Sorption of Ammonia in Mesoporous-Silica Ionic Liquid Composites

Subscriber access provided by La Trobe University Library

Article

Sorption of Ammonia in Mesoporous-Silica Ionic Liquid Composites K. Neil Ruckart, Yuchen Zhang, W. Matthew Reichert, Gregory W. Peterson, and T. Grant Glover Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.6b02041 • Publication Date (Web): 27 Oct 2016 Downloaded from http://pubs.acs.org on October 30, 2016

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

Industrial & Engineering Chemistry Research is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 44

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Industrial & Engineering Chemistry Research

Sorption of Ammonia in Mesoporous-Silica Ionic Liquid Composites

K. Neil Ruckart† , Yuchen Zhang† , W. Matthew Reichert‡ , Gregory W. Peterson± , T. Grant Glover†,∗

†

University of South Alabama Department of Chemical and Biomolecular Engineering 150 Jaguar Dr. Mobile, AL, 36688 †

University of South Alabama Department of Chemistry 6040 South USA Dr. Mobile, AL, 36688

±

Edgewood Chemical Biological Center, 5183 Blackhawk Road, Aberdeen Proving Ground, Maryland, 21010

∗

Author to whom correspondence should be addressed: University of South Alabama Department of Chemical and Biomolecular Engineering 150 Jaguar Dr. Mobile, AL, 36688 Tel.: (251) 460-7462 FAX: (251) 461-1485 e-mail: [email protected]

ACS Paragon Plus Environment


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Abstract

A set of sorbents, built from SBA-15 and a sulfonic-acid task specific ionic liquid, have been synthesized and investigated as a novel means of capturing ammonia from air. The adsorbents contain between 3 and 46 wt% ionic liquid, and the composite that contains the least amount of ionic liquid adsorbs more ammonia than the parent SBA-15. Below 2.0 kPa all of the composites adsorb more ammonia than the parent SBA-15. Breakthrough experiments were conducted and the composite materials adsorb more ammonia than activated carbon in both dry and humid conditions. However, the adsorption data is complex and likely reflects adsorption on the silica surface, solubility of the ammonia in the ionic liquid, adsorption resulting from the interaction of the ammonia with the sulfonic acid functional group, and the interaction of ammonia with water contained in the ionic liquid. The ammonia adsorption capacity of the composites is compared to the ammonia adsorption capacity of numerous other materials including metal organic frameworks, activated carbon, zeolites, MCM-41, zirconium hydroxide, and aerogels. The data show that the ionic liquid composites adsorb more ammonia at low pressure than many known materials. More broadly, the results illustrate that it is possible to functionalize the pores of an adsorbent with an ionic liquid to capture a specific gas in a fixed-bed. Keywords: adsorption, ionic liquids, ammonia, sulfonic acid, SBA-15

1 ACS Paragon Plus Environment

Page 2 of 44

Page 3 of 44

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1

Introduction Ionic liquids have received considerable research attention for the past two decades

due to their chemical and thermal stability, tunable thermophysical properties, solvation potential, and vanishingly low vapor pressures.1 Moreover, the discovery of task-specific ionic liquids (TSILs), which contain functional groups, such as amines or sulfonic acids, expands the range of applications of these materials.2 Recent work has shown that it is possible to impregnate TSILs into the pores of mesoporous silica and utilize the composite adsorbents to capture CO2 .3 Composites of this type are complex and provide several options to tailor the sorption either by changing the ionic liquid, changing the sorbent that holds the ionic liquid, or changing the loading of the ionic liquid contained in the pores. The sorption performance of the composite materials was shown to be a function of the porous material that was used to contain the ionic liquid. In particular, the data show that composites of task specific ionic liquids and mesoporous silica provided higher CO2 adsorption capacities than composites of the same TSILs and activated carbon. With a wide range of tunable parameters, composites of this type may provide solutions to complex separations problems, such as toxic gas filtration. Commonly, the objective of toxic gas filtration systems is to remove toxic chemicals from breathing air. Research examining toxic gas filtration examines the capture of a broad spectrum of chemicals, including chemical warfare agents and toxic industrial chemicals.4 Of the large number of toxic compounds that are targeted for filtration, ammonia is of interest because it is colorless, is common in industrial settings, and has a pungent odor that is detectable by humans at levels as low as 5 ppm.4 Historically, carbon adsorbents have been utilized to filter air because carbon adsorbs a wide range of toxic compounds and can be modified with metals and organic compounds to provide additional filtration capacity.5–7 However, activated carbons, such as BPL activated carbon, typically adsorb considerably smaller amounts of ammonia than other adsorbates, 2 ACS Paragon Plus Environment


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

such as octane.8 In addition to carbon, the adsorption of ammonia has been examined on a number of different adsorbent materials. For example, Helminen et al. measured adsorption isotherms over a pressure range of approximately 0.001-100 kPa of several commercially available materials including activated carbons, silica gels, alumina adsorbents, several zeolites, and various polymeric sorbents.9 Of these materials, Amberlyst 15, a sulfonic acid polymeric adsorbent, displayed the highest capacity, 11.3 mol/kg, at 93 kPa. However, regarding the filtration of toxic gases from air, the capacity of the adsorbent at low pressures is of particular interest because in most cases even trace amounts of toxic materials are unacceptable in breathing air. The Helminen study highlights that 4A, 5A, and 13X zeolites have lower ammonia loadings near atmospheric pressure than Amberlyst 15, but zeolites adsorb ammonia more effectively at low pressures. Unfortunately, zeolite ammonia adsorption capacity is significantly reduced when ammonia is adsorbed in the presence of water vapor.10 Recently, considerable work has been done characterizing the adsorption of ammonia on other porous materials including MOFs, silicas, and metal hydroxides.10–17 Typically, adsorption experiments examine the adsorption of these compounds in both dry and humid air to determine how humidity influences filtration performance. For example, covalent organic framework-10 (COF-10), which has Lewis acid boron sites, a high surface area, and large mesopores, adsorbs 15 mol/kg of ammonia at 1 atm.17 However, the use of this material in humid environments is not possible because of the material’s poor hydrothermal stability. Likewise, MOF-74 and Cu-BTC also show high ammonia adsorption capacity but are not water stable.16, 18 However, the use of MOFs to filter toxic gases is appealing because the surface chemistry can be tailored to target specific adsorbates.4 Others have also utilized specific functional groups to target the adsorption of ammonia. Specifically, Humbeck et al. created porous organic polymers densely functionalized with carboxylic acids that produced ammonia loadings above 17 mol/kg at atmospheric


Page 4 of 44

Page 5 of 44

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


pressure and low pressure uptakes of approximately 2 mol/kg at 0.01 kPa.19 The use of specific functional groups to increase ammonia adsorption has not been limited to MOFs or polymers. The highly regular pore structure and large internal surface areas of ordered mesoporous silicas (OMSs) make them attractive as substrates that can be tailored for specific adsorption tasks, such as ammonia adsorption. For example, it has been detailed in the literature that MCM-41 can be used to support a highly porous carbon lining and that this material can be tailored to adsorb both acidic and basic gases.14, 20 Moreover, it has been shown that the interior of MCM-41 and SBA-15 are both well suited for modification with organic functionalities to tailor the adsorbents to capture ammonia.13 Work has also been done examining the impregnation of MCM-41 with metal salts with some impregnated adsorbents displaying nearly 9 mol/kg of ammonia loading at 0.17 kPa.11 Similarly, these materials have been used to support sulfonic acid groups for catalysis.21, 22 Other adsorbent materials, such as activated carbons and zirconium hydroxide, have been treated with sulfuric acid to functionalize the adsorbent surface and promote ammonia adsorption.15, 23, 24 In particular, Zr(OH)4 treated with sulfuric acid removed significantly more ammonia than the untreated material and captured the gas via the formation of an ammonium sulfate.15 Acid treatments have also been applied to carbons, such as the work of Qajar et al. that showed nanoporous carbons treated with nitric acid can adsorb 17 mol/kg at 101 kPa.25 The use of ionic liquids has been considered as means of separating ammonia because ammonia is soluble in ILs.26 It has been shown that TSILs with hydroxyl functional groups display significantly higher ammonia solubility than conventional ionic liquid (CIL) counterparts.27 However, others have shown that CILs containing copper ions impregnated into mesoporous silica can also be used to capture ammonia.28 Absent from these works is the use of TSIL supported on a high surface area substrate and specifically functionalized to target the adsorption of ammonia. SBA-15 is well suited to



