Scholarly article on topic 'Adsorption of CO2 and H2O on supported amine sorbents'

Adsorption of CO2 and H2O on supported amine sorbents Academic research paper on "Chemical engineering"

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Abstract of research paper on Chemical engineering, author of scientific article — Rens Veneman, Wenying Zhao, Zhenshan Li, Ningsheng Cai, Derk W.F. Brilman

Abstract In this work we have evaluated the H2O and CO2 adsorption characteristics of Lewatit VP OC 1065 in view of the potential application of solid sorbents in post combustion CO2 capture. Here we present single component adsorption isotherms for H2O and CO2 as well as co-adsorption experiments. It was concluded that the sorbent material shows a high affinity in the adsorption of H2O. The adsorption of CO2 alone does not prevent the co- adsorption of large quantities of water and additional measures are necessary to prevent this from negatively affecting the energy demand of the process.

Academic research paper on topic "Adsorption of CO2 and H2O on supported amine sorbents"

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Energy Procedia 63 (2014) 2336 - 2345

GHGT-12

Adsorption of CO2 and H2O on supported amine sorbents

Rens Venemana*, Wenying Zhaob, Zhenshan Lib, Ningsheng Caib, Derk W.F. Brilmana

a. Sustainable Process Technology Group, Green Energy Initiative, Faculty of Science and Technology, University of Twente, P.O. Box

217, 7500 AE Enschede, The Netherlands b. Key Lab for Thermal Science and Power Engineering of MOE, Department of Thermal Engineering, Tsinghua University, Beijing

100084, Peoples Republic of China

Abstract

In this work we have evaluated the H2O and CO2 adsorption characteristics of Lewatit VP OC 1065 in view of the potential application of solid sorbents in post combustion CO2 capture. Here we present single component adsorption isotherms for H2O and CO2 as well as co-adsorption experiments. It was concluded that the sorbent material shows a high affinity in the adsorption of H2O. The adsorption of CO2 alone does not prevent the co-adsorption of large quantities of water and additional measures are necessary to prevent this from negatively affecting the energy demand of the process.

© 2014 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license

(http://creativecommons.Org/licenses/by-nc-nd/3.0/).

Peer-review under responsibility of the Organizing Committee of GHGT-12

Keywords: Adsorption; CO2; H2O; Carbon Capture; supported amines;

1. Introduction

Application of carbon capture and storage (CCS) at fossil fuel burning plants is, among other alternatives, a technically feasible method to significantly reduce the global anthropogenic emission of CO2. However, using the current state-of-art technology, this would result in an increase in the cost of electricity (COE) by 40% mainly due to high cost of carbon capture [1]. This increase in COE is a major hurdle in deployment and the development of a more cost effective capture technology is a main objective in CO2 capture research. The conventional capture

Corresponding author. Tel.: +31 53 489 4418, Fax.: +31 53 489 4718 E-mail address: R.Veneman@utwente.nl

1876-6102 © 2014 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license

(http://creativecommons.org/licenses/by-nc-nd/3.0/).

Peer-review under responsibility of the Organizing Committee of GHGT-12

doi: 10.1016/j.egypro.2014.11.254

process utilizes a mixture of amine molecules, typically MEA, and water to selectively absorb CO2 from flue gases. Already at low temperatures, CO2 dissolves in this absorption liquid (or solvent). By contacting the CO2 containing gas with this solvent in an absorber column, the absorption liquid 'captures' the CO2. Subsequently, the liquid with the dissolved CO2 is transported to a second column, the desorber. Here, the liquid is heated, which causes the solvent to release the CO2 again. This supplies a stream of pure CO2, which is compressed and stored, while the regenerated solvent is pumped back to the absorber column to capture more CO2.

