Factors Affecting the Rate of CO2 Absorption after Partial Desorption

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Factors affecting the rate of CO2 absorption after partial desorption in NaNO3 promoted MgO Atul Kumar Prashar, Hwimin Seo, Won Choon Choi, Na Young Kang, Sunyoung Park, Kiwoong Kim, Da Young Min, Hye Mi Kim, and Yong-Ki Park Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.5b02909 • Publication Date (Web): 25 Mar 2016 Downloaded from http://pubs.acs.org on March 27, 2016

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Factors affecting the rate of CO2 absorption after

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partial desorption in NaNO3 Promoted MgO

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Atul K. Prashar†, Hwimin Seo‡, Won Choon Choi‡, Na Young Kang‡, Sunyoung Park‡, Kiwoong

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Kim‡, Da Young Min‡, Hye Mi Kim‡, Yong Ki Park*§

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†

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India ‡

Center for Carbon Resources Conversion, Korea Research Institute of Chemical Technology,

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Department of Material Science, Akal University, Talwandi Sabo, Bhatinda-151302, Punjab,

Daejeon 34114, Korea §

Center for Convergent Chemical Process, Korea Research Institute of Chemical Technology,

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Daejeon 34114, Korea

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ABSTRACT: Sodium nitrate (NaNO3) and other alkali nitrates are known to accelerate the CO2

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absorption rate of MgO above their melting points. This absorption rate is further enhanced if

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absorption is done after partial desorption. Moreover it does not show any induction period

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which is otherwise present if absorption is done after complete desorption. A thorough study of

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various factors affecting the rate after partial desorption is done in this work. We exposed a

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sample to CO2 for several different periods before partial desorption and exposed to N2 for

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several different periods during partial desorption in a thermogravimetric analyzer. Absorbents

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were also characterized by XRD, BET and SEM and studied in in-situ IR cell to understand the

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changes at molecular scale. The absorbed amount of CO2 with fast initial rate after partial

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desorption is affected by both amount of CO2 absorbed before partial desorption as well as

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amount of MgO formed during partial desorption. In-situ IR studies showed that two phases of

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bulk MgCO3 were formed along with the surface carbonate. It can be concluded from the TGA

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and in-situ IR study that defects in MgO which were introduced from the defect MgCO3 phase

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during partial desorption are responsible for faster rate after partial desorption. It seems that

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substitution of nitrate ions in MgCO3 phase is responsible for the defect MgCO3 phase (out of

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plane bending vibration at 876 cm-1).

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INTRODUCTION: CO2 is one of the major contributors to the greenhouse effect responsible

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for climate changes. Almost 87% of total CO2 being released to the environment by human

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activities comes from the burning of fossil fuels like coal, natural gas and oil. Although there

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have been developed carbon free alternative energy sources, still the use of fossil fuels will

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continue for long period of time to meet the growing demand of energy. So the introduction of

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various CO2 capture and storage systems at various emission sources is currently the best

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practical solution to the greenhouse problem.1,2,3 Carbon capture systems based on aqueous

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absorbents like monoethanol amine and stearically hindered amines are proven mature

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technologies and easily deployable to coal and gas fired power plants.4

But high energy


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demands and high capital costs make the use of these systems limited.5 Various types of solid

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absorbents have been proposed as an alternative material under ambient and non-ambient

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conditions.6,7,8 MgO is one of such solid absorbent and it has large working temperature range

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and applicability in various capture technologies. It is one of the few absorbents (others are

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double salts, hydrotalcite and Mg(OH)2) that can be used in intermediate temperature range

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(250ºC-500ºC).8 This intermediate temperature range is suitable for sorption enhanced water gas

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shift reaction in integrated gasification combined cycle and also medium temperature stage in

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multi-stage fluidized bed CO2 capture process.9,10 Even though MgO can absorb 109 wt% of CO2

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theoretically, its actual capacity is low at ambient pressure (1 bar) since its absorption is limited

