Features of dicyclopentene formation during hydrogenation of dicyclopentadiene

Article abstract of DOI:10.1134/S0965544115080198

General trends and specific features of the reaction of dicyclopentadiene (tricyclo[5.2.1.0^2.6]decadiene-3,8) hydrogenation to dicyclopentene (tricycle[5.2.1.0^2.6]decene-3) with hydrogen in the liquid phase under mild conditions at atmospheric pressure over a finely divided 1% Pd/C catalyst have been studied. The kinetic parameters that characterize the effect of the solvent nature, catalyst concentration, and temperature on the rate of hydrogen uptake in the hydrogenation process have been determined. To substantiate the conclusion of the sequence of saturation of the dicyclopentadiene double bonds in terms of the mechanism of heterogeneous catalysis, their reactivity has been compared. It has been shown that in the presence of a number of functionalized aromatic compounds as a stabilizing additive, the yield of desired dicyclopentene increases to 98.5-99 mol % with the complete conversion of dicyclopentadiene. The structure of dicyclopentadiene and its hydrogenation product dicyclopentene has been confirmed using spectroscopic methods.

Full text of DOI:10.1134/S0965544115080198

ISSN 0965ꢀ5441, Petroleum Chemistry, 2016, Vol. 56, No. 1, pp. 38–43. © Pleiades Publishing, Ltd., 2016.
Original Russian Text © N.V. Vereshchagina, T.N. Antonova, A.A. Il’in, Zh.B. Chirkova, 2016, published in Neftekhimiya, 2016, Vol. 56, No. 1, pp. 46–51.
Features of Dicyclopentene Formation during Hydrogenation
of Dicyclopentadiene
N. V. Vereshchagina, T. N. Antonova, A. A. Il’in, and Zh. V. Chirkova
Yaroslavl State Technical University, Yaroslavl, Russia
eꢀmail: antonovatn@ystu.ru
Received January 15, 2015
Abstracts—General trends and specific features of the reaction of dicyclopentadiene (tricyclo[5.2.1.02.6]decꢀ
adieneꢀ3,8) hydrogenation to dicyclopentene (tricycle[5.2.1.02.6]deceneꢀ3) with hydrogen in the liquid phase
under mild conditions at atmospheric pressure over a finely divided 1% Pd/C catalyst have been studied. The
kinetic parameters that characterize the effect of the solvent nature, catalyst concentration, and temperature
on the rate of hydrogen uptake in the hydrogenation process have been determined. To substantiate the conꢀ
clusion of the sequence of saturation of the dicyclopentadiene double bonds in terms of the mechanism of
heterogeneous catalysis, their reactivity has been compared. It has been shown that in the presence of a numꢀ
ber of functionalized aromatic compounds as a stabilizing additive, the yield of desired dicyclopentene
increases to 98.5–99 mol % with the complete conversion of dicyclopentadiene. The structure of dicyclopenꢀ
tadiene and its hydrogenation product dicyclopentene has been confirmed using spectroscopic methods.
Keywords: dicyclopentadiene, dicyclopentene, liquidꢀphase hydrogenation, finely divided catalyst, doubleꢀ
bond reactivity
DOI: 10.1134/S0965544115080198
Dicyclopentene as the desired product of hydrogeꢀ
nation of dicyclopentadiene can be successfully used
in the synthesis of various oxygenated products with
various functional groups and individual structures,
which is especially important for the production of
biologically active substances and medicaments on
their basis. Furthermore, oxygenꢀcontaining dicycloꢀ
pentene derivatives are of interest for the fabrication of
polymers, liquid crystals, and other materials [1–4].
At the same time, it was found [1] that in the case
of dicyclopentadiene hydrogenation under atmoꢀ
spheric pressure over supported palladium catalysts,
either finely divided or shaped, the yield of target dicyꢀ
clopentene can be as high as 92 mol % and the dihydꢀ
rodicyclopentadiene) (dicyclopentene) to tetrahydꢀ
rodicyclopentadiene (dicyclopentane) ratio is 11.5 : 1.