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

function as a substrate because the silica has a large mesopore, is hydrothermally stable at ambient conditions, and has surface areas near 1000 m2 /g. In regards to capturing ammonia with ionic liquids, acidic ionic liquids, such as 1-methyl-3-(propylsulfonic acid)imidazolium triflate ([mimC3 SO3 H][TfO]), shown in Figure 1, are of particular interest because the sulfonic acid group provides a reactive site for ammonia. Therefore, it is hypothesized that inclusion of a sulfonic acid TSIL inside the pores of SBA-15 will provide an increase in the low pressure adsorption of NH3 while the solubility of ammonia in ionic liquids, and large mesopores of SBA-15, will provide the material a high adsorption loading at 101 kPa of ammonia. To examine this hypothesis, this work details the impregnation of [mimC3 SO3 H][TfO] into the pores of SBA-15 and quantifies the ability of this material to capture ammonia.

2 2.1

Materials and Methods SBA-15 Synthesis Two batches of SBA-15 were prepared using a published procedure.29 3.0 g of Pluronic-

123 was dissolved in 22.4 g of deionized water, followed by the addition of 90 g of 2M HCl. When the solution appeared as a cloudy homogenous mixture 6.5 g of tetraethylorthosilicate (TEOS) was added and the reaction solution was stirred for 24 hours at 40 o C. The solution was transferred to a Teflon lined autoclave and placed in an oven at 100 o C for 48 hours. The product was vacuum filtered, washed with deionized water, and allowed to dry in air overnight. The as synthesized product was calcined in a continuous flow of Zero Air at a ramp rate of 1 o C per minute to 540 o C and held for 10 hours. After the material was calcined it was stored in a desiccator. SBA-15 batch 1 and 2 are designated SBA-15-B1 and SBA-15-B2, respectively.


Page 6 of 44

Page 7 of 44

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


2.2

Synthesis of SBA-15 [mimC3 SO3 H][TfO] Composite The ionic liquid [mimC3 SO3 H][TfO] was prepared following a previously published

procedure.30, 31 Ionic liquid product purity was verified via

13

C and 1 H Nuclear Magnetic

Response (NMR). Composites of adsorbents and ionic liquids were prepared using an incipient wetness impregnation technique. In a typical synthesis, solutions of 250 mg (2 consecutive impregnations) or 500 mg (1 impregnation) of [mimC3 SO3 H][TfO] were dissolved in 2 mL of the specified solvent. These are designated by utilizing the following naming scheme SBA/xxa wt%-[mimC3 SO3 H][TfO], where xx wt% is the amount of ionic liquid impregnated in the pores as determined via thermal gravimetric analysis. Also, for samples that contained the same wt% of ionic liquid but were prepared using different solvents, the letter “a” is added after the specified weight percent to distinguish these samples. The letter “a” is omitted for samples that have a different weight percent of ionic liquid. Several impregnation solvents were examined including pure acetonitrile (ACN), acetone (ACTN), and methanol (MeOH), and mixtures of methanol-acetone and acetonitrile-acetone in various volumetric ratios. For the consecutive impregnations, the material sat overnight at ambient conditions. Prior to the second impregnation, the material was placed in an oven for 2 hours at 80 o C to remove any remaining solvent. After the impregnation period(s), the material was vacuum filtered and gently washed with approximately 5 mL of methanol solvent to remove any excess TSIL from the external surface of the impregnated SBA-15. Subsequently, the material was dried in an oven for 2 hours at 110 o C to remove any remaining solvent. 2.3

Thermogravimetric Analysis A thermogravimetric analyzer (TGA) was used to determine the amount of TSIL

impregnated in the SBA-15 composites. Specifically, a Netzsch TG 209 F1 Iris analyzer was used to heat the samples in a flow of Zero air, from 25-600 o C at a rate of 10 o C per



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

min. A 15-minute isothermal hold at 140 o C was included in the experiment to remove water adsorbed by the composites. The weight lost attributed to the removal of the ionic liquid from the pore was calculated between 250-600 o C to ensure preadsorbed water and solvent has been removed. Data are plotted using sparse markers where a data marker is plotted for every 295 experimental data points. Analysis of the composite of 1-butyl-3methylimidazolium bis(trifluoromethylsulfonyl)imide was completed using a TA Q500 TGA from ambient temperature to 600 o C at 1o C/min in air. 2.4

Adsorption Measurements A Micromeritics ASAP 2020 collected nitrogen adsorption data at 77 K. In a typical

procedure, 100 mg of pristine SBA-15, or composite material, was placed in the analysis tube. The material was degassed for a minimum of 16 hours under vacuum at 200 o C for SBA-15 and 120 o C for the composite materials. The nitrogen data were utilized to determine pore characteristics including BET surface area, pore volume, and pore width. Pore width was calculated using the BJH-KHS method, and pore volume was calculated from the adsorption data at the highest relative pressure in the nitrogen isotherm. Ammonia adsorption isotherm data were measured using the ASAP 2020. The temperature was held constant by submerging the analysis tube in a recirculating water bath with a precision of 0.01 o C. Prior to analysis, samples were degassed following the same procedure that was used to prepare the sample for nitrogen adsorption experiments. In all isotherms open symbols indicate desorption data and closed symbols indicate adsorption data. Lines on all isotherm data plots are guides for the eye. 2.5

Fourier Transform Infrared Spectroscopy Analysis Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectroscopy

data were gathered using a JASCO FTIR-4100 spectrometer with a 4 cm−1 resolution collecting 64 scans averaged over a range of 4000 to 500 cm−1 . 7 ACS Paragon Plus Environment

Page 8 of 44

Page 9 of 44

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


2.6

Microbreakthrough Testing The microbreakthrough system, shown in Figure 2, that was used to collect break-

through curves has been described in detail elsewhere.10 Briefly, powder was packed approximately 4 mm deep into a 4 mm ID glass fritted tube. An ammonia feed gas was established from a pressurized ballast and mixed with a humidified air stream, resulting in a concentration of 2,000 mg/m3 . Breakthrough experiments were conducted at 20 o C, and two experiments were conducted one in dry ammonia and the other at 80 % relative humidity. The samples were regenerated in dry air at 120 o C for 1 h and humid samples were then pre-humidified at 80% RH at 20 o C for 2 h. The total flow through the glass tube was 20 mL/min. The effluent gas was monitored with a photoionization detector as a function of time. The loading was calculated by integrating the effluent curve as detailed previously.10

3

Results and Discussion Several composites were prepared to determine the impact of solvent selection on the

impregnation of the ionic liquid in the pores of SBA-15. The synthesis process involved completing 1 or 2 impregnation steps utilizing mixed and pure solvents of methanol, acetone, and acetonitrile. As detailed in the experimental section, a single impregnation involved placing 500 mg of ionic liquid in 2 mL of solvent and 2 impregnation steps utilized 250 mg in 2 mL of solvent overnight and then repeating the impregnation with an additional 250 mg in 2 mL of solvent. A TGA was used to quantify the amount of ionic liquid contained in the pores as shown in Figure 3 and the results show SBA-15 loosing very little mass, typical of a silica stored at ambient conditions, and the ionic liquid being removed near 350 o C. These data are summarized in Table 1 and it is clear that the solvent selection for 1 impregnation had little impact on the ionic liquid loaded in the pores and all samples are near the average ionic liquid loading of 30 wt %. 8 ACS Paragon Plus Environment