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to surface only. Unmodified MgO has absorption capacity of 0.24 mmol/g at 200ºC.11 Recent

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reports suggest that alkali nitrates (e.g. LiNO3, NaNO3, KNO3 etc.) has promotional effect on the

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absorption capacity of MgO.12,13,14,15 They enhance the absorption rate of carbonation of MgO

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manifold at temperatures above their melting points. The NaNO3/MgO absorbents prepared by

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Zhang et. al. show stable absorption capacity of around 7 mmol·g-1 at 330ºC after decrease in

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absorption capacity for several initial cycles.13 These absorbents show initial induction period of

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10-20 min before the absorption rate becomes faster. They also found that when CO2 is desorbed

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partially from the saturated sample, the absorption in the next cycle is very fast and starts without

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any induction period. The strategy of partially desorbing CO2 before starting the next cycle can

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be of immense practical use in case of NaNO3 promoted MgO. In spite of sacrificing the

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absorption capacity, high absorption rate reduces energy consumption and the footprint of the

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facility. There was no detailed study, and also no possible explanation was given about this

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property of these absorbents. Motivated by these reports, we started a more detailed study of

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factors affecting the rate after partial desorption in NaNO3 promoted MgO absorbents. The


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absorbents prepared in this study were characterized using XRD, BET and studied for their CO2

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uptake using thermogravimetric analysis (TGA). Morphological changes in the NaNO3/MgO

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were also studied using SEM at various stages. We also did an in-situ IR study of the CO2

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absorption process to figure out the changes at the molecular scale at various temperatures.

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EXPERIMENTAL:

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Synthesis:

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Absorbents with different loading of NaNO3 over MgO were prepared by incipient

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impregnation method over high surface area MgO. MgO used here was prepared by the method

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as described in the literature16 using NaOH and MgCl2.6H2O as precursors. The white

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suspension obtained after mixing two components was filtered immediately after stirring for 30

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min. We did not autoclave the white suspension before filtration as described in the literature.16

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The Mg(OH)2 obtained after filtration and washing was calcined at 500ºC in air for 4h with

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heating rate of 5ºC/min. To prepare absorbents with different NaNO3/MgO molar ratios (0.025,

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0.05, 0.09, 0.12 and 0.18), different stock solutions (25 ml each) of NaNO3 in water were

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prepared. From these stock solutions, required amount of solution was impregnated over 2 g of

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MgO (pore volume =0.6 ml/g) according to its pore volume. Samples were dried in a convection

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oven at 120ºC overnight and calcined at 400ºC for 1 h in air.

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Characterization:

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Absorbents synthesized were characterized by powder X-Ray diffraction. It was recorded with

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Regaku Miniflex II desktop X-Ray diffractometer using Cu-Kα radiation (40 kV, 25 mA) at a

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wavelength of 1.54Aͦ and scan rate 4 º/min. Surface areas of the samples were analyzed using N2

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at 77K in Micromeritics ASAP 2420. The samples were degassed at 400ºC for 2h prior to each

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measurement. SEM images of the samples were taken using Tescan Mira 3 LMU FEG with 20


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kV accelerating voltage. Absorption and desorption studies were performed using Setsys

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evolution TGA (Setaram). Before carrying out the absorption studies, the samples were heated

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(10ºC/min) to 400ºC and kept there for 30 min in N2 to remove any pre-absorbed moisture and

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CO2. Static absorption tests were performed by keeping the samples at desired temperature for a

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specific period in pure CO2. In cyclic experiment, absorption was carried out at 330ºC for 5h in

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100% CO2 while desorption was carried out at 400ºC for 1.5h in N2. Heating and cooling rates

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between subsequent cycles were 5ºC/min in N2. Flow of CO2 was kept 16 mL/min during all

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these experiments. N2 flow was also kept same but it was changed to 60 mL/min between two

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spells of CO2 during the study of the effect of partial desorption on absorption rate. In-situ IR

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studies were carried out using Avatar 360 FTIR spectrometer (Nicolet). Sample discs were

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placed inside the in-situ cell having ZnSe windows. The in-situ cell was equipped with an inlet

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and an outlet for gases to keep the sample under desired gas flow. Temperature of the cell was

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controlled using a PID temperature controller and the cell also has an inlet and an outlet for

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cooling water. During the in-situ IR study, absorption was done in pure CO2 at 330ºC while

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desorption was done in pure helium at 450ºC. Flow of both gases was kept 30 mL/min

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throughout the whole IR study.

