One-Step Conversion of NaHCO3 into Formate and Simultaneous

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One-step conversion of NaHCO3 into formate and simultaneous synthesis of AlO(OH) from waste Al-can in water Zhenwei Ni, Heng Zhong, Yang Yang, Guodong Yao, Binbin Jin, and Fangming Jin ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.8b05681 • Publication Date (Web): 24 Feb 2019 Downloaded from http://pubs.acs.org on February 25, 2019

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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.

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ACS Sustainable Chemistry & Engineering

One-step conversion of NaHCO3 into formate and simultaneous synthesis of AlO(OH) from waste Al-can in water Zhenwei Ni a, Heng Zhong a,b,*,Yang Yang a, Guodong Yao a, Binbin Jin a, Fangming Jin a,b,c,* a School

of Environmental Science and Engineering, State Key Lab of Metal Matrix

Composites, Shanghai Jiao Tong University, 800 Dongchuan RD, Shanghai 200240, China b Shanghai

Institute of Pollution Control and Ecological Security, Shanghai 200092, P.R. China

c College

of Biological Chemical Science and Engineering, Jiaxing University, No.56, South Yuexiu Road, Jiaxing 314001, China

*Corresponding authors Heng Zhong: +86-21-54745410, [email protected] Fangming Jin: +86-21-54742283, [email protected]

ACS Paragon Plus Environment

ACS Sustainable Chemistry & Engineering 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: Developing a green and highly-efficient method for CO2 reduction into value-added chemicals with earth-abundant materials and facile hydrogen source is crucial to the practical application of CO2 conversion and utilization. In this study, a new method of reduction of NaHCO3, a model compound of CO2, to formate as a hydrogen storage material by splitting water with waste Al-can as a reductant is proposed. A formate yield up to 65% from bicarbonate was successfully obtained with waste raw Al-can strips as a reductant and water as a hydrogen source. The Al-can converted to powdered AlO(OH) with a surface area of 129.3 m²·g-1 after the reaction, which is a valuable substrate for preparing adsorbents, catalysts, and alumina-derived ceramics. The proposed method not only provides a simple and efficient way to reduce CO2 into value-added chemicals but also develops a new way to produce functional Al materials from waste Al-can.

KEYWORDS: CO2 conversion; waste Al-can; formate; hydrothermal reaction; kinetic conversion; AlO(OH)

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INTRODUCTION Global warming and climate change caused by the increasing concentration of CO2 in atmosphere have threatened the sustainable development of environment and human society [1]. Alleviating and reducing the risk caused by increasing atmospheric CO2 concentration has become a serious global issue that people have to face at present. Utilization of CO2 as a C1 feedstock to produce value-added chemicals is one promising technology to mitigate this problem. However, CO2 is a stable substance and its reduction usually requires large amounts of energy. In traditional method of CO2 hydrogenation, gaseous hydrogen is usually used as both hydrogen source and energy input [2, 3]. Since hydrogen gas is generally produced from fossil resources, the use of gaseous hydrogen requires large quantities of energy and is unsustainable. In addition, the use of gaseous hydrogen brings hydrogen storage, transportation and safety issues. Furthermore, methods of catalytic CO2 hydrogenation usually need elaborately prepared noble-metal catalysts, such as Pd, Au, Ir, Ru, Rh, etc., to activate the stable CO2 molecule

[4-9],

which is also not suitable for a green and sustainable

development. Recently, CO2 reduction with photochemical and electrochemical technologies have attracted increasing research interests, which can extract hydrogen from water as the hydrogen source and use renewable energies directly or indirectly for the CO2 reduction

[10-14].

Although these methods are promising, they are still far

from practical application due to their low yield and/or high cost. Therefore, developing new technologies for a green, sustainable, highly-efficient, and most

3



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importantly, practical way to reduce CO2 into value-added chemicals is still a great challenge and is of great interest. In the Earth’s crust and deep-sea hydrothermal vents, abiogenic organic syntheses via hydrothermal reactions are believed to have a critical relationship with the origin of life on Earth

[15, 16].

These processes involve the reduction of the

dissolved CO2 in high-temperature water to organics such as CH4, accompanying with hydrothermal alteration of minerals

[17, 18].