The main cost driver of the process is the high energy demand, mainly associated with heating the aqueous amine solution from the absorption temperature to the desorption temperature. Applying supported amine sorbents may offer a low-cost capture technology. The operational costs associated with the thermal energy input of the amine scrubbing process make up around 44% of the total CO2 capture costs. A large part of this energy requirement is associated with heating of the aqueous amine solution from the absorption temperature to the desorption temperature and with the evaporation of solvent in the desorber column. Replacing H2O as solvent by a solid support greatly reduces the energy required for CO2 capture as; (1) the evaporation of water is inhibited and (2) the energy required for heating the sorbent up to the desorption temperature is much lower due to the lower heat capacity of solid supports compared to water.

Supported amine sorbents (SAS) consist of a high internal surface-area support (e.g. silica's, polymers, zeolites) with amine functional groups immobilized on or grafted to its surface [2]. The key strengths of this type of sorbents material include high CO2 capacities [3], fast CO2 uptake rates, a low heat of adsorption and relatively mild regeneration conditions compared to other chemical sorbents [3, 4].

Supported amine sorbents are tolerant towards the presence of water in the CO2 containing gas i.e. the CO2 capacity does not degrade in presence of H2O. In many cases H2O was even found to promote the CO2 capacity [2, 5-8]. This is an important strength of these type of sorbents since flue gas contains as much, if not more H2O, than CO2. Still, these sorbent materials also capture significant amounts of H2O under conditions relevant for post-combustion CO2 capture. Franchi et al. [6] reported an adsorption capacities for DEA on pore expanded MCM-41 of 5.37 mol/kg at 28% RH, and Xu et al. [9] measured the adsorption capacity for PEI on MCM-41 to be 2.45 mol/kg and 3.01 mol/kg at 26% relative humidity (RH) and at 31% RH respectively. The sorption capacities reported for H2O in these studies surpass the capacities measured for CO2. Also other materials considered for applications in post-combustion capture as a sorbent or support material (13X, silica supported amines, carbons, etc..) are all known to capture large quantities of H2O under flue gas conditions [10].

In terms of sorbent stability, the process may benefit from the co-adsorption of some of the water present in flue gas. The presence of water during sorbent regeneration suppresses the undesired formation of urea [5, 11-14]. Drage et al. [13] observed CO2 induced deactivation of a PEI impregnated silica supported amine sorbents at temperatures above 135°C. The loss of adsorption capacity was attributed to the bonding of CO 2 into the PEI polymer through the formation of a urea type linkage. Sayari et al. [5] reported that water vapour greatly improved the stability of this type of sorbent material. It was observed that the formation of urea could be completely be reversed by adding steam via hydrolysis of such groups. Even at a relative humidity as low as 0.4% urea formation was strongly inhibited. Desorption was performed here using a N2 as a sweep gas. Therefore, higher partial pressures of water might be needed to prevent urea formation in case the sorbent material was to be regenerated in an atmosphere containing higher concentrations of CO2.

Although the adsorption of small quantities of water might prevent CO2-induced sorbent deactivation, the adsorption of large quantities of water could severely affect the energy demand of the process. In the desorber column temperatures are high and H2O partial pressure are envisioned to be low [3]. Hence a large part of the co-adsorbed water will be released again in the desorber column. In addition to the heat required to desorb the captured CO2, also energy is required to release the co-adsorbed water, resulting in an increase in the parasitic heat demand for capture. The role of water in this process is complex, as the H2O present in flue gas (1) interferes with the CO2 adsorption mechanism [6, 9] and affects (2) the sorbent stability [5, 11-14] as well as (3) the process energy demand. However, the number of studies on the H2O adsorption by supported amine sorbents is limited. Moreover, there is not yet a clear strategy on how to deal with the co-adsorption of water on a process scale. The aim is to identify the most convenient way to deal with water in this adsorption based capture process. In this work we set the arbitrary goal of capturing no more than 0.25 moles of H2O per mole of CO2 captured. This would increase the energy demand of the process with no more than 0.25 GJ/t of CO2 captured which we deem acceptable (assuming the heat of adsorption of water on the sorbent is equal to the heat of condensation).

