Reduction of maleic acid to succinic acid on titanium cathode

Article abstract of DOI:10.1021/op0300185

Electrochemical reduction of maleic acid to succinic acid has been studied. The effect of (i) temperature, (ii) current density, (iii) concentration of H₂SO₄, and (iv) hydrodynamic conditions on conversion of maleic acid and current efficiency has been studied. The reaction was best carried out electrochemically at 40°C at a current density of 625 A m ². The effect of recycling the electrolyte, on conversion and current efficiency, has been reported. Conversion of maleic acid and current efficiency are affected marginally up to the fifth reuse. A material balance has been presented for these recycle studies.

Full text of DOI:10.1021/op0300185

Organic Process Research & Development 2004, 8, 685−688
Reduction of Maleic Acid to Succinic Acid on Titanium Cathode
Arati V. Muzumdar, Sudhirprakash B. Sawant,* and Vishwas G. Pangarkar
Mumbai UniVersity, Institute of Chemical Technology, Matunga, Mumbai - 400019, India
Abstract:
Electrochemical reduction of maleic acid to succinic acid has
been studied. The effect of (i) temperature, (ii) current density,
(iii) concentration of H2SO4, and (iv) hydrodynamic conditions
on conversion of maleic acid and current efficiency has been
studied. The reaction was best carried out electrochemically at
40 °C at a current density of 625 A m-2. The effect of recycling
the electrolyte, on conversion and current efficiency, has been
reported. Conversion of maleic acid and current efficiency are
affected marginally up to the fifth reuse. A material balance
has been presented for these recycle studies.
Introduction
Figure 1. FM01-LC experimental setup.
The preparation of succinic acid (SA) is of great com-
However, reports are not available on the mass transfer
mercial importance, since it finds extensive application in
the synthesis of succinc sulphathiazole, rhodamin S, and also
as an intermediate for the synthesis of a wide variety of
organic compounds.1 Maleic acid is easily reduced to succinic
acid both chemically and electrochemically. Electrolytic
reduction of maleic acid in H2SO4 medium at conventional
cathodes such as rotating lead, platinized platinum, graphite,
mercury, and a zinc single crystal has been reported.2-11
The electrolytic reduction of maleic acid in acidic media
at a Pb cathode in the presence of metal citrate complexes
of Co, Ni, Cu, and Mn has been studied.12 Reduction of
maleic acid at Ti/ceramicTiO2 under galvanostatic and cyclic
voltametric conditions has been examined.13 Reduction of
maleic acid on copper electrode and on copper chelate
electrode in DMF containing 1 M NaClO4 has been reported.
With the Cu electrode, only succinic acid was formed
selectively, but, with the copper chelate electrode, formation
of many byproducts has been reported.14
limitations and effect of batch time on conversion and current
efficiency for this reaction, when it is carried out electro-
chemically. In the present work the effect of a titanium
cathode on current efficiency and conversion of maleic acid
is reported after a detailed study of the various operating
and process parameters. Recycling of the electrolyte was
attempted to improve the economy of the process. The effect
of increased loading of maleic acid and charge passed on
conversion and current efficiency is also studied.
Experimental Section
Materials and Methods. Analytical grade maleic acid,
succinic acid, H2SO4, potassium bromate, potassium bromide,
potassium iodide, sodium thiosulphate, sodium chloride,
starch, and mercuric sulphate were procured by s.d. fine-
chem. Ltd Mumbai, India.
Experimental. The FM01-LC laboratory process package
supplied by ICI Chemicals and Polymers, UK was used
(Figure 1).15,16 All experiments were carried out with a
titanium cathode (0.0064 m2) and a lead anode (0.0064 m2)
with an interelectrode gap maintained at 6 mm. Experiments
were carried out galvanostatically. The electrolysis was
carried out using 0.25-2 M H2SO4 and the current density
in the range of 312.5-781.25 A m-2. The voltage applied
was in the range of 2-5 V. The temperature in the range of
20-40 °C was employed. The flask was kept in a water bath,
which was used for temperature variation. The reaction
mixture from the flask was pumped through the electrolyser
with a magnetically driven PTFE pump. The flow rate was
monitored using a rotameter.
* To whom correspondence should be addressed. Telephone: + 91-22-
4145616. Fax: + 91-22-4145614. E-mail: sbs@udct.org.
(1) Kirk, R. K.; Othmer, D. F. Encyclopedia of Chemical Technology, 3rd ed;
John Wiley & Sons: New York, 1983; Vol. 21, pp 858.
