Polyethylenimine-Magadiite Layered Silicate Sorbent for CO2

Article pubs.acs.org/est

Polyethylenimine-Magadiite Layered Silicate Sorbent for CO2 Capture Rômulo B. Vieira and Heloise O. Pastore* Micro and Mesoporous Molecular Sieves Group, Institute of Chemistry, University of Campinas, Rua Monteiro Lobato 270, 13083-861, Campinas, São Paulo, Brazil S Supporting Information *

ABSTRACT: This paper describes the preparation of a Layered Silicate Sorbent (LSS) for CO2 capture using the layered silicate magadiite and organo-magadiite modified with polyethylenimine (PEI). The sorbents were characterized and revealed the presence of PEI as well as its interaction with CO2 at low temperatures. The thermal stability of sorbents was confirmed by thermogravimetry experiments, and the adsorption capacity was evaluated by CO2-TPD experiments. Two kinds of PEI are present in the sorbent, one exposed PEI layer that is responsible for higher CO2 adsorption because its sites are external and another one, bulky PEI, capable of low CO2 adsorption due to the internal position of sites. The contribution of the exposed PEI layer may be increased by a previous exchange of CTA+, but the presence of the surfactant decreased the total adsorption capacity. MAG-PEI25 reached a maximum adsorption capacity of 6.11 mmol g−1 at 75 °C for 3 h of adsorption and showed a kinetic desorption of around 15 min at 150 °C.

■

Solid sorbents include zeolites,14 molecular baskets,15,16 metalbased sorbents,17 carbon molecular sieves,18 metal organic frameworks (MOF),19 porous polymers,20 and nanoclays.9 The majority of these sorbents are modified with amine groups through impregnation,16,21−25 grafting on the surface,26−29 and impregnation followed by grafting.9,30 Polyethylenimine is a polymeric amine which has been widely used in the preparation of these sorbents, mainly due to the large concentration of amine groups controlled by synthesis conditions, molecular weight, and a moduled primary/ secondary/tertiary amines ratio.31 Song et al. developed the molecular basket sorbent (MBS) and obtained an adsorption capacity of 2.9 mmol g−1 at 75 °C and 50 wt % of PEI impregnated in MCM-41.15,16 After the first studies about this sorbent, others using PEI as an active site for CO2 capture have been performed, evaluating the influence of the support, of the PEI molecular weight, of concentration in the support, and of adsorption temperature.32−34 Song et al. studied the influence of adsorption temperature and found that chains of PEI are more flexible at high temperatures, specifically at 75 °C. FTIR experiments suggested that PEI molecules become more flexible and may stretch their chains inside the pore channels of SBA-15, lowering diffusion barriers. Additionally, they concluded that the increase in PEI molecular weight decreases

INTRODUCTION The technological changes that occurred in the eighteenth century, initiated by the industrial revolution, increased greenhouse gas emissions, specifically atmospheric CO2. In that period, CO2 emissions were around 280 ppm1,2 and reach values up to 390 ppm nowadays.3−5 Thereby, several methods to capture CO2 involving chemical and physical processes were developed. Carbon capture and sequestration (CCS) is one of the technologies employed to protect mankind from the risks of climate changes and the most viable and fast measure to reduce the CO2 emissions.6 CCS includes CO2 capture, compression, transport, and storage and, in the case of power plants, may be used in precombustion, postcombustion, and oxycombustion conditions.7 The most used processes to capture CO2 and other light gases are through cryogenic distillation, membrane purification, and adsorption with liquid and solid sorbents.8 The use of liquid sorbents based in monoethanolamine (MEA) and diethanolamine (DEA) is the technology industrially applied with efficiency, but it is very expensive because of the large amounts of solvent required, besides the large energy demand for regeneration of these liquid amines, corrosion problems, and loss of amines by evaporation or decomposition in power plants.1,9−12 The utilization of solid sorbents offers several advantages when compared with the use of liquid amines. These are low energy requisition, no corrosion, and a reduced loss of sorbent and of separation steps at low CO2 partial pressures.9,13 Furthermore, solids that showed fast adsorption and desorption kinetics, large adsorption capacity, are regenerable and stable.1 © 2014 American Chemical Society

Received: Revised: Accepted: Published: 2472

October 8, 2013 January 2, 2014 January 17, 2014 January 17, 2014 dx.doi.org/10.1021/es404501e | Environ. Sci. Technol. 2014, 48, 2472−2480

Environmental Science & Technology

Article

the content of primary amines in relation to the presence of tertiary amines that are responsible for branching the polymeric chains.35−37 A major problem encountered in these sorbents is the access of CO2 to the inner portions of pores or channels in which adsorption sites are located. In an attempt to reduce or eliminate the diffusion troubles, the layered materials, specifically the layered silicate known as magadiite, have been studied by our group.38−41 It may be used as inorganic support for polymers due mainly to the flexibility of interlayer space and the fact that adsorption sites will not be occluded in pores or channels but distributed in the interlayer space of silicate. Magadiite [Na2Si14O29·(5−10)H2O] is a hydrated layered silicate discovered in 1967 by Eugster.42 Its silicon atoms are in tetrahedral coordination to four oxygen atoms, and the layer surface has negative charges that are counterbalanced by hydrated sodium ions hosted in the interlayer space.41,43 It has silicon Q3((O−/OH)Si(OSi)3) and Q4(Si(OSi)4) giving high reactivity to the layer surface,44 The silicon Q3 sites may be modified through noncovalent and covalent reactions, having a vast field of application, for example, catalysis, building units, ion exchangers, nanosheets, gas storage materials, and selective sorbents.44 In this context, amine groups grafted in the surface of layered silicates were already used in CO2 capture. Sadakane et al.45 studied the behavior of aminopropyl- and aminopropyl/ octadecyl-grafted magadiite. The adsorption capacity and efficiency for aminopropylmagadiite (NH2-mag) were 0.35 mmol g−1 of CO2 and 0.16, respectively, at 25 °C and 1 atm under dry conditions. As for the aminopropyl/octadecylmagadiite (NH2−C18-mag), adsorption capacity and efficiency were 1.20 mmol g−1 of CO2 and 0.52, respectively, under the same reaction conditions. The presence of 0.1 mmol g−1 of octadecyl groups expanded the interlayer space of magadiite to 3.20 nm and improved the diffusion of CO2, increasing their adsorption capacity. Elkhalifah et al.46 studied the CO2 capture using bentonite clays modified with mono-, di-, and triethanolamine (MEA, DEA, and TEA) introduced into the solid through an ion exchange procedure. They obtained results of adsorption capacity in the range of 2.68−3.15 mmol g−1 of CO2 at 25 °C and 10 bar of pressure, under dry conditions. Wang et al.47 developed a new clay, impregnated it with PEI, and studied the CO2 capture. First, the clays were subjected to acid (HCl 6 mol L−1) and alkaline (NaOH 5 mol L−1) treatments. The best sorbent was montmorillonite treated with 6 mol L−1 HCl followed by impregnation with 50% (w/w) PEI, which showed adsorption capacity of 2.54 mmol g−1 of CO2 at 75 °C and 1 atm under dry conditions. The acid or alkaline treatments improved the textural properties and facilitated the access of CO2 to the adsorption sites. Magadiite has an interlayer space of 1.55 nm in the sodium hydrated form able to host large amine compounds, as in the case of PEI. Furthermore, the intercalation of surfactants in interlayer space is one of the modifications which may be made with the magadiite, increasing the interlayer space from 1.55 to 2.79 nm48 in such a way to accommodate a larger amount of PEI. Wang et al.49 proposed a new strategy to improve the CO2 capture: they studied the addition of different types of surfactants and obtained an increase of 41% in adsorption capacity using 55 wt % of PEI and 15 wt % of Span80. The improvement caused by the presence of surfactant is due to the creation of extra access formed by breaking the bulky PEI films and allowing the deeper diffusion of CO2 into the films.49

