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Synthesis, Characterization, and CO2 Adsorptive Behavior of Mesoporous AlOOH-Supported Layered Hydroxides

Authors

  • Dr. Yen-Po Chang,

    1. Department of Materials Sciences and Engineering, National Chiao Tung University, 1001 Ta Hsueh Road, Hsinchu Taiwan 300 (P.R. China), Fax: (+886) 3-5724727
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  • Yu-Chun Chen,

    1. Department of Materials Sciences and Engineering, National Chiao Tung University, 1001 Ta Hsueh Road, Hsinchu Taiwan 300 (P.R. China), Fax: (+886) 3-5724727
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  • Dr. Po-Hsueh Chang,

    1. Department of Materials Sciences and Engineering, National Chiao Tung University, 1001 Ta Hsueh Road, Hsinchu Taiwan 300 (P.R. China), Fax: (+886) 3-5724727
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  • Prof. San-Yuan Chen

    Corresponding author
    1. Department of Materials Sciences and Engineering, National Chiao Tung University, 1001 Ta Hsueh Road, Hsinchu Taiwan 300 (P.R. China), Fax: (+886) 3-5724727
    • Department of Materials Sciences and Engineering, National Chiao Tung University, 1001 Ta Hsueh Road, Hsinchu Taiwan 300 (P.R. China), Fax: (+886) 3-5724727
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Abstract

A novel CO2 solid sorbent was prepared by synthesizing and modifying AlOOH-supported CaAl layered double hydroxides (CaAl LDHs), which were prepared by using mesoporous alumina (γ-Al2O3) and calcium chloride (CaCl2) in a hydrothermal urea reaction. The nanostructured CaAl LDHs with nanosized platelets (3–30 nm) formed and dispersed inside the crystalline framework of mesoporous AlOOH (boehmite). By calcination of AlOOH-supported LDHs at 700 °C, the mesoporous CaAl metal oxides exhibited ordered hexagonal mesoporous arrays or uniform nanotubes with a large surface area of 273 m2 g−1, a narrow pore size distribution of 6.2 nm, and highly crystalline frameworks. The crystal structure of the calcined mesoporous CaAl metal oxides was multiphasic, consisting of CaO/Ca(OH)2, Al2O3, and CaAlO mixed oxides. The mesoporous metal oxides were used as a solid sorbent for CO2 adsorption at high temperatures and displayed a maximum CO2 capture capacity (≈45 wt %) of the sorbent at 650 °C. Furthermore, it was demonstrated that the mesoporous CaAl oxides showed a more rapid adsorption rate (for 1–2 min) and longer cycle life (weight change retention: 80 % for 30 cycles) of the sorbent because of the greater surface area and increased number of activated sites in the mesostructures. A simple model for the formation mechanism of mesoporous metal oxides is tentatively proposed to account for the synergetic effect of CaAl LDHs on the adsorption of CO2 at high temperature.

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