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Carbon Dioxide Fixation via Synthesis of Sodium Ethyl Carbonate in NaOH-dissolved Ethanol Sang-Jun Han, and Jung-Ho Wee Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.6b03250 • Publication Date (Web): 01 Nov 2016 Downloaded from http://pubs.acs.org on November 5, 2016
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Title: Carbon Dioxide Fixation via Synthesis of Sodium Ethyl
3
Carbonate in NaOH Dissolved Ethanol
4 5 6
Sang-Jun Han, and Jung-Ho Wee*
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Department of Environmental Engineering, The Catholic University of Korea
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43 Jibong-ro, Wonmi-gu, Bucheon-si, Gyeonggi-do 420-743, Republic of Korea
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* Corresponding author. Tel.: +82-2-2164-4866; fax: +82-2-2164-4765
12
* E-mail address:
[email protected] or
[email protected] 13
[email protected] or
[email protected] 14
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ABSTRACT
16 17
A CO2-fixing material, sodium ethyl carbonate (SEC), is systematically synthesized via
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carbonation of NaOH dissolved ethanol. The synthesis is conducted by injecting 33.3 vol%
19
CO2 gas into the solution with a concentration of 1-4g NaOH/0.5L ethanol. The SEC
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composition is 97.3 wt%, and NaHCO3 is present in only minor amounts. When the
21
synthesized SEC dissolves in the excess water, it is converted to NaHCO3 precipitate, which
22
can still fix CO2, and ethanol is reproduced in aqueous solution. Therefore, the SEC synthesis
23
and ethanol regeneration process might be an effective means of carbon capture
24
storage/utilization. In addition, SEC thermally decomposes to Na2CO3, CO2, and diethyl ether
25
at 137℃ in an N2 atmosphere and slowly decomposes to Na2CO3·3NaHCO3 with a relatively
26
small release of ethanol and 20% of CO2 fixed in SEC under atmospheric conditions.
27
Furthermore, the main XRD peaks of SEC are herein reported.
28 29
Keywords
30 31
Carbon capture and storage/utilization; Carbon dioxide; Sodium ethyl carbonate; Ethyl ester
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sodium salt; Monoethyl ester sodium salt; Carbonic acid
33
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1. INTRODUCTION
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Many studies on the development of renewable energy sources, increases in energy
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efficiency, and carbon capture, have been conducted to contribute to the efforts to reduce
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carbon emissions.1-4 Carbon capture and storage/utilization (CCSU) is considered to be one
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of the most practical technologies because the CO2 that is generated can be directly reduced.5-
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10
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Mineral carbonation is also an option for CCSU. This process has various
42
advantageous features such as simplicity of process (integrated capture and storage),
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favorable thermodynamics, and permanence of CO2 storage. Furthermore, the abundant raw
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materials such as mineral and industrial residue, which include alkaline component, can be
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used as source materials for CO2 fixation in the process.11-16 However, there are some hurdles
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to overcome for practical use. For example, when the process is carried out in dry-based
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conditions, its efficiency is relatively low.17-20 In addition, although a wet process, in which
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an aqueous solution is used as the solvent to dissolve the source materials such as alkali and
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alkaline earth metals and to produce carbonated materials, gives high CO2 fixation efficiency,
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the traditional wet method is not appropriate for CCSU for carbonated materials two
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significant reasons. The first concerns the solubility of the source materials and carbonated
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materials. Although the solubility of some alkali metals, especially NaOH, which is used in
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the present paper, is very high, it is difficult to use them as source materials because the
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solubility of the corresponding carbonated alkali metals (Na2CO3 or NaHCO3) in aqueous
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solution is also very high. In addition, although carbonated alkaline earth metals such as
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CaCO3 are almost insoluble in aqueous solution, the same is true for their corresponding
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alkaline earth metals, such as Ca(OH)2. The second reason is the great amount of energy -3-
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needed to regenerate or treat the solution that remains after carbonation.20,21
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If these issues can be adequately addressed in a system where an alkali metal (NaOH)
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and an ethanol solution are used as the source material and the solvent, respectively, a wet-
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based process could be developed as another option for CCSU to synergize absorption and
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mineral carbonation.
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In the present system, while the solubility of NaOH in ethanol is very high, the
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solubility of the carbonated alkali metal generated from the carbonation process, presumed to
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be sodium ethyl carbonate (SEC), is very low and, thus, it can be easily precipitated from the
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solution, which is very important in terms of CCSU. In addition, once SEC has been removed
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from the solution, the remaining solution can immediately be reused for the next carbonation
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process. Furthermore, the energy consumed by the current system may be lower than that of a
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water-based system because the specific heat of ethanol is lower than that of water. Therefore,
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the carbonation process using NaOH dissolved in ethanol may have potential as a CCSU
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technology and would appear to be a niche application comparatively of small scale.
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There have been no published reports that aim to reduce CO2 emissions via formation
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of SEC, and only a few related studies, designed for other purposes, have been presented. In
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1859, Bellstein first reported a means of synthesizing SEC by injecting CO2 into a sodium
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ethoxide-absolute alcohol solution.22 At that time, there was little need for further research on
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SEC because of its limited number of applications; it was useful mainly as a carboxylation
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agent for ethoxide.
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In 1974, DOE researchers described the generation of SEC in order to explain the
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development of a process by which ethanol could be regenerated from sodium ion (or other
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compound) dissolved in waste ethanol solution.23 In that study, a pure Na metal-dissolved
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ethanol solution was prepared and a material presumed to be SEC was synthesized by -4-
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injecting CO2 into the solution. The authors dissolved the synthesized materials in water,
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which removed the Na from the solution in the form of precipitated NaHCO3. However, the
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identity of the synthesized materials was solely confirmed by elemental analysis (EA), and
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only their characteristics when dissolved in water were described. The lack of attention paid
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to SEC may be because SEC was only an intermediate compound, not the desired end
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product, and because its chemical and physical properties had never been detailed in any
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official data source.