In this paper, a solid sorbent has been developed by the synthesis of magadiite and the modification through an ion exchange procedure with hexadecyltrimethylammonium bromide (CTAB) and impregnation with PEI. To our knowledge, no reports may be found in the literature about the application of layered silicates in CO2 capture; therefore, this paper is the first that evaluates the use of magadiite impregnated with PEI as a sorbent for the CO2 capture.

■

EXPERIMENTAL SECTION Materials. The following reagents were used in the synthesis of sorbents: sodium metasilicate (Na2SiO3·5H2O, Nuclear, 212.14 g mol−1), nitric acid (HNO3, 63%, Merck), hexadecyltrimethylammonium bromide (CTAB, 99%, ACROS ORGANICS, 364.45 g mol−1), methanol (CH3OH, 99.8%, Sigma-Aldrich), and branched PEI (PEI, Mn ∼800 by LS, Mw ∼600 by GPC, Sigma-Aldrich). Magadiite Synthesis. The synthesis of magadiite was carried out according to Superti et al.38 and Moura et al..40,41 Sodium metasilicate (0.14 mol) was dissolved in distilled water (249.1 mL) and the pH was adjusted at 10.6−10.8 with concentrated HNO3. A gel was formed and was aged for 4h at 74 °C-76 °C. After that, it was transferred to a stainless steel autoclave lined with Teflon for the hydrothermal treatment for 66h at 150 °C. The material was filtered, washed until pH 7.0 and dried in air and named MAG. CTAB Ion Exchange in Magadiite. The ion exchange step was performed by dispersing 1.0 g of magadiite in 100 mL of MiliQ water. Then, CTAB was added and the mixture was kept under magnetic stirring for 24 h at 50 °C. The general formula of magadiite is Na2Si14O29·(5−10)H2O, and CTA+ ions were exchanged at a CTA/Na molar ratio percentage equal to 25. Last, the material was washed until the end of foaming and dried in the air at room temperature. The material was named 25CTA-MAG. Preparation of the Sorbent. Branched PEI layered silicate sorbents were prepared by the impregnation method described previously by Xu et al.15,16 and Goeppert et al.50,51 First, the desired amount of PEI was dissolved in 25 mL of methanol for 1 h. At the same time, MAG or 25CTA-MAG was dispersed in 100 mL of methanol for 1 h. After that, PEI solution was added stepwise under stirring to guarantee a good dispersion of the PEI on the layered silicates. The solution was stirred for 24 h at 60 °C, and the solvent was removed from the mixture at 50 °C by rotoevaporation and dried at 100 °C overnight. The sorbents were named MAG-PEI-x and 25CTA-MAG-PEI-x, where x represents the loading of PEI as weight percentage in the sample. The final material was obtained as a white solid, which agglomerated with increasing concentration of PEI. The amounts of PEI used were between 10 and 25%. Characterization. To confirm the formation of the desired materials, X-ray diffraction (XRD) was performed in a Shimadzu XRD7000 apparatus with a Cu Kα = 1.5406 Å (40 kV, 30 mA) source. Slits of 5 mm were used for dispersion and convergence and 3° for exit. The measurements were obtained between 1.4 and 55° 2θ at room temperature at a scan rate of 2° 2θ min−1. The basal spacing of the layered silicates was calculated by Bragg’s law. Fourier transformed infrared spectroscopy (FTIR) using KBr pellets (0.25 wt %) was performed with the use of a Thermo Nicolet 6700 FTIR spectrophotometer equipped with a DTGS detector (resolution 4 cm−1). Spectra were collected in the range from 400 to 4000 cm−1 by accumulating 128 scans. 2473

dx.doi.org/10.1021/es404501e | Environ. Sci. Technol. 2014, 48, 2472−2480


Article

13

calculations were performed with the Gaussian 09 program, D.01 version. The larger and smaller dimensions of PEI are 2.45 and 2.15 nm, respectively. According to some studies in the literature,33,36,37 branched PEI chains are more flexible when the temperature increases. The PEI impregnation reaction is carried out at 60 °C; therefore, although the dimensions of PEI are larger than the interlayer space of MAG, it is possible that PEI accommodates into the interlayer space due to the flexibility of the chains. Moreover, PEI chains may also be stabilized by hydrogen bonds with silanol groups on the surface of layered silicates; in this way, the interlayer space does not change. Figure 1b−d shows MAG impregnated with PEI and the displacement of the (001) peak at 5.79° 2θ (d = 1.53 nm) to 5.64° 2θ (d = 1.57 nm) after the insertion of PEI. Furthermore, there is an overall decrease of intensity in the region between 24 and 30° 2θ assigned to the presence of PEI. Figure 1e presents the diffractogram of 25CTA-MAG. A weak shoulder at 2.8° 2θ indicates the expansion of the interlayer spaces due to the presence of CTA+ 48 and suggests an increase in the basal distance from 1.53 to 3.15 nm. The low intensity of this peak is due to the fact that only a part of the sodium ions was exchanged by CTA+, however small the concentration of surfactant; it also appears in the infrared spectroscopy (see later). This effect has been reported before by other authors upon the intercalation/ion exchange of surfactants in the interlayer space of layered silicates and clays.52−55 The addition of PEI into CTA-MAG increases considerably the amount of organic molecules into the material; this might be the reason for the halo between 15 and 30° 2θ observed in Figure 1f−h. The presence of the organic portion, however large it may be, did not seem to affect the crystalline structure of these materials. Infrared Spectroscopy (FTIR). Aiming to evaluate the nature of the organization of bonds within a short distance of MAG as well as the modified materials, we used Fourier transform infrared spectroscopy (FTIR) in the frequency range 4000−400 cm−1. Figure S1a shows the spectra of MAG. In the region 3700−3000 cm−1, specifically bands at 3661, 3584, 3447, and 3231 cm−1 are associated with stretching vibrations of water and of OH groups (ν O−H) involved in interlayer hydrogen bonds. Bands at 1669 and 1629 cm−1 are attributed to the deformation vibration of the water molecules (δ H−O− H) H-bonded to each other and to silanol groups and coordinated to the sodium cations. The band at 1234 cm−1 is assigned to the asymmetric stretching (νas Si−O−Si) characteristic of the five-membered rings in the structure of magadiite. The band at 1173 cm−1 with a shoulder at 1200 cm−1 is associated with antisymmetric stretching vibrations of (νas Si− O−Si). Bands at 1083 cm−1 are assigned to a Si−O stretching, involving motion associated with oxygen atoms or described as an antisymmetric mode ←O−Si→ ← O, and the band at 948 cm−1 is due to the asymmetric stretching mode of terminal Si− OH interacting with water. In the 850−650 cm−1 region, bands at 820 and 783 cm−1 are assigned to symmetric stretching modes of ←O−Si−O→ involving silicon modes. Two weak bands at 704 and 691 cm−1 are assigned to the symmetric stretching vibration of Si−O−Si groups from coupling of Si−O stretching motions. In the region between 650 and 500 cm−1 are found the vibrations attributed to bending modes of single and double Si−O−Si rings at 618, 576, 544, and 461 cm−1. The Si−O bending mode is also found in this range. Variation of intensities, shapes, and multiplicities of the bands are related to

