Hydrogenation of n-heptanal, catalyzed by cobalt carbonyl phosphine complex

Article abstract of DOI:10.1134/S1070427215050122

The use of the cobalt carbonyl phosphine complex Co₂(CO)₆(PR₃)₂ (R = C₄H₉) as catalyst precursor allows synthesis of n-heptanol from n-heptanal to be performed with high selectivity.

Full text of DOI:10.1134/S1070427215050122

ISSN 1070-4272, Russian Journal of Applied Chemistry, 2015, Vol. 88, No. 5, pp. 796−799. © Pleiades Publishing, Ltd., 2015.
Original Russian Text © T.E. Krylova, Yu.T. Vigranenko, S.B. Kocheregin, 2015, published in Zhurnal Prikladnoi Khimii, 2015, Vol. 88, No. 5, pp. 753−756.
CATALYSIS
Hydrogenation of n-Heptanal, Catalyzed
by Cobalt Carbonyl Phosphine Complex
T. E. Krylovaa, Yu. T. Vigranenkob, and S. B. Kochereginb
a St. Petersburg State University of Aerospace Instrument Making,
ul. Bolshaya Morskaya 67, St. Petersburg, 190000 Russia
b Kirov State University of Forestry Engineering,
ul. Mirgorodskaya 26-28, St. Petersburg, 191024 Russia
e-mail:lta4455@yandex.ru
Received October 27, 2014
Abstract—The use of the cobalt carbonyl phosphine complex Со2(СО)6(PR3)2 (R = C4H9) as catalyst precursor
allows synthesis of n-heptanol from n-heptanal to be performed with high selectivity.
DOI: 10.1134/S1070427215050122
Higher linear aliphatic aldehydes, in particular,
n-heptanal, are intermediates in synthesis of higher
linear alcohols, which are mainly used as surfactant
components. In Russian, EU, and US industry, aldehydes
are produced by hydroformylation (oxo synthesis):
ensure the same output parameters of petrochemical
processes as industrial heterogeneous catalysts do. Of
particular interest among them are rhodium and cobalt
carbonyl complexes, as they allow reactions (1) and
(2) to be performed on one catalyst in one reactor and,
correspondingly, the step of catalyst separation from
the reaction products to be eliminated from the oxo
synthesis process.
Cat.
RCH=CH2 + CO + H2 → RCH2CH2CHO.
(1)
For the catalyst regeneration, an aqueous solution
of cobalt acetate is added to the reaction product,
and the resulting mixture after mixing is fed to
fractional distillation for isolating commercial C7
alcohols. The process is performed in the syngas
atmosphere. Cobalt transforms into the compound
Co[Co(CO)3P(C4H9)3]2, from which the active form
of the catalyst, HCo(CO)3P(C4H9)3, can be readily
prepared. Among aldehydes, we chose n-heptanal,
because it can be prepared by hydroformylation of
1-hexene in accordance with Eq. (1). 1-Hexene, in
turn, is an intermediate product of polypropylene
oligomerization process commercially implemented in
Russia at OAO Nizhnekamskneftekhim. Cobalt carbonyl
complexes were tested as catalysts, because specifically
these complexes are used for oxo synthesis (propylene
hydroformylation) of butanols and 2-ethylhexanol at
plants in Perm (Russia) and Salavat (Bashkortostan,
Russia).
Reaction (1) is catalyzed by cobalt and rhodium
carbonyl complexes. Hydrogenation of aldehydes into
the corresponding alcohols in industrial oxo synthesis
processes [Eq. (2)] is performed on heterogeneous
catalysts and is characterized by high yields of target
products and high productivity of reaction installations:
Cat.
RCH2CH2CHO + H2 → RCH2CH2CH2OH.
(2)
The drawback of the heterogeneous hydrogenation
of aldehydes prepared by oxo synthesis is the need
for performing, along with the distillation step, an
additional power-consuming step of catalyst separation
from the reaction products. Along with well-known
heterogeneous hydrogenation catalysts, homogeneous
catalysts of reaction (2), containing compounds of
platinum [1], cobalt [2], rhodium [3, 4], and other
Group VIII d elements [5, 6] are also known. They
796