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Two years later, Hirao et al.24 described a new, high-yield method of synthesizing
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alkali alkyl carbonates. First, weakly acidic mixtures of sodium phenoxide (PhONa) and
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sodium alkoxide (p-RC6H4ONa (R; CH3, CH3O, or Br) were dissolved as alkali salts in
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organic solvents such as alcohol, acetone, and tetrahydrofuran. Subsequently, SEC was
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putatively generated with a yield of 63-99% by injecting CO2 into the solution; however, their
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starting material was alkoxide and the synthesis process was relatively complicated. In
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addition, those authors highlighted the kinds of solvent used and the production yield without
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presenting a detailed description of the SEC synthesis process.
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Except for the three aforementioned papers, no direct study on SEC synthesis and
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carbon fixation has yet been reported. However, some papers have been published and
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patents have been filed regarding the synthesis of sodium ethoxide, which can act as a
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precursor for SEC.25-27
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When synthesizing SEC, CO2 acts as the reactant; therefore, CO2 is fixed during the
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synthesis process. SEC, when dissolved in water, can be easily chemically converted to
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insoluble NaHCO3 in ethanol solution, so CO2 is immobilized in the form of insoluble
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NaHCO3. In other words, SEC can be used as a solid material that incorporates the ethanol.
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Therefore, SEC has promising potential for applications as a raw material in related fields, -5-
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such as the formation of solid fuels, disinfectant agents, and alcoholic beverages.
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Furthermore, SEC can be used as a precursor for diethyl ether (DEE) because it produces
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DEE and Na2CO3 via thermal decomposition. Therefore, a method for SEC synthesis,
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disposal, and utilization has a very high potential as an effective CCSU,28-30 and intensive
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study of SEC may be significant in reducing CO2 emissions.
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As previously mentioned, past studies did not focus on CCSU, and SEC was merely
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an intermediary in the processes being studied, rather than the target substance. Furthermore,
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SEC was not systematically synthesized and clearly characterized in the studies. Therefore,
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the chemical and physical properties of SEC, including its X-ray diffraction (XRD)
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characterization, and thermal stability, have not yet been reported.
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In the present study, SEC was directly synthesized injecting gaseous CO2 into a
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NaOH dissolved ethanol solution. SEC purity was confirmed utilizing the following
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analytical techniques, elemental analysis (EA), thermogravimetric analysis (TGA), powder x-
119
ray diffraction (XRD), and scanning electron microscopy (SEM). Additional experiments
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were conducted to examine the chemical and physical features of SEC. These experimental
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results might provide important data regarding development of wet-based CCSU process.
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Finally, the paper also discussed the potential uses for the SEC and ethanol regeneration in
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CCSU technology.
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2. THEORY: Carbonation process for the synthesis of sodium ethyl carbonate (SEC)
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SEC was produced as a precipitate at ambient temperature by the absorption and
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reaction of CO2 in ethanol solution with dissolved NaOH as the limiting reactant. The overall
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scheme of SEC synthesis, which is a three-phase reaction, has been previously reported24 and -6-
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can be expressed by eq 1.
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C H OH l + NaOHaq + CO g → C H OCOONas + H Ol
(1)
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According to previous authors,24 the reaction consists of two consecutive steps, as represented in eqs 2 and 3.
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C H OH l + NaOHaq → C H O Na aq + H Ol
(2)
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C H O Na aq + H Ol → C H OCOONas
(3)
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First, NaOH is dissolved in ethanol solution to generate sodium ethoxide and water
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according to eq 2. Second, as CO2 is injected into the solution, SEC is generated as listed in
142
eq 3. Although eq 1 is the main reaction that takes place under these circumstances and the
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equilibrium of eq 2 is inclined to the right, other reactions do simultaneously occur. A slight
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amount of NaOH dissociates to Na+ and OH- in ethanol solution, as shown in eq 4. Thereafter,
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OH- reacts with the absorbed CO2 to generate HCO3- according to eq 5 and, therefore,
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NaHCO3 is generated as a precipitate, as shown in eq 6. These overall side reactions are
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summarized in eq 7.
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C H OH l + NaOHaq → C H OH l + Na aq + OH aq
(4)
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Na aq + OH aq + CO g → Na aq + HCO aq
(5)
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Na aq + HCO aq → NaHCO s
(6)
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C H OH l + NaOHaq + CO g → C H OHl + NaHCO s
(7)
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Therefore, the main precipitate generated from the carbonation of NaOH dissolved in an
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ethanol solution is SEC, and NaHCO3 may be present in trace amounts. Their relative
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compositions were investigated via various methods in the present work and are detailed in
157
the Results section.
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3. ANALYSIS FOR MATERIAL CONFIRMATION AND CHARACTERIZATION
160 161
3.1. Elemental analysis (EA)
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The first method used to confirm the identity of the synthesized materials was
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qualitative EA of its constituents, C and H. The mass fractions of C and H were analyzed
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with an EA instrument. If the synthesized material were made up of pure SEC, the mass
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fractions of C and H would be 32.14 wt% and 4.46 wt%, respectively. On the other hand, if
167
the material were pure NaHCO3, the mass fractions of C and H would be 14.29 wt% and 1.19
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wt%, respectively. If SEC and NaHCO3 are mixed in the synthesized material, the mass
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fractions of C and H will be intermediate values.
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3.2. Reaction with excess water
172 173 174
The second approach used to identify the synthesized material was to check whether eq 8 occurred stoichiometrically.