C MAS NMR was measured in a Bruker 400 MHz Avance 400 spectrometer. The samples were spun at 10 kHz in a zirconia rotor, and adamantane (C10H16) was used as reference to 13C. The elemental analyses of carbon, hydrogen, and nitrogen (CHN) were performed in a PerkinElmer 2400 Series II CHNS/O Elemental Analyzer. The thermogravimetric analysis was performed in a Setaram Instrumentation SETSYS 16/18 Evolution TGA with an alumina pan under a He atmosphere (16 mL min−1) in a temperature range from 20 to 1000 °C at a heating rate of 10 °C min−1. CO2 Adsorption by Temperature-Programmed Desorption (CO2-TPD). CO2-TPD experiments were performed on a Quantachrome CHEMBET-3000 TPD/TPR instrument equipped with a TC detector. Approximately 100 mg of sorbent was placed in a U-shaped quartz reactor, heated to 150 °C at a rate of 10 °C min−1 and held at this temperature for 3 h under a He flow (30 mL min−1) to eliminate water and adsorbed CO2. Then, the temperature was reduced to 75 °C, and CO2 (5 vol. % in He) flow (20 mL min−1) contacted the sorbent for 3 h. After that, the sample was submitted to a He flow (20 mL min−1) for 1 h and the temperature decreased to 30 °C. The CO2 desorption was carried out between 30 and 150 °C at a rate of 10 °C min−1, and the CO2 adsorption capacity was calculated on the basis of desorption by the external calibration method.

■

RESULTS AND DISCUSSION X-Ray Diffraction (XRD). The X-ray diffraction profiles of MAG, Figure 1a, are similar to those found in the

Figure 1. X-ray diffraction of (a) MAG, (b) MAG-PEI10, (c) MAGPEI20, (d) MAG-PEI25, (e) 25CTA-MAG, (f) 25CTA-MAG-PEI10, (g) 25CTA-MAG-PEI20 and (h) 25CTA-MAG-PEI25.

literature38−41 and present the (001) diffraction plane located at 5.79° 2θ (1.53 nm) and diffraction peaks at 11.53° and 17.25° 2θ from the (002) and (003) planes, besides peaks in the region between 24 and 30° 2θ, which are associated with the crystalline arrangement of the layers. The interlayer space of MAG, 1.53 nm, can be enough to allow the insertion of PEI. The dimensions of PEI were determined with the semiempirical PM6 method, and the 2474



Article

Figure 2. Nuclear magnetic resonance of (a) MAG-PEI10, (b) MAG-PEI20, (c) MAG-PEI25, (d) 25CTA-MAG-PEI10, (e) 25CTA-MAG-PEI20, and (f) 25CTA-MAG-PEI25.

and C3′) are hardly observed. Only in 25CTA-MAG-PEI25 is it possible to identify a weak peak at 165 ppm associated with carbamate ions. Elemental and Thermogravimetric Analyses (CHN and TGA). The elemental analyses of carbon, hydrogen, and nitrogen (CHN) are shown in Table S1 together with the analysis of PEI for comparison. The results of PEI incorporation indicate that the amounts of PEI impregnated into MAG (first column) are close to the calculated values (10, 20, or 25 wt %). The sorbent that was impregnated with 25 wt % of PEI is capable of adsorbing 2.7 mmol g−1 of CO2, considering the stoichiometry of 2 mol N/1 mol CO2. Furthermore, pure PEI adsorbs 11.8 mmol g−1 of CO2, but a large proportion of the internal adsorption remains available after adsorption on the outer layers. This was observed in the studies by Qi et al.,65 where there is the presence of FTIR bands at 1650, 1540, and 1407 cm−1 assigned to RNH3+, C O, and NCOO skeletal vibration due to the formation of carbamate when pure PEI was exposed to CO2, accompanied by the increase in the viscosity of polyethylenimine, increasing diffusional resistance and hampering CO2 access to the internal adsorption sites.64,65 For 25CTA-MAG-PEI, the loads of PEI are similar to those of MAG-PEI shown above: the concentration of N ranges from 2.43 to 5.41 mmol g−1 in MAG-PEI and from 2.92 to 5.31 mmol g−1 (already discounting the N atoms coming from CTA+) in 25CTA-MAG. With regard to the thermal behavior of these sorbents, Figures S2−S5 and Table S2 show the weight loss of these materials upon a temperature increase. For MAG, there is a total weight loss of 11.6% between 20 and 1000 °C. The weight loss is 10.5% (Figure S2) at 113 and 155 °C (Figure S3) and is associated with dehydration of the solid. Table S2 also shows the weight loss of 1.1% (Figure S2) at 294 °C (Figure S3) attributed to the condensation of silanols followed by a loss of water (formation of siloxanes groups).40,66 MAG modified with

framework structure characteristics in layered silicates.38,40,41,56,57After impregnation of PEI, Figure S1b−d, the C−H stretching signals are found at 2958 cm−1, and the bands at 2927 and 2851 cm−1 indicate the antisymmetric and symmetric stretching, respectively.58 Bands at 1573 cm−1 assigned to the N−H deformation in R-NH3+,59 at 1473 cm−1 to the scissoring vibration (δs CH2),58 and at 1380 cm−1 to the C−N stretching vibration58,60 were also observed, confirming that PEI was incorporated into magadiite (MAG). Figure S1e presents the FTIR results to confirm the presence of CTA+ between the layers of magadiite. It is observed that, after the ion exchange, new bands at 2958 cm−1, 2920 cm−1, and 2851 cm−1 appear and are associated with the stretching vibration (ν CH), (νas CH2), and (νs CH2), respectively.58 Additionally, a band of deformation vibration (δs CH) at 1473 cm−1 is characteristic of methyl groups present in the polar part of the surfactant (group N (CH3)3), confirming the CTA+ introduction into the interlayer space of magadiite.40 After impregnation of PEI, Figure S1f−h, vibrations observed are very similar to the ones discussed in Figure S1b−d, confirming also the incorporation of PEI into magadiite modified with CTA+ (25CTA-MAG). 13 C-Nuclear Magnetic Resonance (13C NMR). The 13C NMR data for PEI modified MAG are shown in Figure 2a−c. The peaks at around 39 ppm (C1′), 48.5 ppm (C2′), and 53 ppm (C3′) are associated with methylene groups near primary, secondary, and tertiary amine groups, the secondary amines being more intense.61 Furthermore, a peak around 164.7 ppm is associated with CO from CO2 in the carbamate ion in different interactions involving primary and secondary amines.32,62,63 For 25CTA-MAG modified with PEI, Figure 2d−f, only peaks associated with carbon atoms of CTA+chains at 15.4 (C16), 24.3 (C3), 26.3 (C15), 28.0 (C2), 33.0 (C4− 13), 53.3 (C17−19), and 66.9 (C1) ppm40,43 are clearly seen; the carbon atoms in PEI that appear at 39−48.7 ppm (C1′, C2′, 2475



