Carbon dioxide conversion into the reaction intermediate sodium formate for the synthesis of formic acid

Article abstract of DOI:10.1007/s11164-020-04255-z

Increased carbon dioxide (CO₂) emissions from anthropogenic activities are a contributing factor to the growing global warming worldwide. The economical method to recover and effectively reuse CO₂ is through adsorption and absorption. In this study, CO₂ is absorbed into the solution of sodium hydroxide having various concentrations (0.01, 0.1, 0.5, 1.0, 3.0 and 5.0?N), and the impact of the solution pH on the various product formation was observed. The resultant products formed at different pH of the absorbing solution are sodium carbonate at pH 10, Trona at pH 9, and sodium hydrogen carbonate at pH 8. The products formed are confirmed through X-ray diffraction analysis. After pH optimization, the sodium hydrogen carbonate formed at pH 8 is converted into sodium formate through hydrogenation in the presence of nickel ferrite catalyst at 80 °C and atmospheric pressure. The sodium formate produced is then used as a precursor to synthesize formic acid upon simple reaction with sulfuric acid. A reaction % age yield of 79 ± 0.2% formic acid is noted. Condensed formic acid vapors are later analyzed, using a high performance?liquid chromatography for the qualitative analysis.

Full text of DOI:10.1007/s11164-020-04255-z

Research on Chemical Intermediates
https://doi.org/10.1007/s11164-020-04255-z
Carbon dioxide conversion into the reaction intermediate
sodium formate for the synthesis of formic acid
Muhammad Hanan Masood · Noor Haleem · Iqra Shakeel · Yousuf Jamal1
1
1
1,2
Received: 9 April 2020 / Accepted: 20 August 2020
©
Springer Nature B.V. 2020
Abstract
Increased carbon dioxide (CO ) emissions from anthropogenic activities are a con-
2
tributing factor to the growing global warming worldwide. The economical method
to recover and eꢀectively reuse CO is through adsorption and absorption. In this
2
study, CO is absorbed into the solution of sodium hydroxide having various con-
2
centrations (0.01, 0.1, 0.5, 1.0, 3.0 and 5.0 N), and the impact of the solution pH on
the various product formation was observed. The resultant products formed at diꢀer-
ent pH of the absorbing solution are sodium carbonate at pH 10, Trona at pH 9, and
sodium hydrogen carbonate at pH 8. The products formed are conꢁrmed through
X-ray diꢀraction analysis. After pH optimization, the sodium hydrogen carbonate
formed at pH 8 is converted into sodium formate through hydrogenation in the pres-
ence of nickel ferrite catalyst at 80 °C and atmospheric pressure. The sodium for-
mate produced is then used as a precursor to synthesize formic acid upon simple
reaction with sulfuric acid. A reaction % age yield of 79± 0.2% formic acid is noted.
Condensed formic acid vapors are later analyzed, using a high performance liquid
chromatography for the qualitative analysis.
Keywords Carbon dioxide absorption · Sodium carbonate · Sodium hydrogen
carbonate · Sodium formate · Nickel ferrite · Formic acid
*
Yousuf Jamal
yousuf.jamal@iese.nust.edu.pk
1
Institute of Environmental Sciences and Engineering (IESE), School of Civil and Environmental
Engineering (SCEE), National University of Sciences and Technology (NUST), Sector H-12,
Islamabad 44000, Pakistan
2
School of Chemical and Materials Engineering (SCME), National University of Sciences
and Technology (NUST), Sector H-12, Islamabad 44000, Pakistan
Vol.:(012
1
3456789)
3