This natural phenomenon implies that the

reduction of CO2 into organics could be achieved with earth-abundant metals under hydrothermal conditions. Thus, in our previous research, we have investigated the reduction of CO2 with various zero-valent metals (Fe, Al, Mn, Zn, etc.) under hydrothermal conditions, and the results have shown that CO2 can be selectivity reduced to value-added chemicals such as formate and methane with high yields [19-22]. However, in these previous studies, pure commercial metal powders are used, which causes the concern for relatively high cost. On the other hand, the increasing consumption of canned food and beverage have led to a serious environmental problem of waste aluminum-can (Al-can) pollution. It has been reported that the production of Al-can reached 64 billion cans in 2015 in Europe, which led to serious environmental problems

[23].

However, effective and

suitable ways to treat these huge amounts of waste Al-cans are limited. It has been reported that the recycled Al-can is 69% in 2017

[24].

For the unrecycled Al-can, it is

usually treated as wastes and filled underground. Based on our previous researches [21, 25],

waste Al-can is a promising resource for hydrogen production from 4


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high-temperature water (HTW) to reduce CO2 into value-added chemicals such as formate. Formate is one of the basic organic chemical raw materials, widely being used in the pesticides, leather, dyes, medicine and rubber industries. Recently, formate or formic acid is regarded as a promising hydrogen storage material due to its relatively high hydrogen capacity, high stability, low-toxicity, low-flammability, and biodegradability

[26-28].

If CO2 could be efficiently reduced to formate with waste

Al-can as the reducing agent and water as the hydrogen source, a facile economical method for hydrogenation of CO2 with the abundant waste metal pollutants can be developed. Furthermore, in our previous research, we have successfully demonstrated that CO2 can be reduced into formate with commercial-available Al powder, in which Al has been converted to AlO(OH) after the reaction

[25].

However, in that previous

research, only CO2 conversion was focused. It is known that AlO(OH) is an important precursor for preparation of adsorbents, catalysts, membranes, alumina and alumina-derived ceramics in the industry given to its large surface area and mesoporous structure

[29-31].

However, traditional methods for AlO(OH) synthesis

requires morphological inductive agents, otherwise, the morphology features of AlO(OH) are not in good shape and the pore structure cannot be easily changed through different reaction conditions

[32].

Since Al is converted into AlO(OH) during

the reaction of CO2 with waste Al-can in high-temperature water, the presented research would propose a new method for the AlO(OH) synthesis with waste materials. Compared to our previous report

[25],

the presented research substitutes the

5



commercial Al reagent with waste Al-can and focused not only the conversion of CO2 to formate but also the synthesis of functional material of AlO(OH). Thus, this research can not only provide a simple and efficient way to reduce CO2 into value-added chemicals with waste materials but also develop a new way to produce functional Al materials from waste Al-can.

EXPERIMENTAL Materials. Commercial-available empty can (Pepsi) was employed as the sample material. NaHCO3 was used as the CO2 source to simplify the experiments and to calculate the amount of carbon source accurately. NaHCO3 powder (99.5%), NaOH flake (96%) and formic acid (AR, 98%) were purchased from Sino-pharm Chemical Regent Co., Ltd and were used without further treatment. Deionized water was used through all this study. Experimental Procedures. A series of stainless steel (Swagelok, SUS316) tubular reactors (120 mm length, 3/8 inch o.d.) with end fittings were used throughout this study, which provided an inner volume of 5.7 ml and the scheme can be found in our previous report

[25].

For a typical reaction process, 1 mmol of NaHCO3, 1 – 11

mmol of Al-can strips (the raw Al-can were cut into small strips with a width of 3-4 mm and a length of 60-80 mm), and 2 mL deionized water was loaded into the reactor. Then the reactor was sealed and put into an isothermal oven which had been preheated to the desired temperature. After the reaction, the reactor was taken out of the oven and cooled down to room temperature in a cold-water bath. Liquid samples were collected after being filtered through a 0.22 μm syringe filter. Solid samples 6


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were washed with deionized water and ethanol for 3 times following by vacuum drying at 313 K for 3-5 h before further analysis. Product Analysis. Liquid samples were analyzed by high-performance liquid chromatography (HPLC, Agilent 1260) analyzer equipped with two Shodex RSpak KC-811 columns in series and a refractive index detector (RID). The mobile solvent of the HPLC was 2 mmol·L-1 HClO4 with a flow rate of 1.0 mL·min−1. Solid samples were characterized by X-ray diffraction (XRD) using a Shimadzu XRD-6100 X-ray diffractometer with a rate of 2 degree·min-1. Scanning electron microscopy (SEM) images were obtained with a FEI Sirion-200 field-emission scanning electron microscope operating at an electric voltage of 5 kV. The specific surface area of the solid samples was calculated by applying Brunauer – Emmett – Teller (BET) equation on a BET analyzer (ASAP 2020 PLUS HD88). The sample for BET analysis was pretreated at 523 K for 6 h before the analysis. Element analysis of carbon deposition on AlO(OH) was performed on an elemental analyzer (Vario EL Cube) with helium as the carrier gas. Formate yield was defined as the percentage of formate to the initial bicarbonate on the carbon basis (Eq. (1)). carbon in produced formate, mmol mmol