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RESULTS AND DISCUSSION:

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XRD patterns of NaNO3/MgO samples show distinct phases of MgO and NaNO3 (Figure S1).

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Surface area of samples decreases as NaNO3 content increases (Table S1). NaNO3/MgO

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absorbents were compared for their CO2 absorption uptakes with time at 330ºC (Figure 1).


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Figure 1. CO2 uptake of various samples having different NaNO3/MgO ratios.

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An initial induction period of 20-30 minutes was seen in these absorbents. Increasing the

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NaNO3/MgO ratio higher than 0.09 did not affect the final CO2 uptake of the absorbent. As CO2

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uptake amount as well as rate is not affected by the surface area of the absorbents, this indicates

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that CO2 absorption is bulk property of these absorbents. As MgO conversion is not affected by

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increasing the NaNO3/MgO ration after certain value, this means that an optimum ratio (0.09) of

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the two components is enough for the maximum uptake. Absorbents take a long period of 10h to

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reach near equilibrium state. This long period taken by the absorbents prepared by this method to

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reach near equilibrium state in comparison to reported by earlier authors13 may be due to the

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reason that two phases are not intermixed properly. This may also be attributed to the different

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precursor of MgO used in this case. We subjected the 0.12NaNO3/MgO sample for cyclic

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absorption (5h, 330ºC) and desorption (1.5h, 400ºC) (Figure 2). Its absorption capacity decreased

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in subsequent cycles up to 8 cycles after which it became constant (28% MgO conversion) as

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reported by Zhang et al. also.13


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Figure 2. Cyclic CO2 absorption and desorption by 0.12 NaNO3/MgO at 330ºC.

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SEM images of this sample were taken at various stages during cyclic absorption and

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desorption (Figure 3a-3d). Initial sample shows that MgO and NaNO3 exist as segregated phases.

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SEM image of the sample regenerated after the 1st cycle shows agglomerated MgO particles of

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increased size embedded in NaNO3 particles (Figure 3c). Further increase in size as well as

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reduction in inter-particle MgO boundaries is seen in the SEM image of the sample after the 13th

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cycle (Figure 3d).


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Figure 3. SEM images of 0.12NaNO3/MgO at various stages; Initial (a), after CO2 absorption in

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the 1st cycle (b), regenerated after the 1st cycle (c) and regenerated after the 13th cycle (d).

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Thermogravimetric analysis to study the factors affecting reabsorption after partial

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desorption: As the amount of CO2 absorbed decreased in subsequent cycles up to 8-9 cycles, it

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was difficult to study the factors affecting the rate after partial desorption with a fresh sample.

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For this study, we used the stabilized regenerated sample (0.12NaNO3/MgO). This sample was

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made by exposing the fresh sample to at least 12 cycles of absorption and desorption. We studied

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the effect of the amount of absorbed CO2 before partial desorption as well as time of exposure to

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N2 during partial desorption. First, we designed an experiment in which both of these factors

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were changed simultaneously. In this experiment, the sample was exposed to CO2 for different

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periods (40 min, 70 min, 140 min and 300 min) (1st spell) at 330ºC to make different levels of

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carbonate (MgCO3) in consecutive cycles (Figure 4). Then it was exposed to N2 for different

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periods to desorb partially to almost the same level of carbonate (4.5-5% MgO conversion)

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before again exposing to CO2 (2nd spell) for 1h, which was followed by complete desorption at

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380ºC in N2 in each cycle (Figure 4).


