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The Nature of Adsorbed Carbon Dioxide on Immobilized Amines during Carbon Dioxide Capture from Air and Simulated Flue Gas
Author(s) -
Zhai Yuxin,
Chuang Steven S. C.
Publication year - 2017
Publication title -
energy technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.91
H-Index - 44
eISSN - 2194-4296
pISSN - 2194-4288
DOI - 10.1002/ente.201600685
Subject(s) - carbamic acid , chemistry , adsorption , amine gas treating , zwitterion , sorbent , carbamate , desorption , carbon dioxide , deprotonation , inorganic chemistry , flue gas , ammonium , organic chemistry , molecule , ion
The structure and nature of adsorbed species on solid amine sorbent under various CO 2 concentrations from ambient air (0.04 vol %) to an CO 2 /air stream (15 vol %) have been studied by using in situ IR spectroscopy. The in situ IR study (i) provided evidence to support the zwitterion pathway for CO 2 adsorption/desorption and (ii) allowed the determination of the nature of the adsorbed species. The IR‐observable zwitterion was deprotonated to ammonium carbamate and carbamic acid reversibly. CO 2 adsorbs on the primary amine site as a strongly adsorbed species in the form of ammonium carbamate and on the secondary amine site as a weakly adsorbed species in the form of carbamic acid. Another form of weakly adsorbed species could be ammonium carbamate on the secondary amine. An increase of the concentration of CO 2 in the stream increased the CO 2 capture capacity, the fraction of strongly adsorbed CO 2 , and the binding energy of adsorbed species. A concentration of 400 ppm CO 2 in air competes over 0.5 % of water vapor for adsorption on Class I amine sorbents.