𝑌𝑖𝑒𝑙𝑑 (%) = carbon in the initial NaHCO3,

× 100%

(1)

Water filling rate, which is defined as the ratio of the volume of the water injected into the reactor to the total inner volume of the reactor, was used to denote the water amount used in the reaction.

7



RESULTS AND DISCUSSION Verification of the Formate Production from NaHCO3 with Al-can. First, to examine whether HCO3– can be reduced by waste Al-can in HTW, experiments were carried out with NaHCO3 and Al-can strips at different temperatures. As illustrated in Figure 1, no formate production was observed at temperatures below 523 K. Interestingly, the formate yield increased sharply from almost 0 at 523 K to 58.8% at 573 K. Further increasing the temperature over 573 K did not lead to higher formate yield, suggesting that a reaction equilibrium was reached. From the HPLC chromatogram (Figure 2), only formate peak was observed except for the solvent peak, indicating no formation of other liquid products. To further examine the effect of reaction temperature, solid samples after the reaction at 423, 473, 523 and 573 K were analyzed by XRD (Figure 3). Results revealed that, Al remained as in zero-valent state at temperatures below 473 K, indicating that Al was not oxidized in HTW at these temperatures. However, when the reaction temperature exceeded 523 K, Al peaks disappeared while AlO(OH) peaks were observed from the XRD pattern, indicating that the Al converted to AlO(OH) after the reaction at temperatures over 523 K. These results suggest that a certain reaction temperature was required for the oxidation of waste Al-can with HTW to produce H2 for the HCO3– reduction. The details of the H2 production from the reaction of Al with hot water can be found in our previous report

[25].

It should be noted that the amorphous peaks observed at 423 K

and 473 K in the XRD patterns was probably attributed to the organic film covering on the surface of Al-can. 8


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70 60

Yield of formate (%)

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


50 40 30 20 10 0 400

450

500

550

600

650

Reaction temperature (K)

Figure 1. Effect of reaction temperature on the yield of formate (1 mmol NaHCO3, 9 mmol Al-can strips, 2 mL H2O, 2 h).

Formic acid

Solvent peak

0

5

10

15

20

25

30

Retention time (min)

Figure 2. HPLC chromatogram of liquid sample after the reaction with 1 mmol NaHCO3 and 9 mmol Al-can strips in 2 mL H2O at 573 K for 2 h.

9



Figure 3. XRD patterns of initial Al-can strips and the solid samples after reactions at different temperatures (1 mmol NaHCO3, 9 mmol Al-can strips, 2 mL H2O, 2 h). For the mechanism of AlO(OH) formation, it can be found in detail in our previous report

[25],

only a briefly explanation is given here. As shown in Scheme 1,

Al first reacts with high-temperature water molecule, forming HAlOH, which then converts to Al(OH)2 after reacting with HCO3-. Since Al(OH)2 is very unstable, it undergoes dehydration to form AlO(OH) under the attack of OH– in the solution.

Scheme 1. Proposed mechanism of AlO(OH) formation during the reaction of Al with high-temperature water and NaHCO3.

Reaction Characteristics and Optimization of Reaction Conditions for Formate Production. Subsequently, a series of experiments were conducted over a wide range of different reaction conditions by changing the concentration of reactant, 10


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reaction time, PH, etc to study the reaction characteristics, and optimizing reaction conditions for formate production. First, effect of the water filling rate on the formate yield was investigated. As results summarized in Figure 4, the formate yield slightly increased from 52.6% at 25% water filling rate to 58.8% at 35% water filling rate. Further increasing the water filling rate did not obviously affect the formate yield. 70 60


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


50 40 30 20 10 0 20

25

30

35

40

45

50

55

60

Water filling rate (%)

Figure 4. Effect of water filling rate on the yield of formate (9 mmol Al-can strips, 1 mmol NaHCO3, 2 h, 573 K).

