Colloid and nanosized catalysts in organic synthesis: XVI.1 Continuous hydrogenation of carbonitriles catalyzed by nickel nanoparticles applied on a support

Article abstract of DOI:10.1134/S107036321710005X

Conversion of the starting nitriles and selectivity of the products formation during continuous hydrogenation of various nitriles catalyzed by Ni⁰/Ceokar-2 have been studied as functions of temperature. Performing the process at temperature 120–260°С has led to the formation of a mixture of products containing di- and trialkylamines as well as the corresponding imines and enamines.

Full text of DOI:10.1134/S107036321710005X

ISSN 1070-3632, Russian Journal of General Chemistry, 2017, Vol. 87, No. 10, pp. 2276–2281. © Pleiades Publishing, Ltd., 2017.
Original Russian Text © Yu.V. Popov, V.M. Mokhov, S.E. Latyshova, D.N. Nebykov, A.O. Panov, M.Yu. Pletneva, 2017, published in Zhurnal Obshchei
Khimii, 2017, Vol. 87, No. 10, pp. 1616–1621.
Colloid and Nanosized Catalysts in Organic Synthesis:
XVI.1 Continuous Hydrogenation of Carbonitriles
Catalyzed by Nickel Nanoparticles Applied on a Support
Yu. V. Popov*, V. M. Mokhov, S. E. Latyshova,
D. N. Nebykov, A. O. Panov, and M. Yu. Pletneva
Volgograd State Technical University, pr. Lenina 28, Volgograd, 400131 Russia
*e-mail: tons@vstu.ru
Received May 11, 2017
Abstract—Conversion of the starting nitriles and selectivity of the products formation during continuous
hydrogenation of various nitriles catalyzed by Ni0/Ceokar-2 have been studied as functions of temperature.
Performing the process at temperature 120–260°С has led to the formation of a mixture of products containing
di- and trialkylamines as well as the corresponding imines and enamines.
Keywords: catalysis, nanoparticles, nickel, hydrogenation, nitrile, amine
DOI: 10.1134/S107036321710005X
Hydrogenation of nitriles is a widely used method
of industrial-scale preparation of different amines
applied in pharmacology as well as in textile,
agricultural, and polymer industries.
Hydrogenation of different nitriles in a liquid phase
using colloid nickel and cobalt as catalysts has been
earlier performed [10, 11] (solution in isopropanol,
bubbling with hydrogen, 60–70°С, 10–16 h). Secon-
dary amines have been predominantly obtained using
the nickel catalyst, whereas the cobalt catalyst has
afforded primary amines. The selectivity has been
found dependent on the method of the catalyst
preparation.
Hydrogenation (including industrial-scale) of nitriles
affording primary amines is performed using Ni- and
Co-containing catalysts [2–4]. To avoid the formation
of side products (secondary and tertiary amines), the
process is performed under the elevated pressure of
hydrogen or in the excess of ammonia, due to the high
reactivity of the formed intermediates, imines and
enamines [5]. For example, hydrogenation of nitriles
of lauric acid (30 min, room temperature, 2 MPa)
using supported nickel catalysts has yielded n-dodecyl-
amine with selectivity 98–99% at the nitrile conversion
60–90% [6].
This study aimed to investigate the process of
hydrogenation of aliphatic and aromatic nitriles in a
flow-through reactor using the catalysts based on Ni0
nanoparticles applied onto various supports, namely
γ-Al2O3, activated carbon BAU-A, and aluminosilicate
cracking catalyst Ceokar-2 containing 10 wt % of zeolite
NaY and up to 1.8 wt % of La2O3 (the rest being SiO2)
[12].
Hydrogenation of nitriles at Pt- and Pd-containing
catalysts generally yields di- and trialkylamines [7, 8].
For example, secondary and tertiary amines have been
prepared using Pt and Pt–Pd (1–2 wt %), supported on
modified mesoporous silicate carriers (135–175°С,
atmospheric pressure), the nitrile conversion being 33–
50%; the selectivity with respect to the formation of
the tertiary amine was up to 70% [9].