Article

PEI displays a weight loss between 180 and 350 °C associated with the degradation of PEI chains, these losses are 10.7%, 19.3%, and 24.5% in MAG-PEI10, MAG-PEI20, and MAGPEI25, respectively, very close to the nominal PEI load in each sample; similar results were found by Wang et al.67 For the 25CTA-MAG, there is a weight loss between 180 and 430 °C associated with the elimination of CTA+ chains in different steps, followed by decomposition of PEI chains between 250 and 390 °C;43 these losses are 9.3%, 18.4%, and 22.0% in CTAMAG-PEI10, CTA-MAG-PEI20, and CTA-MAG-PEI25, respectively, considering only PEI, not taking CTA into account. These results suggest that the sorbents are thermally stable until 200 °C; the degradation of organic molecules present in the sorbent begins at 209 °C (Figure S2). Thus, these sorbents were evaluated on their performance in CO2 adsorption by temperature-programmed desorption experiments. CO2-TPD Experiments. Adsorption capacity for the prepared sorbents was evaluated by CO2-TPD experiments; the results are shown in Figure S6a−d and Figure 3a−g. First, a

For MAG-PEIx sorbents, in Figure 3b−d, desorption of CO2 begins at around 65−70 °C, with two peaks at 125−129 and 150 °C. For 25CTA-MAG-PEIx, in Figure 3e−g, the desorption step of CO2 starts at around 64−66 °C, with one peak at 130 °C for 25CTA-MAG-PEI10 and two desorption peaks at 123 and 150 °C for 25CTA-MAG-PEI20 and 117 and 146 °C for 25CTA-MAG-PEI25. These temperatures indicate that there are sites with different basicity in MAG-PEI and 25CTA-MAG-PEI. According to the literature,35 there are two sites of adsorption in PEI, the exposed PEI layer, which is responsible for the majority of CO2 adsorbed, and bulky PEI, which contributes poorly in the adsorption and is formed by agglomeration of the polymer chains into the interlayer space and may suggest the operation of a subsurface diffusion model, where during the heating, carbon dioxide (CO2) is removed from the exposed PEI layer by desorption, leading to two events: either it is swept out from the reactor by the carrier gas or it penetrates into the subsurface region toward bulky PEI. Any adsorbate molecules that penetrate into the subsurface region (bulky PEI) may diffuse back to the surface PEI layer.35,68 In other words, this diffusion model supports the existence of different paths by which CO2 may react on the adsorbent surface. It is noted that the increase of PEI amount decreases the relative contribution of bulky PEI to CO2 sorption that is initially adsorbed in the exposed PEI layer and then diffuses into the bulky PEI; the process is accompanied by diffusion restrictions. Another interesting point shown in Figure 3 and Table 1 is that, for MAG-PEIx sorbents, ca. 62% of desorbed CO2 is Table 1. CO2 Desorption for TPD Profiles over MAG-PEIx and 25CTA-MAG-PEIx Sorbents with Different PEI Loadings, Adsorption Capacity in Different Peaks, and Deconvolution Percentage for the Prepared Sorbents sample MAG-PEI10 MAG-PEI20 MAG-PEI25 25CTAMAGPEI10 25CTAMAGPEI20 25CTAMAGPEI25

Figure 3. CO2-TPD profiles of (a) MAG, (b) MAG-PEI10, (c) MAGPEI20, (d) MAG-PEI25, (e) 25CTA-MAG-PEI10, (f) 25CTA-MAGPEI20, and (g) 25CTA-MAG-PEI25. CO2-TPD conditions: sample weight, 100 mg; gas, 5% vol. CO2/He; temperature of adsorption, 75 °C; time of adsorption, 3 h; flow rate adsorption/desorption, 20 mL min−1. Black line, original graph; green line, calculated graph; blue line, deconvoluted band from layer PEI; red line, deconvoluted band from bulky PEI.

capacitya/ mmol g−1

peak 1/ mmol g−1

deconv./%

peak 2/ mmol g−1

deconv./%

2.79 4.56 6.11 1.06

1.70 2.91 3.67 0.85

61.01 63.88 60.12 80.40

1.09 1.65 2.44 0.21

38.98 36.12 39.88 19.60

4.57

3.38

74.05

1.19

25.95

3.41

2.49

73.12

0.92

26.88

a

Obtained by CO2-TPD and Avrami model. CO2-TPD conditions: sample weight, 100 mg; gas, 5% vol. CO2/He; flow rate adsorption/ desorption, 20 mL min−1, adsorption temperature, 75 °C; adsorption time, 3 h, desorption time, 20 min.

study was conducted in order to obtain the time of maximum adsorption. For that, MAG-PEI10 was submitted to CO2 adsorption for 1, 2, 3, and 5 h until the amount for desorbed CO2 did not change with time. In Figure S6a−d, it is seen that up to 3 h, the sorbent had not reached the maximum adsorption, but after 5 h of adsorption, the desorbed amount of CO2 is almost equal to that of 3 h of adsorption. The adsorption capacity was 1.86, 2.14, 2.79, and 2.78 mmol g−1 of CO2 to 1, 2, 3, and 5 h of adsorption, respectively. Thus, the time of adsorption of 3 h was chosen to perform the adsorption studies. For pure magadiite, MAG, Figure 3a, the CO2-TPD experiment was performed under the same conditions as for all the samples modified with PEI. It is clearly observed that pure MAG is not capable of adsorbing CO2; only a flat baseline was obtained throughout the whole experiment.

attributed to interaction between CO2 and exposed PEI layer (peak 1 increases in Figure 3) and ca. 38% to bulky PEI within the interlayer space. For 25CTA-MAG-PEIx, the presence of CTA+ created different paths for CO2 to access the exposed PEI layer. This is shown by the higher contribution of ca. 78% of the PEI layer and ca. 22% to the bulky PEI. It should be pointed out that the presence of CTA+ decreased the total adsorption capacity to about half of the total adsorption capacity in the absence of CTA+. The best result of adsorption capacity was obtained with the MAG-PEI25 sorbent: 6.11 mmol g−1 at 75 °C. MAG-PEI20 2476



