JOURNAL OF CATALYSIS 180, 51–55 (1998)
ARTICLE NO. CA982261
Glucose Hydrogenation on Ruthenium Catalysts in a Trickle-Bed Reactor
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Pierre Gallezot, Nathalie Nicolaus, Guy Fle`che,† Patrick Fuertes,† and Alain Perrard
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Institut de Recherches sur la Catalyse-CNRS, 2, Avenue Albert Einstein, 69626 Villeurbanne Ce´dex, France;
and †Socie´te´ Roquette Fre`res, 62136 Lestrem, France
Received April 21, 1998; revised August 14, 1998; accepted August 18, 1998
time. To meet the stability challenge, the catalyst should be
resistant to metal sintering and poisoning, but the most cru-
cial point is to avoid metal and support leaching in the acidic
and chelating reaction medium. In a previous work, the ki-
netics of glucose hydrogenation was studied in a trickle-bed
reactor in the presence of kieselguhr-supported nickel cata-
lysts (2). It was shown that glucose was converted to sor-
bitol according to a Langmuir–Hinshelwood rate law where
the reaction between adsorbed glucose and dissociated hy-
drogen was rate-determining. However, the activities de-
creased with time because of the progressive leaching of
both nickel and support. Ruthenium, which is much more
active than nickelin the hydrogenation ofaqueoussolutions
of glucose (3), is potentially a good substitute for nickel in
fixed-bed catalytic processes. Makkee et al. (4) studied the
hydrogenation of glucose and glucose–fructose mixtures
in ruthenium catalysts, but their primary aim was to ob-
tain the highest mannitol yield, which was better achieved
with Cu/SiO2 catalyst combined with enzymatic isomeriza-
tion. Two studies of glucose hydrogenation in a trickle-bed
reactor were conducted by Germain et al. (5) and Arena
(6). The former authors established a rate law but did not
give precise data on selectivities. Arena did not give data on
activities and selectivities, but showed that Ru/Al2O3 cata-
lysts deactivated because of the presence of iron and sulfur
impurities and because the physical properties of the alu-
mina support were modified. In the present work, glucose
hydrogenation was conducted in a trickle-bed reactor in the
presence of carbon-supported ruthenium catalysts. Ruthe-
nium and carbon were chosen because both metal and sup-
port are stable in the reaction medium under hydrogena-
tion conditions. The activities, selectivities, and stabilities
of ruthenium catalysts prepared by anionic adsorption or
cationic exchange were compared.
Glucose in 40 wt% aqueous solution was hydrogenated into sor-
bitol in a trickle-bed reactor over ruthenium catalysts supported on
active charcoal pellets. The metal was loaded by cationic exchange
or anionic adsorption. After reduction, ruthenium was under the
form of 1-nm particles homogeneously distributed throughout the
support. The reaction was conducted at 100ꢁC under 8 MPa of hy-
drogen at 20 L hꢂ1 flow rate. Conversion and selectivity to sorbitol
were studied as a function of residence time. Whatever the mode of
preparation, the catalysts give a total conversion of glucose with an
initial specific activity of 1.1 mol hꢂ1 gRꢂu1. The selectivity to sorbitol
was higher than 99.2% at 100% conversion; however, the liquid flow
rate should be adjusted very accurately because any increase in the
residence time results in a loss of selectivity due to epimerization of
sorbitol into mannitol. The catalyst activity was stable over several
c
weeks and no leaching of ruthenium was detected.
ꢃ 1998 Academic
Press
INTRODUCTION
Sorbitolisa major specialtyproduct prepared bycatalytic
hydrogenation of glucose, which is a cheap and abundant
feedstock obtained from renewable resources, particularly
from starch-containing crops such as maize and wheat. Sor-
bitol is used as an additive in many industrial products, par-
ticularly in the food, cosmetic, and paper industries, and
as a building block in the synthesis of various fine chem-
icals, including vitamin C. Most of the industrial produc-
tion is based on the hydrogenation of glucose in a batch
process employing nickel-based catalysts in powder form,
particularly Raney nickel promoted by various transition
metals. In a previous study (1), the effects of molybdenum,
chromium, iron, and tin promoters on activities and selec-
tivities of Raney nickel were studied. There are currently
strongincentivesto develop continuoushydrogenation pro-
cesses to cope with the increasingly larger demand for sor-
bitol (ca. 700,000 tons/year). The challenge is to obtain a
selectivity to sorbitol higher than 99% at 100% conversion
and a high stability of the catalyst during a long period of
EXPERIMENTAL
Preparation of Catalysts
Extrudates of activated carbon Norit rox 0.8 were em-
ployed because of their high purity, suitable resistance to
attrition, and small size (cylinders of 0.8-mm diameter),
1 To whom correspondence should be addressed. E-mail: gallezot@
catalyse.univ-lyon1.fr.
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0021-9517/98 $25.00
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Copyright ꢃ 1998 by Academic Press
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