Liquid-phase catalytic hydrogenation of 3,4-dichloronitrobenzene over Pt/C catalyst under gradient-free flow conditions in the presence of pyridine

Article abstract of DOI:10.1007/s11172-016-1549-y

Experimental data on nitro compound uptake, the intermediate product accumulation, and the corresponding amine compound generation were obtained on hydrogenating 3,4-dichloronitrobenzene over Pt/C catalyst in the gradient-free flow regime in the presence and absence of pyridine. In addition, a side reaction of dehalogenation was investigated. The role of pyridine admixture on every step of the process was analyzed and the rate of hydrogenation of the nitro compound was determined both in the presence and in the absence of inhibitor.

Full text of DOI:10.1007/s11172-016-1549-y

2040
Russian Chemical Bulletin, International Edition, Vol. 65, No. 8, pp. 2040—2045, August, 2016
Liquidꢀphase catalytic hydrogenation of 3,4ꢀdichloronitrobenzene over
Pt/C catalyst under gradientꢀfree flow conditions in the presence of pyridine
V. G. Dorokhov, G. F. Dorokhova, and V. I. Savchenko
Institute of Problems of Chemical Physics, Russian Academy of Sciences,
1
prosp. Acad. Semenova, 142432 Chernogolovka, Moscow Region, Russian Federation.
Fax: +7 (496) 522 3507. Eꢀmail: vicd@icp.ac.ru
Experimental data on nitro compound uptake, the intermediate product accumulation, and
the corresponding amine compound generation were obtained on hydrogenating 3,4ꢀdichloroꢀ
nitrobenzene over Pt/C catalyst in the gradientꢀfree flow regime in the presence and absence of
pyridine. In addition, a side reaction of dehalogenation was investigated. The role of pyridine
admixture on every step of the process was analyzed and the rate of hydrogenation of the nitro
compound was determined both in the presence and in the absence of inhibitor.
Key words: liquid phase hydrogenation, catalysis, inhibition, aromatic nitro compounds,
gradientꢀfree flow conditions.
Liquidꢀphase catalytic hydrogenation of chlorineꢀconꢀ
The kinetic experiments were carried out under static conꢀ
ditions at atmospheric hydrogen pressure using the method
of the initial rate measurements. It was found that the
taining aromatic nitro compounds over heterogeneous catꢀ
alysts is one of the effective methods for the industrial
production of amine compounds applied to the synthesis
of pharmaceuticals and chemical protection facilities for
plants. The reaction of interest is accompanied by the side
reaction of chloride ion elimination that more or less readiꢀ
ly proceeds over any known catalyst for hydrogenation. In
addition to a decrease in the yield of the target amine
product, dehalogenation causes heavy corrosion of the apꢀ
paratus. Therefore, the research focused on inhibition of
dehalogenation is of importance. The rate of chloride ion
elimination can be reduced either by selecting the optimal
catalyst or by introducing an appropriate admixture into
the reaction medium.
2
effect of the inhibitor on the hydrogenation reactions of
3,4ꢀDCNB and intermediate 3,4ꢀDCPHA is not competꢀ
itive in nature and inhibition of the mentioned reactions is
mainly caused by general influence of the inhibitor on the
3
adsorption of hydrogen on catalytic surface. Meanwhile,
in the presence of pyridine, the rate of dehalogenation of
3,4ꢀDCA is significantly reduced and molecules of chloroꢀ
aniline and hydrogen compete to occupy the active cites
on the surface of the catalyst.