Finely divided catalysts are convenient for practical
implementation of the process. By vigorous agitation,
the threeꢀphase gas–liquid–solid catalyst system is
maintained in a pseudoꢀhomogeneous state, which
ensures the kinetic regime of the reaction [13, 14].
In this paper we present the results of studying the
features of dicyclopentene formation during the
hydrogenation of dicyclopentadiene at atmospheric
pressure using a finely divided 1% Pd/C catalyst.
The hydrogenation of dicyclopentadiene aimed to
produce dicyclopentene (dihydrodicyclopentadiene)
and dicyclopentane (tetrahydrodicyclopentadiene)
was studied by many investigators using platinum
group catalysts or nickel catalysts [4–12] in various
solvents [5, 7, 8], primarily at an elevated hydrogen
pressure (up to 10 MPa) [5–11]. For example, Ualikhꢀ
anova et al. [5] noted that pressure elevation from 0.5
to 2.0 MPa during dicyclopentadiene hydrogenation
on palladium black led to an increase in the rate of the
process. The further increase in pressure to 4.0 MPa,
conversely, reduced the rate by a factor of 4. As shown
in the cited study and noticed by Behr et al. [6], an
increase in the hydrogen pressure has a negative effect
on the selectivity of the reaction. The ratio of the
hydrogenation products dihydrodicyclopentadiene
and tetrahydrodicyclopentadiene on a palladium cataꢀ
lyst with a particle size of 5–7 nm (nanocatalyst) may
range from 7 : 1 to 1 : 8 depending on the pressure
used.
EXPERIMENTAL
Liquidꢀphase dicyclopentadiene hydrogenation
with hydrogen was carried out in the presence of the
finely divided 1% Pd/C catalyst, purchased from the
AllꢀUnion Research and Design Institute for Monoꢀ
mers (VNIPIM), Tula, in a batch volumetric unit or a
flow system in excess hydrogen. Experiments were
evaluated by measuring the hydrogen uptake and the
amount of products in the reaction mixture, which was
analyzed by GLC. The data obtained made it possible
to calculate the effective hydrogen uptake, the (degree
of) conversion of dicyclopentadiene, and the yield of
38

FEATURES OF DICYCLOPENTENE FORMATION
39
the products on a hydrogen absorbed or dicyclopentaꢀ
1
2.0
1.6
1.2
0.8
0.4
2
diene consumed basis. The chromatographic analysis
was performed on Chromatec Kristall 5000.2 instruꢀ
ment using a CRꢀ5 capillary column of 30 m in length
and 0.32 mm in diameter coated with 5% phenyl
(95%) dimethylpolysiloxane, a film thickness of
3
4
0.5 m. The evaporator temperature was 220°С, and
μ
5, 6, 7
the column temperature was programmed from 70 to
160°C at a heating rate of 10°C/min. The carrier gas
(nitrogen) flow rate was 60 cm3/min.
The structure of the reactant dicyclopentadiene
(
endoꢀtricyclo[5.2.1.02.6]decadieneꢀ3,8)
and
its
hydrogenation product dicyclopentene (tricyꢀ
clo[5.2.1.02.6]deceneꢀ3) was confirmed using spectroꢀ
scopic methods. 1H NMR spectra were recorded on a
Bruker DRX_500 instrument in DMSOꢀd6 solutions
at 30°С. As a reference standard for the chemical shift,
0
20
40
60
80 100 120
Time, min
the signals of residual solvent protons in the proton
spectra (ΔδH 2.50 ppm) were used.
Dicyclopentene (tricyclo[5.2.1.02.6]deceneꢀ3). 1H
NMR (500 MHz, DMSOꢀd6): 1.26–1.16 (m, 4 H),
Fig. 1. Rate curves of hydrogen uptake during the hydrogeꢀ
nation of dicyclopentadiene.