Next, the effect of reactant amount on the formate yield was investigated. Results revealed that the formate yield increased from 46.1% to 58.8% when the NaHCO3 amount ascended from 0.5 to 1.0 mmol (Figure 5 (a)). When further increasing the NaHCO3 amount to 2.0 mmol, the formate yield remained relatively stable. For the effect of Al-can amount, the formate yield increased incessantly with the Al-can amount and a 58.8% formate yield was obtained at the Al amount of 9 mmol (Figure 5 (b)). However, an excess amount of Al led to a slight decrease in the yield of formate.

11



Then, effect of reaction time on the formate yield was examined and the results are depicted in Figure 5 (c). The yield of formate was less than 1% when the reaction time was 10 min. However, an appreciably augment of the formate yield to 48% was observed when the reaction time increased to 30 min. These results suggest that the hydrothermal reduction of NaHCO3 requires an initiating stage, which is probably attributed to the reaction of Al with HTW to produce H2. Further prolonging the reaction time to 2 h only led to a slight enhancement of the formate yield to 58.8%. It is well known that the state of HCO3– in aqueous solution is strongly affected by the pH of the solution

[33].

It has also been reported that the pH can affect the Al

oxidation and the selective formate formation

[20, 25].

Thus, the pH of the reaction

solution probably has a significant effect on the formate yield in the presented research. Therefore, effect of pH of the solution on formate yield was studied by adjusting the pH of the starting solution with various amount of NaOH. Results revealed that the formate yield first increased with the NaOH concentration and then decreased sharply when the NaOH concentration exceeding 0.1 mol·L-1 (Figure 5 (d)). The optimum formate yield of 65% was obtained with the addition of 0.1 mol · L-1 NaOH (pH was about 8.6). This is probably because that a moderate amount of OHcan promote the Al oxidation to produce H2 in HTW for the bicarbonate reduction and results in the formation of formate as the product. Formate is more stable and difficult to decompose than formic acid under hydrothermal conditions [34, 35]. However, a high OH– concentration would lead to a transformation of HCO3– to CO32–, which makes it more difficult to generate formate. For verification, the reaction equations of the 12


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conversion of HCO3– to CO32– to formate with Al and water were summarized in Eqs. (2) and (3). 2Al +3Na2CO3 + 4H2O = 2AlO(OH) + 3HCOONa +3NaOH

(2)

2Al + 3NaHCO3 + H2O = 2AlO(OH) + 3HCOONa

(3)

The Gibbs free energies of Eqs. (2) and (3) at 573 K were calculated to be -614.5 kJ·mol-1 and -799.1 kJ·mol-1 respectively by using HSC-Chemistry. According to this result, conversion of HCO3– to HCOO- is more spontaneous than the conversion of CO32– to HCOO-, and it is consistent with the experimental results as discussed above. In addition, formate has been reported to be easy to decompose under high alkaline conditions [36]. As a result, a moderate basic pH of the solution (about 8.6) is crucial to obtain high formate yield in the reduction of HCO3–.

70

70

(a)

50 40 30 20 10 0 0.0

(b)

60



60

0.5

1.0

1.5

2.0

50 40 30 20 10 0

2.5

0

2

NaHCO3 amount (mmol) 70

(c)

60


60 50 40 30 20 10 0 0.0

0.5

1.0

1.5

2.0

2.5

4

6

8

10

12

Al-can strips amount (mmol)

70


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


50

8.6 8.3

Reaction time (h)

(d) 13.8

40

>14

30 20 10 0 0.0

3.0

13.1

0.5

1.0

1.5

NaOH(mol/L)

13


2.0

2.5


Figure 5. Effect of NaHCO3 amount ((a): 9 mmol Al-can strips, 2 mL H2O, 2 h and 573 K), Al-can strips amount ((b): 1 mmol NaHCO3, 2 mL H2O, 2 h and 573 K), reaction time ((c): 9 mmol Al-can strips, 1 mmol NaHCO3, 2 mL H2O and 573 K), and pH value ((d): 9 mmol Al-can strips, 1 mmol NaHCO3, 2 h and 573 K, numbers beside the symbols represent the pH value) on the yield of formate. Effect of Surface Organic Film on NaHCO3 Reduction into the Formate. The Al-cans sold on the market for the canned food and beverage are usually coated with an organic film on the surface, which might affect the oxidation of Al-can in HTW and thus influence the NaHCO3 reduction. To investigate the effect of the surface organic film, Al-can samples with organic film polished off (denoted as Alpolish) by an abrasive paper (W10, 800 mesh) was prepared and its effect on the formate yield was examined. As shown in Figure 6, the formate yield obtained from Al-can with and without organic film had no apparent differences, indicating that the surface organic film has no obvious effect on the reduction of bicarbonate to formate. Also, the effect of Al-can cutting into small particles with a scissor (denoted as Alparticle, with a size of 4-6 mm) on the formate production was studied. As a result, when the reaction was 2 h, no apparent difference in the formate yield was observed between the Alparticle sample and the Al-can strips (see Figure 6). However, when the reaction decreased to 30 min, the formate yield obtained on Alparticle was higher than that obtained with the Alstrip. These results indicate that cutting the Al to particles led to an increase in the surface area of Al compared to the Alstrip, which results in a promotion of the reaction rate. However, the surface area of Al does not affect the 14