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C H OCOONas + H Ol, excess → NaHCO s + C H OHl + H Ol
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(8)
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Although this reaction was briefly mentioned in a previous report,23 no supporting
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evidence was presented to validate the proposed reaction steps. According to eq 8, when SEC
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is dissolved in excess H2O, NaHCO3 is generated and ethanol is reproduced in the solution.
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The final state of eq 8 is the same as when a constant amount of NaHCO3 is present in an
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ethanol-diluted aqueous solution at constant concentration. Therefore, the concentration of
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ethanol reproduced in the solution is theoretically determined by the amount of SEC and H2O
184
that participate in eq 8. In addition, the proportions of SEC and NaHCO3 in the synthesized
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material can be similarly estimated as in EA analysis. If the synthesized material contains
186
NaHCO3, the concentration of ethanol in an ethanol-diluted aqueous solution may be lower
187
than the stoichiometric value. NaHCO3 is very slightly soluble in ethanol, and can be
188
precipitated and separated from the solution as a CO2 fixation material.31
189 190
3.3. Reaction with ambient humidity
191 192
In addition to the two aforementioned methods, the present study proposes two other,
193
new, reactions which confirm the synthesized material to be SEC and verifies those reactions.
194
The first new reaction is denoted as eq 9.
195 196
5C H OCOONas + 4H Og → Na CO ∙ 3NaHCO s + 5C H OHl + CO g
(9)
197 198
When SEC reacts with water at trace concentrations, such as the humidity naturally
199
present in the atmosphere, the result is as shown in eq 9. Therefore, when SEC is exposed to
200
the atmosphere, it very slowly decomposes to Na2CO3·3NaHCO3 and releases ethanol and
201
CO2 to the air. However, the ratio of SEC to NaHCO3 in the synthesized material is difficult -9-
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to estimate with this knowledge.
203 204
3.4. Thermal decomposition
205 206 207
The second proposed reaction involves the thermal decomposition of SEC. The standardized specific thermal decomposition of SEC is expressed in eq 10.
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2C H OCOONas → Na CO s + CO g + C H OC H g
(10)
210 211
Pure SEC seems to thermally decompose to Na2CO3, CO2, and DEE in a high-N2
212
atmosphere. As a result, CO2 and gaseous DEE are released, leaving solid Na2CO3 with a
213
weight loss of 52.7 wt%. We confirmed this reaction by thermogravimetric analysis (TGA).
214
In addition, NaHCO3 thermally decomposes to solid Na2CO3, releasing CO2 and H2O, as
215
shown in eq 11.
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NaHCO s → Na CO s + CO g + H Og
(11)
218 219
Because the total weight loss of eq 11 is 36.9 wt%, measuring the weight loss in the
220
synthesized material enables determination of the compositions of SEC and NaHCO3 via
221
thermal decomposition.
222 223
3.5. Characterization of the synthesized material via X-ray diffraction (XRD) and scanning
224
electron microscopy (SEM) imaging
225
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Based on the results of the four above-mentioned reactions, the main component of the
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synthesized material was identified as SEC. As stated above, no significant, qualitative
228
analysis of SEC, such as its XRD pattern, has yet been reported. Therefore, the XRD pattern
229
of SEC is reported herein.
230 231
4. EXPERIMENTAL METHOD
232 233
4.1. Carbonation as a means of synthesizing sodium ethyl carbonate (SEC)
234 235
Four solutions were prepared by dissolving 1, 2, 3, and 4 g of NaOH (OCI Company
236
Ltd., 99.99%) in 0.5 L of highly purified absolute ethanol (OCI Company Ltd., 99.9%). These
237
solutions were used as the chemical absorbents for CO2 fixation as well as the reactants for
238
SEC synthesis. None of the solutions were saturated with NaOH and all were sufficiently
239
stirred to ensure complete NaOH dissolution in the closed vessel. The four solutions are
240
designated 1g-S, 2g-S, 3g-S, and 4g-S, respectively. The procedure for synthesizing SEC is
241
shown schematically in Figure 1.
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------------------ Figure 1 ------------------
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A Pyrex cylindrical batch reactor (D, 110mm; h, 80mm) was filled with the sample
244
solutions, which were stirred with a magnetic stirrer bar rotating at 200 rpm in the reactor.
245
The temperature of the reactor and gas mixer was maintained at 25℃. Before injecting CO2
246
into the reactor, every gas line in the apparatus and the absorbent were cleaned by N2 purging.
247
CO2 and N2 were mixed in the gas mixer equipped with a temperature controller at a constant
248
proportion. The flow rates were controlled by a mass flow controller at 1 L/min for CO2 and
249
2 L/min for N2. Before the reaction, the gas mixture by-passed the reactor and was directly - 11 -
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fed to a non-dispersive infrared (NDIR)-based gas analyzer (maMos-200, Madur Electronics)
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to confirm that the CO2 gas composition had stabilized at 33.3%. Thereafter, the gas mixture
252
was injected into the reactor via a three-way valve in the apparatus and dispersed in the
253
reactor via a sparger made by glass filter. After passing through the reactor, the gases were
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directed to a condenser maintained at 4℃ by a circulator to eliminate the volatilized ethanol.
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The CO2 concentration in the gas leaving the condenser was measured every second by a gas
256
analyzer in order to determine the final gas composition. The reaction was considered
257
complete when the outgoing CO2 composition reached the level of the initial CO2 feed
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composition, 33.3%. The amount of CO2 absorbed (or reacted) could be calculated based on
259
the variation of the outgoing CO2 composition according to reaction time. The method used
260
to calculate the amount of CO2 absorbed in the reaction was detailed in our previous paper.32
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When the absorption of gas was terminated, a fine white powder (shown in Figure S1 in
262
Supporting Information), which was presumed to be SEC and which had been precipitating
263
continuously throughout the reaction, was enriched in the solution.
