Solid Waste of Fly Ash toward Energy-Efficient CO₂ Capture

Abstract

Catalytic CO 2 absorption−desorption has attracted broad interest due to its potential for improving CO 2 absorption efficiency and reducing energy consumption in CO 2 separation. However, most utilized catalysts are synthetic and pure, with the development of a natural and hybrid catalyst with acid−base bifunctional catalytic characteristics remaining a significant challenge. In this work, three fly ashes (1-FA, 2-FA, and 3-FA) with different compositions were used as catalysts, and the provided synergistic benefits in the overall MEA-CO 2 absorption−desorption processes were evaluated. The results showed that Brønsted acid sites, Lewis acid sites, and Lewis base sites were available on the fly ash surface, which provided proton and electron donation capability. 1-FA exhibited the best catalytic performance by enhancing the CO 2 cyclic absorption capacity by 6.7−26.1%, improving the CO 2 desorption rate with the highest value of 96.0%, and decreasing the sensible heat by 24− 28% compared to MEA as a blank run. Furthermore, 1-FA exhibited comparable catalytic performance to typical HZSM-5. The results of this study demonstrated that fly ash with zero cost and high availability could serve as a good hybrid catalyst candidate for CO 2 absorption and desorption.

Synergistic Catalysis of SO42–/TiO2–CNT for the CO2 Desorption Process with Low Energy Consumption

“…With regard to MEACOO – /MEACOOH, their concentration in the MEA solution with STC-1.0 was decreased compared with the blank test, which illustrated the contribution of STC-1.0 to MEACOO – direct decomposition (eq ). It is believed that the acid sites on the catalyst surface could accelerate the MEACOO – decomposition. , Therefore, STC-1.0 could simultaneously catalyze HCO 3 – and MEACOO – decomposition, consistent with the results obtained from Raman spectra.…”

“…Up to now, several techniques have been developed to decrease the energy consumption of the desorption process, such as electrochemically mediated amine regeneration, novel solvent formulas, and catalysts. − It is widely acknowledged that the addition of solid acid catalysts can facilitate rapid MEA regeneration at a low temperature without requiring facility modifications, such as zeolites, mental oxides, and solid super acids. − In general, metal oxides and solid super acids (SO 4 2– /TiO 2 , SO 4 2– /ZrO 2 , and so on) have stronger acidity, and zeolites possess a comparatively large surface area and centralized pore distribution. A large mesoporous specific surface area and abundant acid sites are both crucial for developing efficient catalysts. , To satisfy these two requirements, supported catalysts have been designed to accelerate MEA regeneration with a lower heat duty.…”

Harnessing Ash for Sustainable CO2Absorption: Current Strategies and Future Prospects

“…Chen, L. et al investigated the catalytic potential of three fly ashes (1-FA, 2-FA, and 3-FA) with diverse compositions for enhancing CO 2 absorption and desorption in MEA absorbent. [124] The experimental results highlight the presence of Bronsted acid, Lewis acid, and Lewis base sites on the fly ash surface, enabling proton and electron donation. Among the fly ashes, 1-FA exhibits superior catalytic performance, as shown in Figure 7, enhancing CO 2 cyclic absorption by 6.7-26.1 %, achieving a 96.0 % increase in CO 2 desorption rate, and reducing sensible heat by 24-28 % compared to blank MEA runs.…”

“…Optimizing conditions, including a high gravity factor of 48.09, liquid-gas ratio of 0.07, and NH2-MCM-41 dosage of 0.1 wt %, led to a 4.7 % improvement in CO 2 capture efficiency. Furthermore, the application of NH2-MCM-41 increased KGa from 0.844 s À 1 to 1.095 s À 1 , while decreasing HTU from 0.019 m to 0.015 m. The high gravity environment notably improved the [124] Copyright 2023 American Chemical Society.…”

“…Figure 7. Cyclic CO 2 Absorption (a) and rate (b) of the MEA solution with and without 1-FA; cyclic CO 2 desorption amount (c) and rate (d) of the MEA solution with and without 1-FA [124]. Copyright 2023 American Chemical Society.…”