= 4 g/dm ; C ,
333 K.
1.38 (1 H dt,
dt, = 9.1 Hz,
(2 H, ddd, = 9.3 Hz,
2.27 (br. s., 1 H), 2.48 (1 H, ddd,
J
= 9.1 Hz,
= 1.6 Hz Hꢀ10), 2.11 (br. s, 1 H), 2.16
= 4.2 Hz, = 2.2 Hz, Hꢀ5),
= 9.3, = 4.2 Hz,
= 1.6Hz, Hꢀ6), 2.97 (1 H, ddd, = 2.4 Hz,
= 4.6 Hz, Hꢀ2), 5.56 (1 H, dddd, = 5.8,
J = 1.6 Hz Hꢀ10’), 1.46 (1 H
3
3
C
= 1.04 mol/dm ; temperature,
cat
0 DCPD
J
J
J
J
J
Solvents: (
1
) 2ꢀpropanol (313 K), (
) toluene, (5–7) toluene with
ꢀdimethylꢀ ꢀphenylenediamine, and
) hydroquinone additives in an amount of 1% of
2) cyclooctane,
J
J
(
(
(
3
5
7
) cyclooctane (323 K), (
4
J
J
J
J
=
=
) ionol, (6)
N,
N
p
C
.
2.5 Hz,
4.6 Hz,
J
J
J
J
J
cat
= 2.2 Hz,
= 4.2 Hz,
J
J
= 0.8 Hz Hꢀ3), 5.67 (1 H, ddd,
= 2.2 Hz, Hꢀ4).
= 5.8,
tane or toluene solution, the hydrogen uptake rate
curves exhibit distinct segments corresponding to the
hydrogenation of a dicyclopentadiene double bond
and then the double bond of dicyclopentene.
RESULTS AND DISCUSSION
Figure 1 shows rate curves of hydrogen uptake durꢀ
The rate of hydrogen uptake in the hydrogenation
of the dicyclopentadiene double bond, as calculated
from the data of Fig. 1, is greater than the rate of satuꢀ
ration of the dicyclopentene double bond in toluene
(by a factor of 6.7) or cyclooctane (by a factor of 2.4)
(Table 1).
ing the hydrogenation of dicyclopentadiene in solvents
of different natures (2ꢀpropanol, cyclooctane, toluꢀ
ene).
According to the data (Fig. 1), the dicyclopentadiꢀ
ene hydrogenation rate is the lowest in the toluene
solution and the highest in the 2ꢀpropanol solution.
The hydrogen uptake rate in 2ꢀpropanol is so high that
It should be noted that in the case of hydrogenation
it cannot be a differentiating solvent in the hydrogenaꢀ in toluene, there was some period of time, during
tion of double bonds. The dicyclopentadiene double which hydrogen was actually not consumed (Fig. 1,
bonds are hydrogenated successively, but continuꢀ curve
ously, almost at the same rate in this solvent (Fig. 1, ing solvent that is a quite obviously preferred choice
curve ). At the same time, in the case of saturation of for the selective hydrogenation of dicyclopentadiene
4). This behavior shows toluene as a differentiatꢀ
1
the double bonds of dicyclopentadiene in a cycloocꢀ to dicyclopentene. The product formation sequence
Table 1. Ratio of rates of the doubleꢀbond hydrogenation reactions of dicyclopentadiene and dicyclopentene depending on
the nature of the solvent
Rate of hydrogenation of DCPD Rate of hydrogenation of DCP
Solvent
Cyclooctane
Cyclooctane
Toluene
T
, K
double bond (
W
ef 1),
double bond (
W
ef 2),
Wef 1/Wef 2
mol/(dm3 min)
mol/(dm3 min)
323
333
333
343
0.0163
0.0343
0.0188
0.0333*
0.0074
0.0142
0.0028
0.0050*
2.20
2.42
6.71; 6.48*
6.65*
Toluene
* According to data in Fig. 3b.