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Finally, the solution was filtered and then the cake was dried in a vacuum oven at 50℃
265
for more than 1 hour to obtain the precipitate (presumed to be SEC) for confirmation and
266
characterization.
267 268
4.2. Confirmation and characterization of the synthesized material
269 270
EA (Perkin Elmer 2400 series II, Perkin Elmer) was used to positively identify the
271
synthesized material as SEC. The C and H compositions in the material were analyzed by EA
272
in CHN mode.
273
The occurrence of the reaction in eq 8 was confirmed by analyzing the ethanol - 12 -
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concentration in an aqueous solution containing the synthesized material. First, a 2.50 wt%
275
ethanol aqueous solution was prepared by dissolving stoichiometric amounts of the
276
synthesized material (presumed to be SEC) calculated based on eq 8 in a given amount of
277
distilled water. The material dissolved readily and completely disappeared in the solution
278
within a short time, releasing a certain amount of heat. Subsequently, a small amount of white
279
powder, presumed to be NaHCO3, was very slowly generated in the solution. Thereafter, the
280
transparent solution that had been obtained by filtration was pre-treated for ethanol analysis.
281
The ethanol composition in the transparent solution was measured by gas chromatography-
282
mass
283
(30m×250µm×0.25µm)). Meanwhile, the filter cakes separated from the solution were dried
284
for more than 3 hours at 50℃ in a vacuum oven and qualitatively analyzed by XRD.
285
spectrometry
(GC-MS,
Agilent
7890,
Agilent
Tech,
DB-WAX
column
To verify eq 9, 3 g of synthesized material in a vial (D; 30 mm, h; 60 mm) was exposed
286
to ambient air (25±3℃, 30-60% relative humidity) for 2 months, and then analyzed by XRD.
287
TGA (TGA N-1000, SCINCO) was used to validate eqs 10 and 11. After the sample was
288
loaded, high-purity N2 gas (99.99%) was fed into the TGA instrument at a flow rate of 25.5
289
mL/min. The weight loss and temperature derivative were measured as the sample was raised
290
from room temperature to 400℃ at a ramp rate of 2℃/min. In addition, to qualitatively
291
measure the final solid product resulting from eq 10, a substantial amount of the synthesized
292
material was thermally decomposed in a high-temperature vacuum tube furnace (GSL-1100,
293
MTI Corp.) under the same conditions as those used for TGA analysis. Thereafter, the final
294
product of eqs 10 and 11 was sampled and analyzed by XRD. All XRD patterns were
295
obtained with a Siemens Bruker AXS D-5000 instrument using Cu Ka1 radiation in Bragg-
296
Brentano reflecting and Debye-Scherrer transmission geometry. The samples were scanned in
297
a 2θ range of 10-90˚ with a step size of 0.2˚ and a scan rate of 1 min per step. In addition, the - 13 -
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particle shape of the synthesized material was measured by scanning electron microscopy
299
(SEM; S-4800, Hitachi).
300 301
5. RESULTS AND DISCUSSION
302 303
5.1. Amount of CO2 absorbed during the synthesis of sodium ethyl carbonate (SEC)
304 305 306 307
Figure 2 shows the theoretical and experimentally observed amounts of CO2 absorbed during the production of SEC in the four NaOH-dissolved ethanol solutions. ------------------ Figure 2 ------------------
308
As CO2 was injected into the solution, a constant amount of CO2 was absorbed and
309
reacted with the components of the solution. The saturation level of CO2 in 500 mL of pure
310
ethanol was 1.88 g, as assessed by conducting an experiment prior to the reaction. The total
311
amount of theoretically-absorbed CO2 in the solution, which is the summation of 1.88 g and
312
the theoretical amount of CO2 reacted based on eq 1, is shown as a dotted line in Figure 2.
313
Overall, the experimentally observed CO2 values were similar to the theoretical values in the
314
four solutions. This offered direct confirmation that the reaction in eq 1 (alone or in
315
combination with that in eq 7) had occurred and proceeded stoichiometrically. However, the
316
slope of the experimental value according to NaOH concentration in the solution was slightly
317
higher than that of the theoretical values. For example, the amount of CO2 absorbed in 1g-S
318
was 2.78g, which was 6.7% smaller than the theoretical amount. However, the experimental
319
value increased and became almost identical to the theoretical value in 2g-S and 3g-S. Finally,
320
the experimental value of CO2 absorbed in 4g-S was slightly larger than the theoretical value.
321
This phenomenon was attributed to the following two side reactions: - 14 -
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322 323
H Ol + CO g → H aq + HCO aq
(12)
324
C H OH l + HCO aq → C H OCOO aq + H Ol
(13)
325 326
In other words, water, the product of eq 1, reacts with the continuously supplied CO2 to
327
generate HCO3- in the solution. After that, HCO3- reacts with ethanol to produce C2H5OCOO-,
328
according to eq 13, until equilibrium is attained. Finally, the water produced from eq 1
329
triggers eqs 12 and 13 and the reactions are intensified according to the concentration of
330
NaOH in the solution. Therefore, the relative amount of CO2 absorbed in a highly
331
concentrated NaOH solution is larger than that in a weakly concentrated solution. However,
332
because this additional CO2 is not directly used for SEC synthesis and cannot be
333
quantitatively included in the theoretical amount of CO2 absorbed, the experimental value of
334
CO2 absorbed in the highly concentrated NaOH solution is larger than the theoretical value.
335
Therefore, the SEC manufacturing process denoted by eq 1 has potential as a new CCSU
336
technology.
