CO<inf>2</inf> capture properties of lithium silicates with different ratios of Li<inf>2</inf>O/SiO<inf>2</inf>: An ab initio thermodynamic and experimental approach

Yuhua Duan, Heriberto Pfeiffer, Bingyun Li, Issis C. Romero-Ibarra, Dan C. Sorescu, David R. Luebke, J. Woods Halley

Research output: Contribution to journalArticle

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Abstract

The lithium silicates have attracted scientific interest due to their potential use as high-temperature sorbents for CO2 capture. The electronic properties and thermodynamic stabilities of lithium silicates with different Li2O/SiO2 ratios (Li2O, Li 8SiO6, Li4SiO4, Li 6Si2O7, Li2SiO3, Li 2Si2O5, Li2Si3O 7, and α-SiO2) have been investigated by combining first-principles density functional theory with lattice phonon dynamics. All these lithium silicates examined are insulators with band-gaps larger than 4.5 eV. By decreasing the Li2O/SiO2 ratio, the first valence bandwidth of the corresponding lithium silicate increases. Additionally, by decreasing the Li2O/SiO2 ratio, the vibrational frequencies of the corresponding lithium silicates shift to higher frequencies. Based on the calculated energetic information, their CO2 absorption capabilities were extensively analyzed through thermodynamic investigations on these absorption reactions. We found that by increasing the Li 2O/SiO2 ratio when going from Li2Si 3O7 to Li8SiO6, the corresponding lithium silicates have higher CO2 capture capacity, higher turnover temperatures and heats of reaction, and require higher energy inputs for regeneration. Based on our experimentally measured isotherms of the CO 2 chemisorption by lithium silicates, we found that the CO 2 capture reactions are two-stage processes: (1) a superficial reaction to form the external shell composed of Li2CO3 and a metal oxide or lithium silicate secondary phase and (2) lithium diffusion from bulk to the surface with a simultaneous diffusion of CO2 into the shell to continue the CO2 chemisorption process. The second stage is the rate determining step for the capture process. By changing the mixing ratio of Li2O and SiO2, we can obtain different lithium silicate solids which exhibit different thermodynamic behaviors. Based on our results, three mixing scenarios are discussed to provide general guidelines for designing new CO2 sorbents to fit practical needs. © 2013 The Owner Societies.
Original languageAmerican English
Pages (from-to)13538-13558
Number of pages12182
JournalPhysical Chemistry Chemical Physics
DOIs
StatePublished - 28 Aug 2013
Externally publishedYes

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Silicates
Lithium
silicates
lithium
Thermodynamics
thermodynamics
sorbents
Carbon Monoxide
Chemisorption
Sorbents
chemisorption
Vibrational spectra
mixing ratios
regeneration
Electronic properties
Oxides
Density functional theory
metal oxides
Isotherms
isotherms

Cite this

@article{bb340d9f69344eb7aaffe5f6cc79a1b2,
title = "CO2 capture properties of lithium silicates with different ratios of Li2O/SiO2: An ab initio thermodynamic and experimental approach",
abstract = "The lithium silicates have attracted scientific interest due to their potential use as high-temperature sorbents for CO2 capture. The electronic properties and thermodynamic stabilities of lithium silicates with different Li2O/SiO2 ratios (Li2O, Li 8SiO6, Li4SiO4, Li 6Si2O7, Li2SiO3, Li 2Si2O5, Li2Si3O 7, and α-SiO2) have been investigated by combining first-principles density functional theory with lattice phonon dynamics. All these lithium silicates examined are insulators with band-gaps larger than 4.5 eV. By decreasing the Li2O/SiO2 ratio, the first valence bandwidth of the corresponding lithium silicate increases. Additionally, by decreasing the Li2O/SiO2 ratio, the vibrational frequencies of the corresponding lithium silicates shift to higher frequencies. Based on the calculated energetic information, their CO2 absorption capabilities were extensively analyzed through thermodynamic investigations on these absorption reactions. We found that by increasing the Li 2O/SiO2 ratio when going from Li2Si 3O7 to Li8SiO6, the corresponding lithium silicates have higher CO2 capture capacity, higher turnover temperatures and heats of reaction, and require higher energy inputs for regeneration. Based on our experimentally measured isotherms of the CO 2 chemisorption by lithium silicates, we found that the CO 2 capture reactions are two-stage processes: (1) a superficial reaction to form the external shell composed of Li2CO3 and a metal oxide or lithium silicate secondary phase and (2) lithium diffusion from bulk to the surface with a simultaneous diffusion of CO2 into the shell to continue the CO2 chemisorption process. The second stage is the rate determining step for the capture process. By changing the mixing ratio of Li2O and SiO2, we can obtain different lithium silicate solids which exhibit different thermodynamic behaviors. Based on our results, three mixing scenarios are discussed to provide general guidelines for designing new CO2 sorbents to fit practical needs. {\circledC} 2013 The Owner Societies.",
author = "Yuhua Duan and Heriberto Pfeiffer and Bingyun Li and Romero-Ibarra, {Issis C.} and Sorescu, {Dan C.} and Luebke, {David R.} and Halley, {J. Woods}",
year = "2013",
month = "8",
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doi = "10.1039/c3cp51659h",
language = "American English",
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CO<inf>2</inf> capture properties of lithium silicates with different ratios of Li<inf>2</inf>O/SiO<inf>2</inf>: An ab initio thermodynamic and experimental approach. / Duan, Yuhua; Pfeiffer, Heriberto; Li, Bingyun; Romero-Ibarra, Issis C.; Sorescu, Dan C.; Luebke, David R.; Halley, J. Woods.