(2) Smigielski, K.; Gora, J.; Kula, J. J. Ind. Chem. 1992, 20 (2), 17-20.
(3) Gora, J.; Smigielski, K.; Kula, J. PL, 148,885 (CI.C07C55/10) 31 Mar 1990,
Applications, 269881, 30 Dec 1987, p 2.
(4) Jain, A.; Misra, R. A. J. Electrochem. Soc. India 1983, 32, 231-233.
(5) Fujita, R.; Sekine, T. Denki Kagaku oyobi Kogyo Butsuri Kagaku. 1982,
50, 491-493.
(6) Vasudevan, D. J. Appl. Electrochem. 1995, 25, 176-178.
(7) Tari, I.; Ryuto, H.; Hirai, T. Denki Kagaku oyobi Kogyo Butsuri Kagaku.
1980, 48, 500-548.
(8) Udupa, H. V.; Venkatchalapathy, M. S.; Kanakam, R. I. Indian Patent 102,-
485, 29 June 1968.
(9) Kudryashov. I. V.; Kochetkov, V. L. Zh. Kiz. Khim. 1967, 41 (7), 1712.
(10) Kanakam, R.; Pathy, M. S. V.; Udupa, H. V. K. Electrochim. Acta 1967,
12 (3), 329-332.
(11) Tajima, S. I.; Mori, T. Denki Kagaku 1986, 24, 461.
(12) Swann, S., Jr.; Chen, C. Y.; Kerfman, H. D. J. Electrochem. Soc. 1952,
99, 460.
(14) Nikulon, V. N.; Shikin, A. N. Technol Inot. 1966, 38, 43.
(15) Vaze, A. S.; Sawant, S. B.; Pangarkar, V. G. J. Appl. Electrochem. 1995,
25, 279-283.
(13) Kanakam, R.; Pathy, M. S. V.; Udupa, H. V. K. J. Electrochem. Soc. India
1967, 16, 98-107.
(16) Vaze, A. S.; Sawant, S. B.; Pangarkar, V. G. J. Appl. Electrochem. 1997,
27, 584.
10.1021/op0300185 CCC: $27.50 © 2004 American Chemical Society
Published on Web 06/18/2004
Vol. 8, No. 4, 2004 / Organic Process Research & Development
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Figure 2. Scheme of recovery of succinic acid and recycling
of the electrolyte.
The solution after electrolysis was concentrated to half
the volume and kept overnight when the product succinic
acid separated out. The succinic acid so obtained was filtered,
given washings with cold water, and dried (Figure 2). It was
identified from its melting point17 and IR spectrum.18 The
purity of the crystallized succinic acid was determined by
HPLC. It was 98.9%. The maleic acid initially added to the
electrolyte, and the maleic acid left unreacted in the
electrolyte after the electrolysis was determined using the
Bromate-Bromide method.19 The conversion of maleic acid
was determined from the amount of maleic acid left
unreacted at the end of the electrochemical reaction.
Figure 3. Effect of batch time on current efficiency at a current
density of 312.5 A m-2 and molarity of H2SO4 as 0.25, 1, and
2 M. ([) M ) 0.25 M, (9) M ) 1 M, (2) M ) 2 M.
Mechanism of the Reaction. The mechanism for the
reduction of maleic acid to succinic acid is as given below.20
the reaction is under a mass transfer controlled regime. The
current density was maintained at 625 A m-2, and a charge
equivalent to 6.9 A h was passed during the reaction. A 0.124
mol amount of maleic acid was used, and the temperature
was maintained at 40 °C. A turbulence promoter in the form
of a Teflon mesh was used in all experiments. Current
efficiency varies in the range of 96.46% to 96.9% for 1446
< Re < 2900. Thus the effect of the Reynolds number on
current efficiency is negligible. It is therefore evident that
there is no mass transfer limitation.
Effect of Concentration of H2SO4 on Current Ef-
ficiency and Conversion. The reaction was carried out using
0.25 M, 1 M, 2 M, and 3 M H2SO4 as an electrolyte. The
current densities (i) 625 A m-2 and (ii) 312.5 A m-2 were
used, and the Reynolds number was kept constant at 2169.
Charge passed was 6.9 A hr, and 0.124 mol of maleic acid
was used in these experiments. Temperature was maintained
at 40 °C. As the molarity of H2SO4 is increased from 0.25
M to 2 M at a current density of 312.5 A m-2, there is an
increase in the current efficiency from 84.71% to 91.36%
(Figure 3). For a current density of 625 A m-2, the current
efficiency increased from 89.59% to 96.86% (Figure 4).