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Nitrogen adsorption isotherm data was used to calculate the changes in BET surface area, pore volume, and pore width as shown in Figure 4 and Table 1. The nitrogen isotherms are consistent with pores that have been filled, blocked, lined, and unmodified. Specifically, the large mesoporous step near 0.6 is consistent with the mesoporosity of the parent SBA-15 indicating that mesopores are still present in the impregnated materials. However, the pore volume has been reduced indicating that ionic liquid is present in the pore structure. The nitrogen adsorption isotherms and properties are consistent with our other work detailing amine TSILs loaded into SBA-15.3 Consistent with the TGA data, the nitrogen adsorption data shows that solvent has little effect on the textural characteristics of the composite materials. Moreover, it is likely that [mimC3 SO3 H][TfO] readily enters the large pores of SBA-15 as long as the ionic liquid is solvated to reduce the viscosity of the pure ionic liquid, and it is likely that other solvents could also be used to produce similar ionic liquid impregnated materials. Although the composites show little sensitivity to the solvent used to complete the impregnation, the data indicate that more ionic liquid has been impregnated in the pores with two impregnation steps. The mesoporosity is still present; however, the data shows that the pore volume has been further reduced and more of the mesoporous character of the isotherm has been removed. It is not clear from the current experiments precisely why two impregnation steps provides increased ionic liquid loading. However, the samples impregnated twice utilize an ionic liquid impregnation solution that is more dilute than the samples impregnated once. Thus, one explanation maybe that the more dilute solution provides better solvation of the ionic liquid and prevents the ionic liquid molecules from associating. The more solvated ionic liquid then more readily enters the pores of SBA-15. It is also possible that 2 impregnations simply allows for more time for the impregnation to take place. However, to fully understand these effects would require a more detailed study, possible including molecular simulations, which is beyond the scope of the current work.


Page 10 of 44

Page 11 of 44

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


While, the large pores of SBA-15 facilitate the transport of [mimC3 SO3 H][TfO], it was hypothesized that washing the composite adsorbents with solvent may impact the physical properties of the materials by removing a portion of the impregnated ionic liquid from the pore. To understand the effects of washing the samples after the ionic liquid had been loaded in the pores, SBA-15 was impregnated twice with [mimC3 SO3 H][TfO] using acetone as the solvent and then the resulting composite was rigorously washed 5 times using 5 mL of solvents during each wash. The resulting composite was then collected, and it was determined via TGA that the sample contained 3.0 wt% of IL. The sample was designated SBA/3.0 wt%[mimC3 SO3 H][TfO]. The nitrogen isotherm of the washed sample is much closer in capacity to the pristine SBA-15 material with only a slight reduction in total nitrogen uptake. The pore size distributions for the materials were calculated from the nitrogen adsorption data and are shown in Figure 5. The sample that was washed heavily shows pores similar to the pristine SBA-15. The pore size distribution indicates that the majority of the ionic liquid has been removed from the pores. The 3.0 wt% that remains is likely found in several locations in the adsorbent including evenly lining the SBA-15 pores, sparsely decorating the interior of the pores, or contained on the surface of the silica. The sample that has been impregnated twice and not washed aggressively, produced a 46 wt% loading of ionic liquid and shows a reduction in pore size and a reduction in peak intensity. The reduction in peak intensity occurs because the pore size distribution is based on the isotherm and the total nitrogen adsorption capacity of the impregnated sample is significantly less than the pure SBA-15 or the washed sample. The reduction pore volume indicates that a significant number of the pores are blocked at the pore mouth or completely filled. Of the pores that are partially filled, the PSD data indicates that these pores have been filed such that the pore size of the impregnated pores has been reduced by approximately 20 ˚ A. These results show that the impregnated TSIL behaves similarly to the bulk ionic



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

liquid with washings solvating the impregnated ionic liquid and removing it from the SBA15 pore. This is significant because it indicates that leaching of the ionic liquid from the pores could occur if the composite is exposed to liquid solvents. Likewise, when considering the impact of different solvents on the physical properties of ionic liquid composite materials, the number of solvent washings, and volume of solvent used to complete the washing, will have an impact on the properties of the composites. 3.1

Ammonia Sorption by SBA-15 Ionic Liquid Composites Ammonia adsorption isotherms are shown in Figure 6, and the data show a range

of adsorption loadings for the materials between 2.5 and 7.6 mol/kg. The sample with the highest capacity, SBA/3.0 wt%-[mimC3 SO3 H][TfO], adsorbed approximately 20% more ammonia at 101 kPa than unmodified SBA-15 even though it contained the least amount of ionic liquid. Composites that contained more than 3.0 wt% of ionic liquid all produced ammonia loadings of approximately 5.5 mol/kg at 101 kPa even though the amount of ionic liquid varied between 27 and 46 wt %. For example, SBA/46 wt%-[mimC3 SO3 H][TfO] and SBA/30 wt%-[mimC3 SO3 H][TfO] differ in ionic liquid loading by 16 wt% and yet the adsorption capacities at 101 kPa are nearly identical. Ammonia adsorption isotherms for all samples listed in Table 1 were measured, but for clarity not all isotherms are shown because the isotherm shape and capacity between 2.0 and 101 kPa was similar for all composites containing between 27 and 46 wt% of ionic liquid. The ammonia adsorption isotherms between 2.0 and 101 kPa of the composite materials that contain more than 3.0 wt% ionic liquid show a reduction in loading relative to the parent SBA-15. For the composite containing 3.0 wt %, the small amount of ionic liquid in the pores provides the mesoporous silica with sulfonic acid functional groups leading to an increase in ammonia adsorption capacity compared to the parent SBA-15 and the other composite materials. The 3.0 wt% material exceeds the capacity of all other materials for ammonia pressures greater than 0.5 kPa as shown in Figure 7. At pressures lower than 0.5 kPa it 11 ACS Paragon Plus Environment

Page 12 of 44

Page 13 of 44

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


appears that there is too little ionic liquid in the composite to provide enough acidic sites to capture large amounts of ammonia. The 3.0 wt% sample exceeds the ammonia capacity of the parent SBA-15 at all points on the isotherms, but at pressures below 0.5 kPa the 3.0 wt% composite has an ammonia adsorption isotherm shape that more closely resembles the mesoporous SBA-15 parent material. It is important to note that the addition of the ionic liquid has increased the ammonia loading at pressures below 0.20 kPa, by approximately 1.0 mol/kg relative to the pristine SBA-15. To support the conclusion that the sulfonic acid was promoting the capture of ammonia and not simply the solubility of ammonia in the ionic liquid, a control sample was prepared using SBA-15 and a conventional ionic liquid without a sulfonic acid group, 1-butyl3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([bmim][Tf2 N]), and was designated SBA/57 wt%-[bmim][Tf2 N]. The ammonia adsorption isotherm of this material is shown in Figure 6 and 7, and the physical properties of this material are listed in Table 1. As expected, this material, showed relatively low ammonia capacity compared to the [mimC3 SO3 H][TfO] impregnated composites. Some ammonia capacity is expected for the conventional ionic liquid because ammonia is highly soluble in select ILs.26 To investigate ammonia adsorption as a function of the loading of ionic liquid in SBA15 four samples were prepared using methanol as a solvent. The physical properties of these samples are summarized in Table 2 and the ammonia isotherms are shown in Figure 8. These samples were prepared using a different batch of SBA-15 than the previous samples, but the physical properties of the SBA-15 between batch 1 and batch 2 are similar as shown in Tables 1 and 2. Consistent with the previous results, the loading of ammonia at approximately 101 kPa are almost identical even though the pore volume has been decreased by up to 86%. It was found that the loading of ammonia at 0.01 kPa is proportional to the amount of ionic liquid impregnated in the sample with the 52 wt% sample having the smallest pore volume and providing the highest loading of ammonia at low pressure.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