337
The process, however, as with other traditional CCSU technologies, may involve
338
economic hurdles. Ethanol price might be one of the important factors influencing the
339
economy. Therefore, reusability of the ethanol seems to be the most critical point in
340
improving the economy of this process. Although the reusability of the solutions was not
341
discussed in the paper, SEC mixed with a small amount of NaHCO3 powder was also
342
produced via direct carbonation in ethanol solution that had been reused six or even seven
343
times without any additional treatment. In addition, the net amount of ethanol solely
344
consumed for SEC synthesis is very small and the ethanol was not difficult to recover leaving
345
NaHCO3 and water according to eq 8. Furthermore, there are a variety of means to increase - 15 -
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346
the economy of the process as being one of the CCSU processes. Theoretically, SEC can be
347
the economically available materials such as the feedstock of solid fuels, disinfectant agents,
348
powdered alcoholic beverages and a precursor for diethyl ether (DEE). Including these SEC
349
application potentials, many of fundamental issues regarding the economy should be
350
intensively reviewed whether it can meet an economically acceptable cost value of CCSU
351
process, 50~150 $/tCO2 avoided. However, it is not easy to be conducted at current stage
352
because the process is suggested as an alternative conceptual methodology in the paper. They
353
will be achieved in near future.
354 355
5.2. Confirmation of the synthesized material
356 357
5.2.1. Element analysis (EA) and reaction with excess water
358 359 360
The compositions of C and H in the synthesized material as measured by EA were compared to the theoretical values in pure SEC and NaHCO3, as listed in Table 1.
361
------------------ Table 1 ------------------
362
The compositions of C and H in the synthesized material were intermediate between
363
those of pure SEC and NaHCO3. Therefore, the synthesized material was physically
364
confirmed to be a mixture of SEC and NaHCO3, and the amounts of each could be quantified.
365
The portion of SEC in the synthesized material based on the composition of C and H in the
366
synthesized material was 98.23 wt% and 96.19 wt%, respectively. Therefore, the main
367
component of the synthesized material is SEC, and NaHCO3 is present in only minor
368
amounts.
369
A constant amount of the synthesized material was dissolved in excess water to verify - 16 -
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eq 8. 2 g of the synthesized material was dissolved in 32.36 g of water to prepare a 2.50 wt%
371
ethanol aqueous solution according to eq 8. However, the real concentration of ethanol in the
372
solution was measured to be 2.42 wt%; this result supports the notion that a slight amount of
373
NaHCO3 is present in the synthesized material. The composition of SEC in the synthesized
374
material can be calculated by the difference between the theoretical and measured ethanol
375
concentration. It was thusly estimated to be 97.60 wt%.
376 377 378
The XRD peaks of the precipitated substance generated from eq 8 are shown in Figure 3. ------------------ Figure 3 ------------------
379
The XRD patterns perfectly matched those of the NaHCO3 standard. These results offer
380
further evidence confirming SEC as the synthesized material. Therefore, when SEC reacted
381
with excess water, CO2 was fixed in the form of NaHCO3 and ethanol was reproduced at a
382
constant concentration in the aqueous ethanol solution.
383 384
5.2.2. Thermogravimetric analysis (TGA)
385 386
The results of TGA analysis of the synthesized material are shown in Figure 4.
387
------------------ Figure 4 ------------------
388
As the temperature increased from 100 to 150℃, the sample weight rapidly
389
decreased to a minimum, at which it remained. SEC, therefore, thermally decomposed in this
390
temperature range. The thermal decomposition point and total weight loss of the sample were
391
137℃ and 52.1%, respectively, while the theoretical weight loss of pure SEC and NaHCO3
392
are 52.7% and 36.9%, respectively. Based on these findings, the SEC composition in the
393
synthesized material was calculated to be 97.21 wt%. - 17 -
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394 395
The XRD patterns of the synthesized materials decomposed in an electrical furnace under the same condition as that of the TGA analysis are shown in Figure 5.
396
------------------ Figure 5 ------------------
397
These XRD patterns perfectly corresponded with those of a standard Na2CO3 sample
398
and, thus, eqs 10 and 11 could be confirmed. However, diethyl ether generated during the
399
decomposition could not be identified.
400 401
5.3. Characterization of the synthesized material
402 403
5.3.1. X-ray diffraction (XRD)
404 405
The combination of the aforementioned results confirmed that the synthesized
406
material was mainly SEC, with a very small amount of NaHCO3. The XRD patterns of the
407
synthesized material were scanned and the result in the maximum intensity range is shown in
408
Figure 6a.
409
------------------ Figure 6 ------------------
410
In Figure 6a, the main peaks do not correspond with those of any previously reported
411
Na, C, O, and H-based substances. In addition, the standard peaks of NaHCO3 are not clearly
412
identifiable. This may be because NaHCO3 is present merely at trace levels and its
413
crystallinity may be very small compared to that of SEC. Nevertheless, to confirm the
414
presence of NaHCO3 as an impurity, the small peaks in the low-intensity zone were
415
magnified, as shown in Figure 6b. Some of the small peaks were identified as those of
416
NaHCO3. Finally, the main peaks shown in Figure 6a are believed to be the standard XRD
417
patterns of SEC; this is the first report of its standard XRD patterns in the published literature. - 18 -
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418
The d value, intensity, and relative intensity of the synthesized materials are summarized in
419
Table S1 in Supporting Information and the expected main peaks of SEC are highlighted.
420 421
5.3.2. Reaction with ambient humidity
422 423 424
The XRD pattern of the synthesized material following exposure to ambient air for two months is shown in Figure 7.
425
------------------ Figure 7 ------------------
426
The exposed material was confirmed to be Na2CO3·3NaHCO3, which supports the
427
validity of eq 9 and the role of water as the limiting reactant in this reaction. Theoretically,
428
when 1 g of SEC is exposed to ambient air, it reacts with 0.13 g of H2O to generate 0.41 g of
429
ethanol and 0.08 g of CO2. Finally, 0.40 g of CO2 was reacted to synthesize 1 g of SEC
430
according to eq 1, and 20% of the CO2 reacted was released, as shown in eq 9, with the
431
balance of CO2 fixed in the form of Na2CO3·3NaHCO3.