M. H. Masood et al.
Introduction
CO from industrial, transportation and other anthropogenic activities is increas-
2
ing all over the world causing global warming. CO in the atmosphere, mostly
2
comes from the generation of electricity from coal, furnace oil, diesel and gas-
oline burning at industries along with biomass burning by humans [1]. CO is
2
one of the greenhouse gases and is a major concern to the environment. With
the increase in population and modernization in lifestyle, energy demand is con-
tinually increasing. To meet these energy demands, many industrial processes are
carried out on a daily basis [2, 3]. The reported threshold concentration of carbon
dioxide in the atmosphere is 350 ppm [4], but due to an increase in energy gen-
eration, this value is increasing daily. It has been reported that between 1880 and
2
012, the overall average temperature of the globe has increased by 0.85° C [5].
Furthermore, carbon dioxide gas emissions are aꢀecting human life on earth in
the form of irregular weather patterns, polar ice caps depletion and glaciers melt-
ing [6]. In order to reduce the carbon dioxide concentration of the open atmos-
phere, several separation techniques have been opted [7]. Removed CO can also
2
be recycled and reused to produce various fuels or chemicals [8, 9]. The commer-
cially utilized carbon dioxide separation techniques are the CO adsorption on a
2
solid catalyst surface [10], absorption in the chemical solvents [11] and ionic liq-
uids [12]. The primary advantage of practicing absorption technique over a large
scale is that the utilized solvent chemical can be rejuvenated by the simple heat-
ing at high temperatures and/or by depressing the system pressures.
Normally, the absorption of CO at source in industries is done by amine
2
scrubbing with chemicals like alkanolamines [13]. Various types of amines that
can be used for absorption are: primary amine or monoethanolamine (MEA),
secondary amine or diethanolamine (DEA), tertiary amine or N-methyl dietha-
nolamine (MDEA), cyclic amine piperazine (PZ) and sterically hindered amines
like 2-amino-2-methyl-1-propanol (AMP) [14]. Alkali metal solutions have also
shown promising trades in the carbon dioxide absorption process. Some of the
beneꢁts of alkali solutions are the multi-reaction by-product formation [15, 16],
whereas there are no reaction products are produced in the case of CO absorption
2
in the amine solutions [17], thus resulting in no value added by reaction products.
During the process of carbon dioxide gas absorption, phase transformation
over a heterogeneous catalyst has also been reported to reduce its concentration in
the industrial exhausts. Christopher et al. [18] have shown carbon dioxide trans-
formation into organic compounds by intermolecular transfer of hydrogen from
metallic hydrogen carbonate solutions, using complex catalysts. Hydrogenation is
an endothermic process that requires high reaction temperatures. Many expensive
catalysts are reported for use in the hydrogenation process like palladium (Pd),
ruthenium (Ru) and rhenium (Re). The presence of these catalysts reduces the
reaction temperatures.
Nickel (Ni) has gained importance for the CO reduction in various chemi-
2
cals at low temperatures [19]. It is most abundant and inexpensive metal. Due to
high activity and high surfaces-to-volume ratio and its nontoxic characteristic,
1
3

