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CO 2 Sorbents with Scaffold‐like CaAl Layered Double Hydroxides as Precursors for CO 2 Capture at High Temperatures
Author(s) -
Chang PoHsueh,
Lee TaiJung,
Chang YenPo,
Chen SanYuan
Publication year - 2013
Publication title -
chemsuschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.412
H-Index - 157
eISSN - 1864-564X
pISSN - 1864-5631
DOI - 10.1002/cssc.201200910
Subject(s) - carbonation , calcination , thermogravimetric analysis , hydroxide , sintering , chemical engineering , annealing (glass) , materials science , sorbent , hydrotalcite , porosity , layered double hydroxides , oxide , nuclear chemistry , chemistry , mineralogy , inorganic chemistry , adsorption , catalysis , metallurgy , organic chemistry , composite material , engineering
A highly stable high‐temperature CO 2 sorbent consisting of scaffold‐like Ca‐rich oxides (CaAlO) with rapid absorption kinetics and a high capacity is described. The Ca‐rich oxides were prepared by annealing CaAlNO 3 layered double hydroxide (LDH) precursors through a sol–gel process with Al(O i P) 3 and Ca(NO 3 ) 2 with Ca 2+ /Al 3+ ratios of 1:1, 2:1, 4:1, and 7:1. XRD indicated that only LDH powders were formed for Ca 2+ /Al 3+ ratios of 2:1. However, both LDH and Ca(OH) 2 phases were produced at higher ratios. Both TEM and SEM observations indicated that the CaAlNO 3 LDHs displayed a scaffold‐like porous structure morphology rather than platelet‐like particles. Upon annealing at 600 °C, a highly stable porous network structure of the CaO‐based CaAlO mixed oxide (CAMO), composed of CaO and Ca 12 Al 14 O 33 , was still present. The CAMO exhibited high specific surface areas (up to 191 m 2 g −1 ) and a pore size distribution of 3–6 nm, which allowed rapid diffusion of CO 2 into the interior of the material, inducing fast carbonation/calcination and enhancing the sintering‐resistant nature over multiple carbonation/calcination cycles for CO 2 absorption at 700 °C. Thermogravimetric analysis results indicated that a CO 2 capture capacity of approximately 49 wt % could be obtained with rapid absorption from the porous 7:1 CAMO sorbents by carbonation at 700 °C for 5 min. Also, 94–98 % of the initial CO 2 capture capability was retained after 50 cycles of multiple carbonation/calcination tests. Therefore, the CAMO framework is a good isolator for preventing the aggregation of CaO particles, and it is suitable for long‐term cyclic operation in high‐temperature environments.