Article

and 25CTA-MAG-PEI20 presented the same adsorption capacity of 4.57 mmol g−1 at 75 °C. Table 1 summarizes the adsorption capacity and efficiency for MAG-PEIx and 25CTAMAG-PEIx samples. The presence of CTA+ modified the access of CO2 to the sites of adsorption in 25CTA-MAG-PEI10 when compared with MAG-PEI10, in that the two peaks associated with CO2 adsorption on the PEI layer and bulky PEI in Figure 3 are more intense in the absence of CTA+. This is probably due to the fact that the presence of large amounts of CTA+ hindered the diffusion of CO2 within the interlayer space. The hindrance of diffusion of CO2 by CTA+ is more evident when comparing 25CTA-MAG-PEI20 and 25CTA-MAG-PEI25 sorbents: if we take into account that the increase in PEI concentration (comparing MAG-PEI20 and MAG-PEI25) causes the increase in the adsorption capacity from 4.56 to 6.11 mmol g−1, the decrease of CO2 adsorption when CTA+ is present in the interlayer space (from 4.57 to 3.41 mmol g−1) confirms that the surfactant molecule is really causing diffusion. The very similar adsorption capacities of MAG-PEI20 and 25CTA-MAG-PEI20 suggest that the limit of CTA+ concentration without disturbance of CO2 diffusion is up to around 20 w/w %; increases of CTA+ concentration above this range decrease the adsorption capacity of CTA-MAG-PEI sorbents. The results of adsorption capacity and efficiency, in Table 2, are larger than calculated values, considering the stoichiometry

Figure 4. Desorption kinetics of (a) MAG-PEI10, (b) MAG-PEI20, (c) MAG-PEI25, (d) 25CTA-MAG-PEI10, (e) 25CTA-MAG-PEI20, and (f) 25CTA-MAG-PEI25.

well reproduced by the Avrami model.78 These observations allow the use of this kinetic model in CO2 desorption studies. Kinetic information was obtained by isothermal desorption of CO2 from MAG-PEI and 25CTA-MAG-PEI at 75 °C, after 3 h of CO2 adsorption. The desorption experiments were fitted with the Avrami model.79

Table 2. CO2 Desorption for TPD Profiles over MAG-PEIx and 25CTA-MAG-PEIx Sorbents with Different PEI Loadings, Amine Group Content, and Efficiency to the Prepared Sorbents sample MAG-PEI10 MAG-PEI20 MAG-PEI25 25CTA-MAGPEI10 25CTA-MAGPEI20 25CTA-MAGPEI25

qt = qe[1 − exp(− (kAt )nA )]

(1)

qea/ mmol g−1

N/mmol g−1

efficiency/ mol CO2 mol N−1

2.79 4.56 6.11 1.06

2.43 4.16 5.41 2.91

1.15 1.10 1.13 0.36

4.57

4.32

1.06

where qt represents the amount of CO2 desorbed at time t, qe is the total amount of CO2 desorbed (adsorbed at equilibrium), kA is the Avrami kinetic constant, and nA is the Avrami exponent and is related to the existence of different reaction mechanisms. The values of qe, nA, and kA where calculated through nonlinear regression. To prove the adequacy of the Avrami model, a function based on the normalized standard deviation was also calculated (eq 2):

3.41

5.31

0.64

∑ [(qt(exp) − qt(calc))/qt(exp)]2

SD (%) =

a

Obtained by CO2-TPD and Avrami model. CO2-TPD conditions: sample weight, 100 mg; gas, 5% vol. CO2/He; flow rate adsorption/ desorption, 20 mL min−1, adsorption temperature, 75 °C; adsorption time, 3 h, desorption time, 20 min.

N−1

× 100

(2)

where SD (%) is standard deviation, qt(exp) is the experimental data of the amount of CO2 desorbed at time t, qt(calc) is the amount desorbed as calculated by the Avrami model, and N is the total number of experimental points. The results are presented in Table 3. The values of nA obtained in the range of 2.77−3.77 confirm that there are different desorption mechanisms;80 these may be

of 2 mol of N to 1 mol of CO2. This difference may be partly associated with the interactions of the silanol groups present in the surface of magadiite layers that may be contributing to part of the of CO2 through reactions as shown in Scheme S1.69−71 CO2 Desorption Kinetics. Figure 4a−f shows the desorption kinects for the sorbents studied here. Desorption of CO2 adsorbed is essentially complete in 15 min, indicating that short cycles may be performed to characterize the PEIMAG nanocomposites for CO2 capture. A kinetic model was applied in order to obtain more details of the kinds of interactions that occur between CO2 and amine groups present in the branching PEI. Some works in the literature72−77 used the Avrami kinetic model to describe the adsorption of CO2 on mesoporous silica modified with alkyl amines. Considering that the desorption of CO2 is the decomposition of alkylammonium carbamate,74 the majority of the decomposition processes are

Table 3. Kinetic Parameters and Standard Deviation Calculated from CO2 Desorption Isotherms Fitted to Avrami Model

