Accepted Manuscript Fast synthesis of mesoporous silica materials via simple organic compounds templated sol-gel route in the absence of hydrogen bond Linzhou Zhuang, Beibei Ma, Siyu Chen, Xunan Hou, Shuixia Chen PII:
S1387-1811(15)00215-2
DOI:
10.1016/j.micromeso.2015.04.007
Reference:
MICMAT 7073
To appear in:
Microporous and Mesoporous Materials
Received Date: 15 August 2014 Revised Date:
16 March 2015
Accepted Date: 6 April 2015
Please cite this article as: L. Zhuang, B. Ma, S. Chen, X. Hou, S. Chen, Fast synthesis of mesoporous silica materials via simple organic compounds templated sol-gel route in the absence of hydrogen bond, Microporous and Mesoporous Materials (2015), doi: 10.1016/j.micromeso.2015.04.007. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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Fast synthesis of mesoporous silica materials via simple organic compounds templated sol-gel route in the absence
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of hydrogen bond Linzhou Zhuang1, Beibei Ma1, Siyu Chen1, Xunan Hou1, Shuixia Chen 1,2*
1. PCFM Lab, School of Chemistry and Chemical Engineering, Sun Yat-Sen University,
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Guangzhou 510275, PR China
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2. Materials Science Institute, Sun Yat-Sen University, Guangzhou 510275, PR China
ABSTRACT
As simple organic compounds that contain no hydroxyl, amino or carboxyl groups
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cannot assemble with the siliceous species through hydrogen bond or electrostatic force, they have not been applied as templates to prepare mesoporous silica materials before. However, in this work it was found that only if the organic compound can
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form homogeneous solution with ethanol and water can it successfully lead the
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formation of mesopores under the catalysis of 5% ammonium hydroxide (NH4OH) solution. The effects of template type, template amount and NH4OH solution concentration on the pore structure of the prepared porous silica were comprehensively studied. The pore size had no direct correlation with the molecular size of the template, but it could be easily adjusted in the range of 2.4 to 6.6 nm
*
Corresponding author. E-mail address:
[email protected]; 1
ACCEPTED MANUSCRIPT through changing the template amount. When using 5% NH4OH solution as the catalyst, the gelation time of siliceous species was ultrashort and therefore the template aggregates could be trapped in the three-dimensional SiO2 matrixes to
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function as the pore-forming agents. However, when the concentration of NH4OH solution was excessive high, like 15%, the gelation reaction was over intense and mesopores cannot be formed in the prepared silica. The mesoporous silica materials
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prepared in this new sol-gel route can be used as good supports of CO2 adsorbents.
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Through loading PEI into the mesopores of the silica materials, the solid amine adsorbents could be easily prepared, and they can keep remarkable CO2 adsorption ability even after 10 adsorption-desorption cycles.
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Keywords: mesoporous silica; organic compound template; fast sol-gel; preparation.
INTRODUCTION
Intense efforts have been focused on ordered mesoporous silica materials since the
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discovery of the M41s family of mesoporous molecular sieves. These mesoporous
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silica materials showed different structural and textural characteristics and could be applied in various fields, including catalysis, drug delivery, molecular host, separation and adsorption.1-3 M41s possess well-ordered pore structures, tunable pore sizes that range from 2.0 to 10.0 nm, large surface areas, and high pore volumes.4 In the preparation process of M41s, the surfactant molecules like cetyltrimethylammonium cation were employed as structure-directing agents, and the mesopores could be formed through the self-assembly between siliceous species and surfactant and the 2
ACCEPTED MANUSCRIPT gelation of the siliceous species.4,5 This self-assembly process was based on the electrostatic interaction. Afterwards, different types of surfactants like anionic-, neutral-, and acid treated surfactants were applied as templates to elaborately design
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the pore structures of mesoporous silica materials, so that new families of mesoporous silica materials (such as SBA,6, 7 MSU,8, 9 and FSM10) could be obtained. Among these routes, the one that uses nonionic surfactants as templates is especially
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important, because this electrically neutral S0I0 self-assembly pathway applies the
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weak hydrogen bond between templates and siliceous species to lead the formation of mesopores, instead of electrostatic force.11 Indeed, it is strongly complementary to the electrostatic interaction pathway in the preparation of mesoporous silica. However, even all these methods can successfully prepare well-ordered mesospores, their
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weaknesses like long preparation period, expensive template cost and narrow range of template choice severely restrict their industrial application. Wei et al developed a new low-cost nonsurfactant route to prepare the mesoporous
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silica materials.12 In this route, the nonsurfactant organic compounds like citric acid,
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malic acid, tartaric acid,13-15 menthol,16 D-glucose, D-maltose,12, 17, 18 urea,19, 20 fatty alcohols21 and cyclodextrin22 could be employed as templates, and via HCl-catalyzed hydrolysis, gelation of siliceous species and removal of the templates, the silica materials with interconnected mesopores can be prepared.20 Their pore volumes and pore sizes can be easily adjusted by varying the amount of added templates.23 The authors claim that it is the hydrogen bonding between the nonsurfactant template aggregates and the siliceous species that directs the formation of mesopores.12, 3
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ACCEPTED MANUSCRIPT However, because of the necessity of hydrogen bonding, the applicable templates here are limited to the organic compounds that contain hydroxyl, amino or carboxyl groups. Besides, NaOH was commonly used in this route to neutralize the silicate-template
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solution, and in most cases it led to a long gelation period, which could be as long as tens of days.16, 17, 18 The narrow range of template choice and long preparation period are the key constraints of this route in the industrial application.
