1,3-Cyclohexadiene hydrogenation in the presence of a palladium-containing catalytic system based on an MOF-5/calixarene composite

Article abstract of DOI:10.1134/S0023158411010058

A palladium-containing material based on the new metal-organic framework structure MOF-5/20% calix[4]arene have been synthesized and characterized by physical and chemical methods for the first time. The catalytic activity of the 3% Pd/MOF-5/20% calix[4]arene composite in partial 1,3-cyclohexadiene hydrogenation into cyclohexene is fairly high and is comparable with that of the 5% Pd/C reference catalyst.

Full text of DOI:10.1134/S0023158411010058

ISSN 0023ꢀ1584, Kinetics and Catalysis, 2011, Vol. 52, No. 1, pp. 94–97. © Pleiades Publishing, Ltd., 2011.
Original Russian Text © V.I. Isaeva, A.L. Tarasov, O.P. Tkachenko, G.I. Kapustin, I.V. Mishin, S.E. Solov’eva, L.M. Kustov, 2011, published in Kinetika i Kataliz, 2011, Vol. 52,
No. 1, pp. 95–98.
1,3ꢀCyclohexadiene Hydrogenation in the Presence
of a PalladiumꢀContaining Catalytic System Based
on an MOFꢀ5/Calixarene Composite
V. I. Isaeva*, A. L. Tarasov, O. P. Tkachenko, G. I. Kapustin,
I. V. Mishin, S. E. Solov’eva, and L. M. Kustov**
Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Moscow, 119991 Russia
*eꢀmail: sharf@ioc.ac.ru
**eꢀmail: LMK@ioc.ac.ru
Received October 16, 2009
Abstract—A palladiumꢀcontaining material based on the new metalꢀorganic framework structure MOFꢀ
5/20% calix[4]arene have been synthesized and characterized by physical and chemical methods for the first
time. The catalytic activity of the 3% Pd/MOFꢀ5/20% calix[4]arene composite in partial 1,3ꢀcyclohexadiene
hydrogenation into cyclohexene is fairly high and is comparable with that of the 5% Pd/C reference catalyst.
DOI: 10.1134/S0023158411010058
Metalꢀorganic frameworks (MOFs) are crystalline calixarene are characterized by a high degree of crysꢀ
porous materials formed by multidentate organic
ligands and metal ions or clusters. An analogy is often
drawn between MOFs and aluminosilicate zeolites—
another class of porous materials [1, 2]. MOFs indeed
possess properties significant for heterogeneous catalꢀ
ysis, namely, a large specific surface area and uniform
pore and cavity size distributions. The unique feature
of the MOFs differentiating them from metal oxides is
the absence of inaccessible (“dead”) spaces [3] like
those existing in zeolites. Due to the large specific surꢀ
face area of the MOF structures, the MOFꢀbased catꢀ
alysts can have a high volume concentration of active
sites ensuring an extraordinarily high degree of disperꢀ
sion of the metal [4]. MOFꢀ5 is the metalꢀorganic
framework structure that has most extensively been
studied to date. It consists of Zn4O clusters and
terephthalate (1,4ꢀbenzenedicarboxylate) bridging
ligands.
tallinity and a large specific surface area. The purpose
of this study is to understand whether these composites
are usable as supports for palladiumꢀcontaining cataꢀ
lysts. The object of this study is the system containing,
in the cavities of the MOFꢀ5 structure, 20 wt %
calix[4]arene in the cone conformation (Fig. 1). The
palladiumꢀcontaining system 3% Pd/MOFꢀ5/20%
calix[4]arene was prepared by incipientꢀwetness
impregnation. This palladium content of the composꢀ
ite is equal the catalytic metal content of the heterogeꢀ
neous catalysts commonly used in hydrogenation (1–
5 wt %). Note that the literature contains no informaꢀ
tion concerning the synthesis of Pd/MOFꢀ
5/calix[4]arene composites and their catalytic appliꢀ
cations. The catalytic performance of the synthesized
material was studied in 1,3ꢀcyclohexadiene (CHD)
hydrogenation as a model reaction. The parameters of
Some authors note the vague resemblance between
calix[n]arenes and MOFs, including the existence of a
macrocycle cavity suitable for host–guest interaction
[5] and, in some cases, the formation a supramolecuꢀ
lar structure having ordered oneꢀdimensional chanꢀ
nels (calix[8]arenes) [6]. Calix[n]arenes have attracted
keen attention from researchers owing to their excelꢀ
lent extraction and coordination properties. Note that
calix[n]arenes are mentioned in the literature as conꢀ
venient objects for modeling of catalytic systems [6, 7].
R
R
OR1
OR1
X
OR1
X
X
X
OR1
R
R
We have recently synthesized new materials based
on the 1,4ꢀbenzenedicarboxylate framework MOFꢀ5
and calix[4]arenes with different structures [8]. It was
demonstrated that the systems containing 5–20 wt %
R = H, R1 = CH2COOH, X = CH2
Fig. 1. Structure of calix[4]arene introduced into MOFꢀ5.
94