2477

sample

qe/ mmol g−1

nA

kA/ min−1

SD/%

R2

MAG-PEI10 MAG-PEI20 MAG-PEI25 25CTA-MAG-PEI10 25CTA-MAG-PEI20 25CTA-MAG-PEI25

2.79 4.56 6.11 1.06 4.57 3.41

3.77 2.83 2.77 3.49 2.86 3.04

0.12 0.13 0.13 0.17 0.15 0.17

5.16 2.03 2.47 2.62 3.49 2.98

0.99735 0.99901 0.99800 0.99954 0.99841 0.99880



Article

(4) Liu, Y.; Wang, Z. U.; Zhou, H. Recent Advances in Carbon Dioxide Capture with Metal-Organic Frameworks. Greenhouse Gases: Sci. Technol. 2012, 2, 239−259. (5) Steeneveldt, R.; Berger, B.; Torp, T. A. CO2 Capture and Storage Closing the Knowing-Doing Gap. Chem. Eng. Res. Des. 2006, 84, 739− 763. (6) Yang, H.; Xu, Z.; Fan, M.; Gupta, R.; Slimane, R. B.; Bland, A. E.; Wright, I. Progress in Carbon Dioxide Separation and Capture: A Review. J. Environ. Sci. 2008, 20, 14−27. (7) Samanta, A.; Zhao, A.; Shimizu, G. K. H.; Sarkar, P.; Gupta, R. Post-Combustion CO2 Capture Using Solid Sorbents: A Review. Ind. Eng. Chem. Res. 2012, 51, 1438−1463. (8) Aaron, D.; Tsouris, C. Separation of CO2 from Flue Gas: A Review. Sep. Purif. Rev. 2005, 40, 321−348. (9) Roth, E. A.; Agarwal, S.; Gupta, R. K. Nanoclay-Based Solid Sorbents for CO2 Capture. Energy Fuels 2013, 27, 4129−4136. (10) Sarmah, M.; Baruah, B. P.; Khare, P. A Comparison Between CO2 Capturing Capacities of Fly Ash Based Composites of MEA/ DMA and DEA/DMA. Fuel Process. Technol. 2013, 106, 490−497. (11) Olah, G. A.; Prakash, G. K. S.; Goeppert, A. Anthropogenic Chemical Carbon Cycle for a Sustainable Future. J. Am. Chem. Soc. 2011, 133, 12881−12898. (12) D’Alessandro, D. M.; Smit, B.; Long, J. R. Carbon Dioxide Capture: Prospects for New Materials. Angew. Chem., Int. Ed. 2010, 49, 6058−6082. (13) Chang, A. C. C.; Chuang, S. S. C.; Gray, M.; Soong, Y. In-Situ Infrared Study of CO2 Adsorption on SBA-15 Grafted with γ(Aminopropyl)triethoxysilane. Energy Fuels 2003, 17, 468−473. (14) Kim, J.; Lin, L.; Swisher, J. A.; Haranczyk, M.; Smit, B. Predicting Large CO2 Adsorption in Aluminosilicate Zeolites for Postcombustion Carbon Dioxide Capture. J. Am. Chem. Soc. 2012, 134, 18940−18943. (15) Xu, X.; Song, C.; Andresen, J. M.; Miller, B. G.; Scaroni, A. W. Novel Polyethylenimine-Modified Mesoporous Molecular Sieve of MCM-41 Type as High-Capacity Adsorbent for CO2 Capture. Energy Fuels 2002, 16, 1463−1469. (16) Xu, X.; Song, C.; Andrésen, J. M.; Miller, B. G.; Scaroni, A. W. Preparation and Characterization of Novel CO2 “Molecular Basket” Adsorbents Based on Polymer-Modified Mesoporous Molecular Sieve MCM-41. Microporous Mesoporous Mater. 2003, 62, 29−45. (17) Mosqueda, H. A.; Vazquez, C.; Bosch, P.; Pfeiffer, H. Chemical Sorption of Carbon Dioxide (CO2) on Lithium Oxide (Li2O). Chem. Mater. 2006, 18, 2307−2310. (18) Wahby, A.; Silvestre-Albero, J.; Sepúlveda-Escribano, A.; Rodríguez-Reinoso, F. CO2 Adsorption on Carbon Molecular Sieves. Microporous Mesoporous Mater. 2012, 164, 280−287. (19) Millward, A. R.; Yaghi, O. M. Metal-Organic Frameworks with Exceptionally High Capacity for Storage of Carbon Dioxide at Room Temperature. J. Am. Chem. Soc. 2005, 127, 17998−17999. (20) Xiang, Z.; Zhou, X.; Zhou, C.; Zhong, S.; He, X.; Qin, C.; Cao, D. Covalent-Organic Polymers for Carbon Dioxide Capture. J. Mater. Chem. 2012, 22, 22663−22669. (21) Xu, X.; Song, C.; Miller, B. G.; Scaroni, A. W. Influence of Moisture on CO2 Separation from Gas Mixture by a Nanoporous Adsorbent Based on Polyethylenimine-Modified Molecular Sieve MCM-41. Ind. Eng. Chem. Res. 2005, 44, 8113−8119. (22) Wang, X.; Ma, X.; Sun, L.; Song, C. A Nanoporous Polymeric Sorbent for Deep Removal of H2S from Gas Mixtures for Hydrogen Purification. Green Chem. 2007, 9, 695−702. (23) Wang, X.; Ma, X.; Xu, X.; Sun, L.; Song, C. MesoporousMolecular-Sieve-Supported Polymer Sorbents for Removing H2S from Hydrogen Gas Streams. Top. Catal. 2008, 49, 108−117. (24) Wang, D.; Sentorun-Shalaby, C.; Ma, X.; Song, C. HighCapacity and Low-Cost Carbon-Based “Molecular Basket” Sorbent for CO2 Capture from Flue Gas. Energy Fuels 2011, No. 25, 456−458. (25) Wang, X.; Ma, X.; Song, C.; Locke, D. R.; Siefert, S.; Winans, R. E.; Möllmer, J.; Lange, M.; Möller, A.; Gläser, R. Molecular Basket Sorbents polyethylenimine−SBA-15 for CO2 Capture from Flue Gas:

associated with the interaction of CO2 with primary and secondary alkyl amine groups and silanol groups as shown in Scheme S2. The values of kA showed that the desorption of CO2 from MAG-PEI was slower than that of 25CTA-MAGPEI, suggesting that the contribution of the stronger bonded CO2 molecules is larger in the absence of CTA+ than in its presence. It was already commented that the presence of CTA+ increases the concentration of CO2 interacting with the exposed PEI layer, therefore, in a weaker interaction. The opposite is found in the absence of CTA+, that is, in MAG-PEI samples. This is probably the reason for the slower kA for MAG-PEI in relation to 25CTA-MAG-PEI. The values shown in Table 3 also confirm the adequacy of the Avrami model by the low values of standard deviation (below of 8%) and a correlation factor between 0.99735 and 0.99954. Summarizing, a novel sorbent was synthesized through the impregnation of PEI into the interlayer space of layer silicate type magadiite and organo-magadiite, which we would like to name Layered Silicate Sorbents (LSS). Magadiite has an interlayer space that may be modified as to diminish diffusional restrictions and the host variable concentration of PEI. The presence of CTA+ surfactant in the concentration studied decreased the adsorption capacity due to the difficulty for CO2 to access the inner sites of adsorption; however the access of CO2 to layered PEI was improved. These sorbents showed maximum adsorption capacities of 6.11 mmolg−1 at 75 °C using 25 wt % impregnated PEI. Moreover, they displayed high thermal stability and fast kinetics of desorption and may be submitted to adsorption/desorption cycles. The Avrami model proved to be a good kinetic model to describe the interaction of CO2 with PEI impregnated in layered silicates.

■

ASSOCIATED CONTENT

* Supporting Information S

The results of FTIR and TG/dTG, schemes mechanism of silylpropylcarbamate species, elemental analysis and weight loss are information is available free of charge via http://pubs.acs.org/.

■

of the proposed and tables with available. This the Internet at

AUTHOR INFORMATION

Corresponding Author

*Phone: 55 19 35213095. E-mail: [email protected]. Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS The authors acknowledge PETROBRAS for the financial support. R.B.V. acknolwledges the scholarship. H.O.P. acknowĺ edges Conselho Nacional de Desenvolvimento Cientifico (CNPq) for the fellowship. The authors are indebted to Prof. Lucas Ducati for his work in calculating the dimensions of PEI.