The decrease in the surface area while maintaining ammonia adsorption capacity is consistent with the ionic liquid being frozen in the silica mesopores during the nitrogen adsorption isotherm. This results in the porosimeter characterizing the ionic liquid as a solid surface. However, during the ammonia adsorption experiments, the ionic liquid solubilizes the ammonia and provides an acid site for ammonia interaction. Therefore, it is recommended that nitrogen adsorption data be used cautiously when characterizing these types of composites. To examine the effects of ambient storage on the capacity of the material the adsorbents were stored in 20 mL vials in ambient air for approximately 1 year. The results of the storage are shown in Figure 9. The nitrogen adsorption isotherms show a significant loss in adsorption capacity while maintaining the mesoporous character of the sample and the ammonia adsorption isotherm shows a slight increase in adsorption capacity. One possible explanation is that long time ambient humidity exposure results in water that has been adsorbed that is not readily desorbed during outgassing, which leads to a sample with an increase in mass and a decrease in nitrogen uptake on a per mass basis. Regarding ammonia, the isotherm capacity is slightly increased as a result of the solubility of ammonia in water. The adsorption of water in the ionic liquid is consistent with the work of others detailing water adsorption in pure ILs and the influence of water on the adsorption properties is consistent with our previous work.3, 32, 33 It was hypothesized that uptake of ammonia on the composites is a result of the sulfonic acid groups promoting acid base reactions similar to the reactions seen on other adsorbent materials. ATR-FTIR spectroscopy was used to further characterize the samples; however, after 1 year of storage new composite samples were prepared to ensure that the FTIR spectra were not influenced by any other adsorbed species. A representative sample was produced using two impregnation steps and methanol as the impregnation solvent. The sample had 61 m2 /g of surface area, an ammonia adsorp-


Page 14 of 44

Page 15 of 44

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


tion capacity of approximately 5 mol/kg at 101 kPa, and was designated SBA/36 wt%[mimC3 SO3 H][TfO]. After measuring the ammonia adsorption isotherm, the FTIR-ATR spectra of the SBA-15, the composite, and the composite after ammonia exposure were measured as shown in Figure 10. Because the ammonia adsorption isotherm system measured the desorption portion of the isotherm, the FTIR-ATR spectra reflect the ammonia that remains on the sample at the last desorption data point. The data shown in Figure 10 are consistent with the formation of an ammonium sulfonate with the post ammonia composite showing a peak near 1450 cm−1 that is not present on either the ionic liquid, or the parent SBA-15, and corresponds to NH4 + .15, 34, 35 Also, peaks near 3170 cm−1 are consistent with NH4 + .15, 35 It is important to note that the intensity of the FTIR data for the ammonia exposed sample is a function of the ATR-FTIR measurement. Specifically, the post ammonia exposed sample shows an increased signal intensity for all the peaks in the spectrum as a result of this sample receiving slightly more pressure on the ATR sample stage than the other samples. The formation of a sulfonate provides an explanation for the increase in the low pressure adsorption capacity of the composites. Specifically, in the low pressure portion of the isotherm an increase in capacity is observed because the mechanism of adsorption has changed from interaction with the walls of SBA-15 to chemical reaction with a sulfonate. Because of the significant increase in the adsorption capacity at pressures below 2.0 kPa, the ability of the materials to capture ammonia in a packed-bed was determined using breakthrough testing and the results are shown in Figure 11. The composite material, SBA/46 wt%-[mimC3 SO3 H][TfO], captured ammonia in both dry (1.8 mol/kg) and humid (3.6 mol/kg) air streams. The breakthrough data for the parent SBA-15 material are also shown in Figure 11 and produced loading of 3.3 and 3.5 mol/kg in dry and humid conditions respectively. The data in Figure 11 show that the parent SBA-15 produced nearly identical loading



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

regardless of the presence of humidity. This likely occurs because the SBA-15 silica material binds water strongly on the silica surface and the water is not removed when regenerated at 120 o C for 1 hour. Thus, during the humid breakthrough experiment the humid gas feed stream had a negligible impact on the capacity of the material. The composite material behaves differently than the parent SBA-15 with the dry capacity of the composite being almost half the capacity as the humid adsorption experiment. During a humid breakthrough experiment the composite material exhibits similar behavior as the parent SBA-15 eventhough the pore volume has been reduced by 93 %. The breakthrough experiments were conducted at 2000 mg/m3 which is equivalent to a partial pressure of 0.29 kPa of ammonia. The loading of ammonia at 0.29 kPa as determined from the isotherm on the parent SBA-15 and the composite material, SBA/46 wt%-[mimC3 SO3 H][TfO], are approximately 1.0 mol/kg and 1.75 mol/kg respectively. The dry breakthrough loading of 1.8 mol/kg of the composite material is consistent with the adsorption isotherm of the composite. However, the ammonia loading of SBA-15 gathered from the breakthrough data, 3.3 mol/kg, is significantly higher than the isotherm value of 1.0 mol/kg. The adsorption isotherms were gathered after regeneration at 120 o C under 5-10 micron vacuum overnight, which likely removed more of the preadsorbed water from the surface of the silica and reduced the loading of ammonia at low pressure. The samples used in the breakthrough experiments, however, were stored at ambient conditions and were regenerated less aggressively leaving preadsorbed water on the surface of the adsorbent and increasing the adsorption capacity. The increase in ammonia adsorption capacity as a result of exposure to water vapor is consistent with other adsorbent materials.10 However, it has been noted previously that water has been shown to improve the yields of some reactions when catalyzed using this type of sulfonic acid ionic liquid, indicating that the effectiveness of the acid to react with ammonia may also be a function of the water present.31, 36


Page 16 of 44

Page 17 of 44

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Although the adsorption capacity of the SBA-15/ionic liquid composites is similar to the parent SBA-15, the mechanism of adsorption is quite different and it is likely that the diffusion and transport mechanisms of the composite materials are very different than the parent SBA-15. Also, the composite materials are likely exhibiting multiple effects in the adsorption isotherm. For example, it is clear from the FTIR that ammonia is retained as an NH4 + species, but ammonia is soluble in ionic liquids and so both solubility and chemically retained ammonia are being reported in the adsorption capacity. Also, the ageing results have shown that the composites are likely hygroscopic. Thus, during the breakthrough experiments that were conducted under humid conditions the composite contained absorbed water in the ionic liquid. Because ammonia is soluble in water, the composites increase in ammonia uptake in humid breakthrough conditions is understandable. The introduction of water into the ionic liquid increases the complexity of the system considerably because the kinetics of water uptake in ionic liquids are complex.32 This is different than the parent SBA-15 silica, which during the ammonia adsorption experiment would contain water as an adsorbed film. Thus, throughout the manuscript we have referred to the composites as adsorbents and have detailed the materials adsorption capacity. However, as explained, this adsorption capacity is likely reflecting acid site reaction, solubility in the ionic liquid, and adsorption on any exposed silica from the parent SBA-15. Thus, it may be more correct to refer to the materials sorption capacity to reflect both adsorption and absorption of ammonia in the materials. In the introduction the adsorption of ammonia on a number of different types of materials was discussed and, numerous adsorbent materials have been examined in the literature as ammonia adsorbents. In many cases these materials are examined in the literature using breakthrough experiments. If single component breakthrough experiments are conducted, such that the bed is eventually saturated and the effluent concentration equals the inlet