432 433
5.3.3. SEM photographs
434 435 436
SEM images of the synthesized SEC are shown in Figure 8. ------------------ Figure 8 ------------------
437
The SEC grain exhibits a rhombic- and plate-type structure. The maximum grain size
438
is about 14.2×19.5 µm, as shown in Figure 8a, with a thickness of approximately 0.5 µm, as
439
shown in Figure 8b. The synthesized SEC was physically very weak and brittle, as
440
demonstrated when the crystal was easily cracked during the SEM analysis.
441
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442
6. CONCLUSION
443 444
In the present paper, a CO2-fixing material was synthesized by absorbing gaseous CO2
445
in NaOH-dissolved ethanol solution. Sodium ethyl carbonate (SEC) was the main component
446
of the synthesized material, along with a very slight amount of NaHCO3, at an average
447
composition of approximately 2.7 wt%. This was confirmed via various analytical methods,
448
such as gas analysis, EA, TGA, GC-MS, XRD, and in a furnace.
449
Although the synthesized SEC is itself a CO2-fixing material, when it dissolves excess
450
water, it is converted to insoluble NaHCO3, which can also fix CO2, and ethanol is
451
reproduced at a constant concentration in the solution. Although the recycling of SEC-
452
separated carbonated solutions was not detailed in the paper, we confirmed that the solution
453
can be reused for the next carbonation cycle by adding NaOH to the solution, without any
454
other treatment, which will be reported in the near future. Therefore, the SEC synthesis and
455
ethanol regeneration process proposed in this paper has the potential to be an effective CCSU
456
technology. However, the CO2 fixing properties described in the paper leave many challenges
457
to be solved for its practical use because the study primarily focused on the SEC synthesis
458
and it characterization. The challenges include the optimum condition determination of the
459
various factors which influence the performance of the process such as the ratio of solids-to-
460
liquid (solution concentration), temperature, pressure (or composition) of feeding gas and etc.
461
In addition, the number of reusable cycles of the ethanol and make-up amount of NaOH for
462
regeneration in the process should be intensively analyzed for feasibility study of the process.
463
However, as aforementioned, the process is suggested briefly as an alternative conceptual
464
methodology with very limited results and thus they will be conducted in near future.
465
Some of the chemical and physical characteristics of the synthesized materials were - 20 -
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466
presented. Chemically, as the synthesized material was exposed to water, which acted as the
467
limiting reactant, in the form of atmospheric humidity, it slowly decomposed to
468
Na2CO3·3NaHCO3 with a relatively small release of ethanol and 20% of CO2 fixed in SEC.
469
Furthermore, SEC thermally decomposed to Na2CO3, CO2, and diethyl ether at 137℃ in an
470
N2 atmosphere. The main XRD pattern of SEC was herein reported, which can be regarded as
471
the standard XRD pattern. These chemical and physical characteristics might offer the
472
constructive information to find the SEC application and to develop the conceptual process of
473
CCSU technology. However, these characteristics should be required a more in-depth
474
analysis and these will be also conducted in near the future.
475 476
Acknowledgements
477 478
This research was supported by Basic Research Program through the National Research
479
Foundation of Korea (NRF) funded by the Ministry of Education (2013R1A1A2A10010414)
480
as well as supported by the Catholic University of Korea, Research Fund, 2015.
481 482
Supporting Information
483 484
Figure S1.Photograph of the synthesized material, sodium ethyl carbonate (SEC).
485 486
Table S1. The d values and intensities in the XRD pattern of the synthesized material; bold an
487
d underlined values are expected to represent the main SEC peaks.
488 489
This information is available free of charge via the Internet at http://pubs.acs.org. - 21 -
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References
491 492
(1) Zheng, X.; Kim J. K. Optimization of Power-Intensive Energy Systems with Carbon
493
Capture. Ind. Eng. Chem. Res. 2011, 50, 11201.
494 495
(2) Yu, J.; Wang, S. Modeling Analysis of Energy Requirement in Aqueous Ammonia Based
496
CO2 Capture Process. Int. J. Greenhouse Gas Control 2015, 43, 33.
497 498
(3) Wan, M. M.; Zhu, H. Y.; Li, Y. Y.; Ma, J.; Liu, S.; Zhu, J. H. Novel CO2-Capture Derived
499
from The Basic Ionic Liquids Orientated on Mesoporous Materials. ACS Appl. Mater.
500
Interfaces 2014, 6, 12947.
501 502
(4) Oh, Y.; Le, V. D.; Maiti, U. N.; Hwang, J. O.; Park, W. J.; Lim, J.; Lee, K. E.; Bae, Y. S.;
503
Kim, Y. H.; Kim, S. O. Selective and Regenerative Carbon Dioxide Capture by Highly
504
Polarizing Porous Carbon Nitride. Ind. Eng. Chem. Res. 2015, 9, 9148.
505 506
(5) Chai, S. H.; Liu, Z. M.; Huang, K.; Tan, S.; Dai, S. Amine Functionalization of
507
Microsized and Nanosized Mesoporous Carbons for Carbon Dioxide Capture. Ind. Eng.
508
Chem. Res. 2016, 55, 7355.
509 510
(6) Zhang, G.; Yang, Y.; Xu, G.; Zhang, K.; Zhang, D. CO2 Capture by Chemical Absorption
511
in Coal-Fired Power Plants: Energy-Saving Mechanism, Proposed Methods, and Performance
512
Analysis. Int. J. Greenhouse Gas Control 2015, 39, 449.