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As ammonium hydroxide (NH4OH) has been proved that it can accelerate the
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gelation speed of siliceous species in the preparation of microporous silica xerogel monoliths,24 in this work we tried to use NH4OH solution as gelation catalyst to prepare mesporous silica materials. Moreover, to extend the range of template choice, we even made an effort to use simple organic compounds containing no hydroxyl,
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amino or carboxyl groups as the templates. These organic compounds can be cyclohexane (CH), methyl cyclohexane (MCH), and limonene (LM) and so on. N2 adsorption-desorption and transmission electron microscope (TEM) results indicated
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that the pore structures of these mesoporous materials were similar to those of
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materials prepared by Wei et al. However, our fast sol-gel route should differ from the nonsurfactant route as the applied simple organic compounds here cannot form hydrogen bond with the siliceous species. For better using this fast sol-gel route to prepare mesoporous silica materials, its synthesis mechanism and influence factors have been comprehensively investigated. This fast sol-gel route is believed to be a facile, economical, and environmental-friendly route to produce mesoporous materials. 4
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EXPERIMENTAL SECTION Reagents
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Tetraethyl orthosilicate (TEOS, >99%), cyclohexane (CH, 99.5%), methyl cyclohexane (MCH, 99%), (R)-(+)-limonene (LM, 95%), DL-menthol (MINT, 99%), and polyethylenimine (PEI, Mw=1800) were purchased from Aladdin Chemistry Co.,
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Ltd., China. Ethanol (AR), hydrochloric acid (HCl, 37%), ammonium hydroxide
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(NH4OH, 29%), tetrahydrofuran (THF, AR), hexane (AR), n-butyl bromide (BBM, 98%), 1, 2-dichloroethane (DCE, 99%) and benzaldehyde (BA, AR) were from Guangzhou Chemical Reagent Factory, China. All reagents were used without further purification. 0.1 M HCl solution and 1%, 5% NH4OH solution were prepared from
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HCl (37%) and NH4OH (29%).
Synthesis of mesoporous silica materials
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As a typical procedure, first, 7.7 g 0.1 M HCl solution and 13.8 g ethanol were
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mixed in a three-neck round bottom flask at room temperature. Then, 20.8 g TEOS was slowly added into the flask with moderate stirring. After stirring for 30 minutes, the mixture became homogeneous, and it was stirred at 70 oC for another 5 hours. Upon cooling to room temperature, 12.2 g of this prehydrolyzed mixture was slowly added into a mixed solution of ethanol (5.0 mL)-simple organic compounds (the amount of CH, MCH, LM or MINT can be 0.5-4.0 g) under agitation. Next, about 1.0 mL 5% NH4OH solution was added to adjust the pH of the silicate-template mixture 5
ACCEPTED MANUSCRIPT to 6, and a pH meter was used to monitor its pH. Gel occurred as soon as the NH4OH solution was dropped into the transparent mixture. The adding speed of NH4OH solution could be as high as 0.1 mL s-1 at first, but when the pH reached up to 5, the
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adding speed should be much lower. During the NH4OH solution adding and stirring process (300 rpm), the mixture got increasingly stickier and finally solidified into white powder. The powder was then placed in a fume hood overnight for drying.
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Finally, the template was removed by heating the powder at 150 oC for 3 hours with
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an electric furnace under air flow. For comparison, a series of control samples were also prepared according to the above procedure, except that 1% NH4OH was used to adjust the pH of the silicate-template solution to 6.