■

REFERENCES

(1) Choi, S.; Drese, J. H.; Jones, C. W. Adsorbent Materials for Carbon Dioxide Capture from Large Anthropogenic Point Sources. ChemSusChem 2009, 2, 796−854. (2) Songolzadeh, M.; Ravanchi, M. T.; Soleimani, M. Carbon Dioxide Capture and Storage: A General Review on Adsorbents. Int. J. Appl. Sci., Eng. Technol. 2012, 70, 225−232. (3) Wurzbacher, J. A.; Gebald, C.; Steinfeld, A. Separation of CO2 from Air by Temperature-Vacuum Swing Adsorption Using DiamineFunctionalized Silica Gel. Energy Environ. Sci. 2011, 4, 3584−3592. 2478



Article

Characterization and Sorption Properties. Microporous Mesoporous Mater. 2013, 169, 103−111. (26) Zheng, F.; Tran, D. N.; Busche, B. J.; Fryxell, G. E.; Addleman, R. S.; Zemanian, T. S.; Aardahl, C. L. Ethylenediamine-Modified SBA15 as Regenerable CO2 Sorbent. Ind. Eng. Chem. Res. 2005, 44, 3099− 3105. (27) Serna-Guerrero, R.; Belmabkhout, Y.; Sayari, A. TriamineGrafted Pore-Expanded Mesoporous Silica for CO2 Capture: Effect of Moisture and Adsorbent Regeneration Strategies. Adsorption 2010, 16, 567−575. (28) Kim, S.; Ida, J.; Guliants, V. V; Lin, J. Y. S. Tailoring Pore Properties of MCM-48 Silica for Selective Adsorption of CO2. J. Phys. Chem. B 2005, 109, 6287−6293. (29) Kassab, H.; Maksoud, M.; Aguado, S.; Pera-Titus, M.; Albela, B.; Bonneviot, L. Polyethylenimine Covalently Grafted on Mesostructured Porous Silica for CO2 Capture. RSC Adv. 2012, 2, 2508−2516. (30) Sanz, R.; Calleja, G.; Arencibia, A.; Sanz-Pérez, E. S. Development of High Efficiency Adsorbents for CO2 Capture Based on a Double-Functionalization Method of Grafting and Impregnation. J. Mater. Chem. A 2013, 1, 1956−1962. (31) Von Harpe, A.; Petersen, H.; Li, Y.; Kissel, T. Characterization of Commercially Available and Synthesized Polyethylenimines for Gene Delivery. J. Controlled Release 2000, 69, 309−322. (32) Drage, T. C.; Arenillas, A.; Smith, K. M.; Snape, C. E. Thermal Stability of Polyethylenimine Based Carbon Dioxide Adsorbents and Its Influence on Selection of Regeneration Strategies. Microporous Mesoporous Mater. 2008, 116, 504−512. (33) Gargiulo, N.; Pepe, F.; Caputo, D. Modeling Carbon Dioxide Adsorption on Polyethylenimine-Functionalized TUD-1 Mesoporous Silica. J. Colloid Interface Sci. 2012, 367, 348−54. (34) Son, W.-J.; Choi, J.-S.; Ahn, W.-S. Adsorptive Removal of Carbon Dioxide Using Polyethyleneimine-Loaded Mesoporous Silica Materials. Microporous Mesoporous Mater. 2008, 113, 31−40. (35) Wang, X.; Song, C. Temperature-Programmed Desorption of CO2 from Polyethylenimine-Loaded SBA-15 as Molecular Basket Sorbents. Catal. Today 2012, 194, 44−52. (36) Wang, X.; Schwartz, V.; Clark, J. C.; Ma, X.; Overbury, S. H.; Xu, X.; Song, C. Infrared Study of CO2 Sorption over “Molecular Basket” Sorbent Consisting of Polyethylenimine-Modified Mesoporous Molecular Sieve. J. Phys. Chem. C 2009, 113, 7260−7268. (37) Wang, X.; Ma, X.; Schwartz, V.; Clark, J. C.; Overbury, S. H.; Zhao, S.; Xu, X.; Song, C. A Solid Molecular Basket Sorbent for CO2 Capture from Gas Streams with Low CO2 Concentration Under Ambient Conditions. Phys. Chem. Chem. Phys. 2012, 14, 1485−1492. (38) Superti, G. B.; Oliveira, E. C.; Pastore, H. O.; Bordo, A.; Bisio, C.; Marchese, L. Aluminum Magadiite: An Acid Solid Layered Material. Chem. Mater. 2007, 19, 4300−4315. (39) Pastore, H. O.; Munsignatti, M.; Mascarenhas, A. J. S. One-Step Synthesis of Alkyltrimethylammonium-Intercalated Magadiite. Clays Clay Miner. 2000, 48, 224−229. (40) Moura, H. M.; Bonk, F. A.; Pastore, H. O. Pillaring Cetyltrimethylammonium-Magadiite: a Stepwise Method to Mesoporous Materials with Controlled Pores Sizes and Distribution. Eur. J. Miner. 2012, 24, 903−912. (41) Moura, H. M.; Bonk, F. A.; Vinhas, R. C. G.; Landers, R.; Pastore, H. O. Aluminium-Magadiite: From Crystallization Studies to a Multifunctional Material. CrystEngComm 2011, 13, 5428−5438. (42) Eugster, H. P. Hydrous Sodium Silicates from Lake Magadi, Kenya: Precursors of Bedded Chert. Science 1967, 157, 1177−1180. (43) Kooli, F.; Mianhui, L.; Alshahateet, S. F.; Chen, F.; Yinghuai, Z. Characterization and Thermal Stability Properties of Intercalated NaMagadiite with Cetyltrimethylammonium (C16TMA) Surfactants. J. Phys. Chem. Solids 2006, 67, 926−931. (44) Takahashi, N.; Kuroda, K. Materials Design of Layered Silicates Through Covalent Modification of Interlayer Surfaces. J. Mater. Chem. 2011, 21, 14336−14353. (45) Ide, Y.; Kagawa, N.; Sadakane, M.; Sano, T. Precisely Designed Layered Silicate as an Effective and Highly Selective CO2 Adsorbent. Chem. Commun. 2013, 49, 9027−9029.