2. Experimental

2.1 Material

The sorbent material used in this study is Lewatit® VP OC 1065 (Lanxess). It is a polystyrene based ion exchange resin (IER) containing primary benzyl amine units [15]. The resins are spherical shaped beads with a diameter between 0.47 and 0.57 mm. The materials' pore volume, pore surface area and average pore size are 27 cm3/g, 50 m2/g and 25 nm respectively.

2.2 CO2 and H2O capacity measurements

The experimental work focusses on measuring adsorption capacities for CO2 and H2O at temperatures and partial pressure relevant for post combustion CO2 capture.

A NETSZCH STA 449 F1 Jupiter thermal gravimetric analyzer (TGA) was used to assess the CO2 adsorption capacity of the sorbent material. In a typical adsorption experiment around 15 mg of sorbent was placed inside the TGA furnace. The sample was heated up to 800C in N2 to desorb any pre-adsorbed CO2 and moisture. The temperature was kept constant until the sample mass stabilized. Then, the sample was cooled down to the desired adsorption temperature after which CO2 was fed to the TGA furnace. The uptake of CO2 by the sorbent sample results in an increase in the sample mass. The sorbent CO2 uptake, in mole.kg-1 sorbent, was calculated from the weight change of the sample during adsorption. Typically, after 4 hours of adsorption time the change in the sample mass was minimal (<0.01 mol/kg/hr) and the measurement was stopped. The adsorption experiments were performed at different temperatures and CO2 partial pressures to obtain the data required to construct an adsorption isotherm. Desired gas compositions were obtained by mixing high purity (grade 5.0) N2 and high purity (grade 5.0) CO2. The specific configuration of the TGA equipment limited the CO2 concentration to a maximum of 80vol% of CO2 at 1 atm.

The H2O adsorption capacity of the sorbent material was measured in a custom built packed bed reactor equipped with a humidifier column, two humidity meters and an infrared CO2 gas analyzers. The humidity meters (Hygrosens FF-20MA-INT-TE0) continuously measured the temperature and relative humidity of the gas entering and leaving the reactor (detection range: T=-30..70C, RH=0..100%). The CO2 analyzer (SIDOR, SICK MAIHAK) was used to monitor the CO2 concentration in the outlet gas of the packed bed column (detection range: 0..15vol%). Two JULABO F32 water baths were used to control the temperature of the adsorber and the temperature of the H2O saturation columns. The CO2 and H2O concentrations in the column inlet gas were controlled by mixing a flow of high purity (grade 5.0) N2 and a high purity (grade 5.0) CO2 flow with a third pre-saturated flow of N2. The flow rates were controlled using three BROOKS mass flow controllers. After mixing of the three gas flows the humidity of the gas was measured. All of the gas lines were heated to temperatures just above the dew point of the gas mixture to prevent condensation of H2O in the gas lines.

In a typical H2O adsorption experiment around 10 gr of dried sorbent material was loaded into the column. After closing the reactor, the reactor was heated up to 80 0C while flushing the column with N2 (500 ml/min) to desorb any remaining CO2 and H2O. The reactor was subsequently cooled and when the desired adsorption temperature was reached, the N2 flush was stopped and the H2O containing gas (500-1000 ml/min) was fed to the column. The experiment was stopped when the inlet partial pressure of H2O was equal to the outlet partial pressure of H2O within the error margin of the humidity meters. CO2/H2O co-adsorption experiments were performed in a similar manner.

Figure 1: Fixed bed setup schematic

3. Results

The experimental results obtained from the TGA apparatus provided CO2 adsorption capacities at different adsorption temperatures and CO2 partial pressures. Figure 2 shows the measured adsorption isotherms at 303.15, 313.15, 343.15, 353.15 and 373.15 for CO2 on Lewatit VP OC 1065.

