| Summary: | 碩士 === 國立中央大學 === 環境工程研究所在職專班 === 101 === Combustion of fossil fuel causes increasing atmospheric CO2 concentration and induces man-made greenhouse effect, hence, developing effective technique for CO2 capture to mitigate its emission has become an important issue. The medium-high temperature CO2 capture technique has the major advantage of decreasing the energy penalty and is of a high capture efficiency at a high CO2 concentration (ca. 15-50%CO2). Material containing CaO is a promising candidate for adsorbing CO2 under elevated temperature, which should be a promising trend in the future. Previous study indicates that the sintering of CaO at high temperature is the major reason for the decay of CO2 capture, resulting in the poor stability of sorbent. This research aims to develop an effective CO2 capturing technology via the preparation and testing of CaO-based layer double hydroxides (LDHs) sorbents. This study focuses on the development of a Ca-Al-CO3 sorbent derived from three kinds of precursors: (I) (Ca-Al-CO3/CaO) (II) Ca(OAc)2-LDH and (III) Ca(NO3)2-LDH. Ca+2 ions are incorporated into layered structure by co-precipitation of Al (NO3)3•9H2O and Na2CO3 under alkaline conditions. The characteristics of synthesized sorbents such as surface area, morphology/particle size and crystalline are determined by BET (Quantachrome), SEM (Hitachi) and PXRD (Bruker), respectively. Sorption properties of CO2 on CaO are monitored by recording weight change of sorbent with a Thermo-gravimetric analyzer (TGA, Netzsch) operated at alternately cycling experiments of adsorption and desorption for CO2 capture. The results showed that the microscopic characters of sorbents were mainly mesoporous. CO2 sorption capacities (g CO2/g sorbent) at 750 °C were in the range of 0.524-0.672 and they were significantly related to sorbents, wherein (Ca-Al-CO3/CaO) (55.8%) >Ca(OAc)2-LDH (52.1%) > Ca(NO3)2-LDH (46.9%). The best Ca-Al-CO3 sorbent was from (Ca-Al-CO3/CaO) that provided at least 96% CO2 sorption recovery after 40 adsorption/desorption cycles. These materials are worthy to be further studied for the modification of alkaline minerals as a potential CO2 sorbent.
Keywords: CO2 capture; Adsorbents; CaO; Ca-Al-CO3 ; Thermal gravimetric analysis(TGA).
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