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

concentration, then the equilibrium loading can be obtained by calculating the area under the breakthrough curve as has been done previously.10 The equilibrium loading is directly comparable; however, the breakthrough time and wave shape are not easily compared due to differences in how the breakthrough experiment is conducted. Moreover, conducting breakthrough experiments using ambient air influences the results because the adsorbate is present with water in a multicomponent adsorption event. Also, the equilibrium loading calculated using breakthrough experiments does not distinguish between adsorption, absorption, or reaction and can reflect all of these events in the equilibrium capacity that is calculated. The performance of several ammonia adsorbents as reported in the literature are listed in Table 3. The purpose of this table is not to provide a comprehensive list of all materials that have been examined as ammonia adsorbents; rather, this table provides context for the performance of SBA-[mimC3 SO3 H][TfO] composites. It is important to keep in mind several items when reviewing the data in this table. First, in all cases data are listed for pressures below 0.5 kPa because we were examining the use of these materials for filtration applications. This is important to note because COF-10 and the nanoporous carbons of Qajar et al., which have loadings of 15 and 17 mol/kg at 1 bar respectively, are not shown because data about the performance of these materials at pressures below 1 kPa was not presented.17, 25 Second, in many cases the regeneration conditions that were used to remove any preadsorbed water may vary slightly between studies. It is possible then that some of the materials show capacities that reflect slightly different amounts of adsorbed water on the surface of the adsorbent. Additionally, in many cases data was available that examined the adsorption of ammonia from both dry air and air streams containing known amounts of humidity. In Table 3 this is distinguished with the word “wet ” next to the sample name. In most cases, humid ammonia breakthrough data were gathered at 20 o C at a relative humidity of 80%. Also, only equilibrium values are reported on the table. Breakthrough data were only


Page 18 of 44

Page 19 of 44

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


included in the table if the breakthrough experiment was allowed to run until the effluent and the feed concentration were equal and the equilibrium capacity of the material determined by completing an integration and mass balance of the breakthrough wave. Unfortunately, this requirement excluded listing several samples made by Bandosz et al. that are well characterized and specifically prepared for ammonia adsorption.38–49 Additionally, the data on the table show the adsorption capacity for the material at the lowest pressure point reported. Therefore, it is likely that some materials, such as ZnCl2 MCM-41, will have an adsorption loading at 0.01 kPa that is competitive with all of the materials listed. This would also hold for a material such as Cu-MCM-BTC, which has a high loading at 0.17 kPa and likely has a significant loading at 0.01 kPa also. When considering materials that are suitable to filter ammonia from air several practical aspects must be considered, including items such as, the cost of the adsorbent, the availability of the material, the ease by which the powder is placed into an engineered form, the mechanical stability of the resulting adsorbent pellet, and the hydrothermal stability of the molecular structure. Many of these are aspects that are beyond the scope of the current fundamental study. Of the materials that are listed Table 3, BSC carbon, BPL carbon, and 13X zeolite are the most readily available as a commercial products and satisfy many of the practical aspects listed previously. Therefore, these materials provide a reasonable baseline upon which to compare our composite adsorbent materials. BPL carbon clearly has limited ammonia capacity and 13X zeolite has been shown to be significantly impacted by ambient water adsorption.9, 10 Therefore, a comparison of SBA-15/ionic liquid composites to BSC carbon is reasonable because this material has capacity for ammonia in both dry and humid conditions and can be purchased commercially. Therefore, ammonia breakthrough curves in both dry and humid conditions were also collected on BSC carbon, which has 830 m2 /g surface area and a pore volume of 0.43 cm3 /g. The BSC carbon produced ammonia breakthrough loadings 1.5 and 2.2 mol/kg in dry and humid conditions, respectively, and



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

the sulfonic acid composite material out performs this broad spectrum carbon adsorbent. When comparing the SBA-15/ionic liquid materials to other novel adsorbents it is clear that the low pressure capacity of 1.53 mol/kg at 0.01 kPa is significant. Specifically, this capacity is higher than many of the materials listed even though the capacities listed for most other materials are listed for pressure higher than 0.01 kPa of ammonia. For example, the SBA-15/ionic liquid composite at 0.01 kPa has a higher capacity for ammonia than Zr(OH)4 at 0.14 kPa. Likewise, the capacity at 0.01 kPa for the SBA/ionic liquid composite exceeds UiO-66-NH2 and is comparable to Fe-MIL-101-SO3 H and porous organic polymers. It is important to note, however, that many of the novel adsorbent materials have adsorption capacities at 1 bar that are much greater than SBA-15 or SBA-15/ionic liquid materials. The table also shows that although many functionalities have been examined in the research literature, only a few adsorbents are available commercially for ammonia adsorption and additional research and optimization are likely required to develop a high capacity commercially viable adsorbent for the filtration of ammonia from air.

4

Conclusion A selection of SBA-15/ionic liquid composite materials have been produced and charac-

terized via isotherm measurements. The results indicate that when preparing these materials using incipient wetness that use of either methanol, acetone, or acetonitrile as the impregnation solvent had little impact on the amount of ionic liquid loaded in the pores; however, the number of impregnation steps did impact the loading the ionic liquid in the pores. In some materials the pore volume of the parent SBA-15 silica was reduced by as much as 93%, but the capacity of the material for ammonia at 101 kPa was almost identical to the parent SBA-15. Although the capacity is similar to the parent material, the adsorption of ammonia in the composite is complex and likely reflect the solubility of ammonia in the ionic liquid, the interaction of ammonia with the acidic site on the TSIL, the adsorption of ammonia on


Page 20 of 44

Page 21 of 44

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


any exposed silica surface, and the influence of water in the IL composite. It was shown that the loading of ammonia at low pressure, 0.29 kPa, is a function of the amount of ionic liquid in the pores with the composite materials exhibiting loadings as high as 1.53 mol/kg at 0.01 kPa. The composites of SBA-15 and acidic ionic liquid outperform other adsorbents, such as UiO-66-NH2 and BSC carbon at low pressures. However, other materials exhibit much higher loadings of ammonia than the SBA-15/ionic liquid composites for pressures beyond approximately 1 kPa. The results show that it is possible to utilize TSILs to place a specific functionality into the pores of high surface area adsorbent and adsorb ammonia in both dry and humid air streams.

5

Acknowledgments We gratefully acknowledge the NASA EPSCoR program, the Alabama Space Grant

Consortium, the Alabama Graduate Research Scholars Program, and the Defense Threat Reduction Agency for financially supporting this research.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

References (1) Zhang, S.; Sun, N.; He, X.; Lu, X.; Zhang,X. Physical properties of ionic liquids: Database and evaluation, J. Phys. Chem. Ref. Data, 2006, 35, 1475-1517. (2) Davis, J.H. Task-specic ionic liquids, Chem. Lett., 2004, 33, 1072-1077. (3) Ruckart, K. N.; O’Brien, R. A.; Woodard, S. M.; West, K. N.; Glover, T. G. Porous solids impregnated with task-specic ionic liquids as composite sorbents, J. Phys. Chem. C, 2015, 119, 20681-20697. (4) Decoste, J.B.; Peterson, G.W. Metal-Organic Frameworks for Air Purification of Toxic Chemicals, Chem. Rev., 2014, 114, 5695-5727. (5) Mahle, J.J.; Peterson, G.W.; Schindler, B.J.; Smith, P.B.; Rossin, J.A.; Wagner, G.W. Role of TEDA as an Activated Carbon Impregnant for the Removal of Cyanogen Chloride from Air Streams: Synergistic Effect with Cu(II), J. Phys. Chem. C, 2010, 114, 20083-20090. (6) Maxwell, A.H.; Rossin, J.A. Effects of airborne contaminant exposure on the physical properties and filtration performance of activated, impregnated carbon, Carbon, 2010, 48, 2634-2643. (7) Peterson, G.W.; Rossin, J.A.; Smith, P.B.; Wagner, G.W. Effects of water on the removal of methyl bromide using triethylene diamine impregnated carbon, Carbon, 2010, 48, 81-88. (8) Johnson, B.J.; Melde, B.J.; Peterson, G.W.; Schindler, B.J.; Jones, P. Functionalized organosilicate materials for irritant gas removal, Chem. Eng. Sci., 2012, 68, 376-382. (9) Helminen, J.; Helenius, J.; Paatero, E.; Turunen, I. Adsorption equilibria of ammonia gas on inorganic and organic sorbents at 298.15 K, J. Chem. Data, 2001, 46, 391-399. 21 ACS Paragon Plus Environment