Under static conditions, hydrogenation process needs
to be realized with low conversions (up to 5—7%) of the
4
feed compound. In this case, adsorption of nitro comꢀ
1
Earlier, we showed that with the introduction of pyriꢀ
pound and intermediate 3,4ꢀDCPHA is so strong that the
ensuing transformation of 3,4ꢀDCA, which is weakly adꢀ
sorbed on the catalyst, is nearly negligible. The processes
of deep conversion are noticeably activated at high conꢀ
versions of the initial and intermediate products. At enꢀ
hanced conversions, hydrogenation of nitro compound and
transformation of the intermediate product seem to proꢀ
ceed independently with respect to conversion of the genꢀ
erated amine compound. Actually, if the process is perꢀ
formed in a batch reactor, all these reactions proceed
simultaneously and interfere with each other. Nevertheless,
under static condition these effects are unlikely to be noꢀ
ticed. One can detect these only when the process is invesꢀ
tigated in a gradientꢀfree flow reactor. However, when
hydrogenation is performed in a flow regime in the presꢀ
ence of highly dispersed catalyst powders, the particles of
the catalyst may be washed out from the reactor with the
reaction flow. We managed to find the conditions at which
dine admixture into the reaction medium in catalytic
hydrogenation of chlorineꢀcontaining aromatic nitro comꢀ
pounds it is possible to effectively inhibit the side reactions
of dehalogenation of chlorineꢀcontaining amine products.
However, the inhibitor affects every step of catalytic hyꢀ
drogenation of aromatic nitro compounds. Hence, in order
to investigate the influence of pyridine explicitly, experiꢀ
mentally found rates of the reactions proceeding in the
presence and absence of pyridine admixtures need to be
compared. Moreover, the parameters affected by the inꢀ
hibitor it is nessary to determine.
Earlier we described the effect of pyridine, which was
used as an admixture, on the rate of hydrogenation of
3
,4ꢀdichloronitrobenzene (3,4ꢀDCNB) as well as on the
rate of hydrogenation of the intermediate compound,
,4ꢀdichloroꢀNꢀphenylhydroxylamine (3,4ꢀDCPHA), and
3
1
the amino product, i.e. 3,4ꢀdichloroaniline (3,4ꢀDCA).
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 2040—2045, August, 2016.
066ꢀ5285/16/6508ꢀ2040 © 2016 Springer Science+Business Media, Inc.
1

Liquidꢀphase catalytic hydrogenation
Russ.Chem.Bull., Int.Ed., Vol. 65, No. 8, August, 2016
2041
hydrogenation proceeds without removal of the catalyst
from the reactor. The experimental procedure for the perꢀ
formance of hydrogenation of nitro compounds over fineꢀ
grained catalysts in the gradientꢀfree flow regime was
described earlier.2
The experimental procedures for hydrogenation performed
in the presence and absence of pyridine have a number of differꢀ
ences. In the experiments conducted without inhibitor, the iniꢀ
tial solution was directly introduced in the reaction mixture conꢀ
taining the catalyst and nitro compound solution and prelimiꢀ
nary hydrogenation of the initially loaded starting nitro comꢀ
pound was not performed. On the contrary, several portions of
The purpose of the present study is to reveal features of
hydrogenation of 3,4ꢀDCNB under gradientꢀfree flow conꢀ
ditions at atmospheric hydrogen pressure both in the presꢀ
ence and absence of pyridine. It was important to obtain
the kinetic data on every step of hydrogenation process,
while taking into account that the reactions proceed simulꢀ
taneously in the presence of heterogeneous catalyst at difꢀ
ferent conversion of the initial feed compound. The deꢀ
tailed information is hardly obtainable when the experiꢀ
ments are carried out in a static regime. At the same time,
in the case of the gradientꢀfree flow regime, all the characꢀ
teristics of the process are maintained constant and the
3
,4ꢀDCNB diluted in IPA and contained inhibitor were conseꢀ
quently reduced using static method untill the constant residual
activity of the catalyst was achieved. The obtained solution with
the inhibitor was then introduced in the reactor and the process
reached steadyꢀstate conditions. Application of this procedure
significantly reduces the time needed to reach steady state.
A decrease in the catalytic activity during the experiment did not
exceed 1%.
Under the above described conditions, the hydrogenation
process is controlled by internal diffusion. The estimation of the
diffusional factors was published earlier.6
By varying the feed rate of the starting mixture (w) it was
possible to determine the stationary concentrations of the initial
compounds and the reaction products at different contact times,
3
reaction system is under the steadyꢀstate conditions. That
is particularly important for heterogeneous reactions. On
the other hand, activity and selectivity of the catalyst under
the steadyꢀstate condition can noticeably be different from
the initial parameters, especially in a multistep process.