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Figure 4. Experimental design to study the combined effect of MgCO3 amount (before partial

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desorption) and exposure time in N2 during partial desorption on rate of reabsorption; each cycle

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involves exposure to CO2 for different period (40 min, 70 min, 140 min and 300 min in 1 , 2 ,

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3 and 4 cycle respectively) followed by N2 exposure for different periods to desorb CO2 to the

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same level of MgO conversion (4 - 4.5%) and then again to CO2 for 60 min.

st

rd

nd

th

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We subjected this sample to partial desorption in N2 at the absorption temperature as we found

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that desorption starts at the same temperature if gas atmosphere is changed to N2. It was cooled

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down to RT and heated again to 330ºC before the start of the next cycle. In the 1st spell of CO2,

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the sample absorbed different amount of CO2 in each cycle which is obvious as it was exposed to

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different times in CO2. It showed induction time (10 min) in each cycle and absorbed CO2 with

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almost the same initial rate as indicated by almost similar slope of the curves (Figure 5A). In the

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2nd spell of CO2, the sample absorbed with a fast initial rate in comparison to the 1st spell which


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is clear from the higher slopes of various curves for initial few minutes in Figure 5B. The sample

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absorbed without any induction period in the 2nd spell of CO2 (Figure 5B).

157 st

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Figure 5. Comparison of the initial absorption rates in the 1 spell of CO2 after complete

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desorption (A) and the 2 spell of CO2 after absorbing to different levels of MgO conversion in

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the 1 spell and then desorbing to the same level of carbonate (B).

nd

st


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Table 1 shows the MgO conversion in 1st spell, decrease in conversion during desorption and

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increase in MgO conversion in each cycle. As the amount absorbed in 1st spell increases the

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amount desorbed to reach the same level of carbonate increases.

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Table 1. MgO conversion during various stages of absorption and desorption in experiment

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as described in Figure 4.

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The amount absorbed for initial 30 minutes in the 2nd spell is always more than absorbed in 1st

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spell for the same period of time in each cycle (Figure 6). The amount of absorbed CO2 with an

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initial faster rate in the 2nd spell increased as the amount absorbed in the 1st spell of CO2

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increased.


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Figure 6. MgO conversion for initial 30 minutes in 1st and 2nd spell of CO2 in various cycles.

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It increases from 1st to 4th cycle in the 2nd spell while in the 1st spell it is not much different in

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each cycle (Figure 6). As the composition of sample in each cycle before the 2nd spell (after

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partial desorption) is same therefore this change in absorption behavior is due to structural

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changes which are introduced in to sample either during CO2 absorption in the 1st spell or during

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desorption.

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To clarify the effect of the amount of MgCO3 before partial desorption as well as amount

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desorbed during partial desorption separately, we designed two experiments by changing one of

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the two variables while keeping the other same. Firstly, we conducted the experiment by

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changing the exposure time in CO2 in 1st spell while keeping the exposure time in N2 same so

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that amount desorbed remains same. We exposed the sample to CO2 (1st spell) for different

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periods in consecutive cycles (10 min, 30 min, 1 h, 1.5 h, 2 h and 3 h in 1st , 2nd, 3rd, 4th, 5th and

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6th cycle respectively) followed by N2 exposure for 30 min(Figure 7). Then it was again exposed


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to CO2 for 30 min (2nd spell) before completely desorbing by heating the sample to 400 ºC for 1h

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in N2 in each cycle.

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Figure 7. Experimental design to show the effect of MgCO3 content before partial desorption on

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absorption after partial desorption; each cycle involves exposure to CO2 (1st spell) for different

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periods (10 min, 30 min, 1 h, 1.5 h, 2 h and 3 h in 1st, 2nd, 3rd, 4th, 5th and 6th cycle respectively)

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followed by N2 exposure for 30 min and then 30 min in CO2 again in each cycle (2nd spell).

