A study of the nitrate ion dissociation in fused nitrates

Kust, Roger N.

doi:10.31274/rtd-180813-473

Cited by 4 publications

(5 citation statements)

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“…This introduction of nitrite salts shortened the lag time to initiation of the accelerating increase in uptake, increased the uptake rate, and elevated the plateau value. As reported by Kust et al, 41,42 alkali metal nitrites in the molten state have higher concentrations of oxide ions (O 2− ) than do the nitrates at the same cation composition. The ability of the nitrite salts to accommodate higher concentrations of oxygen ions allows the fast generation of carbonate ions (CO 3 High regenerability under repeated cycles of CO 2 uptake and release is an indispensable requirement for practical CO 2 adsorbents used in commercialized CCUS systems.…”

Section: Resultsmentioning

confidence: 70%

Colloidal Nanoclusters of MgO Coated with Alkali Metal Nitrates/Nitrites for Rapid, High Capacity CO₂ Capture at Moderate Temperature

2015

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Colloidal nanoclusters of metal oxides constitute a promising new class of building blocks for a range of advanced functional materials. Herein, we report on the development of colloidal nanoclusters of MgO for CO2 capture prepared by a novel nonhydrolytic sol–gel reaction followed by the deposition of alkali metal salts by methanol evaporation-induced surface precipitation. The CO2 uptake exceeded 11.7 mmol g–1 (514.8 mg CO2 per 1 g of adsorbent) in 30 min in the presence of 100% dry CO2 under ambient pressure (1 bar) at 340 °C and reached 15.7 mmol g–1 (690.8 mg CO2 per 1 g of adsorbent) in 4 h. Colloidal nanoclusters possessing multiple inner grain boundaries and rough surfaces allowed for a dramatic increase in active surface area of MgO coated with thin layers of alkali metal salts and enabled the rapid conversion of MgO to MgCO3 with high conversion ratio. It was also discovered that the CO2 uptake loading and the regenerability of the sorbents can be enhanced on introduction of nitrite salts to the coating layer through the formation of magnesium nitro or nitrate species, which increased the critical thickness of product layers and mitigated the degradation of nanoclusters over the repeated sorption/desorption cycles.

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Section: Resultsmentioning

confidence: 70%

Colloidal Nanoclusters of MgO Coated with Alkali Metal Nitrates/Nitrites for Rapid, High Capacity CO₂ Capture at Moderate Temperature

2015

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“…2− and, thus, enabling fast nucleation and growth of MgCO 3 . 39,40 In this case, the sodium nitrite sample reacted with the magnesium precursor to form Na 2 CO 3 with the solid state during the carbonation process, resulting in partial losses of the available molten nitrate promoters.…”

Section: Methodsmentioning

confidence: 99%

Study on MNO₃/NO₂ (M = Li, Na, and K)/MgO Composites for Intermediate-Temperature CO₂ Capture

et al. 2018

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Molten salt [MNO3/NO2 (M = Li, Na, and K)]-promoted MgO composite-type CO2 adsorbents with high capacity and cycling stability are fabricated by controlled hydrolysis along with an incipient impregnation approach. The remarkable results of molten salts on the CO2 capture performance of MgO adsorbents and the CO2 capture capacities with different loadings and calcination and adsorption temperatures were comprehensively investigated. Notably, optimized NaNO3-promoted MgO exhibited the highest CO2 capture capacity of 17.0 mmol g–1 at 350 °C and maintained excellent regenerability through multiple cycles. The initial CO2 uptakes of MNO3/NO2 (M = Li, Na, and K)/MgO composites follow the order of NaNO3 (17.0 mmol g–1) > LiNO3 (14.1 mmol g–1) > NaNO2 (12.5 mmol g–1) > KNO2 (9.3 mmol g–1) > KNO3 (5.0 mmol g–1). Furthermore, NaNO3 and KNO3 with good chemical stability are the effective constituents for the NaNO3 system and KNO3/KNO2-promoted system, respectively, and preserved their original form after the interaction with CO2. The NaNO2 system consists of NaNO3 and Na2CO3 to form double carbonates Na2Mg(CO3)2 after CO2 adsorption. The morphology and structure of the MgO skeleton and the introduction of promoters are essential factors for intermediate-temperature CO2 capture.