1,3ꢀCYCLOHEXADIENE HYDROGENATION IN THE PRESENCE
95
Table 1. Textural characteristics of the supports used in the preparation of the Pdꢀcontaining catalysts
Total pore volume,
cm3/g
Micropore volume
V
Mesopore volume
V
Support
S
BET, m2/g
micro, cm3/g
meso, cm3/g
Carbon SKTꢀ4A
MOFꢀ5/20% calix[4]arene
1269
550
0.66
0.29
0.54
–
0.12
–
this reaction will be compared with the characteristics
(
λ
= 1.54 Å), the Bragg–Brentano reflection techꢀ
of the same reaction over the conventional hydrogenaꢀ nique, and the Debye–Scherrer transmission geomeꢀ
tion catalyst Pd/C.
EXPERIMENTAL
try. Infrared diffuse reflectance spectra were recorded
at room temperature on a Nicolet Protégé 460 specꢀ
trometer. Before examination, the samples were
pumped at 200°С for 1 h. For a satisfactory signalꢀtoꢀ
noise ratio, 500 spectra were coadded. CO (10 Torr)
was adsorbed at room temperature and was then desꢀ
orbed in vacuo. Deuterated acetonitrile CD3CN was
adsorbed at room temperature and a saturation vapor
pressure of 96 Torr.
Preparation of the Catalysts
3% Pd/MOFꢀ5/20% calix[4]arene. The MOFꢀ
5/20% calix[4]arene composite was obtained by direct
mixing [8]. A mixture of terephthalic acid (0.507 g,
3.5 mmol), calix[4]arene (0.11 g), and triethylamine
(0.85 ml) was dissolved in 40 ml of
mamide (DMF) at room temperature. Simultaꢀ
neously, Zn(OAc)2 2H2O (1.699 g, 7.74 mmol) was
N,Nꢀdimethylforꢀ
Performing the Reaction in a Flow Reactor
⋅
CHD was fed into the reactor using a syringe dosꢀ
ing pump. The catalyst charge was 0.1 cm3. The
Н2/CHD ratio was 2.5. The reaction was carried out at
dissolved in 50 ml of DMF. The solution of the zinc
salt was gradually added to the solution of the organic
reactants (0.5 h, 20 C). The resulting white crystalline
°
atmospheric pressure, T = 40–170°С, and a CHD liqꢀ
precipitate was separated by centrifugation, washed
with DMF (three times, 10ꢀml portions), and dried in
°
1
uid hourly space velocity (LHSV) of 2–12 h⎯ . The
catalysate was analyzed on a Model 3700 chromatoꢀ
graph (Soviet Union) using a capillary column (25 m)
vacuo (10–3 Torr, 200
C). Calix[4]arene to be introꢀ
duced into the MOF cavities was synthesized using a
standard procedure [9].
and the SEꢀ54 phase in the isothermal mode at 80°С
.
The Pdꢀcontaining catalyst (3% Pd/MOFꢀ
5/calix[4]arene) was prepared by the incipientꢀwetꢀ
ness impregnation of the MOF composite with a
Pd(OAc)2 solution in absolute chloroform in a similar
way to the Pd/MOFꢀ5 system (in the latter case,
MOFꢀ5 was impregnated with a Pd(acac)2 solution)
[10]. The solution of Pd(OAc)2 (0.032–0.050 g,
0.050–0.074 mmol) in chloroform (0.30 ml) was
added slowly to a preꢀevacuated MOFꢀ5 sample
(0.5 g), and the solvent was then distilled off under
RESULTS AND DISCUSSION
The initial composite system, MOFꢀ5/20%
calix[4]arene, is characterized by a large specific surꢀ
face area of 550 m2/g (Table 1) and a high degree of
crystallinity (Fig. 2). According to Xꢀray diffraction
data, the crystallinity of the MOF structure persists
both after the introduction of Pd and after the catalytic
reaction.
The IR spectrum of acetonitrileꢀd3 adsorbed on the
MOFꢀ5/20% calix[4]arene composite (Fig. 3) indicates
the presence of strong Lewis acid sites (Zn2+). The shift
continuous stirring. Next, the Pd(OAc)2/MOF
5/calix[4]arene system was pumped at 20 for 4 h
and at 150 for another 4 h.
ꢀ
°
C
°
С
of the
C N stretching frequency for adsorbed acetoniꢀ
≡
5% Pd/C. The reference catalyst was prepared by trileꢀd3 (2306 cm–1) relative to the same frequency for
impregnating the support—activated carbon SKTꢀ4A gaseous acetonitrile (2253 cm–1) is 53 cm–1.
(1 g,
Н2PdCl4 (1 ml) containing 0.015 g/ml Pd. The prodꢀ
uct was dried in air at 90 (3 h) and was then calcined
S
BET = 1269 m2/g)—with an aqueous solution of
As follows from the IR spectra of adsorbed
CD3CN, the introduction of 3 wt % Pd into MOFꢀ
5/20% calix[4]arene does not affect the strength of the
Lewis acid sites (Fig. 3).
The electronic state of palladium in 3% Pd/MOFꢀ
5/20% calix[4]arene was studied by IR spectroscopy of
adsorbed CO. The IR spectra of adsorbed CO (Fig. 4)
°
С
at 300°C (2 h) in flowing air (10 ml/min). Before perꢀ
forming the reaction, the catalyst samples were
reduced in flowing hydrogen (10 ml/min) at 200°С
for 1 h.
The specific surface area of the supports was calcuꢀ show stretching bands typical of carbon monoxide
lated from nitrogen adsorption data using the BET adsorbed on palladium [12, 13]. The band at 2128 cm–1
equation by the procedure described by Klyachkoꢀ is due to CO adsorbed on Pd+ sites in a linear configuꢀ
Gurvich [11]. Xꢀray diffraction patterns were obtained ration. The band at 2079 cm–1 is due to CO adsorbed
on a DRON 3M diffractometer using Cu
K
1 radiation linearly on metallic palladium. The band at 1938 cm–1
α
KINETICS AND CATALYSIS Vol. 52
No. 1
2011

