Conclusions
benzonitrile increases and a single phase was reached. The phase
behavior of benzylamine and dibenzylamine was also checked.
Benzylamine showed an interesting behavior as described in
Fig. 4, which represents the carabamate formation at P < 12
MPa (Fig. 4a) and solubility at higher pressure (P ≥ 12 MPa;
In conclusion, it has been demonstrated that scCO is a potential
2
medium to facilitate the hydrogenation of benzonitrile to the
corresponding primary amine. Without using any additive,
high conversion (90.2%) and selectivity for the primary amine
Fig. 4b). Similarly, dibenzylamine also shows solubility in CO
2
(
~91%) were achieved over the Pd/MCM-41 catalyst. The
product distribution was found to depend on different reaction
parameters such as CO and H pressure, temperature and the
nature of the support. Simple tuning of the CO pressure resulted
in the formation of the secondary amine, dibenzylamine, which
was assisted by the interaction of CO with the reactant and also
at higher pressure.
2
2
2
2
by the acidic support of C, instead of neutral MCM-41. In the
studied experimental conditions, Pd/C was deactivated easily,
whereas Pd/MCM-41 can be recycled. Preliminary experiments
with other substituted nitriles show a strong influence of the
nature of the substituted group on the activity and selectivity.
The simple methodology presented here could be highly rele-
vant for further development of a clean chemical process for
hydrogenation of nitriles.
Fig. 4 Phase behavior study of benzylamine (a) P < 12 MPa (b) P ≥ 12
MPa.
Notes and references
Experimental
1
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Materials
Benzonitrile (Wako Pure Chemicals) was used as received.
Carbon dioxide (>99.99%) was supplied by Nippon Sanso Co.
Ltd. The 1% Pd/C, 5% Pd/Al
from Aldrich, 5% Rh/Al from Wako Pure chemicals and Pd,
2
O
3
, 5% Pt/C and 5% Rh/C were
2
O
3
Pt, Ni and Rh/MCM-41 were synthesized in our lab.
Catalytic activity
3
57.
◦
The hydrogenation of benzonitrile was studied at 50 C over 1%
Pd/MCM-41 catalyst. All reactions were carried out in a 50 ml
stainless steel batch reactor placed in a hot air circulating oven.
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2
2
The details are given elsewhere. Briefly, 0.1 g of catalyst and
.0 g of the reactant were introduced into the reactor. After the
required temperature was attained, H , followed by CO , was
1
2
2
3
4
charged into the reactor using a high-pressure liquid pump and
then compressed to the desired pressure. The product liquid was
separated from the catalyst simply by filtration and identified
by NMR and GC-MS, followed by quantitative analysis using
a GC (HP 6890) equipped with capillary column and flame
ionization detector. For all results reported, the selectivity is as
concentration of the product
5
6
A. Kleemann, J. Engel, B. Kutscher, D. Reichert, Pharmaceutical
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follows: % selectivity =
×100
7
8
B. Wanderott, Z. Metallkd., 1965, 56, 63.
total concentration of products
S. Gomez, J. A. Peters, J. C. Van der Waal, W. Zhou and T.
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9
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Phase behavior
1
67.
1
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The phase behavior of benzonitrile was studied in a 10 ml high
pressure view cell fitted with a sapphire window. The cell is placed
over a magnetic stirrer and connected to a pressure controller,
to regulate the pressure inside the view cell. In addition, a
temperature controller was also used to maintain the desired
2
007, 26, 5940; S. Enthalaer, D. Addis, K. Junge, G. Erre and M.
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◦
temperature of 50 C. The substrate was introduced into the
view cell at a constant hydrogen pressure of 2 MPa while CO
2
3
pressure was varied between 7–14 MPa and the phase behavior
was monitored. The reaction mixture exhibited a biphase at
and M. Studer, M., Adv. Synth. Catal., 2003, 345, 103; S. Gomez,
J. A. Peters and T. Maschmeyer, Adv. Synth. Catal., 2002, 344,
1037.
P < 10 MPa, but with increasing CO
2
pressure the solubility of
9
2 | Green Chem., 2010, 12, 87–93
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