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The amount absorbed in the 1st spell of CO2, desorbed during partial desorption as well as

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absorbed in initial 10 minutes and also in 30 minutes in 2nd spell in each cycle is given in table 2.


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described in Figure 7.

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The amount desorbed during partial desorption increases as the amount absorbed in the 1st spell

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increases up to 5th cycle. In this case however difference in the amount absorbed in the 2nd spell

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during the 30 minutes and desorbed during the N2 exposure is not much when amount absorbed

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in the 1st spell is small. But this difference increases as the amount absorbed in the 1st spell

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increases. This is also indicated by the increase in the initial slope of graphs in the 2nd spell as

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amount absorbed in the 1st spell increases up to 5th cycle (Figure 8).


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Figure 8. Comparison of absorption rates in the 2 spell of CO2 after exposing to different level

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of MgO conversion in the 1 spell followed by 30 min in N2.

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This phenomenon could mean that structural changes which causes initial faster rate during the

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2nd spell are introduced in the sample during the 1st spell as the initial slope of graph increases

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with the increase in the extent of carbonation before the partial desorption.

st

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To study how the amount desorbed as well exposure time in N2 influences the rate of

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absorption after partial desorption, the sample was exposed to N2 for different periods (0.5, 1, 3,

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5, 8 and 12h) in consecutive cycles after exposing sample to CO2 (1st spell) for the same period

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of time (5h) in each cycle (Figure 9).


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Figure 9. Experimental design to show the effect of desorption time in N2 on absorption after

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partial desorption; each cycle involves 5 h in CO2 (1st spell) followed by N2 exposure for

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different periods (0.5, 1, 3, 5, 8 and 12 h in 1st, 2nd, 3rd, 4th, 5th and 6th cycle respectively) and

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then 30 min in CO2 (2nd spell) followed by complete desorption before the next cycle.

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After that sample was exposed to CO2 for 30 minute in each cycle. The MgO conversion in 1st

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spell of CO2, decrease in MgO conversion during partial desorption, increase in MgO conversion

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in 2nd spell of CO2 as well total amount absorbed after 2nd spell of CO2 is given in table 3.

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described in Figure 9.

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The sample reached near equilibrium state and absorbed almost constant amount of CO2 (31.6 -

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32.8%) during the 1st spell in each cycle (Figure 9 and table 3).

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The amount desorbed in N2 increases in consecutive cycles as time in N2 is increased (Figure

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10A). The amount absorbed in 30 minute in 2nd spell increases in consecutive cycles up to 5th

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cycle as the amount desorbed during N2 exposure increases (table 3 and Figure 10 A). But the

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initial slope of the graphs in 2nd spell of CO2 decreases after 2nd cycle onwards in consecutive

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cycles (Figure 10B). The amount absorbed for the 30 min in the 2nd spell is always more than

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absorbed in the 1st spell of CO2 for the same period of time (Figure 10 A). This increase in

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amount of CO2 in 2nd spell of CO2 indicates that rate is faster in the 2nd spell. The total amount

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absorbed during the 2nd spell is always more (5-11%) than absorbed during 1st 5 cycles. This

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indicates that partial desorption enhances rate as well as increases equilibrium amount. This

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means that overall structure of the partially desorbed absorbent is changed. The increase in

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reactivity of MgO with CO2 after partial desorption and its decrease as desorption progresses

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indicates that structural features of MgO which are responsible for its enhanced activity in


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partially desorbed state are also lost in the desorption process. These structural features must be

240

transferred to MgO from MgCO3 as reactivity during partially desorbed state is also influenced

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by carbonate amount before partial desorption.

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243 244

Figure 10. MgO conversion for initial 30 minutes in 1st spell of CO2 (a), decrease in MgO

245

conversion during partial desorption (b) and MgO conversion for initial 30 minutes in 2nd spell of


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CO2(c) (A); Comparison of absorption rates in 2nd spell of CO2 for initial 10 minutes in 1st, 2nd ,

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3rd, 4th, 5th and 6th cycle represented by curve a, b, c, d, e and f respectively (B).