Carbon dioxide conversion into the reaction intermediate…
nickel has been used in the hydrogenation reactions. Nickel-based nanoparticles
facilitate the reactions in the production of formates. Due to these characteris-
tics, nickel has become the preferred option to use as a metal catalyst [20]. Chen
et al. [21] have reported the synthesis of organic acids by the reduction of sodium
hydrogen carbonate using Ni powder catalyst supported with hydrazine mono-
hydrate (N H ·H O), as a reductant and reported a 50% reaction yield of formic
2
4
2
acid at 300° C. Wang et al. [22] has studied the hydrogenation of carbonate solu-
tions by using a nonporous Ni catalyst and have reported 86.6% yield of formic
acid from sodium hydrogen carbonate (NaHCO ) at 200° C. Chiang et al. [23]
3
have studied the hydrogenation of CO over the Cu/ZnO/Al O catalysts at 30 bar
2
2
3
pressure while keeping the H /CO mixture ratio (1:1) at 40° C. They reported
2
2
only 7.6% reaction yield of formic acid. Zhao et al. [24] performed experiments
for formic acid synthesis by using sodium carbonate (Na CO ) as an additive and
2
3
rhodium phosphine complex [RhCl (mtppms) ] as a catalyst and attained 35%
3
yield of formic acid at 50° C. Formic acid has multiple uses in hydrogen storage
and production and the released hydrogen conversion into several chemicals [25].
Formic acid can be used as acidiꢁers for animal feeds and hydrogen source mate-
rial for several alcohols, amines and alkynes [26].
Based on the literature review, the objective of this research work is to (1) syn-
thesize the reaction products of CO gas absorption into the sodium hydroxide solu-
2
tion of diꢀerent concentrations and pH, while keeping the absorption temperature
low; (2) synthesize the formic acid by the conversion of absorption reaction product
sodium hydrogen carbonate into an intermediate reaction product sodium formate,
in the presence of nickel ferrite heterogeneous catalyst, followed by the reaction of
sodium formate with sulfuric acid and the condensation of the formic acid vapors.
Experimental details
Materials
In order to conduct the experiments, following chemicals were used: sodium hydrox-
ide, NaOH, 99.0% pure (Merck), iron nitrate, Fe(NO ) , 98% pure (Merck), nickel
3
3
nitrate, Ni(NO ) , 98% pure (Sigma Aldrich), and Sulfuric acid H SO , 98% pure
3
2
2
4
(
Sigma Aldrich); carbon dioxide (CO ) gas cylinder with 99% purity (Pakistan Pure
2
Gases Company); and pure zinc metal (Biocare Scientiꢁc Company, Pakistan). All
chemicals were utilized as received without any further puriꢁcation.
Batch CO absorption reactions
2
For CO absorption, six concentrations of sodium hydroxide aqueous solution
2
(
0.01, 0.1, 0.5, 1.0, 3.0 and 5.0 N) were prepared by dissolving NaOH pellets
into 500 mL of distilled water. The experimental setup is shown in Fig. 1. The
temperature of the CO absorbing sodium hydroxide solution was maintained
2
at room temperature (25° C). The CO gas was bubbled through the solution
2
1
3

M. H. Masood et al.
Fig. 1 Experimental setup for CO absorption
2
[
27] at a ꢂow rate of 0.4 L/min, and the pH of the system was monitored for the
whole period of the absorption by keeping electronic pH meter in the solution.
CO was absorbed in the solution until the ꢁnal solution pH dropped to 10, 9
2
and 8 from the starting pH of the sodium hydroxide solution. The total absorp-
tion time was also noted. In all the experimental work, a new CO absorbed
2
solution was prepared for reaching the ꢁnal desired pH of the solution. Absorp-
tion solutions were prepared from pH 10 to pH 8 to ꢁnd out the optimum pH at
which maximum sodium hydrogen carbonate is produced. Once the solution pH
reduced to the desired pH, the ꢂow of CO was stopped and the reacted solu-
2
tion was oven-dried at 105° C for 24 h and weight of the product obtained at the
respective pH was noted down.
X-ray diꢀraction (XRD, D8 Advance Germany) of the product crystals was
performed to analyze the type of the product formed at each solution ꢁnal pH.
The XRD pattern obtained was then analyzed and compared using the MDI Jade
5
.0 software. The XRD peaks were matched with the reference peaks.
Synthesis of nickel ferrite catalyst
The nickel ferrite (NiFe O ) catalyst for the reaction was produced by mixing
2
4
a solution of nickel nitrate (0.24 g/mL) and iron nitrate (0.12 g/mL). The two
solutions were mixed thoroughly in a beaker while stirring at 100 rpm. The mix-
ture pH was adjusted at pH 12 by adding 1 N sodium hydroxide solution drop
by drop. Mixing proceeded at 80° C for 3 h, and the reaction mixture was then
allowed to settle down overnight. A mixture paste was formed that was washed
with distilled water until pH 7 was achieved. It was then oven-dried at the
1
6
10° C for 24 h. The dried crystals produced were placed in a muꢃe furnace for
h at 850° C. Produced nickel ferrite was then analyzed by XRD and scanning
electron microscope (SEM, VGA 3, China) analyzer.
1
3