HYDROGENATION OF n-HEPTANAL
797
Table 1. Influence of temperature on the rate and selectivity of n-heptanal hydrogenation. P = 20.0 MPa, [Co] = 0.1 wt %; CO : H2 =
1 : 1 (by volume); Со : P(C4H9)3 = 1 : 2; loaded amounts: 114.9 g (140 × 10–3 dm3) of n-heptanal, 121.3 g (140 × 10–3 dm3) of
hexane (solvent)
Content in reaction products, wt %
Selectivity with
respect
to n-heptanol, %
n-Heptanal
conversion, %
Т, °С
Reaction time, s
n-heptanal
n-heptanol
HBBPs
160
0
48.6
45.4
42.0
–
3.0
6.0
–
0.3
0.8
–
6.2
12.7
–
97.5
95.3
7.2 × 103
1.08 × 104
180
200
0
48.6
40.5
28.5
–
7.1
17.7
–
1.2
3.7
–
15.9
40.3
–
93.3
87.7
7.2 × 103
1.08 × 104
0
48.6
31.1
7.6
–
15.9
34.1
–
1.8
7.4
–
35.9
84.3
–
89.8
82.1
7.2 × 103
1.08 × 104
and were analyzed by gas–liquid chromatography under
the following conditions: 3-m stainless steel column;
Reoplex-400 liquid phase, 15 wt % on Chromaton
N-AW-DMCS (fraction 0.16–0.20 mm); column
temperature 140°С; flame ionization detector (FID),
detector temperature 160°C; vaporizer temperature
200°С; carrier gas argon; flow rates, dm3 s–1: argon 5 ×
10–4, air 6.7 × 10–4.
EXPERIMENTAL
The n-heptanal hydrogenation was studied in a 0.5 dm3
high-pressure batch reactor with airtight electric drive
[7]. The kinetic control of the n-heptanal hydrogenation
(3) was ensured by stirring the liquid phase at a high rate
(~47 rps).
T, cat.
The hydroformylation is performed at increased syngas
pressure, up to 30 MPa, which is necessary for ensuring the
thermalstabilityofcobaltandrhodiumcarbonylcomplexes
at 110–180°С.Among cobalt complexes acting as catalyst
precursors, dicobalt octacarbonyl Со2(СО)8 and the
cobalt carbonyl phosphine complex Со2(СО)6[P(C4H9)3]2
are the most frequently used. Under the conditions of
reaction (1), they form true hydroformylation catalysts:
cobalt hydrocarbonyl НСо(СО)4 and phosphine-
substituted cobalt hydrocarbonyl НСо(СО)3[P(C4H9)3],
in accordance with the equations of activation of these
catalyst precursors:
C6H13CHO + H2
C6H13CH2CH2OH.
(3)
The installation also included buffer vessels for carbon
monoxide, hydrogen, and syngas, and also ~0.01 dm3
high-pressure samplers that could be cut off. The
reactor purged with carbon monoxide was charged with
a solution of Co2(CO)8 in hexane and with a modifier,
tributylphosphine P(C4H9)3, after which syngas CO +
H2 was fed to a pressure of 10.0 MPa, and heating and
stirring were switched on. n-Heptanal was charged into
the high-pressure loading vessel purged with argon and
syngas. On reaching the temperature of the experiment,
n-heptanal was transferred into the reactor by the syngas
pressure, and the pressure in the reactor was raised to
20.0 MPa. When studying the influence of the partial
pressures of hydrogen (H2) and carbon monoxide (CO),
syngas of preset composition was prepared in the buffer
vessels, was fed into the reactor, and was used for
transferring n-heptanal from the loading vessel. Liquid
phase samples were taken in the course of the experiment
T, cat.
Со2(СО)8 + H2
2HСо2(СО)4,
(4)
(5)
Co2(CO)6[P(C4H9)3]2
Co(CO)3P(C4H9)3,
Performing reaction (1) in the presence of
HCo(CO)3P(C4H9)3 allows the pressure to be decreased
to 20.0 MPa, the yield of linear aldehydes to be
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798
KRYLOVA et al.
Table 2. Influence of the partial pressure of hydrogen on the rate and selectivity of n-heptanal hydrogenation. PCO = 10.0 MPa;