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Characterization
N2 adsorption-desorption isotherms at -196 oC was measured with an automatic gas adsorption instrument (ASAP2020, Micromeritics Corp., USA) in a relative pressure
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range from 10-6 to 1. Vtotal was calculated based on the N2 amount adsorbed at P/P0 =
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0.95. SBET and pore size distribution were calculated through Brunauer-Emmett-Teller (BET) method and density functional theory (DFT) method, respectively. The average pore size was calculated by Barrett-Joyner-Halenda (BJH) analysis from the desorption branch of the isotherms. Scanning electron microscope (SEM, S4800, Hitachi, Japan) was used to observe the morphology and microstructure of the samples, while transmission electron microscope (TEM, JEM-2010HR, JEOL, Japan) was applied to observe their pore structure. Elemental analysis (EA, Analysen 6
ACCEPTED MANUSCRIPT systeme GmbH Elementar Vario EL, Germany) was applied to determine the nitrogen, carbon and hydrogen contents of the solid amine adsorbents. The crystal structure of the silica materials was determined by small-angle powder X-ray diffraction (XRD,
scan rate of 1.0° min-1 in the range of 0.8 to 8.0°.
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D8 ADVANCE, BRUKER Textile Technologies GmbH & Co. KG, Germany) at a
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Preparation of PEI-impregnated mesoporous silica materials
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2.0 g PEI was dissolved in 5.0 mL ethanol after stirring for 15 minutes, and then 2.5 g mesoporous silica material (prepared using CH, MCH or LM as template) was added into the solution. The mixture was continuously stirred at 80 oC for 2 hours and then centrifuged at 11000 rpm for 5 minutes. After being dried at 70 oC for 12 h, the
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adsorbent can be obtained, and denoted as CH-PEI, MCH-PEI or LM-PEI.
CO2 adsorption procedures
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2.0 g of the solid amine adsorbent was placed into an adsorption column (Φ=1.3
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cm), and dry N2 gas was introduced into the column for 20 minutes at a rate of 30 mL min-1 to remove the air and residue water. Then to measure the CO2 adsorption amount of the adsorbent, dry CO2/N2 mixed gas was introduced into the column at a rate of 30 mL min-1, and the CO2 inlet/outlet concentrations were determined by an Agilent 6820 gas chromatograph equipped with a thermal conductivity detector. After CO2 adsorption, the adsorbents were regenerated by N2 flow at 95 oC for 20 minutes.
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RESULTS AND DISCUSSION Preparation of mesoporous silica materials using NH4OH solution of different concentrations as catalysts
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Under the catalysis of NH4OH solution of different concentrations, two series of silica materials were prepared using 2.0 g CH, MCH, LM and MINT as the templates, while two other silica materials were prepared without adding organic compounds for
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comparison.
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When 1% NH4OH solution was used as the catalyst, the gelation of siliceous species was slow, and it took about 5 minutes to obtain the white solidified gel. The N2 adsorption-desorption isotherms and pore size distributions of the samples prepared in this condition are shown in Figure 1 and their pore structure parameters
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are listed in Table 1. It can be seen that except the one prepared using MINT as template, all the samples exhibited the type I reversible isotherms which identified the formation of micropores.25, 26 These micropores resulted from the trapped solvent
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molecules (ethanol and H2O) during gelation process. Their average pore sizes and
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pore volumes were all about 2.3 nm and 0.259 cm3 g-1. As for the sample using MINT as template, it showed the type IV isotherms with H2 hysteresis loop, which indicated the successful formation of mesopores.26 Moreover, its average pore size reached up to 3.2 nm and pore volume to 0.523 cm3 g-1. These results demonstrated that only MIINT can function as pore-forming agent in this condition. This is because that the hydroxyl groups of MINT can help form stable assemblies between template aggregates and the siliceous species through hydrogen bonding during the slow 8
ACCEPTED MANUSCRIPT gelation process. Without the hydrogen bonding, the template aggregates cannot assemble with siliceous species and tended to escape from the three-dimensional SiO2 matrixes; therefore after sol-gel reaction only rigid gels consisting of SiO2 and
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solvent-filled micropores can be obtained.27 When using 5% NH4OH solution as the catalyst, the gelation of siliceous species was much faster, and the prepared samples showed distinctly different pore structures.
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Figure 2 shows their N2 adsorption-desorption isotherms and pore size distributions.
