Journal of Molecular Catalysis B: Enzymatic 56 (2009) 179–184 Contents lists available at ScienceDirect Journal of Molecular Catalysis B: Enzymatic journal homepage: www.elsevier.com/locate/molcatb Novel regenerable potassium-based dry sorbents for CO 2 capture at low temperatures Soo Chool Lee a , Ho Jin Chae a , Soo Jae Lee a , Yong Hee Park a , Chong Kul Ryu b , Chang Keun Yi c , Jae Chang Kim a,∗ a Department of Chemical Engineering, Kyungpook National University, 1370 Sangyeuk-dong, Buk-gu, Daegu 702-701, Republic of Korea b Korea Electric Power Research Institute, Daejeon 305-380, Republic of Korea c Korea Institute of Energy Research, Daejeon 305-343, Republic of Korea article info Article history: Available online 29 July 2008 Keywords: CO2 Absorption ZrO2 K2CO3 KHCO3 abstract A novel potassium-based dry sorbent (KZrI) was developed for CO 2 capture at a low tempera- ture range between 50 ◦ C and 200 ◦ C. The CO 2 absorption and regeneration properties of this novel regenerable potassium-based dry sorbent were measured in a fixed-bed reactor during multiple absorp- tion/regeneration cycles at low temperature conditions (CO 2 absorption at 50–100 ◦ C and regeneration at 130–200 ◦ C). The total CO 2 capture capacity of the KZrI sorbent was maintained during the multiple CO 2 absorption/regeneration cycles. The XRD patterns and FTIR analyses of the sorbents after CO 2 absorp- tion showed the KHCO 3 phase only except for the ZrO 2 phase used as support. Even after 10 cycles, any other new structures resulting from the by-product during CO 2 absorption were not observed. This phase could be easily converted into the original phase during regeneration, even at a low temperature (130 ◦ C). The KZrI sorbent developed in this study showed excellent characteristics in CO 2 absorption and regen- eration in that it satisfies the requirements of a large amount of CO 2 absorption (91.6mg CO 2 /g sorbent) and the complete regeneration at a low temperature condition (1atm, 150 ◦ C) without deactivation. © 2008 Elsevier B.V. All rights reserved. 1. Introduction Carbon dioxide (CO 2 ) is a major greenhouse gas that is released into the air due to the use of fossil fuels. As a consequence, CO 2 causes global warming, which may be disastrous to the environ- ment. It can be removed from flue gas and waste gas streams by various methods such as membrane separation, absorption with a solvent, and adsorption using molecular sieves [1–6]. These meth- ods, however, are costly and consume a lot of energy. One of the improved techniques for the removal of CO 2 is the chemical absorption of CO 2 with dry regenerable sorbents. The use of dry sorbents can be highly cost-effective and an energy efficient way to remove CO 2 [7–24]. Alkali metal carbonates such as Na 2 CO 3 and K 2 CO 3 react with CO 2 and H 2 O and transform to alkali metal hydrogen carbonates after CO 2 absorption by the following reaction: M 2 CO 3 + CO 2 +H 2 O ⇋ 2MHCO 3 (M = Na, K) [7–20]. Water vapor is always necessary in forming potassium hydrogen carbonate in all reactions as shown in the absorption mechanism. Alkali ∗ Corresponding author. Tel.: +82 53 950 5622; fax: +82 53 950 6615. E-mail address: kjchang@knu.ac.kr (J.C. Kim). metal-based sorbents are employed in CO 2 absorption at low tem- peratures (50–70 ◦ C) with thermal regeneration easily occurring at low temperatures below 200 ◦ C. Hirano et al. have proposed a modified chemical-absorption method capable of cyclic fixed-bed operations for the recovery of carbon dioxide from flue gases over K 2 CO 3 -on-carbon [8]. The sorption of CO 2 on the K 2 CO 3 –Al 2 O 3 composite sorbent, in the presence of water vapor, was studied by in-situ IR spectroscopy and X-ray diffraction analysis [11]. Sev- eral studies regarding an efficient chemical absorption over K 2 CO 3 , which was supported either on activated carbon [7–9,17,18] or on other porous matrices such as silica gel, Al 2 O 3 and vermiculite [11–13], were also reported using cyclic fixed-bed operations under moist conditions. Lee et al. reported that the K 2 CO 3 /TiO 2 sorbent showed excellent CO 2 absorption and regeneration properties [17]. In particular, the formation of the KHCO 3 crystal structure only after CO 2 absorption is reported to be an important factor for regenera- tion, even at low temperatures, unlike K 2 CO 3 /Al 2 O 3 which formed a new alloy structure like KAl(CO 3 ) 2 (OH) 2 . Several additives or supports such as SiO 2 , Al 2 O 3 , CaO, MgO, zeolites and others have been used in alkali metal-based sorbents to absorb CO 2 . Nonethe- less, these sorbents except for K 2 CO 3 /TiO 2 and K 2 CO 3 /activated carbon have a disadvantage in that there is a decrease of reactiv- ity during multiple absorptions/regenerations at low temperatures 1381-1177/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.molcatb.2008.07.007