The catalysts were prepared via impregnation of the
supports with an aqueous solution of nickel(II)
chloride, followed by separation of the impregnated
support via filtration and reduction of the nickel ions
with aqueous solution of sodium borohydride as
described in [1].
To study the activity of the prepared catalysts in the
nitriles hydrogenation, we performed gas-phase hydro-
genation of pentanenitrile at 180°С and atmospheric
1
For communication XV, see [1].
2276

COLLOID AND NANOSIZED CATALYSTS IN ORGANIC SYNTHESIS: XVI.
(a) (b)
2277
3 μm
500 nm
Fig. 1. SEM images of a surface of Ni/Ceokar-2 on 3 µm (a) and 500 nm (b) scales.
pressure, the hydrogen feeding rate being 0.75 L h–1
gcat–1 and that of the nitrile being 0.9 mL h–1 gcat–1. The
secondary amine was the major hydrogenation product
using the Ni0/Ceokar-2 catalyst (selectivity 74% at the
nitrile conversion 83%). When Ni0/BAU-A or
Ni0/γ-Al2O3 was used as the catalyst a significant
fraction of unsaturated compounds was formed, the
selectivity of the secondary amine formation being in
both cases 30% at the nitrile conversion 35–40%. The
study of the catalysts durability revealed that the
Ni0/Ceokar-2 one retained the catalytic activity during
at least 15 h of the process, whereas Ni0/γ-Al2O3 and
Ni0/BAU-A were deactivated within 5 and 2 h, respec-
tively. The deactivation of metal catalysts during
hydrogenation of nitriles is due to the chemisorption of
nitriles or imines at their surface [13–16]. In view of
the stability, the Ni0/Ceokar-2 catalyst was chosen for
further investigation.
The surface of the Ni0/Ceokar-2 catalyst was
studied by means of SEM. As seen in Fig. 1, the
support surface was covered by large (200–1000 nm)
nickel agglomerates (Fig. 1a) formed of the smaller
particles as well as by smaller (80–100 nm) particles
(Fig. 1b). It was found that the average content of
nickel at the surface equaled 7 wt %; the smaller
agglomerates (Fig. 1b) contained 7% of nickel, and
larger agglomerates (Fig. 1a) contained 11% of nickel.
nitrile 1e. The reaction was performed at temperatures
120–260°С and atmospheric pressure, at constant feed
of the nitrile and hydrogen.
The obtained mixtures were analyzed by gas-liquid
chromatography and chromato–mass spectrometry.
The products composition coincided with the scheme
of transformations during nitriles hydrogenation
discussed in the literature [2]. In particular, the reac-
tion mixture contained secondary 3a–3e and tertiary
5a–5e amines as well as the corresponding imines 2a–
2e and enamines 4a–4d (Scheme 1).
The study of the conversion of nitrile 1a and the
selectivity of formation of amines 3a and 5a, imine 2a,
and enamine 4a as functions of temperature revealed
that the increase in the hydrogenation temperature led
to linear increase in the conversion, the selectivity of
the process remaining practically constant. The highest
conversion of nitrile 1a was 83% at 200°С, the
selectivity being equal 74% with respect to the
secondary amine 3a and 20% with respect to the
tertiary amine 5a (Fig. 2).
In the case of nitrile 1b, the conversion became
constant (close to quantitative yield) at temperature
above 200°С. The highest conversion of nitrile 1b was
99% at 260°С, the selectivity equaled 64% with
respect to di-n-butylamine 3b and 13% with respect to
tri-n-butylamine 5b. The formation of intermediate
hydrogenation product enamine 4b was observed. The
selectivity of the formation of the secondary amine 3b
increased with temperature (Fig. 3).
To investigate the effect of temperature on the com-
position of the reaction mixture during hydrogenation
on the Ni0/Ceokar-2 catalyst, we studied the reaction
of different nitriles: n-pentanenitrile 1a, n-butyronitrile
1b, isobutyronitrile 1c, propionitrile 1d, and benzo-
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2278
S, %
POPOV et al.
x, %
S, %
x, %
t, °C
t, °C
Fig. 2. Conversion (х, %) of propionitrile 1a (1) and
selectivity (S, %) of the hydrogenation products formation
as a function of temperature (t, °С): (2) 3a, (3) 2a, (4) 4a,
and (5) 5a.