513
- 22 -
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Page 22 of 40
Page 23 of 40
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
514
(7) Uma Maheswari, A.; Palanivelu, K. Carbon Dioxide Capture and utilization by
515
Alkanolamines in Deep Eutectic Solvent Medium. Ind. Eng. Chem. Res. 2015, 54, 11383.
516 517
(8) Kumar, S.; Saxena, S. K.; Drozd, V.; Durygin, A. An Experimental Investigation of
518
Mesoporous MgO As a Potential Pre-Combustion CO2 Sorbent. Mater. Renew. Sustain.
519
Energy 2015, 4, 1.
520 521
(9) Meng, L. Y.; Park, S. J. MgO-Templated Porous Carbons-Based CO2 Adsorbents
522
Produced by KOH Activation. Mater. Chem. Phys. 2012, 137, 91.
523 524
(10) Labus, K.; Tarkowski, R.; Wdowin, M. Modeling Gas–Rock–Water Interactions in
525
Carbon Dioxide Storage Capacity Assessment: A Case Study of Jurassic Sandstones in
526
Poland. Int. J. Environ. Sci. Technol. 2015, 8, 2493.
527 528
(11) Samanta, A.; Zhao, A.; Shimizu, G. K.; Sarkar, P.; Gupta, R. Post-Combustion CO2
529
Capture Using Solid Sorbents: A Review. Ind. Eng. Chem. Res. 2011, 51, 1438.
530 531
(12) Lu, H.; Reddy, E. P.; Smirniotis, P. G.; Calcium Oxide Based Sorbents for Capture of
532
Carbon Dioxide at High Temperatures. Ind. Eng. Chem. Res. 2006, 45, 3944.
533 534
(13) Hosseini, T.; Selomulya, C.; Haque, N.; Zhang, L. Indirect Carbonation of Victorian
535
Brown Coal Fly Ash for CO2 Sequestration: Multiple-Cycle Leaching-Carbonation and
536
Magnesium Leaching Kinetic Modeling. Energy Fuels 2014, 28, 6481.
537
- 23 -
ACS Paragon Plus Environment
Industrial & Engineering Chemistry 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
538
(14) Guo, Y.; Li, C.; Lu, S.; Zhao, C. K2CO3-Modified Potassium Feldspar for CO2 Capture
539
from Post-Combustion Flue Gas. Energy Fuels 2015, 29, 8151.
540 541
(15) Wang, C.; Yue, H.; Li, C.; Liang, B.; Zhu, J.; Xie, H. Mineralization of CO2 Using
542
Natural K-Feldspar and Industrial Solid Waste to Produce Soluble Potassium. Ind. Eng. Chem.
543
Res. 2014, 53, 7971.
544 545
(16) Sanna, A.; Maroto-Valer, M. M. CO2 Capture at High Temperature Using Fly Ash-
546
Derived Sodium Silicates. Ind. Eng. Chem. Res. 2016, 55, 4080.
547 548
(17) Azdarpour, A.; Asadullah, M.; Mohammadian, E.; Junin, R.; Hamidi, H.; Manan, M.;
549
Daud, A. R. M. Mineral Carbonation of Red Gypsum via pH-Swing Process: Effect of CO2
550
Pressure on The Efficiency And Products Characteristics. Chem. Eng. J. 2015, 264, 425.
551 552
(18) Zingaretti, D.; Costa, G.; Baciocchi, R. Assessment of Accelerated Carbonation
553
Processes for CO2 Storage Using Alkaline Industrial Residues. Ind. Eng. Chem. Res. 2013, 53,
554
9311.
555 556
(19) Lee, J. B.; Ryu, C. K.; Baek, J. I.; Lee, J. H.; Eom, T. H.; Kim, S. H. Sodium-Based Dry
557
Regenerable Sorbent for Carbon Dioxide Capture from Power Plant Flue Gas. Ind. Eng.
558
Chem. Res. 2008, 47, 4465.
559 560
(20) Pasquier, L. C.; Mercier, G.; Blais, J. F.; Cecchi, E.; Kentish, S. Reaction Mechanism for
561
the Aqueous-Phase Mineral Carbonation of Heat-Activated Serpentine at Low Temperatures - 24 -
ACS Paragon Plus Environment
Page 24 of 40
Page 25 of 40
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
562
Industrial & Engineering Chemistry Research
and Pressures in Flue Gas Conditions. Environ. Sci. Technol. 2014, 48, 5163.
563 564
(21) Hosseini, T.; Haque, N.; Selomulya, C.; Zhang, L. Mineral Carbonation of Victorian
565
Brown Coal Fly Ash Using Regenerative Ammonium Chloride–Process Simulation and
566
Techno-Economic Analysis. Appl. Energy 2016, 175, 54.
567 568
(22) Franchimont, A. P. N. On Sodium-Alkyl Carbonates. Proc. R. Neth. Arts Sci. 1909, 12,
569
303.
570 571
(23) Gallegos, A.; Shimazaki, T.; Oliva, R. M. Sodium Removal, Storage, and Requalification
572
of Components; Atomics International Div, 1974.
573 574
(24) Hirao, I.; Kito, T.; Funamoto, T.; Murakami, T.; Usami, K. Carboxylation of Phenol
575
Derivatives. XXII. Formation of Alkali Alkyl Carbonate by the O-Carboxylation of Alcohol
576
in the Presence of an Alkali Salt of a Weak Acid. Bull. Chem. Soc. Jpn. 1976, 49, 2775.
577 578
(25) Chandran, K.; Nithya, R.; Sankaran, K.; Gopalan, A.; Ganesan, V. Synthesis and
579
Characterization of Sodium Alkoxides. Bull. Mater. Sci. 2006, 29, 173.
