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Explaining steam‐enhanced carbonation of CaO based on first principles
Author(s) -
Yang Peng,
Duan Lunbo,
Tang Hongjian,
Cai Tianyi,
Sun Zhao
Publication year - 2018
Publication title -
greenhouse gases: science and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.45
H-Index - 32
ISSN - 2152-3878
DOI - 10.1002/ghg.1822
Subject(s) - adsorption , carbonation , density functional theory , flue gas , chemistry , chemical engineering , dispersion (optics) , calcium carbonate , population , inorganic chemistry , materials science , computational chemistry , organic chemistry , physics , demography , sociology , engineering , optics
Calcium‐based sorbents have been regarded as effective agents for capturing CO 2 from industrial flue gas. Recent studies have shown that steam can enhance the carbonation performance of calcium‐based sorbents. In this paper, a CaO (001) surface was made to investigate the micro‐level mechanism of steam‐enhanced carbonation based on first principles calculations. Charge transfer and bond population were calculated to evaluate an interaction effect between adsorbates and the CaO (001) surface. Individual adsorption of CO 2 and H 2 O was compared with binary adsorption and co‐adsorption of the two molecules on the CaO (001) surface, based on dispersion‐corrected density functional theory (DFT‐D) calculations. First, the predicted adsorption energies suggest the O‐top site is the best site. It forms carbonate‐like structure and hydroxyl‐like structure for the individual adsorption of CO 2 and H 2 O. Binary adsorption calculations indicate that H 2 O is more easily adsorbed by the CaO (001) surface than CO 2 . The adsorption of H 2 O and CO 2 adsorption are promoted in comparison with their individual adsorption on the CaO (001) surface. Moreover, the analysis of adsorption energies and partial density of states (PDOS) suggests that a H 2 O‐CaO (001) surface (CaO (001) surface that has already adsorbed H 2 O) is more reactive than the clean CaO (001) surface for CO 2 adsorption, which further supports the idea that the steam‐enhanced mechanism is an Eley–Rideal (E–R) mechanism, which means H 2 O is adsorbed on the CaO surface, and then CO 2 is adsorbed. © 2018 Society of Chemical Industry and John Wiley & Sons, Ltd.