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reaction equilibrium since the starting Al amount was the same. These results are of great significance in large-scale industrial application since using the raw Al-can without complicated pretreatment can significantly simplify the process and decrease the cost. 70

2h 30 min

60


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


50 40 30 20 10 0

Alparticle Alstrip Alpolish Al-can with different pretreatments

Figure 6. Effect of different pretreatment of Al-can on the formate yield after 30 min or 2 h reaction. (9 mmol Al-can, 1 mmol NaHCO3, 2 mL H2O, 573 K). Characterization of the AlO(OH) Product. Figure 7 (a) and (b) show the photographs of Al-can strips before the reaction and the solid samples after the bicarbonate reduction reaction, respectively. As already discussed in Figure 3, this solid powder after the reaction was AlO(OH). These results indicate that although Al-can strips were used in the hydrothermal reduction of bicarbonate to formate, the Al converted to powdered AlO(OH) after the reaction. Then, SEM analysis of the Al-can strips before reaction and AlO(OH) powder after the reaction were performed. 15



It can be seen from Figure 7 (c) that a relatively smooth surface structure of the Al-can strips was observed. However, interestingly, a clear rod-like structure was formed for the AlO(OH) powder after the reaction (Figure 7 (d) and (e)). AlO(OH) is an important precursor for preparation of adsorbents, catalysts, membranes, alumina and alumina-derived ceramics in industry given to its large surface area and mesoporous structure [29-31]. Thus, surface area of the AlO(OH) after the reaction was further checked by BET analysis. Based on the N2 adsorption-desorption isotherms (Figure 8), results revealed that the surface area of AlO(OH) was 96.9 m²·g-1. It has been reported that the surface area of an AlO(OH) sample specifically synthesized at low temperature (248 K) is 101.7 m² · g-1

[37].

Compared with this result, the surface

area of the AlO(OH) obtained in the presented research is competitive. Since the Al-can usually coated with an organic film, which might lead to a carbon deposition on the produced AlO(OH) after the reaction. The AlO(OH) sample obtained from Alstrip after the reaction was subjected to element analysis, and the result revealed that only 0.63% of carbon was detected, suggesting the carbon deposition is negligible. To further investigate the effect of Al-can pretreatment on the formed AlO(OH), BET surface areas, pore volumes and pore diameters of the AlO(OH) samples obtained from Alstrip, Alparticle, and Alpolish were analyzed and compared. As summarized in Table 1, the surface areas, pore volumes, and pore diameters of Alstrip and Alpolish were similar, suggesting polishing the Al to remove the organic film does 16


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not obviously affect the produced AlO(OH). However, the surface area and pore volume of Alparticle was larger than those of Alstrip and Alpolish, which indicates that cutting the Al-can into particles is effective to promote the surface area and pore volume of the obtained AlO(OH).

Table 1. Surface area, pore volume and pore diameter of AlO(OH) samples obtained from different starting materials a Surface area/m²·g-1

Pore volume/cm³·g-1

Pore diameter/nm

Alstrip

96.9

0.15

6.8

Alpolish

89.0

0.18

6.7

Alparticle

129.3

0.24

6.2

Starting material

a Reaction

conditions: 9 mmol starting material (Alstrip or Alpolish or Alparticle), 1

mmol NaHCO3, 2 mL water, 573 K, 2 h.

Thus, the presented research provided not only a simple and efficient method to reduce bicarbonate to formate with water as the hydrogen source but also demonstrated a new strategy for hydrothermal synthesis of AlO(OH) material with a high surface area from waste Al-can materials.

