(506d) Development of Advanced Solid Sorbent for CO2 Capture from Flue Gas

It is widely agreed that carbon capture, utilization and storage (CCUS) technologies offer a promising pathway for affordable, secure and reliable sources of clean energy. In the United States, about 30% and 21% of total US greenhouse gas (GHG) emissions come from fossil fuel-fired power plants and industrial sectors, respectively, which will continue for decades to come. Capture of CO₂ from large sources of emissions such as coal-fired power plants, is of critical importance in mitigating the GHG effect. Molecular basket sorbents (MBS) consisting of functional polymers immobilized in nano-porous materials have shown great potential as highly selective, high-capacity solid sorbent for CO₂ capture [1-3]. In this paper, we report our recent study on the influences of silica support, PEI loading amount, PEG additive, as well as the sorption temperature on the sorption performance of MBS for CO₂ capture [4]. The results suggest that the pore properties of MBS play a more important role in the CO₂ sorption capacity, rather than those of the supports alone. MBS with 3D pore structure exhibits higher CO₂ sorption capacity and amine efficiency than those with 2D-structured support. Among the sorbents studied, fumed silica (HS-5) based MBS showed the highest CO₂ sorption capacity in the temperature range of 30 to 95 °C, probably due to its unique interstitial pores formed by the aggregation of polymer-loaded SiO₂ particles. It was also found that the temperature dependence is directly related to the PEI surface coverage layers. The more PEI surface coverage layers, the higher diffusion barrier for CO₂ and the stronger temperature dependence of CO₂ capacity. 3D MBS exceeds 2D MBS at the same PEI coverage layers due to lower diffusion barrier. Adding PEG can significantly enhance the CO₂ sorption capacity and improve amine efficiency of all MBS, most likely by alleviating the diffusion barrier within PEI bulk layers through the inter-molecular interaction between PEI and PEG. Furthermore, in a practical application effort, we teamed up with the engineers from RTI International and conducted a pilot-plant scale test using a fluidized-bed adsorption-desorption system [5]. The preparation of molecular basket sorbent was successfully scaled up to pilot-plant scale in a large quantity (~150 kg per batch) through collaboration with our partner RTI under DOE support [5]. The testing data showed that that the sorbent is capable of rapid CO₂ removal and exhibits the ability to capture > 90% of CO₂ in flue gas, suggesting a potential to replace the prevalent amine-scrubbing process.

[1] Ma, X.L.; Wang, X.X.; Song, C.S. J. Am. Chem. Soc., 2009, 131, 5777-5783.

[2] Wang, X.X.; Schwartz, V.; Clark, J.C.; Ma, X.L.; Overbury, S.H.; Xu, X.C.; Song, C.S. J. Phys. Chem. C, 2009, 113, 7260-7268.

[3] Wang, X.X.; Ma, X.L.; Schwartz, V.; Clark, J.C.; Overbury, S.H.; Zhao, S.Q.; Xu, X.C.; Song, C.S. Phys. Chem. Chem. Phys., 2012, 14, 1485-1492.

[4] Zhang, L.; Wang, X.X.; Fujii, M.; Yang, L.J.; Song, C.S. J. Energy Chem. 2017, 26, 1030-1038.

[5] Nelson, T.; Kataria, A.; Soukri, M.; Famer, J.; Mobley, P.; Tanthana, J.; Wamg, D.X.; Wang, X.X., Song. C.S. Bench-scale development of an advanced solid sorbent-based CO₂ capture process for coal-fired power plants. DOE-NETL final scientific/technical project report, 2016. https://www.osti.gov/servlets/purl/1301858.