Carbon dioxide conversion into the reaction intermediate…
Catalytic conversion of sodium hydrogen carbonate to sodium formate
through hydrogenation in the presence of nickel ferrite catalyst
To produce the sodium formate (NaHCO ) from sodium hydrogen carbonate
2
(
NaHCO ), the reaction was carried out in a reactor attached with a round bottom
3
ꢂask. Hydrogen gas was produced in the ꢂask by the reaction of zinc metal rings
with sulfuric acid. Sodium hydrogen carbonate (100 mL, 1 M) was put into the
reactor. Two hundred milligrams of nickel ferrite catalyst was introduced into the
reactor; then, the hydrogen gas was bubbled into the sodium hydrogen carbonate
solution for 2 h at a temperature of 80° C and at the atmospheric pressure. The
solution was stirred at 100 rpm, and after the completion of the reaction, the left
solution was evaporated at 105° C for 24 h to obtain the sodium formate attached
over the nickel ferrite catalyst surface. This material was then stored in air tight
bags until further use.
Synthesis of formic acid
For the synthesis of formic acid, 5 g of sodium formate material produced in the
hydrogenation reaction of sodium hydrogen carbonate in the presence of nickel
ferrite catalyst was converted into formic acid by reacting it with 5 mL of the sul-
furic acid. The sulfuric acid was added to dissolve out all of the sodium formate
from the nickel ferrite catalyst surface. The formic acid and sodium sulfate were
obtained as the reaction product and byproduct, respectively. The vapors of formic
acid were condensed to get formic acid in the liquid phase. The sodium sulfate
solids from the reaction mixture were made dissolved in water and dried in the
oven at 100 ± 5° C for 24 h. Sodium sulfate and formic acid were then analyzed
by XRD and high-performance liquid chromatography (HPLC), respectively, hav-
ing a column of C-18 Merck, UV detector and a mobile phase (buꢀer+ methanol,
9
5:5) solution, keeping a ꢂow rate of 1 mL/min. (HPLC model: Agilent 1100
series).
Results and discussion
Absorption mechanism of CO in sodium hydroxide solution
2
Carbon dioxide absorption in sodium hydroxide solution is explained by the follow-
ing mechanism [28–30]. When the sodium hydroxide solution is prepared, it eas-
+
−
ily dissociates into Na ions and OH ions. As CO is passed through the sodium
2
hydroxide solution, it is physically transformed into the aqueous phase as shown in
Eq. 1.
CO (g) → CO (aq)
2
2
(1)
1
3

M. H. Masood et al.
As the carbon dioxide absorbs in the sodium hydroxide solution, it reacts with the
−
−
3
OH ions and form HCO ions as shown in Eq. 2.
−
CO (aq) + OH (aq) ⇌ HCO (aq)
−
3
2
(2)
−
3
−
−2
3
HCO ions formed further react with OH ions and convert into CO ions as
shown in Eq. 3.
−
3
−
HCO (aq) + OH (aq) ⇌ H O(I) + CO (aq)
−2
3
2
(3)
Equations (2) and (3) are highly reversible reactions.
Equation (3) is more dominant than Eq. (2). As the absorption reaction proceeds
−
3
−2
3
toward pH 10, depletion of HCO ions occur in the solution and more CO ions are
−2
+
formed. These CO ions react with Na ions and form the Na CO product. The
3
2
3
overall reaction is shown in Eq. 4:
2
NaOH(aq) + CO (g) → Na CO (aq) + H O(I)
2 2 3 2
(4)
pH=10.
Considering Eq. (3), for a solution with pH<10, the backward reaction domi-
−
nates with more HCO ions formed in the solution. At pH>10, the forward reaction
3
−
3
2
dominates with the greater production of CO ions in the solution.
As more carbon dioxide is fed into the solution, the Na CO formed in the solu-
2
3
tion reacts more with the CO and converts into NaHCO as shown in Eq. 5.
2
3
Na CO + H O + CO → 2NaHCO
2
3
2
2
3
(5)
pH=8.
In this way, more amount of NaHCO is produced at pH<10 and maximum at
3
pH=8.
Impact of sodium hydroxide solution concentration on absorption time
Figure 2 interprets the results of CO2 absorption in sodium hydroxide solution until
the starting pH of the solution is dropped to pH 9. The minimum time to reach pH
9
was 3 min in the solution concentration of 0.01 N and was 17 h and 68 h for 3 N
and 5 N sodium hydroxide solution, respectively. This is due to the fact that increas-
+
ing the sodium hydroxide solution concentration increases the concentration of Na
−
and OH ions in the solution, which increases the time for their neutralization. This
results in the further absorption of CO gas in the solution due to which time to
2
achieve the desired pH increases [28, 31, 32].
It was further noted in Fig. 3 that a minimum of 381 mg of product crystals was
obtained at 0.01 N solution, while 65,000 mg and 121,000 mg were measured for
3
N and 5 N sodium hydroxide solution, respectively, when the solution’s initial pH
was dropped to pH 9 by carbon dioxide absorption. Minimum alkalinity was noted
for 0.01 N solution was 24 mg/L equivalent of CaCO , and maximum alkalinity
3
3
was 38,000 mg/L and 67,000 mg/L equivalent of CaCO for 3 N and 5 N solution,
respectively. This increase in alkalinity shows the increasing reaction of the CO
2
1
3