17



Figure 7. (a): photo of Al-can strips before reaction; (b): photo of AlO(OH) powder after reaction; (c): SEM image of the initial raw Al-can strips; (d) and (e): SEM images of AlO(OH) powder after reaction (9 mmol Al-can strips, 1 mmol NaHCO3, 0.1 mol·L-1 NaOH, 2 mL water, 2 h, 573 K).

18


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100

120

Quantity Adsorbed (cm /g STP)

(a) 80

3

3


60 40 20 0 0.0

0.2

0.4

0.6

0.8

1.0

Relative Pressure (P/Po)

100

(b)

80 60 40 20 0 0.0

0.2

0.4

0.6

0.8

1.0


160

(c)

140 120

3


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


100 80 60 40 20 0 0.0

0.2

0.4

0.6

0.8

1.0


Figure 8. N2 adsorption–desorption isotherms of AlO(OH) obtained from (a) Alstrip, (b) Alpolish, and (c) Alparticle. Kinetic Study of HCO3- Reduction to HCOO-. Based on the above experimental results and our previous studies, the overall reaction equation for the hydrothermal reduction of HCO3- into HCOO- with Al-can as the reductant in HTW can be summarized as in Eq. (3). Thus, the reaction rate of HCO3- conversion is v= - d[HCO3-] / dt = k[HCO3-]

(4)

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where v is the reaction rate, [HCO3-] is the concentration of HCO3- in the solution, k is the reaction rate constant at a given temperature, and t is the reaction time. Then, by integrating Eq. (4), one can obtain ln [HCO3-] = - kt + c

(5)

Based on this equation, variation of ln [HCO3–] versus reaction time at 553, 563, 573 and 583 K and their linear fittings are plotted in Figure 9 (a). From the slope of the linear fittings, the reaction rate constants (k) were calculated to be 0.0009, 0.0021, 0.0207, 0.0851 s-1 at 553, 563, 573 and 583 K, respectively. According to the Arrhenius equation, ― 𝐸𝑎

(6)

𝑘 = 𝐴𝑒 𝑅𝑇

where A is the pre-exponential factor and Ea is the activation energy, after taking the natural logarithm of both sides of Eq. (6), one can obtain

ln𝑘 =

― 𝐸𝑎 𝑅𝑇

(7)

+ln𝐴

Thus, the activation energy (Ea) can be derived from the slope of the lnk versus 1/T. As illustrated in Figure 9 (b), the activation energy of the reduction of NaHCO3 into HCOONa was calculated to be 50.6 kJ·mol-1.

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-2

6.4

(b)

(a)

-1

553 K 563 K 573 K 583 K

lnk = -51329 T + 85.498 2 R = 0.9706

-4 -1

-

6.0

-3

lnk (s )

6.2

ln[HCO3 ]

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


-5 -6

5.8

-7 5.6 10

12

14

16

18

-8 0.00170

20

0.00172

Time (min)

0.00174

0.00176

0.00178

0.00180

0.00182

-1

1/T (K )

Figure 9. (a): Variations of ln[HCO3-] versus time and their liner fittings obtained in the reduction of bicarbonate to formate at different temperatures (9 mmol Al-can strips, 1 mmol NaHCO3, 2 mL H2O); (b): Variations of lnk versus 1/T and its liner fitting. Finally, a brief economic analysis was made according to Equation (3) and the market prices of reactants and products shown in Table 2. When using the result of the formate yield of 65%, 1 mol Al with 1.5 mol NaHCO3 would lead to a production of 1 mol AlO(OH) and 0.975 (1.5 × 0.65) mol HCOONa. If ignoring the reaction cost, the reactant cost is 1×27×0.125+1.5×84×0.03=7.16 RMB, and the product value is 1×60×0.7+1.5×68×0.128×0.65=50.49 RMB. Therefore, the profit is considerable, and the proposed method is economic.

21



Table 2. Market price of reactants and products in the proposed process Material

Price (RMB/g)

Producer and product number

Al-can

0.125

Pepsi Co., Inc

NaHCO3

0.03

HCOONa

0.128

Sinopharm Chemical Reagent Co., Ltd (10018960-500g) Sinopharm Chemical Reagent Co., Ltd (30166918-500g) Shanghai Macklin Biochemical

AlO(OH)

0.7

Co., Ltd (B861547-500g）

CONCLUSIONS In this study, a new method of converting bicarbonate to formate using water as a facile hydrogen source and simultaneous synthesis of AlO(OH) with a high surface area from waste Al-can was proposed. A formate yield up to 65% from the bicarbonate was successfully obtained at 573 K for 2 h. Surface organic film of the Al-can has no obvious effect on the formate yield, which is crucial to simplify the reaction procedure and is significant to practical applications. The Alpartlce converted to powdered AlO(OH) with a surface area of 129.3 m²·g-1 after the reaction, which is competitive to those specially prepared AlO(OH) samples in previous reports. The activation energy of NaHCO3 reduction to HCOONa was 50.6 kJ · mol-1. This study provided an experimental basis for the industrial reuse of waste Al-can and an economical and effective way to reduce the CO2.