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In-situ IR Study:

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In order to study the changes happening in the absorbent at molecular scale, CO2 absorption

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process was studied using 0.12NaNO3/MgO in the in-situ IR cell at 330ºC. IR spectral changes

251

happening in the sample in the out of plane bending region of carbonate and nitrate ions (800-

252

920 cm-1) were monitored during the absorption process. The sample had been subjected to

253

absorption and desorption in the in-situ IR cell for 8 cycles until it started absorbing constant

254

amount of CO2 in each cycle. The carbonate amount formed was estimated by the integrated area

255

of the out of plane bending vibrations of carbonate ion.


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Figure 11. Changes in out of plane bending region at various time intervals during CO2

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absorption (A), during desorption in He (B), during CO2 reabsorption after partial desorption at

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330ºC (C) and deconvolution of carbonate peaks at various intervals (2 min in CO2 (a), 23 min in

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CO2 (b), after 30 min in He during partial desorption(c) and after 9 min in CO2 during

261

reabsorption(d)) (D).


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IR spectral changes in the out of plane bending region (800-920 cm-1) in the 9th cycle at

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different time intervals during CO2 absorption (1st spell) at 330ºC, desorption in helium at the

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same temperature and reabsorption (2nd spell) after partial desorption are shown in the figure

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11A, B and C respectively. Area in the carbonate out of plane bending region (846-916 cm-1) at

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various stages i.e. after the 1st spell (after 23 min in CO2), after partial desorption (after 30 min in

267

He) and after the 2nd spell of CO2 (9 min in CO2) is decovoluted to show the various carbonate

268

peaks (Figure 11D). Various IR peaks seen in out of plane bending region are enlisted in table 4.

269 270

Table 4. Vibrations observed due to various species in out of plane bending region with their

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peak maxima.

272

IR spectra before the start of CO2 injection (initial) shows a peak (825cm-1) only due to the out

273

of plane bending vibration of nitrate ion (Figure 11A).17 The 1st minute IR spectra after starting

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CO2 flow into IR cell show appearance of a broad peak due to two overlapping vibrations with

275

maxima at 862 cm-1 and 876 cm-1 (Figure 11A). Peak with maximum at 862 cm-1 belongs to

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various surface carbonates and it does not grow further with time indicating that sample becomes

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saturated with surface carbonates within one minute.18, 19 Peak with maximum at 876 cm-1 grows

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rapidly as time progresses with appearance of immediately overlapping peak with maximum at

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890 cm-1 (Figure 11A). The formation of a peak at 890 cm-1 is also followed by simultaneous

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formation of a shoulder at 853 cm-1. The peak at 890 cm-1 and the shoulder peak at 853 cm-1 are

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due to pure MgCO3 phase18 while the overlapping peak with maximum at 876 cm-1 does not


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correspond to pure MgCO3. The peak at 876 cm-1 indicates some changes in the structure of

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carbonate ion in the lattice of MgCO3. As the formation of MgCO3 happens in molten sodium

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nitrate as described by earlier authors

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nitrate groups get substituted in the lattice of MgCO3 and result in defective phases. Such type of

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nitrate group substitutions are reported in Mg(OH)2 structures formed by hydration of MgO in

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Mg(NO3)2 or LiNO3 solutions.21, 22 The substitution of nitrate ion in MgCO3 phase and mixing of

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two phases is feasible as both MgCO3 and NaNO3 have same lattice structure. Such introduction

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of nitrate ion in the lattice of MgCO3 can cause distortion of the carbonate ion symmetry which

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may be responsible for the appearance of a new peak of carbonate ion at 876 cm-1. The nitrate

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out of plane bending at 825 cm-1 undergoes 40% decrease in area in the 1st minute indicating

292

immediate interaction between the gaseous CO2 and molten nitrate (Figure 11A). After the 2nd

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minute onwards, it undergoes slow decrease in area, which stops after sample becomes saturated

294

with carbonate. When the sample is exposed to helium at the same temperature, the area of

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carbonate peaks decreases confirming that desorption starts at the same temperature (Figure

296

11B). The nitrate out of plane bending vibration regains its original area, which has decreased

297

due to its interaction with CO2 within one minute on starting the He injection (Figure 11B).

