Accelerated Testing of PEI-Silica Sorbent Pellets for Direct Air Capture

[Geoengineering News]

https://pubs.acs.org/doi/10.1021/acsomega.4c05639

Authors

Harshul V. Thakkar, Andrew J. Ruba, John A. Matteson, Michael P. Dugas, Rajinder P. Singh

https://doi.org/10.1021/acsomega.4c05639

Published November 6, 2024

Amine-based sorbents have shown exceptional CO2 uptake for direct air capture (DAC). However, amine degradation is a major issue for this class of materials, hindering their deployment for large-scale DAC. In this study, a comprehensive evaluation of polyethylenimine (PEI) sorbents was conducted to understand their degradation under process-relevant environments for the DAC of CO2. A solvent-minimized silica-supported PEI-sorbent powder synthesis method using centrifugal mixing was developed. Unlike traditional solvent-assisted impregnated sorbent synthesis methods, the centrifugal mixing method enabled a 94% reduction in volatile and toxic organic solvent use in pelletized sorbent synthesis. The pelletized sorbents exhibited CO2 adsorption capacities consistent with traditional fabrication methods for PEI-based solid sorbents (about 1 mmol/g). The pelletized sorbent degradation behavior was evaluated at three different regeneration temperatures (80, 100, and 120 °C) under nitrogen (N2), ambient air (21% O2), and saturated dry and wet (75% relative humidity (RH)) CO2 environments using fixed-bed breakthrough (BT) experiments. Additionally, accelerated testing (AT) protocols that mimic industrial DAC conditions were developed to assess the long-term stability of the PEI-silica pellets. Our results indicate that the sorbent degrades rapidly (ca. 94% within 24 h) at 120 °C in ambient air (21% O2), demonstrating the detrimental impact of oxygen when compared to an O2-free environment. AT performed for 100 h (equivalent to 33, 100, and 100 cycles) continuously at 80, 100, and 120 °C reveals that dry CO2-induced degradation of the PEI-silica sorbent pellets is 30–40% and 40–50% more than the degradation measured in wet CO2 and inert (pure N2) environments.

Source: ACS PUBLICATIONS