Fig. 3. Conversion (х, %) of nitrile 1b (1) and selectivity
(S, %) of the hydrogenation products formation as a
function of temperature (t, °С): (2) 3b, (3) 2b, (4) 4b, and
(5) 5b.
The complete conversion in hydrogenation of
nitrile 1c was reached at 200°С, the selectivity of the
formation of the secondary amine 3c being 96%
(Fig. 4). The high selectivity of the formation of amine
3c over the entire examined temperature range was due
to steric hindrance during the formation of the gem-
diamine intermediate accompanying the addition of the
amine 3c to aldimine, the product of the first stage of
hydrogenation of nitrile 1c.
rature up to 200°С followed by a plateau region. The
highest conversion of nitrile 1d was 99% at 200°С, the
selectivity being 56% with respect to di-n-propylamine
3d and 40% with respect to tri-n-propylamine 5d. The
increase in temperature led to the increase in the
selectivity of formation of the secondary amine 3d,
reaching 84% at 260°С (Fig. 5).
The trend in the change in conversion of aromatic
nitrile 1e was similar to that for the hydrogenation of
aliphatic nitriles (Fig. 6). The highest selectivity with respect
to the secondary amine 5e (77%) was reached at 200°С.
In the case of hydrogenation of nitrile 1d linear
increase was revealed in the conversion with tempe-
Scheme 1.
H2
H2
R1
N
1a_1e
R1
R1
NH2
NH2
NH
H2
R1
N
R1
R1
N
R1
R1
N
R1
R1
NH3
H
H
2a_2e
3a_3e
R1
R1
R3
H2
R3
N
R1
R1
N
R1
NH3
R2
N
R1
R2
5a_5e
4a_4d
NH2
R1 = Bu (a), Pr (b), i-Pr (c), Et (d), Ph (e); R2 = Pr (4a), Et (4b), Me (4c, 4d); R3 = H (4a, 4b, 4d), Me (4c).
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COLLOID AND NANOSIZED CATALYSTS IN ORGANIC SYNTHESIS: XVI.
2279
x, %
S, %
x, %
S, %
t, °C
t, °C
Fig. 5. Conversion (х, %) of nitrile 1d (1) and selectivity
(S, %) of the hydrogenation products formation as a
function of temperature (t, °С): (2) 3d, (3) 2d, (4) 4d, and
(5) 5d.
Fig. 4. Conversion (х, %) of nitrile 1c (1) and selectivity (S,
%) of the hydrogenation products formation as a function
of temperature (t, °С): (2) 3c, and (3) 2c.
The formation of amine 5e when using the
Ni0/Ceokar-2 catalyst could not be explained by the
above-given scheme, since the corresponding enamine
could not be formed [17].
In summary, the effect of temperature on the conver-
sion of nitriles and selectivity of their transformations
during hydrogenation on the Ni0/Ceokar-2 catalyst was
studied. It was found that the reaction performed at
120–260°С, the feed of the nitrile and hydrogen being
It is known that amine 5e can be formed during
hydrogenation of nitrile 1e via hydrogenolysis of the
gem-diamine intermediate 8, formed in its turn via
nucleophilic addition of dibenzylamine 3e to
benzylimine 7 (Scheme 2) [2].
–1
0.9 mL h–1 gcat and 0.5–1 L h–1 gcat–1, respectively,
resulted in the formation of the mixtures containing di-
and trialkylamines as well as the corresponding imines
and enamines. The temperature range of 200–220°С
was optimal regarding the formation of di- and tri-
alkylamines.
A peculiar feature of the discussed reaction was the
formation, along with the hydrogenation products, of
the product of their hydrogenolysis (toluene) and
further transformations of the latter at elevated tempera-
ture. For example, dealkylation of toluene was
observed when using an acidic support, the yield of
benzene was increased with the increase in tempera-
ture. For example, the selectivity at 260°С equaled
18% with respect to benzylamine, 20% with respect to
amine 3e, 8% with respect to amine 5e, 30% with
respect to toluene, and 25% with respect to benzene.
