title: Mechanisms of absorption and desorption of CO2by molten NaNO3-promoted MgO.
abstract: In order to realize carbon capture and sequestration (CCS), a technology proposed to circumvent the global warming problem while maintaining the present level of economic activity, the development of efficient carbon-capturing agents is of prime importance. In addition to the prevailing amine-based agents that operate at temperatures lower than 200 °C, agents that can operate at higher temperatures are being considered to reduce the cost of CCS. For the mid-temperature (200-500 °C) operation, alkali nitrate-promoted MgO is a promising candidate; whose detailed reaction mechanisms are not yet fully understood, however. In the present study, we have performed a comprehensive investigation on the mechanisms of CO2absorption and desorption of NaNO3-promoted MgO. Highly efficient CO2absorbents were obtained by decomposing Mg5(CO3)4(OH)2·4H2O with NaNO3intimately mixed with it. Our collective data, including isothermal CO2uptake curves, MgO solubility in molten NaNO3, and observations on the reaction of MgO wafers with CO2, indicate that the absorption takes place in the molten NaNO3medium in which both CO2and MgO are dissolved. MgCO3is formed inside the molten promoter through the nucleation and growth steps. The decomposition of MgCO3back to MgO, that is desorption of CO2, is also facilitated by molten NaNO3, which we attribute to the decreased relative stability of MgCO3with respect to MgO when in contact with molten NaNO3. The relative affinity of molten nitrate to MgO and MgCO3was estimated by measuring the 'contact angles' of nitrate on them. Implications of our findings for the real applications of alkali nitrate-promoted MgO absorbents with numerous repeated cycles of absorption and desorption of CO2are discussed.
authors.affiliation: Department of Chemistry, Sungkyunkwan University, Suwon 16419, Korea. ywkwon@skku.edu.
authors.forename: Seung-Ik
authors.initials: SI
authors.lastname: Jo
authors.affiliation: Department of Chemistry, Sungkyunkwan University, Suwon 16419, Korea. ywkwon@skku.edu.
authors.forename: Young-In
authors.initials: YI
authors.lastname: An
authors.affiliation: Department of Chemistry, Sungkyunkwan University, Suwon 16419, Korea. ywkwon@skku.edu.
authors.forename: Kang-Yeong
authors.initials: KY
authors.lastname: Kim
authors.affiliation: Department of Chemistry, Sungkyunkwan University, Suwon 16419, Korea. ywkwon@skku.edu.
authors.forename: Seo-Yeong
authors.initials: SY
authors.lastname: Choi
authors.affiliation: Department of Chemistry, Sungkyunkwan University, Suwon 16419, Korea. ywkwon@skku.edu.
authors.forename: Jin-Su
authors.initials: JS
authors.lastname: Kwak
authors.affiliation: Department of Chemistry, Sungkyunkwan University, Suwon 16419, Korea. ywkwon@skku.edu.
authors.forename: Kyung-Ryul
authors.initials: KR
authors.lastname: Oh
authors.affiliation: Department of Chemistry, Sungkyunkwan University, Suwon 16419, Korea. ywkwon@skku.edu.
authors.forename: Young-Uk
authors.identifier: http://orcid.org/0000-0002-7720-3805
authors.initials: YU
authors.lastname: Kwon