Platinum-containing catalyst supported on a metal-organic framework structure in the selective oxidation of benzyl alcohol derivatives into aldehydes

Article abstract of DOI:10.1134/S0023158411020212

The platinum catalyst supported on the metal-organic framework structure MOF-5 is usable in the selective oxidation of vanillyl and piperonyl alcohols into the corresponding aldehydes.

Full text of DOI:10.1134/S0023158411020212

ISSN 0023ꢀ1584, Kinetics and Catalysis, 2011, Vol. 52, No. 2, pp. 273–276. © Pleiades Publishing, Ltd., 2011.
Original Russian Text © A.L. Tarasov, L.M. Kustov, V.I. Isaeva, A.N. Kalenchuk, I.V. Mishin, G.I. Kapustin, V.I. Bogdan, 2011, published in Kinetika i Kataliz, 2011, Vol. 52,
No. 2, pp. 282–285.
PlatinumꢀContaining Catalyst Supported on a MetalꢀOrganic
Framework Structure in the Selective Oxidation
of Benzyl Alcohol Derivatives into Aldehydes
A. L. Tarasov, L. M. Kustov*, V. I. Isaeva**, A. N. Kalenchuk, I. V. Mishin,
G. I. Kapustin, and V. I. Bogdan
Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Moscow, 119991 Russia
eꢀmail: *LMK@ioc.ac.ru, **sharf@ioc.ac.ru,
Received October 16, 2009
Abstract
—The platinum catalyst supported on the metalꢀorganic framework structure MOFꢀ5 is
usable in the selective oxidation of vanillyl and piperonyl alcohols into the corresponding aldeꢀ
hydes.
DOI: 10.1134/S0023158411020212
The catalytic activity of supported metals depends anisaldehyde, etc. [5]. This reaction is interesting in
considerably on the nature of the support [1]. The the context of the strong dependence of the oxidation
method of preparing heterogeneous catalysts supꢀ route on the nature of the catalyst [6]. The convenꢀ
ported on metalꢀorganic framework structures tional foreign technology based on this process [7]
(
MOFs) was suggested by Opelt et al. [2].
produces large amounts of liquid waste, is very energyꢀ
intensive, and consumes large amounts of noble metꢀ
als. There have been examples of use of cadmium,
cerium, indium, lanthanum, copper, yttrium, magneꢀ
sium, and zinc ions as promoters in the oxidation of
benzyl alcohol derivatives on conventional catalysts,
such as Pt/C [8]. However, in spite of the high conꢀ
sumption of the promoter, no significant reduction of
the necessary platinumꢀgroup metal content of the
catalyst has been attained.
The unique feature of the MOFs is that they have
no space inaccessible to an adsorbate (“dead” space)
3]. In addition, due to the open architecture of the
[
MOFs, the diffusion coefficients of reactant molecules
in these materials are somewhat smaller than in the
solvent bulk; that is, mass transfer is not hampered in
this case [3].
There is only scarce information concerning the
use of MOFꢀsupported heterogeneous catalysts in the
aerobic oxidation of alcohols. It was demonstrated
that the palladiumꢀcontaining MOF with the molecuꢀ
lar formula [Pd(2ꢀpymo)2]n (2ꢀpymo = 2ꢀhydroxypyriꢀ
midinolate) is catalytically active in the aerobic oxidaꢀ
tion of 3ꢀphenylpropꢀ2ꢀenꢀ1ꢀol (cinnamic alcohol)
into cinnamic aldehyde. The selectivity of this hybrid
catalyst toward the target product is as high as 74%
EXPERIMENTAL
Catalyst Preparation
The support for the Ptꢀcontaining catalysts was the
synthesized metalꢀorganic framework MOFꢀ5 and
activated carbon SKTꢀ4A. The textural characteristics
of the supports are presented in Table 1.
(
20 h, ~100% conversion).
Here, we report the preparation of an MOFꢀ5–
5
% Pt/MOFꢀ5. MOFꢀ5 was synthesized by direct
supported Ptꢀcontaining system and demonstrate that
this system is usable as a catalyst in the aerobic oxidaꢀ
tion of piperonyl and vanillyl alcohols into the correꢀ
sponding aldehydes. MOFꢀ5, which is the best studied
representative of the new family of porous materials, is
built of Zn O clusters and terephthalate (benzeneꢀ1,4ꢀ
dicarboxylate) bridging ligands and has the molecular
mixing of terephthalic acid and Zn(NO ) 6H O [9].
3 2
2
An MOFꢀ5 sample was examined by Xꢀray diffraction
on a DRONꢀ3M diffractometer using Cu radiation
K
α
(
λ
= 1.54 Å). The specific surface area (SBET) was
determined from nitrogen adsorption data (–196°C
)
4
using a volumetric technique and was calculated using
the BET equation [10].
formula [Zn O(BDC)3] (BDC = benzeneꢀ1,4ꢀdicarꢀ
4
boxylate).
The Ptꢀcontaining catalyst was prepared by the
The catalytic oxidation of benzyl alcohol derivaꢀ same procedure as was developed for the Pd/MOFꢀ5
tives into aldehydes is an industrially important proꢀ system (incipientꢀwetness impregnation) [11]. A soluꢀ
cess, providing the basis for producing vanillin from tion of [Pt(NH ) ]Cl (0.04 g, 0.11 mmol) in 0.58 ml
3
4
2
guaiacol, heliotropine (piperonal) from pyrocatechol, of water was gradually added to prepumped MOFꢀ5
273