96
ISAEVA et al.
Table 2. 1,3ꢀCyclohexadiene hydrogenation at atmospheric pressure*
Concentration, wt %**
Catalyst
LHSV, h–1
T,
°
C
Х
, %
S,
wt %
СН
benzene
CH= 1,3ꢀCH= =
3% Pd/MOFꢀ5/20%
calix[4]arene
2
8
40
40
40
60
80
40
40
40
80
100
99.2
76.8
100
0.9
99.1
58.8
46.0
73.0
99.6
97.5
93.4
92.4
83.1
78.0
–
–
0.9
40.4
30.8
27.0
0.4
–
0.8
23.2
–
42.2
40.1
27.0
0.4
12
8
–
–
8
100
100
–
–
5% Pd/C
2
2.5
–
2.5
–
8
99.8
6.5
–
6.4
0.2
0.9
0.8
16.4
12
2
99.1
99.2
83.6
6.8
–
6.7
14.6
2.2
1.6
2.7
14.5
1.8
2
160
*X is the CHD conversion and S is selectivity in terms of partial CHD hydrogenation into cyclohexene.
**CH, saturated hydrocarbons; CH=, unsaturated hydrocarbons; 1,3ꢀCH==, CHD.
pertains to bridging CO adsorbed on metallic pallaꢀ ~40% even for mixtures containing excess hydrogen at
an H2/CHD molar ratio of 2.5.
dium. CO desorption in vacuo reduces the stretching
frequency for CO linearly adsorbed on metallic pallaꢀ
dium to 2045 cm–1.
For 5% Pd/C, we observed that, under severe reacꢀ
tion conditions (LHSV = 2 h–1,
T
>
80 С), partial
°
CHD hydrogenation is accompanied by cyclohexene
disproportionation into benzene and cyclohexane. No
benzene results from CHD hydrogenation over 3%
Pd/MOFꢀ5/20% calix[4]arene under the same condiꢀ
tions. No side disproportionation reaction was also
observed in cyclohexene hydrogenation over the pallaꢀ
diumꢀcontaining system 3% Pd/MOFꢀ5 [14]. The
In this study, we compared the 3% Pd/MOFꢀ
5/20% calix[4]arene and 5% Pd/C catalysts in terms
of CHD conversion and hydrogenation selectivity.
The results of these catalytic tests are presented in
Table 2. In the case of the composite catalyst 3%
Pd/MOFꢀ5/20% calix[4]arene, selectivity for partial
CHD hydrogenation into cyclohexene increases
markedly as LHSV is raised to 8–12 h–1, reaching
~40%, and decreases with increasing temperature at a
fixed LHSV. Note that the cyclohexene selectivity is
Absorbance, Kubelka–Munk units
0.4
2262
2
0.3
1
0.2
0.1
0
2306
2110
2300
2200
2100
1
Wavenumber, cm−
5
10
15
20
, deg
25
30
35
2
θ
Fig. 3. IR spectra of CD CN adsorbed on (
5/20% calix[4]arene and
calix[4]arene.
1
) MOFꢀ
3
Fig. 2. Xꢀray diffraction data for the MOFꢀ5/calix[4]arene
composite.
(2) 3% Pd/MOFꢀ5/20%
KINETICS AND CATALYSIS Vol. 52
No. 1
2011