580 581
(26) Chandran, K.; Kamruddin, M.; Ajikumar, PK.; Gopalan, A.; Ganesan, V. Kinetics of
582
Thermal Decomposition of Sodium Methoxide and Ethoxide. J. Nucl. Mater. 2006, 358, 111.
583 584
(27) Vacek, J. Alkali Metal Alcoholates There of. C.S. Patent 213,119, 1984.
585
- 25 -
ACS Paragon Plus Environment
Industrial & Engineering Chemistry 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
586
(28) Lin, P. H.; Wong, D. S. H. Carbon Dioxide Capture and Regeneration with
587
Amine/Alcohol/Water Blends. Int. J. Greenhouse Gas Control 2014, 26, 69.
588 589
(29) Alves, D. C.; Silva, R.; Voiry, D.; Asefa, T.; Chhowalla, M. Copper Nanoparticles
590
Stabilized by Reduced Graphene Oxide for CO2 Reduction Reaction. Mater. Renew. Sustain.
591
Energy 2015, 4, 1.
592 593
(30) Zhong, N.; Liu, H.; Luo, X.; Al-Marri, M. J.; Benamor, A.; Idem, R.; Tontiwachwuthikul,
594
P.; Liang, Z. Reaction Kinetics of Carbon dioxide (CO2) with Diethylenetriamine and 1-
595
Amino-2-propanol in Nonaqueous Solvents Using Stopped-Flow Technique. Ind. Eng. Chem.
596
Res. 2016, 55, 7307.
597 598
(31) Lide, D. R. CRC Handbook of Chemistry and Physics. 85th ed. CRC Press: Boca Raton,
599
FL, 2004.
600 601
(32) Han, S. J.; Yoo, M.; Kim, D. W.; Wee, J. H. Carbon Dioxide Capture Using Calcium
602
Hydroxide Aqueous Solution as the Absorbent. Energy Fuels 2011, 25, 3825.
603
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List of Tables
605 606
Table 1
607
Composition of C and H in the synthesized material, in pure sodium ethyl carbonate (SEC),
608
and in pure NaHCO3. Materials
Elemental composition (wt%) C
H
Pure SEC
32.14
4.46
Pure NaHCO3
14.29
1.19
Synthesized material
31.73
4.30
609
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610
List of Figures
611 612
Figure 1. Schematic diagram for sodium ethyl carbonate (SEC) synthesis via absorption of
613
CO2 in NaOH-dissolved ethanol solution. (1) CO2 cylinder, (2) N2 cylinder, (3) Mass flow
614
controller, (4) Gas mixer, (5) Temp controller, (6) Sparger, (7) Magnetic stirrer, (8) pH meter,
615
(9) EC meter, (10) pH/EC recorder, (11) Condenser, (12) Gas analyzer, and (13) Computer
616
used for data acquisition.
617 618
Figure 2. Theoretical and experimental amounts of CO2 absorbed to create the synthesized
619
material, sodium ethyl carbonate (SEC), in each solution.
620 621
Figure 3. XRD patterns of the precipitated substance generated by dissolving the synthesized
622
material, sodium ethyl carbonate (SEC), in excess water.
623 624
Figure 4. TGA results of the synthesized material, sodium ethyl carbonate (SEC).
625 626
Figure 5. XRD patterns of the thermally decomposed substance of the synthesized material,
627
sodium ethyl carbonate (SEC).
628 629
Figure 6. XRD patterns of the synthesized material, sodium ethyl carbonate (SEC), in the
630
high (a) and low (b) intensity zone.
631 632
Figure 7. XRD patterns of the synthesized material, sodium ethyl carbonate (SEC), exposed
633
to ambient air for two months. - 28 -
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634 635
Figure 8. SEM images of the synthesized material, sodium ethyl carbonate SEC: (a) upper
636
view and (b) side view.
637
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For Table of Contents Only
639
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Figure 1. Schematic diagram for sodium ethyl carbonate (SEC) synthesis via absorption of CO2 in NaOHdissolved ethanol solution. (1) CO2 cylinder, (2) N2 cylinder, (3) Mass flow controller, (4) Gas mixer, (5) Temp controller, (6) Sparger, (7) Magnetic stirrer, (8) pH meter, (9) EC meter, (10) pH/EC recorder, (11) Condenser, (12) Gas analyzer, and (13) Computer used for data acquisition. 217x142mm (96 x 96 DPI)
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Figure 2. Theoretical and experimental amounts of CO2 absorbed to create the synthesized material, sodium ethyl carbonate (SEC), in each solution. 130x127mm (300 x 300 DPI)
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Figure 3. XRD patterns of the precipitated substance generated by dissolving the synthesized material, sodium ethyl carbonate (SEC), in excess water. 151x114mm (300 x 300 DPI)
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Figure 4. TGA results of the synthesized material, sodium ethyl carbonate (SEC). 163x113mm (300 x 300 DPI)
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Figure 5. XRD patterns of the thermally decomposed substance of the synthesized material, sodium ethyl carbonate (SEC). 151x114mm (300 x 300 DPI)
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Figure 6. XRD patterns of the synthesized material, sodium ethyl carbonate (SEC), in the high (a) and low (b) intensity zone. 174x189mm (300 x 300 DPI)
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Figure 7. XRD patterns of the synthesized material, sodium ethyl carbonate (SEC), exposed to ambient air for two months. 154x114mm (300 x 300 DPI)
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Figure 8. SEM images of the synthesized material, sodium ethyl carbonate SEC: (a) upper view and (b) side view. 127x95mm (96 x 96 DPI)
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Industrial & Engineering Chemistry Research
Figure 8. SEM images of the synthesized material, sodium ethyl carbonate SEC: (a) upper view and (b) side view. 127x95mm (96 x 96 DPI)
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139x94mm (96 x 96 DPI)
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