274
TARASOV et al.
Table 1. Textural characteristics of the supports used in the preparation of the Ptꢀcontaining catalysts
2
3
3
3
Support
SBET, m /g Total pore volume, cm /g Micropore volume, cm /g Mesopore volume, cm /g
Carbon support SKTꢀ4A
1269
1000
0.66
0.52
0.54
–
0.12
–
MOFꢀ5
Table 2. Catalyst testing data for piperonyl alcohol oxidation at 80°С
Catalyst
Alcohol/catalyst weight ratio
Time, min
30
Conversion, %
Selectivity, %
9
5
*
% Pt/SKTꢀ4A*
20
62.0
100
100
99.6
100
100
60
%Pt /MOFꢀ5
5
30
50.8
96.1
60
Data from [8].
(
0.38 g) under continuous stirring. The solvent was The heterogeneous catalyst was filtered out, and the
evaporated at room temperature for 2 h. Next, the sysꢀ initial alcohol and the resulting aldehyde were multiꢀ
tem was pumped while raising the temperature to ply extracted with chloroform with separation of the
300
°С
(5 h).
organic and aqueous phases.
The alcohols and the corresponding aldehydes in
the organic phase were identified by GLC on a Model
9
% Pt/C (reference catalyst). Activated carbon
SKTꢀ4A (10 g, 0.05–0.1 mm size fraction) was loaded
with platinum by incipientꢀwetness impregnation with
3
700 chromatograph (capillary column SEꢀ54, 25 m)
in a temperatureꢀprogrammed mode (temperature
rise to 100 over 4 min and then to 280 at a rate of
0 K/min).
an aqueous H PtCl6 solution (10 ml). Paraformaldeꢀ
2
°
С
°С
hyde (10 wt %) as the reductant was added to the aqueꢀ
ous solution. After the supporting of platinum, the
sample was placed on a filter and was washed with disꢀ
tilled water until free of Cl ions. Thereafter, the cataꢀ
lyst was dried at 90
2
–
RESULTS AND DISCUSSION
The MOFꢀ5 sample that was synthesized to be plaꢀ
°
°
C
for 2 h, calcined in flowing air in
a flow reactor (300
C, 2 h), cooled in flowing nitrogen
to room temperature, reduced in flowing H2 tinized had a high degree of crystallinity, which perꢀ
(
30 ml/min) while raising the temperature to 300 C at sisted up to 330
°
°
C
, and a large specific surface area
a rate of 100 K/h, and cooled to room temperature in (Table 1). The Xꢀray diffraction pattern of this MOF
flowing nitrogen.
structure (figure) coincided with the diffraction patꢀ
tern calculated for MOFꢀ5 [12]. The metalꢀorganic
framework retained its crystallinity after the introducꢀ
tion of platinum. The catalytic activity of the 5%
Pt/MOFꢀ5 system was studied in the aerobic oxidaꢀ
tions of piperonyl alcohol into piperonal and of vanilꢀ
lyl alcohol into vanillin.
Conducting the Oxidation Reaction in a Batch Reactor
The reactor (20ꢀml glass test tube) was charged
successively with 2 g of piperonyl alcohol (2,4ꢀmethꢀ
ylenedioxyphenylmethanol) or vanillyl (3ꢀmethoxꢀ
ysalicylic) alcohol, 10 ml of 0.25–1.25 N NaOH,
0
.1 ml of 0.05 M lead acetate (Pb(OAc) ) as the catalyst
2
Piperonyl Alcohol Oxidation
activator, and 0.1–0.5 g of the catalyst (substrate/cataꢀ
lyst = 5–20 by weight). The reactor was purged with
air, and the stock was heated to 60–80°С. The catalyst
and alcohol in the alkaline solution were agitated by
intensive air bubbling (50 ml/min). Thirty (sixty) minꢀ
utes after the initiation of the reaction, the reaction
O
O
O
O
OH
(
Cat
)
O
O2
In piperonyl alcohol oxidation with air, the activity
mixture was sampled for a GLC analysis. After the and selectivity of the MOFꢀ5–supported catalyst was
completion of the reaction, samples of the reaction compared to those of the conventional Pt/C catalyst.
mixture were transferred into separatory funnels and It is clear from the experimental data listed in Table 2
were acidified there with hydrochloric acid to pH 7. that the activity of the 5% Pt/MOFꢀ5 catalyst is comꢀ
KINETICS AND CATALYSIS Vol. 52
No. 2
2011