Carbon dioxide conversion into the reaction intermediate…
Fig. 2 Impact of solution concentration on absorption time to reach pH=9
Fig. 3 Impact of solution normality on product formation and solution alkalinity
absorption with the strength of sodium hydroxide solution. Furthermore, it can be
said that the minimum sodium hydroxide solution normality required for product
formation by the absorption of CO should be above 1 N. Above this solution nor-
2
mality, the alkalinity of the solution suppresses while the amount of product formed
increases.
XRD analysis of products formed at diꢀerent solution pH
XRD analysis of the crystals produced in 3 N solution at pH 9 is shown in Fig. 4,
conꢁrming the formation of the reaction product Trona, having a chemical formula
of Na CO .NaHCO .2H O. The XRD analysis showed major peaks presence at 2θ,
2
3
3
2
◦
◦
◦
◦
1
8.3 , 29.2 , 33.9 and 44.8 which correspond to the planes (400), (211), (411)
and (802). On software analysis, all peaks showed the presence of the same product
1
3

M. H. Masood et al.
Fig. 4 XRD analysis of Trona
Trona [28]. Trona has multiple uses like in the glass, cement manufacturing indus-
tries, and as an animal feed additive for the dairy industry; also it ꢁnds an applica-
tion for the removal of acid gases like oxides of sulfur from ꢂue gases and as a
source for soda ash manufacturing industries. Figure 5 shows the XRD analysis of
product crystals formed at solution pH 8 and shows the presence of pure sodium
Fig. 5 XRD analysis of sodium hydrogen carbonate
1
3

Carbon dioxide conversion into the reaction intermediate…
◦
◦
◦
◦
hydrogen carbonate. Major peaks were present at 2θ, 27.70 , 29.0 , 30.2 , 34.6 and
4
4.7° which attribute to the plane (101), (130), (220), (121) and (240), respectively.
Similarly, XRD analysis of the crystals obtained at pH 10 is shown in Fig. 6. It has
revealed the presence of pure sodium carbonate crystals. Sharp peaks were prom-
◦
◦
◦
◦
inent at 2θ, 30.0 , 34.3 , 37.8 and 41.3 which match to the plane (002), (310),
(
112) and (400), respectively. This reveals that the solution pH has a major eꢀect on
the type of the product formed.
Impact of solution pH on the weight of absorption products formed
In the 3 N sodium hydroxide solution, the weight of sodium hydrogen carbonate
crystals formed were higher than that of sodium carbonates, i.e., 76.6 g and 20.6 g at
pH 8 and pH 10, respectively. While the weight of Trona crystals formed was 65.0 g
under the presence of same reactants, sodium hydroxide solution and carbon diox-
ide, at pH 9.
Impact of CO absorption on sodium hydroxide solution exhaustion time
2
Results showed diꢀerent exhaustion times at diꢀerent pH when carbon diox-
ide was absorbed in the 3 N sodium hydroxide solution. The starting 3 N solution
pH was 13.75. The exhaustion time to reach a new solution pH was of the order:
pH13<pH12<pH11 up to.
pH 8 as shown in Fig. 7.
The higher CO reaction rate is observed at higher solution pH where the con-
2
+
−
centration of Na and OH ions in the solution is also high while the reaction rate
becomes slower at low solution pH values [28, 30, 33].
Fig. 6 XRD analysis of sodium carbonate
1
3