Application of gradientꢀfree flow conditions for the study
of such complicated process as hydrogenation of aromatic
nitro compounds in the presence of pyridine allows us
precisely evaluate the influence of inhibitor on every step
of the process in the presence of initial compounds, interꢀ
mediates, and final products and describe the observed
effects using math equations.
which were determined from the equation К = w[A ]/g, where
0
w is the volume feed rate (L h– ), [A ] is the starting concentraꢀ
1
0
–
1
tion of nitro compound in the reaction mixture (mol L ), g is
the catalyst weight (1.00 g).
Results and Discussions
Figure 1 shows the experimental data describing the
effect of the contact time (К) on the relative concentraꢀ
tion (С /A ) of 3,4ꢀDCA, 3,4ꢀDCNB, 3,4ꢀDCPHA, and
i
0
chloride ion at hydrogenation of 3,4ꢀDCNB in the presꢀ
ence and absence of inhibitor.
Experimental
As it can be seen in Fig. 1, introduction of inhibitor
does not change the quantitative composition of the reacꢀ
tion mixture. Nevertheless, as the analysis of the mixture
shows, the reactions of chloride ion abstraction proceed
with a considerably larger extent in the absence of pyridine.
Thus at low values of К, produced aniline undergoes
hydrogenation. In the presence of pyridine, monochloroꢀ
aniline is the main product of dehalogenation and aniline
The procedure for the experiments carried out under gradiꢀ
entꢀfree flow conditions was described earlier. Hydrogenation
3
of 3,4ꢀDCNB was performed in a duckꢀshaped temperatureꢀ
controlled shaker reactor at 50±0.2 °С. The rate of hydrogen
uptake was independent of the number of shakings (i.e. intensity of
4
mixing). The content of nitro compounds, nitroso derivatives,
corresponding amine product, and intermediate 3,4ꢀDCPHA in
the reaction mixture was determined voltammetrically using
is formed in very small amounts. When К is lower than
5
three electrode scheme. The content of chloride ion was estiꢀ
–1 –1
0
.06 mol g
h , concentration of 3,4ꢀDCPHA is reꢀ
mated by potentiometric measurements using mercurimetry
technique.
markably higher in the presence of pyridine than in its
absence (Fig. 2).
Commercial 3,4ꢀdichloronitrobenzene (Specifications TUꢀ
The relationship between relative concentration of
3,4ꢀDCPHA and the contact time is described by a volcanoꢀ
type curve. Moreover, in the presence of pyridine, the peak
6
ꢀ01ꢀ1005ꢀ75) was doubly distilled and doubly recrystallized from
isopropanol (after purification, m.p. 39.6 °C, 99.7—99.9%). Isoꢀ
propanol (reagent grade, Specifications TUꢀ6ꢀ09402ꢀ75) was
used as received. The catalyst was platinum supported on carbon
BPLꢀ2.5 (Specifications TUꢀ602ꢀ7ꢀ99ꢀ78) with 2.2±0.2% Pt.
The particle size of the catalyst was 80—200 мm. The catalyst
is observed at lower values of К (0.06—0.07 mol g–
1
h )
–1
and the maximum concentration of 3,4ꢀDCPHA is ca. 1.3
lower than that observed in the absence of inhibitor. In the
(
1.00 g) was loaded into the reactor containing 30–35 mL of the
–
1 –1
range of К from 0.026 to 0.052 mol g
h , concentration
solution. Reagent grade pyridine used as the inhibitor was doubly
distilled from dry alkali (b.p. 115.5–115.6 °C). Hydrogen (USSR
State Standard GOST 3020ꢀ80) was applied as a reducing agent.
The starting concentrations of 3,4ꢀDCNB in IPA solution
were about 0.41—0.43 mol L . Pyridine concentration was about
0
of 3,4ꢀDCPHA in the reaction mixture without inhibitor
is noticeably lower than the concentration values found in
the presence of pyridine admixture. Nevertheless, the maxꢀ
imum concentration of 3,4ꢀDCPHA obtained in the presꢀ
ence of inhibitor is significantly lower. This result can
–1
–
1
.05 mol L .