Page 22 of 44

Page 23 of 44

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(10) Glover, T. G.; Peterson, G. W.; Schindler, B. J.; Britt, D.; Yaghi, O. MOF-74 building unit has a direct impact on toxic gas adsorption, Chem. Eng. Sci. 2011, 66, 16-170. (11) Furtado, A. M.; Wang, Y.; Glover, T. G.; LeVan, M. D. MCM-41 impregnated with active metal sites: Synthesis, characterization, and ammonia adsorption, Microporous Mater., 2011, 142, 730-739. (12) Furtado, A. M. B.; Liu, J.; Wang, Y.; LeVan, M. D. Mesoporous silica-metal organic composite: synthesis, characterization, and ammonia adsorption, J. Mater. Chem. 2011, 21, 6698-6706. (13) Furtado, A. M. B.; Barpaga, D.; Mitchell, L. A.; Wang, Y.; DeCoste, J. B.; Peterson, G. W.; LeVan, M. D. Organoalkoxysilane-grafted silica composites for acidic and basic gas adsorption, Langmuir, 2012, 28 17450-17456. (14) Barpaga, D.; LeVan, M. D. Functionalization of carbon silica composites with active metal sites for NH3 and SO2 adsorption, Microporous Mater. 2016, 221, 197-203. (15) Glover, T. G.; Peterson, G. W.; DeCoste, J. B.; Browe, M. A. Adsorption of ammonia by sulfuric acid treated zirconium hydroxide, Langmuir, 2012, 28, 10478-10487. (16) Peterson, G. W.; Wagner, G. W; Balboa, A.; Mahle, J.; Sewell, T.; Karwacki, C. J.; Ammonia vapor removal by Cu3 (BTC)2 and its characterization by MAS NMR, J. Phys. Chem. C, 2009, 113, 13906-13917. (17) Doonan, C. J.; Tranchemontagne, D. J.; Glover, T. G.; Hunt, J. R.; Yaghi, O. M.; Exceptional ammonia uptake by a covalent organic framework, Nat. Chem., 2010, 2, 235-238. (18) Burtch, N.C.; Jasuja, H.; Walton, K.S. Water Stability and Adsorption in MetalOrganic Frameworks, Chem. Rev., 2014, 114, 10575-10612. 22 ACS Paragon Plus Environment


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(19) Humbeck, J. F. V.; McDonald, T. M.; Jing, X.; Wiers, B. M.; Zhu, G.; Long, J. R. Ammonia capture in porous organic polymers densely functionalized with Bronsted acid groups, J. Amer. Chem. Soc., 2014, 136, 2432-2440. (20) Glover, T. G.;Dunne, K. I.; Davis, R. J.; LeVan, M. D. Carbonsilica composite adsorbent: Characterization and adsorption of light gases, Micropoous Mater., 2008, 111, 1-11. (21) Bandyopadhyay, M.; Shiju, N.; Brown, D. MCM-48 as a support for sulfonic acid catalysts, Catal. Commun., 2010, 11, 660-664. (22) Kwon, O.; Park, S.; Seo, G. Exceptional performance of sulfonic acid-incorporatedMCM-41 mesoporous materials prepared using a silane containing polysulde linkages in the acetylation of anisole, Chem. Commun., 2007, 4113-4115. (23) Petit, C.; Kante, K.; Bandosz, T. J. The role of sulfur-containing groups in ammonia retention on activated carbons, Carbon, 2010, 48, 654-667. (24) Huang, C.-C.; Li, H.-S.; Chen, C.-H. Effect of surface acidic oxides of activated carbon on adsorption of ammonia, J. Hazard. Mater., 2008, 159, 523-527. (25) Qajar, A.; Peer, M.; Andalibi, M.R.; Rajagopalan, R.,; Foley, H.C. Enhanced ammonia adsorption on functionalized nanoporous carbons, Microporous Mater., 2015, 218, 1523. (26) Yokozeki, A.; Shiett, M. B. Ammonia solubilities in room-temperature ionic liquids, Ind. Eng. Chem. Res., 2007, 46, 1605-1610. (27) Palomar, J.; Gonzalez-Miquel, M.; Bedia, J.; Rodriguez, F.; Rodriguez, J. J.; Taskspecic ionic liquids for efficient ammonia absorption, Sep. Purif. Technol., 2011, 82, 43-52. 23 ACS Paragon Plus Environment

Page 24 of 44

Page 25 of 44

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(28) Kohler, F. T. U.; Popp, S.; Klefer, H.; Eckle, I.; Schrage, C.; Bohringer, B.; Roth, D; Haumann, M.; Wasserscheid, P. Supported ionic liquid phase (silp) materials for removal of hazardous gas compounds efficient and irreversible NH3 adsorption, Green Chem., 2014, 16 (2014) 3560-3568. (29) Thielemann, J. P., Girgsdies, F., Schlgl, R.; Hess, C.; Pore structure and surface area of silica SBA-15: inuence of washing and scale-up, Beilstein J. Nanotech., 2011, 2, 110-118. (30) Yoshizawa, M.; Hirao, M.; Ito-Akita, K.; Ohno, H.; Ion conduction in zwitterionictype molten salts and their polymers, J. Mater. Chem., 2001, 11, 1057-1062. (31) Cole, A. C.; Jensen, J. L.; Ntai, I.; Tran, K. L. T; Weaver, K. J.; Forbes, D. C.; Davis, J.H. Novel bronsted acidic ionic liquids and their use as dual solvent catalysts, J. Amer. Chem. Soc., 2002, 124, 5962-5963. (32) Cao, Y.; Chen, Y.; Lu, L.; Xue, Z.; Mu, T. Water Sorption in Functionalized Ionic Liquids: Kinetics and Intermolecular Interactions, Ind. Eng. Chem. Res., 2013, 52, 2073-2083. (33) Tran, C.D.; De Paoli Lacerda, S.H.; Oliveira, D. Absorption of Water by RoomTemperature Ionic Liquids: Effect of Anions on Concentration and State of Water, Appl. Spectrosc. 2003, 57, 152-157. (34) Townsend, T. M.; Allanic, A.; Noonan, C.; Sodeau, J. R. Characterization of sulfurous acid, sulte, and bisulte aerosol systems, J. Phys. Chem. A, 2012, 116 4035-4046. (35) Long, J.W.; Wallace, J.M.; Peterson, G.W.; Huynh, K. Manganese Oxide Nanoarchitectures as Broad-Spectrum Sorbents for Toxic Gases, ACS Appl. Mater. Interfaces, 2016, 8, 1184-1193.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(36) Forbes, D.C.; Weaver, K.J. Bronsted acidic ionic liquids: the dependence on water of the scher esterication of acetic acid and ethanol, J. Mol. Catal. A: Chem., 2004, 214, 129-132. (37) Peterson, G.W.; Mahle, J.; Blaboa, A.; Wagner, G.; Sewell, T.; Karwacki, C.J. Evaluation of MOF-74, MOF-177, and ZIF-8 for the Removal of Toxic Industrial Chemicals, U.S. Army Research Development and Engineering Command, Edgewood Chemical Biological Center Technical Report, 2008, ECBC-TR-659. (38) Seredych, M.; Ania, C.; Bandosz, T.J. Moisture insensitive adsorption of ammonia on resorcinol-formaldehyde resins, J. Hazard. Mater., 2016, 305, 96-104. (39) Seredych, M.; Bandosz, T. J. Mechanism of Ammonia Retention on Graphite Oxides: Role of Surface Chemistry and Structure. J. Phys. Chem. C 2007, 111, 15596-15604. (40) Seredych, M.; Rossin, J. A.; Bandosz, T. J. Changes in Graphite Oxide Texture and Chemistry upon Oxidation and Reduction and Their Effect on Adsorption of Ammonia. Carbon 2011, 49, 4392-4402. (41) Seredych, M.; Bandosz, T. J. Manganese Oxide and Graphite Oxide/MnO2 Composites as Reactive Adsorbents of Ammonia at Ambient Conditions. Microporous Mesoporous Mater. 2012, 150, 5563. (42) Seredych, M.; Bandosz, T. J. Combined Role of Water and Surface Chemistry in Reactive Adsorption of Ammonia on Graphite Oxides. Langmuir 2010, 26, 54915498. (43) Petit, C.; Bandosz, T. J. Graphite Oxide/Polyoxometalate Nanocomposites as Adsorbents of Ammonia. J. Phys. Chem. C 2009, 113, 3800-3809. (44) Petit, C.; Bandosz, T. J. MOF-Graphite Oxide Nanocomposites: Surface Characterization and Evaluation as Adsorbents of Ammonia. J. Mater. Chem. 2009, 19, 6521-6528. 25 ACS Paragon Plus Environment

