Development of Regenerable MgO-Based Sorbent Promoted with K₂CO₃ for CO₂ Capture at Low Temperatures

Abstract

To improve their CO2 absorption capacity, alkali-based sorbents prepared by impregnation and wet mixing method of potassium carbonate on supports such as activated carbon and MgO (KACI30, KACP30, KMgI30, and KMgP30), were investigated in a fixed bed reactor (C02 absorption at 50-100 degrees C and regeneration at 150-400 degrees C). Total CO2 capture capacities of KMgI30-500 and KMgP30-500 were 178.6 and 197.6 mg CO2/g sorbent, respectively, in the presence of 11 vol % H2O even at 50 degrees C. The large amount of CO2 capture capacity of KMgP30-500 and KMgI30-500 could be explained by the fact that MgO itself, as well as K2CO3, could absorb CO2 in the presence of water vapor even at low temperatures. In particular, water vapor plays an important role in the CO2 absorption of MgO and KMgI30-500 even at low temperatures below 60 degrees C, in marked contrast to MgO and CaO which can absorb CO2 at high temperatures. The CO2 capture capacity of the KMgI30-300 sorbent, however, was less than that of KMgI30-500 due to the formation of Mg(OH)2 which did not absorb CO2. MgO based-sorbents promoted with K2CO3 after CO2 absorption formed new structures such as K2Mg(CO3)2 and K2Mg(CO3)2 x 4(H2O), unlike KACI30 which showed only the KHCO3 crystal structure. The new Mg-based sorbents promoted with K2CO3 showed excellent characteristics in that it could satisfy a large amount of CO2 absorption at low temperatures, a high CO2 absorption rate, and fast and complete regeneration.

ab initio Thermodynamic Study of the CO2 Capture Properties of M2CO3 (M = Na, K)- and CaCO3-Promoted MgO Sorbents Towards Forming Double Salts

“…4(b) and 4(c). As listed in Table 3, compared to pure MgO, the MgO + K 2 CO 3 mixture only has about 10 K increase on its T 1 and T 2 values, which indicates that adding K 2 CO 3 (or K 2 O) does not increase the maximum CO 2 capture temperature much, but could affect its CO 2 capture capacity and kinetics as demonstrated experimentally in the literatures (Lee et al, 2006(Lee et al, , 2008Xiao et al, 2011). As we know that another potential advantage of mixing solids is to gain entropy and to increase the surface area of active part of the solid for having faster reaction rate.…”

“…A similar double salt Cs 2 Mg(CO 3 ) 2 was also observed in the Cs promoted triglyceride transesterification over MgO nanocatalysts (Montero et al, 2010). The K 2 CO 3 -promoted MgO-based sorbent was investigated by several research groups (Lee et al, 2006;Lee et al, 2008;Xiao et al, 2011). Their results showed that its CO 2 capture capacity could be as high as 197.6 mg CO 2 /g, and after CO 2 absorption the double salts K 2 Mg(CO 3 ) 2 and K 2 Mg(CO 3 ) 2 ·4(H 2 O) were formed.…”

“…Accordingly, solid sorbent materials have been proposed for capture of CO 2 through a reversible chemical transformation. Among them, alkali and alkaline metal oxide based solid sorbents can play an important role for CO 2 capture as they can be used over a wide temperature range (Stamnore and Gilot, 2005;Lee et al, 2006;Lee and Kim, 2007;Siriwardane et al, 2007;Lee et al, 2008;Sorescu, 2009, 2010;Duan et al, 2011).…”

“…Improving its practical CO 2 capacity is the key issue in order to use MgO as CO 2 sorbent. Recent studies showed that when MgO was doped with alkali and alkaline metal carbonates, its CO 2 capture capacity increased and its maximum absorption temperature could be shifted (Mayorga et al, 2001;Lee et al, 2008;Montero et al, 2010;Zhang et al, 2013). For example, when Na 2 CO 3 doped into MgO, the CO 2 capacity of the newly formed sorbent is 1-7 mmol CO 2 /g depending on the temperature and dopant loading (Mayorga et al, 2001).…”

Characteristics of Spray-Dried K₂CO₃-MgO Solid Sorbent for CO₂ Capture from Power Plant Flue Gas

“…Solid sorbents based on alkali and alkali earth metals using Al 2 O 3 (Lee et al, 2011), activated carbon (Hirano et al, 1995;Hayashi et al, 1998;Lee and Kim, 2007), TiO 2 (Lee et al, 2006), MgO (Lee et al, 2008b), ZrO 2 (Lee et al, 2009(Lee et al, , 2013 and SiO 2 (Lee et al, 2006), etc. as supporters with various preparation methods have been reported in the literature.…”