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Xu C, Wang Z, Wang F, Tang Z. NaNO 3-Promoted MgO-Based Adsorbents Prepared from Bischofite for CO 2 Capture: Experimental and Density Functional Theory Study. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:5001-5010. [PMID: 38388338 DOI: 10.1021/acs.langmuir.4c00222] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/24/2024]
Abstract
MgO has broad application potential in CO2 capture at intermedium temperatures. In this paper, the effects of NaNO3 doping on the properties of MgO prepared by using waste bischofite as the raw material were investigated to improve the performance of the CO2 capture. MgO-doped NaNO3 exhibited excellent CO2 capture performance at 320 °C with a maximum adsorption capacity of 36.62 wt %. MgO-doped NaNO3 has good cycling stability after 10 adsorption-desorption cycle experiments. In addition, CO2 adsorption on pure MgO and MgO-NaNO3 surfaces was investigated in accordance with density functional theory. Calculation results show that doping with NaNO3 allows more electrons to be transferred from the MgO substrate to the CO2 molecule. MgO-doped NaNO3 can lead to an increase in adsorption energy, resulting in a more stable structure after adsorption and thereby promoting adsorption. The result of this study provides an effective method for the comprehensive utilization of salt lake resources.
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Affiliation(s)
- Chunhui Xu
- Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Xining 810008, China
- Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China
- College of Energy and Power Engineering, Inner Mongolia University of Technology, Hohhot 010051, China
| | - Zirui Wang
- Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China
| | - Feng Wang
- College of Energy and Power Engineering, Inner Mongolia University of Technology, Hohhot 010051, China
| | - Zhongfeng Tang
- Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Xining 810008, China
- Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China
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Rekhtina M, Bugaev A, Dunstan MT, Dal Pozzo A, Nadjafi M, Borca C, Huthwelker T, Abdala PM, Müller CR. Probing the Local Structure of Na in NaNO 3-Promoted, MgO-Based CO 2 Sorbents via X-ray Absorption Spectroscopy. CHEMISTRY OF MATERIALS : A PUBLICATION OF THE AMERICAN CHEMICAL SOCIETY 2023; 35:10060-10069. [PMID: 38107192 PMCID: PMC10720340 DOI: 10.1021/acs.chemmater.3c02077] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/16/2023] [Revised: 11/15/2023] [Accepted: 11/15/2023] [Indexed: 12/19/2023]
Abstract
This work provides insight into the local structure of Na in MgO-based CO2 sorbents that are promoted with NaNO3. To this end, we use X-ray absorption spectroscopy (XAS) at the Na K-edge to interrogate the local structure of Na during the CO2 capture (MgO + CO2 ↔ MgCO3). The analysis of Na K-edge XAS data shows that the local environment of Na is altered upon MgO carbonation when compared to that of NaNO3 in the as-prepared sorbent. We attribute the changes observed in the carbonated sorbent to an alteration in the local structure of Na at the NaNO3/MgCO3 interfaces and/or in the vicinity of [Mg2+···CO32-] ionic pairs that are trapped in the cooled NaNO3 melt. The changes observed are reversible, i.e., the local environment of NaNO3 was restored after a regeneration treatment to decompose MgCO3 to MgO. The ex situ Na K-edge XAS experiments were complemented by ex situ magic-angle spinning 23Na nuclear magnetic resonance (MAS 23Na NMR), Mg K-edge XAS and X-ray powder diffraction (XRD). These additional experiments support our interpretation of the Na K-edge XAS data. Furthermore, we develop in situ Na (and Mg) K-edge XAS experiments during the carbonation of the sorbent (NaNO3 is molten under the conditions of the in situ experiments). These in situ Na K-edge XANES spectra of molten NaNO3 open new opportunities to investigate the atomic scale structure of CO2 sorbents modified with Na-based molten salts by using XAS.