2
042
Russ.Chem.Bull., Int.Ed., Vol. 65, No. 8, August, 2016
Dorokhov et al.
Ci/A0
a
C/A
25
a
1
0
0
0
0
.0
.8
.6
.4
.2
1
1
20
1
1
5
0
5
2
3
2
4
0
.05
0.10
0.15 K/mol g–1 h–1
0
.05
0.10
K/mol g–1 h–1
Ci/A0
b
D/C
b
1
0
0
0
0
.0
.8
.6
.4
.2
1
0
1
8
6
4
2
2
3
1
2
4
0
.05
0.10
K/mol g–1 h–1
Fig. 1. The relative concentration (С /A ) of the components as
i
0
a function of the contact time of hydrogenation of 3,4ꢀDCNB in
a gradientꢀfree flow reactor in the absence (a) and presence of
pyridine (b): 3,4ꢀDCA (1), 3,4ꢀDCNB (2), 3,4ꢀDCPHA (3),
0
.05
Fig. 3. Relative concentrations of (С/А) 3,4ꢀDCPHA and
,4ꢀDCNB (a) and the concentration ratio of (D/C) 3,4ꢀDCA
0.10
K/mol g–1 h–1
–
Cl (4).
3
and 3,4ꢀDCPHA (b) as a function of the contact time in the
absence (1) and presence of pyridine (2).
Ci/A0
provide evidence that the passway of the intermediate prodꢀ
uct consumption in the presence of inhibitor is changed.
Figure 3 illustrates the effect of the contact time on the
ratio of concentrations of 3,4ꢀDCPHA to 3,4ꢀDCNB (С/А),
as well as on that of 3,4ꢀDCA to 3,4ꢀDCPHA (D/C).
As shown in Fig. 3, а, in the range of К from 0.0052 to
0
0
0
0
0
0
.30
.25
.20
.15
.10
.05
1
2
–
1
–1
0
.031 mol g
h
the ratio of the stationary concentraꢀ
tions of 3,4ꢀDCPHA and 3,4ꢀDCNB (С/А) is nearly conꢀ
stant. In the presence of inhibitor the ratio is 11—12, while
without inhibitor it is 21—23. With further increase in the
contact time the С/А ratio decreases. Moreover, the deꢀ
crease is more gradual in the presence of pyridine. Such
behavior of the concentration ratio of 3,4ꢀDCPHA and
0
.05
0.10
K/mol g–1 h–1
3
,4ꢀDCNB is not observed when hydrogenation is carried
out under static conditions. The ratio of the stationary
concentrations of 3,4ꢀDCA and 3,4ꢀDCPHA (D/C) (see
Fig. 3, b) regularly decreases in the range of К from 0.0052
Fig. 2. Relative concentration of 3,4ꢀDCPHA (С /A ) as a funcꢀ
tion of the contact time in the absence (1) and presence of
pyridine (2).
i
0

Liquidꢀphase catalytic hydrogenation
Russ.Chem.Bull., Int.Ed., Vol. 65, No. 8, August, 2016
2043
V/mol g–1 h–1
Vc/mol g–1 h–1
a
0
0
0
0
0
0
.30
.25
.20
.15
.10
.05
1
0
0
0
0
.04
.03
.02
.01
1
2
2
3
4
0
.05
0.10
K/mol g–1 h–1
V/mol g–1 h–1
b
0.10 K/mol g–1 h–1
0
0
0
0
.20
.15
.10
.05
0.05
Fig. 5. Dependence of the accumulation rate of 3,4ꢀDCPHA
Vc) on the contact time in the absence (1) and presence of the
1
(
inhibitor (2).
although, as it follows from Fig. 2, the concentration of
,4ꢀDCPHA is lower in the presence of pyridine.