T = 180°C; reaction time 1.08 × 104 s; [Co] = 0.1 wt %; Со : P(C4H9)3 = 1 : 2; loaded amounts: 114.9 g (140 × 10–3 dm3) of
n-heptanal, 121.3 g (140 × 10–3 dm3) of hexane (solvent)
Content in reaction products, wt %
Selectivity with respect
P(H2), MPa
n-Heptanal conversion, %
to n-heptanol, %
n-heptanal
n-heptanol
HBBPs
10.0
15.0
20.0
28.5
24.4
19.5
17.7
20.3
23.6
3.7
4.3
5.8
40.3
48.9
59.7
87.7
84.3
80.1
Table 3. Influence of the partial pressure of carbon monoxide on the rate and selectivity of n-heptanal hydrogenation. P(H2) =
7.0 MPa; T = 180°C; reaction time 1.08 × 104 s; [Co] = 0.1 wt %; Со : P(C4H9)3 = 1 : 2; loaded amounts: 114.9 g (140 × 10–3 dm3)
of n-heptanal, 121.3 g (140 × 10–3 dm3) of hexane (solvent)
Content in reaction products, wt %
Selectivity with respect
РCO, MPa
n-Heptanal conversion, %
to n-heptanol, %
n-heptanal
n-heptanol
HBBPs
30.8
6.0
10.0
14.0
16.4
13.2
9.6
1.6
1.5
0.9
36.4
29.7
21.1
91.3
90.1
34.1
38.3
92.2
increased, and the hydrogenating function of the catalyst
to be considerably enhanced compared to НСо(СО)4.
Therefore, we chose Cо2(СО)6[P(C4H9)3]2 as precursor.
We examined the influence of temperature, contact time,
and partial pressures of hydrogen and carbon monoxide
on the rate and selectivity of the hydrogenation of
n-heptanal into n-heptanol:
side reactions such as crotonic condensation of n-heptanal
and other transformations yielding high-boiling by-
products (HBBPs). An increase in the hydrogen partial
pressure from 10.0 to 20.0 MPa also leads to an increase in
the n-heptanal conversion (from 40.3 to 59.7%, Table 2),
i.e., accelerates reaction (6).
Carbon monoxide, on the contrary, inhibits the
n-heptanal hydrogenation. For example, as the partial
pressure PCO is increased from 6.0 to 14.0 MPa (Table 3),
the n-heptanal conversion decreases from 36.4 to 21.1%,
with no appreciable changes in the selectivity with respect
to n-heptanol.
n-C6H13CHO + H2
T = 60–200°C
C6H13CH2CH2OH.
(3)
P = 20 MPa,
cat HCo(CO)3P(C4H9)3
Based on the results obtained, optimum conditions
were found for performing reaction (6) to prepare
n-heptanol from n-heptanal with high selectivity:
T = 200°С, P = 20.0 MPa, СО : Н2 = 1 : 1 (by
volume), contact time 1.08 × 104 s, [Co] = 0.1 wt %,
Со : P(C4H9)3 = 1 : 2.
Preliminary experiments have shown that reaction (6)
starts to occur at a noticeable rate at 160°С.Above 200°С,
Cо2(СО)6[P(C4H9)3]2 starts to decompose. Therefore, we
chose for the study the temperature interval 160–200°С.
The rate of reaction (6) increases with temperature. For
example, whereas at 160°С and contact time of 1.08 ×
104 s the n-heptanal conversion was 12.7%, at 200°С it
was 84.3% in the same time (Table 1).
CONCLUSIONS
(1) Effective catalyst for selective hydrogenation
of n-heptanal to n-heptanol, generated in situ from
Cо2(СО)6[P(C4H9)3]2, was found.
The selectivity with respect to n-heptanol decreases
with increasing contact time because of the occurrence of
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HYDROGENATION OF n-HEPTANAL
Catal. A, 2010, vol. 372, no. 1, pp. 201–212.
799
(2) Optimum conditions were found for preparing
n-heptanol from n-heptanal in the presence of
Cо2(СО)6[P(C4H9)3]2.
5. Casey, C.P., Strotman, N.A., Beetner, S.E., et al.,
Organometallics, 2006, vol. 25, no. 5, pp. 1230–1235.
6. Gulyas, H., Benyei, A.C., and Bakos, I., Inorg. Chim. Acta,
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