There is also an increase in the conversion as the molarity
of H2SO4 increases from 0.25 to 2 M. For an H2SO4
concentration of 3 M, the reaction had to be terminated due
to formation of thick charred mass. Hence 2 M H2SO4 was
used in subsequent experiments.
Results and Discussion
Effect of Hydrodynamic Conditions. Experiments were
carried out at different velocities of the electrolyte to
determine whether the flow rate of the electrolyte has any
effect on the rate of the reaction and to ascertain whether
Effect of Temperature on Current Efficiency and
Conversion. The effect of temperature on the progress of
the reaction was investigated at 20, 30, 40, and 50 °C with
all other parameters unaltered. The current density was
maintained at 625 A m-2 at the electrolyte flow Reynolds
number of 2169. A charge equivalent to 6.9 A h was passed
for 0.124 mol of maleic acid, dissolved in 500 mL of 2 M
(17) The Merck Index An Encyclopedia of Chemicals, Drugs, and Biologicals,
11th ed.;Grassell, A. G., Ed.; Merck & Co: USA, 1983; pp 1399.
(18) Atlas of Spectral Data and Physical Constants for Organic Compounds;
Grasselli, J. S., Ed.; CRC Press: Boca Raton, FL, 1973; p B-637.
(19) Siggia, S.; Hann, J. G. QuantitatiVe Organic Analysis; J. Wiley & Sons:
New York, 1979; p 301.
(20) Rifi, M. R.; Covitz, F. H. Introduction to Organic Electrochemistry; Union
Carbide Corporation, Research and Development Department Bound Brook,
New Jersey; Marcel Dekker: 1974; pp 228-231.
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Figure 4. Effect of batch time on current efficiency at a current
density of 625 A m-2 and molarity of H2SO4 as 0.25, 1, and 2
M. ([) M ) 0.25 M, (9) M ) 1 M, (2) M ) 2 M.
Figure 6. Effect of current density on conversion and current
efficiency for reduction of maleic acid to succinic acid. (9)
Current efficiency (Ce) (%), ([) Conversion (Conv) (%).
resinous mass. Thus, at 50 °C, the current efficiency
decreased sharply to 91.14% as shown in Figure 5.
Effect of Current Density on Current Efficiency and
Conversion. The reaction was carried out using a current
density in the range of 312.5-781.25 Am-2 at 40 °C. The
Reynolds number was maintained at 2169, and the charge
passed was 6.9 A h. Maleic acid (0.124 mol) was dissolved
in 500 mL of 2 M H2SO4. At a current density of 625 A
m-2, 96% current efficiency was obtained. But when the
current density was increased to 781.25 A m-2, formation
of resinous matter was observed. Resinous matter may be
formed due to polymeric condensation of maleic acid.6
Consequently the current efficiency dropped sharply to
90.7% as shown in Figure 6.
Effect of Batch Time on Current Efficiency and
Conversion. Reactions were carried out at different molari-
ties (H2SO4: 0.25 M/1 M/2 M) and at different current
densities (312.5 A m-2 and 625 A m-2). The Reynolds
number was maintained at 2169, and the charge passed was
6.9 A h. In each experiment, 0.124 mol of maleic acid was
dissolved in 500 mL of the electrolyte. The reaction
temperature was maintained at 40 °C. As the reaction
proceeds, the formation of succinic acid increases and the
availability of the reactant, i.e., maleic acid, decreases. Thus
conversion goes on increasing while the current efficiency
decreases with time (Figures 3 and 4). When the current
density was maintained at 312.5 A m-2 with the molarity of
H2SO4 as 0.25 M, the conversion increased from 25.42% to
84.71%; at a molarity of 1 M, the conversion increased from
26.9% to 89.59%, and at a molarity of 2 M the conversion
increased from 27.34% to 91.36%. For the current density
of 625 A m-2, there was a similar increase in the conversion.
For 0.25 M H2SO4, the conversion increased from 52.33%
to 89.59%; for 1 M H2SO4, the conversion increased from
Figure 5. Effect of temperature on conversion and current
efficiency for reduction of maleic acid to succinic acid. (9)
Current efficiency (Ce) (%), ([) conversion (Conv) (%).