The CO2 highest capacity observed in the measurements performed was 2.95 mol/kg resin measured at 306K in 70 vol% of CO2. Alesi et al. reported that the maximum theoretical amine loading is expected to be in the order of 6.7 mol N/kg resin [15] for this type of IER. A CO2 loading of 2.95 mol/kg then corresponds to a amine efficiency of 0.44 mol CO2 per mol N2, which is typical for these kind of sorbent materials.

One of the most important parameters in this capture process is the sorbent's cyclic operating capacity. This parameter will for a large part determine the heat demand of the process. Especially the partial pressure of CO2 and the temperature during sorbent regeneration have a large impact on this cyclic adsorption capacity. Since we are aiming here to produce a high purity CO2 product gas, the sorbent will be regenerated in an atmosphere with a high CO2 content. This regeneration method has our preference over alternative regeneration methods like vacuum swing adsorption or steam regeneration [3]. Under the adsorption conditions relevant for post-combustion CO2 capture and sorbent regeneration at 140°C at a CO2 partial pressure of 80 kPa, the sorbent material can cyclically capture 1.8 mol/kg.

Based on the experimental data, the isosteric heat of adsorption was calculated using the Clausius-Clapeyron equation. The adsorption heat of 87 kJ/mol lies in the range typical for CO2 adsorption by amine molecules [8, 17].

3,0 2,5 2,0 1,5 1,0 0,5 0,0

P--X-'-'-'-*......"

A / ,0

-----------

.-■-•'A-----'

-------

___________________

-----"D" —-v

... - X- — -x------- x

______A---------------------A

._.-0-------------------

□ 303.15 K X313.15 K O343.15 K A353.15 K 0373.15 K B413.15 K

Pco2(kPa)

Figure 2: CO2 adsorption isotherms for Lewatit VP OC 1065 at 30°C, 40°C, 80°C, 100°C and the measured capacity

of the sorbent at 140°C and a CO2 partial pressure of 80 kPa.

Figure 3 shows the measured H2O adsorption capacities at different relative humidities. As a reference, the adsorption capacities of DEA on pore expanded MCM-41 (5.37 mol/kg at 28%RH, [6]) and PEI on MCM-41 (2.45 mol/kg and 3.01 mol/kg at 26%RH and 31%RH respectively, [7]) were plotted in the same graph as well as the H2O sorption capacity of Zeolite 13X and SiO2 gel. The highest observed H2O sorption capacity for Lewatit VP OC 1065 was 12,5 mol/kg at a relative humidity of 95%. At these high levels of saturation, water condenses inside the pores of the sorbent material and this high H2O loading approaches the H2O capacity for a completely filled pore space of 14.4 mol/kg respectively. Based on the experimental data, the isosteric heat of adsorption was calculated using the Clausius-Clapeyron equation. The adsorption heat of 43 kJ/mol is close the condensation heat of water which suggest that indeed condensation/pore filling occurs at higher relative humidities.

Analysis of the pore volume distribution showed that the sorbents' micropore volume was minimal (0.003272 cm3/g) and more than 95% of the pore volume is attributed to pores larger than 10 nm. Hence, pore filling will most likely not be the main mechanism for H2O uptake in the humidity range from 10%RH to 60%RH. Moreover, polymeric resins with a poly (styrene-divinylbenzene) matrix were found to have a very limited H2O capacity (<1 mol/kg) at relative humidities lower than 60%RH [18, 19] due to the hydrophobic nature of the material. The relatively high H2O capacities (5.8 mol/kg at 60%RH) observed for Lewatit VP OC 1065 might therefore be attributed to the presence of amine molecules on the pore surface increasing the affinity towards the adsorption of water. Figure 3 also shows the H2O adsorption capacity for other sorbent materials studied for their application in post combustion CO2 capture. The adsorption capacities of DEA on pore expanded MCM-41 (5.37 mol/kg at 28%RH, [6]) and PEI on MCM-41 (2.63 mol/kg and 3.24 mol/kg at 26%RH and 31%RH respectively, [7]) are in the same order as the capacities measured for the IER and also both well above the targeted working capacity even at relatively low saturation levels of around 30%RH. The adsorption capacities observed for Zeolite 13X under the same conditions are even higher than that of Lewatit VP OC 1065 and the MCM-41 based supported amine sorbents shown in the graph. Especially at relative humidities below 60%RH, Zeolite 13X shows much higher adsorption capacities for water than the sorbent studied here. This is most probably attributed to the smaller pore sizes of 13X, compared to the sorbent studied here, in which pore filling occurs at lower relative humidities. It is also important to mention here that the H2O capacity of the sorbent material is only a function of the relative humidity. Hence all data presented in Figure 4 fall onto one curve that is the curve presented in Figure 3 for Lewatit VP OC 1065.