EXPERIMENTAL
Chromato–mass spectral analysis was performed
using a Saturn 2100 T/GC3900 instrument (EI, 70 eV).
Quantitative GLC analysis of the reaction mixtures
was carried out using
a
Kristallyuks-4000M
chromatograph (tstart 100–210°С, tevaporator 250°С, polar
column HP-5, l 50 m, d 0.32 mm, nitrogen as the
carrier gas, flame ionization detector, tdetector 250°C,
Scheme 2.
H2
NH
+
N
NH2
H
N
N
NH3
7
3e
8
5e
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 87 No. 10 2017

2280
S, %
POPOV et al.
N-Propylidenepropylamine (2a). Mass spectrum,
x, %
m/e (Irel, %): 99.9 (21) [M + 1], 98.9 (6) [M], 69.9
(100), 42.0 (59), 41.0 (50), 43.0 (45).
Di-n-propylamine (3a). Mass spectrum, m/e (Irel,
%): 102.0 (76) [M + 1], 100.8 (7) [M], 72.0 (100), 44.0
(87), 41.1 (32), 43.0 (27), 42.0 (17).
Tri-n-propylamine (5a). Mass spectrum, m/e (Irel,
%): 143.9 (10) [M + 1], 143.1 (1) [M], 113.9 (100),
85.9 (60), 58.0 (12), 43.9 (9), 115.0 (8), 142.0 (5).
b. Hydrogen feeding rate 0.75 L h–1 gcat–1, nitrile 1a
feeding rate 0.9 mL h–1 gcat–1, 240°С. Conversion of
nitrile 1a 96%. Yield: 80% of di-n-propylamine 3a,
13% of tri-n-propylamine 5a, and 2.5% of N-
propylidenepropylamine 2a.
t, °C
Fig. 6. Conversion (х, %) of nitrile 1e (1) and selectivity (S,
%) of the hydrogenation products formation as a function
of temperature (t, °С): (2) 5e, (3) 3e, (4) PhNH2, (5)
PhCH3, and (6) C6H6.
Hydrogenation of n-butyronitrile 1b. Hydrogen
feeding rate 1 L h–1 gcat–1, nitrile 1b feeding rate
0.9 mL h–1 gcat–1, 260°С. Conversion of nitrile 1b
99.9%. Yield: 61.5% of di-n-butylamine 3b, 13% of tri-
n-butylamine 5b, and 23% of butyl-1-idenedi-n-butyl-
amine 4b.
acetonitrile as the solvent). Scanning electron micro-
scopy studies were performed using a FEI Versa 3D
DualBeam instrument (working distance 10 mm, ETD
detector of the secondary electrons, CBS detector of
the backscattered electrons, EDS elemental analysis).
Di-n-butylamine (3b). Mass spectrum, m/e (Irel,
%): 130.0 (26) [M + 1], 128.7 (2) [M], 44.1 (100), 85.9
(39), 41.1 (31), 42.0 (17), 57.0 (62), 43.0 (5).
Catalyst preparation. Ceokar-2 support (fraction
1–1.5 mm), 2 g, was impregnated during 1 day with a
solution of nickel chloride prepared via dissolution of
0.5 g of NiCl2·6H2O in 4 mL of water. The impre-
gnated support was filtered off and washed several
times with water. The reduction with NaBH4 was
performed by adding three 0.1 g portions of the
reductant at room temperature. The reduction with
each portion was carried out during 2 min.
Butyl-1-idenedi-n-butylamine (4b). Mass spec-
trum, m/e (Irel, %): 184.2 (2) [M + 1], 44.0 (100), 85.9
(49), 41.1 (12), 57.0 (55), 156.1 (4).
Tri-n-butylamine (5b). Mass spectrum, m/e (Irel,
%): 186.0 (16) [M + 1], 142.0 (100), 99.9 (90), 58.0
(60), 143.0 (10), 141.1 (8).
Hydrogenation of isobutyronitrile 1c. Hydrogen
feeding rate 0.75 L h–1 gcat–1, nitrile 1c feeding rate
0.9 mL h–1 gcat–1, 200°С. Conversion of nitrile 1c
100%. Yield: 96% of diisobutylamine 3c and 3.5% of
N-isobutylideneisobutylamine 2c.
