology Laboratory, Pittsburgh, PA

² URS, Pittsburgh, PA

Amine-based sorbents are being considered as an alternative to the energy intensive aqueous monoethanolamine (MEA) scrubbing process for post-combustion CO₂ capture from coal-fired power plants.  A successful sorbent must be stable under moist conditions present during adsorption and regeneration steps.  This communication evaluates the stability of amine sorbents under humid conditions and the impact of silane agent addition on the stability of these sorbents. 

Amine sorbents were prepared by impregnation of polyethyleneimine (PEI) on silica cross-linked with different aminosilanes.  One such aminosilane is 3-aminopropyltrimethoxy silane (APTES).  Sorbents with four PEI/APTES weight ratios were prepared: 0, 0.4, 1, and 2.3.  CO₂ adsorption-desorption cycling was conducted on these sorbents using a fixed bed reactor.  The baseline performance of the sorbents was determined by testing them under dry cycles.  CO₂ sorption was carried out at 60°C using a gas mixture of 10% CO₂/He at 100 sccm.  Desorption was conducted under helium, starting at 60°C and then ramping up to 105°C.  These sorbents were then tested using a gas composition of 10% CO₂-8% H₂O/He to determine both their stability when exposed to H₂O and the impact of silane addition on the moisture loading.  The sorbents were regenerated under steam conditions at 105°C as well.  The gas effluent was monitored with a mass spectrometer. 

It has been found that as the amount of PEI in the sorbent increased, the CO₂ uptake increased as well; from 1.4 for a PEI/APTES ratio of 0 to 2.6 mmolCO₂/g sorbent for a PEI/APTES ratio of 2.3.  CO₂ capture in the presence of 8% H₂O did not negatively impact the sorbents.  Indeed, a positive impact was seen on the CO₂ uptake of the sorbents, and the increase is proportional to the increase in the PEI/APTES ratio.  For a PEI/APTES ratio of 0 only a 4% increase in CO₂ uptake was seen in contrast to an 18% increase for a PEI/APTES ratio of 2.3.  Regenerating the sorbents under steam conditions had a slight negative impact on the sorbents with PEI/APTES ratios of 0 and 0.4, whereas the remaining sorbents were fairly stable. 

The impact of multiple steam cycles on the aforementioned sorbents and on sorbents cross-linked with various silane agents will be presented as well as their characterization prior to and following steam exposure.