期刊
CHEMSUSCHEM
卷 6, 期 6, 页码 1076-1083出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/cssc.201200910
关键词
carbon dioxide capture; high temperature; layered double hydroxides; mesoporous materials; metal oxides
资金
- National Science Council of Taiwan [102-3113-P-042A-005]
A highly stable high-temperature CO2 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 CaAlNO3 layered double hydroxide (LDH) precursors through a sol-gel process with Al(OiP)3 and Ca(NO3)2 with Ca2+/Al3+ ratios of 1:1, 2:1, 4:1, and 7:1. XRD indicated that only LDH powders were formed for Ca2+/Al3+ 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 CaAlNO3 LDHs displayed a scaffold-like porous structure morphology rather than platelet-like particles. Upon annealing at 600 degrees C, a highly stable porous network structure of the CaO-based CaAlO mixed oxide (CAMO), composed of CaO and Ca12Al14O33, was still present. The CAMO exhibited high specific surface areas (up to 191m2g-1) and a pore size distribution of 3-6nm, which allowed rapid diffusion of CO2 into the interior of the material, inducing fast carbonation/calcination and enhancing the sintering-resistant nature over multiple carbonation/calcination cycles for CO2 absorption at 700 degrees C. Thermogravimetric analysis results indicated that a CO2 capture capacity of approximately 49wt% could be obtained with rapid absorption from the porous 7:1 CAMO sorbents by carbonation at 700 degrees C for 5min. Also, 94-98% of the initial CO2 capture capability was retained after 50cycles 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.
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