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For the silica material prepared without adding template, it still showed the type I reversible isotherms, and its average pore size and pore volume were about 2.4 nm and 0.330 cm3 g-1 (Table 1). With respect to the other four samples, they all showed the type IV isotherms with H2 hysteresis loops, and their average pore sizes and pore
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volumes reached up to ~4.7 nm and ~0.749 cm3 g-1, respectively. These results demonstrated that all these organic compounds can act as the pore-forming agents here. However, because CH, MCH and LM are all the organic compounds that contain
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no groups to form hydrogen bond with siliceous species, the mechanism of our fast
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sol-gel route should differ from that of nonsufactant route. Actually, when 5% NH4OH solution was used as the catalyst, the gelation of siliceous species was so fast that the simple organic compounds could not escape and were trapped in the three-dimensional SiO2 matrixes to function as the pore-forming agents, even they could not form stable assemblies with the siliceous species through hydrogen bonding. Meanwhile, the similar average pore sizes and pore volumes of the samples suggested that the pore structure had no direct correlation with the molecular size of the template. 9
ACCEPTED MANUSCRIPT But it could be determined by the template amount in the silicate-template mixture. As shown in Figure 3, with the augment of the template amount, the H2 hysteresis loop became greater in magnitude and shifted to higher relative pressures (P/P0). When the
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template amount increased from 0.5 g to 2.0 g, the size of the template aggregates increased, and therefore the average pore size of the prepared material increased from ~3.0 nm to ~4.7 nm, while the pore volume increased from ~0.375 cm3 g-1 to ~0.749
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cm3 g-1 (Table 2). The small-angle XRD pattern of the mesoporous silica prepared
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using 2.0 g MINT as template is shown in Figure 4. This pattern consists of a single broad diffraction peak concentered at the 2θ of 1.18°, which corresponds to a d-spacing of 7.5 nm (calculated from the Bragg equation). From the difference between d-spacing and pore size (4.9 nm), it can be estimated that the mesoporous
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material might have a thick pore wall. The broadness of the single peak and the absence of other peaks in small-angle XRD pattern also indicated the lack of long-range ordered structure.20 However, excessive templates could cause the
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macroscopic phase separation of the templates from the gels, and result in the silica
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materials with disordered porous structures. When the template amount reached to 4.0 g, the BET average pore size and pore volume sharply increased to ~12.0 nm and ~1.296 cm3 g-1, respectively. NH4OH solution of excessive high concentration could also lead to the disordered
porous structure. When 15% NH4OH was added, the gelation was so fierce that bubbles were observed forming in the solution, and a foam-like gel can be obtained after the sol-gel reaction. After removing the template, no type IV isotherms with H2 10
ACCEPTED MANUSCRIPT hysteresis loop can be observed in the N2 adsorption-desorption isotherms of the material (Figure 5). Therefore, when applying this fast sol-gel route in the preparation of the mesoporous silica materials, the NH4OH solution concentration should be
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carefully adjusted. Based on the above results, we postulate that only if the simple organic compound can form homogeneous solution with ethanol and water can it be applied as the
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template in our synthesis route. To verify the versatility of the fast sol-gel route, five
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other simple organic compounds with different physicochemical properties were used as templates (3.0 g), and 5% NH4OH solution as catalyst to prepare the silica materials. These organic compounds were tetrahydrofuran (THF), hexane, n-butyl bromide (BBM), benzaldehyde (BA) and 1, 2-dichloroethane (DCE), which cannot
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form hydrogen bond with siliceous species but can form homogeneous solution with ethanol and water. From Figure 6 it can be known that all the samples showed the type IV isotherms with H2 hysteresis loops, and their average pore sizes and pore
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volumes further increased to ~6.6 nm and ~1.042 cm3 g-1, respectively (Table 3),
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which are comparable to those of MCM-41 and SBA-15. These results confirmed that this fast sol-gel route can greatly expand the range of template choice and be a versatile method to prepare mesoporous silica materials.
Application of the mesoporous silica materials The performance of the prepared mesoporous silica materials as supports was examined with their CO2 adsorption properties at 40 oC. Three solid amine adsorbents, 11
ACCEPTED MANUSCRIPT CH-PEI, MCH-PEI and LM-PEI were obtained through loading PEI into the silica materials prepared using 2.0 g CH, MCH and LM as templates. For comparison, a solid amine adsorbent that using SBA-15 as support (SBA-15-PEI) was also prepared.