(46) Elkhalifah, A. E. I.; Maitra, S.; Bustam, M. A.; Murugesan, T. Effects of Exchanged Ammonium Cations on Structure Characteristics and CO2 Adsorption Capacities of Bentonite Clay. Appl. Clay Sci. 2013, 83−84, 391−398. (47) Wang, W.; Xiao, J.; Wei, X.; Ding, J.; Wang, X.; Song, C. Development of a New Clay Supported Polyethylenimine Composite for CO2 Capture. Appl. Energy 2014, 113, 334−341. (48) Okutomo, S.; Kuroda, K.; Ogawa, M. Preparation and Characterization of Silylated-Magadiites. Appl. Clay Sci. 1999, 15, 253−264. (49) Wang, J.; Long, D.; Zhou, H.; Chen, Q.; Liu, X.; Ling, L. Surfactant Promoted Solid Amine Sorbents for CO2 Capture. Energy Environ. Sci. 2012, 5, 5742−5749. (50) Meth, S.; Goeppert, A.; Prakash, G. K. S.; Olah, G. A. Silica Nanoparticles as Supports for Regenerable CO2 Sorbents. Energy Fuels 2012, 26, 3082−3090. (51) Goeppert, A.; Meth, S.; Prakash, G. K. S.; Olah, G. A. Nanostructured Silica as a Support for Regenerable High-Capacity Organoamine-Based CO2 Sorbents. Energy Environ. Sci. 2010, 3, 1949−1960. (52) Ogawa, M.; Iwata, D. Arrangements of Interlayer Quaternary Ammonium Ions in a Layered Silicate, Octosilicate. Cryst. Growth Des. 2010, 10, 2068−2072. (53) Hu, Z.; He, G.; Liu, Y.; Dong, C.; Wu, X.; Zhao, W. Effects of Surfactant Concentration on Alkyl Chain Arrangements in Dry and Swollen Organic Montmorillonite. Appl. Clay Sci. 2013, 75−76, 134− 140. (54) Kooli, F.; Yan, L. Thermal Stable Cetyltrimethylammonium− Magadiites: Influence of the Surfactant Solution Type. J. Phys. Chem. C 2009, 113, 1947−1952. (55) Kooli, F. Effect of C16TMA Contents on the Thermal Stability of Organo-Bentonites: In Situ X-Ray Diffraction Analysis. Thermochim. Acta 2013, 551, 7−13. (56) Huang, Y.; Jiang, Z.; Schwieger, W. Vibrational Spectroscopic Studies of Layered Silicates. Chem. Mater. 1999, 11, 1210−1217. (57) Flanigen, E. M.; Khatami, H.; Szymansky, H. A. Infrared Structural Studies of Zeolite Frameworks. In Molecular Sieve Zeolites-I; American Chemical Society: Washington, DC, 1974; pp 201−229. (58) Silverstein, R. M.; Webster, F. X.; Kiemle, D. J. Spectrometric Identification of Organic Compounds; John Wiley & Sons, Inc.: New York, 2005; Vol. 21, pp 72−108. (59) Subagyono, D. J. N.; Liang, Z.; Knowles, G. P.; Webley, P. a.; Chaffee, A. L. PEI Modified Mesocellular Siliceous Foam: A Novel Sorbent for CO2. Energy Procedia 2011, 4, 839−843. (60) Zhao, Y.; Shen, Y.; Bai, L.; Hao, R.; Dong, L. Synthesis and CO2 Adsorption Properties of Molecularly Imprinted Adsorbents. Environ. Sci. Technol. 2012, 46, 1789−1795. (61) Sayari, A.; Heydari-Gorji, A.; Yang, Y. CO2 -Induced Degradation of Amine-Containing Adsorbents: Reaction Products and Pathways. J. Am. Chem. Soc. 2012, 134, 13834−13842. (62) Sayari, A.; Belmabkhout, Y. Stabilization of Amine-Containing CO2 Adsorbents: Dramatic Effect of Water Vapor. J. Am. Chem. Soc. 2010, 132, 6312−6314. (63) Belmabkhout, Y.; Serna-Guerrero, R.; Sayari, A. Amine-Bearing Mesoporous Silica for CO2 Removal from Dry and Humid Air. Chem. Eng. Sci. 2010, 65, 3695−3698. (64) Qi, G.; Fu, L.; Choi, B. H.; Giannelis, E. P. Efficient CO2 Sorbents Based on Silica Foam with Ultra-Large Mesopores. Energy Environ. Sci. 2012, 5, 7368−7375. (65) Qi, G.; Wang, Y.; Estevez, L.; Duan, X.; Anako, N.; Park, A. A.; Li, W.; Jones, C. W.; Giannelis, E. P. High Efficiency Nanocomposite Sorbents for CO2 Capture Based on Amine-Functionalized Mesoporous Capsules. Energy Environ. Sci. 2011, 4, 444. (66) Eypert-Blaison, C.; Michot, L. J.; Humbert, B.; Pelletier, M.; Villiéras, F. Hydration Water and Swelling Behavior of Magadiite. The H+, Na+, K+, Mg2+, and Ca2+ Exchanged Forms. J. Phys. Chem. B 2002, 106, 730−742. 2479



Article

(67) Wang, J.; Chen, H.; Zhou, H.; Liu, X.; Qiao, W.; Long, D.; Ling, L. Carbon Dioxide Capture Using Polyethylenimine-Loaded Mesoporous Carbons. J. Environ. Sci. 2013, 25, 124−132. (68) Leary, K. J.; Michaels, J. N.; Stacy, A. M. TemperatureProgrammed Desorption: Multisite and Subsurface Diffusion Models. AIChE J. 1988, 34, 263−271. (69) Bacsik, Z.; Ahlsten, N.; Ziadi, A.; Zhao, G.; Garcia-Bennett, A. E.; Martín-Matute, B.; Hedin, N. Mechanisms and Kinetics for Sorption of CO2 on Bicontinuous Mesoporous Silica Modified with nPropylamine. Langmuir 2011, 27, 11118−11128. (70) Yue, M. B.; Sun, L. B.; Cao, Y.; Wang, Z. J.; Wang, Y.; Yu, Q.; Zhu, J. H. Promoting the CO2 Adsorption in the Amine-Containing SBA-15 by Hydroxyl Group. Microporous Mesoporous Mater. 2008, 114, 74−81. (71) Bacsik, Z.; Atluri, R.; Garcia-Bennett, A. E.; Hedin, N. Temperature-Induced Uptake of CO2 and Formation of Carbamates in Mesocaged Silica Modified with n-Propylamines. Langmuir 2010, 26, 10013−10024. (72) Zhao, A.; Samanta, A.; Sarkar, P.; Gupta, R. Carbon Dioxide Adsorption on Amine-Impregnated Mesoporous SBA-15 Sorbents: Experimental and Kinetics Study. Ind. Eng. Chem. Res. 2013, 52, 6480− 6491. (73) Wang, J.; Stevens, L. A.; Drage, T. C.; Wood, J. Preparation and CO2 Adsorption of Amine Modified Mg−Al LDH via Exfoliation Route. Chem. Eng. Sci. 2012, 68, 424−431. (74) Sun, Z.; Fan, M.; Argyle, M. Desorption Kinetics of the Monoethanolamine/Macroporous TiO2-Based CO2 Separation Process. Energy Fuels 2011, 25, 2988−2996. (75) Heydari-Gorji, A.; Sayari, A. CO2 Capture on PolyethylenimineImpregnated Hydrophobic Mesoporous Silica: Experimental and Kinetic Modeling. Chem. Eng. J. 2011, 173, 72−79. (76) Serna-Guerrero, R.; Sayari, A.; Belmabkhout, Y. Further Investigations of CO2 Capture Using Triamine-Grafted PoreExpanded Mesoporous Silica. Chem. Eng. J. 2010, 161, 513−519. (77) Monazam, E. R.; Shadle, L. J.; Miller, D. C.; Pennline, H. W.; Fauth, D. J.; Hoffman, J. S.; Gray, M. L. Equilibrium and Kinetics Analysis of Carbon Dioxide Capture Using Immobilized Amine on a Mesoporous Silica. AIChE J. 2013, 59, 923−935. (78) Kinefuchi, I.; Yamaguchi, H.; Sakiyama, Y.; Takagi, S.; Matsumoto, Y. Inhomogeneous Decomposition of Ultrathin Oxide Films on Si(100): Application of Avrami Kinetics to Thermal Desorption Spectra. J. Chem. Phys. 2008, 128, 164712−6. (79) Avrami, M. Kinetics of Phase Change. I General Theory. J. Chem. Phys. 1939, 7, 1103−1112. (80) Cestari, A. R.; Vieira, E. F. S.; Vieira, G. S.; Almeida, L. E. The Removal of Anionic Dyes from Aqueous Solutions in the Presence of Anionic Surfactant Using Aminopropylsilica–a Kinetic Study. J. Hazard. Mater. B 2006, 138, 133−141.

2480


Polyethylenimine-Magadiite Layered Silicate Sorbent for CO2

Recommend Documents