298

When CO2 injection is started again (reabsorption), the change in nitrate ion gets reversed

299

(decrease in the area of 825 cm-1 peak) and follow the same pattern as they follow during the 1st

300

spell of CO2 (Figure 10C). The 2nd spell also shows comparatively faster increase in the area of

301

bulk carbonate peaks than the 1st spell and the sample reaches to near equilibrium stage within 3

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minutes confirming that absorption after the partial desorption is faster (Figure 11C). A

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comparison of absorption rate by plotting the integrated area of carbonate peaks in the 1st and 2nd

304

spell of CO2 is given in figure 12.

13, 15

it is possible that during formation of MgCO3, some


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Figure 12. Variation of overall absorbance of carbonate ion with time in 1st (a) and 2nd spell of

307

CO2 (b)

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As described in the thermogravimetry study, such faster absorption rate after partial desorption is

309

caused by some structural features in MgO which are transferred from MgCO3 phase. It is

310

possible that defective MgCO3 phase formed here due to substitution of nitrate group as shown

311

in IR study results in the formation of such features in MgO. As the CO2 binding in these

312

absorbent happens at triple phase boundaries13 it is possible that enhanced activity is caused by

313

defective MgO which is spread all over the absorbents at these boundaries. MgO with high

314

reactivity has been known to be formed from the Mg(OH)2 having defective structures due to

315

substitution of nitrate, acetate and carbonate groups.21,22 Similarly to this, it is also possible that

316

such defects in MgO are transferred from the defective phase of MgCO3 and these defects cause

317

the faster absorption rate after partial desorption. Both nitrate ion and carbonate ion must be

318

responsible for the defects in the MgO phase. Such defected MgO phase probably gets converted

319

to pure MgO phase during the course of desorption due to decomposition of carbonate groups.

320

Hence absorption rate after partial desorption decreases as time in N2 is increased.


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The findings in this work give hints to how to operate CO2 capture facilities with NaNO3-

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promoted MgO. The sorbents can capture larger amount of CO2 in the same time with partial

323

desorption comparing to the case of full desorption even though they cannot use their full

324

capacity. This operation saves large amount of energy by reducing the blower power

325

consumption if this sorbent is used in a fluidized bed and also capital cost by reducing the

326

facility size. Further characterization of this absorbent at partially desorbed stage depending

327

upon the history of absorption and desorption is in progress.

328

ASSOCIATED CONTENT

329

Additional information on characterization using X-ray diffraction and N2–sorption studies of

330

various absorbents. This material is available free of charge via the Internet at

331

http://pubs.acs.org.

332

AUTHOR INFORMATION

333

Corresponding Author

334

*Y. K. Park. Phone: +82-42-8607672; E-mail: [email protected].

335

Notes

336

The authors declare no competing financial interest.

337

ACKNOWLEDGMENT

338

This work was supported by the Korea CCS R&D Center (KCRC) grant funded by the Korea

339

government (Ministry of Science, ICT & Future Planning, no. 2014M1A8A1049248).

340

REFERENCES

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1. Crowley, T. J.; Berner, R. A. Science 2001, 292, 870−872.


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8. Wang, Q.; Luo, J.; Zhong Z.; Borgna, A. Energy Environ. Sci. 2011, 4, 42-55.

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2013, 54, 144-149 10. Park, Y.-K.; Seo, H.; Choi, W. C.; Kang, N. Y.; Park, S.; Min, D. Y.;Kim, K.; Lee, K. S.; Moon, H. K.; Cho, H. H.; Lee, D. K. Energy Procedia, 2014, 63, 2266-2279.

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Factors Affecting the Rate of CO2 Absorption after Partial Desorption

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