Without inhibitor, the rate of chloride ion elimination
increases (see Fig. 4). When the contact time increases from
3
2
3
–
1
–1
a lowest value up to 0.094 mol g
h , the rate of chloride
–
ion formation (w[Cl ]) increases, reaches a maximum and
then decreases. One can assume that in the absence of the
inhibitor the abstraction of chloride ion is not the only
reaction proceeding at low contact times, and the side
processes involving aniline can occur in the reaction system.
In the presence of inhibitor, the accumulation rate of chlorꢀ
ide ion gradually is reduced with increasing contact time.
Taking into account literature data and the results deꢀ
scribed above, catalytic hydrogenation of 3,4ꢀDCNB in
lower (С —С ) aliphatic alcohols, which contain water,
4
0
.05
0.10 K/mol g–1 h–1
Fig. 4. Dependences of the rates of uptake of Н (1) and 3,4ꢀ
DCNB (2) as well as accumulation of 3,4ꢀDCA (3) and chloride
ion [Cl ]•10 (4) on the contact time in the absence (а) and
presence of the inhibitor (b).
2
–
2
to 0.12 mol g–1 h–1. However, at К above 0.12 mol g–1 h–1
it approaches a constant value.
1
4
in the presence of Pt/С catalyst in neutral and acid media
can be described by the following scheme.
It seems important to consider the impact of the conꢀ
tact time on the rates of hydrogen uptake (V ), nitro comꢀ
Н
pound consumption (V ), amine compound production
a
–
Scheme 1
(
V ), and chloride ion production (w[Cl ]) (Figs 4 and 5).
d
In the presence of inhibitor, the rate of 3,4ꢀDCNB
consumption (V ) (see Fig. 4) at high contact time deꢀ
a
creases nearly twoꢀfold, whereas the rate of hydrogen upꢀ
take (V ) shows ca. a 1.8ꢀfold decrease.
h
Correlation between the rate of 3,4ꢀDCA formation
(
Vd) and K parameter (see Fig. 4) both in the presence and
absence of pyridine is described by a curve with a maxiꢀ
mum. It is worth noting that in the presence of the inhibiꢀ
3
,4ꢀDCNB
3,4ꢀDCPHA
3,4ꢀDCA
tor, V magnitude decreases about 1.6 times.
d
At K ranging from 0.0052 to 0.073 mol g h–1, the
intermediate product (see Fig. 5) is accumulated faster in
the presence of inhibitor. With at further increase in the
–1
–
1
–1
contact time (K > 0.073 mol g
h ) the intermediate
product is accumulated faster in the absence of pyridine,
Monochloraniline
Aniline

2
044
Russ.Chem.Bull., Int.Ed., Vol. 65, No. 8, August, 2016
Dorokhov et al.
The addition of the first hydrogen molecule to a nitro
both hydrogenation of RNO and disproportionation of
2
compound results in the formation of nitroso compound.
However, in our experiments we failed to detect the comꢀ
pound in the reaction mixture, even in trace amounts.
Obviously, under the applied conditions the nitroso comꢀ
pound is more reactive and can be adsorbed on the cataꢀ
lyst stronger than the initial nitro compound. That is why
it can be considered as an acceptor of hydrogen. Accordꢀ
ingly, the starting nitro compound, 3,4ꢀDCNB, converts
into 3,4ꢀDCPHA without desorption of nitroso compound
into the reaction medium.
3,4ꢀDCPHA without participation of hydrogen.
6
Earlier, we showed that the kinetic constants of hyꢀ
drogenation of a nitro compound can be determined by
graphical linearization of the equation which describes
the rate of consumption of this compound:
V = k f /[1 + b C/(b A) + b D/(b A)],
А
A
H
c
a
d
a
where V is the consumption rate of the nitro compound
A
–1 –1
(
(
mol g
mol g
h
); kA is the rate constant of hydrogenation
–1 –1
h ); b , b , b , А, С, D are the adsorption coeffiꢀ
a
c
d
Generated 3,4ꢀDCPHA can attach one hydrogen molꢀ
ecule and suffer transformation into the amine product
through hydrogenation. It also can undergo disproporꢀ
tionation which is catalyzed by Pt/С and form amine
cients and concentrations of 3,4ꢀDCNB, 3,4ꢀDCPHA,
and 3,4ꢀDCA, respectively; fH is the efficiency factor for
hydrogen. In the absence of pyridine the referred equation
transforms into:
7
product, nitroso compound, and water. The obtained
nitroso compound is hydrogenated to 3,4ꢀDCPHA. Hence
Scheme 1 of nitro compound transformation can be supꢀ
(
1)
8—9
plemented by Scheme 2.