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Affiliation(s)
- Margarita Rekhtina
- Laboratory
of Energy Science and Engineering, Department of Mechanical and Process
Engineering, ETH Zürich, Leonhardstrasse 21, 8092 Zürich, Switzerland
| | - Aram Bugaev
- Paul
Scherrer Institute, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
| | - Matthew T. Dunstan
- Department
of Chemistry, University of Cambridge, Cambridge CB2 1EW, U.K.
| | - Alessandro Dal Pozzo
- Laboratory
of Energy Science and Engineering, Department of Mechanical and Process
Engineering, ETH Zürich, Leonhardstrasse 21, 8092 Zürich, Switzerland
- Laboratory
of Industrial Safety and Environmental Sustainability, Department
of Civil, Chemical, Environmental and Materials Engineering, Alma
Mater, Studiorum—Università
di Bologna, Via Terracini
28, 40131 Bologna, Italy
| | - Manouchehr Nadjafi
- Laboratory
of Energy Science and Engineering, Department of Mechanical and Process
Engineering, ETH Zürich, Leonhardstrasse 21, 8092 Zürich, Switzerland
| | - Camelia Borca
- Paul
Scherrer Institute, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
| | - Thomas Huthwelker
- Paul
Scherrer Institute, Forschungsstrasse 111, 5232 Villigen PSI, Switzerland
| | - Paula M. Abdala
- Laboratory
of Energy Science and Engineering, Department of Mechanical and Process
Engineering, ETH Zürich, Leonhardstrasse 21, 8092 Zürich, Switzerland
| | - Christoph R. Müller
- Laboratory
of Energy Science and Engineering, Department of Mechanical and Process
Engineering, ETH Zürich, Leonhardstrasse 21, 8092 Zürich, Switzerland
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Rekhtina M, Krödel M, Wu YH, Kierzkowska A, Donat F, Abdala PM, Müller CR. Deciphering the structural dynamics in molten salt-promoted MgO-based CO 2 sorbents and their role in the CO 2 uptake. SCIENCE ADVANCES 2023; 9:eadg5690. [PMID: 37379379 DOI: 10.1126/sciadv.adg5690] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2023] [Accepted: 05/23/2023] [Indexed: 06/30/2023]
Abstract
The development of effective CO2 sorbents is vital to achieving net-zero CO2 emission targets. MgO promoted with molten salts is an emerging class of CO2 sorbents. However, the structural features that govern their performance remain elusive. Using in situ time-resolved powder x-ray diffraction, we follow the structural dynamics of a model NaNO3-promoted, MgO-based CO2 sorbent. During the first few cycles of CO2 capture and release, the sorbent deactivates owing to an increase in the sizes of the MgO crystallites, reducing in turn the abundance of available nucleation points, i.e., MgO surface defects, for MgCO3 growth. After the third cycle, the sorbent shows a continuous reactivation, which is linked to the in situ formation of Na2Mg(CO3)2 crystallites that act effectively as seeds for MgCO3 nucleation and growth. Na2Mg(CO3)2 forms due to the partial decomposition of NaNO3 during regeneration at T ≥ 450°C followed by carbonation in CO2.
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Affiliation(s)
- Margarita Rekhtina
- Laboratory of Energy Science and Engineering, Department of Mechanical and Process Engineering, ETH Zürich, Leonhardstrasse 21, 8092 Zürich, Switzerland
| | - Maximilian Krödel
- Laboratory of Energy Science and Engineering, Department of Mechanical and Process Engineering, ETH Zürich, Leonhardstrasse 21, 8092 Zürich, Switzerland
| | - Yi-Hsuan Wu
- Laboratory of Energy Science and Engineering, Department of Mechanical and Process Engineering, ETH Zürich, Leonhardstrasse 21, 8092 Zürich, Switzerland
| | - Agnieszka Kierzkowska
- Laboratory of Energy Science and Engineering, Department of Mechanical and Process Engineering, ETH Zürich, Leonhardstrasse 21, 8092 Zürich, Switzerland
| | - Felix Donat
- Laboratory of Energy Science and Engineering, Department of Mechanical and Process Engineering, ETH Zürich, Leonhardstrasse 21, 8092 Zürich, Switzerland
| | - Paula M Abdala
- Laboratory of Energy Science and Engineering, Department of Mechanical and Process Engineering, ETH Zürich, Leonhardstrasse 21, 8092 Zürich, Switzerland
| | - Christoph R Müller
- Laboratory of Energy Science and Engineering, Department of Mechanical and Process Engineering, ETH Zürich, Leonhardstrasse 21, 8092 Zürich, Switzerland
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