H2SO4 for all the experiments. With the increase in the
temperature from 20 °C to 40 °C, the current efficiency
increased from 93.8% to 96.9% as shown in Figure 5. In
this electrochemical reduction of maleic acid to succinic acid,
formation of resinous matter was not observed when the
temperature was maintained between 20°C to 40°C. The
melting point and the IR spectrum of the final product was
compared with those of the authentic sample. When the
temperature was increased beyond 40 °C, there was appar-
ently a side reaction, which gave rise to formation of a tarry
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687

Table 1. Effect of electrolyte recycling on conversion and
current efficiencya
maleic acid
present in the
electrolyte at
current
the start of succinic acid
number of conversion efficiency each cycle
weighed
(g)
cycles
(%)
(%)
(gm)
0
1
2
3
4
96.78
96.69
96.40
96.20
95.90
96.94
96.82
96.64
96.42
96.22
29.68
29.89
29.99
30.23
30.34
28.40
29.22
29.32
29.41
29.50
a Conditions: current density ) 625 A m-2, 2 M H2SO4 is used as the
electrolyte, Maleic acid ) 0.124 mol (30 g), charge passed ) 6.9 A h, temperature
) 40 °C, Reynolds number ) 2169.
After every cycle, 30 g of maleic acid was added to the
recycled electrolyte (500 mL). The amount of maleic acid
present in the electrolyte at the beginning and the end of
each run was determined titrimetrically using the Bromate-
Bromine method. After every run, the electrolyte was
concentrated and then cooled to get crystallized succinnic
acid. It was filtered, washed with cold water, dried, and
weighed (Figure 2). The electrolyte concentration was
determined by the acid-base titration. Then it was diluted
to the initial concentration with the cold water that was used
for washings of the succinic acid crystals from the previous
batch. The electrolyte was then recycled after addition of
30 g of maleic acid.
Recycling of the electrolyte showed that the conversion
and current efficiency are marginally affected up to the fifth
reuse. This reuse of electrolyte can substantially reduce
production cost as well as the waste disposal problem when
reaction is carried out at a large scale level. The total succinic
acid obtained after five cycles was 145.85 g as shown in
Table 1. The recovery was 92%.
Figure 7. Effect of loading of maleic acid on conversion and
current efficiency. ([) Conversion (L1) L1 ) 0.124 mol of maleic
acid. (9) Conversion (L2) L2 ) 0.248 mol of maleic acid. (2)
Conversion (L3) L3 ) 0.497 mol of maleic acid.
55.14% to 94.02%; and for 2 M, the conversion increased
from 56.8% to 96.9%.
Effect of Loading of Maleic Acid and Charge Passed
on Current Efficiency and Conversion. Experiments were
carried out at a current density of 625 A m-2, with 2 M
H2SO4 as the electrolyte, using (i) 0.124 (L1), (ii) 0.248 (L2),
and (iii) 0.497 (L3) mol of maleic acid. The charge passed
was 6.9, 13.8, and 27.6 A h, respectively. The Reynolds
number was maintained at 2169. The temperature was
maintained at 40 °C. It was observed that the current
efficiency and conversion remain unaffected as the loading
of maleic acid and charge passed is increased. For L1, the
current efficiency observed was 96.9%. When the loading
is increased to 0.248 mol, the current efficiency remained
unaffected, while at L3 it increased to 98.41%. (Figure 7).
Recycle Studies. Succinic acid formed in the reaction is
recovered from the electrolyte by concentration of the
electrolyte followed by crystallization. The mother liquor
obtained from the filtration and washing of succinic acid
crystals contains H2SO4, succinic acid, and the unreacted
maleic acid. Recycle of this mother liquor as an electrolyte
for subsequent batches was investigated to reduce/eliminate
the problem of disposal of the mother liquor.
Conclusions
A study of the effect of various operating variables on
the electrochemical reduction of maleic acid to succinic acid
has indicated that a current density of 625 A m-2 and 2 M
H2SO4 as an electrolyte in the temperature range around 40
°C are most favorable for high current efficiency and
maximum conversion of maleic acid to succinic acid. With
further increase in the current density, temperature, and
molarity of H2SO4, there is a decrease in the current
efficiency due to formation of resinous matter. The electrolyte
can be successfully recycled 4 times, with 92% overall
recovery of SA, without affecting the current efficiency.
Recycle studies were carried out at the current density
625 A m-2 and a molarity of H2SO4 of 2 M. The Reynolds
number was kept unaltered at 2169. The charge equivalent
to 6.9 A h was passed during each reaction cycle with the
temperature being maintained at 40 °C.
Received for review April 14, 2003.
OP0300185
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