16,0 14,0 12,0 10,0 8,0 & 6,0 4,0 2,0

OLewatit VP OC 1065 (This work) aSAS (Xu et al. 2005, Franchi et al. 2005) O Zeolite 13X (Wang et al. 2009) □ SiO2 (Wang et al. 2009)

0,0 0,0001

0,01 P/P,

Figure 3: H2O capacity as a function of the relative humidity for Zeolite 13X, silica gel, Lewatit VP OC 1065 and sorbents prepared by Franchi et al. [6] and Xu et al. [7]. The data shown for Lewatit was measured at temperatures

between 20 and 80°C

® 8,0 15

& 6,0 4,0 2,0 0,0

2 4 6 8

PH2O (kPa)

Figure 4: H2O adsorption isotherms for Lewatit VP OC 1065 at 40°C, 50°C and 75°C.

The dewpoint of flue gas is around 47°C before entering the adsorber column which corresponds to a saturation level of 67% RH at the gas inlet temperature. Under these conditions this sorbent material is capable of adsorbing around 8 mol H2O/kg. These high saturation capacities lead to the following important conclusion regarding the co-adsorption of water in the sorbent based process: The adsorption of H2O in the adsorber column of the post combustion capture process is not limited by the equilibrium capacity of the sorbent material under adsorption conditions. Instead, the H2O working capacity is supply limited, i.e. the sorbent will adsorb practically all H2O entering the column given there is enough contact time. This is not only true for this particular sorbent. Any sorbent with a H2O capacity higher than its CO2 capacity will adsorb practically all water entering the adsorber. This includes also Zeolite 13X. Even if the adsorption temperature is increased to, say, 100°C in order to lower the relative humidity in the column, the H2O equilibrium capacity will still be around 1.5 mol/kg which is far above the targeted capacity and will hence not lead to a lower (parasitic) H2O working capacity. Moreover, a higher adsorption temperature will lower the CO2 working capacity.

The development of a sorbent that does not bind water would solve the issue entirely. It needs to be stressed however that this sorbent should have a saturation capacity not higher than 0.5 mol/kg at relative humidities around 70-90% RH. In case the saturation capacity is higher than 0.5 mol/kg, the H2O co-adsorption will still be limited by the inlet molar flow of H2O and the resulting H2O working capacity of this 'hydrophobic' sorbent will then be effectively the same as for Lewatit VP OC 1065 or Zeolite 13X.

One way to prevent the co-adsorption of large quantities of water is by lowering the relative humidity of the incoming flue gas. Lowering the dewpoint of the flue gas to 15 °C would lower the amount of water adsorbed to ~0.25 mol/mol CO2 adsorbed. This requires 0.2 GJ of cooling duty per tonne of CO2 captured in addition to the 0.25 GJ/t of heat required to desorb the co-adsorbed water.