The adequacy of this scheme
is indirectly supported with the experimental data preꢀ
sented below.
In the presence of pyridine it can be written as
(2)
Scheme 2
where VH is a current rate of hydrogen uptake; V 0 is the
H
rate of hydrogen uptake in a regime where it is indepenꢀ
*
dent of the contact time; k and k are the rate constants
A
А
of nitro compound consumption in the absence and presꢀ
ence of pyridine, correspondingly.
By processing the experimental data and using the Eqs (1)
*
*
and (2), the relationships between b /b and b /b , b /b ,
d
a
d
a
c
a
*
*
and b /b can be determined as well as the ratio of b /b
d
c
a
c
*
*
to b /b can be evaluated.
c
d
Figure 6 shows linearization of the Eqs (1) and (2) in
the absence and presence of inhibitor, respectively. The
obtained values of the constants are presented in Table 1.
As it follows from the data given in Table 1, admixꢀ
ture of pyridine in the reaction mixture makes adsorpꢀ
tion of the amine product less preferable compared with
adsorption of the nitro compound and Nꢀarylhyrdoxyꢀ
Under the conditions of hydrogenation, the generated
RNO cannot be desorbed from the catalyst surface into
the solution.
The amine product, 3,4ꢀDCA, undergoes side dehaloꢀ
genation with the chloride ion being abstracted just thereꢀ
from.8
Scheme 2 includes disproportionation of 3,4ꢀDCPHA
that was usually neglected in the earlier investigations of
the kinetics of hydrogenation of aromatic nitro comꢀ
pounds. According to the Scheme 2, the reaction is indeꢀ
pended of hydrogen pressure, so a definite amount of the
amine product and nitroso compound is generated directꢀ
ly without involvement of hydrogen. Nevertheless, hydroꢀ
genation of the obtained nitro compound proceeds avoidꢀ
ing the step of desorption from the catalytic surface. This can
give a favourable ground for the suggestion that conversion
of nitro compound, if it follows the referred pathway,
may depend on hydrogen pressure. Thus theoretically,
1
lamine. As we showed earlier, adsorptions of pyridine
and 3,4ꢀDCA are competitive and pyridine suppresses adꢀ
Table 1. The ratio of adsorption coefficients in Eqs (1)
and (2)
Ratio of the
adsorption
coefficients
Conditions of hydrogenation
in the absence
in the presence
of pyridine
of pyridine
ba/b
ba/bd
bc/bd
c
10.5
64.0
16.1
112.1
111.0
119.2
3,4ꢀDCPHA can be formed via oneꢀstep hydrogenation of
the starting RNO and RNH can be obtained through
2
2

Liquidꢀphase catalytic hydrogenation
Russ.Chem.Bull., Int.Ed., Vol. 65, No. 8, August, 2016
2045
[
VA0VH0/(V V ) – 1]•A/C
a
pensated by corresponding decrease in the rate of conꢀ
sumption of the initial nitro compound. Hence in this
range of the contact time the intermediate product conꢀ
centration is higher in the presence of inhibitor. When the
A
H
8
7
6
5
4
3
2
1
–
1
–1
contact time is above 0.05 mol g
h , the concentration
of 3,4ꢀDCPHA decreases faster in the presence of inhibiꢀ
tor. Such behavior is attributed to the predominate realꢀ
ization of the second scheme of the intermediate product
consumption, the reaction rate of which markedly deꢀ
creases in the presence of pyridine.
