Organic Process Research & Development 2003, 7, 769−773
Kinetics of Liquid-Phase Catalytic Hydrogenation of Benzophenone to
Benzhydrol
Sunil P. Bawane and Sudhirprakash B. Sawant*
UniVersity Institute of Chemical Technology, UniVersity of Mumbai, Matunga, Mumbai - 400 019, India
Abstract:
catalyst, and Andrews et al. obtained 80% yield using Raney
Catalytic hydrogenation of benzophenone to benzhydrol was
carried out in 2-propanol using Raney nickel as a catalyst at
hydrogen pressures in the range of 800-2200 kPa, reaction
temperatures 323-343 K, catalyst loadings 4-20 g dm-3 and
benzophenone concentrations 0.44-1.32 mol dm-3. Effects on
the hydrogenation of benzophenone to benzhydrol of various
catalysts (Pd/BaSO4, Pd/C, Pt/C, Raney nickel, Pd/CaCO3) and
solvents (methanol, 2-propanol, xylene, toluene, hexane, dim-
ethylformamide) have been reported. Speed of agitation beyond
17 rps had no effect on the progress of reaction. Benzophenone
can be selectively hydrogenated to benzhydrol, and the initial
rate of hydrogenations showed first-order dependence with
respect to the hydrogen partial pressure and catalyst loading
and zero-order dependence with respect to benzophenone
concentration. The activation energy for the catalytic hydro-
genation of benzophenone was found to be 56 kJ mol-1. A
Langmuir-Hinshelwood-type kinetic model with hydrogen
from the liquid-phase attacking adsorbed benzophenone has
been proposed.
nickel catalyst and 2-propanol.8-9 Kumbhar et al. studied
the hydrogenation of benzophenone to benzhydrol over Ni
and Ni-based bimetallic Ni-Cu and Ni-Fe catalysts. The
hydrogenation was accompanied by the formation of ether
and 1-methoxy-1,1-diphenylmethane in addition to the
expected hydrogenation product, benzhydrol.10 Hideyuki et
al. used homogeneous rhodium, ruthenium, iridium, and
platinum catalysts for the hydrogenation of benzophenone
to obtain benzhydrol in 90% yield.11 Sajiki et al. have used
10% Pd/C-ethylenediamine complex as a catalyst to obtain
89% yield of benzhydrol.12
However, limited kinetic information concerning the
catalytic hydrogenation of benzophenone to benzhydrol has
been published.10-12
Materials
Introduction
Benzophenone, 2-propanol, methanol, toluene, xylene,
hexane, and dimethylformamide used were of laboratory
reagent grade and obtained from S.D. Fine Chemicals,
Mumbai, India. Hydrogen (cylinder purity 99.98%) was
obtained from India Oxygen Limited, Mumbai, India, and
was used as such. Commercially prepared 5%Pd/C, 5%Pd/
BaSO4, 5%Pt/C, 5%Pd/CaCO3 were obtained from Parekh
Platinum Ltd, Mumbai, India, and Raney nickel was obtained
from Monarch Chemicals, Mumbai, India.
The hydrogenation of benzophenone is a well-known
route to obtain benzhydrol that is widely used as an
intermediate for the commercial production of pharmaceutical
substances. The conventional reduction process using zinc
and aqueous alkali is known to generate substantial waste.
Reduction using stoichiometric but expensive sodium boro-
hydride gives rise to similar problems.1 The catalytic
hydrogenation of benzophenone can be utilized as the
simplest technical route for the synthesis of benzhydrol. It
is usually carried out in alcoholic solvents in the presence
of various metallic catalysts but produces diphenylmethane,
an over-reduction product. Gosser obtained 97% yield of
benzhydrol and 86% conversion of benzophenone in tert-
butanol as a solvent with the use of Lindlar, lead-poisoned
Pd/CaCO3 catalyst.1 Various methods have been reported for
the synthesis of benzhydrol.2-7 Upadhya et al. have reported
91% yield of benzhydrol in the hydrogen-transfer process
with 2-propanol and Ni-stabilized zirconia (Zr0.8Ni0.2O2)
Experimental Section
Experiments were carried out in an autoclave (diameter
) 65 mm, capacity ) 100 mL). The reactor had provisions
for automatic temperature control, variable agitation speed
(pitched blade turbine, diameter ) 35 mm), a safety rupture
disk, and the sampling of the liquid phase. The appropriate
quantities of the benzophenone, the solvent, and the catalyst
were added to the clean and dry autoclave. Before heating
(8) Upadhya, T. T.; Katdare, S. P.; Sabde, D. P.; Ramaswamy, V.; Sudalai, A.
Chem. Commun. 1997, 1119.
(1) Gosser, L. W. U.S. Patent 4,302,435, 1981.
(2) Linn, D. E.; Halpern, J. J. Organomet. Chem. 1987, 330, 155.
(3) Ying, W.; Xio, T. G.; Jian, J.; Jian, P. X.; Zheng, F. C. Zhonguo Kexue
Jishu Daxue Xuebao 2000, 30, 500; Chem. Abstr. 2000, 133, 362506.
(4) Li, J.; Zhou, W.; Zhang, X. Huaxue Shiji 1993, 15, 61; Chem. Abstr. 1994,
119, 48993.
(5) Scott, L. T.; Carlin, K. J.; Schultz, T. H. Tetrahedron Lett. 1978, 47, 4637.
(6) Timmler, H. Ger. Offen. 1196602, 1971.
(7) Stanley, S. G.; Rudolf, S. E. J. Chem. Soc. D 1970, 21, 1428.
(9) Andrews, M. J.; Pillai, C. N. Ind. J. Chem. 1978, 16B, 465.
(10) Kumbhar, P. S.; Rajadhyaksha, R. A. In Heterogeneous Catalysis and Fine
Chemicals III; Guisnet, M. et al., Eds.; Elsevier Science Publishers:
Amsterdam, 1993.
(11) Hideyuki, I.; Kunihika, M.; Takao, I.; Takeshi, O.; Ryoji, N. Jpn. Kokai
Tokkyo Koho Jp. 1997, 11, 189; Chem. Abstr. 1999, 131, 87717.
(12) Sajiki, H.; Hattori, K.; Hirota, K. J. Chem. Soc., Perkin Trans. 1 1998,
4043.
10.1021/op030016k CCC: $25.00 © 2003 American Chemical Society
Published on Web 07/24/2003
Vol. 7, No. 5, 2003 / Organic Process Research & Development
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