It is clear that CO2 and H2O do not bind to the sorbent in the same way, considering the large difference in heat of adsorption and capacity. Still, the presence of H2O could influence the sorption of CO2 through for example physical interaction between CO2 and H2O or shielding of amine active sites by H2O. Figure 5 shows the CO2 adsorption capacities for Lewatit VP OC 1065 under dry and humid conditions. The presence of water does not seem to have a detrimental effect on the CO2 capacity; the CO2 capacities are even little higher in the measurements with water present. This is phenomenon has been noticed before for supported amine sorbents [6, 20-22] and is usually attributed to the interference of H2O in the adsorption mechanism. Water can act as a free-base, resulting in the formation of bicarbonate in presents of water vapor whereas carbamate is formed when water is not present. This changes the reaction stoichiometry; in the presence of water one amine group could theoretically react with one CO2 molecule whereas two amine molecules are required to bind one molecule of CO2 under dry conditions. Alesi et al. also observed the formation of carbamate on Lewatit VP OC 1065 [15]. In these co-adsorption experiments, the water capacity was not significantly affect by the presence of CO2.

O.......

OCO2 capacity without water present ■ CO2 capacity with water present

Pco2(kPa)

Figure 5: CO2 capacities for Lewatit VP OC 1065 measured in the fixed bed at different CO2 partial pressures and at 70°C in presence of water (6 kPa) and under dry conditions.

4. Conclusion

In this work we have evaluated the H2O and CO2 adsorption characteristics of Lewatit VP OC 1065 in view of the potential application of solid sorbents in post combustion CO2 capture. Based on the experimental results presented here we conclude that:

• Lewatit VP OC 1065 can adsorb much more (4-5 times) H2O than CO2 under adsorption conditions relevant for post-combustion CO2 capture.

• The equilibrium water capacity seems to be only a function of the relative humidity in the gas phase; all data point measured here fall onto one curve when the capacity is plotted against the relative humidity in the gas phase.

• The presence of water in the gas phase does not seem to negatively impact the CO2 adsorption capacity.

• Due to high equilibrium capacities, the adsorption of H2O in the adsorber column of the post combustion capture process is not limited by the equilibrium capacity of the sorbent material under adsorption conditions. Instead, the H2O working capacity is supply limited, i.e. the sorbent will adsorb practically all H2O entering the column given there is enough contact time.

• One way to prevent the co-adsorption of large quantities of water is by lowering the relative humidity of the incoming flue gas. Lowering the dewpoint of the flue gas to 15 °C would lower the amount of water adsorbed to approximately 0.25 mol/mol CO2 adsorbed. This requires 0.2 GJ of cooling duty per tonne of CO2 captured in addition to the 0.25 GJ/t of heat required to desorb the co-adsorbed water.

Acknowledgement

This research has been carried out in the context of the CATO-2-program. CATO-2 is the Dutch national research program on CO2 Capture and Storage technology (CCS). The program is financially supported by the Dutch government (Ministry of Economic Affairs) and the CATO-2 consortium partners.

References

[1] Fisher KS, Beitler C, Rueter C, Searcy K, Rochelle DG, Jassim DM, Integrating MEA Regeneration with CO2 Compression and Peaking to Reduce CO2 Capture Costs, in, 2005, pp. Medium: ED; Size: 757.

[2] Ebner AD, Gray ML, Chisholm NG, Black QT, Mumford DD, Nicholson MA, Ritter JA, Suitability of a solid amine sorbent for CO2 capture by pressure swing adsorption, Industrial and Engineering Chemistry Research, 50 (2011) 5634-5641.

[3] Veneman R, Li ZS, Hogendoorn JA, Kersten SRA, Brilman DWF, Continuous CO 2 capture in a circulating fluidized bed using supported amine sorbents, Chemical Engineering Journal, (2012).

[4] Sjostrom S, Krutka H, Evaluation of solid sorbents as a retrofit technology for CO2 capture, Fuel, 89 (2010) 1298-1306.

[5] Sayari A, Belmabkhout Y, Stabilization of amine-containing CO2 adsorbents: Dramatic effect of water vapor, Journal of the American Chemical Society, 132 (2010) 6312-6314.

[6] Franchi RS, Harlick PJE, Sayari A, Applications of Pore-Expanded Mesoporous Silica. 2. Development of a High-Capacity, Water-Tolerant Adsorbent for CO2, Industrial & Engineering Chemistry Research, 44 (2005) 80078013.