ACKNOWLEDGEMENTS

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The authors gratefully acknowledge the financial support from the State Key Program of National Natural Science Foundation of China (No. 21436007), and the National Key R& D Program of China (2017YFC 0506004).

REFERENCES 1. Nejat, P.; et al. A global review of energy consumption, CO2 emissions and policy in the residential sector (with an overview of the top ten CO2 emitting countries). Renewable and Sustainable Energy Reviews, 2015, 43, 843-862. 2. Bulushev, D.A. and J.R.H. Ross. Heterogeneous catalysts for hydrogenation of CO2 and bicarbonates to formic acid and formates. Catalysis Reviews, 2018, 60 (4), 566-593. 3. Saeidi, S.; et al. Mechanisms and kinetics of CO2 hydrogenation to value-added products: A detailed review on current status and future trends. Renewable and Sustainable Energy Reviews, 2017, 80, 1292-1311. 4. Panagiotopoulou, P. Hydrogenation of CO2 over supported noble metal catalysts. Applied Catalysis A: General, 2017, 542, 63-70. 5. Azua, A.; S. Sanz.; E. Peris. Water-soluble IrIII N-heterocyclic carbene based 23



Page 24 of 27

catalysts for the reduction of CO2 to formate by transfer hydrogenation and the deuteration of aryl amines in water. Chemistry, 2011, 17 (14), 3963-3967. 6. Gogate, M.R.; R.J. Davis. Comparative study of CO and CO2 hydrogenation over supported Rh–Fe catalysts. Catalysis Communications 2010, 11, 901-906. 7. Upadhyay, P.; V. Srivastava. Synthesis of Monometallic Ru/TiO2 Catalysts and Selective Hydrogenation of CO2 to Formic Acid in Ionic Liquid. Catalysis Letters, 2015, 146 (1), 12-21. 8. Zhong, H.; et al. Interconversion between CO2 and HCOOH under Basic Conditions Catalyzed by PdAu Nanoparticles Supported by Amine-Functionalized Reduced Graphene Oxide as a Dual Catalyst. ACS Catalysis, 2018, 8 (6), 5355-5362. 9. Li, N.; et al. Enhanced Photocatalytic Performance toward CO2 Hydrogenation over Nanosized TiO2-Loaded Pd under UV Irradiation. The Journal of Physical Chemistry C, 2017, 121 (5), 2923-2932. 10. Wu, J.; et al. CO2 Reduction: From the Electrochemical to Photochemical Approach. Advanced Science, 2017, 4 (11), 1700194. 11. Bonin, J.; A. Maurin.; M. Robert. Molecular catalysis of the electrochemical and photochemical reduction of CO2 with Fe and Co metal based complexes. Recent advances. Coordination Chemistry Reviews, 2017, 334, 184-198. 12.

Kim,

C.;

et

al.

Insight

into

Electrochemical

CO2

Reduction

on

Surface-Molecule-Mediated Ag Nanoparticles. ACS Catalysis, 2016, 7 (1), 779-785. 13. Chu, S.; et al. Photoelectrochemical CO2 Reduction into Syngas with the Metal/Oxide Interface. Journal of the American Chemical Society, 2018, 140 (25), 7869-7877. 14. Sato, S.; T. Arai.; T. Morikawa. Toward Solar-Driven Photocatalytic CO2 Reduction Using Water as an Electron Donor. Inorganic Chemistry, 2015, 54 (11), 5105-5113. 15. Etiope, G.; B. Sherwood Lollar. Abiotic Methane on Earth. Reviews of Geophysics, 2013, 51 (2), 276-299. 16. Foustoukos, D.I.; W.E.S. Jr. Hydrocarbons in Hydrothermal Vent Fluids The Role 24