Page 26 of 44

Page 27 of 44

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(45) Petit, C.; Liangliang, H.; Jagiello, J.; Kenvin, J.; Gubbins, K. E.; Bandosz, T. J. Toward Understanding Reactive Adsorption of Ammonia on Cu-MOF/Graphite Oxide Nanocomposites. Langmuir 2011, 27, 1304313051. (46) Petit, C.; Karwacki, C.; Peterson, G.; Bandosz, T. J. Interactions of Ammonia with the Surface of Microporous Carbon Impregnated with Transition Metal Chlorides. J. Phys. Chem. C 2007, 111, 12705-12714. (47) Petit, C.; Bandosz, T. J. Activated Carbons Modified with Aluminum-Zirconium Polycations as Adsorbents for Ammonia. Microporous Mesoporous Mater. 2008, 114, 137147. (48) Bandosz, T. J.; Petit, C. On the Reactive Adsorption of Ammonia on Activated Carbons Modified by Impregnation with Inorganic Compounds. J. Colloid Interface Sci. 2009, 15, 329-345. (49) Petit, C.; Bandosz, T. J. Removal of Ammonia from Air on Molybdenum and Tungsten Oxide Modified Activated Carbons. Environ. Sci. Technol. 2008, 42, 3033-3039.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 28 of 44

Figure Cations Fig. 1. The [mimC3 SO3 H][TfO] ionic liquid that is impregnated into the pores of SBA-15 to promote ammonia capture. Fig. 2. The system used to measure ammonia breakthrough curves. Fig. 3 Thermal gravimetric analysis of composite materials to determine the mass of ionic liquid contained in the pore. Fig. 4. Nitrogen adsorption isotherms for various composites of SBA-15 and sulfonic acid ionic liquid. Lines are guides for the eye and not model fits. Open markers indicate desorption and closed markers adsorption. Fig. 5. Pore size distribution of composites of SBA-15 and sulfonic acid ionic liquid showing a reduction in pore volume as a function of ionic liquid loading. Mesopores are present in all materials regardless of the amount of impregnated ionic liquid. Fig. 6 Ammonia adsorption isotherms at 25 o C for a selection of SBA-15 and [mimC3 SO3 H][TfO] ionic liquid composite materials. The data shows the composite containing the least amount of ionic liquid adsorbs more ammonia at 101 kPa than all other samples. Lines are guides for the eye and not model fits. Open markers indicate desorption and closed markers adsorption. Isotherms for other samples were measured but are not shown as the isotherm shape and capacity between 2 and 101 kPa was found to be similar for all samples with ionic liquid loadings between 27 and 46 wt %. Fig. 7 The low pressure region of the ammonia adsorption isotherms at 25 o C for composites of SBA-15 and [mimC3 SO3 H][TfO] ionic liquid. The functional group contained in the ionic liquid increases the ammonia capacity of the material at pressures below 2 kPa compared to the parent SBA-15.


Page 29 of 44

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Fig. 8 Ammonia adsorption isotherms at 25 o C for sulfonic acid composites containing different amounts of ionic liquid prepared using the same solvent. The insert shows the low pressure region of the ammonia adsorption isotherms. Lines are guides for the eye and not model fits. Open markers indicate desorption and closed markers adsorption. Fig. 9 Nitrogen adsorption isotherms of a composite sample after 1 year of aging. The decrease in capacity likely results from the adsorption of ambient water. (a) Ammonia adsorption isotherms for the aged composites with the increase in ammonia capacity consistent adsorption of water. (b). Lines are guides for the eye and not model fits. Open markers indicate desorption and closed markers adsorption. Fig. 10 FTIR-ATR data showing the formation of a sulfonate species after the composite materials have been exposed to ammonia as seen with changes in the 3200 cm−1 wavenumber region (a) and the with the peak formed near 1450 cm−1 wavenumbers (b). Fig. 11 Breakthrough curves of SBA-15 and [mimC3 SO3 H][TfO] ionic liquid composite material.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

H3C N

O

N

S O

F O F

Page 30 of 44

S O F O

Figure 1


OH

Page 31 of 44

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 2



100

(a)

95 90

Mass Lost (%)

85

Pure SBA-15 1 Impregnation

80

SBA/27 wt%-[mimC3SO3H][TfO] SBA/29 wt%-[mimC3SO3H][TfO] SBA/30a wt%-[mimC3SO3H][TfO] SBA/30 wt%-[mimC3SO3H][TfO] SBA/34 wt%-[mimC3SO3H][TfO]

75 70 65 60 55 50 45 50

100

150

200

250

300

350 400 o Temp ( C)

450

500

550

600

650

700

450

500

550

600

650

700

100

(b)

90 80 70

Mass Lost (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 32 of 44

60 Pure [mimC3SO3H][TfO] Pure SBA-15

50 40

2 Impregnations SBA/3.0 wt%-[mimC3SO3H][TfO] SBA/39 wt%-[mimC3SO3H][TfO] SBA/40 wt%-[mimC3SO3H][TfO] SBA/44 wt%-[mimC3SO3H][TfO] SBA/46 wt%-[mimC3SO3H][TfO]

30 20 10 0 50

100

150

200

250

300

350

400 o

Temp ( C)

Figure 3


Page 33 of 44

(a)

35

-1

Amount Adsorbed (mmol g )

30 25 20

SBA-15 SBA-[mimC3SO3H][TfO] 1 Impregnation SBA/27 wt% -[mimC3SO3H][TfO] SBA/29 wt% -[mimC3SO3H][TfO] SBA/30a wt% -[mimC3SO3H][TfO] SBA/30 wt% -[mimC3SO3H][TfO] SBA/34 wt% -[mimC3SO3H][TfO]

15 10 5

0.0

0.2

0.4 0.6 o Relative Pressure (P/P )

0.8

1.0

0.8

1.0

35

(b)

SBA-15

30 -1


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


25 20

SBA-[mimC3SO3H][TfO]-2 Impregnations SBA/3.0 wt% -[mimC3SO3H][TfO] SBA/39 wt% -[mimC3SO3H][TfO] SBA/40 wt% -[mimC3SO3H][TfO] SBA/44 wt% -[mimC3SO3H][TfO] SBA/46 wt% -[mimC3SO3H][TfO]

15 10 5 0 0.0

0.2


Figure 4



-3

50x10

SBA-15 SBA/3.0 wt%-[mimC3SO3H][TfO] SBA/46 wt%-[mimC3SO3H][TfO] 40

30

3

dV/dw (cm /g Å)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 34 of 44

20

10

0 0

20

40

60

80

100

120

Pore Width (Å)

Figure 5


140

160

180

200

Page 35 of 44

8

7

-1

Amount Adsorbed (mmol NH3 g )

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


6

5

4

3

2 Pure SBA-15-B1 SBA/3.0 wt%-[mimC3SO3H][TfO] SBA/30 wt%-[mimC3SO3H][TfO] SBA/46 wt%-[mimC3SO3H][TfO] SBA/57 wt%-[bmim][Tf2N]

1

0 0

10

20

30

40

50

60

70

Absolute Pressure (kPa)