[7] Xu X, Song C, Miller BG, Scaroni AW, Influence of Moisture on CO2 Separation from Gas Mixture by a Nanoporous Adsorbent Based on Polyethylenimine-Modified Molecular Sieve MCM-41, Industrial & Engineering Chemistry Research, 44 (2005) 8113-8119.

[8] Li W, Choi S, Drese JH, Hornbostel M, Krishnan G, Eisenberger PM, Jones CW, Steam-Stripping for Regeneration of Supported Amine-Based CO2 Adsorbents, Chemsuschem, 3 (2010) 899-903.

[9] Xu X, Song C, Miller BG, Scaroni AW, Influence of moisture on CO2 separation from gas mixture by a nanoporous adsorbent based on polyethylenimine-modified molecular sieve MCM-41, Industrial and Engineering Chemistry Research, 44 (2005) 8113-8119.

[10] Wang Y, Levan MD, Adsorption Equilibrium of Carbon Dioxide and Water Vapor on Zeolites 5A and 13X and Silica Gel: Pure Components, JChem Eng Data, 54 (2009) 2839-2844.

[11] Sayari A, Heydari-Gorji A, Yang Y, CO2-Induced Degradation of Amine-Containing Adsorbents: Reaction Products and Pathways, Journal of the American Chemical Society, 134 (2012) 13834-13842.

[12] Sayari A, Belmabkhout Y, Da'na E, CO2 Deactivation of Supported Amines: Does the Nature of Amine Matter?, Langmuir, 28 (2012) 4241-4247.

[13] Drage TC, Arenillas A, Smith KM, Snape CE, Thermal stability of polyethylenimine based carbon dioxide adsorbents and its influence on selection of regeneration strategies, Microporous and mesoporous materials, 116 (2008) 504-512.

[14] Heydari-Gorji A, Sayari A, Thermal, Oxidative, and CO2-Induced Degradation of Supported Polyethylenimine Adsorbents, Ind Eng Chem Res, 51 (2012) 6887-6894.

[15] Alesi WR, Kitchin JR, Evaluation of a Primary Amine-Functionalized Ion-Exchange Resin for CO2 Capture, Industrial & Engineering Chemistry Research, 51 (2012) 6907-6915.

[16] Serna-Guerrero R, Belmabkhout Y, Sayari A, Modeling CO2 adsorption on amine-functionalized mesoporous silica: 1. A semi-empirical equilibrium model, Chemical Engineering Journal, 161 (2010) 173-181.

[17] Gray ML, Hoffman JS, Hreha DC, Fauth DJ, Hedges SW, Champagne KJ, Pennline HW, Parametric Study of Solid Amine Sorbents for the Capture of Carbon Dioxide, Energ Fuel, 23 (2009) 4840-4844.

[18] Long C, Li Y, Yu WH, Li AM, Adsorption characteristics of water vapor on the hypercrosslinked polymeric adsorbent, Chemical Engineering Journal, 180 (2012) 106-112.

[19] Bardina IA, Zhukova OS, Kovaleva NV, Lanin SN, The adsorption of H2O and D2O on porous polystyrene adsorbents, Russ JPhys Chem a+, 81 (2007) 1525-1531.

[20] Su F, Lu C, Kuo S-C, Zeng W, Adsorption of CO2 on Amine-Functionalized Y-Type Zeolites, Energy & Fuels, 24 (2010) 1441-1448.

[21] Hiyoshi N, Yogo K, Yashima T, Adsorption characteristics of carbon dioxide on organically functionalized

SBA-15, Microporous andMesoporousMaterials, 84 (2005) 357-365.

[22] Hicks JC, Drese JH, Fauth DJ, Gray ML, Qi G, Jones CW, Designing Adsorbents for CO2 Capture from Flue Gas-Hyperbranched Aminosilicas Capable of Capturing CO2 Reversibly, Journal of the American Chemical Society, 130 (2008) 2902-2903.