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“…Kust et al determined potentiometrically that the oxygen ion concentration at 300 °C formed by eq 2 is 2 × 10 −7 mol L −1 , corresponding to 8 × 10 −11 mol g MgO −1 for a typical NaNO 3 -promoted MgO sorbent, which is 8 orders of magnitude lower than the oxygen concentration at the surface of MgO (see Figure S17 for calculations). 47,48 Furthermore, alkali metal nitrates heated to temperatures above their melting point can thermally decompose, leading to the formation of nitrites 49 NO NO 1/2O…”

Section: Do Oxygen Atoms From Nano 3 Participate In the Carbonation R...mentioning

confidence: 99%

Uncovering the CO₂ Capture Mechanism of NaNO₃-Promoted MgO by ¹⁸O Isotope Labeling

Landuyt

Kumar

Yuwono

et al. 2022

JACS Au

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MgO-based CO2 sorbents promoted with molten alkali metal nitrates (e.g., NaNO3) have emerged as promising materials for CO2 capture and storage technologies due to their low cost and high theoretical CO2 uptake capacities. Yet, the mechanism by which molten alkali metal nitrates promote the carbonation of MgO (CO2 capture reaction) remains debated and poorly understood. Here, we utilize 18O isotope labeling experiments to provide new insights into the carbonation mechanism of NaNO3-promoted MgO sorbents, a system in which the promoter is molten under operation conditions and hence inherently challenging to characterize. To conduct the 18O isotope labeling experiments, we report a facile and large-scale synthesis procedure to obtain labeled MgO with a high 18O isotope content. We use Raman spectroscopy and in situ thermogravimetric analysis in combination with mass spectrometry to track the 18O label in the solid (MgCO3), molten (NaNO3), and gas (CO2) phases during the CO2 capture (carbonation) and regeneration (decarbonation) reactions. We discovered a rapid oxygen exchange between CO2 and MgO through the reversible formation of surface carbonates, independent of the presence of the promoter NaNO3. On the other hand, no oxygen exchange was observed between NaNO3 and CO2 or NaNO3 and MgO. Combining the results of the 18O labeling experiments, with insights gained from atomistic calculations, we propose a carbonation mechanism that, in the first stage, proceeds through a fast, surface-limited carbonation of MgO. These surface carbonates are subsequently dissolved as [Mg2+···CO3 2–] ionic pairs in the molten NaNO3 promoter. Upon reaching the solubility limit, MgCO3 crystallizes at the MgO/NaNO3 interface.

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A study of the nitrate ion dissociation in fused nitrates

Cited by 4 publications

References 0 publications

Colloidal Nanoclusters of MgO Coated with Alkali Metal Nitrates/Nitrites for Rapid, High Capacity CO₂ Capture at Moderate Temperature

Colloidal Nanoclusters of MgO Coated with Alkali Metal Nitrates/Nitrites for Rapid, High Capacity CO₂ Capture at Moderate Temperature

Study on MNO₃/NO₂ (M = Li, Na, and K)/MgO Composites for Intermediate-Temperature CO₂ Capture

Uncovering the CO₂ Capture Mechanism of NaNO₃-Promoted MgO by ¹⁸O Isotope Labeling

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A study of the nitrate ion dissociation in fused nitrates

Cited by 4 publications

References 0 publications

Colloidal Nanoclusters of MgO Coated with Alkali Metal Nitrates/Nitrites for Rapid, High Capacity CO2 Capture at Moderate Temperature

Colloidal Nanoclusters of MgO Coated with Alkali Metal Nitrates/Nitrites for Rapid, High Capacity CO2 Capture at Moderate Temperature

Study on MNO3/NO2 (M = Li, Na, and K)/MgO Composites for Intermediate-Temperature CO2 Capture

Uncovering the CO2 Capture Mechanism of NaNO3-Promoted MgO by 18O Isotope Labeling

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Colloidal Nanoclusters of MgO Coated with Alkali Metal Nitrates/Nitrites for Rapid, High Capacity CO₂ Capture at Moderate Temperature

Colloidal Nanoclusters of MgO Coated with Alkali Metal Nitrates/Nitrites for Rapid, High Capacity CO₂ Capture at Moderate Temperature

Study on MNO₃/NO₂ (M = Li, Na, and K)/MgO Composites for Intermediate-Temperature CO₂ Capture

Uncovering the CO₂ Capture Mechanism of NaNO₃-Promoted MgO by ¹⁸O Isotope Labeling