PETROLEUM CHEMISTRY Vol. 56
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40
VERESHCHAGINA et al.
molecule to that in the fiveꢀmembered ring of dicycloꢀ
0.8
0.6
0.4
0.2
pentene depends on the solvent nature, but it is invariꢀ
ant to the initial concentration of the substrate in the
feed solution and the reaction temperature.
3
2
To confirm the experimental data on the preferenꢀ
tial hydrogenation of the double bond in the bicycloꢀ
heptene moiety of the dicyclopentadiene molecule, we
performed a comparative assessment of the reactivity
of the double bonds of the hydrocarbons subject to
hydrogenation using a quantumꢀchemical method
(DFT simulation) with the ab initio/6ꢀ31 G** basis
set. As a doubleꢀbond reactivity index, the electroꢀ
1
0
100
200
300
400
Time, min
static term of the Klopman equation (
I
= |q1 q2|/l) was
⋅
Fig. 2. Reactant consumption and product buildup rate
curves in the dicyclopentadiene hydrogenation process.
Solvent: toluene;
used. It was calculated from the values of charge on
carbon atoms at the double bonds with taking account
of the bond lengths [15]. The simulation results
describing the properties of the double bonds are preꢀ
sented in Table 2.
3
3
C
= 0.8 mol/dm ;
C
= 4 g/dm ;
0 DCPD
cat
temperature, 338 K.
) dicyclopentadiene, (
pentane.
(1
2) dicyclopentene, (3) dicycloꢀ
As follows from the data in Table 2, the Klopman
charge/charge term for tricyclo[5.2.1.02.6]decadieneꢀ
3,8 has a lesser value for the double bond of the bicyꢀ
cloheptene (norbornene) moiety (8–9 position).
Therefore, this double bond has a lower order with
respect to the electrons that form it (i.e., is rehybridꢀ
ized) and, hence, a higher reactivity in the hydrogenaꢀ
tion reaction as compared with the double bond in the
3–4 position of this molecule or the dicyclopentene
during the hydrogenation of dicyclopentadiene in the
toluene solution is shown in Fig. 2.
The resulting ratio of the rates of hydrogenation of
dicyclopentadiene double bonds is confirmed by the
data on separate hydrogenation of dicyclopentadiene
to dicyclopentene (dihydrodicyclopentadiene)) and
dicyclopentene to dicyclopentane (tetrahydrodicycloꢀ
pentadiene) over 1% Pd/C at their equal initial conꢀ
centrations in the toluene solution (Figs. 3a, 3b;
Table 1).
double bond (quantity 1/I, Table 2).
The fact that the selective reduction leaves intact
the double bond between the C3–C4 carbon atoms of
Thus, the ratio of the rate of double bond saturation the tricyclo[5.2.1.02.6]decadieneꢀ3,8 molecule was
in the bicycloheptene moiety of the dicyclopentadiene confirmed by spectral data (NMR, COSY spectra).
(b)
(a)
2
'
3
'
343 К
333 К
1
2.0
1.5
1.0
0.5
0.04
0.03
0.02
0.01
343 К
333 К
2
3
1
4
3
2
4
0
200
400
600
800
Time, min
0
0.2 0.4 0.6 0.8 1.0
n(H )/n of substrate
2 0
Fig. 3. Rate curves for (a) substrate consumption in the hydrogenation of (1, 2) dicyclopentadiene to dicyclopentene and (3, 4
dicyclopentene to dicyclopentane and ( ', ') dicyclopentene and dicyclopentane buildup rate curves, respectively. (b) Temperaꢀ
ture dependence of the rate of the process.
)
2
3
3
3
Solvent: toluene,
C
= 2.0 mol/dm ,
C
= 4 g/dm .