Page 25 of 27 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


of Chromium-Bearing Catalysts. Science, 2004, 304 (5673), 1002-1005. 17. MCCOLLOM, T.M.; J.S. SEEWALD. A reassessment of the potential for reduction of dissolved CO2 to hydrocarbons during serpentinization of olivine. Geochimica et Cosmochimica Acta, 2001, 65 (21), 3769-3778. 18. McCollom, T.M.; J.S. Seewald. Experimental constraints on the hydrothermal reactivity of organic acids and acid anions: I. Formic acid and formate. Geochimica et Cosmochimica Acta, 2003, 67 (19), 3625-3644. 19. Duo, J.; et al. NaHCO3- enhanced hydrogen production from water with Fe and in situ highly efficient and autocatalytic NaHCO3 reduction into formic acid. Chemical Communications, 2016, 52 (16), 3316-3319. 20. Lyu, L. et al.; No catalyst addition and highly efficient dissociation of H2O for the reduction of CO2 to formic acid with Mn. Environmental Science & Technology, 2014, 48 (10), 6003-6009. 21. Jin, F.; et al. High-yield reduction of carbon dioxide into formic acid by zero-valent metal/metal oxide redox cycles. Energy & Environmental Science, 2011, 4 (3), 881-884. 22. Zhong, H.; et al. Selective conversion of carbon dioxide into methane with a 98% yield on an in situ formed Ni nanoparticle catalyst in water. Chemical Engineering Journal, 2019, 357, 421-427. 23. Stotz, P.M.; et al. Environmental screening of novel technologies to increase material circularity: A case study on aluminium cans. Resources, Conservation and Recycling, 2017, 127, 96-106. 24. Can Manufacturers Institute. http://www.cancentral.com/media/news/cans-aremost-recycled-drinks-package-world (Accessed at December 25, 2018). 25. Yao, G.; et al. Hydrogen production by water splitting with Al and in-situ reduction of CO2 into formic acid. International Journal of Hydrogen Energy, 2015, 40 (41), 14284-14289. 26. Jiang, H.L.; et al. Liquid-phase chemical hydrogen storage: catalytic hydrogen generation under ambient conditions. ChemSusChem, 2010, 3 (5), 541-549. 25



27. Mellmann, D.; et al. Formic acid as a hydrogen storage material - development of homogeneous catalysts for selective hydrogen release. Chemical Society Reviews, 2016, 45 (14), 3954-88. 28. Zhong, H.; et al. Formic Acid-Based Liquid Organic Hydrogen Carrier System with Heterogeneous Catalysts. Advanced Sustainable Systems, 2018, 2 (2), 1700161. 29. Milanović, M.; et al. Nanocrystalline boehmite obtained at room temperature. Ceramics International, 2018, 44 (11), 12917-12920. 30. Wu, X.; B. Zhang.; Z. Hu. Large-scale and additive-free hydrothermal synthesis of lamellar morphology boehmite. Powder Technology, 2013, 239, 155-161. 31. Xu, D.; H. Jiang.; M. Li. A novel method for synthesizing well-defined boehmite hollow microspheres. Journal of Colloid and Interface Science, 2017, 504, 660-668. 32. Tang, Z.; et al. Synthesis of flower-like Boehmite (γ-AlOOH) via a one-step ionic liquid-assisted hydrothermal route. Journal of Solid State Chemistry, 2013, 202, 305-314. 33. Zhong, H.; et al. Effect of CO2 Bubbling into Aqueous Solutions Used for Electrochemical Reduction of CO2 for Energy Conversion and Storage. The Journal of Physical Chemistry C, 2014, 119 (1), 55-61. 34. Amuthambigai, C.; C.K. Mahadevan.; X. Sahaya Shajan. Growth, optical, thermal, mechanical and electrical properties of anhydrous sodium formate single crystals. Current Applied Physics, 2016, 16 (9), 1030-1039. 35. Savage, P.E. Organic Chemical Reactions in Supercritical Water. Chemical Reviews, 1999, 99, 603-621. 36. Yasaka, Y.; et al. Kinetic and Equilibrium Study on Formic Acid Decomposition in Relation to the Water-Gas-Shift Reaction. The Journal of Physical Chemistry A, 2006, 110, 11082-11090. 37. Yang, Y.; et al. Effects of synthetic conditions on the textural structure of pseudo-boehmite. Journal of Colloid and Interface Science, 2016, 469, 1-7.

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TOC

TOC graphic Synopsis: The present work provides an experimental basis for the industrial treatment of waste Al-can and an economical and effective way to reduce CO2.

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One-Step Conversion of NaHCO3 into Formate and Simultaneous

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