M. H. Masood et al.
Fig. 7 Three Normal (3 N) sodium hydroxide solution exhaustion time (hr=hour, min=minute) to reach
a diꢀerent solution pH from the initial value. The solution starting pH was 13.75 at time t=0 s
Nickel ferrite analysis
Nickel ferrite catalyst produced was used in the hydrogenation reaction of sodium
hydrogen carbonate. Figure 8 shows the XRD results of the catalyst produced.
Various researchers have used XRD and SEM analyses to determine the molecu-
lar structure and morphology of nickel ferrite catalyst. XRD results of this work
Fig. 8 XRD analysis of nickel ferrite
1
3

Carbon dioxide conversion into the reaction intermediate…
are in accordance with reported works of Silva et al. [34], Lin et al. [35] and
Nejati et al. [36].
The sharp peaks in XRD analysis show the purity and crystalline structure of
the catalyst produced.[37, 38]. MDI Jade 5.0 software analysis showed the domi-
◦
◦
◦
◦
◦
◦
◦
nating peaks obtained at 2θ, 30.3 , 35.7 , 37.3 , 43.3 , 53.8 , 57.3 and 62.9
which attribute to the plane (220), (311), (222), (400), (422), (511) and (440),
respectively.
The SEM analysis of nickel ferrite revealed that the average particle size of the
catalyst was 49.7 nm, which was well within the range earlier reported [37]. Fig-
ure 9 shows the spherical homogenous morphology of the nickel ferrite produced.
Agglomeration was observed due to high energy dissipation and gases escape.
The same agglomeration pattern was observed in the past study of Fu et al. [39]
and Silva et al. [34].
Production of sodium formate
Sodium formate was produced from the hydrogenation of sodium hydrogen car-
bonate that was obtained at pH = 8 by the absorption of CO in NaOH solution.
2
The sodium formate synthesis reaction was carried out in the presence of nickel
ferrite catalyst due to fact that nickel ferrite provides a medium for hydrogen car-
rier [40]. Besides, nickel ferrite has the surface property of decomposing CO ,
2
i.e., double bond of carbon with oxygen into a single bond between carbon and
−
oxygen [41]. Thus, during hydrogenation of sodium hydrogen carbonate, CO
3
is decomposed into CO and sodium formate is formed as shown in Eq. 6 and
2
Fig. 10.
Ni(Fe O )
2
4
NaHCO + H ⟶ NaHCO + H O
(6)
3
2
2
2
Fig. 9 SEM image of Nickel Ferrite catalyst
1
3

M. H. Masood et al.
Fig. 10 Proposed overall mechanism of formic acid production by using a nickel ferrite catalyst
Synthesis and analysis of formic acid
The reaction of sodium formate produced with sulfuric acid showed a reaction
%
age yield of 79 ± 0.2%. The proposed overall reaction mechanism of formic acid
synthesis in this work from sodium hydrogen carbonate is shown in Fig. 10. The
mechanism shows that hydrogen molecule comes in contact with Ni sites, and
it dissociates into hydrogen atoms and adsorbed on Ni atoms. Further, oxygen
−
molecules of NaHCO are attracted toward Fe site and HCOO anion produces
3
+
and attached to Fe atoms. While Na gets anchored with Ni sites by replacing the
hydrogen. After that, another H atom from H SO again makes the bond with Ni
2
4
+
site replacing the Na . Finally, the formic acid is produced, as the surface of cata-
lyst reduces. Similar kind of reaction ꢁndings are reported earlier for formic acid
synthesis by using bimetallic catalysts [20, 23, 24].
For formic acid analysis, HPLC test was performed by running standard formic
acid and its retention time was found to be 3.12 min. While the retention time of
the produced formic acid is noted to be 3.10 min as shown in Fig. 11.
Formic acid from the reaction was separated upon vapor condensation using
condensation assembly with round bottom ꢂask. No formic acid was lost during
the reaction as the decomposition of formic acid produces carbon monoxide only
at very high temperatures of 1000° C and above [42, 43]. However, the tempera-
ture in current experimental work for formic acid vaporization only reached up
◦
to 100 ± 5 C. This resulted in the production of formic acid vapors only. Formic
acid vapors produced were condensed continuously in the condenser assembly.
In this study, the catalyst was not reused. Production of reaction by-product,
sodium sulfate, further conꢁrmed the reaction between the sulfuric acid and
sodium formate. XRD analysis of sodium sulfate formed during the reaction is
◦
shown in Fig. 12. Sharp peaks of the product crystal were obtained at 2θ, 19.0 ,
◦
◦
◦
2
9.0 , 32.0 and 48.7 which correspond to the planes (111), (004), (131) and
1
3