In: Physical Chemistry Chemical Physics, 28.08.2013, p. 13538-13558.

Research output: Contribution to journalArticle

TY - JOUR

T1 - CO2 capture properties of lithium silicates with different ratios of Li2O/SiO2: An ab initio thermodynamic and experimental approach

AU - Duan, Yuhua

AU - Pfeiffer, Heriberto

AU - Li, Bingyun

AU - Romero-Ibarra, Issis C.

AU - Sorescu, Dan C.

AU - Luebke, David R.

AU - Halley, J. Woods

PY - 2013/8/28

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N2 - The lithium silicates have attracted scientific interest due to their potential use as high-temperature sorbents for CO2 capture. The electronic properties and thermodynamic stabilities of lithium silicates with different Li2O/SiO2 ratios (Li2O, Li 8SiO6, Li4SiO4, Li 6Si2O7, Li2SiO3, Li 2Si2O5, Li2Si3O 7, and α-SiO2) have been investigated by combining first-principles density functional theory with lattice phonon dynamics. All these lithium silicates examined are insulators with band-gaps larger than 4.5 eV. By decreasing the Li2O/SiO2 ratio, the first valence bandwidth of the corresponding lithium silicate increases. Additionally, by decreasing the Li2O/SiO2 ratio, the vibrational frequencies of the corresponding lithium silicates shift to higher frequencies. Based on the calculated energetic information, their CO2 absorption capabilities were extensively analyzed through thermodynamic investigations on these absorption reactions. We found that by increasing the Li 2O/SiO2 ratio when going from Li2Si 3O7 to Li8SiO6, the corresponding lithium silicates have higher CO2 capture capacity, higher turnover temperatures and heats of reaction, and require higher energy inputs for regeneration. Based on our experimentally measured isotherms of the CO 2 chemisorption by lithium silicates, we found that the CO 2 capture reactions are two-stage processes: (1) a superficial reaction to form the external shell composed of Li2CO3 and a metal oxide or lithium silicate secondary phase and (2) lithium diffusion from bulk to the surface with a simultaneous diffusion of CO2 into the shell to continue the CO2 chemisorption process. The second stage is the rate determining step for the capture process. By changing the mixing ratio of Li2O and SiO2, we can obtain different lithium silicate solids which exhibit different thermodynamic behaviors. Based on our results, three mixing scenarios are discussed to provide general guidelines for designing new CO2 sorbents to fit practical needs. © 2013 The Owner Societies.

AB - The lithium silicates have attracted scientific interest due to their potential use as high-temperature sorbents for CO2 capture. The electronic properties and thermodynamic stabilities of lithium silicates with different Li2O/SiO2 ratios (Li2O, Li 8SiO6, Li4SiO4, Li 6Si2O7, Li2SiO3, Li 2Si2O5, Li2Si3O 7, and α-SiO2) have been investigated by combining first-principles density functional theory with lattice phonon dynamics. All these lithium silicates examined are insulators with band-gaps larger than 4.5 eV. By decreasing the Li2O/SiO2 ratio, the first valence bandwidth of the corresponding lithium silicate increases. Additionally, by decreasing the Li2O/SiO2 ratio, the vibrational frequencies of the corresponding lithium silicates shift to higher frequencies. Based on the calculated energetic information, their CO2 absorption capabilities were extensively analyzed through thermodynamic investigations on these absorption reactions. We found that by increasing the Li 2O/SiO2 ratio when going from Li2Si 3O7 to Li8SiO6, the corresponding lithium silicates have higher CO2 capture capacity, higher turnover temperatures and heats of reaction, and require higher energy inputs for regeneration. Based on our experimentally measured isotherms of the CO 2 chemisorption by lithium silicates, we found that the CO 2 capture reactions are two-stage processes: (1) a superficial reaction to form the external shell composed of Li2CO3 and a metal oxide or lithium silicate secondary phase and (2) lithium diffusion from bulk to the surface with a simultaneous diffusion of CO2 into the shell to continue the CO2 chemisorption process. The second stage is the rate determining step for the capture process. By changing the mixing ratio of Li2O and SiO2, we can obtain different lithium silicate solids which exhibit different thermodynamic behaviors. Based on our results, three mixing scenarios are discussed to provide general guidelines for designing new CO2 sorbents to fit practical needs. © 2013 The Owner Societies.

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