Hydrogenation reaction. The reaction was
performed in a flow-through reactor at atmospheric
pressure at 120–260°С. The moist reduced catalyst
was fed in the reactor between the glass layers of the
filling attachment and dried in a hydrogen flow at 120°С
just before the reaction. The laboratory rector was
made of a 12Х18Н10Т steel tube of internal diameter
9 mm placed in an oven with the heating zone height
50 mm. Temperature inside the reactor was measured
using a thermocouple. The hydrogen feeding rate was
adjusted with a GV-7 hydrogen generator.
N-Isobutylideneisobutylamine (2c). Mass spec-
trum, m/e (Irel, %): 128.0 (34) [M + 1], 126.8 (6) [M],
84.0 (100), 41.0 (57), 56.9 (51), 56.0 (40), 42.0 (26),
70.0 (10).
Diisobutylamine (3c). Mass spectrum, m/e (Irel,
%): 130.0 (16) [M + 1], 128.7 (2) [M], 86.0 (100), 57.0
(30), 41.0 (30), 44.0 (19), 42.1 (10).
Hydrogenation of n-pentanenitrile 1d. Hydrogen
feeding rate 0.75 L h–1 gcat–1, nitrile 1d feeding rate
0.9 mL h–1 gcat–1, 220°С. Conversion of nitrile 1d
83%. Yield: 61% of di-n-pentylamine 3d, 17% of tri-
n-pentylamine 5d, and 6% of N-pentylidenepentyl-
amine 2d.
Hydrogenation of propionitrile 1a. a. Hydrogen
feeding rate 0.75 L h–1 gcat–1, nitrile 1a feeding rate
0.9 mL h–1 gcat–1; 200°С. Conversion of nitrile 1a 99%.
Yield: 56% of di-n-propylamine 3a, 40% of tri-n-
propylamine 5a, and 3.5% of N-propylidenepropyl-
amine 2a.
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N-Pentylidenepentylamine (2d). Mass spectrum,
m/e (Irel, %): 156.0 (100) [M + 1], 98.1 (94), 41.0 (29),
42.0 (25), 56.0 (24).
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%): 158.0 (36) [M + 1], 156.8 (2) [M], 44.0 (100),
100.0 (47), 43.0 (12), 41.0 (9).
Tri-n-pentylamine (5d). Mass spectrum, m/e (Irel,
%): 228.2 (14) [M + 1], 170.0 (100), 114.0 (55), 58.0
(40), 171.0 (12).
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Hydrogenation of benzonitrile 1e. a. Hydrogen
feeding rate 0.5 L h–1 gcat–1, nitrile 1e feeding rate
0.9 mL h–1 gcat–1, 260°С. Conversion of nitrile 1e 91%.
Yield: 17% dibenzylamine 3e, 7% of tribenzylamine
5e, and 16% of benzylamine, 27% of toluene, and 23%
of benzene.
Dibenzylamine (3e). Mass spectrum, m/e (Irel, %):
198.0 (2) [M + 1], 197.0 (11) [M], 91.0 (100), 106.0
(59), 65.0 (24), 92.0 (22), 51.0 (12).
Tribenzylamine (5e). Mass spectrum, m/e (Irel, %):
288.0 (4) [M + 1], 287.0 (18) [M], 91.0 (100), 210.0
(24), 196.0 (20), 65.0 (18), 92.0 (12).
b. Hydrogen feeding rate 0.5 L h–1 gcat–1, nitrile 1e
feeding rate 0.9 mL h–1 gcat–1, 180°С. Conversion of
nitrile 1e 64.8%. Yield: 3% of dibenzylamine 3e, 57%
of tribenzylamine 5e, and 4% of benzylamine.
c. Hydrogen feeding rate 2 L h–1 gcat–1, nitrile 1e
feeding rate 0.9 mL h–1 gcat–1, 180°С. Conversion of
nitrile 1e 91%. Yield: 5% of dibenzylamine 3e, 65% of
tribenzylamine 5e, and 20% of benzylamine.
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