1,3ꢀCYCLOHEXADIENE HYDROGENATION IN THE PRESENCE
97
2. Lee, J.Y., Farha, O.K., Roberts, J., Schedt, K.A.,
Nguen, S.B.T., and Hupp, J.T., Chem. Soc. Rev., 2009,
vol. 38, p. 1450.
3. Czaja, A.U., Trukhan, N., and Mueller, U., Chem. Soc.
Rev., 2009, vol. 38, p. 1284.
Absorbance, Kubelka–Munk units
0.20
2079
1938
0.15
4. Mueller, U. and Ceder, C., J. Phys. Chem. B, 2005,
vol. 109, p. 17974.
5. Shin, D.ꢀM., Kim, T.H., Chung, G., and Kim, K., Colꢀ
loids Surf., A, 2005, vol. 257, p. 461.
6. Bergougnant, R.D., Robin, A.Y., and Fromm, K.M.,
0.10
2128
Tetrahedron, 2007, vol. 63, p. 10751.
7. Gutsche, C.D., Calixarenes Revisited, Cambridge: The
2120
1913
0.05
1
Royal Society of Chemistry, 1998.
2045
2
3
8. Isaeva, V.I., Tkachenko, O.P., Brueva, T.R., Kapusꢀ
tin, G.I., Afonina, E.V., Mishin, I.V., Gryunert, V.,
Kustov, L.M., Solov’eva, S.E., and Antipin, I.S., Russ.
J. Phys. Chem. A, 2011, vol. 85, no. 2, p. 293.
4
0
2200
2100
2000 1900
1
Wavenumber, cm−
9. Iwamoto, K. and Shinkai, S., J. Org. Chem., 1992,
vol. 57, p. 7066.
10. Sabo, M., Henschel, A., Fröde, H., Klemm, E., and
Kaskel, S., J. Mater. Chem., 2007, vol. 17, p. 3827.
11. KlyachkoꢀGurvich, A.L., Izv. Akad. Nauk SSSR, Ser.
Khim., 1961, no. 10, p. 1884.
Fig. 4. IR spectra of CO adsorbed on 3% Pd/MOFꢀ5/20%
calix[4]arene recorded ( ) after adsorption and (2–4) after
adsorption followed by pumping at 23°С for ( ) 1 and (
2 h and ( ) thereafter at 50°С for 30 min.
1
2
3)
4
12. Sheppard, N. and Nguyen, T.T., Adv. Infrared Raman
Spectrosc., 1978, vol. 5, p. 67.
13. Davydov, A.A., IKꢀSpektroskopiya v khimii poverkhnosti
okislov (IR Spectroscopy Applied to the Chemistry of
Oxide Surfaces), Novosibirsk: Nauka, 1984.
above experimental data point to the advantages of the
highly ordered MOF and MOF/calixarene systems
over activated carbons with an irregular structure as
supports for heterogeneous catalysts [15].
14. Isaeva, V.I., Tkachenko, O.P., Mishin, I.V., Kapusꢀ
tin, G.I., Kostin, A.A., Klementiev, K.V., and Kusꢀ
tov, L.M., Stud. Surf. Sci. Catal., 2008, vol. 174,
p. 463.
REFERENCES
1. Qui, L.ꢀG., Gu, L.ꢀN., and Zhang, L.ꢀD., J. Solid
State Chem., 2009.
15. Sabo, M., Henschel, A., Fröde, H., Klemm, E., and
Kaskel, S., J. Mater. Chem., 2007, vol. 17, p. 3827.
KINETICS AND CATALYSIS Vol. 52
No. 1
2011