0
cat
PETROLEUM CHEMISTRY Vol. 56
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FEATURES OF DICYCLOPENTENE FORMATION
41
Table 2. Energy characteristics of dicyclopentadiene and dicyclopentene and reactivity indices of their double bonds
Hydrocarbon
to be
hydrogenated
Charge
on carbon
atoms,
Total energy,
kcal/mol
Bond length,
l
, nm
I
×
103
1/
I
10–3
×
q
10
1
–C8=C9–
C8. 0.009
–C8=C9–
–C8=C9–
9
2
–241180.4
0.13221
C9. 0.015
1.021
0.9793
7
3
6
5
8
4
Dipole moꢀ
ment (total)
0.1020
(–384.345)
–242732.2
–C3=C4–
C
3. –0.024
4. 0.007
–C3=C4–
–C3=C4–
0.13194
C
1.273
0.7854
10
–C3=C4–
C
3. –0.0125
4. –0.0125
–C3=C4–
–C3=C4–
1
6
9
2
7
3
8
0.13223
C
1.1816
0.8463
5
4
Dipole moment
(total) 0.1396
(–386.818)
Similar quantumꢀchemical calculations using the completion is proportional to the initial concentration
B3LYP/6ꢀ31G* basis set were performed earlier by of the substrate in the solution. Nonetheless, in order
Zou et al. [10] to explain the specifics of dicyclopentaꢀ to obtain dicyclopentene, it is reasonable to use rather
diene hydrogenation to dicyclopentane (tetrahydrodiꢀ concentrated solutions of dicyclopentadiene in toluꢀ
ene (30 wt %; 2.10 mol/dm3). Thus, the productivity
of equipment can be enhanced in the case of possible
implementation of the process.
cyclopentadiene) on a skeletal nickel catalyst (SRNAꢀ
4) at a hydrogen pressure of 1.5 MPa. The set of their
calculation results allowed the cited authors to conꢀ
clude that the double bond of the norbornene moiety
of the dicyclopentadiene molecule is superior in reacꢀ
tivity. However, they found that both 3,4ꢀdihydrodicyꢀ
clopentadiene and 8,9ꢀdihydrodicyclopentadiene are
formed as hydrogenation intermediates, which are
then hydrogenated to tetrahydrodicyclopentadiene in
the parallel reactions, but the double bond in the norꢀ
bornene moiety of dihydrodicyclopentadiene disapꢀ
pears at a higher rate. According to the reported data
[10], the nickel catalyst is not selective in the hydrogeꢀ
nation of the dicyclopentadiene double bonds, unlike
the palladium catalyst (1% Pd/C) used in this work.
The hydrogenation rate is affected by the partial
pressure of hydrogen in the system and the mixing effiꢀ
ciency of the reaction components. As the partial presꢀ
sure of hydrogen in the nitrogen–hydrogen mixture
increases in the range of 0.06–0.090 MPa, the rate of
hydrogenation increases proportionally (Fig. 4b). The
proportionality saturates at a hydrogen pressure of
0.095–0.11 MPa, i.e., when the pressure in the system
is close to atmospheric. Apparently, the dicyclopentaꢀ
diene hydrogenation process over the finely divided
catalyst at atmospheric pressure occurs in the absence
of not only internal, but also external diffusion conꢀ
straints, i.e., in the kinetic region.