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The pore characteristics and amine efficiencies of the solid amine adsorbents are summarized in Table 4. Their reproducibility and stability towards CO2 adsorption were comprehensively tested. It can be seen that even the amine efficiencies of our
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adsorbents (~35%) were all lower than that of SBA-15-PEI (41.5%), our adsorbents
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possessed much better reproducibility and stability (Figure 7). As shown in Figure 7a, the CO2 adsorption amount of SBA-15-PEI sharply decreased by about 50% only after 5 adsorption-desorption cycles. This is because that SBA-15 possessed well-ordered hexagonal pore channels (Figure 8a),28 from which the physically loaded amine could
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easily leak out during the regeneration process, leading to a serious deterioration in CO2 adsorption performance. With respect to our adsorbents (Figure 7b-d), their adsorption amounts showed no decrease even after 10 adsorption-desorption cycles.
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The excellent regeneration ability of our adsorbents could be attributed to the
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interconnected mesopores of the silica supports, in which the loaded amine could be steadily retained (Figure 8b). These results also verified that the mesoporous silica materials prepared via the fast sol-gel route could be good supports of solid amine adsorbents.
Preparation principles of mesoporous silica materials by using simple organic compounds as templates 12
ACCEPTED MANUSCRIPT To better use our fast sol-gel route to prepare mesoporous silica materials, its preparation principles are illustrated in Figure 9. For the organic compounds that can form homogeneous solutions with ethanol and water, as well as assemble with the
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siliceous species through hydrogen bonding, they are able to stay in the three-dimensional SiO2 matrixes and act as the pore-forming agents both in fast gelation condition (I) and in slow gelation condition (II). But for the organic
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compounds that cannot form hydrogen bond with siliceous species, the key step is to
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keep the gelation speed of the siliceous species much faster than the escape speed of the template by using NH4OH solution of adequate concentration as catalyst, so that the organic compounds can stay in the SiO2 matrixes and fulfill their missions (III). If the gelation speed fails to exceed the template escape speed, the template would
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experience phase separation, and only a rigid microporous silica material could be obtained (IV). According to these principles, we also try to adapt our fast sol-gel route
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to the preparation of other mesoporous materials, such as mesoporous titania.
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CONCLUSIONS
Under the catalysis of 5% NH4OH solution, mesoporous silica materials have been
successfully prepared via simple organic compounds templated sol-gel route in the absence of hydrogen bond. This versatile, low-cost and eco-friendly sol-gel route can be easily used to prepare mesoporous silica materials with large surface areas and pore volumes, and greatly expand the range of template choice. The pore size can be adjusted within the range between 2.4 and 6.6 nm simply by altering the template 13
ACCEPTED MANUSCRIPT amount. The formation of the mesopores is attributed to the appropriate gelation speed: when using 5% NH4OH as catalyst the gelation speed of siliceous species is fast enough to trap the template aggregates in three-dimensional SiO2 matrixes, and
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the trapped template aggregates can play the role of pore-forming agent. After loading PEI, the prepared adsorbent can keep remarkable CO2 adsorption capacity even after
ACKNOWLEDGEMENTS
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multiple adsorption-desorption cycles.
The authors gratefully acknowledge the financial support provided by the National Natural Science Foundation of China (Grant No. 51173211), Science and Technology
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Project of Guangdong Province (2014A030313192).
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ACCEPTED MANUSCRIPT FIGURES Figure 1. The N2 adsorption-desorption isotherms at 77.35 K (a) and pore size distributions (b) of the porous silica prepared by using 1% NH4OH solution as
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catalyst. Figure 2. The N2 adsorption-desorption isotherms at 77.35 K (a) and pore size distributions (b) of the porous silica prepared by using 5% NH4OH solution as
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catalyst.
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Figure 3. The N2 adsorption-desorption isotherms at 77.35 K (a) and pore size distributions (b) of the porous silica prepared by using different amount of CH, MCH, LM and MINT as templates.
Figure 4. Small-angle XRD pattern of the mesoporous silica prepared using 2.0 g
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MINT as template.
Figure 5. The N2 adsorption-desorption isotherms at 77.35 K (a) and pore size
as catalysts.