PLATINUMꢀCONTAINING CATALYST SUPPORTED
275
20
5
37
θ
, deg
Xꢀray diffraction pattern of synthesized MOFꢀ5.
parable with the activity of the 9% Pt/SKTꢀ4A cataꢀ that the Pt content of the MOFꢀsupported catalyst is
lyst, which has a higher platinum content. Both catꢀ
alysts show ~100% selectivity toward the target
product.
almost two times lower (5 wt %) and the target product
selectivity of this catalyst is several times higher. In
addition, only 0.2% resinous products were observed
in the catalysate obtained with the MOFꢀsupported
catalyst.
Vanillyl Alcohol Oxidation
Note also that the Pt/MOFꢀ5 system retains its
catalytic activity in vanillyl alcohol oxidation under
static conditions over 10 reaction cycles, without platꢀ
inum being washed out into the solution.
H CO
H CO
3
3
(
Cat
)
OH
O
O2
HO
HO
Thus, it was demonstrated that the Pt/MOFꢀ5 is an
efficient catalyst for obtaining vanillin and piperonal
via the aerobic oxidation of benzyl alcohol derivatives.
The activity and selectivity of Pt/MOFꢀ5 is comparaꢀ
ble with those of the conventional heterogeneous catꢀ
Vanillin synthesis is an industrialꢀscale process, so
it is of interest to compare the catalytic performances
of the catalytic systems in this reaction.
It is clear from the data presented in Table 3 that the
MOFꢀ5–based system is much less active than the
conventional 9% Pt/SKTꢀ4A catalyst. Note, however, alyst Pt/C.
Table 3. Catalyst testing data for vanillyl alcohol oxidation at 80°C and an alcohol/catalyst ratio of 20 (onꢀstream time of 1 h)
Reaction mixture composition, wt %
Catalyst
Resins, wt %
Conversion, %
Selectivity, %
vanillin
alcohol
9
% Pt/SKTꢀ4
90.0
24.3
5.2
4.8
0.2
94.8
24.5
94.9
99.2
5% Pt /MOFꢀ5
75.5
KINETICS AND CATALYSIS Vol. 52
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2
76
TARASOV et al.
6. Tkachenko, O.P., Kustov, L.M., Tarasov, A.L., Kleꢀ
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