Figure 6


80

90

100

110


3

-1


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 36 of 44

2

Pure SBA-15-B1 SBA/3.0 wt%-[mimC3SO3H][TfO] SBA/30 wt%-[mimC3SO3H][TfO] SBA/46 wt%-[mimC3SO3H][TfO] SBA/57 wt%-[bmim][Tf2N]

1

0 0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4


Figure 7


1.6

1.8

2.0

Page 37 of 44

8 SBA-15-B2 7

6

SBA-[mimC3SO3H][TfO] SBA/7 wt% -[mimC3SO3H][TfO] SBA/16 wt% -[mimC3SO3H][TfO] SBA/25 wt% -[mimC3SO3H][TfO] SBA/52 wt% -[mimC3SO3H][TfO]

-1


5

4 -1


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


3

2

1

2

1

0 0.0

0.2

0.4 0.6 0.8 1.0 1.2 Absolute Pressure (kPa)

1.4

0 10

30

50

70


Figure 8


90

110


25 SBA/25 wt% -[mimC3SO3H][TfO] pristine SBA/25 wt% -[mimC3SO3H][TfO] after 1 year ambient storage

(a) -1


20

15

10

5

0 0.0

(b)

0.2


0.8

1.0

8 SBA/25 wt% -[mimC3SO3H][TfO] pristine SBA/25 wt% -[mimC3SO3H][TfO] after 1 year of ambient storage

7

-1


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 38 of 44

6 5 4 3 2 1 0 10

30

50

70


Figure 9


90

110

Page 39 of 44

(a)

SBA-15

Transmittance

SBA-15 IL composite

SBA-15 IL composite post NH3 exposure

4000

3600

3200

2800

2400

2000

1600

-1

1200

800

Wavenumber (cm )

(b)

SBA-15

SBA-15 IL composite

Transmittance

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1167 cm

-1

SBA-15 IL composite post NH3 exposure

1030 cm 1455 cm

-1

-1

1165 cm

-1

1029 cm

1750

1500

1250

-1

-1

1000

Wavenumber (cm )

Figure 10 38 ACS Paragon Plus Environment

750


1.0

0.8

SBA/46 wt%-[mimC3SO3H][TfO] Dry SBA/46 wt%-[mimC3SO3H][TfO] Humid SBA-15 Dry SBA-15 Humid

Ammonia C/Co

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 40 of 44

0.6

0.4

0.2

0.0 0

1000

2000

3000

4000

Normalized Time (min/g)

Figure 11


5000

6000

7000

Page 41 of 44

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Table 1: Pore Characterization of SBA-15 Ionic Liquid Composites. Impregnation Solvents

[cm3 /g]

Pore Volume Decrease [%]

BET Surface Area [m2 /g]

Pore Width BJH [nm]

1.13

-

770

9.5

MeOH - 80% ACTN MeOH - 60% ACTN MeOH - 40% ACTN MeOH - 20% ACTN ACN 100%

0.50 0.41 0.47 0.45 0.34

55.6 63.6 58.5 60.1 69.6

265 212 242 229 171

8.2 8.3 8.3 8.1 7.8

ACTN 100% 50% MeOH - 50% ACTN 75% MeOH - 25% ACTN MeOH 100% ACN 100% ACN 50% - 50% ACTN

1.05 0.23 0.08 0.20 0.13 0.05

6.3 79.4 92.7 82.5 88.7 95.6

719 115 36 93 58 30

9.2 7.8 7.6 8.0 7.9 7.9

SBA-15-B1 1 Impregnation SBA/27 wt%-[mimC3 SO3 H][TfO] SBA/30a wt%-[mimC3 SO3 H][TfO] SBA/29 wt%-[mimC3 SO3 H][TfO] SBA/30 wt%-[mimC3 SO3 H][TfO] SBA/34 wt%-[mimC3 SO3 H][TfO] 2 Impregnations SBA/3.0 wt%-[mimC3 SO3 H][TfO] SBA/39 wt%-[mimC3 SO3 H][TfO] SBA/46 wt%-[mimC3 SO3 H][TfO] SBA/40 wt%-[mimC3 SO3 H][TfO] SBA/44 wt%-[mimC3 SO3 H][TfO] SBA/57 wt%-[bmim][Tf2 N]

-

20% 40% 60% 80%

Pore Volume



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 42 of 44

Table 2: Pore Characterization of SBA-15 Ionic Liquid Composites. Pore Volume [cm3 /g]

Pore Volume Decrease [%]

BET Surface Area [m2 /g]

Pore Width BJH [nm]

NH3 loading at ≈ 101 kPa [mol/kg]

NH3 loading at ≈ 0.01kPa [mol/kg]

SBA-15-B2

1.25

-

845

103

5.8

0.07

SBA/7 wt%-[mimC3 SO3 H][TfO] SBA/16 wt%-[mimC3 SO3 H][TfO] SBA/25 wt%-[mimC3 SO3 H][TfO] SBA/52 wt%-[mimC3 SO3 H][TfO]

1.02 0.87 0.74 0.18

18.2 30.7 40.0 85.5

600 472 393 88

9.7 9.7 9.0 7.8

5.8 5.5 5.7 5.3

0.02 0.40 0.62 1.4


Page 43 of 44

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Table 3: Materials Considered for the Adsorption of Ammonia

Materiala SBA-15 SBA-15 wet SBA/46 wt%-[mimC3 SO3 H][TfO] SBA/46 wt%-[mimC3 SO3 H][TfO] wet SBA-15 SBA/46 wt%-[mimC3 SO3 H][TfO] Porous Organic Polymers Fe-MIL-101-SO3 H UiO-NH3 Cl UiO-66-NH2 BSC carbon BSC carbon wet Na-MnOx aerogel Na-MnOx aerogel wet MCM-41 Cu-MCM-BTC ZnCl2 MCM-41 Functionalized MCM-41 ZrOH4 ZrOH4 wet MOF-74 MOF-74 wet 13X zeolite 13X zeolite wet BPL carbon BPL carbon wet Cu-BTC Cu-BTC wet ZIF-8 ZIF-8 wet

Ammonia Pressure kPa 0.29 0.29 0.29 0.29 0.01 0.01 0.01d 0.01d 0.01d 0.01d 0.29 0.29 0.29 0.29 0.17 0.17 0.17 0.17 0.14 0.14 0.14 0.14 0.14 0.14 0.14 0.14 0.14 0.14 0.12 0.12

Ammonia Loadingb mol/kg 1 3.5 1.8 3.6 0.07 1.53 2 1.45 1.5 0.5 1.5 2.2 4.8 2.3 2 5.2 8.88 1.3-7.0f 2.2 1.9 2.3-6.7f 1.7-4.3f 2.86 0.62 0.17 0.29 6.6 2.8 0.06 0.12

a For

Measurement Typec

Reference

isotherm breakthrough (bt) bt bt isotherm isotherm isotherm isotherm isotherm isotherm bt bt bt bt bte bte bte bte bt bt bt bt bt bt bt bt bt bt bt bt

this work this work this work this work this work this work 19 19 19 19 this work this work 36 36 12 12 11 13 15 15 10 10 10 10 10 10 16 16 37 37

data collected via breakthrough experiments the materials are designated dry or wet to indicate the adsorption of ammonia from an air stream containing water vapor (80 % relative humidity at 293 K). b Regeneration conditions may be different if the materials are not part of the same study, which will likely impact the reported ammonia loading. c Isotherm data collected at 298 K. Breakthrough data collected at 293 K unless specified otherwise. d Pressure read from an isotherm plot and should be considered approximate. e Breakthrough data collected at 298 K. f Several related materials reported in the cited reference and a capacity range is shown to summarize.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

84x38mm (300 x 300 DPI)

ACS Paragon Plus Environment

Page 44 of 44

Sorption of Ammonia in Mesoporous-Silica Ionic Liquid Composites

Recommend Documents