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distributions (b) of the porous silica prepared by using 5% NH4OH and 15% NH4OH
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Figure 6. The N2 adsorption-desorption isotherms at 77.35 K (a) and pore size distributions (b) of the porous silica prepared by using 3.0 g of THF, hexane, BBM, BA and DCE as templates. Figure 7. CO2 adsorption capacities of SBA-15-PEI (a) and the adsorbents using CH (b), MCH (c) and LM (d) as templates at each regeneration cycle (adsorbent mass: 2.0 g; adsorption temperature: 40 oC; N2: 27 mL min-1; CO2: 3 mL min-1 ). Figure 8. TEM images of SBA-15 (a) and CH-2.0 g (b). 19
ACCEPTED MANUSCRIPT Figure 9. Principles for preparing the mesoporous silica materials using simple
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organic compounds as templates.
20
ACCEPTED MANUSCRIPT Tables Table 1. The pore characteristics of silica materials using NH4OH solution of different concentrations as catalyst. NH4OH
Stotal
Vtotal
amount (g)
concentration
(m2 g-1)
(cm3 g-1)
(%) 1
585
CH-1%
2.0
1
531
MCH-1%
2.0
1
594
LM-1%
2.0
1
MINT-1%
2.0
1
Blank-5%
0
5
CH-5%
2.0
MCH-5%
2.0
LM-5%
2.0
2.2
0.241
2.3
0.261
2.4
533
0.253
2.4
619
0.523
3.2
606
0.330
2.4
5
576
0.751
4.7
5
561
0.744
4.8
5
580
0.717
4.5
5
627
0.784
4.7
TE D
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0.281
M AN U
0
2.0
pore size (nm)
Blank-1%
MINT-5%
Average
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Template
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Sample
ACCEPTED MANUSCRIPT Table 2. The pore characteristics of silica materials using different amounts of CH, MCH, LM and MINT as templates and 5% NH4OH solution as catalyst. Template
Template
Stotal
Vtotal
Average
type
amount
(m2 g-1)
(cm3 g-1)
pore size
(g)
(nm)
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Sample
CH
0.5
640
MCH-0.5 g
MCH
0.5
608
LM-0.5 g
LM
0.5
669
0.363
3.0
MINT-0.5 g
MINT
0.5
631
0.410
3.1
CH-1.0 g
CH
1.0
683
0.534
3.5
MCH-1.0 g
MCH
1.0
631
0.631
3.7
LM-1.0 g
LM
1.0
652
0.651
3.6
MINT-1.0 g
MINT
1.0
573
0.607
3.7
CH-2.0 g
CH
2.0
576
0.751
4.7
MCH-2.0 g
MCH
2.0
561
0.744
4.8
LM
2.0
580
0.717
4.5
MINT
2.0
627
0.784
4.7
CH-4.0 g
CH
4.0
462
1.353
11.5
MCH-4.0 g
MCH
4.0
405
1.254
12.4
LM-4.0 g
LM
4.0
437
1.265
11.8
MINT-4.0 g
MINT
4.0
437
1.312
12.2
M AN U
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MINT-2.0 g
EP
LM-2.0 g
0.385
3.0
0.342
3.0
SC
CH-0.5 g
ACCEPTED MANUSCRIPT Table 3. The pore characteristics of silica materials using 3.0 g of THF, hexane, BBM, BA and DCE as templates and 5% NH4OH solution as catalyst. Template
Template
Stotal
Vtotal
Average
type
amount
(m2 g-1)
(cm3 g-1)
pore size (nm)
THF
3.0
548
0.985
6.6
hexane
hexane
3.0
577
1.003
6.2
BBM
BBM
3.0
551
1.075
6.7
BA
BA
3.0
503
1.084
7.0
DCE
DCE
3.0
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THF
SC
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Sample
564
1.063
6.5
ACCEPTED MANUSCRIPT Table 4. The pore characteristics and amine efficiencies of the solid amine adsorbents
Sample
SBET
Vtotal
(m2 g-1)
(cm3 g-1)
Amine
Adsorption
Amine
content
capacity
efficiency
(mmol g-1)
(mmol g-1)
(%)
---
---
---
---
---
---
---
---
1.61
41.5
0.96
34.7
534
1.441
---
CH
576
0.751
---
MCH
561
0.744
---
LM
580
0.717
---
SBA-15-PEI
332
0.853
3.88
CH-PEI
287
0.374
2.77
MCH-PEI
223
0.291
3.46
1.26
36.4
LM-PEI
235
0.310
3.28
1.18
35.9
SC
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ACCEPTED MANUSCRIPT Highlights · Mesoporous silica can be fabricated in the absence of hydrogen bond or electrostatic force. · Effects of NH4OH concentration and template type on the pore design of the prepared silica
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were revealed. · The mesoporous silica with disordered channels showed a good support for solid amine
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adsorbent preparation.