To sum up, hydrogenation of 3,4ꢀDCNB over Pt/C
catalyst both in the presence and absence of pyridine was
studied under gradientꢀfree flow conditions. It was shown
that the inhibitor affects the conversion of the initial nitro
compound to a much smaller extent than the reaction of
dehalogenation.
1
00
200
300
400
500 D/C
An influence of inhibitor on the rate of accumulation
and consumption of the intermediate 3,4ꢀDCPHA was
investigated. It was shown that a specific passway folꢀ
lowed by the reaction of disproportionation plays a particꢀ
ular role in the pattern of conversion of the intermediate
compound and it decreases its maximum concentration of
this product in the reaction medium.
An influence of inhibitor on dehalogenation of the obꢀ
tained chlorine derived amine product was investigated. It
was established that introduction of pyridine inhibits side
reactions such as chloride ion eliminating and suppresses
a deeper conversion of aniline.
[
VA0VH0/(V V ) – 1]•A/C
b
A
H
1
1
0
0
0
.25
.00
.75
.50
.25
References
1
. V. G. Dorokhov, V. I. Savchenko, Kinet. Catal. (Engl. Transl.),
014, 55, 445 [Kinetika i Kataliz, 2014, 55, 467].
2
5
50
75
100
125
D/C
2
Fig. 6. Graphical analysis of Eqs (1) and (2) based on data of
hydrogenation of 3,4ꢀDCNB in the absence (a) and presence of
pyridine (b).
2. S. L. Kiperman, Vvedenie v kinetiku geterogenyh katalꢀ
iticheskih reaktsii [Introduction to the kinetics of heterogeneous
reactions], Nauka, Moscow, 1964, 508 pp. (in Russian).
3
. D. V. Sokol´skii, Gidrirovanie v rastvorah [Hydrogenation in
solutions], Izd. AN KazSSR, AlmaꢀAta, 1962, 281 pp.
(
in Russian).
. V. G. Dorokhov, V. I. Savchenko, Kinet. Catal. (Engl. Transl.),
991, 32, 49 [Kinetika i Kataliz, 1991, 32, 60].
. Pat. USSR No. 1217087, Byull. Izobret. [Invention Bull.],
000, No. 36 (in Russian).
. V. G. Dorokhov, V. I. Savchenko, Kinet. Catal. (Engl. Transl.),
996, 37, 229 [Kinetika i Kataliz, 1996, 37, 245].
sorption of the latter and decrease the rate of the following
reactions. At the same time, pyridine nonꢀcompetitively
diminishes the rate of hydrogenation of nitro compound,
while the rate of consumption of the intermediate product
has a complicated pattern in the presence of pyridine.
An increase in the concentration of the intermediate prodꢀ
uct within low contact time interval in the presence of
pyridine indicated above (see Fig. 2) can be explained by
a weaker adsorption of the intermediate product compared
to nitro compound. A decrease in the maximum concenꢀ
tration of the intermediate product in the presence of inꢀ
hibitor may be related to an increased reaction rate of
4
5
6
1
2
1
7. V. I. Savchenko, T. V. Denisenko, S. Ya. Sklyar, V. D. Simoꢀ
nov, Zh. Organ Khim. (Engl. Transl.), 1975, 11, 2149 [J. Org.
Chem. USSR, 1975, 11].
. T. V. Denisenko, V. I. Savchenko, V. D. Simonov, S. Ya.
Sklyar, Zh. Organ Khim. (Engl. Transl.), 1982, 18, 1498
8
[
J. Org. Chem. USSR, 1982, 18].
9
. V. D. Simonov, T. V. Denisenko, V. I. Savchenko, S. Ya.
Sklyar, N.M. Ryazanova, Khim. Promyshlenost´ [Chem.
Industry], 1977, 579 pp. (in Russian).
3
,4ꢀDCPHA into the amine product caused by disproporꢀ
tination proceeded in the presence of added pyridine.
In the range of low contact times (up to 0.05 mol g–1 h ),
a decrease in the rate of hydrogenation of the intermediate
product in the presence of pyridine, actually, is not comꢀ
–1
Received January 27, 2016;
in revised form June 7, 2016