Figure 4a shows the dependence of the rate of
hydrogen uptake during the hydrogenation of dicycloꢀ
pentadiene to dicyclopentene upon the catalyst conꢀ
centration. Its change in the range of 2–7 g/dm3 leads
to a proportional increase in the reaction rate, irreꢀ
spective of the nature of the solvent (toluene, 2ꢀproꢀ
panol), thereby indicating that the test reaction is first
order with respect to the catalyst. On the other hand,
The calculated value of the effective activation
energy for the reaction of dicyclopentadiene hydrogeꢀ
nation to dicyclopentene depends on the nature of the
solvent and lies within 52–64 kJ/mol (Table 3). The
finding suggests that the hydrogenation of dicyclopenꢀ
tadiene to dicyclopentene under the given conditions
the hydrogenation rate of dicyclopentadiene does not can be assigned in terms of its kinetic parameters to
depend on its initial concentration in the solution type III hydrogenation reactions (by Sokol’skii’s clasꢀ
(Fig. 4a) and, hence, the reaction is zero order in the sification) [16, 17], in which the rateꢀlimiting step is
reactant. The time taken by a zeroꢀorder reaction for hydrogen activation on the catalyst surface.
PETROLEUM CHEMISTRY Vol. 56
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42
VERESHCHAGINA et al.
(а)
0 DCPD, mol/dm3
(b)
C
0
0.5
1.0
1.5
2.0
2.5
2
0.08
0.06
0.04
0.02
0.04
4
1
0.02
3
0
0.06
0
2.0
4.0
cat, g/dm3
6.0
8.0
0.08
PH , MPa
0.10
C
2
Fig. 4. Dependence of the hydrogen uptake rate on (a) the initial concentration of dicyclopentadiene and catalyst concentration
and (b) the partial pressure of hydrogen.
Solvents: (1, 2) 2ꢀpropanol, (3, 4) toluene.
In some studies on the hydrogenation of dicycloꢀ zation under hydrogenation conditions in a toluene
solution with the aim to increase the yield of the
desired product dicyclopentene. These compounds
pentadiene [7–10], the effective activation energy of
saturation of its double bonds was found to be noticeꢀ
were
naphthylamine,
p
ꢀhydroxydiphenylamine, hydroquinone,
β
ꢀ
ably lower: E1st = 3.19–24.7 kJ/mol,
E2st = 12.20–
N,
N
ꢀdimethylꢀ ꢀphenylenediamine,
p
40.9 kJ/mol. As noted by Sokol’skii [16], a significant
difference in the values of the activation energy of the
hydrogenation reaction is quite acceptable since the
hydrogenation of the same compound under widely
varying conditions (catalyst, reaction temperature,
solvent, hydrogen pressure) can follow different, often
related mechanisms.
2,6ꢀdiꢀtertꢀbutylꢀ4ꢀmethylphenol (ionol), which are
inhibitors of radical chain processes. The stabilizing
additives, regardless of their structure, do not affect
the rate of hydrogenation of the dicyclopentadiene
and, next, the dicyclopentene double bond (Fig. 1,
curves 5–7), but they can increase the selectivity for
dicyclopentene (tricyclo[5.2.1.02.6]deceneꢀ3) from
92% [1] to 98.5–99 mol % with the almost complete
conversion of dicyclopentadiene [2]. Apparently, the
additives are able to modify the catalyst surface and,
consequently, enhance the differentiating properties
of toluene in the sequential saturation of double
bonds.
Since dicyclopentadiene is an unsaturated hydroꢀ
carbon capable of polymerizing, several functionalꢀ
ized aromatic compounds taken in an amount of 1–
5% of 1% Pd/C catalyst mass were used for its stabiliꢀ
Table 3. Kinetic parameters of dicyclopentadiene hydrogeꢀ
nation to dicyclopentene
To summarize, the successive saturation of double
bonds during the hydrogenation of dicyclopentadiene
endoꢀtricyclo[5.2.1.02.6]decadieneꢀ3,8) over 1%
Wef
,
(
T
, K
E
eff, kJ/mol
Y
mol/(dm3 min)
Pd/C with differentiation of their saturation rates
ensures the selective formation of dicyclopentene (triꢀ
cyclo[5.2.1.02.6]deceneꢀ3).
Cyclooctane
313
323
333
0.008
0.016
0.035
63.8 3.2
Toluene
2.09
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Translated by S. Zatonsky
PETROLEUM CHEMISTRY Vol. 56
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2016