Carbon dioxide conversion into the reaction intermediate…
Fig. 11 HPLC analysis of formic acid
Fig. 12 XRD analysis of sodium sulfate
(
135), respectively, conꢁrming the crystal structure of sodium sulfate and the
completion of the reaction.
Table 1 shows the comparison of catalyst used, operating temperature and
%
age yield of formic acid produced with this study. It shows that in this study,
formic acid is produced at a lower temperature and a high %age yield is obtained
as compared to previous works.
1
3

M. H. Masood et al.
Table 1 Comparison of formic acid %age yield produced with literature. From CO absorption and
2
hydrogenation of the solution
S. no Literature
Yield (%) Tem-
perature
°C)
Catalyst used
References
(
1
2
3
4
Chen et al. (2015)
Wang et al. (2017)
Chiang et al. (2018) 7.6
Zhao et al. (2011) 35
50
86.6
300
200
140
50
N H .H O over Ni catalyst
Nonporous Ni catalyst
[21]
[22]
[23]
[24]
2
4
2
Cu/ZnO/Al O3
2
Rhodium phosphine complex
[
RhCl(mtppms) ]
3
5
6
Chiang et al. (2017) 13
140
300
Cu/CuCr O4
[44]
2
Wu et al. (2009)
15.6
Ni as catalyst and Fe as a reductant [45]
Fe/Ni ratio 1:1
7
This Study
79± 0.2
80
Nickel ferrite catalyst
NiFe O )
Current work
(
2
4
Conclusions
The absorption of CO and the time of exhaustion of the sodium hydroxide
2
solution increase with an increase in the strength of sodium hydroxide solution
and decreasing pH of the solution respectively. In addition, absorption reac-
tion products are solution pH dependent. At solution pH 10, sodium carbonate
is formed, and at pH 8, sodium hydrogen carbonate is formed while pH 9 gives
Trona. Hydrogenation of sodium hydrogen carbonate in the presence of nickel
ferrite catalyst produces sodium formate that is a precursor for formic acid syn-
thesis. The hydrogenation process is endothermic. In the present study, addition
◦
of nickel ferrite catalyst lowered the hydrogenation temperature up to 80 C. The
formic acid was synthesized from the sodium formate by the reaction with sul-
furic acid. The %age yield of formic acid produced was noted 79 ± 0.2%. The
produced formic acid qualitative analysis by HPLC proved its production in the
reaction. Further, XRD analysis conꢁrmed the reaction by-product sodium sulfate
formation. This work has shown that the value-added marketable products can be
synthesized from the absorption of the pollutant gas CO into the sodium hydrox-
2
ide solution.
Acknowledgements The authors would like to acknowledge research funds provided by the School
of Civil and Environmental Engineering, National University of Sciences and Technology, Islamabad,
Pakistan.
Compliance with ethical standards
Conꢀict of interest The authors ꢁnd no conꢂicts of interest in this work.
Geolocation information The reported work has been carried out in Islamabad, Pakistan.
1
3

Carbon dioxide conversion into the reaction intermediate…
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